特高含水期油藏剩余油分布新认识——以孤岛油田中一区Ng~上3砂组为例

New understanding of remaining oil distribution in oil reservoirs at extra-high water-cut stage:A case of Upper Ng3 sand group in Zhongyi area,Gudao Oilfield

特高含水期是陆相油藏开发的重要阶段,而剩余油研究是特高含水期油藏提高采收率的基础。根据孤岛油田中一区特高含水期的3口密闭取心井和17口新钻井资料,从平面、层间和层内对剩余油的分布特征和富集规律进行分析。结果表明,特高含水期剩余可动油在研究区普遍分布、局部富集,矿场生产动态实践也验证了该认识的正确性。根据研究区夹层分布规律及储层韵律性建立了全遮挡型、半遮挡型和韵律型3大类剩余油局部富集模式,其中,半遮挡型剩余油局部富集模式可进一步分为油井遮挡型、水井遮挡型和井间遮挡型3小类,韵律型剩余油局部富集模式可进一步分为正韵律型和均匀型2小类。新认识突破了特高含水期剩余油高度分散、局部集中的传统认识,对河流相老油田的剩余油挖潜具有重要意义。

Extra-high water-cut stage is an important period of continental reservoir development. Study on remaining oil is the basis of enhanced oil recovery in the oil reservoirs at extra-high water-cut stage. Based on data of three sealed coring wells and 17 newly drilled wells at extra-high water-cut stage in Zhongyi area of Gudao Oilfield,the distribution characteristics and enrichment regularities of the remaining oil are analyzed from plane,interlamination and interlayer. The results show that remaining movable oil distributes broadly and enriches locally at extra-high water-cut stage,which is also verified by the dynamic production behaviors of the oilfield. Based on interlayer distribution pattern and rhythm of the reservoir,three local enrichment modes of the remaining oil are established,including whole-barrier type,half-barrier type and rhythm type. The half-barrier type may be further classified into oil well barrier type,water well barrier type and cross-well barrier type. The rhythm type can be further classified into positive rhythm type and uniform type. The new results change the traditional understandings of high dispersion and local enrichment of the remaining oil at extra-high water-cut stage,which has important significance on tapping the potential of remaining oil in fluvial facies of old oilfields.