Did you know... Pamukkale is a travel HOT spot?
Pamukkale is a western Turkish town known for the mineral-rich thermal waters that cascade over steep, white terraces that reach over 100 meters (~330 feet) high. Across the terraces, there are a total of 17 hot springs, which range in temperature from 35-100 degrees Celsius (95-212 degrees Fahrenheit) year-round. The name in Turkish means “cotton castle” as it resembles the cotton plantations in central Turkey.
However, the white terraces are not cotton – they’re travertine rock! Travertine is a form of limestone that is deposited over time by mineral waters, most commonly, hot springs. The mass of hot springs sources in the area produces high amounts of calcium carbonate in the water so when the water hits the open air, it becomes white travertine rock.
Before it was Pamukkale, the site used to be the lively Greco-Roman city Hierapolis. Hierapolis was a spa city founded in 190 BC. Just like today, it was one of Turkey’s most popular hot springs. The ruins of the city are well preserved and hold what is known as Cleopatra’s pool, who is said to have bathed there, along with many other historically famous people.
The hot springs are open to the public to swim and relax in, and they have been known to be great for healing.
Did you know... that Paris has used geothermal energy to heat the homes of more than 2 million people?
You might not think that Paris, the city of love, would be a major producer of geothermal energy – but it is! Paris has been using geothermal energy to heat houses since 1969.
Under the famous city are two deep aquifers containing hot water. Since 1969, Paris has been working on many geothermal projects. Today, there are around fifty supply networks in the city that heat almost 250,000 homes.
The main aquifer, the Dogger, is about 1,500-2,000 meters (~4,900-6,600 feet) deep. The rock that hosts the aquifer is 150-170 million years old and is made of limestone. It has a temperature of about 60 degrees Celsius. While the Dogger is full of mineral salts that make produced water unfit for consumption, the heat can be used for district heating. This geothermal resource supplies energy to buildings in the northern, eastern, and southern parts of Paris, but to the west it falls below a threshold temperature that makes drilling and production uneconomic.
Currently, SIPPEREC (the Paris intercommunal union for energy and communication networks) is exploring the idea of drilling into the Triassic rock layer, which underlies the Dogger at 2,100 meters (~6,870 feet) depth. The temperature of the water at this level is about 80 degrees Celsius – 20 degrees higher than the Dogger. If successful, utilizing the Triassic layer would allow development in the western part of the Paris region but full-scale exploration awaits approval from regulatory authorities and the state.
As of 2020, drilling into the Dogger costs about 5 million euros per well. Of course, drilling deeper costs more, and the cost of drilling into the Triassic layer is about 9 million euros per well. However, because of the hotter water temperature, production here could be cheaper as less water would be required. SIPPEREC says that network users' charge could be lowered as well.
The new heating networks are scheduled for completion in November of this year with the benefit of conserving annual emissions of 30,000 tonnes of CO2.
Did you know... geothermal wells can be highly deviated too?
Just as in the oil industry, the first geothermal wells were all vertical, which remains common practice mainly because it is cost-effective. The maximum depth is typically about 10,000 feet (3 km). Deviated geothermal wells have been drilled too, extending laterally over horizontal distances up to about 5,000 feet (1.5 km) and dipping at angles of less than 45° as measured from the vertical. In most geothermal fields, the rock formations are made up of volcanic and sedimentary rocks.
New groundbreaking developments are now happening in the geothermal industry borrowing methods used for unconventional hydrocarbon development. Recently, a well having a long horizontal leg was drilled for the DEEP geothermal project in the Williston Basin, Saskatchewan, Canada.
The type of rocks being drilled into for geothermal development are relevant because up until now very few have reservoirs hosted by granitic rock, which is abrasive and hard on wear and tear of downhole equipment. Examples of such wells include 14-2 at Roosevelt Hot Springs, WD-1A at Kakkonda, Habanero 1 in the Cooper Basin, 33A-7 at Coso and OTN-3 in Finland. Of these, WD-1A has the hottest bottom hole temperature (~500°C), and OTN-3 is the deepest, but for this rock type, highly deviated wells are absent.
The new deep well at Utah FORGE, 16A(78)-32 is thus notable. It shows that the drilling of sub-horizontal well trajectories in granitoid are achievable. Such highly deviated wells are required for EGS wells in order to intersect a large number of sub-vertical fractures and to maximize energy production.
Figure showing the geothermal well profiles, host rocks and deviation angles: conventional wells in red; sedimentary basin wells in green (Saskatchewan, Canada; Groß Schönebeck, Germany); metamorphic-plutonic well in blue (Helsinki, Finland); granitoid wells in black (Roosevelt Hot Springs, Utah; Kakkonda, Japan; Cooper Basin, Australia; Soultz-sous-Forêts, France; Coso, California); granitoid well in pink (Utah FORGE).
Ayling et al. 2016, Geothermics 63, 15-26. https://www.sciencedirect.com/science/article/pii/S0375650515000395
Kwiatek et al. 2019, Science Advances,5 (https://advances.sciencemag.org/content/5/5/eaav7224)
Ledésert & Hébert 2012, Heat Exchangers - Basics Design Applications, 447-504, https://doi.org/10.5772/34276
Muraoka et al. 1998, Geothermics, 27:507-535. https://www.sciencedirect.com/science/article/pii/S0375650598000315
Sabin et al 2016, Proceedings Stanford Geothermal Workshop (https://pangea.stanford.edu/ERE/pdf/IGAstandard/SGW/2016/Sabin.pdf)
Zimmerman et al. 2010, Geothermics, 39, 59-69 (https://www.sciencedirect.com/science/article/pii/S0375650509000674)
Did you know that the first wells were drilled over 2000 years ago?
Drilling is an ancient technology and it has long been used to explore for natural resources and to produce fluids such as water, brine, oil and gas that occur underground. The Chinese drilled shallow wells over 2000 years ago to produce brine. The first oil wells were drilled in the 1800s and up through the early 1900s, wells were vertical and limited to depths of a few hundred to a couple of thousand feet. By the 1970s, depth records were being broken starting with Bertha Rogers No. 1 which was drilled to over 31,000 feet (9.5 km) to explore for gas in the Anadarko basin, Oklahoma, USA. In 1979, the Kola Superdeep scientific well in Russia was drilled to over 40,000 feet (12.2 km), making it the deepest well in the world. In 2009, the deepest oil well was completed to 35,000 feet (10.6 km) from the Deepwater Horizon platform in the Gulf of Mexico.
The idea of drilling a slanted deviated well by directional drilling was realized in the 1930s. Today, the drilling of highly deviated wells is commonplace in the exploration and production of oil and gas reservoirs. The Chayvo oil field in Russia is the site of several record-breaking deviated wells that are drilled to depths of about 3,000 feet (0.9 km) with a long horizontal reach exceeding 40,000 feet, the longest of which is O-14. For comparison, geothermal wells are generally drilled to no more than 10,000 feet (3 km), and if deviated, they are done so at modest angles of less than 45°.
There are several reasons for drilling deviated wells such as increasing the section or length of well interval through rocks that are rich in oil (or gas). In some cases, there are obstacles (e.g., town or lake), which means the resource has to be accessed from the side rather than vertically from the surface. In other cases, there are logistical advantages to clustering a number of deviated wells on a single pad as is common in offshore oil platforms.
Figure shows the depth ranges of the deepest and longest wells in comparison to wells that are commonly drilled in geothermal production fields.
Did you know… that Reykjavík is a city of geothermal energy?
Did you know that the city of Reykjavík, the capital of Iceland, is widely recognized for its geothermal energy? Many first think of the word ‘ice’ when hearing Iceland, but surprisingly Iceland is also known for its use of Earth’s heat. Due to its geological location directly on the mid-Atlantic ridge, it is constantly supplied by an enormous amount of underground magmatic and geothermal heat. The literal translation of Reykjavík is “steamy bay” that comes from the steam discharge associated with natural geothermal activity.
Aware of the underground heat available, Icelanders have learned to adapt to their environment. Since the arrival of the first Scandinavian settlers in the late 800s, Icelanders have utilized geothermal sources for bathing and cooking. One of their popular traditional foods, Hverabrauð, is a bread loaf cooked in the steam from a geyser for 24 hours. Up into the early part of the 20th century, coal was the main source of energy and air pollution was a serious problem. To address this, the first geothermal pipelines were installed in 1934, and since then Reykjavík has been continuously expanding geothermal utilization. Reykjavík now has the largest district heating system in the world (700 MWthermal), which is run by Orkuveita, and more than 60 million cubic meters of hot water flow through the distribution system. Hot water supply comes from low temperature geothermal areas around Reykjavik and from high temperature geothermal fields in the Hengill area to the east of the city. These hotter resources are mainly used to generate electricity, but a significant amount of heat also supplies the district heating scheme. The combination of geothermal fields and hydroelectric dams means that more than 99% of all the electricity used in Iceland comes from renewable sources.
Did you know that some species incubate their eggs using geothermal heat?
Megapodes represent a family of birds that are also known as incubator birds. They are found across Australasia, and they are known for their unique strategies to keep their eggs warm and safe. Depending on the local environment, incubating strategies range from building a massive nest with stacks of decaying vegetation to laying eggs in warm ground heated by the sun. Certain species of megapode occurring on volcanic islands in the Bismarck archipelago, Solomon Islands, Vanuatu, Tonga, and Micronesia bury and incubate their eggs in geothermally heated ground. Megapodes originated in Australia, and as they evolved, they spread northward and eastward to tropical islands of the southwest Pacific. The use of thermal ground by just a few species of Megapode to incubate eggs appears to be simply a matter of opportunity.
The incubation of eggs in thermal ground, however, is not just for the birds. Their ancient ancestors, dinosaurs, may have been similarly opportunistic. The recently discovered Sangasta nesting site in northwest Argentina provides definitive evidence that neosaupods used geothermally heated ground to incubate their eggs. Much like humans, some animals have used geothermal heat when and where it is easily available.
Grellet-Tinner, G. and Fiorelli, L.E., 2010, A new Argentinian nesting site showing neosauropod dinosaur reproduction in a Cretaceous hydrothermal environment: Nature Communications, 1:32, DOI: 10.1038/ncomms1031
Harris, R.B., Birks, S.M. and Leaché, A.D., 2014, Incubator birds: biogeographical origins and evolution of underground nesting megapodes (Galliformes: Megapodiidae): Journal of Biogeography, v. 41, p. 2045-2056.
Geothermal energy has great benefits for people, but did you know that there are animals that use natural thermal heat in the form of hot springs and warm ground?
Macaques, better known as snow monkeys, are found throughout the main Japanese Island of Honshu, and they are famous for soaking in local volcanic hot springs. Their bathing habit is a recent phenomenon that was first observed at Korakukan Onsen, a local guest house, in 1962. Snow monkeys seem to have adapted this habit from observing humans in the hot springs. Since then, this behavior has been passed onto rest of their troops, and it has now become a part of their daily routine. Snow monkeys bathe in hot springs to preserve body heat to survive the cold and rigid winters, but recent studies have proven they also do this as a form of stress relief.
Matsuzawa, T., 2918, Hot-spring bathing wild monkeys in Shiga-Heights: origin and propagation of a cultural behavior: Primates, v. 59, p. 209-213.
Takeshita, R.S.C., Bercovitch, F.B., Kinoshita, K. and Huffman, M.A., 2018, Beneficial effect of hot spring bathing on stress levels in Japanese macaques: Primates, v. 59, p. 215-225.
Did you know that the direct use of geothermal energy can be used to raise alligators?
The direct use of geothermal energy can apply to almost any activity that requires heating (and cooling) for industrial, residential and agricultural purposes. The heat is transferred by hot ground water in the temperature range of 20-120°C (70-250°F) which is produced from shallow wells and then distributed through surface pipework. One very popular direct use application of geothermal energy is for bathing in natural hot springs. Spas all over the world use naturally produced hot water for recreational and therapeutic purposes. In Utah, the Crystal Hot Springs offers warm and mineral-rich baths which attracts numerous visitors throughout the year.
Another direct use application is space heating that may serve a single, stand-alone structure, or more commonly multiple buildings, which are linked by a pipeline that supplies hot water. For regions that are subject to cold winters, this is a cost effective means of heating without contributing to atmospheric pollution. District heating has been in use since the late 1890s when the city of Boise, Idaho started using geothermal energy to heat buildings. District heating is also popular in China, Iceland, France, Germany, Hungary and New Zealand. In the state of Utah, the prison at the Point of the Mountain uses district heating for 330,000 sq. ft. of prison space, saving thousands of dollars over conventional heating systems.
This type of geothermal energy is even used to heat greenhouses to grow plants. The Milgro complex in Newcastle, Utah is one of the largest producers of poinsettias and chrysanthemums in the USA; it uses geothermally heated greenhouses to grow its flowers. This type of energy is also used to heat ponds for aquaculture and fish farming. The warm springs near Grantsville, Utah are filled with warm, mineral-rich water that supports a variety of fish and are also an attraction for scuba-diving activities. Fish breeders in Idaho farm a range of species, including ones requiring geothermally heated ponds, which famously once included alligators!
Did you know how geothermal energy is utilized?
The three most common applications are heat pumps, direct use, and electricity generation. Geothermal heat pumps extract heat from the shallow subsurface for heating in the winter and reject the heat back into the ground in the summer for cooling. Heat pump systems are the fastest growing use of geothermal energy in the world. They can be installed in individual homes or large buildings. Gardner Hall at the University of Utah is one of several large buildings in Utah using heat pumps for heating and cooling. Heat pumps do not require a source of hot water, instead they use the natural thermal energy in the ground at less than 5 feet depth.
Where hot water occurs in the shallow subsurface at temperatures between 35° and 150°C (95-300°F), it can be used directly for bathing and spas, heating buildings, and for industrial purposes such as vegetable drying and raising fish. The poinsettias and chrysanthemums sold in grocery and garden stores are grown in a 24 acre geothermally heated greenhouse complex in Newcastle, Utah.
Geothermal power plants produce electricity from hot water with temperatures ranging from about 150° to 320°C (300 to 600°F). The lower temperatures can be found throughout the western USA; the highest temperatures are common around volcanoes, including those making up the Pacific Ring of Fire.
The hottest geothermal wells produce steam, which is used to spin turbines for electric generation. Where just hot water is produced, a heat exchanger is used to boil a secondary fluid to produce vapor that spins the turbine. Once the electricity is generated, the water is injected back into the hot subsurface reservoir where it is reheated. Recently, the University of Utah signed a contract with Cyrq Energy for 20 megawatts of geothermal electricity. This geothermal electricity will provide about one third of the University of Utah’s power requirements.
Did you know that Utah is No.3* in the United States for its production of geothermal energy?
The State of Utah is responsible for 2.8 % of the national geothermal power production. The United States leads the world in the amount of electricity generated with geothermal energy, producing about 16.7 billion kilowatthours (kWh), equal to 0.4% of total national electricity generation. Utah is one of the eight states that are producing geothermal energy, and currently has three geothermal electric plants. The three generation facilities are at Roosevelt Hot Springs by Utah Power and CalEnergy Corp., Thermo Hot Springs by Raser, and Cove Fort Station of Utah Municipal Power Association. While the state of Utah is now capable of generating 72 megawatts**, the Utah Governor’s Office of Energy believes it can increase geothermal power generation by another 2,200 megawatts hoping to bring more clean and renewable energy into the state’s power source.
*California leads the nation’s geothermal energy generation with a national share of 71.9 %, and Nevada follows second with 21.7%
**A megawatt can power between 750 and 1,000 homes