冯雪磊, 马凤山, 赵海军, 刘港, 郭捷. 2016: 页岩气封存顶板变形破裂的机理与数值模拟. 工程地质学报, 24(s1): 290-298. DOI: 10.13544/j.cnki.jeg.2016.s1.044
    引用本文: 冯雪磊, 马凤山, 赵海军, 刘港, 郭捷. 2016: 页岩气封存顶板变形破裂的机理与数值模拟. 工程地质学报, 24(s1): 290-298. DOI: 10.13544/j.cnki.jeg.2016.s1.044
    FENG Xuelei, MA Fengshan, ZHAO Haijun, LIU Gang, GUO Jie. 2016: NUMERICAL SIMULATION AND MECHANISM OF DEFORMATION AND FRACTURE OF SHALE GAS CAP ROCK. JOURNAL OF ENGINEERING GEOLOGY, 24(s1): 290-298. DOI: 10.13544/j.cnki.jeg.2016.s1.044
    Citation: FENG Xuelei, MA Fengshan, ZHAO Haijun, LIU Gang, GUO Jie. 2016: NUMERICAL SIMULATION AND MECHANISM OF DEFORMATION AND FRACTURE OF SHALE GAS CAP ROCK. JOURNAL OF ENGINEERING GEOLOGY, 24(s1): 290-298. DOI: 10.13544/j.cnki.jeg.2016.s1.044

    页岩气封存顶板变形破裂的机理与数值模拟

    NUMERICAL SIMULATION AND MECHANISM OF DEFORMATION AND FRACTURE OF SHALE GAS CAP ROCK

    • 摘要: 由于页岩气赋存机理的特殊性,页岩气成藏受保存条件及顶板类型的影响。封存顶板岩层对页岩气封盖影响极大。本文对页岩气藏封存顶板的破裂机理进行理论分析,并建立模型对顶板进行数值模拟。顶板岩层破裂与注水压力、岩石抗拉强度、地应力有关。封存顶板的破裂机理为压裂初始阶段,储层膨胀变形,封存顶板受压产生剪切裂纹,压裂液进入顶板,当注水压力小于最小主应力时,岩层发生剪切破裂,注水压力达到最小主应力和地应力之和时,岩石发生剪切破裂和张性破裂,裂缝增加并扩展,形成网状体系。数值模拟结果显示,压裂注水会在储层产生水力破坏区域,注水压力升高,水力破坏区域扩大并相互叠加影响,使得水力破坏集中于中间注水口的上部,当顶板岩层内部出现水力破坏区域时,岩石会发生破裂产生裂缝。在储层压裂的整个过程中,开始1h内,裂缝在储层内发展,顶板保持稳定,空隙水压力和变形很小,顶板岩层底部有少量裂纹。压裂2h,顶板底部裂缝增多,岩石空隙水压力上升,且顶板发生变形,中间变形最为明显。压裂3h,裂缝从顶板底部延伸到上部,岩层内部裂缝快速发育,空隙水压力持续升高,变形加大。数值模拟的结果与破裂机理的分析结果相吻合。

       

      Abstract: Due to the special nature of the occurrence mechanism of shale gas, storage conditions and type of cap affectshale gas reservoir. Dense overburden rock have a great impact on shale gas capping, take a greater role in the decision of reservoir fracturing technology. This article is for theoretical analysis of cap rock fracture mechanism for shale gas reservoir. and establish the numerical simulation model for cap rock. The cap rock fracturing is related to water injection pressure, rock tensile strength and in-situ stress.the fracture mechanism of cap rock includes two stages. The fracturing initial stage, the reservoir deformation, cap rock occurs shear crack, fracturing fluid into cap rock. When water injection pressure is less than the minimum principal stress, shear fracture rock When water injection pressure is the sum of least principal stress and tensile strength of rock, rock occurs tensile failure, the process of fracture involves tensile and shear failure, fracture increase and expand, form a mesh system. Numerical simulation results show that the high pressure water can produce hydraulic destruction in the reservoir area. With water injection pressure rising, hydraulic damage area expanded and occurs superimposition effect, result in the hydraulic failure focus on upper part of the middle water injection. In the whole process of reservoir fracturing, 1 hour later, the cracks of the reservoir develop, the cap rock stability, rock pore water pressure and deformation is small, there are small cracks at the bottom of cap rock. After fracturing 2 hours, cracks at the bottom of cap rock increase, rock pore water pressure rise, and rock occurs deformation, deformation is most obvious in the middle. After fracturing 3 hours, cracks extend from the bottom of the roof to the upper, cracks rock in internal rapidly develop, rock pore water pressure and deformation value increasing. The results of numerical simulation is consistent with the results of mechanism analysis of fracture.

       

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