Behavior of Dissolved Oxygen in Oil Field Brine
- George G. Bernard (The Pure All Co.) | Glenn A. Marsh (The Pure All Co.)
- Document ID
- Society of Petroleum Engineers
- Journal of Petroleum Technology
- Publication Date
- May 1952
- Document Type
- Journal Paper
- 119 - 122
- 1952. Original copyright American Institute of Mining, Metallurgical, and Petroleum Engineers, Inc. Copyright has expired.
- 4.3.4 Scale, 4.2.3 Materials and Corrosion
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- 177 since 2007
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It is often assumed that aerated oil field brines which are to be injected underground contain dissolved oxygen in amounts which will cause appreciable corrosion. Through the use of a new portable dissolved oxygen meter, accurate determinations were made at three brine conditioning plants. At two older plants, dissolved oxygen concentration in the final treated brine was found to be almost zero in spite of aeration during the conditioning process. At a new plant, dissolved oxygen was initially present but disappeared soon after the brine was "inoculated" with oxygen-free brine from one of the other plants. Corrosion tests at the two older plants have substantiated predictions that the brines would not be corrosive. These results show that mechanical deaeration may not always be required in brine treating plants.
The present work was undertaken to add to our knowledge of aeration and deaeration of oil field brines in brine conditioning plants. It is commonly assumed that brines which are exposed to the air soon become more or less saturated with dissolved oxygen. Since oxygen-containing brines are known to be corrosive, precautions are often taken to keep air out of brine through the use of closed systems or mechanical deaeration.
The study of oxygen in brine has been seriously hampered in the past because of the lack of a suitable analytical tool. The standard Winkler method for the determination of dissolved oxygen is satisfactory for use in fresh water, but not in many oil field brines. Corrections have to he made for a number of reducing substances such as ferrous iron and hydrogen sulfide which are commonly present in natural brines. Very often the correction factors are much greater in magnitude than the amounts of oxygen which are to he determined, and consequently erroneous results are obtained. Also, erratic Winkler data are obtained when appreciable concentrations of calcium and magnesium salts are present.
The first step in carrying out a systematic study involved designing a portable dissolved oxygen apparatus which would operate in natural brines. Subsequently, this apparatus was used in three brine conditioning plants. Dissolved oxygen data obtained here, and certain corrosion rate data, illustrate the interesting behavior of oxygen in these oil field brines.
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