Chena Geothermal Area
Area Overview
Geothermal Area Profile |
| Location: | Fairbanks, Alaska | |
| Exploration Region: | Alaska Geothermal Region | |
| GEA Development Phase: | Operational"Operational" is not in the list (Phase I - Resource Procurement and Identification, Phase II - Resource Exploration and Confirmation, Phase III - Permitting and Initial Development, Phase IV - Resource Production and Power Plant Construction) of allowed values for the "GEADevelopmentPhase" property. | |
| Coordinates: | 65° 3' 9.00", -146° 3' 20.88" | |
Resource Estimate |
| Mean Reservoir Temp: | 98°C371.15 K <br />208.4 °F <br />668.07 °R <br /> | [1] |
| Estimated Reservoir Volume: | 2.74 km³2,740,000,000 m³ <br />3,583,784,696.06 yd³ <br />2,740,000,000,000 L <br />17,234,081,509.8 bbl(oil) <br />22,978,775,349.14 bbl(US) <br /> | |
| Mean Capacity: | 0.4 MW400 kW <br />400,000 W <br />400,000,000 mW <br />4.0e-4 GW <br />4.0e-7 TW <br /> | [2] |
| USGS Mean Reservoir Temp: | 95°C368.15 K <br />203 °F <br />662.67 °R <br /> | [3] |
| USGS Estimated Reservoir Volume: | 1 km³ | [3] |
| USGS Mean Capacity: | 2.75 MW | [3] |
The first production well for the ORC power plant module was Well #6, located adjacent to the hot springs and drilled to a depth of 130 ft (see Figure 8). This well was replaced by a new production well, Well #7, once an improved conceptual understanding of the shallow system was achieved during the GRED III Phase I exploration program. This new production well was drilled to 713 ft. The pipeline transporting the geothermal fluid is an 8-inch-diameter insulated HDPR pipe which is 3,000 ft in length. The heat loss between the production well and the power plant is 1.8°F. After some experimentation, TG #7 was selected as the main injection well. TG #7 demonstrated a high injectivity index and was drilled to a depth of 702 ft.[11]Using "ReferenceForChena Power LLC.2007" as property chain is not permitted during the annotation process.
Research and Development Activities
At the recommendation of the DOE Geothermal Technologies Program, UTC approached Chena Hot Springs Resort in 2004 with the idea of testing its PureCycle 200 modular ORC power generation system at Chena Hot Springs. The PureCycle 200 module had previously been applied towards the utilization of waste heat from industrial processes, and UTC’s new objective was the cost reduction of geothermal power generation equipment from $3,000/kWhr installed to $1,300/kWh installed. Specifically, UTC’s objective at Chena was the demonstration of the feasibility of electricity production from a 165°F geothermal resource with 98% availability at a cost of less than $0.05/kWh.[11]Using "ReferenceForChena Power LLC.2007" as property chain is not permitted during the annotation process.
UTC engineered its PureCycle 200 module design to cater to geothermal applications. Some modifications included changing the working fluid to R134a refrigerant to allow the use of less expensive, commercially available components; developing low cost heat exchangers; modifying the turbine design; and adapting the heat exchanger design. Generally, a low-temperature resource such as the Chena Geothermal Area, with wells producing fluids at 74°C (165°F), is not a suitable candidate for an ORC power plant because the temperature is too low. However, due to the availability of cold (3°C, 37°F) river water year-round, an ORC cycle is possible with a thermal efficiency of 8%.[17] The first UTC ORC module was designed to be water-cooled in order to take advantage of this cold water resource at Chena. The water supply system was engineered to require no pumping, reducing the parasitic load of the system. The second ORC module can be cooled with air or water.[11]Using "ReferenceForChena Power LLC.2007" as property chain is not permitted during the annotation process.
As of 2009, the Chena power plant is the lowest temperature geothermal resource utilized for electricity production in the world.[18] The project has received international recognition, including: the Project of the Year Award from Power Engineering Magazine; the Green Power Leadership Award from DOE and the Environmental Protection Agency; and the R&D 100 Award from DOE.[9]
A collaboration was established in 2009 between Chena Power, UTC, Pratt & Whitney Power Systems, and Quantum Resources Management. Their objective is to apply the PureCycle modules to a mobile power generation platform for coproduction of electricity from oil and gas wells using similar technology as applied at the Chena Geothermal Area.[18] This technology has been applied at the Peppermill Resort and Casino in Reno, NV. Also, a mobile power plant is generating 220 kW in Utah utilizing 600 gpm of 210°F water.[18]
Technical Problems and Solutions
When the power plant was originally built, the operators experienced problems with the cold water supply during the late winter and early spring due to cold ambient temperatures (dropping to -50°F) and a lower water table. ORC Unit #1 was temporarily shut down due to these issues. The installation of a second air-cooled condenser and the construction of a cooling pond were the recommended solutions to pursue in 2007.[9] As of 2007, during the summer months, the ORC modules are water-cooled from a gravity-fed well, and during the winter the units are air-cooled to bypass the problems created by the lower regional water table.[16]
On May 10, 2007, a fire started in the power plant module warehouse. Work was being done on the exterior of the building to install supports for an overhead door and the welding sparks fell inside the building, causing the fire. Since the building was vacant at the time, the fire was not immediately apparent. The building suffered moderate fire damage but none of the main power plant components were compromised. Burning insulation that fell on top of the power plant modules melted much of the electrical wiring along with the control panel. Due to the cold water running through the plant during the fire, no thermal breakdown of the modules’ oil or working fluid occurred. The working fluid used, R134a, is a non-flammable refrigerant and did not present a hazard due to accidental fluid release. The Chena crew was able to restart ORC#2 after a month, and ORC#1 was anticipated to be operational again in early July.[9]
From 2007-2010, produced temperatures from the production wells Well #7 and TG-8 steadily declined to 159° from 165°F. As a result, the overall electrical production of the geothermal power plant was reduced. This prompted the deep drilling of Well TG-12 during GRED III Phase II in order to respond to the temperature loss and locate a hotter resource with increased geothermal fluid flow. However, the well was drilled into an outflow zone and encountered a temperature reversal at 2,700 ft.[10]
Geology of the Area
Geologic Setting |
| Tectonic Setting: | Non-Tectonic | [12][5] |
| Controlling Structure: | Fault Intersection, Intrusion Margins and Associated Fractures | [19][5] |
| Topographic Features: | [8] | |
| Brophy Model: | Type A: Magma-heated, Dry Steam Resource | [12][5] |
| Moeck-Beardsmore Play Type: | CV-2b: Plutonic - Inactive Volcanism, CV-3: Extensional Domain"CV-2b: Plutonic - Inactive Volcanism, CV-3: Extensional Domain" is not in the list (CV-1a: Magmatic - Extrusive, CV-1b: Magmatic - Intrusive, CV-2a: Plutonic - Recent or Active Volcanism, CV-2b: Plutonic - Inactive Volcanism, CV-3: Extensional Domain, CD-1: Intracratonic Basin, CD-2: Orogenic Belt, CD-3: Crystalline Rock - Basement) of allowed values for the "MoeckBeardsmoreType" property. | |
Geologic Features |
| Modern Geothermal Features: | Hot Springs | [4] |
| Relict Geothermal Features: | ||
| Volcanic Age: | Not related to Quaternary volcanism | [12] |
| Host Rock Age: | 90 Ma | [19][5] |
| Host Rock Lithology: | Granitic Pluton | [4] |
| Cap Rock Age: | ||
| Cap Rock Lithology: | ||
The Chena Geothermal Area is located centrally within the Yukon-Tanana Upland, a region characterized by rounded mountain highlands between the Yukon and Tanana Rivers. The Chena Hot Springs are one of approximately 30 hot springs found in a 2,000-mile-long thermal belt, the CAHSB, extending from the Seward Peninsula to the Yukon Territory. The majority of the thermal springs along this trend are low- to moderate-temperature systems, typically located on the margin of a granitic pluton (Figure 9).[8] These plutons range from mid-Cretaceous to early Tertiary age and many have been identified with anomalously high concentrations of the radioactive elements uranium and thorium.[20] The Chena Geothermal Area is not related to Quaternary volcanism and has no known major structural features within a 30-mile radius.[8] [12]
The Chena Hot Springs are located at an elevation of 1,170 ft in the Monument Creek Valley. Mountains border this area to the southwest and northeast, reaching an altitude of ~3,500 ft.[8] The Chena granitic pluton, which hosts the Chena Hot Springs, has an areal extent of 5x40 km^2 and is surrounded by Paleozoic metamorphic rocks. The age of the Chena pluton was determined to be 59 Ma based on K-Ar dating of biotite from a monzogranite rock sample,[21] but subsequent sampling has indicated an original age around 90 Ma based Ar-Ar dating and hornblende spectral analysis.[20] Hydrothermal alteration exists in the plutonic rocks but no evidence of intense clay alteration due to steam is present.[8]
Based on the geological mapping, rock sampling, and surface and airborne geophysical measurements collected during the GRED III Phase I Project, a conceptual model and sequence of geological events for the Chena Geothermal Area has been proposed.[22]Using "ReferenceForKolkerLarsenNewberryKeskinenn.d." as property chain is not permitted during the annotation process. Studies of the Chena pluton indicate three distinct intrusive phases: the early Cretaceous, the mid-Cretaceous, and the early Tertiary. Kolker et al. have posited a mid-Cretaceous pluton underlain by a radioactive early Tertiary pluton. This early Tertiary pluton is hypothesized to have reset the Ar-Ar ratios in the hornblende of the mid-Cretaceous granite at 59 Ma, as measured by Biggar (1973).[21][20] Early Tertiary outcrop similar to the proposed pluton exists to the north and northeast of the Chena Geothermal Area and is correlated with radiometric measurements of anomalously high radioactivity. The radiometric data also assisted in the constraint of the southern boundary of the pluton, which is now accepted to be at Monument Creek as opposed to 2 km further to the south.[8] The airborne EM and surface resistivity data produced anomalies which were not consistent with one another nor with the thermal pattern recorded through well measurements, yielding largely inconclusive results. The magnetic measurements produced a signature typical of granitic terrains (i.e., relatively flat and featureless).[8]
The geothermal fluids at Chena contain high concentrations of boron, lithium, and fluorine, which is characteristic of early Tertiary granites measured in other regions of Interior Alaska. The depth and geometry of the Tertiary pluton is not constrained. However, the geothermal wells did not penetrate this pluton, indicating a depth greater than the maximum drilled depth of ~300 m.[5] This conceptual understanding of the Chena Geothermal Area indicates a favorable geological setting to host a geothermal system.[8]
Hydrothermal System
Property "HydroSystem" (as page type) with input value "The Chena geothermal system consists of two distinct episodes of hydrothermal activity as depicted through fluid inclusion and alteration assemblage pattern analyses. The propylitic alteration phase likely occurred during the early Tertiary and is not related to the modern geothermal fluids. Lower reservoir temperature (80° - 120°C) hydrothermal alteration is related to the present-day geothermal system. Water samples analyzed by SMU revealed a minor variation between the isotopic composition of local meteoric water and the geothermal fluid, providing evidence that the geothermal fluids originated under modern climatic conditions.'"`UNIQ--ref-0000006C-QINU`""`UNIQ--ref-0000006D-QINU`"' </br></br>The main shallow upflow zone of the Chena Geothermal Area is 600 m long by 90 m wide. Stable isotope analysis indicates the geothermal fluids are of meteoric origin with a circulation time less than 3,000 years. The estimated depth of circulation of the system is hypothesized at 3,300 m and it is predicted that 120°C geothermal fluids should be encountered at approximately 500 - 1000 m depth. The Chena geothermal system is proposed as a fault/fracture-dominated geothermal system, although it is not associated with any major regional structural features.'"`UNIQ--ref-0000006E-QINU`"' A northwest-trending subvertical fault zone is the conduit for the geothermal fluid upwelling based on airborne resistivity maps and geological data. The deep thermal fluids are proposed to enter the shallow system approximately 500 m to the west of the hot springs, flowing to the east and mixing with groundwater to create a shallow convective system beneath the springs.'"`UNIQ--ref-0000006F-QINU`""`UNIQ--ref-00000070-QINU`"' </br></br>The temperature-gradient hole drilling program yielded additional information regarding the hydrothermal system. Eleven temperature-gradient holes were drilled in addition to the eight shallow wells that were already drilled, and temperature and pressure logs were run in each hole and well. Select wells were flow-, interference- and injection-tested during the exploration program.'"`UNIQ--ref-00000071-QINU`"' The temperature-gradient hole drilling program delineated production and injection zones, and enabled a better understanding of the connectivity of the reservoir.'"`UNIQ--ref-00000072-QINU`"' Further deep drilling of Well TG-12 was carried out during the GRED III Phase II project, but a temperature reversal was encountered at 2,700 ft, and the anticipated temperatures of 200°F were not achieved. However, the information gained from Well TG-12 contributed to the reservoir model and conceptual understanding of the system.'"`UNIQ--ref-00000073-QINU`"'" contains invalid characters or is incomplete and therefore can cause unexpected results during a query or annotation process.The Chena geothermal system consists of two distinct episodes of hydrothermal activity as depicted through fluid inclusion and alteration assemblage pattern analyses. The propylitic alteration phase likely occurred during the early Tertiary and is not related to the modern geothermal fluids. Lower reservoir temperature (80° - 120°C) hydrothermal alteration is related to the present-day geothermal system. Water samples analyzed by SMU revealed a minor variation between the isotopic composition of local meteoric water and the geothermal fluid, providing evidence that the geothermal fluids originated under modern climatic conditions.[5][8]
The main shallow upflow zone of the Chena Geothermal Area is 600 m long by 90 m wide. Stable isotope analysis indicates the geothermal fluids are of meteoric origin with a circulation time less than 3,000 years. The estimated depth of circulation of the system is hypothesized at 3,300 m and it is predicted that 120°C geothermal fluids should be encountered at approximately 500 - 1000 m depth. The Chena geothermal system is proposed as a fault/fracture-dominated geothermal system, although it is not associated with any major regional structural features.[12] A northwest-trending subvertical fault zone is the conduit for the geothermal fluid upwelling based on airborne resistivity maps and geological data. The deep thermal fluids are proposed to enter the shallow system approximately 500 m to the west of the hot springs, flowing to the east and mixing with groundwater to create a shallow convective system beneath the springs.[5][12]
The temperature-gradient hole drilling program yielded additional information regarding the hydrothermal system. Eleven temperature-gradient holes were drilled in addition to the eight shallow wells that were already drilled, and temperature and pressure logs were run in each hole and well. Select wells were flow-, interference- and injection-tested during the exploration program.[8] The temperature-gradient hole drilling program delineated production and injection zones, and enabled a better understanding of the connectivity of the reservoir.[12] Further deep drilling of Well TG-12 was carried out during the GRED III Phase II project, but a temperature reversal was encountered at 2,700 ft, and the anticipated temperatures of 200°F were not achieved. However, the information gained from Well TG-12 contributed to the reservoir model and conceptual understanding of the system.[10]
Heat Source
Property "HeatSource" (as page type) with input value "The crustal heat source of the Chena Geothermal System is due to the radioactive decay of uranium, thorium, and potassium within the early Tertiary pluton. Radiogenic heat production calculations indicate an anomalously high heat production value which may contribute to the elevated geothermal gradient at relatively shallow depth.'"`UNIQ--ref-00000074-QINU`""`UNIQ--ref-00000075-QINU`"' Helium isotope analysis confirms there is no magmatic or mantle input to the Chena geothermal system, providing further evidence of a crustal heat source.'"`UNIQ--ref-00000076-QINU`"' The Chena Geothermal Area is a fault-dominated, low-temperature convective geothermal system with a high heat producing granite as the heat source.'"`UNIQ--ref-00000077-QINU`"'" contains invalid characters or is incomplete and therefore can cause unexpected results during a query or annotation process.The crustal heat source of the Chena Geothermal System is due to the radioactive decay of uranium, thorium, and potassium within the early Tertiary pluton. Radiogenic heat production calculations indicate an anomalously high heat production value which may contribute to the elevated geothermal gradient at relatively shallow depth.[5][19] Helium isotope analysis confirms there is no magmatic or mantle input to the Chena geothermal system, providing further evidence of a crustal heat source.[19] The Chena Geothermal Area is a fault-dominated, low-temperature convective geothermal system with a high heat producing granite as the heat source.[5]
Geofluid Geochemistry
Geochemistry |
| Salinity (low): | 282 | [19][5] |
| Salinity (high): | 388 | [19][5] |
| Salinity (average): | 335 | [19][5] |
| Brine Constituents: | Alkali-chloride type waters with elevated B, Li, and F concentrations, a pH of 9, and TDS between 282 - 288 ppm. | [19][5] |
| Water Resistivity: | ||
Geochemical analyses from the geothermal wells in the Chena Geothermal Area present a relatively consistent chemical composition of alkali-chloride type waters with a pH around 9 and elevated boron, lithium, and fluorine concentrations. The total dissolved solids concentration ranges between 282 - 388 ppm. The chalcedony geothermometer is the most appropriate geothermometer to apply for Chena Hot Springs because of the low temperature of the hot springs, the chalcedony identified in the geothermal well cuttings, and the lacking feldspar-mica assemblage in the reservoir rocks. A reservoir temperature of ~100°C was indicated. Fluid inclusion analyses suggest a reservoir temperature between 100 and 120°C.[5]
NEPA-Related Analyses (1)
Below is a list of NEPA-related analyses that have been conducted in the area - and logged on OpenEI. To add an additional NEPA-related analysis, see the NEPA Database.
| Document # | Analysis Type | Applicant | Application Date | Decision Date | Lead Agency | Development Phase(s) | Techniques |
|---|---|---|---|---|---|---|---|
| GFO-04-236b, GFO-10-367 | Chena Hot Springs Resort | Golden Field Office | Geothermal/Exploration | Slim Holes |
Exploration Activities (35)
Below is a list of Exploration that have been conducted in the area - and cataloged on OpenEI.
Add a new Exploration Activity
References
- ↑ Ruggero Bertani. 2005. World Geothermal Power Generation 2001-2005. Proceedings of World Geothermal Congress; Turkey: World Geothermal Congress.
- ↑ 2.0 2.1 2.2 400 kw Geothermal Power plant at Chena Hot Springs, Alaska
- ↑ 3.0 3.1 3.2 U.S. Geological Survey. 2008. Assessment of Moderate- and High-Temperature Geothermal Resources of the United States. USA: U.S. Geological Survey. Report No.: Fact Sheet 2008-3082.
- ↑ 4.0 4.1 4.2 4.3 4.4 4.5 4.6 Gerald Ashley Waring,Richard Bryant Dole,Alfred A. Chambers. 1917. Mineral Springs of Alaska. (!) : US Government Printing Office.
- ↑ 5.00 5.01 5.02 5.03 5.04 5.05 5.06 5.07 5.08 5.09 5.10 5.11 5.12 5.13 5.14 5.15 5.16 5.17 Amanda M. Kolker. 2008. Geologic Setting of the Central Alaskan Hot Springs Belt: Implications for Geothermal Resource Capacity and Sustainable Energy Production [Thesis]. [ (!) ]: University of Alaska Fairbanks.
- ↑ 6.0 6.1 6.2 6.3 6.4 6.5 6.6 6.7 John W. Lund. 2006. Chena Hot Springs. Geo-Heat Center Quarterly Bulletin. 27(3):2-4.
- ↑ 7.0 7.1 7.2 7.3 Jennifer Bogo. Geothermal Power in Alaska Holds Hidden Model for Clean Energy - Popular Mechanics [Internet]. 2008. [updated 2008;cited 08/06/2013]. Available from: http://www.popularmechanics.com/science/environment/4245896
- ↑ 8.00 8.01 8.02 8.03 8.04 8.05 8.06 8.07 8.08 8.09 8.10 8.11 8.12 8.13 8.14 8.15 Gwen Holdmann,Dick Benoit,David Blackwell. 2006. Integrated Geoscience Investigation and Geothermal Exploration at Chena Hot Springs, Alaska. (!) : Phase I final report prepared for the Dept. of Energy Golden Field Office under award DE-FC36-04GO14347.
- ↑ 9.0 9.1 9.2 9.3 9.4 9.5 Gwen Holdmann. 2007. The Chena Hot Springs 400kw Geothermal Power Plant: Experience Gained During the First Year of Operation. Chena Geothermal Power Plant Report, Chena Power Plant, Alaska. 1-9.
- ↑ 10.0 10.1 10.2 10.3 10.4 10.5 10.6 EERE. 2010. 4.2.1 GRED Drilling Award- GRED III Phase II. (!) : EERE.
- ↑ 11.00 11.01 11.02 11.03 11.04 11.05 11.06 11.07 11.08 11.09 11.10 11.11 Chena Power LLC.. 2007. 400kW Geothermal Power Plant at Chena Hot Springs, Alaska. Final Report prepared for Alaska Energy Authority. (!) .
- ↑ 12.00 12.01 12.02 12.03 12.04 12.05 12.06 12.07 12.08 12.09 Kamil Erkan,Gwen Holdman,David Blackwell,Walter Benoit. 2007. Thermal Characteristics of the Chena Hot Springs Alaska Geothermal System. In: PROCEEDINGS, Thirty-Second Workshop on Geothermal Reservoir Engineering Stanford University, Stanford, California. Stanford Geothermal Workshop; 2007; (!) . (!) : (!) ; p. (!)
- ↑ 2007. ALASKA ENERGY AUTHORITY Alaska Geothermal Development: A Plan. (!) : (!) .
- ↑ 14.0 14.1 Bernie Karl. 2010. GRED III Phase II. p.
- ↑ 15.0 15.1 15.2 15.3 15.4 Eugene M. Wescott,Donald L. Turner. 1982. Geothermal Energy Resource Assessment of Parts of Alaska. (!) . (!) .
- ↑ 16.0 16.1 Dick Benoit,Gwen Holdmann,David Blackwell. 2007. Low Cost Exploration, Testing, and Development of the Chena Geothermal Resource. GRC Transactions. 31:147-152.
- ↑ Joost J. Brasz,Bruce P. Biederman,Gwen Holdmann. 2005. Power Production from a Moderate-Temperature Geothermal Resource. In: GRC annual meeting; 2005; Reno, Nevada. (!) : (!) ; p. (!)
- ↑ 18.0 18.1 18.2 Bernie Karl,Ian-Michael Hebert,Jesse Warwick. 2009. Electric Power Generation Using Geothermal Fluid Coproduced from Oil and/or Gas Wells. GRC Transactions. 33: (!) .
- ↑ 19.0 19.1 19.2 19.3 19.4 19.5 19.6 19.7 Amanda M. Kolker,B.M. Kennedy,R.J. Newberry. 2008. Evidence for a Crustal Heat Source for Low-Temperature Geothermal Systems in the Central Alaskan Hot Springs Belt. GRC Transactions. 32:225-230.
- ↑ 20.0 20.1 20.2 Amanda M. Kolker,Rainer Newberry,Jessica Larsen,Paul Layer,Patrick Stepp. 2007. Geologic Setting of the Chena Hot Springs Geothermal System, Alaska. In: Proceedings of the Thirty-second Workshop on Geothermal Reservoir Engineering, Stanford University, Stanford, CA, USA. Stanford Geothermal Workshop; 2007; (!) . (!) : (!) ; p. 416-423
- ↑ 21.0 21.1 Norma Biggar. 1973. A Geological and Geophysical Study of Chena Hot Springs, Alaksa [M.Sc. Thesis]. [Fairbanks, Alaska]: University of Alaska.
- ↑ Amanda M. Kolker, Jess Larsen, Rainer Newberry, and Mary Keskinen. 2006. Chena Hot Springs GRED III Project: Final Report Geology, Petrology, Geochemistry, Hydrothermal Alteration, and Fluid Analyses. Fairbanks, AK: University of Alaska Fairbanks.
List of existing Geothermal Resource Areas.
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