Abstract: Natural gas in Yanchang Gas Field Ordos Basin was explored relatively late. Paleozoic gas reservoir is buried deeply and difficult to explore. In order to explore the accumulation pattern of gas reservoirs in this area, the accumulation characteristics and enrichment pattern of Paleozoic gas reservoirs in the south of Yanchang Gas Field were studied in terms of stratigraphic distribution, tectonic features, sedimentary facies and reservoir controlling factors based on sedimentological principles. The study showed that the relatively high-quality reservoirs in Yanchang Gas Field were the key to natural gas formation and enrichment, and the reservoir size determined the scale of the gas reservoir; the development of high-quality reservoirs was mainly controlled by paleo-geomorphology, rock type and late diagenesis; high-quality reservoirs were mainly developed in deltaic distributary channels and estuary dams, and the quartz-rich sedimentary system was high in natural gas enrichment. There is much for reference of the study results to the exploration and development of Paleozoic gas reservoirs in Yanchang Gas Field.

Key words: gas reservoir, key controlling factors for hydrocarbon accumulation, enrichment law, tight reservoir, Ordos Basin, Yanchang Gas Field