Drilling Offshore Western Greenland - ICE
Authors: Hammett D.S. , Finney Gary S. 
Published: October 2008

The western Greenland Shelf is in the early stages of exploration. There are various factors which make exploration drilling particularly difficult and shorten the operating season, i.e. ice packs, ice bergs and weather. Two summer drilling seasons, 1976 and 1977, have resulted in the drilling of five exploration wells while utilizing special dynamically stationed drilling vessels which can move in fast, position without anchors, drill and evade icebergs by fast disconnect procedures and subsea acoustic re-entries. This paper presents the pre-engineering and operating experience of two vessels used in the summer of 1977 to drill three wells within an 81 day period while dealing with the hostile, remote environment of Greenland. During the 81 day drilling period, 82 icebergs, varying in size from 8 thousand to 7.5 million tons, were sighted and tracked at locations within a 25 mile radius of the SEDCO drilling sites.

INTRODUCTION

The Western Greenland Shelf, where oil companies obtained leases in 1975, covers an area of 4.5 million acres. The Greenland lease area is illustrated on Figure 1 and compares in size to the oil exploration area between the Ekofisk, and Brent Fields in the North Sea. The northern and southern boundaries of the Greenland area are 68°N and 63°N, respectively. The western boundary of the lease is at a water depth of 2,000' near the middle of the Davis Stratis and within 30 miles of the Canadian border. Investigations carried out over the years by the Geological Survey of Greenland of the Cretaceous Lower Tertiary sedimentary sequence in the Diski-Nugssaq area had shown that the shales on land had a considerable content of organic material and that these shales, to a certain extent, were suitable as source rocks, mainly for gas. In addition, there are in the land area porous and permeable sandstones which could be good reservoir rocks. Combined marine and airborne investigations show that this land area constituted a local embayment separated from the extensive offshore sedimentary basin to the west and southwest in part by a Precambrian gneiss ridge, in part by an area of Tertiary basalts. It was logical to assume that sedimentary rocks of similar type and age extended below the continental shelf. In addition, it was tempting to make comparisons with the Labrador Shelf, where encouraging amounts of gas had been found in two wells drilled before 1975. Since the grant of concessions in the spring of 1975, the concessionaires have shot about 15,000 km of seismic lines. With the exception of the southern-most concession area between 63°00' and 63°30'N where the amount of seismic data available before 1975 was very little, the new seismic data have confirmed the earlier seismic mapping and provided more detail without altering the general configuration. Before 1976, the only wells drilled near the Davis Straits area were along the Canadian Labrador coast; 660 miles south; 540 miles further south along the Flemish Shelf; and 180 miles further south to Sable Island. Greenland was a vast exploration area with no subsurface drilling information.