Shale Gas in China: Reality and Dream

Abstract

China extracted shale gas of 23, 500∼24, 600 m3/d from the Lower Cambrian Qiongzhusi Shale Formation in Weiyuan gas field of Sichuan Basin in 1966. This shale interval, however, was considered less prospective because the Sinian Doushantuo Formation dolomite reservoir was defined as the target layer for drilling at that time. Forty years later, this black shale interval became attractive as triggered by the “Shale Gas Evolution” in North America. In 2005, by learning from shale gas mode of the United States, PetroChina Research Institute of Petroleum Exploration and Development (RIPED) reviewed the existing well data of the region where the Weiyuan and Longchang gas fields and the Changning structure were located within the Southern Sichuan Basin. In order to re-examine the gas shows and geochemical property and to evaluate the gas potential of shale strata within the Upper Ordovician Wufeng Formation-Lower Silurian Longmaxi Formation and the Lower Cambrian Qiongzhusi Formation. On that basis, for the entire Sichuan Basin and adjoining regions, PetroChina has carried out a geologic survey on organic-rich shales, drilled shallow shale gas appraisal wells, evaluated the shale gas resource potential, and defined some favorable targets for shale gas exploration and development by 2008. W201, the first shale gas appraisal well of China, drilled by PetroChina in 2009, initially produced 17, 000 m3/day from the Wufeng-Longmaxi Formation shale and 10, 800 m3/day from the Qiongzhusi Formation shale, marking the commencement of shale gas exploration and development activities in China. Thus far, China has received shale gas flow from marine, transitional-limnetic coaly and lacustrine shales in many regions, such as Sichuan, Chongqing, Guizhou, etc. The commercialization of marine shale gas has been achieved in Sichuan and Chongqing totaling 0.2 billion cubic meters of shale gas production in 2013. Through an overall review on the progress of shale gas exploration and development in China, we concluded that the geological conditions for shale gas in China are extremely complex. First, the most sedimentary basins in China belong to superimposed basins, all of them have experienced the depositional evolution from marine to terrestrial facies, and three types of shales were well developed including marine, transitional, and terrestrial organic-rich shales. Second, the conditions of shale gas formation and accumulation in China are favorable and shale gas resource has a great potential for further development in China. Third, like North America, the marine organic-rich shales of China have the best and most realistic shale gas exploration and development prospects. But it faces technical, environmental, regulatory, infrastructural and other challenges that are likely to delay rapid shale gas development. Fourth, until now, although the exploration and exploitation of shale gas in China are relatively low, very good signs have been emerged to prove that China has good prospects in the future.