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This paper provides insight into the Caisson ESP Technology Maturation for subsea boosting systems with high GOR and viscous fluids. It will focus on the developmental research on the effects of viscosity and two phase (liquid & gas) fluids on electric submersible pumps (ESPs), which are multistage centrifugal pumps for deep boreholes. The Electrical Submersible Pump (ESP) system is an important artificial lift method commonly used for subsea boosting systems. Multiphase flow and viscous fluids cause problems in pump applications. Free gas inside an ESP causes many operational problems such as loss of pump performance or gas lock conditions (Barrios 2010 [6]). The objective of this study is to predict the operational conditions that cause degradation and gas lock. This paper provides a summary on the Technology maturation for a high scale ESP Multi-Vane Pump (MVP) for high GOR fields to in support of Shell's BC-10 developments. These novel projects continue the long tradition of Shell's leadership in the challenging deepwater environment. This paper will describe the capability and effects of viscosity and two phase (liquid & gas) fluids using a MVP 875 series G470 as a charged pump in a standard ESP system 1025 series tandem WJE 1000 mixed-type pump. Extensive testing and qualification of the subsea boosting system was undertaken prior to field considerations. Testing was conducted at the world's only 1500-hp ESP test facility capable of controlling multi-phase fluid viscosities and temperatures. A comprehensive suite of tests was performed in conjunction with Baker Hughes Centrilift replicating the expected conditions and performance requirements for Shell's deepwater assets. This paper describes the subsea boosting system maturity process, and reports the effects of viscosity and two phase liquid - gas fluids on ESPs. The test facility work was performed using pumps with ten or more stages moving fluids with viscosity from 2 to 400 cP at various speed, intake pressure, and gas void fractions (GVF, aka gas volume fractions). The testing at Shell's Gasmer facility revealed that the MVP-ESP system is robust and performance tracked theoretical predictions over a wide range of two-phase flow rates and light-viscosity oils

Computational Fluid Dynamics (CFD) is used to investigate the hydraulic performance of a centrifugal pump within the electrical submersible pump (ESP) unit in single-phase flow. The geometry consists of a three-stage centrifugal pump with an impeller and a diffuser in each stage. The stage performance is influenced by the inlet and outlet conditions of the stage, and therefore, three stages were modeled. The simulations were run at 3,500 RPM for various flow rates within the operating range. The k-ε turbulence model and the shear stress transport (SST) turbulence model were used to compare the capabilities of the model on performance predictions. Simulations were run in steady and unsteady flow conditions with a single vane and a full pitch model. Hydraulic performance such as efficiency, pump head, and break horse power (BHP) obtained from numerical analysis were compared with the test results to validate the CFD model. The comparison results revealed that the CFD overpredicts the pump head and underpredicts the BHP by 5 to 10%. The discrepancy between measurements and predictions are reasonable because the hydraulic leakage and bearing power losses are not modeled in CFD. The overall predicted efficiency is higher than the measurements because of overpredicted head and underpredicted BHP. Comparing numerical simulations with different turbulent models showed no significant difference between the k-ε model and the SST model. The steady/ unsteady flow comparison also showed similarity in the hydraulic performance near the best efficiency point. For design purposes, steady flow simulation with a single vane and the k-ε model were used to cut computational time.

The Peregrino field is located in Campos Basin approximately 85 km offshore from Cabo Frio in Brazil. The oil in Peregrino is heavy with a gravity of 14° API. First phase of field development will be accomplished by two drilling capable wellhead platforms tied back to a central FPSO. A Total of 30 producer and 7 water injector wells are planned for this phase.One of the most critical factors in offshore operations is physical space. Flow allocation devices like test separators can be bulky due to the large capacities required to operate with heavy oil. These and the gear required for their control and efficient operation like heaters can be among the most space consuming equipment onboard. Multiphase flow meters are also available for flow allocation purposes; however its accuracy is highly impacted by heavy oils. The slow gas flashing out of heavy oils affects the representativeness of necessary pressure-volume-temperature (PVT) characterization.Downhole Venturi meters were other alternative considered when deciding about the flow allocation method for Peregrino. These were initially left behind basically due to two factors; the economical impact related with a single unit required per well and the limited data available regarding its uncertainty with viscous oil. The changing oil/water conditions in Peregrino can be a challenge from a viscosity modeling point of view. Therefore a decision was made in favor of the flow allocation based in Electric Submersible Pumps (ESPs) performance. This technique has been used with success in wells with very high water cuts but it's a novel approach in viscous oil.Improving the accuracy of this approach required multiple tests with the submersible pump models selected for Peregrino field. The tests were performed in a high viscosity flow loop in Claremore and covered a wide range of viscosities and speeds. This paper outlines the test results and presents the principles of flow allocation in Peregrino.

The paper reports on developmental research on the effects of viscosity and two phases, liquid–gas fluids on ESPs which are multi stage centrifugal pumps for deep bore holes. The test facility work was performed using pumps with ten or more stages moving fluids with viscosity from 2 to 2500 cP at various speed, intake pressure and Gas Void Fractions (GVF). For safety considerations the injected gas was restricted to nitrogen or air. The results are a series of curves representing the performance degradation of the pump. Note that in some cases the pump performances actually improved with increasing viscosity. The resulting information will allow a better understanding and more accurate prediction of performance than has been previously available. The data indicates a significant difference in performance correction when compared to the information available from the Hydraulics Institute.