Clean Alternate Energies: Geothermal Breakthrough Emerges From Shale Revolution
Originally published on Forbes.com on January 17, 2024
Two current projects are definitely encouraging for commercial application of geothermal technology as a non-intermittent renewable energy source.
If the world does reach net-zero by 2050, meaning the energy supply is carbon-free, then a third of this energy will come from systems that have much in common with oil and gas industry skills and resources: offshore wind, liquid biofuels, biomethane, hydrogen fuel, geothermal energy.
Future scenarios for oil and gas
In BP’s scenarios for the future, the Russian war in Ukraine is likely to swing the pendulum away from “business as usual” and toward the Paris goal of “net-zero emissions” by 2050. This scenario, called War Accelerated, can be taken as BP’s best guess for the future.
In contrast to the current enthusiasm in the US oil and gas industry, BP forecasts a drastic reduction in fossil energies from 83% now to 28% by 2050. Coal will fall the most, oil will fall, and natural gas may or may not fall. BP says natural gas is an X-factor because of an ever-rising demand for LNG around the world.
BP projects that renewable energies, such as wind and solar and batteries, will rise from 12% now to 58% by 2050. One of these renewable energies is geothermal. The US has a tremendous potential resource of heat energy in hot rocks beneath the surface. A distinct advantage is this heat energy is continuous — not intermittent, like wind and solar.
Two recent projects are testing and proving that shale technology can be adapted to extract energy from hot rocks deep underground. The oil and gas drilling industry initiated the shale industry in 2003. A typical horizontal well, 2 miles long, is fracked up to 40 times along its length to make oil and gas production commercial. The shale revolution reignited the US oil and gas industry so that the US became independent in oil and gas production – for the first time in 60 years.
The US Department of Energy (DOE) has funded a project called FORGE where hot granite rock is being drilled and fracked using the best oil and gas technology. An overall goal is to test commercial applications.
In a commercial setting, cold water would be pumped down one well and pass through an array of hydraulically created fractures, acquiring heat in the process. The hot water would be produced to the surface through a production well. At the surface, standard geothermal technology would drive turbines that generate electricity. The produced water, after heat has been taken out, would be recirculated.
John McLennan, Department of Chemical Engineering, University of Utah, is the co-principal investigator for this DOE project.
Six wells have been drilled to date. Five of these wells are vertically drilled monitoring wells, designed to be a field laboratory. Fiber optic cables and geophones in the monitoring wells can map the growth of hydraulic fractures that interconnect an injection well, which has been drilled, with an upcoming production well.
The injection well was drilled to a measured depth of 10,987 ft, where the true vertical depth is 8520 ft below ground level. Then continued as a lateral at 65° to the vertical, for about 4,300 feet. The direction of the lateral favors hydraulic fractures being orthogonal to the well.
The third stage of injection suggests pseudo-radial fracture growth. This favors a separation between the existing injector and the future producer on the order of 300 ft. A commercial scenario may require greater offset than this, but this experimental program needs to first establish the ability to interconnect two adjacent wells with hydraulic fracturing.
The production well was drilled in mid-2023 parallel to the injection well but is offset 300 ft vertically above that well (Figure 1). It was drilled to intersect microseismic clouds from three modestly-sized hydraulic fractures done in April 2022. An injection test pumped cold water at 7.5 barrels per minute and monitored the pressure. A connection was confirmed but indicated that additional injection would be required to bring the connection to a level for commercial application.
An additional seven hydraulic fracturing stages in the injector are planned for the spring of 2024. First, slickwater will be bullheaded down to extend the three fractures created previously. Then six additional fracturing stages will be pumped with varying clusters per stage – up to eight clusters which is commercial scale. Proppant will be pumped in all stages (100 mesh and 40/70 mesh) and the treating fluid will be slickwater or crosslinked guar.
During the completion of the production well in 2023, three fiber optic cables were cemented in the casing – to provide a laterally continuous measure of temperature, acoustic events, and wellbore strain. This will make it possible to find out where the new fractures “hit” the production well. These locations will then be perforated, isolated, and fractured to improve the connection between the two wells. The water circulation in each zone will be evaluated using a spinner survey in each well.
The FORGE site will not be a power producer. It is intended to be used to test and develop technologies that will promote the commercialization of this type of geothermal energy.
In the fall of 2023, Google and geothermal developer Fervo Energy said its Project Red is supplying 3.5 MegaWatts (MW) of electricity to NV Energy, a Las Vegas utility. This could power 2,600 houses at one time, a small contribution, but this is better than 40 other geothermal systems in the world, said Fervo. They also claim a continuous source of clean energy that uses minimal land surface area, as compared with wind and solar.
Geothermal energy did supply the US with 3,700 MegaWatts (MW) in 2022 but this is only 0.4% of total supply. The DOE said it could supply thirty times this amount, or 90,000 MW, by 2050.
The Google connection is interesting. In 2022 Google set a goal for all of its offices and data centers to operate carbon-free by 2030. Google has backed the new geothermal power plant which is now transporting clean green electricity to the grid in Nevada, where some large Google data centers exist.
At the Project Red site, two wells have been drilled down to 7,700 ft, and then kicked off to two horizontal wells 3,250 ft in length in hard impermeable rock. The horizontal legs are fracked along their length to create a permeable reservoir. Presumably, water is pumped down one well and across to exit the other well. While underground, the water is heated to 376 F degrees which eventually produces steam that runs turbines at the surface to produce electricity.
The cost of electricity at Project Red is greater than DOE’s target of $45/MWh by 2035. But costs will fall when Project Red is scaled up to a new 400 MW commercial project in Utah called Cape Station. Fervo has already started drilling the first of 100 vertical wells in the new project that could start producing electricity in 2026 and reach full scale in 2028.