A critical comparison of TDH calculation models in manual ESP design procedures

Abstract

The design of an ESP installation is started with the selection of the centrifugal pump, the heart of the system. To choose the ESP pump, one must calculate the installation's Total Dynamic Head (TDH) that is a measure of the required pressure increment to be generated by the pump under the operating conditions. Although this is a basic task in the installation design process, some controversies still exist in the industry about the way TDH should be calculated and many of the standard literature sources recommend an incorrect formula. The paper discusses the available TDH calculation models for single-phase and multiphase flow conditions. The traditional formula widely used in hand calculations is derived and its validity in other than gasless oil production is shown to be highly questionable. The correct formula for single-phase liquid flow is developed, and the calculation error committed by the traditional model is compared to the results of the proper formula. The incorrect model is shown to produce predominantly higher TDH values than the correct one; this fact seemingly increases the safety of pump selection. For increased reliability and in multiphase flow conditions the use of computer programs is advised.