Pub Date : 2025-10-01DOI: 10.1016/S1876-3804(25)60649-5
K Caleb DARKO , Yanbo LIU , Thomas SCHUMAN , Mingzhen WEI , Baojun BAI
To understand the applicability of high-temperature preformed particle gel (HT-PPG) for control of short-circuiting in enhanced geothermal systems (EGSs), core flooding experiments were conducted on fractured granite cores under varying fracture widths, gel particle sizes and swelling ratios. Key parameters such as injection pressure, water breakthrough pressure, and residual resistance factor were measured to evaluate HT-PPG performance. The gel exhibited strong injectability, entering granite fractures at pressure gradients as low as 0.656 MPa/m; HT-PPG yields a superior sealing performance by significantly reducing the permeability; and dehydration occurs during HT-PPG propagation, with a dehydration ratio ranging from 4.71% to 11.36%. This study reveals that HT-PPG can be injected into geothermal formations with minimal pressure yet provides strong resistance to breakthrough once in place. This balance of injectability and sealing strength makes HT-PPG effective for addressing thermal short-circuiting in EGS reservoirs.
{"title":"Laboratory investigation of high-temperature preformed particle gels for fluid control in granite cores for geothermal applications","authors":"K Caleb DARKO , Yanbo LIU , Thomas SCHUMAN , Mingzhen WEI , Baojun BAI","doi":"10.1016/S1876-3804(25)60649-5","DOIUrl":"10.1016/S1876-3804(25)60649-5","url":null,"abstract":"<div><div>To understand the applicability of high-temperature preformed particle gel (HT-PPG) for control of short-circuiting in enhanced geothermal systems (EGSs), core flooding experiments were conducted on fractured granite cores under varying fracture widths, gel particle sizes and swelling ratios. Key parameters such as injection pressure, water breakthrough pressure, and residual resistance factor were measured to evaluate HT-PPG performance. The gel exhibited strong injectability, entering granite fractures at pressure gradients as low as 0.656 MPa/m; HT-PPG yields a superior sealing performance by significantly reducing the permeability; and dehydration occurs during HT-PPG propagation, with a dehydration ratio ranging from 4.71% to 11.36%. This study reveals that HT-PPG can be injected into geothermal formations with minimal pressure yet provides strong resistance to breakthrough once in place. This balance of injectability and sealing strength makes HT-PPG effective for addressing thermal short-circuiting in EGS reservoirs.</div></div>","PeriodicalId":67426,"journal":{"name":"Petroleum Exploration and Development","volume":"52 5","pages":"Pages 1378-1388"},"PeriodicalIF":8.0,"publicationDate":"2025-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145398580","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-08-01DOI: 10.1016/S1876-3804(25)60621-5
Lianhe SUN , Haizhu WANG , Gensheng LI , Bin WANG , Sergey STANCHITS , Zelong MAO , Yaochen ZHANG , Alexey CHEREMISIN , Yong ZHENG , Jiacheng JIN
To elucidate the mechanism by which supercritical CO2 (SCCO2)-water-shale interactions during CO2 energized fracturing influence proppant embedment in lacustrine shale, shale samples from the Bohai Bay Basin were selected for SCCO2-water-shale interaction experiments. X-ray diffraction (XRD), SEM large-area high-resolution imaging, automated mineral identification and characterization system (AMICS), and nanoindentation tests were employed to examine the micro-mechanical damage mechanisms of fracture surfaces and the evolving patterns of proppant embedment characteristics. The results reveal that: Prolonged interaction time reduces the contents of dolomite, feldspar, and clay minerals, while quartz content increases, with dolomite showing the most pronounced dissolution effect. As interaction time increases, the hardness and elasticity modulus of shale follow a power-law decay pattern, with the peak degradation rate occurring at 1 d, followed by a gradual decline of degradation velocity. Increasing interaction time results in growth in both the number and depth of embedment pits on the sample surface. After more than 3 d of interaction, clustered proppant embedment is observed, accompanied by the formation of deep embedment pits on the surface.
{"title":"Micromechanical damage and proppant embedment patterns of fracture surfaces in lacustrine shale CO2 pre-pad energized fracturing","authors":"Lianhe SUN , Haizhu WANG , Gensheng LI , Bin WANG , Sergey STANCHITS , Zelong MAO , Yaochen ZHANG , Alexey CHEREMISIN , Yong ZHENG , Jiacheng JIN","doi":"10.1016/S1876-3804(25)60621-5","DOIUrl":"10.1016/S1876-3804(25)60621-5","url":null,"abstract":"<div><div>To elucidate the mechanism by which supercritical CO<sub>2</sub> (SCCO<sub>2</sub>)-water-shale interactions during CO<sub>2</sub> energized fracturing influence proppant embedment in lacustrine shale, shale samples from the Bohai Bay Basin were selected for SCCO<sub>2</sub>-water-shale interaction experiments. X-ray diffraction (XRD), SEM large-area high-resolution imaging, automated mineral identification and characterization system (AMICS), and nanoindentation tests were employed to examine the micro-mechanical damage mechanisms of fracture surfaces and the evolving patterns of proppant embedment characteristics. The results reveal that: Prolonged interaction time reduces the contents of dolomite, feldspar, and clay minerals, while quartz content increases, with dolomite showing the most pronounced dissolution effect. As interaction time increases, the hardness and elasticity modulus of shale follow a power-law decay pattern, with the peak degradation rate occurring at 1 d, followed by a gradual decline of degradation velocity. Increasing interaction time results in growth in both the number and depth of embedment pits on the sample surface. After more than 3 d of interaction, clustered proppant embedment is observed, accompanied by the formation of deep embedment pits on the surface.</div></div>","PeriodicalId":67426,"journal":{"name":"Petroleum Exploration and Development","volume":"52 4","pages":"Pages 1041-1052"},"PeriodicalIF":8.0,"publicationDate":"2025-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144903611","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-08-01DOI: 10.1016/S1876-3804(25)60612-4
Liang XIONG , Dongxia CHEN , Yingtao YANG , Ling ZHANG , Sha LI , Qiaochu WANG
Taking the second member of the Xujiahe Formation of the Upper Triassic in the Xinchang structural belt as an example, based on data such as logging, production, seismic interpretation and test, a systematic analysis was conducted on the structural characteristics and evolution, reservoir diagenesis and densification processes, and types and stages of faults/fractures, and revealing the multi-stage and multi-factor dynamic coupled enrichment mechanisms of tight gas reservoirs. (1) In the early Yanshan period, the paleo-structural traps were formed with low–medium maturity hydrocarbons accumulating in structural highs driven by buoyancy since reservoirs were not fully densified in this stage, demonstrating paleo-structure control on traps and early hydrocarbon accumulation. (2) In the middle–late Yanshan period, the source rocks became mature to generate and expel a large quantity of hydrocarbons. Grain size and type of sandstone controlled the time of reservoir densification, which restricted the scale of hydrocarbon charging, allowing for only a small-scale migration through sand bodies near the fault/fracture or less-densified matrix reservoirs. (3) During the Himalayan period, the source rocks reached overmaturity, and the residual oil cracking gas was efficiently transported along the late-stage faults/fractures. Wells with high production capacity were mainly located in Type I and II fault/fracture zones comprising the late-stage north-south trending fourth-order faults and the late-stage fractures. The productivity of the wells was controlled by the transformation of the late-stage faults/fractures. (4) The Xinchang structural belt underwent three stages of tectonic evolution, two stages of reservoir formation, and three stages of fault/fractures development. Hydrocarbons mainly accumulated in the paleo-structure highs. After reservoir densification and late fault/fracture adjustment, a complex gas-water distribution pattern was formed. Thus, it is summarized as the model of “near-source and low-abundance hydrocarbon charging in the early stage, and differential enrichment of natural gas under the joint control of fault-fold-fracture complex, high-quality reservoirs and structural highs in the late stage”. Faults/fractures with well-coupled fault-fold-fracture-pore are favorable exploration targets with high exploration effectiveness.
{"title":"Accumulation mechanism and enrichment model of deep tight sandstone gas in second member of Upper Triassic Xujiahe Formation, Xinchang structural belt, Sichuan Basin, SW China","authors":"Liang XIONG , Dongxia CHEN , Yingtao YANG , Ling ZHANG , Sha LI , Qiaochu WANG","doi":"10.1016/S1876-3804(25)60612-4","DOIUrl":"10.1016/S1876-3804(25)60612-4","url":null,"abstract":"<div><div>Taking the second member of the Xujiahe Formation of the Upper Triassic in the Xinchang structural belt as an example, based on data such as logging, production, seismic interpretation and test, a systematic analysis was conducted on the structural characteristics and evolution, reservoir diagenesis and densification processes, and types and stages of faults/fractures, and revealing the multi-stage and multi-factor dynamic coupled enrichment mechanisms of tight gas reservoirs. (1) In the early Yanshan period, the paleo-structural traps were formed with low–medium maturity hydrocarbons accumulating in structural highs driven by buoyancy since reservoirs were not fully densified in this stage, demonstrating paleo-structure control on traps and early hydrocarbon accumulation. (2) In the middle–late Yanshan period, the source rocks became mature to generate and expel a large quantity of hydrocarbons. Grain size and type of sandstone controlled the time of reservoir densification, which restricted the scale of hydrocarbon charging, allowing for only a small-scale migration through sand bodies near the fault/fracture or less-densified matrix reservoirs. (3) During the Himalayan period, the source rocks reached overmaturity, and the residual oil cracking gas was efficiently transported along the late-stage faults/fractures. Wells with high production capacity were mainly located in Type I and II fault/fracture zones comprising the late-stage north-south trending fourth-order faults and the late-stage fractures. The productivity of the wells was controlled by the transformation of the late-stage faults/fractures. (4) The Xinchang structural belt underwent three stages of tectonic evolution, two stages of reservoir formation, and three stages of fault/fractures development. Hydrocarbons mainly accumulated in the paleo-structure highs. After reservoir densification and late fault/fracture adjustment, a complex gas-water distribution pattern was formed. Thus, it is summarized as the model of “near-source and low-abundance hydrocarbon charging in the early stage, and differential enrichment of natural gas under the joint control of fault-fold-fracture complex, high-quality reservoirs and structural highs in the late stage”. Faults/fractures with well-coupled fault-fold-fracture-pore are favorable exploration targets with high exploration effectiveness.</div></div>","PeriodicalId":67426,"journal":{"name":"Petroleum Exploration and Development","volume":"52 4","pages":"Pages 907-920"},"PeriodicalIF":8.0,"publicationDate":"2025-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144903447","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-08-01DOI: 10.1016/S1876-3804(25)60622-7
Qingyou LIU , Tao HUANG
Based on the finite-discrete element method, a three-dimensional numerical model for axial impact rock breaking was established and validated. A computational method for energy conversion during impact rock breaking was proposed, and the effects of conical tooth forward rake angle, rock temperature, and impact velocity on rock breaking characteristics and energy transfer laws were analyzed. The results show that during single impact rock breaking with conical tooth bits, merely 7.52% to 12.51% of the energy is utilized for rock breaking, while a significant 57.26% to 78.10% is dissipated as frictional loss. An insufficient forward rake angle increases tooth penetration depth and frictional loss, whereas an excessive forward rake angle reduces penetration capability, causing bit rebound and greater energy absorption by the drill rod. Thus, an optimal forward rake angle exists. Regarding environmental factors, high temperatures significantly enhance impact-induced rock breaking. Thermal damage from high temperatures reduces rock strength and inhibits its energy absorption. Finally, higher impact velocities intensify rock damage, yet excessively high velocities increase frictional loss and reduce the proportion of energy absorbed by the rock, thereby failing to substantially improve rock breaking efficiency. An optimal impact velocity exists.
{"title":"Impact rock-breaking mechanisms and energy transfer laws of conical tooth bits in hot dry rocks","authors":"Qingyou LIU , Tao HUANG","doi":"10.1016/S1876-3804(25)60622-7","DOIUrl":"10.1016/S1876-3804(25)60622-7","url":null,"abstract":"<div><div>Based on the finite-discrete element method, a three-dimensional numerical model for axial impact rock breaking was established and validated. A computational method for energy conversion during impact rock breaking was proposed, and the effects of conical tooth forward rake angle, rock temperature, and impact velocity on rock breaking characteristics and energy transfer laws were analyzed. The results show that during single impact rock breaking with conical tooth bits, merely 7.52% to 12.51% of the energy is utilized for rock breaking, while a significant 57.26% to 78.10% is dissipated as frictional loss. An insufficient forward rake angle increases tooth penetration depth and frictional loss, whereas an excessive forward rake angle reduces penetration capability, causing bit rebound and greater energy absorption by the drill rod. Thus, an optimal forward rake angle exists. Regarding environmental factors, high temperatures significantly enhance impact-induced rock breaking. Thermal damage from high temperatures reduces rock strength and inhibits its energy absorption. Finally, higher impact velocities intensify rock damage, yet excessively high velocities increase frictional loss and reduce the proportion of energy absorbed by the rock, thereby failing to substantially improve rock breaking efficiency. An optimal impact velocity exists.</div></div>","PeriodicalId":67426,"journal":{"name":"Petroleum Exploration and Development","volume":"52 4","pages":"Pages 1053-1063"},"PeriodicalIF":8.0,"publicationDate":"2025-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144902831","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-08-01DOI: 10.1016/S1876-3804(25)60617-3
Jixin HUANG , Hongjun WANG , Fang XU , Mengying YANG , Junfeng ZHAO , Peijia LI , Chenqing LI , Zeqiang LIU , Ying XIONG , Xiucheng TAN
By integrating core observations, logging data and seismic interpretation, this study takes the massive Cretaceous carbonates in the M block of the Santos Basin, Brazil, as an example to establish the sequence filling pattern of fault-bounded isolated platforms in rift lake basins, reveal the control mechanisms of shoal-body development and reservoir formation, and reconstruct the evolutionary history of lithofacies paleogeography. The following results are obtained. (1) Three tertiary sequences (SQ1–SQ3) are identified in the Lower Cretaceous Itapema–Barra Velha of the M block. During the depositional period of SQ1, the rift basement faults controlled the stratigraphic distribution pattern of thick on both sides and thin in the middle. The strata overlapped to uplift in the early stage. During the depositional period of SQ2–SQ3, the synsedimentary faults controlled the paleogeomorphic reworking process with subsidence in the northwest and uplifting in the northeast, accompanied with the relative fall of lake level. (2) The Lower Cretaceous in the M block was deposited in a littoral-shallow lake, with the lithofacies paleogeographic pattern transiting from the inner clastic shoals and outer shelly shoals in SQ1 to the alternation of mounds and shoals in SQ2–SQ3. (3) Under the joint control of relative lake-level fluctuation, synsedimentary faults and volcanic activity, the shelly shoals in SQ1 tend to accumulated vertically in the raised area, and the mound-shoal complex in SQ2–SQ3 tends to migrate laterally towards the slope-break belt due to the reduction of accommodation space. (4) The evolution pattern of high-energy mounds and shoals, which were vertically accumulated in the early stage and laterally migrated in the later stage, controlled the transformation of high-quality reservoirs from “centralized” to “ring shaped” distribution. The research findings clarify the sedimentary patterns of mounds and shoals and the distribution of favorable reservoirs in the fault-controlled lacustrine isolated platform, providing support for the deepwater hydrocarbon exploration in the subsalt carbonate rocks in the Santos Basin.
{"title":"Sequence stratigraphy analysis and lithofacies paleogeography reconstruction of isolated platform in a rift lake basin: Implications for deepwater hydrocarbon exploration in the subsalt of Santos Basin, Brazil","authors":"Jixin HUANG , Hongjun WANG , Fang XU , Mengying YANG , Junfeng ZHAO , Peijia LI , Chenqing LI , Zeqiang LIU , Ying XIONG , Xiucheng TAN","doi":"10.1016/S1876-3804(25)60617-3","DOIUrl":"10.1016/S1876-3804(25)60617-3","url":null,"abstract":"<div><div>By integrating core observations, logging data and seismic interpretation, this study takes the massive Cretaceous carbonates in the M block of the Santos Basin, Brazil, as an example to establish the sequence filling pattern of fault-bounded isolated platforms in rift lake basins, reveal the control mechanisms of shoal-body development and reservoir formation, and reconstruct the evolutionary history of lithofacies paleogeography. The following results are obtained. (1) Three tertiary sequences (SQ1–SQ3) are identified in the Lower Cretaceous Itapema–Barra Velha of the M block. During the depositional period of SQ1, the rift basement faults controlled the stratigraphic distribution pattern of thick on both sides and thin in the middle. The strata overlapped to uplift in the early stage. During the depositional period of SQ2–SQ3, the synsedimentary faults controlled the paleogeomorphic reworking process with subsidence in the northwest and uplifting in the northeast, accompanied with the relative fall of lake level. (2) The Lower Cretaceous in the M block was deposited in a littoral-shallow lake, with the lithofacies paleogeographic pattern transiting from the inner clastic shoals and outer shelly shoals in SQ1 to the alternation of mounds and shoals in SQ2–SQ3. (3) Under the joint control of relative lake-level fluctuation, synsedimentary faults and volcanic activity, the shelly shoals in SQ1 tend to accumulated vertically in the raised area, and the mound-shoal complex in SQ2–SQ3 tends to migrate laterally towards the slope-break belt due to the reduction of accommodation space. (4) The evolution pattern of high-energy mounds and shoals, which were vertically accumulated in the early stage and laterally migrated in the later stage, controlled the transformation of high-quality reservoirs from “centralized” to “ring shaped” distribution. The research findings clarify the sedimentary patterns of mounds and shoals and the distribution of favorable reservoirs in the fault-controlled lacustrine isolated platform, providing support for the deepwater hydrocarbon exploration in the subsalt carbonate rocks in the Santos Basin.</div></div>","PeriodicalId":67426,"journal":{"name":"Petroleum Exploration and Development","volume":"52 4","pages":"Pages 982-1000"},"PeriodicalIF":8.0,"publicationDate":"2025-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144902827","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-08-01DOI: 10.1016/S1876-3804(25)60620-3
Esteves Pedro ARANHA , Angelica Nara POLICARPO , Augusto Marcio SAMPAIO
This study introduces a novel methodology and makes case studies for anomaly detection in multivariate oil production time-series data, utilizing a supervised Transformer algorithm to identify spurious events related to interval control valves (ICVs) in intelligent well completions (IWC). Transformer algorithms present significant advantages in time-series anomaly detection, primarily due to their ability to handle data drift and capture complex patterns effectively. Their self-attention mechanism allows these models to adapt to shifts in data distribution over time, ensuring resilience against changes that can occur in time-series data. Additionally, Transformers excel at identifying intricate temporal dependencies and long-range interactions, which are often challenging for traditional models. Field tests conducted in the ultradeep water subsea wells of the Santos Basin further validate the model’s capability for early anomaly identification of ICVs, minimizing non-productive time and safeguarding well integrity. The model achieved an accuracy of 0.954 4, a balanced accuracy of 0.969 4 and an F1-Score of 0.957 4, representing significant improvements over previous literature models.
{"title":"A Transformer-based approach for anomaly detection in intelligent well completions","authors":"Esteves Pedro ARANHA , Angelica Nara POLICARPO , Augusto Marcio SAMPAIO","doi":"10.1016/S1876-3804(25)60620-3","DOIUrl":"10.1016/S1876-3804(25)60620-3","url":null,"abstract":"<div><div>This study introduces a novel methodology and makes case studies for anomaly detection in multivariate oil production time-series data, utilizing a supervised Transformer algorithm to identify spurious events related to interval control valves (ICVs) in intelligent well completions (IWC). Transformer algorithms present significant advantages in time-series anomaly detection, primarily due to their ability to handle data drift and capture complex patterns effectively. Their self-attention mechanism allows these models to adapt to shifts in data distribution over time, ensuring resilience against changes that can occur in time-series data. Additionally, Transformers excel at identifying intricate temporal dependencies and long-range interactions, which are often challenging for traditional models. Field tests conducted in the ultradeep water subsea wells of the Santos Basin further validate the model’s capability for early anomaly identification of ICVs, minimizing non-productive time and safeguarding well integrity. The model achieved an accuracy of 0.954 4, a balanced accuracy of 0.969 4 and an F1-Score of 0.957 4, representing significant improvements over previous literature models.</div></div>","PeriodicalId":67426,"journal":{"name":"Petroleum Exploration and Development","volume":"52 4","pages":"Pages 1029-1040"},"PeriodicalIF":8.0,"publicationDate":"2025-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144902830","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-08-01DOI: 10.1016/S1876-3804(25)60626-4
Lin WU , Zhengmeng HOU , Liehui ZHANG , Truitt Christian LÜDDEKE
A coupled PHREEQC-MATLAB simulation approach is proposed to investigate the dynamic changes in rock porosity, gas storage capacity, formation water salinity, and reservoir temperature driven by biogeochemical interactions during cyclic underground bio-methanation (UBM) of CO2 and H2, and to quantitatively examine how the evolution of these parameters influences CH4 production efficiency. The results indicate that during the cyclic UBM of CO2-H2, the formation water undergoes a dynamic acid-base alternation, leading to periodic mineral dissolution and precipitation with limited impact on rock porosity. Across different mineral systems, the maximum CH4 production rate remains consistently around 3.6×10−3 mol/(L·d) in each cycle. With an increasing number of cycles, under high initial salinity conditions, the metabolic water produced by methanogens can significantly reduce the formation water salinity, gradually enhancing the CH4 production rate to levels comparable with those under low initial salinity. Additionally, the increased volume of produced water reduces the gas storage capacity of the reservoir. This reduction becomes more pronounced at higher initial CO2-H2 pressures, accompanied by a more significant increase in CH4 production rate increment. Furthermore, the heat generated by methanogen metabolism leads to an increase in reservoir temperature, with the extent of temperature rise significantly influenced by heat loss. If the heat loss is neglected, the reservoir temperature can increase by up to 17.1 °C after five cycles (10 years). When the reservoir has a higher initial temperature, the elevated thermal conditions may reduce CH4 production efficiency.
{"title":"A simulation study of biogeochemical interactions in cyclic underground bio-methanation of carbon dioxide and hydrogen","authors":"Lin WU , Zhengmeng HOU , Liehui ZHANG , Truitt Christian LÜDDEKE","doi":"10.1016/S1876-3804(25)60626-4","DOIUrl":"10.1016/S1876-3804(25)60626-4","url":null,"abstract":"<div><div>A coupled PHREEQC-MATLAB simulation approach is proposed to investigate the dynamic changes in rock porosity, gas storage capacity, formation water salinity, and reservoir temperature driven by biogeochemical interactions during cyclic underground bio-methanation (UBM) of CO<sub>2</sub> and H<sub>2</sub>, and to quantitatively examine how the evolution of these parameters influences CH<sub>4</sub> production efficiency. The results indicate that during the cyclic UBM of CO<sub>2</sub>-H<sub>2</sub>, the formation water undergoes a dynamic acid-base alternation, leading to periodic mineral dissolution and precipitation with limited impact on rock porosity. Across different mineral systems, the maximum CH<sub>4</sub> production rate remains consistently around 3.6×10<sup>−3</sup> mol/(L·d) in each cycle. With an increasing number of cycles, under high initial salinity conditions, the metabolic water produced by methanogens can significantly reduce the formation water salinity, gradually enhancing the CH<sub>4</sub> production rate to levels comparable with those under low initial salinity. Additionally, the increased volume of produced water reduces the gas storage capacity of the reservoir. This reduction becomes more pronounced at higher initial CO<sub>2</sub>-H<sub>2</sub> pressures, accompanied by a more significant increase in CH<sub>4</sub> production rate increment. Furthermore, the heat generated by methanogen metabolism leads to an increase in reservoir temperature, with the extent of temperature rise significantly influenced by heat loss. If the heat loss is neglected, the reservoir temperature can increase by up to 17.1 °C after five cycles (10 years). When the reservoir has a higher initial temperature, the elevated thermal conditions may reduce CH<sub>4</sub> production efficiency.</div></div>","PeriodicalId":67426,"journal":{"name":"Petroleum Exploration and Development","volume":"52 4","pages":"Pages 1102-1112"},"PeriodicalIF":8.0,"publicationDate":"2025-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144903517","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-08-01DOI: 10.1016/S1876-3804(25)60615-X
Qiang XU , Wenjie YANG , Long WEN , Shuangjian LI , Bing LUO , Di XIAO , Zhanfeng QIAO , Shijun LIU , Minglong LI , Jie GUO , Xianfeng TAN , Shuyuan SHI , Xiucheng TAN
This study reconstructed the paleo-uplift and depression pattern within the sequence stratigraphic framework of the Mid-Permian Maokou Formation, Sichuan Basin, investigated its tectono-sedimentary mechanisms and its control on paleogeomorphology and large-sale shoals based on analysis of outcrops, loggings and seismic data. The results show that the Maokou Formation comprises two third-order sequences, six fourth-order sequences (SSQ1–SSQ6), and four distinct slope-break zones developing progressively from north to south. Slope-break zones I–III in the northern basin, controlled by synsedimentary extensional faults, exhibited a NE-trending linear distribution with gradual southeastward migration. In contrast, slope-break zone IV in the southern basin displayed an arcuate distribution along the Emeishan Large Igneous Province (ELIP). The evolutions of these multistage slope-break zones governed the Mid-Permian paleogeomorphy in the Sichuan Basin transformations from a giant, north-dipping gentle slope (higher in the southwest than in the northeast) in the early-stage (SSQ1–SSQ2) to a platform (south)-basin (north) pattern in the middle-stage (SSQ3–SSQ5). Ultimately, a further depression zone developed in the southwestern basin during the late-stage (SSQ6), forming a paleo-uplift bounded by two depressions. The developments of the Mid-Permian paleogeomorphic configuration reflected the combined control by the rapid subduction of the Mianlüe Ocean and the episodic eruptions of the Emeishan mantle plume (or hot spots), which jointly facilitated the formation of extensive high-energy shoal facies belts along slope-break zones and around paleo-volcanic uplifts.
{"title":"Controlling effects of the Mid-Permian multistage slope-break zones on paleogeomorphology and large-scale shoals in the Sichuan Basin, SW China","authors":"Qiang XU , Wenjie YANG , Long WEN , Shuangjian LI , Bing LUO , Di XIAO , Zhanfeng QIAO , Shijun LIU , Minglong LI , Jie GUO , Xianfeng TAN , Shuyuan SHI , Xiucheng TAN","doi":"10.1016/S1876-3804(25)60615-X","DOIUrl":"10.1016/S1876-3804(25)60615-X","url":null,"abstract":"<div><div>This study reconstructed the paleo-uplift and depression pattern within the sequence stratigraphic framework of the Mid-Permian Maokou Formation, Sichuan Basin, investigated its tectono-sedimentary mechanisms and its control on paleogeomorphology and large-sale shoals based on analysis of outcrops, loggings and seismic data. The results show that the Maokou Formation comprises two third-order sequences, six fourth-order sequences (SSQ1–SSQ6), and four distinct slope-break zones developing progressively from north to south. Slope-break zones I–III in the northern basin, controlled by synsedimentary extensional faults, exhibited a NE-trending linear distribution with gradual southeastward migration. In contrast, slope-break zone IV in the southern basin displayed an arcuate distribution along the Emeishan Large Igneous Province (ELIP). The evolutions of these multistage slope-break zones governed the Mid-Permian paleogeomorphy in the Sichuan Basin transformations from a giant, north-dipping gentle slope (higher in the southwest than in the northeast) in the early-stage (SSQ1–SSQ2) to a platform (south)-basin (north) pattern in the middle-stage (SSQ3–SSQ5). Ultimately, a further depression zone developed in the southwestern basin during the late-stage (SSQ6), forming a paleo-uplift bounded by two depressions. The developments of the Mid-Permian paleogeomorphic configuration reflected the combined control by the rapid subduction of the Mianlüe Ocean and the episodic eruptions of the Emeishan mantle plume (or hot spots), which jointly facilitated the formation of extensive high-energy shoal facies belts along slope-break zones and around paleo-volcanic uplifts.</div></div>","PeriodicalId":67426,"journal":{"name":"Petroleum Exploration and Development","volume":"52 4","pages":"Pages 952-967"},"PeriodicalIF":8.0,"publicationDate":"2025-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144902825","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-08-01DOI: 10.1016/S1876-3804(25)60616-1
Yunyan NI , Deyu GONG , Chun YANG , Limiao YAO , Ye ZHANG , Chun MENG , Jinchuan ZHANG , Li WANG , Yuan WANG , Guoliang DONG
Based on geochemical data from natural gas samples across spring water systems and sedimentary basins, including Songliao, Bohai Bay, Sanshui, Sichuan, Ordos, Tarim and Ying-Qiong, this paper systematically compares the geochemical compositions of abiogenic versus biogenic gases. Emphasis is placed on the diagnostic signatures of abiogenic gases in terms of gas composition, and carbon, hydrogen and helium isotopes. The main findings are as follows. (1) In hydrothermal spring systems, abiogenic alkane gases are extremely scarce. Methane concentrations are typically less than 1%, with almost no detectable C2+ hydrocarbons. The gas is dominantly composed of CO2, while N2 is the major component in a few samples. (2) Abiogenic alkane gases display distinct isotopic signatures, including enriched methane carbon isotopic compositions (δ13C1>–25‰ generally), complete carbon isotopic reversal (δ13C1>δ13C2>δ13C3>δ13C4), and enriched helium isotope (R/Ra>0.5, CH4/3He≤106 generally). (3) The hydrogen isotopic composition of abiogenic alkane gases may be characterized by a positive sequence (δD1<δD2<δD3), or a complete reversal (δD1>δD2>δD3), or a V-shaped distribution (δD1>δD2, δD2<δD3). The hydrogen isotopic compositions of methane generally show limited variation (about 9‰), possibly due to hydrogen isotopic exchange with connate water. (4) In terms of identifying gas origin, CH4/3He-R/Ra and δ13CCO2–R/Ra charts are more effective than CO2/3He-R/Ra chart. These new geological insights provide theoretical clues and diagnostic charts for the genetic identification of natural gas and further research on abiogenic gases.
{"title":"Isotopic fractionation and identification of abiogenic alkane gases in China","authors":"Yunyan NI , Deyu GONG , Chun YANG , Limiao YAO , Ye ZHANG , Chun MENG , Jinchuan ZHANG , Li WANG , Yuan WANG , Guoliang DONG","doi":"10.1016/S1876-3804(25)60616-1","DOIUrl":"10.1016/S1876-3804(25)60616-1","url":null,"abstract":"<div><div>Based on geochemical data from natural gas samples across spring water systems and sedimentary basins, including Songliao, Bohai Bay, Sanshui, Sichuan, Ordos, Tarim and Ying-Qiong, this paper systematically compares the geochemical compositions of abiogenic versus biogenic gases. Emphasis is placed on the diagnostic signatures of abiogenic gases in terms of gas composition, and carbon, hydrogen and helium isotopes. The main findings are as follows. (1) In hydrothermal spring systems, abiogenic alkane gases are extremely scarce. Methane concentrations are typically less than 1%, with almost no detectable C<sub>2+</sub> hydrocarbons. The gas is dominantly composed of CO<sub>2</sub>, while N<sub>2</sub> is the major component in a few samples. (2) Abiogenic alkane gases display distinct isotopic signatures, including enriched methane carbon isotopic compositions (<em>δ</em><sup>13</sup>C<sub>1</sub>>–25‰ generally), complete carbon isotopic reversal (<em>δ</em><sup>13</sup>C<sub>1</sub>><em>δ</em><sup>13</sup>C<sub>2</sub>><em>δ</em><sup>13</sup>C<sub>3</sub>><em>δ</em><sup>13</sup>C<sub>4</sub>), and enriched helium isotope (<em>R</em>/<em>R</em><sub>a</sub>>0.5, CH<sub>4</sub>/<sup>3</sup>He≤10<sup>6</sup> generally). (3) The hydrogen isotopic composition of abiogenic alkane gases may be characterized by a positive sequence (<em>δ</em>D<sub>1</sub><<em>δ</em>D<sub>2</sub><<em>δ</em>D<sub>3</sub>), or a complete reversal (<em>δ</em>D<sub>1</sub>><em>δ</em>D<sub>2</sub>><em>δ</em>D<sub>3</sub>), or a V-shaped distribution (<em>δ</em>D<sub>1</sub>><em>δ</em>D<sub>2</sub>, <em>δ</em>D<sub>2</sub><<em>δ</em>D<sub>3</sub>). The hydrogen isotopic compositions of methane generally show limited variation (about 9‰), possibly due to hydrogen isotopic exchange with connate water. (4) In terms of identifying gas origin, CH<sub>4</sub>/<sup>3</sup>He-<em>R</em>/<em>R</em><sub>a</sub> and <em>δ</em><sup>13</sup>C<sub>CO2</sub>–<em>R</em>/<em>R</em><sub>a</sub> charts are more effective than CO<sub>2</sub>/<sup>3</sup>He-<em>R</em>/<em>R</em><sub>a</sub> chart. These new geological insights provide theoretical clues and diagnostic charts for the genetic identification of natural gas and further research on abiogenic gases.</div></div>","PeriodicalId":67426,"journal":{"name":"Petroleum Exploration and Development","volume":"52 4","pages":"Pages 968-981"},"PeriodicalIF":8.0,"publicationDate":"2025-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144902826","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-08-01DOI: 10.1016/S1876-3804(25)60618-5
Yifan SONG , Lirong DOU , Kunye XIAO , Dingsheng CHENG , Yebo DU , Li WANG , Shengqiang YUAN , Xinshun ZHANG
Based on two-dimensional/three-dimensional seismic and logging data, combined with the analysis of low-temperature thermochronology data, the unconformity surface characteristics and the patterns and dynamic mechanisms of inverted structures in the Doseo Basin in the Central and West African rift systems are systematically analyzed. Seismic profiles reveal two key inversion unconformable surfaces in the basin, i.e. the T5 interface within the Upper Cretaceous and the T4 interface at the top of the Cretaceous, which control the development of inverted structures in the basin. Four types of inverted structures, i.e. fault-associated, thrust, fold, and back-shaped negative flower, are identified. Spatially, they form six inverted structural belts trending in NE-NEE direction. The thermal history simulation of apatite fission track reveals two rapid cooling events in the late Late Cretaceous (85–80 Ma, cooling by 15 °C) and the Eocene–Oligocene (30–40 Ma, cooling by 35 °C), corresponding respectively to the formation periods of the T5 and T4 interface. The dynamics analysis of structural inversion indicates that the structural inversion in the Late Cretaceous was controlled by the subduction and long-range compression within the Tethys Ocean in the north of African Plate, while the structural inversion in the Eocene–Oligocene was drived by the stress transmission from the African–Eurasian collision. The two events were all controlled by the continuous tectonic regulation of the intracratonic basin by the evolution of the Tethys tectonic domain. The two periods of structural inversion enhanced the efficiency of oil and gas migration by controlling the types of traps (anticline and fault-related traps) and fault activation, precisely matching the hydrocarbon generation peaks of the Lower Cretaceous source rocks in the Late Cretaceous and Eocene, thereby controlling the formation of large-scale oil and gas reservoirs in the Doseo Basin. This geological insight provides a critical basis for the theoretical research on the evolution and hydrocarbon accumulation of inverted structures in discrete strike-slip rift systems.
{"title":"Characteristics, genetic mechanism and hydrocarbon accumulation of inverted structures in the Doseo Basin, Chad","authors":"Yifan SONG , Lirong DOU , Kunye XIAO , Dingsheng CHENG , Yebo DU , Li WANG , Shengqiang YUAN , Xinshun ZHANG","doi":"10.1016/S1876-3804(25)60618-5","DOIUrl":"10.1016/S1876-3804(25)60618-5","url":null,"abstract":"<div><div>Based on two-dimensional/three-dimensional seismic and logging data, combined with the analysis of low-temperature thermochronology data, the unconformity surface characteristics and the patterns and dynamic mechanisms of inverted structures in the Doseo Basin in the Central and West African rift systems are systematically analyzed. Seismic profiles reveal two key inversion unconformable surfaces in the basin, i.e. the T<sub>5</sub> interface within the Upper Cretaceous and the T<sub>4</sub> interface at the top of the Cretaceous, which control the development of inverted structures in the basin. Four types of inverted structures, i.e. fault-associated, thrust, fold, and back-shaped negative flower, are identified. Spatially, they form six inverted structural belts trending in NE-NEE direction. The thermal history simulation of apatite fission track reveals two rapid cooling events in the late Late Cretaceous (85–80 Ma, cooling by 15 °C) and the Eocene–Oligocene (30–40 Ma, cooling by 35 °C), corresponding respectively to the formation periods of the T<sub>5</sub> and T<sub>4</sub> interface. The dynamics analysis of structural inversion indicates that the structural inversion in the Late Cretaceous was controlled by the subduction and long-range compression within the Tethys Ocean in the north of African Plate, while the structural inversion in the Eocene–Oligocene was drived by the stress transmission from the African–Eurasian collision. The two events were all controlled by the continuous tectonic regulation of the intracratonic basin by the evolution of the Tethys tectonic domain. The two periods of structural inversion enhanced the efficiency of oil and gas migration by controlling the types of traps (anticline and fault-related traps) and fault activation, precisely matching the hydrocarbon generation peaks of the Lower Cretaceous source rocks in the Late Cretaceous and Eocene, thereby controlling the formation of large-scale oil and gas reservoirs in the Doseo Basin. This geological insight provides a critical basis for the theoretical research on the evolution and hydrocarbon accumulation of inverted structures in discrete strike-slip rift systems.</div></div>","PeriodicalId":67426,"journal":{"name":"Petroleum Exploration and Development","volume":"52 4","pages":"Pages 1001-1016"},"PeriodicalIF":8.0,"publicationDate":"2025-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144902828","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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