Gas Effect in ESP System Stage by Stage Analysis

Abstract

Abstract One of the main problems regarding the use of artificial lift method by Electric Submersible Pump (ESP) systems is the presence of gas in the pump. This paper presents and describes an analysis of ESP systems using a stage by stage calculation to determine intake and discharge pressures to adjust total dynamic head (TDH) for each stage of the pump. The modeling was designed acknowledging free gas in the pump and iterative calculations are applied to recalculate, for each stage, fluid characteristics and physical properties, such as viscosity, density, formation volume factor, surface tension, solubility ratio, oil-gas ratio (OGR), and other flow characteristics along the tubing, like temperature and pressure. Developed modeling validation was achieved by comparisons in two scenarios. In the first one, fixed values of intake pressure and changeable values of GOR were used to assess gas effect. In the tests for the second scenario, fixed values of OGR and changeable values of intake pressure were used. Necessary research was done through a developed computational tool used to size ESP components. The results were different from those obtained with usual calculations and it may be implied that the developed modeling is more accurate to determine parameters related to this artificial method. Also, the results were more consistent and closer to the actual behavior of multiphase flow phenomena within the tubing because each stage has its characteristics individually evaluated. These observations may have effect on the number of pump stages and influence in choosing the adequate equipment of the system.