煤层气藏强化开采各向异性力学性质分析

针对煤层多重孔隙系统空间非连续分布、力学属性各向异性的特点，综合考虑注气强化开采过程中多组份多过程物质运移特征，构建了正交各向异性等效连续煤层流固耦合模型，据此进一步剖析了煤层各向异性力学性质及其对孔渗参数与注采能力的影响。煤层各向异性的力学属性，导致开发过程中储层水平应力与应变的动态变化存在明显的方向性特征，沿力学强度或杨氏模量大的方向变化相对较大，进而带来裂缝宽度、渗透率及其变化的方向性差异，同时致使孔隙度、渗透率以及气体吸附浓度空间分布的非均质性，最终造成与横观各向同性介质不同的煤层气生产与CO2注入预测结果。研究成果对煤层气开发过程中孔渗参数及注采能力的准确预测具有重要意义。

Anisotropic Mechanical Property Analysis of Enhanced Coalbed Methane Recovery by Gas Injection

A coupled fluid flow and geomechanics model on basis of the orthotropic anisotropic and equivalent continuous media treatment is proposed for enhanced coalbed methane recovery by gas injection, with consideration of spatial discontinuous distribution for multiple pore system and anisotropic mechanical property of coal seam, as well as multi-component multi-process transportation. Further analysis of the anisotropic mechanical properties and its impact on porosity and permeability as well as injection and production capacity are conducted. Anisotropic mechanical properties of coal seam make dynamic alteration of horizontal stress and strain show obvious directional differences, which means bigger alteration at the direction with larger mechanical strength or young''s modulus, and the same case for fracture width, permeability and its alteration. In addition, it also creates the heterogeneity of the spatial distribution in porosity, permeability and gas adsorption concentration, which results in difference on predication results of coalbed methane production and CO2 injection between orthotropic anisotropic and transversely isotropic reservoir. The research can provide accurate prediction of pore/permeability and injection/production capacity during CBM development.