Reservoir Prediction Of Changxing Formation Bio-reef In The East Side Of Kaijiang-Liangping Trough In Sichuan Basin

Reef of Changxing Formation is one of the main exploration layers of natural gas in Sichuan Basin.The paleogeographic pattern of the eastern Sichuan is different,the types of reefs are diverse,the reservoir types are diverse,and the reservoir prediction is difficult.This paper attempts to reconstruct the paleogeographic pattern of the Changxing Formation in the eastern Kaijiang-Liangping trough in the eastern Sichuan area,classify the reef types and summarize the seismic response characteristics by establishing a fine well-seismic framework,combined with drilling,well logging,core materials et al..The shape of Kaijiang-Liangping trough is generally asymmetric and the south tends to closed in the XingLongchang-DaMaoping area.The reef type can be divided into:steep slope margin reef,gentle slope margin reef,slope reef and reef complex,mainly developed in the second group third group of Changxing Formation.The difference in reef types is mainly controlled by paleomorphic morphology,the slow slope of the platform edge of a wide band leads to double row of reefs in WuBaiti area,in contrast,the steep slope of the platform edge of a narrow band leads to single row of reefs in HuangLongchang area,and the slope reef grow before margin reef.The reefs in southern slow slope of Kaijiang-Liangping trough is relatively poor,resulting in extensive development of gentle slope margin reef.The seismic response characteristics of the reef are quite different.The margin reef in eastern side of the trough are small in size and are characterized by mound-like uplift,weak-medium weak amplitude or disorder reflection inside,the reef seismic reflection time is about 80 ms.But the slope reef has not mound uplift characteristics,expressed as the medium weak amplitude wave reflection or disorder reflection in the strong reflection background of the slope face,and the reef seismic reflection time is about 50 ms.The seismic response of the reefs in the slow slope is different,and the scale of mound uplift is different with inner bedding configuration composed of weak-medium strong amplitude reflection or disorder reflection,and the reef two-way seismic reflection time is between 50-70ms.We discuss the temporal and spatial characteristics of the reefs in the Changxing Formation on the eastern side of the Kaijiang-Liangping trough,and conclude that the reefs in the area are mainly developed in the reef cap microfacies of the second group third group of Changxing Formation.Based on seismic attribute analysis,seismic facies analysis,paleogeomorphic restoration,the reef distribution is described,and the seismic response of the reef reservoir is studied by seismic forward modeling,the application of low frequency shadowing in the prediction of reef reservoir is discussed,finally,divided reef favorable reservoir development zones in research area.