Geology of giant gas fields in China

Twenty-five gas fields with recognized ultimate recoveries larger than 25 billion cubic meters have been found in six basins in China. The earliest was found in 1959 and the latest in 2005. Recognition of more recent discoveries as giants will probably further increase the population. Examination of reservoir age, lithology, trap and depositional environment leads to the conclusion that there are no diagnostic characteristics common to all of the giants. However, coaly source rocks, traps in close proximity to major gas kitchens, reservoirs and caprocks with reasonable quality, late gas accumulation and continuous gas supply are the preferred parameters. Uncommonly thick reservoir rocks or unusual development of porosity and permeability are not required. The fact that giant gas fields exist in reasonable numbers and have been discovered steadily through the years suggests that more efforts are needed to find the remaining gas resources in China.