Hydrocarbon recovery operations use large amounts of water, some of which is routinely treated with biocides to control microbes both topside and downhole. Recent studies have demonstrated that this strategy for microbial control is not always effective. Without a comprehensive microbial control management program, microorganisms proliferate and may adversely affect recovery operations, damage physical assets, and decrease hydrocarbon quality. For example, in situ growth of microorganisms causes souring, plugs the formation, and increases microbially influenced corrosion (MIC). Microbial challenge testing was carried out to compare efficacies of selected commercially-available biocides and new products with better sustainability profiles to resolve these pertinent microbial problems. Whenever possible, the testing conditions simulated those in formations or pipelines.
Water and some chemical additives used in hydrocarbon recovery serve as nutrients for microorganisms, supporting large populations that result in the formation of biofilm, increased the risk of MIC, and decrease the quality and production efficiency of hydrocarbons. Therefore, it is essential to implement an effective microbial control program for both top-side operations and downhole reservoirs.
A microbial audit of a fractured North American shale gas well identified high microorganism counts in the flow-back water and in the injection water. The incumbent biocide only offered inhibitory effects for less than seven days. Laboratory studies identified more effective treatments to control planktonic bacteria, reduce souring, and control MIC-associated microbes. If the most effective chemistries were employed, often in combinations, effective control of the indigenous microbial community could be maintained for prolonged periods while reducing the environmental footprint of the treatments.
Effective microbial control in hydrocarbon recovery operations can be attained by tailoring appropriate biocides to specific sites, alone and in combination, to reduce or eliminate microbially-based problems, protect physical assets, and reduce harm to the environment.