Numerical investigation of fluid-driven near-borehole fracture propagation in laminated reservoir rock using PFC2D
Numerical investigation of fluid-driven near-borehole fracture propagation in laminated reservoir rock using PFC2D
复制标题
使用 PFC2D 对层状储层岩石中流体驱动的近井裂缝扩展进行数值研究
DOI：
10.1016/j.jngse.2016.11.010
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发表时间：
2016-11-01
影响因子：
--
通讯作者：
Han, Zhenhua
中科院分区：
文献类型：
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作者：
Zhou, Jian;Zhang, Luqing;Han, Zhenhua
水力压裂是一种有用的工具，用于提高页岩气开发的渗透性，增强地热系统，以及使用高压注入压裂液到致密储层岩石中的地质碳封存。为了充分利用水力压裂技术，必须充分理解流体注入引起的裂缝起裂和扩展的机理。本文采用基于二维颗粒流程序（PFC2D）的离散颗粒模型，开展了水力压裂模拟工作。首先，针对不同地应力条件下水力压裂破裂压力的解析解，对所建立的模型进行了验证。其次，利用室内层状储层岩石单轴压缩试验优化的细观参数对模型进行了验证。最后，进行了一系列的水力压裂模拟工作，研究了弱层、地应力比、注液速率和流体粘度对井眼压力历史、水力裂缝几何形状和孔隙压力场的影响。结果表明，层状油藏中水力裂缝的扩展受地应力状态和储层岩石强度各向异性的共同控制。随着注液量的增加，裂缝扩展需要更高的破裂压力，裂缝几何形状将变得复杂。此外，低粘度流体可以更容易地从钻孔渗透到周围岩石中，导致有效应力的减小并导致较低的破裂压力。此外，裂缝的几何形状对流体粘度敏感，主裂缝更容易沿着最大主应力方向扩展。(C)2016爱思唯尔B.V.保留所有权利。
Hydraulic fracturing is a useful tool for enhancing permeability for shale gas development, enhanced geothermal systems, and geological carbon sequestration using high-pressure injection of a fracturing fluid into tight reservoir rocks. Mechanisms of fluid injection-induced fracture initiation and propagation should be well understood to take full advantage of hydraulic fracturing. In this paper, hydraulic fracturing modeling work was developed using discrete particle modeling based on two-dimensional particle flow code (PFC2D). Firstly, the developed model is validated against the analytical solutions of the breakdown pressure for the hydraulic fracturing process under varied in-situ stress conditions. Secondly, the model is tested using the microscopic parameters optimized from laboratory Uniaxial Compressive Test for laminated reservoir rock. Lastly, a series of hydraulic fracturing simulation work was performed to study the influence of weak layers, in-situ stress ratio, fluid injection rate and fluid viscosity on the borehole pressure history, the geometry of hydraulic fractures and the pore-pressure field. It is found that the hydraulic fracture propagation in laminated reservoir is controlled by both in situ stress state and strength anisotropy of the reservoir rock. With fluid injection rate increasing, higher breakdown pressure is required for fracture propagation and complex fracture geometry will develop. Furthermore, low viscosity fluid can more easily penetrate from the borehole into the surrounding rock, causing a reduction of the effective stress and leading to a lower breakdown pressure. Moreover, the geometry, of the fractures is found to be sensitive to the fluid viscosity, and the major fractures propagate more easily along the maximum principle stress direction. (C) 2016 Elsevier B.V. All rights reserved.