The A3 fault block in the southern part of the Alshan structural belt in the eastern part of the Manite depression in the northeastern part of the Erlian Basin,Inner Mongolia,has gone through a period of anhydrous oil recovery,low water content development,and medium low water content development since its development.Currently,it is a period of high water content development for the fault block,entering a bottleneck period of development,and the development contradiction is prominent.The study focuses on the identification of sedimentary structures,grain size characteristics,and electrical characteristics of logging curves in the fourth section of the Alshan formation and the first section of the Tengger formation in the Lower Cretaceous of the A3 Fault Block.The results indicate that:(1)During the Alxanian period,nearshore underwater fan inner fan and fan subfacies developed,and by the end of the Tengger formation sedimentation,shoreline shallow lake subfacies developed;(2)Affected by the northern Anan Fault on the plane,the sand bodies are mostly distributed in a northeast southwest direction.During the vertical sedimentation process,water enters the sedimentary system tract,and the water gradually deepens from bottom to top,expanding the water body;(3)Due to the physical property changes caused by phase change,the remaining oil potential is restricted.Under the guidance of sedimentary facies and combined with actual production conditions,the relatively enriched areas of remaining oil are searched.Based on the research of regional tectonic background,source direction,and spatiotemporal evolution,summarize the sedimentary model of the nearshore underwater fan in the A3 fault block,and search for high-quality reservoirs to provide geological basis for oilfield development.
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