| 流体-地质力学耦合建模表征水力压裂诱发地震:以加拿大Fox Creek地区为例 |
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| 引用本文： | 惠钢,陈胜男,顾斐.流体-地质力学耦合建模表征水力压裂诱发地震:以加拿大Fox Creek地区为例[J].地球物理学报,2021,64(3):864-875. |
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| 作者姓名： | 惠钢 陈胜男 顾斐 |
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| 作者单位： | 加拿大卡尔加里大学化学与石油工程系,卡尔加里 T2N1N4;中国石油勘探开发研究院,北京 100083 |
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| 基金项目： | 加拿大卓越研究基金项目(The Canada First Research Excellence Fund)资助 |
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| 摘 要： | 随着水力压裂技术在页岩气开发中的广泛应用,加拿大西部盆地的诱发地震活动显著增加.目前对于诱发地震的综合表征方法还不成熟.本文采用一种综合地质、岩石力学及流体力学的研究方法,对Fox Creek地区2015年2月8日发生的M 3.0诱发地震事件进行了综合表征.首先,利用高分辨率三维反射地震资料,采用蚂蚁体追踪技术识别潜在断层.其次,利用测井曲线和压裂施工数据等资料定量求取岩石力学及地应力参数,建立三维地质力学模型,明确水力压裂缝的空间扩展规律.最后,建立流体-地质力学耦合模型,计算水力压裂过程中断层附近的孔隙压力及局部应力变化,利用摩尔-库仑破裂准则判定断层激活的时间与空间位置,揭示本次诱发地震事件的触发机制并提出风险控制对策.结果表明,三条由Precambrian基底向上延伸至Duvernay地层的近垂直断层在水平井压裂过程中被激活.由于水平井的部分压裂缝与断层沟通,注入流体沿断层的高渗透破裂带向下迅速扩散,在基底位置激活断层并诱发M 3.0地震事件.其中孔隙压力增加是本例中断层活化的主要因素.现场措施表明,增大压裂水平井与已知断层之间的距离被可以有效地降低地震风险.因此在进行水平井钻井及压裂作业之前,明确地下断层的分布位置至关重要.
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| 关 键 词： | 诱发地震 水力压裂 断层活化 流体-地质力学耦合模型 摩尔-库仑破裂准则 风险控制策略 |
Coupled fluid-geomechanics modeling to characterize hydraulic fracturing-induced earthquakes:Case study in Fox Creek,Canada |
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| HUI Gang,CHEN ShengNan,GU Fei.Coupled fluid-geomechanics modeling to characterize hydraulic fracturing-induced earthquakes:Case study in Fox Creek,Canada[J].Chinese Journal of Geophysics,2021,64(3):864-875. |
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| Authors: | HUI Gang CHEN ShengNan GU Fei |
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| Affiliation: | (Department of Chemical and Petroleum Engineering,Calgary T2N1N4,Canada;Research Institute of Petroleum Exploration and Development,Beijing 100083,China) |
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| Abstract: | Along with the wide application of hydraulic fracturing techniques in the development of shale gas reservoirs,a salient increase in induced earthquakes has been reported recently in the Western Canada Sedimentary Basin.However,the comprehensive charaterzation of fracturing-induced seisicmicity has not been well investigated.In this paper,an integrated method combining geology,geomechanics,and hydrodynamics is utilized to investigate the M 3.0 induced earthquake that occurred in Fox Creek on February 8,2015.First,the ant tracking approach is utilized to identify the pre-existing fault through the high-resolution 3D seismic survey.The mechanical parameters and in-situ stress tensors are derived from the well logging and treatment data.Additionally,the 3D geomechanical model is built up and utilized to simulate the propagation of hydraulic fractures.The fluid-geomechanical coupling model is then established to calculate the pore pressure and local stress variation in the vicinity of the fault during and after fracturing operations.Finally,the Mohr-Coulomb failure criterion is employed to determine the spatiotemporal activation of related faults and reveal the triggering mechanisms of induced earthquakes.The results show that three near-vertical faults were activated during hydraulic fracturing,all of which extended upward from the Precambrian basement to the Duvernay Formation.Because of the hydrology communication between inferred faults and the stimulated well,some injected fracturing fluids diffused downward along the high-permeability fault damage zone,activating the fault in the basement and triggering the M 3.0 earthquake.The increase in pore pressure is the predominant controlling factor in the process of fault activation.Field measurements show that enlarging the distance between the horizontal wellbore and the known fault had been demonstrated effective in mitigating the potential risks of earthquakes.Therefore,it is essential to determine the distribution of the subsurface faults prior to the drilling and hydraulic fracturing operations of horizontal wells in the unconventional reservoirs. |
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| Keywords: | Induced earthquakes Hydraulic fracturing Fault activation Coupled fluid-geomechanics model Mohr-Coulomb failure criterion Mitigation strategy |
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