库车坳陷巴什基奇克组致密砂岩气储层成岩相分析

Diagenetic Facies Analysis of Tight Sandstone Gas Reservoir of Bashijiqike Formation in Kuqa Depression

通过岩心观察并综合利用普通薄片、铸体薄片、阴极发光、扫描电镜和压汞等资料,对克深气田巴什基奇克组致密砂岩储层的岩石学、物性及孔隙结构特征、成岩作用、成岩矿物、所处成岩阶段和成岩演化序列等特征进行了研究。结果表明:储层经历压实、胶结、溶蚀和破裂等成岩作用,现今正处于中成岩A期。根据成岩作用类型和强度、成岩矿物及其对储层物性的影响将储层划分为压实致密、碳酸盐胶结、伊/蒙混层充填、不稳定组分溶蚀和成岩微裂缝5种成岩相。选取声波时差、电阻率、自然伽马、密度和中子等测井曲线,通过岩心薄片资料刻度测井归纳了不同成岩相的测井响应特征,由此建立了各成岩相的测井识别准则。并对克深区块各井的测井资料进行了处理,得到了各单井成岩相剖面展布特征,结合试气资料表明,成岩微裂缝相常与构造裂缝伴生因而含气性最好,而在无裂缝的叠加作用时,不稳定组分溶蚀相含气性最好,压实致密、碳酸盐胶结和伊/蒙混层充填相则对应干层。通过成岩相的深入分析是进行致密砂岩气储层综合评价和有利发育区带预测的重要方法。

The lithology characteristics,reservoir property and pore structure,diagenesis,diagenetic minerals,diagenetic environment,diagenetic stage and diagenetic evolution sequence of Bashijiqike Formation tight sandstone reservoirs are studied by making full use of normal thin sections,casting thin sections,cathode luminescence,scanning electron microscope analysis data and mercury injection test data.The results show the reservoirs have experienced diagenesis such as compaction,cementation,corrosion and fracturing.It is now in the phase A of middle diagenetic stage.Then five types of diagenetic facies are divided based on type and intensity of diagenesis,diagenetic minerals and their effect on the reservoir quality.They are:tight compaction facies;,carbonate cemented facies,mixed-layer illite-smectite filling facies,diagenetic micro-fracture facies and corrosion of unstable components facies.According to the various well logging response characteristics of different types of diagenetic facies,five normal logging curves which are sensitive to the diagenetic facies are chosen to characterize the diagenetic facies.They are:neutron logging(CNL),density logging(DEN),acoustic slowness(AC),natural gamma ray(GR),array induction log(M2R2).Thus we can set up the logging recognition model and standard of diagenetic facies.Actual log data of wells in Keshen area were processed using this method,and the diagenetic facies of Bashijiqike Formation reservoir in this well is figured out on the vertical profile.When the logging recognition results of diagenetic facies of Bashijiqike Formation are corresponded with the actual gas test data,it is found that the diagenetic micro-fracture facies are always coexisting with tectonic fractures.When there are no tectonic fractures,the gas bearing property of the layer with the corrosion of unstable component facies is the best,while the diagenetic facies such as tight compaction facies,carbonate cemented facies and mixed-layer illite-smectite filling facies correspond to the dry layers.It is an effective way to comprehensively evaluate the reservoir and predict the sweet spot of tight gas sandstones by analyzing the diagenetic facies.