| Various types of carbonate reservoir develope in Tarim Basin, but many previous studies indicate that the reservoir properties are of the characteristics of strong heterogeneities. Aiming at solving the shortage, this paper deals with the geological characteristics of Yingshan formation in the central uplift area of Tarim Basin. According to seismic interpretation and typical wells analysis, the sequence stratigraphy of Yingshan formation has been analyzed firstly. On the basis of sequence analysis, lithology, reservoir space types, diagenesis, pore evolution and physical property, etc. are investigated secondly. Finally, the reservoir of Yingshan formation is divided into Karst reservoir and Dolomite reservoir to discussed systematically, including genetic mechanism and main controlling factors. In addition, all these study are under the theoretical guidance of P.R.Vail's classic sequence stratigraphy and sedimentary petrology and reservoir geology.Based on absorbing the studied results of former geologists, drilling and logging dates show that there exists a high GR section (about10~30m) at the bottom of Lianglitage formation,which can be comparative to Qiaerbake formation. Considering the geological background, we initially puts forward that the Qiaerbake formation presents in the interesting area. On the theory basis of the P.R.Vail's classic sequence stratigraphy, with well drilling (the sign of the exposure, the lithologic association, the gamma anomaly), well logging and seismic as recognition method, five sequence boundary and four third-order sequences could be identified in Yingshan formation. every sequence develops transgression system tract (TST) and high system tract (HST),but the low system tract (LST) is hardly found. Lithology feature demonstrates the depositional environment of Yingshan formation is feeble rimmed or rimless platform. The sedimentary facies include restricted platform, open platform and platform margin. Sedimentary facies planar distribution within the sequence framework are different in different third-order sequences. The location of platform margin are also various, by combining the clue of locating border along slope.This paper has seen departmental standard and carbonate rock structural genetic classification as fundamental framework and guidebook, put forward structural genetic clascification criteria of Yingshan carbonate rock in the interesting area. With the ananlying of lithofacies, diagenesis, reservoir space and physical property, the law found within third-order sequence is that high system tract(HST) controlled by sequence takes an essential role in the evolution of pore. The reservoir spaces contain non-selective solution dissolved pore, cavity, vuggy and fracture. They combination can be compartmentalize four types, i.e. dissolved pore type, dissolved pore-fracture type, karst cave type and fracture type. The best one for reservoir is dissolved pore-fracture type.The reservoir of Yingshan formation can be divided into karst reservoir and dolomite reservoir to explore their genetic mechanism and controlling factors. The syndepositional karstification does not develop in the reservoir of Yingshan formation, but mainly controlled by epigenetic karstification and burial karstification. The epigenetic karstification distribute widely with obvious longitudinal zoning and discrepancy in different areas. And karst reservoir development is related to paleogeography, karstification stages, sedimentary facies and high frequency sequences. Dolomite reservoir whose reservoir space dominated by intercrystalline pore and intercrystalline solution pore is intimately controlled by dolomitization (evolution of dolomitie structure), short-term exposure caused by subordinated fluctuation of sea level and later structurally controlled hydrothermal alteration(burial karstification). Especially, aggressive hydrothermal fluid transfers through open fault and encourage dolomization in the volcano-magma active period of Permian.The hydrothermal dolomization makes new solution pore born, which is beneficial to discover the inner buried dolomite reservoir.As a result, the favourable exploration area has been pointed out by statistical characteristics of reservoir properties and analysis of typical reservoirs in the end. |
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