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Elastomers are widely used in downhole tools for oilfield applications and are often exposed to gases, such Carbon Dioxide (CO2), and Hydrogen Sulfide(H2S) in addition to the produced hydrocarbons and water. Successful drilling operations and reservoir management involve the use of tools of appropriate metallurgy and sealing materials. Depending on the environment (High Pressure High Temperature, H2S, CO2, or others), the sealing property of the elastomers may fail, leading to HSE (Health, Safety & Environment) and operational related incidents. Examples of such incidents are the undesired production of fluids, contamination of ground water, and the consequent loss of time and profits. Consequently, the selection of the sealing material used for downhole oilfield applications is critical and needs to be carefully considered, either for short-term drilling operations or for long-term completion activities. Elastomer compatibility studies covering a variety of media such as diesel, oil- and water-based muds, and brine are available in the literature. However, compatibility to super critical fluids like pure CO2 or H2S are not widely documented and even difficult to find in public domain. This paper describes a testing methodology to investigate the behavior of selected elastomers under CO2 environment at different temperatures and pressures. It focuses on the swelling behavior of different materials upon contact with CO2. Two testing methodologies are investigated. One is using a High Pressure High Temperature autoclave from "Parr Instrument". It allows samples to be simultaneously exposed to two different environments; the wet supercritical CO2 and CO2-saturated fluid. The second is using a High Pressure High Temperature Visio-Cell equipped with a high resolution camera. The benefit of such a set-up is that it allows a "real-time visualization" of individual particles while in contact with CO2. Results obtained show the HPHT Visio-cell to be the best fit for assessing the behavior of the tested material. Additionally, some components appear to swell less with CO2 than others. |
