煤储层渗透率动态变化模型与模拟研究

Dynamic variation model of reservior permeability during the development of coalbed methane

为深入认识开发过程中煤储层渗透率的动态变化特征,修正前人基于有效应力与煤基质收缩耦合影响的煤储层孔隙度和渗透率动态变化理论模型,应用沁水盆地南部生产区块煤层气排采数据及煤储层相关参数,模拟研究区煤层气开发过程中煤储层孔隙度和渗透率动态变化特征,并进行了储层参数敏感性分析。研究表明:煤储层孔隙度和渗透率动态变化具有明显的阶段性,需要建立分阶段预测模型;排采制度合理的情况下,煤储层孔隙度和渗透率会经历先降低后升高的阶段,且随着储层压力的降低,克林肯伯格效应作用明显,气相渗透率增加,煤储层渗透率改善效果明显好于孔隙度改善效果;煤储层渗透率动态变化明显,受控于孔隙压缩系数、弹性模量和朗格缪尔体积,以弹性模量的影响最为显著。

To understand dynamic variation character of reservior permeability indevelopment process, re- vising predecessors＇ s theoretical model on porosity and permeability which takes effective stress and shrinkage of coal matrix into account, applying CBM wells production data and the relevant parameters of coal reservoir in Fanzhuang block, the paper simulated dynamic variation character of reservior permea- bility and porosity, and analyzed reservior parameter＇ s sensitivity. The analysis showed that dynamic var- iation of reservior porosity and permeability is staged and staging prediction model should be built ; Under the condition of reasonable drainage system, reservior porosity and permeability will reduce first and rise then;With the loss of the reservoir pressure, the Klinkenberg effect becomes obvious, and the gas-phase permeability increases, and permeability＇ s amplification exceeds porosity＇ s; Dynamic variation of re- servior porosity and permeability is influenced by pore compressibility, modulus of elasticity and Lang- muir volume, especially modulus of elasticity.