煤层气窜流–扩散过程及其对开发效果的影响

THE CHANNELING-DIFFUSION PROCESS OF COALBED METHANE AND THEIR INFLUENCES ON DEVELOPMENT EFFECT

基于煤层气的赋存和运移规律,综合考虑煤层气从煤基质中解吸,并以扩散和窜流方式进入煤层割理,通过渗透和扩散方式从割理流入生产井筒的过程,将煤层气在微孔中的非平衡吸附模型与气水两相渗流模型耦合,建立了双重介质煤层气藏拟稳态渗流数学模型。采用该模型研究了窜流和扩散机理对开发效果的影响。结果表明:窜流和扩散对开发后期产气量的影响较明显,窜流因子或扩散系数越大,后期产气量越多。

Based on the occurrence and migration law of coalbed methane,and the analysis of coalbed methanedesorption from matrix of coal by way of channeling and diffusion,through the process from which the cleat tothe production borehole by way of permeation and diffusion,then coupling the unequilibrium adsorption model ofcoalbed methane in the Millipore with gas-water two-phase percolation model together,the Dual media coalbedmethane reservoir simulation steady state percolation mathematical model is formed.A homologous numericalmodel is established according the ADI-FDTD method.For channeling and diffusion method,we make a researchon their influences on development effectiveness based on this model.The results show that channeling and diffusionhave greater influences on gas production in the late period.The greater the channeling factor or diffusion coefficientare,the higher the gas production is.