The Parque das Conchas development is located in the BC-10 block 75 miles southeast of Vitoria int the Campos Basin, offshore Brazil. Shell is the operator with a 50% equity share, with joint venture partners Petrobras (35%) and ONGC (15%). The current development consists of three hydrostatically pressurized medium to heavy oil reservoirs (Abalone, Ostra and Argonauta B West) in water depths ranging from 5430 ft to 6310 ft (1655 m to 1923 m). One of the key enabling technologies at the heart of the subsea system infrastructure is the mudline boosting system consisting of Modulo de Bombeio or Pumping Unit (MOBO) caisson ESPs installed inside Artificial Lift Manifolds (ALMs) 1) . Oil from the individual subsea wells flows into the MOBO caisson ESPs and from there the ESPs pump the oil up to the floating production, storage and offloading (FPSO) vessel. The ALMs are located approximately 5½ miles (8.85 km) from the FPSO (see Figs. 1 and 2). This paper will describe how the design for these special longlife ESPs was developed, how a stack-up test was performed on land in the US, and how the pumps were deployed in the field. In the second part, the first operations for pulling two of the ESPs are described. The whole assembly consisting of the MOBO, 32-in. caisson and ESP completion was lifted in open water to the rig with a total assembled weight of 169 tons (171.7 metric tons). Figure 1: BC-10 Field layout overview.

The Shell operated Parque das Conchas fields of the Brazilian deepwater block BC-10 utilize ESPs as the sole artificial lift method. Unlike traditional in-well deployed ESP systems, the ten BC-10 ESPs are deployed inside relatively shallow – 100m - caissons distributed across three subsea gathering areas, or Artificial Lift Manifolds at water depths from 1650 to 1900m. The integrated caisson, ESP and inflow/outflow valving is deployed and retrieved as a single unit and hence derives the name of a Pump Module, or Modulo de Bomba in Portuguese, or MOBO for short. As ESPs have much shorter run lives compared to the approximate 25 year field life, the BC-10 subsea operations asset team is responsible for managing and executing the rig based ESP replacement intervention campaigns, or Mobo interventions. As of 2015, nine ESP replacements have been executed in four campaigns. This paper examines the diverse aspects associated with the ongoing efforts to maintain the artificial lift system of BC-10 before, during and after a rig intervention campaign. Topics covered include the ESP failure analysis, equipment sparing philosophy, equipment and tooling preparations, offshore execution, vendor relationships and overall project management. Finally, learnings obtained during the four years of near continuous preparation and execution of MOBO interventions are discussed along with some planned future improvements.

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The ESP system is an important artificial lift method commonly used for medium-to high-flow-rate wells for subsea developments. Multiphase flow and viscous fluids can cause severe problems in pump applications. Free gas inside an ESP causes operational problems and lead to system failures. Under two-phase flow conditions, loss of pump performance or gas lock condition can be observed. Under viscous fluids, the pump performance degrades as well. This paper provides a model 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 theoretical study includes a mechanistic model based on for the prediction of the degradation due to bubble accumulation. The model comprises a one-dimensional force balance to predict occurrence of the stagnant bubbles at the channel intake as a main cause of deviation from homogeneus flow model.The testing at Shell"s Gasmer facility revealed that the ESP system performed as theoretical over the range of single flowrates and light viscosity oils up to Gas Volume Fractions (GVF) around 25%. ESP performance observed gas lock condition at gas fraction higher than 45%. Homogeneous Model has a fairly good agreement with pump performance up to 30% GVF. Pump flowrate can be obtained from electrical current and boost for all range of GVF and speed. Correlation depends strongly in fluid viscosity and pump configuration.The main technical contributions of this study are the determination of flow patterns under two important variables, high viscosity and two-phase flow inside the ESP to predict operational conditions that cause pump head degradation and the beginning of bubble accumulation that lead to surging . For similar applications, pump performance degradation can be predicted in viscous environment and two-phase flow conditions. 1.

This paper provides an overview of the qualification process of the highest power ESP ever installed into a hydrocarbon production system for artificial lift. The unit was selected and configured to interface with the existing deepwater offshore inflow and outflow systems without changes to the completion string or riser. The overall objective was to maximize the production capacity in terms of lift and flow rate given topsides power supply and running diameter constraints. The initial requirement was to identify a suitable supplier that could provide a hardware solution with a high technical readiness level. The team first reviewed the hydraulic performance of the existing production systems and modeled the potential for improvement with the new equipment configuration given an expected efficiency and power factor for the proposed motor. The ESP equipment was configured with components that had multiple qualification and validation testing requirements. The motor and associated high voltage connector were key differences from the existing systems. The pump design was modified to accommodate projected operating ranges including additional stages for the necessary head requirements. The new subcomponents were subjected to application specific testing to qualify the designs for operating conditions with multiple technical assurance reviews conducted by the end user and supplier company technical discipline authorities. Full scale flow testing at a dedicated facility (Gasmer) for Caisson gas/liquid separator ESP systems, and component installation stackup tests for fit and interfaces were completed to validate the performance in multiphase flow and identify hardware changes needed for the completion design and the intervention procedures. The qualification program was completed successfully, and a unit was deployed without incident, into a deepwater mudline caisson that has since been operated for live hydrocarbon production. The performance has met expectations and the unit efficiency and demonstrated capacity will allow for increased production. The use of a detailed qualification program that includes focused testing for individual system components and validation through full scale system integration testing ensures flawless deployment of technology improvements for critical well applications. The system is the highest power ESP for hydrocarbon production. It includes a novel completion design to accommodate the effective running diameter for the motor. The use of a unique shroud design to stay within running diameter constraints allowed for minor modifications to the completion string design without system changes to the riser or caisson. This was both cost effective and reduced the time needed for development and manufacturing.