The Parque das Conchas (BC10) field offshore Brazil, operated by Shell and owned together with ONGC and QPI, has challenging reservoir conditions. Several subsea fields with viscosities ranging from 1 to 900 cP and gas volume fractions between 5% and 70% require subsea boosting to lift production fluids to the FPSO facility. Since first oil in 2009, a unique method of subsea separation and boosting has been deployed on BC-10, utilizing vertical caisson separators with Electrical Submersible Pumps (ESP's) to pump well fluids from up to 2000m water depth to the FPSO facility. Maintenance of the ESP assemblies requires an intervention using a MODU (Mobile Offshore Drilling Unit).
Shell pursued an alternative subsea boosting solution using Mudline Pump (MLP) technology, with the objective to reduce field Opex and increase redundancy. The MLP was conceived as a retrofit module, which was to be fully compatible with the existing infrastructure. This includes using existing variable frequency drives, high voltage umbilicals, subsea mechanical interfaces, controls, hydraulics, and chemical injection. Despite the prior development of a 3 MW (megawatt) MudLine Pump (MK1), the specifics of the BC10 application required further development and qualification. The design pressure was increased from 5,000 psi to 7,500 psi, which required requalification of motor and barrier fluid circuit components. Additionally, the challenging multiphase flow conditions led to the development of an innovative control strategy to maximise the production window, whilst ensuring safe operating conditions for the pump within the existing system constraints.