Oil accumulation and concentration regularity of volcanic lithostratigraphic oil reservoir:A case from upper-plate Carboniferous of KA-BAI fracture zone,Junggar Basin

The controlling factors and the regularity of accumulation and enrichment are revealed in the upper-plate Carboniferous volcanics in Karamay-Baikouquan(KA-BAI)fracture zone,Junggar Basin.The oil derived from the lower-plate Permian accumulates to the upper-plate via faults,unconformities and Carboniferous reservoirs,and is trapped by heavy-oil,faults and the Baijiantan mud-belt,thus forming the upper-plate lithostratigraphic reservoir.This upper-plate Carboniferous reservoir is charged effectively on the flat,and shows a stair-pattern vertically.The reservoir has the fracture-pore double porosity,and strong heterogeneity.The volcanic eruption facies and effusion facies near faults are the major areas of oil/gas concentration and high production.In 2005,the proved oil in place is more than 50 million tons,and the 3rd order oil in place is more than 180 million tons in the area,showing a good prospect for oil exploration.