STP717

    Degradation of Elastomers in Geothermal Environments

    Published: Jan 1980


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    Abstract

    The thermochemical degradation and sealing capability of various commercial O-rings in geothermal brine was evaluated at elevated temperatures and pressures to facilitate the selection of suitable elastomeric seals for the cable heads of geothermal logging tools. The extent of degradation was determined by measuring the change in tensile properties and glass transition temperatures that occurred as a result of exposure to brine at 548 K (275°C) and 34 MPa (5000 psi). The sealing capabilities of the O-rings in brine under these conditions were evaluated, using O-ring fixtures that simulated the cable head of a commercial logging tool. All of the elastomers became degraded to some extent. The elastomers that retained some measure of elasticity and also were not breached by brine in seal tests were the perfluoroelastomers, ethylenepropylene rubbers, and a peroxide-cured fluoroelastomer. Data obtained on the properties of aged specimens of these elastomers suggest that the most likely mode of degradation was chain scission. Nitrile rubber, silicone, and the peroxide-cured fluoroelastomer suffered a complete loss of elasticity and failed as seals. Data obtained on the properties of these elastomers indicate that extensive cross-linking took place. Polychloro-p-xylylene coatings were found to inhibit the rate of degradation in both brine and steam/sour gas environments.

    Keywords:

    thermochemical degradation, elastomers, geothermal brine, chain scission, cross-linking, coatings, seals, perfluoroelastomers, ethylene-propylene rubbers, silicones, fluoroelastomers, nitrile rubbers, scaling, corrosion


    Author Information:

    Arnold, C
    Chemist, Sandia Laboratories, Albuquerque, N. Mex.

    Bieg, KW
    Chemist, Sandia Laboratories, Albuquerque, N. Mex.

    Coquat, JA
    Chemist, Sandia Laboratories, Albuquerque, N. Mex.


    Paper ID: STP30070S

    Committee/Subcommittee: G01.09

    DOI: 10.1520/STP30070S


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