Abstract

Over the past three years experience has been gained with the installation of Spars in deep water using Heerema's Deepwater Construction Vessel (DCV) Balder and Semi Submersible Crane Vessels (SSCV) Hermod and Thialf. The facilities involved are the Horn Mountain, Gunnison, Holstein and Mad Dog Spars, each with their specific characteristics and associated challenges. The offshore installation of the moorings, hulls and topsides for these projects required utilization of the equipment to its maximum limit. Technical challenges involved among others the fibre rope moorings, the Loop and Eddy currents which frequently influenced the installation area and the interaction between installation vessel and Spar when setting major topsides. The paper describes how the technical challenges were tackled and how emphasis was given on feeding knowledge back to subsequent projects. In particular the paper will address the lessons learned both from a technical point of view as well as from a project management and contracting stand point. Because DCV Balder can switch from facility installation mode (mooring systems and topsides) to pipeline installation mode, schedule flexibility and risk mitigation were added advantages to the operator.

Introduction

Operators, designers and contractors have had to learn fast over the past few years. Under the stringent requirements regarding health, safety and environment and profitability, the move into deeper water, with new technology and increased scale in structures and field sizes, is a challenge for all.

In addition a number of contractors have introduced new equipment which has the ability to answer the installation needs in deep water. The learning process involved in understanding the opportunities of the new equipment (both by the contractor as well as by the other parties) was, and is, considerable. This required joint development of methods and designs. These have, over the course of the four projects, increasingly improved to take full benefit of the available equipment.

Key lessons which were learned over the past four Spar projects were;

  • The approach and equipment (DCV Balder) applied in these Spar projects have led to on-time delivery, without damage to assets and with limited Lost Time Incidents.

  • The ability to change project modes from pipelay to facility installation or visa versa in an overall contract covering several scopes limits the effect of external (environmental or fabrication) impacts and potential delays for a client. This schedule flexibility is seen as a strong asset in using a multipurpose field development vessel such as the DCV Balder.

  • In deeper water the (Eddy) current environment has become an important factor which needs to be taken into account in installation design and contract conditions.

  • Standardization has been part of the project execution philosophy. It was experienced however that the drivers to reduce cost on facility and field development are quite different for the various players.

In the paper it is shown that where a large number of experienced parties have come together to enable execution of the projects, methods and understanding have developed to such an extent that Spar installation has evolved from a developing capability into an established capability.

This content is only available via PDF.
You can access this article if you purchase or spend a download.