Assessment of the Decomposition Kinetics of Sulfur-Containing Biocides to Hydrogen Sulfide at Simulated Downhole Conditions

Abstract

North American production of liquefied natural gas is at an all-time high in large part due to shale gas extraction from unconventional reserves. In producing shale gas, hydraulic fracturing in combination with horizontal drilling is often used to create a path to free the hydrocarbons embedded in the reservoir. Biocides are incorporated into the fluid during drilling and fracturing for preventing activity from both native and non-native bacteria and potential reservoir souring (biogenic generation of H 2 S). Certain sulfur-containing biocides have been reported to be used as part of the fracturing fluid in several reservoirs. Our research has shown that at high-temperature downhole conditions, some of these compounds can decompose and generate unwanted H 2 S and organosulfur compounds as byproducts. In the case of dazomet, a sulfurcontaining biocide, the decomposition products underwent hydrolysis under downhole conditions to produce undesirable H 2 S, CS 2 , and CH 3 SH. A second biocide tested, methylisothiazolinone, eliminated sulfur and generated H 2 S by sulfur dehydrogenation of the reaction intermediates. Our findings highlight the chemical transformation that sulfur-containing biocides could undergo under hydraulic fracturing conditions. In these circumstances H 2 S and organosulfur compounds can be generated.

Hydrogen Sulfide Measurement of Degraded Corrosion Inhibitor with Glass Tube Detector in Oil & Gas Industry

“…Due to this condition, the CI mixture with TGA content, which was stable at room temperature (Sigma-Aldrich, 2021), could be unstable and decomposed to produce H 2 S. The increasing ambient temperature could raise the reaction rate of H 2 S formation from sulfur-containing chemicals, such as TGA. This phenomenon was similar with other sulfur containing chemicals, such as 2,5-dimercapto-1,3,4-thiadiazole (DMTD) and 2-amino-1,3,4thiadiazole (ATD) (Marrugo-Hernandez et al, 2019).…”

“…The formation of H 2 S gas in the product occurs due to the chemical decomposition process of TGA, as the active ingredient of CI containing sulfur, which is influenced by changes in pressure and temperature (Marrugo-Hernandez, Prinsloo, and Marriott, 2019). In the oil and gas industry business process, CI products are generally produced and supplied by the chemical producer and delivered to the oil and gas operation area with a long distribution process, starting from the chemical plant, port-toport transfer, and overland by trucks.…”

“…It is recommended to measure the thermochemical sulfate reduction reaction (TSR), as the H 2 S gas formation process from TGA, by analyzing through gas chromatography (Marrugo-Hernandez et al, 2019). By knowing the rate of formation of H 2 S, the company evaluates a more appropriate capsize and provides recommendations to the chemical supplier to install it at each drum.…”