Development And Main Controlling Factors Of Reservoir In The Xixiangchi Group,Central And Northern Sichuan Basin

With the breakthrough of natural gas exploration in the Xixiangchi Group in the Weiyuan area and central Sichuan Basin,it is urgent to evaluate the development,distribution and exploration potential of the Xixiangchi reservoirs in the northern Sichuan Basin.Based on outcrop,core,drilling and logging data,thin section,rock geochemistry,as well as reservoir physical property analysis and testing,this study sedimentary petrology,reservoir geology and other related theories to study the sequence,sedimentary facies,reservoir genesis and distribution of the Xixiangchi Group in the northern Sichuan Basin by comparing with the reservoir development and distribution in the central Sichuan Basin.Some understandings have been obtained as follows:(1)The development and distribution of the Xixiangchi reservoir and the thick shoal is consistent.The thickness of the reservoirs in the central Sichuan Basin is mainly between 10 and 60 meters,and they are mainly distributed in the area facing the platform depression on the eastern flank of the paleo-uplift.The thickness of the reservoir in the northern Sichuan Basin is mainly between 10 and 20 meters,and it is scattered on the plane;(2)The shoal is the material basis for the formation of the reservoir,which is controlled by the paleogeographical pattern on the plane,and controlled by the relative sea level change vertically.The central Sichuan Basin has the background of uplift and sag paleogeomorphology.The shoal is mainly developed in the paleo-uplift flank and the edge of the platform depression on the plane,and is mainly developed in the highstand system tract vertically.The paleogeomorphology in the northern Sichuan Basin is gentle,with little change on the plane of shoals,and is controlled by high-frequency sequences vertically,with thin single layer thickness and small cumulative thickness;(3)Dissolution is the key to reservoir formation.The central Sichuan Basin mainly developed eogenetic karstification reservoirs,which were later affected by epigenetic karstification.Epigenetic karstification reservoirs are mainly developed in the northern Sichuan Basin.