缝洞型油藏剩余油形成机制及改善开发效果研究

采用数值模拟方法研究了缝洞单元剩余油形成机制和改善水驱开发效果方法。研究表明：油水重力分异作用导致溶洞内残余油和束缚水含量决定于流出侧缝洞连接点位置,从而得到了残余相饱和度表达式；油水密度差、缝洞连接关系和缝洞单元压力系统是影响缝洞型油藏剩余油形成和分布的三个因素,油水密度差是根本原因,缝-洞连接关系是主控因素,而缝洞单元压力系统则属于次要原因；提出了水驱后续注气开发、高含水期转换注采关系开发、注水井提液开发三种提高采收率技术,可不同程度降低剩余油饱和度,但各种方式的优劣并不是绝对的,需要根据缝洞连接方式和注采井与缝洞单元连接位置进行优选。

Formation mechanism of remaining oil and improve development effect in fractured-cavity reservoir

The formation mechanism of remaining oil and the EOR after water flooding are studied by numerical simulation. The results show that residual phase saturation is decided by the junction positions between fractures and cave of the flow-out end for oil-water gravity differentiation. Based on this conclusion, the expressions of residual phase saturation are obtained. The major factors that influence the remaining oil contain oil-water density difference, the junction between fractures and caves and the pressure system in the fractured-cavity unit. oil-water density difference is the central cause, the junction between fractures and caves is the controlling factor, and the pressure system is a side factor. At last, three ways to enhance oil recovery are put forward: gas injection after water flooding, transformation of injection-production well system, and development by extracting water in injection wells. Each of them has its advantage under certain conditions and an optimized way can be got according to the junctions between fractures and caves and the relative positions of injection and production wells linking with fractured-cavity unit.