冯雪磊, 马凤山, 赵海军, 等. 2021. 断层影响下的页岩气储层水力压裂模拟研究[J].工程地质学报, 29(3): 751-763. doi: 10.13544/j.cnki.jeg.2020-372.
    引用本文: 冯雪磊, 马凤山, 赵海军, 等. 2021. 断层影响下的页岩气储层水力压裂模拟研究[J].工程地质学报, 29(3): 751-763. doi: 10.13544/j.cnki.jeg.2020-372.
    Feng Xuelei, Ma Fengshan, Zhao Haijun, et al. 2021. Numerical simulation of hydraulic fracturing in shale gas reservoirs under fault influence [J].Journal of Engineering Geology, 29(3): 751 -763. doi: 10.13544/j.cnki.jeg.2020-372.
    Citation: Feng Xuelei, Ma Fengshan, Zhao Haijun, et al. 2021. Numerical simulation of hydraulic fracturing in shale gas reservoirs under fault influence [J].Journal of Engineering Geology, 29(3): 751 -763. doi: 10.13544/j.cnki.jeg.2020-372.

    断层影响下的页岩气储层水力压裂模拟研究

    NUMERICAL SIMULATION OF HYDRAULIC FRACTURING IN SHALE GAS RESERVOIRS UNDER FAULT INFLUENCE

    • 摘要: 断层对页岩气储层压裂改造有重要影响,甚至诱发深部地震事件和近地表环境问题。本文采用多物理场耦合方法,基于渗流和应力耦合理论,研究储层水力压裂过程中断层以及封闭顶板中水力破坏区域的产生与演化机理,并分析讨论流体沿高渗通道运移扩散机理,研究结果表明:(1)断层改变储层水力破坏区域形态并且扩展了水力压裂破坏空间。较高注水压力使储层水力破坏区域扩大到封闭顶板和底板,水力破坏区域受断层影响而沿着断层带快速发育延伸。高注水压力导致断层水力压裂破坏高度急剧增加,储层封闭性发生改变。(2)在页岩储层高风险地质构造和较高注水压力条件下,水力压裂作业产生岩石破裂和裂缝局部活化诱发的微地震事件,但难以导致破坏性地震事件,多属于断层或较大断裂局部区域产生的水力耦合破坏及可能诱发的较小地震事件。(3)水力破坏区域贯通到断层带内诱发流体沿断层带迁移,断层带的渗透率较高,水力破坏区域与上部高渗透岩层贯通会加快流体的逃逸速度,增大压裂液污染上部地层的风险,导致压裂效率降低,影响储层压裂改造,降低了页岩气开发价值。

       

      Abstract: Fault has significant impact on the hydraulic fracturing operations in shale gas reservoir, and even induces deep seismic events and near-surface environment issues. This article adopts the multi-physics coupling method and considered the coupling progress of seepage and stress. The appearance、extend and evolution of hydraulic damage area in the fault and closed caprock during hydraulic fracturing in shale reservoirs are simulated and analyzed. The mechanism of fluid migration and diffusion along high permeability channels is analyzed at last. The main conclusions can be drawn as follows: (1)Fault changes the shape of reservoir hydraulic damage area and expands the space of the hydraulic fracturing damage area. High water-injection pressure extends reservoir hydraulic damage area to the closed cap rock and bottom plate. The hydraulic damage area is obviously affected by the fault and developed along the fault rapidly. High water-injection pressure leads to a sharp increase in the height of fault hydraulic damage area, resulting in changes in reservoir sealing integrity. (2)Under the conditions of internal high-risk geological structures and high water-injection pressures in shale reservoirs, hydraulic fracturing operations produce micro-seismic events induced by rock rupture and local reactivation of fractures, but it is difficult to cause destructive seismic events. Most of seismic events are possibly induced by regional hydraulic coupling damage during reactivation of fault or large fractures. (3)The penetration of the hydraulic damage zone into the fault induces fluid migration along the fault zone. Considering the higher permeability in fault damage zone, the well-connected pathway of the hydraulic damage zone and the upper high-permeability rock formation can speed up the escape of fluid and increase the risk of fracturing fluid contaminating the upper formation. This leads to a decrease in fracturing efficiency and reduces the economic value of shale gas development.

       

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