Abstract:

Delingha region is located in the northeastern of Qaidam Basin, where oil and gas exploration and research level is low. Based on field geological investigation drilling and seismic interpretation, this paper analyzes Lower Paleozoic petroleum accumulation conditions, including source rock, reservoircaprock conditions, sourcereservoircaprock combination and transporting condition. According to the structural conditions and surrounding discoveries, we have defined the Lower Paleozoic petroleum systems in the research area. In Delingha region, there are two sets of source rocks, including Sinian Quanji Group mudstone formed in coastal tidal flat facies and Ordovician Shihuigou Formation shale formed in shallowbathyal facies. 46% of Sinian source rocks achieved effective source rocks standards, with the average TOC of 0.72%, and 38% of Ordovician source rocks achieved effective source rocks standards, with the average TOC of 0.77%. Organic matter types mainly belong to typeⅠ. Thermal evolution has entered into the high and over mature stages. There are clastic and carbonate reservoirs in the study area, whose dominant reservoir facies are delta front and platform margin reef, while carbonate reservoir space are mainly made up of fractures and solution pores. Based on the analysis of source rock characteristic and surrounding discoveries, Delingha region is divided into Z∈(?) and OO(?) suppositional petroleum systems.

Key words: petroleum systems, reservoir conditions, source rock conditions, Delingha region