煤层气连续管排液采气一体化工艺研究与应用

Research and Application of the Integrated Technology of Liquid Drainage and CBM Production by Coiled Tubing

在国内煤系地层天然气勘探开发中,煤层出水导致井筒积液,必须采取有效的排液措施。为此,提出了煤层气连续管排液采气一体化工艺,设计了排液采气井下工具,优化了井口悬挂密封结构,建立了工艺模型与作业设计方法,对比分析了多种规格连续管在不同井口压力条件下临界携液流量与沿程摩阻的变化情况,并将工具在大吉-平04井进行了现场应用。分析结果表明:连续管排液采气一体化工艺实现了一趟管柱两种工艺,达到了高效和节省成本的目的;研制的井下工具既可以实现带压作业,又可以实现注氮、生产及无压井作业;外径38.1 mm连续管在沿程损失不大的情况下更容易达到生产临界携液流量。研究结论可以为煤层气控压稳产提供技术参考。

In the exploration and development process of natural gas in coal measure strata in China,water out of coal beds leads to liquid loading in wellbores.Therefore,it is necessary to take the measures to drain the liquid effectively.In this paper,an integrated technology of liquid drainage and coalbed methane(CBM)production by coiled tubing is proposed,and the downhole tool for liquid drainage and CBM production is designed.The wellhead suspension sealing structure is optimized.Process model and operation design method are established.The variation of the critical liquid carrying flow rate and the friction resistance along the way of various coiled tubing under different wellhead pressure conditions are comparatively analyzed.In addition,it is applied on site in Well Daji-P04.The results show the integrated technology of liquid drainage and CBM production by coiled tubing implement two processes in one trip and achieves the target of high efficiency and cost saving.The developed downhole tool can not only realize snubbing operation,but also nitrogen injection,production and well killing free operation.As for OD 38.1 mm coiled tubing,the critical liquid carrying flow rate is likely to reach when the loss along the way is not great.The research results can provide the technical support for CBM pressure-control production stabilization.