A dual poroelastic model for CO2-enhanced coalbed methane recovery
A dual poroelastic model for CO2-enhanced coalbed methane recovery
复制标题
CO2 强化煤层气采收率的双孔隙弹性模型
DOI：
10.1016/j.coal.2011.01.004
复制
发表时间：
2011-05-01
影响因子：
5.6
通讯作者：
Pone, Denis
中科院分区：
文献类型：
--
作者：
Wu, Yu;Liu, Jishan;Pone, Denis
尽管CO2强化煤层气（ECBM）开采已经得到了广泛的研究，但在原位条件下煤基质-裂隙相互作用对煤渗透率演化的影响仍不清楚。在以往的研究中，煤岩基质-裂隙相互作用的影响并未与二元气体输运系统严格耦合。在这项工作中，一般的孔隙度和渗透率模型的开发，明确量化的二元混合物（CO2和CH 4）和双固体介质（煤基质和裂缝）之间的相互作用下的整个频谱的机械条件跨越规定的原地应力通过约束位移。这些模型被实施到一个完全耦合的有限元（FE）模型的煤变形，二元气体流动和运输的矩阵系统，和二元气体流动和运输的裂缝系统。有限元模型反映了在力学影响与二元气体输运系统没有严格耦合的情况下，由于有效应力效应而产生的重要非线性响应，并应用该模型对沁水盆地南部无烟煤单井注水微先导试验结果进行了模拟。模拟的CH 4生产率与观察到的生产历史吻合得很好。除此之外，模拟结果还表明：（1）CO2注入使总压梯度增大;（2）随着CO2注入的进行，CO2分压增大，而CH 4分压减小;（3）在不注入CO2的情况下，特定点处的CH 4含量几乎呈线性减小，而在注入CO2的情况下，特定点处的CH 4含量呈指数减小;（4）不注CO2时，甲烷产率呈线性下降，而注CO2时甲烷产率急剧上升;（5）不注CO2时，煤渗透率几乎呈线性上升，而注CO2时，煤渗透率几乎呈指数下降;（7）累积CO2注入量也与注入压力成正比。(C)2011 Elsevier B. V.保留所有权利。
Although CO2-enhanced coalbed methane (ECBM) recovery has been comprehensively investigated, the impact of coal matrix-fracture interactions on the evolution of coal permeability under in-situ conditions is still unclear. In prior studies on this issue, the influences of coal matrix-fracture interactions have not rigorously coupled with the binary gas transport system. In this work, general porosity and permeability models are developed to explicitly quantify the interactions between binary mixtures (CO2 and CH4) and dual solid media (coal matrix and fracture) under the full spectrum of mechanical conditions spanning prescribed in-situ stresses through constrained displacement. These models are implemented into a fully coupled finite element (FE) model of coal deformation, binary gas flow and transport in the matrix system, and binary gas flow and transport in the fracture system. The FE model represents important non-linear responses due to the effective stress effects that cannot be recovered where mechanical influences are not rigorously coupled with the binary gas transport system.The FE model is applied to simulate the results of a single well injection micro-pilot test performed in the anthracitic coals of the South Qinshui basin, Shanxi Province, China. The modeled CH4 production rates are in good agreement with the observed production history. In addition to this agreement, model results also demonstrate (1) CO2 injection increases the total pressure gradients; (2) as the CO2 injection progresses the partial CO2 pressure increases while the partial CH4 pressure decreases; (3) without CO2 injection the CH4 content at a specific point decreases almost linearly while with the CO2 injection the CH4 content at a specific point decreases exponentially; (4) without CO2 injection the CH4 production rate decreases linearly while with CO2 injection the CH4 production rate increases dramatically; (5) without CO2 injection coal permeability increases almost linearly while with CO2 injection coal permeability decreases near exponentially; (6) CO2 injection enhances cumulative CH4 production and the enhancement is proportional to the injection pressure; and (7) cumulative CO2 injection volume is also proportional to the injection pressure. (C) 2011 Elsevier B.V. All rights reserved.