Prediction of Wear and Stresses While Drilling Through a Riser Flex Joint

Abstract

Flex joints in risers introduce abrupt directional changes along the drillstring. High drillstring stresses and flex joint wear rates are introduced, particularly when the drillstring tension is high. An analysis procedure is presented which finds the drillstring/flex joint contact loads in the vicinity of the flex joint as a function of the tension in the drillstring at the flex joint. The tensile and contact loads of the drillstring at the riser are used to estimate the wear rate on the flex joint and the axial and bending stresses in the drillstring. This example shows the value of the procedure in estimating maximum allowable angles for the flex joint.