煤储层物性对甲烷解吸及采出的影响

Impact of coal reservoir physical property on coalbed methane desorption and production

影响煤层气解吸采出的诸多因素作用于煤储层,体现为煤储层允许煤层气扩散渗流或导流的能力,所以在研究气体解吸特性时煤储层自身的物性值得重点探讨。基于这一点,对比研究了高低煤阶煤的物性差异,探讨了其对气体解吸采出的影响。研究表明,低煤阶煤分子结构较松散,孔隙度高,高煤阶煤分子结构紧密,孔隙度低,降压解吸过程中低煤阶煤物性变好,高煤阶煤物性变差。罐装煤样解吸和室内模拟实验揭示,物性是决定气体解吸的关键要素,这也是低煤阶煤储层含气量低但仍具有很大开发潜力的根本原因。低煤阶煤层孔渗较好,压降传播快,在开采过程中可形成自卸压效应。高煤阶煤层孔渗较差,压降传播慢,为了提高单井产量必须采用大型压裂或分支井技术等措施。

The factors influencing coallbed methane（CBM） desorption and production act on coal reservoir, and are reflected as the ability of reservoir allowing CBM to diffuse and permeate. So the coal res-ervoir physical property should be paid more attention when doing research on gas desorption. For this reason, the physical property differences between high and low rank coal reservoirs were studied, and the impact of physical property differences on gas desorption and production were discussed. The results show that the molecular structure of low rank coal is loose, and the porosity is high. However, the molecular structure of high rank coal is tight, and the porosity is low. The physical property of low rank coal is better, whereas, that of high rank coal is worse during gas desorption. Both canister desorption of coal and simulation experiment imply that reservoir physical property is the key element of influencing gas desorption, which is also the underlying reason of low rank coal＇s high development potential despite low gas content. The low rank coal has better porosity and permeability, and in which the pressure spreads fast, so self-relieving pressure effect can be formed easily during exploitation. The high rank coal has poor porosity and permeability, and in which the pressure spreads slowly, so massive fracturing and multilateral well technique should be adopted in order to increase single well yield.