岩石压裂渗流微震实验与数值分析

发布时间：2018-02-28 15:48

本文关键词： 孔隙压力三轴压缩实验微地震监测计算流体力学 CE/SE算法　出处：《中国地震局地壳应力研究所》2015年硕士论文　论文类型：学位论文

【摘要】：流体在地震和断裂活动过程中的作用是一个典型的水文地球物理问题,与地震破裂过程中的慢滑移和应变能的加速积累有着密切的关系。其中孔隙压的作用问题是关注的焦点,也是地震流体动力过程研究的核心问题。本论文选择四川盆地的下沙溪庙组砂岩地层的岩心,开展岩石压裂渗流微震实验和数值分析,探索地震活动过程与流体孔隙压力演化之间的关系。主要结论如下。以岩石压裂渗流微震实验为基础,对砂岩岩心进行饱和三轴压缩实验,研究孔隙压与流体饱和度对岩石物性和声发射活动的影响。实验结果表明,随着围压和孔隙压力的增加,地震波速度增加。地震波振幅对围压变化敏感。地震压缩波的到时揭示了流体的运移过程。孔隙压力与饱和度削弱了岩石的强度,缩短变形破坏所需的时间。孔隙压梯度对裂隙的扩展影响显著。应用FLAC3D软件针对上述三轴压缩实验进行数值模拟。推导出显式有限差分格式与隐式差分格式计算稳定性准侧。采用岩石压裂渗流微震实验的参数,建立完全饱和状态下砂岩三轴压缩的数值模型,计算轴向加载过程以及干燥状态下砂岩的压缩破坏过程。采用上下边界扩展方式,克服了上下界面局部形对计算结果的影响。采用缩短加载速率,将数值迭代时间转化为物理时间。数值计算的变形结果与实验结果基本一致。孔隙压的演化揭示了岩石由弹性向塑性变形以及屈服的动态变形与破坏过程。孔隙压梯度对剪切变形影响显著。对不可压缩流体的孔隙方柱绕流采用二阶精度时-空守恒元和解元(CE/SE)算法进行了数值计算,分析了不同达西数、不同雷诺数等参数对流动过程的影响。数值结果表明孔隙方柱绕流参数随雷诺数变化规律与实体方柱绕流一致,受孔隙介质影响,方柱边界压力及升力系数变化范围相应减小,涡脱频率增大。
[Abstract]:The effect of fluid in the earthquake and active fault in the process is a typical hydrological geophysical problems, and slow slip and strain during earthquake rupture can accelerate the accumulation are closely related. The effect of pore pressure is the focus of attention, is also on the dynamic process of earthquake fluid core problem. This paper choose Sichuan Basin Shaxi Temple group sandstone core, carry out the rock fracturing microseismic seepage experiment and numerical analysis, explore the relationship between seismic activity and pore pressure evolution. The main conclusions are as follows. The rock fracture seepage microseismic experiment based on sandstone cores, three saturated uniaxial compression experiment, influence on rock physical activities study of acoustic emission of pore pressure and fluid saturation. The experimental results show that with the increase of confining pressure and pore pressure, the seismic wave velocity increases. The amplitude of seismic waves on the confining pressure Sensitive. Seismic compression wave then reveals the migration process of fluid. The pore pressure and saturation weakens the strength of the rock deformation and failure, shorten the time required. The pore pressure gradient on crack extension was significant. Application of FLAC3D software in view of the above three axial compression experiments were simulated. Derive the explicit finite difference scheme stability calculation of quasi side and implicit difference scheme. The seepage parameters of rock fracturing microseismic experiment, establish fully saturated numerical model of three axial compression under the condition of sandstone, sandstone failure process calculation of axial compression loading process and the drying condition. The upper and lower boundary extension methods to overcome the influence on the local shape of calculation interface results. By shortening the loading rate, the numerical iteration time into physical deformation time. The numerical results are consistent with the experimental results. The evolution of pore pressure To reveal the dynamic rock from elastic to plastic deformation and yield deformation and failure process. The pore pressure gradient on the effect of shear deformation on flow significantly. By two order precision around the pore column incompressible fluid and the space time conservation element (CE/SE) algorithm for the numerical calculation, analysis of the different Darcy number effects of different parameters, the Reynolds number of flow process. The numerical results show that the Reynolds number variation and solid flow around square cylinder consistent parameters of pore flow around a square cylinder, the influence of porous media, the variation range of square column boundary pressure and lift coefficient decrease, vortex shedding frequency increases.

【学位授予单位】：中国地震局地壳应力研究所
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：P315.8

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