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Pictures of the Future
The Magazine for Research and Innovation

The Future of Energy

A Flair for Oil Production

Due to its high hydrogen sulfide content, oil field gas must be purified before it can be used for electricity generation. At Siemens' test laboratory in Frankfurt, Hans Wolfgang Nickelfeld checks the filling level of a container holding a liquid used to extract H2S and other components from oil field gas.

Siemens is developing technologies designed to separate harmful substances in the gas that is normally flared at oil production sites. The result: gas that can be used on site to run generators, thus reducing environmental impact by limiting the need for added power supplies.

It seems like a waste. Wherever oil is produced flares are often seen flickering from the ground or from tall stacks. Flares burn the gas that is brought to the surface with the oil. Processing these gases for sale is uneconomical, and the gas usually contains too much corroding hydrogen sulfide (H2S) for power generation. Yet the flares release carbon dioxide, a greenhouse gas, sulfur oxides, and harmful soot into the atmosphere, which explains why environmental regulations continue to place further restrictions on this practice worldwide.

New technology from Siemens offers an option for using this gas, which is referred to as “sour gas” due to its high H2S content. The technology cleans the gas so it can be burned by gas turbines, which in turn generate power. “This technology requires very little space and helps oil production facilities operate more energy-efficiently and comply with environmental regulations,” explains project manager and engineer Ralph Joh from the Siemens Power and Gas Division.

Thanks to a research effort at Siemens, gases generated on deep sea drilling rigs no longer need to be flared off. Instead, platform operators can reuse the gases to generate electricity.

Putting Desulfurized Sour Gas to Work

During the past couple of years Siemens acquired the gas turbine divisions of Rolls Royce Energy and Dresser-Rand, an American equipment and service supplier for the oil and gas industry. In view of this, Siemens engineers are tackling challenges that extend beyond the desulfurization of gases associated with oil production. Gas compressors assist oil production by helping to store CO2, as do low-emission electric motors, which replace fault-prone diesel engines in unconventional gas fields.

According to the IEA, global energy demand is expected to grow by a third from 2015 to 2040. And the share of natural gas and oil production is expected to increase over time.

The technology for scrubbing hydrogen sulfide from gases is based on a novel detergent solution containing amino acid salts, which binds the hydrogen sulfide in sour gas and turns it into pure nonhazardous sulfur. The captured gas meets the specifications for running a gas turbine. “We reduce the percentage of H2S to a level where conventional gas turbines can use it without a problem, and at the same time we reduce sulfur oxide emissions” says Rüdiger Schneider, head of Siemens’ Power and Gas Fuel Flexibility Technology Field.  The first pilot facility based on this technology is now in operation in Joh’s laboratory in Frankfurt. The next step is to apply the technology to a biogas plant where sour gas is formed.

All of this is important because we will probably continue to depend on fossil fuels for the foreseeable future. Indeed, according to the independent International Energy Agency (IEA), global energy requirements are expected to grow by a third from 2015 to 2040. And the share of natural gas and oil production as a percentage of the total worldwide energy supply are expected to increase over time.


Ultrasonic Carbon Dioxide Compressor

In some areas natural gas contains high levels of carbon dioxide, as is the case in Norway’s Sleipner gas field in the North Sea. To meet the requirements of pipeline-quality natural gas, CO2 separation has been taking place there since 1995. Nearly a million tons of such separated CO2 is injected into sandstone under the field’s seabed every year. – It is believed that the Dresser-Rand business, which is part of Siemens’ Power and Gas Division, has the largest installed base of CO2 compression equipment, with more than 450 units worldwide.

With funding from the US Department of Energy, the Dresser-Rand business has developed a supersonic compressor named “DATUM S compressor.” A full-scale prototype of the DATUM S unit is now being tested in the United States at the company’s Olean, New York facility. “Historically, industry standards required that the flow of gas had to remain below Mach 1,” says Mark Kuzdzal, who is responsible for the commercialization of the new technology at Dresser-Rand. “The DATUM S compressor, however, has broken the sound barrier.”

The compressor has a number of benefits. It requires one-third less space than competing systems because, thanks to acceleration rates never achieved before, it processes gas in fewer compression stages. Because it is smaller, it incurs lower material and production costs. What’s more, the compressor’s high pressure ratio produces mid-grade, useable heat, resulting in less heat being expelled to the environment, thereby reducing associated water consumption. When the resulting waste heat is returned to the system, the system’s energy efficiency during operation is significantly better than that of conventional compressors. All of these factors reduce costs.

Replacing Diesel Engines with Gas Turbines

Fracking, which in recent years has proliferated in the U.S., does not enjoy the best environmental image. During a typical multi-week drilling operation, dozens of trucks transport diesel engines and pumps to wellheads, which are often located in remote areas. Yet diesel engines are susceptible to problems, and their emissions are being subjected to increasingly stringent standards. “As a result, some operators have shown interest in using electric motors to drive gas turbines as an alternative to diesel engines,” says Udo Reckels from the Dresser-Rand business. Studies have shown that electric motors result in lower emissions, are more reliable, and are more cost effective than diesel systems over a ten-year period. In addition, the use of electric motors reduces the need for trucks, thus also reducing the need for personnel – and associated space.

The first pilot project is slated to begin in the U.S. in late summer 2017. Small, rugged Siemens 501-K gas turbines will be used along with a medium-voltage network and electric motors, each of which will control around three frac pumps. A pipeline network similar to those common in North Dakota and Texas will supply the gas for the turbines. Once delivered, the plant can be commissioned within six hours and will be quieter than conventional plants. According to Reckels, “Such a plant will be no louder than a normal conversation, just under 60 decibels.” Music to the ears compared to a diesel system, which can be louder than a rock concert.

Hubertus Breuer
Picture credits: from top: 2. Picture Kjetil Alsvik/Statoil