Stationkeeping & Mooring

With the first offshore well drilled from a moored tender assist MODU (Mobile Offshore Drilling Unit) in 1947, the need to handle mooring system’s anchors, buoys and mooring lines for drilling, construction and pipe laying barges was born.  In the early to late 1950s in the Santa Barbara Channel, California, coring units and MODUs with small anchors and only 4 to 6 mooring wire ropes were handled by standard tug boats with their normal towing winches.  Corresponding conventional anchor handling tugs were used in the Gulf of Mexico and Mid East for construction.  As construction and pipe laying barges increased in size as did MODUs, their mooring system components also grew in size and complexity necessitating larger purpose built AHVs (Anchor Handling Vessels) with more horsepower fitted with gantry cranes, open stern decks with the bridge on the bow, and “stern rollers” to help lift equipment on the deck.  In the ‘60s and early ‘70s the development of multipurpose vessels (AHTs, Anchor Handling Tug Supply Vessels) appeared that could handle mooring equipment, act as a supply vessel and also tow MODUs and construction barges.  As mooring line components further increased in size, weight and length due to increased water depth requirements and more severe operating environments, it became necessary to develop better seamanship and even more capable AHVs with large bow thrusters for maneuverability, sophisticated navigation systems to set/retrieve anchors, and innovative deck equipment to handle the larger mooring equipment.  Further development led to AHTS’ that could also carry large quantities of liquid mud as well as dry bulk material. Today AHVs and AHTS’ have grown into ships with some over 250 ft. long, bollard pulls of over 200 tons, over 20,000 Hp with twin controllable pitch (CP) screws, and double winches that can each pull and brake over 1,500,000 lbs as well as conduct dynamical payout with long work wires to handle large anchor and chain loads.

Recognizing the pioneering efforts of the following individuals and organizations that contributed to this technology:

William (Bill) Bright, Dino Chouest, Laney Chouest, Burt Keenan, Charlie Slater, Nolty Theriot, Ken Waldorf, Tony Wilbraham, Edison Chouest Offshore, Farstad Shipping ASA, Maersk Supply Service, Offshore Logistics (Bristow Group Inc.), Offshore Supply Association Ltd., Smit-Lloyd (now Smit International N.V.), Tidewater, United Towing (now Maersk Supply Service), Zapata Marine Services (now Tidewater).

Initially, floating rigs were positioned by an array of anchors and cables. As water depths increased, these became uneconomical to install. In 1983, Shell selected the Sonat Offshore Discoverer Seven Seas with its Honeywell DP control system to conduct drilling in 7500 ft. of water off the East Coast of the US. Loss of position in those depths was economically prohibitive, and the risk of a possible oil spill was unacceptable. Because of these risks, Shell instituted a NASA-developed safety program called FMEA (Failure Mode Effects Analysis) raising the odds of failure to four years.  In 1991, Sonat Offshore working with Simrad, further upgraded the DP system for the Discoverer 534, a sister rig using Simrad’s modular redundant control system to further increase failure possibility to over five years. By 1995, DP had become universally accepted.

Recognizing the pioneering efforts of the following individuals and organizations that contributed to this technology:

Q. Wayne Dean, Peter A. Fougere, Robert P. Herrmann, Dr. Nils Albert Jenssen, Howard L. Shatto, Henry Van Calcar, and Carl Wickizer

Honeywell Offshore Division (now Wartsila Marine Solutions), Shell, Simrad Inc. (now Kongsberg Maritime), and Sonat Offshore Drilling (now Transocean)

Anchors for floating vessels have evolved from ancient times. The earliest anchors were stones that had holding power of less than their own weight. By the early 1900s the stockless anchor had been developed. That style anchor was, and still is, widely used on merchant and naval ships because it is easily stowed in the hawse pipe. The stockless anchor has a holding power of about twice its weight in air. In the late 1930s Richard S. Danforth and his nephew, Robert Danforth Ogg, developed the theory and designs for a light weight, drag embedment anchor. U.S. Patent 2,249,546 was granted to Richard S. Danforth on July 15, 1941. The Danforth anchor developed holding power of about ten times its weight in air and was widely used on landing craft during World War II.

The U.S. Navy built on Danforth’s work and developed the STATO anchor with a holding power of about twenty times its weight. Mr. R.C. Towne, of the U.S. Naval Civil Engineering Laboratory at Port Hueneme, California, was instrumental in that effort and that organization published standardized test data on anchor holding powers that has been very useful to the offshore industry. In subsequent years numerous specialized, high holding power anchor designs have been developed for the offshore construction and drilling industries. These specialized anchors have holding powers of about twenty five times their weight and were a vital component in the large drilling and construction vessels for areas such as the Gulf of Mexico and the North Sea.

Some of the pioneers in these more recent developments are Peter Bruce, of Bruce Anchor Limited in the U.K.; Rob van den Haak, of Vryhof Ankers B.V. in the Netherlands; and Peter J. Klaren, of Anker Advies Bureau B.V. in the Netherlands.

Recognizing the pioneering efforts of the following individuals and companies who contributed to the development of this technology:

Richard Stevens Danforth, Robert Danforth Ogg, Richard C. Towne, Peter Bruce, Rob van den Haak, Peter J. Klaren

U.S. Naval Civil Engineering Laboratory, (Naval Facilities Engineering Service Center), Bruce Anchor Limited, Vryhof Ankers B.V., Anker Advies Bureau B.V. (Wortelboer Jr. B.V.)

The use of polyester cables for deepwater mooring started in the 1980s by Marlow Ropes, a UK Company. Petrobras began installing polyester mooring systems immediately, leading to the P-19 and P-26 installations. Another program, set out to qualify advanced polyesters with standard polyester as a base case. The superior performance of standard polyester proved it to be the best solution at lowest cost. Leading the way were BP and Shell. BP installed the system on its Mad Dog platform and Kerr McGee equipped the first cell-spar, Red Hawk.

Recognizing the pioneering efforts of the following individuals and organizations that contributed to this technology: Ray Ayers Ph. D., Steven Banfield, Luis Claudio Sousa Costa, Cesar Del Vecchio, Paul Devlin, Felix Dyhrkopp, John Flory, Jenifer Tule Ham, John W. S. Hearle Ph. D., Mike Parsey, David Petruska, Hongbo Shu, Richard Snell, Richard W. P. Stonor Ph. D.,Sim Whitehill, and Mitch Winkler BP, BSEE, Chevron, DeepStar, Kerr McGee (now Anadarko), Marlow, Noble Denton (now DNV GL), Petrobras, RPSEA, Shell, Stress Engineering, Tension Technology Inc., and Whitehill Manufacturing Company

The need to predict spread-mooring systems’ capabilities to hold vessels on location grew with increasing water depths starting in the mid 1960’s.  In 1969, a computer program was developed that could calculate mooring-lines configurations and forces with up to 12 lines of different compositions. Deepwater mooring systems were first used by Humble Oil and Refining in the late 1960’s in the Santa Barbara Channel.  In 1973, the API Task Group on Mooring Gear was formed that led to a number of API RP’s.  The dynamic effect of vessel motion and mooring line interaction was interjected into the spread mooring systems analysis using frequency and time-domain methods.  The interaction of mooring and marine riser analysis and operation were developed in the late 1970’s.  Since that time, the sophistication and detail of mooring analysis and its application has become an industry and government requirement.

Recognizing the pioneering efforts of the following individuals and organizations that contributed to this technology:

Roy B. Adams, Mark Childers, Chi-Tat Thomas Kwan, and Dr. Barry Miller

Exxon Production and Research Company (EPRCO), Global Maritime,

ODECO (now Diamond Offshore Drilling), and Netherlands Ship Model Basin

Scroll to top