North Brawley Geothermal Area
Geothermal Area Profile
|Exploration Region:||Gulf of California Rift Zone|
|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:||266°C539.15 K
|Estimated Reservoir Volume:||10.21 km³10,210,000,000 m³
|Mean Capacity:||50 MW50,000 kW
|USGS Mean Reservoir Temp:||250°C523.15 K
|USGS Estimated Reservoir Volume:||9 km³|||
|USGS Mean Capacity:||138 MW|||
The North Brawley Geothermal Area lies within Imperial Valley, in southern California between the Salton Sea and the U.S. - Mexico border. Nine other geothermal areas have been identified in Imperial Valley, four of which have been developed. The Salton Sea Geothermal Area is the largest and most highly productive geothermal area in Imperial Valley. The other developed geothermal fields are East Mesa Geothermal Area, Heber Geothermal Area, and the North Brawley Geothermal Area. The four undeveloped geothermal areas are also located within Imperial Valley are: Mt Signal Geothermal Area, South Brawley Geothermal Area, Pilger Estates Hot Springs Geothermal Area, and Chocolate Mountains Geothermal Area. The East Brawley Geothermal Area is in the process of being developed; drilling of wells and construction of a 50 MW power plant began in 2012. Out of all the geothermal areas in Imperial Valley, North Brawley was first to be utilized, with a 10 MW experimental power plant that went online in 1980. The small experimental power plant was only in service for five years before being decommissioned.
North Brawley is also the most recently developed geothermal area with a new 50 MW binary power plant (Figure 1) that was completed in 2008. The North Brawley power plant is owned and operated by Ormat Technologies, Inc. and was placed into service under a 20-year Power Purchase Agreement with Southern California Edison (SCE) on January 15, 2010.The new power plant consists of five Ormat Energy converter units that are all water cooled. The working fluid in the binary rankine cycle is isopentane.
History and Infrastructure
Operating Power Plants: 1
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Developing Power Projects: 0
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Power Production Profile
|Gross Production Capacity:||35 MW35,000 kW
|Net Production Capacity:|
|Power Purchasers :||
Geothermal resources in the Imperial Valley have been recognized for over a century, but early development ran into difficulties due to the presence of hypersaline geothermal fluids, which cause harsh corrosion and scaling problems and make development problematic and expensive. The early development attempts in the 1960s in Imperial Valley were not successful and development halted until the oil crisis in the 1970s, which sparked a shift towards the development of alternative energy and put geothermal energy back on the table in Imperial Valley.
In 1975 Union Oil Company (Unocal) began drilling deep exploration wells in the North Brawley Geothermal Area and the Salton Sea Geothermal Area. Early in 1975 a discovery well was drilled about 3.2 km north of the town of Brawley; it led to further drilling and the construction of a 10 MW experimental plant which was completed in 1980 and operated by SCE. In 1980 there was also a proposal to directly utilize hot water from North Brawley for sugar beet processing, but this project was cancelled due to lack of flow from the well drilled for the project. The experimental power plant project continued, however, and was the first successful flash-steam project in the U.S. It demonstrated that steam from high salinity brine could be utilized for power production.
The high salinity brines produced from the reservoir ranged from 5% -25% salt by weight. Operation of the power plant is complicated by high concentrations of dissolved solids in the geothermal fluids. Observed scaling rates of up to 76 cm/year were recorded. Scaling due to these dissolved solids created the need to periodically shut the plant down for maintenance, however the plant has maintained an average capacity factor of 52%. Scales often clogged reinjection pumps, filtration screens, and control valves. Injection and production wells would also collect buildup of scaling which, over time, reduced steam supply to the power plant. The plant was decommissioned in 1985 due to heavy metal sulfide scaling problems in the production wells. The power plant was designed to be portable, and the turbine and generator were mounted to a single skid unit. The turbine and generator were later transported and reused at the Salton Sea Geothermal Area. The total capital cost of the experimental plant, including some costs from prior research, was approximately $16.3 million. The plant operated at 10 MW (gross) and had 0.8 MW of parasitic load, which resulted in a net gain of 9.2 MW. This was sold to the Imperial Irrigation District for about 17 ¢/ KWh. Overall, the experimental power plant was a successful project because a great deal was learned about how to utilize geothermal fluids with high levels of dissolved solids and corrosive gases.
The 10 MW experimental power plant utilized the deep high temperature (>200°C) fluids from the reservoir, which resulted in an un-economical approach, due to scaling and corrosion problems from the hypersaline fluids and non-condensable gasses. The new approach that Ormat has taken with its 50 MW binary plant at North Brawley is utilization of lower temperature (149-204°C), shallower fluids in a zone of matrix dominated permeability. There are fewer dissolved solids in this fluid, so the hope is that scaling and corrosion problems will be more manageable. This approach has not yet proven to be economical due to problems with injection wells and failures of pumps, as discussed in the Technical Problems section of this review.
Exploration wells for the new power plant were drilled by Ormat beginning in 2007. The exploration wells were drilled to test the geothermal fluids in shallow sands for their scaling and corrosion properties. Five wells were drilled in total; they ranged in depth from 967-1372 m and temperatures from 137-186 °C. Data collected from the wells indicate that the geothermal brine was of sufficient temperature, with low heavy metal concentrations, and not hypersaline, thus could be utilized for commercial power generation.
North Brawley Area Timeline
1960s: Early development attempts in Imperial Valley fail.
1970s: Oil crisis sparks renewed interest in geothermal resource exploration in Imperial Valley by Unocal, Chevron, and Grace Geothermal Company.
1975: Unocal and Chevron begin deep exploration drilling in the North Brawley and Salton Sea areas.
1980: A 10 MW experimental power plant operated by South California Edison is brought online at North Brawley, becoming the first successful flash-steam project in the U.S.
1985: The North Brawley power plant is decommissioned due to heavy metal sulfide scaling problems in the production wells. The portable power generation unit was moved and reused at the Salton Sea Geothermal Area.
2006: Ormat Nevada, Inc. resumes geothermal exploration and development in the North Brawley area.
2007: Ormat begins drilling wells for a new power plant. The wells accessed a lower temperature brine with lower dissolved solid content that was more favorable for geothermal power production.
Regulatory and Environmental Issues
The main environmental concern regarding the utilization of fluids from the North Brawley Geothermal Area is sinking of the land. Land subsidence is closely monitored and could become a potential disaster because the area is mainly agricultural land. The elevation at North Brawley is 41 m below sea level, so even a small amount of subsidence could easily disrupt water flow patterns and irrigation systems in the surrounding agricultural areas. To date, no major problems related to ground subsidence have been reported at North Brawley.
Another ongoing issue at North Brawley is regulating the scaling and corrosion problems caused by the hypersaline geothermal brine. Scaling problems have been the main culprit of equipment failures, well production decline, and temporary shutdowns of the power plant. Scaling was the reason the original experimental power plant was decommissioned and the reason the new binary power plant is losing money. Non-cash impairment charges caused North Brawley to have a net loss of $236.4 million in 2012. Most of the unexpected costs and lower-than-expected production have been related to equipment failures due to scaling and corrosion.
There are no future plans to expand production at North Brawley as of 2013.
First Discovery Well
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Geothermal exploration in Imperial Valley began in the 1960s, but the first geothermal exploration specifically at North Brawley began in the 1970s by Union Oil Company (Unocal), Chevron Oil Company, and Grace Geothermal Company. Many geophysical studies were conducted and many temperature gradient wells were drilled during the initial exploration in the early 1970s. Unocal drilled a total of 39 temperature gradient wells at a depth of 76 m and Grace Geothermal Corporation drilled 13 at a depth of 152 m. The thermal gradient wells revealed an anomaly roughly 26 km2 with a temperature gradient of 7°C/30 m. In 1975, Unocal began drilling deep exploration wells-- 14 in total. Chevron also drilled two deep wells on the western side of the known geothermal area. The geothermal reservoir was discovered to have temperatures of 274°C at 1524-2134 m depth. The reservoir is highly fractured and productive with well head pressures of around 450 psig and mass flow rates of 5292-7560 kg/s.
In 1980, a 10 MW experimental power plant began operations for several years. After the plant shut down there was little exploration activity at North Brawley until 2006, when Ormat Nevada, Inc. restarted exploration and development practices in North Brawley.
Many geophysical studies have been done in North Brawley throughout the years: seismic refraction, electrical resistivity, and gravity, to name a few; however the details on many of these studies are proprietary and in unpublished reports. A large amount of regional geophysical studies have been done as well; these studies cover the entire Imperial Valley but do not focus specifically on North Brawley. The Salton Sea Geothermal Area has been the focus of the majority of geophysical studies for geothermal areas in the region.
Well Field Description
Well Field Information
|Number of Production Wells:|
|Number of Injection Wells:|
|Number of Replacement Wells:|
|Average Temperature of Geofluid:||520 271°C544.15 K
|Sanyal Classification (Wellhead):||High Temperature|||
|Reservoir Temp (Geothermometry):|
|Reservoir Temp (Measured):|
|Sanyal Classification (Reservoir):||High Temperature|||
|Depth to Top of Reservoir:||1524 m1.524 km
|Depth to Bottom of Reservoir:||4572 m4.572 km
|Average Depth to Reservoir:||2286m2.286 km
Early development of the North Brawley well field began in the 1970s. Three companies drilled wells between 1970 and 1980: Unocal, Chevron Oil Company, and Grace Geothermal Company. A total of 52 thermal gradient wells ranging in depth from 76-152 m, as well as 16 deep exploratory wells were drilled during the early exploration period (Figure 2). In 2007, exploratory drilling commenced for the new power plant owned by Ormat, producing a total of 5 new wells that ranged in depth from 967-1372 m and temperatures from 137-186°C.
Research and Development Activities
North Brawley has been the site of intense R&D for methods for utilizing hyper-saline brines and mitigating scaling and corrosion problems. The 10 MW experimental plant was the beginning of efforts to learn about proper procedures and equipment to use when utilizing fluids saturated in dissolved solids. Another example of successful research that occurred at North Brawley is a study conducted using iridium-192 radiography. The goal of this research was to find a method that could be used to detect scaling in pipelines without having to dismantle the pipes. Using this method, the thickness of scale in pipelines can be detected to within 1-2 mm accuracy without having to stop power plant operations. Corrosion in pipelines can also be detected using this method.
Technical Problems and Solutions
The new North Brawley Power Plant has faced several challenges which have prevented full power production since it began operation. The plant is designed for a capacity of 50 MW; however, since it began operation in 2008 it has only produced between 20 and 33 MW. The reasons for lower production are un-dissolved sand in geothermal fluids, injection field circulation pathways being inhibited, problems with filtration and cleanout of injection wells, and failures of production pumps in the early operation. These problems have caused a net loss of revenue for Ormat due to lower energy production and unexpected costs related to problems with the injection well filtration and separation systems, drilling and modifying injection wells, adding injection pumps, adding new production wells, and building the pipelines for new wells. When the plant was placed into service the well field had a capacity of 35 MW; however, production was less because some wells were forced to be left idle until improved pumps could be installed.
Ormat decided in January 2013 to stop pouring money into investments for raising the power output and to instead settle with the current output of approximately 27 MW. As a result of this decision, Ormat expects to record a non-cash pre-tax charge for impairment. The impairment charge is estimated to be up to $230 million; however Ormat believes the impairment charge will not cause them to default on their other financial obligations, nor will it negatively affect future operations.
Geology of the Area
|Controlling Structure:||Displacement Transfer Zone, Fault Intersection|||
|Brophy Model:||Type D: Sedimentary-hosted, Volcanic-related Resource|||
|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 of possible values (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) for this property.|
|Modern Geothermal Features:||Blind Geothermal System|||
|Relict Geothermal Features:|
|Host Rock Age:|
|Host Rock Lithology:||Arkosic and quartz dominated sandstones|||
|Cap Rock Age:|
|Cap Rock Lithology:||Clay-dominated rock|||
The North Brawley Geothermal Area sits within Imperial Valley, in southern California between the Salton Sea and the U.S. - Mexico border. Imperial Valley is made up of a large fault zone that separates the North American Plate from the Pacific Plate. The Brawley Seismic Zone, in the center of Imperial Valley, is at a transitional zone where the southern tip of the San Andreas Fault and the northern Imperial Fault meet. The faulting patterns are complicating and there are likely numerous secondary faults that do not have an obvious surface expression. The area is susceptible to large earthquakes and surface rupturing. In August of 2012, the Brawley area experienced an earthquake swarm with the largest event being magnitude 5.4. Luckily, because it is a rural area, no one was hurt and very little damage was done to buildings.
Imperial Valley is a wide, flat, featureless expanse of land that stretches from the Mexico border to the Salton Sea. There are several small volcanic hills in the northern and southern ends of Imperial Valley. Elevations in the valley range from 14 m above sea level to 70.4 m below sea level at the Salton Sea. The elevation at the North Brawley Power Plant is 41 m below sea level. Natural subsidence and subsidence rates due to geothermal utilization are closely monitored in the valley; due to the low elevation, agricultural lands can be negatively affected if subsidence due to geothermal production is not controlled.
The North Brawley Geothermal Area lies within Imperial Valley, which is part of the Salton Trough, a geologic feature that stretches through the valley from the Salton Sea to the Gulf of California and contributes the heat for geothermal resources within Imperial Valley. The San Andreas Fault runs through the Salton Trough, causing a spreading center. The fault zone mostly trends northwest to southeast, but the region is very complex structurally. In the Salton Trough there is a zone of en echelon adjustments along the San Andreas Fault system including the North Brawley Geothermal Area. A minor fault called the Brawley Fault Zone runs right through the geothermal area. The northern end of the Brawley Fault begins in the geothermal area and trends northwest to southeast. This fault has had microseismic activity associated with it and is considered to be capable of future displacement. In 1975, a low magnitude earthquake swarm at depths between 4 and 8 km occurred along the Brawley Fault Zone. Besides the faults, the geologic structure of the area is nothing more than flat agricultural land that lies over wide alluvium and marine deposits.
The Imperial Valley floor makes up a trough filled with tertiary aged, deltaic, and lacustrin sands and shales. The surface layer is made up of Quaternary alluvial lacustrine and some volcanic materials. The sedimentary basin is roughly 6700 m deep before bedrock is reached. Dominant lithological features found from drill holes are thick layers of clay-dominated rocks consisting of more than 75% clay. These clay layers are between 300 and 600 meters deep and form a cap rock that seals the geothermal system. The cap rock has caused very limited vertical circulation of fluids, which has resulted in the buildup of excess heat in the system. Below the clay-dominated cap rock are sections of arkosic and quartz-dominated sandstones.
Typical lithology has been derived from a geothermal well (Jiminez 1). It is as follows:
- 0-113 m: Unconsolidated sediments made of soft clays, gravel, pebbles, and sand
- 113-162 m: Mostly brown and grey clay with thin bands of sand
- 162-253 m: About 60% brown and grey clay and 40% silt and unconsolidated sand
- 253-469 m: About 80% brown and grey clay and 20% silt and unconsolidated sand
- 469-549 m: About 80% brown and grey calcareous clay stone and 20% fine grained, semi-consolidated, calcite cement, arkosic, sandstone, and some clay
- 549-966 m: About 50% Calcareous fissile clay stone and 50% fine grained, semi-consolidated, calcite cement, arkosic, sandstone, and some clay. Pyrite, quartz, and calcareous siltstone grains begin to show
- 966-2932 m: 65-75% calcareous shale, 20-30% very fine to medium grained semi-friable calcite cemented quartz sandstone with pyrite crystals, nodules, and cement between some quartz grains.
Groundwater in the Imperial Valley flows toward the center of the valley and northwesterly toward the Salton Sea. The main sources of groundwater are from the Colorado River, irrigation water, and canal seepage. The geothermal reservoir exists within arkosic- and quartz-dominated sandstones which lie beneath a clay cap rock layer at 300-600 m depth. The geothermal system is, for the most part, separated from shallow ground water flow, so there is very little natural recharge of the geothermal system and recharging requires injection wells.
The heat source for North Brawley and the Imperial Valley region is believed to be due to plate movements causing the valley to spread. The spreading causes basement rock at depths of 5-6 km to fracture, allowing hot magma to seep up. The hot magma is the source which is heating deep groundwater.
The most current reservoir information indicates that the main central portion of the Brawley geothermal anomaly is egg-shaped and roughly 13 km2. At current utilization depths of around 915 m, the highest measured temperature is 210°C and the average temperature of the geothermal brine being utilized is 149°C.
|Brine Constituents:||chlorine, sodium, potassium, and calcium. Silica concentrations are 527 mg/l and total dissolved solids measure 82,900 mg/l.|||
The North Brawley Geothermal Reservoir is classified as a high temperature (>260°C), hyper-saline brine resource, with levels of total dissolved solids exceeding 20%. Geothermal fluids at North Brawley are saturated in dissolved solids, which have caused problems by precipitating out of solution, thus clogging pathways and limiting circulation in production and injection wells.
Detailed geochemistry tables are provided in an environmental impact report prepared in 1979 before the first experimental power plant was constructed. This report provides data on non-condensable gases recorded from two wells and chemical analysis of brine composition from geothermal fluid. The most dominant non-condensable gases are carbon dioxide, methane, nitrogen, hydrogen sulfide, and ammonia; other non-condensable gases such as hydrogen, boron, mercury, and arsenic are detected in trace amounts. Total non-condensable gas measured in weight percent of steam is between 7.1 and 9.4%. These non-condensable gases can cause rapid corrosion problems in steel casings and surface equipment.
Geothermal brine composition at North Brawley consists mainly of chlorine, sodium, potassium, and calcium. Silica concentrations are 527 mg/l, and total dissolved solids measure 82,900 mg/l. Other metals that are found in the reservoir fluids include lead (80-250 ppm), zinc (500-900 ppm), and anomalous silver concentrations. These metals form hard, dark, heavy scales which impede flow from the wells.
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.
|DOI-BLM-CA-670-2010-107||CX||Ormat Nevada, Inc.||17 December 2008||26 May 2010||BLM||Geothermal/Well Field||Production Wells|
Exploration Activities (16)
Below is a list of Exploration that have been conducted in the area - and cataloged on OpenEI. Add a new Exploration Activity
- Skip Matlick and Tim Jayne. 2008. Brawley—Resurrection of a Previously Developed Geothermal Field. GRC Transactions. 32(1):159-162.
- Geothermex Inc.. 2004. New Geothermal Site Identification and Qualification. Richmond, CA: California Energy Commission. Report No.: P500-04-051. Contract No.: 500-04-051.
- Karl Gawell. 04/03/2014. Statement of Karl Gawell, Executive Director, Geothermal Energy Association Before the Senate Select Committee on California’s Energy Independence & Assembly Select Committee on Renewable Energy Economy in Rural California. Personal Communication sent to Senate Select Committee on California’s Energy Independence & Assembly Select Committee on Renewable Energy Economy in Rural California.
- 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.
- PCL Construction Leaders. North Brawley Geothermal Power Plant Project Overview [Internet]. 2014. North Brawley Geothermal Power Plant. PCL Construction. [cited 2013/08/19]. Available from: http://www.pcl.com/Projects-that-Inspire/Pages/North-Brawley-Geothermal-Power-Plant.aspx#
- Mariana Eneva,David Adams,Giacomo Falorni,Jessica Morgan. 2013. Applications of Radar Interferometry to Detect Surface Deformation in Geothermal Areas of Imperial Valley in Southern California. In: PROCEEDINGS, Thirty-Eighth Workshop on Geothermal Reservoir Engineering. Stanford Geothermal Conference; 2013; Stanford University. Stanford University: (!) ; p. (!)
- Ormat Technologies, Inc.. Ormat Technologies Inc. North Brawley, California USA [Internet]. [updated 2013;cited 2013]. Available from: http://www.ormat.com/case-studies/north-brawley-california-usa
- Ormat Technologies Inc.. Ormat Technologies Inc. Ormat Technologies, Inc. Announces a Non-Cash Pre-Tax Charge for Impairment to Its North Brawley Geothermal Power Plant [Internet]. [updated 2013;cited 2013]. Available from: http://www.ormat.com/news/latest-items/ormat-technologies-inc-announces-non-cash-pre-tax-charge-impairment-its-north-braw
- Giza Singer Even. North Brawley Power Plant Asset Impairment Analysis [Internet]. 2012. [updated 2012/01/01;cited 2012/01/01]. Available from: http://www.sec.gov/Archives/edgar/data/1296445/000119312512118396/d316623dex991.htm
- Whitescarver, Olin D.. 1984. Development Operations Hypersaline Geothermal Brine Utilization Imperial County, California. (!) : U.S. Department of Energy. Report No.: N/A.
- Kendal S. Robinson. 1981. Status of Direct Heat Application Projects. Geothermal Resources Council Transactions. 5(N/A):563-566.
- Raymond Cedillo,Roger N. Yamasaki. 1981. The Brawley 10 MWe Power Plant, Unit 1. Geothermal Resources Council, TRANSACTIONS. .
- Lynn McLarty,Marshall J. Reed. 1992. The US Geothermal Industry: Three Decades of Growth. Energy sources. 14(4):443-455.
- D. L. Gallup. 1986. External Surveillance of Geothermal Scale Deposits Employing Iridium-192 Radiography. Geothermal Resources Council Transactions. 10(N/A):317-322.
- Darrell L. Gallup. 2011. Brine pH Modification Scale Control Technology. 2. A Review.pdf. GRC Transactions. 35(N/A):609-614.
- California Division of Oil, Gas, and Geothermal Resources. 1985. Brawley Power Plant Abandoned. Geothermal Hot Line. 15(2):76-77.
- Skip Matlick,Tim Jayne. 2008. Brawley Resurrection of a Previously Developed Geothermal Field. GRC Transactions. 32(N/A):159-162.
- R.C. Edmiston,W.R. Benoit. 1984. Characteristics of Basin and Range Geothermal Systems with Fluid Temperatures of 150°C to 200°C. In: Transactions. GRC Annual Meeting; 1984/08/26; Reno, NV. Davis, CA: Geothermal Resources Council; p. 417-424
- Think Geoenergy. Ormat's North Brawley plant with 17MW short of its 50MW potential [Internet]. [updated 40219;cited 2010]. Available from: http://thinkgeoenergy.com/archives/3654
- Ormat Technologies, Inc.. Ormat Technologies Inc. Ormat Technologies Reports 2012 Fourth Quarter and Year End Results [Internet]. [updated 2013;cited 2013]. Available from: http://www.ormat.com/news/latest-items/ormat-technologies-reports-2012-fourth-quarter-and-year-end-results
- Karen L. Jones, Patrick D. Johnson, Stephen Young (The Aerospace Corporation). 2011. Imperial Irrigation District: Geothermal Resource Assessment. Arlington, VA: The Aerospace Corporation.
- County of Imperial Planning Department. 1979. Final Environmental Impact Report: North Brawley Ten Megawatt Geothermal Demonstration Facility. (!) : WESTEC SERVICES, INC.. Report No.: N/A.
- Edmunds, Stahrl W.. 1977. Geothermal Development in Imperial County. Geothermal Resources Council, TRANSACTIONS. 1(N/A):81-83.
List of existing Geothermal Resource Areas.
Some of the content on this page was part of a case study conducted by: NREL Interns