BASIC GEOLOGICAL AND GEOCHEMICAL BACKGROUND OF UNCONVENTIONAL GAS RESOURCES IN CHINA

China is rich in unconventional gas resources of tight sandstone gas, shale gas, coalbed methane and gas hydrates. Tight sandstone gas predominates, of which the reserve and production account for one-third of the whole country, mainly in Sichuan and Ordos Basins. The proven reserves of coalbed methane resources are large, but the level of current exploration and development are relatively low. Shale gas resource has great potential in China. Under the influence of the global "shale gas revolution", China has rendered extensive exploration in the field recently, but it remains in the stage of exploration. It is confirmed that there are three kinds of shale in China, i.e. the marine shale, terrestrial shale and shale in marine and non-marine transitional sequences. Sichuan is the most favorable area. Gas hydrate resource is mainly in the South China Sea and the permafrost area in the Qilian Mountain. Preliminary estimation shows that there is enormous resource potential for exploration. Based on the current exploration situation and data available, we made an in-depth investigation of the basic geological and geochemical background of unconventional gas resources in China in this paper for the purpose to accelerate the pace of exploration and development of unconventional gases.