Analysis of Possible Applications of Dual ESPs—A Reservoir-Engineering Perspective

Abstract

Relatively few field installations of a dual-electric submersiblepump (DESP) completion have been reported. In general, the purpose of the second pump was either to increase the pumping capacity, or to act as a backup to improve the reliability of the pumping system. However, DESPs potentially can address a much wider range of reservoir management challenges. This paper will analyze the performance of a DESP in a range of reservoir scenarios. It will show how DESP performance can be modeled by use of commercially available, coupled, well-performance and reservoir-simulation tools.Four DESP applications were analyzed. Where possible, the robustness of the numerical-modeling results will be compared with analytical predictions. DESPs gave improved oil production and recovery in reservoirs with strong aquifer support and became progressively more attractive in a layered-reservoir scenario as the pressure difference between the production zones increased. However, while DESPs had no significant advantages in a long, horizontal well placed in a homogeneous reservoir, they can increase recovery in a tilted, layered reservoir. A slim, deepwater well completed with a lower-capacity downhole pump and a larger (multiwell) seabed booster pump was shown to be a potentially attractive solution for some reservoir developments.This work provides a comparison of the drivers for the choice of a single electric submersible pump (SESP) and a DESP in the scenarios studied. It illustrates a modeling methodology and provides DESP-selection guidelines, thus aiding the increased application of this technology. MethodologyThe studies were carried out with the help of a two-phase (oil and water) simulation of a 3D reservoir model using the Eclipse TM 100 package. Wellflo TM was used to model the vertical-lift performance for the produced fluids through the wellbore and the pump performance under the various reservoir conditions. The results obtained were transferred to the Eclipse TM models in the form of vertical-flow-performance (VFP) tables. A detailed description of the model used as input for comparison of the Eclipse TM , the Wellflo TM and the analytical solutions is listed in Tables 1 and 2. Simulation results using the Eclipse TM and Wellflo TM programs were compared with appropriate analytical solutions where possible (see Appendix).