International Journal of Oil, Gas and Coal Technology (36 papers in press)

Regular Issues

• X-ray photoelectron spectroscopy investigation of nitrogen and sulphur functionalities during pyrolysis of Dongqu coal mine and Yachen coal mine of Shanxi province  
  by Meihua Wang, Yunkun Wang, Chao Bu, Yu Feng, Xudong Zhao, Wen Yang 
  Abstract: In this paper, samples from Dongqu coal mine and Yachen coal mine in Shanxi Province were pyrolysed at 300 to 900?. The X-ray Photoelectron Spectroscopy (XPS) was carried out to study the occurrence characteristics of nitrogen and sulphur in raw coal and semi-coke coal at different temperatures. The results showed that with the increase of pyrolysis temperature, pyrrole transforms into pyridine; quaternary nitrogen content decreases gradually; and nitrogen oxide content increases first and then decreases at high temperatures. The inorganic sulphur in coal is transformed into organic sulphur at high temperatures, and thiol (thioether) and pyrite in both coals are decomposed completely at 600?. Desulphurisation should focus on unstable and abundant inorganic sulphur. Understanding the occurrence characteristics and transformation rules of nitrogen and sulphur in coal through the results of this study is of great significance for promoting coal processing and utilisation, and reducing environmental pollution. [Received: January 14, 2024; Accepted: July 07, 2024]
  Keywords: X-ray photoelectron spectroscopy; XPS; Dongqu coal mine; Yachen coal mine; semi-coke; elements; occurrence characteristic.
  DOI: 10.1504/IJOGCT.2025.10071891
   
  
• Advancing drag coefficient correlations for non-spherical particles in power-law fluids  
  by Can Polat 
  Abstract: This study addresses the critical challenge of predicting the settling velocity of non-spherical particles in non-Newtonian fluids. Two established correlations between drag coefficient and particle Reynolds number were refined to enhance their applicability to non-spherical particles in Power-law fluids. A systematic analysis of model coefficients across varying particle sphericities revealed the necessity of quantifying the coefficients with particle shape. By incorporating sphericity and optimising model parameters using experimental data, the complex interplay between drag coefficient, particle Reynolds number, and particle shape is captured, demonstrating improved flexibility at low particle Reynolds numbers and accurate representation of upward concavity observed at high particle Reynolds numbers. These improvements are reflected as a decrease in mean relative errors over a wide range of particle Reynolds numbers and sphericities, and in the predictive capability demonstrated in model validation tests. [Received: February 15, 2025; Accepted: May 31, 2015]
  Keywords: settling velocity; drag coefficient; particle Reynolds number; power-law fluids; non-spherical particles.
  DOI: 10.1504/IJOGCT.2025.10071910
   
  
• Performance and emission analysis of a homogeneous charge compression ignition engine fuelled with compressed natural gas  
  by Naveen Kumar, Pawan Kishore Jha, R.C. Singh 
  Abstract: The present study investigates the impact of different HCCI percentages on key engine parameters such as brake thermal efficiency (BTE), volumetric efficiency, exhaust gas temperature (EGT), and gaseous emissions, including NOX, HC, and CO. A data acquisition unit (DAU) was used to control the auto-ignition timing of the HCCI mode, ensuring precise and consistent combustion at different operating conditions. The results suggest that 20% HCCI offers the best trade-off of performance and emissions, achieving high brake thermal efficiency (BTE) with minimal HC and CO emissions. Higher HCCI percentages lower BTE and volumetric efficiency due to reduced combustion temperatures and intake air displacement, while NOX emissions significantly decrease at 60%-80% HCCI, though HC and CO emissions rise beyond 40% due to incomplete combustion. CO2 emissions increase with load but decline at higher HCCI levels, whereas O2 emissions remain largely stable. HCCI technology presents a promising pathway for cleaner and more efficient engines, supporting sustainable transportation with continued refinement. [Received: 4 April 2025; Accepted: 22 May 2025]
  Keywords: compressed natural gas; CNG; emission; engine performance; ethanol; HCCI diesel engine.
  DOI: 10.1504/IJOGCT.2025.10072263
   
  
• Study on the disturbance law of natural fracture on ground stress field  
  by Zhaohui Dai, Qin Li, Siyang Qiu, Xiangyi Yi, Wenling Chen, Ying Sun 
  Abstract: The change of in-situ stress field in reservoir has a significant effect on the stability of natural fractures and the effectiveness of hydraulic fracturing. Based on the theory of fracture mechanics, a two-dimensional numerical model of reservoir rock disturbed by natural fractures is established, and the variation law and influence range of stress field around natural fractures are simulated by finite element method. The results show that: 1) the existence of natural fractures disturbs the magnitude and direction of the in-situ stress field. The range of stress disturbance increases quadratically with the increase of natural fracture length; 2) according to the compressive and tensile stress, different regions can be quantitatively divided around the natural fracture. When the natural fracture angle is 30 - 60, the stress disturbance is the most obvious; 3) the degree of stress concentration at both ends of natural fractures is positively correlated with stress difference or Youngs modulus. [Received: March 28, 2024; Accepted: June 28, 2024]
  Keywords: ground stress field; natural fracture; geo-stress balance; stress-deflection; stress disturbance range.
  DOI: 10.1504/IJOGCT.2025.10072286
   
  
• Crossing the digital Rubicon: innovation pathways and strategic choices in Chinas coal industry transformation  
  by Xue Lei, Xueguo Xu, Huijuan Qiao 
  Abstract: This study examines how digital transformation impacts total factor productivity (TFP) in Chinese coal enterprises through technological innovation. Using panel data from A-share listed coal companies (2012-2022), we find that digital transformation significantly enhances TFP by fostering innovation in decision making, production techniques, and business models. We uncover a nuanced relationship between government subsidies and innovation: moderate subsidies amplify digital transformations positive effects, while excessive subsidies may crowd out independent innovation. Managerial short-termism can impede technological advancement and diminish digitalisation benefits. Heterogeneity analysis shows digitalisations positive impacts are more pronounced in central regions and state-owned enterprises. This research contributes to the discourse on industrial policy, technological change, and sustainable development in carbon-intensive industries. It offers insights for policymakers navigating energy transition, emphasising the importance of balanced government support, long-term managerial vision, and targeted digital strategies in fostering innovation and productivity growth. [Received: February 4, 2025; Accepted: July 2, 2025]
  Keywords: digital transformation; total factor productivity; TFP; technological innovation; coal industry; energy transition.
  
  
• Optimised design and evaluation of cement slurry for HPHT well integrity in Basin X  
  by Hai T. Nguyen, Khaled A. Elraies, Tarek Al-Arbi Ganat, Tu V. Truong 
  Abstract: This study presents the development and evaluation of a high-performance cement slurry specifically engineered for the complex high-pressure, high-temperature (HPHT) conditions of Basin X, offshore Vietnam. Unlike generalised HPHT slurry formulations in prior studies, this research addresses a region-specific challenge, incorporating a customised combination of silica-based stabilisers, synthetic retarders, and manganese tetroxide weighting agents to mitigate strength retrogression and ensure long-term well integrity. The slurry demonstrated exceptional performance, achieving a mixability rating of 4/5, stable rheological behaviour across temperature ranges (plastic viscosity of 50 cP; yield point of 20 lb/100 ft2), and fluid loss under 50 ml/30 minutes. It maintained thickening times suitable for placement even at elevated temperatures and reached compressive strengths of 474.1 psi at 12 hours and 931.5 psi at 24 hours. By addressing both operational risks and geological challenges unique to Basin X, this study delivers a tailored, field-tested slurry design that advances HPHT cementing practices and supports safe, reliable well operations under extreme subsurface conditions. [Received: October 4, 2024; Accepted: July 2, 2025]
  Keywords: high-pressure; high-temperature; HPHT; slurry design; production liner; cement additives; strength retrogression; early setting.
  DOI: 10.1504/IJOGCT.2025.10072649
   
  
• Sensitivity and critical values of prediction indexes of gas outburst of composite coal seams based on energy theory  
  by Weiwei Su, Yujin Qin, Shouqing Lu 
  Abstract: The accurate prediction of gas outbursts plays a crucial role in preventing and managing these events, which can have devastating effects on the safety of miners. In order to improve the accuracy, a new model for gas expansion energy was developed based on energy theory and combined with both steady diffusion and unsteady diffusion models. The relationship between outburst energy, regional prediction indexes, and coal seam depth was discussed, it is proposed that for soft and hard composite coal seams (SHCS), the gas content, with a critical value of 9.00 m3/t, was determined as the regional prediction index. Mover, it was discovered that local prediction indexes were significantly responsive to alterations in gas pressure. Notably, the K1, with a critical value of 0.60 mL/(g min0.5), was identified as the primary local prediction index. The results of these investigations establish a robust theoretical basis for enhancing the precision of gas outburst prediction indexes. [Received for review: June 2, 2024; Accepted: March 7, 2025]
  Keywords: soft coal; composite coal seams; regional prediction index; local prediction index; outburst energy.
  DOI: 10.1504/IJOGCT.2025.10072802
   
  
• Forecasting future demand for coal, oil and gas: application with related to smart cities  
  by Ravi Kumar 
  Abstract: Forecasting future demand for coal, oil, and gas is essential for ensuring energy security, optimising resource allocation, and supporting strategic planning - particularly in the context of developing smart cities. This study explores advanced forecasting techniques to predict the consumption patterns of fossil fuels, using a data-driven framework that integrates historical consumption trends, economic indicators, and environmental policies. The objective is to enable policymakers and urban planners to make informed decisions that balance energy needs with sustainability goals. By applying machine learning algorithms and time-series models, the analysis offers insights into future energy demand under different scenarios. The results highlight the ongoing importance of coal, oil, and gas in urban infrastructures, while also emphasising the need for a gradual transition to renewable sources. This research provides a valuable tool for smart cities to plan their energy mix, reduce emissions, and align with global climate objectives through proactive energy demand forecasting. [Received: January 20, 2025; Accepted: July 23, 2025]
  Keywords: smart meter data: communication: data pre-processing: benchmark models: natural gas: smart meter dataset.
  DOI: 10.1504/IJOGCT.2025.10072952
   
  
• Study on gas-water-sand-hydrate foam flow and discharge in the wellbore during hydrate depressurisation production  
  by Haitaio Li, Xuefei Zhang, Na Wei, Jianyong Feng, Zhaolong Ge, Shuning Yi, Liehui Zhang, Bjørn Kvamme, Richard Banks Coffin 
  Abstract: To address sand and water production in hydrate reservoirs that affect the production efficiency, this study innovatively considers the application of foam drainage to hydrate production scenarios. Using a multi-physics field coupling approach, a numerical model of continuous foam drainage in wellbores based on the liquid- and solid-carrying models and other models is developed, and its evaluation accuracy was verified to be up to 95% by comparing with the indoor experimental data. Correlation factor analysis showed that increasing nitrogen injection rate, gas production rate and gas-liquid ratio enhanced liquid and solid transport efficiency. However, both excessive foam viscosity and overly low viscosity adversely affect system performance. Under South China Sea hydrate trial conditions, the study employed model predictions and multi-factor analysis to determine optimal foam injection rates for varying water/sand production levels. The findings provide theoretical guidance for optimising continuous foam drainage technology in hydrate wells, aiding in productivity enhancement. [Received: May 18, 2025; Accepted: July 8, 2025]
  Keywords: foam drainage; wellbore fluid accumulation; reservoir sand production; natural gas hydrate; numerical simulation.
  DOI: 10.1504/IJOGCT.2025.10073241
   
  
• Developing a novel correlation for the design of vane-type demisters in two-phase separators  
  by Mehdi Fadaei, Mohammad Javad Ameri, Yousef Rafie, Mahdi Hosnani, Mehran Ghasemi 
  Abstract: Among the various components that affect the performance of multi-phase separators, vane type demisters are particularly significant. In this study, we evaluate a chosen correlation by considering a gas-liquid separator pilot. In this paper, we utilised the Souders-Brown and Burkholz correlations to design the vane type demisters. We conducted laboratory experiments to investigate the performance of the manufactured vane type demisters under controlled conditions. To minimise the discrepancy between experimental and theoretical outcomes, an adjustment factor must be applied to the equations. Additionally, we developed a CFD model to simulate the vane type demister, which was then validated using the experimental data. We have generated additional supplementary data in order to develop a dimensionless curve to calculate the correction factor for the Souders-Brown and Burkholz correlations for field operations. This factor can be used to predict the performance of a vane-type demister under various operational conditions. [Received: May 1, 2024; Accepted: August 7, 2024]
  Keywords: novel; correlation; design; vane; demisters; separators.
  DOI: 10.1504/IJOGCT.2025.10073250
   
  
• Numerical simulation of hydraulic fracture propagation in hot dry rock reservoirs integrating wellbore-reservoir-fracture  
  by Dagang Ji, Jingen Deng, Yongcun Feng, Xiaorong Li, Shuai Zhang 
  Abstract: Hot dry rock (HDR) represents a typical high-temperature, ultra -low permeability reservoir, where hydraulic fractures must be created to provide efficient heat-exchange pathways for geothermal energy extraction. In this paper, a fully thermal-hydro-mechanical (THM) coupled numerical model for HDR reservoirs’ hydraulic fracturing was established to study the hydraulic fracture propagation mechanism and reservoir mechanical response characteristics under low-temperature shock. The half-fracture length calculated by the KGD model was compared with the simulation results to verify the model's accuracy. The results show that the tensile stress and temperature gradient at the low-temperature shock boundary are relatively high. After the rock fractures, the temperature and tensile stress values inside the rock decrease but their range expands. The hydraulic fracture morphology is more sensitive to reservoir temperature than to the thermal expansion coefficient. Furthermore, the temperature hysteresis effect produced by the increase in injection displacement reduces the thermal stress at the fracture tip. [Received: September 6, 2024; Accepted: August 11, 2025]
  Keywords: rock mechanics; hot dry rock reservoirs; fracture propagation; thermal-hydro-mechanical coupled.
  DOI: 10.1504/IJOGCT.2025.10073280
   
  
• Study on the self-healing law of cracks in borehole sealing materials based on mineralisation reaction  
  by Leilei Si, Tongyu Zhao, Jianping We, Banghua Yao, Yiran Zhu, Boyang Zhang 
  Abstract: Gas disasters threaten coal mine safety, necessitating effective sealing methods for gas extraction. This study proposes self-healing borehole-sealing (SHBS) material based on complexation-precipitation principles to address traditional grouting's limitations caused by secondary cracks. Experiments revealed SHBS achieved self-healing in 24 h for 0.82 mm cracks and 48 h for 1.49 mm cracks. Comparative analyses (SEM/XRD/Raman) showed SHBS contains unique minerals like wollastonite and cancrinite alongside conventional hydration products. Self-healing products primarily consist of calcium carbonate, quartz, albite, and anorthite formed through carbonation and secondary hydration. Reaction equations explain carbonate/silicate/aluminate formation mechanisms. The material demonstrates potential for enhancing gas drainage efficiency by sustaining seal integrity through autonomous crack repair, offering a promising solution for prolonged mine safety. [Received: July 15, 2024; Accepted: July 31, 2025]
  Keywords: crack self-healing; gas extraction; grouting sealing; self-healing products; carbonation.
  DOI: 10.1504/IJOGCT.2025.10073434
   
  
• Geopolitical dynamics and the sustainable future of global energy supply chains  
  by Saurav Negi, Shantanu Trivedi 
  Abstract: The ongoing geopolitical crisis in Europe has had a global impact on the energy sector, underscoring the pivotal role that geopolitics plays in stabilising or destabilising energy supply chains. Beyond the immediate disruption, this crisis imparts valuable lessons for future resilience in global energy management. Amid an environment shaped by energy market volatility, resource scarcity, and climate concerns, this study examines the current state of the energy supply chain and the profound influence of geopolitical factors on its security and sustainability. Using a narrative literature review approach, this paper examines how geopolitical factors, including the RussiaUkraine conflict and Middle East tensions, influence energy security and accelerate the transition toward renewable and low-carbon energy solutions. The findings reveal critical insights into the operational state of the energy supply chain, illustrating how geopolitics is influencing energy security and sustainability efforts. The study also outlines a pathway forward, encouraging stakeholders to adopt a holistic perspective that includes all significant influences on the energy ecosystem. This paper offers comprehensive recommendations for sustainability strategies and policies that integrate considerations for energy security, environmental sustainability, and geopolitical risk. [Received: December 14, 2024; Accepted: August 20, 2025]
  Keywords: energy supply chain; energy security; sustainability; geopolitical crisis; supply chain resilience.
  DOI: 10.1504/IJOGCT.2025.10073511
   
  
• Multi-dimensional integrated monitoring 3D model and high-precision real-time analyzing method of multipoint microleakage field in the well site of underground gas storage  
  by Xianjian Zou, Weimin Han, Feng Chen, Huan Song 
  Abstract: This study addresses significant challenges including low detection accuracy, multiple placement points, diverse influencing factors, and unstable performance of microleakage detection sensors at underground gas storage well sites. It proposes a point-line-surface multidimensional integrated monitoring 3D model for well site layout and a cost-effective, high-precision real-time analysis method for multipoint microleakage fields. Two or three point-type natural gas sensors and one linear-type laser methane detector were amalgamated to monitor potential gas leakages at key points on the well site in real time. To achieve high-precision real-time monitoring and early warning of natural gas leakages across the entire well site, a point-line-surface multidimensional integrated monitoring 3D model was developed. This model was used to simulate the multipoint microleakage patterns of the well site, followed by an analysis of the microleakage field using a cost-effective, real-time analysis method, reducing the false alarm rate of safety monitoring and early warning systems. [Received: March 20, 2025; Accepted: June 19, 2025]
  Keywords: underground gas storage; microleakage model; safety monitoring; multi-dimensional integration; laser sensor.
  DOI: 10.1504/IJOGCT.2025.10073659
   
  
• Contemporaneous and lagged transmission mechanism among geopolitical risks, uncertainty and energy prices: a spatial heterogeneity perspective  
  by Shuiyang Chen, Bin Meng, Wenyu Xu 
  Abstract: Due to market spatial differentials, geopolitical risks and uncertainty from various sources exhibit diverse transmission mechanisms, both contemporaneous and lagged, in the globalised energy market. We employ geopolitical risk indices for six major global regions and utilise a novel connectedness approach to analyse the heterogeneous impacts of various sources of geopolitical risks and uncertainty on the energy market. Our findings indicate that geopolitical risks in Europe (North and East) and North America wield the greatest influence. Asia and Oceania, along with South America, significantly impact the energy market. The US economic policy uncertainty demonstrates a stronger explanatory power for energy prices. The total connectedness is 92.61%, with 56.18% caused by contemporaneous dynamics while 36.43% the lagged. Lagged dependencies elucidate a substantial portion of the market risk dynamics. Major geopolitical conflicts result in reduced contemporaneous shocks and heightened lagged shocks. Our conclusions underscore the need for policymakers and traders to discern the heterogeneous impacts and lagged effects of diverse geopolitical risks and uncertainty on the energy market, ensuring comprehensive risk management and robust trading decisions. [Received: November 15, 2024; Accepted: July 23, 2025]
  Keywords: geopolitical risk; uncertainty; energy market; connectedness; spatial heterogeneity.
  DOI: 10.1504/IJOGCT.2025.10073681
   
  
• Different treatment techniques of oilfield produced water - a review  
  by Aarzoo Mayur Jobanputra, Balasubramanian Ragunathan, Swastik Mazumder, Aastha Maurya, Arth Padaria 
  Abstract: Oilfield produced water (OPW) is an inextricably linked component in crude oil recovery processes. It is the most significant type of waste generated during hydrocarbon production. It contains high concentrations of organic and inorganic salts, heavy metals and sand particles. Exploration and production operations also generate large volumes of brine water. Due to the complex and hazardous composition of OPW, it cannot be discarded into the environment. With respect to the global rise in industrial activities, crude oil production has increased considerably, subsequently, the generation of OPW. This makes it necessary to manage OPW in a sustainable and eco-friendly manner. Currently, the focus is on treating OPW to make it suitable for reuse. Various physicochemical and biological methods are used for its treatment. This article discusses the reuse of OPW and different treatment methods. The regulation of different parameters such as oil-in-water in OPW, as employed by the industry are reviewed. [Received: March 30, 2024; Accepted: February 21, 2025]
  Keywords: exploration; petroleum; produced water; treatment methods.
  DOI: 10.1504/IJOGCT.2025.10074387
   
  
• Condensation pattern of moist blast furnace gas in pipelines  
  by Yuwen Liu, Xinmin Liu, Dawei Zhang, Wenqiang Sun 
  Abstract: During pipeline transport, acidic condensate containing chloride ions precipitates from dry-dedusted blast furnace gas (BFG) as its temperature decreases. To investigate the mechanisms of this phenomenon, this study analyses heat transfer processes in BFG condensation within pipelines and proposes a computational model to predict condensate formation. Using this model, the study determines the amount and location of condensate precipitation under different ambient temperatures, and variations in BFG temperature, pressure, pH, and chloride ion concentration along the pipeline. Computational results indicate that at 20 C ambient temperature, condensate starts precipitating at 1,100 m from the pipeline inlet. When ambient temperature decreases to -10 C, the precipitation point shifts to 2,200 m from the inlet. Lower ambient temperatures result in condensate forming farther from the pipeline inlet. [Received: March 26, 2025; Accepted: July 14, 2025]
  Keywords: blast furnace gas; BFG; condensate; chloride ion; pipeline transport; computational modelling.
  DOI: 10.1504/IJOGCT.2025.10074502
   
  
• Risk analysis and safety enhancement for tank inspection and maintenance using track cross theory and vortex tube technology  
  by Xing Chen, Peng Wang, Dongxu Gao, Rui Huang, Li Liang 
  Abstract: The inspection and maintenance of storage tanks are essential daily tasks in the production and operation of oil and gas fields. Based on on-site production analysis, the primary issues include a poor working environment (characterised by high temperatures and low oxygen levels) and operation process risk (such as unclear worker status and improper procedures). This study utilised on-site production practices to explore and implement two technologies namely, the risk control system and vortex tube technology in the inspection and maintenance of storage tanks. The research yielded remarkable results. Test results indicate that: 1) the risk control system effectively strengthens supervision during operations, monitors risk points with the assistance of mechanical devices, and mitigates the impact of personnels inadequate safety awareness and technical skills; 2) the application of vortex tube technology significantly improves working conditions within confined spaces by regulating temperature and continuously supplying air, thereby ensuring the physical well-being of personnel. [Received: July 28, 2025; Accepted: September 24, 2025]
  Keywords: risk control system; vortex tube; storage tank; confined space; occupational safety.
  DOI: 10.1504/IJOGCT.2025.10074754
   
  
• Predicting model of natural gas price based on a multi-strategy GWO-LSTM algorithm  
  by Hanyu Xie, Changjun Li, Wenlong Jia, Jie He 
  Abstract: The price of natural gas fluctuates in the stock market, thus an accurate price prediction is a key indicator for the development of medium and long-term planning in the industry. Here, the daily price fluctuation of natural gas is treated as a nonlinear and non-stationary time series prediction. The LSTM model and the LSTM combined with the grey wolf algorithm were adopted for training and testing. A multi-strategy GWO-LSTM model is proposed, which improves the global search ability and convergence speed by using chaotic variable search to replace random search, adding adaptive weight coefficient, and modifying control parameters. The prediction of the improved model compared with other methods is carried out using Henry Hub gas price data, which has been logarithmically processed to improve the distribution characteristics and remove the outliers. The improved algorithm has better performance in the convergence speed, prediction error, and stronger adjustment of trend fluctuation. [Received: July 12, 2024; Accepted: January 9, 2025]
  Keywords: natural gas price; neural network; long short-term memory; LSTM; prediction algorithm.
  DOI: 10.1504/IJOGCT.2026.10075629
   
  
• Mechanical properties and acoustic-emission energy-frequency characteristics of gas-bearing coal under different stress paths  
  by Erhui Zhang, Baokun Zhou, Changfeng Li, Chaoyang Zhu, Liang Sun 
  Abstract: Gas-bearing coal-rock dynamic hazards threaten mining safety, but their mechanisms under complex stress paths are unclear. This study examined the mechanical properties and acoustic emission (AE) energy-frequency characteristics of gas-bearing coal under three stress paths: meso-shear, confining pressure unloading, and triaxial compression. Key findings include: 1) different paths caused significant variations in the size and location of Mohr stress circles due to changes in effective stress and stress differences; 2) The AE energy-frequency fractal characteristics showed a consistent damage evolution pattern across all paths initial fluctuation, followed by a steady decrease, and a final drop to a minimum at rupture though specific values and evolution rates differed; 3) the average fractal dimension increased with gas pressure and was highest under meso-shear, followed by confining pressure unloading and triaxial compression. These results offer insights for early warning of coal-gas disasters and improved coalbed methane extraction. [Received: September 11, 2024; Accepted: September 21, 2025]
  Keywords: gas-bearing coal; different stress paths; acoustic emission energy frequency; strength properties; fractal dimension.
  DOI: 10.1504/IJOGCT.2026.10075630
   
  
• Research on the prediction method of rock uniaxial compressive strength using digital drilling technology  
  by Zhaoyu Wen, Mingming He, Mingchen Ding, Haoteng Wang, Qin Zhao 
  Abstract: The uniaxial compressive strength (UCS) of rock is one of the key indicators for evaluating its mechanical properties. This study employed self-developed equipment to conduct drilling experiments on sandstone and limestone. The segmented drilling method enhanced data continuity, accuracy, and controllability. Results showed that the uniaxial compressive strength (UCS) obtained by this method had lower variability, with the average value in the second stage being 4.42 MPa higher than in the first stage. The friction coefficient, derived from the relationship between drilling parameters and cutting force, combined with rock type, was used to establish a UCS prediction model. The discrepancy between model-predicted UCS values and those from uniaxial compression tests was only 4.44%, verifying the method s reliability. This study provides an efficient in-situ assessment method for rock mechanical properties. [Received: October 31, 2024; Accepted: December 6, 2024]
  Keywords: digital drilling; uniaxial compressive strength; segmented drilling method; model prediction.
  DOI: 10.1504/IJOGCT.2026.10075851
   
  
• Study on flow-induced variations in permeability characteristics of silty clay sediments from the perspective of fine migration and channelisation  
  by Man Huang, Dongchao Su, Zhirui Zhao, Yuzhe Cheng, Yiheng Ma, Yajie Mao, Zhun Zhang, Fulong Ning 
  Abstract: The well productivity is closely related to the permeability of sediments left by the decomposition of natural gas hydrate (NGH). To investigate the permeability evolution of silty clay sediments under fluid flow, column flow experiments were conducted with reconstituted sediment samples from core data in the Shenhu Sea Area. The results indicate that fluid flow can remarkably change the permeability of clay silty sediments. Even a small flow rate can reduce sediment permeability. There exists a critical flow rate that can improve sediment permeability. At a certain flow rate, the permeability fluctuates irregularly rather than monotonic variation. As the flow rate increases, the sediment average permeability first decreases then increases and finally decreases. The large porosity, increased fine sand content, and high clay content aggravate the flow-induced permeability damage. The work provides a reference for stimulation and protection of NGH reservoirs. [Received: December 12, 2024; Accepted: March 27, 2025]
  Keywords: natural gas hydrate; NGH; clay silty sediments; flow-induced permeability variations; fine migration; channelisation.
  DOI: 10.1504/IJOGCT.2026.10076051
   
  
• FAME analysis and chromatographic studies of sunflower oil biodiesel  
  by Vishal Kumar, Debasish Das 
  Abstract: This article explains about the base-catalysed transesterification process that was used to extract sunflower biodiesel from the sunflower seeds of Indian origin. The experiment was conducted at optimum conditions of 60 C reaction temperature, with a 9:1 (methanol/oil) molar ratio, 0.45% w/w KOH catalyst and 350 rpm stirring speed for 60 minutes. The base catalysed transesterification technique is used to produce biodiesel with an optimal yield (89%). GC-MS is currently being utilised to investigate the methyl esters of biodiesel generated from sunflower oil. The efficacy of gas chromatography-mass spectrometry (GC-MS; Shimadzu, Japan) was tested in the analysis and detection of FAME-fatty acid methyl ester content in sunflower biodiesel. Using FAME analysis, the fuel characteristics of sunflower oil biodiesel were also calculated and discussed in relation to ASTM D6751 standards for biodiesel. [Received: April 14, 2023; Accepted: April 18, 2025]
  Keywords: sunflower biodiesel; transesterification; methyl esters; characteristics; FAME analysis.
  DOI: 10.1504/IJOGCT.2026.10076175
   
  
• Machine learning-based prediction strategy for sustainable diesel engine operation using a tri-fuel blend  
  by Naseem Khayum, Jakeer Hussain Shaik, Krishna Kumar Pandey, Y. Nandakishora 
  Abstract: The investigation involves the introduction of acetylene at different flow rates to evaluate its effects on critical performance and emission parameters of a low heat rejection (LHR) diesel engine run on ternary blend. Advanced machine learning methodologies, especially random forest regression (RFR) and polynomial regression (PR), are utilised to forecast the engine’s performance and emissions. The findings demonstrate that the LHR engine, powered by the ternary blend and augmented with acetylene induction, exhibits a large improvement in brake thermal efficiency (BTE) and substantial decreases in hydrocarbon (HC) and carbon monoxide (CO) emissions and nevertheless, there is a simultaneous increase in NOx emissions. RFR demonstrates more accuracy in predicting performance and emission characteristics than PR among the utilised predictive models. Furthermore, the utilisation of machine learning models demonstrates significant efficacy in precisely forecasting engine performance and emission metrics, providing a dependable approach for enhancing engine operations. [Received: January 24, 2025; Accepted: July 3, 2025]
  Keywords: acetylene; ternary blend; low heat rejection diesel engine; machine learning.
  DOI: 10.1504/IJOGCT.2026.10076374
   
  
• Leakage detection method of acoustic emission pipeline based on deep convolutional neural network transfer learning  
  by Xinying Wang, Haojie Tian, Honglei Che, Haiqun Chen 
  Abstract: In this study, we propose a transfer learning method based on a deep convolutional neural network (DCNN-TL), where a gas pipeline system simulates various degrees of pipeline leakage with valve openings, generating original acoustic emission (AE) signal data under different conditions. We convert the AE signals into three-channel images, denoise them using Gaussian-non-local mean (G-NLM) joint filtering, and use these as input for a convolutional neural network (CNN). Six pre-trained CNN models undergo iterative training. The results show that the average accuracy of the pre-trained CNN model on the AE image dataset improves by 3.35%, 9.02%, 5.35%, 6.74%, 10.09%, and 4.80%, respectively. This method avoids reliance on expertise and complex signal processing, is computationally efficient, and enables precise pipeline leak detection in various operational scenarios. [Received: February 18, 2025; Accepted: July 3, 2025]
  Keywords: convolutional neural network; CNN; transfer learning; acoustic emissions; pipeline leak detection.
  DOI: 10.1504/IJOGCT.2026.10076495
   
  
• Data-driven analysis and predictive modelling of PDC and tricone bit performance in field drilling operations  
  by Azirulkheen Song Bin Muhamad Azlan, Bashir Suleman Busahmin, Amer Dermirovic 
  Abstract: Bit type and controllable drilling parameters strongly influence rate of penetration (ROP), torque/drag, and non-productive time (NPT). This study compares field performance of polycrystalline diamond compact (PDC) and tricone bits and develops predictive models for ROP and bit wear using multi-well metadata and surface drilling measurements. After quality control and data imputation, key features including mechanical specific energy (MSE), depth-normalised weight on bit (WOB), and torque were engineered. Gradient boosting, XGBoost, and elastic net models were evaluated for ROP prediction, while logistic regression, random forest, and XGBoost were applied for wear classification using grouped cross-validation. Results show that PDC bits achieve higher ROP at comparable WOB but are more sensitive in interbedded formations, whereas tricone bits require higher torque yet maintain steadier MSE in abrasive intervals. The proposed workflow supports data-driven bit selection and parameter optimisation to reduce bit-related NPT while balancing ROP and cost per meter. [Received: 18 August 2025; Accepted: 16 October 2025]
  Keywords: PDC bit; tricone bit; bit wear prediction; rate of penetration; ROP; stick-slip; non-productive time; NPT.
  DOI: 10.1504/IJOGCT.2026.10076496
   
  
• The formation mechanism of laumontite and its effect on reservoir quality in Upper Triassic Chang-63 tight oil sandstones, Ordos Basin  
  by Guichao Du, Qianshan Zhou, Ruiliang Guo, Yuanhao Li, Mingxian Wang, Ying Wang, Xingyu Huang 
  Abstract: Based on porosity-permeability measurements, thin-section petrography, SEM observations, and XRD analyses, the diagenetic features of sandstones from the Chang 63 reservoir were investigated. The results indicate that three distinct stages of laumontite cementation developed during burial. Laumontite initially precipitated as pore-filling cement during the syngenetic to early diagenetic stages, controlled by sedimentary environment, provenance, and feldspar albitisation. During mesodiagenesis, laumontite re-precipitated from alkaline pore fluids, with Ca2+, Na+, and SiO2 derived from dissolution of earlier cements and detrital minerals. Early laumontite cement inhibited compaction and helped preserve primary porosity, whereas its subsequent dissolution significantly enlarged pore spaces and improved pore-throat connectivity. The overall impact of laumontite on reservoir quality is therefore dual and strongly dependent on the intensity of dissolution processes. [Received: September 6, 2023; Accepted: December 1, 2024].
  Keywords: laumontite; diagenesis; reservoir quality; Yanchang Formation; Ordos Basin.
  DOI: 10.1504/IJOGCT.2026.10076677
   
  
• Experimental study on combustion, exergy and emission analyses in a dual-fuel compression ignition engine using hydrogen and biodiesel  
  by Krishnamani Selvaraj, Rajamohan Ganesan, M. Yogeshkumar, M. Harikishore 
  Abstract: Hydrogen is a promising energy source for internal combustion engines because of its reliability, production from renewable energy sources, and clean combustion products. Hydrogen could be used in the diesel engine in dual-fuel mode with significant engine modifications. In this research work, combustion and exergy analyses were carried out to investigate the performance of the dual-fuel engine employing diesel and frying oil methyl ester (biodiesel) as a pilot fuel. In the compression ignition engine, the hydrogen is fumigated with the intake air stream at different volume flow rates of 3, 6, and 9 litres per minute, biodiesel as a pilot fuel. A diesel engine is modified and operated as a dual-fuel engine with biodiesel as a pilot fuel. The maximum brake thermal efficiency of the dual-fuel engine with biodiesel (B100) is 34.10%, 32.04%, 30.79%, and 29.82% corresponding to different hydrogen energy shares of 9.89%, 6.19%, 2.97%, and 0% is observed at the rated load condition. The maximum exergy efficiency of 46.34% is achieved with dual fuel engine using hydrogen fumigation at the engine rated load. The unburnt HC, CO, and smoke emissions are observed to be decreased with an increase in the hydrogen flow rate. [Received: May 21, 2025; Accepted: October 6, 2025]
  Keywords: dual fuel engine; biodiesel; hydrogen fumigation; exergy analysis; combustion characteristics; emissions.
  DOI: 10.1504/IJOGCT.2026.10076731
   
  
• Graphene and graphene nanoribbons: insights into structure, properties, production, and applications in the oil and gas industry - a comprehensive review  
  by Wael A. Farag, Ahmad B. A. Alazmi, Muhammad Nadeem 
  Abstract: This paper provides a comprehensive overview of graphite, graphene, and graphene nanoribbons (GNRs), highlighting their evolution and significance in mechanical and electrical applications. It explores the transformation of graphite into graphene and further into GNRs, which exhibit exceptional physical, electronic, and electrical properties compared to other members of the graphene family. Particular attention is given to the edge structures of GNRs, which play a crucial role in determining their metallic or semiconducting behaviour based on the configuration. The paper also investigates various synthesis methods for GNR production and examines the impact of integrating GNRs into polymer matrices, which significantly enhances their properties and expands their applicability. The primary focus is on leveraging these advancements for innovative applications in the oil and gas industry, demonstrating GNRs’ potential to revolutionise this sector. This review aims to broaden the understanding of GNR properties and inspire further research into their diverse applications, with a special emphasis on their transformative potential in the petroleum industry. [Received: July 4, 2023; Accepted: December 2, 2024]
  Keywords: carbon; graphene; graphite; graphene nanoribbons; GNRs; polymer nanocomposites; oil & gas; petroleum.
  DOI: 10.1504/IJOGCT.2026.10076780
   
  
• Study on wax deposition and its influence during shutdown and restart process of high waxy crude oil pipeline  
  by Wu Liu, Yupeng Guo, Bin Zheng, Liyuan Guo, Qihang Xue 
  Abstract: The Bozi crude oil pipeline transports waxy crude oil, and there is a risk of difficulty in restarting the pipeline due to wax gelation during shutdown in cold environments. In this study, a three-field coupling model - encompassing heat transfer, fluid flow, and wax deposition was developed to simulate the shutdown and restart processes of the entire Bozi crude oil pipeline. The results indicate that, within the maximum safe shutdown duration of the Bozi pipeline, the wax deposition rate during the restart phase increased significantly compared to that during shutdown. Additionally, the required restart pressure was found to be closely related to the crude oil temperature at the time of shutdown. Wax deposition also accelerated the reconstruction of the temperature field during restart. Notably, the peak wax deposition consistently occurred in the transitional zone between hot and cold oil, diminishing progressively as the restart advanced. [Received: August 11, 2025; Accepted: November 25, 2025]
  Keywords: high wax content crude oil; shutdown temperature drop; restart pressure; wax deposition.
  DOI: 10.1504/IJOGCT.2026.10076781
   
  
• Experimental study on heat transfer in heavy oil reservoirs during in-situ combustion  
  by Jiuzhi Sun, Yunjie Shu, Yi Pan, Yanchao Wang, Juan Huang, Zhaoxuan Li 
  Abstract: Heavy oil and extra-heavy oil, characterised by their high viscosity, extraction difficulties, and low oil recovery, critically require efficient extraction methodologies. The in-situ combustion (ISC) technique offers a promising solution by injecting air into the reservoir to ignite heavy oil, using heat to improve recovery; however, its intricate mechanisms necessitate further optimisation. This study established an indoor simulation platform to investigate the effects of ignition temperature, porosity, gas injection rate, and injection duration on heat transfer. The experimental results showed that ignition temperature, porosity, and gas injection rate have significant effects on the oxidation and combustion of heavy oil. At 240°C, the combustion front struggled to propagate, while at 280°C, it stabilised with peak temperatures above 400°C. Increasing porosity promoted temperature rise, and the combustion front propagated optimally at a gas injection rate of 1,600 mL/min. However, at 1,800 mL/min, combustion became too intense, hindering front propagation. Extending the reaction time increased the propagation distance, but due to the limitation of reservoir fuel, continuous propagation was not possible. This study provided significant experimental and theoretical guidance for further exploration and optimisation of the ISC technique, contributing to the enhancement of unconventional energy extraction. [Received: November 8, 2024; Accepted: April 4, 2025]
  Keywords: heavy oil; in-situ combustion; combustion property; enhanced oil recovery; reservoir heat transfer.
  DOI: 10.1504/IJOGCT.2025.10070803
   
  
• Quantitative characterisation of storage space and oil occurrence in low-maturity organic-rich shales: a case study of 3rd member of Chang 7 formation on the Southern Margin of Ordos Basin, China  
  by Dongling Xia, Wenchao Fang, Xuejie Qin, Jun Pu, Houjian Gong, Hong Qiu 
  Abstract: The fluid vacuum imbibition experiments were performed to quantitatively evaluate the storage space and oil occurrence in low-maturity organic-rich shales. Results showed that: 1) the imbibition volume of water was significantly lower than that of oil, reflecting the important influence of organic pores on the storage space and occurrence state in shale reservoirs; 2) the average inorganic porosity is 3.0% and average organic porosity is 0.6%, the storage space of low mature shales is mainly composed of inorganic pores. In contrast to high-maturity shales, the porosity of low-maturity shales decreases with increasing TOC; 3) the average volume proportion of free-state oil is 32.5%, and the average volume proportion of dissolved-state oil is 67.5%. In contrast to high-maturity shales, low-maturity shale oil mainly exists as dissolved-state, and as TOC increases, the volume proportion of dissolved-state oil increases, which is unfavourable for oil mobility. [Received: September 12, 2024; Accepted: March 20, 2025]
  Keywords: shale oil; low-maturity; storage space; oil occurrence; organic matter.
  DOI: 10.1504/IJOGCT.2026.10076759
   
  
• Simulation and optimisation for DMR natural gas liquefaction unit  
  by Ahmed S. Fathalla, Mohammed Hefny, Monica Toderas, Moustapha Salem Mansour, Fathy Shokry 
  Abstract: Dual mixed refrigerants natural gas liquefaction technology (DMR) has been simulated to determine the optimal operational parameters in terms of flowrate ratios for the mixed refrigerants utilised to maintain main cryogenic heat exchangers' stability and prevent temperature profile distortion as result of insufficient heat transfer throughout the main cryogenic heat exchangers that logically will occur if the cooling medium (refrigerants) flowrates will vary. This study examines specific ratios between two mixed refrigerants (MR1, MR2 vapour, MR2 liquid) and liquefied natural gas (LNG) produced, particularly during operations at varying feed gas flowrates. The study resulted in optimal operating zones, which are indicated by ratios such as LNG to MR2L (0.199 to 1.79), MR2V to MR2L (0.49), and MR1/MR2L (1.24 to 2.031) and those ratios showed resulted high production rate without compromising the integrity of the machinery or the operational procedures employing specific flow rate ratios. [Received: January 17, 2025; Accepted: April 22, 2025]
  Keywords: simulation; Aspen HYSYS; liquefied natural gas; LNG; optimisation; dual mixed refrigerant unit.
  DOI: 10.1504/IJOGCT.2025.10071556
   
  
• Research on the sucker rod automation of minor workover operations based on process reconfiguration  
  by Jixiang Yue, Lingling Wang, Wenyu Zhu, Yangli Zhou, Hongying Zhu, Kunyuan He 
  Abstract: Automating operations is challenging due to the structural characteristics of the sucker rod. This article proposes an automation approach based on process reconstruction, which includes wellhead positioning, 90-degree flipping of the upper and lower rods, and vertical replacement; alternating between gentle and harsh clamping while using a double sucker rod and elevator guidance system; combining hoisting and clamping through the elevator's rotary action on the flange and core; enabling simultaneous operations and process improvements; and visible master/slave control. Using the sucker rod as an example to split the process path, Gantt chart analysis is used to propose improvement measures. The completion of the on-site prototype manufacturing application demonstrates the practicality of both the equipment and process, as well as a significant increase in operational efficiency compared to manual methods. This technology leads the development of automation in minor workover operations and makes the non-landing operation mode of vehicle-mounted root box pipe poles feasible. [Received: November 25, 2024; Accepted: February 22, 2025]
  Keywords: wellhead automation; workover service; process reconfiguration; rotating elevator; vertical tubing and sucker rod connection operations.
  DOI: 10.1504/IJOGCT.2025.10074936
   
  
• Deformation characteristics and structural evolution mechanism of bituminous coal under thermo-hydro-mechanical-chemical coupling  
  by Jianhang Shi, Zengchao Feng, Zhenhua Li, Guoying Wang, Dong Zhou 
  Abstract: Studying the thermal deformation characteristics of coal under thermo-hydro-mechanical-chemical coupling is crucial for analysing roof stability, surface subsidence, and heat injection channel formation during the in situ pyrolysis mining of coal. Therefore, in this study, the deformation characteristics, gas production characteristics, and pore structure evolution as well as strength of bituminous coal during carbonisation and steam pyrolysis were explored. The results show that: 1) coal sample deformation can be divided into two stages: softening and pyrolysis deformation. Softening deformation depends solely on temperature, and pyrolysis deformation is affected by the severity of coal pyrolysis; 2) the deformation of bituminous coal and the evolution of pore and crack structures influence each other. Deformation promotes changes in pore and crack structures, and these structural changes serve as the internal drivers of deformation; 3) below 400°C, steam injection accelerates the softening deformation of bituminous coal. Meanwhile, above 400°C, deformation intensifies considerably under steam pyrolysis conditions owing to increased gas production of the coal sample compared to that during carbonisation. [Received: August 12, 2024; Accepted: April 9, 2025]
  Keywords: bituminous coal; carbonisation; steam pyrolysis; deformation; high temperature and high pressure.
  DOI: 10.1504/IJOGCT.2025.10071136
   
  
• Multi-response optimisation of waste cooking oil transesterification for improved biodiesel yield and quality using RSM  
  by Rohit Khatri, Om Prakash Jakhar 
  Abstract: This study presents a multi-response optimisation technique for the waste cooking oil biodiesel production process. The study's objective is to use the multi-response optimisation technique to find the optimal set of input parameters for the transesterification process for biodiesel yield and kinematic viscosity simultaneously. The experimental runs were developed using the box Behnken design (BBD) approach, and the multiple responses were analysed using response surface methodology (RSM). ANOVA was conducted to investigate the impact of parameters on the response. Chemical composition was determined by a GC-MS test, and the conversion of waste cooking oil (WCO) to esters was assessed using ¹HNMR and a FTIR test. The present study reports an impressive yield of 96.6% and a kinematic viscosity of 5.4 cSt for biodiesel production. The accuracy of the data was confirmed by determining R² values, which were found to be 97% and 94% for biodiesel yield and kinematic viscosity, respectively. [Received: September 22, 2024; Accepted: April 21, 2025]
  Keywords: biodiesel; transesterification; multi-response optimisation; ANOVA; box Behnken design; BBD; Fourier-transform infrared; FTIR; gas chromatography-mass spectrometry; GC-MS; ¹HNMR.
  DOI: 10.1504/IJOGCT.2025.10071793