U.S. Department of Energy - Energy Efficiency and Renewable Energy
Geothermal Technologies Office
Scientists Charged Up by Oil Wells' Latent Power
January 17, 2006
It's the bane of the oil field: water. Companies spend millions drilling a well, and down-hole surveys show it will yield only water. Or their old, formerly robust oil and gas wells give way over the years to nothing but water.
All a producer can do in such circumstances is call out the concrete trucks and plug the well.
But two Texas academic researchers say these dry holes and wet holes could be an alternative energy gusher waiting to be tapped, particularly in a "hot zone" in eastern and coastal Texas that extends into Louisiana and Arkansas.
The heat from that worthless, troublesome salt water, they say, could be turned into electricity, a whole lot of electricity.
"I know there's huge potential along the Gulf Coast," said Richard Erdlac, a research scientist at the University of Texas of the Permian Basin. "I see a lot of potential for companies to use that on-site to reduce their expenses. From there it can go to producing electricity for the (statewide) grid. . . . You want to talk about thinking outside the box? Let's really start doing it."
David Blackwell, a Southern Methodist University geophysics professor, co-authored a September article in the Oil and Gas Journal on the potential of oil field water for generating electricity.
Just using water from existing wells in Texas and six other states, Blackwell writes, could generate up to 5,000 mega- watts, or about twice the peak load of Austin Energy.
Put another way, that's like adding three or four nuclear power plants.
But relying only on old wells could vastly understate the potential, Blackwell and Erdlac say.
The several hundred thousand wells drilled in Texas during the past century are an informational gold mine that could point the way to drill for, in effect, electricity.
"There are estimates for the Gulf Coast of up to 100,000 megawatts," Blackwell said.
What Blackwell and Erdlac have in mind is basically an extension of a geothermal subindustry that already exists in California and other Western states that are affected by tectonic activity, such as the shifting of underground plates, which creates heat.
Wells in those regions generally reach superheated basement rocks at 10,000 feet or more below the surface and produce either steam or hot water. The steam or hot water is then used to move turbines, which in turn generate electricity.
In the central United States, where the hottest basement rock is much deeper, the theory is that geothermal power could instead be generated from the sandstone and limestone formations above the basement rock, the strata where oil and gas is generally found.
Blackwell is focusing on existing wells and fields.
Most wells start out making almost no briny water, only hydrocarbons such as oil and gas, because engineers are able to determine where the hydrocar- bon-bearing rock formations are and punch holes in the pipe opposite only those areas.
But over time, as oil and gas are removed, water tends to move up from below and begin joining the flow.
Given the expense, much of it to purchase electricity to run pumping units and to dispose of the water, a well making 2 barrels of oil and 200 barrels of water a day becomes a losing proposition and is shut down.
In so-called waterfloods, water is injected into wells to push the remaining oil to other wells. Such fields produce an enormous amount of water and have centralized collection facilities.
Blackwell envisions installing generating units at these central points. A unit that generates 250 kilowatts, enough to supply about 165 homes, would be about bedroom-size and cost about $400,000, he said.
The problem is, most of the state's waterflood operations are in West Texas, where temperatures at the bottom of existing wells are cooler, typically below 200 degrees Fahrenheit.
The hotter area (about 3 to 4 miles down) exists east of Interstate 35, for reasons that even experts such as Blackwell and Erdlac say are not entirely clear.
Erdlac, noting the large swath from Laredo to Texarkana with unusually hot subsurface temperatures, envisions drilling wells from scratch and seeking water on purpose.
This is a tougher proposition, because the truly hot water of 250 degrees F or more needed to generate electricity in volume is at 18,000 feet and below. Such wells can cost $10 million to $20 million to drill, which would take a lot of electricity to justify.
Erdlac says, however, that some oil and gas might be found in the process, helping pay back the investment.
So how does the oil industry view all this?
"They've got their eyes open and ears open," said Prentice Creel, a Halliburton Co. petroleum engineer who serves on the Society of Petroleum Engineers board. "You have a tremendous number of wells that are already in the ground, already producing, and all you have to do is throw something out there to collect the energy."
In the end, such solutions are inevitable, Creel said, given that oil and gas are finite resources on the downhill side of their life cycles.
Earth's heat, meanwhile, is seemingly inexhaustible.
"Can it be done? Yes, it can be done," Creel said. "And it's going to be done eventually because it's going to have to be done, because we have to have electricity."
Ben Wear, AMERICAN-STATESMAN STAFF
15 January 2006, Austin American-Statesman © 2006 Austin American Statesman.