Thesis (M.Sc.) - Cairo University - Faculty of Engineering - Department of Metallurgical Engineering

Many studies assumed that wellbore instability issues were due to physical and chemical interactions between rocks and drilling fluids. However impact of drillstring vibration on wellbore stability was neglected. This work focus on: a- determining type of vibration mechanisms and major factors lead to drillstring shocks on wellbore wall; b- studying different rock failure mechanisms and computing drillstring vibration limits that can harm wellbore. Investigation results in a clear correlation between whirl vibration and initiation of lateral shocks on wellbore wall. Drill collar length and drillstring revolutions per minutes (RPM) are the major factor of developing these shocks. Drillstring vibration can collapse wellbore by three failure mechanisms: rock compressive failure, rock fatigue, and reduction in rock strength. Authors developed a new model to predict hot ranges for drillstring vibration that collapses wellbore that can be used as an early detector for harmful shocks of drillstring vibration on wellbore stability

Issued also as CD