层理倾角对富碳酸盐页岩裂缝扩展规律影响的直剪试验离散元模拟

doi:10.3969/j.issn.2096-1693.2025.03.024

石油科学通报 ›› 2025, Vol. 10 ›› Issue (6): 1199-1214. doi: 10.3969/j.issn.2096-1693.2025.03.024

层理倾角对富碳酸盐页岩裂缝扩展规律影响的直剪试验离散元模拟

李军亮¹^,², 张奎华²^,³, 冯海风⁴, 刘鑫金¹^,², 刘志娜⁴^,^*(), 秦峰¹^,², 陈涛¹^,², 王勇¹^,², 闫嘉杰⁴, 苑贵亭¹^,², 于福生⁴, 魏晓亮¹^,⁵

1 中国石化胜利油田分公司勘探开发研究院，东营 257015
2 页岩油气富集机理与高效开发全国重点实验室，东营 257015
3 中国石化胜利油田分公司，东营 257000
4 中国石油大学(北京)地球科学学院，北京 102249
5 中石化胜利油田博士后工作站，东营 257015

收稿日期:2025-06-05 修回日期:2025-09-17 出版日期:2025-12-30 发布日期:2025-12-30
通讯作者: *刘志娜(1982年—)，博士，副教授，主要从事构造地质学与岩石力学方面的研究，zhina.liu@cup.edu.cn。
作者简介:李军亮(1975年—)，博士研究生，主要研究方向为页岩油地质综合研究工作，lijunliang.slyt@sinopec.com。
基金资助:
国家科技重大专项“渤海湾盆地济阳坳陷古近系陆相页岩油勘探开发技术与集成示范”(2024ZD1405100);国家自然科学基金企业创新发展联合基金项目(U24B6002);中国石油化工集团有限公司项目(P23084);中国石油化工集团有限公司项目(P24027)

Discrete element simulation of direct shear tests for investigating the influence of bedding dips on fracture propagation in carbonate-rich shale

LI Junliang¹^,², ZHANG Kuihua²^,³, FENG Haifeng⁴, LIU Xinjin¹^,², LIU Zhina⁴^,^*(), QIN Feng¹^,², CHEN Tao¹^,², WANG Yong¹^,², YAN Jiajie⁴, YUAN Guiting¹^,², YU Fusheng⁴, WEI Xiaoliang¹^,⁵

1 Exploration and Development Research Institute, Sinopec Shengli Oilfield Company, Dongying 257015, China
2 National Key Laboratory of Shale Oil and Gas Enrichment Mechanism and Efficient Development, Dongying 257015, China
3 Sinopec Shengli Oilfield Company, Dongying 257000, China
4 College of Geosciences, China University of Petroleum, Beijing 102249, China
5 Sinopec Shengli Oilfield Postdoctoral Workstation, Dongying 257015, China

Received:2025-06-05 Revised:2025-09-17 Online:2025-12-30 Published:2025-12-30

摘要/Abstract

摘要：

本研究针对渤海湾盆地济阳坳陷东营凹陷沙三下-沙四上亚段富碳酸盐质页岩，结合离散元模拟与声发射监测方法，构建直剪试验数值模型，分析不同层理倾角下的裂纹扩展规律和能量演化特征，建立层理倾角、应力状态与裂缝数量的定量关系。结果表明：(1)直剪作用下，高剪应力诱发约45°雁列状张裂缝，扩展后与沿层理剪切裂隙贯通，形成宏观破裂带；随层理倾角增大，破裂带由阶梯状转为“之”字形，非均质性增强；(2)破裂机制受层理倾角控制，低角度以沿层剪切为主，高角度转为基质张-剪复合破裂；(3)起裂、损伤和峰值应力随倾角增大先升后降，在40°~50°达到最大；(4)裂纹扩展分为起裂、快速扩展(占85%以上)和慢速扩展三阶段，张裂纹占82.6%，剪裂纹占17.4%且多沿层理分布；(5)数值模拟、岩芯观察与室内试验均显示相似扩展模式，包括沿层剪裂隙和斜切或穿层张裂隙。层理倾角是控制裂缝发育的关键因素，直接影响裂缝方向、复杂程度和改造体积。研究成果为陆相页岩天然裂缝的成因与预测提供理论支持，对提升页岩油开采效率和作业安全具有重要意义。

关键词: 离散元, 声发射, 页岩, 裂纹扩展, 破裂机制

Abstract:

This study focuses on the carbonate-rich shale of the lower Sha-3 to upper Sha-4 sub-members in the Dongying Sag of the Jiyang Depression within the Bohai Bay Basin. Based on the discrete element simulation and acoustic emission monitoring test methods, a numerical model for shale direct shear tests was constructed. The study systematically revealed the crack propagation laws and energy evolution characteristics under different bedding dip angles, and established a quantitative relationship between bedding dip angle, stress state, and the number of micro-fractures. The research results show that: (1) During direct shearing, high shear stress induces en echelon tensile fractures with an approximate 45° angle. After expansion, these fractures connect with shear fractures developed along the bedding to form a macroscopic fracture zone. As the bedding dip angle increases, the fracture zone gradually transitions from a stepped shape to a “zigzag” shape, exhibiting significant heterogeneity. (2) The shale fracture mechanism is dependent on the bedding dip angle: under low dip angles, shear fracture along the bedding is dominant; as the dip angle increases, the dominant fracture mechanism gradually shifts to matrix tensile-shear composite fracture. (3) The initiation stress of fractures is relatively low, and its variation with the bedding dip angle is not obvious; however, the damage stress and peak stress of fractures increase first and then decrease with the increase of the dip angle, reaching their peaks within the range of 40° to 50°. (4) Based on acoustic emission monitoring, it is found that crack propagation can be divided into three stages: initiation, rapid expansion (contributing 85% of the total number of cracks), and slow expansion. Tensile cracks account for 82.6%, while shear cracks (accounting for 17.4%) are mainly distributed along the bedding. (5) A comprehensive comparison of numerical simulation results, shale core fracture characteristics, and laboratory direct shear test results reveals similar fracture propagation laws, including shear fractures developed along the bedding plane and tensile fractures that obliquely cut (or penetrate) the bedding. The bedding dip angle is a key factor controlling the shale fracture development pattern, directly affecting the fracture propagation direction, complexity, and reconstruction volume. The findings of this study provide a theoretical basis for explaining the genetic mechanism and development pattern of natural fractures in continental shales, and also offer scientific support for the prediction of natural fractures in shale oil and gas exploration and development, which is of great significance for improving shale oil recovery efficiency and ensuring operational safety.

Key words: discrete element method, acoustic emission, shale, crack propagation, fracture mechanism

中图分类号:

李军亮, 张奎华, 冯海风, 刘鑫金, 刘志娜, 秦峰, 陈涛, 王勇, 闫嘉杰, 苑贵亭, 于福生, 魏晓亮. 层理倾角对富碳酸盐页岩裂缝扩展规律影响的直剪试验离散元模拟[J]. 石油科学通报, 2025, 10(6): 1199-1214.

LI Junliang, ZHANG Kuihua, FENG Haifeng, LIU Xinjin, LIU Zhina, QIN Feng, CHEN Tao, WANG Yong, YAN Jiajie, YUAN Guiting, YU Fusheng, WEI Xiaoliang. Discrete element simulation of direct shear tests for investigating the influence of bedding dips on fracture propagation in carbonate-rich shale[J]. Petroleum Science Bulletin, 2025, 10(6): 1199-1214.

https://sykxtb.cup.edu.cn/CN/Y2025/V10/I6/1199

图/表 13

图1 直剪试验颗粒流模型图

Fig. 1 Particle flow model of direct shear test

表1 颗粒流模型微观参数表

Table 1 Microscopic parameters of the particle flow model

属性	页岩	层理面
线性接触模量/GPa	3	1
线性接触法/切向刚度比	1.5	1.5
线性接触颗粒摩擦系数	0.2	0.2
平行粘结模量/GPa	3	1
平行粘结法/切向刚度比	1.5	1.5
平行粘结抗拉强度/MPa	20	6
平行粘结粘聚力/MPa	60	6
平行粘结内摩擦角/°	40	35

图2 室内试验与颗粒流模型剪切应力-剪切位移曲线对比

Fig. 2 Comparison of shear stress-shear displacement curves between physical experiments and particle flow models

图3 室内试验与颗粒流模型累积声发射振铃计数随切向位移变化曲线对比

Fig. 3 Comparison of cumulative acoustic emission counts versus shear displacement in physical experiments and particle flow models

图4 页岩裂缝扩展规律对比

Fig. 4 Comparison of fracture propagation laws in shales

图5 颗粒流试验剪切破裂面(DZ组)

Fig. 5 Results of shear failure surface in particle flow models (DZ group)

图6 颗粒流试验微裂纹分布(DZ组)

Fig. 6 Distribution of microcracks in particle flow models (DZ group)

图7 颗粒流试验剪切位移图(DZ组)

Fig. 7 Shear displacement in particle flow models (DZ group)

图8 DZ组累积声发射振铃计数随切向位移增加曲线

Fig. 8 Curve of cumulative acoustic emission counts in DZ group with the increase of shear displacement

图9 三个关键力学阈值随试样层理倾角变化

Fig. 9 Three key mechanical thresholds varying with the bedding dip angle

图10 微裂纹数量随切向位移变化曲线

Fig. 10 Curve of the number of microcracks varying with shear displacement

图11 模型微裂纹数量随层理倾角变化对比(图中方块代表裂纹总数，三角形代表张裂纹，圆形代表剪裂纹)

Fig. 11 Comparison of the number of microcracks in the model with the variation of bedding dips (The squares in the Fig. represent the total number of cracks, triangles represent tensile cracks, and circles represent shear cracks)

图12 SJ系列和DZ系列模型比较图

Fig. 12 Comparison of SJ series and DZ series models

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层理倾角对富碳酸盐页岩裂缝扩展规律影响的直剪试验离散元模拟

Discrete element simulation of direct shear tests for investigating the influence of bedding dips on fracture propagation in carbonate-rich shale

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