FEATURES AND GENESIS OF GAS RESERVOIRS IN THE JIANGHAN BASIN

The Jianghan basin is a Cretaceous-Paleogene rifted basin developed on Yangtze paraplatform and also a typical continental petroliferous basin containing salt layers. The exploration activities are focused on oils for quite some time. The well Tan-32 drilled recently has obtained a gas discovery in the Neogene Guanghuasi Formation, with a tested gas flow of 135 300 m3/d. This is the first discovery of natural gas in the Cretaceous-Paleogene in the Jianghan basin. The genesis of the gas is studied based on correlation of the geochemical features between the existing associated gas reservoirs and that in Tan-32 wellblock by using the data of gas component and isotope like carbon and hydrogen. It is concluded that both the gas in the gas reservoirs and the gas in the associated gas reservoirs are oil-related gas in the Jianghan basin, and no abiogenetic gas or biogenetic coal-related gas have been discovered in the Jianghan basin.