“Global oil supply could struggle to keep pace with demand after 2020, risking a sharp increase in prices, unless new projects are approved soon, according to the latest five-year oil market forecast from the International Energy Agency.” ( IEA; Newsroom » News » 2017 » March)
Global oil service companies and end-users must be able to find new oil reserves, get to it quickly and safely, and maximize recovery. For these non-conventional reserves, the industry is forced to expose valuable equipment to extreme temperatures, high pressures, and corrosive fluids and gases. Avoiding costly downtime, extending service life, operational safety, and improved recovery are at the forefront of an engineer’s mind when designing a oilfield equipment system. Achieving the highest level of reliability and efficiency while minimizing risk starts with cutting-edge materials.
This continued demand and tightening of oil supply in addition to the desire to maximize the production process will keep the industry going forward and provide continued demand for high performance products. Polyetheretherketone, PEEK, and Polyphenylenesulfide, PPS, are two of the premier structural thermoplastics used in the oilfield.
Oilfield applications for these two polymers are primarily structural and/or seal related. Structural related applications include back-up rings, separators, and housing applications. They are considered seal related when designed in a sealing system as the primary seal and often, in the same application, as the designed back-up.
PEEK is commercially offered in a variety of grades. Typical oilfield grades tend to be higher in molecular weight and often are injection molded in net, near-net or billet shapes to maximize the mechanical properties. PEEK’s high strength, good strain capability and excellent chemical resistance sets PEEK apart and is the reason for its high desirability for many oilfield applications. PEEK has become the structural material of choice anytime a chemical environment enters the API defined HPHT (High Pressure/High Temperature) range i.e. pressure above 15,000 psi “or” temperature above 350°F. PEEK is often used to the temperature range of +/-450°F, but has been used to higher temperatures where necessary, and to differential pressures in excess of 20 ksi.
Industry Standards, such as API, NORSOK and ISO, are requiring qualification of thermoplastics to new requirements as is exemplified by NORSOK M710, “Qualification of Non-Metallic Sealing Materials and Manufacturers.” The current draft version of NORSOK M710 Rev 3, as well as ISO 23936-1, trend towards a material stability testing requirement. However, PEEK is quite stable in H2S to high concentrations at high temperature and, in some cases, does not show enough degradation in the testing temperature range to allow a stability prediction. ISO 23936-2 Appendix C mentions: “If no ageing occurs and the property levels stay within the specified limits at the test temperatures, then the material can be described as having indefinite life at the lowest test temperature and temperatures below this.”
Conventus is a key partner for PEEK specialty compound formulation and also offers a competitive line of virgin (granule and powder), GF, CF, and bearing grade PEEK. They help make the correct material selection for the design requirements and application environment.
PPS has been used in the oilfield even longer than PEEK and was the first truly structural thermoplastic to achieve commercial production (circa 1973) and subsequent application in the industry as an Engineering Thermoplastic. Although first versions to be commercially produced were low in molecular weight and designed to be used as coatings, further polymer manufacturing process improvement provided the pathway for broader application. While these improved versions were branched polymers and as such were somewhat brittle, they were and still are quite good in both strength properties, other than impact, and very good in chemical resistance. Later versions of linear PPS have made in-roads into providing a material which has greater resistance to impact while maintaining very good chemical resistance.
PPS key features include:
PPS is ideally suited for precise tolerance machined components due to its minimal moisture absorption, high heat resistance and a very low coefficient of linear thermal expansion combined with stress-relieving manufacturing. For these reasons, PPS has found many applications as a metal replacement. PPS is ideally suited for structural applications in corrosive environments or as a replacement for PEEK components operating at temperatures below 425°F.
PPS has excellent chemical resistance as there are no known solvents for PPS at temperatures below 392°F. It is very stable in steam, acids, bases, and hydrocarbons and has an upper continuous application temperature in the range of +/- 400°F.
Conventus has the knowledge to ensure proper selection and application of many PPS formulations. Contact us today for new projects and/or when looking to reduce cost on existing PPS applications.