Omar Al Assad, Justin Barton, Kalpesh Singal, Shyam Sivaramakrishnan

Downhole Dynamometer Card Validation Method

Omar Al Assad, Justin Barton, Kalpesh Singal, Shyam Sivaramakrishnan General Electric - Global Research Center

Abstract

Downhole dynamometer cards (pump cards) are a critical input for modern rod pump controllers. They provide information about pump fillage and downhole pump loading that are used by standard variable speed drive (VSD) algorithms to maintain pump fillage as well as advanced control methods such as fluid pound avoidance to protect the equipment and extend its life. In addition, they represent an important tool for downhole pump diagnostics.

This study illustrates an approach to validate the accuracy of the calculated pump card by using a supervisory control algorithm that takes as an input pump cards computed from the two main methods used in the industry, the Fourier Series (FS) and Finite Difference (FD) methods. Changes in well conditions or operational set points can affect the above mentioned pump card calculation methods in a variety of ways. Therefore, the supervisory algorithm associates a confidence level to the obtained pump card by comparing in real time the differences between both of the computation algorithm outputs. A low confidence level can disqualify the obtained pump card for real time control purposes or for diagnostic purposes. A comparative analysis will be presented using simulation test cases for different downhole pump conditions and operational speeds.

Key words: Downhole Dynamometer Card, Rod Pump, Pump Card, Fourier Series Method, Finite Difference Method