Abstract: The A’nan depression is the main hydrocarbon generating depression in the Erlian basin, and conducting structural-lithological exploration around the rich hydrocarbon generating trough is one of the important strategies for the future of this area. Based on seismic, core, drilling, and analytical data from the research area, this article systematically summarizes the formation conditions of structural-lithological oil and gas reservoirs, and summarizes oil and gas enrichment models in the Tengger Formation of the A’nan depression. The results indicate that the black mudstones in the A 4 Member and Teng 1 Member are high-quality source rocks in oil window with high organic matter abundance, and are the main hydrocarbon supply layers in the study area. The physical properties of the reservoir in the central zone of the underwater distributary channel facies in Teng 2 Member are good. The reservoir was covered by a large set of thick mudstone, forming a good reservoir-seal combination. The vertical faults and lateral sandbodies and regional unconformities served as good transport and accumulation channels. A “flower shaped” enrichment model controlled by source faults and a “stepped” enrichment model controlled by source edge faults and surfaces were established for the Ha’nan buried hill belt and the Menggulin anticline belt, respectively. Both oil and gas enrichment modes are jointly controlled by structure and lithology. The dominant migration and accumulation of oil and gas point to the central zone of the underwater distributary channel facies, where the reservoir has excellent physical properties and a large thickness, making it a sweet spot for oil and gas in structural-lithological traps.

Key words: A’nan depression, structure-lithology oil and gas reservoir, accumulation conditions, enrichment mode, Tengger Formation