新疆库拜煤田铁列克矿区地应力分布及其对煤层气开发的影响

地应力、煤储层渗透率和煤储层压力等是影响煤层气开发的重要因素。通过分析新疆库拜煤田铁列克矿区注入/压降试井及原地应力测试数据,结合铁列克矿区煤层气井日产气量分析,研究了新疆库拜煤田铁列克矿区地应力变化规律及其对煤层气开发的影响,分析了铁西矿区和铁东矿区煤储层地应力特征及其对煤储层物性的影响。结果表明:(1)地应力状态在垂向上发生变化,埋深处于550~650 m、650~850 m和850~1 200 m时,地应力状态类型依次为σ_H>σ_v>σ_h、σ_H≈σ_v>σ_h和σ_v>σ_H>σ_h;(2)埋深850 m处既是垂直主应力和最大水平主应力的转换点也是渗透率趋势变化点,指示了地应力对渗透率的控制作用;(3)渗透率和煤储层压力与地应力分别呈负相关和正相关关系;(4)地应力对产能的负效应大于地应力对产能的正效应,使典型日产气量随着地应力的增大而减小;(5)铁西矿区和铁东矿区中部煤储层碎粒煤较发育、吸附孔体积和含气量均较大,是煤层气开发的有利区带。研究成果可为库拜煤田下一步煤层气开发提供理论指导。

In-situ Stress Distribution and Its Influence on Coalbed Methane Development in Tielieke Mining Area,Kubai Coalfield,Xinjiang

In-situ stress, coal reservoir permeability and coal reservoir pressure are the important factors on coalbed methane development.Based on the analysis of injection/fall-off well analysis and in-situ stress measurement data, and combined with the analysis of daily gas production of coalbed methane wells in the Tielieke mining area (Kubai coalfield, Xinjiang), we study the characteristics of in-situ stress distribution at Tielieke and its influence on CBM development.The results show that: (1) the in-situ stress state changes vertically, with σ_H>σ_v>σ_h, σ_H≈σ_v>σ_h and σ_v>σ_H>σ_h at 550-650 m, 650-850 m and 850-1,200 m reservoir depth, respectively; (2) 850 m depth is not only the conversion point of the vertical principal stress and the maximum horizontal principal stress, but also the transition point of permeability trend. This demonstrates the in-situ stress the control on permeability; (3) the in-situ stress correlates negatively with permeability, but positively with coal reservoir pressure; (4) for the in-situ stress, its negative effect of on productivity is greater than its positive effect on productivity, and hence the typical daily gas production decrease with increasing in-situ stress; (5) the central coal reservoirs in Tiexi and Tiedong mining areas have relatively developed granular coal, large adsorption pore volume and gas content, which are favorable intervals for CBM development.Our results provide theoretical guidance for further CBM development in the Kubai coalfield.