A System For Offshore Drilling In the Arctic Islands

Abstract

Abstract This paper describes the ‘method used to drill an expendable delineation well from an ice platform 8 miles offshore in the Hecla and Gripe? Bay of the Arctic Ocean. Planning pf the Panarclic Tonn etal CS W Hecla N-52 well began in early 1978. However, a considerable amount of horizontal ice movement data had been collected in 1971 and 1972 in several areas of the Arctic Islands to determine the feasibility of drilling from the ice in the latter months of the’ Winter.(1) The design and construction of the ice platform, the drilling 1'ig selected for the project, the subsea equipment used and the sequence of operations which were followed to drill the Hecla N-52 well are presented in the paper Flooding of the ice platform began on November 28, 1973 and was completed on February 3, 1974. The Hecla, N-52 well was spudded on March 6 and the rig was released on April 15, 1974. Performance of the ice platform and the special subsea equipment used during the drilling period is reviewed. Operating experience gathered from the Hecla N-52 well demonstrates that drilling an offshore well in. certain areas of the Arctic Ocean from the ice is feasible. Introduction IN ITS OPERATIONS OVER the past five years, Panarctic Oils Ltd. has used heavy aircraft on ocean ice airstrips and moved heavy loads by truck across the ocean ice between islands, recognizing that the thick. ocean ice is capable of being used to advantage in the late winter months. Ice strength calculations indicated that it should be possible to drill offshore wells using the ocean ice as a platform for a conventional landtype rig. The feasibility of drilling offshore with a slim-hole land rig was demonstrated in the spring of 1973 when a small 150-ton Gardner-Denver 2000 drilling rig was used to drill four stratigraphic tests ranging in depth from 833 to 1700 feet in Kristoffer Bay near Ellef Ringnes Island. The wells were drilled from 1 to 3.5 miles from shore in water depths ranging from 137 to 290 feet. Natural ocean ice, ranging in thickness from 6 to 8 feet, proved to be adequate to support the weight of the rig, for the average 8-day drilling period, with no problems. Successful completion of the stratigraphic test program, and the results of a load test conducted on natural ice (discussed later in this paper), led to the drilling of the Panaretie Tenn etal CS W Hecla N-52 well in 1974. The expendable delineation well was drilled to a depth of 3080 feet in a known gas field using a conventional rig capable of drilling to 6000 feet, Because the weight of the rig could not be supported by natural ice thickness, an ice platform had to be constructed. Geographic Location The Hecla N-52 wellsite is located in the Hecla and Griper Bay, 1800 miles north of Calgary, 950 miles south of the North Pole and 8 miles east of the Sabine Peninsula on Melville Island, N.W.T. as shown in Figures 1 and 2.