The primary purpose of a drilling marine riser system is to allow circulation of fluids into and out of the wellbore, help maintain well control, and guide items into and out of the wellbore. The roots of riser analysis start with the Mohole project in 1950. The first floating drilling rigs to utilize a metal marine riser were the CUSS 1 (Continental, Union, Shell, and Superior Oil) and D-1 (Offshore Co.) in 1957. Initially for very shallow water, simple column analysis was considered adequate but as water depths increased the industry realized it was necessary to understand the physics, materials of the structure and operating parameters to recommend adequate top tension and vessel position limits.
The technology advanced slowly until floating drilling became a priority for several oil companies. In 1965, the CUSS 1, drilling for Humble Oil & Refining Co., set a world water depth record of 632 feet in the Santa Barbara Channel and was a precursor for the deepwater Santa Barbara Channel OCS lease sale in 1968. Key operators were Chevron, Shell Oil, and Humble Oil, each building and modifying floating rigs while developing proprietary technology. It was apparent to these companies and emerging riser manufacturers that more comprehensive riser analysis methods were needed for the static and dynamic issues in deepwater riser analysis, design and operation.
Between 1965 and 1973, several professional papers had been published, revealing much of the early analysis technology. The critical effect of mud density on required riser tension was discovered and named the effective tension principle. By 1973, riser analyses had incorporated dynamic behavior from wave-induced motions of the riser and the vessel.
This first phase in the ability to analyze, predict behavior and operate drilling risers was a key factor in the successful evolution of floating drilling to 1,500 feet of water, laying the foundation for future advances to greater water depths.
Recognizing the pioneering efforts of the following individuals and organizations that contributed to this technology:
Gerald L. Barksdale, Ben G. Burke, Mark A. Childers, William Fischer, Clinton Gosse, John Lacy, Milton Ludwig and Danny R. Tidwell,
Cameron Iron Works, Esso (now ExxonMobil), Shell, Standard Oil (now Chevron).
The marine riser is used in drilling as a pathway between a floating drilling rig and the subsea well during drilling. For production, the riser provides a vertical pipeline that carries oil and gas from the sea floor to the floating production platform. Both are essential for deepwater oil and gas development.
The advances in the 1970’s were consideration of riser dynamics in loads, environment, and the response motions of the riser. In the 1980’s, use of riser equations was facilitated by the rapid evolution of computing power. The more powerful computers enabled more thorough and accurate analysis techniques.
A pioneering program version was called ‘DERP’ (for ‘Darned’ Efficient Riser Program), developed by Stress Engineering Services (SES) working for Cameron Iron Works. Lawrence Krolikowski and Tom Gay (Exxon Production Research Co.) joined with the SES engineers to develop computational advances involving linearization for the frequency domain. In the early 1980s, DERP was extended to the industry, and became available for customer PCs. The sensitivity of the riser analysis results to operating input parameters challenged analysts and operations people to use design bases that were both practical and provided adequate safety margins. In the early years, each offshore operator and contractor developed their own design parameters. Mark Childers cataloged the resulting wide variation in recommended tensions and in 1980 published the first suggested uniform parameters.
An API Task Group chaired by Paul Stanton worked through the many technical and risk issues facing industry-wide standard parameters and published RP 2Q “Design and Operation of Marine Drilling Riser Systems” in 1984. With Phase 2 technology, drilling marine risers moved to 7,500 feet of water depth by 1987 and in to 10,000 feet in 2004. Comprehensive analysis, appropriate safety margins, and sound operation of marine risers have been essential to working in deepwater and hostile offshore environments.
Recognizing the pioneering efforts of the following individuals and organizations that contributed to this technology:
Mark A. Childers, Early Denison, Joe Fowler, Allen Fox, Terry N. Gardner, Tom Gay, Lawrence P. Krolikowski, Joe Roche, Charles P. Sparks, Paul Stanton, Riddle Steddum, and Ron Young Cameron Iron Works, Exxon Production Research Company, Hydril (now GE Oil & Gas), Institut Français du Pétrole (now IFP Energies nouvelles (IFPEN)), Mechanics Research Institute, Shell Oil Company, Sonat Offshore Drilling (now Transocean), and Stress Engineering Services
Floating rigs used marine risers to guide items in and out of the wellbore on the sea floor. Air buoyancy tanks attached to the riser distributed the load. As operating depths increased, problems with air-can risers increased. In the late 1960’s pneumatic/hydraulic tensioners were invented that allowed larger tensions to be placed on the riser. This also isolated it from vessel motion. In the 70s, syntactic foam buoyancy was introduced. Humble Oil & Refining Co used syntactic foam buoys strapped on a 16 inch marine riser. In deeper water, foam buoyancy issues including water absorption, hydrostatic compression, impact resistance and attachment schemes were solved. Today syntactic foam is the backbone of deep-water riser technology, satisfying structural integrity for drilling and production risers.
Recognizing the pioneering efforts of the following individuals and organizations that contributed to this technology:
Hugh Bezner, Robert E. Bradbury Jr., Dave Cook, Dr. William R. (Bill) Cuming, George M. Savage, Bruce Watkins, and Lou W. Watkins
Emerson & Cuming (now Trelleborg Offshore), Humble Oil & Refining Company (now ExxonMobil), Offshore Company (now Transocean), and Regan Forge & Engineering Company (now GE Oil & Gas)
The riser connecting a floating drilling vessel to the sea floor must be supported to keep it from buckling. Buoyant chambers provide sufficient uplift to keep the riser constantly tensioned and permit it to be free standing when not connected to the drilling vessel. However, there was a risk that should the riser become disconnected from the seabed it would bob to the surface damaging the rig. Thus, the idea was to keep the riser at neutral buoyancy using flotation and support it using tensioners, In the mid 1960’s, The Rucker Company introduced their hydro-pneumatic tensioner systems using hydraulic pressure to stroke multiple compensation cylinders as the drilling vessel moves up and down. The hydraulic pressure is powered by air pressure stored in accumulators. The air either expands or is compressed as the cylinder rods stroke in and out. Cables run from the rods over sheaves mounted under the drill floor and are connected to the top of the riser keeping it positively tensioned. This same technology is used on the majority of floating drilling vessels today.
Recognizing the pioneering efforts of the following people and companies who contributed to the development of this technology:
Douwe “D” de Vries, John W. Prud’homme, Aaron “Dusty” Rhodes, George Savage,
(GlobalSantaFe) now Transocean, Inc.,
The Offshore Company (Transocean Inc.),
Petroleos Mexicanos (PEMEX),
The Rucker Company (Shaffer a Varco Co.), Shell
A major technical problem facing the early designers of floating drilling equipment was to devise a method for providing a closed circuit mud circulating system between the well at the sea floor and the drilling vessel at the surface.
In 1946, Union Oil Co. of California (Unocal) and Continental Oil Co. (Conoco) formed a joint venture to obtain cores offshore from floating vessels. In 1948, Unocal filed a patent on a technique using a marine riser to provide both a conduit for the drill pipe and a necessary return path for mud and cuttings.
By 1953, Unocal and Conoco had been joined by The Superior Oil Co. and Shell Oil Co. in an organization called the CUSS Group. CUSS installed a coring rig on a small wooden hulled ex-Navy patrol craft, the Submarex, and successfully drilled holes as deep as 2,700 feet in shallow waters off the coast of California. At that time however, return circulation was provided by rubber hoses connected to a circulating head which sealed around the drill pipe at the seabed.
In 1957, the CUSS Group, using the vessel CUSS I offshore California, and the Offshore Co., using the vessel D-1 offshore Trinidad, successfully implemented a true marine riser. Both designs incorporated a slip joint at the top to accommodate vessel heave.
Enhancements were provided in 1963 when the Offshore Co. added control lines and choke and kill lines to the basic riser configuration. Later improvements involved the means for latching individual riser sections together. The leader in developing these coupling improvements is generally acknowledged to be Regan Forge and Engineering Co.
Recognizing the pioneering efforts of the following individuals and companies who contributed to the development of this technology:
Robert F. Bauer, George Savage, Bruce Watkins
CUSS Group [Conoco, Unocal, The Superior Oil Co. (ExxonMobil) and Shell Oil Co.], The Offshore Co. (Transocean Inc.), and Regan Forge (ABB Vetco Gray).
In 1960, H. D. Cox of Shell filed a patent for a floating offshore platform with numerous suspended steel catenary risers (SCR). The SCR is an extension of a pipeline curving upward from the sea floor in a catenary shape, hung off and connected to the platform. A catenary arc is defined as the natural trajectory assumed by a flexible member lying on a horizontal surface, when one end is lifted above that surface under the influence of gravity. Principal advantages over a vertical rigid riser is that the SCR can readily accommodate the motion of the floating facility and it is easier to install as there is no connection needed on the sea floor between the pipeline and the riser. SCR risers can be connected to subsea manifolds and laid on the seabed in advance as wells are completed; then when the floating production facility arrives on station the free ends of the SCRs are captured and simply pulled up by a cable to be connected to the floating facility.
This idea was ahead of its time as floating production systems were not needed until much later. The idea was first used to repair an 8 inch oil pipeline riser torn loose from a platform damaged by Hurricane Camille in 1969.
During the 1980’s, Shell continued to advance SCR technology in preparation for deepwater applications in the Gulf of Mexico. The first SCRs installed on a floating structure were the two 12 inch pipeline risers connected to Shell’s Auger Tension Leg Platform in 1994. Steel catenary risers have proven to be an effective, efficient and safe means of connecting deepwater export and import risers to deepwater floating facilities. Since 1994, more than 200 have been installed on deepwater floating production systems.
Recognizing the pioneering efforts of the following individuals and organizations that contributed to this technology:
Don Allen, Dr. Ray Ayers, Don Barry, Frans Kopp, Carl Langner, Ed Phifer, Richard Swanson and E. G. “Skip” Ward.
Shell International Exploration and Production, Inc.