Installation of a Subsea Completion In the Canadian Arctic Islands

Abstract

Abstract In April 1978, the world"s first Arctic subsea producing gas well was successfully completed and produced to shore by means of a wet tree and flowline bundle. This paper describes the unique design of a combination land and offshore drilling rig and air-transportable blowout preventer for drilling and completing subsea wells from a floating ice platform. The design, installation and connection of the flowline bundle and shore crossing protection system is described as an integral part ofthe over-all completion. The completion demonstrated the ability to develop the extensive gas reserves offshore in the Canadian Arctic Islands. INTRODUCTION In 1974, Panarctic Oils Ltd. developed a system to drill exploratory gas wells offshore between the Canadian Arctic Islands(1,2). Since 1974, exploratory drilling from ice platforms (Figure in full paper) has been successfully conducted, proving the existence of substantial natural gas deposits offshore in the Arctic Islands. As this system of exploratory drilling has been effective in water depths ranging from 60 to 365 m and up to 35 km from shore (Fig. 1), it is apparent that the system has wide application within the Arctic Islands. For this reason, in 1976 planning commenced to develop a system for drilling and completing an Arctic offshore gas well and for constructing and installing a marine flowline bundle to an onshore control facility using the thick ocean ice as a work platform. This project involved the design and construction of a new and larger ice-supported rig, a larger and more conventional subsea B.O.P. stack, a subsea tree and flowline connector, flowlines and contro lines to shore, and shore-based test facilities. Project Location In order to minimize the total cost of the project, a location was chosen to meet the following requirements:A minimum length of flowline.A well location in deep enough water to be free of ice scour.A relatively steep shore crossing to minimize the length of pipe requiring protection from sea ice.A suitable onshore area for pipe makeup.A reasonably level area of seabed in the vicinity of the wellhead where the flowline connection was to take place. The location selected was Drake F-76 (Fig. 1), on the east side of Sabine Peninsula in the Drake Point gas field. The location was 1200 m offshore in 55 m of water. Drilling and Completion Systems A study was conducted in 1976 by Tri Ocean Engineering of Calgary to determine the most suitable means of drilling, completing and testing an offshore well, to demonstrate technology that can be used to develop offshore gas reserves in the Arctic Islands. Design Criteria Conceptual design criteria were based on four years of prior ice platform drilling experience.System components were to be designed to function in water depths to 460m.The drilling rig was to be a 3600-m-capacity land rig modified to enable drilling and completing offshore wells during the winter months and land wells during the summer months.