采动区远程卸压煤层气抽采地面井产能影响因素

以淮南矿区远程卸压煤层气地面井抽采工程实践为依托,通过工程试验和系统分析,探讨了远程卸压煤层气地面井的产能特点及其影响因素。研究结果表明,远程卸压煤层气地面井的产能曲线可分为两个阶段,在较短时间内顺利完成第Ⅰ阶段的井才能有较高产能。研究还显示,煤层气地面井产能受地层结构和采动影响较大。在研究区,当地层结构为松散层厚度406 m,基岩与松散层厚度比值0.74,下保护层与被保护层间距为66~70 m,且平均采高≤2.2 m,平均产煤低于3 898 t/d时,利于远程卸压煤层气地面井抽采;当松散层厚度430 m,11-2煤和13-1煤层间距74 m,基岩与松散层厚度比值0.7时,卸压煤层气地面直井成功率较低,此时,可通过改变井位和优化井身结构来适应地层结构的变化,提高地面井抽采成功率。

Analysis of productivity impact factors for coalbed methane drainage by remote pressure relief of surface well in mining area

The objectives of this paper were to analyze impact factors and the characteristics of gas productivity for remote pressure relief of coalbed methane by surface wells in mining area. Production trends and their impact factors have been studied for 9 wells on 3 longwall panels in Huainan coal mining area. The results indicated that the gas productivity of remote pressure relief of CBM drainage could be divided into two obvious stages. Well which can accomplish the first stage in short time would get better gas production. Strata structures and mining activities greatly influenced the gas production of surface well. It was favourable to gas drainage by surface wells while the average coal extraction volume was less than 3 898 tons per day and the average mining height was less than 2.2 m if the strata structure around the well was that thickness of loose bed was less than 406 m, the ratio of the bedrock thickness to loose bed thickness was over 0.74, the interval between protective seam and protected seam was on the range of 66-70 m. Whereas it was unfavourable to remote pressure relief of CBM drainage while the strata around the well was that loose bed thickness was larger than 430 m, the space between protective seam and protected seam was more than 74 m, the ratio of the thickness between loose bed and bedrock was less than 0.7. But the gas production can be improved by changing well location and optimizing wellbore structure.