Ice Management In The Labrador Sea

Abstract

Introduction The Labrador Sea is known as a hostile environment to all forms of marine activities. The region is buffetted by numerous storms every year which bring high winds, severe seastates and superstructure icing. For vessels attempting to navigate through the region the presence of icebergs present a year round hazard and sea ice, present during the winter and spring months, restricts the trafficability of vessels. It is in this environment that the Labrador Group of Companies has undertaken an extensive program of exploratory drilling over the last decade. To date, some 23 wells have been drilled by this consortium, primarily on the offshore banks and the saddles between these banks. To ensure a safe and successful drilling operation, special attention has been given to the environmental constraints and programs have been developed to minimize their effect. In this paper we will present some of the aspects of the iceberg problem and the ice management techniques in place to deal with them. Setting Icebergs are found throughout the region encompassed by the permit acreage within the Labrador Sea. It is difficult to generalize on the presence of icebergs over the entire Labrador Sea region as their presence is variable in time and space. There exists an annual variation which sees the largest numbers of icebergs present in the May and June period, decreasing throughout the summer to a local minimum in October and November and then increasing to a late spring peak. The variability between years, in terms of the total numbers of icebergs recorded, is largely unknown in this region although there are large differences between a light and a heavy iceberg season. Farther south, at the boundary of the Grand Banks, the variation is from a minimum of zero icebergs to a maximum of about four times the mean annual value. The distribution of icebergs within the Labrador Sea shows a decrease in the number of icebergs present with increasing distance from the coastline. Also, at a given point in lime more icebergs will be present in northerly regions than in those farther south. The reduced fluxes with distance offshore and southward along the coast indicate both the deterioration of icebergs and the divergence of icebergs from the surveyed region. A variety of mechanisms, both mechanical and thermal, influence the decay of icebergs in this corridor and their interrelationships are only qualitatively understood. The Equipment On the Labrador Shelf drillships have been used predominantly. Their deck load and cargo capacity permits operation in remote areas with minimum resupply. Dynamically positioned drillships have been preferred due to their ability to move off and back onto a well quickly when threatened by Ice or icebergs. This capability maximizes vessel safety and minimizes costs due to downtime. The dynamic positioning system enables such a drilling unit to maintain position over the wellhead using ship's power alone.