With a capacity of 727 million barrels, the U.S. Strategic Petroleum Reserve (SPR) is the world’s largest stockpile of government-owned emergency crude oil.
Established after the 1973-74 oil embargo, the SPR provides the nation with a powerful response option should a disruption in oil supplies threaten the U.S. economy. It is also the critical component for the United States to meet its International Energy Agency obligation to maintain emergency oil stocks and it provides a national defence fuel reserve.
The oil is stored in fabricated salt domes created by injecting fresh water into the salt deposits, which dissolves the salt leaving an open cavern for storage. To retrieve oil from the salt caverns, water is pumped in from the bottom and since oil floats on water, the oil rises to the surface and can then be transferred to interstate pipelines or loaded into ships.
When oil is added into storage, brine water is pumped out for disposal. DM Petroleum Operations Company manages and operates the SPR under contract to the U.S. Department of Energy (DOE). DM has been the SPR management and operating (M&O) contractor since 1993. The company manages four storage sites: two in Louisiana and two in Texas.
The problem
The U.S. Environmental Protection Agency (EPA) requires periodic integrity tests on each brine disposal line at the SPR’s site for leak detection. The flow rate is measured simultaneously at a point on shore and at a second point, miles out into the Gulf of Mexico near the dispersion nozzles. The meters are transported by barge offshore, inserted for testing purposes, then removed from the line and stored until the next tests are conducted. The onshore and offshore flows measured by the flowmeters are compared to determine if the pipeline has a leak. The criterion for a successful test is a difference of 4% or less between the two measurements.
Once each year, usually between May and June when the weather tends to be calm and before the hurricane season starts, the two lines in Texas are tested. The Big Hill Brine Line in Jefferson County Texas is a 22 km long, 1200 mm diameter pipe and is one of the DOE’s toughest flowmetering applications. The second site is a 600 mm pipeline located approximately 10 km offshore. In the past, a pitot tube type meter was used to profile the pipe and measure the flow at the two points.
The valuable time required by divers to accomplish flow profiling on the Gulf Sea floor and less than satisfactory results led to a search for a better means of measurement. A lift boat, essentially a barge with legs, is used to transport the meters, crew and divers out to the offshore site. Once at the site, the legs are lowered to lift the barge off the water, providing a stable working platform. Divers locate the opening in the pipe, which is at a depth of about 15 m for the Big Hill Brine Line, and insert the FPI meter sensor. Once inserted, brine is pumped through the pipe and the flow data is collected and recorded at one minute intervals for a minimum two hour test period.
The same type of test is simultaneously conducted on shore. The shore crew connects McCrometer’s converter directly to a laptop to convert the electrical signal from the sensor to live flow rates. The integrated system then compares the offshore and onshore measurements. A difference of 4% or less is considered a successful test. The tests are submitted to the EPA, and it is with these results that the EPA determines whether to renew SPR’s discharge permit.
The solution
The Big Hill Brine Line was tested by DM using FPI Mag flowmeters. The FPI Mag replaced the problematic pitot tube meters. The recorded flows from the FPI Mag meters matched to within 0.21% and proved them as an excellent choice for this demanding task.
The original FPI Mag meters and subsequent generations of the product have been in continuous use for periodic testing service since their original adoption for this application. The latest test, again conducted with FPI Mag meters, confirms their performance results.
Cost-effective for new or retrofit applications because of its compact insertion design, the FPI Mag meter fits easily into limited access confined spaces. It can also be removed from pipes under pressure for easy inspection, cleaning or calibration verification without an expensive shutdown and restart sequence, helping cut plant maintenance and instrument ownership costs.
Conclusion
“Over the years, the product has been upgraded from the original fibreglass construction to steel. The more rugged the product is the better for this tough environment. After more than a decade of periodic testing service, the FPI Mag flowmeter continues to demonstrate performance accuracy in demanding environments. The meter’s unique multi-point sensing capability combined with intelligent signal conversion and a robust package design make it an excellent choice in a wide range of industrial process water measurement applications.”
For more information contact Stuart Brown, UIC Instrumentation, +27 (0)31 468 2561, stuartb@uic.co.za, www.uic.co.za
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| Email: | guyw@uic.co.za |
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