51316-7731-The Selection and Performance of Oil and Gas Biocides for Extended Microbial Control

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Product Number: 51316-7731-SG

ISBN: 7731 2016 CP

Author: Jon Raymond

Publication Date: 2016

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It is well understood that sulfate reducing bacteria (SRB) acid-producing bacteria (APB) and facultative anaerobic bacteria may cause a range of problems in oil and gas applications including the production of hydrogen sulfide (souring) microbially influenced corrosion (MIC) and additive spoilage. These problems may ultimately reduce the quality of the hydrocarbon produced decrease the durability of structural assets and accelerate formation damage. Microbial contaminants may originate from poorly treated source waters and process fluids (e.g. drilling fluids) as well as resident organisms existing in the subsurface environment.The antimicrobial performance of oil and gas biocides is dependent on their stability and compatibility with key environmental parameters in applications such as hydraulic fracturing and water flooding. For an extended microbial control program the biocide must survive and function under varying conditions. The most aggressive conditions involve the downhole environment where temperature and salinity extremes may occur and interactions with the substrata (rocks mineral soil hydrocarbons) create a complex set of interacting influences.This study investigated the interactions of several oil and gas biocides in the presence of varying temperatures process additives and subsurface matrices. The effect of the variables on chemical stability was determined analytically and the resulting impact on residual efficacy was assessed by microbial viability. Stability profiles were determined over a range of different water types and temperatures up to 70° C over extended periods of time. Certain actives were more adsorptive to solid rock substrata than others. Cationic (surface active) biocides tended to bind to soil and rock and be removed from the water phase relatively quickly whereas non-surface active biocide chemistries showed better compatibility with subsurface materials. Testing included both static and dynamic model systems at temperatures up to 70° C. In general adsorption of the biocide to the rock matrix correlated with reduced biocide performance. The results of these studies provide insight and guidance into the selection and use of oil and gas biocides for downhole applications where compatibility with complex environmental parameters is required in order to provide long-term extended microbial control.