New Future for Depleted Wells
Bypassed Thermal Energy Has Value
Tapping into formation water rather than hydrocarbons when drilling a well is guaranteed to disappoint even the most stoic prospector – but, perhaps, unnecessarily.
In fact, a water “discovery” has the potential to open the door to a whole new opportunity in sedimentary basins in many areas – including the state of Texas.
Many thousands of wells already drilled in the Lone Star state are deep enough to encounter temperatures more than 250 degrees F, and sometimes exceeding 400 degrees F, at varying depths and in different geographic areas.
The extremely hot brine existing at these depths essentially is a sleeping heat energy giant boasting thousands of exajoules to be used for power generation, according to AAPG member Richard Erdlac, director of geothermal research and commercialization at Energy America Geothermal in Midland, Texas.
To put this in perspective: One exajoule per year, as defined in a report released by Lawrence Berkeley Laboratory scientists, is equivalent to 470,000 barrels of oil per day.
The Price is Right?
It is noteworthy that investigations to evaluate Texas heat reserves and resource value suggest that a Texas geothermal industry could rival the existing Texas oil and gas industry in economic value, Erdlac noted.
“I looked at some of the work done in the ‘70s (via the U.S. Department of Energy) and looked at the potential amount of resource being talked about back then, ” Erdlac said. “When I started doing the numbers, assuming a value of the resource at a little over five cents a kilowatt hour, I was getting billions of dollars on a yearly basis, consistently year after year.
“When I did this, oil was $43 a barrel and gas a little over $5 per Mcf, and that’s obviously changed,” Erdlac added. “But oil and gas in Texas is getting less and less in volume each year, even if the price goes up. ”
Just as operators often re-enter abandoned wells to go after new oil and gas zones, they could just as well re-enter them to produce hot water and then extract the heat to generate power.
“For the oil and gas industry to continue treating hot water as waste is equivalent to flaring natural gas as once was the custom in the industry, ” Erdlac said. “No one wanted it, and now it has value.”
He noted it’s the same thing with thermal energy, but thermal has a distinctive plus in that it ’s renewable – you extract the water, and additional quantities move into the formation.
Also, the deeper the water resides in the earth, the hotter it gets.
Some Like It Hot
It’s common to think of geothermal energy in terms of steam, but the resource isn’t always in vapor form. When producing extremely hot water, a variety of processes can be used to extract the heat at the surface.
It is noteworthy that sedimentary basins are oil and gas country, and the geothermal industry is unaccustomed to dealing with these types of systems. Yet focusing only on traditional geothermal areas limits the future growth of this resource.
Partnering with oil and gas companies would bring expertise and data that standalone geothermal operators would have to develop internally at their own expense.
Joining together also would benefit the oil and gas concern, which likely could produce what ordinarily would be uneconomic amounts of hydrocarbons, with the geothermal side of the operation providing the needed economic boost to make the project viable.
Erdlac noted that the Massachusetts Institute of Technology released a study early this year acknowledging the huge potential for geothermal energy, which can be compared to fossil fuels when it comes to power generation capacity.
“Once a power plant gets going, it’s going for long periods of time,” Erdlac noted. “It has a high capacity factor – that may mean it’s in operation maybe 98 percent of the year and going 24/7.
“Geothermal has a 90, 95, 98 percent capacity factor – it’s on par with nuclear, natural gas, coal-fired power plants.”
Erdlac is convinced that the time has come to actively pursue this power source in Texas.
“There’s a huge amount of thermal energy in Texas,” he noted, “and the oil and gas industry has tapped into it and said, ‘Well, we can’t use it.’
“The thing is, it’s still there and being replenished over time, so it’s very advantageous to go after it.”