LAUSR

Water invasion is a common phenomenon in gas reservoirs with active edge-and-bottom aquifers. Due to high reservoir heterogeneity and production parameters, carbonate gas reservoirs feature exploitation obstacles and low recovery factors. In this study, combined core displacement and nuclear magnetic resonance (NMR) experiments explored the reservoir gas–water two-phase flow and remaining microscopic gas distribution during water invasion and gas injection. Consequently, for fracture core, the water-phase relative permeability is higher and the co-seepage interval is narrower than that of three pore cores during water invasion, whereas the water-drive recovery efficiency at different invasion rates is the lowest among all cores. Gas injection is beneficial for reducing water saturation and partially restoring the gas-phase relative permeability, especially for fracture core. The remaining gas distribution and the content are related to the core properties. Compared with pore cores, the water invasion rate strongly influences the residual gas distribution in fracture core. The results enhance the understanding of the water invasion mechanism, gas injection to resume production and the remaining gas distribution, so as to improve the recovery factors of carbonate gas reservoirs. 边底水活跃气藏发生水侵是一种常见现象。研究区为碳酸盐岩气藏,因储层非均质性强、生产 任务重,气藏发生严重水侵,影响开发效果,并将导致气藏采收率低。本文采用岩心驱替实验和核磁 共振技术相结合的方法,研究了碳酸盐岩气藏水侵过程和注气复产过程中,气液两相渗流规律以及剩 余气微观分布规律。研究结果表明,在水侵过程中,裂缝型岩心较孔隙型岩心的液相相对渗透率高、 共渗区窄;在不同水侵速度下,裂缝型岩心的采收率最低。在注气复产过程中,注气对裂缝型岩心降 低含水饱和度、恢复部分气相相对渗透率的效果突出。剩余气量及其分布与岩心物性相关,水侵速度 对裂缝型岩心剩余气的分布影响较大,但对孔隙型岩心的影响小。研究结果进一步提高了对碳酸盐岩 气藏水侵机理、注气复产以及剩余气分布的认识,为提高该类型气藏采收率提供依据。