This paper emphasizes the application of the so-called SEAL Atmospheric System as a subsea manifolding station. Following some introductory remarks, the paper includes a brief description of the existing SAS prototype in terms of its basic hardware components and associated subsystems, and a review of its testing history, especially highlighting events of' the past year and plans for completing the testing program. It then analyzes how the SAS-particularly its major hardware component, the Subsea Work Enclosure--can be utilized as a subsea manifold system.
During recent years, a subsea production system has been designed, built, and initially tested. It has been identified in the past as the SEAL* Atmospheric System, and previously described in technical literature. 1,2,3** Initially, the SAS was designed as a multi-well production/ manifold station, where the base is used as a subsea drilling template for deviated wells drilled peripherally and connected directly. It may also be used, however, as a collection manifold station for remote, widely-spaced, vertically drilled wells with individual subsea completions, connected to it by flow lines. In either case its use as a man folding station is a straightforward concept, and this role is stressed in the Sections that follow.
For completeness sake, a brief description of the SEAL Atmospheric System is included herein. It consists of three basic elements of hardware: namely, the base, the wellhead connector assembly, and the subsea work enclosure. It also includes a number of associated supporting subsystems. A full scale prototype was constructed to prove the practicality of the system's design and to test its operational reliability.
The prototype base, shown schematically in Figure 1, was constructed under contract to SEAL by Brown and Root, substantially of structural piping. It is about 50 feet square, 26 feet high, and weighs approximately 140 tons in air, with positive buoyancy in water with pipes un flooded. A circular base has also been designed, to serve as a template for drilling deviated wells from the sea floor, when the system is projected for use in a production configuration. For example, a base 80 feet in diameter has been designed to accommodate the drilling of up to 18 wells. The actual size and shape of the base are flexible, therefore, provided structural and operational requirements are satisfied.1,2,3
Serving as the focal point of the system, the Subsea Work Enclosure (SWE) provides a dry environment on the sea floor at atmospheric pressure, in which normal oil field equipment may operate, maintained by oil field personnel. The SWE prototype, shown in Figures 2 and 3, is a subsea structure constructed of thick alloy steel, measuring 54~ feet high, 16~ feet in base diameter, and designed for an operating depth of 1500 feet. Its geometric shape as a stepped cylinder was designed to optimize the internal piping and equipment arrangement and the external connection of wells completed around its periphery.