Research status and prospects for marine-continental shale gases in China

Shale gas has become one of the hot spots of unconventional natural gas exploration.At present, domestic and overseas research for shale gases is carried out mostly on marine formations;however, research for marine-continental shale gases is still at the initial stage.In China, marine-continental shales rich in organic matter are mainly distributed in the Benxi, Taiyuan and Shanxi formations of Carboniferous and Permian age in the Ordos, Qinshui and southern North China basins in the north, and the Longtan Formation of Permian age in the southwestern Sichuan Basin, the western Guizhou province, and the central Hunan and southern Hunan depressions in the south.This paper summarizes present research results for marine-continental shale gases in China, and shows that the kerogen types of marine-continental shales are mainly II and III.Except for the south and east of the southern North China Basin, organic matter maturity is generally high, commonly greater than 1.5 %Ro and is in the high mature and over-mature stages.The lithofacies of marine-continental shales change rapidly and the thickness of a single layer is typically thin, often interbedded with coals, tight sandstones, and even limestones.As a result, separately developing shale gases from such thin layers will face a great challenge in development costs and technology.The joint development of shale gases, tight gases and coal bed gases from multiple target layers will be an effective new strategy.