Within 48 hours of Buffalo coming on-stream at the turn of the millennium, the facility was producing in excess of its 40,000b/d design capacity. It has since had an uptime of 98%. The field came into production 15 months after project sanction.
Buffalo is located in the northern Timor Sea, with Laminaria 12km to the north-west and Elang around 55km to the south-east. The Buffalo reservoir lies under the shallow water Big Bank – measuring 12km in length and about 3km in width. This is flat, with a water depth ranging from 27-30m, while its edges drop off nearly vertically to approximately 330m.
The field is operated by BHP Petroleum (50%), on behalf of Canadian Petroleum. (50%)
The Buffalo field was discovered in October 1996, when BHPP tested the Buffalo 1 well. The well flowed at 12,000b/d of light 53deg API oil. The oil has a particularly low GOR of 120.
Following the discovery, BHPP embarked on a 20-month 3D seismic acquisition/interpretation programme.
BHPP drilled a Buffalo delineation well, although a series of nearby exploration wells all failed to find additional reserves.
The field has probable reserves in excess of 20 million barrels. This could be produced at high rates with only two to three wells, and drained in less than three years.
For a field-production strategy, BHPP decided on a rig-installed, minimum wellhead platform, located on the Big Bank, tied back to a permanently moored, leased (BHPP operated) and converted FPSO, just off the bank, in deep water.
The FPSO used to develop Buffalo was originally built in 1976, as the 105,000dwt merchant tanker Spirit.
The overall leased FPSO, riser, rigid flowline and offshore installation contract was let to Modec, of Japan. The FPSO was converted into the Buffalo Venture at the Jurong Shipyard.
The Buffalo Venture has a length of 288m, a beam of 39m and a draught of 15m.
Sofec was responsible for the provision of single-point mooring. In turn, it subcontracted the swivel to Framo of Norway. Modec also subcontracted the design and project management of the process modules to Schlumberger, in Singapore.
The process modules were built by Hup Seng Engineering.
The FPSO left the shipyard for harbour trials on 8 November and departed Singapore for the Timor Sea on 18 November 1999. It has a crew size of 19.
WELLHEAD PLATFORM (WHP)
This was designed by Worley Engineering and built by ASC-Engineering, of Adelaide.
The five-wellhead unmanned steel platform is located on Big Bank. It produces crude oil (plus some associated gas and water) from two development wells. The WHP is remotely controlled from the FPSO, via an umbilical. Oil, gas and water flow to the permanently moored Buffalo Venture, via rigid steel flowlines and flexible catenary risers.
The 330t platform was towed from Adelaide in an upright position to the field, where it was installed by the Reading and Bates jack-up rig, Ron Tappmeyer.
ICON Engineering installed the wellhead platform. The structure was loaded out and transported in a 21-day tow, from Adelaide, in the vertical position. At Darwin, the mooring and installation equipment was added prior to departure for the field. ICON also carried out the hookup and commissioning.
The Buffalo project used rigid steel flowlines in a pliant wave configuration (provided by Coflexip Stena Offshore). This included distributed buoyancy and it was tethered to the seabed by two gravity bases per riser.
The wellhead platform was tied back to the Buffalo Venture by two 2km rigid steel three-phase lines, as well as one telemetry umbilical.
Two anchors sit in water less than 30m deep, while the other four sit at a depth of over 300m. The shallow/deep single-point mooring (SPM) was designed by Sofec, in Houston. Sofec contracted Malaysian Shipyard & Engineering to build the mooring.
The FPSO, showing the single-point mooring.
The Buffalo Venture FPSO.
The wellhead platform.
Process equipment on the Buffalo Venture.
Adding buoyancy modules during the riser installation.
Installation of the wellhead platform by the Ron Tappmeyer.
Towing the wellhead platform to the Big Bank.
The FPSO, showing single-point mooring and swivel.
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