Composites have long been recognized as an enabling technology in deepwater drilling scenarios, because the materials are able to stand up to the harsh subsea environment while delivering lower overall system weight. They form the structures of floating drilling platforms (from framing and flotation systems to step ladders and cable trays) and there has been great focus on piping, where composites enable applications even in ultradeep oil and gas extraction projects, at depths greater than 1,500m. Top tensioning and flotation systems, installation expenses and deployment time, and longevity of asset life are all areas where high-performance composites can outperform traditional technologies in riser, jumper, intervention line, cabling and umbilical applications.
In 2015, Trelleborg Offshore US Inc. (Houston, TX, US) and partner Landing String Solutions LLC (Madisonville, LA, US) were in the spotlight, unveiling the world’s first composite buoyancy system deployed on a drill pipe landing string, that is, with buoyancy elements around the drill pipe inside the riser pipe. Manufactured by Trelleborg, the patented Landing String Buoyancy system is slated for deployment by a major oil company sometime in 2016. Integration of buoyancy elements within the riser enables the drilling contractor to deploy larger quantities of casing, thus reducing rig time, maximizing efficiency and reducing cost. The buoyancy system is designed to offset the landing string weight by up to 80% in some cases and enable safer and more cost-effective deepwater oil and gas operations, says Trelleborg. Buoyancy is achieved with Trelleborg’s low-density syntactic foam system. which consists of a combination of Trelleborg-manufactured hollow glass Eccospheres (a combination of microspheres and macrospheres) to provide uplift. Further, all buoyancy installation hardware is fully composite (there are no metal fasteners/components), with composite stop collars on each joint of the drill pipe, which hold the buoyancy in place. The buoyancy system is qualified for a maximum pressure rating of 413.69 bar.
Meanwhile, an unprecedented US onshore energy boom during the past decade has brought the country to near fossil-fuel energy independence and put composite manufacturers to work producing a new, expendable well technology. Credit goes to a growing global technology called hydraulic fracturing, often termed “fracking” or, more correctly, “frac’ing.” As the name implies, the process artificially fractures low-permeability rock strata with explosives and then injects pressurized, sand-laced solutions into those fractures to facilitate oil and natural gas extraction. According to the Society of Petroleum Engineers (SPE, Richardson, TX, US), 60% of all new oil and gas wells globally are frac’ed, and 2.5 million frac’ing procedures have occurred since 2012 — more than 1 million of them in the US alone.
A single wellbore requires 10-40 multi-part, consumable tools called “frac plugs” (and accompanying “frac balls”) to pressurize and perforate multiple oil- or gas-producing layers, called “stages.” Demand for these downhole parts exceeds 20,000 units per week, or more than 1 million units annually, according to one oilfield composites expert. Demand is high for these critical parts, which typically are made with composites because the composite is relatively easy to drill through at the end of the frac’ing operation, to make room for completion equipment.
Frac balls typically measure from 25.4 to 146 mm in diameter, while frac plugs commonly range from 114 to 140 mm in diameter and 560 to 760 mm in length. In service, balls and plugs must endure high temperatures (121°C-177°C) and pressures (³69 MPa), yet must be designed to enable operators to drill through them in minutes at the conclusion of frac’ing operations to clear the pipe for gas/oil extraction. Composite balls and plugs, today, are typically made from glass fiber and epoxy or phenolic resin, which are easier to mill out than previous metal versions and can withstand higher pressures and temperatures than traditional plastic and dissolvable-salt balls. But that could change. Thermoplastics, such as polyetheretherketone (PEEK) towpregs, might provide even greater pressure endurance (to 200 MPa), and other systems might provide a way to eliminate drilling (see “A critical market sector: Downhole composites in oil and gas” under “Editor’s Picks”). But for 2015, it’s a hot market for thermoset composites.