大宁—吉县地区5号煤层现今地应力预测及其对煤层气开发的影响
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国家自然科学基金重点项目《深部煤层气储渗系统优化改造机理及产出效应》(42130802)资助。


Prediction of present-day in-situ stress in the 5# coal seam of Daning-Jixian area: Implications for coalbed methane development
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    摘要:

    现今地应力场对煤储层渗透率具有极其重要的控制作用。我国鄂东大宁-吉县地区煤层气资源丰富,然而该区现今地应力研究程度较低,不利于该地区煤层气的高效开发。为查明大宁-吉县地区主采煤层现今地应力场特征,本次研究利用三维有限元数值模拟方法对下二叠统山西组5# 煤层现今地应力分布进行预测。结果表明,5# 煤层现今地应力表现为正断型应力机制。鄂东大宁-吉县5# 煤层最大水平主应力在15.4~21.6 MPa之间,最小水平主应力在9.8~14.4 MPa之间,构造变形的复杂性会对地应力分布产生影响。现今地应力控制压裂裂缝扩展,研究区现今地应力状态下的压裂裂缝沿着NNW-SSE方向垂直扩展。研究区5# 煤层应力差大部分小于6 MPa,具备形成复杂裂缝网络的地应力基础。煤层渗透率随有效地应力的增大呈指数减小,有效地应力越大,煤储层的渗透性越差。研究区东南部远离断层,又是应力降低区域,煤层气易在此地发生聚集,形成煤层气储藏的丰富区。研究成果可为研究区煤层气效益开发提供地质基础与科学指导。

    Abstract:

    The permeability of coal reservoirs is largely controlled by the present-day in-situ stress field to a great extent. The Daning-Jixian area of eastern Ordos Basin is rich in coal-bed methane resources, However, The lack of ground stress studies in this region, makes it difficult for coalbed methane to be developed effectively there. To identify the characteristics of the present-day in-situ stress field in the Daning-Jixian area, this study uses 3D finite element numerical simulation to predict the present-day in-situ stress distribution in the 5# coal seam of Lower Permian Shanxi Formation. The results indicate that the present-day in-situ stress indicates a normal faulting stress regime in the 5# coal seam. The 5# coal seam in the eastern Ordos Basin has a horizontal maximum principal stress between 15.4 MPa and 21.6 MPa, and a horizontal minimum principal stress between 9.8 MPa and 14.4 MPa. The distribution of ground stress may be impacted by how complex tectonic deformation is. Hydraulic fractures in the study area propagate vertically along the NNW-SSE direction under the present-day in-situ stress condition. The stress difference in the 5# coal seam in the study area is mostly less than 6 MPa, which favors to generate a complicated fracture network. The coal permeability declines exponentially as effective in-situ stress rises. Coalbed methane is anticipated to build up in the southeast of the study region, which is far from the fault and a stress reduction area, creating a rich area for coalbed methane reserves. The study results can offer a geological foundation and scientific guide for the development of coalbed methane in the study area.

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于国栋,鞠玮,杨兆彪. 大宁—吉县地区5号煤层现今地应力预测及其对煤层气开发的影响[J]. 科学技术与工程, 2024, 24(13): 5286-5295.
Yu Guodong, Ju Wei, Yang Zhaobiao. Prediction of present-day in-situ stress in the 5# coal seam of Daning-Jixian area: Implications for coalbed methane development[J]. Science Technology and Engineering,2024,24(13):5286-5295.

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  • 收稿日期:2023-06-05
  • 最后修改日期:2023-10-09
  • 录用日期:2023-10-11
  • 在线发布日期: 2024-05-17
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