Volcanic Reservoir Characteristics And Distribution In The Southern Songliao Basin, NE China

The southern area of Songliao basin has large exploration potential. In recent years, the exploration of volcanic rocks in this area gained great breakthrough, however, volcanic reservoir has the characteristics of multiple rock types, strong heterogeneity, complex diagenesis which are unfavorable to volcanic rock reservoirs exploration and development. So this paper in view of the problems of exploration and development of these constraints, by using core observation, casting thin sections identification, scanning electron microscope and mercury injection test and analysis methods to study volcanic rock reservoir petrology characteristics, reservoir space types, microscopic characteristics, diagenesis, pore structure and physical characteristics in the south Songliao basin and summarize the control factors and distribution of favorable reservoir. It can be concluded as following:Volcanic rock reservoir space can be divided into primary porosity, secondary porosity, fractures 3 classes, 10 subclasses. The formation and distribution of reservoir space are controlled by lithological facies and diagenetic mode. Volcanic rocks in this area can be divided into 4 categories, 22 subcategories which mainly are volcanic lava; Volcanic facies can be divided into 5 categories 12 subcategories which mainly are eruption facies. Volcanic rocks in this study area with diagenetic evolution process, after experiencing volatile release, burial compaction, cementation, dissolution and diagenesis. The reservoir space is mainly the residues of primary pores and secondary pores, and volatile escaping, devitrification, dissolution can improve reservoir properties, while the diagenesis of compaction, pressure solution and replacement may increase the reservoir properties. The study of petrophysical this area shows that the porosity range is between 2% ~ 15%, permeability range is between 0.01x10-3 ~ 0.12x10-3μm2, which can be concluded that the characteristics of porosity and permeability in this area is high performance, low-porosity, low-permeability. Microscopic pore structure study shows that volcanic rocks pore structure in this area are mainly classe Ⅲ and class Ⅳ which have the characteristics of large pore throat, widely distribution and great displacement pressure, so the macropores in volcanic rocks in this study area is controlled by the small throat, and the fluids in pores cannot be easily produced.In this paper, the author believed that volcanic rocks in this area are mainly controlled by the lithology-lithofacies and diagenesis. The study of favorable reservoir distribution pattern of acid, intermediate lava flow is based on the seismic interpretation, cores and casting thin sections observation and logging data. The favorable reservoir of acid lava flow supposed to distribute at the top where developed various types of reservoir space. The favorable reservoir of intermediate lava flow also mainly distributed at the top where weathered crust can be easily developed included dissolved pores and fractures whereas the bottom is tight. Also, the top of intermediate lava flow belongs to mid-high porosity and permeability and the bottom belongs to mid-low porosity and permeability.