地质力学学报

The marine environment and organic matter enrichment model of the intracontinental Upper Yangtze Craton during the Middle Triassic

TANG Song, WANG Xianfeng, CHEN Anqing, ZHOU Linlang, QI Yan, PENG Qiu, QIAN Yangjiaojiao, YUE Dali

Objective The exploration of marlstone reservoirs represents a current frontier for expanding oil and gas resources. The recent discovery of unconventional marine oil and gas in the Lei 3-2 sub-member of the Middle Triassic Leikoupo Formation in Well CT-1 reveals a new prospective area. However, the organic matter enrichment mechanisms and exploration potential of this sub-salt lagoon marlstone remain unclear, hindering further exploration. Methods This study, focusing on Well CT-1 in the central Sichuan Basin, investigates the organic matter enrichment mechanism through rock mineralogy and paleo-oceanographic geochemical proxies. This study also characterizes the reservoir properties and distribution via reservoir characterization and sedimentary facies analysis to evaluate its potential. Results The marlstone was deposited in an anoxic, deep-water lagoon of a carbonate platform with high paleo-productivity. The enrichment of organic matter, with an average total organic carbon (TOC) content of 1.16% (reaching up to 1.78%), was co-controlled by these reducing conditions and high productivity. Analyses (CT and SEM) of the high-quality "sweet spot" intervals show that the storage space is predominantly composed of nano- to micro-scale pores and microfractures, with porosity exceeding 3%. The reservoir developed in a deep-water, marlstone- and gypsum-rich lagoon within an epicontinental sea carbonate platform. Conclusion The widespread distribution of deep-water lagoons during the deposition of the Lei 3-2 sub-member is associated with a maximum flooding event. Concurrently, the prevailing monsoon climate significantly enhanced weathering and nutrient input, while the overlying regressive evaporites provided a seal for long-term and efficient organic matter preservation. [Significance] Comprehensive analysis suggests that the extensively distributed, organic-rich deep-water lagoon marlstone formed during this transgression in the intracontinental sag of the Upper Yangtze Craton is not only a viable unconventional exploration target but also likely acts as a hydrocarbon source for conventional reservoirs within the Leikoupo Formation.

Mechanisms of stress evolution and infill-well fracture disturbance in shale gas reservoirs with natural weak planes

RUAN Qi, ZHANG Liehui, ZHAO Yulong, ZHANG Deliang, ZHENG Shizhuo

Objective Mid-to-deep shale gas reservoirs exhibit a composite fracture–matrix structure, in which internal weak planes play an essential role in stress evolution and fracture propagation. Few studies have treated natural fractures as both hydraulic and mechanical weak planes simultaneously, nor has there been systematic and quantitative analysis of the impact of these fractures on four-dimensional stress evolution and fracture propagation in infill-wells during production. Methods To address these knowledge gaps, this study conducts laboratory tests to obtain the normal stiffness and hydraulic properties of weak planes, and develops a four-dimensional stress evolution model for mid-to-deep shale gas reservoirs that captures the coupled hydraulic–mechanical weakening behavior of natural fractures. The model is then used to analyze how weak planes perturb the in-situ stress field and the morphology of hydraulic fractures in infill-wells at different stages of production. Results Low-stiffness weak planes are prone to deformation, with reduced internal stress and stress concentration at fracture tips. Moreover, the disturbance of the maximum horizontal principal stress increases progressively with the growing angle between the weak plane and the principal stress direction, while the minimum horizontal principal stress exhibits a non-monotonic response: first decreasing, then increasing. During production, the deviation of stress orientation is more pronounced when mechanical weak planes are considered. Correspondingly, infill well fractures extend farther along the original maximum horizontal stress direction when not in contact with fracture zones, while the lateral expansion is enhanced and the propagation along the original maximum horizontal stress is shortened. These differences remain relatively unchanged over time, reflecting the fact that weak planes primarily influence stress disturbance in the early stages, becoming stable later on. Conclusions This study reveals how weak planes disturb the four-dimensional stress evolution. It provides theoretical guidance and practical reference for stress management and fracture optimization in hydraulic fracturing and infill development of mid-to-deep shale gas reservoirs.

Impact of middle to late Triassic climate change on organic matter enrichment in hydrocarbon source rocks of the Chang 7 Member, Yanchang Formation, southeastern Ordos Basin

LU Man, DUAN Guoqiang, ZHANG Tongxi, HUANG Tianhua, WANG Zhaoyang, LI Dewei

Objective The middle to late Triassic was a period of critical climatic transition in Earth's history. Multiple global humid climate events during this time profoundly impacted both marine and terrestrial depositional environments, facilitating the development of marine and continental source rocks. Methods This study focuses on the hydrocarbon source rocks of the seventh member of the Yanchang Formation (Chang 7 Member) in the southeastern Ordos Basin. Based on integrated elemental geochemical and molecular organic geochemical analyses, this study explores the relationship between middle to late Triassic humid climatic events and organic matter enrichment in lacustrine settings. Results The lower to middle interval of Submember 3 of Chang 7 Member (695–660 m in depth) is characterized by high total organic carbon content and good hydrocarbon generation potential. Chemical weathering indices indicate that this interval was deposited underwarmer and more humid climatic conditions, while the overlying upper portion of Submember 3 and Submembers 2 and 1 were deposited under cooler and drier conditions. By combining global characteristics of middle to late Triassic humid events with palynostratigraphy, zircon U–Pb geochronology, and carbon isotope stratigraphy, this study links the lower to middle interval of the Submember 3 and the middle to late Triassic Ladinian–Carnian humid climate event. Conclusions The findings suggest that, under the influence of humid climate events, enhanced terrestrial nutrient influxes stimulated primary productivity in the lake. Concurrently, intensified water column stratification and bottom-water anoxia created favorable conditions for organic matter preservation, leading to the deposition of high-quality source rocks. Following the event, the climate shifted towards colder and drier conditions. This reduced terrestrial input, decreased primary lake productivity, lowered oxygen depletion in the water, and led to less favorable conditions for organic matter preservation and enrichment. [ Significance] This study not only provides new evidence for paleoclimatic and paleoenvironmental reconstruction during the middle to late Triassic but also offers an important reference for understanding organic matter enrichment mechanisms during major climatic transitions in Earth’s history.

Intelligent prediction method and application of single-well in-situ stress in shale reservoirs driven by multi-source data

SHEN Baojian, LI Dan, HE Jianhua, XU Bilan, WU Yanfeng, WANG Ruyue, JIANG Rui, LI Ruixue, HUO Zhizhou, LIU Kun

Objective Deep shale reservoirs are characterized by high temperature, high pressure, elevated in situ stress, and strong plasticity. Conventional in-situ stress testing methods and log interpretation models, often calibrated under simplified laboratory conditions, suffer from limited predictive accuracy, high operational cost, and poor generalizability—challenges that constrain their utility in guiding shale gas exploration and development. Methods Focusing on a structurally complex shale gas block in southern Sichuan as a representative case, we integrated dynamic and static multi-source data across drilling, logging, testing, and production stages. Along with experimental measurements of the physical and mechanical properties of rock under different conditions, we developed a hybrid stress prediction model by combining machine learning techniques with geomechanical principles. This multi-method, log-based intelligent prediction framework enables the generation of high-resolution in-situ stress profiles for efficient shale gas development. Results In the first member of the Longmaxi Formation (Long-1 Member), organic content, confining pressure, and lamination structures significantly influence mechanical anisotropy, particularly in Beds 1–4, which exhibit stronger anisotropy than the upper beds. Based on these findings, we developed a mechanically calibrated anisotropic stress interpretation model for deep shales. Using laboratory- and field-calibrated synthetic stress datasets, we established a standardized stress database for the southern Sichuan shale reservoir. Key sensitive logging parameters, including shear wave slowness, resistivity, acoustic logs, and Young's modulus were identified via Pearson correlation analysis. An optimized XGBoost model achieved interpretation accuracies above 90% for all three principal stress components, with an RMSE of 6.63, an MAE of 3.89, and a coefficient of determination (R²) of 0.91, indicating strong robustness and generalizability. The results revealed four distinct stress barrier layers from the Wufeng Formation to the Longmaxi Formation, and the top of Bed 1 and Bed 6 acted as dominant stress-sealing interfaces. Localized compressive stresses induced by fold-related deformation further enhanced vertical stress compartmentalization and increased the minimum horizontal principal stress, thereby exerting significant influence on hydraulic fracturing performance. Conclusions The study revealed the geological factors controlling the mechanical anisotropy of the shale in the Long-1 Member, and established an isotropic in-situ stress interpretation model suitable for deep shale reservoirs accordingly. An integrated intelligent model, L-XGBoost, was adopted to achieve a prediction accuracy exceeding 90% for three-dimensional in-situ stresses. The research also clarified the development characteristics of four sets of stress barrier layers within the Long-1 Member shale and their impact on fracturing effectiveness. Significance These insights provide a scientific basis for fine-scale stratigraphic subdivision and three-dimensional well pattern design for shale gas development in the tectonically complex southeastern Sichuan Basin.

Research progress and development trends of low-friction drilling fluid for shale gas

SUN Jinsheng, CAI Wenhui, WANG Jintang, LYU Kaihe, ZHAO Ke, ZHANG Junhao

Objective Shale gas is an important unconventional natural gas resource in China, boasting significant potential reserves. Deep shale gas reservoirs generally have specific geological characteristics, such as low porosity and permeability, strong abrasiveness, and high temperature and pressure. Technical problems often arise during drilling, such as wellbore instability, friction in the long horizontal section, and large torque. Low-friction drilling fluid technology is key to safe and efficient drilling in deep shale gas reservoirs. Methods Based on an investigation of the current state of shale gas exploration and development in the world, this paper analyzes the evaluation index of drilling fluid lubricity and its drag reduction mechanisms, including, among others, lubrication film formation, rolling friction, and wettability regulation. Results This paper systematically reviews the lubrication performance and research progress of various low-friction drilling fluid systems, such as water-based and oil-based drilling fluid systems. Conclusions It is proposed that, in the future, it will be necessary to continue to strengthen the research and development of new, high-performance drilling fluid lubricants; to promote the intelligent and green transformation of drilling fluid systems; and to facilitate the multi-objective coordination between lubrication and wellbore stability technologies to meet the challenges posed by complex formations. [Significance] This research provides strong technical support for the safe and efficient development of global shale gas, for enhancing the productivity of deep oil and gas reserves.

Early Access

Cover Page

2026, 32(1).

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Contents

2026, 32(1): 1-4.

Abstract (55) HTML (31) PDF (407KB)(73)

2026, 32(1): 1-2. doi: 10.12090/jissn.1006-6616.20253201

Abstract (74) HTML (34) PDF (312KB)(88)

Research progress and development trends of low-friction drilling fluid for shale gas

SUN Jinsheng, CAI Wenhui, WANG Jintang, LYU Kaihe, ZHAO Ke, ZHANG Junhao

2026, 32(1): 3-14. doi: 10.12090/j.issn.1006-6616.2025151

Abstract (195) HTML (93) PDF (826KB)(150)

The marine environment and organic matter enrichment model of the intracontinental Upper Yangtze Craton during the Middle Triassic

TANG Song, WANG Xianfeng, CHEN Anqing, ZHOU Linlang, QI Yan, PENG Qiu, QIAN Yangjiaojiao, YUE Dali

2026, 32(1): 15-30. doi: 10.12090/j.issn.1006-6616.2025055

Abstract (171) HTML (48) PDF (6043KB)(150)

Assessment of shale gas enrichment factors and delineation of favorable exploration zones in the first submember of the first member of the Longmaxi Formation, Tiangongtang area, southwestern Sichuan

LIU Shengjun, YUE Wenhan, LIU Yongyang, NI Jia, FANG Rui, DING Jieming, XU Fei, FAN Cunhui, XIA Tong, XU Lu

2026, 32(1): 31-48. doi: 10.12090/j.issn.1006-6616.2025103

Abstract (141) HTML (55) PDF (7930KB)(143)

Geochemical characteristics and geological implications of dark shale in the second submember of the first member of the Qiongzhusi Formation, Ziyang–Weiyuan area, China

XIE Shengyang, YANG Xuefeng, LI Bo, ZHAO Shengxian, ZHANG Jian, ZHANG Chenglin, LIU Jiawei, ZHANG Deliang, HUANG Shan, CHEN Xin, LIU Yongyang, ZHU Ning, WANG Gaoxiang, YIN Meixuan

2026, 32(1): 49-66. doi: 10.12090/j.issn.1006-6616.2025125

Abstract (138) HTML (43) PDF (3013KB)(138)

Hydrocarbon generation potential of deeply buried shales within the Jurassic transitional Badaowan Formation, central Junggar Basin

ZENG Zhiping, LI Baoqing, WANG Jinduo, LIU Hui, LI Shaojie, GAN Runkun

2026, 32(1): 67-83. doi: 10.12090/j.issn.1006-6616.2025111

Abstract (140) HTML (52) PDF (2322KB)(127)

Genesis of organic-rich shales in the Fengcheng Formation, southern Mahu Sag: Evidence from organic petrology, biomarkers, and isotopes

CHEN Shanhe, QI Hongyan, WANG Wei, WANG Zhenlin, LI Yanghu, TANG Fukang, GUO Shouxin, FU Zhenghang

2026, 32(1): 84-106. doi: 10.12090/j.issn.1006-6616.2025146

Abstract (139) HTML (36) PDF (2821KB)(123)

Impact of middle to late Triassic climate change on organic matter enrichment in hydrocarbon source rocks of the Chang 7 Member, Yanchang Formation, southeastern Ordos Basin

LU Man, DUAN Guoqiang, ZHANG Tongxi, HUANG Tianhua, WANG Zhaoyang, LI Dewei

2026, 32(1): 107-123. doi: 10.12090/j.issn.1006-6616.2025139

Abstract (145) HTML (54) PDF (1927KB)(124)

Refined characteristics and evaluation of shale reservoirs in the Wulalike Formation, central-western margin of the Ordos Basin

MA Mingyang, XIE Mengyu, ZHANG Dongdong, WANG Qianping, LIU Wenhui, WANG Tong, LI Fengjiao, SUN Wenyi, GUAN Xiaohan

2026, 32(1): 124-141. doi: 10.12090/j.issn.1006-6616.2025117

Abstract (116) HTML (43) PDF (6221KB)(67)

Mechanisms of stress evolution and infill-well fracture disturbance in shale gas reservoirs with natural weak planes

RUAN Qi, ZHANG Liehui, ZHAO Yulong, ZHANG Deliang, ZHENG Shizhuo

2026, 32(1): 142-158. doi: 10.12090/j.issn.1006-6616.2025144

Abstract (177) HTML (45) PDF (3948KB)(122)

Experimental study on the elastic–plastic deformation and failure behavior of deep shale with well-developed inclined bedding

HUO Tingwang, WANG Daobing, SHENG Mao, DONG Yongcun, WANG Qiuyan, HUANG Weihan, YU Bo

2026, 32(1): 159-183. doi: 10.12090/j.issn.1006-6616.2025133

Abstract (162) HTML (46) PDF (3621KB)(139)

Refined characterization of the 3D fracture complexity index based on Well-Seismic Integration

ZHANG Jinfa, FENG Yongcun, HE Bing, MA Sijia, WEI Jingyi, DENG Jin'gen

2026, 32(1): 184-196. doi: 10.12090/j.issn.1006-6616.2025059

Abstract (112) HTML (60) PDF (9867KB)(125)

Study on the influence of in-situ stress changes on shale fracture propagation considering the effect of effective stress coefficients

ZHANG Chenxi, TANG Huiying, TANG Yuxin, CHEN Yue, DENG Wenbin

2026, 32(1): 197-212. doi: 10.12090/j.issn.1006-6616.2025145

Abstract (143) HTML (49) PDF (2631KB)(117)

Evaluation of post-fracturing production efficiency in shale oil horizontal wells based on behind-casing fiber-optic monitoring

WAN Youyu, LIN Hai, ZHOU Wei, LIU Zhen, JIANG Haoyan, XIE Guiqi, LIU Shiduo, LIU Yong, YANG Jianxuan, WU Kunyu

2026, 32(1): 213-226. doi: 10.12090/j.issn.1006-6616.2025090

Abstract (139) HTML (36) PDF (2202KB)(115)

Intelligent prediction method and application of single-well in-situ stress in shale reservoirs driven by multi-source data

SHEN Baojian, LI Dan, HE Jianhua, XU Bilan, WU Yanfeng, WANG Ruyue, JIANG Rui, LI Ruixue, HUO Zhizhou, LIU Kun

2026, 32(1): 227-244. doi: 10.12090/j.issn.1006-6616.2025126

Abstract (195) HTML (49) PDF (3480KB)(151)

An intelligent lithofacies identification method for well logging of deep carbonate rocks incorporating sequence stratigraphic prior information

ZHANG Mingdi, LI Meng, LIU Yuanyang, HUANG Yuan, CUI Shuyue

2026, 32(1): 245-257. doi: 10.12090/j.issn.1006-6616.2025108

Abstract (137) HTML (75) PDF (6100KB)(140)

Governing factors and mechanisms of CO₂ microscale sweep efficiency in shale reservoirs based on causal machine learning

JIANG Jiatong, ZHANG Yihang, SONG Zhaojie, YAN Ruisheng, ZHENG Lijun, ZHANG Kaixing, LI Peiyu, HUANG Shengjie, TANGPARITKUL Suparit

2026, 32(1): 258-271. doi: 10.12090/j.issn.1006-6616.2025116

Abstract (125) HTML (46) PDF (3811KB)(118)

J.S.Lee’s scientific thought and the pioneering of China’s offshore oil industry (1954–1971): A study based on archival research and strategic practice

ZHAO Man

2026, 32(1): 272-284. doi: 10.12090/j.issn.1006-6616.2025180

Abstract (94) HTML (43) PDF (6991KB)(134)

Inside Front Cover

2026, 32(1).

Abstract (48) PDF (11557KB)(38)

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2026, 32(1).

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2026 No.2

The stress changes of the 2025 Dingri M 6.8 earthquake on the surrounding areas

ZHANG Chenchen, WAN Yongge, GUAN Zhaoxuan, ZHAO Jiebin, WANG Runyan, ZHOU Mingyue

2026, 32(2): 1-14. doi: 10.12090/j.issn.1006-6616.2025072

Abstract (127) HTML (30) PDF (4603KB)(139)

Composition, tectonic framework, and evolution of the Luxi Orogenic Belt in the North China Craton during the Late Neoarchean

WANG Dongming, HU Jianmin, ZHAO Yuanfang, YAN Jiyuan, GONG Wangbin, ZHANG Zhigang

2026, 32(2): 1-27. doi: 10.12090/j.issn.1006-6616.2025033

Abstract (338) HTML (64) PDF (8668KB)(162)

Refined Characterization and Analysis of Shallow Crustal Stresses Based on Hydraulic Fracturing Data

XIONG Sijie, MA Xiaodong, YANG Yuehui, WU Bangchen, LI Awei, SUN Dongsheng

2026, 32(2): 1-13. doi: 10.12090/j.issn.1006-6616.2025096

Abstract (27) HTML (5) PDF (4228KB)(29)

Tectonic evolution of the Sumatran Fault: synthesis and perspective

GUO Lin, CHU Yang, LIN Wei, LEI Yiyang, LIU Tanjie, GUO Yilin, MENG Lingtong

2026, 32(2): 1-22. doi: 10.12090/j.issn.1006-6616.2025067

Abstract (399) HTML (96) PDF (5012KB)(162)

Geochemical characteristics of Late Paleozoic–Early Mesozoic volcanic rocks in Heiyingshan, Beishan Orogenic Belt: evidence of the transition from subduction to collision of the Paleo-Asian Ocean

DING Yiwen, SHAO Zhaogang, CHEN Yanfei, CHEN Xuanhua, LI Bing, YU Wei, XU Daxing, HAN Lele

2026, 32(2): 1-16. doi: 10.12090/j.issn.1006-6616.2025017

Abstract (391) HTML (68) PDF (3655KB)(145)

Study of disaster-prone geological structures and instability modes of typical goaf landslides in mountainous areas of southwest China

ZHANG Haoxiang, ZHU Sainan, YAO Leihua, GAO Feng, ZHANG Limei, YANG Long, TAN Weijia, DAI Xusheng, GAO Yu

2026, 32(2): 1-16. doi: 10.12090/j.issn.1006-6616.2025047

Abstract (231) HTML (42) PDF (2507KB)(145)

The evolution of the Sinian–Early Cambrian E’xi Trough in the Central Yangtze region and its geological significance for natural gas

CHEN Ke, LU Yanxin, WANG Yuluo, LI Fei

2026, 32(2): 1-17. doi: 10.12090/j.issn.1006-6616.2025048

Abstract (12) HTML (3) PDF (4934KB)(14)

Characteristics of current in-situ stress field and engineering zoning evaluation of complex structural areas: A case study of the Longmaxi shale reservoir in the southeastern Sichuan Basin margin

MA Shunting, LI Ruixue, CHEN Xinhao, DU Yifei, DENG Hucheng, HE Jianhua, YANG Hong, WEI Limin

2026, 32(2): 1-18. doi: 10.12090/j.issn.1006-6616.2025057

Abstract (34) HTML (5) PDF (6093KB)(1)

Analysis of the three-dimensional in situ stress state and underground cavern stability of a pumped storage hydropower station in Xinjiang, China

ZHANG Xiaofei, WANG Jiming, ZHANG Peng, LI Zhengzheng, Li Changhu, OUYANG Jiangquan

2026, 32(2): 1-16. doi: 10.12090/j.issn.1006-6616.2025076

Abstract (294) HTML (58) PDF (2443KB)(153)

Analysis of structural plane stability in the Panlong lead–zinc mine, Guangxi, China and its engineering implications

HUANG Xiaopan, WANG Chenghu, YANG Chengwei, LIU Jikun, XIAO Haifan

2026, 32(2): 1-13. doi: 10.12090/j.issn.1006-6616.2025083

Abstract (278) HTML (64) PDF (2443KB)(152)

A calculation method of the reservoir Biot coefficient based on the Griffith criterion and the equivalent inclusion theory

ZHANG Hui, PEI Chenyang, WANG Zhimin, LIU Lei, LI Jing, LIU Yishuai, WU Zekun

2026, 32(2): 1-10. doi: 10.12090/j.issn.1006-6616.2025086

Abstract (99) HTML (12) PDF (869KB)(133)

Research on high-precision one-dimensional geomechanical modeling of shale oil reservoirs

HOU Shuoyang, WANG Xiaoqiong, XIAN Chenggang, GE Hongkui, ZHONG Yi

2026, 32(2): 1-13. doi: 10.12090/j.issn.1006-6616.2025094

Abstract (31) HTML (9) PDF (2515KB)(40)

A refined evaluation method for in situ stresses in orthotropic shale formations

ZENG Bo, GUI Junchuan, HUANG Haoyong, MA Tianshou, CUI Shuai, ZHONG Guanghai, XU Ersi

2026, 32(2): 1-17. doi: 10.12090/j.issn.1006-6616.2025002

Abstract (10) HTML (3) PDF (1539KB)(8)

Numerical simulation of the influence of normal stress on sub-instability synergy of strike-slip faults

DAI Shuhong, SUN Zhaoyang

2026, 32(2): 1-13. doi: 10.12090/j.issn.1006-6616.2025022

Abstract (358) HTML (104) PDF (2031KB)(1)

Tectonic evolution of the WesternYangtze Block during the Ediacaran–Cambrian: Evidence from detrital zircon U-Pbgeochronology

Zhiqiang SHI, Le SUN, ZHANG Hong, PEI Jinyun, LI Wei

doi: 10.12090/j.issn.1006-6616.2025065

[Abstract](5) [PDF 2116KB](4)

Abstract:
[Objective] The Yangtze Block was a crucial component of the Gondwana supercontinent. During the Ediacaran-early Cambrian, its western margin underwent a marked transition from carbonate-dominated to siliciclastic-dominated depositional environments. However, the tectonic dynamics controlling this sedimentary facies shift of early Cambrian sedimentation remain poorly constrained. The exposed thick Early Cambrian terrigenous clastic rocks on the western Yangtze Block are key archives for tracing sediment sources and studying the geotectonic background of the Early Cambrian .[Method] This study carried out systematic detrital zircon U-Pb geochronology and whole-rock element analysis on the lower Cambrian Qiongzhusi Formation on the western Yangtze Block to study above question. [Results] The results indicate: (1) The clastic rocks exhibit high-field-strength elements (HFSEs) and large-ion lithophile elements (LILEs; e.g., Th, Zr, Hf, Ba, Pb) consistent with upper crustal compositions, whereas Sr, Sc, V, Cr, Cu, Ni, and Zn show depletion relative to upper continental crust (UCC)-particularly pronounced for Sr, Cr, V, and Cu. The immobile elements (Th, Sc, Hf, Zr, Ho) and rare earth elements (RREEs; e.g, La, Ce, Yb) suggest a dominantly felsic igneous provenance of the upper continental crust; (2) Primary age clusters of detrital zircon U-Pb ages in the Qiongzhusi Formation are ca.590-500Ma and ca.880-720 Ma, with subordinate groups at 1900-1500 Ma and 2500-2400 Ma. [Conclusions]Integrated with regional data and prior studies, we propose that the early Cambrian detritus was largely derived from the Ediacaran-Early Cambrian magmatic rocks in the Longmenshan tectonic belt (Ediacaran-early Cambrian), and the late Neoproterozoic felsic magmatic rocks of the Panxi-Hannan magmatic arc, Ailaoshan Magmatic Arc and the Jiangnan Orogen. The Proto-Tethyan Ocean's subduction beneath the western Yangtze during the Ediacaran-early Cambrian converted the western Yangtze from a passive to an active continental margin, and formed a late Ediacaran-early Cambrian magmatic arc. This arc supplied voluminous early Cambrian detritus, ultimately shifting the western Yangtze margin to a siliciclastic-dominated depositional system. [Significance]These findings reveal the provenance linkages between the western Yangtze and adjacent orogenic belts, thereby providing critical constraints for reconstructing the tectonic and paleogeographic evolution of the South China Block during the Ediacaran-Early Cambrian.

A 4400-Year-Old Extreme Paleo-Storm Surge Recorded in the Dongzhai Port Chenier, Hainan Island, China

ChaoQun WANG, DongXia SUN, YaoLing ZHANG, XiaoXiao YANG, Lei ZHANG, DaoGong HU

doi: 10.12090/j.issn.1006-6616.2025073

[Abstract](32) [PDF 3542KB](50)

Abstract:
Identifying paleo-storm surge deposits and extreme storm surge events holds significant scientific and practical importance for understanding the recurrence patterns of super typhoon-induced surges and predicting future storm hazards. Current research predominantly focuses on historical and modern storm surges, with less attention given to prehistoric extreme surges. This study investigates a 3.2-m-thick chenier at Wushu Village, Dongzhai Port, Hainan Island. Analyses of sedimentary structures, shell provenance, accelerator mass spectrometry (AMS)¹⁴C dating, and estimates of overtopping deposit elevation demonstrate that this chenier records an extreme storm surge event approximately 4400 years ago. The chenier's overtopping deposits accumulated on a Late Pleistocene alluvial plain landward of the Holocene highstand paleo-shoreline. Nine AMS ¹⁴C dates on shells range from 4402 to 6647 cal yr BP, exhibiting age reversals and co-occurrence of younger and older shells. The deposit is well-sorted and displays sedimentary structures diagnostic of high-energy deposition, including hummocky cross-stratification, current cross-stratification, and erosional scours. Comparative analysis of shell assemblages and ages between the chenier and underlying paleo-lagoon deposits within Dongzhai Port indicates that the chenier shells were reworked from these older lagoon sediments. The reconstructed paleo-elevation of the overtopping deposits indicates a storm surge height of 5.5 m above modern sea level. This exceeds the 4.58 m surge documented during the 2014 Super Typhoon Rammasun along the Dongzhai coast. Considering the potential influence of astronomical tides on total water levels, we infer that the extreme storm surge height 4400 years ago was likely superimposed on a contemporaneous high astronomical tide.

Evaluation of Source Rocks and Oil Source Correlation in Chang 7-Chang 6 Member of Yanchang Formation in Jingbian Area, Ordos Basin

SiWei TANG, Hui XUE, YouJun TANG, ShuMin WANG, GuangMing HU, Geng LI, FangTingYu SHI

doi: 10.12090/j.issn.1006-6616.2025050

[Abstract](47) [PDF 2632KB](53)

Abstract:
Objective The Chang 7 and Chang 6 Members of the Yanchang Formation in the Jingbian Area of the Ordos Basin constitute significant source rock intervals. However, systematic studies on their hydrocarbon generation potential and contributions to petroleum accumulation remain limited, which constrains further exploration efforts in this region. Therefore, this study integrates geochemical analytical methods to systematically characterize the distribution and the geochemical properties of the Chang 7 and Chang 6 source rocks in the Jingbian area, as well as the geochemical signatures of the crude oils from the Yan 9 and Chang 2 reservoirs in the Jingbian Oilfield. Methods By comparing the geochemical parameters between the local Chang 6 and Chang 7 source rocks and the Zhangjiatan Shale in the center of the basin, the potential sources of the oils in the Yan 9 and Chang 2 reservoirs were identified. Results The results demonstrate that the Chang 7 source rocks are high quality, with widespread distribution and considerable thickness. They are characterized by Type I-II₂ kerogen and are in the mature stage. The biomarker characteristics indicate mixed organic matter inputs, deposited in a reducing environment with low salinity. The low Pr/Ph and high C₂₇/C₂₉ regular sterane ratios further suggest that the organic matter is predominantly derived from aquatic algae and other lower organisms, consistent with a reducing, fresh to brackish water depositional environment. In contrast, the Chang 6 source rocks are of medium to high quality, containing Type II₂-III kerogen and are generally in the low-to-mature stage. The moderate Pr/Ph and low C₂₇/C₂₉ regular sterane ratios reflect a predominance of terrigenous higher plant input, deposited under a weakly reducing environment. The oil-source correlation results reveal that the Yan 9 and Chang 2 oils are of the same origin, primarily derived from the Chang 7 source rocks, with a minor contribution from the Chang 6 Member. Conclusion (1) the Chang 7 Member is the primary, high-quality source rock in the Jingbian area, superior to the Chang 6 Member in terms of thickness, lateral distribution, organic richness, and hydrocarbon generation potential. (2) Distinct biomarker signatures differentiate the Chang 7 (aquatic/algal, reducing), Chang 6 (terrigenous, weakly reducing), and distal Zhangjiatan (highly aquatic, strongly reducing) source rocks. (3) The Yan 9 and Chang 2 crude oils share a common origin and are primarily sourced from the local Chang 7 source rocks, with a possible minor contribution from the Chang 6 Member. The oils show no direct genetic link to the Zhangjiatan Shale in the basin center, supporting a predominantly local hydrocarbon sourcing model for the Jingbian area. Significance This study provides crucial geochemical evidence for a local hydrocarbon system within the Jingbian area, resolving previous ambiguities regarding oil sources and assessing the resource potential in the Jingbian Area, Ordos Basin.

Research on mechanical parameter prediction and modeling methods based on statistical regression and prestack inversion—Taking a particular area in the Bonan Depression as an example

Bin WANG, Han XIAO, XueMin NIU, RuiXuan ZHANG, Xing GE

doi: 10.12090/j.issn.1006-6616.2025084

[Abstract](90) [PDF 1153KB](128)

Abstract:
Abstract: [Objective] In the development of unconventional oil and gas, there exist problems such as complex reservoir structure and unclear rock mechanical properties. During the design of horizontal well trajectories and fracturing schemes, it is necessary to rely on rock mechanical models for segment and cluster division and design, thereby increasing the modification volume, reducing the risk of set changes, and achieving efficient development of unconventional oil and gas. The rock mechanics model can simultaneously reflect the continuous changes of mechanical parameters in the longitudinal and transverse directions with high resolution in the target area of the horizontal well trajectory. Therefore, in response to the model requirements, this paper provides a mechanical parameter prediction and modeling method based on statistical regression and prestack inversion. [Methods] Basing on the core test data and logging data, the quantitative relationship between elastic parameters and rock mechanical parameters is established and analyzed. Then, three-dimensional prestack inversion is performed using both drilling data and seismic data to obtain precise elastic parameters, including longitudinal wave velocity, density, Poisson's ratio, and Young's modulus. [Results] The application of this method in the tight glutenite reservoirs of the Bonan Sag has yielded significant and practical results. First, a robust quantitative relationship between mechanical and elastic parameters was established. The statistical regression relationship between Young's modulus and Uniaxial Compressive Strength (UCS) demonstrated a strong correlation (e.g., R² > 0.75), validating the feasibility of predicting rock mechanical strength from elastic parameters in this glutenite formation. Statistical analysis confirmed that the mechanical parameters of these highly compacted, low-porosity glutenites are primarily controlled by lithology and gravel content, exhibiting a very weak correlation with burial depth. This justifies the use of a unified predictive model across the entire studied depth interval. Second, a high-resolution 3D mechanical parameter model was constructed. A depth-domain structural model was built using logging data and a smoothed time-depth velocity field. Following attribute extraction, a comprehensive 3D mechanical parameter model for the target block was established. This model effectively overcomes the discreteness and non-continuity inherent in core and logging data, accurately characterizing the continuous lateral and vertical variations of mechanical properties. Third, the results are directed toward engineering application. To fully leverage the high vertical and lateral resolution of the mechanical parameter volume, the calculated seismic attributes were integrated into the 3D geological model based on engineering requirements. This outcome provides an accurate model for fracturing design, enabling precise assessment of the rock mechanical distribution along horizontal well sections, rational design of stage and cluster placement, optimization of pumping parameters, and enhancement of fracture conductivity. Consequently, it significantly increases the stimulated reservoir volume, effectively boosting single-well productivity and recovery rates. [Conclusion] The study leads to the following main conclusions: The integrated methodology of pre-stack inversion and statistical regression is a viable and effective solution for predicting 3D mechanical parameters in tight glutenite reservoirs. This method builds a bridge between petrophysical and seismological parameters, effectively resolving the challenge of poorly constrained rock mechanical properties in complex unconventional reservoirs. The constructed 3D mechanical parameter model provides a more reliable geological basis for optimizing well trajectories and fracturing designs. [Significance] The primary significance of this research lies in providing a reliable and scalable method for 3D rock mechanical parameter prediction and modeling, possessing substantial theoretical innovation and practical application value. It offers a dependable data foundation and a theoretical framework for defining mechanical boundaries and optimizing fracturing designs in heterogeneous tight reservoirs. This approach holds significant potential for improving fracturing efficiency and maximizing production in challenging tight glutenite formations.

MA Zhanrong, LI ZhenHong, LIU JianPing, HU AiPing, LinLin KOU

doi: 10.12090/j.issn.1006-6616.2025031

[Abstract](67) [PDF 3282KB](135)

Abstract:
[Objective] The dolomite of Ordos basin west margin complex tectonic belt Ordovician Kelimoli Formation as a high quality reservoir for natural gas exploration, its genesis mechanism and the relationship between sedimentary environment and tectonic superimposed transformation, there are still many disputes, which restricts the guidance of oil and gas exploration.[Methods] Based on comprehensive test and analysis including thin-section identification, cathodoluminescence, carbon-oxygen isotope, X-ray diffraction order, geochemical rare earth and trace elements, and strontium isotope, combined with the regional tectonic evolution process, this study explores the genetic mechanism of dolomite.[Results] Cathodoluminescence overall exhibits a relatively weak dark brown coloration with distinct ring bands, and authigenic quartz and saddle-shaped dolomite as hydrothermal minerals are visible, characterized by features of multi-stage recrystallization and burial origin. Carbon and oxygen isotope characteristics indicate that the dolomite has a burial origin. The overall order of the dolomite shows a relatively low degree, and the higher the temperature, the lower the order, suggesting that the dolomite formed in an environment with relatively high temperature and rapid crystallization rate. The rare earth element partitioning pattern is characterized by positive Ce and positive Eu anomalies, indicating that the formation process of dolomite is the result of internal fluid adjustment and redistribution within the diagenetic system under relatively closed, high-temperature, and high-pressure conditions. The lower the Sr content and the higher the Fe and Mn element contents, overall showing the characteristics of multi-stage superimposed modification under deep burial conditions. The strontium isotope values of medium to coarse-grained dolomite are significantly close to the average value of crustal source strontium isotopes, which may have been affected by crustal source strontium carried by synchronous tectonic activities.[Conclusion] Research indicates that dolomite formation is primarily attributed to deep burial, while also undergoing superimposed tectonic fluid modification. The evolution of Ordovician Krimolli Formation dolomite is closely linked to the deep fault system. During the co-deposition period, this fault system controlled the development of high-energy terraces. In the subsequent tectonic activity phase, the deep fault system became a fluid migration channel, facilitating the superimposed modification of dolomite bodies.[Significance] Research results can provide a fundamental support for the efficient exploration of oil and gas resources.

ZHU Shu, ZHANG Quan, WANG Yanbing, LI Jin, LI Renjie, HUANG Yong, LI Benliang, LIU Fucai, YAN Yuping

doi: 10.12090/j.issn.1006-6616.2025170

[Abstract](141) [PDF 2408KB](161)

Abstract:
The Jiali Fault on the southeastern margin of the Tibetan Plateau is a key boundary structure for the southeastward extrusion of plateau material. Its geometric distribution and activity are crucial for understanding the tectonic evolution of the plateau and assessing regional engineering risks. However, the precise spatial location and Holocene activity of its southeastern segment (Guxiang to Gongrigabu section) have long been controversial due to rugged terrain and thick vegetation cover. Targeting this key contentious segment, this study integrated multiple methods, including high-resolution remote sensing interpretation, field geological and geomorphological surveys, drilling and trenching exposure, and magnetotelluric sounding, to systematically investigate the fault's spatial distribution, structural characteristics, and activity. The results indicate that the southern branch of the Jiali Fault Zone continuously extends along a line from south of Guxiang, through Gionala, Jinzhunongba, to Langqiunongba. Tectonic geomorphic evidence such as fault troughs, sag ponds, pressure ridges, bedrock fault mirrors, and horizontal slickensides were identified via remote sensing and field investigations. Magnetotelluric data revealed clear low-resistivity fracture zones, and drilling core samples exposed significant fault-related rocks. This evidence collectively confirms the existence and distribution of the fault within this segment. Combined with regional paleoseismic studies, it is concluded that this segment has the potential for Holocene activity. The research further systematically analyzed the deep engineering effects potentially triggered by fault activity, including surrounding rock deterioration, cosismic offset, high in-situ stress, seismic motion amplification, water inrush and mud gushing, geothermal anomalies, and secondary disasters at tunnel portals. The research results not only provide key geological constraints for improving the tectonic model of the southeastern Tibetan Plateau but also offer indispensable scientific basis for the planning, seismic design, and risk prevention and control of major projects (such as the Sichuan-Tibet Railway) traversing the fault zone.

Wu Chengjie^1,2，Zeng Huaien^1,2,3，Chen Jun⁴，FengYu⁵ , Li xi^2,3，WeiPengcheng^2,3,Yan Baorui^1,2

chengjie wu, HuaiEn CENG, jun chen, Yu FENG, xi li, pengcheng wei, baorui yan

doi: 10.12090/j.issn.1006-6616.2025077

[Abstract](248) [PDF 1363KB](134)

Abstract:
Accurate prediction of landslide displacement is a crucial component of landslide early warning systems. This paper proposes a landslide displacement prediction model based on Gaussian Process Regression (GPR) combined with diverse time-series feature engineering, achieving high-precision displacement prediction and uncertainty quantification. TAKING THE BAZIMEN LANDSLIDE AS AN EXAMPLE, During the feature engineering phase, displacement lag features, rolling mean of rainfall, rolling variance of reservoir water level, and displacement change rate are constructed. Additionally, temporal decomposition features including monthly and quarterly components are extracted. SUBSEQUENTLY, EMPLOY THREE-FOLD TIME SERIES CROSS-VALIDATION, ALONG WITH A GRID SEARCH SCHEME, TO OPTIMIZE HYPERPARAMETERS IN CONJUNCTION WITH THE TIME SERIES CROSS-VALIDATION STRATEGY, THEREBY MITIGATING THE RISK OF OVERFITTING IN THE SMALL-SAMPLE SCENARIO. The results demonstrate that after incorporating multi-source temporal features, the prediction coefficients of determination (R²) for monitoring points ZG110 and ZG111 at the Bazimen Landslide significantly increase to above 0.99. Metrics such as MAE, RMSE, and MAPE are substantially reduced, indicating a significant improvement in prediction accuracy. This study integrates probabilistic modeling with feature interpretability analysis. The proposed method achieves high-precision landslide displacement prediction in small-sample environments while simultaneously quantifying prediction uncertainty. It provides effective decision support for landslide risk early warning and engineering safety assessment.

Tectonic stress field characteristics in Wushi , Xinjiang and the stress impact of the Wushi M7.1 earthquake

ZeYao SONG, YongGe WAN, PeiYuan GU, MingYue ZHOU

doi: 10.12090/j.issn.1006-6616.2025085

[Abstract](265) [PDF 2767KB](158)

Abstract:
[Objective] The Wushi region in Xinjiang is located at the intersection of multiple tectonic units, making it a key area for stress concentration and release. Although previous studies have revealed some characteristics of the tectonic stress field in this region, there is still a lack of in-depth and systematic analysis regarding the potential impact of the 23 January 2024 Wushi M 7.1 earthquake on the regional stress field. Therefore, adopt more systematic focal mechanism data to conduct a detailed analysis of the regional tectonic stress field characteristics and to explore the influence of the Wushi M 7.1 earthquake on the regional stress field. The aim is to provide more comprehensive scientific references for understanding the regional seismogenic environment and predicting future seismic activity.[Methods] Using the damped stress tensor inversion method and incorporating data from multiple institutions, we analyzed the stress field in different subregions of the study area and compared the changes in the tectonic stress field before and after the earthquake.[Results] The results of the stress field inversion show that, except for the area near the Jiashi seismic group, the R value is greater than 0.5, and the azimuth of the maximum principal compressive stress in the Wushi region gradually rotates from approximately NNW in the south to near N—S in the north, the azimuth is from 168.75° to 183.45°, and plunge angle is from 6.85° to 19.58°, it is in a compressive stress state. The Jiashi seismic area cluster shows a strike-slip feature of NNE—SSW compression and NWW—SEE extension.The northern area of the Jiashi seismic shows a thrust stress state, while the southern area presents a strike-slip stress state. By comparing and analyzing the regional stress field changes before and after the Wushi earthquake, it is found that the optimal principal compressive stress direction before the earthquake was N—S direction, and deviated by 12.53° in azimuth after the earthquake, with a spatial rotation angle of 15.06°. This indicates that this earthquake had a relatively small impact on the stress field of this area, which meaning that the stress field did not undergo significant changes after the earthquake, and still remains in the compressive stress system. [Conclusion] The tectonic stress field in the Wushi region is subject to N—S compression from the collision of the Indian plate with the Eurasian plate on the western margin of the Tibetan Plateau to form a strong near-north-south horizontal compression, and the stress from the plate collision is transmitted to the northeast to the Tian Shan orogenic belt, which leads to the shortening of the crust and retrograde thrusting between the Tarim Basin and the Tian Shan. The Wushi M 7.1 earthquake had a relatively minor impact on the regional stress field. The stress system of the entire area is still controlled by deep tectonic activities. The overall stress field is consistent, but the seismic cluster in northern Jiashi is located at the junction of the northern margin of the Tarim Plate and the Tianshan Mountains, presenting a thrust stress mechanism. This area is the plate tectonic transition boundary between the Tarim Basin and the Tianshan orogenic belt.[Significance] By analyzing the characteristics of the tectonic stress field in the Wushi region of Xinjiang and the impact of the Wushi M 7.1 earthquake on the regional stress field, the characteristics of the stress field and the effect of earthquakes on the regional stress field. This contributes to a deeper understanding of the tectonic relationship between the Tianshan orogenic belt and the Tarim Basin. In addition, the northern part of the Jiashi seismic exhibits a thrust stress mechanism, which is inferred to represent a tectonic transition boundary between the Tarim Basin and the Tianshan orogenic belt. This finding holds significant implications for regional tectonic segmentation and seismic hazard assessment.

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Supervisor： China Geological Survey

Sponsor： Institute of Geomechanics, Chinese Academy of Geological Sciences; Geological Society of China (GSC)

Editor-in-Chief： DENG Jun

ISSN 1006-6616

CN 11-3672/P

Post Issue Number 82-124

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