Mechanics Analysis And Application Of Bottom Hole Assembly In Re-entry Well

Based on the bottom hole assembly (BHA) for the study, considered the structure of drilling tolls and the gap between the wall and the drilling tools, and the well-path, the nonlinear mechanical model for BHA is established. The model can describe the slim drilling tools and the small gap of re-entry wells. At the same time, for the free contact and friction at different depth and different direction of the circumference, the " gap element of multi-contact and friction" and spatial beam element are applied to analyze with finite element for nonlinear mechanical problems for BHA .The contact state of BHA with the wall and the forces and the deformation of drilling bit is acquired, the ability of BHA at re-entry well is completed and the software is complied ,combined the oblique method of drilling tools. For BHA of re-entry well, the holding and descending BHA is designed for vertical wells, while the increasing holding and descending BHA is designed for 10°, 30°, 50°, 70°inclined segment. The effect of the structure of drilling tools (the diameter of stabilizer, where the stabilizer is placed), WOB, inclination angle, the expansion rate of the drill bit to the ability of BHA is analyzed, and these are theoretical basis for the design of BHA and the selection of drilling parameters. Through the application of Xing 4-40-Cexie623 well, the deviation between the theoretical inclination ratio and the inclination ratio at drilling of the designed tower drilling tools is -0.14°/ 100m,so the reliable analysis theory for the design of BHA and practical BHA can be acquired.