Research On Operation Optimization For Coalbed Methane Mining-gathering System

Coalbed methane recently has been widely used as a clean fuel rather than released directly to the air in a traditional way.CBM now is one of the most important kind of unconventional energy.Since CBM was beginning to be developed and used just around 10 years ago,gathering techniques of conventional gas field are always used in CBM field regardless of their difference in production as their different occurrence state under-earth.During the 11^th and 12^th Five-year Plan,the solution to these problems were mostly discussed and studied.In the 11^th Five-year Plan“a multipoint access,flexible gathering planning”concept was put forward.Based on this conception,the problems about optimum design of gathering system were mainly studied during the12^th Five-year Plan.And in this section,matching problem in different wells was considered one of the key factor that affect operation costs.But it wasn't discussed in details.In this paper,based on the achievements during the 11^th and 12^th Five-year Plan,by synthesizing surface gathering system,CBM wells and coal seam,the way matching the under-earth facilities and surface system were analyzed to determine optimum scheme for operation and design.In terms of surface gathering system,CBM wells and coal seam,those in the study were the typical branched networks,casing gas-producing vertical well and homogeneous coal seam.In this paper,constrain conditions under-earth and on surface were all been taken into consideration,including pore structure of coal seam,desorption rules of CBM,inflow performance of CBM wells,gas-well production allocation principles and flow rules of gas in gathering networks.The mathematical model was established by maximizing gas yield.A software was developed based on JAVA to search the optimal solution using a method combined genetical algorithm with predator and prey mechanism.For example,by dealing with the data using the software mentioned above came up with an evaluation of the operation state showing the suitability among gas-wells,gathering networks and drainage equipment.According to different evaluation index various arithmetic methods were proposed correspondingly.The calculation results indicate that inter-well interference exists indeed when operation parameters are setting irrationally.It becomes even worse in some extreme conditions.Meanwhile the results also show that the optimization scheme put forward during the 12^th Five-year Plan was feasible.