Many of the polymers used in oil and gas applications come into contact with a variety of fluids from relatively benign hydrocarbons to more aggressive treatment chemicals and sour fluids. These can affect polymers by swelling them to different degrees which affects performance and their mechanical properties which may be more disruptive.
Compatibility testing from Element confirms whether a polymer/fluid combination will be satisfactory throughout its use in service or to identify whether there are any reasons for concern regarding deterioration in its short term or long term use.
The three critical questions we answer through our testing programs about a materials use are:
- How much does it swell?
- Is there any evidence of chemical deterioration?
- Is the material suitable for the intended service, or is additional evaluation required?
We then use the answers to these questions to screen material candidates during selection.
The compatibility test is not designed to just quantify polymer durability, i.e. how long the material will last within a given chemical environment. This issue is far more involved and requires a program of (usually thermally) accelerated fluid exposure tests. However, it is often the case with chemically hostile fluids that certain polymer types are significantly degraded within a short period of time. Increasing temperature and/or the concentration of reactive species quickens the rate of material deterioration. Compatibility immersion tests tend to be run at the service operating temperature of the component, and vapor pressure of the fluid.
Material performance is tracked by measuring changes in mass, volume, hardness and tensile property levels. The test is run until equilibrium swelling has been attained or the specimens are chemically degraded, whichever comes first.
30 day soak tests are quite often common, with 4 or 5 interruptions to make measurements.Element has been running polymer compatibility tests for more than 25 years, with fluids such as
- Treatment chemicals (corrosion, scale, hydrate, asphaltene inhibitors, wax dissolvers, scavengers)
- Completion brines (e.g., zinc bromide);
- Drilling muds;
- Stimulation acids (e.g., hydrochloric, acetic);
- Control (hydraulic).
Element's Engaged Experts have considerable experience in reviewing polymer/fluid compatibility for oilfield applications. A paper review can (i) reduce test requirements by eliminating specific fluids and/or materials where compatibility is known or strongly suspected, and (ii) indicate likely performance of remaining polymer/fluid permutations.
Acceptance criteria for swelling and tensile property level change can be applied to assist in making judgments about material compatibility. Widely specified criteria for sealing elastomer compounds are
- Volume change: +25/-5%
- Tensile: +/-50% (50% and 100% modulus, tensile strength, strain at break)
- Visual inspection: no dissolution, cracking, blistering or physical deformation.
The final version of the compatibility test report from Element includes material and test fluid information, sample preparation and procedural details, charts of mass, volume, hardness and tensile property levels versus exposure time for each material, representative images of material condition and results interpretation.