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.
Celebrating its 10th anniversary this year, Geo-Energie Suisse AG (GES) is a Swiss company focused on deep geothermal energy for electricity and heat production. The founding members include municipal utilities and regional energy supply companies from all over Switzerland. Geo-Energie Suisse employs ten people, and it is also supported by numerous external specialists.
The company aims to develop deep EGS projects in crystalline rocks through the use of multi-stage stimulation to increase the permeability of the rock while reducing the seismic risk. Haute-Sorne is the company’s most advanced project in Switzerland. Its setting shows many similarities with the Utah FORGE project, which makes the collaboration with the University of Utah-based team particularly exciting.
Geo-Energie Suisse core competencies reside in seismic risk assessments, seismic monitoring and real time seismic data processing and evaluation. At Utah FORGE, GES intends to test and validate new methods and downhole instruments and bring them to the next level of innovation. GES is also assisting in the design of the seismic monitoring program, as well as conducting numerical analyses of the seismic data.
The figure shows the results of resolution and sensitivity numerical modelling performed by GES to assess the optimal configuration of monitoring boreholes and sensors at Utah FORGE. Section-view (left) and map-view (right) of the monitoring boreholes and the first of two deep, highly deviated wells (16A(78)-32) that will be used to create the reservoir.
At the end of 2020, Geo-Energie Suisse succeeded in obtaining technical proof of its multi-stage stimulation concept. The successful demonstration took place in the Bedretto Underground laboratory for Geosciences and Geoenergy of the ETH Zurich in the Swiss Alps. Innovative sensors, measurement and control techniques were tested for the first time and enabled the observation and control of the hydraulic stimulations. These techniques increase safety when creating geothermal reservoirs in crystalline rock. In addition, a seismicity forecasting method, developed by ETH Zurich, was also successfully implemented in the demonstration project. GES will now validate the findings gained in the Bedretto Laboratory at the Utah FORGE test site in the high-temperature range.
This figure shows the spatial distribution of the microseismicity that occurred in 10 temporally staggered intervals and spatially isolated stimulation zones leading to permanent microcracks in the granite rock.
The Swiss Federal Office of Energy supports the deep geothermal project in Haute-Sorne and especially the innovations that will substantially reduce the risk of induced seismicity for deep EGS projects. The Swiss, Utah FORGE and the international geothermal industry will be well served by such improvements in safety and the success of future EGS projects.
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
This well is the fourth and deepest of a cluster of vertical seismic monitoring wells that are located near the toe of 16A(78)-32. The well was drilled vertically to a total depth of approximately 9,000 feet about 1300 feet north of 58-32.
Well 56-32 will be fully cased (5 ½ inch) and used for deployment of seismic sensors during stimulation experiments. A Silixa DAS fiber optic cable 7500 feet long will be cemented along the outside the casing. During the drilling of 56-32, MSE (Mechanical Specific Energy) calculations and PDC bits will be used to optimize penetration rates as was successfully utilized in the drilling of 16A(78)-32. Below 7500 feet depth, mud hammer bits will be trialed and evaluated for drilling performance.
Update February 8:
Well spudded at 4am.
Update February 9:
Drilled to 380 ft depth.
Update February 10:
Drilled to 3,300 ft depth. The basement contact was crossed at 3,100 ft.
Update February 17:
Drilled to 5,840 ft depth.
Update February 21:
Well reached TD of 9,145 ft depth.
This well, as well as the deep, highly deviated 16A(78)-32, was drilled with specially modified polycrystalline diamond composite or PDC bits. These bits proved superior to the tricone bits used in drilling the previous wells.
According to Reed Hycalog, the bit manufacturer, drilling well 56-32 set a record for a bit run of 1208 ft in 53 hours, drilling on average 25 ft/hr in hot, crystalline granite.
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.
Utah FORGE Chooses 17 Selectees to Begin Negotiations:
University of Utah to award $46 M for research in Enhanced Geothermal System development
17 selectees chosen to enter negotiations in 5 topic areas
SALT LAKE CITY, UT., Feb. 24, 2021 – The Utah Frontier Observatory for Research in Geothermal Energy (FORGE) at the University of Utah is pleased to announce it has chosen 17 project selectee applications for negotiations for the FORGE Solicitation 2020-1. The selectees could receive a combined total of up to $46 M over the next 3 years.
The topic areas and the selectees include:
Topic # and Title
Topic 1: Devices suitable for sectional (zonal) isolation along both cased and open-hole wellbores under geothermal conditions
1 to 3
Welltec; PetroQuip Energy Services; Colorado School of Mines
Topic 2: Estimation of stress parameters
1 to 3
Battelle Memorial Institute
Lawrence Livermore National Laboratory
University of Oklahoma
Topic 3: Field-scale characterization of reservoir stimulation and evolution over time, including thermal, hydrological, mechanical, and chemical (THMC) effects
1 to 4
Lawrence Berkeley National Laboratory
Topic 4: Stimulation and configuration of the well(s) at Utah FORGE
1 to 3
Fervo Energy Company
University of Texas at Austin
Topic 5: Integrated Laboratory and Modeling studies of the interactions among THMC processes
1 to 6
Pennsylvania State University
Lawrence Livermore National Laboratory
US Geological Survey
University of Oklahoma
“There is enormous untapped potential for enhanced geothermal systems (EGS) to provide clean and reliable electricity generation throughout the United States,” said Dr. Kathleen Hogan, Assistant Deputy Under Secretary for Science. “These investments in EGS research support President Biden’s mission to take on the climate crisis by pushing the frontiers of science and engineering and creating jobs in cutting-edge clean energy fields.”
Utah FORGE is a dedicated underground field laboratory sponsored by the U. S. Department of Energy’s Geothermal Technologies Office. It is working on developing, testing, and accelerating breakthroughs in EGS. Solicitation 2020-1 was the first formal call for research proposals on EGS technologies from the Utah FORGE Program. More information about Solicitation 2020-1 is available HERE.
“Utah FORGE looks forward to collaborating closely with the scientists and engineers of the project teams on technologies that will promote commercialization of this inexhaustible and non-polluting energy source,” said Joseph Moore, Ph.D. and Principal Investigator of the Project. “We were impressed with the caliber of all of the applicants who submitted proposals and anticipate additional solicitations in the future.”
To download the official press release follow this LINK
Utah FORGE team has successfully completed drilling of its first highly deviated deep well. Drilling was completed 60 days ahead of schedule.
The upper part of the well was drilled vertically through approximately 4,700 feet of sediments before penetrating into high strength, crystalline granite. The well was deviated at a 65° angle from vertical after reaching a depth of 6000 ft. This angle was maintained for the remainder of the well’s trajectory. The well ultimately reached a true vertical depth of 8,559 feet, and a total measured depth of 10,987 feet. Preliminary measurements indicate temperatures at the “toe” of the well will exceed 442°F (228°C). Approximately 74 ft of core of the granitic and metamorphic rocks that will form the FORGE reservoir was also recovered.
“We are incredibly pleased with the success of the well” said Joseph Moore, Ph.D. and Principal Investigator of Utah FORGE. “It was drilled under complicated conditions and will serve as a prototype for similar wells around the world.”
With this well successfully completed, a series of tests can be run to facilitate the development of the EGS resource. Some of the tests will include determining the stress conditions through short-term injection experiments, during which microseismicity will be carefully monitored. Other tests will allow for the interpretation of the orientation and distribution of the existing and induced fractures in the granite, which will form the pathways for water to circulate and heat up in the newly created EGS reservoir. In the future, a sister well will be drilled to form the basis of an EGS.
About Utah FORGE: The Utah FORGE project is managed by the Energy & Geoscience Institute at the University of Utah. Funding for the project is provided by the U.S. Department of Energy. The FORGE site is located near the town of Milford in Beaver County, Utah, on the western flank of the Mineral Mountains. Near term goals are aimed at perfecting drilling, stimulation, injection-production, and subsurface imaging technologies required to establish and sustain continuous fluid flow and energy transfer from an EGS reservoir.