Aqualin Biocide In Injection Waters
Authors: Jorda R. M. , Shearer L. T. 
Published: December 2007

AQUALIN Biocide, a Shell Chemical Company formulation consisting of 85 percent by weight acrolein, has been used with unusual success in injection waters for control of microorganisms. Complete control of various strains of bacteria has been experienced in all cases in which tests have been made. Injection of acrolein in low concentrations into anaerobic injection water systems is accomplished with a positive displacement pump. The results of the laboratory and field experiments are presented, and chemical feeding techniques are described.

Introduction

All industries that utilize large amounts of water have encountered microbiological problems of varying degrees. However, only in recent years has the petroleum industry recognized the problems created by bacterial organisms in oilfield water treating. With the advent of large-scale secondary recovery by means of waterflooding, larger quantities of water have been both produced and injected. The bacteria problem was originally ignored in many of these operations, and only when serious problems were encountered did the oil industry become aware of the effect of microorganisms in water systems.

With the recognition of the microbial problems of water injection came the investigation of control measures. In early investigations, poisons were found to be ineffective because of the ability of the microbes to develop immunities. Further study revealed that cationic organics, such as diamines, quaternary ammonium chlorides, and other amines, provide good control of the most troublesome organisms, but the cost was high and the bactericide-selection procedure was lengthy. During the last decade, bacteria control in oilfield operations has generally been achieved with amines.

If bacterial action in any system is severe enough to interfere with operations, it follows that a "universal", inexpensive bactericide to eliminate the problem would be desirable. This product should not greatly change the chemical and physical properties of the water, other than to destroy the bacteria. The most important properties which should not be altered are pH, surface and interfacial tension, and viscosity so that further treatment will not be needed to alleviate the changes. Hundreds of bactericides have been studied within Shell research groups to find a product meeting these requirements. Our findings relating to the effectiveness of acrolein are described in this paper.

OCCURRENCE AND CONTROL OF WATER-BORNE MICROORGANISMS

Water treating to control microorganisms is a highly selective problem. For example, bacterial contamination of the same degree may be tolerated in one system but not in another. Consequently, each water considered for use must be tested separately. If bacteria are present, and the nature of the system is conducive to their growth, it must further be determined what damage, if any, can be expected. If bacteria problems are anticipated, suitable bactericides must be chosen. Knowledge of the occurrence of microorganisms in water provides a sound basis for investigating these problems.

The number of microorganisms which exist in waters considered for use in waterfloods and disposal systems varies greatly. The type of system employed determines the types of organisms and the problems they present. Aerobic systems are generally conducive to the growth of iron bacteria, fungi, algae, and capsulated bacteria. The iron bacteria are probably the most important of these, since they can produce very tenacious, gelatinous slimes of ferric hydrate capable of fouling water lines and plugging injection wells. These bacteria can grow in waters containing less than one to over eight parts per million oxygen, but they require iron salts to sustain their metabolism.

Algae require direct exposure to sunlight and a source of carbon dioxide to sustain photosynthesis, but they do not require direct exposure to the atmosphere, as do the molds and fungi.

P. 771^