Distribution Characteristics of Fractures in the Volcanic Reservoirs of Songliao Basin, China

Abstract

In order to clarify the relationship between fractures and gas accumulation, using data of cores, image logs and experimental analysis, we analyzed the fracture genetic types, development characteristics, controlling factors, distribution rules and formation periods. And then, by combining the evolution of source rock, activity periods of gas source faults and the evolution of cap rock sealing ability in the study area, we discussed the relationship between tectonic fractures and gas accumulation. The results show that there exist primary fracture and secondary fracture in the volcanic rocks of Yingcheng Formation in Songliao Basin. Between the two types, the secondary facture is dominant. Tectonic fractures are controlled by lithology, lithofacies and faults in the plane, and by unconformities vertically, with the characteristics of distribution of cycles. The tectonic fractures formed in three phases, wherein the second period coincides with the hydrocarbon generation peak period. During the second period, gas source faults are active and cap rock had a better sealing ability. This period is the main hydrocarbon accumulation stage in the study area.