Subsurface safety valves (SSSVs), which are standard and often statutorily required in the oil and gas industry for upper completions, were first developed in the late 1930s. Operators sought to drill more high-pressure wells, often near populated areas or, conversely, offshore or very isolated areas, making the need for a device to protect the wells from uncontrolled flow increasingly apparent. The need was made even more urgent by the fact that the uncontrolled flow could be caused by accident or by damage to the surface equipment, which at the time was quite common.
By the 1970s three companies had established themselves as industry leaders as SSSV suppliers in the field: Otis Engineering (now Halliburton), Baker Hughes (now Baker Hughes, a GE company) and Camco Products and Services (now Schlumberger). Implementation of SSSVs grew, but it was not until the Piper Alpha incident of the late 1980s that regulations truly shifted. The explosion on Piper Alpha and resulting oil and gas fires that destroyed the platform served as the impetus for global regulatory mandates that SSSVs be deployed in offshore wells.
The watchword for the 21st century oil industry has been reliability, as offshore, deepwater workovers in many wells cost tens of millions of dollars. As such, reliability became the primary focus and mission of the engineering team at Tejas Research & Engineering as it moved to design and deliver reliable, high-performing products. In the late 2000s the energy industry and governments worldwide revisited the use of SSSV deployment requirements, which had not seen much change since the Piper Alpha incident more than two decades prior. The consensus was that when reliable SSSVs are present, a blowout and oil spill are virtually impossible. Therefore, many governments, such as the EU, now require SSSVs in all wells—even those on land.
Modern developments in SSSV design have sought to address the industry’s challenges and the issues that arise in more complex reservoirs and harsher downhole environments through additional testing and research to optimize the valves’ technical specifications. While the basic functionality of the valves has not changed for some time, the standard to which the valves are engineered and manufactured is now shifting, thanks in part to a new partnership between Tejas Research & Engineering and National Oilwell Varco (NOV). It is a partnership bolstered by Tejas’ involvement on the American Petroleum Institute’s (API) 14A standards subcommittee.
NOV has built its portfolio of completion and production products and technologies since the company’s acquisition of Trican Well Service’s completion tools division in mid-2016. As the breadth of NOV’s completions business expanded to include multistage fracturing and multizone completions, among other disciplines, it became clear that a missing link for upper completions was SSSVs. The company partnered with Tejas Research & Engineering to commercialize a line of SSSVs representing a new industry standard in design and reliability.
Tejas Research & Engineering sprang from the Camco tradition that pioneered many pivotal developments in SSSV design. The R&D and engineering for safety valve products are conducted in Tejas’ HP/HT facility in The Woodlands, Texas, where SSSVs with pressure requirements of 25,000 psi and 260 C (500 F) are designed, tested, qualified and produced.
Tejas’ model TRSV(E) SSSVs are tubing-retrievable, surface- controlled, normally closed devices installed in oil and gas wells to control tubing fl ow. Metal-to-metal seals are used in 100% of Tejas’ tubing-retrievable product line, which has products that are rated to 10,000 psig and are suitable for temperatures up to 176 C (349 F) at moderate setting depths. Higher temperature/pressure/setting depths/slimline diameters are available for custom order. The TRSSSV series are API-14A V1 certified and adaptable to any standard or premium tubing thread. The system features a large fullbore, where the inside diameter (ID) is equivalent or greater tubing than the tubing ID to which the SSSV is attached. Additionally, it has either flat flappers (2⅜ in. to 3½ in.) or curved flappers (4½ in. to 7 in.) and a single rod piston featuring nonelastomeric dynamic seals. The TRSSSV is available in either equalizing or nonequalizing trims. The valve is controlled hydraulically with a ¼-in. control line in the well’s annulus, enabling valve closure during an emergency shutdown.
The new safety valve builds upon lessons learned in valve design over Tejas Research & Engineering’s entire history. Previous valves have achieved significant milestones— including one design that has more than 8,000 valves in use without a single failure or degradation in performance. Completions have evolved since those early designs, and new valves need to withstand significantly higher temperatures, working pressures and setting depths as well as accommodate different diameters. The new valve product line meets the rigorous quality standards outlined in API Specification 14A and tested beyond the specifications in Revision 12, including Annex H, which specifically addresses the verification and validation requirements for use in HP/HT environments.
An evolution in safety valve standards means the industry can be more confident that well control incidents will not occur. As regulations continue to change and become stricter, it is imperative that safety valves maintain their rigorous quality and durability while being able to handle even more challenging well environments.
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