Study On Coalbed Methane Engineering Condition And Development Strategy In Eastern Yunnan And Western Guizhou

Based on geological and engineering data in Enhong and Laochang blocks,estern Yunnan and western Guizhou,this paper firstly analyzes the stimulation conditions and characteristic of stimulation fractures propagation,meanwhile,studies water production conditions of CBM(coalbed methane)wells and development strategy.The study shows that the compressive strength,extension strength and Young modulus of coal in studing areas are higher,Poisson's ratio is smaller and the difference on mechanical properties between coal seams and their roof/floord is smaller,compared to that in Qinshui basin.Secondly the coal body structure is very complicated and coal seams in some places near the faults always have poor coal body.Thirdly,the in-situ stress magnitude is slightly weaker than that in southern Qinshui basin,both the normal stress regime and strike-slipe regime could be identified in studying area.Simulation results by Monte-Carlo method show that stimulation fratures in Enhong and Laochang block will continue its direction when the nature fracture dip is respectively less than 60° and 65°,and vice visa.Moreover,when stimulation fractures contact with interface between coal seam and its roof/floor,they will be inclined to keep its original trace as interiaminar minimum stress difference is less than 2MPa in Enhong and 1MPa in Laochang,on the contrary,they will extent alond the this interface.The aquosity of coal bearing is weak in Enhong block,which has slight influence on CBM drainage.However,the limestone of Moukou group in Laochang block will be possible to have influence on drainage and cause high water production in some extent.Multi-stage stimulation is suitable for CBM development in studying area and the coal permeability will be improved to 1mD and even 10 mD through stimulation.Calcite filling in the coal is a typical characteristic in studying area,it is better to consider acidification when stimulating coal seams.In addition,drainage water from multiple coal seams in order with proper rhythm.