A method for identification of CBM co-production reservoir based on the volume fraction difference of desorption gas components

Coal seam group is widely distributed in China. Its typical characteristics are many layers of coal seam and large interval between layers. At present,multiple coal seams in coal seam group have been difficult to identify the source of coalbed methane and formulate reasonable plan for coalbed methane production in multiple coal seams,resulting in low output and development efficiency of coalbed methane. Therefore,taking the Guqiao well field in Huainan mining area as an example,based on the analysis results of desorption gas test of coal seam samples,the characteristic information of desorption gas component volume fraction is extracted,the standard template of identification of desorption gas source in coal seam is established,and 5 test wells are taken as examples for preliminary identification.Furthermore,the method of identification of gas source in multiple coal seam combination production is studied. The results show that the desorption gas of coal seam contains abundant information about the source of gas. Based on the volume fraction difference of desorption gas components in the four layers coal seam,the characteristic volume fraction ratio data of CH₄/C₂₊,N₂/C₂₊,CO₂/C₂₊ and N₂/CO₂ are extracted,and the standard template of single layer coal seam of intersection diagram method and cobweb method is established. Using this standard template,the gas sources of 5 test wells were identified,and it was concluded that the gas contribution of Guqiao well field was mainly 13-1 coal and 11-2 coal,and 6-2 coal and 1 coal was very little. It is thinking that the large interval is the main factor affecting the superposition of multiple coal seam combination production in Guqiao well field. The evaluation process,which consists of three steps:extracting the characteristic volume fraction of desorption gas,setting up the standard template of the characteristic volume fraction of desorption gas of single coal seam,and identifying the source of coalbed methane,can be quickly and accurately used to identify the source of coalbed methane from multiple coal seam combination production.