地学前缘 ›› 2024, Vol. 31 ›› Issue (5): 344-357.DOI: 10.13745/j.esf.sf.2024.6.26

• 变质岩和煤储层裂缝研究 • 上一篇    下一篇

深层煤岩微构造对现今地应力的控制机理

唐志潭1(), 刘敬寿1,2,*(), 闫霞3,4, 冯延青3,4, 蒋恕1, 张滨鑫2, 张冠杰1, 付一鸣2   

  1. 1.中国地质大学(武汉) 构造与油气资源教育部重点实验室, 湖北 武汉 430074
    2.中国地质大学(武汉) 资源学院, 湖北 武汉 430074
    3.中联煤层气国家工程研究中心有限责任公司, 北京 100095
    4.中石油煤层气有限责任公司, 北京 100028
  • 收稿日期:2023-11-15 修回日期:2024-06-22 出版日期:2024-09-25 发布日期:2024-10-11
  • 通信作者: * 刘敬寿(1989—),男,教授,博士生导师,主要从事油区构造解析、储层地质力学方面的教学与科研工作。E-mail: liujingshou@126.com
  • 作者简介:唐志潭(2000—),男,硕士研究生,主要从事储层地质力学、储层裂缝等研究工作。 E-mail: tzt1251960927@163.com
  • 基金资助:
    国家自然科学基金项目(42102156);山东省自然科学基金项目(ZR2020QD035);中国地质大学(武汉)“地大学者”人才岗位科研启动项目(2022046)

The control mechanism of deep coal rock microstructure on in situ stress

TANG Zhitan1(), LIU Jingshou1,2,*(), YAN Xia3,4, FENG Yanqing3,4, JIANG Shu1, ZHANG Binxin2, ZHANG Guanjie1, FU Yiming2   

  1. 1. Key Laboratory of Tectonics and Petroleum Resources of Ministry of Education, China University of Geosciences (Wuhan), Wuhan 430074, China
    2. School of Earth Resources, China University of Geosciences (Wuhan), Wuhan 430074, China
    3. Zhonglian Coalbed Methane National Engineering Research Center Co., Ltd, Beijing 100095, China
    4. PetroChina Coalbed Methane Co., Ltd, Beijing 100028, China
  • Received:2023-11-15 Revised:2024-06-22 Online:2024-09-25 Published:2024-10-11

摘要:

深部煤层气的勘探开发不能简单套用浅部煤层气的勘探开发理论,原因之一在于深煤层地应力制约了煤层气的吸附/解析、渗流等过程,决定了煤层裂隙的有效性,并影响着水平井轨迹设计。因此,开展深部地应力变化规律研究对煤层气的勘探开发具有重要意义。本文以鄂尔多斯盆地大吉区块为例,利用阵列声波测井、微地震监测数据和岩心测试等资料,综合考虑深层煤岩微构造类型与产状、边界应力条件和顶底板岩石力学性质组合等因素,利用ANSYS有限元软件,建立微构造三维地质力学模型,全面分析了微构造的类型、产状和对煤层应力的控制机理。研究结果表明:煤层微构造越平缓,应力分布越均匀,反之应力越容易集中;煤层微构造产状对煤层应力的影响主要为:随着煤层微构造曲率的增大,挠曲处水平应力差会随之增大,且挠曲处周缘水平最小主应力也会越集中。由微构造类型与煤层力学性质、顶底板岩性、边界应力条件等因素交叉模拟得到,正向微构造下的煤层应力与泊松比呈正相关,与杨氏模量呈负相关,而负向微构造则相反。当顶板为灰岩时,煤层应力大小受微构造类型变化影响比顶板为砂岩时更显著。区域应力大小对深部煤层应力的影响相对较小。论文研究成果可为深部煤层地应力成因机制分析、煤层气高效开发和地质工程一体化实践提供有益的参考。

关键词: 微构造, 地应力, 深层煤岩, 大吉区块, 有限元模拟

Abstract:

The theory of shallow coalbed methane (CBM) exploration and development cannot be directly applied to deep CBM partly due to the effect of in situ stress. In situ stress in deep coal beds restricts the process of CBM adsorption/desorption and seepage, determines the effectiveness of coalbed fissures, and affects the design of horizontal well trajectory. Thus the pattern of in situ-stress change in deep coal seams is of great significance to the exploration and development of CBM. In this paper, taking the Daji block in Ordos Basin as an example, using data from array acoustic logging, microseismic monitoring, and core testing, considering the microstructure types and attitude, boundary stress conditions, and combination of mechanical properties of top and bottom slabs, we established a three-dimensional geomechanical microstructural model of deep coal beds by using ANSYS finite element software to comprehensively analyze the control mechanism of microstructure types and attitute on in situ stress in deep coal beds. Results show that with smoother microstructure the stress distributes more uniformly; conversely, the stress concentrates more easily. The influence of the attitute of microstructure on in situ stress in coal seams is mainly as follows: as the curvature of the microstructure increases, the differential horizontal stress at the bending point increases, and the minimum principal stress increasingly concentrates around the bending point. According to cross-simulation between microstructure type and mechanical properties of coal seam, lithology of top/bottom slabs, and boundary stress conditions, in situ stress under positive curvature is positively correlated with Poisson’s ratio and negatively correlated with Young’s modulus, whereas the opposite is true under negative curvature. Compared to with sandstone top slab, the magnitute of in situ stress in coal seams with limestone top slab is more significantly affected by the change of microstructure type. The magnitude of the regional stress has relatively small influence on in situ stress in deep coal seams. The research results provide an useful reference for the genetic analysis of in situ stress in deep coal beds, and for the efficient development of coalbed methane and the practice of geoengineering integration.

Key words: microstructure, in situ stress, deep coal rock, Daji Block, finite element simulation

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