Geological Evaluation And Optimization Of Coalbed Methane In Enhong And Laocang Mining Area

According to previous research materials in Laochang and Enhong mining areas,this paper precisely described the reservoir characteristics of two mining areas,and analysed the differences of reservoir and influence factors of gas content and adsorption capacity.Considering the high crustal stress and the thin coal seam and plenty layers in the study area,this paper built up a complete set of method for dividing the structure of coal body,and analysed the reservoir characteristics of different structure of coal body.Besides,since there are some differences between Laochang and Enhong mining areas,different evaluation criteria systems were established and selection of favorable areas in horizontal direction and selection of dessert sections in vertical direction were conducted,which will provide guidance suggestions for the exploration and development in the future.Laochang mining area was in a marine-terrestrial transitional environment at the time of the Late Permian,and from the end of the Longtan mid-period to the Changxin period,various coal accumulation conditions were most conducive to coal gathering.And the Longtan Formation and the Changxin formation can be divided into four 3-level sequences,eight system tracts,and twelve 4-level sequences.The coal forming stage of Enhong mining area was a typical upper delta plain Coal gathering environment,and the distribution range of marine facies was relatively small.Enhong mining area can be divided into 4 three level sequences,and 10 four level sequences.Pore structures in the study area are divided into three categories,and pore types mainly consist of micro-pores and small pores.Pore specific surface area is mainly contributed by micro-pores and small pores,and pore volume is mainly controlled by mesopores.According to the results of isothermal adsorption experiment,the adsorption capacity of Laochang mining area is greater than that of Enhong mining area,but the reservoir ratio in Enhong mining area is greater than that of Laochang mining area.Besides,the adsorption capacity is influenced by microcomponent,pore system,coal forming environment,etc.Furthermore,the gas content of Laochang mining area is greater than that of Enhong mining area,and the coal bed methane is mainly composed of methane,but the Enhong mining area contains plenty of heavy hydrocarbons.In the horizontal direction,three?types of favorable zones and two?types of favorable areas are selected in Enhong mining area,and one?types of favorable zones and three?favorable areas are selected in Laochang mining area.In the vertical direction,the most favorable layers are 8#,16# and 19#,followed by 7+8#,9#,13# and 21#,and 16# and 19# are the most favorable combination segments.The most favorable dessert sections in Laochang mining area are 16# and 19#,followed by 7#,7+8# and 8#.7#,7+8#,8# and 16# and 19# can be combined to exploit,and 16# and 19# are the most favorable coalbed segments in the vertical direction.