Neal Hot Springs Geothermal Area
Geothermal Area Profile
|Exploration Region:||Snake River Plain|
|GEA Development Phase:||Operational"Operational" is not in the list of possible values (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) for this property.|
|Mean Reservoir Temp:||156°C429.15 K
|Estimated Reservoir Volume:|
|Mean Capacity:||33 MW33,000 kW
|USGS Mean Reservoir Temp:||150°C423.15 K
|USGS Estimated Reservoir Volume:||2 km³|||
|USGS Mean Capacity:||30 MW|||
Neal Hot Springs Geothermal Area is located about 19 km east-north-east of the town of Vale in eastern Oregon. The Geothermal area has recently been developed (Figure 1) with a 22 MW (net) power plant that began producing commercially under a 25-year power purchase agreement (PPA) on November 16, 2012. The PPA has been made with Idaho Power Company at a rate of 96.00 USD per megawatt-hour. The price is set to rise annually with a calculated 25-year levelized price of $117.65 per megawatt-hour. The power plant consists of three 7.33 MW units; installation of all three units was completed in July 2012. The power plant is owned and operated by U.S. Geothermal Inc., a renewable energy company focused on developing geothermal resources. U.S Geothermal Inc. also owns the power plants at the Raft River Geothermal Area and the San Emidio Desert Geothermal Area. Funding for the Neal Hot Springs project was made possible by the U.S. Department of Energy’s (DOE’s) Loan Guarantee Solicitation for Innovative Energy Efficiency, Renewable Energy and Advanced Transmission Distribution, Technologies which is authorized under Title XVII of the energy policy act of 2005. The DOE granted a loan of 96.8 million USD for the project, which was 67% of the total cost of 143.6 million USD.
History and Infrastructure
Operating Power Plants: 1
|Add a new Operating Power Plant|
Developing Power Projects: 2
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Power Production Profile
|Gross Production Capacity:||22 MW22,000 kW
|Net Production Capacity:|
|Power Purchasers :||
The power plant at Neal Hot Springs is a first-of–its-kind binary plant which uses R134a refrigerant in a supercritical cycle as the working fluid. The power plant is also the first to undergo a pre-fabricated modular construction method for all of the major plant components. The facility is air cooled; thus, power output can change significantly depending on outside temperatures. For example, in the winter the facility reached a net output of 29.8 MW, which is 7.8 MW above its rated capacity.
A 16.6 km transmission line and substation connecting the Neal Hot Springs project to the grid was completed in 2012 by Idaho Power Company. The power lines are rated for up to 36 MW of transmission capacity.
Neal Hot Springs Area Timeline
1979: The first well to encounter the geothermal resource at Neal Hot Springs is drilled by Chevron Minerals. The geothermal potential of the area was recognized, however the binary power generation technology did not exist at the time.
2006: U.S. Geothermal Inc. leases the Neal Hot Springs property. The company conducts several geophysical surveys in preparation for exploration drilling.
2008: The first production well (NHS-1) at Neal Hot Springs is successfully completed by U.S. Geothermal.
2009: A second production well (NHS-5) is completed at Neal Hot Springs by U.S. Geothermal.
2009-2010: Several thermal gradient wells are drilled across the property to better delineate the extent of the geothermal resource.
2011: Students and faculty from the Colorado School of Mines, Boise State University, and Imperial College London complete a series of geophysical studies at Neal Hot Springs.
2012: The 22 MW Neal Hot Springs Geothermal Plant begins commercial power production.
Regulatory and Environmental Issues
Neal Hot Springs is well situated as far as environmental impact issues. The power plant and wells are not visible from any highways or from any residents that are unassociated with the project. There are no unique or endangered plant or animal species in the area and no objections have been raised amongst the community regarding the power plant. There are also no negative cultural impacts. The power plant is air cooled, which makes water constraints more lenient. The companies only environmental reporting is monthly production and injection reports, and an annual water quality report.
First Discovery Well
|Depth:||860 m0.86 km
|Initial Flow Rate:||
|Flow Test Comment:|
The first discovery well was drilled by Chevron Minerals in 1979. High temperatures and a loss of drilling fluid circulation were encountered in the drill hole at 860 m depth. Surface discharge of the geothermal fluids showed potential reservoir temperatures of 155-175°C. Commercial geothermal potential was realized from this discovery well, but binary technology for utilizing geothermal fluids of low temperatures was not economically attractive at the time so further exploration and development did not occur until 27 years later. In 2006 U.S. Geothermal Inc. leased the property which covers 24.9 km2. In 2006 and 2007 magnetic and gravity surveys were conducted by U.S. Geothermal; in 2008 they began drilling, successfully completing the first production well on May 23, 2008. From 2009-2010 thermal gradient wells were drilled across the geothermal field to gain a better understanding of the geothermal resource.
Between the first discovery well in 1979 and the purchase of the property by U.S. Geothermal in 2006, no geophysical studies were documented. Geothermal energy production in the area was not considered during that time period because the resource temperature was low and binary technology was not economical. It was not until U.S. Geothermal purchased the property with the intention of development that any geophysical studies were conducted. U.S Geothermal had gravity and magnetic surveys conducted and then began thermal gradient and exploratory drilling. The majority of geophysical studies conducted in the area were performed during a geophysics field camp in 2011 by students and faculty from the Colorado School of Mines, Boise State University, and Imperial College London. During the field camp many different techniques were performed: gravity, magnetic, paleomagnetic, electromagnetic, DC resistivity, self potential, deep seismic reflection, shallow seismic reflection, vertical seismic profiling, passive seismic monitoring, and controlled source audio magnetotellurics. Details about each of these surveys can be found in the activities section of this review.
Well Field Description
Well Field Information
|Number of Production Wells:||4|||
|Number of Injection Wells:||5|||
|Number of Replacement Wells:|
|Average Temperature of Geofluid:||286 141°C414.15 K
|Sanyal Classification (Wellhead):||Very Low Temperature|||
|Reservoir Temp (Geothermometry):|
|Reservoir Temp (Measured):||169°C442.15 K
|Sanyal Classification (Reservoir):||Low Temperature|||
|Depth to Top of Reservoir:||762 m0.762 km
|Depth to Bottom of Reservoir:||914 m0.914 km
|Average Depth to Reservoir:||838 m0.838 km
The first production well (NHS-1) was completed on May 23, 2008. It reached a depth of 703 m and produced geothermal fluids at 136°C, which flowed at a rate of 76 liters/second. Drilling of the well was stopped 114 m shy of the original drilling target due to high torque on the drill bit and loss of drilling mud into the formation. Original estimates from flow tests predicted the well would be capable of producing 5-6 MW. A second flow test revealed a flowing temperature of 141°C and a flow rate of 130 liters/second (Table 1) confirming the original predictions of a 5-6 MW capability.
The second production well (NHS-5) was completed on October 15, 2009. This well reached 883 m depth and hit a large fracture at 852 m, which caused a total loss of drill mud circulation. The down hole temperature in this well was 141°C, the same as in NHS-1. A flow rate of 95 liters/second was recorded.
The third production well (NHS-8) was completed in October 2010. This well reached the geothermal reservoir at 1098 m depth. The down hole temperature in this well was 142°C and a flow rate of 175 liters/second was recorded.
The fourth production well (NHS-2) was completed in November 2010. This well reached the geothermal reservoir at 979 m depth. The down hole temperature in this well was 142°C and a flow rate of 191 liters/second was recorded.
|NHS-10||Not Published||751||69||Not Published|
|NHS-3||Not Published||Not Published||Not Published||Not Published|
|NHS-4||Not Published||Not Published||Not Published||Not Published|
|NHS-11||Not Published||Not Published||Not Published||Not Published|
|NHS-13||Not Published||Not Published||Not Published||Not Published|
|NHS-6||Not Published||Not Published||Not Published||Not Published|
After the fourth production well, the total geothermal fluid production for a sustainable 23 MW of generation was accomplished and no further production wells were needed. The bottom hole diameter of all the production wells is 12.25 inches.
The first injection well (NHS-10) was completed in 2010 and reaches a depth of 751 m. It can sustain an injection rate of 69 liters/second and is predicted to maintain this rate for the life of the project. There are six injection wells total; four large-diameter wells (NHS-3, NHS-4, NHS-11, and NHS-13) and two slim-hole injection wells (NHS-10 and NHS-6).
All of the well field information is current as of August 2013.
Research and Development Activities
Research and development efforts have gone toward the air cooled condenser (ACC) system at Neal Hot Springs. It is a first-of-its-kind system which utilized a smaller number of large fans rather than many smaller fans. The standard smaller fans measure 3.7 m in diameter and would require 270 units. The new system utilizes 10 m fans and only requires 30 units (Figure 2). Installation of the larger fans required higher capital costs; however operation, maintenance, and power saving costs resulted in significant savings of over $1.6 million in the first year. Fewer fans result in fewer parts to be maintained. Also, direct drive motors are being utilized for the fans; therefore there is no need for belts or gearbox drives, which further reduces maintenance costs. The large-fan design has virtually eliminated hot air recirculation, thus increasing the cooling efficiency and plant output as well as reducing parasitic load compared to the conventional smaller fans. This new ACC design not only applies to geothermal but could apply to any air-cooled power plant.
Technical Problems and Solutions
Problems at the power plant have been relatively minimal; however necessary turbine upgrades were made in April and May of 2013, and the plant only had an operating capacity of 72.2% during the quarter. Another problem the plant suffered during the second quarter of 2013 was unseasonably high temperatures, and since the plant is air cooled the high outside temperatures caused a reduction in production. Besides those two minor issues, plant operations appear to be going very smoothly; no reports of any major problems have been made to date.
Geology of the Area
|Modern Geothermal Features:||Hot Springs|||
|Relict Geothermal Features:|
|Host Rock Age:||Miocene|||
|Host Rock Lithology:||Basalt|||
|Cap Rock Age:|
|Cap Rock Lithology:|
The Neal Hot Springs Geothermal Area is on the edge of the Oregon-Idaho Graben geologic formation (Figure 3). This formation consists of a synvolcanic graben straddling the western margin of the North American craton. The Oregon-Idaho formation has been interpreted as a relatively modern part of the Mesozoic cratonic boundary and/or as a northwestern arm of the Basin and Range. Normal faulting dominates the formation and extensional direction is east-west as indicated by north-striking fault and dike structures.
The Vale Fault Zone borders the western edge of the geothermal area (see figure). The Vale formation consists of segmented north-west trending, oblique-slip faults and lineaments. It makes up the northern end of the Basin and Range and is dominated by west-north-west extension. The two extensional geologic formations that intersect at Neal Hot Springs form complex fault trends and an area of anomalously thin continental crust.
The Neal Hot Springs Geothermal Area consists of hot springs that emanate from opaline sinter mounds located north of Bully Creek. The geothermal area is located in a broad zone where a regional north-striking normal fault system and a north-west-striking normal fault system intersect (Figure 4). The north-striking fault system is within the Oregon-Idaho Graben and the northwest-striking system is in the Snake River Plane, also known as the Vale Fault Zone. Both of the fault zones look as if they have had Quaternary displacement. It is believed that the high permeability facilitating hydrothermal activity in the geothermal area is caused by multiple fault splays and horse-tailings at the fault intersections of the west-dipping fault zone. Geologic mapping and geophysical studies show that the most dominant structures at the hot springs are steeply-dipping (60°) normal faults to the southwest that form a half-graben basin.
The Neal Hot Springs Geothermal Area sits within Paleogene/Neogene volcanic and volcanoclastic rocks, containing basalt flows, ash-flows, dikes, tuffs, and tuffaceous lake sediments. The regional stratigraphy consists of five main formations and numerous sub-formations. The main formations are the Basalt of Malheur Gorge, the Hog Creek Formation, the Calc-alkaline Flows, the Alkalic Flows, and various sedimentary deposits. The Basalt of Malheur Gorge is considered the basement rock in the geothermal area because it is the oldest known stratigraphic unit in the area. Well logs from the geothermal area pass through many different formations and sub formations. Figures 5 and 6 illustrate the stratigraphy found in the geothermal system.
Fault trends from the Oregon-Idaho Graben and the Western Snake River Plain intersect at Neal Hot Springs and produce pathways for the geothermal fluids to reach the surface. A large fault dipping 60° to the southwest was detected in seismic and electrical surveys and is likely the main pathway for heated water flow in the geothermal system. The area has high geothermal gradients, due to complex extensional tectonics, which cause thin crust and high permeability in the area. The main upwelling of geothermal fluids is thought to come from a fault to the west of the hot springs. There is also a hydrothermal system related to a fault to the east which brings up fluid of lower temperature, although it is unclear whether the eastern fault is connected to the main reservoir or not.
Thermal activity at Neal Hot Springs is structurally controlled. Crustal extension has thinned the crust and provided a shallow regional heat source. This anomalously thin crust is the cause of such high thermal gradients.
Geothermometry analysis was done on geothermal fluids from the first production well to estimate the reservoir temperature at deeper locations. Chalcedony and sodium-potassium-calcium geothermometers were analyzed. The chalcedony geothermometer indicated reservoir temperatures of 161° C and the sodium-potassium-calcium geothermometer indicated reservoir temperatures of 177° C.
NEPA-Related Analyses (4)
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.
|DOE-EA-1676||EA||US Geothermal Inc||2 December 2009||United States Department of Energy||Geothermal/Power Plant|
|DOI-BLM-OR-V040-2009-0059-CX||CX||US Geothermal Inc||17 September 2009||14 November 2009||Bureau of Land Management||Geothermal/Exploration|
|DOI-BLM-OR-V040-2009-0059-EA||EA||US Geothermal Inc||2 December 2009||United States Department of Energy||Geothermal/Power Plant|
|DOI-BLM-OR-V040-2011-0008-EA||EA||US Geothermal Inc||18 October 2010||2 June 2011||Bureau of Land Management||Geothermal/Well Field||Development Drilling
Well Testing Techniques
Exploration Activities (23)
Below is a list of Exploration that have been conducted in the area - and cataloged on OpenEI. Add a new Exploration Activity
- U.S. Geothermal Announces Successful Completion of First Well At Neal Hot Springs
- Benjamin Matek. Geo-energy [Internet]. Geothermal Energy Association. [updated 2015/04/28;cited 2015/04/28]. Available from: http://geo-energy.org/
- 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.
- U.S. Geothermal Inc. (U.S. Geothermal Inc.). 2013. U.S. Geothermal Inc. Announces Final Completion of the Innovative Technology Neal Hot Springs Power Plant. Boise, Idaho: U.S. Geothermal Inc.. Report No.: N/A.
- U.S. Geothermal Inc.. U.S. Geothermal Inc. Neal Hot Spring Project [Internet]. [updated 2013;cited 2013]. Available from: http://www.usgeothermal.com/NealHotSpringProject.aspx
- U.S. Geothermal Inc.. 2012. U.S. Geothermal Inc. and Subsidiaries. Washington, D.C.: UNITED STATES SECURITIES AND EXCHANGE COMMISSION. Report No.: 001-34023.
- U.S. Geothermal Inc. (U.S. Geothermal Inc.). 2009. U.S. Geothermal Signs Interconnection Agreement for Neal Hot Springs Power Project. Boise, Idaho: U.S. Geothermal Inc.. Report No.: N/A.
- U.S. Geothermal Inc. (U.S. Geothermal Inc.). 2008. U.S. Geothermal Receives Drilling Permit for Neal Hot Springs Project. Boise, Idaho: U.S. Geothermal Inc.. Report No.: N/A.
- U.S. Geothermal Inc. (U.S. Geothermal Inc.). 2008. U.S. Geothermal Announces Successful Completion of First Well at Neal Hot Springs. Boise, Idaho: U.S. Geothermal Inc.. Report No.: N/A.
- U.S. Geothermal Inc. (U.S. Geothermal Inc.). 2009. U.S. Geothermal Completes Second Successful Production Well at Neal Hot Springs Project. Boise, Idaho: U.S. Geothermal Inc.. Report No.: N/A.
- U.S. Geothermal Inc. (U.S. Geothermal Inc.). 2010. Idaho Public Utilities Commission Approves Neal Hot Springs Power Purchase Agreement. Boise Idaho: U.S. Geothermal Inc.. Report No.: N/A.
- U.S. Geothermal Inc. (U.S. Geothermal Inc.). 2010. U.S. Geothermal Drills Prolific Well at Neal Hot Springs. Boise, Idaho: U.S. Geothermal Inc.. Report No.: N/A.
- U.S. Geothermal Inc. (U.S. Geothermal Inc.). 2010. U.S. Geothermal Drills Another Prolific Well at Neal Hot Springs Completes Production Wells Needed for Project. Boise Idaho: U.S. Geothermal Inc.. Report No.: N/A.
- Colorado School of Mines and Imperial College London (Colorado School of Mines and Imperial College London). 2011. Geophysical Characterization of a Geothermal System Neal Hot Springs, Oregon, USA. Golden, Colorado: Colorado School of Mines and Imperial College London. Report No.: N/A.
- U.S. Department of Energy. 2009. Environmental Assessment for Department of Energy Loan Guarantee for U.S. Geothermal’s Neal Hot Springs Geothermal Facility in Vale, Oregon. Washington D.C.: U.S. Department of Energy. Report No.: DOE/EA-1676.
- U.S. Geothermal Inc.. U.S. Geothermal Inc. / Gallery [Internet]. [updated 2013;cited 2013]. Available from: http://www.usgeothermal.com/Gallery.aspx?p=NealHotSpring
- U.S. Geothermal Inc.. 2012. Two of Three Power Plant Modules at Neal Hot Springs Are Producing up to 16.8 Megawatts. Boise, Idaho: U.S. Geothermal Inc.. Report No.: N/A.
- U.S. Geothermal Inc. (U.S. Geothermal Inc.). 2008. U.S. Geothermal Announces More Test Results from the Neal Hot Springs Production Well and a Key Addition to Senior Staff. Boise Idaho: U.S. Geothermal Inc.. Report No.: N/A.
- U.S. Geothermal Inc.. 2010. US Geothermal Updates Status of Development Projects New Wells Drilled at Neal Hot Springs. Boise Idaho: (!) . Report No.: N/A.
- Kevin Kitz,Ryan Elliott,Ian Spanswick. 2012. Economic and Performance Benefits Resulting From the Use of Large Diameter Fans on Air Cooled Heat Exchangers (A Case Study in the Use of Large Fan Air Cooled Condensers at the Neal Hot Springs Geothermal Power Plant, Oregon). Geothermal Resources Council Transactions. 36(N/A):95-103.
- Joel H. Edwards,James E. Faulds. 2012. Preliminary Assessment of the Structural Controls of Neal Hot Springs Geothermal Field, Malhuer County, Oregon. Geothermal Resources Council Transactions. 36(N/A):891-895.
- Clinton Colwell,Kasper VanWijk,Lee Liberty,Ian Warren,Andre Revil. 2012. Integrated Geophysical Exploration of a Known Geothermal Resource: Neal Hot Springs. N/A: Society of Exploration Geophysicists. p.
List of existing Geothermal Resource Areas.
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