裂缝-孔洞储层连通溶洞模式注气效果研究

针对缝洞碳酸盐岩油藏主要进行自喷采油或停喷后注水替油作业，导致本体溶洞内存在大量剩余油的问题，开展了缝洞碳酸盐岩油藏注气采油开发效果的研究。对裂缝孔洞储层连通溶洞模式进行模型简化，计算分析氮气、甲烷及二氧化碳气体的注入适应性，通过物理模拟方法对该类储层进行自喷、注水及注气模拟实验，并建立了注气开发分析方法，结果表明，对于该类储层溶洞连通底水规模越大，裂缝孔洞储层物性越好，注气开发效果越差，且随注气周期增加，缝洞体的弹性能量逐渐增大。在矿场条件下，应选择上部裂缝孔洞储层物性较差，溶洞连通底水规模较小的缝洞体进行注气实践；建立弹性产率与压缩系数的线性关系式，可预测气顶体积、油水能量及周期产出量等参数，为注气效果评价提供一定依据。

Effectiveness of Gas Injection in Fractured Vuggy Reservoirs Connected to Caves

Oil flowing production or water injection replacement is mainly applied to carbonate reservoirs, which may result in a large quantity of oil remaining in the caverns. To solve the problem, we conducted research on the effects of gas injection in carbonate reservoirs. First, the fractured and vuggy reservoir communication cave model was simplified, and computational analysis of the adaptability of nitrogen, methane, and carbon dioxide was performed. Physical simulation was applied to flowing, water flooding, and gas injection experiments, and the gas injection development analysis method was developed. The results demonstrate that in such reservoirs, the gas displacement effect is poor with larger scale of bottom water and better physical properties of fractured and porous reservoirs. With an increase in the gas injection cycle, the fracture-cave elastic energy increases. Thus, in field production, we could carry out the gas injection operation in fracture caves, with poor physical properties in the upper fractured and porous reservoirs, and caves with smaller quantities of bottom water. Establishing linear equations of elastic production rate and compression coefficient can predict the gas volume, energy, and water cycle output parameters and provide a foundation for gas injection effect evaluation.