页岩气水平井井筒清洁技术的难点及对策

页岩气储层采用水平井钻井和大型加砂压裂能够获得增产,但气井井筒堵塞的问题也频繁出现,如何清除钻塞作业残余的桥塞碎屑及砂粒,确保页岩气井井下生产通道的畅通,成为气井安全生产的重要环节。为此,在分析水平井井筒清洁生产技术现状的基础上,总结了页岩气水平井井筒清洁处理面临的技术难点,结合当今世界页岩气井井筒清洁技术的进展,对清洁工具及工艺、工作液性能进行技术攻关,研发了清洁处理工具,提出了清洁处理技术对策,并对其现场应用效果进行了评价分析。研究结果表明:①所研发的针对大通径桥塞处理的套磨打捞一体化工具,可实现工具入井后对大通径桥塞的套铣、打捞一次性作业;②形成的换向旋流冲砂工艺在长水平段中作业时能避免砂粒沉降,能实现将砂粒冲洗出井筒的目标;③常压及高压井可以选用气井返排液、KCl、CaCl2溶液等作为工作液,而低压井则可选用泡沫流体作为工作液;④对于低压井,通过优化设计局部压差打捞工具形成局部压差吸附的方式带动井内碎屑物或沉砂进入工具内部,进而完成打捞作业。结论认为,所形成的适合页岩气水平井的井筒清洁工艺技术为后期大规模页岩气井筒清洁处理奠定了基础。

Wellbore cleaning technologies for shale-gas horizontal wells: Difficulties and countermeasures

Applying horizontal well drilling and large-scale sand fracturing in shale gas reservoirs can increase production, but the problem of gas wellbore blockage occurs frequently. How to remove the residual bridge plug debris and sand in plug drilling operation and ensure that the downhole production channel of a shale gas well is unblocked is important in the safe production of the shale gas well. In this paper, the current situations of the wellbore cleaning technology for horizontal wells were analyzed, and the technical difficulties in the wellbore cleaning treatment of shale gas horizontal wells were summarized. Then, based on the development of wellbore cleaning technologies for horizontal wells all over the world, technical researches were carried out on the cleaning tools and technologies and the working fluid performance, and cleaning treatment tools were researched and developed. Finally, the technical countermeasures of cleaning treatment were put forward and their field application effects were analyzed. And the following research results were obtained. First, the milling-fishing integrated tool developed to treat large-diameter bridge plug can realize the washover and fishing of large-diameter bridge plug by one trip after running in the hole. Second, when the reverse cyclone sand-washing tool is applied in long horizontal sections, it can prevent sand from settling so as to reach the target of flushing sand out of wellbore. Third, for normal pressure and high pressure wells, gas well backflow fluid, KCl and CaCl2 solution can be used as working fluid, while for low pressure wells, foam fluid can be used. Fourth, for low pressure wells, the negative pressure fishing tool was designed and optimized to drive debris or sediment into the tool by forming local negative pressure adsorption, so as to complete the fishing operation. In conclusion, this new wellbore cleaning technology suitable for shale-gas horizontal wells lays a foundation for large-scale wellbore cleaning treatment of shale gas wells.