Productivity Analysis Of Coalbed Methane And Optimization Of Well Type

Coalbed methane is a kind of new high-quality energy,its effective development and using,can not only improve China's energy structure,increase the supply of energy,alleviate the energy problem pressure,but also reduce the mine disasters and protect the atmospheric environment.China's coalbed methane development started late,the technology is not complete,the influence factors of coalbed methane production are complex,different well type has its advantages and problems,to research on coalbed methane productivity analysis and well optimization can provide scientific advice for the development of coalbed methane.Combining with the process of desorption,diffusion,output and seepage flow theory,this paper established a mathematical flow model considering the permeability sensitivity and the effect of capillary,then used Galerkin method based on finite element analysis to get the finite element's weak integral form of mathematical model of coalbed gas water flow.Based on FEPG finite element program automatic generation platform and Fortran language,this paper compiled the corresponding coalbed methane productivity analysis program,compared with the COMET3 numerical simulation,then analysed productivity of fractured vertical well.The results showed that:(1)The product process of coalbed methane gas is controlled by three links of gas desorption,diffusion and transfusion,which are related with each other closely and affects each other mutually.(2)Fracture reduces resistance of pressure transmission,is conducive to the expansion of the pressure drop scope,then improves coalbed methane productivity.(3)The larger the conductivity and length is,the higher the gas production will be,but it is not unlimited and needs to optimize the fracture parameters.At the same time,this paper combined the characteristics of the study area coalbed reservoir,used coalbed methane numerical simulation software to study well network and density of fractured vertical wells,the fracture parameters of fractured horizontal wells,optimization on the number branch of multi-lateral wells.The results showed that:(1)The fractured vertical well productivity decreases with the enhancement of permeability heterogeneity,the fractured horizontal well productivity with reasonable drilling azimuth increases with enhancement of permeability heterogeneity,multi-lateral well productivity has small effect of permeability heterogeneity.(2)This paper determined the well network shape of fractured vertical well is square,optimize the pattern size and fracture parameters,at the same time,optimized well length and fracture parameter of the fracturing horizontal well,and number branch of the multi branch well.(3)In the coal bed with relatively small permeability,gas content and thickness,multi-lateral well has good adaptability,in contrast,gas production capacity of different well type is approaching.