Ultra-High Sour Gas and Associated Chemical Environments Testing of Elastomers for use in Intervention Equipment for Safe Operations

Abstract Sour gas (H2S) levels present in deep gas reservoirs can reach ultra-high concentrations above 25%. The need for chemically resistant and mechanically robust elastomers to assure seal integrity is critical for safe intervention operations. Elastomers chosen for such applications should be able to resist attack by sour gas (H2S) in elevated partial pressures of 2,000 psi or 40% concentration and various aggressive field chemicals, and be resistant to rapid gas decompression (RGD) caused primarily by carbon dioxide (CO2) and sour gas. This paper investigates combined chemical effects of various harsh test mixtures that simulated ultra-high sour environments on the physical and mechanical properties of a range of different fluorinated elastomers to determine the degree to which they were affected. Twenty-four materials in total, comprising twelve FKMs, nine FEPMs, and five FFKMs, sourced from different vendors, were chosen to be tested in nine different combined chemical environments. Initial elastomer selection was based on expected performance against conditions encountered in ultra-high H2S environments with favor given to factors such as RGD resistance, chemical degradation, amine resistance, extrusion resistance, high hardness, etc. Bespoke testing was divided into three main segments - initial H2S screening test in a generic kerosene/water mixture, chemical compatibility testing with intervention chemical formulations ultra-high H2S environments, rapid gas decompression (RGD) testing in ultra-high H2S environments. Testing was performed according to ASTM D412 using Die C specimens. Hardness, Mass/Volume, Tensile Strength, Elongation at Break, 50% Modulus were evaluated against acceptance criteria that were taken from ISO 23936-2. Measurements of fluid fill levels before and after each phase were taken to assess if quantities of fluid were being lost from the liquid bulk phase. Results of the entire test program offered significant insight into the behavior of the tested materials and the general effects of fluid vapors used in each test. FKM and FFKM materials in general returned the most compatible results after exposure to the published test environments. Low temperature grades of FKM and FFKM tended to exhibit greater compatibility with all the test environments at the test conditions, while FEPM materials performed poorly in comparison to FKM and FFKM.