China's onshore oil/gas exploration domain has been changing a lot in the past decade.Before the advancement of sag-wide oilbearing theory,secondary tectonic belt was the major domain of exploration.After that,the domain has been transferred to hydrocarbon rich depressions.Besides,breakthrough has been made in high mature and overmature strata of deep superimposed basins,based on the theory of successive generation of natural gas from organic materials.So high mature and overmature strata became the major s...