Reservoir Characteristics And Evaluation Of Donghe Sandstone Of The Upper Devonian In Tarim Basin

The Tarim Basin contains plenty of petroleum resources and is important base to stabilize the east and develop the west. So far, it has discovered oil and gas resources in more than 10 strata such as Cambrian, Devonian, Carboniferous, Triassic, Jurassic, Paleogene and Neogene. Donghe sandstone is distributed in Central and Northern Tarim areas. It is the most important sedimentary reservoir deposited in marine though the geology age is in dispute. Diagenesis, pore evolution and reservoir characteristics are studied in detail based on researches of the regional geological setting and depositional sequence development guided by the basic theory of the lithology and reservoir geology, combined with the comprehensive analyses of the well log, core and test datas, and the favorable exploration areas have been evaluated objectively.Four types of sedimentary facies can be identified, such as fluvial facies, estuary facies, shore facies and fan-delta facies based on theories and approaches of sedimentology, sedimentary petrology, focused on marine clastic reservoir of Donghe sandstone of Tarim Basin, integrated with lithology, sedimentary, texture, sedimentary structure, log curve.Observations of rock thin-sections and casting thin-sections and results of SEM and CLM analysis show that the main diagenesis of the clastic strata in the study area include compaction (pressolution), authigenic mineral cementation, metasomatism and filling and corrosion. Based on research of the characteristics and stages of diagenesis, the Donghe sandstone is mainly in the A stage of late diagenesis in the central-Tarim and B stage of late diagenesis in the northern part. The major reservoir space is mainly secondary intergranular pores.Based on study of reservoir physical properties of the Donghe sandstone, the reservoir quality is better in the central-Tarim than in the north. In the northern-Tarim area, porosity and permeability are lower, and anisotropic is stronger. Factors affecting clastic reservoir petrophysic properties include the sequence stratigraphic framworks, the sedimentary facies and the diagenesis.With the studies of the reservoir, the favorable reservoir locates around well Tazhong 4 to Tazhong 40 to Tazhong 46 areas in the central and well Donghe1 to Hanan1 to Hade5 areas in the northern-Tarim.