The first member of the Dainan Formation in the Qintong Sag of the Subei Basin

characterized by its shallow burial and excellent physical properties

is identified as a key exploration target for high-quality hydrocarbon reserves. This study applies basic theories and technical methods such as sequence stratigraphy

sedimentology

and geochemistry

and integrates seismic

drilling core

and logging data to conduct a comprehensive analysis of sedimentary microfacies and oil and gas accumulation conditions under the sequence stratigraphic framework of the first member of Dainan Formation in Qintong Sag. The study shows that the fan delta front facies belt is a favorable area for the development of lithologic oil reservoirs

and the sand shale interbed near the largest lake flooding surface is the optimal reservoir cap combination vertically

The formation of oil and gas reservoirs in the first member of Dainan Formation is jointly controlled by the structural background

sedimentary facies belts

and regional strike slip structural belts. The study categorizes the oil reservoirs into two major categories and five subcategories. After drilling

it has been confirmed that large-scale integrated structural lithologic oil reservoirs have been discovered

and the exploration results are significant.