Sandbody Genesis and Hydrocarbon Accumulation Mechanism of Beach-Bar of Tongbomiao Formation in Tanan Depression

Beach-bar deposit is a typical sedimentary system in the shore shallow lake sedimentary environment, which is mainly composed of thin interbedded deposits. In recent years, with the exploration of lithologic reservoirs, it has gradually become the focus of geologists. Around the combination characteristics and difficulties in hydrocarbon accumulation of the beach-bar in Tanan depression, this paper studies the sedimentary characteristics and distribution rules of beach-bar sand in the period of Tongbimiao formation in Tanan depression, and makes clear the accumulation model and enrichment rules of beach-bar sand reservoir in Tongbomiao formation. The results show that the beach-bar sand in Tongbomiao formation of Tanan depression is mainly of two genesis: the beach-bar sand of the lateral margin formed by the modification of the front edge of the delta sedimentary system by the lake waves and formed by the control of the basement paleouplift, and the distribution morphology is mainly controlled by the palaeowind direction and palaeogeomorphic during the sedimentary period. The accumulation model can be divided into the composite accumulation model of “source reservoir integration” and the lateral accumulation model of “source-reservoir docking”, which are respectively developed in the near-source sag and the middle of ancient slope zone. The research results have certain guiding significance for the accurate development of Tanan oilfield.