ANALYSIS OF DRILLSTRING WHIRLING

While drillstring rotates along its axis,its rotating along the wellbore axis is defined as whirling.The concept,causes and states were described,while the possibilities and main influences of different types of whirling were analized by working out the force used to overcome the friction under different whirling angular velocity.It is thought more force would be used while forming the whirl,and it becomes static once formed,while decreasing annular could not increase the frequency of alternate stress infinitely.The paper explain the causes of drill collar of f-center wear and bottom hole multi-convex graph based on drillstring whirling,the influence to well deviation was analized too.