Hot dry rock geothermal prospects, 1981

,L zyxwvutsrqponmlkjihgfedcb zyxwvutsrqponm Los Alamos National Laboratory Is operated by the Unlverslty of California for the Unlted States Department of Energy under contract W-7405-ENG-36. TITLE: AUTHOR(S): SUBMITTEDTO: zyxwvutsrq HOT DRY ROCK GEOTHERMAL PROSPECTS, 1981 F. E. Goff , 6-4 A. W. Laughlin, G-4 J. Aldrich, 6-4 M. E. Ander, 6-7 B. H. Arney, 6-4 E. Decker, 6-7 zy J. Gardner, 6-4 Heiken, G-DO A. J. Kron, G-4 C. M. LaDelfe, 6-7 R. A. Pettitt, 6-2 S. S. Shannon, G-9 G. Technical Program Committee for the 1981 Annual Meeting of Geothermal Energy, The International Success Story, Geothermal Resources Council, Houston, TX, October 25-29, 1981. n LosAlamos National Laboratory LosAlamos,New Mexico 87545 FORM NO. 038 R4 Sf. NO. 129 5/81 DISCLAIMER This report was prepared as an account of work sponsored by an agency of the United States Government. Neither the United States Government nor any agency Thereof, nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States Government or any agency thereof. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or any agency thereof. DISCLAIMER Portions of this document may be illegible in electronic image products. Images are produced from the best available original document. zyxwvutsrq zyxwvut HOT DRY ROCK GEOTHERMAL PROSPECTS, 1981 F. Goff, A. Laughlin, J. Aldrich, M. Ander, 8. Arney, E. Decker, J. Gardner, 6. Heiken, A. Kron, C. LaDelfe, R. P e t t i t t and S. Shannon Los Alamos National Laboratory Los Alamos, NM 87545 SITE I1 PROSPECTS, 1981 ABSTRACT The h o t dry rock (HDR) s i t e selection and resource evaluation team a t Los Alamos National Laboratory has been assessing roughly 24 s i t e s w i t h i n the USA as candidates f o r development of a second geothermal Potential sites we have HDR examined f a l system. l broadly i n t o three categories anomalies: according thermal Table 1 l i s t s basic geologic and geophysical data a t 24 HDR prospect s i t e s i n the conterminous USA (Figure 1). An extended Table which includes references f o r each s i t e can be obtained by w i n g the authors. accounting Although tohfi spossible l i s t i s HDR by nor i tmeans a complete zyxwvut zyx zyxwvuts t o 1.theQuaternary nature o f magmatheir prospects, anomalies, i tte cdisplays a f u l l range f thermal t o n i c settings, and o reservoir hydrothermal ( 'volcanic' o r 'igneous') systems such as The Geysers - Clear Lake region, California, 2. regional thermal anomalies of tectonic o r i g i n such as the Basin and Range Province o f the Southwest, and 3. pre-Quaternary p l u t o n i cGranite, and metamorphic complexesAlthough such ass i tthe Conway New Hampshire. es w i t h both e l e c t r i c a l generation and d i r e c t use p o t e n t i a l have been considered, DOE has directed us t o concentrate our e f f o r t s on e l e c t r i c a l sgeneration i t e s . C r i t es ri ti ae f ourt i lai zsuccessful HDR e lectrical i n g current technology rocks t o be considered i n the choice o f S i t e 11. The m a j o r i t y o f s i t e s are located i n the t e c t o n i c a l l y and v o l c a n i c a l l y a c t i v e western USA where heat flow and thermal gradients a r e e r e l a t i v e l y high (generally > 1.5 HFU and 2 35 C/km) (Sass e t and al., Nathenson, 1980; Kron1980). and Heiken, Guffanti Eastern 1980; and midwestern thermal anomalies are o f smaller size and are thought t o r e s u l t from high radiogenic heat production i n some plutons and/or from tbasement h i c k i n srocks. u l a t i n g sedimentary blankets overlying r e q u i r e temperatures 2 200 C, depths 5 5/km, and r v o i r e rocks. w i t h these cimpermeable h a r a c t e r i s t ircess eonly x i s t i n Sites the western USA. Potential a t most s i t e s consist o f ( cr reysset ravl o 1 ii nr e )rocks plutonicmetamorphic The significanceissues, o f other environmental water c r irti eg rhitas , such p u b las ic v i s a b i l i t y , and p r e e x i s t i n g power networks have basement HDR r e s et rhveo i r prototype rocks a t Fenton Hresembling ill, New theMexico, locality. Exceptions t o t h i s norm occur not y e t been evaluated. throughout the western USA where r e s e r v o i r rocks of metasediments, metavolcanics, shallow Los Alamos National Lab a c t i v e l y engaged i n HDR geothermal exploration throughout the conterminous USA since HDR energy e x t r a c t i o n was proved t e c h n i c a l l y f e a s i b l e i n 1977 (Tester and Albright, 1979; Murphy, 1980). Our HDR exploration e f f o r t consists of three p r i n c i p a l facets; 1. evaluation o f the HDR resource o f the conterminous USA, 2. evaluation o f geophysical methods t o help locate HDR prospects, and 3. evaluation o f candidate s i t e s f o r the second HDR geothermal system. One of our most important near-term goals (Fiscal Year 1982) i s t o help i d e n t i f y HDR S i t e 11. The object o f t h i s summary i s t o l i s t prospect s i t e s which we are evaluating and t o discuss technological and geological considerations t h a t must be weighed before a second HDR s i t e I s chosen. zyxwvutsrqpo Figure 1. Map showing approximate locations o f 24 HDR prospects i n Table 1. zyxwvut zyx zyxwvutsrq zyxwvutsrqpo zyxwvutsrqp zyxwvutsrqponmlkjih zyxwvutsrq menaP InmwlY UIE Aqwrluw Wtna. A2 Cwatle m e . U Sprlniervllle. U C1e.r b k e regton. caw mt swr. u 13 11 15 16 17 18 19 10 21 22 23 24 m. w, on Val*. OR l o o m v d t lbt -a. UT I*twaeda/Crwn. ?lUtlIlat~ nutilceta riuwnm Intrus. hi. Xntruw.lDaaalt XraClf1.d Baawlt S t r a t 1 f l . d Baswlt riuvlceta s k c b t e r n a r y pluronlc end = e t m o r p h l c rooka. kwrmbrlwn U v l n s a t o n Rlllw, U e ~ r a i c kwcmbrlan 35-11 55 50 PMXiSCM. 4 0 I*WZOiC B rr1wssic hecmbrian 2130 2100 *zoo 22 D2 D3 13 23 26 38 60-70 30 D6 27 25-55 55-65 13.5 23 %E 3z51 ~6~' 50-75 65 21110 2150 2130 4 0 =a 13-26 32-36 25-27 60-90 53-60 45 24 ;SI hwrmbrlwn hacmbrlan und. Volcanica. h r t i w r y bcene? nood ~ a s w l t .h r t i w r y *in. mns. ?)ut.. Tertiary: hecrmbrlwn I n e i s s Depth tou WDR tmp. e t a p . e 5 lm, I*aervolr. 2 h, 'C .C lo 5 D3.5 35-55 A5 40 260 4 0 2150 2100 2.:: L3 L7 8 L7 D3 ?3 13 D2 210 w200 ,200 2350 2250 RSO 2250 ,250 2135 2110 2135 el30 w200 2300 2200 >2bO locwlfy undermy Eaplete omplete mderway stwrted mdermy underway mderwy underuwy undermy undrrway Eap1.t. -- D250 2120 2300 D300 21110 00p1.t. EQpl*C* underuwy underuwy Jtarta cmp1.c. at8rt.d C w n Jtudy m d e r w y ewse atudy CQp1.t. underway undermy underuay ZZOO 2150 40 270 d0 ,100 t115 s t a t u s or h e l l . . HOR Evwlurtion 2050 %?50 s refjlonal t h e m a 1 wnanwllea of b c t o n l c o r l s l n . V s Qutrmwry volcanic f l e l d . ( ) s ucondwry hewt y Conductive t h e m 1 s r n d i e n t i n deep lmpeneable w n e ( I f Imom) o r estlmwte I r a srwdlent wlls. Dcpth requ1r.d u) ~ s t w b l l w hHDR reservoir u s l a rock at m1ntm.u of 200'C (not depth to orywt.lllne y Grwdlrnt m y b. leas i n deep h w d r l w n bas.a.nt. Table 1. mnd/cr l m p . n a a b l e bwwaent rocks). L i s t o f 24 hot d r y rock prospects i n the USA w i t h c r i t i c a l data regarding r e s e r v o i r rocks, conductive temperature gradient and expected temperatures a t depth. i n t r u s i v e bodies, and s t r a t i f i e d volcanics are being considered. Because extensive r e s e r v o i r t e s t s have n o t been conducted i n these a l t e r n a t e l i t h o l o g i e s , it i s not known how d i f f i c u l t i t would be t o create a HDR energy system w i t h i n them. ' c0nd.y trmp. Crwd.. 'Wb Sier-Lv. Bath.. U e w w l c Uer-Yev. L t h . . I*wwlc Wu. C w l l f . Mth.. UewwlC Idaho Bath.. ~ w a . 9 l c .tio&ont. b a s m e n t . hleoroio hwrmbrlm hecmbrian Conmy Crwn.. Jurarslc: U t t l r r o n h.. L v o n i a n h e c m b r l wn hecrmbrlwn kwrmbrlan Jureswlc-Tertl.ry E* Bio C r d e r i f t . M vallew Cwlderw. 111 Zuni U p l l f t . YX a s e r t hwk. NV B a l e Valley. NV O y y a U k e . BY m a t Aurorw. MY , b i r a . 111 Brother8 f a u l t ume. 01 I o n w t l o n and bg. t l f born) look u brig Valley Cwldtra. s a l t o n Trough. w Ilomtwln W e . ID P l W f l e l d . IU mu k d r l d . m Western Lbrwskw 12 mite l b u n t a l n s . M hr HDR b a e r v p Conductive thermal gradients l i s t e d i n Table 1 represent the g r i d i e n t a t depth below alluvium, sediments, etc. where obtainable. Some s i t e s e x h i b i t higher temperature gradients i n these o v e r l y i n g l i t h o l o g i e s which would imply anomalously high estimates o f temperatures i n deeper impermeable units. Temperatures estimated a t 2 km depth are robably v a l i d t o Many +20°C over an area o f 10 k$ o r more. locations have 2 km deep wells w i t h published bottom hole temperatures t o substantiate the figures listed. Estimates a t 5 km depth considerably more speculative bfcause they calculated by extrapolating a best' value of conductive gradient below a deep l e v e l having temperature control. The depth l i s t e d t o reach HDR r e s e r v o i r s i s simply the estimated depth needed t o reach the 200 C isotherm; t h a t is, rock h o t enough f o r comnercial generation o f electricity. The depth ' o f r e s e r v o i r i s an fmportant economic consideration i n construction -of. HDR energy systems. The s i t e s l i s t e d i n Table 1 vary co i n the status o f preliminary HDR evalua Many are complete, whereas. some, such as S Trough have been b a r e l y i n i t i a t e d . Two 100 k Maryland (D'Appol sites a t . Crisfield, Consulting .Engineers, 1981) and Mountain Home, Idaho have been the subject of ccmprehenstve case studies. Los Alamos has publlshed numerous reports on many o f these s i t e s and associated geol ogiclgeochemi c a l /geophysical problems, which are available t o the interested reader. Many s i t e s have been previously evaluated f o r convent i o n a l geothermal resources by the US Geological Survey and other organizations. I n such cases, Los Alamos has merely reevaluated the area i n l i g h t o f the constraints o f HDR development. SOME CONSIDERATIONS FOR HDR SITE I1 The prototype Phase I HDR system a t Fenton H i l l , New Mexico (Figure 2) e x t r a c t s heat a t a COMPARISON OF FENTON HILL Figure 2. aEsuacH AND ENGINEERING SYSTEMS Schematic diagram showing Phase. 1. and Phase I 1 HDR systems. g-; 34 . zyxwvutsrqponmlkjihgfedcbaZYXWVUTS Goff, e t a1 depth o f 3 km from Precambrian plutonicmetamorphic basement. This system, d r i l l e d on the west margin o f Valles Caldera (Table l), posspses a deep temperature gradient o f 60 /km, a bottom-hole temperature o f 200'C and a power output o f 3-5 raJ(t). Drilling of boreholes f o r the Phase I 1 system, designed t o show Commercial f e a s i b i l i t y , i s n e a r l y complete. When these two wells are connected b y hydraulic fracturing, water w i l l be c i r c u l a t e d t o depths o f 4.4 km a t a bottom-hole temperature o f 325'C. Expected power output i s 10-20 MU(e) using 3-5 v e r t i c a l fractures. Because the boreholes o f Phase I1 are d i r e c t i o n a l l y d r i l l e d toward Valles Caldera (and i t s shallow, locajized heat source), thermal gradient approaches 90 C/km a t 4.4 km. - - - zyxwvutsrq Our experience a t Fenton H i l l enables us t o specify an "optimal" HDR S i t e 11. This experience shows t h a t d r i l l i n g costs and problems increase dramatically below depths o f 3 km as a r e s u l t o f the increased temperature and the requirement f o r d i r e c t i o n a l d r i l l i n g . Precise d i r e c t i o n a l d r i l l i n g i s required t o produce i n c 1ined boreholes , the preferred configuration. Hydraulic f r a c t u r i n g a t great depth creates vertical to near-vertical fractures which i n c l i n e d boreholes ar? best able t o u t i l i z e . Temperatures above 300 C present special problems f o r d r i l l i n g tools, casing, cements, logging t o o l s and logging cable. A minimum depth f o r f u t u r e HDR systems o f approximately 1.5-2 km i s required by the necessity o f confining the hydraulic fractues by about one f r a c t u r e diameter o f overlying impermeable rock t o prevent loss o f injected f l u i d . Because o f these problems and the f a c t t h a t commercial e l e c t r i c a l generation requires f l u i d temperatures o f a t l e a s t 200'C, we would consider as "optimal" an HDR system having a temperature o f 200-3OO'C a t depths o f 2-4 km. Such l i m i t s would eliminate a l l s i t e s east o f the Rocky Mountains from consideration as HDR S i t e I 1 using c u r r e n t l y available technology. As technology Improves, these l i m i t s w i l l expand t o greater depths and a broader range of temperatures. Another major consideration i s the character he r e s e r v o i r rock. Los Alamos has not y e t developed the technology t o create HDR r e s e r v o i r s i n rocks other than plutonic-metamorphic rocks. Hot d r y wells are known throughout the western USA t h a t are d r i l l e d i n other l i t h o l o g i e s . Engineering a HDR r e s e r v o i r i n them w i l l r e q u i r e additional t e s t s and experiments. Until this i s accomplished, the success o f HDR S i t e 11 may be comprimised unless c r y s t a l l i n e r e s e r v o i r rock i s used again. HOT PROSPECTS know enough about them t o suggest a t a r g e t area f o r m r e d e t a i l e d evaluation. O f the four, Long Valley i s the l e a s t desirable becaus? o f i t s r e l a t i v e l y low thermal gradient o f 38 Clkm and because i t s geologic s e t t i n g i s i d e n t i c a l t o the prototype system a t Fenton H i l l (Gambill, 1981). A s i t e near Clear Lake, C a l i f o r n i a w i l l r e q u i r e development o f a r e s e r v o i r i n Franciscan metasediments o r metavolcanics instead o f ' c r y s t a l l i n e ' basement. The Mountain Home, Idaho s i t e i s doubtful because we do not have a r e l i a b l e estimate o f depth, t o rocks o f the Idaho Batholith, the preferred r e s e r v o i r rock. In contrast, Roosevelt Hot Springs appears t o be a 'safe b e t ' f o r HDR development because of high temperatures over a broad area and because we know the approximate depth t o impermeable granite and gneiss i n several h o t d r y wells (East, 1981). Such a s i t e would r e q u i r e the l e a s t development o f new technology t o achieve success. ACKNOWLEDGMENTS Many o f the ideas contained i n t h i s sumnary have been s t r o n g l y influenced by Mort Smith and John Rowley o f Los Alamos National Laboratory. This e f f o r t was sponsored by US DOE, Department o f Geothermal Energy. REFERENCES D'Appolonia Consulting Engineers, Inc., 1981, Evaluation o f hot d r y rock exploration techniques i n the A t l a n t i c Coastal Plain: a test s i t e on the Delmana Penninsula o f Maryland and Virginia. Los Alamos S c i e n t i f i c Laboratory Informal Report, LA-8800-MS, 28 p. East, J., 1981, Hot d r y rock geothermal p o t e n t i a l of Roosevelt Hot Springs Area: Review o f data and recomnendations. Los Alamos S c i e n t i f i c Laboratory Informal Report, LA-8751-HDR, 45 p. Gamblll, 0. T., 1981, Preliminary h o t d r y rock geothermal evaluation o f Long Val l e y Caldera, California. Los Alamos S c i e n t i f i c Laboratory Informal Report, LA-8715-HDR, 22 p. Guffantl, M. and Nathenson, M., 1980. Preliminary map o f temperature gradients i n the conterminous United States. Geoth. Resources Council Trans. 4 ~ 5 3 . zyxwvuts zyxwvu zyxwvutsr The f o u r ' h o t t e s t ' prospects among those evaluated b y Los Alamos f o r S i t e I1 considerat i o n are: 1. Clear Lake, C a l i f o r n i a ; 2. Long l i f o r n i a ; 3. Mountain Home, Idaho; osevelt Hot Springs, Utah. Other s i t e s may be as 'hot' o r ' h o t t e r ' b u t we do not Geothermal graStates. Geoth. Murphy, H. D., ed., 1980. Evaluation o f the second hot d r y rock geothermal energy reserv o i r . Los Alamos S c i e n t i f i c Laboratory I n f o r mal Report, LA-8354-MS. J. H., Blackwell, D. D., Chapman, D. S., Costain, J. K., Decker, E. R., Lawver, L. A., and Swanberg, C. A., 1980. Heat flow from the c r u s t o f the US i n Touloukian, Y.S., Judd, W. R., and Roy, R. eds., Physical properties o f rocks amd minerals. McGraw-Hill, Chap. 13. r, $ zyxwvut zyxwvutsrqponmlk zyxwvutsrqponm zyxwvutsrqponm zyxwvut .I Goff e t a l . Tester. J. W. and Albright, J. N., eds., 1979. Hot dry rock energy extraction f i e l d t e s t : 75 days o f operation o f a prototype reservoir a t Fenton H i l l . Los Alamos S c i e n t i f i c Laboratory Ir,formal Report, LA-7771-MS. 4