The gas reservoirs of the upper Triassic Xiangxi group in the Sichuan basin are typically tight, low-permeable Sandstones. The gas comes from the coal seams of the same group. The Bajiaochang gasfleld is one of the large gasfields originated from coal in the Sichuan basin.
The authigemic clay minerals such as illite and chlorite form the inner coating in the pore space of the reservoirs, which not only leads to the extreme low permeability of the gas reservoir, but also is the main cause damaging the reservoir. The productivity of the gas well is low, very hard to get it into commercial production.
The reservoirs are very sensitive to water and acid, so general acidizing does not restore and improve their permeability.
The fracturing experiments with sand as proppant have been carried out in recent years, demonstrating that the reservoir can easily be fractured and proppantpacked, and hence should be stimulated. To treat this kind of low-permeable reservoir with both preventing damage and fracturing treatment should get economical benefit.