Study on pressure characteristics and difference causes of coal reservoirs in Bide-Santang Basin of western Guizhou

In order to study the characteristics of coal reservoir pressure and its differential causes in the Bide-Santang Basin of western Guizhou, the pressure data of the main coal reservoirs were obtained by using the reservoir pressure method and the injection pressure drop well testing method, and the reservoir pressure characteristics were analyzed. The causes of pressure difference were also discussed. The results show that the main coal seams in the study area are dominated by the normal-low pressure reservoir pressure, and high-pressure reservoirs are locally present. The high pressure reservoirs were mainly distributed in the partial exploration areas of Shuigonghe Syncline in mid basin, and the eastern part of the Agong and Zhuzang Syncline. The low pressure reservoirs were mainly located in Bide syncline in west and Bainiqing Syncline in north. The main geologic factors affecting reservoir pressure were buried depth of coal seam, structural conditions and crustal stress, permeability, gas pressure and hydro-dynamic condition. The groundwater flow in the shallow stratum is active and the influencing factors are complex, resulting in variable reservoir pressure conditions. The low permeability caused by the crustal stress, the excellent sealing function of roof and floor, and the weak hydrodynamic conditions were the potential reasons for the abnormal high pressure. The tectonic uplift denudation in late Yanshan Mountain, open fracture development, and better run off conditions were the major reasons for low pressure in shallow reservoirs.