Optimization of Heat Extraction Performance from Multiple Borehole Reservoir Systems-Towards the Enlargement of Geothermal Reservoirs and Enhancement of Heat Extraction-

建立了裂隙型干热岩地热储三维模拟模型FRACSIM-3D。该模型综合考虑了水力增产过程中岩石-流体的力学相互作用，定量预测了三维储层的生长动态。在该模型中，预先存在的裂缝是随机生成的。假设硬币形裂缝的分形尺寸分布具有随机取向。在注入压力恒定的条件下，通过将裂隙岩体的连通性映射到规则的立方体网格上，模拟了流体在离散裂隙网络中的流动。流体流动由达西定律方程近似。由于裂缝剪切偏移，来自注入井的流体压力引起裂缝的孔径的增长。裂缝扩张的计算需要多次迭代：每次重新求解模拟裂缝系统的完整流动模型并重新计算剪切位移u 关于我们 从上一次迭代中读出内部破裂压力。数值模型是根据Hijiori HDR油藏的现场数据进行校准的。例如，对储层中裂缝及其开度的不同随机初始分布进行了一系列数值计算。的分布，这导致了一个很好的协议的数值计算和实验检测Hijiori水库的体积和生长方向，被选为一个合适的模拟天然裂缝介质。该模型用于评估Hijiory油藏的适当应力状态，因为通过不同的实验技术获得的相关现场数据不是很可靠。最新版本的FRACSIM-3D集成了多井眼注入井和生产威尔斯井系统。该模型的改进使得分析不同井眼系统布置方式对储层产能的影响成为可能。针对不同的几何钻孔结构进行了大量的数值试验。在此基础上，提出了以较少的有效井眼数提供相应油藏采收率的生产井和注水威尔斯井的优化布置方案。少

An improved three-dimensional simulation model (FRACSIM-3D) for the fractured hot-dry-rock (HDR) geothermal reservoir is developed. It incorporates the mechanical rock-fluid interaction during hydraulic stimulation and quantitatively predicts the 3D reservoir growth behavior. In this model the pre-existing fractures are generated stochastically. The fractal size distribution of the penny-shaped fractures with random orientation is assumed. The fluid flow through the discrete fracture network is simulated by mapping the connectivity of the fractured rock to a regular cubic grid under condition of constant injection pressure. The fluid flow is approximated by the Darcy law equation. The fluid pressure from the injection well induces the growth of the fractures' apertures due to the fracture shear offset. Computation of the fracture dilation requires several iterations: solving the complete flow model simulating the fracture system anew each time and recalculating the shear displacement u … More sing the inner fracture pressure from the previous iteration. The numerical model is calibrated on the basis of the field data available for the Hijiori HDR reservoir. For instance, the series of numerical computations was carried for the different randomly seeded initial distributions of fractures and their apertures within the reservoir. The distribution, which leads to a good agreement of the numerically obtained and experimentally detected Hijiori reservoir's volume and growth direction, was chosen as an appropriate one for simulating the natural fractured media. The model was used for the assessment of the adequate stress regime of the Hijiory reservoir since the related field data obtained by the different experimental technique are not very reliable. The latest version of FRACSIM-3D incorporates the multi-borehole system of injection and production wells. This improvement of the model makes possible to analyze the effect of different borehole system arrangement on the reservoir productivity. A number of numerical experiments for the different geometrical boreholes configurations have been conducted. As a result, the optimal arrangements of the production and injection wells, which provide the relevant reservoir recovery rate with lesser amount of active boreholes, are proposed. Less