Forthcoming articles

International Journal of Oil, Gas and Coal Technology

International Journal of Oil, Gas and Coal Technology (IJOGCT)

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International Journal of Oil, Gas and Coal Technology (71 papers in press)

Regular Issues

  • An improved cubic law for shale fracture considering the effect of loading path   Order a copy of this article
    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   Order a copy of this article
    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   Order a copy of this article
    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)   Order a copy of this article
    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   Order a copy of this article
    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.
    DOI: 10.1504/IJOGCT.2020.10029711
  • Effect of moisture content on methane diffusion in kaolinite by Molecular dynamics simulations   Order a copy of this article
    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   Order a copy of this article
    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   Order a copy of this article
    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   Order a copy of this article
    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), 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   Order a copy of this article
    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   Order a copy of this article
    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   Order a copy of this article
    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   Order a copy of this article
    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   Order a copy of this article
    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.
    DOI: 10.1504/IJOGCT.2020.10029041
  • A simple and robust model for prediction of liquid-loading onset in gas wells   Order a copy of this article
    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   Order a copy of this article
    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   Order a copy of this article
    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   Order a copy of this article
    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   Order a copy of this article
    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.
    DOI: 10.1504/IJOGCT.2020.10026719
  • Cost Factors and Statistical Evaluation of Gas Transmission Pipeline Construction and Compressor-Station Cost in the United States, 2014-2019   Order a copy of this article
    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   Order a copy of this article
    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   Order a copy of this article
    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   Order a copy of this article
    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   Order a copy of this article
    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.
    DOI: 10.1504/IJOGCT.2020.10028831
  • Well Placement Optimization using a Productivity Potential Area Map   Order a copy of this article
    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   Order a copy of this article
    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   Order a copy of this article
    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   Order a copy of this article
    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 process chain, oil refineries are generally considered to be the most polluting phase but oil storage units also have an adverse impact on the environment. Since there is no life cycle assessment (LCA) study focusing on the storage units in India, this study will help in identifying the potential environmental 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 identified.
    Keywords: life cycle assessment; LCA; oil storage units; transportation; environmental impact; fuels; India; SimaPro; emissions; impact categories; climate change.
    DOI: 10.1504/IJOGCT.2020.10030826
  • Influence of hydrodynamic cavitation pretreatment on coal flotation   Order a copy of this article
    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   Order a copy of this article
    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   Order a copy of this article
    by Mamta Sharma, Trisrota Bhowmick, Vivek Mishra 
    Abstract: The present investigation was aimed to characterise the natural cokecoal (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. [Received: August 14, 2019; Accepted: April 23, 2020]
    Keywords: float-sink; heat altered coal; petrography; igneous activity; Indian coal; India.
    DOI: 10.1504/IJOGCT.2020.10030270
  • Practical method for air sampling and analysis of some natural gas odorant   Order a copy of this article
    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   Order a copy of this article
    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   Order a copy of this article
    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   Order a copy of this article
    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
    Keywords: coal spontaneous combustion (CSC); air volume reduction; fire trend determination; classification warning; spontaneous combustion index.

  • A robust multi-objective optimization model for natural gas supply chain design under uncertainty: A case study   Order a copy of this article
    by Rozita Daghigh, Mir Saman Pishvaee 
    Abstract: The appropriate design of a complex natural gas supply chain becomes a critical issue for both academics and practitioners. To deal with the design of complicated natural gas supply chain, a mixed integer non-linear programming model is developed in this paper. Two conflicting objectives including the minimization of the total cost and the maximum unfulfilled demands are considered subject to technical and logical pipeline and compressor constraints. Since a number of critical parameters are tainted with imprecision in the proposed model, a robust possibilistic programming approach is applied to handle the inherent uncertainty. A natural gas network in Iran is used as a case study to verify and validate the developed model.
    Keywords: Natural gas supply chain; Multi-objective optimization; Robust optimization; Uncertainty.

  • A Review of Onshore and Offshore Pipeline Construction and Decommissioning Cost in the United States Part 1. Specifications, Cost Estimation and Onshore Construction   Order a copy of this article
    by Mark J. Kaiser 
    Abstract: The cost to construct and decommission oil and gas pipelines in the United States varies widely between onshore and offshore regions as well as within each area, depending on numerous factors. The purpose of this review is to evaluate publicly available data sources for onshore and offshore pipeline installation and decommissioning activities in the United States. The activities and processes involved, factors that impact cost, cost statistics and limitations of analysis are presented for onshore and offshore pipeline installation and decommissioning. Similarities and differences between processes and the tradeoffs involved in design and construction are described to better understand the cost differences that arise between projects. In Part 1 of a two-part review, an overview of pipeline manufacturing and API 5L specifications introduce relevant terminology and basic pipeline requirements, and a description of cost estimation procedures, normalization, and data sources provides the evaluation framework. A description of U.S. onshore pipeline construction cost data and analysis concludes the paper.
    Keywords: benchmarking; cost statistics; offshore vs. onshore; pipeline construction; pipeline decommissioning.

  • A Review of Onshore and Offshore Pipeline Construction and Decommissioning Cost in the United States Part 2. Offshore and Deepwater Decommissioning Cost Algorithms   Order a copy of this article
    by Mark J. Kaiser 
    Abstract: In the second part of this two-part review on the cost to construct and decommission oil and gas pipelines in the United States, summary data of offshore pipeline construction and decommissioning cost are described, along with hypothetical pipeline decommissioning cost algorithms for the deepwater Gulf of Mexico. Similarities and differences between design and construction tradeoffs are described to better understand the cost differences that arise between projects. Significant temporal impacts enter cost statistics due to inflation, market conditions, regulatory and technology changes, and spatial impacts arise due to differences in geologic conditions, infrastructure, and terrain. Most factors are unobservable and not available for evaluation, but there are many similarities in processes and infrastructure that allow normalized cost to serve as a useful first-order benchmark.
    Keywords: benchmarking; cost statistics; offshore vs. onshore; pipeline construction; pipeline decommissioning.

  • Analysis of dependence structure among investor sentiment, policy uncertainty and international oil prices   Order a copy of this article
    by Mobeen Ur Rehman, Seema Narayan 
    Abstract: The behavioral aspect of finance and economics has an embedded importance in the literature. This paper provides an evidence of the interrelationship of international oil prices with economic policy uncertainty, consumer sentiments and US investor sentiment proxies. To test the underlying dependence structure, we employ time invariant and time- varying copula methods due to dynamic return patterns of our sampled indices. Our analysis reveals an underlying relationship of investor sentiments and economic policy uncertainty with international oil prices not only during normal periods but also in the periods of financial turmoil. Results of our nonlinear causality highlight potential of bidirectional spillover between oil prices and investor sentiment indices across all quantiles. This helps in understanding the that a volatile international oil market may have significant impact on investor sentiments and economic policy uncertainty and vice versa.
    Keywords: Investor sentiment; economic uncertainty; oil prices; dependence structure.

  • Effects of n-butanol/ calophyllum inophyllum biodiesel blend injection on the combustion characteristics of Reactivity Controlled Compression Ignition Engine   Order a copy of this article
    by Gowtham M, Prakash Ramakrishnan 
    Abstract: The present experiment work implements the reactivity controlled compression ignition (RCCI) technique in analysing the combustion, performance and emissions (regulated and unregulated) characteristics of diesel engine. A high reactivity calophyllum inophyllum biodiesel blend (B20) is directly injected inside the cylinder and a low reactivity n-butanol fuel is injected in three different ratios (10, 20 and 30% by vol basis) into the inlet manifold section using electronic control unit. This study reveals that the brake thermal efficiency increased by 4.32%, oxides of nitrogen, smoke, acetaldehyde, benzaldehyde, hexanaldehyde, are reduced 19.31%, 8.82%, 12.19%, 11.71% and 37.02%, respectively compared to diesel at full load condition. The carbon monoxide, hydro carbons, formaldehyde, crotanaldehyde are increased by 15.23%, 20.87%, 15%, and 13.23% compared with neat diesel fuel. The cylinder pressure and heat release rate are increased by 18%, 29.15% with n-butanol 30% injection due to the advanced start of combustion, high cylinder temperature, and better mixture formation. The brake specific fuel consumption, propanaldehyde, ethanol, acrolein and benzene emission are found to be increased during all load conditions.
    Keywords: Calophyllum inophyllum methyl ester; n-butanol; diesel engine; ECU; combustion; performance; regulated emission; Unregulated emission.

  • A comparative analysis and rapid performance prediction of polymer flooding process by coupling reservoir simulation with neural networks.   Order a copy of this article
    by Negar Zarepakzad, Emre Artun, Ismail Durgut 
    Abstract: Accelerated
    Keywords: reservoir simulation; chemical enhanced oil recovery; polymer flooding; artificial neural networks; data-driven modeling; screening model.

  • Russias geo-energy interests and secessionist conflicts in Central Asia: Karakalpakstan and Gorno-Badakhshan   Order a copy of this article
    by Jose Antonio Pena-Ramos 
    Abstract: The break-up of the Soviet Union heralded a highly unstable decade of decline for Russia, while also generating numerous conflicts in the post-Soviet space. Russia regained influence at global and, chiefly, regional level from 2000, with the coming to power of Vladimir Putin and the rise in the price of hydrocarbons. Energy policy arguably played an essential role in this situation. Central Asia, the scenario of two secessionist conflicts at present, is crucial to Russian geo-energy interests. This article examines and discusses the impact of these conflicts on Russias geo-energy interests, in particular since Putin came to power. Our conclusion is that, in a context of Russian dominance of the post-Soviet space and direct Russian intervention in secessionist conflicts in the South Caucasus and Eastern Europe in defence of its geo-energy interests, the two post-Soviet secessionist conflicts in Central Asia (Karakalpakstan and Gorno-Badakhshan) have greatly benefited Russian geo-energy interests.
    Keywords: secessionist conflicts; Central Asia; energy policy; hydrocarbons; geo-energy interests; Russia; Uzbekistan; Karakalpakstan; Tajikistan; Gorno-Badakhshan.

  • Modeling of coal flotation responses based on operational conditions by random forest   Order a copy of this article
    by Xiangning Bu, Amir Taghizadeh Vahed, Sina Ghassa, Saeed Chelgani 
    Abstract: Coal consumption is one of the critical factors in the economy of China. Flotation separation of coal from its inorganic part (ash) can reduce environmental problems of coal consumption and improve its combustion. This investigation was used random forest (RF) as an advanced machine learning method to rank flotation operations by variable importance measurement and predict flotation responses based on operational parameters. Fifty flotation experiments were designed, and performed based on various flotation conditions and by different variables (collector dosage, frother dosage, air flowrate, pulp density, and impeller speed). Statistical assessments indicated that there is a significant negative correlation between yield and ash content. Experiments indicated that in the optimum conditions, yield and ash content would be 80 and 9%, respectively. Variable importance measurement by RF showed that frother has the highest effectiveness on yield. Outcomes of modeling released that RF can accurately be used for ranking flotation parameters, and generating models within complex systems in mineral processing.
    Keywords: Coal; Flotation; Advanced machine learning; Random forest; Yield.

  • Interpretation of Displacement Fields Around Hydraulic Fracture Tip Using Digital Image Correlation Method   Order a copy of this article
    by Jingnan Dong, Mian Chen, Musharraf Zaman 
    Abstract: Hydraulic fracture is of crucial importance in the enhancement of unconventional oil and gas production. A small-scale hydraulic fracture device based on double cantilever beam theory is used to induce Mode I hydraulic fracture. Using digital image correlation method, an experimental technic is developed to identify the full-field displacement of the 2-dimensional hydraulic fracture tip. Conclusion shows that the crack tip position extracted from the non-linear fitting conforms well to the optical microscope observation. The sizes and the morphologies of the process zone near the hydraulic fracture tip are different in various materials.
    Keywords: hydraulic fracture tip; digital image correlation; full-field displacement; Williams’ series; process zone.

  • Does Crude Oil Price Respond to US Oil and Gas Industry Value Chain Economics   Order a copy of this article
    by Chamil W. Senarathne, Wei Jianguo 
    Abstract: This paper examines whether the crude oil price responds to industry value chain economics (i.e. economic return on capital employed) in the oil and gas industry of the United States. Fama-French five-factor regression shows that the variations in profitability of firms (risk factor) is unrelated to equity risk premium in the oil and gas industry as the risk of industry value chain operation could be diversified away by appropriately managing the activities in the value chain operation and the size risk factor becomes idiosyncratic in the industry. The EVA in the industry value chain operation is negatively and significantly related to crude oil price and this asymmetric relationship is caused by the cost implications of value chain operation. Reinvestment of dividend increases the expectations of capital providers about their value of investments (i.e. enhancement of capital appreciation). This is because the firms will have to make sufficient investments (i.e. capital and avenue expenditure) to ensure long-term growth of the firms which will eventually increase the price of crude oil due to cost escalations on capacity expansion. The negative association between industry production of crude oil (IPD- mining) and crude oil price indicates that, when the value chain economics are increased, the firms will have the opportunity to increase the operating (i.e. production) capacity by reinvesting the dividends in equity. The Granger-causality test reveals that the EVA has a significant causal effect on oil price and the policy uncertainty significantly Granger cause EVA. VEC estimation results also suggest that, except for the significant response of EVA to policy uncertainty and EVA to oil price, the responses of oil price to EVA and oil price to policy uncertainty have shown to be significant in the medium term but weaker in the short- and long-run. The responses of policy uncertainty to EVA and policy uncertainty to oil price are highly and significantly fluctuating around the neutral zone. Shocks to oil price and policy uncertainty cause weaker fluctuations in EVA, and the variation of the fluctuations in EVA due to the shocks to oil price is considerably significant. The suggestions and implications of these findings for industry policymaking are discussed.
    Keywords: Fama-French regression: Economic value addition: Crude oil price: Policy uncertainty; Value chain economics; Granger-causality; Vector autoregression: Variance decomposition.

  • Natural Gas Treatment by Membrane- Case Study of Liquefied Natural Gas Plant of Arzew-Algeria   Order a copy of this article
    by Amina MEZOUAGH, Belkacem ABSAR, Maghnia HAMOU MAAMAR, Omar BELHAMITI 
    Abstract: A calculation method for predicting the performances of multicomponent gas mixture through a membrane permeator is presented. Two mathematical models are developed to study the effect of the circulation of feed and permeate inside the membrane module. The circulation modes explored are the co-current and the countercurrent flow pattern. The mathematical model developed in the case of countercurrent flow pattern is subject to the split boundary value problem. To solve this problem a numerical approach is developed combining the (0,2) Jacobi multi-wavelets method and the decoupling and quasi-linearization iterative technique. The developed models are then used to predict the performances of a membrane module designed for the treatment of a natural gas load (case study of the Liquified Natural gas plant of Arzew-Algeria). The obtained results show clearly the efficiency of the countercurrent compared to the co-current flow pattern: high product purity is obtained for the same recovery rate.
    Keywords: Membrane gas separation; mathematical modeling; (0,2) Jacobi multi-wavelets method; cocurrent and countercurrent flow pattern.

  • Hydrocarbon potential, maturity and depositional environment of the source rocks in the southwestern part of the Naga Schuppen Belt, India   Order a copy of this article
    by Mousumi Gogoi, Neeraj Mathur, T. Satish Kumar, Temsulemba Walling, Sarat Phukan 
    Abstract: The Oligocene Barail Group of the Naga Schuppen Belt, exposed along the Dimapur-Kohima road section, Nagaland is classified into three formations, viz. Laisong, Jenam, and Renji Formations. The organic matters of carbonaceous shales of the Laisong and Jenam Formations have been evaluated by Rock-Eval pyrolysis, biomarker analysis, and organic petrographical analysis under the present study. The organic matters are represented mostly by mixed Type II&III and Type III kerogens in the Laisong Formation and Type III and IV kerogens in the Jenam Formation that are predominantly of terrestrial origin deposited in an oxic deltaic-terrigenous environment. Rock-Eval parameters are indicative of the presence of marginal amount of organic matter to act as petroleum source with poor generative potential. Maturity parameters of Rock-Eval pyrolysis and biomarker analysis and vitrinite reflectance measurements are indicative of the presence of immature to early mature organic matters in the Laisong Formation and early to mid-mature organic matters in the Jenam Formation. This is unusual as the Laisong Formation occupies stratigraphically lower position than the Jenam Formation. This mismatch was possibly caused by many episodes of rapid differential heating to high temperature followed by cooling related to active tectonics of the Naga Schuppen Belt through the geological past. The occurrence of several thrust faults of regional scale and highly deformed nature of the sediments in the Naga Schuppen Belt point to such possibility.
    Keywords: Barail Group; Oligocene; Naga Schuppen Belt; Rock-Eval pyrolysis; biomarkers; organic petrology; source rock potential; depositional environment.

  • Risk assessment in oilfield services project management   Order a copy of this article
    by Mladen Radisic, Ognjen Radisic, Maja Radisic 
    Abstract: The paper aims to present the importance of project risk assessment within exploration and production (E&P) sector, namely oilfield services. In this paper some major project related issues in the field have been highlighted, such as potential risks present within drilling rig preparation projects. The central research of this paper includes systematic risk overview of the several already undertaken drilling rig preparation projects. Furthermore, based on the applied risk assessment methodology the proposals how to successfully identify, analyze and respond to project risks are given. Therefore, presented results of the paper provide oilfield services project managers with an easy-to-use risk assessment guideline.
    Keywords: API Q2; drilling rig; project management; risk management; risk analysis.

  • Prediction and Optimization of Gas Lift Performance Using Artificial Neural Network Analysis   Order a copy of this article
    by Ahmed Elgibaly, Mohsen Elnoby, Moataz El-Tantawy 
    Abstract: Gas lift is one of the most widespread methods of artificial lift technologies used when wells production rate drops below the economic limit. Gas Lift is employed to maintain the production above the available limit by means of injecting gas into the tubing through the casingtubing annulus and a gas lift orifice installed in the tubing. Gas lift has been widely used in the oil fields that suffer from sand production. It is also used in deep and deviated wells and on offshore platforms. Lifting costs for a large number of wells are generally low. However, capital costs of compression stations are very rnhigh, so it is necessary to optimize gas lift wells by determining the optimum gas lift injection rate and optimum oil rate for each well. In this paper, conventional nodal analysis models using Pipesim software were used to predict the optimization parameters based on wells flowing survey, reservoir and well parameters and calculations of multiphase flow behavior. Artificial neural network (ANN) models were also used based on gas lift databases and gas lift monitoring systems. ANN models were trained to obtain the optimum structure and then tested against pipesim models.rn It has been concluded that ANN has an excellent competing ability for gas lift optimization prediction compared to conventional methods and can be used interchangeably. This technique can considerably help in the immediate optimal design of gas lift wells.
    Keywords: Gas Lift Performance and Optimization; Prediction; Artificial Neural Network; Optimum Oil Rate; Optimum Gas Lift Rate; Pipesim; Matlab.

  • Structural and Swelling Study of Karharbari Coal with Various Combinations of solvent   Order a copy of this article
    by Yash Jaiswal, Sunder Lal Pal, Lav Kush 
    Abstract: Swelling kinetics of Karharbari coal in various combinations of solvents such as T/PY, T/PNT, T/FLT, T/ANT, T/MNAP, T/NAP, T/FL, T/D were studied using the solvent swelling technique. The values of equilibrium swelling ratio Qe and diffusional exponent n were calculated to find the nature of diffusion while changing temperature and solvent combinations. Results conclude that with an increase in swelling temperature the nature of swelling shifts from relaxation controlled diffusion to the Fickian diffusion controlled. The activation energies with different solvents were also calculated to suggest the actual energy barrier for swelling of coal. Structural changes in coal due to penetration of solvents were also determined by using FTIR analysis of all combinations of solvents. The resultant energy barriers for swelling of coal was found to be hydrogen bond (H-bond). This work also includes the percentage extraction of H-bond obtained for all combinations of solvents. The results obtained firmly conclude that the solvent combination of tetralin and pyrene (T/PY) is the best combination of solvents for the pretreatment of coal for coal liquefaction.
    Keywords: Coal swelling; Karharbari coal; Structural change of coal; H bond extraction; and yield.

  • Study on CO2 Diffusion Process in Heavy Oil Saturated Porous Media Using Experiment and Simulation   Order a copy of this article
    by Wei Liu, Lin Du, Wen Liu, Xiaoyuan Qin, Xin Luo 
    Abstract: CO2 diffusion coefficient is an important and fundamental parameter for CO2 enhanced oil recovery (EOR) and storage. In this paper, a mathematical model was developed to simulate the CO2 diffusion process in the heavy oil saturated porous media. Theoretically, the mathematical model was integrated with the gas state equation to calculate the CO2 diffusion coefficient in porous media. Then, the pressure decay methodology was applied to measure the CO2 diffusion coefficient in the heavy oil saturated porous media. Experimentally, the diffusion coefficient was determined by fitting the experiment data with the pressure decay model. Using the measured diffusion coefficient as an input parameter, the CO2 diffusion process in porous media was simulated and the factors that affected the diffusion process was analyzed in this paper. The simulation results show that diffusion direction on the rock surface is in the tangential direction of the rock and points to where the CO2 concentration potential decreases. Furthermore, the diffusion process was also affected by the size of pores and throats, and the contact area of CO2 and heavy oil.
    Keywords: CO2; Heavy oil; Porous media; Diffusion coefficient; Simulation analysis.

  • Stress-seepage Bidirectional Coupling Analysis of a Horizontal Well with Multi-Stage Fractured Fractures   Order a copy of this article
    by Shubo Zhang, Gang Wang, Ke Wang, Hengjie Luan, Letang Sun, Wei Han 
    Abstract: To explore the gas production performance of a horizontal well with multi-stage fractured fractures in a shale gas reservoir, a mathematical model considering stress-seepage bidirectional coupling and the stress sensitivity of permeability was developed. A finite element model of the shale gas reservoir and a horizontal well with multi-stage fractured fractures was established in this study, and the coupling calculation between the two dimensions of the fracture-reservoir was performed. The results show that the influence of the stress-seepage interaction cannot be neglected for shale gas production from the reservoir. The key factor affecting the production of the reservoir is the complexity of the fractured fractures, and a higher complexity indicates a higher productivity. This result also implies that it is unreasonable to consider only primary fractures in the fractured horizontal well analysis. The higher initial reservoir permeability does not necessarily result in higher gas production under coupling conditions. However, in the early stage of production, the higher initial reservoir permeability leads to a considerable gas production rate. The permeability of fractures and the bottom hole pressure have less influence on the reservoir productivity.
    Keywords: shale gas reservoir; fractured horizontal well; stress-seepage bidirectional coupling; productivity.

  • Modelling Hydrocarbon Generation and Migration in Tertiary Source Rocks of Deepwater, Phu Khanh Basin, Offshore Vietnam   Order a copy of this article
    by Huy Nguyen Xuan, Dung Ta Quoc, Trang Nguyen Thi Thu, Hoang Cu Minh, Min Baehyun, Delia Anne-Marie Androne, Binh Kieu Nguyen 
    Abstract: This study modelled a petroleum system to analyze the history of basin evolution, maturity, and hydrocarbon generation in the deepwater of the Phu Khanh Basin, offshore Vietnam. The paleo heat flow, surface-water interface temperatures, and paleo water-depth were modelled using existing wells occurring in shallow to deep marine environments. Based on the geochemical analysis, the Oligocene and Lower-Middle Miocene source rocks are predominantly a mixture of type II and type III kerogens, with differences in distribution and maturation level. In the Phu Khanh Basin, hydrocarbon generation started during the Early Miocene. Petroleum migrated to a trap and accumulated in an uplift structure in the sandstone and carbonate reservoirs of the Lower Miocene formation. The results of this study can assist in defining the distribution of reservoir locations for future field development planning in the Phu Khanh Basin.
    Keywords: Phu Khanh Basin; hydrocarbon generation; migration; heat flow; source rock.

  • Invaded water flowback capability of high volatile bituminous coal after nitrogen displacing: From a perspective of fracture and seepage pore structural complexities   Order a copy of this article
    by Xin Li, Xuehai Fu, Jijun Tian, Xueliang Liu, Yanyan Ge, Meng Wang, Shun Liang 
    Abstract: Water-based fracturing is applied for stimulating coal reservoir. However, invasion of water can result in low flowback efficiency and low coalbed methane (CBM) yield. Nitrogen injection is an effective method to enhance CBM production. In this study, nitrogen displacing water experiments using water saturated high volatile bituminous coal were conducted, during which magnetic resonance imaging (MRI) tests were applied to determine flowback capability. To research the relationship between flowback capability and complexities of fracture and seepage pore, characterizing methods including Micro-CT and mercury intrusion porosimetry (MIP) were used. The results show that flowback capabilities of complex structural seepage pores and fractures were low. Water is easily flooded into simple structural seepage pores and fractures, and water flowback capabilities of these simple spaces are relative higher, compared with those of the complex ones. Water phase trapping during nitrogen displacing water happens due to water imbibition and Jamin effect occurring in complex structural seepage pores and fractures.
    Keywords: coalbed methane; retained water; permeability; magnetic resonance imaging; pore structure; flowback; nitrogen injection; high volatile bituminous coal.

  • A new approach for the prediction of combustible sulfur in coal in terms of coal washability data and calorific value   Order a copy of this article
    by Gokhan Sarihan, Sait Kizgut, Serdar Yilmaz, Mehmet Bilen 
    Abstract: In this study, determination of petrographical properties and washability characterization for Uzulmez District (Zonguldak Coal Basin) coals were realized. Float and sink analysis was carried out on the samples taken from Uzulmez Basin (4 coal seam) and their washability figures were obtained. In the context of this study, it was proposed that each coal seam has its own function for total sulfur content and calorific value. Finally, not only sulfur percentages in each float and sink fraction and each size group were determined but also sulfur percentages in ash of corresponding coal seam samples were obtained. Repeatedly, total sulfur and calorific value diagrams were plotted and the corresponding correlation coefficients were obtained. The reason behind calorific value steep decrease from float fraction to sink fraction and corresponding total sulfur amount increase from sink fraction to float fraction was discussed. The discussion furtherly resulted in understanding of combustible and non-combustible distribution of sulfur and a new method of determining this proportion was proposed. The above mentioned diagrams showed that the combustible sulfur percentages analyzed (both in coal and ash) and predicted has correlation coefficients of 0.90 for PIC (R2=0.90) coal seam, 0.78 for PIRIC (R2=0.78) coal seam, 0.79 for NASIFOGLU (R2=0.79) coal seam and 0.90 for PIC (R2=0.85) coal seam, respectively.
    Keywords: Zonguldak Coal; petrographic analysis; density float; washability; size fractions; combustible and non-combustible sulfur.

  • Impact of Temperature Increases on Formation of Carbon Monoxide during Lignite Storage   Order a copy of this article
    by Petr Buryan 
    Abstract: This article presents our research on formation of carbon monoxide through low temperature oxidation of lignite coal during its long-term storage in the coal bunkers of fluidized bed boilers. We analyzed lignite samples from B
    Keywords: storage; lignite; carbon monoxide; coalbunker.

  • Forming Optimization and Mechanical Analysis of an Expandable Profile Liner for Leakage Plugging in Oil and Gas Wells   Order a copy of this article
    by Le Zhao, Qingquan Duan 
    Abstract: The preliminary application of expandable profile liner technology (EPLT) provides an effective solution for operational challenges associated with borehole instabilities and drilling troubles control without wellbore shrinkage. This study simulates the forming and expansion processes of four kinds of differently cross-sectional shapes of expandable profile liners (EPLs) by using the finite element software ABAQUS. The results of the simulation reveal that the eight-shaped cross section has lower residual stress, better forming stability, and easier expansion characteristics. Aiming to attain the cross section with minimum residual stress and strain, we studied two forming processes with considering the mold assemblies, loading sequences, and loading displacements to optimize the section shape of a ?241.3 mm EPL, which is meaningful for engineering applications. By simulating and analyzing the expansion process of EPLs made of three different materials with three different wall thicknesses, this study obtains data on the internal pressure strength and collapse strength to provide a basis for selecting the best EPL to meet the engineering strength requirements.
    Keywords: expandable profile liner; forming optimization; residual stress and strain; internal pressure strength; collapse strength.

  • Petroleum crude slate effect on H-Oil performance   Order a copy of this article
    by Dicho Stratiev, Ivelina Shishkova, Ilian Kolev, Dobromir Yordanov, Vesislava Toteva 
    Abstract: 16 petroleum crudes and an imported atmospheric residue originating from Russia, Azerbaijan, Greece, Italy, Kuwait, Iraq, Iran, Saudi Arabia, Tunisia, and USA have been processed in the LUKOIL Neftohim Burgas (LNB) refinery, and their effect on the ebullated bed vacuum residue H-Oil hydrocracking (EBVRHC) performance has been evaluated. The vacuum residue conversion in the LNB H-Oil EBVRHC varied between 55 and 82% depending on the crude blend processed in the LNB refinery. It has been established that among all vacuum residue SARA fractions during EBVRHC, the resins have the highest conversion, followed by the naphtheno-aromatics while the saturates shows the lowest conversion. Depending on the petroleum crude origin the behavior of the most problematic VR asphaltene fraction has been found to be different suggesting distinct propensity of the asphaltenes from the different petroleum crudes to participate in radical recombination reactions leading to the formation of additional amounts of core-condensed asphaltenes.
    Keywords: petroleum crude; hydrocracking; vacuum residue; SARA; conversion; sedimentation.

  • Study on Application Timing and Solution Performance Optimization of Composite System after Polymer Flooding   Order a copy of this article
    by Leiting Shi, Shijie Zhu, Xiaoqin Zhang, Yuchi Zhou, Zhongbin Ye 
    Abstract: The appropriate application timing and application system of compound flooding can maximize the recovery after polymer flooding. Taking a polymer flooding heavy oil reservoir as an example, the application timing and solution performance of the composite system are analyzed and studied respectively. The results show that the application time of composite flooding should be at the end of the effective mobility control time of polymer flooding after the disappearance of polymer action. The timing is also when the adsorption and retention of polymer solution in porous media has little influence on the water cut law in the subsequent water flooding process. Viscosity of polymer solution has little effect on the mobility control of subsequent water flooding, but RRF has greater effect. Increasing RRF can effectively prolong the effective flow control of polymer flooding. Among the solution properties of the composite system, the contribution of solution viscosity is relatively larger, accounting for 54.88%. After considering the effect of the complete polymer flooding control process (polymer flooding + subsequent water flooding = displacement of 0.44 PV), a composite system with a viscous system as the main component (100200 mPa
    Keywords: polymer flooding; mobility control; combination flooding; application timing; oil displacement effect.

  • The spatial distribution of the strike angles derived from EIGEN 6C4 gravity model - A new possibility for oil&gas exploration?   Order a copy of this article
    by Jaroslav Klokocnik, Jan Kostelecky, Ales Bezdek, Vaclav Cilek 
    Abstract: We discovered a correlation between the combed strike angles (one of the gravity functions derived from a gravity field model) and regions with oil, gas, shale gas deposits or ground water, paleolakes or impact craters. The spatial distribution of the combed strike angles may indicate a new cheap and accessible geophysical tool for recognition of some potential oil and gas areas. We work with the global gravity field model EIGEN 6C4 providing a ground resolution of about 10 km and a precision typically 10 mGal. First we test the well-known oil/gas fields; this attests the success of the proposed methodology. Then we extrapolate outside the known zones. The new method may be an inexpensive tool for frontier areas in terms of decreasing the risk of deposit exploration. An extensive supplementary material is available.
    Keywords: Oil/gas exploration theory; Oil/gas exploration methodology; Physical geodesy; Satellite gravimetry; Earth's gravity field models; EIGEN 6C4 gravity field model; Geoapplications; Gravity aspects (descriptors); Gravity disturbancies; Marussi tensor; gravity aspects; virtual deformations; Combed strike angles; Correlation between combed strike angles and oil/gas deposits; Impact craters.

  • An Efficient Design for a Downhole Water Loop to Control Water Production from Oil Wells   Order a copy of this article
    by Mohammadsajjad Zeynolabedini, Mehdi Assareh 
    Abstract: Water production in oil and gas wells is an important problem regarding water treatment costs and environmental constraints. Down-hole water loop (DWL) production is one of the techniques to decrease water production. This method produces water from upper part of water zone and reinjects water back to lower part of this zone to prevent water upward movement to oil zone. An optimized design of DWL is important to decrease produced water, which is addressed in this work based on a case study from literature. At the beginning, a comparative study of conventional production and DWL is performed, to show DWL relative importance, based on decrease in watercut and increase in oil production rate. The net present value (NPV) of DWL technique is 4.52E+07 [$], while the NPV of conventional production is 3.26E+07 [$]. Prior to optimization, DWL sensitivity to the opening lengths, distance between upper and lower openings in water zone (water drainage-injection distance or D/I spacing) and water drainage rate are analyzed. Two different optimization procedures, sequential and simultaneous, are applied to find an optimized design. The NPVs are improved in this way considerably, from 4.52E+07 [$] to 7.07E+08 [$] in simultaneous mode and 6.99E+08 [$] in sequential mode. Finally, anisotropy effects are analyzed, and it is shown that by increasing the anisotropy ratio, NPV decreases, since tendency of water invasion to oil zone increases.
    Keywords: Production operation; Down-hole water loop; Oil wells; Stochastic optimization; Water production Control.

  • Experimental study and CFD investigation of environment friendly drilling fluid   Order a copy of this article
    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.
    DOI: 10.1504/IJOGCT.2020.10029376
  • Development of oil-based drilling fluid using iron oxide magnetic (Fe3O4) with superior properties leading to real time rheological control   Order a copy of this article
    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.
    DOI: 10.1504/IJOGCT.2019.10023858
  • Analysis of fluid property variations across the Barnett and Eagle Ford Shale using fuzzy logic   Order a copy of this article
    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.
    DOI: 10.1504/IJOGCT.2020.10029343
  • Assessing the influence of key parameters on an iterative ensemble-based method   Order a copy of this article
    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.
    DOI: 10.1504/IJOGCT.2020.10029379
  • Investigating reservoir stresses and strain effects during production from coal bed methane gas reservoir on reservoir properties and gas production – a numerical study   Order a copy of this article
    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.
    DOI: 10.1504/IJOGCT.2020.10029342
  • Biodiesel production from waste cooking oil using copper doped zinc oxide nanocatalyst – process optimisation and economic analysis   Order a copy of this article
    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.
    DOI: 10.1504/IJOGCT.2020.10029377

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   Order a copy of this article
    by Ali Oz 
    Abstract: This study was conducted to investigate the effect of diesel fuels on in-cylinder pressure, engine performance and exhaust emissions. In this study, common-rail diesel engine was used with a cylinder volume of 1,500 cc. The engine was operated at 1,750 rpm and 40-100 Nm fixed engine loads. Besides, diesel fuel without any addition and L5Cu-added diesel fuel with four variables at 60 Nm of engine torque was examined by multivariate regression analysis, and pressure equations were produced. As a result, the engine at 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 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. [Received: March 30, 2020; Accepted: April 26, 2020]
    Keywords: common-rail diesel engine; L5Cu additive; engine performance; in-cylinder pressure; exhaust emissions; multivariate regression method.
    DOI: 10.1504/IJOGCT.2020.10030038
  • Automated char classification using image analysis and artificial intelligence   Order a copy of this article
    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 devolatising of coal during combustion of it and signify the foremost step in the ignition method. Char particles are categorised 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 characterisation may be executed automatically with advantages like fast processing and consistency. In this article, we attempt to suggest an automated scheme for classification of char into its reactive and non-reactive groups using image analysis and artificial intelligence methods. Subsequently, the proposed system is recognised to be an efficient technique for characterisation of char with more accurate results in reduced computational time. [Received: 20 December 2019; Accepted: 26 April 2020]
    Keywords: coal; char; image analysis; artificial intelligence; deep learning.
    DOI: 10.1504/IJOGCT.2020.10032803
  • Relationship between microstructure and fracture toughness in B2O3-doped 8YSZ ceramics   Order a copy of this article
    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.

  • A New Algorithm to Improve Energy Efficient of Coal-Fired Thermal Power Plant by Determining Optimum Excavation Parameters in Opencast Lignite Mines   Order a copy of this article
    by Ali Can OZDEMIR, Ahmet DAG 
    Abstract: An essential problem in the production of lignite is the produced lignite fail to meets the working conditions of the coal-fired thermal power plant. This leads both an increase in the unit energy cost and a decrease in energy efficiency. This study was aimed that these problems would be eliminated by determining the optimum excavation parameters which minimized the standard deviation value of the calorific value. Therefore, computer software was developed for the lignite mines having low calorific value and working with the bucket wheel excavator. This software was applied to K??lak
    Keywords: Thermal Power Plant; Opencast Lignite Mine; Excavation Parameter; Optimization; Energy Efficiency.