Study On Sedimentary Facies And Reservoir Characteristics Of Guxi Buried Hill Of Upper～Paleozoic

Strata of Guxi buried hill of Upper-Paleozoic consist of Benxi Formation, Taiyuan Formation of Carboniferous and Shanxi Formation, Lower Shihezi Formation, Upper Shihezi Formation of Permian. Shiqianfeng Formation is absent in this area. Using data of seismic, mud logging, log, core and grain, combining with the correlations of single well facies and profile facies, the systemic studies of sedimentary characterization and spacial spreads of sand bodies are done. The result indicates that sedimentary environment of Guxi buried hill of Upper-Paleozoic is ocean-land transitional environment. Offshore shallow sea and coastal swamp are grown in the Benxi Formation. Alternative deposition of coastal swamp and offshore sea is developed in Taiyuan Formation. Lacustrine deposition and delta facies are developed in the Shanxi Formation. Braided river delta deposits in the lower Shihezi Formation and Wanshan Member, lower Kuishan Member of Upper Shihezi Formation. The braided river delta plain subfacies is mainly developed. Moreover, braided river deposits in the Upper Kuishan Member and the Shiqianfeng Formation.Based on the study of sedimentary facies, combining with the thin section, the SEM and the testing data, the diagenetic characteristic, the reservoir space, the pore structure and the reservoir development law are studied. The result shows that there are four diagenetic events which are compaction, cementation, replacement and dissolution in Guxi buried hill of Upper-Paleozoic. Diagenetic stage is at A1～C period of late diagenesis. Dissolution pore, constricted fissure and structure fracture are the main reservoir space. The pore structure includes large hole with large throat, medium hole with medium throat, small hole with small throat and small hole with microthroat. And the second and the third type play the leading role. Developing degree and distribution of secondary pore are controlled by the sedimentation, the diagenesis, the thermal evolution of organic matter, the tectonism and so on.Based on the synthetic analysis of sedimentation, diagenesis and reservoir properties, classification and evaluation of reservoir of Guxi buried hill of Upper-Paleozoic are done. The second and the third reservoir dominate in the reservoir of Guxi buried hill of Upper-Paleozoic. Well Yi 132, Yi 134 and Yi 136 have apparent good reservoir conditions horizontally. Vertically, debouch bar of the lower and upper Shihezi Formation, underwater branch channel and braided channel of the upper Shihezi Formation have favorable reservoir properties and good oil-gas accumulation which can be acted as the next exploration focus.