Multiple Well Man foldProduction Station

The station consists of three basic hardware components—the base, the wellhead connector assembly, and the subsea work enclosure. It also includes a number of associated supporting subsystems. A full-scale prototype has been constructed and tested.

Oilfield Scale Model Drilling Rigs
Fig. 4-5 SEAL bell system.

a) Base

The prototype base (Figure 4-6) is composed of structural piping and is about 50 feet square, 26 feet high. It weighs approximately 140 tons in air, with positive buoyancy in water with pipes unflooded. A circular base was 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 of 80 feet in diameter was designed to accommodate drilling up to 18 wells. The actual size and shape of the base are flexible, provided structural and operational requirements are satisfied.

b) Subsea Work Enclosure

The subsea work enclosure (SWE) provides a dry environment on the sea floor at atmospheric pressure in which normal oilfield equipment may operate. It is maintained by

WCA GUIDE POSTB)

WCA GUIDE LINE®

Subsea Pile Template

BUOY(S)

HAUL L'NE

pile

Fig. 4-6 Base for SEAL system.

BUOY(S)

HAUL L'NE

WCA GUIDE POSTB)

WCA GUIDE LINE®

pile

Fig. 4-6 Base for SEAL system.

oilfield personnel. The SWE prototype (Figures 4-5,4-7, and 4-8) is a subsea structure consisting of thick alloy steel measuring 54Vis feet high and I6V2 feet in base diameter. It is designed for an operating depth of 1,500 feet, weighs 230 tons in air, and is just slightly buoyant in water.

The unit's stepped-cylinder shape was designed to optimize internal piping and equipment arrangement and the external connection of wells completed around its periphery. However, the size and shape of the SWE depend on a number of physical variables, including water depth, number of associated wells, properties of hydrocarbon fluids, production rates, pressures, field characteristics, etc. c) Wellhead Connector Assembly

This assembly serves as a flow-line link betweed peripheral wellheads and the SWE. A prototype assembly was constructed to connect two wellheads with the SWE through one of its penetrator openings. Early design constraints imposed very wide spatial and azimuthal toler-

submersible mating ring matng a transfer section

25 inch diameter control section b foot diameter

30 inch diameter transfer compartment handling lug submersible mating ring matng a transfer section

25 inch diameter control section b foot diameter

30 inch diameter transfer compartment handling lug

SERVICE a EQUIPMENT SECTION

top 5 feet (above base)

hatch 49 7 feet deck f 39.7 feet penetrations 370 feet deck d 2b7 feet deck c 207 feet deck b 127 feet deck a 55 feet (above base) 0 feet base connection hLÖWLINl-'EutjM

43 feet

Fig. 4-7 Subsea work enclosure.

SERVICE a EQUIPMENT SECTION

hLÖWLINl-'EutjM

43 feet top 5 feet (above base)

hatch 49 7 feet deck f 39.7 feet penetrations 370 feet deck d 2b7 feet deck c 207 feet deck b 127 feet deck a 55 feet (above base) 0 feet base connection

  1. 4-7 Subsea work enclosure.
  2. Thus, the prototype (shown in Figure 4-9) allows for a variation of± 18 inches between the two wellheads, ± 18 inches between the well couplet and the SWE penetrator, and up to 5 degrees misalignment in either element. It is evident that with today's drilling technology, tolerances of this magnitude are unnecessary and new designs are being initiated which will considerably simplify the connector assembly, d) Supporting Subsystems

Internally, the SWE prototype consists of an upper control section and a lower service section. The control section houses the electrical equipment and the supervisory control system's remote units. The service section houses all piping

SWE HYDRAULIC
Well Control System Offshore
Fig. 4-9 Wellhead connector.

equipment involved in producing oil, including a gas-oil separator designed for individual well testing with the capability to automatically run pump-down tools. The prototype also includes life support and environmental control systems, hydraulic and electrical systems, a bilge pumping system, a supervisory control system for automation and monitoring, and a personnel transfer bell for transporting staff to the SWE. e) Testing History

The prototype manifold/production station was dry-land tested in Long Beach, California in 1971, using dead crude oil and gaseous nitrogen to simulate field conditions. The use of the two-phase fluid permitted check-out of the test separator located in the lower portion of the MWE.

In 1972, the unit was transported to the Gulf of Mexico and placed on the ocean floor in 247 feet of water in Main Pass Block 293A near a Sun Oil Company production platform. Production from live wells on the platform was introduced into the system for testing under almost real conditions, including more than 90 automatic operations of the pump-down tool system. During the test period, the personnel transfer bell was used more than 60 times to carry men and materials into the MWE.

Figure 4-10 shows the MWE on a circular base, through which deviated wells are drilled. Figure 4-10A demonstrates the application of the MWE in commingling production from vertically drilled wells completed with the single-well system.

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