Characteristics Of The Carboniferous Volcanic Reservoirs And Hydrocarbon Accumulation In The Slope Of The Eastern Fukang Depression

On the basis of previous researches on Carboniferous volcanic reservoirs in the Fudong Slope Zone,field investigation and indoor data analysis of outcrop profiles,core observation,thin section identification,physical property analysis,logging data and seismic data interpretation,rock pyrolysis,carbon isotopes and biomarkers are used to study the lithology,lithofacies,reservoir characteristics,reservoir controlling factors,reservoir types and oil source characteristics of the Carboniferous volcanic rocks in this area.The main achievements and understandings are as follows:(1)The main volcanic rocks of Carboniferous are andesite,basalt,intermediate-basic volcanic breccia,tuff and other volcanic clastic rocks.There are volcanic passageway facies,eruption facies,overflow facies and volcanic sedimentary facies in the study area.The reservoir spaces of volcanic reservoir are mainly secondary dissolved pores and fractures with medium-high porosity and low permeability.(2)The process of diagenetic transformation includes the cold solidification and rock formation stage,the epigenesis stage and the burial diagenesis stage,in which the dissolution of supergene and the filling of burial period have great influence on the physical properties of reservoir.(3)The reservoir properties of volcanic reservoir are greatly affected by lithology,lithofacies,unconformity and late stage fault.The reservoirs in the area of near-source facies,strong weathering and leaching area,fracture development and weak filling zone have good quality.(4)The oil and gas reservoirs in the working area are divided into the top Carboniferous reservoirs and the Carboniferous insider reservoirs.The top oil and gas reservoirs take the top weathering crust of the Carboniferous system as the reservoir,and the reservoir cap assemblage with the bottom mudstone of the Permian system.The Permian and Carboniferous source rocks entered the peak period of hydrocarbon generation and expulsion in the Cretaceous.Hydrocarbon migration and accumulation are mainly carried out along the top of Carboniferous unconformities and Carboniferous top faults.The inside oil and gas reservoirs of Carboniferous are composed of internal volcanic rocks of Carboniferous,and tuff as caprock assemblage.The source rocks from Carboniferous entered the peak of hydrocarbon expulsion in the Cretaceous.Oil and gas migration and accumulation along Carboniferous insider Class III fault forms the authigenic and self-storage hydrocarbon reservoir.(5)At present,the main direction is to look for the oil and gas reservoirs with inside scale in the Carboniferous,including the top buried hill type,the fault-lithologic type oil and gas reservoirs.The two kinds of Carboniferous targets are less distributed in the southern part of Beisantai,and are mainly distributed along the Xiquan fault of the Beisantai uplift,which is the main area of Carboniferous exploration in the future.