晋城寺河井区煤矿采空区煤层气地面抽采关键技术研究

随着煤层气勘探的不断深入,煤矿采空区煤层气已成为煤矿区煤层气重要资源之一。基于晋城矿区寺河井区煤矿采空区分布特征,通过地质分析、采空区煤层气成分、浓度试验和资源量模型计算等方法系统研究了煤矿采空区煤层气资源条件及地面抽采关键技术,揭示了采空区煤层气赋存规律,给出了不同赋存状态下煤层气资源量计算模型和方法,探索了煤矿采空区煤层气地面抽采关键技术。研究表明,煤矿采空区煤层气来源于煤柱及残留煤层、邻近未采煤层和围岩中的游离气和吸附气。根据吸附气和游离气资源量计算模型计算寺河井区煤层气总资源为213.016×10⁸m³,其中游离气资源为0.102×10⁸m³,吸附气资源为212.914×10⁸m³。采煤方法和采空区密闭性对采空区煤层气的来源和富集程度有重要影响。针对采空区上部岩体裂隙发育特征,将采空区煤层气抽采井身结构由二开优化为三开结构,实现了二开固井封闭断裂带上部含水层,三开下入割缝套管护壁,有效解决了采空区上部含水层涌水对钻井井身稳定性影响及抽采效果等问题。在此基础上,研发了潜孔锤+压缩空气(氮气)钻井工艺,用氮气取代空气作为循环介质,形成了安全揭露含气断裂带钻井工艺技术,为采空区煤层气安全抽采探索了有效途径。

Study on key technology for surface extraction of coalbed methane in coal mine goaf from Sihe Wells Area,Jincheng

The coalbed methane(CBM)of coal mine goaf has become one of the important resources with the continuous deepening of CBM exploration.Based on the analysis of goaf distribution characteristics in Sihe Wells Area of Jincheng Mining Area,the resource condi?tions of CBM in goaf,the key technology of surface extraction are systematically studied through geological analysis,CBM composition,concentration experiment in goaf,and resource model calculation.The occurrence law of CBM in goaf is revealed,the calculation model and method of CBM resources under different occurrence states are given,and the key technology of surface extraction of CBM in goaf is explored.It is shown that the CBM in coal mine goaf comes from free gas and adsorbed gas in coal pillar,residual coal seam,adjacent un?developed coal seam,and surrounding rock.According to the calculation model of adsorbed gas and free gas,the total resource of CBM in Sihe Wells Area is 213.016×10⁸m³,among them,the free gas resource is 0.102×10⁸m³,and the adsorbed gas resource is 212.914×10⁸m³.The coal mining method and goaf airtightness have an important impact on the source and enrichment degree of CBM in goaf.Ac?cording to the characteristics of fracture development in the upper part of goaf,the wellbore structure of CBM extraction wells in goaf is op?timized from the second opening to the third opening.The upper aquifer of the fracture zone is sealed by cementing in the second opening,and the slotted casing protection is installed in the third opening,which effectively solves the problems of the drilling stability and the pumping effect caused by water gushing from the upper aquifer of the goaf.On this basis,the drilling technology of down-the-hole hammer(DTH hammer)+compressed air(nitrogen)has been developed.Nitrogen is used to replace air as circulating medium and a set of drilling technology for safely exposing gas bearing fracture zones is formed,which provides an effective way for safe extraction of coalbed methane in goaf.