Discrete fracture modeling using Centroidal Voronoi grid for simulation of shale gas plays with coupled nonlinear physics
Discrete fracture modeling using Centroidal Voronoi grid for simulation of shale gas plays with coupled nonlinear physics
复制标题
DOI：
10.1016/j.fuel.2015.09.038
复制
发表时间：
2016
期刊：
影响因子：
7.4
通讯作者：
Yuhang Wang;Mohammad Shahvali
中科院分区：
文献类型：
--
作者：
Yuhang Wang;Mohammad Shahvali
开发能够稳健有效地预测非常规油藏产量的数值模拟器至关重要。在本文中，我们详细描述了我们最近开发的页岩气模拟器的公式、灵活性和模拟结果。这项工作的第一个组成部分包括水力裂缝的离散裂缝建模 (DFM)。为了捕获裂缝阶段和水平井附近的流动瞬变，我们开发了一种基于质心 Voronoi 曲面细分 (CVT) 的网格化算法。为了表示水力裂缝，我们根据用户所需的细化在裂缝阶段周围填充节点。填充的节点被视为约束，并在后续迭代期间保持静止。对于矩阵区域，我们使用两步算法来生成网格。第一步，我们通过最小化沿相邻节点之间的杆的力来细分域，类似于质量弹簧或桁架系统。在下一步中，我们执行迭代网格优化以生成质心 Voronoi 曲面细分。本文的第二部分目标是表示广泛的物理现象，包括气体滑移、气体吸附/解吸和气体的高速非达西流动。我们的公式是完全隐式的，允许最多两相（水和气体）流动。为了避免手动计算与耦合非线性方程组相对应的雅可比行列式，我们利用自动微分（AD），使我们能够轻松地合并非线性控制方程，几乎无需额外成本。我们进行了敏感性研究，以研究不同参数对页岩气区块产量以及模拟器计算效率的影响。
It is critical to develop numerical simulators that can robustly and efficiently predict production from unconventional reservoirs. In this paper, we describe in detail the formulation, flexibility and simulation results of our recently developed shale gas simulator. The first component of this work includes Discrete Fracture Modeling (DFM) of hydraulic fractures. To capture the flow transients near fracture stages and horizontal well, we develop a gridding algorithm based on Centroidal Voronoi Tessellation (CVT). To represent the hydraulic fractures, we populate nodes around fracture stages based on the refinement that is required by the user. The populated nodes are viewed as constraints and are kept stationary during the subsequent iterations. For matrix region we use a two-step algorithm to generate the mesh. In the first step, we tessellate the domain by minimizing the forces along the bars between adjacent nodes, analogues to mass-spring or truss systems. In the next step, we perform an iterative gird optimization to generate Centroidal Voronoi Tessellation. The second component of the paper targets representation of a wide range of physical phenomena including gas slippage, gas adsorption/desorption, and high velocity non-Darcy flow of gas. Our formulation is fully implicit and allows for flow of up to two phases (water and gas). To avoid manual calculation of the Jacobian corresponding to the coupled nonlinear system of equations, we utilize Automatic Differentiation (AD), allowing us to readily incorporate the nonlinear governing equations at nearly no extra cost. We perform sensitivity studies to investigate the effect of different parameters on production from shale gas plays as well as on computational efficiency of the simulator.