ABSTRACT

Acrolein (2-propenal) is a microbiocide that has been used to mitigate bacterial problems in oilfield systems. The applications are widespread and include production and injection wells, surface equipment, and water injection systems. The applications include both onshore and offshore facilities throughout the world. The purported biocidal mechanism is the attack of sulfhydryl and amine groups on bacterial proteins by the a,ß-conjugated double bond resulting in disruption of enzyme systems and destruction of integrity of structural proteins. The reactivity with sulfides also renders acrolein effective as an H2S scavenger and iron sulfide dissolver, two byproducts of sulfate-reducing bacteria (SRB) metabolism. This paper reviews a number of case histories highlighting acrolein?s biocide performance to mitigate microbiologically influenced corrosion and other oilfield bacterial problems. Also included is a compilation of laboratory studies comparing the efficacy of acrolein with other microbiocide chemistries against diverse populations of bacteria from the oilfield environment. In 89% of the laboratory studies conducted, acrolein shows superior biocide performance against general aerobic and facultative anaerobic bacteria (GAB) and SRB in a cost competitive manner. Its properties of oil solubility and biofilm penetrability render it a versatile and effective biocide for targeting persistent sessile populations of bacteria that are often inaccessible to conventional biocides. Due to its low minimum inhibitory concentration, acrolein finds success not only in batch applications but also in continuous treatment programs.

INTRODUCTION

Bacteria have a major adverse effect on oilfield systems, causing numerous problems related to formation face damage, biofouling, iron sulfide scaling, hydrogen sulfide generation, emulsification, and microbiologically influenced corrosion (MIC). These problems are frequently treated symptomatically, which may provide temporary solutions but can ultimately lead to more serious long term effects. The more direct approach is to target the bacterial populations with a biocide that can mitigate the microbial problem at the source. There are several common chemistries that are used in the oilfield to control problematic bacteria. These chemistries include oxidizing biocides, such as chlorine and bromine and their derivatives, and nonoxidizing biocides such as aldehydes, quaternary amines, quaternary phosphonium salts, brominated compounds (e.g. bronopol and DBNPA), and isothiazalones. In order to perform adequately in an oilfield system a biocide must satisfy a number of criteria:1

? It must be effective with respect to the spectrum of bacteria, speed of kill, and minimum

inhibitory concentration.

? It must be cost effective with respect to cost and concentration.

? It must be safe with respect to personnel and environment.

? It must be compatible with system fluids and with other treatment chemicals.

? It must satisfy handling requirements such as corrosivity and stability.

Ultimately, the chemistry must be carefully selected for the desired application and this selection should be supported by laboratory screening and field monitoring to ensure success of the program.1

Acrolein

Acrolein is a unique compound among the various chemistries of oilfield microbiocides. This small 3-carbon vinyl aldehyde is highly reactive chemically due to a carbon-carbon double bond conjugated with the double bond of an aldehyde carbonyl:2 Acrolein

The biocidal efficacy of acrolein at low dosages stems from its ability to denature proteins and inhibit several enzyme systems within the living cell

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