Upper Cambrian-Ordovician reservoir characteristics in Well Gucheng-4 area, Tarim Basin

Abstract: Based on the data of regional geologic background, core, and thin section, this paper studies the characteristics of sedimentary facies and reservoirs of the Upper Cambrian-Ordovician in Well Gucheng-4, Tarim Basin, and points out the potential and targets of petroleum exploration in the Gucheng break slope. Collapsed breccias are deposited in platform margins of the Upper Cambrian; Ordovician Penglaiba, Yingshan, and Yijianfang Formations sediments are controlled by eophyton, and lime mud mound facies of shallow glacis of platform frontal margin; Strumae limestone is deposited in the Ordovician Tumuxiuke Formation; and slope continental shelf abyssal basin facies controll the sediments in the Ordovician Queerqueke Formation. The Upper Cambrian dolomite is a better reservoir, which is controlled by deposition environment, dolomitization, and structural fractures. The Ordovician limestone reservoir is poor because of most primary pores being filled by cementation. The favorable exploration targets may lie in the north and west of the Well Gucheng-4 area. Key words: Tarim Basin, Well Gucheng-4, break slope, sedimentary facies, reservoir characteristic