In a major advance in centrifugal compressor technology, Dresser-Rand has successfully engineered, manufactured and tested what are believed to be the world’s highest density centrifugal compressors for re-injection service.
While the units will be used in the oil and gas upstream market, the technology is applicable to other market segments requiring the compression of carbon dioxide and heavy gases such as urea production and carbon capture and sequestration. The units, which compress a mixture of natural gas and carbon dioxide, will be installed on floating production, storage and offloading (FPSO) vessels destined for the “pre-salt” fields offshore Brazil.
The first ship (Cidade de São Paulo) will have two trains and will operate in the Guará BM-S-9 oil field. The second ship (Cidade de Paraty) will have the other two trains and operate in the Lula NE (formerly Tupi NE; BM-S-11) field. Both are located in the Santos Basin in water depths of approximately 2,000 meters. An estimated 120,000 barrels of oil and 5 million standard cubic meters of gas per day will be processed by each of these FPSOs.
Dresser-Rand booked these orders in the first quarter of 2010.
The compressors were tested in accordance with ASME’s PTC-10 Type I industry standard at full load and actual field conditions and achieved a discharge pressure in excess of 560 bar (8,120 psi) compressing the CO2-rich gas while exhibiting a very robust and stable rotor dynamic behavior, generally considered the greatest challenge in this class of machinery. Typically, as pressures and densities increase, the logarithmic decrement (log dec – a measure of stability) decreases in traditional multistage compressor designs. However, as these units were subjected to greater pressure and density, test measurements demonstrated an increasing log dec, so the compressors became more stable. In fact, test measurements show that Dresser-Rand reached stability levels that are 30 to 60 times higher than minimum industry standards.
In this particular instance, Dresser-Rand has engineered and successfully tested its centrifugal compression technology for applications that previously have only been done by pumps. So far, Dresser-Rand has reached 56 percent of the density of water at discharge conditions and is looking at how it can raise that to 70 to 80 percent. Furthermore, the technology significantly reduces capital expenditure, footprint, weight, and operating costs, while increasing reliability by eliminating the need to install, operate and maintain high-pressure injection pumping systems downstream of the compression system. With this new DATUM® high-pressure and high-density compression technology, the total footprint required by a conventional compression and pumping module can be reduced by approximately 50 percent while its weight can be reduced by approximately 35 percent or more, depending on the exact configuration. For example, what used to require separate natural gas injection compressors and multiple CO2 injection pumps can now be done using a DATUM injection compressor capable of handling an average upstream hydrocarbon gas blend (22-23 MW) as well as a heavy, CO2-rich gas blend (e.g., >39 MW) to reach the same discharge pressure level.
In addition to it being smaller, lighter and more reliable than a traditional pumping system, it can also be produced in less time. The cycle time for this machine from time of order through successful load testing was less than 14 months. The cycle time for a pumping system for this type of service might typically average about 18 months, and would require additional time and resources on the client’s side to project manage, install, commission and start-up. With this high-pressure and high-density compressor technology Dresser-Rand offers, the client can start producing earlier.
“This new technology gives our clients a proven option to replace the more expensive CO2 pumping systems that were previously thought to be the only feasible solution for high-pressure CO2 re-injection applications. It will enable clients to remove one of the highest technology risks of all the compression duties typically found in upstream applications, whether offshore or onshore,” said Jesus Pacheco, executive vice president, New Equipment Worldwide for Dresser-Rand.