基于三轴压缩模拟试验的页岩低阻成因机制  

Genetic mechanism of low resistance in shale analyzed via triaxial compression tests

作　　者：高天 刘睿 徐璐 陈增裕 李佳明 龙思宇 廖强 刘鹏 李鹏艳 GAO Tian;LIU Rui;XU Lu;CHEN Zengyu;LI Jiaming;LONG Siyu;LIAO Qiang;LIU Peng;LI Pengyan(College of Geosciences,China University of Petroleum(Beijing),Beijing 102249,China;School of Geosciences and Technology,Southwest Petroleum University,Chengdu 610500,China)

机构地区：[1]中国石油大学(北京)地球科学学院,北京102249 [2]西南石油大学地球科学与技术学院,成都610500

出　　处：《地质科技通报》2025年第2期224-237,共14页Bulletin of Geological Science and Technology

基　　金：国家自然科学基金项目“五峰-龙马溪组页岩孔隙结构的构造压实调整机制研究”(42072184)。

摘　　要：川南地区五峰-龙马溪组页岩气储层在多个地区出现低电阻异常现象。统计显示,低阻页岩(<10Ω·m)与构造断裂带在空间分布上存在叠合关系。为揭示页岩电阻率与构造断裂带之间的关联机制,基于薄片鉴定、X射线衍射分析、激光拉曼光谱分析、全岩沥青反射率测定以及常规物性分析等手段,确定了页岩试样的岩石学特征和地球化学特征;基于三轴压缩物理模拟试验确定了变形过程中页岩试样电阻率的变化特征,明确了裂缝发育及盐水的侵入对页岩低阻现象的影响。结果表明:黏土矿物、黄铁矿和高热演化程度有机质相对均一的页岩试样,在饱和不同浓度盐水后,电阻率显著降低,且电阻率降低幅度(95.07%~98.70%)与盐水质量浓度之间存在正相关关系;饱和盐水的页岩试样受压破裂后电阻率进一步降低,范围介于5.7~25.7Ω·m之间(平均值为13.3Ω·m),且页岩试样饱和盐水后的电阻率与其破裂后的电阻率符合正相关线性关系。页岩内部裂缝系统的发育后导电流体的侵入,是页岩电阻率降低的主要控制因素。页岩受压破裂后电阻率的降低幅度受到入侵溶液浓度和裂缝发育程度的双重影响。研究成果解释并补充了构造断裂带对页岩电阻率的影响机制,丰富了低阻页岩成因机制理论,对低阻页岩层段的勘探开发具有重要意义。[Objective]The gas-rich Wufeng-Longmaxi shale of the southern Sichuan Basin exhibits low-resistance anomalies in multiple areas.Statistical analysis reveals that the low-resistivity zone(<10Ω·m)in the Wufeng-Longmaxi shale is spatially associated with tectonic faults.This study aims to reveal the coupling mechanism between shale resistivity and tectonic faults.[Methods]This study determines the petrological and geochemical characteristics of outcrop samples obtained from the Wufeng-Longmaxi shale in the southern Sichuan Basin through thin-section identification,X-ray diffraction,laser Raman spectroscopy,whole-rock asphalt reflectance,and conventional physical property analyses.The characteristics of resistivity change in the shale during deformation were analyzed through triaxial compression tests.The impacts of fracture system generation and conductive fluid intrusion on low-resistivity shale were also clarified.[Results]The results show that the resistivity of shale samples,which have similar characteristics of clay minerals,pyrite,organic matter content,and thermal maturity level,significantly decreased after saturation with brines of various salinities.A positive correlation was observed between the resistivity reduction(95.07%-98.70%)and brine salinity.After reaching the compressive strength,the resistivity reduction of the brine-saturated samples varies from 5.7Ω·m to 25.7Ω·m(average:13.3Ω·m).This reduction shows a linearly positive correlation with the resistivity observed post cracking.The intrusion of conductive fluid and the generation of the fracture system in shale are the primary controlling factors for resistivity reduction.The resistivity after cracking is influenced by both the intruded saltwater salinity and fracture density.[Conclusion]This research elucidates the influence mechanism of tectonic fault zones on shale resistivity and enhances the theoretical framework for understanding the genesis of low-resistivity shale,with significant implications for the exploration and development of

关 键 词：低阻页岩 低阻成因 裂缝 地层水 四川盆地 五峰-龙马溪组 三轴压缩模拟试验 

分 类 号：P618.13[天文地球—矿床学]