Research On Lithologic And Lithofacies Characteristics And Potential Reservoir Of The Carboniferous Volcanic Rocks In Chunfeng Oilfield

Oil reservoirs are drilled one after another in Carboniferous vocanic rocks in Chunfeng Oilfield,which makes the Carboniferous be another important exploration targets inChunfeng Oilfield.However,the carboniferous vocanic rocks are featured by complex lithology,unknown spatial distribution of lithology and lithofacies and reservoir development,so this article use different geological data solve these problems.Xibeikulasi Formation in Carboniferous System is the target formation,which can be divided into four members and thirteen sub-member,corresponding to different times of the volcanic eruption through the analysis of seismic and logging data.With the data of core observation,thin section analysis,geochemical analysis and seismic and logging data,the types of volcanic rocks can be identified and the identification criteria of different lithology can be established.There are two types of volcanic rocks in the study area,including intermediate-basic lava rocks and pyroclastic rocks.The lava rocks include basalt,andesite basalt,basaltic andesite and andesite,while the pyroclastic rocks can be divided into volcanic agglomerate,volcanic breccias and tuff according to the structure or can be divided into basaltic tuff,mixed tuff,andesite tuff and tuff according to the constituents.The crossplots and star charts of the criteria for the identification of different lithology is developed according to analyze the logging response characteristics of rocks.Based on the lithology analysis,the lithofacies in the study area can be divided into erupting facies,flowing facies and volcanogenic sedimentary facies.The spatial distribution of lithologic facies can be determined by the analyses of seismic profile.Erupting facies.are mainly distributed in the southeast part and flowing facies and volcanogenic sedimentary facies are developed from southeast to northwest.The demarcation of flowing facies and volcanogenic sedimentary facies are along the main fracture in the area.According to the observation of corn,thin sections and scanning electron microscope,we find the volcanic reservoirs are characterized by complex reservoir space and pore throat structure and divide the reservoir space into pores,cracks and fault fracture zones which are the primary reservoir spaces.Different lithologies develop their own reservoir types and have different reservoir properties.Thus,the lithology controls the development of the reservoir to some degree.And according to the analysis of horizontal and vertical distribution of physical parameters,the reservoir in the research area is controlled by the lithofacies and the weathering leaching process.Crack and fault fracture zone can be formed by tectonic movement,which provides good geological conditions for the migration and accumulation of oil and gas.According to the comprehensive analysis of the distribution of reservoir physical parameter and the controlling factors of reservoir,we view the unconformity and the erupting facies and flowing facies which are close to the fault as the favourable exploration targets.