In order to select the most suitable pump, Refer to the pump selection data table in the manufacturer’s catalog for pump type, range and pump performance curve. Based on expected fluid production rate and casing size, select the pump type which will be operating within the recommended operating range and nearest to the pump’s peak efficiency.
When two or more pump types have similar efficiencies at the desired production rate, the following recommendations should be considered to select the most adaptable pump to the well conditions:
The shape of the pump performance curve:
The ability of a pump to adapt to changes in well performance depends on the characteristic shape of the pump performance curve. A pump with a steep characteristic (i.e. large change in head with respect to flow rate) is less suited to a well with poorly defined inflow performance (IPR), especially if it is intended to produce with a fixed drawdown. For such pumps, a small loss in IPR translates to a large fall in pump intake pressure and may result in gas locking. Conversely, the head produced by a pump with a flatter characteristic will change less for a given change of flow rate and can therefore be used over a wider variety of IPR’s with limited changes in intake pressure.
The presence of free gas in the tubing above the pump changes the fluid density, consequently reduces the required discharge pressure. Also the performance of centrifugal pumps is considerably affected by the presence of free gas in the pumped fluid. The pump starts producing lower than normal head as the produced GLR (Gas to Liquid Ratio) at the pumping conditions increases beyond a critical value. The critical value of the ratio or percentage of free gas present at the pump intake to the total volume of fluid depends on the pump impeller design (typical critical values are shown in the article “ESP: Gas handling device “). Therefore, it is essential to determine the percentage of free gas by volume at the pumping conditions in order select the proper pump and gas handling device (if required).
Percentage of free gas by volume:
Assuming that Solution GOR (Rs), Gas Volume Factor (Bg) and Oil Formation Volume Factor (Bo) are known, the total volume of fluids and the percentage of free gas released at the pump intake should be calculated.
Centrilift has established a nine-step procedure to design the appropriate electrical submersible pump in order to have an efficient and cost-effective performance. This article gives an overview of the ESP nine step design procedure and outlines the procedure as a manual process to illustrate the design steps. Each of the nine steps will be explained in detail in the next articles.
Specific examples will be worked through in each step of the ESP design.
This nine step procedure is a basic hand-design of simple water and light crude oil. For more complicated well conditions, such as high GOR, viscous oil, high-temperature wells, there are many of available ESP design software (e.g. Prosper software – Product of Petroleum Expert; Pipesim software – Product of Schlumberger; Autograph PC software – Product of Baker Hughes; Solution Sizing Software – Product of General Electric; DesignRite Software – Product of Schlumberger). The fashion of use of each of these ESP design software will be presented and explained in detail in upcoming articles in our website.