彬长矿区煤层气水平对接井欠平衡钻井技术

Under-balanced Drilling Technology for CBM Horizontally-butted Wells in Binchang Mining Area

为了增加彬长矿区煤层气水平对接井后期的排采效果,采用欠平衡钻进技术施工水平对接井;通过建立数学模型对环空压力损耗、井底欠压值的范围以及直井注气的流量控制等关键技术参数进行计算,并应用于彬长矿区某对接井组的钻井工艺。数学计算和现场应用结果表明:彬长矿区适合采用欠平衡水平对接井的施工,当水平段长度小于600 m时,可采用注液量0.45 m^3/min和注气量35.5 m^3/min的方式达到井底欠平衡状态;当水平段长度大于600 m时,可采用注液量0.6m^3/min和注气量35.5 m^3/min的方式达到部分井段可控过平衡状态,进而实现了煤层段较大进尺的同时有效保护了储层,后期增产效果明显。

In order to strengthen the drainage effect of CBM horizontally-butted wells in later stage in Binchang Mining Area, under-balanced drilling technology is adopted for the construction of horizontally-butted wells. In this process, through establishing the mathematical model, the key technical parameters of annular pressure loss, the range of bottom hole pressure and flow control of gas injection in vertical well are calculated. Moreover, this technology is adapted to drilling technology in Binchang Mining Area butted well group. Mathematical calculation and field application results show that it is suitable for the Binchang Mining Area to adapt under-balanced horizontally-butted wells. When the horizontal section length is less than 600 m, the injection volume of 0.45 m3/min of liquid and 35.5 m3/min of gas can be set to achieve the under-balanced state of bottom of well; when the horizontal section length is more than 600 m, the injection volume of 0.6 m3/min of liquid and 35.5 m3/min of gas can be set to achieve that part of wells are controlled in the slightly over-balanced state so as to realize the large footage in coal seam, to effectively protect the reservoir and greatly increase the production in later stage.