Pictures of the Future        Herbst 2008

Electrifying Extraction

Around 90 % of global oil reserves are bound up in tar sands and schists. Although expensive, extracting oil from these reservoirs is becoming increasingly viable. Siemens is developing a revolutionary, induction-based process that promises to obviate excavation, cut water demand, and significantly boost profits.

Bernd Wacker and his team want to heat up tar sand using an induced current. In this way, oil can be extracted in a greener way than is the case with open pit mining (pictures below)

When Bernd Wacker, a researcher for Siemens, flips the switch mechanism in his laboratory in Erlangen, Germany, you’d best run for cover. At that point up to 400 A of current shoots through a thermally insulated copper loop into a small sandbox and heats up the grains of quartz soaked in salt water. If the observer doesn’t keep to the safety clearance of one meter, things can quickly get uncomfortable. "You can receive superficial burns if you wear a conductive item such as a wristwatch," explains Wacker. "Things really get heated up."

The thing that is giving visitors the jitters is also having an electrifying effect on Wacker, who works at Siemens Corporate Technology. That’s because his experiment could prove that moist sand can be warmed by electromagnetic induction alone—in other words, not through the heat from a coil, for instance. "The setup behaves much the way as does a pot of spaghetti on an induction stove," says Wacker. The current-carrying copper coil gives rise to an alternating magnetic field that generates eddy currents in conductive materials. Such eddy currents heat the metallic pot—or sand soaked in salt water, as the case may be.

And the result is a whiff of revolution in Wacker’s lab. Why? Because if the process developed by Siemens researchers succeeds in heating up bituminous sands in Canada with the help of the induction effect, it will mean that oil can be extracted from viscous sludge in a way that is more effective and environmentally compatible than conventional methods.

That would be a method with a future, given the enormous reserves lying under the Canadian wilderness. Experts suspect that the sandy soils contain around 178 billion barrels of crude oil, barely 3 % of which has been exploited since the 1960s. Although the extraction of the coveted raw material is nearly three times as expensive as conventional oil production, the rising price of oil is ensuring that even the most costly procedure is becoming increasingly viable. Canadian energy authority NEB estimates that a total of US $94 billion will have been invested in production by 2015. Oil sand production ought to then triple as a result.

The problem is that extracting that oil isn’t exactly the best thing for Canada’s natural environment. Today, the most common extraction method is also the most environmentally damaging one. "Around 70 % of Canadian oil sands are extracted through open pit mining," says Michael Koolman from the Siemens Energy Sector. "Huge areas are cleared, and then excavators roll in." According to Koolman, who is an oil and gas expert, the wilderness is literally turned upside down. Moreover, large amounts of methane—a greenhouse gas 21 times more harmful than CO₂—are released during excavation. The extracted tar sand is then mixed with water and separating agents. The heavy sand settles out; the oil collects in a foam on top and can be skimmed off. An additional problem is the large amount of water used. "The water table sinks, for example, and this can have negative effects on the ecosystem," says Koolman. He estimates that open pit mining will continue for approximately the next 20 to 30 years until reserves close to the surface have been exploited.

Full Steam Ahead. Since 2002 a less intrusive extraction method has been developed for getting at oil buried as much as 60 m beneath the surface. In this so-called in-situ method, steam at a temperature of up to 300 °C is injected under high pressure into the reservoir through a pipe. A 25-cm-thick drainage line runs about 6 m beneath the steam inducer. After the tar sands have been "steamed" for a few weeks, the pressure and temperature in the deposit increase and the reservoir becomes more permeable. At this point, a mixture of bitumen—a substance similar to tar—and water slowly separates from the grains of sand and drips into the 1,000-m-long drain line. It can then flow to the end of the line and be extracted from there. In this way a total of about 1,000 barrels of bitumen per borehole can be obtained each day. In a further step in the process, the viscous mass is separated from the water and processed into synthetic crude oil. The remaining water is re-purified and supplies the boiler at a later time.

This method spares the environment from being excavated; however, water and energy consumption are still high. "This is where our electromagnetic induction process comes in," says Wacker. The method developed by his team will initially be used to support the on-site process, making it considerably more effective. An inductor that is roughly as thick as an arm and looks similar to a cable runs parallel to the steam pipe in the earth. "The operator then sends electrical energy into the reservoir and an alternating magnetic field is generated around the inductor," explains Wacker. "This field creates eddy currents in the conductive sand that slowly heat up the bitumen and mineralized water on the tar sand grains." Droplets of bitumen finally separate from the grains and flow into the drain line. When combined with conventional steam injection, over 20 % more material can be extracted in the same time, depending on reservoir conditions. Because of the high yield, the specific water consumption is dramatically reduced, adds Koolman. "Normally four barrels of water must be turned to steam to produce one barrel of bitumen. With our process only half of this would be needed." Depending on extraction time and the geological composition of the reservoir, steam injection could be avoided altogether; the tar sand could be processed with electrical induction alone. "The advantage of this method would be that absolutely no water would be needed. Energy use would also be lower," explains Koolman. In the in-situ process the steam injector would consume up to 12 MW of power. The induction process, on the other hand, requires considerably less electricity. Siemens experts consider their method to be advantageous because if reservoir pressure becomes excessively high, the hot steam could break through the overburden along with flammable gases, igniting oil in the immediate subsurface environment and presenting a serious fire risk. "Electric current is considerably easier to control," says Koolman.

At present, the induction method is in operation only in a sandbox at Siemens’ Erlangen campus. But by 2010 a pilot system in Canada’s prairie province of Alberta may show what it’s capable of. "For that project, we will first have to design an entirely new induction cable," says Wacker. This represents a new challenge for our engineers, as up to now the inductors have been restricted to kitchen stoves and measured a maximum of 2 m in length. "In contrast, when it comes to Alberta, we will need a cable several kilometers in length that is also resistant to high temperatures and voltages," he explains.

Extensive simulations confirm that the researchers‘ idea could succeed. A computer evaluated the 20-year life cycle of a typical tar sand reservoir. Here, for the first time, the Siemens experts have connected a conventional reservoir simulator to an electromagnetic simulator.

The result was clear, reports Wacker enthusiastically. "With our induction process the customer’s profit would increase by around 20 %."
                                                                                                              Florian Martini