International Journal of Oil, Gas and Coal Technology (11 papers in press)

Regular Issues

• Thermo-hydro-mechanical-damage coupling mechanism and failure behaviour of caprock in SAGD operations  
  by Haijing Wang, Chao Zhang, Bo Zhou, Shifeng Xue, Peng Jia, Xiuxing Zhu 
  Abstract: A coupled thermo-hydro-mechanical-damage model considering anisotropic stiffness degradation of rock after shear damage is developed for the first time, and the coupling mechanism and failure behaviour of caprock in steam assisted gravity drainage (SAGD) operations are systematically investigated using analytical and numerical approaches. New insights into the failure characteristics of caprock were obtained. The damage of caprock is mostly induced by shear and initiates near the interface directly opposite the well pair in the earliest stage of SAGD production, and propagates rapidly to form a main crack. The vertical and zigzag main crack may penetrate the caprock, while the secondary cracks on both sides are mostly inclined and straight that they cannot penetrate the caprock. Failure modes of caprock are observed including penetrating crack, non-penetrating crack and interface damage. This study will be helpful in accurately evaluating the caprock integrity and efficiently breaking interbedded shale or mudstone layers in thermal recovery reservoirs. [Received: 2 June 2023; Accepted: 13 February 2024]
  Keywords: thermo-hydro-mechanical-damage; THMD; analytical analysis; numerical simulation; caprock failure; steam assisted gravity drainage; SAGD.
  
  
• Paleoenvironment and petroleum potential of the lacustrine shales in the Lower Cretaceous Shahezi Formation of the Southern Songliao Basin, NE China  
  by Zhengjian Xu, Shu Jiang, Xiaodong Hu, Wenchao Zhang, Xiaogang Li, Shaohua Xu, Nini Zhang 
  Abstract: The occurrence of conventional and unconventional hydrocarbons is directly determined by organic matter (OM)-rich shales in fault-controlled sedimentary basins. Through integrated analyses of organic petrology, element concentrations, bulk organic geochemical characteristics, hydrocarbon generation, and expulsion of the Shahezi shales, we have conducted comprehensive studies on the paleoenvironment, OM source, and petroleum potential of the Shahezi shales. 1) The Shahezi deposition occurred under a cold and semi-humid to semi-arid paleoclimate, and sub-reducing to reducing redox conditions, favorable for OM preservation. 2) The OM origins of shales are primarily a mixture of aquatic microorganisms and terrestrial higher plants. 3) The shales demonstrate a fair to excellent source rock potential. 4) Oil generation began around 130 Ma, while gas generation started around 105 Ma. 5) The shales have reached the hydrocarbon expulsion threshold. 6) The occurrence of burial-deep tight gas reservoirs, is predominantly controlled by the outer boundary of the shale distribution.
  Keywords: Lacustrine shale; Paleoenvironment; Organic matter origin; Petroleum potential; Shahezi Formation; Southern Songliao Basin.
  
  
• Simulation study on frictional resistance and influencing factors of flexible screen pipe tripping into horizontal wellbore  
  by Zhongzhi Hu, Junliang Li, Li Wang, Jinbo Wang, Xinyang Liu, Kong Yang 
  Abstract: Flexible sand control screens play a crucial role in the operation and economic benefits of ultra-short radius wells. We established a calculation model for the motion friction resistance of flexible screens and a criterion for contact between screen units and wellbore walls. Case analysis clarified the correlation between several key factors (e.g. maximum allowed swing angle, friction coefficient, insertion speed, and total length of screen units) and the frictional resistance of flexible screens. We utilized the overall distribution of contact point positions and the compressed distance between adjacent screen unit centroids to analyze the conversion mechanism of screen friction resistance from linear to nonlinear rapid accumulation. We also explored measures to improve the extension capacity of flexible screens. Our findings provide a basis for the optimization design of flexible screen structures and the assessment of their maximum extension capacity.
  Keywords: flexible screen; sand control; multi-body dynamics simulation; frictional resistance.
  
  
• Lithofacies identification and prediction of Chang 73 shale oil reservoirs in Ordos Basin: insights from the multi-resolution graph-based clustering analysis  
  by Ruiliang Guo, Junhong Jia, Guangjun Xu, Fei Liu, Jingzhou Zhao, Yubin Bai, Weitao Wu, Lei Cao 
  Abstract: The Chang 7 section of Yanchang Formation of the Ordos Basin contains abundant shale oil resources, making it the core area for exploration and development of lacustrine shale oil in recent years However, the strong spatial heterogeneity of shale makes lithofacies identification and prediction a key challenge in shale oil reservoir development This study divides the lithofacies of the Chang 73 shale oil reservoir into 4 types based on sedimentary structure, mineral composition, and TOC content, namely high TOC tuffaceous laminated shale, high TOC argillaceous laminated shale, moderate TOC felsic laminated shale, and moderate TOC felsic bedded mudstone Multi-resolution graph-based clustering analysis (MRGC) was used to perform cluster analysis on lithofacies sensitive logging, including GR, AC, DEN, RT, and SH, and the electrofaices was compared with single well lithofacies to establish the range model of logging values for different lithofacies, which can be used for rapid identification of lithofacies.
  Keywords: Ordos Basin; Yanchang Formation; Shale oil; Lithofacies; MRGC.
  
  
• A new methodology for optimising production in an integrated model using a genetic algorithm  
  by Mehdi Fadaei, Mohammad Javad Ameri, Yousef Rafie 
  Abstract: Optimisation of the production of an integrated model is the best method to increase production from hydrocarbon reservoirs. Constraint optimisation of an integrated model using a genetic algorithm can optimise and govern production. This paper presents a novel method for optimising integrated production systems. The novel approach is constraint optimisation with a genetic algorithm. The elements of the integrated model are the reservoir, well, choke, pipeline, and separator. One of the essential issues in integrated modelling is evaluating flow regimes before surface equipment. The target function of this study is maximising oil in the stock tank. The constraint for optimisation approaches is that no slug flow regime has formed at the separator inlet. The optimisation integrated model with the genetic algorithm increases the oil in the stock tank by about 16 %. [Received: March 6 2023; Accepted: February 13 2024]
  Keywords: new; optimising; production; integrated; genetic; algorithm.
  
  
• Effect of a Vortex Plate on Turbulent Flow within an Axial Hydrocyclone for Preliminary Water Separation  
  by Meili Liu, Pingping Qiao, Zhengrui Hu, Yaoyuan Zhang, Jiaqing Chen 
  Abstract: The conflict between separation efficiency and pressure drop has emerged as a key factor affecting the widespread adoption and application of hydrocyclones for preliminary water separation. This study presents a novel approach to enhance hydrocyclone performance by leveraging turbulent coherent structures. A vortex plate, designed to interfere with turbulence-coherent structures was placed within the blade region, and its impact on the flow field was investigated through numerical simulations. The findings reveal that this method selectively alters the turbulent micro-flow field, reducing drag losses without affecting the macro time-averaged flow field. Consequently, it successfully addresses the inherent conflict between separation efficiency and pressure drop. An appropriately positioned vortex plate exhibited remarkable outcomes, including a significant 74% reduction in the offset distance of the vortex center, a 1.56% increase in water separation efficiency, a 12.68% reduction in HPO concentration, and an 18.1% reduction in underflow pressure.
  Keywords: hydrocyclone; vortex plate; separation efficiency; pressure drop.
  
  
• Comprehensive evaluation of geology and engineering integration of XTT tight oil reservoir  
  by Xiu Li, Chengwen Liu, Tengwen Luo, Bingquan Ai, Aifeng Li, Luyao Gao, Shenglun Zhou 
  Abstract: The XTT Development Zone C7 offers promising exploration and evaluation potential. However, challenges arise due to factors such as strong heterogeneity, thin sand layers, and unstable distribution. These issues make it hard to identify the best drilling locations, often termed as 'sweet spots', especially in horizontal well deployment. This study uses both indoor experiments and field logging data. By building upon previous research, we: 1) calculated the rock's mechanical parameters; 2) created a model for petrophysical parameters; 3) established an in-situ stress model. From this data, we proposed a method to evaluate the sweet spots. This method combines both geological and engineering perspectives. Using this approach, we devised a sweet spot index specifically for the C7 region. Consequently, the XTT reservoir was categorised into three types to guide drilling operations. Our results indicate that type I and type II reservoirs are most suitable for development. The practical results from drilling and development validate our methodology's effectiveness. This research lays a foundation for deciding future drilling locations and optimising reservoir development. [Received: June 22, 2023; Accepted: October 15, 2023]
  Keywords: tight oil; rock mechanical parameters; geology-engineering integration; sweet spot.
  DOI: 10.1504/IJOGCT.2024.10063390
   
  
• Advanced calculation method for rheological characterisation of non-Newtonian drilling fluids using Herschel-Bulkley model  
  by Can Polat 
  Abstract: Determining Herschel-Bulkley model coefficients from rotational viscometers can be a challenging process. The variation of shear rates according to the rheological model type may bring uncertainty in the regression process evaluated for the estimation of the model coefficients. In this study, the derivation of the equation required for proper determination of the Herschel-Bulkley model coefficients is presented. The derivation process in question revealed the dependence on the Gaussian hypergeometric function. Attempts to determine all coefficients by means of the derived equation appear to yield unrealistic yield points. In this respect, yield point was estimated priorly using Bingham plastic model which was formulated using low speed/dial reading values. The method employed for parameter estimation additionally covers the solution for the not fully developed flow that occurs at low rotational speeds. The accuracy of the proposed method is demonstrated by making comparison with the measured frictional pressure loss data. [Received: September 24, 2023; Accepted: December 24, 2023]
  Keywords: Herschel Bulkley model; non-Newtonian drilling fluids; rheological characterisation; Gaussian hypergeometric function; advanced calculation; rotational viscometer; rheological model; yield point.
  DOI: 10.1504/IJOGCT.2024.10063392
   
  
• Review of the research progress on the application of blockchain technology in the oil and gas industry  
  by Shi Ding, Zhonghui Li, Arnaud Regis Kamgue Lenwoue, Yubo Li, Chuanfu Tang, Wentie Sun, Pengjie Hu, Wuchang Zhang 
  Abstract: Blockchain, as a distributed ledger technology is a decentralised, transparent and traceable technology. It has rapidly developed during the last decade and is widely used in many industries such as the oil and gas engineering. This study first describes the development, classification, characteristics and key technologies of the blockchain technology. Then, the application of blockchain and the challenges currently encountered during its implementation in the oil and gas industry are summarised. Finally, some feasible solutions are presented to overcome these challenges. The current work provides a deep insight of the main research progress of the application of blockchain technology in the oil and gas industry and is expected to enable the further development of this sector. [Received: May 18, 2023; Accepted: December 12, 2023]
  Keywords: research progress; blockchain technology; oil and gas industry; application.
  DOI: 10.1504/IJOGCT.2024.10063391
   
  
• Study and application of evaluation method for fracability of deep CBM reservoir - taking the Daning-Jixian block in the Ordos Basin as an example  
  by Duo Wang, Zhidi Liu 
  Abstract: The key to increasing production of deep coalbed methane is to evaluate the fracability of the reservoir, but existing methods cannot meet the requirements of fracability evaluation. This study is based on the close relationship between the main controlling factors of fracability and the operation pressure during the sand carrying fluid stage. AHP was used to determine the weights of the main controlling factors of fracability in coal seams and roof and floor, and based on this, a deep coalbed methane reservoir fracability evaluation model was established. The fracability of the 8 # coal seam and the roof and floor of the Daning Jixian block was evaluated using this model, and the evaluation results can be confirmed by the on-site fracturing operation and the fracability indoor experimental results. Therefore, this model can provide good technical support for the stimulation and transformation of deep coalbed methane reservoirs. [Received: August 2, 2023; Accepted: November 27, 2023]
  Keywords: deep CBM; AHP; main control factors; operation pressure; fracability.
  DOI: 10.1504/IJOGCT.2024.10063389
   
  
• An experimental investigation on preparation and performances of two diesel blends of karanj oil methyl ester  
  by Sushovan Chatterjee 
  Abstract: Solvent extraction of karanj seed was found more efficient over traditional mechanical means for oil extraction from raw seed as the former one tested more yield. The extracted oil was subjected to acid catalyst esterification and subsequently followed by alkali catalysed transesterification to produce fatty acid methyl ester. Physical, chemical and petrochemical features of the ester as well as two different blends with diesel (B10 and B20) were measured and compared with neat diesel. Performances of these fuels were tested in an unmodified single cylinder, water cooled, four stroke direct injection type diesel engine. On sample testing it was revealed that, the emission of carbon monoxide and hydrocarbon was less than what noticed during testing diesel alone, although the emission of oxides of nitrogen was somewhat more than what noticed in available diesel engine test results while using diesel only as fuel. [Received: November 19, 2021; Accepted: October 30, 2023]
  Keywords: Pongamia pinnata; extraction; esterification; transesterification; biodiesel; engine performance.
  DOI: 10.1504/IJOGCT.2024.10063358