注水压裂条件下软煤裂隙损伤与煤层气渗透耦合特征

Coupling characteristics of soft coal fracture damage and coalbed methane seepage under water fracturing condition

针对豫西“三软”煤层的低渗性与流变性,探讨了复杂地质条件下主采二1煤层生、储气层的变形特征.基于ABAQUS平台进行软件二次开发,讨论了注水压裂条件下二1煤裂隙的应力与损伤特性;利用T-P损伤演化准则的Cohesive单元,揭示了软煤裂隙的张裂宽度与延伸距离之间的近似线性关系.模拟结果表明,注水压力条件下,软煤裂隙的应力与损伤演化是一个随时间逐渐发展的过程,在5～ 10 MPa静荷载作用下,注水1～2h,软煤裂隙的损伤范围约为80～100 m,从而大幅度地改善了“三软”煤层低渗性能.

In order to study the hypotonic and rheological particularity of a ＂ three soft＂ coal seam in west Henan,the detormation characteristics of a Ⅱ1 coal seam as gas-generation strata and gas-preservation strata are discussed.In addition,the characteristics of stress and damage of coal fracture are explored under fracturing conditions by using ABAQUS platform.Pore pressure cohesive elements and T-P Damage Evolution criterion were used to describe the approximately linear relationship between the soft coal fracture crack width and an extending distance.The research results show that the soft coal fracture stress and damage evolution have a gradual development process over time under water injection fracturing.When the static injection pressure is 5 ～ 10 MPa and the injection time is about 1 ～ 2 h,the fracture damage range of soft coal can basically be 80 ～100 m.The hypotonic performance of a ＂three soft＂ coal seam will be improved greatly.