Methodology to Evaluate the Performance and Stability of Hydrogen Sulphide Scavengers

Abstract

It is known that some H2S scavengers have the potential to cause fouling either from reaction products or by the influence of their chemistry on brine scaling potential. A series of methods for assessing the performance of the H2S scavengers and the likely hood of the generation of unwanted reaction by products is described along with the utility of each test methodology under different production conditions The performance of triazine- and aldehyde-based H2S scavengers are compared in a suite of laboratory tests, including liquid phase tests examining residual sulphides in solution and by measuring H2S in the gas phase using an in situ H2S detector. The tests are capable of differentiating between the performances of different H2S scavengers over a range of different test conditions and are applicable to those of the production process where scavengers are used. The work also shows that the absolute performance and relative performance or ranking of different scavengers is affected by the test methodology adopted and the work therefore illustrates the importance of selecting an appropriate test methodology for the intended field application. The efficiency of the scavengers was determined both under bulk liquid phase conditions and also by the contact time required to reduce the initial gas phase H2S concentration to the desired level and by calculating the scavenging capacity. This work presents both apparatus and methods which can be used for the evaluation and comparison of H2S scavengers. It describes primarily experimental design aspects and challenges associated with differentiating between free (unscavenged) H2S and reacted (i.e. scavenged / trapped) H2S in bulk liquid phase tests often utilised for preliminary screening of scavengers and recommends a procedure to allow such tests to be conducted routinely. Works then compare results with more conventional gas stream monitoring approaches. This work presented and the approaches described will then assist in the screening and product selection process and provides information on the conditions under which un-desirable solid by-products may be generated.