Enhanced geothermal system

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Enhanced geothermal system: 1 Reservoir, 2 Pump house, 3 Heat exchanger, 4 Turbine hall, 5 Production well, 6 Injection well, 7 Hot water to district heating, 8 Porous sediments, 9 Observation well, 10 Crystalline bedrock

An enhanced geothermal system (EGS) generates geothermal electricity without the need for natural convective hydrothermal resources. Until recently, geothermal power systems have exploited only resources where naturally occurring heat, water, and rock permeability are sufficient to allow energy extraction.[1] However, by far the most geothermal energy within reach of conventional techniques is in dry and impermeable rock.[2] EGS technologies enhance and/or create geothermal resources in this hot dry rock (HDR) through a variety of stimulation methods, including 'hydraulic stimulation'.


When natural cracks and pores do not allow economic flow rates, the permeability can be enhanced by pumping high-pressure cold water down an injection well into the rock. The injection increases the fluid pressure in the naturally fractured rock, triggering shear events that enhance the system's permeability. As long as the injection pressure is maintained, a high matrix permeability is not required, nor are hydraulic fracturing proppants required to maintain the fractures in an open state. This process is termed hydro-shearing,[3] perhaps to differentiate it from hydraulic tensile fracturing, used in the oil and gas industry, which can create new fractures through the rock in addition to expanding the existing fractures.[4]

Water travels through fractures in the rock, capturing the rock's heat until forced out of a second borehole as very hot water. The water's heat is converted into electricity using either a steam turbine or a binary power plant system.[5] All of the water, now cooled, is injected back into the ground to heat up again.

EGS technologies can function as baseload resources that produce power 24 hours a day. Unlike hydrothermal, EGS may be feasible anywhere in the world, depending on the economic limits of drill depth. Good locations are over deep granite covered by a 3–5 kilometres (1.9–3.1 mi) layer of insulating sediments that slow heat loss.[6] Advanced drilling techniques may be able to drill into hard crystalline rock at depths of up to or exceeding 15 km, which would give access to higher-temperature rock (400°C and above) around the world.[7] An EGS plant is expected to have an economical lifetime of 20–30 years using current technology.[8]

EGS systems are currently being developed and tested in Australia, France, Germany, Japan, Switzerland, and the United States. The largest EGS project in the world is a 25-megawatt demonstration plant currently being developed in Cooper Basin, Australia. Cooper Basin has the potential to generate 5,000–10,000 MW.

Research and development[edit]

Map of 64 EGS projects around the world

EGS technologies use a variety of methods to create additional flow paths inside reservoir rocks. Past EGS projects around the world have used combinations of hydraulic, chemical, thermal, and explosive stimulation methods. EGS projects also include those at the edges of current hydrothermal geothermal sites where drilled wells intersected hot, yet impermeable, reservoir rocks and stimulation methods were used to enhance that permeability. The table below shows both large and small EGS projects around the world.[9][10]

Name Country State/region Year Start Stimulation method References
Mosfellssveit Iceland 1970 Thermal and hydraulic [11]
Fenton Hill USA New Mexico 1973 Hydraulic and chemical [12]
Bad Urach Germany 1977 Hydraulic [13]
Falkenberg Germany 1977 Hydraulic [14]
Rosemanowes UK 1977 Hydraulic and explosive [15]
Le Mayet France 1978 Hydraulic ,[16][17]
East Mesa USA California 1980 Hydraulic [18]
Krafla Iceland 1980 Thermal [19]
Baca USA New Mexico 1981 Hydraulic [18]
Geysers Unocal USA California 1981 Explosive [18]
Beowawe USA Nevada 1983 Hydraulic [18]
Bruchal Germany 1983 Hydraulic [20]
Fjällbacka Sweden 1984 Hydraulic and chemical [21]
Neustadt-Glewe [de] Germany 1984 [20]
Hijiori Japan 1985 Hydraulic [22]
Soultz France 1986 Hydraulic and chemical [23]
Altheim Austria 1989 Chemical [24]
Hachimantai Japan 1989 Hydraulic [25]
Ogachi Japan 1989 Hydraulic [26]
Sumikawa Japan 1989 Thermal [27]
Tyrnyauz Russia Kabardino-Balkaria 1991 Hydraulic ,[28][29]
Bacman Philippines 1993 Chemical [30]
Seltjarnarnes Iceland 1994 Hydraulic [31]
Mindanao Philippines 1995 Chemical [32]
Bouillante France 1996 Thermal [33]
Leyte Philippines 1996 Chemical [34]
Hunter Valley Australia 1999 [8]
Groß Schönebeck Germany 2000 Hydraulic and chemical [35]
Tiwi Philippines 2000 Chemical [36]
Berlin El Salvador 2001 Chemical [37]
Cooper Basin: Habanero Australia 2002 Hydraulic [38]
Cooper Basin: Jolokia 1 Australia 2002 Hydraulic [38]
Coso USA California 1993, 2005 Hydraulic and chemical [39]
Hellisheidi Iceland 1993 Thermal [40]
Genesys: Horstberg Germany 2003 Hydraulic [41]
Landau [de] Germany 2003 Hydraulic [42]
Unterhaching Germany 2004 Chemical [43]
Salak Indonesia 2004 Chemical, thermal, hydraulic and cyclic pressure loading [44]
Olympic Dam Australia 2005 Hydraulic [45]
Paralana Australia 2005 Hydraulic and chemical [46]
Los Azufres Mexico 2005 Chemical [47]
Basel [de] Switzerland 2006 Hydraulic [48]
Lardarello Italy 1983, 2006 Hydraulic and chemical [49]
Insheim Germany 2007 Hydraulic [50]
Desert Peak USA Nevada 2008 Hydraulic and chemical [51]
Brady Hot Springs USA Nevada 2008 Hydraulic [52]
Southeast Geysers USA California 2008 Hydraulic [53]
Genesys: Hannover Germany 2009 Hydraulic [54]
St. Gallen Switzerland 2009 Hydraulic and chemical [55]
New York Canyon USA Nevada 2009 Hydraulic [56]
Northwest Geysers USA California 2009 Thermal [57]
Newberry USA Oregon 2010 Hydraulic [58]
Mauerstetten Germany 2011 Hydraulic and chemical [59]
Soda Lake USA Nevada 2011 Explosive [60]
Raft River USA Idaho 1979, 2012 Hydraulic and thermal [61]
Blue Mountain USA Nevada 2012 Hydraulic [62]
Rittershoffen France 2013 Thermal, hydraulic and chemical [63]
Klaipėda Lithuania 2015 Jetting [64]
Otaniemi Finland 2016 Hydraulic [65]
South Hungary EGS Demo Hungary 2016 Hydraulic [66]
Pohang South Korea 2016 Hydraulic [67]
FORGE Utah USA Utah 2016 Hydraulic [68]
Reykjanes Iceland 2006, 2017 Thermal [69]
Roter Kamm (Schneeberg) Germany 2018 Hydraulic [70]
United Downs Deep Geothermal Power (Redruth) UK 2018 Hydraulic [71]
Eden (St Austell) UK 2018 Hydraulic [72]
Qiabuqia China 2018 Thermal and hydraulic [73]
Vendenheim France 2019 [74]


The Australian government has provided research funding for the development of Hot Dry Rock technology.[75]

European Union[edit]

The EU's EGS R&D project at Soultz-sous-Forêts, France, has recently connected its 1.5 MW demonstration plant to the grid. The Soultz project has explored the connection of multiple stimulated zones and the performance of triplet well configurations (1 injector/2 producers).[76]

Induced seismicity in Basel led to the cancellation of the EGS project there.

The Portuguese government awarded, in December 2008, an exclusive license to Geovita Ltd to prospect and explore geothermal energy in one of the best areas in continental Portugal. An area of about 500 square kilometers is being studied by Geovita together with the Earth Sciences department of the University of Coimbra's Science and Technology faculty, and the installation of an Enhanced Geothermal System (EGS) is foreseen.

South Korea[edit]

The Pohang EGS project was started in December 2010, with the goal of producing 1 MW.[77]

Deep drilling experience gained under the drilling of the first of two wells from the project, was shared at a conference in 2015.[78]

The 2017 Pohang earthquake may have been linked to the activity of the Pohang EGS project. All research activities on the site was stopped in 2018.

United Kingdom[edit]

Cornwall is set to host a 3MW demonstration project, based at the Eden Project, that could pave the way for a series of 50-MW commercial-scale geothermal power stations in suitable areas across the country.[79]

A commercial-scale project near Redruth is also planned. The plant, which has been granted planning permission,[80] would generate 10 MW of electricity and 55 MW of thermal energy and is scheduled to become operational in 2013–2014.[81]

United States[edit]

Early days — Fenton Hill[edit]

The first EGS effort — then termed Hot Dry Rock — took place at Fenton Hill, New Mexico with a project run by the federal Los Alamos Laboratory.[82] It was the first attempt to make a deep, full-scale EGS reservoir.

The EGS reservoir at Fenton Hill was first completed in 1977 at a depth of about 2.6 km, with rock temperatures of 185 °C. In 1979 the reservoir was enlarged with additional hydraulic stimulation and was operated for about 1 year. The results demonstrated that heat could be extracted at reasonable rates from a hydraulically stimulated region of low-permeability hot crystalline rock. In 1986, a second reservoir was prepared for initial hydraulic circulation and heat extraction testing. In a 30-day flow test with a constant reinjection temperature of 20 °C, the production temperature steadily increased to about 190 °C, corresponding to a thermal power level of about 10 MW. Due to budget cuts, further study at Fenton Hill was discontinued.

Working at the edges—using EGS technology to improve hydrothermal resources[edit]

EGS funding languished for the next few years, and by the next decade, US efforts focused on the less ambitious goal of improving the productivity of existing hydrothermal resources.

In fiscal year 2002, preliminary designs for five projects employing EGS technology were completed and the Coso Hot Springs geothermal field at the US Naval Weapons Air Station in China Lake, California was selected for full-scale development. Two additional projects were selected for preliminary analysis at Desert Peak in Nevada and Glass Mountain in California. Funding for this effort totaled $1.5 million. The effort was continued in 2003 with an additional $3.5 million.[citation needed]

In 2009, The US Department of Energy (USDOE) issued two Funding Opportunity Announcements (FOAs) related to enhanced geothermal systems. Together, the two FOAs offered up to $84 million over six years. [83]

The DOE followed up with another FOA in 2009, of stimulus funding from the American Reinvestment and Recovery Act for $350 million, including $80 million aimed specifically at EGS projects,[84]


In February 2014, the Department of Energy (DOE) announced the intent to establish "a dedicated subsurface laboratory called the Frontier Observatory for Research in Geothermal Energy (FORGE)"[85] in order to investigate and develop enhanced geothermal technology. In August 2016, it was announced that the proposed sites had been narrowed to two (in Utah and Nevada), expected to be reduced to one the following year.[86] In June 2018 the Department of Energy announced that a location outside of Milford, Utah had been selected to host the FORGE laboratory. Over a five-year period, the University of Utah will receive up to $140 million for cutting edge geothermal research and development.[87]

The FORGE site is located 350 km south of Salt Lake City, Utah along the Colorado Plateau and Basin and Range Province transitional zone. The underlying geology is primarily composed of intrusive Oligocene through Miocene batholith rock emplaced into Precambrian metamorphic (Gneiss) and Paleozoic sedimentary rocks.[88][89] This site is west of the Mineral Mountains and about two km east of the north–south trending Opal Mond Fault (OMF), perpendicular to the east–west trending Negro Mag Fault (NMF).[88][90] The FORGE is dominated by a fault-fracture mesh system with Opal Mound Fault one of the most active features of the FORGE site.[89][91] The fault structures vary from steeply dipping faults west of the Mineral Mountains to more gently steeping faults to the east of the FORGE site.[89][88] The Enhanced Geothermal System (EGS) reservoir of the FORGE site is located approximately between 1525 and 2896 meters (~5,000-10,000 ft) depth and lies between a temperature range of 175-225 degrees Celsius.[92] The EGS reservoir is in rock aged from 8 Ma to 25.4 Ma.[93][94][95] Located east of the FORGE site is Roosevelt Hot Springs, a hydrothermal area with temperatures ranging from about 100 degrees Celsius at the surface to over 250 degrees Celsius at a depth of roughly 4000 meters (13,123.4 ft).[91] The temperatures of Roosevelt Hot Springs (RHS) indicate the presence of cooling magma in the shallow crust.[91]

More than 80 shallow gradient wells (less than 500 m depth) and 20 deeps wells (greater than 500 m depth) have been drilled at and near the FORGE site since the 1970s.[96][97] Analyses from the shallow well data shows that the encountered granitic rocks are dry, or not producing fluids, but are elevated in temperature.[96] A lack of fluid production by the underlying granitic rocks indicates these rocks are impermeable and that the FORGE site is a classic example of a hot dry rock energy producing system.[92] The thermal grounds of the FORGE site covers most of the northern Milford valley.[96][97] The highest temperature wells (greater than 80 degrees Celsius) are located east of the OMF above the RHS hydrothermal system.[97] Near-surface profiles (less than 80 m depth) of temperature gradient are similar in central, southern and western sectors of the FORGE site at roughly 70 degrees Celsius per km and do not exceed 270 drees Celsius, even at higher temperature wells west of the FORGE site.[97]

Cornell University — Ithaca, NY[edit]

Developing EGS in conjunction with a district heating system is a part in Cornell University's Climate Action Plan for their Ithaca campus.[98] The project began in 2018 with the preparatory phase to determine feasibility, gain funding and monitor baseline seismicity.[99] The project received $7.2 million in funding from the USDOE.[100] A test well will be drilled in spring of 2021, at a depth of 2.5 –5 km targeting rock with a temperature > 85 °C. The site is planned to supply 20% of the campus' annual heating load. Promising geological locations for reservoir have been proposed in the Trenton-Black River formation (2.2 km) or in basement crystalline rock (3.5 km).[101]

EGS "earthshot"[edit]

In September 2022, the Geothermal Technologies Office within the Department of Energy's Office of Energy Efficiency and Renewable Energy announced an "Enhanced Geothermal Shot" as part of their Energy Earthshots campaign.[102] The goal of the Earthshot is to reduce the cost of EGS by 90%, to $45/megawatt hour by 2035.[103]

Other federal funding and support[edit]

The Infrastructure Investment and Jobs Act authorized $84 million to support EGS development through four demonstration projects.[104] The Inflation Reduction Act extended the Production Tax Credit for renewable energy sources (including geothermal) until 2024 and included geothermal energy in the new Clean Electricity PTC which begins in 2024.[105]

In December 2022, US Energy Secretary Jennifer Granholm described geothermal as one of her favorite topics.[106]

Induced seismicity[edit]

Some induced seismicity is inevitable and expected in EGS, which involves pumping fluids at pressure to enhance or create permeability through the use of hydro-shearing and hydraulic fracturing techniques. Hydro-shear stimulation methods seek to expand and extend the connectivity of the rock's existing fractures to create a better fluid network for the transfer of heat from the rock to the fluid.[107][108] Seismicity events at the Geysers geothermal field in California have been strongly correlated with injection data.[109]

The case of induced seismicity in Basel merits special mention; it led the city (which is a partner) to suspend the project and conduct a seismic hazard evaluation, which resulted in the cancellation of the project in December 2009.[110]

According to the Australian government, risks associated with "hydrofracturing induced seismicity are low compared to that of natural earthquakes, and can be reduced by careful management and monitoring" and "should not be regarded as an impediment to further development of the Hot Rock geothermal energy resource".[111] However, the risks of induced seismicity vary from site to site and should be considered before large scale fluid injection is begun.

CO2 EGS[edit]

The Geothermal Energy Centre of Excellence at the University of Queensland has been awarded AUD 18.3 million for EGS research, a large portion of which will be used to develop CO2 EGS technologies.

Research conducted at Los Alamos National Laboratories and Lawrence Berkeley National Laboratories examined the use of supercritical CO2, instead of water, as the geothermal working fluid, with favorable results. CO2 has numerous advantages for EGS:

  1. Greater power output
  2. Minimized parasitic losses from pumping and cooling
  3. Carbon sequestration
  4. Minimized water use
  5. CO2 has a much lower tendency to dissolve minerals and other substances than water, which greatly reduces scaling and corrosion of system components

CO2 is, however, much more expensive and somewhat more difficult to work with than water.

EGS potential in the United States[edit]

Geothermal power technologies.

A 2006 report by MIT,[8] and funded by the U.S. Department of Energy, conducted the most comprehensive analysis to date on the potential and technical status of EGS. The 18-member panel, chaired by Professor Jefferson Tester of MIT, reached several significant conclusions:

  1. Resource size: The report calculated the United States total EGS resources from 3–10 km of depth to be over 13,000 zettajoules, of which over 200 ZJ would be extractable, with the potential to increase this to over 2,000 ZJ with technology improvements — sufficient to provide all the world's current energy needs for several millennia.[8] The report found that total geothermal resources, including hydrothermal and geo-pressured resources, to equal 14,000 ZJ — or roughly 140,000 times the total U.S. annual primary energy use in 2005.
  2. Development potential: With an R&D investment of $1 billion over 15 years, the report estimated that 100 GWe (gigawatts of electricity) or more could be installed by 2050 in the United States. The report further found that "recoverable" resources (accessible with today's technology) were between 1.2 and 12.2 TW for the conservative and moderate recovery scenarios respectively.
  3. Cost: The report found that EGS could be capable of producing electricity for as low as 3.9 cents/kWh. EGS costs were found to be sensitive to four main factors:
    1. Temperature of the resource
    2. Fluid flow through the system measured in liters/second
    3. Drilling costs
    4. Power conversion efficiency

Hot dry rock (HDR)[edit]

Hot dry rock (HDR) is an extremely abundant source of geothermal energy that is difficult to access. A vast store of thermal energy is contained within hot, dry crystalline basement rocks found almost everywhere deep beneath Earth's surface.[112] A method for the extraction of useful amounts of geothermal energy from HDR originated at the Los Alamos National Laboratory in 1970, and Laboratory researchers were awarded a US patent covering it.[113]

This technology has been tested extensively with multiple deep wells drilled in several field areas around world including the US, Japan, Australia, France, and the UK.[114]

Map of current and planned superhot rock energy projects

It continues to be the focus of sizable government-led research studies involving deep drilling and rock studies. Thermal energy has been recovered in reasonably sustainable tests over periods of years and in some cases electrical power generation was also achieved. Ongoing efforts are underway to further develop and test EGS technologies in hot dry rock systems.[115] EGS in hot dry rock has not yet been commercialized, but one estimate suggests a possible price of $20-35 per MWh for nth-of-a-kind power plants.[116]


Although often confused with the relatively limited hydrothermal resource already commercialized to a large extent, HDR geothermal energy is very different.[117] Whereas hydrothermal energy production can exploit hot fluids already in place in Earth's crust, an HDR system (consisting of the pressurized HDR reservoir, the boreholes drilled from the surface, and the surface injection pumps and associated plumbing) recovers Earth's heat from hot but dry regions via the closed-loop circulation of pressurized fluid. This fluid, injected from the surface under high pressure, opens pre-existing joints in the basement rock, creating a man-made reservoir which can be as much as a cubic kilometer in size. The fluid injected into the reservoir absorbs thermal energy from the high-temperature rock surfaces and then conveys the heat to the surface for practical use.


The idea of deep hot dry rocks heat mining was described by Konstantin Tsiolkovsky (1898), Charles Parsons (1904), and Vladimir Obruchev (1920).[118]

In 1963 in Paris, a geothermal heating system that used the heat of natural fractured rocks was built.[118]

The Fenton Hill project was the first system for extracting HDR geothermal energy from an artificial formed reservoir; it was created in 1977.[118]


Planning and control[edit]

As the reservoir is formed by the pressure-dilation of the joints, the elastic response of the surrounding rock mass results in a region of tightly compressed, sealed rock at the periphery—making the HDR reservoir totally confined and contained. Such a reservoir is therefore fully engineered, in that the physical characteristics (size, depth at which it is created) as well as the operating parameters (injection and production pressures, production temperature, etc.) can be pre-planned and closely controlled. On the other hand the tight compression and confined nature of the reservoir severely limits that amount and the rate at which energy can be extracted.

Drilling and pressurization[edit]

As described by Brown,[119] an HDR geothermal energy system is developed, first, by using conventional drilling to access a region of deep, hot basement rock. Once it has been determined the selected region contains no open faults or joints (by far the most common situation), an isolated section of the first borehole is pressurized at a level high enough to open several sets of previously sealed joints in the rock mass. By continuous pumping (hydraulic stimulation), a very large region of stimulated rock is created (the HDR reservoir) which consists of an interconnected array of joint flow paths within the rock mass. The opening of these flow paths causes movement along the pressure-activated joints, generating seismic signals (microearthquakes). Analysis of these signals yields information about the location and dimensions of the reservoir being developed.

Production wells[edit]

Typically, an HDR reservoir forms in the shape of an ellipsoid, with its longest axis orthogonal to the least principal Earth stress. This pressure-stimulated region is then accessed by two production wells, drilled to intersect the HDR reservoir near the elongated ends of the stimulated region. In most cases, the initial borehole becomes the injection well for the three-well, pressurized water-circulating system.


In operation, fluid is injected at pressures high enough to hold open the interconnected network of joints against the Earth stresses, and to effectively circulate fluid through the HDR reservoir at a high rate. During routine energy production, the injection pressure is maintained at just below the level that would cause further pressure-stimulation of the surrounding rock mass, in order to maximize energy production while limiting further reservoir growth. However, the limited reservoir size limits reservoir energy. Meanwhile high pressure operation adds significant cost to piping and pumping systems.


The volume of the newly created array of opened joints within the HDR reservoir is much less than 1% of the volume of the pressure-stimulated rock mass. As these joints continue to pressure and cooling -dilate, the overall flow impedance across the reservoir is reduced, leading to a high thermal productivity. If the cooling leads to cooling fractures in a way that exposes more rock then it is possible that these reservoirs may improve over time. To date reservoir energy growth is only reported to come from new expensive high pressure well stimulation efforts.

Feasibility studies[edit]

The feasibility of mining heat from the deep Earth was proven in two separate HDR reservoir flow demonstrations—each involving about one year of circulation—conducted by the Los Alamos National Laboratory between 1978 and 1995. These groundbreaking tests took place at the Laboratory's Fenton Hill HDR test site in the Jemez Mountains of north-central New Mexico, at depths of over 8,000 ft (2,400 m) and rock temperatures in excess of 180 °C.[120] The results of these tests demonstrated conclusively the engineering viability of the revolutionary new HDR geothermal energy concept. The two separate reservoirs created at Fenton Hill are still the only truly confined HDR geothermal energy reservoirs flow-tested anywhere in the world.

Fenton Hill tests[edit]

Phase I[edit]

The first HDR reservoir tested at Fenton Hill, the Phase I reservoir, was created in June 1977 and then flow-tested for 75 days, from January to April 1978, at a thermal power level of 4 MW.[121] The final water loss rate, at a surface injection pressure of 900 psi (6.2 MPa), was 2 US gallons per minute (7.6 L/min) (2% of the injection rate). This initial reservoir was shown to essentially consist of a single pressure-dilated, near-vertical joint, with a vanishingly small flow impedance of 0.5 psi/US gal/min (0.91 kPa/L/min).

The initial Phase I reservoir was enlarged in 1979 and further flow-tested for almost a year in 1980.[122] Of greatest importance, this flow test confirmed that the enlarged reservoir was also confined, and exhibited a low water loss rate of 6 gpm. This reservoir consisted of the single near-vertical joint of the initial reservoir (which, as noted above, had been flow-tested for 75 days in early 1978) augmented by a set of newly pressure-stimulated near-vertical joints that were somewhat oblique to the strike of the original joint.[citation needed]

Phase II[edit]

A deeper and hotter HDR reservoir (Phase II) was created during a massive hydraulic fracturing (MHF) operation in late 1983.[122] It was first flow-tested in the spring of 1985, by an initial closed-loop flow test (ICFT) that lasted a little over a month.[123] Information garnered from the ICFT provided the basis for a subsequent long-term flow test (LTFT), carried out from 1992 to 1995.

The LTFT comprised several individual steady-state flow runs, interspersed with numerous additional experiments.[124] In 1992–1993, two steady-state circulation periods were implemented, the first for 112 days and the second for 55 days. During both tests, water was routinely produced at a temperature of over 180 °C and a rate of 90–100 US gal/min (20–23 m3/h), resulting in continuous thermal energy production of approximately 4 MW. Over this time span, the reservoir pressure was maintained (even during shut-in periods) at a level of about 15 MPa.

Beginning in mid-1993, the reservoir was shut in for a period of nearly two years and the applied pressure was allowed to drop to essentially zero. In the spring of 1995, the system was re-pressurized and a third continuous circulation run of 66 days was conducted.[125] Remarkably, the production parameters observed in the two earlier tests were rapidly re-established, and steady-state energy production resumed at the same level as before. Observations during both the shut-in and operational phases of all these flow-testing periods provided clear evidence that the rock at the boundary of this man-made reservoir had been compressed by the pressurization and resultant expansion of the reservoir region.

As a result of the LTFT, water loss was eliminated as a major concern in HDR operations.[126] Over the period of the LTFT, water consumption fell to just 7% of the quantity of water injected; and data indicated it would have continued to decline under steady-state circulation conditions. Dissolved solids and gases in the produced fluid rapidly reached equilibrium values at low concentrations (about one-tenth the salinity of sea water), and the fluid remained geochemically benign throughout the test period.[127] Routine operation of the automated surface plant showed that HDR energy systems could be run using the same economical staffing schedules that a number of unmanned commercial hydrothermal plants already employ.

Test results[edit]

The Fenton Hill tests clearly demonstrated advantages of a fully engineered HDR reservoir over naturally occurring hydrothermal resources, including EGS. With all the essential physical characteristics of the reservoir—including rock volume, fluid capacity, temperature, etc.—established during the engineered creation of the reservoir zone, and the entire reservoir volume enclosed by a hyperstressed periphery of sealed rock, any variations in operating conditions are totally determined by intentional changes made at the surface. In contrast, a natural hydrothermal “reservoir”—which is essentially open and therefore unconfined(having boundaries that are highly variable)—is inherently subject to changes in natural conditions. On the other hand the less confined, more complex, lower pressure, and more pervasively fractured natural systems support much higher well flow rates and low cost development of energy generation.[citation needed]

Another advantage of an HDR reservoir is that its confined nature makes it highly suitable for load-following operations, whereby the rate of energy production is varied to meet the varying demand for electric power—a process that can greatly increase the economic competitiveness of the technology.[128] This concept was evaluated near the end of the Phase II testing period, when energy production was increased by 60% for 4 hours each day, by a programmed vent-down of the high-pressure reservoir regions surrounding the production borehole. Within two days it became possible to computerize the process, such that production was automatically increased and decreased according to the desired schedule for the rest of the test period. The transitions between the two production levels took less than 5 minutes, and at each level steady-state production was consistently maintained. Such load-following operations could not be implemented in a natural hydrothermal system or even in an EGS system because of the unconfined volume and boundary conditions. Load following almost never improves economics for geothermal development because the fuel cost is effectively paid up front, so delaying use just hurts the economics. Normal geothermal systems have also (by necessity) been applied to follow loads but this kind of generation increases maintenance costs and generally reduces revenue (in spite of the higher prices for some of the load).[citation needed]

The experiments at Fenton Hill have clearly demonstrated that HDR technology is unique, not only with respect to how the pressurized reservoir is created and then circulated, but also because of the management flexibility it offers. It has in common with normal hydrothermal technology only that both are based on wells that produce hot water that runs generators.[citation needed]

Soultz tests[edit]

In 1986 the HDR system project of France and Germany in Soultz-sous-Forêts was started. In 1991 wells were drilled to 2.2 km depth and were stimulated. However, the attempt to create a reservoir was unsuccessful as high water losses was observed.[129][8]

In 1995 wells were deepened to 3.9 km and stimulated. A reservoir was created successfully in 1997 and a four-month circulation test with 25 L/s (6.6 USgal/s) flow rate without water loss was attained.[8]

In 2003 wells were deepened to 5.1 km. Stimulations were done to create a third reservoir, during circulation tests in 2005-2008 water was produced at a temperature of about 160 °C with low water loss. Construction of a power plant was begun.[130] The power plant started to produce electricity in 2016, it was installed with a gross capacity of 1.7 MWe.[131] The 1.7 MW test plant is purely a demonstration plant. In comparison normal geothermal power plant development typically involves initial plants from 10 to 100 MW. These plants can be commercially successful but are much cheaper than HDR system, with shallower wells, that produce orders of magnitude more energy, into inexpensive pipelines and power plants. It seems possible that breakthroughs will occur that allow us to access the tremendous amounts of stored heat energy in deep rock using HDR technology but very few breakthroughs appear to be on the horizon especially when compared to the rapid progress being made on much lower risk solar/battery combinations.[citation needed]

Unconfirmed systems[edit]

There have been numerous reports of the testing of unconfined geothermal systems pressure-stimulated in crystalline basement rock: for instance at the Rosemanowes quarry in Cornwall, England;[132] at the Hijiori[133] and Ogachi[134] calderas in Japan; and in the Cooper Basin, Australia.[135] However, all these “engineered” geothermal systems, while developed under programs directed toward the investigation of HDR technologies, have proven to be open—as evidenced by the high water losses observed during pressurized circulation.[136] In essence, they are all EGS or hydrothermal systems, not true HDR reservoirs.

Related terminology[edit]

Enhanced geothermal systems[edit]

The EGS concept was first described by Los Alamos researchers in 1990, at a geothermal symposium sponsored by the United States Department of Energy (DOE)[137]—many years before the DOE coined the term EGS in an attempt to emphasize the geothermal aspect of heat mining rather than the unique characteristics of HDR.

HWR versus HDR[edit]

Hot Wet Rock (HWR) hydrothermal technology makes use of hot fluids found naturally in basement rock; but such HWR conditions are rare.[138] By far the bulk of the world's geothermal resource base (over 98%) is in the form of basement rock that is hot but dry—with no naturally available water. This means that HDR technology is applicable almost everywhere on Earth (hence the claim that HDR geothermal energy is ubiquitous). On the other hand an uneconomic resource is actually just energy storage and not useful.

Typically, the temperature in those vast regions of the accessible crystalline basement rock increases with depth. This geothermal gradient, which is the principal HDR resource variable, ranges from less than 20 °C/km to over 60 °C/km, depending upon location. The concomitant HDR economic variable is the cost of drilling to depths at which rock temperatures are sufficiently high to permit the development of a suitable reservoir.[139] The advent of new technologies for drilling hard crystalline basement rocks, such as new PDC (polycrystalline diamond compact) drill bits, drilling turbines or fluid-driven percussive technologies (such as Mudhammer [140]) may significantly improve HDR economics in the near future.

Further reading[edit]

A definitive book on HDR development, including a full account of the experiments at Fenton Hill, was published by Springer-Verlag in April 2012.[120]


  • DOE, Department of Energy (United States)
  • EGS, Enhanced geothermal system
  • HDR, Hot dry rock
  • HWR, Hot wet rock
  • ICFT, Initial closed-loop flow test
  • LTFT, Long-term flow test
  • MHF, Massive hydraulic fracturing
  • PDC, Polycrystalline diamond compact (drill bit)

See also[edit]


  1. ^ Lund, John W. (June 2007), "Characteristics, Development and utilization of geothermal resources" (PDF), Geo-Heat Centre Quarterly Bulletin, Klamath Falls, Oregon: Oregon Institute of Technology, vol. 28, no. 2, pp. 1–9, ISSN 0276-1084, archived from the original (PDF) on 2010-06-17, retrieved 2009-04-16
  2. ^ Duchane, Dave; Brown, Don (December 2002), "Hot Dry Rock (HDR) Geothermal Energy Research and Development at Fenton Hill, New Mexico" (PDF), Geo-Heat Centre Quarterly Bulletin, Klamath Falls, Oregon: Oregon Institute of Technology, vol. 23, no. 4, pp. 13–19, ISSN 0276-1084, archived from the original (PDF) on 2010-06-17, retrieved 2009-05-05
  3. ^ Pierce, Brenda (2010-02-16). "Geothermal Energy Resources" (PowerPoint). National Association of Regulatory Utility Commissioners (NARUC). Retrieved 2011-03-19.
  4. ^ Cichon, Meg (2013-07-16). "Is Fracking for Enhanced Geothermal Systems the Same as Fracking for Natural Gas?". RenewableEnergyWorld.com. Retrieved 2014-05-07.
  5. ^ US Department of Energy Energy Efficiency and Renewable Energy. "How an Enhanced Geothermal System Works". Archived from the original on 2013-05-20.
  6. ^ "20 slide presentation inc geothermal maps of Australia" (PDF).
  7. ^ "Superhot Rock Energy: A Vision for Firm, Global Zero-Carbon Energy". Clean Air Task Force. October 2022.
  8. ^ a b c d e f Tester, Jefferson W. (Massachusetts Institute of Technology); et al. (2006). The Future of Geothermal Energy – Impact of Enhanced Geothermal Systems (EGS) on the United States in the 21st Century (PDF). Idaho Falls: Idaho National Laboratory. ISBN 0-615-13438-6. Archived from the original (14MB PDF) on 2011-03-10. Retrieved 2007-02-07.
  9. ^ Pollack, Ahinoam (2020). "Gallery of 1D, 2D, and 3D maps from enhanced geothermal systems around the world".
  10. ^ Pollack, Ahinoam (2020). "What Are the Challenges in Developing Enhanced Geothermal Systems (EGS)? Observations from 64EGS Sites" (PDF). World Geothermal Congress. S2CID 211051245. Archived from the original (PDF) on 2020-07-13.
  11. ^ Thorsteinsson, T.; Tomasson, J. (1979-01-01). "Drillhole stimulation in Iceland". Am. Soc. Mech. Eng., (Pap.); (United States). 78-PET-24. OSTI 6129079.
  12. ^ Brown, Donald W.; Duchane, David V.; Heiken, Grant; Hriscu, Vivi Thomas (2012), Brown, Donald W.; Duchane, David V.; Heiken, Grant; Hriscu, Vivi Thomas (eds.), "Serendipity—A Brief History of Events Leading to the Hot Dry Rock Geothermal Energy Program at Los Alamos", Mining the Earth's Heat: Hot Dry Rock Geothermal Energy, Springer Geography, Berlin, Heidelberg: Springer, pp. 3–16, doi:10.1007/978-3-540-68910-2_1, ISBN 978-3-540-68910-2
  13. ^ Stober, Ingrid (2011-05-01). "Depth- and pressure-dependent permeability in the upper continental crust: data from the Urach 3 geothermal borehole, southwest Germany". Hydrogeology Journal. 19 (3): 685–699. Bibcode:2011HydJ...19..685S. doi:10.1007/s10040-011-0704-7. ISSN 1435-0157. S2CID 129285719.
  14. ^ Rummel, F.; Kappelmeyer, O. (1983). "The Falkenberg Geothermal Frac-Project: Concepts and Experimental Results". Hydraulic Fracturing and Geothermal Energy. Mechanics of elastic and inelastic solids. Springer Netherlands. 5: 59–74. doi:10.1007/978-94-009-6884-4_4. ISBN 978-94-009-6886-8.
  15. ^ Batchelor, A. S. (1987-05-01). "Development of hot-dry-rock geothermal systems in the UK". IEE Proceedings A. 134 (5): 371–380. doi:10.1049/ip-a-1.1987.0058. ISSN 2053-7905.
  16. ^ Cornet, FH (1987-01-01). "Results from Le Mayet de Montagne project". Geothermics. 16 (4): 355–374. doi:10.1016/0375-6505(87)90016-2. ISSN 0375-6505.
  17. ^ Cornet, F. H.; Morin, R. H. (1997-04-01). "Evaluation of hydromechanical coupling in a granite rock mass from a high-volume, high-pressure injection experiment: Le Mayet de Montagne, France". International Journal of Rock Mechanics and Mining Sciences. 34 (3): 207.e1–207.e14. doi:10.1016/S1365-1609(97)00185-8. ISSN 1365-1609.
  18. ^ a b c d Entingh, D. J. (2000). "Geothermal Well Stimulation Experiments in the United States" (PDF). Proceedings World Geothermal Congress.
  19. ^ Axelsson, G (2009). "Review of well stimulation operations in Iceland" (PDF). Transactions - Geothermal Resources Council.
  20. ^ a b Пашкевич, Р.И.; Павлов, К.А. (2015). "Современное состояние использования циркуляционных геотермальных систем в целях тепло- и электроснабжения". Горный информационно-аналитический бюллетень: 388–399. ISSN 0236-1493.
  21. ^ Wallroth, Thomas; Eliasson, Thomas; Sundquist, Ulf (1999-08-01). "Hot dry rock research experiments at Fjällbacka, Sweden". Geothermics. 28 (4): 617–625. doi:10.1016/S0375-6505(99)00032-2. ISSN 0375-6505.
  22. ^ Matsunaga, I (2005). "Review of the HDR Development at Hijiori Site, Japan" (PDF). Proceedings of the World Geothermal Congress.
  23. ^ Genter, Albert; Evans, Keith; Cuenot, Nicolas; Fritsch, Daniel; Sanjuan, Bernard (2010-07-01). "Contribution of the exploration of deep crystalline fractured reservoir of Soultz to the knowledge of enhanced geothermal systems (EGS)". Comptes Rendus Geoscience. Vers l'exploitation des ressources géothermiques profondes des systèmes hydrothermaux convectifs en milieux naturellement fracturés. 342 (7): 502–516. Bibcode:2010CRGeo.342..502G. doi:10.1016/j.crte.2010.01.006. ISSN 1631-0713.
  24. ^ Pernecker, G (1999). "Altheim geothermal plant for electricity production by ORC-turbogenerator" (PDF). Bulletin d'Hydrogéologie.
  25. ^ Niitsuma, H. (1989-07-01). "Fracture mechanics design and development of HDR reservoirs— Concept and results of the Γ-project, Tohoku University, Japan". International Journal of Rock Mechanics and Mining Sciences & Geomechanics Abstracts. 26 (3): 169–175. doi:10.1016/0148-9062(89)91966-9. ISSN 0148-9062.
  26. ^ Ito, Hisatoshi (2003). "Inferred role of natural fractures, veins, and breccias in development of the artificial geothermal reservoir at the Ogachi Hot Dry Rock site, Japan". Journal of Geophysical Research: Solid Earth. 108 (B9): 2426. Bibcode:2003JGRB..108.2426I. doi:10.1029/2001JB001671. ISSN 2156-2202.
  27. ^ Kitao, K (1990). "Geotherm. Resourc. Counc. Trans" (PDF). Cold-water Well Stimulation Experiments in the Sumikawa Geotheral Field, Japan.
  28. ^ Дядькин, Ю. Д. (2001). "Извлечение и использование тепла земли". Горный информационно-аналитический бюллетень (научно-технический журнал) (9): 228–241.
  29. ^ Алхасов, А.Б. (2016). Возобновляемые источники энергии. М.: Издательский дом МЭИ. p. 108. ISBN 978-5-383-00960-4.
  30. ^ Buoing, Balbino C. (1995). "Recent Experiences in Acid Stimulation Technology by PNOC-Energy Development Corporation, Philippines" (PDF). World Geothermal Congress 1995.
  31. ^ Tulinius, Helga; Axelsson, Gudni; Tomasson, Jens; Kristmannsdóttir, Hrefna; Guðmundsson, Ásgrímur (1996-01-01). Stimulation of well SN12 in the Seltjarnarnes low-temperature field in SW-Iceland (Report).
  32. ^ Malate, Ramonchito Cedric M. (2000). "SK-2D: A CASE HISTORY ON GEOTHERMAL WELLBORE ENHANCEMENT, MINDANAO GEOTHERMAL PRODUCTION FIELD, PHILIPPINES" (PDF). Proceedings World Geothermal Congress 2000.
  33. ^ Sanjuan, Bernard; Jousset, Philippe; Pajot, Gwendoline; Debeglia, Nicole; Michele, Marcello de; Brach, Michel; Dupont, François; Braibant, Gilles; Lasne, Eric; Duré, Frédéric (2010-04-25). Monitoring of the Bouillante Geothermal Exploitation (Guadeloupe, French West Indies) and the Impact on Its Immediate Environment. World Geothermal Congress 2010. pp. 11 p.
  34. ^ Malate (2003). "ACID STIMULATION OF INJECTION WELLS IN THE LEYTE GEOTHERMAL POWER PROJECT, PHILIPPINES". Twenty-Second Workshop on Geothermal Reservoir Engineering, Stanford University. S2CID 51736784.
  35. ^ Zimmermann, Günter; Moeck, Inga; Blöcher, Guido (2010-03-01). "Cyclic waterfrac stimulation to develop an Enhanced Geothermal System (EGS)—Conceptual design and experimental results". Geothermics. The European I-GET Project: Integrated Geophysical Exploration Technologies for Deep Geothermal Reservoirs. 39 (1): 59–69. doi:10.1016/j.geothermics.2009.10.003. ISSN 0375-6505.
  36. ^ Xu, Tianfu. "Scaling of hot brine injection wells: supplementing field studies with reactive transport modeling". TOUGH Symposium 2003.
  37. ^ Barrios, L. A. (2002). "Enhanced Permeability by Chemical Stimulation at the Berlín Geothermal field" (PDF). Geothermal Resources Council Transactions. 26.
  38. ^ a b Holl, Heinz-Gerd (2015). What did we learn about EGS in the Cooper Basin? (Report). doi:10.13140/RG.2.2.33547.49443.
  39. ^ Evanoff, Jerry (2004). "STIMULATION AND DAMAGE REMOVAL OF CALCIUM CARBONATE SCALING IN GEOTHERMAL WELLS: A CASE STUDY" (PDF). Proceedings of the World Geothermal Congress. S2CID 199385006. Archived from the original (PDF) on 2020-02-27.
  41. ^ Tischner, Torsten (2010). "New Concepts for Extracting Geothermal Energy from One Well: The GeneSys-Project" (PDF). Proceedings World Geothermal Congress.
  42. ^ Schindler, Marion (2010). "Successful Hydraulic Stimulation Techniques for Electric Power Production in the Upper Rhine Graben, Central Europe" (PDF). Proceedings World Geothermal Congress.
  43. ^ Sigfússon, B. (1 March 2016). "2014 JRC geothermal energy status report : technology, market and economic aspects of geothermal energy in Europe". Op.europa.eu. doi:10.2790/959587. ISBN 9789279540486.
  44. ^ Pasikki, Riza (2006). "COILED TUBING ACID STIMULATION: THE CASE OF AWI 8-7 PRODUCTION WELL IN SALAK GEOTHERMAL FIELD, INDONESIA". Thirty-First Workshop on Geothermal Reservoir Engineering.
  45. ^ Bendall, Betina. "Australian Experiences in EGS Permeability Enhancement –A Review of 3 Case Studies" (PDF). Thirty-Ninth Workshop on Geothermal Reservoir Engineering.
  46. ^ Albaric, J.; Oye, V.; Langet, N.; Hasting, M.; Lecomte, I.; Iranpour, K.; Messeiller, M.; Reid, P. (1 October 2014). "Monitoring of induced seismicity during the first geothermal reservoir stimulation at Paralana, Australia". Geothermics. 52: 120–131. doi:10.1016/j.geothermics.2013.10.013. ISSN 0375-6505.
  47. ^ Armenta, Magaly Flores (2006). "Productivity Analysis and Acid Treatment of Well AZ-9ADat the Los Azufres Geothermal Field, Mexico" (PDF). GRC Transactions. 30.
  48. ^ Häring, Markus O.; Schanz, Ulrich; Ladner, Florentin; Dyer, Ben C. (1 October 2008). "Characterisation of the Basel 1 enhanced geothermal system". Geothermics. 37 (5): 469–495. doi:10.1016/j.geothermics.2008.06.002. ISSN 0375-6505.
  49. ^ Carella, R.; Verdiani, G.; Palmerini, C. G.; Stefani, G. C. (1 January 1985). "Geothermal activity in Italy: Present status and future prospects". Geothermics. 14 (2): 247–254. doi:10.1016/0375-6505(85)90065-3. ISSN 0375-6505.
  50. ^ Küperkoch, L.; Olbert, K.; Meier, T. (1 December 2018). "Long‐Term Monitoring of Induced Seismicity at the Insheim Geothermal Site, GermanyLong‐Term Monitoring of Induced Seismicity at the Insheim Geothermal Site, Germany". Bulletin of the Seismological Society of America. 108 (6): 3668–3683. doi:10.1785/0120170365. ISSN 0037-1106. S2CID 134085568.
  51. ^ Chabora, Ethan (2012). "HYDRAULIC STIMULATION OF WELL 27-15, DESERT PEAK GEOTHERMAL FIELD, NEVADA, USA" (PDF). Thirty-Seventh Workshop on Geothermal Reservoir Engineering.
  52. ^ Drakos, Peter (2017). "Feasibility of EGS Development at Brady Hot Springs, Nevada" (PDF). US DOE Geothermal Office.
  53. ^ Alta Rock Energy (2013). Engineered Geothermal SystemDemonstration ProjectNorthern California Power Agency, The Geysers, CA (Report). doi:10.2172/1134470. OSTI 1134470.
  54. ^ Tischner, T. (2013). "MASSIVE HYDRAULIC FRACTURING IN LOW PERMEABLESEDIMENTARY ROCK IN THE GENESYS PROJECT" (PDF). Thirty-EighthWorkshop on Geothermal Reservoir Engineering.
  55. ^ Moeck, I.; Bloch, T.; Graf, R.; Heuberger, S.; Kuhn, P.; Naef, H.; Sonderegger, Michael; Uhlig, S.; Wolfgramm, M. (2015). "The St. Gallen Project: Development of Fault Controlled Geothermal Systems in Urban Areas". Proceedings World Geothermal Congress 2015. S2CID 55741874.
  56. ^ Moeck, Inga (2015). "The St. Gallen Project: Development of Fault Controlled Geothermal Systems in Urban Areas" (PDF). Proceedings World Geothermal Congress 2015.
  57. ^ Garcia, Julio; Hartline, Craig; Walters, Mark; Wright, Melinda; Rutqvist, Jonny; Dobson, Patrick F.; Jeanne, Pierre (1 September 2016). "The Northwest Geysers EGS Demonstration Project, California: Part 1: Characterization and reservoir response to injection". Geothermics. 63: 97–119. doi:10.1016/j.geothermics.2015.08.003. ISSN 0375-6505.
  58. ^ Cladouhos, Trenton T.; Petty, Susan; Swyer, Michael W.; Uddenberg, Matthew E.; Grasso, Kyla; Nordin, Yini (2016-09-01). "Results from Newberry Volcano EGS Demonstration, 2010–2014". Geothermics. Enhanced Geothermal Systems: State of the Art. 63: 44–61. doi:10.1016/j.geothermics.2015.08.009. ISSN 0375-6505.
  59. ^ Mraz, Elena; Moeck, Inga; Bissmann, Silke; Hild, Stephan (31 October 2018). "Multiphase fossil normal faults as geothermal exploration targets in the Western Bavarian Molasse Basin: Case study Mauerstetten". Zeitschrift der Deutschen Gesellschaft für Geowissenschaften. 169 (3): 389–411. doi:10.1127/zdgg/2018/0166. S2CID 135225984.
  60. ^ Ohren, Mary (2011). "Permeability Recovery and Enhancements in the Soda Lake Geothermal Field, Fallon, Nevada" (PDF). GRC Transactions. 35.
  61. ^ Bradford, Jacob (2015). "Hydraulic and Thermal Stimulation Program at Raft River Idaho, A DOE EGS" (PDF). GRC Transactions.
  62. ^ Petty, Susan (2016). "Current Status of Geothermal Stimulation Technology" (PDF). 2016 GRC Annual Meeting Presentations.
  63. ^ Baujard, C (1 January 2017). "Hydrothermal characterization of wells GRT-1 and GRT-2 in Rittershoffen, France: Implications on the understanding of natural flow systems in the rhine graben". Geothermics. 65: 255–268. doi:10.1016/j.geothermics.2016.11.001. ISSN 0375-6505.
  64. ^ Nair, R. (2017). "A case study of radial jetting technology for enhancing geothermal energy systems at Klaipėda geothermal demonstration plant" (PDF). 42nd Workshop on Geothermal Reservoir Engineering.
  65. ^ Ader, Thomas; Chendorain, Michael; Free, Matthew; Saarno, Tero; Heikkinen, Pekka; Malin, Peter Eric; Leary, Peter; Kwiatek, Grzegorz; Dresen, Georg; Bluemle, Felix; Vuorinen, Tommi (29 August 2019). "Design and implementation of a traffic light system for deep geothermal well stimulation in Finland". Journal of Seismology. 24 (5): 991–1014. doi:10.1007/s10950-019-09853-y. ISSN 1573-157X. S2CID 201661087.
  66. ^ Garrison, Geoffrey (2016). "The South Hungary Enhanced Geothermal System (SHEGS) Demonstration Project" (PDF). GRC Transactions.
  67. ^ Kim, Kwang-Hee; Ree, Jin-Han; Kim, YoungHee; Kim, Sungshil; Kang, Su Young; Seo, Wooseok (1 June 2018). "Assessing whether the 2017 Mw 5.4 Pohang earthquake in South Korea was an induced event". Science. 360 (6392): 1007–1009. Bibcode:2018Sci...360.1007K. doi:10.1126/science.aat6081. ISSN 0036-8075. PMID 29700224. S2CID 13876371.
  68. ^ Moore, Joseph (2019). "The Utah Frontier Observatory for Research in Geothermal Energy (FORGE): An International Laboratory for Enhanced Geothermal System Technology Development" (PDF). 44th Workshop on Geothermal Reservoir Engineering.
  69. ^ Friðleifsson, Guðmundur Ómar (2019). "TheReykjanes DEEPEGS Demonstration Well –IDDP-2" (PDF). European Geothermal Congress 2019.
  70. ^ Wagner, Steffen (2015). "PetrothermalEnergyGenerationin Crystalline Rocks (Germany)" (PDF). Proceedings World Geothermal Congress 2015.
  71. ^ Ledingham, Peter (2019). "The United Downs Deep Geothermal Power Project" (PDF). 44th Workshop on Geothermal Reservoir Engineering.
  72. ^ "Understanding geothermal power". Eden Project. 15 February 2014.
  73. ^ Lei, Zhihong; Zhang, Yanjun; Yu, Ziwang; Hu, Zhongjun; Li, Liangzhen; Zhang, Senqi; Fu, Lei; Zhou, Ling; Xie, Yangyang (1 August 2019). "Exploratory research into the enhanced geothermal system power generation project: The Qiabuqia geothermal field, Northwest China". Renewable Energy. 139: 52–70. doi:10.1016/j.renene.2019.01.088. ISSN 0960-1481. S2CID 116422325.
  74. ^ Bogason, Sigurdur G. (2019). "DEEPEGS project management -Lessons learned". European Geothermal Congress 2019.
  75. ^ "Geothermal Drilling Program". Archived from the original on 2010-06-06. Retrieved 2010-06-03.
  76. ^ See French Wikipedia: Soultz-sous-Forêts — Soultz is in the Alsace région of France.
  77. ^ "DESTRESS - Pohang". DESTRESS H2020. DESTRESS. Retrieved January 3, 2019.
  78. ^ YOON, Kern-Shin; JEON, Jae-Soo; HONG, Hoon-Ki; KIM, Ho-Geun; A., Hagan; Park, Jung-Hun; YOON, Woon-Sang (19–25 April 2015). Deep Drilling Experience for Pohang Enhanced Geothermal Project in Korea (PDF). Proceedings World Geothermal Congress 2015 Melbourne. Melbourne, Australia.
  79. ^ "Tories pledge support for deep geothermal energy projects". New Energy Focus. www.newenergyfocus.com. May 15, 2009. Archived from the original on August 17, 2009. Retrieved 2009-06-11.
  80. ^ "'Hot rocks' geothermal energy plant promises a UK first for Cornwall". Western Morning News. August 17, 2010. Retrieved August 21, 2015.[permanent dead link]
  81. ^ "Plans for geothermal plant at industrial estate are backed". This is Cornwall. www.thisiscornwall.co.uk. November 23, 2009. Archived from the original on March 8, 2012. Retrieved 2010-01-21.
  82. ^ Tester 2006, pp. 4–7 to 4–13
  83. ^ "EERE News: DOE to Invest up to $84 Million in Enhanced Geothermal Systems". 2009-03-04. Retrieved 2009-07-04.
  84. ^ "Department of Energy – President Obama Announces Over $467 Million in Recovery Act Funding for Geothermal and Solar Energy Projects". 2009-05-27. Archived from the original on 2009-06-24. Retrieved 2009-07-04.
  85. ^ Geothermal Technologies Office (February 21, 2014). "DOE Announces Notice of Intent for EGS Observatory". Department of Energy. Archived from the original on 2015-03-24.
  86. ^ "Energy Department Announces $29 Million Investment in Enhanced Geothermal Systems Efforts". Washington, DC: Department of Energy. Aug 31, 2016.
  87. ^ "Department of Energy Selects University of Utah Site for $140 Million Geothermal Research and Development". Department of Energy. Department of Energy. Retrieved 9 March 2020.
  88. ^ a b c Knudsen, Tyler; Kleber, Emily; Hiscock, Adam; Kirby, Stefan M. "QUATERNARY GEOLOGY OF THE UTAH FORGE SITE AND VICINITY, MILLARD AND BEAVER COUNTIES, UTAH" (PDF). doi:10.34191/mp-169-b. Retrieved 2021-11-08.
  89. ^ a b c Kirby M., Stefan. "REVISED MAPPING OF BEDROCK GEOLOGY ADJOINING THE UTAH FORGE SITE" (PDF). doi:10.34191/MP-169-A. Retrieved 2021-11-08.
  90. ^ Rahilly, Kristen; Simmons, Stuart; Fischer, Tobias P. "Carbon Dioxide Flux and Carbon and Helium Isotopic Composition of Soil Gases Across the FORGE Site and Opal Mound Fault, Utah". doi:10.34191/mp-169-i. Retrieved 2021-11-08.
  91. ^ a b c Moore, Joseph; McLennan, John; Pankow, Kristine; Simmons, Stuart; Podgorney, Robert; Wannamaker, Philip; Jones, Clay; Rickard, William; Xing, Pengju (February 10–12, 2020). "The Utah Frontier Observatory for Research in Geothermal Energy (FORGE): A Laboratory for Characterizing, Creating and Sustaining Enhanced Geothermal Systems" (PDF). Workshop on Geothermal Reservoir Engineering Stanford University, Stanford, California: 1–10.
  92. ^ a b Moore, Joseph; McLennan, John; Allis, Rick; Pankow, Kristine; Simmons, Stuart; Podgorney, Robert; Wannamaker, Philip; Bartley, John; Jones, Clay; Rickard, William. "The Utah Frontier Observatory for Research in Geothermal Energy (FORGE): An International Laboratory for Enhanced Geothermal System Technology Development" (PDF). Workshop on Geothermal Reservoir Engineering Stanford University, Stanford, California.
  93. ^ NIELSON, DENNIS L.; EVANS, STANLEY H., JR.; SIBBETT, BRUCE S. (1986-06-01). "Magmatic, structural, and hydrothermal evolution of the Mineral Mountains intrusive complex, Utah". GSA Bulletin. 97 (6): 765–777. doi:10.1130/0016-7606(1986)97<765:MSAHEO>2.0.CO;2. ISSN 0016-7606.
  94. ^ Coleman, Drew S.; Walker, J. Douglas (1992). "Evidence for the generation of juvenile granitic crust during continental extension, Mineral Mountains Batholith, Utah". Journal of Geophysical Research: Solid Earth. 97 (B7): 11011–11024. doi:10.1029/92JB00653. ISSN 2156-2202.
  95. ^ Aleinikoff, J. N.; Nielson, D. L.; Hedge, C. E.; Evans, S. H. (1986). "Geochronology of Precambrian and Tertiary rocks in the Mineral Mountains, south-central Utah". US Geological Survey Bulletin. 1622: 1–12.
  96. ^ a b c Allis, Rick; Moore, Joe; Davatzes, Nick; Gwynn, Mark; Hardwick, Christian; Kirby, Stefan; McLennan, John; Pankow, Kris; Potter, Stephen; Simmons, Stuart (February 22–24, 2016). "EGS Concept Testing and Development at the Milford, Utah FORGE Site" (PDF). Standford University in Standford CA, 41st Workshop on Geothermal Reservoir Engineering. SGP-TR-209: 13 – via Pangea.Standford.edu.
  97. ^ a b c d Allis, Rick (2018). "Thermal Characteristics of the FORGE site, Milford, Utah" (PDF). Geothermal Resources Council Transactions. 42–15.
  98. ^ Whang, Jyu et al. "2013 Climate Action Plan & roadmap 2014-2015" Cornell University 2013. Retrieved on 2020-12-07
  99. ^ "Cornell's Commitment to a Sustainable Campus – Earth Source Heat". earthsourceheat.cornell.edu. Retrieved 2020-12-08.
  100. ^ "$7.2M grant funds exploratory research into Earth Source Heat". Cornell Chronicle. Retrieved 2020-12-08.
  101. ^ Tester, Jeffery et al. "District Geothermal Heating Using EGS Technology to Meet Carbon Neutrality Goals: A Case Study of Earth Source Heat for the Cornell University Campus". Proceedings World Geothermal Congress. April 26- May 2, 2020. Retrieved on 2020-12-07
  102. ^ "DOE Launches New Energy Earthshot to Slash the Cost of Geothermal Power". Department of Energy. Retrieved 18 January 2023.
  103. ^ "Enhanced Geothermal Shot". Department of Energy. Retrieved 18 January 2023.
  104. ^ Ben Lefebvre; Kelsey Tamborrino. "Meet the renewable energy source poised for growth with the help of the oil industry". Politico. Retrieved 18 January 2023.
  105. ^ "Inflation Reduction Act Summary" (PDF). Bipartisan Policy Center. August 4, 2022.
  106. ^ Ben Lefebvre; Kelsey Tamborrino. "Meet the renewable energy source poised for growth with the help of the oil industry". Politico. Retrieved 18 January 2023.
  107. ^ Tester 2006, pp. 4–5 to 4–6
  108. ^ Tester 2006, pp. 8–9 to 8–10
  109. ^ Majer, Ernest L.; Peterson, John E. (May 21, 2008). The Impact of Injection on Seismicity at The Geyses, California Geothermal Field (Report) – via escholarship.org.
  110. ^ Glanz, James (2009-12-10), "Quake Threat Leads Swiss to Close Geothermal Project", The New York Times
  111. ^ Geoscience Australia. "Induced Seismicity and Geothermal Power Development in Australia" (PDF). Australian Government. Archived from the original (PDF) on 2011-10-11.
  112. ^ "Superhot Rock Energy: A Vision for Firm, Global Zero-Carbon Energy". Clean Air Task Force. November 2022.
  113. ^ Potter, R. M., Smith, M. C., and Robinson, E. S., 1974. “Method of extracting heat from dry geothermal reservoirs,” U. S. patent No. 3,786,858
  114. ^ Ball, Philip. "Superhot Rock Project Map". Clean Air Task Force.
  115. ^ Adler, Ben. "Geothermal energy poised for boom, as U.S. looks to follow Iceland's lead". Yahoo News. Retrieved 18 January 2023.
  116. ^ "A Preliminary Techno-Economic Model of Superhot Rock Energy". Clean Air Task Force. December 2022.
  117. ^ Brown, D. W., 2009. "Hot dry rock geothermal energy: Important lessons from Fenton Hill," in Proceedings, 34th workshop on geothermal reservoir engineering (February 9–11, 2009: Stanford, CA). SGP-TR-187, pp. 139–142
  118. ^ a b c Дядькин, Ю. Д. (2001). "Извлечение и использование тепла земли". Горный информационно-аналитический бюллетень (научно-технический журнал).
  119. ^ Brown, D. W., 1990. “Hot dry rock reservoir engineering,” Geotherrm. Resour. Counc. Bull. 19(3): 89–93
  120. ^ a b Brown, D. W., Duchane, D. V., Heiken, G., and Hriscu, V. T., 2012. Mining the Earth’s Heat: Hot Dry Rock Geothermal Energy, Springer-Verlag, Berlin and Heidelberg, 655 pp ISBN 3540673164
  121. ^ Dash, Z. V., Murphy, H. D., and Cremer, G. M. (eds.), 1981. “Hot dry rock geothermal reservoir testing: 1978–1980,” Los Alamos National Laboratory Report LA-9080-SR, 62 pp
  122. ^ a b Brown, D. W., and Duchane, D. V., 1999. "Scientific progress on the Fenton Hill HDR project since 1983,” Geothermics 28(4/5) special issue: Hot Dry Rock/Hot Wet Rock Academic Review (Abe, H., Niitsuma, H., and Baria, R., eds.), pp. 591–601
  123. ^ Dash, Z. V., et al., 1989. "ICFT: an initial closed-loop flow test of the Fenton Hill Phase II HDR reservoir,” Los Alamos National Laboratory report LA-11498-HDR, Los Alamos NM, 128 pp
  124. ^ Brown, D. W., 1993. “Recent flow testing of the HDR reservoir at Fenton Hill, New Mexico,” Geothermal Program Review XI, April, 1993. U.S. Department of Energy, Conservation and Renewable Energy, Geothermal Division, pp. 149–154
  125. ^ Brown, D. W., 1995. “1995 verification flow testing of the HDR reservoir at Fenton Hill, New Mexico,” Geothermal Resources Council annual meeting (October 8–11, 1995: Reno, NV) Trans. Geotherm. Resour. Counc. 19:253–256
  126. ^ Brown, D., 1995. "The US hot dry rock program—20 years of experience in reservoir testing," in Proceedings of the World Geothermal Congress (May 18–31, 1995: Florence, Italy), International Geothermal Association, Inc., Auckland, New Zealand, vol. 4, pp. 2607–2611
  127. ^ Brown, D. W., Duchane, D. V., Heiken, G., and Hriscu, V. T., 2012. Mining the Earth’s Heat: Hot Dry Rock Geothermal Energy, Springer-Verlag, Berlin and Heidelberg, Chapter 9, pp. 541–549
  128. ^ Brown, D. W., and DuTeau, R. J., 1995. "Using a hot dry rock geothermal reservoir for load following," in Proceedings, 20th annual workshop on geothermal reservoir engineering (January 27–29, 1995: Stanford, CA). SGP-TR-150, pp. 207–211
  129. ^ Baria, R., Baumgärtner, J., Gérard, A., Jung, R., and Garnish, J., 2002. “European HDR research programme at Soultz-sous-Forêts (France); 1987–1998,” in Geologisches Jahrbuch special edition (Baria, R., Baumgärtner, J., Gérard, A., and Jung, R., eds.), international conference—4th HDR Forum (September 28–30, 1998: Strasbourg, France). Hannover, Germany, pp. 61–70
  130. ^ Nicolas Cuenot; Louis Dorbath; Michel Frogneux; Nadège Langet (2010). "Microseismic Activity Induced Under Circulation Conditions at the EGS Project of Soultz-Sous-Forêts (France)". Proceedings World Geothermal Conference.
  131. ^ Justine MOUCHOT; Albert GENTER; Nicolas CUENOT; Olivier SEIBEL; Julia SCHEIBER; Clio BOSIA; Guillaume RAVIER (February 12–14, 2018). "First Year of Operation from EGS geothermal Plants in Alsace, France: Scaling Issues". 43rd Workshop on Geothermal Reservoir Engineering. Stanford University: 1, 3. Retrieved 25 May 2020.
  132. ^ Parker, R. H., 1989. “Hot Dry Rock Geothermal Energy, Phase 2B Final Report of the Camborne School of Mines Project,” Vol. 1–2, Pergamon Press, Oxford, U.K.
  133. ^ Matsunaga, I., Niitsuma, H., and Oikaya, Y., 2005. "Review of the HDR development at Hijiori Site, Japan,” in Proceedings, World Geothermal Congress (April 24–29, 2005: Antala, Turkey), pp. 3861–3865
  134. ^ Ito, H., and Kaieda, H., 2002. "Review of 15 years experience of the Ogachi Hot Dry Rock Project with emphasis on geological features," in Proceedings, 24th New Zealand geothermal workshop (November 13–15, 2002: University of Auckland, Auckland, New Zealand), pp. 55–60
  135. ^ Chopra, P., and Wyborn, D., 2003. "Australia's first hot dry rock geothermal energy extraction project is up and running in granite beneath the Cooper Basin, NE South Australia," in Proceedings, The Ishihara Symposium: Granites and Associated Metallogenesis (July 22–24, 2003: Macquarie University, Sydney, Australia), pp. 43–45
  136. ^ Brown, D., DuTeaux, R., Kruger, P., Swenson, D., and Yamaguchi, T., 1999. Table 1: “Fluid circulation and heat extraction from engineered geothermal reservoirs,” Geothermics 28(4/5) special issue: Hot Dry Rock/Hot Wet Rock Academic Review (Abé, H., Niitsuma, H., and Baria, R., eds.), pp. 553–572
  137. ^ Brown, D. W., and Robinson, B. A., 1990. “Hot dry rock technology,” in Proceedings, Geothermal Program Review VIII (April 18–20, 1990: San Francisco, CA). CONF 9004131, pp. 109–112
  138. ^ Armstead, H. C. H., and Tester, J. W., 1987. Heat Mining, E. & F. N. Spon, London and New York, pp. 55–58
  139. ^ Tester, J. W., Herzog, H. J., Chen, Z., Potter, R. M., and Frank, M. G., 1994. “Prospects for universal geothermal energy from heat mining,” Science and Global Security Vol. 5, pp. 99–121
  140. ^ Souchal, R., 2017, High-Power Mudhammer Drilling: A promising solution for deep geothermal reservoirs, Geotherm Deep Geothermal Energy Congress proceedings

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