Arctic Offshore Drilling A Technical Development and Economic Evaluation

ABSTRACT This paper presents a concept of an Arctic drill hull for drilling in Arctic offshore water. It has a conical-shaped, non-self-propelled hull that provides ice-breaking capability while held in position with a pretensioned multipoint mooring system. The objective is to allow drilling to continue for as many months of the year as possible. An overriding need is to assure that the system will survive under all Arctic conditions, regardless of whether or not drilling is taking place. INTRODUCTION Recent discoveries of oil and gas in the Canadian Arctic, plus the presence of favorable geological formations in many other Arctic regions, have generated interest in the need for drilling capability in the area's offshore waters. The hostile environment provides a challenge to the conceptual designer to develop a feasible system within realistic cost boundaries. The object of this paper is to describe a concept for providing this capability in a feasible and cost effective manner. In order to reach the economic objectives, it will be necessary that the equipment be making hole as much of the time as possible to obtain maximum revenue. It must also have the inherent capability of survival under all Arctic conditions. The Arctic drill hull is shown in Fig. 1. It is a conical-shaped floating platform moored to the sea floor. The hull has ice-breaking capability because of its ability to ride up vertically when exposed to horizontal ice forces. The weight of the hull then produces a downward force that breaks the ice. This concept was utilized by General Dynamics in the development of an Arctic drift barge1 for the National Science Foundation. The barge was initially designed to be implanted in the Arctic ice pack for scientific observations and to collect data over a period of several years. This paper first selects the parameters of geographic location so that specific environmental criteria can be utilized. The drilling equipment is established to drill a typical hole in that region. The basic concept is then developed into a complete system by establishing the necessary subsystems. The ice-breaking capability is estimated and the results of initial model testing is presented. An economic evaluation is conducted to determine economic factors. SELECTED PARAMETERS Because of the wide range of environmental conditions that exists in the Arctic, it appears that, in the design of an offshore oil-drilling system, a given engineering solution may not be satisfactory for all areas. Accordingly, a particular geographic area was selected during the initial stage of concept development so that specific environmental conditions could be established for design purposes. The area selection and the resulting environmental parameters are discussed below, followed by a description of drilling requirements. Geographic Location The area selected is the Mackenzie River ocean basin of the Beaufort Sea, as shown in Fig. 2. This area was selected because it appears to be one of the first areas in which offshore drilling will be attempted. Geological conditions are favorable for oil finds, and leases are presently held by major Canadian oil companies.