First Arctic Subsea Pipelines Moving to Reality
Authors: Braden Anthony , Manikian Vic , Rice Dan , Swank Greg , Hinnah Dennis , Monkelien Kyle , Walker Jeff 
Published: October 2008

Two offshore development projects which involve subsea arctic pipelines are being proposed by British Petroleum Exploration (BP). Both projects are located in the central Beaufort Sea, offshore the North Slope of Alaska. The Northstar Development Project pipeline is located on State of Alaska submerged lands (Ref. 1). The Liberty Development Project pipeline is located on both State of Alaska submerged lands and the Federal Outer Continental Shelf (OCS) (Ref. 2). The State of Alaska has been conducting an ongoing technical review of the Northstar pipeline Right-of-Way (ROW) application over the last 30 months. The Liberty pipeline is in the preliminary engineering design stage. This paper reviews the engineering approaches being considered to accommodate unique arctic conditions, with emphasis on ice gouging and strudel scour and permafrost. The major environmental issues associated with a subsea arctic pipeline, including oil spill detection, will also be reviewed. The paper will focus on the regulatory aspects of the pipeline and ROW, rather than the design specifications of the pipeline itself.

Introduction

The Northstar Development Project (NDP) is located approximately 21 miles northwest of Deadhorse, Alaska, in 39 feet of water. Oil will be produced from an offshore man-made gravel island, processed to sales quality and transported through the Northstar pipeline. A utility pipeline is also proposed to be constructed within the same ROW. The offshore segment of the pipelines will be 6 miles. The pipeline route will be almost directly due south from the production island, will cross between offshore barrier islands and make landfall at Point Storkersen. The onshore portion of the oil pipeline would continue south and connect with the Trans Alaska Pipeline System (TAPS), Pump Station One. Alternative routes for the onshore portion of the utility pipeline to potential injection gas sources are being evaluated. Figure 1 is a map locating the Northstar project and proposed pipeline route(s). The Liberty Development Project (LDP) is located about 20 miles to the northeast of Deadhorse, in 22 feet of water. Similar to Northstar, the LDP proposes an oil sales pipeline and a smaller utility line within the same ROW. The offshore segment of the Liberty pipeline will also be about 6 miles long: about 1.5 miles on the Federal OCS and about 4.5 miles on State of Alaska submerged lands. The applicants preferred offshore route is south-southwest of the production island, with a landfall m the central Foggy Island Bay area, and about two miles west of the Kadleroshilik River. The onshore segment of the pipeline will tie-in to another new onshore pipeline currently being constructed for BP's Badami Development Project, approximately 14 miles east of Liberty. Figure 2 is a map locating the Liberty Development Project and proposed pipeline route. The two projects share a number of similarities. Both projects propose to use a man-made gravel island production platform, with stand-alone processing facilities. They also propose to install the pipeline(s) during the winter season using conventional earth-moving equipment operating from the sea ice surface; pipeline(s) will be laid in a trench and buried. The shore approach for both projects also involve burying the pipeline(s) some distance inland, then bring them above ground through a purpose-built gravel pad.