利用流体包裹体评价碳酸盐岩储层埋藏孔洞充填强度的新方法:以塔里木盆地为例

Application of fluid inclusion in evaluating holes filling strength of carbonate reservoir:A case history from Tarim Basin

海相碳酸盐岩已经成为我国油气资源的重要接替领域,岩溶孔洞等次生储集体是碳酸盐岩重要的储层空间。但是,深埋条件下岩溶储层的难以预测性是影响碳酸盐岩油气勘探的重要难题之一。碳酸盐岩水岩反应的溶解-沉淀平衡原理指示,溶解或溶解-沉淀平衡区域不形成或很少形成流体包裹体,而沉淀区域伴随着新矿物的产生多形成流体包裹体,包裹体发育期次代表了地质历史中流体活动期次。据此原理推断,流体包裹体发育期次越多的区域,早期岩溶填充作用越强,储层埋藏孔洞保存越差,反之则好。文中基于溶解-沉淀平衡原理,利用塔里木盆地塔中和塔北地区奥陶系孔、洞和裂缝充填物流体包裹体数据,结合地质埋藏史,对研究区埋藏填充作用时空发育史进行还原,确定不同程度充填区,采用逆向思维圈定无充填或弱充填的有利孔洞保持区。此方法在塔里木盆地奥陶系碳酸盐岩储层中的应用实践表明,其结果与岩心及钻测井工程方法结果吻合,证实了其可行性,对埋藏期岩溶孔洞保存条件较好的区域能够做出有效预测。流体包裹体分析为我们提供了一种切实可行的埋藏期孔洞充填强度评价的新方法,对正确评价埋藏岩溶储层质量具有重要的理论和实际意义。

Marine carbonate has been an important succeading hydrocarbon prospecting domain in our country,in which the secondary space,such as karst cavity,is an important reservoir.However,the unpredictability of the buried karst reservoir is a challenge for carbonate hydrocarbon prospecting.Dissolution-deposition equilibrium theory of water-rock interaction in carbonate rocks indicates that there was little fluid inclusion in dissolution zone or dissolution-deposition equilibrium zone and many fluid inclusions were generated in deposition zone accompanying new mineral generation.The development phases of fluid inclusions suggest the fluid active phases during the geological history.Based on this,the following idea was deduced：the packing action is more obvious where there are more development phases of fluid inclusion,and thus the reservoir is relatively worse,and vice versa.In this paper,based on dissolution-deposition equilibrium theory,using fluid inclusion data of Ordovician hole filling in Tarim Basin,combined with geology of burial history,the buried karst reservoir＇s packing time-space history of the research area can be restored,and the karst reservoir zones of varying degrees of packing were fixed,and the beneficial reservoir area can be located under reverse thinking.The application of this method to the Ordovician carbonate formation of Tarim Basin area proves its feasibility;the result shows that the prediction of the fluid inclusion method is almost identical with the core observation and drilling or logging results.By this approach,we can predict the better reservoir correctly.On the whole,the fluid inclusion approach provides a feasible method in evaluating hole filling strength in strata environment.This is significant both in theory and practice for the buried karst reservoir evaluation.