Formation mechanism of karst reservoir in buried hill, North Jiangsu Basin

By means of core observation,thin-section identification as well as carbon and oxygen isotope analysis,the reason for the differences of karst reservoir generation between well XG1 and well XC₁ in buried hill of Xinghua city of the North Jiangsu Basin has been studied,and the formation mechanism of karst reservoir in buried hill has been concluded.The rock fabric exposed on karst surface and the karst landform during Indosinian and the middle Yanshanian are the main controlling factors for karst reservoir generation in the study area.They also explain the differences of karst reservoir generation between the above-mentioned 2 wells.Strong warping at the end of Sanduo period not only deformed the karst setting on buried hill surface,but also activated underground fluid,which intensified corrosion in well XC₁.It was favorable for secondary pore generation,and unfavorable for the preservation of buried hill reservoir.The explorations for buried hill reservoir should be focused on the passive side of border fault of sag,and the saddle between low uplifts of Mesozoic-Cenozoic as well as the Lower Paleozoic crystalline dolomite buried hill below slope.