A 2004 report by the World Bank provided the shocking news: Every year, energy producers waste more than $40 billion by burning off gas at their oil fields and sending it into the atmosphere.

By Dan Rafter

The World Bank’s latest statistics estimate that energy producers annually waste 110 billion cubic meters of natural gas—gas that could be transformed into usable energy—by flaring it. This is a tremendous waste. It’s also harmful to the environment. Such massive flaring sends an estimated 350 million tons of carbon dioxide into the atmosphere every year, the World Bank says. The 2004 World Bank report, which was conducted by the US National Oceanic and Atmospheric Administration, estimates that, in 2003, 5.5% of global gas production—and 27% of US gas consumption—was lost to flaring.

The Global Gas Flaring Reduction Partnership—run by the World Bank—reports that global flaring levels have remained steady for the past 20 years, despite the many individual government- and company-led efforts that have successfully reduced the practice at individual sites. These efforts have produced a limited impact, mainly because global oil production has increased, the partnership says. There is hope, though, and it comes in the form of microturbines. Several energy producers across the US are teaming with microturbine manufacturers, and research centers on pilot programs designed to transform into usable power, the sour gas that oil fields flare, vent, and waste.

One of the recent successes took place in the tiny town—population of 88, according to the 2000 US Census—of Newburg, ND. For nearly two years, Amerada Hess Corp., a global energy producer that runs oil fields across the world, ran a pair of Capstone-manufactured microturbines at an oil field in this town in western North Dakota. The goal of the pilot program was to test the economic sense of generating power with a microturbine, fueled with the sour natural gas that is produced, and usually flared, along with oil.

The University of North Dakota, Energy & Environmental Research Center (EERC) conducted the pilot program, which ended earlier this year. The pilot program proved a success, says Maripat Sexton, a communications specialist with Amerada Hess Corp. The microturbines, using gas that would normally be flared into the atmosphere, successfully generated enough power to run water pumps that are used to recover oil at the field. Sexton says that Amerada Hess was so impressed with the program, that company officials are discussing when they will revisit it again. Amerada Hess hopes to one day operate several microturbines at its oil fields, a plan that would significantly reduce the amount of natural gas the corporation flares at its production facilities.

These were the results that Darren Schmidt, research manager at UND’s EERC, was hoping for when the demonstration project began, in 2004. “The real success stories for microturbines are when you can run them on gases that are not covered under their warranties, or that are out of spec,” Schmidt says. “That’s what happened here. You are taking something that is normally flared or vented, and creating value from it by producing power and decreasing emissions. That’s a benefit, to not only the energy producers, but also a way to address a serious environmental concern.”

The Experiment
The two Capstone model C 65-kW microturbine systems in North Dakota combined to produce about 130 kW of energy, Schmidt says. The engines reduced total emissions from flaring operations at the field by an average of 75%. The pilot program worked, because, with minor modifications, the Capstone microturbines were able to operate successfully on the low-Btu gas that the oil field in Newburg historically had flared. The microturbines ran on gas that contained 280 to 290 Btus per standard cubic foot.

This is the key—most engines cannot run on such low-Btu gas. “We are confident that we can run these microturbines, even with gases that are at 200 Btus per standard cubic feet,” Schmidt says. “We’ve run tests that have been successful down to 120 Btu per cubic feet. But, the efficiency does start to drop as you go below 200 Btu.”

The production of oil, specifically the process of pumping it out of the ground, creates certain associated gases, Schmidt says. These gases can range from high-Btu gas, such as propane, all the way down to gases with low- heating values. These low-heating-value gases are usually diluted with nitrogen or carbon dioxide. Some of these associated gases have high sulfur contents. Most times, they also have a high amount of moisture.

All of this presents a challenge to energy producers who want to capture these associated gases and turn them into usable power. Using microturbines, though, officials at the North Dakota EERC have provided oil producers with one blueprint for a way to do this. “The challenge is to go into a remote site to generate a small amount of power, and have a gas-preparation system that remains cost effective,” Schmidt says. “You need to provide a system that is not overly complicated or expensive, cleans gas appropriately, and supplies it to the turbines.”

Microturbines were the perfect choice for Amerada Hess’ Newburg oil field, largely because the small engines boast a higher sulfur tolerance than do reciprocating engines. Microturbines also produce a low level of emissions, are quiet, and require little maintenance. This last benefit is important in an isolated area like an oil field.

The ability to tolerate high levels of sulfur, of course, is equally important. Without it, the microturbines would be useless in an oil field. The microturbines that operated in Newburg could tolerate a sulfur level of 7%, Schmidt says. A comparable piston engine could only tolerate a sulfur level of 0.1%. It would also require an oil change after 90 days.

The Capstone microturbines, in comparison, could operate five years without an oil change. The goal of the pilot program was to determine if the microturbines could compress and clean the flared gas at a low enough cost to make operating the turbines, on a larger scale, a plan that made economic sense. The program was also designed to determine whether the turbines could operate when exposed to high-sulfur conditions. Capstone’s microturbines, with their patented air-bearing technology, are designed to tolerate fuel impurities such as high-sulfur compounds.

The pilot program passed both of these challenges. So, now the question is an obvious one: Are oil companies aware of the benefits that microturbines—and their ability to convert wasted gas into energy—can bring them?

Schmidt, at least, has a positive answer to this question. He sees a day, not too far in the future, when a significant number of energy producers do turn to microturbines to take advantage of a power source they’ve wasted for far too long.

“This does fall into the category of new technology, so, obviously, there is a learning curve here for the oil companies,” he says. “But, one of the areas in which this technology can make a significant impact is the development of new production. You can provide your own electricity to a site from the gases that are produced, versus waiting for utility infrastructure to come to you. Financially, that is very significant.”

And this is only one benefit that he sees from this technology. Turning flared gas into usable energy has an obviously positive effect on the environment. “This addresses a serious environmental concern,” Schmidt says. “This would allow oil producers to use the gas they are flaring. It enables a more environmentally friendly way to utilize the gas and to gain value out of the gas.”

Oil companies, and other energy producers, should be paying even more attention to microturbines than they already do, Schmidt says. The machines, which are largely hassle-free once installation is complete, make perfect sense for remote oil fields.

“The question always comes up, why should we use microturbines instead of other technologies?” he says. “Microturbines require considerably less maintenance than do other engine technologies. That is beneficial for remote applications. You can run a piston engine off gas, too, but you have to be prepared to spend a lot of time to maintain the machine. Microturbines save a significant amount of space, too, because of their compact size.”

Capturing Flared Gas
Dave Stinton, manager of the distributed energy program at Oak Ridge National Laboratory in Tennessee, spends a lot of time studying new distributed generation technology, including microturbines. He sees a bright future when it comes to using the compact engines to capture and transform the gas that oil producers and mines have long wasted.

Other engineers, scientists, and environmentalists seem to agree. The Department of Energy, in partnership with Natural Resources of Canada held, annual microturbine application workshops every January from 2001 through 2006. Many of the presentations during the workshops focused on projects, in which microturbines turned flare gas into usable energy.

“This is very much an active business right now,” Stinton says. “It’s particularly a focus in California, where they have environmental concerns about gases coming off landfills. For the last five years or more, the number of companies that have been installing microturbine systems at landfills in that state has increased significantly.”

This doesn’t mean, though, that there isn’t much work to be done by both microturbine manufacturers and energy producers, to improve the technology behind and methods of capturing and transforming sour gas. “You have to realize, and I saw this while I was touring some sites in the Los Angeles area, that the microturbines are very small,” Stinton says. “Some of these landfills are putting off such a large volume of gas that the microturbine systems I’ve seen at those landfills are maybe generating 400 to 500 kilowatts of electricity. But, they are only capturing one or two percent of the gas being flared—the rest of that gas is still being flared.”

Despite the many benefits of using microturbine systems to capture flared gas, there are still hurdles for the industry to overcome, Stinton says. And, one of the biggest problems that he sees has to do with the waste heat that the microturbine systems produce. Energy producers and landfill operators receive an economic boost from the electricity that the microturbines on their sites produce. They can use it to either power machinery at their plants or they can sell any excess amount to their public utility.

But, what about the waste heat that the same systems produce? Currently, Stinton says, producers receive no economic value for this heat. That has to change to make investing in microturbine technology a truly valuable proposition for energy companies, he says. “In general, if you are going to pay for the fuel, you are not going to make a profit if you are not using all the waste heat all of the time. In fact, people that really know what they are doing will size their microturbine systems for the amount of waste heat that they can use. They won’t size it for the electricity.”

Microturbines sound appealing, because the gas that they are capturing and
using for fuel is free, Stinton says. But, that doesn’t mean that there aren’t some steep costs involved in using that free source of power. These costs include the expense of installing a piping system to collect the gas and the expenses involved with cleaning up the gas before it can be burned. In fact, some microturbine manufacturers won’t even warranty the systems, unless their clients purchase the cleanup systems they sell. Too often, the manufacturers have found, clients say they already have their own gas-cleanup systems, but, when put to the test, these systems don’t work effectively.

If more energy producers could find an economical way to use this waste heat, he says, it’d be easier for them to absorb the costs associated with operating a microturbine system. “This presents a problem for, say, landfill operators. You can’t send that waste heat long distances to other places. It’s not cost-effective to do that. There has to be some use for that waste heat. You can send it through an absorption chiller to make cold water. But, at the landfill, there is usually no one located there to use that waste heat. The companies generate the electricity from the systems, of course, and use that for their own internal use, but, they still don’t have much use for the waste heat.”

Schmidt is happy with the results of his center’s experiment in Newburg. But, he’s realistic, too, and says that a large impact from microturbines and other methods of distributed generation won’t be felt any time soon. The EERC got its start working with microturbines and sour gas three years ago. That’s when the center ran a pilot program in northwestern Minnesota. That project involved a 30-kW microturbine system, that was operating on captured gas that had a high-sulfur content. That project succeeded, just as the one in Newburg did. This bodes well for the future of the technology, Schmidt says. “Using these gases can be a financially significant benefit for companies across the country. It’s a distributed technology, so you are relying on many small sites that will add up to make a big impact. I think that will eventually happen.”

He also says he and his fellow engineers at the EERC are ready to invest the time and effort into making sure it does. “We will make whatever technological improvements we can make to make sure this is a viable option,” Schmidt says.

IL-based, Dan Rafter is a technical writer.

DE - May/June 2008