Removal of hydrogen sulfide from natural gas is a primary concern for many producers. Many natural gas systems throughout the South Texas area have H2S concentrations that range from less than 10 ppm to more than 1000 ppm. While amine units are usually efficient at removing H2S cost-effectively, the high capital cost has encouraged the development of other treatment methodologies for the removal of low to moderate quantities of H2S from natural gas. One such method is the injection of liquid chemical scavengers directly into the gas stream. The chemical scavenger reacts with the H2S and forms a product that is removed from the gas by separation equipment, such as a scrubber.

Although the chemistries of the scavenger reactions are fairly well known, the efficiency and therefore the cost-effectiveness of removing H2S by this method is highly dependent on system conditions and architecture. Many parameters impact the efficiency of liquid H2S scavenger application. Important factors include mixing, a function of several parameters such as gas velocity and injection method, and retention time, which is the time available at a specific set of conditions to achieve maximum scavenger efficiency. Based on these and other factors, a field study was undertaken to evaluate the effects of system conditions, architecture modifications, and of specialized equipment types on improving the efficiency of H2S removal. This paper will present field data and describe the mass balance efficiencies of several types of scavenger applications including injection into existing systems, the use of retention treating loops, and bubble towers for the removal of H2S.

The use of mass balance calculations during the project allowed for careful assessment of scavenger efficiencies in a variety of conditions and treatment scenarios. Mass balance is a useful tool when liquid scavenger testing includes several formulations of varying concentrations. The results of the field evaluation provided data that led to a better understanding of liquid scavenger usage and applications limits. The improved understanding of treatment envelopes allows field users to more efficiently identify candidate scavenger processes and make more informed decisions on process selection for removal of H2S from natural gas streams.

Keywords:
workplace hazard, reaction, separation equipment, oilfield chemistry, upstream oil & gas, spe 94303, natural gas stream, h2s management, champion technology, gas stream
Subjects:
Production Chemistry, Metallurgy and Biology, Health, Noise, chemicals, and other workplace hazards, Corrosion inhibition and management (including H2S and CO2)
Copyright 2005, Society of Petroleum Engineers
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