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Aeration of injection waters can create numerous problems. Corrosion of equipment, scale deposition and injection well plugging can reduce the profitability of a waterflood by affecting the ability to get the correct volumes of water into the proper zones at the proper time for efficient sweep and recovery. Operation of a "closed", air-free system will minimize many of these problems. problems. Practical approaches to the successful operation of such systems involve design and operation of water sources, oxygen removal from aerated sources, and maintenance of oxygen-free conditions throughout the system. Day-today operation, monitoring techniques and "oxygen conscious" personnel are important.
If the statistics were available, we would probably find that aeration of the water is a bigger cause of problems in injection systems than any other single cause.
The role of oxygen in the corrosion reaction in water systems has long been recognized; and corrosion resistant materials, coatings and linings were used in early systems.
Oxygen (air) plays an equally important role in creating problems of deposits and injection well plugging. Aeration of a stable underground water results in the loss of stabilizing gases as well as oxidation of precipitable solids. This leads to the formation of scales, deposits and well plugging solids. Mixing an aerated supply water with a stable subsurface water can lead to similar problems. Installation of a "closed system" has been the approach to minimizing these effects.
The selection of the mode of operation of a water injection system is, of course, an economic balance which must consider the overall profit of a project throughout its life. Some factors are obvious, i.e., costs of failures, failure repairs and well cleanouts. However, many of the less obvious factors may be even more significant in a waterflood, such as, loss of injection capacity, plugging of tight zones, downtime, etc.