Petroleum Science最新文献

{"title":"Natural fractures and their effectiveness in deep tight sandstone reservoirs of foreland thrust belts in the southern Junggar Basin, China","authors":"Guo-Ping Liu ,&nbsp;Zhi-Jun Jin ,&nbsp;Lian-Bo Zeng ,&nbsp;Xiao-Xuan Chen ,&nbsp;Mehdi Ostadhassan ,&nbsp;Zhe Mao ,&nbsp;Jian-Kang Lu ,&nbsp;Song Cao","doi":"10.1016/j.petsci.2025.04.001","DOIUrl":"10.1016/j.petsci.2025.04.001","url":null,"abstract":"<div><div>Strong tectonic activities and diagenetic evolution encourage the development of natural fractures as typical features in deep tight sandstone reservoirs of foreland thrust belts. This study focused on the Jurassic in the southern Junggar Basin to comprehensively analyze the fracture characteristics and differential distribution and, ultimately, addressed the controlling mechanisms of tectonism and diagenesis on fracture effectiveness. Results revealed that the intensity of tectonic activities determines the complexity of tectonic fracture systems to create various fracture orientations when they have been stronger. The intense tectonic deformation would impact the stratum occurrence, which results in a wide range of fracture dip angles. Moreover, as the intensity of tectonic activities and deformations weakens, the scale and degree of tectonic fractures would decrease continuously. The control of tectonism on fracture effectiveness is reflected in the notable variations in the filling of multiple group fractures developed during different tectonic activity periods. Fractures formed in the early stages are more likely to be filled with minerals, causing their effectiveness to deteriorate significantly. Additionally, the strong cementation in the diagenetic evolution can cause more fractures to be filled with minerals and become barriers to fluid flow, which is detrimental to fracture effectiveness. However, dissolution is beneficial in improving their effectiveness by increasing fracture aperture and their connectivity to the pores. These insights can refine the development pattern of natural fractures and contribute to revealing the evolutionary mechanisms of fracture effectiveness in deep tight sandstone reservoirs of foreland thrust belts.</div></div>","PeriodicalId":19938,"journal":{"name":"Petroleum Science","volume":"22 8","pages":"Pages 3086-3100"},"PeriodicalIF":6.1,"publicationDate":"2025-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145048700","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Rift marginal coarse-grained sediment gravity flow deposits in the Eocene Dongying Depression, Bohai Bay Basin, China: Balancing tectonic and climatic controls","authors":"Rong-Heng Tian ,&nbsp;Ben-Zhong Xian ,&nbsp;Peng Chen ,&nbsp;Lin Zhao ,&nbsp;Naveed Ur Rahman ,&nbsp;Muhammad Ubaid Umar ,&nbsp;Qian-Ran Wu ,&nbsp;Qian Li ,&nbsp;Wen-Miao Zhang ,&nbsp;Jian-Ping Liu ,&nbsp;Si-Rui Chen","doi":"10.1016/j.petsci.2025.06.009","DOIUrl":"10.1016/j.petsci.2025.06.009","url":null,"abstract":"<div><div>Previous studies have indicated that sediment gravity flow deposits developed in lacustrine active extensional rift basins are primarily influenced by tectonics and to a lesser extent by climate. Our present work reveals that climate can obscure the effect of tectonic subsidence by regulating sediment supply; conversely, tectonics can impede the sedimentary manifestation of climatic impacts. Here a case study has been presented to assess the impact of climate-modulated rapid lake-level rise and tectonic subsidence on the development of coarse-grained gravity flow deposits in the Dongying rift margin of the Bohai Bay Basin, eastern China. The lithofacies analysis reveals frequent bed amalgamation, abundant thick massive coarse-grained deposits, widespread cross bedding and plant fragments, and incomplete composite bed formed by high-energy erosion, indicating that the hyperpycnal flow is an important mechanism driving the deposition of these coarse-grained sediments. Detailed sequence stratigraphic analysis and sediment dispersal pattern suggest that the long-striped nearshore subaqueous fan systems induced by outburst-flood hyperpycnal flow distributed along the border fault, are primarily controlled by long-term tectonics, while the rapid rise of lake level driven by short-term climate change possibly intensifies seasonal flood-generated hyperpycnal flow occurrences and consequently promotes the basinal fan progradation. The maximum scale of these coarse-grained gravity flow deposits of the basinal fan systems are typically attained during the transgressive systems tract, which deviates from the classical sequence stratigraphic model. Furthermore, it presented a continuous transition from the proximal to the distal part, encompassing traction flows and turbidity currents during the periods of relatively stable tectonics. Nevertheless, gravel-rich debris flows appear to predominate the dispersion of coarse-grained sediments during periods characterized by intense tectonic activity. The coarse-grained gravity flow deposits in the lacustrine rift margin reported here, challenge the traditional beliefs: this study suggests that subaqueous deposits abundantly preserved in the transgressive setting.</div></div>","PeriodicalId":19938,"journal":{"name":"Petroleum Science","volume":"22 8","pages":"Pages 3168-3188"},"PeriodicalIF":6.1,"publicationDate":"2025-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145048695","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Enhanced recovery in heavy oil reservoirs with interlayers using flue gas-assisted VH-SAGD: A 2D visualization study","authors":"Bin-Fei Li ,&nbsp;Bo-Liang Li ,&nbsp;Xin-Ge Sun ,&nbsp;Di Zhu ,&nbsp;Sen Chen ,&nbsp;Zhao-Min Li ,&nbsp;Lei Tao ,&nbsp;Jun-Hao Zhang","doi":"10.1016/j.petsci.2025.05.007","DOIUrl":"10.1016/j.petsci.2025.05.007","url":null,"abstract":"<div><div>The potential of the vertical-horizontal well hybrid SAGD technique for developing shallow heavy oil reservoirs is gradually being realized. However, challenges remain in terms of low thermal efficiency and high carbon emissions in reservoirs with interlayers. Currently, there is limited research on the low-carbon strategy of coupling exhaust gas from steam boilers with the VH-SAGD technique. Herein, considering heterogeneity, a series of flue gas-assisted VH-SAGD experiments were conducted employing a high-performance 2D visualization model. The mechanism of enhanced recovery of flue gas in VH-SAGD and the effect of its injection methods were studied, with a focus on steam chamber development and oil saturation distribution. Crucially, the interlayer length was optimized to enhance oil recovery, providing a new perspective for well location design in heavy oil reservoirs with interlayers. The results showed that flue gas, as an additive, could fully exploit the well-type advantage of VH-SAGD. By supplementing energy at the reservoir top, flue gas effectively promoted steam chamber development, expanded the oil drainage area of VH-SAGD, and increased the oil recovery from 58.9% to 71.7%. The flow channels formed by pre-injection flue gas accelerated the early-stage expansion of the steam chamber while also inducing lateral migration of steam, slowing steam rise, and consequently increasing the heating range within the low-permeability layer. When the distance between the vertical and horizontal wells was set to twice the interlayer length, the negative effects of the interlayer were more effectively turned into advantages. Because when the lateral development distance of the steam chamber in the low-permeability layer slightly exceeds the interlayer, enhanced heating of the lower part of the reservoir occurred through vertical convection of rising steam and returning condensate. The research results contribute to reducing carbon emissions from steam-based heavy oil extraction while advancing the maturity of VH-SAGD.</div></div>","PeriodicalId":19938,"journal":{"name":"Petroleum Science","volume":"22 8","pages":"Pages 3418-3433"},"PeriodicalIF":6.1,"publicationDate":"2025-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145048247","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Identification and distribution patterns of the ultra-deep small-scale strike-slip faults based on convolutional neural network in Tarim Basin, NW China","authors":"Hao Li ,&nbsp;Jun Han ,&nbsp;Cheng Huang ,&nbsp;Lian-Bo Zeng ,&nbsp;Bo Lin ,&nbsp;Ying-Tao Yao ,&nbsp;Yi-Chen Song","doi":"10.1016/j.petsci.2025.06.008","DOIUrl":"10.1016/j.petsci.2025.06.008","url":null,"abstract":"<div><div>The isolated fracture-vug systems controlled by small-scale strike-slip faults within ultra-deep carbonate rocks of the Tarim Basin exhibit significant exploration potential. The study employs a novel training set incorporating innovative fault labels to train a U-Net-structured CNN model, enabling effective identification of small-scale strike-slip faults through seismic data interpretation. Based on the CNN faults, we analyze the distribution patterns of small-scale strike-slip faults. The small-scale strike-slip faults can be categorized into NNW-trending and NE-trending groups with strike lengths ranging 200–5000 m. The development intensity of small-scale strike-slip faults in the Lower Yingshan Member notably exceeds that in the Upper Member. The Lower and Upper Yingshan members are two distinct mechanical layers with contrasting brittleness characteristics, separated by a low-brittleness layer. The superior brittleness of the Lower Yingshan Member enhances the development intensity of small-scale strike-slip faults compared to the upper member, while the low-brittleness layer exerts restrictive effects on vertical fault propagation. Fracture-vug systems formed by interactions of two or more small-scale strike-slip faults demonstrate larger sizes than those controlled by individual faults. All fracture-vug system sizes show positive correlations with the vertical extents of associated small-scale strike-slip faults, particularly intersection and approaching fracture-vug systems exhibit accelerated size increases proportional to the vertical extents.</div></div>","PeriodicalId":19938,"journal":{"name":"Petroleum Science","volume":"22 8","pages":"Pages 3152-3167"},"PeriodicalIF":6.1,"publicationDate":"2025-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145048696","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Logging evaluation of acoustic anisotropy and its relationship with “sweet spots” in lacustrine shale oil reservoirs: The Fengcheng Formation of the Mahu Sag, China","authors":"Song Wang ,&nbsp;Gui-Wen Wang ,&nbsp;Hai-Zhu Wang ,&nbsp;Meng-Jie Liu ,&nbsp;Li-Liang Huang ,&nbsp;Yu-Yue Huang ,&nbsp;Zhi-Shi Wang ,&nbsp;Shi-Qian Li","doi":"10.1016/j.petsci.2025.05.014","DOIUrl":"10.1016/j.petsci.2025.05.014","url":null,"abstract":"<div><div>China's lacustrine shale oil reserves are abundant, making it a key area for future exploration and development. Most lacustrine shales feature a mix of mineral compositions and interlayer sedimentary structures. High-quality reservoirs exhibit significant heterogeneity, which influences the stress distribution during fracturing, leading to complex fracture network patterns. This complexity presents challenges for the comprehensive well logging evaluation of the geological-engineering \"double sweet spots\" in shale oil, severely restricting efficient development. This study focuses on the impact of shale sedimentary layering on the radial slowness of dipole shear waves. It employs rock physics experiments combined with advanced well logging techniques to explore the relationship between reservoir anisotropy caused by sedimentary layering and reservoir quality, thereby establishing a logging evaluation method for vertical identification of \"sweet spots\" in lacustrine shale oil. The shales in the Fengcheng Formation of the Mahu Sag into three types according to sedimentary structure scale: laminated, interlayer, and massive. Each type has different mineral compositions, affecting reservoir quality and fracturing potential. Laminated shales develop more fractures under stress along the beddings, showing moderate anisotropy, with reservoir capacity dependent on intercrystalline porosity within carbonate layers. Interlayer shales easily form complex fracture networks, exhibiting significant anisotropy, and their reservoir capacity depends on the porosity within sandy bands. Massive mudstones have the fewest fractures under stress, appearing isotropic with reservoir capacity dependent on matrix pore size. The intensity of reservoir anisotropy correlates positively with storage capacity and the propensity to form irregular and complex fracture networks during hydraulic fracturing. In sections without natural fractures, a larger difference between fast and slow shear waves corresponds to a radial profile shift towards warm tones, indicating stronger anisotropy and better reservoir quality, thus forming complex fracture networks during fracturing. Conversely, a smaller difference leads to a profile energy shift towards cooler tones, indicating stronger isotropy and poorer reservoir quality, hindering the formation of complex fracture networks during hydraulic fracturing. In sections with natural fractures, the difference between fast and slow shear waves exhibits erratic behavior, showing a cross-pattern in radial profiles, indicating strong anisotropy. The presence of natural fractures can synergize with induced fracture networks to form more complex systems, significantly enhancing reservoir productivity.</div></div>","PeriodicalId":19938,"journal":{"name":"Petroleum Science","volume":"22 8","pages":"Pages 3133-3151"},"PeriodicalIF":6.1,"publicationDate":"2025-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145048697","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The occurrence, origin, and enrichment of helium in the Wufeng-Longmaxi shale gas in the Sichuan Basin, China","authors":"Yan-Yan Chen ,&nbsp;Shi-Zhen Tao ,&nbsp;Wei Wu ,&nbsp;Xiang-Bai Liu ,&nbsp;Cheng-Peng Song ,&nbsp;Zuo-Dong Liu ,&nbsp;Qing-Yao Liu ,&nbsp;Lin Wei ,&nbsp;Jian-Rong Gao ,&nbsp;Yue Chen","doi":"10.1016/j.petsci.2025.05.011","DOIUrl":"10.1016/j.petsci.2025.05.011","url":null,"abstract":"<div><div>Helium is a valuable natural resource used widely in high-tech industries because of its unique physical and chemical properties. The study of helium in shale gas is still in its infancy, and the content, genesis, and enrichment patterns of helium in shale gas are not yet clear. In this paper, the concentrations and isotopic characteristics of helium were investigated in the Wufeng-Longmaxi shale gas in the Sichuan Basin and the periphery areas. The analytical results show that the concentrations of helium in the southern Sichuan shale gas fall in the range of 0.018–0.051 vol% with an average of 0.029 vol%. The helium abundance in Weiyuan shale gas are relatively low compared to those in conventional natural gas pools from the same area (generally greater than 0.20 vol%), reflecting the significance of long distance migration to the enrichment of helium in gas pools. The relatively low ratios of ³He and ⁴He in shale gas indicate that most of the helium are crustal derived helium. Further quantitative estimate based on helium, neon, and argon isotopic ratios suggest almost 100% crustal helium source. The helium residing in shale reservoirs can be deconvoluted into the indigenous helium generated in-situ by shale and exogenous helium generated from external helium source rocks and charged through faults and/or fractures networks. According to preliminary calculations, external helium source is required to meet the threshold of an economic helium-rich field of helium concentration of 0.1 vol% except for particular areas with extraordinarily high uranium and thorium concentration. Based on detailed study on typical helium-rich shale gas reservoirs, major advantageous features for helium's enrichment in shale gas include: (1) high-quality helium source rocks, (2) effective migration paths, and (3) diminished dilution effects of shale gas. Shale gas plays with underlying ancient cratonic basement, well developed source-connecting faults, and moderate pressure coefficient are potential targets for helium exploration.</div></div>","PeriodicalId":19938,"journal":{"name":"Petroleum Science","volume":"22 8","pages":"Pages 3119-3132"},"PeriodicalIF":6.1,"publicationDate":"2025-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145048698","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Research on the in-situ catalytic pyrolysis of heavy oil by 2D layered MOF and its catalytic mechanism","authors":"Chi Li ,&nbsp;Ji-Xiang Guo ,&nbsp;Li Wang ,&nbsp;Wen-Long Zhang ,&nbsp;Peng-Cheng Xue ,&nbsp;Chen-Hao Gao","doi":"10.1016/j.petsci.2025.04.023","DOIUrl":"10.1016/j.petsci.2025.04.023","url":null,"abstract":"<div><div>China possesses abundant heavy oil resources, yet faces challenges such as high viscosity, underdeveloped production technologies, and elevated development cost. Although the in-situ catalytic viscosity-reduction technology can address certain technical, environmental, and cost problems during the extraction process, the catalysts often suffer from poor stability and low catalytic efficiency. In this study, a green and simple room-temperature stirring method was employed to synthesize a class of highly efficient and stable 2D MOF catalysts, which possess the capability to conduct in-situ catalytic pyrolysis of heavy oil and reduce the viscosity. Under the condition of 160 °C, a catalyst concentration of 0.5 wt%, and a hydrogen donor (tetralin) concentration of 2 wt%, the viscosity-reduction rate of Fe-MOF is as high as 89.09%, and it can decrease the asphaltene content by 8.42%. In addition, through the structural identification and analysis of crude oil asphaltenes, the causes for the high viscosity of heavy oil are explained at the molecular level. Through the analysis of catalytic products and molecular dynamics simulation, the catalytic mechanism is studied. It is discovered that Fe-MOF can interact with heavy oil macromolecules via coordination and pore-channel effects, facilitating their cracking and dispersal. Furthermore, synergistic interactions between Fe-MOF and the hydrogen donor facilitates hydrogenation reactions and enhances the viscosity-reducing effect. This study provides a novel strategy for boosting heavy oil recovery and underscores the potential of 2D MOFs in catalytic pyrolysis applications.</div></div>","PeriodicalId":19938,"journal":{"name":"Petroleum Science","volume":"22 8","pages":"Pages 3434-3446"},"PeriodicalIF":6.1,"publicationDate":"2025-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145048245","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Numerical analysis of dispersion, attenuation, and seismic effects in a porous rock saturated with three-phase immiscible fluids","authors":"Xin Luo ,&nbsp;Xue-Hua Chen ,&nbsp;Tong Li ,&nbsp;Gui-Rong Luo ,&nbsp;Peng Wang","doi":"10.1016/j.petsci.2025.04.024","DOIUrl":"10.1016/j.petsci.2025.04.024","url":null,"abstract":"<div><div>Multiphase flow in porous rock is of great importance in the application of many industrial processes, including reservoir delineation, enhanced oil recovery, and CO₂ sequestration. However, previous research typically investigated the dispersive behaviors when rock saturated with single or two-phase fluids and conducted limited studies on three-phase immiscible fluids. This study investigated the seismic dispersion, attenuation, and reflection features of seismic waves in three-phase immiscible fluid-saturated porous rocks. First, we proposed the calculation formulas of effective fluid modulus and effective fluid viscosity of multiphase immiscible fluids by taking into account the capillary pressure, reservoir wettability, and relative permeability simultaneously. Then, we analysed the frequency-dependent behaviors of three-phase immiscible fluid-saturated porous rock under different fluid proportion cases using the Chapman multi-scale model. Next, the seismic responses are analysed using a four-layer model. The results indicate that the relative permeability, capillary pressure parameter, and fluid proportions are all significantly affect dispersion and attenuation. Comparative analyses demonstrate that dispersion and attenuation can be observed within the frequency range of seismic exploration for a lower capillary parameter <em>α</em>₃ and higher oil content. Seismic responses reveal that the reflection features, such as travel time, seismic amplitude, and waveform of the bottom reflections of saturated rock and their underlying reflections are significantly dependent on fluid proportions and capillary parameters. For validation, the numerical results are further verified using the log data and real seismic data. This numerical analysis helps to further understand the wave propagation characteristics for a porous rock saturated with multiphase immiscible fluids.</div></div>","PeriodicalId":19938,"journal":{"name":"Petroleum Science","volume":"22 7","pages":"Pages 2828-2850"},"PeriodicalIF":6.1,"publicationDate":"2025-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144757536","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Enhancing shale oil recovery with water-alternating-CO2 injection through radial borehole fracturing","authors":"Jia-Cheng Dai ,&nbsp;Tian-Yu Wang ,&nbsp;Ye Zhang ,&nbsp;Zhi-Ping Zhang ,&nbsp;Chun-Lin Zeng ,&nbsp;Kang-Jian Tian ,&nbsp;Jing-Bin Li ,&nbsp;Shou-Ceng Tian ,&nbsp;Gen-Sheng Li","doi":"10.1016/j.petsci.2025.04.021","DOIUrl":"10.1016/j.petsci.2025.04.021","url":null,"abstract":"<div><div>This paper introduces a novel approach combining radial borehole fracturing with Water-Alternating-Gas (WAG) injection, enabling simultaneous WAG injection and shale oil production in a single vertical well. A numerical reservoir model incorporating the modified exponential non-Darcy law, stress sensitivity, and diffusion is established. The spatial distribution of permeability reduction shows that stress sensitivity enhances the non-Darcy effect, with apparent permeability decreasing to 0–92.1% of the initial value, highlighting the importance of maintaining reservoir pressure. Continuous CO₂ flooding leads to early gas breakthrough, while continuous water flooding has less displacement efficiency. A 30% water-to-gas injection time ratio improves oil production and delays gas breakthrough compared to continuous CO₂ injection. Optimal conditions for effective recovery are identified as an initial production period of 100 d and a well vertical spacing of 30 m. This study compares the production capacity of WAG operations under radial borehole fracturing and horizontal well fracturing. When the number of wells is two for both cases, the production capacity of radial borehole fracturing is comparable to that of five-stage horizontal well fracturing, indicating that radial borehole fracturing can serve as an alternative or supplement to horizontal well fracturing when the reservoir volume is limited. This study offers a new method and theoretical basis for the efficient development of shale oil.</div></div>","PeriodicalId":19938,"journal":{"name":"Petroleum Science","volume":"22 7","pages":"Pages 2950-2966"},"PeriodicalIF":6.1,"publicationDate":"2025-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144757538","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"A multi-scale and multi-mechanism coupled model for carbon isotope fractionation of methane during shale gas production","authors":"Jun Wang ,&nbsp;Fang-Wen Chen ,&nbsp;Wen-Biao Li ,&nbsp;Shuang-Fang Lu ,&nbsp;Sheng-Xian Zhao ,&nbsp;Yong-Yang Liu ,&nbsp;Zi-Yi Wang","doi":"10.1016/j.petsci.2025.03.034","DOIUrl":"10.1016/j.petsci.2025.03.034","url":null,"abstract":"<div><div>Prediction of production decline and evaluation of the adsorbed/free gas ratio are critical for determining the lifespan and production status of shale gas wells. Traditional production prediction methods have some shortcomings because of the low permeability and tightness of shale, complex gas flow behavior of multi-scale gas transport regions and multiple gas transport mechanism superpositions, and complex and variable production regimes of shale gas wells. Recent research has demonstrated the existence of a multi-stage isotope fractionation phenomenon during shale gas production, with the fractionation characteristics of each stage associated with the pore structure, gas in place (GIP), adsorption/desorption, and gas production process. This study presents a new approach for estimating shale gas well production and evaluating the adsorbed/free gas ratio throughout production using isotope fractionation techniques. A reservoir-scale carbon isotope fractionation (CIF) model applicable to the production process of shale gas wells was developed for the first time in this research. In contrast to the traditional model, this model improves production prediction accuracy by simultaneously fitting the gas production rate and <em>δ</em>¹³C₁ data and provides a new evaluation method of the adsorbed/free gas ratio during shale gas production. The results indicate that the diffusion and adsorption/desorption properties of rock, bottom-hole flowing pressure (BHP) of gas well, and multi-scale gas transport regions of the reservoir all affect isotope fractionation, with the diffusion and adsorption/desorption parameters of rock having the greatest effect on isotope fractionation being <em>D</em>∗/<em>D</em>, <em>P</em>_L, <em>V</em>_L, <em>α</em>, and others in that order. We effectively tested the universality of the four-stage isotope fractionation feature and revealed a unique isotope fractionation mechanism caused by the superimposed coupling of multi-scale gas transport regions during shale gas well production. Finally, we applied the established CIF model to a shale gas well in the Sichuan Basin, China, and calculated the estimated ultimate recovery (EUR) of the well to be 3.33 × 10⁸ m³; the adsorbed gas ratio during shale gas production was 1.65%, 10.03%, and 23.44% in the first, fifth, and tenth years, respectively. The findings are significant for understanding the isotope fractionation mechanism during natural gas transport in complex systems and for formulating and optimizing unconventional natural gas development strategies.</div></div>","PeriodicalId":19938,"journal":{"name":"Petroleum Science","volume":"22 7","pages":"Pages 2719-2746"},"PeriodicalIF":6.1,"publicationDate":"2025-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144757590","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}