单弯螺杆钻具下入套管可行性分析

为满足造斜和复合钻井的需要，常需使用单弯外壳螺杆钻具。由于套管内径较小，螺杆钻具壳体存在结构弯角，弯螺杆钻具能否顺利下入井口段套管是目前现场面临的一个重要问题。研究单弯螺杆钻具通过井口套管时的力学特性，对于指导现场合理选取螺杆钻具组合具有重要意义。采用有限元法，分析了172 mm单弯螺杆钻具在下入直井段244 mm套管时的应力分布规律，以及不同弯角大小对单弯螺杆钻具下入性的影响。结果表明，结构弯角小于2.5°时，172 mm单弯螺杆钻具能够依靠自重顺利下入244 mm套管，螺杆钻具结构弯角为2.75°时，需要额外施加外力才能将螺杆钻具强行压入套管。

Feasibility analysis of single bend screw tripping

To meet the need of kicking off and compound drilling, the single-bending screw drill tool is often required. However, because of the small diameter of casing, and the structure bends of screw drill shell, whether the screw drill can trip through the casing of the well head section is an important issue at the moment. It is significant to study the mechanical characteristics during the screw pass through the casing in the well head, for appropriately selecting the screw drill. The finite element method was taken to analyze the stress distribution law when the 172 mm single bent screw drill trip into the 244 mm casing, and the effects of bent angles on the running process. The results showed that when the structure bends was less than 2.5°, the 172 mm single bend screw drill was able to trip into 244 mm casing by itself, while when the structure angle of the screw drill is greater than 2.75°, additional external force was need to press the screw drill into the casing.