Generation Characteristics of Natural Gas from the Coal Measures in Guang'an Area of Central Sichuan Basin

Guang'an gas field,a gas field in the central Sichuan basin, has a very considerable geological reserve of natural gas from the Xujiahe Formation coal measures which is not very perfect.In order to give the reason,the generation characteristics of natural gas from the Xujiahe Formation coal measures in the Guang'an area was studied by means of the MSSV pyrolysis experiment and chemical kinetic method.The result indicates that natural gas was mainly generated during the Middle-Late Jurassic(156.6-140 Ma),a relative short period.The total amount of gas generation is 0.89×1012-1.86×1012 m3 and more than 7.26% gas was accumulated.The gas generation intensity is 3.35×108-11.83×108 m3/km2 which is lower than the usual value(20×108 m3/km2) for a great gas field.It is the efficient accumulation of natural gas that results in the formation of a great gas field with a relative low gas generation intensity in Guang'an area.Besides the presummarized factors,the generation of amount gas in a short period is an important reason resulting in the efficient accumulation of natural gas in Guang'an area.With a superior accumulation condition,the threshold of source rock for forming a great gas field can be lowered properly.