AUV- and Satellite Imagery-Based Ice Management Around Critical Infrastructure
Authors: Gustafson Einar , Hancock Chris , Hall Richard 
Published: December 2011

The increase in human activity in the Arctic region has led to a need for improved monitoring, surveillance and management of the region. Weather conditions change rapidly, and the presence of sea ice poses an increased risk to ships and platforms. For these reasons, the need for frequently updated information about the ice edge, icebergs, and ice floes, wind and wave conditions has increased, in order to help reduce the risk of contamination from an industrial accident. In particular, there is a need for an integrated ice management system to detect, measure, track and manage ice around a drilling platform or ship operating in ice-infested waters. Such a system needs to employ advanced technological solutions to obtain adequate information about the dynamic ice conditions around an asset, in order to manage the risk of damage.

Concepts have been developed for an integrated ice management system, using satellite images and autonomous underwater vehicles (AUVs), in combination with supporting ice management infrastructure such as ice-breaker vessels. The system employs satellite images to initially detect and track ice floes typically 100 nautical miles away from the drilling asset, and uses this information to task a fleet of AUVs to investigate suspected risks (for example icebergs or multi-year ice floes) and to accurately measure the thickness and extent of the ice in order to estimate the risk to the drilling asset. This will allow each ice object to be placed in a priority list defining when each ice object needs to be managed.

The paper demonstrates how ice objects, both floes and icebergs, either within the ice-pack or in open water can be automatically tracked over a period of time by using satellite imagery. The ITSARI (Iceberg Tracking Using SAR Images) algorithm, originally developed to track icebergs in the Antarctic, has been adapted to track individual sea ice floes in Arctic conditions. Ice floes are identified and tracked using brightness values and shape characteristics. The algorithm has also been adapted to detect the fast ice edge and pack ice edge. The paper further describes a baseline AUV ice-mapping survey, and highlights three different concepts of operations for the AUV segment. These include a) distributed, b) centralized, both of which refer to placement of subsea AUV docking stations, and c) surface L&R-based, a concept which relies on ice-breaker vessels for rapid transit and L&R of the AUVs.

Introduction

Kongsberg Gruppen (KOG) has, through their two subsidiaries Kongsberg Maritime (KM) and Kongsberg Satellite Services (KSAT), developed supporting concepts for ice management by use of satellite data and AUVs. Ice management is a field in rapid expansion within the offshore industry, motivated by the need to protect both valuable assets and human lives throughout the life of oil or gas fields located in ice-infested waters. Typically, ice breaker vessels are a necessity, with their primary function being to physically break up ice floes into smaller, less threatening, pieces. Knowledge about the mass of ice drifting towards a drilling or production asset at all times is of critical importance to enable an efficient ice management system. This is a three-dimensional measurement problem, involving measuring the areal extent of the ice as well as the vertical ice profile. The former is readily visible on high-resolution satellite imagery, whereas the latter can only be achieved with sufficient accuracy by taking a closer look at the underside of the ice. Measuring the underside of ice is possible by use of long-range, ice-hardened and reliable AUVs. There is a strong synergy between using satellite imagery to not only measure the areal extent of ice floes, but also to determine the bounding coordinates of the required AUV under-ice mission.