An array of new technologies either commercial or nearly commercial is set to improve recovery from fields with subsea-completed wells.
The recent Offshore Technology Conference highlighted several technologies, including those for lowering subsea drilling and operations costs as well as those for subsea processing, multiphase boosting, and wet-gas compression.
Statoil
Statoil ASA has several initiatives for improving oil recovery from subsea-completed fields. Statoil’s average recovery from these fields is 45.1%, but presentations at OTC said the company aims to increase this by 10% to move closer to the 60% recovery factor for its fields completed with dry-tree wells off platforms.
One of its nearly complete projects is the deployment of a subsea processing station at Tordis field off Norway (OGJ, May 7, 2007, p. 20). Developed by Kongsberg FMC and scheduled for installation in August, the station includes a separation vessel, desander, and injection pump for removing and disposing of most of the water and sand into an injection well as well as a multiphase booster pump for moving the oil, gas, and remaining bs&w to topsides processing.
With this subsea installation, Statoil expects the field’s recovery factor to increase to 55% from the current 49%, which equates to an additional 35 million bbl of oil during the next 15-17 years.
Statoil is also lowering the costs of drilling and completing subsea wells. Its R&D efforts have developed a riserless light-well intervention vessel for reducing by one-third the costs of wireline service previously done from a semisubmersible. The vessel will be ready for work in 2008 and will operate at a cost of $150,000/day.
Another technology Statoil expects will reduce subsea well costs is through-tubing rotary drilling equipment placed on a dynamically positioned rig. The technology will allow sidetracks to be drilled in subsea wells for additional drainage. Statoil expects the system to be operational in 2007 and estimates that each sidetrack will cost $10 million.
Statoil plans to install a subsea raw seawater injection pump to support the reservoir pressure in Tyrihans oil field from Day 1. It expects Tyrihans to start producing in 2009, depending on processing capacity on the Kristin field semisubmersible production unit.
The company also is involved in developing subsea wet-gas compression and may start deploying the technology in 2011-12.
Last year Norsk Hydro, which now is part of Statoil, awarded Aker Kvaerner a contract for a subsea compression pilot for Ormen Lange gas and condensate field in the Norwegian Sea. Aker Kvaerner expects a final decision on the deployment in 2011.
Total
Later this year, Total E&P Nederland BV will install the world’s first all-electric subsea production trees on two gas wells in 121 ft of water off the Netherlands in K5F field. Total expects the installation to improve production. Cameron Drilling & Production Systems manufactured the trees.
All-electric trees also can be a part of Cameron’s CAMFORCE subsea processing system, which includes a Curtiss-Wright Flow Control Corp. and Leistriz AG subsea twin-screw multiphase pump, an all-electric separation unit, and a multiple application reinjection system (MARS). BP will install the first MARS on King oil field in the Gulf of Mexico.
Cameron describes MARS as a USB (Universal Serial Bus) port for subsea completions that allows installation of multiple processing technologies directly onto the subsea completion without disturbance to existing equipment. These technologies include such components as boosting, metering, and well stimulation.
Petrobras
Petrobras is another company with plans to deploy more subsea technology in several fields off Brazil, especially in those with limited deck space for additional processing equipment. As with Statoil in Tordis field, Petrobras has needs for separating out water from the oil subsea and reinjecting the water into disposal wells as well as for subsea boosting of the produced oil.
One problem it faces is the breaking of oil-water emulsions from fields producing heavy oil, such as the 20° gravity oil from Marlim field.
Presentations at OTC said Petrobras expects to implement subsea processing off Brazil in the next 5 years, with such mature fields as Marlim and Pampo having immediate potential for such equipment. Future needs are in fields such as Marlim Sul, Albacora, Marlim Leste, and Jubarte.
Petrobras will install subsea multiphase boosting in its Jubarte Phase II development. The company recently awarded Aker Kvaerner a contract for eight subsea boosting pumps as part of the artificial lift required to produce the heavy oil found in the field.