PCP Axial Load: Theory and Lab Results

Abstract

Accurate estimation of pump axial load in Progressing Cavity Pump (PCP) applications is an important aspect of the installation design. It affects the calculation of rod stresses, and therefore the determination of the rod string torque capacity. In deviated wells, it also directly affects the calculated rod-tubing contact loads, and therefore the evaluation of wear related issues. This paper discusses the current theory related to the calculation of axial load in PCP applications, in light of laboratory test results obtained with 25 different pump models.

The axial load is normally estimated by multiplying the differential pressure across the pump by an effective pump cross sectional area. However, given the complexity of the pump geometry, it is not straightforward how to properly calculate this effective area. In the paper, it is shown that intuitive choices, such as the circle defined by the rotor minor diameter, the circle defined by the rotor major diameter, or the pump cavity area, do not yield adequate results.

A new method is suggested that not only matches quite well the extensive laboratory data for single-lobe pumps but also matches reasonably well the limited data available for multi-lobe pumps.

 

Author: Alhanati, F. J. S., & Skoczylas, P.

Publisher: SPE Annual Technical Conference and Exhibition, 26-29 September, Houston, Texas

Year: 2004

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