Heavy-oil technology may be a perfect fit for geothermal power

Sep 14, 2017

While the economic future of greenfield heavy-oil projects is in serious doubt these days, one prominent applied research group in Canada said that some of the technologies involved with heavy oil have the potential to be used around the world.

The catch is that the technologies—specifically those involved in steam-assisted gravity drainage (SAGD)—would be primarily used not to produce oil, but geothermal power.

“We believe that Alberta has been doing geothermal backwards for 30 years,” said Brian Wagg, director of business development at Edmonton-based C-FER Technologies, who explained how SAGD centers on pushing large volumes of steam into the ground via injection well where it heats viscous oil to a point at which it flows freely into a producing well.

Brian Wagg – Director of business development, C-FER Technologies

The concept that C-FER is promoting is termed an enhanced geothermal system and involves sending cool water down an injector well to become heated by moving through a nonhydrocarbon-bearing rock formation.

The geologically heated water is then pumped back to surface from a producing well at temperatures between 300°F and 390°F (150°C–200°C). At such temperatures, the water can be run through a heat exchanger to flash-evaporate a common form of butane, the expanding vapors of which would spin a turbine to generate electricity.

The novelty here is not the process described above; it is that C-FER wants the geothermal sector to begin using new SAGD technologies to make capturing rock heat more efficient and improve the output of this type of power plant. To prove whether the idea is feasible, C-FER is seeking partners for a new joint ­industry project that it recently proposed.

The ultimate aim is to design a dual-well geothermal plant capable of generating between 1 MW and 5 MW. That is comparable to a wind turbine that may generate between 2 MW and 3 MW. There is one big advantage with the geothermal route vs. other renewables: the former can generate baseload power when the sun is not shining and when the wind is not blowing.

A Win for Everyone?

One of C-FER’s chief motivations is to help Canadian oilfield equipment manufacturers and service companies expand their businesses beyond the struggling heavy-oil sector.

There is also an upside for SAGD operators who expend significant sums on building and operating gas-burning power plants to create steam from local water sources. Wagg suggests that after drilling their SAGD oil wells, operators could extend a pad site to drill enough of these enhanced geothermal wells to meet all their local electricity needs.

Geothermal companies could benefit by having lower exploration risks. Wagg explained that enhanced geothermal wells should theoretically be low-risk endeavors since the subsurface gets hotter the deeper you drill. However, the real challenge lies in creating a network of fractures that can efficiently move water between the injector and the producer in such a way that it avoids cooling the rock through channeling.

And for regions of the world suffering from energy poverty, the application of SAGD and closed-loop geothermal technologies may be even more impactful as a cheap and reliable source of zero-emission energy.

Technology Transfer

To reduce the risks associated with drilling an enhanced geothermal well, the good news is that there is no shortage of established oilfield solutions. Among those developed specifically for SAGD are high-temperature electrical submersible pumps (ESPs), downhole flow control devices, thermal well casing connections, coiled tubing instrumentation, and specialized cement for zonal isolation.

But because of the disconnect between the petroleum and geothermal industries, the geothermal sector has sometimes gone looking for a custom solution that was already developed for heavy oil.

Wagg noted one instance in which a geothermal operator consulted with Canadian experts on a well intervention solution only to find that it already existed in an equipment catalogue. The piece of kit was a wellhead with side ports that allow coiled tubing to be run without pulling out production tubing.

“That’s just one example of a technology developed here in Alberta that the geothermal industry isn’t really aware of,” Wagg said.

Two other key technologies will be required to make the perfect geothermal well: horizontal drilling and multistage hydraulic fracturing. Both are needed if geothermal operators want to vastly increase their well’s output by enlarging the area where injected water can contact high-temperature rock.

Some geothermal wells have been drilled directionally, but horizontal drilling is less common. And single-stage hydraulic fracturing has been used too, but not the multistage techniques that create the 20 to 50 fracturing clusters that define modern shale well designs.

Early-Stage Engineering

To bring this well concept closer to reality, C-FER’s joint industry project first needs to complete the front-end engineering work and modeling to show that SAGD technology can change the financial equation of enhanced geothermal systems—which historically has not been that good, hence their limited use. The next step would be to find companies willing to drill pilot wells and see how well they work with technologies originally developed for the heavy-oil sector.

But because of stiff competition from cheap natural gas, coal, and hydroelectric generation, Alberta may not be the likeliest place for this approach to geothermal to see widespread application.

It could, however, be the best place to test the concept, according to Wagg, who cited both Alberta’s local expertise and challenging geology. “We’ve got some of the coldest rock around,” he said. “So if we can make it viable here, then it should work just about anywhere.”

Written by Trent Jacobs (originally published in the Journal of Petroleum Technology).

Top image: Geothermal plants like this in Iceland may benefit from the technologies designed to produce heavy oil with hot steam. Source: Getty.