Published by the New Mexico Bureau of Geology and Mineral Resources • A Division of New Mexico Tech

Summer 2006

Geothermal energy is theheat energy that is generatedand stored in the earth. Thisheat represents one of thelargest energy resources avail-able to mankind. Geothermalenergy can be used to produceelectricity economically, orthe heat may be applied in adirect-use fashion (such asgreenhouse heating) for anyprocess that requires largeamounts of hot water or low-grade steam less than 300° F.When used in a sustainablemanner, geothermal energy isa renewable energy resource.Geothermal energy has a smaller landand environmental footprint than allcurrently used conventional and renewable energy technologies.Practically no carbon dioxide emissionsresult from geothermal energy use.Because geothermal energy producescontinuous or base load power, electricity production in the UnitedStates from geothermal energy wasgreater than the power produced bywind and solar energy combined overthe last ten years. When geothermalenergy is applied in a direct-use fashion, substantial energy savingsaccrue to the user when compared tonatural gas. Given the large geothermalresource base in New Mexico and thehuge array of potential applications, theenvironmental and economic benefitsto the state could be enormous.

Geothermal ResourcesAccessible geothermal resources represent the heat that is stored in the

conventionally drillable upper part ofthe earth’s crust. This heat is continuallyaugmented by radioactive decay of natural uranium, thorium, and potassiumin the earth’s crust, and by heat that isconducted into the crust from the hotter core and mantle below. In otherwords, the crust acts as a low-gradenuclear reactor, with added heat fromthe earth’s interior. In regions withyoung and active volcanoes, locallyintense heat may be introduced intothe crust by magma that rises upwardfrom partially melted regions of themantle through weaknesses in the crust.

The most economic geothermalresources result from geologic processesthat allow convection to concentratedeep-seated heat at economically drillable depths. All current geothermalusers in New Mexico use convectiveresources that naturally circulate waterthrough deep-seated bedrock, sweepingup the heat and transporting it upwardinto shallow reservoirs. Fault zones can

help concentrate and redirectthe hot water flow upward.Where these systems intersectthe surface, hot springs arefound. Heat from active oryoung volcanoes is not necessarily required for thistype of geothermal resource.The subsurface shape of a typical convective geothermal reservoir may resemble a smallisolated summer cumulo-nimbus cloud or thunderhead.The lateral outflow plume ofgeothermal convection is analogous to the anvil orstretched top of the thunder-

head, whereas the upflow zoneresembles the rising cauliflower-likebulk of the thunderhead. The mostpermeable portions of the upflow zoneand the shallow lateral discharge aremost easily and economically exploited.

Some of the largest geothermalresources in New Mexico are associatedwith deep and confined (artesian)aquifers or conductive geothermalreservoirs. Temperatures in conductiveresources result from the increase intemperature with depth. Most of thewestern half of New Mexico has hightemperature gradients that typicallyrange from 1.6° F to 2.5° F per 100feet in depth (as opposed to 1.1° F to1.4° F per 100 feet in depth typicallyfound elsewhere). Because deep wellsare required to tap these resources, theyhave higher upfront costs. However,where large heating loads are required,the overall economics have advantagesover fossil fuels.

GEOTHERMAL ENERGY IN NEW MEXICO

Snapdragons at Burgett Geothermal Greenhouses near Cotton City.

NEW MEXICO EARTH MATTERS 2 SUMMER 2006

Classification of Uses and ResourcesA common geothermal resource classification uses temperature. High-temperature resources are greater than350° F and are suitable for large-scaleelectrical generation for sales on thetransmission grid. Intermediate-temperature resources are between 190°and 350° F and are increasingly usedfor smaller-scale power generation forsales over the grid or for on-site power.Low-temperature resources are less than190° F and at least 15° to 30° F abovethe local mean annual surface temperature. Low-temperature resourcesare the most common in New Mexico.They can be used in a variety of direct-use geothermal heating applications,including greenhouses, aquaculture(fish farms), space and district heating,and many industrial uses such as cook-ing, curing, or drying that require largeamounts of low-grade heat. High- and

intermediate-temperature geothermalresources may also be used indirect-use applications by “cascad-ing” residual heat from powerproduction to lower-temperatureapplications, enhancing the overallefficiency and economics of use.

Current Geothermal Use in New Mexico Electric PowerGeothermal electricity has beenproduced at the 30-acre BurgettGeothermal Greenhouse in theAnimas Valley near Cotton City.The facility extracts energy in acascaded fashion, whereby 230° Fwater from geothermal wells is first fedinto the power plant heat exchangers ata rate of 1,200 gallons per minute; the185° F outflow from the power plant isused to heat greenhouses. Electricity isproduced with binary-cycle power technology that employs heat exchangersto allow the geothermal water to boil asecond, lower-boiling-point workingfluid (in this case isopentane). Thepressurized vapor of the working fluidcirculates in a closed loop to drive turbines in three modular units and togenerate almost 1 megawatt of electricity,most of which is used on location. TheBurgett power plant is currently shutdown for modifications.

Geothermal AquacultureGeothermal energy offers several advan-tages for fish culture. Many species have

accelerated growthrates in warm water.Geothermal water canbe used as a growthmedium, adding to theagriculture receipts inthe state without consumptive use ofvaluable fresh water.The AmeriCultureTilapia Farm atCotton City raisestilapia, a tasty warmwater fish that isbecoming increasinglypopular. TheAmeriCulture TilapiaFarm is heated with a400-foot-deep geother-mal well, at muchlower costs than it

could be heated with fossil fuels. Fromeggs produced on site, AmeriCulturegrows and markets tilapia fry to growersand researchers nationwide and sellsadult tilapia to restaurants across theSouthwest. In addition, AmeriCulturehas contracted Barber-Nichols, Inc. ofDenver, Colorado, to design a binary-cycle power plant to provide electricityfor the fish farm water pumps andrefrigeration. Funding is providedthrough a cost-share grant with theU.S. Department of Energy.

Geothermal Space and District HeatingThe aridity and high elevation of partsof New Mexico create significant heatingloads on cold winter nights. Whereshallow geothermal resources co-existwith large heating demands, geothermalspace and district heating have costadvantages over fossil fuels. A districtgeothermal heating system on the NewMexico State University campus in LasCruces was in operation from 1982until 2004. It used as much as 260 gallons per minute of 147° F water,pumped from a depth of 744 to 971feet with a campus geothermal well.Geothermal water was passed through aheat exchanger to heat fresh water thatwas fed into hot water loops on campusas needed. The cooled geothermalwater was injected back into the reservoir margin beneath the campusgolf course. Geothermal water was usedto heat dorms, academic buildings, andathletic facilities on the eastern third ofthe campus. The system also providedhot water for showers in the dorms andathletic facilities. At present, the

Tilapia fry fromeggs produced onsite at AmeriCulture,Inc. near Animas, New Mexico.

Temperature ranges of applications ideally suited to geothermalenergy (modified from Geothermal Energy Uses, courtesy of theGeothermal Education Office, 2005).

geothermal injection well requiresreplacement, and the system needsupgrades after 22 years of service.

At Gila Hot Springs, a 300-foot-deepflowing well provides 165° F water forgeothermal heating of a trailer court,rental cabins, store, and several homes.The New Mexico Institute of Miningand Technology at Socorro is currentlyassessing the feasibility of installing acampus geothermal district heating system in conjunction with a cost-sharegrant from the U.S. Department ofEnergy.

Geothermal GreenhousesThe best-known use of geothermalenergy in New Mexico is for green-houses. Geothermal greenhousesaccount for nearly half of the green-house acreage in the state. New Mexicoleads the nation in geothermal green-house acreage. The success and growthin the geothermal greenhouse industryin New Mexico can be attributed toseveral factors, including abundant sunshine and low humidity, inexpensiveland, co-existence of geothermalresources with fresh water, a good agricultural labor force, and favorableshallow geothermal resources. Currentgeothermal greenhouses use wells less

(30 acres) near Cotton City is probablythe largest business in Hidalgo County.The Masson Radium Springs Farmgeothermal greenhouse (16 acres) is thelargest employer in northern Doña Ana

NEW MEXICO EARTH MATTERS 3 SUMMER 2006

than 1,000 feet deep, with resourcetemperatures ranging from 143° to230° F.

Geothermal Heat PumpsGround-coupled heat pumps allowspace heating and cooling through theuse of heat exchange loops that areburied horizontally in the ground orinstalled vertically in wells. In winter,heat is extracted from the earth andconcentrated by the heat pump forindoor heating. In summer, indoor heatis removed and placed in the ground.Several large geothermal heat pumpinstallations heat and cool publicschools in New Mexico.

Economic ImpactThe geothermal heating cost for NewMexico geothermal greenhouses is currently less than $1.50 per millionBtu, compared to more than $11 permillion Btu for natural gas with boilerlosses. This represents a savings of morethan $2.5 million for the state’s twolarge geothermal greenhouses.Geothermal greenhouse sales are esti-mated at $27 million and rank amongthe top ten in agriculture sector grossreceipts in the state.

The Burgett Geothermal Greenhouse

NMSU/SWTDI Doña Ana 0.5 1.4 $14,000 aquaculture

Masson Radium Springs Farm Doña Ana 30.0 79.0 $790,000 16-acre greenhouse

Radium Hot Springs Doña Ana 0.3 0.8 $8,000 spa

Faywood Hot Springs Grant 0.9 2.3 $23,000 spa

Gila Hot Springs Grant 2.1 5.4 $54,000 district heating

Burgett Geothermal Greenhouse Hidalgo 70.1 184.2 $1,800,000 30-acre greenhouse

AmeriCulture Tilapia Farm Hidalgo 9.0 23.7 $240,000 aquaculture

Ojo Caliente Rio Arriba 0.6 1.6 $16,000 spa

Jemez Springs Bath House Sandoval 0.9 2.3 $23,000 spa

Giggling Star, Jemez Springs Sandoval 0.6 1.6 $16,000 spa

Charles Motel, T or C Sierra 0.4 1.0 $10,000 spa

Fire Water Lodge, T or C Sierra 0.4 1.0 $10,000 spa

Geronimo Springs Museum, T or C Sierra 0.1 0.3 $3,000 space heating

Hay-Yo-Kay Hot Springs, T or C Sierra 0.4 1.0 $10,000 spa

Marshall Hot Springs, T or C Sierra 0.4 1.0 $10,000 spa

River Bend Hot Springs, T or C Sierra 0.4 1.0 $10,000 spa

Sierra Grande Lodge, T or C Sierra 0.4 1.0 $10,000 spa

Artesian Bath House, T or C Sierra 0.4 1.0 $10,000 spa

TOTALS 117.9 309.6 $3,057,000

Cacti at Southwest Technology DevelopmentInstitute’s geothermal greenhouse, NewMexico State University.

Estimated annual energy use and savings for geothermal applications in New Mexico. Figures assume an annual30 percent use of installed geothermal direct-use heating capacity.

Site County Installed Annual Annual Useheating energy use, energycapacity, billion savings

million Btu/hour Btu/year

County. Geothermal spas at OjoCaliente, Jemez Springs, Faywood HotSprings, Gila Hot Springs, and themany spas in Truth or Consequencesattract important tourism dollars toNew Mexico.

Future PotentialGeothermal development resembles oiland gas in leasing, royalties, anddrilling. Exploration and evaluation ofgeothermal resources borrow method-ologies used in oil and gas, groundwater, and mineral exploration.Geothermal energy is environmentallyfriendly. In most cases, spent geothermal fluids are injected back intothe reservoir. With the use of heatexchangers, harmful scaling and corrosion is eliminated and fluidscan be isolated from both the naturalenvironment and surface geothermalequipment.

One impediment to geothermalgrowth is the initial capital costsassociated with resource exploration,testing, and well drilling. However,geothermal energy has the advantageof low operations and maintenancecosts, without the volatility associatedwith fuel costs. Most of the surfaceequipment used by geothermal operations is “off the shelf ” and haswell-known engineering characteris-tics and costs. This is especially truewith direct-use installations.

The Valles caldera in the JemezMountains has proven geothermalreserves capable of generating asmuch as 20 megawatts or more ofpower. This resource has a probablemagmatic heat source.Environmentally sensitive

development of the Vallesgeothermal resource could provide royalty income to sustain and operate the VallesCaldera National Preserve andprovide cost-stable power to thesurrounding pueblos.

Small-scale geothermal electricpower at less than 20 megawattsis likely in the next few years atseveral sites in New Mexico.Some of the generation is likelyto be done in conjunction withcascaded direct use in a com-bined heat and power mode.

With the passage of theEnergy Policy Act of 2005, formerlyunfair federal royalty rules for direct-usegeothermal energy are being modified toallow for an equitable fee structure thatshould encourage additional growth. Inrecent years, the U.S. Department ofEnergy has sponsored an outreach pro-gram, Geopowering the West, to educatethe public and to encourage the development of all forms of geothermalenergy. The Web site for theGeopowering the West is found atwww.eere.energy.gov/geothermal/gpw/

Geothermal energy is a potentiallypowerful vehicle for rural economicdevelopment in New Mexico. Futureuses of geothermal energy may includechile and onion drying, cheese and milk

processing, and process heat for biofuelsrefining. Small-scale electrical powergeneration is very likely to expand inthe cascaded mode with direct-usedevelopment. Because deep-seatedsaline water and oil field brines may behot, geothermal desalinization andpower generation may augmentenhanced recovery of oil and gas andhelp sustain both our valuable watersupply and our petroleum industry. Forinstance, oil field water flood operationscould extract the heat of deep-seated oilfield brines to generate geothermalbinary-cycle power before reservoirinjection for enhanced oil recovery. Thepower would be used for pump jacksand other oil field electricity require-ments or placed on the transmissiongrid. The heat may also have use inmultistage vacuum distillation of brinesto produce desalinated water. The accessible geothermal resource base inNew Mexico is vast, and the options for economic use are growing.

—James C. WitcherWitcher and Associates

Las Cruces, New Mexico

Jim Witcher is a geologist with nearlythree decades of experience with geothermal exploration and development.

For More InformationThe following Web sites offer awealth of information on geothermal energy resources and development.

U.S. Department of Energywww.energy.gov

Geothermal Education Officewww.geothermal.marin.org

Geothermal Energy Associationwww.geo-energy.org

Geothermal Resources Councilwww.geothermal.org

National Renewable EnergyLaboratory

www.nrel.gov

All photos by Rob Williamson,courtesy of National RenewableEnergy Laboratory. Adult tilapiainset on page 2 courtesy of Damon Seawright of AmeriCultureTilapia Farm.

Geothermal resources in New Mexico.

Heat exchangers, pumps, and tank at MassonRadium Springs Farm geothermal greenhouses. Heatexchangers are used to transfer heat from geother-mal water to a closed-loop fresh water heatingsystem.

NEW MEXICO EARTH MATTERS 4 SUMMER 2006

NEW MEXICO EARTH MATTERS 5 SUMMER 2006

Volume 6, Number 2Published twice annually by the

NEW MEXICO BUREAU OF GEOLOGYAND MINERAL RESOURCES

Peter A. ScholleDirector and State Geologist

a division ofNEW MEXICO INSTITUTE OF

MINING AND TECHNOLOGYDaniel H. López

President801 Leroy Place

Socorro, New Mexico 87801-4796 (505) 835-5420

Albuquerque Office2808 Central SE Albuquerque

New Mexico 87106 (505) 366-2530

Visit our main Web sitegeoinfo.nmt.edu

Board of RegentsEx Officio

Bill RichardsonGovernor of New Mexico

Beverlee J. McClureSecretary of Higher Education

AppointedRichard N. Carpenter

President2003–2009, Socorro

Jerry A. ArmijoSecretary/Treasurer

2003–2009, Sante FeAnn Murphy Daily2005–2011, Santa FeSidney M. Gutierrez

2001–2007, AlbuquerqueMichaella J. Gorospe2005–2007, Socorro

Editors L. Greer PriceJane C. Love

Layout Thomas Kaus

GraphicsThomas Kaus Leo Gabaldon

Kathryn Glesener

Earth Matters is a free publication. Forsubscription information please call (505) 835-5490, or e-mail us at

pubsofc@gis.nmt.edu

Cover photo of Ship Rock, New Mexico© Gary Rasmussen

Marshall Reiter grew up in Pittsburgh,Pennsylvania, and graduated from theUniversity of Pittsburgh with a B.S.degree in physics. An interest in geophysics was sparked by RobertStoneley, a visiting professor fromCambridge, and Marshallcontinued his education ingeophysics at theUniversity of Utah andVirginia PolytechnicInstitute. His Ph.D.research on heat flow insouthwestern Virginiacaught the attention ofAllan Sanford, professor ofgeophysics at the NewMexico Institute of Miningand Technology, andMarshall was offered ateaching position inJanuary 1970. During his years in thedepartment, Marshall and his students’geothermal studies identified the RioGrande rift as a ribbon of high heat flowfrom central Colorado to El Paso.

Marshall moved from the college division of New Mexico Tech to the NewMexico Bureau of Geology and MineralResources in April 1975, although hecontinued to direct graduate students’research. From the late 1970s through theearly 1980s he and the students collectedheat-flow measurements in deep hydrocarbon wells to establish the regionalheat-flow gradient below ground waterflow. Their work suggested a lower crust-upper mantle heat source beneath the SanJuan Mountains in southwesternColorado, an interpretation that is consistent with recently published seismicinvestigations.

Geothermal studies continue to beMarshall’s main research interest as well asrock and earthquake mechanics. Trackingthe thermal history of the San Juan Basinled Marshall and his students back to newhydrogeothermal investigations in theSocorro area. In his current researchMarshall uses terrestrial heat flow measurements in the pursuit of regionalhydrologic information. Geophysicistshave long recognized that the conductivegeothermal gradient within the earth canbe disturbed by ground water flow, thusskewing the measurements of terrestrialheat flow. Conversely, they realized that

temperature logs not only provide heat-flow data but can also reveal characteristicsof the hydrologic regime. Marshall and hiscolleagues at New Mexico Tech have beenable to: (1) estimate rates of both horizontaland vertical (up and down) ground water

flow, (2) locate geologicfeatures that controlground water flow patterns,and (3) estimate regionalrecharge. Marshall hasstudied and interpretedheat-flow data and theirpossible correlation tohydrologic data throughoutNew Mexico: from the San Juan Basin and south-eastern boundary of theColorado Plateau to theAlbuquerque Basin andalong the Rio Grande rift

in the Socorro area, Jornada del Muerto,Roswell Basin, and Pecos River valley.

During the past few years Marshall hasbegun applying his geothermal studies inthe Albuquerque Basin to climate change.In the Southwest, heat transfer in thevadose zone, the unsaturated zone abovethe water table, is typically dominated byconduction. Monitoring temperatures inthe vadose zone may enable one to observechanging trends in ground surface temperature possibly related to changes inclimate. Loss of natural vegetation andpaving during urbanization seem to resultin ground surface heating at one study sitein the Albuquerque Basin.

Measurements of subsurface temperaturegradients and heat flow can also serve todetermine the depth and temperature atthe base of the crustal layer where mostcontinental earthquakes occur. Marshall iscurrently comparing the subsurface temperature gradients along the SanAndreas fault in California with thosealong the Coyote fault near Socorro, New Mexico.

In his 36+ years at New Mexico Tech,Marshall has published more than 60papers in professional journals and serialpublications. Marshall and his wife,Bonnie, have two sons and a daughter, andone grandson. Bonnie taught at SocorroMiddle School for 12 years as a readingspecialist. Since retiring from teaching,Bonnie often accompanies Marshall onfield trips to help with the measurements.

STAFF PROFILEMarshall Reiter

Principal Senior Geophysicist

Circular 212—Quaternary faulting and soil formation onthe County Dump fault,Albuquerque, New Mexico by J.P. McCalpin, S. S. Olig, J. B. J.Harrison, and G. W. Berger,2006, 36 pp., ISBN 1-883905-18-4. $10.00 plus shipping andhandling.

The Albuquerque–Santa Fe urbancorridor is one of the fastest growingareas in the western United States.Twenty-seven Quaternary-age faults have been identified with-in 40 km of downtown Albuquerque. The faults are associatedwith the Rio Grande rift and are responsible for 10 earth-quakes of MMI (Modified Mercalli Intensity) V or greatersince 1849.

The County Dump fault is a 35-km-long, north-trendingnormal fault that is located in an area of suburban developmentwest of the Albuquerque metropolitan area. The fault dipseastward under the city.

This study describes the recent activity of the County Dumpfault and assesses its potential earthquake hazard. To morefully understand the fault’s paleoseismic history, the authorsundertook a study that included measuring the height of thescarp formed by the fault, opening multiple trenches across thefault, describing stratigraphic and structural features in thetrenches and sampling soil horizons exposed, and collectingsamples for thermoluminescence dating. The pattern observedin the trenches suggests that the fault moves at intervals ofabout 20,000–40,000 years and results in displacements ofapproximately 1 m or less. The last three ground ruptures haveestimated ages of 30,000, 45,000, and 80,000 years ago. Thepublication includes detailed 2-color trench profiles and perspective drawings.

NEW MEXICO EARTH MATTERS 6 SUMMER 2006

New Mexico Bureau of Geologyand Mineral Resources

New Mexico Institute ofMining & Technology

801 Leroy PlaceSocorro, New Mexico 87801-4796

Return service requested

NEW PUBLICATIONS

NONPROFIT ORGANIZATION

U.S. Postage

PAIDPERMIT NO. 1888

ALBUQUERQUE, NM

Open-file Report (OFR) 496—Preliminary geologic map of theAlbuquerque–Rio Ranchometropolitan area and vicinity,Bernalillo and SandovalCounties, New Mexico, compiledby Sean Connell, 2006. Availablein electronic format only.

This digital geologic map is acompilation of sixteen 7.5-minutequadrangles and comprises an areaof 2,500 square kilometers of the Albuquerque Basin of north-central New Mexico. Prepared at a scale of 1:50,000, the mapdepicts the geology underneath the cities of Albuquerque and RioRancho and surrounding areas. It was completed in order to better characterize geologic controls on ground water resources andgeologic hazards in this rapidly growing urban region. It is currently available in electronic format only, free on the bureau’sWeb site at www.geoinfo.nmt.edu/publications/ or it may be purchased on CD ROM for $10 plus shipping. Digital files currently available include three plates, as follows:

Plate 1a: Geologic map and explanation (6.3 Mb PDF) Plate 1b: Geologic map with shaded relief (21.9 Mb PDF) Plate 2: Geologic cross sections & derivative maps (5.2 Mb PDF)

Digital GIS data and graphics files will be available soon, aswell as a report on the geology of the map area. A printed mapsheet (1:50,000) of this compilation will be available in 2007.

A complete list of open-file reports published by the NewMexico Bureau of Geology and Mineral Resources is availableon our Web site. Some of these reports are available for freedownloading directly from the site, all are available in electronicformat on CD ROM for $10.00 plus shipping through thePublication Sales Office. For more information, visit our Website at www.geoinfo.nmt.edu or call us at 505-835-5490.