The Manifold

This unit (Figure 4-20) is the heart of the entire system. It is

Pump-down tool line

Production manifold section 1

Disconnects

Hydraulic-control line

Production manifold section 2

Production Manifold

Pump-down tool crossover valwe

Pig-launch magazine

Production line Gas-injection fine Waterflaod and production line Pump-down toot Une

To assembly

Front bulkhead section

Pump-down tool line

To assembly

Production manifold section 1

Pump-down tool crossover valwe

Pig-launch magazine

End hufkheod section

Disconnects

Hydraulic-control line

Production manifold section 2

Front bulkhead section

Production line Gas-injection fine Waterflaod and production line Pump-down toot Une

Fig. 4-20 Production manifold for Exxon SPS. &

made up of all the necessary piping to carry out the assignments of the SPS. It is rectangular shaped with well-rounded corners to allow use of pump-down tools. In the prototype, its shape is almost square because the design is based on three wells. But the square can be elongated to a rectangle by adding manifold sections for additional wells.

The manifold is fail-safe. If hydraulic power is lost, or if any abnormal conditions exist, all valves close and the system is left in a safe condition.

The manifold is designed to permit use of pump-down tools, to provide for individual well tests, to handle injection of chemicals for inhibition of corrosion or hydrate formation, and to provide for artificial lift and control producing rates through remotely adjustable chokes.

The manifold is actually a dual system which permits injection of pressure-maintenance fluids through one group of wells while simultaneously producing another group. Further, the manifold has the capability of pigging all lines in the system.

To achieve all these functions, the manifold consists of 5 lines. Two large lines can be used for high and low-pressure gathering systems, or one can be used for production and the other for injection. Two other lines are multipurpose lines that can be used for inhibitor injection, well testing, and pump-down tools. The fifth line is for gas-lift gas distribution.

Each well is connected to all of these lines. This makes the system relatively complex but eliminates addition of new equipment as producing conditions change. The manifold is ready to handle production from the time the well starts flowing, through the artificial-lift period, and on to abandonment. The manifold can handle pressure-maintenance chores as needed and perform well repair and maintenance via the pump-down system. It is designed for initial installation with all these capabilities so nothing need be added at a later date.

Only two kinds of joints are in the manifold—welded joints and mechanically locked metal-to-metal seals. They provide long life and good reliability.

To insure safety in the manifold, it was designed according to the most stringent code requirements. This was done to take advantage of all available technology in metallurgy, design for high stress levels, and fabrication procedures. Exxon engineers felt that a rigid code would include the toughest requirements in these three areas.

The multipurpose lines are rated at 5,000 psi, the gas-lift lines at 1,500 psi, and the large gathering manifold at 3,000 psi. On completion of fabrication, these lines will be tested at twice these rated pressures. All welds are 100% X-rayed.

The Wells

Wells drilled to produce through the SPS are rigged foT pump-down tools, using strings of 3V2-inch tubing. Each well is equipped with a full-opening, surface-controlled, hydraulically operated down-hole safety valve, located below the mudline. The valves are fail-safe and are held open by hydraulic pressure.

At the Xmas tree, there is a conventional fail-safe master valve which passes produced fluids through looped lines to the manifold. The looped lines permit passage of the pump-down tools.

The trees are moTe simply constructed than conventional trees in that the wing valves and other appurtenances have been moved to the manifold. Collet connectors join the wellhead to the manifold. A specially designed tool applies hydraulic pressure to the mating part of the connection to complete the joint.

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