Seriously folks you read it right… fracking (an actual technical term for hydraulic fracturing) hot dry rock reservoirs — a technique that is already pretty well understood and is widely used in the oil and gas sectors to squeeze out extra production from low permeable deposits – has the potential to open up vast hot dry rock “heat” reservoirs for use as a reliable geothermal energy source. According to a 400 page MIT study The Future of Geothermal Energy sponsored by the Department of Energy (DOE) and published in 2007 the economically recoverable potential for “Heat Mining” in the US could grow to a cumulative installed generating capacity of 100GW in less than fifty years. This is a significant amount of electric energy production and because it is reliable and predictable it is suitable for critical base load generation. In addition to the electric energy generation it could also provide vast amounts of additional co-generated heat energy as well.
The MIT study found that: “Geothermal energy from EGS represents a large, indigenous resource that can provide base-load electric power and heat at a level that can have a major impact on the United States, while incurring minimal environmental impacts. With a reasonable investment in R&D, EGS could provide 100 GWe or more of cost-competitive generating capacity in the next 50 years. Further, EGS provides a secure source of power for the long term that would help protect America against economic instabilities resulting from fuel price fluctuations or supply disruptions. Most of the key technical requirements to make EGS work economically over a wide area of the country are in effect, with remaining goals easily within reach. This achievement could provide performance verification at a commercial scale within a 10- to 15-year period nationwide.”
What the Frak is Fracking?
Fracking is a technical term for hydraulic fracturing of deep rock deposits, developed and perfected by the oil & gas industry in which a high pressure fluid is injected into a deep (oil or gas bearing in the case of the Oil & Gas industry) geologic formation in order to fracture the rock and make it more permeable. In fracking the high pressure fluid spreads out from the bore hole creating a spreading fracture zone around it. The fractures are kept open by injecting sand or small ceramic beads – called poppants – into the spreading cracks that are mixed in slurry with the water.
Fracking has gotten a bad name with environmentalists because the oil and gas industry commonly mixes other (secretive and polluting) additives into the working fluid designed to chemically enhance the physical hydraulic pressure effects with the oil or gas bearing rocks. These additives then pollute the aquifers within those rock deposits. The additives are used in the oil and gas industry because the objective is to extract the physically AND chemically bonded hydrocarbons contained within the rock formation.
Fracking is also used in the water industry in order to increase the flow of water into a bore hole. In this case, only a pure water and poppant (i.e. sand or ceramic bead) slurry is forced down the well and into the spreading fracture zone. This is also what would be done for geothermal hot rock fracking, because the objective is purely the physical cracking or fracturing of a zone of hot rocks in order to make them water permeable and thus able to produce hot water or steam.
University of Utah Pilot Study
The University of Utah is going to carry out a five year $10.2 million study to study the feasibility of using hydraulic fracturing to enhance a dry rock reservoir.
EGI geologist Joe Moore – who will head the research effort at U.S. Geothermal Inc.’s Raft River power plant in southeast Idaho – says most geothermal power in the United States now is produced west of the Rocky Mountains, where hot rocks are found closest to the surface.
“Hot rock is present across the United States, but new methods have to be developed to use the heat in these rocks to produce geothermal power,” says Moore. “We want to use oil and gas industry techniques to create pathways in the rock so that we can use the heat in the rocks to generate electricity.”
“There’s incredible potential in Utah and other states for geothermal development,” he adds. “Engineered geothermal systems [in which water is injected to enhance natural cracks in the rock] could provide a means of developing these resources much faster.”
The U.S. Department of Energy on September 4 signed an agreement with the University of Utah and EGI to pay almost $7.4 million of the project’s cost.
To find out more about other DOE financed programs that have been recently announced see our article that investigates this subject: Geothermal Heats Up With $350M New Stimulus Funding from Government
Stimulating Geothermal Power by Cracking Hot Rock
To produce geothermal power, hot rock is not enough. The rock also must be permeable to the flow of water and-or steam, says John McLennan, an engineer at EGI. Many geothermal reservoirs have heat, but the rock is impermeable, which is the problem at the Raft River well known as RRG-9.
The experiment will try to make RRG-9 into an effective injection well because U.S. Geothermal must inject more water into the ground to increase the productivity of its existing production wells. Moore says all the water-injection “stimulations” will be done during 2010, with the well monitored over the rest of the five-year study period. All the water will come from production wells, not from streams.
Researchers will first let cold water flow into the hot rocks around the 6,000-foot-deep well, hoping to crack them extensively, and then pump water into the ground under high pressures to force the cracks to open wider. The goal of this “hydraulic stimulation” is to create a network of underground conduits that connect the well with underground cracks that already carry hot water.
“When the cold water reaches the hot rock it will crackle,” Moore says. “Stimulation is the process of generating new cracks.”
Apex Petroleum Engineering Inc. of Englewood, Colo., will help design the water injection operations to create “hydraulic fractures.” Apex HiPoint’s monitoring equipment will listen to microseismic activity in the rural area to determine the extent of the cracking and thus the growth of the underground geothermal reservoir. Groundwater flow and pressures will be monitored.
Moore says three “stimulations” will occur. During the first two, relatively cool water (40 to 135 degrees Fahrenheit) will flow into the well to crack the rock at a depth of 6,000 feet. Then, a third “stimulation” will involve pumping large volumes of water into the well at high pressure to expand the cracks and keep them open to the flow of water and steam.
Dry Rock Enhanced Geothermal can help America to Become More Energy Independent
Especially in the western half of the North American land mass there exist large deposits of hot dry rock at depths that are relatively close to the surface and that can be economically developed over the next few decades to provide a steady reliable source of electric and heat energy that will help America achieve some degree of energy independence and help our country transition away from dependence on fossil fuels. One of the attractions of geothermal energy is its predictability and thus suitability for providing the critical base load generating capacity.
This is one of the hurdles that most renewable energy systems such as wind and solar (thermal or PV) power present. The wind may or may not blow, the sky may be cloudy and it is very hard to predict – in the long term – what conditions will be like. This fickleness of solar and wind power is remediated by adding on energy storage capacity to these systems and combining them with hydro systems, which can easily be switched on and off and thus can act like gigantic batteries. However in order for the grid to be able to deliver stable predictable power a significant portion of its electric power must come from predictable and reliable base load generating sources.
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Currently the large coal fired or nuclear thermoelectric power plants provide this base load capacity. Geothermal has the potential to step in and provide a significant portion of the western interconnects base load capacity allowing polluting and aging coal fired and nuclear plants to be more easily retired.
The Water Problem
One concern that needs to be addressed is the water issues in the dry western part of the continent. How much water will these geothermal systems require to create the steam reservoirs? And critically how will the steam in the steam cycle in the thermoelectric plants be cooled? Wet cooling in fact uses a lot of water, which is quite scarce in much of the west.
All forms of thermoelectric power production, especially those in water poor regions face this same water problem. Water is a scarce and vital resource and big thermoelectric power plants, especially those that employ wet cooling are very large consumers of water. This is an intractable and difficult problem that will not go away because it is inconvenient. Dry cooling is one technique that can be used to significantly reduce water consumption, but only at the cost of reduced power output. This is so because these radiative cooling systems require large and well ventilated radiators in order to shed the waste heat.
One alternative proposal is the atmospheric vortex engine, which we hope to cover in detail in a future article.
Conclusion
Of course geothermal cannot answer all of our energy needs and is only one part of the mix of things we will need to do in order to transition away from our addiction to coal, gas and oil. But there is no single silver energy bullet in our future – although it must be said, the pro-nuclear crowd would argue that nuclear energy is the silver bullet, but they fail – IMO — to address the waste and other issues and often base their assumptions on paper designs that have never actually been built (i.e. Gen IV reactors)
We need to both become much more energy efficient and learn to use less and to diversify our energy sources away from our increasing dependence on unreliable politically unstable foreign fossil energy reserves.
Our future energy landscape will need a whole range of niche producers with an emphasis on widely distributed energy generation and storage. Enhanced geothermal energy sources could provide a large part of this future mix, especially in the western half of the continent. Mining heat could become one of our largest single sources of energy and that sounds pretty fracking hot to me.
