Accumulation and exploration of petroleum reservoirs in west slope of northern Songliao Basin, China

On the basis of the present situation of oil and gas exploration and geological research of the west slope in the northern Songliao Basin, the factors controlling reservoir formation, oil and gas migration and accumulation, have been re-examined from the aspects of structure, deposition and reservoir formation. The results show that: (1) The west slope is a gentle slope overlapping to the west on the oil and gas migration path, where there develop nose structures on the side near the hydrocarbon generation sag and a series of NE structural belts, which are favorable places for oil and gas accumulation. (2) The west slope can be further divided into the upper slope and the lower slope, and there are many kinds of oil and gas reservoirs, including structural, structural-lithologic and lithologic ones. In the upper slope, the major oil layer is Saertu controlled by structure; in the lower slope, multi-layers are oil-bearing, and the oil reservoirs are mostly composite ones. (3) Faults, unconformity surfaces and continuous sand bodies are the main channels of oil and gas migration; structure, sand body and fault jointly control the oil and gas enrichment in the slope; and the matching relationship between micro-amplitude and sand body, small fault and sand body control the oil and gas accumulation. On the basis of the above research, fine identification and effectiveness evaluation technology of composite trap has been developed through extensive study. Combination traps were identified by combining multiple technologies, including fault classification, micro-amplitude structure identification, fine sedimentation research, and lithologic trap identification by waveform indication inversion; and then the relationship between fault and sand body, structural amplitude and sand body configuration were analyzed to set up the evaluation criteria of effective trap. According to the criteria, the traps were selected to enhance the exploration success rate. © 2020, The Editorial Board of Petroleum Exploration and Development. All right reserved.