The Construction of Artificial Islands in the Beaufort Sea

Abstract

Arctic petroleum exploration has moved offshore into the ice-covered waters of the Beaufort Sea. Artificial earth-fill islands have been used successfully as temporary shallow-water drilling platforms. Introduction Petroleum exploration activities in the offshore Arctic Petroleum exploration activities in the offshore Arctic were initiated in the mid-1960's, when permits covering acreage on the Arctic continental shelf were issued to several petroleum exploration companies (Fig. 1). At that time, Imperial Oil Ltd. obtained permits in the shallow waters of the Beaufort Sea adjacent to the Mackenzie River delta. Preliminary studies of offshore drilling feasibility that were undertaken during the late 1960's soon brought to light the tremendous dearth of knowledge concerning the offshore Arctic environment. It was apparent that the major problems to be solved while developing the technology required to support offshore Arctic drilling were (1) the definition of forces exerted on stationary structures by the mobile annual and multiyear ice; (2) the influence of violent, shortduration summer storms; (3) an apparent scarcity of easily accessible construction materials; and (4) the mobilization of suitable construction equipment that would be effective during the short open-water operating season. In 1969 Imperial initiated data-gathering and ice-testing programs; these were followed in succeeding yens by many additional studies sponsored by Imperial and other interested Arctic operators. Numerous concepts, both conventional and unique, were considered for Arctic offshore drilling. These concepts included artificial islands, bottom-founded mobile structures, monopods, cones, and ice-breaking floating vessels. These are all viable concepts and may have application for a specific set of conditions. However, Imperial determined that the dredged artificial island was the safest and most economically attractive type of structure for use in support of its exploration drilling program. In 1971 a permit was received from the Canadian ept. of Indian Affairs and Northern Development authorizing construction of an experimental island at what was later to become Imperial Immerk B-44 wellsite. Construction began early in Aug. 1972 but, under the terms of the permit, drilling operations were not to take place until the stability of the structure under winter ice conditions had been assessed adequately. This initial island proved to be a stable and competent platform. To date, Imperial has drilled eight exploratory platform. To date, Imperial has drilled eight exploratory wells from islands constructed in water depths ranging from 5 to 25 ft (Fig. 2). Environment Very few regions of the world experience greater extremes of weather conditions than those encountered in the Arctic. During the summer months of July through September, temperatures may reach a high of 80 degrees F, dropping to −60 degrees F for much of the winter period. Strong winds and shifting ice during both summer and winter add to the difficulties of working in this harsh and inhospitable climate. The environment of the shallow shelf north of the Mackenzie River delta is influenced by two dominant factors: the polar ice cap, and outflow from the Mackenzie River system. JPT P. 365