煤层气水平井注氮增产改造技术

Gas output improvement and reconstruction technology of coalbed methane horizontal well by nitrogen injection

针对七元煤矿低孔、低压、低含水饱和度、高变质程度的煤储层特点和筛管完井煤层气解吸困难情况,为了实现瓦斯治理与煤层气共同开发的需要,探索出一套煤层气水平井筛管完井下的注氮增产改造技术。利用顶替排液、氮气驱替、憋井放喷3种氮气改造模式的不同特点,实施多次＂注氮-憋压-放喷＂作业,通过注氮改造可以清除近井污染,沟通煤层割理裂隙,改善井筒远处煤层渗透率,建立单相气体渗流通道,实现煤层气高效开发的目的。结果表明：七元煤矿5组水平井实施注氮增产改造技术后,单井日产气量提高3-20倍,实现了单井产量的突破。

According to the seam reservoir features of the low porosity,low pressure,low water saturation and high metamorphic degree and the desorption difficult condition of coalbed methane in the screen pipe and completion in Qiyuan Mine,in order to realize the requirements of the gas control and coalbed methane joint development,a completed gas output improvement and reconstruction technology by nitrogen injection was discovered under the screen pipe and completion of the coalbed methane horizontal well.With the different features of the displaced drainage liquid,nitrogen displacement,suppressed well and blowout three nitrogen reconstruction modes applied,multi nitrogen injection,pressure suppressed,blowout operations were conducted.With the nitrogen injection reconstruction,the pollution near the well could be cleaned,the seam cleat cracks could be linked up,the seam permeability far from the mine shaft was improved,a single phase gas seepage channel was established and the high efficient development target of the coalbed methane was realized.The results showed that after the gas output improvement and reconstruction technology of coalbed methane horizontal well by nitrogen injection in Qiyuan Mine was used,a daily gas production of a single well was improved by 3 - 20 times and a breakthrough of a single well production was realized.