Kittiwake Loading Buoy (KLB): A New Lease on Life

Abstract

ABSTRACT A large loading buoy, installed for 14 years in a North Sea field, was converted, incorporating the latest technology and operating experience, for a new application as the sole offloading facility in a newly developed oil field. In spite of a significant design change to the mooring of the system the buoy body of approximately 800 tonnes could be reused for 30 more years of service life. An expensive upending operation was avoided by an inshore conversion, executed afloat at a sheltered deep location. INTRODUCTION North-Sea oil fields started to be developed some 20 years ago with production platforms. None of the first platforms contained any storage for the produced oil and as pipeline construction was not advanced, efficient offloading into shuttle tankers became a vital requirement. First installations used the conventional CALM buoys which required improvement to cope with the especially harsh environment of the North Sea. The first tailor-made offloading buoy was conceived and installed in the AUK-Field in 1974, called the ELSBM (Exposed Location Single Buoy Mooring) -> (See reference OTC-Paper 3805). The ELSBM was in service in this field until 1988, initially operating as the sole system which allowed oil export and towards the end as a stand by system after the tie-in to the FULMAR-Field. The Operator SHELL-EXPRO, who was preparing the development of the Kittiwake Field, decided to look at the feasibility of reusing the available and redundant ELSBM in this new field. Engineering of improvement, based on operating experience and implementation of features developed for other offloading systems in the North Sea, were contracted by the Operator in early 1988 to Single Buoy Moorings Inc., whose sister company Gusto had built the original system. The ELSBM was converted accordingly and is now in operation providing offloading of all produced oil from the Kittiwake Production Platform into shuttle tankers. The refurbished buoy is called KLB (Kittiwake Offloading Buoy). DESCRIPTION OF ORIGINAL AUK-BUOY (ELSBM) The ELSBM consisted of along, slim, cylindrical buoy with a diameter varying from 8.6 to 12 m and a draft of 52 m. It was anchored to the sea-bed with an eight chain pattern of 3" size chains. A large fender structure with rubber fender elements and wood protection surrounded the top of the buoy providing protection from supply vessels. A rotating head, permitted weather-vaning mooring and contained storage reels for a single 10" offloading hose string and a mooring hawser. A helideck allowed access for maintenance crew visits. A 50,000 DWT passive tanker could be moored to offload in sea states of up to 3.6 m significant waves. The activation of the hose and hawser reel was by a counterweight descending into the center well of the buoy via pulleys and steel cables. The shuttle tanker had to fish a floating pick up line out of the water and then un-reel the hose and mooring hawser by heaving in on this line.