Water-Filled Fire Protection System for Bare Steel Structures at Ekofisk
Authors: Martell Paul J. 
Published: December 2007

A unique system of water-filled, interconnected, tubular structural members is used to protect against exposure to fire in the Ekofisk field. This paper discusses the system and outlines its advantages over conventional paper discusses the system and outlines its advantages over conventional protection systems. protection systems. Introduction

Tubular steel structures, including entire jackets and deck sections of template-type platforms, can be protected against exposure to fire by keeping the structural members full of water. The heat of the fire is absorbed by the water. Pressure from the fire pumps, steam pressure from the evaporation of water, natural convection, or any combination of these will cause the water to circulate through a system of intercommunication openings. Steam and/or hot water vented from the system will be replaced with colder water from the pumping system. The temperature of the steel is thereby maintained at a safe level for structural integrity.

This paper discusses how this concept was applied to specific structures in the Phillips Norway Group acreage of the Norwegian North Sea,

The Phillips Norway Group consists of the following companies: Phillips Petroleum Co. Norway (36.960 percent), Norske Fina A/S (30.000 percent), Norsk Agip percent), Norske Fina A/S (30.000 percent), Norsk Agip A/S (13.040 percent), Norsk Hydro Produksjon A/S (6.700 percent), Elf Norge A/S (5.396 percent), Total Marine Norge A/S (4.047 percent), Aquitaine Norge A/S (2.698 percent), Eurafrep Norge A/S (0.456 percent), Coparex Norge A/S (0.399 percent), and Cofranord A/S (0.304 percent).

Storage Tank

The Phillips Norway Group has a 1-million-bbl oil storage tank in the Ekofisk field of the Norwegian North Sea that was designed to prevent production interruptions during bad weather when loading from buoys is not possible. It soon became evident that, with possible. It soon became evident that, with modifications, the tank could be used to support production facilities that would otherwise require additional platforms. platforms. The storage tank is a unique, reinforced concrete structure resting on the sea floor in 230 ft of water. It was constructed while floating in a fjord near Stavanger, Norway, towed to sea, and installed in its present position. The original design included an operating deck over position. The original design included an operating deck over the tank that protrudes about 66 ft (20 m) above sea level Early in the construction stage, it was determined to extend this deck (designated the 20-m deck) to span the approximately 60-ft distance from the tank to the concrete breakwater wall that circumscribes and protects the tank proper from the open seas. This breakwater wall extends about 50 ft above sea level and shares the common mat foundation with the tank (Fig. 1).

The annulus area of the 20-m deck is about 300 ft in diameter, with a 180-ft-diameter hole that contains the original operating deck. It was designed with steel to meet a rigid weight limitation imposed by the depth of the towing route, to provide the economic advantage of being constructed in the fjord rather than 200 miles offshore, and to meet a critical deadline imposed by a scheduled towing date. It was decided to use this new deck space for production support equipment only after the deck design production support equipment only after the deck design was nearing completion and prefabrication of structural elements had begun.

Ekofisk Center, as this facility is known, is the nerve renter for the entire field and was designed to handle a maximum daily production of 2.2 Bcf of gas and 1.0 million bbl of oil from Ekofisk and its satellite fields.

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