Numerical Simulation On Influence Of CBM Drainage Parameters On Productivity

The CBM in China is very rich.In the growing shortage of oil and other conventional energy situation,it's very important to develop the CBM career for the economic development and the social progress in China.Therefore,it has a certain guiding significance for the CBM well exploitation reasonably and effectively to formulate a reasonable drainage strength,and it is necessary for the drainage strength to study the numerical simulation of the CBM drainage,and determine the factors of the CBM production capacity based on the seepage mechanics,CBM drainage and other related knowledge.It is based on the complex geological conditions of Liu block to establish the gas-water flow solid coupling seepage model of the CBM drainage considering the anisotropy of the reservoir permeability and the occurrence,desorption,diffusion,seepage and other features of the CBM reservoir,and it is composition of the permeability model,the coal deformation equations and the fluid flow equation.It study the simulation calculation of the flow solid coupling seepage model to use the COMSOL Multiphysics multi-physics coupling software,and it is provided a theoretical basis for the CBM production continuously,stably and slowly through studying the different pressure drop rate for the influence law of the pressure and production,and to determine the optimal solution of the pressure drop rate.It shows that: it's influential for the CBM production to select the pressure drop rate.When the pressure drop rate is constant,it is formed a semi-elliptical-type pressure contours as the well center to extend to the distant with the increase of drainage time,and it shows a decreasing trend from the well away area to the wellhead;When the drainage time is constant,it is increased for the pressure drop extended range with the pressure drop rate reducing;when the differential pressure is constant,it is increased for the drainage time with the pressure drop rate reducing.And it is increased for the daily and the cumulative production and reduced for the degree of the attenuation with the pressure drop rate reducing.But it isn't better for the drainage effect and smaller for the pressure drop rate,it shows that 0.01MPa/d is the best numerical.And it is used to study the CBM fracture parameter optimization.