Improving the alluminum drill pipes stability by optimizing the shape of protector thickening

Abstract

The methods of improving the durability of elements of the drill string were analyzed. A mathematical model of elastic deformation is developed and the loss of stability of aluminum drill pipe with inner and outer near-end protector thickenings in the middle section is investigated under the action of torque and axial compressive force. Based on the results of numerical analysis, we determined the magnitudes of critical loads: the torque and axial force, at which the loss of stability of pipe occurs depending on the different shapes of protector thickening. It was established that the shape of protector thickening does not exert significant influence on the magnitude of critical axial force, but to a larger extent affects the magnitude of critical torque at which the loss of stability of aluminium drill pipe occurs.

We proposed to improve the stability of aluminum drill pipe by optimizing the shape of protector thickening and received exponential dependence, which describes such a streamlined shape. Protector thickening of the optimal shape provides, compared to other characteristic shapes, better performance characteristics: higher stability of pipe and lower hydraulic resistance to the motion of washing fluid. We developed a new design of aluminum drill pipe with a protector thickening of streamlined shape that retains stability up to the critical values of axial force 36209 N and torque 152270 Nm.