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Sustainable Biocide Formulations to Deliver Controlled Post Fracture Souring Management

Experimental work has demonstrated that novel combinations of the preservative 1,3-Dimethylol-5,5-dimethylhydantoin and tetrakis hydroxymethyl phosphonium sulfate (THPS).can provide synergistic biocidal performance against commonly found oilfield bacteria.

Product Number: 51317--9115-SG
ISBN: 9115 2017 CP
Author: Stephanie Edmunds
Publication Date: 2017
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Hydraulic fracturing used in unconventional shale gas and oil extraction uses large amounts of water which needs to be treated with biocides to prevent microbial degradation of the fracturing fluids and subsequent microbial contamination of the reservoir. Biocide selection for treatment of the fracturing fluids ‘on the fly’is normally based upon rapid speed of kill in the source water and compatibility with the fluid system. However a growing requirement is to deliver an holistic biocide package that can also provide protection post fracturing in the reservoir where the newly opened fracture faces introduction of nutrients and degradable carbon sources provide a favourable environment for microbial growth.Many of the commonly used fracturing biocides are inactive in the reservoir either due to adsorption onto surfaces deactivationby the reservoir temperature or presence of hydrogen sulfide (in the case of sour reservoirs). For these reasons either slower acting preservatives that can retain their activity or formulations of THPS that have good tolerance to temperature and are not inactivated by hydrogen sulfide may be used.Experimental work has demonstrated that novel combinations of the preservative 13-Dimethylol-55-dimethylhydantoin and THPS can provide synergistic biocidal performance against commonly found oilfield bacteria . Whilst 13-Dimethylol-55-dimethylhydantoin can be considered a functional equivalent to biocides such as dimethyl oxazolidine its controlled release profile appears to supplement and enhance the performance of THPS when either co-applied or co-formulated and results observed over an extended time period. Combinations of13-Dimethylol-55-dimethylhydantoin and other THPS formulations provide a rapid kill of planktonic sulphate reducing bacteria and acid producing bacteria and additionally show good penetration of established bacterial biofilms. The deployment of these biocides in combination will offer a sustainable approach for ‘on the fly’ reservoir treatment and forimproving flow-back water quality by providing longer term control of souring within the microfractures whilst alleviating biogenic sulfide production both as hydrogen sulfide and limiting iron sulfide deposits. The total amount of biocide required will be reduced compared to the separate addition of the individual components.

Key words: Sustainable, biocide, unconventional, hydraulic fracturing, tetrakishydroxymethyl phosphonium sulphate, bacteria, 1,3-Dimethylol-5,5-dimethylhydantoin, reservoir, post fracture, souring.

 

Hydraulic fracturing used in unconventional shale gas and oil extraction uses large amounts of water which needs to be treated with biocides to prevent microbial degradation of the fracturing fluids and subsequent microbial contamination of the reservoir. Biocide selection for treatment of the fracturing fluids ‘on the fly’is normally based upon rapid speed of kill in the source water and compatibility with the fluid system. However a growing requirement is to deliver an holistic biocide package that can also provide protection post fracturing in the reservoir where the newly opened fracture faces introduction of nutrients and degradable carbon sources provide a favourable environment for microbial growth.Many of the commonly used fracturing biocides are inactive in the reservoir either due to adsorption onto surfaces deactivationby the reservoir temperature or presence of hydrogen sulfide (in the case of sour reservoirs). For these reasons either slower acting preservatives that can retain their activity or formulations of THPS that have good tolerance to temperature and are not inactivated by hydrogen sulfide may be used.Experimental work has demonstrated that novel combinations of the preservative 13-Dimethylol-55-dimethylhydantoin and THPS can provide synergistic biocidal performance against commonly found oilfield bacteria . Whilst 13-Dimethylol-55-dimethylhydantoin can be considered a functional equivalent to biocides such as dimethyl oxazolidine its controlled release profile appears to supplement and enhance the performance of THPS when either co-applied or co-formulated and results observed over an extended time period. Combinations of13-Dimethylol-55-dimethylhydantoin and other THPS formulations provide a rapid kill of planktonic sulphate reducing bacteria and acid producing bacteria and additionally show good penetration of established bacterial biofilms. The deployment of these biocides in combination will offer a sustainable approach for ‘on the fly’ reservoir treatment and forimproving flow-back water quality by providing longer term control of souring within the microfractures whilst alleviating biogenic sulfide production both as hydrogen sulfide and limiting iron sulfide deposits. The total amount of biocide required will be reduced compared to the separate addition of the individual components.

Key words: Sustainable, biocide, unconventional, hydraulic fracturing, tetrakishydroxymethyl phosphonium sulphate, bacteria, 1,3-Dimethylol-5,5-dimethylhydantoin, reservoir, post fracture, souring.

 

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