The Oooguruk offshore Arctic flowline system design, construction and operation satisfy the unique conditions presented by this shallow water Beaufort Sea location. The bundled 3-phase 12 × 16-inch pipe-in-pipe production flowline, 8-inch water injection, 6-inch gas lift/injection and 2-inch diesel fuel flowlines were installed along with power and communications cables offshore the North Slope of Alaska during 2007. The maximum water depth along the flowline route was only 7 feet but the location immediately offshore the Colville River Delta presented challenges with the flowline loading conditions, thermal interactions with the local environment and construction procedures. Key features of this flowline system include addressing flow assurance requirements for combined offshore/overland sections, strudel scour, subsea permafrost thaw consolidation, upheaval buckling, limit state design for bending, winter construction procedures and flowline leak detection systems. The subsea power cables consisted of separate cables for each conductor in order to be compatible with trucking all materials to the remote site. The dual fiber optic communications cables are being utilized with a distributed temperature sensing system to monitor the flowline burial conditions and supplement the multiple flowline leak detection systems. Introduction The Oooguruk oil field is located 6 miles offshore the North Slope of Alaska, in the Beaufort Sea. The site is partially sheltered from the more severe sea ice and wave conditions of the Arctic Ocean by its shallow water depths and a series of barrier islands offshore of eastern Harrison Bay. However, the field's shallow water location near the Colville River Delta provides its own challenges for the safe design, construction and operation of a flowline system to support the offshore field development. The flowline system transports 3-phase produced fluids, gas, water and diesel fuel and includes power and communications cables. Conventional pipeline design requirements must be integrated with the complex thermal interactions of the Arctic environment and the unique offshore arctic loading conditions. Pioneer Natural Resources Alaska, Inc. is developing the Oooguruk Unit along with partner, Eni Petroleum Co. Inc. on state leases in the Beaufort Sea, west of Oliktok Point (Hall, 2008.) Oil wells are being drilled from an artificial gravel island (Oooguruk Drill Site or ODS), located in four feet of water and tied back to new onshore facilities (Oooguruk Tie-in Pad or OTP) near drillsite 3H, within the Kuparuk River Unit (KRU.) Existing KRU facilities will process the produced fluids and transport the oil 40 miles further east to the Trans Alaska Pipeline System. KRU will also supply injection water and injection/fuel gas to Oooguruk. The Oooguruk flowline design needed to be cost effective and installed on a schedule matching Pioneer's field development plans. Flowline safety and minimizing impact to the fragile Arctic environment are fundamental project requirements for all North Slope field developments. Oooguruk follows BP's Northstar project as the second Beaufort Sea oil field to be developed using subsea pipelines (Lanan, 2001.) Additional planned Beaufort Sea field developments applying subsea pipelines include Eni Petroleum's Nikaitchuq oil field and other future projects.
A civil engineering perspective is presented on the design and construction of exploration and production islands in the nearshore Alaskan Beaufort Sea. Pioneer Natural Resources' 2003 Thetis exploration ice islands and the subsequent 2006 Oooguruk production island in East Harrison Bay are highlighted. Engineering design issues are discussed including special techniques required for the severe ice, wave and permafrost environment. The effectiveness of using frozen gravel foundations, which must be designed for seabed settlement, gravel thaw-settlement and creep settlement, are discussed. Construction techniques and schedules have been developed to make use of the readily available ice and gravel. Monitoring performance is an important post-construction activity. Potential issues are identified with preventative and remedial solutions described.Three offshore exploration wells were drilled using conventional land-based equipment from grounded ice platforms during the course of one winter. Subsequently, a gravel production island was built in the same area using material hauled from shore. Seabed settlement and the thaw instability of frozen gravel are uniquely addressed in the design and construction of the island.An economical approach has been described for building temporary exploration structures and permanent production structures in shallow, protected nearshore waters of the Alaskan Beaufort Sea. The methods have applicability for accessing smaller offshore oil and gas fields in the Alaskan Beaufort Sea and in other cold regions of the world where similar marine conditions exist.
This paper focuses on the coastal engineering aspects of the Oooguruk Project, which represents the third offshore production facility to be created in the Alaskan Beaufort Sea. The primary components of the project include a man-made island ("Offshore Drillsite") constructed during the first nine months of 2006 in a water depth of approximately 4.5 ft, and a 5.7-mile subsea flowline bundle installed between the Offshore Drillsite and the mainland shore during the following winter. Due primarily to its location in shallow water, the Oooguruk Project is exposed to less severe wave and ice conditions than the two offshore production facilities constructed previously in the Alaskan Beaufort Sea. Nevertheless, significant design challenges were presented by the financial constraints imposed by smaller field economics, and by the project's location in an active river delta subject to vigorous strudel scouring. The 4-cy gravel bag armor selected for use on the Offshore Drillsite represents a cost-effective means of protecting the side slopes against wave and ice attack, based on the experience acquired at previous exploration and production sites in the Alaskan Beaufort Sea as well as the island's performance during its first year in existence. The long-term rate of bluff recession at the site of the Oooguruk flowline shore crossing, 3.3 ft/yr, reflects two distinctly different oceanographic regimes: periods dominated by easterly storms, when erosion is modest or negligible due to reduced water levels during storm events, and periods dominated by westerly storms, when elevated water levels promote rapid erosion by permitting storm waves to impact the bluff face. The data acquired over the past three years indicate that ice gouging of the seabed is of negligible importance in the Oooguruk project area. Conversely, strudel scouring is widespread and sufficiently energetic to expose the flowline bundle. Of particular concern are man-made slots or holes in the winter ice sheet created to facilitate installation or maintenance of the flowline, in that they may promote preferential scouring on the flowline route.
The Oooguruk project is located in the Alaskan Beaufort Sea and consists of a 6 acre gravel drill site approximately 5 miles offshore in 4.5 feet of water. The drill site is connected to an onshore facility by a complex flowline system consisting of a 5.7 mile subsea buried flowline bundle which transitions onshore to a 2.3 mile traditional North Slope above ground flowline support system. Approximately 38 horizontal extended reach wells will be drilled into two horizons to develop the field. Drilling commenced in December 2007 and the field is scheduled to come online in 2008.This paper generally describes the Oooguruk field development concept, project execution strategy and the challenges faced during planning and construction. Details regarding island design, environmental design criteria, pipeline design and construction, and drilling rig capabilities are included in other technical papers.
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