Alaskan Beaufort Sea Exploration and Production Islands - Civil Design and Construction

Abstract

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.

Coastal Engineering Design of the Oooguruk Project

“…Ice loads also were considered in the design of the Offshore Drillsite (Lucas, 2008), but are relatively mild due to the shallow water depths at the site. Ice loads also were considered in the design of the Offshore Drillsite (Lucas, 2008), but are relatively mild due to the shallow water depths at the site.…”

“…An overview of the field development is provided by Hall (2008), while the design of the civil facilities and pipeline bundle are discussed by Lucas, et al (2008) and Lanan, et al (2008), respectively. This paper focuses on the coastal engineering aspects of the Oooguruk Project, with emphasis on four specific topics: (1) oceanographic design conditions, (2) slope protection for the offshore drillsite, (3) erosion of the mainland shore at the flowline shore crossing, and (4) potential disturbance of the flowline by ice gouges and strudel scours.…”

Oooguruk Project Field Development Concept and Execution

“…The island is designed to survive the environmental conditions for the area (Leidersdorf, 2008;Lucas, 2008). The gravel drill site has approximately 6 acres of working area and an elevation of approximately 13 feet above mean sea level with slope protection provided by gravel bags.…”

“…Otherwise, the time required for the drill site to settle into the sea floor would have been substantially longer, lingering over several seasons thus impacting the stability of the drill site facilities (Lucas, 2008). The ice along the offshore haul road route and over the drill site location was completely grounded.…”

“…As such, an impermeable material was installed vertically in the gravel on three sides of the conductor area (Lucas, 2008). The gravel remains frozen during the entire mining, hauling and dumping operations.…”