Abstract

When it is necessary to waterflood producing reservoirs located offshore, the obvious source of water is from the sea. While the concept of using this water is simple, the necessary steps to make the water suitable for injection must be carefully analyzed along with close attention to the mechanical system and the equipment necessary to handle large amounts of seawater.

Analysis of the problem must begin with the seawater itself as it pertains to chemical and physical properties, scaling tendencies, organisms and other sea life, along with a recommended depth from which the water is lifted on to the platform for further treatment. This treatment can involve several types of filtration and processes for oxygen control.

Chemical injection to control scale and marine life must be carefully evaluated not only from the standpoint of being effective, but also for its cost, logistic availability, and effects on materials of the mechanical system.

The type of filtration must be chosen from a wide variety of available systems, and the factors to be evaluated will include reliability, cost, maintenance and operating requirements, platform weights and space, logistics, etc.

Oxygen control methods also require careful evaluation and can range from a simple scavening technique to a complex vacuum deareation plant.

The mechanical system to lift, treat, monitor, and inject seawater must be suitable to resist the very corrosive nature of the liquid, but also must be reliable for long term operations.

Very careful attention must be made of all materials of construction of the entire system and especially those parts involving coatings, linings, and plastics.

When the seawater plant is in operation, a well designed quality control and monitoring system is absolutely essential for the long term operation of the plant and for protection to the reservoir.