Research On Volcanic Lithofacies, "Lithology-electric Property" Relationship And Characteristics Of Volcanic Reservoirs Of Cretaceous YingCheng Formation, Shengping Gas Field, Northern Songliao Basin

In recent years, great progress has been made in natural gas exploration in deep zones at Xujiaweizi area, northern Songliao basin. The gas exploration in the Daqing Oil Field has entered a strategic breakthrough period as the geologists pay more attention to the deep zones and with gas-bearing fields being constantly found in deep volcanic zones.Volcanic rocks in the Cretaceous YingCheng Formation are the main gas reservoir at Xujiaweizi area. Petrology and lithofacies and their spatial and distributions, volcanic activity and eruptive cycles, "lithology-electric property" relationship, characteristics of fractures and fissures and their recognitions, porosity types and their distribution, diagenetic evolution, and parameters controlling the reservoir quality are studied in this paper, based upon description and observation of drilling cores, identification of blue epoxy resin-impregnated thin sections, measurement and analytical methods including electron scan microscope (ESM), porosity and permeability measurement, capillary pressure analysis, energy-spectrum analysis, major and trace element analysis, accompanied with the well log and seismic interpretation data. The volcanic lithofacies model and standard for recognition of gas-bearing volcanics have been constructed, and the prospecting gas-bearing area is assessed, based upon the above integrated research work.This study shows that in this area the majority of the volcanic lithology is rhyolite ,secondly there is the dacite and tuff, The volcaniclastic rock and the lava are the major type of rock.The dominating reservoir space are the dissolved primary pore and dissolved cavity developed in the top or bottom of the extravasation facies,the primary inter-breccia pore developed in the explosive facies.The reservoir's capability basically depend on the lithology and facies of volcanic, tectonism, diagenesis, weathering , the location of reservoir, and the thickness of volcanic.