Several test procedures have been developed to evaluate the performance of H2S scavengers in the laboratory. One of these procedures is based on a semi-batch continuous stirred-tank reactor (CSTR) concept with a constant flow of a gas containing H2S. This procedure has been implemented at high pressures and temperatures (HP/HT) to evaluate the effect of several parameters (e.g., temperature, pressure, oil type, brine chemistry, water cut, pH, CO2/H2S concentrations) on the scavenging capacity of different chemicals. However, in many field applications, H2S scavengers are injected at suitable points in the system with the expectation of having the H2S concentration reduced below target levels before the fluid reaches certain parts. Therefore, not only the scavenging capacity but also its kinetics need to be considered when selecting an H2S scavenger for specific applications.

A kinetic model was developed and implemented to assist in the interpretation of H2S scavenger test results obtained from the CSTR with continuous gas flow procedure. Using this kinetic model, parameters related to the H2S scavenger reaction kinetics can be extracted and used for qualifying chemicals for a specific application. This kinetic model also simulates the effect of different test parameters on the experimental results and can be used to extrapolate laboratory results to field conditions.


H2S scavengers (SC) are commonly injected into multiphase pipelines transporting oil, water, and gas when the H2S concentration is relatively low (ppm levels) but higher than the maximum allowable H2S concentration in systems located downstream, due to integrity, safety or tariff limitations. Under these situations, it is expected that the H2S scavenger injected in some points of the system (e.g., subsea) be capable of reducing the H2S concentration before reaching certain parts of the system (e.g., topsides). In this case, the H2S scavenger should be selected not only based on its capacity, but also on its kinetics at the expected field conditions.

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