Analysis of Hydrocarbon accumulation period of Yanchang Formation and Yan 'an Formation in Zhenjing-Shuangcheng area, Ordos Basin

Zhenjing-Shuangcheng is located in the northern Shaanxi region of the Ordos Basin, which is relatively far from the Chang 7 hydrocarbon generation center. The mechanism of oil and gas accumulation has become a difficult point in oil and gas exploration in the northern Shaanxi region. The study of oil and gas reservoir formation stages aids in assessing the process of oil and gas accumulation. To comprehend the reservoir formation stages of the target strata in this area, the homogenization temperature method of fluid inclusions is employed, coupled with analyzing inclusion characteristics to ascertain the reservoir formation stages. The experimental results show that the fluid inclusions in the sandstone of the Yan'an Formation and the Upper Yanchang Formation in the Zhenjing-Shuangcheng area are mainly saline inclusions and hydrocarbon bearing saline inclusions. The main peak of the homogenization temperature of fluid inclusions in the upper segment of the extension group is 90-120 ℃; The main peak of the homogeneous temperature of fluid inclusions in the Yan'an Formation is 80-110 ℃. Based on the burial history map of the work area, it is believed that the oil and gas filling period in the upper part of the Yanchang Formation was in the middle and late stages of the Early Cretaceous, from 124 to 109 Ma ago; The Yan'an Formation is from the late Early Cretaceous period, dating back to 112-94 Ma ago; This indicates that the oil and gas reservoirs of the Upper Yanchang Formation and Yan'an Formation in the Zhenjing-Shuangcheng area were formed during the same period of the Early Cretaceous (124-94 Ma). This understanding provides assistance for the study of oil and gas accumulation mechanisms in the Triassic and Jurassic periods in the Yuanyuan area of northern Shaanxi.