Evaluation and prediction of the performance of positive displacement motor (PDM)

Positive displacement motors (PDM) are being used extensively due to the in creased drilling of horizontal/extended reach wells as well as the deepenin g of vertical wells. Knowing motor performance is essential to ensure drill ing success. To enhance the technology and make the system effective, a com plete performance envelope of the motor in use is required. In the traditio nal way, the performance of a PDM can be described by pressure drop vs. tor que and rotational speed. For a particular type of motor, the RPM curves ar e different at different flow rates. :Although it is very difficult to full y describe the motor performance with limited testing, a good prediction is critical for motor selection and operation. In addition, the performance o f a PDM operating with compressible fluid decreases drastically as compared to the operation with incompressible fluids. In this paper, analysis of th e test results for various PDMs from different PDM suppliers are presented. Correlations have been developed, based on the test data, to describe PDM performance with incompressible fluids.