Coupled poroelastic modelling of hydraulic fracturing-induced seismicity: Implications for understanding the post shut-in ML 2.9 earthquake at the Preston New Road, UK
Coupled poroelastic modelling of hydraulic fracturing-induced seismicity: Implications for understanding the post shut-in ML 2.9 earthquake at the Preston New Road, UK
复制标题
水力压裂诱发地震活动的耦合孔隙弹性模型：对理解英国普雷斯顿新路关井后 ML 2.9 地震的启示
DOI：
10.1002/essoar.10508628.1
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发表时间：
2021
期刊：
影响因子：
--
通讯作者：
Cao W
中科院分区：
文献类型：
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作者：
Cao W
注后地震活动与水力压裂相关，给水力压裂作业带来了巨大挑战。本研究旨在确定2019年8月英国普雷斯顿新路（Preston New Road）关闭后ml2.9地震的因果机制，其中有三种可能的机制，即关闭后孔隙压力扩散、非超压断层上的孔隙弹性应力和超压断层上的孔隙弹性应力。为了模拟页岩储层对现场水力压裂作业的水力学响应，开发了一个3D全耦合孔隙弹性模型，该模型考虑了孔隙弹性固体变形、多孔岩石和裂缝结构中的流体流动以及水力压裂引起的压力扰动。在此基础上，进一步评价了导致此次地震的PNR‐2断层的库仑应力变化和地震活动性。模型结果表明，尽管孔隙弹性应力可能对断层滑动起促进作用，但孔隙压力的增加在触发断层滑动中起主导作用。在三种可能的机制中，关井后孔隙压力扩散在库仑应力变化、地震活动速率、断层滑动时间和破裂面积方面最有利。耦合模拟结果表明，ml2.9关闭后地震的发生是一个三阶段的过程，首先是裂缝尖端的扩展，刺激了周围的储层，然后是与导电PNR - 2断层的水力连接，随后孔隙压力扩散到导电PNR - 2断层，最终断层在孔隙压力增加的直接影响下活化。
Post‐injection seismicity associated with hydraulic stimulation has posed great challenges to hydraulic fracturing operations. This work aims to identify the causal mechanism of the post shut‐inML2.9 earthquake in August 2019 at the Preston New Road, UK, amongst three plausible mechanisms, that is, the post shut‐in pore pressure diffusion, poroelastic stressing on a non‐overpressurized fault, and poroelastic stressing on an overpressurized fault. A 3D fully coupled poroelastic model that considers the poroelastic solid deformation, fluid flow in both porous rocks and fracture structures, and hydrofracturing‐induced pressure perturbations was developed to simulate the hydromechanical response of the shale reservoir formation to hydraulic fracturing operations at the site. Based on the model results, Coulomb stress changes and seismicity rate were further evaluated on the PNR‐2 fault responsible for the earthquake. Model results have shown that increased pore pressure plays a dominant role in triggering the fault slippage, although the poroelastic stress may have acted to promote the slippage. Amongst the three plausible mechanisms, the post shut‐in pore pressure diffusion is the most favored in terms of Coulomb stress change, seismicity rate, timing of fault slippage and rupture area. The coupled modeling results suggested that the occurrence of the post shut‐inML2.9 earthquake was a three‐staged process, involving first propagation of fracture tips that stimulated surrounding reservoir formations, then hydraulic connection with and subsequent pore pressure diffusion to the conductive PNR‐2 fault, and eventually fault activation primarily under the direct impact of increased pore pressure.