用于全过程欠平衡钻井施工的井下封井器

针对常规的欠平衡钻井工艺不能解决起下钻、完井等作业过程中井底欠平衡压差的连续保持,无法实施全过程的欠平衡作业问题,研制了可用于全过程欠平衡钻井作业的井下控制工具——井下封井器。室内试验与现场应用情况表明(1)采用井下封井器实现了全过程的欠平衡钻井,显著提高了欠平衡钻井工艺水平和作业水平,起下钻过程中不需预先加入重钻井液,因此可有效地保护和发现油气层;(2)井下封井器与使用不压井强行起下钻设备相比,大大减少钻井作业时间,其适应性和使用性能更好,完全可以取代不压井强行起下钻设备。

Development and application of downhole hole-closure device in the overall process of underbalanced drilling operation

For the common underbalanced drilling technology, the continuous bottomhole underbalanced pressure difference cannot be maintained during the roundtrip and well completion and the underbalanced operation cannot be realized during the overall process. Therefore, the downhole hole-closure device, a downhole control tool used in the underbalanced drilling operation, is developed. The laboratory experiment and field use indicate that the overall process of underbalanced drilling is realized by using the downhole hole-closure device, remarkably improving the technical level and operating level of underbalanced drilling. There is no need to add heavy drilling fluid in advance during the round trip operation, therefore protecting and discovering oil and gas formations effectively. Compared with the running device against pressure without killing the well, the downhole hole-closure device can greatly reduce the drilling time with better adaptability and performance and can completely replace the former.