Impacts of Tetrakis-hydroxymethyl Phosphonium Sulfate (THPS) Based Biocides on the Functional Group Activities of Some Oil Field Microorganisms Associated with Corrosion and Souring.

Aim: To determine the biocidal efficacy of THPS based biocides currently used in oil fields to control souring and corrosion. Methodology: By direct monitoring of inhibition of cell growth and inhibition of microbial functional group activities such as the ability to reduce sulfate and generate sulfide by sulfate reducing bacteria (SRB), reduce nitrate to nitrite by heterotrophic nitrate reducing bacteria (hNRB) and oxidation of sulfide and reduction of nitrate by sulfide oxidizing, nitrate reducing bacteria( so-NRB) using CSB-K medium. Results: We observed that higher doses of THPS (>400 ppm) was required to considerably inhibit the ability of SRB to reduce sulfate and generate hydrogen sulfide. It was also observed that the activities of SRB were more affected by the THPS biocides than those of hNRB and so-NRB. Conclusion: We conclude that SRB may have developed low level microbial resistance to THPS based biocides as higher doses are required to inhibit their activities. It is therefore recommended that THPS should be used in combination with other biocides or metabolic inhibitors for it to be effective at lower concentrations.

Impacts of Some Non-oxidizing Biocides on the Functional Group Activities of Some Problem Causing Microorganisms in Oil Production Facilities.

Aim: To determine the impacts of some non-oxidizing biocides such as glutaradehyde, sodium azide, isothiazolone on the functional group activities of some oil field microorganisms Methodology: Samples of non-oxidizing biocides were obtained from Microcheck and the inhibition of some functional group activities in produced and injection water samples were determined using CSB-K medium. Results: Glutaradehyde and sodium azide exhibited relatively high level inhibition while isothiazolones exhibited low level inhibition. Glutaradehyde further demonstrated a positive selective inhibitory activity. While SRB activities were inhibited by over 78%, that of hNRB and so-NRB were affected by less than 38%. Conclusion: Glutaradehyde can be developed to an efficient biocide with a positive selective action and can work in synergy with beneficial microbes to eliminate the problem causing ones.

The level of Inhibition of Microbial Functional Group Activities by Some Oxidizing Agents Commonly used as Biocides in Oil field Operations.

Aim: To determine the level of inhibition of microbial functional group activities such as the ability to reduce sulfate to sulfide by sulfate reducing bacteria (SRB), reduce nitrate to nitrite by the heterotrophic nitrate reducing bacteria (hNRB), and oxidize sulfide and reduce nitrate by sulfide oxidizing, nitrate reducing bacteria (so-NRB) by some oxidizing biocides like chlorine, bromine and ozone. Methodology: Samples of the oxidizing biocides were obtained from Microcheck and the inhibition of some functional group activities in produced and injection water samples were determined using CSB-K medium. Results: Ozone was found to be more effective than chlorine and bromine in the inhibition of functional group activities at lower concentrations. Conclusion: More research effort is required to see if ozone can work in synergy with other biocides to improve on its efficiency.