Kraken Field UK North Sea

Kraken Field UK North Sea

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OVERVIEW

Project type: Before FEED for a heavy, high viscosity oil development 

Customer: Nautical Petroleum (subsequently bought by EnQuest) 

Location: UK North Sea 

CHALLENGE

The Kraken oil field is a heavy, high viscosity oil development with a low reservoir pressure. The challenge set by Nautical was to confirm the facilities requirement from wellhead to point of export to match the planned reservoir development and ensure that CAPEX and OPEX supported an economic project.

UNDERSTANDING

The challenge for Genesis was: 

  • To develop credible facilities solutions and justify concept selection to support an economic development; 

  • Confirm the technical feasibility for the relatively novel artificial lifting mechanism; 

  • Confirm the technical feasibility for the relatively novel reservoir pressure support mechanism. 

SOLUTION

The technical work of facilities development, definition, costing and option selection was undertaken following Genesis practice and with cooperation from suppliers of specialist equipment.  The selected concept was three drill centres tied back to an FPSO.  Downhole hydraulic submersible pumps (HSPs) were selected as the artificial lift mechanism, powered by hot water, with hot water injection for reservoir pressure support.  The open loop hot water hydraulic system created a water-phase continuous production stream at an elevated temperature to overcome many of the problems of high viscosity oil production.  The penalty was a high water loading on the FPSO, resulting in very large separators and water treatment systems, but alleviated oil/water separation and gas disengagement issues. Also, cold restart problems were minor as provision was made to circulate the hot water before opening the wells. Heat and power demands were high and majorly influenced the topsides and subsea facilities. 

The subsea and riser design requirements were also onerous with an extensive network of lines, all insulated to retain heat, operating at high temperature.  Material selection and stress issues were overcome and the use of riser base manifolds kept the number of risers to a manageable level for the turret selected. 

RESULTS

The team undertook much flow assurance work: extensive liaison with the supplier of the HSPs, studies to select the arrangement of heat and power provision and definition of the topsides and marine requirements of the FPSO.  Genesis supported Nautical and subsequently EnQuest, in discussions and negotiations with FPSO providers. The project passed the concept selection decision gate and progressed to the point of subsea and FPSO FEED contract award. 

The Genesis scope ceased at this point when Nautical Petroleum was bought by EnQuest and the project was later moved to Aberdeen.