气藏型地下储气库建库注采机理与评价关键技术

气藏型地下储气库是目前全球最主要的地下储气库类型,其工作气量约占全球各类储气库总工作气量的75%。为了提高气藏型地下储气库(以下简称储气库)建库地质方案设计的科学性和可靠性、优化储气库运行参数,从储气库多周期大流量强注强采的基本特点出发,综合采用物理模拟和数值模拟两种技术手段,重点研究了复杂地质条件气藏改建储气库圈闭动态密封性和气水高速交互渗流机理,建立了盖层、断层动态密封性评价和库容参数评价的关键技术。研究结果表明:(1)储气库注采工况交变应力对盖层原始静态毛细管密封和力学完整性具有不同程度的弱化作用,采用动态突破压力、剪切安全指数等指标可以全面量化评价圈闭的密封性;(2)基于高速注采互驱实验揭示的孔隙局部动用机理,建立了以有效含气孔隙为基础的储气库库容量设计方法。矿场应用实例表明,该技术应用于大型多层H储气库,有效指导了储气库建库地质方案设计,该储气库经过5个周期注采后达容率为91.8%,调峰能力由投产初期的2.7×10~8 m~3快速增至36.3×10~8 m~3,运行指标与方案设计吻合程度高。

Injection–production mechanisms and key evaluation technologies for underground gas storages rebuilt from gas reservoirs

Underground gas storages (UGSs) rebuilt from gas reservoirs is the most popular UGS type in the world. It accounts for 75% of the total active gas of all gas storages. In order to design more scientific and reliable geological schemes for constructing the underground gas storages rebuilt from gas reservoirs and optimize the UGS operation parameters, we analyzed the UGS basic characteristics of multi-cycle high-rate injection and production. Then, the dynamic sealing capacity of traps and the water–gas high-speed interactive flow mechanism of UGSs rebuilt from gas reservoirs with complex geological conditions were investigated by both physical simulation and numerical simulation. Finally, the key technologies for evaluating the dynamic sealing capacity of caprocks and faults and the storage capacity parameters were developed. Some results were obtained. First, the alternating stress in the process of UGS injection and production weakens the original static capillary sealing capacity and mechanical integrity of caprocks to different extents, and the trap sealing capacity can be quantified and evaluated comprehensively by using dynamic breakthrough pressures, shear safety indexes and other indicators. Second, a UGS capacity design method based on effective gas-bearing pores was developed according to the local pore-based recovery mechanism revealed in the high-speed gas–water mutual flooding test. Field application in the multi-layer UGS of H shows that these technologies provide an effective guidance for the design of geologic schemes. After five cycles of injection and production, its ramp-up ratio reached 91.8% and the peak shaving capacity increased quickly to 36.3×108 m3 from 2.7×108 m3 in the early stage of production. Moreover, the operation indicators matched well with the design.