Gas phase changing law and development mode of coalbed methane under condition of scale development

In order to scientifically guide the coalbed methane development,based on the production information of WL1 well group,the paper discovered the coal reser voir features and its fluid feature variation law under the condition of the coalbed methane scale development.The study showed that under the scale development conditio n,with a long term sustained water drainage and pressure reduction of the coalbed methane well network,a regional pressure drop was steadily formed,the coalbed methan e in large scope were desorbed and the coalbed methane were changed from an adsorption state to a free state.Under a role of buoyancy force,the coalbed methane in fre e state would be gathered at a high level location and under a role of gravity,water in the seam fractures would be gathered in low level location and that was gas and wate r difference phenomenon. According to the gas and water difference theory,the rational layout of development well network,production well with the first construction at the | ow location and other plans were provided in order to improve the scale development effect.