Page 234 - Petroleum and Gas Field Processing

9

Produced Water Treatment

9.1 INTRODUCTION

Production of crude oil and natural gas is usually associated with the
production of water. During the early life of the petroleum fields,
water-free production of oil and gas is normally experienced. However,
water will eventually be produced later. The produced water may be water
that exists within the petroleum reservoir as connate water or bottom
water. Alternatively, water may be produced as a result of water-flooding
operations, where water is injected into the reservoir to enhance the
recovery.
Water production presents serious operating, economic, and
environmental problems. Production of water with the crude oil or
natural gas reduces the productivity of the well due to the increased
pressure losses throughout the production system. This may either result in
reduced production or necessitate the installation of costly artificial lifting
systems to maintain the desired production levels. Production of water
also results in serious corrosion problems, which add to the cost of the
operation. As discussed in the previous chapters, production of water with
the crude oil or natural gas requires the use of three-phase separators,
emulsion treatment, and desalting systems, which further add to the cost
of the operation.
In most situations, the produced water has no value and should be
disposed of. In other situations, the produced water may be used for water
flooding or reservoir pressure maintenance. The produced water, collected
from the separation, emulsion treatment, and desalting systems, contains
hydrocarbon concentrations that are too high for environmentally safe
disposal. The presence of the hydrocarbon droplets in the water makes it
difficult to inject the water into disposal wells or into water-injection wells

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