Shiyou shiyan dizhi (Jan 2022)
Accumulation characteristics of continuous sand conglomerate reservoirs of Upper Permian Upper Wuerhe Formation in Manan slope area, Junggar Basin
Abstract
A large continuous conglomerate reservoir has been recently discovered in the Upper Permian Upper Wuerhe Formation on the southern slope of Mahu Sag, Junggar Basin. In order to timely summarize, enrich and develop the theory of continuous oil and gas geology, and to provide a basis for deepening regional exploration, it was studied in this paper the reservoir forming elements and reservoir characteristics based on the fine structure interpretation, sedimentary system study and reservoir-cap combination analysis of these reservoirs. The results showed that the source rocks of Fengcheng Formation on the southern slope were widely distributed, with a large thickness, good type and high maturity. In four major material source systems including Zhongguai, Karamay, Baijiantan and Dabasong fans, the sand conglomerate reservoirs in the first and second members of Upper Wuerhe Formation overlapped continuously, and formed a stable reservoir-caprock assemblage with the widely developed mudstone caprock of the third member of Upper Wuerhe Formation. Near EW-oriented deep strike-slip faults and unconformities widespread in the sag provided pathways for hydrocarbon migration and accumulation. The Upper Wuerhe Formation is a "foreland-depression" replacement-type deposit. Under the background of large formation pinch-out zone, a large area of continuous lithologic traps was developed, forming stratigraphic, lithologic and fault-lithologic oil reservoirs. The Zhongguai and Karamay fans are found to have a high potential for exploration and still have many remaining oil and gas points. The Baijiantan and Dabasong fans have similar sedimentary background with the Zhongguai fan, and have a lower exploration degree, which are key area for future exploration.
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