岩溶洞穴型油藏描述中的几种方法——以塔北轮古西油田为例

以塔里木盆地北部轮古西奥陶系碳酸盐岩岩溶洞穴型油藏为例,针对几个制约油田高效开发的重要问题,采用了相应的油藏描述技术对策:(1)在分析岩溶成因的基础上,对三维地震数据进行岩溶洞穴分层解释,描述不同洞穴层发育特征;(2)采用岩溶沟谷趋势面法确定油水界面,指导避水开发;(3)通过岩石物理分析,确定了用于识别泥质充填洞穴的泥质指示因子,然后运用地震反演技术,筛选出未被泥质充填的有效储层。通过这三项技术方法的实施,弄清了四层洞穴储层的分布特征以及它们与供油的关系;厘清了油水在洞穴储层中的赋存特征;发现岩溶斜坡的充填程度高于岩溶台地;最后评价出三类残丘含油单元。三项技术对策在岩溶洞穴型油藏描述方面具有较强适用性,可为相同类型油藏的高效开发提供技术借鉴。

Methods of Reservoir Description for Karst Caved Reservoirs:An Example from Lunguxi Oil Field,Tarim Basin

The Ordovician karst caved reservoirs are the typical“residual buried-hill pools”at Lunguxi Oil Field in Tarim Basin. Three technical methods are suggested and applied to deal with problems in reservoir development. (1) Based on the analysis of karst origin, 3D seismic data are applied to interpret the hierarchical karst caves and describe development characteristics of different cave layers; (2) Oil-water interface can be determined by the karst valley trend surface to guide for preventing water in development period; (3) Based on the analysis of rock physics, the mud indicative factor is obtained, which can be used to detect the caves whether filled with mud or not, and then choose the effective reservoirs without filling by seismic inversion. By implementing above methods, the distribution characteristics of caved reservoirs are made clear in different four beds. The relationship of oil and water occurrence in caved reservoirs is clarified. It is proved that there are higher filling content in karst slope than in karst platform. Three kinds of residual oil units are evaluated.