轮古西奥陶系古潜山油藏油水界面的分布规律和控制机理

Distribution and differential entrapment mechanism of the oil-water interface within Ordovican in the west part of Lungu buried hill oil field

碳酸盐岩古潜山油藏储层非均质性强烈,油、水分布特征十分复杂.以现代岩溶理论为指导,通过对轮古西奥陶系古潜山岩溶地表古水系的详细分级刻画,采用趋势面分析方法对古潜山岩溶残丘次级进行了划分,结合单井油水界面判识结果,对残丘级次的控油规律进行了综合分析,并运用油气差异聚集原理阐述了其控制机理.研究结果揭示了古潜山油藏部分油井油水界面分布受控于不同次级的残丘,从运移近源低部位向高部位油水界面呈抬升趋势,由一级残丘控制向二级残丘控制变化.这一分布规律本质上是油气差异聚集过程中不断抬升的岩溶沟谷决定的溢出点和相对独立的缝洞单元联合控制的.这一认识可为油藏开发方案的制定和调整提供重要依据.

The distribution of oil-water interface in the west part of Lungu buried hill oil field is very com-plicated because of its heterogeneity of karst modified carbonate reservoir.In this study,we use some meth-ods including geomorgraphy and the seismic attribute extraction techniques to sub-divided the river rank of fluviokarst,then perform the trend surface analysis for different rank of rivers to grade the karst monad-nock.We also use direct,static pressure crosscoupling and the original formation pressure methods to calcu-late the oil-water interface of each well.The corrletion between trend surface to oil-water interface of wells shows that the first-and second-grade trend surface influence the distribution of oil-water interface in dif-ferent monadnock.From Lungun 15 well area in southwest to Lungun 9 well area of middle part,The oilwater interface rise from the first-to second-grade trend surface of monadnock,influenced by fault which resulted in complicated oil-water interface of some wells.This distribution characteristics can not be com-pletely explained by classical theory of differential entrapment because of its reservoir heterogeneity be-sides spill-point determined from karst river valley.High hydrocarbon-producing well tend to be controlled by the first-grade trend surface of monadnock.