The Valve Manufacturers Association held its annual Technical Seminar & Exhibits at the Hilton NASA Clear Lake in Houston, March 8-9. More than a dozen speakers presented on a variety of topics that centered on “Prevailing Challenges and Solutions for the Oil & Gas/Petrochemical Industries.”
Gobind Khiani, AIMs specialist (valves), Cenovus Energy, was among the presenters at the VMA Technical Seminar, and he spoke about oil processing and production valve requirements for steam-assisted gravity drainage (SAGD) in the Alberta oil sands.
While the oil sands of Alberta have been developed for many years, constant research and development continues to increase efficiency and reduce the environmental impact of mining and drilling for the heavy oil.
The oil sands, located in northern Alberta, are a mix of sand, water, clay and a heavy oil called bitumen. The resource, to date considered the world’s largest oil reserve, is the biggest energy development in history. Only 20% of the oil is close enough to the surface that it has to be mined, a process that has been going on for more than 40 years. It is the most visible process, and that which is most closely connected to oil sands development in the public eye. The remaining 80% is deep underground and specialized drilling techniques, which have only been possible on a commercial scale for about 10 years, are required.
Cenovus Energy is a pioneer in the development of one of those technologies, SAGD. According to Khiani, it reduces the company’s consumption of water, natural gas and electricity while minimizing disturbance of the land.
In SAGD, two pipes, about 2 meters apart, are sunk deep into the earth. They are then drilled horizontally through the bitumen reserve. On the surface is the well pad where steam is injected through one of the pipes from one side of the building, and oil and water returns from the reserve through the other pipe, to the other side of the building. The mixture of water and oil is sent by pipeline back to the processing plant to be separated. Most of the water is reused to generate new steam, while the oil is treated before being sent for refining.
The steam-to-oil ratio (SOR) in land-locked Alberta was originally as high as 7 to 8 barrels of steam to get one barrel of oil. To produce that steam, natural gas must be burned to heat the water, so efficiency is paramount, both from a cost perspective and for greenhouse gas emissions. Now Cenovus has a SOR of about 2, among the lowest in the industry. This means much lower emissions, less water usage, lower operating cost and a smaller surface footprint.
Khiani said, “Technology innovation plays a major role in helping us achieve our environmental improvements. Across the Cenovus operations, our technology development teams are working on about 140 different projects.” He continued, “In fact, three-quarters of the technology projects are expected to further improve our environmental performance. Our goal at Cenovus is to introduce at least one new commercial technology into our operations every year. In 2011 we did this with our blowdown boiler technology.”
Continual technological improvements extend to valves, and proper maintenance of the various valves used in the process is critical. Typical valves used in the SAGD process include gate, globe and check valves, from 3 to 30 inches in diameter, pressure classes 600 to2500ASME class, pressure seal and bolted bonnet, although the majority are pressure seals. The most important component is the gasket/pressure seal ring and the segment ring. “Other than replacing the seals, the pressure seal valve works and works and never fails. And an important rule is never to attempt to reuse pressure seal rings,” said Khiani.
Other types of valves in use include high-performance triple offset butterfly valves, ball valves, gate, globe and check valves. Most of these valves are actuated by either pneumatic or electric actuators due to extreme weather. The metallurgy can be very exotic such as duplex, superduplex, cast steel or stainless steel with Monel trim. This is necessary because of the high salt content of the water and the huge temperature ranges, from -20° F to 1112° F (-29° C to 600° C).
One member of the audience at the technical seminar where Khiani spoke said he was surprised at the use of pressure-seal bonnets because they are known to trap pressure and cause lots of problems, including explosions, injuries and lawsuits. But Khiani said those are not problems on these sites because of extremely cold weather in Alberta.
About the presenter: Gobind Khiani, BSc, MEng, Valve Specialist and AML Advisor, Cenovus Energy, Calgary, AB, Canada
Gobind is a Registered Professional Engineer. He has worked in the oil, gas and nuclear industries since 1992 and has been actively involved with valves throughout his career. His career experience started with Transmark Group in UK and Dubai and includes valve manufacturing with Velan, Crane Energy and then his current position with Cenovus Energy Inc. He has helped numerous users in selecting the right valve product for the desired process conditions and helped improve on asset integrity management programs