增强型地热系统压裂和开采方案研究

增强型地热系统(Enhanced Geothermal System, EGS)是一种通过介质循环(水或CO2)来提取深部低渗、高温岩体中地热资源并将其用来发电及供暖的工程技术集成。水力压裂是EGS储层改造的主要方式, 储层改造的好坏直接关系到EGS最终的产能状况, 因此针对具体地质条件选择合适的水力压裂方案具有重要意义。本文基于大庆莺深2井的测井资料, 根据其地应力及岩性变化情况选定EGS开采潜力储层, 采用水平井及张开型压裂的储层改造方式, 对潜力储层进行了多种压裂方案数值模拟分析, 根据压裂模拟结果建立三维水热耦合模型, 进行了EGS发电潜力评估分析, 最终得出莺深2井EGS开采的最优压裂方案和开采方案。研究结果得出:水力裂缝的几何性质主要受地应力、支撑剂粒径和砂比影响, 在EGS中宜采用低砂比、阶梯式的泵注程序。同时, 在采用一注两抽的三水平井开采模式下, 10条裂缝的最优注入速率是30kg,s-1, 运行20a的发电量是0.60～1.23MW。

THE RESEARCH OF HYDRAULIC FRACTURING AND DEVELOPMENT STRATEGY IN ENHANCED GEOTHERMAL SYSTEM

Enhanced geothermal system(EGS)could extract deep geothermal resource from low permeability hot rock through media circulation. Based on the real geological and logging data of one abandoned well YS 2, we first studied the conditions existing in the deep formation. A 3D fracturing model was created and various fracturing schemes have been numerically conducted. Subsequently, we performed the hydro-thermal simulations with different injection rates through the different fracture reservoirs generated by the hydraulic fracturing. Last, depending on the research results above, we obtained the optimal fracturing and operation strategies. The results indicate that in the optimal fracture reservoir, an electrical power of 0.60～1.23MW(10 fractures) over a 20 years period could be achieved when the 3 horizontal wells system was adopted and injection rate was 30kgs-1.