旋转固井扭矩计算

旋转固井是目前国际上最先进的固井新工艺之一，在固井施工中，通过转盘带动套管串旋转，提高水泥浆的顶替效率，提高固井质量。旋转固井的主要特点是通过机械方法施加扭矩使管串旋转。因此，扭矩的正确计算对于该工艺的设计与安全顺利施工具有重要的意义。根据旋转固井基本原理以及井下管柱软杆力学分析模型，建立了旋转固井扭矩计算模型和最大允许扭矩计算模型，并采用实际施工数据对该模型进行了验证。结果表明：采用所建立的旋转固井扭矩计算模型计算的结果具有较好的吻合性；在旋转尾管固井实际施工中，当水泥浆返入到套管重合段后，由于水泥浆的强携砂能力以及环间的减小，扭矩将升高。最大允许扭矩的计算模型能有效地指导现场安全施工，避免井下事故以及排除套管损坏带来的安全开采隐患。

TORQUE COMPUTATION IN ROTATION CEMENTING

Rotation cementing is one of the most advanced technologies in the world which is to make casing string rotate through turntable in order to improve displacement efficiency and cementing quality. Since rotation cementing is mainly characterized by forcing string to rotate through adding torque by mechanical means, the correct calculation on torque is of importance in both design and safe operation. So, based on rotation cementing theory and mechanical analyzing model on soft column of downhole string, the calculation models on rotation cementing torque and the allowed maximum torque are established which are evaluated by the actual constructing data. The result shows that the calculating result from the model on rotation cementing torque is consistent with the actual data, torque increases because of decrease on slurry's carrying capacity and annular space when slurry returns to casing's overlapped section in practical operation of rotation cementing while the calculating model on the allowed maximum torque can give an efficient instruction on field operation, avoid downhole accident, and mitigate risks brought by casing failures.