National Supply Builds 15,000-Psi Subsea BOP And Wellhead System
National Supply Company has shipped to British Petroleum Ltd. a unique 15,000-psi subsea wellhead system to be used in the North Sea.
The BOP stack and individual components were s u c c e s s f u l ly tested in December at National's Houston Wellhead Plant and shipped on schedule for subsea installation.
The new National system features a unique "crossover" that allows a 15,000 psi completion within existing 10,000-psi-rated equipment. This approach offers the customer the higher rated equipment at considerable savings. BP engineers came to National Supply for assistance after running into unexpectedly high pressures in the North Sea. No subsea wellhead system then available was rated for more than 10,000 psi. Without properly rated equipment, the potential of the discovery could not be properly assessed. National's engineers designed the new 15,000-psi BOP stack and wellhead equipment to be used with e x i s t i n g 10,000-psirated equipment.
The advantages to this approach are: • The well could be drilled in and established with readily available equipment.
• Use of standard National wellhead components saves on well costs.
• The system requires fewer new components.
• The system could be used with BP's existing National equipment. The BOP stack is a relatively "straightforward" development of the concepts used in the company's present designs. It used two 15,000-psi double-ram preventers for the main BOP assembly and a 10,000-psi annular preventer for the lower riser package. This 11-inch, 15,000-psi wellhead design concept is the first application on a National Sea King 13-5/8-inch, 10,000-psi wellhead. This design can be utilized in all other sizes of National's 10,000-psi Sea King wellhead equipment.
The key advantage to this system is the flexibility it provides the customer. It allows him to upgrade his National equipment to higher ratings when required. National Supply developed the industry's first underwater product unit, placed in Lake Erie in 1957, and designed the first subsea production unit to go into operation in the North Sea. A division of Armco Steel Corporation, National Supply Company m a n u f a c t u r e s the most complete line of oil-field drilling machinery and related equipment in the industry.
For additional information on the 15,000-psi subsea wellhead system, write to William Marmac, National Supply Co., Division of Armco Steel Corporation, 1455 West Loop South, Houston, Texas 77027.