Abstract
Mercaptans are volatile organosulfur compounds produced in natural environments and together with H2S, constitute the most common sulfur-containing contaminants present in sour crude oil and natural gas condensate. One of the most viable options for removing low quantities of mercaptan, usually below 200 ppm, is the use of mercaptan scavengers. In particular, those scavengers referred to as nonregenerative because they react irreversibly to thiol species and convert them to a more inert form. They can be applied in batches in a liquid or solid form inside bubble towers or packed bed scrubbers but also via continuous direct injection into the produced fluids. Although in most cases the methods of screening H2S or mercaptan scavengers are the same, there is no detailed study in the literature of the experimental challenges associated with their use in the presence of a mixture of mercaptans and different test fluids. To address this issue, a laboratory apparatus was used to simulate an inline scavenger injection test. The system supplies a constant stream of a gas mixture comprised of methyl, ethyl, propyl, and isopropyl mercaptan at a fixed amount through the test fluid comprised of water or hydrocarbon until a steady state concentration in the fluid is achieved. By studying the solubility profiles of the mercaptan mixture in aqueous and hydrocarbon fluids the most adequate test conditions to perform the inline injection experiment including temperature, gas flow rate, and scavenger concentration were determined. This optimization process allowed us to simultaneously calculate the scavenger uptake of different chemistries for each alkyl mercaptan in one single test. The results provide a better view of the behaviour and efficiency of mercaptan scavengers in conditions closer to those found in the oilfield.
