++++ Introduction

Figure 6. Produced water treatment

It also places limits on other forms of contaminants. This still means that the

equivalent of up to one barrel of oil per day in contaminants from the above

production is discharged into the sea, but in this form, microscopic oil drops

are broken down quickly by natural bacteria.

Various pieces of equipment are used. This illustration shows a typical water

treatment system. Water from the separators and coalescers first goes to a

sand cyclone, which removes most of the sand. The sand is further washed

before it is discharged.

The water then goes to a hydrocyclone, a centrifugal separator that

removes oil drops. The hydrocyclone creates a standing vortex where oil

collects in the middle and water is forced to the side.

Finally the water is collected in the water de-gassing drum. Dispersed gas

slowly rises and pulls remaining oil droplets to the surface by flotation. The

surface oil film is drained, and the produced water can be discharged to sea.

Recovered oil in the water treatment system is typically recycled to the third

stage separator.

Gas treatment and compression

The gas train consists of several stages, each taking gas from a suitable

pressure level in the production separator's gas outlet, and from the previous

stage.

A typical stage is

shown on the right.

Incoming gas (on

the right) is first

cooled in a heat