Laboratory testing to qualify several materials for high strength fastener applications for two projects has shown that, in the presence of cathodic protection, nickel alloys 718 and 725 offer the best resistance to hydrogen embrittlement and are available in the strength/size required for high pressure and moderate temperature applications for sub-sea applications.
Hydrogen sulfide gas produced by sulfate reducing microorganisms (SRM) creates significant challenges in the petroleum industry including corrosion concerns, product devaluation, and significant health risks. Biocides and inhibitors are often employed to control these detrimental activities. Recently, co-injection of a synergistic blend of biocides and the SRM inhibitor, nitrite, was proposed as an effective means to control biogenic sulfide production, however, the method only addressed inhibition of SRM activity and not kill. Inhibition can have the undesirable consequence of allowing SRM to resume full activity once the inhibitor is depleted, thus requiring the continuous input of expensive chemicals to maintain control. On the other hand, biocides are designed to reduce SRM concentrations thus reducing the need to add additional chemical until the SRM population re-establishes. Lab results, using an SRM field enrichment, demonstrated that the sequential injection of nitrite inhibitor followed by glutaraldehyde led to an 8-log reduction in SRM while only a 2-log reduction when co-injecting these chemicals at equivalent concentrations. It is proposed that pretreatment with the inhibitor, nitrite, or other respiratory inhibitor, results in a reduction in cellular ATP of the SRM creating a sublethal stress response allowing for their enhanced kill upon subsequent biocide addition.