大佛寺煤矿地下含水层对煤层气开采的影响分析

Analysis on influence of underground aquifers on coal-bed methane mining in Dafosi coal mine

矿井地下含水层的赋存、径流特征不仅影响煤层气的含量大小及煤层开采,而且对煤层气井的排采有重要影响.大佛寺煤矿延安组合煤地层以上自上而下发育含水层七层,隔水层六层,其中与主采4#煤层开采及煤层气赋存有关的含水层分别为延安组下段4上煤-4煤间砂岩含水层、延安组上段4上煤以上砂岩含水层、直罗组下部砂岩含水层、宜君组砾岩含水层及洛河组砂岩含水层.为研究地下含水层对煤层气开采的影响,论文在阐述地下含水层发育特征基础上,利用煤层气开采井取得的水化学指标经分析对比,得出4#煤煤层气井的排采水主要来自煤层顶板4上煤～4煤间砂岩含水层段水的认识;依据该含水层距离煤层的间距、含水层厚度大小及矿井构造发育程度等指标,提出了圈定水文地质条件有利的煤层气开发区段的标准是煤层距顶板充水含水层较远,间距大于10 m,构造上处于背斜部位,不利区段的的标准是煤层距顶板充水含水层间距小于3 m,构造上断层发育或顶板含水层厚度在10 m以上,断层发育.

Occurrence of mine underground aquifers and its flow characteristics have an effect not only on volume of the coal-bed methane content, hut also on drainage of coal-bed methane wells. 7 aquifers and 6 impermeable layers were developed over the coal-bearing stratum for Yanan group of Dafosi Coal Mine. The aquifers related to the No. 4 coal seam mining and CBM occurrence are 4^上 - 4 coal seam sandstone aquifer of the lower section of Yanan group,sandstone aquifer over 4^上coal seam of the upper section of Yanan group, sandstone aquifer below Zhiluo group, sandstone aquifer of Lijin group and sand- stone aquifer of Luohe group. Based on development characteristics of the underground aquifer, it is concluded that the drainage water of CBM well is mainly from coal roof 4^上 - 4 coal seam sandstone aquifer section through the analysis and comparison of the water and chemical indicators from extraction of coalbed methane wells. Put forward that a standard for delineating of the CBM development block with favorable hydrogeological conditions is that coal seam is comparatively far from the roof＇ s water-filling aquifer on the basis of the space between the aquifer and coal tural development degree of the mine. When the space seam, the thickness of the aquifer, and the strucis over 10 m,it is structurally back-incline location, and the standard for unfavorable section is that the space between coal seam and roof＇ s water-filling aquifer is less than 3 m, structural fault development or roof＇ s aquifer thickness is over 10 m.