International Journal of Oil, Gas and Coal Technology (76 papers in press)
An improved cubic law for shale fracture considering the effect of loading path
by Yiyu Lu, Xiayu Chen, Honglian Li, Jiren Tang, Lei Zhou, Shuaibin Han
Abstract: Massive multi-stage hydraulic fracturing to form one large-scale stimulated reservoir volume (SRV) with a complex fracture network is a key technique in shale gas development. A natural fracture system may contribute significantly to gas production. Fracture aperture are the key parameter for determining flow characteristics of jointed rock media and changes due to loading and unloading behavior. In this study, according to the consolidation model for soil, a hydraulic aperture model was proposed to describe aperture variation in a complex loading path with a parabolic function. The numerical results and experimental data showed good agreement. A numerical study of the hydro-mechanical model was conducted to determine the influences of loading path and nonlinear effects on fluid flow at field scale. In this specific simulation, the total flow volume considering the influence of loading path only decreased by 14%, and considering the influence of loading path decreased by 28%, meanwhile influence of two factors resulted in a 39% reduction of the total flow volume.
Keywords: shale fracture;loading-path;hydraulic aperture model;improved cubic law.
Experimental study on the feasibility of using water emulsified diesel as CI engine fuel
by Pijush Kanti Mondal, Bijan Kumar Mandal
Abstract: In this article, authors have investigated the combustion, performance and emission characteristics of a four-stroke water cooled CI engine using water emulsified diesel (WED) as fuel containing 5% to 20% water by volume. The emulsions have been prepared using ultrasonicator. The stability behaviours of these prepared WEDs are analysed based on the measured values of polydispersity index (PDI) and water particle size in the emulsion. Improved combustion characteristics are found for WEDs than those with pure diesel. Higher brake thermal efficiency and mechanical efficiency are found for emulsified diesel compared to pure diesel. The neat SFC is found to be lower than that with pure diesel. Significant reductions in emissions of pollutants like NOx and smoke are observed. At full load, no significant difference is observed in CO emission. The emissions of CO2 and O2 have also been measured and analyzed.
Keywords: Water emulsified diesel; ultrasonicator; combustion; brake thermal efficiency; emission.
Narrow Distillation Cuts for an Improved Characterization of Crude Oil: An Insight on Heteroatoms in Heavy Fraction Molecules
by Hendrik Muller, Qasim Saleem, Emad A. Alawi, Donya A. Alsewdan, Imran A.S. Naqvi, Asem H. Al-Saleh, Tawfiq A. Al-Rowaished
Abstract: A light Arabian crude oil was separated by distillation into 27 fractions, including 25 very narrow distillation cuts, the light ends, and a vacuum residue (VR) , which were extensively characterized using standard methods. Overall, the properties matched well with those predicted by H/CAMS software, indicating a successful distillation. Then, quantitative 13C NMR spectroscopy, SIMDIS, and molecular weight (MW) distribution by mass spectrometry were used to derive an improved correlation between the MW and boiling point for the entire crude oil, in particular for the VR fraction. This allowed determining the mass fractions of sulfur and nitrogen containing compounds across the crude oil boiling range, reaching up to approximately 100 % in the VR fraction. The corresponding low abundance of pure hydrocarbon molecules in the VR fraction is important for modeling purposes and processing technologies.
Keywords: Petroleum crude oil; distillation; ASTM; APPI time-of-flight mass spectrometry; sulfur content; 13C NMR.
Comparison of polymer-based slag-mud slurries used for drilling jobs of steam stimulated wells in the Lagunillas oilfield (Venezuela)
by Juan Jesús Martín-del-Río, Gonzalo Márquez, Vicente Flores-Alés, Emilio Romero, Olga Rey, Marco Guzmán
Abstract: The mud-to-cement conversion or slag-mix technology displays several advantages when compared to conventional well cementing operations. This alternative method means to combine drilling fluids, accelerators, and finely granulated slag as the hydraulic material. Steam injection is commonly used to improve crude oil production in the Lagunillas field (state of Zulia, NW Venezuela). This work compares the use of two slag-mix systems containing two polymer-based drilling muds during cementing of injection wells: an aqueous drilling fluid and an oil-in-water emulsion mud. The aqueous formulations under study and a typical slag-mud slurry containing lignosulfonate show relatively similar values for most physic-mechanical properties. In contrast, the slag-mix emulsion system under consideration shows distinctive rheological and filtration behaviors compared to the other study polymer-based slag-mud slurry, but similar mechanical properties.
Keywords: slag-mud slurry; polymer-based drilling mud; mechanical behavior; steam injection; Lagunillas field.
Estimation of carbon dioxide injection into reservoirs potential to enhance oil production and reduce CO2 emissions to the atmosphere
by Edyta Kuk, Jerzy Stopa, Pawe? Wojnarowski, Micha? Kuk
Abstract: The carbon dioxide injection into mature oil reservoirs makes it possible to increase the oil recovery and reduce CO2 emissions to the atmosphere. The analysis of the CO2-EOR method applicability on a given reservoir requires forecasting of the production most often conducted with the use of compositional simulators with a high degree of complexity. Due to the increasing popularity of the CO2-EOR method a new methodology for preliminary evaluation of its impact on the oil recovery based on the material balance equation was proposed in this paper. On the basis of the proposed methodology the novel computer application was developed. The obtained results indicate that the developed solution makes it possible to quickly and effectively estimate the potential of the carbon dioxide injection into oil reservoirs to achieve a synergistic environmental effect. [Received: July 19, 2019; Accepted: August 12, 2019]
Keywords: CO2-EOR; material balance; production forecasting; CO2 sequestration; enhanced oil recovery; EOR.
Effect of moisture content on methane diffusion in kaolinite by Molecular dynamics simulations
by Bin Zhang, Tianhe Kang
Abstract: The diffusion behaviors of methane in kaolinite with water contents ranging from 0-5wt% have been analyzed by molecular dynamics (MD) simulations. The results indicate that methane molecules can jump between adjacent holes in the kaolinite matrix. Methane diffusion coefficient is very low (3.28
Keywords: molecular dynamics; kaolinite; moisture content; diffusion.
A Numerical Scheme and Real Options Modeling for Evaluation of a Hypothetical Oil Field under Uncertainties
by Behnam Aminrostamkolaee, Mohammad Hossein Ghaemi, Ali Safdari-Vaighani, Mahdiye Rostamkhani, Matin Sadat Borghei, Mohammad Hossein Pourkazemi, Abbas Shakeri, Teymour Mohammadi
Abstract: This paper uses real options for evaluation of a hypothetical oil field under uncertainties. We have supposed that this oil field is located in Saudi Arabia. Our evaluation includes uncertainties of oil price and exchange rate. The analysis is done both for the fixed exchange rate regime and for the floating exchange rate regime. The proposed approach enables us to take the advantage of real option valuation to overcome the shortcoming of the discounted cash flow (DCF) method which neglects uncertainties. This paper uses an explicit finite difference method (FDM) to approximate the solution of the resulting equation. The numerical experiments show that the impact of the exchange rate, oil price volatility and the correlation coefficient between returns of oil price and exchange rate on the value of an oil extracting project is significant. In addition, the behavior of the project value is studied as a function of exchange regime.
Keywords: Fixed and Floating Exchange Rate Regimes; Oil Field Value; Real Option; Uncertainties; Hypothetical Oil Field; Finite Difference Method.
Ensembling methods for countrywide short term forecasting of gas demand
by Andrea Marziali, Emanuele Fabbiani, Giuseppe De Nicolao
Abstract: Gas demand is made of three components: Residential, Industrial, and Thermoelectric Gas Demand. Herein, the one-day-ahead prediction of each component is studied, using Italian data as a case study. Statistical properties and relationships with temperature are discussed, as a preliminary step for an effective feature selection. Nine "base forecasters" are implemented and compared: Ridge Regression, Gaussian Processes, Nearest Neighbours, Artificial Neural Networks, Torus Model, LASSO, Elastic Net, Random Forest, and Support Vector Regression (SVR). Based on them, four ensemble predictors are crafted: simple average, weighted average, subset average, and SVR aggregation. We found that ensemble predictors perform consistently better than base ones. Moreover, our models outperformed Transmission System Operator (TSO) predictions in a two-year out-of-sample validation. Such results suggest that combining predictors may lead to significant performance improvements in gas demand forecasting.
Keywords: Natural gas; time series forecasting; neural networks; statistical learning; ensemble methods.
Research on Molecular Engineering and Molecular Management for petroleum energy and its Applications
by Qing Wu, Baocheng Qiu, Baoqing Deng, Yi Liu, Yi Zhang
Abstract: How to utilize petroleum resource, re-recognize and re-match resources, catalysts, and processes, have been a critical topic. Based on above mentioned points, molecular engineering & management for petroleum has attracted more and more attention from industrial and academic community. The molecular engineering and management should be framework of many key techniques, which include the following aspects: 1) The molecular level characterization of petroleum and its fractions; 2) Informational description of oil molecule information; 3) The correlation between oil molecule information and reactivity and the establishment of molecular dynamics model; 4) Simulation and optimization to maximize the value of oil resources and assets. Meanwhile, the molecular engineering and management should focus on the simulation and computing techniques, such as Molecular Type Homologous Series matrix (MTHS), Monte Carlo, Lumping and Refactoring of Entropy Maximum (REM), et.al. Many examples of the application in research, production and operations management were also introduced in this paper.
Keywords: Molecular engineering; Molecular management; Characterization; Molecular database; Reaction rule database; Dynamic models; Simulation and optimization.
Experimental Research and Numerical Simulation: Strength and Rupture patterns of Coal under Brazilian Tensile Test
by Jun Zhang, Xiaoxuan Li, Yuwei Li, Feiyu Tao, Maosen Yan
Abstract: Coal seam contains well-developed weak planes known as cleats. The strength and rupture patterns of coal with different cleat directions are significantly different in Brazilian tensile test (BTT). In this paper, a series of Brazilian tensile tests of coal specimens under different inclination angles of face cleat were carried out. Based on the experimental data, the influence of cleat direction on the failure strength (FS) and rupture patterns of coal specimens was analyzed. Then the analytical model to calculate the anisotropic failure strength of coal under Brazilian test conditions was derived. The model cannot only predict the rupture patterns of coal specimens with different cleat directions and calculate the corresponding failure strength, but also can reflect the effect of cleat density on the strength. In the simulation, the rupture patterns of numerical model also fall into four types, which are consistent with the experimental results. The cleat density has no influence on the rupture patterns, but will decrease the failure strength. The connectivity of butt cleats is the key to determine whether the coal shear along the face cleats or butt cleats.
Keywords: Coal; Brazilian tensile test; rupture patterns; failure strength; cleat density; cleat connectivity.
Chemical and Structural Characterization of nC7 Asphaltenes Extracted from Atmospheric Tower Bottom and Low Waxy Crude Oil from Indian Reservoir
by Siddhant Kumar Prasad, Jitendra S. Sangwai
Abstract: Detailed studies on asphaltenes from Indian sources are scarce. In this study, nC7 asphaltenes were extracted from an atmospheric tower bottom and a low waxy crude oil using IP143 based method and characterized using elemental analysis, nuclear magnetic resonance, Fourier-transform infrared spectroscopy, matrix-assisted laser desorptiontime of flight mass spectroscopy, x-ray diffraction, and scanning electron microscopy. Results show that both asphaltenes differ widely in structures and molecular weights. It was deduced that both asphaltenes might have formed from kerogen degradation process resulting in higher oxygen content. Lower molecular weight and structural parameters (NMR) of atmospheric tower bottom asphaltene could be due to degradation of aliphatic part during preheating before atmospheric distillation process. Although dispersed, the XRD derived aromaticity of petroleum asphaltenes seems to vary inversely with stacking height and average diameter of the aromatic sheets, possibly due to compact structure of the cluster resulting from decreased stack height.
Keywords: Asphaltenes; Atmospheric tower bottom; Characterization; Structure; Waxy crude oil.
Forecasting residential gas demand: machine learning approaches and seasonal role of temperature forecasts
by Emanuele Fabbiani, Andrea Marziali, Giuseppe De Nicolao
Abstract: Gas demand forecasting is a critical task for energy providers as it impacts on pipe reservation and stock planning. In this paper, the oneday- ahead forecasting of residential gas demand at country level is investigated by implementing and comparing five models: Ridge Regression, Gaussian Process (GP), k-Nearest Neighbour, Artificial Neural Network (ANN), and Torus Model. Italian demand data from 2007 to 2017 are used for training and testing the proposed algorithms. The choice of the relevant covariates and the most significant aspects of the pre-processing and feature extraction steps are discussed in depth, lending particular attention to the role of one-day-ahead temperature forecasts. Our best model, in terms of Root Mean Squared Error (RMSE), is the ANN, closely followed by the GP. If the Mean Absolute Error (MAE) is taken as an error measure, the GP becomes the best model, although by a narrow margin. A main novel contribution is the development of a model describing the propagation of temperature errors to gas forecasting errors that is successfully validated on experimental data. Being able to predict the quantitative impact of temperature forecasts on gas forecasts could be useful in order to assess potential improvement margins associated with more sophisticated weather forecasts. On the Italian data, it is shown that temperature forecast errors account for some 18% of the mean squared error of gas demand forecasts provided by ANN.
Keywords: natural gas; time series forecasting; statistical learning; Gaussian Process; neural networks; weather forecast; temperature.
Proxy Modeling for Rapid Optimization of Miscible CO2-WAG Injection in Heterogeneous Clastic Reservoirs: A Case Study from Southern Iraqi Oil Fields
by Ahmed Jaber, Mariyamni Awang, Karl Stephenc
Abstract: Multiple simulation runs are required to optimize and quantify uncertainty and sensitivity analysis to determine and rank the impact of reservoir and operating parameters on the incremental oil recovery (?RF) under miscible CO2-WAG flooding. The Central Composite Design (CCD) was employed to create a statistical proxy model for ?RF as a function of seven reservoir and operating parameters. Statistical analysis was employed to check the model adequacy. The importance and effect of variables that result to higher predicted ?RF were investigated. As an analog of the Nahr Umr reservoir, the reservoir understudy, the proxy model can be roughly applied to predict the ?RF during the miscible CO2-WAG injection at depending on uncertainty. The reliability of the proxy model has been demonstrated based on many statistical tools.
Keywords: Proxy modeling; Miscible CO2-WAG injection; Response surface modeling; Heterogeneous clastic reservoir.
Optimum design of natural gas trunk line using simulated annealing algorithm
by Abolfazl Zolfaghari, Moein Izadi, Hamideh Razavi
Abstract: Pipelines as natural gas transmission system is capable to transport a huge volume of gas. Trunkline or mainline is an important part of the system which carries high-pressure natural gas through large-diameter pipes from processing plant to consumption regions. A considerable investment is required for the construction of such pipelines as the major part of the gas transportation system. Furthermore, the cost of trunk line construction depends mainly on design and operating parameters. Thus, finding optimal values for the parameters which minimise the investment over the life of the system, i.e., life cycle cost, could be quite advantageous. In this paper, an approach based on annealing algorithm and a more comprehensive mathematical model presented in the literature is proposed to find optimal values for the design of natural gas trunk line. The life cycle cost is considered as the objective function of the proposed optimisation process. [Received: April 27, 2019; Accepted: November 9, 2019]
Keywords: optimum design; trunkline; simulated annealing algorithm; life cycle cost; LCC; pipeline; natural gas; optimisation; decision making; objective function.
A simple and robust model for prediction of liquid-loading onset in gas wells
by Liehui Zhang, Chengcheng Luo, Yonghui Liu, Yulong Zhao, Chunyu Xie, Chuan Xie
Abstract: Accurate prediction of liquid loading is of great importance for production optimization in gas wells. In this paper, the authors present a simple and accurate empirical model based on attached-film reversal for predicting liquid-loading onset in vertical and horizontal gas wells. Unlike established and complicated analytical models based on force balance, this model is developed from the empirical flooding equation by matching the experimental data from previous studies. Further, this model adopts the Belfroid angle-correction term for horizontal gas wells. Compared with the traditional entrained-droplet models, this model considers the effect of pipe diameter and liquid velocity. This study investigated the effect of pressure on the predicted critical gas velocity and scaled up low pressure by comparing some other analytical models. This model was also validated against the experimental data and field data. Results show that the presented model is capable of accurately predicting liquid-loading onset in gas wells.
Keywords: liquid-loading onset; critical gas velocity; attached-film reversal; entrained-droplet reversal; angle-correction term.
Experimental investigation on shale gas transport characteristics in nanopores under high temperature and high pressure
by Jing Sun, Dehua Liu, Xiang Zhu, Wenjun Huang, Liang Chen
Abstract: In this paper, we carried-out shale gas diffusion behavior experiments under high temperature and pressure conditions (HPHT). Molecular membranes samples with a uniform pore size replacing shale cores is used in this experiment for the first time. The results show that: (1) The equation of shale gas diffusion coefficient and pore size was established. As the pore diameter increases, the diffusion coefficient increases exponentially. (2) The concentration gradient of shale gas in a nanoporous medium also has an impact on the diffusion capacity. (3) The greater the pressure, the smaller the diffusion coefficient in the confined pores. The diffusion coefficient increases as the temperature increases. (4) A new diffusion coefficient calculation method was proposed. The results provide theoretical guidance for the microscopic transport mechanism of methane transfer in the porous media of shale gas and tight sandstone reservoirs. The experiment is for the first time to use molecular membranes samples with a uniform pore size replacing shale cores.
Keywords: shale gas; nanopores; diffusion behavior; transport characteristics.
A new method to analyse gas flowrate of goaf vertical wells with mining activities on extra-thick coalbeds
by Wei Xiong, Yong Chen, Cheng Tan, Houquan Zhou
Abstract: Goaf well is an important technical measure to address the safety hazard and energy waste caused by desorption gas flooding into the working face due to the original stress balance of coalbed being destructed by mining activities. However, because of the high level of the coal-rock disturbance, gas production characteristics of goaf wells are different from those of the traditional coalbed gas wells. In this paper, permeability - the important factor affecting the gas production rate of goaf wells was taken as the research object, a function expression of permeability versus the characterization parameters of fracture development (volume strain) in coal-rock was established, and the permeability of extra-thick coalbed after mining was calculated with a numerical software. The area was divided into the original zone, the mining affected zone, the fracture development zone, and the re-compacted zone, with regularities in permeability changes in different zones analyzed and spatial scale expressions of permeability established. In the meanwhile, a model of gas production rate in goaf wells was established, and the function expression of gas production rate was discussed for goaf wells at different locations and with different permeability and gas extraction radius relations. The measured data of the #2 goaf well in Weijiadi Coal Mine was divided into 4 stages according to the slope change of the gas production rate curve, the actual measurements of gas production rate and the theoretical calculated values were compared and analyzed, thereby the model was amended and verified.
Keywords: fracture generation; permeability evolution; gas production characteristics; gas extraction radius; volumetric strain.
Assessment of wind-induced responses for large offshore jacket platform based on HFFB tests
by Hongbing Liu, Guoming Chen, Liping Sun, Benrui Zhu, Ao Huang, Yipei Zhao
Abstract: This paper focuses on wind sensitivity of large offshore jacket platform subjected to hurricane, and a scale model are tested in a boundary wind tunnel under 0~360
Keywords: large offshore jacket platform; wind tunnel test; HFFB; wind-induced vibration; wind-induced response.
Carbonate and Sandstone Rocks Dissolution; lnvestigation during injection of Smart Carbonated Water
by Payam Soleimani, Seyed Reza Shadizadeh, Riyaz Kharrat
Abstract: One of the most interesting enhanced oil recovery methods is carbonated water. This subject has been noticed especially during recent years for addressing out its effective mechanisms. When smart brine is used for carbonated water injection, there is a competency between ions and carbon dioxide to be dissolved in water. Therefore, the produced carbonated water results in higher recovery factor due to the activation of coupled mechanisms. Whenever smart carbonated water is injected, an acidic media is provided which results in mineral dissolution and transfer from the porous media to the fluid. In this paper, it is intended to investigate how do carbonate and sandstone cores are affected when smart carbonated water is injected by using core flooding tests and mineral analysis. It is found that rock dissolution depends on brine concentration and rock minerals. The highest rock dissolution was detected in carbonate and to less extent in sandstone cores. [Received: August 20, 2019; Accepted: December 13, 2019]
Keywords: mineral dissolution; effective porosity and permeability; pores and throats; smart carbonated water; SCW; carbonate and sandstone cores.
Cost Factors and Statistical Evaluation of Gas Transmission Pipeline Construction and Compressor-Station Cost in the United States, 2014-2019
by Mark J. Kaiser, Mingming Liu
Abstract: Oil and gas pipelines are designed for their operating conditions, constructed with quality certified steel, assembled with qualified personnel and pass multiple inspections before operations. The costs of constructing pipelines will vary widely from area to area depending on the length and diameter of the pipeline, population density, the terrain, right of way requirements, and the number of river, rail and road crossings. From 2014-2019, 2063 miles of gas transmission pipeline and 1.9 million horsepower compression regulated by the Federal Energy Regulatory Commission were installed in the United States at a normalized cost of $5.72 million per mile and $3030 per horsepower. In this paper, gas transmission pipeline construction and compressor-station cost statistics are evaluated on an aggregate and project average basis, and regression cost models are constructed for each. Cost factors in pipeline construction and compressor-station installation are described in detail. Aggregate metrics are the most stable and reliable statistic, and probably the most representative, but for small samples significant restrictions apply. There are large cost deviations in pipeline construction and much smaller deviations for compressor-stations. Route length and line diameter are the only variables needed to develop robust linear models of pipeline construction cost.
Keywords: Cost factors; pipeline construction cost; compression cost; regression cost models; statistical analysis.
Investigations of water saturation and fractal characteristics in tight sandstone gas reservoirs using centrifugation and NMR experiments
by Aifen Li, Weibing Tian, Xiaoxia Ren, Shuaishi Fu, Dongdi Cui, Qi Fang, Min Ma, Josephine Yapcheptoyek
Abstract: In this paper, the petrophysical properties were analysed by X-ray diffraction (XRD), scanning electron microscope (SEM) and nuclear magnetic resonance (NMR) experiments, and the centrifugation and NMR experiments were conducted to investigate the water saturation and fractal characteristic in tight sandstone gas reservoirs. Experimental results showed that connate water saturation increases with decrease in permeability. Average connate water saturation, connate water saturation at the paraxial end and NMR connate water saturation are 58.4%~80.6%, 37.3%~60.7% and 64.6%~84.6%, respectively. The optimum centrifugal force is 1.70~2.40MPa. A formula for calculating average water saturation was derived for different permeability cores. In addition, three models for calculating connate water saturation were presented. Finally, the fractal characteristics of pore throat using the improved NMR method were analysed. Results showed that the structure and surface of pore throat are irregular and heterogeneous, and the distribution of connate water becomes more complex and irregular after the centrifugation, compared with the saturated state.
Keywords: water saturation; connate water; tight sandstone gas; NMR; centrifugation; pore throat; fractal.
Investigation into coals of different ranks using FTIR and Raman spectroscopy, X-ray diffraction and thermo-kinetic analyses
by Ayokunle Balogun, Farid Sotoudehniakarani, Armando McDonald
Abstract: Two sub-bituminous (Onyeama mine, Nigeria and Powder River Basin, US) and one bituminous (CNX Coal Resources, US) coal samples were subjected to structural and chemical characterisation. The FTIR and Raman spectroscopy, X-ray diffraction and other physico-chemical techniques were deployed for this purpose. The coal ranking and aromaticity were evaluated from specific peaks on the XRD diffractogram. The coal samples were also subjected to thermo-kinetic analysis. The HHV for the coal samples ranged from 26.0 to 33.8 MJ/kg. Relatively, the Nigerian coal demonstrated an exceptionally high surface area; approximately 29.0 m2/g, while Wyomings and Pennsylvanias respectively recorded 0.4 and 3.9 m2/g. The ratio of band intensities,I_D⁄I_G was computed from Raman spectroscopy to be between 0.84 and 0.94 for the coal samples. Furthermore, the kinetics parameters deduced from TGA measurements revealed that thermal decomposition of coal is better modelled as a multi-step reaction mechanism.
Keywords: sub-bituminous coal; XRD; Raman spectroscopy; kinetics; FTIR; thermo-kinetic; TGA; activation energy; band intensities; HHV.
Optimization of Technological Parameters for Coupled Liquid CO2 Fracturing-Huff and Puff Treatment in Tight Oil Reservoirs
by Bo Xiao, Tingxue Jiang, Baoping Lu
Abstract: Coupled liquid CO2 fracturing huff and puff treatment is combination of CO2 stimulation and CO2 EOR, aiming to maximize the productivity of tight oil reservoirs. The major difference lies in soaking time after CO2 injection completed, which is not incorporated in conventional fracturing operation. In this work, we develop an analytical procedure and methods for analyzing technological parameters during coupled liquid CO2 fracturing huff and puff treatment. Several parameters, such as fracture length, fracture conductivity, fracture spacing, CO2 injection volume, soaking time, bottom hole flowing pressure(BHFP) are studied. Compositional numerical model is employed to simulate the flow process and interaction of CO2 and oil in reservoir. The cubic Peng-Robinson equation of state is used for phase behavior calculations. Orthogonal analysis method is then utilized to analyze the sensitivity of technological parameters and optimization is implemented accordingly. The results show that the production rate of coupled liquid CO2 fracturing huff and puff treatment is better than both CO2 fracturing treatment and CO2 huff and puff treatment. From the perspective of cumulative recoverable reserves, it is found that BHFP is the most important parameter, while soaking time has minimal impact. The half-length, spacing and conductivity of fractures are also major factors influencing the production performance. The optimum intervals of these factors are all existed. The research has valuable guiding significance for design and optimization of field operation.
Keywords: Coupled Liquid CO2 Fracturing-Huff and Puff Treatment; Optimization; Parameters; Tight oil.
A Novel Interpretation Approach for Production Logging
by Ahmed Ali, Ahmed Gawish, Said Salem, Adel Salem, Ahmed Elgibaly
Abstract: Production logging (PL) is the industry standard method to evaluate wells and reservoir performance. This paper introduces guidelines for PL interpretation. The recommended interpretation strategy depends on an intensive study of hundreds of production logging cases covering the commonly encountered interpretation challenges in the Gulf of Suez. This study has three main objectives: the first is selecting the best water-oil slippage model, the second is finding an alternative for spinner to quantify flow rate, and the third is selecting the best liquid-gas slippage model. There are also other challenges that the study finds solutions to understand and solve all of them. The study finds that temperature and bubble counts are good alternatives for spinner data. In addition, ABB-deviated and Artep models are the best water-oil and liquid-gas slippage models. [Received: September 29, 2019; Accepted: February 12, 2020]
Keywords: challenge; multiphase flow; production logging; slippage; communication; bubble counts; temperature.
Well Placement Optimization using a Productivity Potential Area Map
by Jihun Jung, Dongkwon Han, Sunil Kwon
Abstract: This paper presents a method for placing wells during the development of oil and gas fields, and during production. Traditional well placement methods are time-consuming and expensive due to the complex processes involved. A well placement model developed using an optimization algorithm that automatically searches for the best well locations can help increase efficiency, provide objective decision making, and reduce risk. Current models that combine reservoir simulation and optimization algorithms have long computation times and have difficulties with heterogeneous reservoirs. A productivity potential map (PPM) derives well locations from static reservoir properties and can describe the properties of a heterogeneous reservoir. However, it can only determine values at individual locations and cannot consider the interference of pressure drops at well production site. Thus, we have defined a new concept called the productivity potential area map, which uses the sum total of all PPM values influenced by each well, and a radius of investigation equation, to select well locations in a reservoir. Using this concept, we demonstrate that it is possible to quickly determine well locations with good productivity and identify the most promising areas.
Keywords: reservoir engineering; well location; productivity potential map; well placement optimization; oil production.
Real-time quality metering of propanated biomethane
by Taras Koturbash, Agnieszka Bicz, Vladimir Kutcherov
Abstract: This paper presents a correlative method for the real-time measurement of quality characteristics of propanated biomethane for pipeline injection according to the European and Swedish regulations. The target quality properties (superior calorific value and Wobbe index) were predicted by the developed regression model based on the measurement of a selected set of physical properties of the gas samples. The measured physical properties are the thermal conductivity, the carbon dioxide concentration, the speed of sound, and the sound attenuation parameter measured as the ultrasonic signal dampening at 1 MHz. The empirical model of the sound attenuation parameter was developed for selected gases in order to predict a sufficient amount of data points for training the regression model. The developed regression model was tested experimentally and demonstrated good agreement with chromatographic analyses.
Keywords: Calorific value; Wobbe index; biomethane; propanated biomethane; ultrasonic measurement; speed of sound; ultrasound attenuation; correlative method; natural gas; time of flight; gas analysis.
The Cooling Range of Liquid CO2 on Loose Coal through Experimental Investigation
by Xiaowei Zhai, Hui Ge, Dariusz Obracaj
Abstract: Liquid CO2 injection could be a significant method to control the risk of spontaneous coal combustion in mining industry. A designed experimental platform was used to investigate the cooling characteristics of liquid CO2 and the temperature variations in loose coal. Concretely, the cooling phenomena on both the horizontal and vertical planes were analyzed by changing the mass flow rate of liquid CO2 and the diameter of injection nozzle. The results revealed that two cooling regions were formed in the vertical sections. As the injection time increased, the two cooling regions would disseminate and finally overlap because of the heterogeneity in the permeability and gravity sediment. The obtained functions of the furthest cooling influence of liquid CO2 for both different injection nozzles and different mass flow rates corresponded to different nonlinear logarithmic functions. Changing the diameter of injection nozzle had a more promoting effect on the increase of low-temperature range.
Keywords: Spontaneous coal combustion; liquid CO2 injection; cooling phenomena; phase transition; cooling influence; cooling parameter.
Life Cycle Assessment of Oil storage Unit in India
by Shilpi Shrivastava, Seema Unnikrishnan
Abstract: In spite of so many technological innovations, India is still dependent on other countries for fulfilling the demand for oil. In the oil supply chain, oil refineries are generally considered to be the most polluting phase but oil storage unit also has an adverse impact on the environment. Since there is no Life cycle assessment (LCA) study focusing on the storage unit in India, this study will help in identifying the potential hotspots which have the highest impact on the environment. The life cycle phases considered in the study are transportation (from the refinery to storage tanks), storage, and dispatch (from storage tanks to fuel stations) of finished fuel. For impact assessment simapro v7 and ecoinvent database is used. The results show that in the oil storage unit, the highest impact is from the transportation phase. Transportation is causing a serious threat to the environment because conventional fuels are being used for transportation which is mainly responsible for the major impact categories.
Keywords: Life Cycle Assessment; oil storage units; transportation; environmental impact; fuels; India; Simparo; Emissions; impact categories; climate change.
Influence of hydrodynamic cavitation pretreatment on coal flotation
by Hua Han, Huaifa Wang, An Liu
Abstract: The flotation of fine coal particles has been a long-standing challenge in coal processing industry. In this study, the influence of hydrodynamic cavitation pretreatment (HCP) on coal flotation was investigated. A special HCP experiment system was designed for the conditioning of pulp based on the cavitation phenomenon through a venturi tube. Flotation results indicate that, compared with the conventional flotation method, HCP increases combustible recovery of concentrate by about 5%, besides, 50% collector dosage or 25% frother dosage can be saved with HCP under the same combustible recovery of concentrate. Meanwhile, HCP enhances the flotation rate constant by 9.41%. The sieving analysis of flotation products reveals that HCP flotation has a better response for fine coal particles relative to that of coarse coal particles. The bubble observation tests confirm the existence of micro-nano bubbles generated by HCP and the selective generation of micro-nano bubbles on the surface of coal. In addition, HCP leads to an obvious improvement of dispersion of collector. The aggregation of fine coal particles caused by HCP is another important contribution for the coal flotation.
Keywords: coal flotation; hydrodynamic cavitation pretreatment; fine particles; micro-nano bubbles; collector dispersion; aggregation.
Visualization and investigation of water retention in tight oil reservoir via real sandstone micro-models
by Yafei Liu, Yuhan Shi, Haien Yang, Tianjiang Wu, Xiong Liu, Shun Liu, Desheng Zhou
Abstract: Hydraulic fracturing is considered as an effective approach for the development of tight oil reservoirs. Unlike conventional reservoirs, after a large volume injection of the fracturing fluid, the flowback rate in tight oil reservoirs is considerably lower whereas the underlying mechanism explaining water retention remains unclear. Therefore, in this work, to investigate the water retention mechanism, fracturing fluid injection and particularly oil production process were emulated within real tight rock chips. Displacement and water retention events were directly visualized and captured using a microscope. As a result, the discrepancy between temporary and permanent residence of water inside the pore space was clarified. Additionally, Nuclear Magnetic Resonance (NMR) scanning was incorporated to study the pore-scale fluid flow behaviors. Results show that a large portion of water was retained in smaller pores and water retention rate is positively correlated with oil recovery implying invaded water replaced the oil and resided in the pore space therefore increasing the mobile oil in the formation as oil flowing back. This work proposed an interpretation of water retention mechanism in tight oil reservoir after hydraulic fracturing and provided an insight to optimize the development and production of tight oil reservoirs.
Keywords: hydraulic fracturing; water retention; tight oil reservoir.
Significance of Washability on Heat Altered Coal from Jharia and Raniganj Coalfields, India
by Mamta Sharma, Trisrota Bhowmick, Vivek Mishra
Abstract: The present investigation was aimed to characterise the natural coke bearing coal (NCC) or heat-altered coal products through washability, technological property and petrography. NCC of Permian age from Jharia and Raniganj coal basins, India were subjected to beneficiate and the microscopy was performed on the different specific gravity fractions. The yield of washed coals and contents of macerals showed many variations in both the case studies due to the influence of igneous intrusion. However, we can use both NCC products in the different industrial application such as metallurgy, carbon artefact, power plant, fluidised bed combustion (FBC) and for blending purpose despite of their mutual differences.
Keywords: Float-sink; Heat altered coal; Petrography; Igneous activity; Indian coal.
Practical method for air sampling and analysis of some natural gas odorant
by Rezvan Zendehdel, Faezeh Abass Gohari, Behjat Jafari Tehrani, Zohre Amini, Majid Mahdian Dehkordi, Hakime Nouri Parkestani, Mohammad Sadat
Abstract: In this study, a method was presented for sampling and analysis of co-exposure to gas odorants such as Methyl Ethyl Sulfide (MES), Dimethyl Sulfide (DMS) and Tert-Butyl Mercaptane (TBM). An impregnated fiber glass with mercuric acetate was used for air sampling of odorants. In this study, odorant assessment was optimized with respect to the mercuric acetate, type of solution for odorant releasing and type of solvent for liquid-liquid extraction. Air sampling simulation was provided by standard preparation in tedlar bag. Odorants were analysed by gas chromatography equipped with mass spectrometry. Odorants released from 7% impregnated filters by 20% hydrochloric acid. MES, DMS and TBM was extracted by dichloroethane. Inter-day and intra-day coefficients variation was found to be lower than 11 by the recovery higher than 94%. According to the results of the recent study, a practical and reliable method was presented for air sampling and analysis of DMS, EMS and TBM.
Keywords: Gas Odorant; Air Sampling; Method Development.
Oil-Soluble Organic Polymer Driven from Aloe Vera as Drag Reducing Agent for Crude Oil Flow in Pipelines
by Wafaa K. Mahmood, Samar S.H., Wafaa A. Kadhim, HAYDER A. ABDULBARI
Abstract: In the present work, an organic, oil-soluble drag-reducing agent (DRA) is introduced and experimentally tested. The new additive is driven from Aloe Vera mucilage extracted directly from the Aloe Vera plant. Polymer grafting process was implemented to change the solubility of the new additives from water-soluble to oil-soluble. Drag reduction solutions are prepared by mixing certain additives concentrations (200 to 600 wppm ) with the crude oil. Each solution was rheologically tested to examine the effect of the additives on the viscosity and viscoelastic properties of the crude oil. The drag reduction performance was examined using a closed-loop liquid circulation system specially designed and fabricated for the present work. The experimental results showed that the viscosity of the solutions decreases when the concentration of the additives increases without affecting the crude oil entity (Newtonian behavior) with noticeable dramatic changes in the viscoelastic properties. A maximum drag reduction percentage of 82% was achieved with an additive concentration of 600 wppm. Finally, the resistance of the new additives to mechanical shear forces was high and increased exponentially with the concentration.
Keywords: Drag reduction; Crude Oil; Polymer; Aloe Vera; Rheology; Viscoelasticity.
Evolution of Future World Coal Consumption: Insights from a Distribution Dynamics Approach
by Xunpeng Shi, Tsun Se Cheong, Victor Jing Li
Abstract: Global efforts in limiting coal consumption will be undermined if new major coal users emerge, however, very few studies have been conducted on the emergence of prospective coal users. The objective of this paper is thus to investigate how likely some developing countries will emerge to be significant coal users. The distribution dynamics approach is adopted to examine the evolution and transitional dynamics of coal consumption. Ergodic distributions and mobility probability plots are constructed for each grouping so as to provide detailed information on the current pattern and future development. Our study finds that some low-income and lower middle-income economies may increase their coal consumption in the future if coal remains to be a cheap energy source, while the countries in other income groups have entirely different behaviours. The findings suggest that global policy coordination focusing on the prospective coal users should be adopted.
Keywords: Coal consumption; growth potential; distribution dynamics; mobility probability plots.
A Multi-index-classified Early Warning Method for Spontaneous Combustion of Coal under Air Leakage Blocking
by Hu Wen, Yin Liu, Jun Guo, Yongfei Jin, Xuezhao Zheng
Abstract: Judging development trends in coal spontaneous combustion accurately has long been a global problem. Once a spontaneous combustion phenomenon is found, the coal temperature tends to reach or exceed the critical temperature. To address this problem, the coal spontaneous combustion characteristic parameter testing device is used to simulate the air reduction environment after the coal low temperature oxidation reaches the critical temperature, and long-flame coal was tested. CO and C2H4 were selected as index gases, and the Graham (G), CO/CO2 and 100× (C2H4/CO) were chosen as the composite indexes for multi-level comprehensive analysis. The results show that the volume fraction of the index gases will have a balance point involving the air volume and temperature action during the process of heating up (the coal sample is 140-150 ?). The gas index can only be used to judge the development trend and the characteristic temperature point for the initial stage of spontaneous combustion; the development of oxidation at low temperature can be effectively predicted by using the value of G, while the CO/CO2 and 100×(C2H4/CO) can be used as auxiliary indexes before and after the balance point of the value of G. Based on this information, a single index grading method for coal spontaneous combustion to establish early warning standards was created, and a multi-index early warning method for comprehensive classification was proposed. The results have scientific and practical significance for determining the development trend of coal spontaneous combustion fires in long-flame coal and for the effective fire prevention and extinguishing work.
Keywords: coal spontaneous combustion (CSC); air volume reduction; fire trend determination; classification warning; spontaneous combustion index.
Evaluating the effect of using micronised barite on the properties of water-based drilling fluids
by Abdelmjeed Mohamed, Salaheldin Elkatatny, Mohamed Mahmoud, Reyad Shawabkeh, Abdulaziz Al-Majed
Abstract: Solids sag and formation damage are serious problems encountered while drilling with barite-weighted drilling fluids. The objective of this study is to investigate the effect of reducing barite particle size on rheological properties, fluid stability, and filter cake removal. Barite samples with different particle sizes were prepared using sieve analysis and ball milling technique. Micronized barite (8 μm) showed a moderate stability with zeta potential measurements for a pH range greater than 8. Solubility tests showed good enhancement in barite removal as the particle size was reduced, with a difference of around 11 g/L between the largest size (75-106 μm) and the micronized size of barite. HPHT filtration test results confirmed the solubility results with 5 wt.% enhancement in filter cake removal efficiency as barite particle size was reduced to micronized size. [Received: December 4, 2017; Accepted: December 17, 2018]
Keywords: micronised barite; weighting material; water-based; drilling fluid; rheological properties; stability; filter cake removal.
Potential application of the CO2-assisted gravity drainage process in a mature oil field: insights from reservoir-scale EOR evaluation
by Watheq J. Al-Mudhafar, Dandina N. Rao
Abstract: The gas-assisted gravity drainage (GAGD) process was implemented through continuous and cyclic immiscible injection to enhance the recovery of bypassed oil in the upper sandstone reservoir in the South Rumaila oil field, located in Southern Iraq. A compositional simulation model was constructed for the carbon dioxide (CO2) flooding evaluation through the GAGD process implementations. After achieving history matching, 20 vertical CO2 injectors and 11 horizontal oil producers were placed in top reservoir and oil zone, respectively. The immiscible CO2-GAGD performance was evaluated for 10 years of future prediction. The continuous and cyclic immiscible GAGD cases resulted in reaching recovery factor of 14.5% and 21.3% given the remaining oil, respectively. However, the recovery factor given the remaining oil was 7.6% through primary production by the end of prediction period. Additionally, the obtained amount of oil in 10 years primary production can be produced in only one year by the continuous case and in 8 months by the cyclic case. Consequently, the optimal implementation of the GAGD process is by adopting the cyclic CO2 flooding that efficiently enhance the recovery of bypassed oil. [Received: December 30, 2017; Accepted: December 17, 2018]
Keywords: gas-assisted gravity drainage; GAGD; immiscible CO2 flooding; enhanced oil recovery; South Rumaila field; insights learned.
Research on gas percolation and catastrophe behaviour of gas-bearing coal under low index
by Tie Li, Xianwei Hu, Zongzhi Wu
Abstract: Abnormal gas emission, coal and gas outburst may occur on the coal seam whose gas pressure and content are below catastrophe threshold, when the mine is deeply exploited. In order to study this catastrophe mechanism, solidfluid coupling experimental system with single degree of freedom and bidirectional loading is proposed. Gas percolation and catastrophe behaviour are studied through low pressure loading in this experiment, obtaining the following conclusions: 1) gas flow curve of gas-bearing coal shows asymmetric U shape; 2) coal sample suffers catastrophe gas emission after its rupture and instability under low pressure of 0.4 MPa and 0.15 MPa; 3) stress threshold of catastrophe gas-bearing coal sample is negatively related with coal gas pressure; 4) primary fracture of gas-bearing coal sample is consolidated when elastic deformation reaches 50% ~ 60% of elastic process, blocking gas percolation. However, gas percolation channel will be reopened after one yield or several yields. [Received: March 3, 2018; Accepted: November 18, 2018]
Keywords: gas-bearing coal sample; solid-fluid coupling; gas percolation; low index; coal catastrophe.
Insights into the co-combustion of coal and biomass mixtures using a copper-based oxygen carrier in chemical looping combustion
by Mayur D. Kevat, Tamal Banerjee
Abstract: Chemical looping with oxygen uncoupling (CLOU), variant to chemical looping combustion (CLC), is working on strategies to transport gaseous oxygen for fuel combustion. The present work reports the process simulation of CLOU of a coal-biomass mixture with CuO oxygen carrier. Variations in the different parameters are compared by replacing pure coal with an equal fraction of coal-biomass mixture. The presence of alkaline earth metals in biomass is seen to increase the coal char conversion in the fuel reactor. The predicted carbon capture efficiency is found to increase with the fuel reactor temperature range of 900 to 965°C irrespective of fuel used. The carbon capture efficiency was also varied with the solids flow rate varying from 3.48 to 13.64 kg/h. The thermal power output for the coal-biomass mixture is further compared with published literature for pure coal in context of its CLOU mode of operation. [Received: March 2, 2018; Accepted: November 26, 2018]
Keywords: CLOU; coal; biomass; energy analysis; Aspen.
Measurement of coalbed gas content of Indian coalfields: a statistical approach
by Mohammad Asif, Mallikarjun Pillalamarry, D.C. Panigrahi, Paul Naveen, Keka Ojha
Abstract: Sixty coal samples from different Indian coal fields were collected and characterised to analyse the gas content, petrography and composition. The gas content of coal samples was directly determined using a canister desorption test and statistically correlated with various parameters using regression analyses. The newly developed correlations are based on Langmuir, Ryan, and Kim correlations and modified to fit the data best. The gas content was observed to be a strong function of the proximate parameters i.e. fixed carbon, volatile matter, moisture content, and ash content as resulted from regression analyses. Vitrinite reflectance was also found to affect the gas content of the coal seams. To check the significance of calculated results, a paired-samples t-tests have been performed for 42 coal samples. Results confirmed the validity of the New Langmuir and New Ryan correlations with good confidence, i.e., t = –2.1, p < .05. [Received: April 26, 2018; Accepted: December 24, 2018]
Keywords: coalbed methane; gas content; proximate analysis; adsorption isotherm.
Thermal and kinetic characteristics of the catalytic effect of different catalysts on the combustion of coal-char blends
by Yingjie Hu, Zhiqiang Wang, Xingxing Cheng, Chunyuan Ma
Abstract: Thermal and kinetic characteristics of the catalytic effect of CaO/MnO2/Fe2O3 on the combustion of coal-char blends were investigated with thermogravimetric analysis. Different characteristic parameters obtained from TG-DTG curves were used to determine the combustion characteristic of samples. A sectioning method was adopted to study the kinetics at the stage I and II of samples combustion. The kinetic parameters of samples were also determined according to the Coats-Redfern method. The experimental results indicated that, in stage I, the catalysts promoted volatile matter release and combustion decreased the ignition temperature; in stage II, the catalysts accelerated the combustion of fixed carbon in char. The ignition properties and the combustion properties all increased with catalysts addition. Fe2O3 and CaO exhibited effective catalytic effect on reducing the activation energy in the stage I and II of coal-char blends combustion. The catalytic effect of MnO2 in the stage II was not obvious. Therefore, Fe2O3 and CaO were considered having more catalytically active than MnO2 in coal-char blends combustion. [Received: May 30, 2018; Accepted: December 17, 2018]
Keywords: coal-char blends; catalysts; kinetics; combustion; thermal analysis; ignition properties; combustion properties.
Mechanistic study and performance evaluation of steam assisted gravity drainage using direct visualisation of pore-level experiments
by Omid Mohammadzadeh, Nima Rezaei, Ioannis Chatzis
Abstract: In this paper, insights into the pore-scale physics of SAGD process are presented through analysis of a systematic series of SAGD visualisation experiments, conducted using optical imaging technique and glass-etched micromodels of capillary networks. The steam chamber propagation was found to be influenced by the randomly-distributed fingering of the invading steam front near the mobile oil-steam chamber interface. The steam fingering was extensive during the vertical growth of the steam chamber where the steam buoyant front was protruding through the pores containing a continuum of oil. The steam fingering phenomenon was also observed during the outward propagation of the steam chamber near its lateral wings, but to a lesser extent. The rate of pore-scale horizontal interface advancement was constant at each elevation along the height of the micromodels. The average pore-level SAGD sweep rates as well as the net cumulative steam to oil ratio were correlated using an analytical model. [Received: March 15, 2018; Accepted: February 11, 2019]
Keywords: steam assisted gravity drainage; SAGD; pore-scale; visualisation; heavy oil; bitumen; heat losses.
Efficient prediction for porosity only using logging data: a case study of lacustrine carbonate reservoirs of IARA oilfield
by Yufeng Gu, Zhidong Bao, Zhenhua Rui, Xinmin Song
Abstract: Statistical methods are capable of revealing variation trends of study cases by only processing source data. N-way analysis of variance and multivariate linear fitting are a few excellent examples. Then in order to cast off the reliance on using physical model parameters, a statistical method combined N-way analysis of variance and multivariate linear fitting is proposed. This article discloses the function of proposed method in terms of porosity prediction when only logging data is available. The data used for verification derives from the lacustrine carbonate reservoirs of IARA oilfield. Five experiments are well-designed to analyse capability of the method on porosity prediction. Experiment results prove that the proposed method can only utilise logs to predict porosity, and the predicted outcomes are accurate. The proposed method can be viewed as a new tool to obtain porosity data when only logs are handled. [Received: March 8, 2018; Accepted: February 14, 2019]
Keywords: logging interpretation; porosity prediction; N-way analysis of variance; multivariate linear fitting; fitting correction.
Risk assessment of large crude oil depot based on interpretative structural model and system dynamics
by Li-Qiong Chen, Yu-Xiang Feng, Hong-Long Zhen, Qiao-Chu Li, Jing-Yang Lu
Abstract: In this paper, the interpretative structural model is used to determine the causality among the risk factors and a system dynamics model is established. The method is applied to the risk analysis of a large crude oil depot. The results show that the safety atmosphere and supervision play critical roles on the risk of the oil depot. At the mature stage of risk development, improvements in the equipment risk and management risk has the greatest impact on the overall risk. The degree of education, equipment usage time, safety atmosphere and supervision are the key risk factors for the human, equipment, environmental and management risk subsystems, respectively. This result provides a scientific basis to understand the trend of risk dynamic, risk evolution mechanism and fundamental risk factors and fundamentally prevent the occurrence of large crude oil depots. [Received: March 16, 2018; Accepted: December 17, 2018]
Keywords: risk assessment; interpretative structural model; system dynamics; large crude oil depot.
An investigation of the performance of an ignition compression engine using ethanol-butanol-diesel mixtures
by Roberto Guimarães Pereira, Ithamar Ribeiro Rangel
Abstract: The low solubility of ethanol in the diesel oil has motivated the study of ternary mixtures using butanol like co-solvent. Within this approach several mixtures were tested in the MBB OM355/6A engine, obtaining, in some cases, a performance equal to or greater than that of diesel oil. The volume proportions of butanol, ethanol and diesel for each fuel tested were, respectively: 3%, 7% and 90%; 3.5%, 8% and 88.5%; 5%, 7.5% and 87.5%; 4.5%, 8% and 87.5%; 5%, 10% and 85%. The results obtained in the dynamometric bench tests, the rheological parameters and the physicochemical properties of the mixtures are presented. The mixture with 3% of butanol, 7% of ethanol and 90% of diesel [MD10(3+7)BE] showed the best performance in the engine tests, with brake specific fuel consumption lower than diesel fuel, for all engine speed at full load, and with brake thermal efficiency higher than diesel fuel, for all engine speed at full load. [Received: December 16, 2017; Accepted: December 18, 2018]
Keywords: energy; diesel engine; ethanol; butanol.
Engine performance and emission profile of Simarouba glauca biodiesel and blends
by Sabariswaran Kandasamy, Selvakumar Sundararaj
Abstract: Engine performance and emission characteristics of biodiesel produced from Simarouba oil were investigated in the present study. The biodiesel of Simarouba oil and its blends were run in single cylinder Kirloskar make four stroke, water cooled engine at different load conditions. The maximum brake thermal efficiency (BTE) was observed in the blend of B20 and the average percentage of efficiency obtained was 47.5% whereas the efficiency of standard diesel was 49.01%. The maximum brake specific fuel (BSFC) consumption was found in the blend of B20. The average percentage of BSFC obtained was 0.367 kg/kWh whereas 0.359 kg/kWh obtained for diesel. In terms of emission profile, emissions of carbon monoxide (CO), hydrocarbon (HC), carbon dioxide (CO2) and smoke emission were reduced with a marginal increase in NOx emission. [Received: December 12, 2017; Accepted: January 12, 2019]
Keywords: Simarouba biodiesel; brake thermal efficiency; CO2 emission; NOx emission; smoke emission; blends; smoke density.
Trends and dynamic relations between crude oil prices and energy employment: a panel analysis approach
by Shuming Bai, Kai S. Koong, Fan Wu
Abstract: This research employs panel data to analyse the trends of 21 energy occupations in ten NAICS energy sectors in the USA and the relationships among oil prices, oil production, and energy jobs by sector and nationwide from 2002 to 2016. We highlight several major findings: 1) energy sectors do matter (statistically and significantly different) for the same job titles; 2) the largest and smallest energy hires are consistent and robust; 3) the most and best jobs are mostly created in the upstream and related services sectors; 4) majority of the energy occupations grow faster than those for the nation; 5) energy jobs are strongly associated with oil prices and production; 6) energy jobs, oil prices, and US oil production play significant roles in the national employment. To our knowledge, this panel analysis of energy sector jobs is the first of its kind. The findings could be useful to various energy stakeholders and policy makers for adopting effective employment strategies and policies. [Received: June 16, 2018; Accepted: February 11, 2019]
Keywords: US oil field production; WTI oil prices; NAICS energy sectors; energy occupational employment; panel data.
Micro-nano pore throat structure and occurrence characteristics of tight sandstone gas: a case study in the Ordos Basin, China
by Fengjiao Wang, Chaoyang Hu, Yikun Liu, Jiqiang Zhi
Abstract: To characterise the pore structure, pore throat size and movable fluid occurrence state, a case study was conducted on the Sulige tight sandstone gas field in Ordos Basin. The experiments contented mercury intrusion capillary pressure, nuclear magnetic resonance (NMR), centrifugal test and routine core analysis. The relationship between microscopic pore structure and macroscopic performance was established. The micropores in Sulige tight sandstone gas field is the dominant factor affecting the microscopic pore throat structure characteristics. The transport ability in pore throat is mainly affected by the size of throat and the pore-throat ratio. Due to the frequent alternation of larger pores and smaller pores, the fluid seepage resistance increases greatly, which is attributed to poorer percolation capacity of tight sandstone gas reservoir. The results are also of great significance for the quantitative characterisation of pore structure characteristics and for industry petroleum exploration of tight sandstone gas reservoirs. [Received: June 15, 2018; Accepted: March 29, 2019]
Keywords: tight sandstone gas reservoir; pore throat structure; fluid occurrence state; constant speed mercury intrusion; nuclear magnetic resonance; Sulige gas field; Ordos Basin; China.
Numerical simulation and three-phase pressure transient analysis considering capillary number effect – case study of a gas condensate reservoir
by Kambiz Davani, Shahin Kord, Omid Mohammadzadeh, Jamshid Moghadasi
Abstract: When the wellbore pressure drops below the dew point pressure of gas in a gas condensate reservoir, there is the possibility of condensate bank build-up and wellbore blockage. These adverse processes result in development of different mobility zones around the wellbore which complicates the pressure transient test analysis. The focus of this study is on the analytical and numerical analysis of pressure testing data obtained from a well in a target gas condensate reservoir. First, the well test data were analytically interpreted through which several well and reservoir parameters were identified such as condensate bank radius, gas effective permeability, mechanical skin and skin due to non-Darcy flow. A three-phase compositional reservoir model was then built using the analytical solution, for numerical analysis of the pressure transient data as well as validation of the analytical results. This numerical model was then used to estimate well deliverability and predict future reservoir performance. [Received: August 17, 2018; Accepted: March 15, 2019]
Keywords: gas condensate reservoir; well testing analysis; condensate dropout; numerical simulation.
Investigation on gas hydrate formation properties in a spiral flow using a flow loop
by Yongchao Rao, Yi Sun, Shuli Wang, Hao Ge, Boyang Ding, Minguan Yang
Abstract: A series of experiments were performed in a high pressure hydrate experimental loop using spiral flow. The impacts of varying flow rate, pressure, temperature, and twist rate on hydrate formation have been studied in this paper. The experimental results showed that the flow patterns occurring in the experiments were classified into the spiral wavy stratified flow, the spiral bubble flow, the spiral annular flow, and the spiral dispersed flow. The induction and formation time in a spiral flow loop decreased with increasing pressure, and increased with the increasing temperature. The twist rate of twisttape had an influence on hydrate formation. The hydrate formation time decreased with decreasing twist rate. The initial gas liquid rate and twist rate had significant effects on the gas consumption during hydrate formation. The kinetic model of hydrate formation in a spiral flow loop was established. The proposed model was verified both qualitatively and quantitatively. [Received: March 16, 2018; Accepted: March 29, 2019]
Keywords: gas hydrates; spiral flow; flow pattern; formation kinetic model.
Performance prediction of different recovery mechanisms during steam injection in non-fractured and naturally fractured light oil reservoirs
by Tonya Ross, Babak Shabani, Hamid Rahnema
Abstract: It is well known that steam injection exhibits positive result in heavy oil reservoirs. In theory, the same application has the potential to be applied in light oil reservoirs to boost the production. The performance prediction model for a nine-spot steam flood pattern reservoir was developed using the SPE fourth comparative solution model to analyse the impact of different recovery mechanisms during steam injection for the light fluid sample in non-fractured and naturally fractured reservoirs. This model accounts for the variation in permeability and thickness for each layer generated. The heterogeneous model was represented by 1/8 of a nine-spot pattern unit. The simulation model examines the comparison between non-fractured and naturally fractured reservoirs. Simulation results indicate vaporisation is the dominant recovery mechanism in a naturally fractured reservoir, whereas fluid displacement and wet ability are the dominant recovery mechanisms for a non-fractured light oil reservoir. [Received: February 24, 2018; Accepted: August 27, 2018]
Keywords: light oil reservoir; steam injection; non-fractured reservoir; fractured reservoir; recovery mechanisms.
Numerical simulation of hydrate slurry flow characteristics in vertical pipes based on population balance theory
by Shupeng Yao, Yuxing Li, Wuchang Wang, Guangchun Song, Kai Jiang, Zhengzhuo Shi
Abstract: Solid fluidised mining uses mechanical means to break down hydrates in the seabed. Then the hydrates will be mixed with seawater and transported to secondary crushing and other pre-treatments. Finally, the hydrates will enter the vertical lift pipe and be sent to the platform or mining ship. Therefore, the study of the flow characteristics of hydrate slurry in vertical pipes is of great significance for hydrate mining. To study the effect of different working conditions on the flow characteristics of hydrate slurry in vertical pipes, the flow characteristics of hydrate slurry in vertical pipes were simulated using the population balance theory based on hydrate particle aggregation dynamics. This paper focuses on the simulation of the flow characteristics of hydrate slurry with different initial particle sizes, concentrations and velocities, and according to the simulation results, the flow characteristics of hydrate slurry such as pressure drop, concentration distribution, and hydrate particle size distribution are analysed. The results of this study can provide referenced for the flow characteristics of hydrate slurry in hydrate mining. [Received: October 6, 2018; Accepted: March 29, 2019]
Keywords: hydrate slurry; vertical pipe; numerical simulation; flow characteristics; population balance theory.
Numerical investigations of airflow patterns on a longwall face
by Zhongwei Wang, Ting Ren, Jian Zhang
Abstract: To thoroughly understand the ventilation flow characteristics on a longwall face, six computational fluid dynamics (CFD) models representing six consecutive longwall operating scenarios were developed. Key features of the longwall equipment and an immediate goaf were embedded into the models to obtain a realistic ventilation flow field. The occurrence of flow separation at both intersections of maingate/tailgate and face were revealed by the model results. Control measures are therefore suggested to minimise the potential accumulation of hazardous gas and dust within the flow separation zones. Significant air leakage to the goaf would occur if maingate curtain were not used. The impact of shearer position and its cutting direction on face ventilation was regional, indicating the stability of face ventilation system. These new insights into the complex longwall ventilation flow patterns will eventually be beneficial to the hazardous gas and dust management at longwall faces of underground coal mines. [Received: May 16, 2018; Accepted: August 9, 2018]
Keywords: CFD modelling; longwall airflow patterns; flow separation; shearer position; cutting sequence.
Volumetric flow and pressure gradient-based leak detection system for oil and gas pipelines
by Mukarram Riaz, Ishtiaq Ahmad, Muhammad Nasir Khan, Muhammad Asim Mond, Amna Mir
Abstract: The leakage in oil and gas pipelines results economic losses to petroleum companies and causes damages to the environment. It may occur due to corrosion in the pipe or intentional or unintentional damage by third party intervention. A prompt and accurate leak detection and localisation system is very essential. In this paper, we have developed a nonlinear adaptive model for detection and localisation of leak based on correlation of pressure and volumetric flow at the pipe inlet and outlet. The characteristic changes in the flow mechanics and thermodynamics along a given length of pipeline such as pressure, flow and temperature are adopted in the model. A compensated volume balancing method is proposed for leak detection based on conservation laws of mass, momentum and energy. Leak localisation is based on presence of pressure gradient in the vicinity of the leak. The simulation results show the superior performance of our proposed model. [Received: September 24, 2018; Accepted: March 10, 2019]
Keywords: leak detection; volumetric flow; pressure gradient; volume balancing.
Analysing and characterising horizontal well performance in rectangular closed gas reservoirs considering non-Darcy flow conditions
by Salam Al-Rbeawi
Abstract: This paper investigates the impact of non-Darcy flow, represented by rate-dependent skin factor (DQSC), on pressure profiles, flow regimes, and productivity indices of horizontal wells extending in conventional and unconventional gas reservoirs. It introduces a new simplified technique for characterising reservoir performance under different non-Darcy flow impacts. The outcomes of this study are summarised as: 1) understanding the conditions at which non-Darcy flow could have considerable effects on reservoir performance; 2) estimating the deviation in productivity index caused by non-Darcy flow. The most interesting points in this study are: 1) the ability to estimate rate-dependent skin factor from well test analysis by observing early time radial flow regime; 2) all flow regimes, unlike pressure behaviors and productivity index, are not affected by non-Darcy flow; 3) productivity index declines sharply for high rate-dependent skin factor at early production time while pseudo-steady state productivity index is not affected by non-Darcy flow. [Received: April 12, 2018; Accepted: May 9, 2018]
Keywords: non-Darcy flow; rate-dependent skin factor; non-Darcy flow coefficient; reservoir modelling; fluid flow in porous media; reservoir performance; productivity index.
Optimisation of biodiesel production and engine performance from Simarouba oil in compression ignition engine
by Ashish Dewangan, Ashok Kumar Yadav, Ashis Mallick, Avdhesh Tyagi
Abstract: In present work, Simarouba seed oil has been evaluated as a feasible feedstock for biodiesel production. An optimum yield of 98.1% was achieved at a temperature of 55°C; methanol/oil molar ratio as 6:1; time duration of 60 min; and catalyst concentration of 1 wt. %. Then, the Simarouba biodiesel-diesel blends were tested to assess the performance of engine and its emission characteristic. The B10, B20, B30, and B50 blends of Simarouba methyl ester (SME) showed average reduction of 2.8, 6.5, 7.8, and 14.3% in BTE respectively and an average 3.18, 5.94, 7.18, and 15.54% higher energy consumption than mineral diesel. At higher load conditions UHC, CO, and smoke emissions were found lesser while CO2 and NOx emissions were found higher for all SME blends in comparison to diesel. [Received: August 4, 2017; Accepted: February 28, 2019]
Keywords: Simarouba oil; optimisation; Taguchi method; biodiesel; CI engine; transesterification; performance; emissions.
Real-time hydrocarbons sweet spot identification in shale formations while drilling horizontally using geo-mechanical and geophysical parameters
by Alberto Lopez Manriquez, Kamy Sepehrnoori
Abstract: This work presents an innovative comprehensive approach to properly identify intervals with the most favourable potential and properties to produce hydrocarbons known as hydrocarbons 'sweet spots'. The approach is applied to horizontal wells in shale formations but not limited to this scenario. One of the singularities of this work rests on the proposal that rock properties are obtained from logging while drilling (LWD) techniques. This self-supported methodology is applied to characterise the reservoir from the stand points of geo-mechanics, geophysics, and geopressure. Rock and fluid properties measured along the horizontal section of the well while drilling served to generate a synthetic acoustic log. Changes in trends of geo-mechanical and geophysical properties such as brittleness and acoustic impedance are used as indicators of hydrocarbons presence. Ultimately, the methodology is proposed to properly select the intervals to complete and to optimise the length of the horizontal section of the well. [Received: March 23, 2017; Accepted: September 5, 2018]
Keywords: hydrocarbons sweet spot; geo-mechanics; brittleness; acoustic impedance; logging while drilling; LWD; unconventional shales; reservoir pressure prediction.
Experimental study and CFD investigation of environment friendly drilling fluid
by Soheil Akbari, Khashayar Mohammadzadeh, Seyed Hassan Hashemabadi
Abstract: Environment-friendly drilling fluids have been developed recently, which protect the environment and satisfy needs of drilling engineering. In this study, to investigate the advantage of using environment-friendly drilling fluid, four (three vegetable and one diesel) oil-based fluids were prepared and their rheological properties were compared. Results showed that all fluids follow non-Newtonian Herschel-Bulkley model with high accuracy, and increasing of temperature results reduction of the fluid's apparent viscosity. Then, in order to study the cutting carrying capacity of the prepared drilling fluids in wellbore, a 3D form of steady-state computational fluid dynamics (CFD) model is used to simulate the flow in different conditions. The CFD results indicated that the vegetable oil muds represent better cutting transportation, especially in lower flow rates. For the fluid velocity of 0.75 m/s by increasing temperature from 320 to 363 K in constant pressure, the cutting transportation has been decreased by 4.21% and 3.07% for diesel and vegetable muds respectively. [Received: April 19, 2018; Accepted: May 10, 2019]
Keywords: oil-based drilling fluid; vegetable oil; diesel oil; computational fluid dynamics; CFD; cutting transport; temperature.
Inhibition of asphaltene precipitation by hydrophobic CaO and SiO2 nanoparticles during natural depletion and CO2 tests
by Yaser Ahmadi, Babak Aminshahidy
Abstract: This paper addressed the effects of hydrophobic synthesized calcium oxide (CaO) and commercial silicon dioxide (SiO2) nanoparticles on the inhibition of asphaltene precipitation after asphaltene adsorption on the nanoparticles surface. CO2-oil interfacial tension (IFT) behaviours and batch experiment results were used for surveying asphaltene adsorption in the presence of nanoparticles, and natural depletion and CO2 tests were done as a source of precipitation methods. The studied crude oil was located inunstable regions from the aspect view of asphaltene precipitation with a colloidal instability index (CII) of 1.392. The Langmuir isotherm modelled the asphaltene adsorption data well in the presence of both nanoparticles. Based on the results of CO2-oil interfacial tension, batch experiment and asphaltene precipitations during natural depletions and carbon dioxide tests, CaO not only adsorbed more asphaltene in compared to SiO2 but also had the best application for precipitation inhibition. [Received: May 24, 2018; Accepted: October 24, 2018]
Keywords: CaO nanoparticle; SiO2 nanoparticle; asphaltene precipitation; asphaltene adsorption.
Development of oil-based drilling fluid using iron oxide magnetic (Fe3O4) with superior properties leading to real time rheological control
by Masoud Ghasemi Dehkordi, Pacelli L.J. Zitha, Yasaman Hosseinzadeh Dehaghani, Morteza Belbasi
Abstract: Magnetorheological fluids have the ability to exhibit a wide range of rheological properties when exposed to an external magnetic field. In this paper, an applicable oil-based magnetorheological drilling fluid is prepared using iron oxide magnetic particles (Fe3O4). In order to prove the ability and performance of the prepared fluid, vibrating sample magnetometer (VSM) and magnetorheology tests have been performed. VSM measurements showed that permeability and saturation magnetization are 0.1615 and 135.3017 emu/gr, respectively. This test generates the hysteresis curve of the sample which shows that the behaviour of this fluid is soft magnetism i.e. it is very sensitive and is easily magnetized by the application of very small magnetic fields. Furthermore, magnetorheology measurements were conducted for magnetic fields ranging from 0 to 0.1T and the measured values are compared with rheology tests of conventional drilling fluids. The results indicate a noticeable increase in apparent viscosity and shear rate. [Received: January 29, 2019; Accepted: June 17, 2019]
Keywords: smart fluids; magnetorheological drilling fluid; magnetorheology; vibrating sample magnetometer; oil-based mud; rheological control.
An improved ultrasonic disaggregation method for analysis of minerals in shales
by Wenda Zhou
Abstract: Traditional disaggregation methods for mineral separation of sedimentary rocks are not appropriate for shales with complex mineralogy and grain sizes. In this study, we improved the ultrasonic disaggregation and stepwise separation method for minerals in shales, and applied it to analyse shale samples from the Silurian Longmaxi Formation of the Sichuan Basin, China. The Longmaxi Formation shales are mainly composed of clay minerals, quartz, calcite, dolomite, albite, and K-feldspar, and are cemented by SiO2. This method processes shale samples as ultrasonic disaggregation followed by stepwise separation of minerals using gravitational deposition and centrifugation. Field emission scanning electron microscope (FE-SEM) images were obtained for different components of this ultrasonic disaggregation and stepwise separation method. Information obtained by this method can also be used to quantify the hydrodynamic forces acting on the Longmaxi Formation sediments during the syngenetic stage. [Received: October 25, 2018; Accepted: November 21, 2018]
Keywords: disaggregation; shale minerals; ultrasonication; mineral grain size; critical incipient velocity.
Analysis of fluid property variations across the Barnett and Eagle Ford Shale using fuzzy logic
by Ting Sun, Hamid Rahnema, Ali Takbiri-Borujeni, Shan-E-Zehra Lashari, Ali Reza Edrisi
Abstract: The objective for this study is to perform an investigation of the areal and vertical geospatial fluid property variations across the Barnett and Eagle Ford based on publicly-available PVT data (97 Barnett wells and 153 Eagle Ford wells). A modified multi-contact recombination procedure has been implemented to the PVT data of the reported well stream compositions for Barnett to improve estimates of in-situ reservoir composition. The Eagle Ford data were utilised without modifications as this shale play is known to be highly under-saturated. The results of modified multi-contact recombination procedure for Barnett are plotted on a ternary diagram and show that the majority of the wells were dry gas to retrograde gas. For Eagle Ford, ternary diagrams indicated the fluid type, vertical variations of OGR, C7+ and API gravity. Maps were created to review areal variations of these properties (API gravity, C7+, and initial OGR). The study was further speculated by applying fuzzy pattern recognition algorithms. The application of fuzzy logic provided additional insight to the reservoir fluid's PVT behaviour in understudy shale formations. [Received: August 23, 2018; Accepted: May 6, 2019]
Keywords: Barnett Shale; Eagle Ford Shale; fuzzy logic; fluid property variations.
Effects of ambient pressure on diffusion kinetics in coal during methane desorption
by Bing Zhang, Hanpeng Wang, Liang Yuan, Zhongzhong Liu, Yuqiang Zhang, Shucai Li, Junhua Xue, Shugang Wang
Abstract: To elucidate the influence of ambient pressure on diffusion kinetics during gas desorption, which is of great significance to the efficient development of coalbed methane, a methane desorption experiment was carried out on coal particles under different ambient pressures, and diffusion coefficients for each test time were solved by the unipore diffusion model. The experiment was carried out using our independently developed 'coal particle methane desorption meter' to overcome the difficulty that the existing equipment could not achieve a constant ambient pressure higher than atmospheric pressure. The results show that during methane desorption in coal particles, the diffusion coefficient was not constant but gradually decreased with time, showing a power function relationship. In addition, the diffusion coefficient decreased linearly with increasing ambient pressure, and the degree of influence was related to time. This research will play an important role in improving the unipore diffusion model and elucidating the gas production mechanisms. [Received: February 2, 2018; Accepted: May 9, 2018]
Keywords: coal particle; methane desorption; ambient pressure; desorption time; diffusion kinetics; diffusion coefficient; coalbed methane; unipore diffusion model.
Assessing the influence of key parameters on an iterative ensemble-based method
by Ricardo Vasconcellos Soares, Célio Maschio, Denis José Schiozer
Abstract: Ensemble-based methods generate interesting results regarding history-matching processes. However, there are several parameters that can have a large impact on the final response of the process. Therefore, this work presents a comprehensive study of the following parameters of an ensemble-based method, the ES-MDA: different petrophysical images in the initial ensemble, inflation factor (α), measurement error (CD) and truncated singular value during the matrix inversion process (TSV); aiming to understand how each parameter affects data match, uncertainty reduction, and production forecast. Results showed that different initial ensembles have a major impact when using a small number of models, and minor effects for a large number of models. Inflation factors and CD have a high impact on the whole process (data match, uncertainty reduction, and production forecast), and TSV has a minor impact on the process. Finally, careful analysis of these parameters and further research is required to obtain better results. [Received: December 15, 2018; Accepted: June 17, 2019]
Keywords: history matching; ensemble smoother with multiple data assimilation; ES-MDA; localisation; covariance inflation; truncated singular value; TSV; measurement error; initial ensemble.
Multi-well placement optimisation using sequential artificial neural networks and multi-level grid system
by Ilsik Jang, Seeun Oh, Hyunjeong Kang, Juhwan Na, Baehyun Min
Abstract: This study suggests a sequential artificial neural network (ANN) method coupled with a multi-level grid system to optimise multi-well placement in petroleum reservoirs. As the number of scenarios for placing wells increases exponentially with the number of wells, the difficulty in finding the global optimum increases accordingly due to the intrinsic uncertainty of ANNs. The multi-level grid system can reduce the size of the search space by allocating only one well grid block per several grid blocks in the basic grid system. A higher level of grid system consists of finer grid blocks to gradually improve the resolution of the grid system. Repetitive implementation of the sequential ANN at each level of the grid system narrows the search space, and the global optimum is determined. The proposed algorithm is validated with applications to two- and three-infill-well problems in a coal-bed methane (CBM) reservoir. [Received: March 16, 2018; Accepted: September 19, 2018]
Keywords: sequential artificial neural network; multi-level grid system; multi-well placement; optimisation.
Key factors influencing the low-field NMR characterisation of gas- and oil-bearing shales: a case study of the shales from the southern Sichuan Basin and Dongying sag, China
by Chen Chen, Shuangfang Lu, Pengfei Zhang, Junqian Li, Wenbiao Li, Siyuan Wang
Abstract: The response characteristics of transverse relaxation time (T2) of key experimental parameters [waiting time (TW), number of scans (NS) and echo number (NECH)], sample size and probe fluid, are analysed systematically based on NMR experiments of oil- and gas-bearing shales from the Shahejie Formation in Dongying sag and the Wufeng and Longmaxi Formations in the southern Sichuan Basin. The results indicate that: 1) the optimised NMR parameters for TW, NS and NECH are 1,500 ms, 64 and 6,000, respectively, which will ensure higher accuracy and signal-to-noise ratio (SNR); 2) the total signal amplitude of the T2 spectrum increases with decreasing grain size. The T2 spectra of shale which grain size bigger than 10 mesh can characterize the shale PSD; 3) water porosity clearly decreases with increasing brittle minerals but decreasing clay content than n-dodecane-saturated porosity, which indicates the hydration of clay and brittle minerals together controls the reconstruction of PSD. [Received: May 30, 2018; Accepted: October 24, 2018]
Keywords: shale; low-field nuclear magnetic resonance; NMR; waiting time; TW; number of scans; NS; grain size; probe liquid; echo number; NECH; signal-to-noise ratio; SNR.
Investigating reservoir stresses and strain effects during production from coal bed methane gas reservoir on reservoir properties and gas production – a numerical study
by Subhashini Nainar, G. Suresh Kumar
Abstract: The effects of stresses and strains, occurring in a reservoir, on the cumulative gas production and the petrophysical properties are studied. Existing strain and stress model equations have been used to analyse the coupled effect of matrix shrinkage and cleat compressibility change on reservoir properties. A coal bed methane (CBM) gas reservoir, low permeable and undersaturated, is semi-analytically modelled. A nearly suitable model from among them is eventually proposed to predict the cleat permeability and gas production existing in the field using a dynamic drainage area (DDA) approach. These results vary with the production time. The strain model predicts gas production values and the stress models predict a range of cleat permeability variation values close to field values. Cleat permeability and cleat porosity both affect gas productivity but in the opposite manner. [Received: December 29, 2018; Accepted: May 14, 2019]
Keywords: stress models; strain model; cleat compressibility; sorption strain; dynamic drainage area; DDA; coal.
Experimental study on the viscosity-temperature characteristics and rheological properties of offshore heavy oil
by Meng Cao, Linsong Cheng, Shijun Huang, Yongchao Xue, Mengge Du, Yanwei Yang, Yun Xia, Xiao Chen
Abstract: The viscosity-temperature characteristics and rheological properties of heavy oil were investigated experimentally. Experimental results indicate that viscosity is sensitive to temperature, and it is a binary function of temperature and shear rate meeting preferably Arrhenius equation. In addition, the semi-log curve of viscosity-temperature can be divided into three regions and there is no obvious turning point, which exhibits that the internal microstructure of heavy oil during the heating process changes gradually. Besides, activation energy of low temperature range is higher than that of high temperature range. Moreover, the heavy oil always behaves as Newtonian fluid when temperature is higher than crystallisation temperature. Furthermore, on condition that temperature is less than crystallisation temperature, the heavy oil behaves as pseudo-plastic fluid characterising shear thinning phenomenon when shear rate is less than critical shear rate, and it presents as Bingham fluid with yield stress when shear rate falls between 10 and 50 s−1. [Received: March 16, 2018; Accepted: October 24, 2018]
Keywords: offshore heavy oil; viscosity-temperature characteristics; rheological property; activation energy; crystallisation temperature; critical shear rate.
Biodiesel production from waste cooking oil using copper doped zinc oxide nanocatalyst – process optimisation and economic analysis
by R. Sandhya, R. Velavan, J. Ravichandran
Abstract: India is the world's third largest consumer of energy. India's energy consumption consists of 44% coal, biomass and waste 24%, petroleum and other liquids 23% and other renewable sources such as wind, solar, nuclear and biofuels. Due to the shortage of diesel and increasing prices, biodiesel gained its importance as an alternate to the petroleum based fuels. This paper deals with the transesterification of waste cooking oil to biodiesel with copper doped zinc oxide nanocatalyst under varying parameters such as oil to methanol ratio (1:2-1:5 mol), catalyst loading (2-8% w/w), reaction time (30-60 minutes) and temperature (40-70°C). Results show that the maximum yield of about 97.7% was obtained at optimum reaction conditions. This result is further validated. The economic analysis of biodiesel production is carried out and the cost of biodiesel per litre works out to be 68 rupees INR ($0.99). [Received: August 3, 2018; Accepted: June 1, 2019]
Keywords: biodiesel; waste cooking oil; transesterification; copper doped zinc oxide; nanocatalyst; synthesis; characterisation; process parameters; economic analysis; optimisation; oil; gas and coal technology.
Synergy of fluid sampling and subsea processing, key to maximising offshore asset recovery
by Nimi Abili, Athanasios Kolios
Abstract: The acquisition of accurate fluid samples for deepwater development is crucial for the correct evaluation of oil reserves. Samples collected from topside facilities do not represent the fluid being measured on the seabed. The injections of chemicals such as methanol and corrosion inhibitors, etc., downstream of the meter, and possible liquid separation or hold-up, are typical issues. Employing subsea multiphase flowmetre measurements in the underwater environment presents some significant challenges. Due to the fact that subsea multiphase flowmetre is not 'fit-and-forget' instrumentation hardware, changes in the inputs from the flow stream's actual properties can lead to errors in flowmetre data capture. A mechanistic model is employed, using the fluid properties that are equivalent to the flow stream being measured, to predict reliable reservoir fluid characteristics on the production flow stream. The present paper explores the synergy in successful application of fluid sampling and subsea processing to maximise offshore asset recovery. [Received: April 15, 2018; Accepted: August 27, 2018]
Keywords: synergy; multiphase flowmetre; mechanistic model; fluid sampling; subsea processing; oil; gas; technology; OPEX; deepwater asset recovery.
Optimisation of the LNG supply chain: a literature overview
by Ignacio De La Peña-Zarzuelo, María Jesús Freire-Seoane, Carlos Pais-Montes
Abstract: Liquefied natural gas (LNG) is playing a prominent role in current global maritime transport and port operations. The industry, in which a wide range of agents are involved, is expanding rapidly. However, applied research into LNG operations research (OR) is still in its infancy. The goal of this investigation is to assess the literature that deals with OR LNG logistics chains. Existing studies fall into two groups: those that consider pricing as the most important factor; and those that focus on the inventory and routing problem (IRP) and the routing and scheduling problem (RSP). Our review of the literature reveals that there are seven emergent areas of research which are linked to the use of new programming paradigms, the introduction of climate factors and possible changes in trade flow patterns caused by factors such as the widening of the Panama Canal or the opening of the Arctic Bridge. [Received: May 18, 2017; Accepted: January 16, 2019]
Keywords: operations research; simulation; liquefied natural gas; LNG; routing and scheduling problem; RSP; inventory and routing problem; IRP.
Nexus between energy consumption, health expenditure and economic growth in Australia
by Ronald Ravinesh Kumar, Peter Josef Stauvermann, Syed Jawad Hussain Shahzad
Abstract: Focussing on Australia, we examine the effects of energy consumption and health expenditure on output within the extended neo-classical Solow growth model. We use the ARDL bounds and non-Granger causality procedures for a sample period 1971-2014, to analyse the short-run and long-run effects of energy consumption and health expenditure on economic growth. Additionally, we examine the threshold values of energy and health expenditure. It is noted that in the long-run, energy consumption vis-à-vis output has a U-shaped relationship and the health expenditure has an inverted U-shaped relationship. The minimum energy consumption per capita necessary for growth needs to be at least 4,849 kilograms of oil equivalent, whereas the maximum amount of health expenditure, in real terms, should not exceed AU$ 5,959 per person. In terms of causality, we note a unidirectional causality from income, capital stock (investment) and health expenditure to energy consumption; and bidirectional causality between health expenditure and income. [Received: March 23, 2018; Accepted: November 18, 2018]
Keywords: energy consumption; health expenditure; economic growth; nonlinear; Australia.
Geological controls on coalbed methane accumulation and optimisation strategy for gas productivity: a case study in eastern Ordos Basin, China
by Kui Zhu, Xinyi Song, Fan Lu, Bo Jiang, Changshen Wang, Guoyong Yang, Zhengjie Chen
Abstract: Drainage conditions can significantly affect the coalbed methane (CBM) production, which is accomplished by reducing the gas partial pressure in the coal seam. This can be achieved by pumping the formation water or gas injection. In this study, the Baode region is selected to study the drainage conditions and production characteristics on the early stage of CBM production. The temporal trends of water production, wellhead pressure and gas production have been analysed. Results show that the favourable burial depth for CBM accumulation between 500 and 700 m. Sandy mudstone and mudstone are beneficial to CBM preservation. The wellhead pressure should be maintained between 0.4 MPa and 1.0 MPa, and the optimal range of wellhead pressure lies between 0.5 and 0.8 MPa for stable production. The gas production increases with increased water production when the wellhead pressure has become progressively stable in the middle phase of early stage. [Received: September 9, 2018; Accepted: October 24, 2018]
Keywords: coalbed methane production; water production; wellhead pressure; gas production.
Special Issue on: ICCESEN-2019 Sustainable Research on Geo-Energy and Geo-Environmental Sciences
Investigation of the effect of L5Cu compound in diesel fuel on In-cylinder Pressure, Engine Performance and Exhaust Emissions
by Ali Oz
Abstract: This study was conducted to investigate the effect of diesel fuels on in-cylinder pressure, engine performance (brake thermal efficiency and specific fuel consumption) and exhaust emissions. In this study, a 4-cylinder, 4-stroke, water-cooled common-rail diesel engine was used with a cylinder volume of 1500 cc. The engine was operated at a fixed engine speed of 1750 rpm and 40, 60, 80 and 100 Nm fixed engine loads. Besides, diesel fuel without any addition and L5Cu-added diesel fuel with 4 variables at 60 Nm of engine torque was examined by multivariate regression analysis, and pressure equations were produced. Furthermore, regression analysis of crank angle pressure change data obtained under the operating conditions of the engine with only diesel fuel and diesel+L5Cu fuel was performed and the obtained results were highlighted. As a result, the engine at low engine loads of 40 and 60 Nm, which was also fed with L5Cu additive, was found to have reduced the specific fuel consumption and thermal efficiency by 1,9% and 0,73% respectively; however, at 80 and 100 Nm high engine loads, it was found to have increased by 0.3% and 0.7% respectively. It was concluded that while the L5Cu additive at all engine loads caused a severe reduction in HC emission, it failed to result in a clear change in NOx and CO2 emissions.
Keywords: Common-rail diesel engine; L5Cu additive; engine performance; in-cylinder pressure; exhaust emissions; multivariate regression method.
Automated Char Classification using Image Analysis and Artificial Intelligence
by Alpana ., Satish Chand, Subrajeet Mohapatra, Vivek Mishra
Abstract: Coal is one of the most available resource of energy worldwide, and is used vigorously. Char particles are formed by devolatizing of coal during combustion of it and signify the foremost step in the ignition method. Char particles are categorized into two reactive phases based on their morphologies by experts, namely reactive and non-reactive. These are taken into consideration to estimate the impact of coal on the burners performance. Presently, the semi-automatic method is followed by industries to determine the classification of char groups. This conventional method is time-consuming and subjective. Char characterization may be executed automatically with advantages like fast processing and consistency. In this article, we attempt to suggest an automated scheme for the classification of char into its reactive and non-reactive groups using image analysis and artificial intelligence methods. Subsequently, the proposed system is recognized to be an efficient technique for the characterization of char with more accurate results in reduced computational time.
Keywords: Coal; Char; Image Analysis; Artificial Intelligence; Deep Learning.
Relationship between microstructure and fracture toughness in B2O3-doped 8YSZ ceramics
by Bülent Aktas
Abstract: 8 mol.% yttria-stabilized cubic zirconia (8YSZ) ceramics are used as a solid electrolyte in solid oxide fuel cells at high temperatures. However, 8YSZ ceramics can easily break during operation due to low fracture toughness. This study aims to increase the breaking toughness of 8YSZ at room temperature owing to the addition of boron oxide (B2O3). Therefore, in this study, the effect of B2O3 addition on sinterability and mechanical properties of 8YSZ was investigated using Micro-Vickers hardness tester and scanning electron microscope (SEM). B2O3 was added by the colloidal method to 8YSZ at 1, 5, and 10 wt.% amounts. B2O3-doped 8YSZ powders were pressed at a pressure of 250 MPa in a steel die with a diameter of 10 mm. B2O3-doped 8YSZ samples were sintered at different temperatures (1300-1500 oC). A relative density of approximately 99% was obtained at 1500 oC in the B2O3-doped samples. While the B2O3 addition at 1 wt.% content caused a decrease in the grain size of the 8YSZ, and then when the content was > 1 wt.%, it increased. The B2O3 addition to 8YSZ caused an increase in densities, due to occur liquid phase sintering at the grain boundaries of 8YSZ. The mechanical properties results showed that fracture toughness of 8YSZ increased with B2O3 addition, and the hardness decreased with B2O3 addition. The fracture toughness of 8YSZ was increased from 1.64 to 3.39 MPa.m1/2 owing to B2O3 addition. The reason for the increase in the fracture toughness by B2O3 addition was due to bridging the cracks of the B2O3 that precipitated as a second phase at the grain boundaries of 8YSZ. In conclusion, it was found that the fracture toughness of 8YSZ could be improved by B2O3 addition.
Keywords: 8 mol.% yttria-stabilized cubic zirconia (8YSZ); B2O3; Liquid phase sintering; Fracture toughness.