Realising the Inherent Value in Decommissioning Assets
Authors: Fraser J.R. , Southern A.W. , Hume I. , Kent D.A. , Winckers A. 
Published: December 2007

To date the debate surrounding the issue of decommissioning has almost exclusively focused on the legislative, technical, fiscal, environmental, timing and cost elements of facilities removal. These elements do indeed represent the key criteria that will determine the process; nevertheless the fact that we focus upon them tends to detract from the serious application of innovation for end use opportunities.

This paper attempts to address this imbalance by identifying and qualifying the opportunities available to access and realise the significant value inherent in even the most mature of the facilities.

The paper also illustrates how the application of existing proven technology has been utilised in other applications to create an added value result and how these techniques and technologies can be applied in the decommissioning process with equally impressive outcomes.

As with many of the 'breakthroughs' in our industry of recent years it has not been the limitations of existing technology that have proved the stumbling blocks but the mind set of the great majority of players. The paper develops the challenges to current practices and perceptions that are necessary if we are indeed to prevent the loss of real value to our industry.

The thrust of the paper is to demonstrate that there exists the potential for real alternatives to the view that deep-sea disposal or onshore scrapping are the only realistic options for disposal.

Introduction

AMEC Process and Energy has recently completed decommissioning studies for two North Sea installations, each of which is owned and operated by separate major oil companies. In performing the research for these studies the offshore sector of AMEC PLC, AMEC Process and Energy, collaborated with the onshore and inshore sectors, AMEC Civil Engineering and AMEC Marine. This collaboration resulted in the development of a number of reuse alternatives to disposal or scrapping that are financially viable, environmentally friendly and a benefit to society. During the study periods, AMEC worked closely with Smit International in order to achieve a high level of definition for the marine operations required for the decommissioning and reuse activities.

Recovery from the field

The recovery methods considered in the studies involved two floating structures and thus simply involved towing the installations to sheltered deep water for dismantling. However, the dismantling and reuse procedure described below is also applicable to the substructures of many fixed platforms. Such structures could be recovered either whole or in sections by lifting or by use of buoyancy (existing inherent buoyancy or by adding temporary buoyancy tanks). Lifting can be performed by crane vessels or by barge mounted sheerlegs. Alternatively, a barge fitted with deck mounted winches or strand jacks can lift and suspend the structure below the barge while it is transported to the reuse or dismantling site.

Dismantling

The options to dismantle the structures were based upon suitable deepwater facilities at which AMEC has a controlling interest or at which provisional agreements to enter a lease agreement have been provisionally reached.

Locations at Espevik in Norway and Loch Kishorn in Scotland were assessed as potentially suitable inshore sites for the dismantling operations. The sites were further assessed for their suitability to temporarily ground the substructures during the final stages of dismantling. The Loch Kishorn site has the additional benefits of a dry dock and quayside although the tow distance is longer than the route to Espevik. The studies proposed a parallel dismantling operation for the substructure and the topsides. P. 381^