• 论文
主办单位:煤炭科学研究总院有限公司、中国煤炭学会学术期刊工作委员会
煤层气井排采中不同应力机制下含断裂煤储层稳定性分析
  • Title

    Stability analysis of fractured coal reservoirs under different stress mechanisms in coalbed methane well drainage

  • 作者

    章朋孟雅刘超英郭元岭闫相宾蔡利学程喆

  • Author

    ZHANG Peng, MENG Ya, LIU Chaoying, GUO Yuanling, YAN Xiangbin, CAI Lixue, CHENG Zhe

  • 单位

    中国石化石油勘探开发研究中国地质大学(北京)能源学院煤与煤层气共采国家重点实验室

  • Organization
    Research Institute of Petroleum Exploration & Development, Sinopec;College of Geosciences and Surveying Engineering, China University of Mining and Technology-Beijing;State Key Lab of Coal and Coalbed Methane Co-mining
  • 摘要

    排采过程中地应力动态调整易导致储层断裂失稳破坏,影响煤层气井开采效率。为研究不同应力机制条件下煤层气井排采过程中含断裂煤储层的稳定性,基于煤储层地应力动态变化模型,推导了不同应力机制下含断裂煤储层稳定性判别模型,分析了排采过程煤储层断裂稳定性变化规律,提出了含断裂煤储层稳定性评价指标(Fcr)。根据实际数据,对沁水盆地南部郑庄区块含断裂煤储层稳定性开展了动态评价。研究表明:含断裂煤储层稳定性受断裂面摩擦系数控制,当排采过程中煤储层破裂面剪切应力与正应力的比值超过破裂面的摩擦系数时,煤储层沿破裂面发生相对摩擦滑动。排水降压和初始产气阶段,不同应力机制条件下,含断裂煤储层稳定性均不断增强。稳定产气和衰减阶段,煤层气不断解吸,产生基质收缩效应,含断裂煤储层稳定性在正断层和走滑断层应力机制下不断减弱,在逆断层应力机制下不断增强。基质收缩效应越强,含断裂煤储层稳定性变化速率越快。假设郑庄区块煤储层为水平展布的各向同性的孔弹性介质,不同井位附近存在最优角度断裂面,排水降压及初始产气阶段,含断裂煤储层在正断层和走滑断层应力机制区域,Fcr分别减小和增大,稳定性分别降低和增强,变化幅度较小,主体仍位于稳定性中等区;稳定产气和衰减阶段,Fcr均加速减小,稳定性显著降低,部分区域降至稳定性较差区,甚至失稳破坏。

  • Abstract

    The dynamic adjustment of in-situ stress in the process of drainage and production can easily lead to the fracture, instability and damage of the reservoir, which affects the production efficiency of coalbed methane wells. In order to study the stability of fractured coal reservoirs in the process of coalbed methane well drainage and production under different stress mechanisms, based on the dynamic variation model of in-situ stress,the stability discrimination model of fractured coal reservoirs under different stress mechanisms was deduced. The variation law of fracture stability of coal reservoirs during drainage and production was proposed, and the stability evaluation index (Fcr) of fractured coal reservoirs was proposed. Based on actual data,a dynamic evaluation of the stability of fault-bearing coal reservoirs in the Zhengzhuang block in the southern Qinshui Basin was carried out.It indicates that: ① the stability of fractured coal reservoir was determined by fault friction coefficient. When the ratio of shear stress to normal stress on the fracture surface of the coal reservoir exceeds the friction coefficient of the fracture surface during the drainage and production process, the coal reservoir will undergo relative frictional sliding along the fracture surface. ② In the stage of drainage and pressure reduction and initial gas production, the stability of fractured coal reservoir is enhanced under different stress mechanisms. During the stage of stable gas production and attenuation, CBM is continuously desorbed, resulting in matrix shrinkage effect. The stability of fault-bearing coal reservoirs is constantly weakened under the stress mechanism of normal faults and strike-slip faults, and continuously enhanced under the stress mechanism of reverse faults. The change rate of coal reservoir stability increases with the enhancing of matrix shrinkage effects.③ It is assumed that coal reservoirs of Zhengzhuang block is a horizontally distributed isotropic pore-elastic medium, and there are optimal angle fracture surfaces near different well positions. In the stage of drainage and depressurization and initial gas production, the Fcr value in the normal fault and strike-slip fault stress mechanism area of the fault-bearing coal reservoir decreases and increases respectively, the stability decreases and increases respectively, the change range is small, and the main body is still located in the moderate stability area; in the stable gas production and decay stages, the Fcr value decreases rapidly, the stability decreases significantly, and some areas fall to the area of poor stability, or even destabilize.

  • 关键词

    含断裂煤储层煤层气井排采储层稳定性郑庄区块地应力

  • KeyWords

    fractured coal reservoir;coalbed methane dpeltion;fault stability;Zhengzhuang Block;in-situ stress

  • 基金项目(Foundation)
    2020年度山西省科技计划揭榜招标资助项目(20201101002-03);国家自然科学基金资助项目(42002181)
  • 引用格式
    章朋,孟雅,刘超英,等.煤层气井排采中不同应力机制下含断裂煤储层稳定性分析[J].煤炭科学技术,2022,50(3):169-175.
    ZHANG Peng, MENG Ya, LIU Chaoying,et al.Stability analysis of fractured coal reservoirs under different stress mechanisms in coalbed methane well drainage[J].Coal Science and Technology,2022,50(3):169-175.
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