裸眼封隔器完井注低密度液的井控风险及对策

Well control risks and countermeasures in well completion with open-hole packers while pumping injection of low density liquid:A case study of LG022-H2 well,Sichuan Basin

近年来,随着裸眼封隔器完井工艺技术的推广应用,在低孔低渗非均质油气藏取得了很好的增产效果,但在实际注替钻井液施工中却时常遭遇溢流显示,也增加了作业过程中的井控风险。为此,以LG022-H2井在作业中连续发生的2次溢流情况为例,通过系统分析该工艺在注替钻井液工况的环空液柱压力变化,找到了引起溢流的地质工程原因:1下完管柱注入低密度KCl液体使环空液柱压力低于地层流体压力;2丢手后使用清水替出井内钻井液,封隔器管柱内外形成的负压差使井底单流阀失效;3封隔器提前坐封,可能封闭地层溢出的带压气体,敞井换装油管头作业处于无控状态等成为作业中的井控风险。进而提出了完善设计内容、严格审查核实并严密组织施工的针对性措施和进一步完善该项技术的建议。为类似作业方案制订及施工中的井控安全分析提供了重要依据。

In recent years, with the wide application of well completion with open-hole packers to develop low porosity, low permeability and heterogeneous oil and gas reservoirs, an outstanding yield-increasing effect has been achieved. But in practice, overflow often occurred in the process of filling up the hole, which has become the well control risk in actual operation. Therefore, from the changes of annulus fluid column pressure in filling-up operation in the two cases of overflow occurred in the LG022-H2 well, Sichuan Basin, we discovered the original reasons as follows. First, the filled low-density KCl made the annulus fluid column pressure lower than the formation fluid pressure after the string running was completed. Second, when the round trip was made to inject clean water to drive out the in-hole mud, the negative pressure of inside and outside of the packer string caused the failure of the check valve at the bottom hole. Third, well-control risks were easily delivered by many other factors, for example, the packer setting ahead of schedule would result in the overflowed pressurized gas from the formation being sealed, or oil tubings altered in open-hole operation would be out of control. On this basis, we put forward countermeasures to mitigate the well-control risks with detailed content, strict check and well-organized implementation. This study provides a valuable reference for the program design of similar operation and well-control risk analysis.