中阶煤有效弹性力学性质研究

煤的力学性质是制定钻完井与煤层气开发方案和工程措施的重要依据，也是影响煤层气储层改造效果的重要因素。煤内部含有大量的内生裂隙、构造裂隙和微孔隙，在不同应力条件下其力学参数具有显著差异。目前关于煤在不同应力条件下的有效力学参数变化规律及其内在原因的研究成果还较为欠缺，通过三轴压缩试验，可对不同应力状态下中阶煤有效弹性力学性质进行研究。研究表明，不同应力作用下煤的变形受孔隙、裂隙影响显著；在弹性变形阶段，随着围压的增加，中阶煤的有效弹性模量及有效泊松比有增加趋势，煤的有效弹性模量及有效泊松比与围压间呈非线性关系，且当围压增大到一定程度后有效弹性模量及有效泊松比趋于恒定。对应力状态影响煤有效弹性力学性质进行分析，给出了基于三轴压缩试验的含张裂缝中阶煤有效弹性模量及有效泊松比经验公式，同时对公式的适用性进行了分析。

Research on effective elastic mechanical properties of medium rank coal

The mechanical properties of coal are the basic data for the design of drilling completion programs, coal bed methane development plans and construction methods; and the important factors which influencing the effect of reservoir reconstruction. The mechanical parameters of coal under different stress conditions are significantly changed caused by the existence of large plenty of endogenous fractures, structural fractures and micropores. At present, researches on the changing rules of the effective mechanical parameters of coal under different stress conditions, and the internal causes for those changing rules are relatively lacking. By triaxial compression tests, the characteristics of effective elastic mechanical parameters of medium rank coal under different stress conditions are studied. The results show that the deformation of coal under different stress conditions is significantly affected by the pore and fracture. In the elastic deformation stage, the effective elastic modulus and effective Poisson's ratio of medium rank coal increase with the increase of confining pressure. The effective elastic modulus and effective Poisson's ratio of coal present a nonlinear relationship with confining pressure respectively; and their values tend to be constant when the confining pressure increases to a certain degree. Based on the triaxial compression test, the effect mechanism of stress conditions on the effective elastic properties of coal is analyzed; empirical formulas of the effective elastic modulus and effective Poisson's ratio are given for medium rank coal with extensional fractures in it. Meanwhile, the applicability of the formulas is analyzed.