Nodal Analysis by Use of ESP Intake and Discharge Pressure Gauges

Abstract

Summary Electrical submersible pumps (ESPs) are often not only equipped with bottomhole-pressure gauges, but more frequently contain discharge pressure gauges as well. This combination of gauges can be used to extend the classical nodal-analysis approach with an extra component. Inclusion of an additional discharge pressure gauge allows for the construction of two sets of inflow and outflow equations: one set where the selected node is the pump intake and one set where the selected node is the pump discharge. A graphical method demonstrates how to evaluate these two sets of equations simultaneously. This graphical method is then further condensed into a few simple and easy to use guidelines. Six possible situations can be faced during operation of an ESP: improving/decreasing performance upstream of the intake pressure gauge, improving/decreasing performance between the intake and the discharge pressure gauges, and improving/decreasing performance downstream of the discharge pressure gauge. Analysis of the changes in intake and discharge pressures can quickly identify which one of these six scenarios is affecting the production performance, thus enabling the breakdown of the production system into the reservoir performance, ESP performance, and tubing performance. Several field examples of oil wells completed with ESPs that contain intake and discharge pressure gauges illustrate the benefit of this procedure. This method is applicable for any downhole pump with intake and discharge pressure gauges. Even if pump maps are not available, or when the well's liquid-flow rates are not (accurately) known, it is a reliable method to localize downhole production problems. This approach makes full use of the advantages of multiple downhole gauges; nodal analysis in combination with intake and discharge pressure gauges is a quick, inexpensive, and powerful method to determine the location of production problems, so appropriate actions can be taken to maximize well performance.