Identification signs for sedimentary facies of complex carbonate oil reservoirs - the case study on North Tluwa Oilfield in the eastern margin of the Pre-Caspian Basin

摘要

In this paper, the method to confirm the sedimentary environments and microfacies of reservoirs of complex carbonate oil reservoirs was illustrated on the basis of cores and logging data. The sedimentary environments of reservoirs are petrographically confirmed on the basis of rock color, sedimentary structure, paleontology and rock types. Red rocks are the products of oxidation environments and grey rocks represent the sedimentation of reducing environments. Stable structures indicate lower energy of water bodies and cross bedding is deposited in the water bodies with high energy. From the aspect of electrofacies, shale content is higher in low-energy environments but lower in high-energy environments. Gamma ray is of low value. And dolomite content is higher in evaporative platforms and restricted platforms than in open platforms. And then, the case study was conducted on North Tluma Oilfield in the eastern margin of the Pre-Caspian Basin. And based on the cores and logging data, it is ascertained that KT-I reservoir is deposited in the environment of open platform-restrict platform-evaporative platform and KT-II reservoir is the product of open platform.