HVDC Enables Subsea Active Production Technology

Abstract

Abstract A growing number of projects are employing some form of subsea processing. Integrated system approaches to subsea processing, commonly known as SubseaActive Processing Technologies (SAPT), can require a great deal of power. Subsea boosting and/or separation pumps can easily reach 3 MW each; withmultiple pump installations quickly adding up to a substantial demand on a hostfacility. When the power transmission distances approach 100 km or more, ACpower distribution becomes less and less practical. For this reason, powerindustry leaders envision the future installation of offshore electricalutility infrastructures based on High Voltage DC (HVDC) TransmissionTechnology, just as they are presently employed for land based utilities. Taking advantage of these large HVDC offshore power grids for small, isolatedsubsea installations requiring only moderate power levels calls for adaptingHVDC technology to a scale sized to the power requirements of theseinstallations. The HVDC Power Buoy concept, proposed for isolated SAPTinstallations requiring subsea power in the range of 10 to 20 MW, is one suchadaptation. This paper will present the HVDC Power Buoy concept and its keycomponents; the benefits and drivers for its development; the perceivedqualification challenges as well as the target applications for thetechnology. Introduction To introduce the HVDC Power Buoy concept, a subsea completion, with subseaprocessing included, with a tieback distance of 150 km and a total subsea powerrequirement of 15MVA @ 0.7 PF (10.5 MW) is used as a demonstrative test case. First, the case of providing AC power to the subsea completion is considered toillustrate the issues associated with AC power transmission. Then, as analternative, an HVDC Power Buoy with a HVDC power transmission link ispresented to show the advantages of this approach. Since the HVDC PowerBuoy is a new concept, the technical gaps are then identified with suggestedpaths forward to mitigate said gaps. By enabling the use of HVDC powertransmission, the HVDC Power Buoy concept is expected to make Subsea ActiveProcessing Technology practical for many isolated and otherwise stranded subseafields.