ABSTRACT
The presence of hydrogen sulfide (H2S) in a reservoir poses a major threat to oilfield asset integrity and oil and gas production. In addition to contributing to corrosion, H2S is extremely toxic and devalues produced fluids and gases. Not managing the consequences of a sour reservoir can eventually lead to costly well shut-ins and lost production time. While H2S can be formed through natural chemical reactions, a varied population of microorganisms capable of metabolizing an array of sulfur compounds is responsible for the biotic production of H2S. Current chemical treatment options for remediation of biotic reservoir souring include targeting microbial populations with a biocide or using calcium nitrate to selectively grow microorganisms that metabolize nitrate instead of sulfur compounds. We have recently identified a number of novel compounds that have been proven successful in the laboratory to prevent H2S production by directly targeting the sulfate-reducing population. In this study, we compare these novel compounds to chemistries currently employed to prevent sulfidogenesis, and we introduce an increased-throughput screening method to evaluate sulfide inhibition. Since the novel compounds consistently performed well in synthetic brine compared to other commonly used chemistries, we also provide results detailing the efficacy of these novel compounds in a variety of other conditions as well. These findings further expand our understanding of the existing and potential treatment strategies intended to combat the deleterious effects of biotic reservoir souring.
A reservoir is termed ”sour” when hydrogen sulfide (H2S) is present, which poses a major threat to the oil and gas industry due to the substantial health and economic impacts of souring. H2S is an extremely toxic and corrosive gas that can challenge the asset integrity of a system in many ways, such as H2S stress cracking and plugging by iron sulfide precipitation.1 While the presence of H2S in a reservoir can occur by natural geochemical reactions, this study focuses on the issue of biotic H2S production initiated by sulfate-reducing microorganisms within a reservoir. Sulfate reducing bacteria (SRB) and archaea (SRA) are capable of metabolizing multiple sources of sulfur, such as sulfate and thiosulfate, to respire H2S and contribute to reservoir souring.2-4 These microorganisms can exist indigenously downhole in a reservoir or are commonly introduced into a reservoir in the drilling and completion process and through injection water during secondary oil recovery.5-7 Once colonizing at the wellbore, the SRB/SRA can utilize the volatile fatty acids, sulfur sources, and other nutrients present in the fluids and reservoir to produce H2S that will move through the reservoir to a producing well and mediate its corrosive/toxic effects.
