EFFECTS OF PIPE/FORMATION INTERACTION ON THE RUNNING FORCE IN HIGH-CURVATURE WELL BORES

摘要

The present paper outlines the derivation of a fourth order nonlinear differential equation of the radial displacement of a pipe as it advances along curved hole sections and presents selected finite element results for two pipe sizes of 114.3 and 127 mm running through curved holes of radii of curvatures of 10, 50, and 100 m. The paper also includes the effect of pipe/formation interaction on the running forces required to push the pipe through curved holes and identifies where contact takes place along the 90 degree buildup sections using a general purpose finite element program ANSYS. It was found that contact takes place at the top and bottom of the bore hole walls for short radii (R < 50 m) along the 90 degree buildup sections caused by pipe bending. However, it was observed that contact takes place mostly at the bottom side of the bore hole for radii of curvatures greater than 100 m. The change in directions of the pipe as it advances further along curved sections was found to increase the running force as well as the bending stresses in the joints. Finite element results revealed that the running force at the k.o.p decreases by 71% as the hole radius changes from 10m to 50 m and by 90% as the hole radius changes from 10m to 100 m.