Study On Depositional Facies And Reservoir Characteristics Of Cambrian And Ordovician In Eastern Tarim Basin

It has been proven that high-quality hydrocarbon source rocks were developed in the Cambrian and the Lower Ordovician in the eastern Tarim Basin, thus the prospecting of reservoir has become the key for oil and gas exploration in this area. This research focused on the evaluation of the reservoirs through the analysis of strata distribution, depositional facies and their evolution, reservoir petrology, reservoir physical properties and the factors controlling reservoir development. Based on the seismic reflection, logging and testing data, eight kinds of facies were identified in the research area in the Cambrian and Ordovician, including evaporated platform, restricted platform, open-platform, platform margin, foreslope, shelf, basin and turbidite facies. Through the combination of seismic facies with depositional facies from drilling and outcrops, the spatiotemporal distribution of depositional system were studied, which indicated that in the Cambrian and Mid-Lower-Ordovician, the undercompensation shelf basin facies are mainly developed in the Manjiaer depression and east to it, the platform facies are west to manjiaer depression, and slope facies and platform margin facies are around the edge of Manjiaer depression, and in the Upper Ordovician, thick turbidite deposition was developed in the Kuluketage and Manjiaer area. There are three types of reservoirs from Cambrian to Ordovician in the eastern Tarim Basin, including dolomite, limestone and clastic ones. The petrology, pore type, reservoir type, porosity and permeability of the three types of reservoir are studied in this paper. After discussing the controlling factors of reservoir quality, the different types of reservoir in the eastern Tarim Basin were evaluated. On the basis of the research of depositional facies and reservoir characteristics, three prospective zones for oil and gas exploration were identified. They are reef and bank reservoirs along the platform margin in the Cambrian and Lower-Ordovician, the dolomite reservoirs in the Cambrian, and turbidite reservoirs in the Mid-Ordovician.