Differences in formation process of tight sandstone gas reservoirs in different substructures in Changling Fault Depression, Songliao Basin, NE China

Abstract

The tight sands reservoirs in the Lower Cretaceous Denglouku Formation in Changling Fault Depression of Songliao Basin, NE China were taken as study object. The burial history, thermal evolution history and hydrocarbon generation history of source rock, accumulation stage and porosity evolution history of typical tight sandstone reservoirs in the central deep depression belt, east slope belt and east structural belt were examined by the dissection based on the fundamental features of tight sandstone gas reservoirs, to find out the differences in their formation process, the coupling relationship between source and reservoir of different substructures, then the favorable exploration areas can be confirmed. The east structural belt has the best source rocks and reservoirs, where the Denglouku Formation tight sandstone formed reservoirs earliest when the reservoirs were not tightened yet with features of one stage accumulation. The sandstone of the Denglouku Formation in the east slope belt formed reservoirs secondly and shows one stage accumulation but two charging peaks, the first charging peak occurred when the reservoirs were not tightened, the second charging peak occurred when the sandstone was tightened already. The sandstone of the Denglouku Formation in central deep depression belt formed reservoir the latest when the reservoirs were densified already with the features of one stage accumulation. The study shows that the east structural belt has the best coupling relationship between source rocks and reservoirs, and is the most favorable exploration area for tight gas in the Changling Fault Depression. Key words: substructural belt, tight sandstone gas reservoir, formation process, Lower Cretaceous Denglouku Formation, Changling Fault Depression, Songliao Basin