Reactions involving fracturing chemical additives with implication in delayed H2S production
Date
2019-09-06
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Abstract
Shale gas is fast becoming the primary source of liquefied natural gas, a must needed fuel in a society trying to lower carbon emissions. When producing shale reservoirs, hydraulic fracturing in combination with horizontal drilling are the chosen technologies to extract hydrocarbons economically and efficiently. An issue faced during production from hot shale gas reservoirs (T > 100 °C) is the presence of hydrogen sulfide (H2S) and organo-sulfur compounds (CxHy-SH) in the production fluids. These sulfur species can have a significant economic impact on the overall production as the gas now has to be treated to remove the unwanted components. In this work, the decomposition of selected chemical additives contained within fracturing fluids are investigated as an alternative explanation to the H2S formation in hot shale sweet gas reservoirs. Initially, high-pressure and high-temperature decomposition/hydrolysis of sulfur-containing biocides and corrosion inhibitors were studied, and the mechanisms of H2S generation were proposed. Although the results were definitive, sulfur-containing additives are not always applied. Therefore, in researching a more universal explanation of non-biogenic souring, an undeniable fact came to light: the water used in hydraulic fracturing is not degassed, thus it is saturated with oxygen at field conditions. As such, the oxygen present in the fluid can react with native H2S to generate elemental sulfur. Under downhole conditions elemental sulfur can react with hydrocarbons regenerating H2S. For this reason and to further prove this hypothesis, the kinetics and equilibrium products of sulfur-methanol reaction in aqueous conditions was studied under various downhole conditions e.g. temperature, pressure, pH and salinity.
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Keywords
Shale gas, hydrogen sulfide, Hydraulic fracturing
Citation
Marrugo Hernandez, J. J. (2019). Reactions involving fracturing chemical additives with implication in delayed H2S production (Doctoral thesis, University of Calgary, Calgary, Canada). Retrieved from https://prism.ucalgary.ca.