Discussion on the geological conditions of forming Wangyingzi coal-bed methane reservoir in Fuxin coal field

Wangyingzi coal-bed methane reservoir is located in Wangyingzi coal mine of Fuxin coal field in the west part of Liaoning Province. A natural gas outrush occurred when the tunneling was being made at north flank for constructing the coal mine. The tunnel had to be plugged because of its high gas outrush rate. Up to now the natural gas with an average rate of more than 5 000 m3/d has been developed and utilized for over ten years. In order to survey the genetic type and resource potential of the natural gas reservoir, a synthetic study on the characteristics of geochemistry and gas outrush and the geological conditions of occurrence was carried out by the authors. Through such a study it is thought that the natural gas in the reservoir mainly came from the coal measure strata of the Fuxin Formation. The shape of the gas production rate curve over the years is similar to that of the production curve of coal-bed methane well, however, there is some difference between them, which results mainly from the coal-bed methane desorbed and accumulated in the fractures because of the water drainage and depressurization in the early stage of constructing the coal mine. Wangyingzi area has fair prospects for coal-bed methane because the coal measure strata at this area are of the geological conditions as large thickness, abundant resources and high permeability.