TOPOGRAPHIC EXPRESSION OF SUBSURFACE STRUCTURES AND ITS APPLICATION IN PETROLEUM EXPLORATION

East China oil province,with block faulting as its main structural expression,consists of Bohai Wan basin and Mongolia-Xingan rift basins,whose subsurface structures usually show good topographic expresstion.The differential compaction due to the relief of basin base and thickness change in young cover rocks,and long development of inherited structures result in an internal relation necessary between the subsurface structures and their topographic expression.Thus the information of topographic expression is useful for the explanation of subsurface structure.There are vivid examples of petroleum exploration success with the application of topograpI1ic information both home and abroad.Its application is particularly significant in a preliminary petroliferous estimation in a basin(or a depression or sag)during the preparation of a back-up campaign of exploration.Topographic informaiton can be used to ascertain the plane spreading scale and size of a basin,further to determine the linear geologic structures of the basin,including classes I II major faults,oil-generating depressed trough,structural belts as well as local structures,and to analyse sedimentary facies.Undoubtedly,it may be helpful for making a precise strategic policy and plan of petroleum exploration,and determination of working and financial amounts,and for a higher rate of exploration success.