DESIGN AND PERFORMANCE ANALYSIS FOR EQUIDISTANT LINING OF PDM

PDM(Positive displacement motor)is suitable for drilling directional wells because of its advantages,but it still could not be used for deep wells,high-density mud wells and small-curvature wells widely.The PDM's conventional lining is a screw surface,it is a variable-thickness elastomer stator.It has poor capability to withstand the high mud pressure and a soft mechanism characteristic,is easy to leak,wear and tear,and its efficiency will descend continually.Therefore,the development and application of PDM with the short,high-power,high pressure drop and low rotation speed has become an important tache to improve the drilling efficiency and save drilling cost.In this paper,the equidistant rubber lining of PDM was designed,the mechanics experiments of NBR were carried out,the FEA models of equidistant lining and the conventional one were established for calculating.The results indicated,under the same mud pressure when comparing with the conventional one,the equidistant lining has less deformation;with the same magnitude of interference,it has a better seal capability.The equidistant PDM can gain the same torque with less length than the conventional one.