Main controlling factors of volcanic oil and gas distribution and charging capacity evaluation of Huoshiling Formation in Longfengshan area

There are two sets of petroliferous strata developed in the Huoshiling Formation volcano in the Longfengshan area of the Changling fault Depression. The oil and gas have the characteristics of "near source gas, far source oil rich", the abundance of oil and gas decreases from the depression zone to the western tectonic belt, and is enriched in the top and middle of volcanic rocks in longitudinal direction, and widely distributed along faults in plane. In this paper, the controlling factors of hydrocarbon distribution in volcanic rocks are discussed from the perspectives of source rock development condition, reservoir physical property and transport condition by means of seismic, well logging and geochemical data, cores and microsections observation, CT scanning and inclusion analysis. The results show that the oil and gas distribution in the volcanic rock mass in Longfengshan area is mainly affected by the following factors: the thermal evolution degree of the source rock controls the oil and gas phase distribution, and the source and reservoir configuration determines the oil and gas capture probability; The distribution characteristics of high-quality volcanic rock reservoir can control the distribution range of oil and gas, and the vertical development difference of primary, secondary dissolution and fracture high-quality reservoirs determines the vertical accumulation of oil and gas. The fault and unconformity control the migration of oil and gas from the depression zone to the slope zone and the western tectonic zone, and its transport performance and the micro-transport structure of internal fractures ultimately determine the location of oil and gas accumulation. The distribution of overlying layers in and above volcanic rocks, the type of reservoir-cap combination and the configuration of broken cap prevent the oil and gas loss and control the oil and gas enrichment horizon. Based on the differences of main controlling factors of hydrocarbon accumulation in volcanic rocks, the effective source rock thickness, volcanic reservoir physical properties, reservoir-cap combination characteristics and transport conditions are taken as indicators to evaluate the hydrocarbon charging capacity of volcanic rocks, and the measured values of the above factors are divided into several intervals. According to the distribution range of the evaluation index, each interval is evaluated. Finally, according to the calculation results of the established oil and gas charging capacity evaluation formula, the evaluation results have a good correspondence with the current oil and gas distribution, and the results have certain guiding significance for determining the direction of oil and gas exploration in the later period.