Abstract: Recently, SINOPEC obtained high-yield industrial oil and gas flows in the third member of the Oligocene Weizhou Formation in well W4 in Weixi area of the Beibuwan Basin, and achieved a breakthrough in oil and gas exploration in the New Area of the Beibuwan Basin. An oil-source correlation was made and the major factors control-ling oil and gas accumulation were studied based on the test results of crude oil and related drill core samples from well W4 in the Paleogene, combined with new exploration data from the study area and crude oil test results from the adjacent areas. The third member of Weizhou Formation in well W4 is a fault block type oil and gas reservoir, and the crude oil of which came from the mature hydrocarbon source rock of the Liushagang Formation. Hydrocarbon accumulation was controlled by two key factors including the lateral sealing characteristics of faults and cap rock conditions.