The main factor influencing reservoir quality of K1yc tight sandstones within volcano-sedimentary succession in the Dehui fault-depression of Songliao Basin, NE China

Abstract

The main factor influencing high-quality reservoirs of the Lower Cretaceous Yingcheng Formation (K1yc) sandstones in the Dehui Fault-Depression of the Songliao Basin, NE China within volcano-sedimentary succession is still obscure. In the study area, K1yc sandstone reservoirs has exhibited stronger heterogeneity and more complicated diagenetic alteration than terrigenous clastic sandstones. In this paper, K1yc sandstone reservoirs have been characterized through the aspects of petrology, physical property, and pore-types and -throat size. Accordingly, methods including core analysis, thin section, X-ray diffraction, scanning electron microscopy have been used in the study. Finally, the main factor controlling high-quality reservoirs within volcano-sedimentary successions has been concluded. The results reveal that the abundance of authigenic illite clays with forms of fibrous pore-bridging or lath-like pore filling primarily and rapidly reducing the reservoir performance. The chlorite coatings of framework grains should not effectively retard cementation process. Volcanic rock fragments are widespread within the volcano-sedimentary successions and tend to be dissolved by pore fluids, as then illitization should be the most important origin of authigenic illites. It has a critical significance for predicting high-quality reservoirs in the K1yc tight sandstones.