The Research on the Biggest Borehole Curvature that Allowed through for the Rotating Casing

With the development of highly-deviated well cementing techniques, rotating casing cementing technology has got more and more attention. The rotating casing technique can improve the displacement efficiency of cement paste, and then enhance the quality of well cementation. In the stuck section, the rotating casing can redress the well to make the casing run sequentially. The casing endures shear stress in rotating, besides axial stress, bending stress, circumferential stress and radial stress which are produced by inside and outside casing pressure stress. These forces make it more complicated when calculate the maximum curvature in rotating condition than that without rotation. The paper, by analyzing the casing stresses in rotating condition, assumes a stress model of the casing infinitesimal for rotating casing. It puts forward the calculation method for the maximum allowable borehole curvature in casing bucking deformation, or when casing couplings and thread seal fail under rotating condition. It also determines the biggest borehole curvature that allowed though, laying a base for the design and construction of the highly-deviated well casing.