The oil and gas market has remained remarkably stable recently, bolstered by the high price of oil and strong worldwide demand. With refining capacity finite and political unrest in major oil producing countries such as Venezuela, Angola and Iran, the price may rise even higher. Since most "easy to reach" reserves have been tapped, the price of oil is predicted to remain at or above record levels for at least two to three years. Even the slightest hiccup in production or refining will cause significant price spikes. A hurricane disrupting offshore production or a refinery explosion can have major implications on supply. Unless more refining capacity is added, there will be no immediate relief for oil prices.
Oil and gas prices have fluctuated, almost cyclically, about once every decade. In past downturns, oil service companies did not have sufficient financial reserves to weather production slowdowns, so some smaller companies declared bankruptcy. In the recent oil boom, oil service companies have been making record profits and have not spent the money. They are retaining cash because they have learned from past oil pricing cycles to prepare for a sudden drop in prices. Most people in the industry feel oil companies have finally retained sufficient cash reserves to protect themselves in a market downturn.
$35/barrel is generally accepted as the breakeven point for drillers to make money. Obviously, with oil over the $100/barrel mark, there is plenty of money to go around. The major oil companies have issued contracts for equipment backlogged for three to four years with oil service companies. This suggests industry experts are confident the price and demand for oil will remain high for possibly the next five years.
In the past few months, oil supply companies have noticed a pick up in new orders and an increase in specialized projects requested from the big oil companies. These specialized projects are for tools to drill and produce deeper wells that were previously unreachable. Deeper wells mean higher temperatures and pressures, approaching 550-deg and 35,000-psi. Consequently, oil service companies are pushing sealing companies for new seal materials and designs to cope with these extremes.
This search for better seals has been a boon and a bane for seal companies. On one hand, the aggressive applications force seal companies to work more efficiently and become more innovative. Alternatively, the aggressive push for better materials and seal designs has forced seal companies to technology and innovation limits. Time is of the essence to extract oil from the ground. This compressed timeline strains resources and does not allow for thorough or extensive testing and material development.
In the past, rubber materials like NBR or FKM and plastics like PPS could address most equipment sealing needs, but new materials, such as polyetheretherketone (PEEK) and perfluoroelastomers (FFKM), are now required.
FFKM, the ultimate in elastomer sealing, is virtually inert and has almost universal resistance to media and gases. For aggressive downhole environments, its polymer architecture has been tailored to optimize chemical and heat resistance. One perfluoroelastomer range consists of several materials with varying properties. For example, one compound is engineered to withstand high temperatures up to 608-deg F, others for steam up to 500-deg F and another for general service up to 464-deg F. There is even a compound with a dense molecular structure to minimize the effects of explosive decompression.
PEEK is a cost effective, high modulus plastic resistant to almost all downhole fluids and effective up to 400-deg F. PEEK is typically used as seal backup device or bearing material, but can be designed for use as a sealing element, depending on conditions. Because of the varying array of applications, PEEK is available in several compounds-one range of PEEK includes a basic unfilled compound for general service up to a filled compound for low friction, high load bearing applications.
However, oil drilling and service companies are beginning to reach the operational limits of PEEK, so new variants of PEEK, called PEK and PEKK, are now needed. PEK and PEKK have higher glass transition temperatures than PEEK, which means they retain their properties at higher operating temperatures. These high modulus plastics are relatively new materials to the oil and gas market and are not extensively used. This will change as demand grows for specialized materials.
An effective alternative, especially in dynamic situations, are polytetrafluoro- ethylene (PTFE) based materials. They are compatible with virtually all media and have excellent friction characteristics for rotating or reciprocating applications. Depending on conditions, PTFE can be used up to 500-deg F or higher if supported properly. PTFE is available in dozens of filled compounds with fillers ranging from carbon and glass fibers for extrusion resistance, to carbon and bronze fillers for wear resistance to no fillers at all. PTFE has no elasticity, so it must be energized with an elastomer or metal spring. This energizer maintains a constant force on the PTFE, keeping it against the mating hardware or sealing surface to ensure a positive seal.
Another option is metal seals, especially if processes involve severe static situations as found on some connectors or flanges. These metal seals can operate in temperatures from cryogenic up to 1562-deg F and in pressures from hard vacuum to 145,038-psi. However, care must be taken with hardware design to control tolerances since metal seals operate with a critical squeeze zone. In addition, metal seals must be used only in static applications, typically in a face seal configuration, as seen in flanges and pipe joint connections.
No matter which seal design is chosen, equipment engineers should work with a company specializing in oil and gas sealing. The unique demands of the oil and gas industry require special attention to media, pressure and temperature. The seal supplier must be able to support claims they make about their materials with detailed test results or a proven track record. In addition, it is preferable if they can offer developmental services, perhaps with FEA modeling and in-house application testing.
