Preliminary assessment of Nevado del Ruiz geothermal potential from laboratory measurements of thermal properties
a ; 1 a a b
Maria Isabel Vélez
, Daniela Blessent , Idalia Jacqueline López , Jasmin Raymond
a 1
Universidad de Medellin, Medellín, Colombia.
[email protected]
b
Institut National de la Recherche Scientifique, Centre-Eau Terre Environnement, Québec, Qc, Canada
Paper number: SG14B-0368
INTRODUCTION
GEOLOGICAL SETTING
THERMAL CONDUCTIVITY AND SPECIFIC HEAT DATA
The temperature at depth was estimated according to Fourier's law
q= - λ*dT/dz
T = T +q*(dz/-λ)r o
-2
q: heat flow (W m )
-1 -1
-λ: rock thermal conductivity (W K m )
z: depth (m)
T : reservoir temperature (K)r T : surface temperature (K)o
The heat flow value (q) for the area was calculated according to the temperature gradients from two exploration wells reaching a depth of 300 meter (Rojas, 2012). The average heat flow equals to 187.3
-2
mW m was used to estimate the temperature at depth (Figure 6).
RESSOURCE ASSESSMENT
C o l o m b i a i s a n a t t r a c t i v e c o u n t r y f o r g e o t h e r m a l e n e r g y p r o d u c t i o n d u e t o t h e p r e s e n c e o f r e c e n t v o l c a n i c a c t i v i t y, i n t h e c e n t r a l a n d w e s t e r n A n d e s m o u n t a i n r a n g e s , w h e r e o c c u r s t h e c o n v e r g e n c e o f N a z c a a n d S o u t h A m e r i c a n t e c t o n i c p l a t e s ( F i g u r e 1 ) . T h e N e v a d o d e l R u i z i s a n a c t i v e s t r a t o v o l c a n o l o c a t e d i n L o s N e v a d o s N a t u r a l N a t i o n a l P a r k , i n t h e m i d d l e o f t h e c e n t r a l m o u n t a i n r a n g e ( F i g u r e 2 ) . G e o t h e r m a l r e s e a r c h i n t h i s r e g i o n b e g a n i n 1 9 6 8 w i t h a g e o t h e r m a l r e g i o n a l r e c o n n a i s s a n c e s t u d y. ( A l f a r o e t a l . , 2 0 0 0 ) . T h e fi r s t e x p l o r a t o r y w e l l w a s d r i l l e d i n 1 9 9 7 , a t t h e We s t s i d e o f t h e v o l c a n o . T h e w e l l c o u l d n o t r e a c h t h e p l a n n e d d e p t h o f 2 0 0 0 m b e c a u s e i t d e v i a t e d , u p t o 4 2 d e g r e e s , a n d r e a c h e d o n l y a d e p t h o f 1 4 6 6 m . N e v e r t h e l e s s , s e v e n l i t h o l o g i c a l u n i t s w i t h h y d r o t h e r m a l a l t e r a t i o n s w e r e i d e n t i fi e d a n d t h e m e a s u r e d b o t t o m - h o l e t e m p e r a t u r e w a s a b o u t 2 0 0 ° C . R e c e n t r e s e a r c h e s c o n c e r n e d h y d r o t h e r m a l a l t e r a t i o n ( F o r e r o , 2 0 1 2 ) , k i n e m a t i c c h a r a c t e r i s t i c s o f w e s t w a r d f a u l t s ( M e j i a , 2 0 1 2 ) , g e o c h e m i c a l a n d t h e r m a l e v o l u t i o n ( R a y o , 2 0 1 2 ) , a n d g e o e l e c t r i c a l r e s i s t i v i t y s u r v e y s ( R o j a s , 2 0 1 2 ) . O t h e r s t u d i e s s h o w e d t h a t f a u l t s m a y a c t a s p r e f e r e n t i a l fl o w p a t h s f o r g e o t h e r m a l fl u i d s ( M e j i a e t a l . , 2 0 1 2 ) . N e v e r t h e l e s s , t h e r e a r e n o p u b l i s h e d s t u d i e s a b o u t r o c k t h e r m a l p r o p e r t i e s . T h i s w o r k f o c u s e s o n t h e e v a l u a t i o n o f t h e r m a l p r o p e r t i e s ( t h e r m a l c o n d u c t i v i t y a n d s p e c i fi c h e a t ) o f 6 2 r o c k s a m p l e s c o l l e c t e d i n s u r f a c e o u t c r o p s d u r i n g a fi e l d t r i p i n N o v e m b e r 2 0 1 4 . T h e s e t h e r m a l p r o p e r t i e s c o u p l e d t o h e a t fl o w v a l u e s , a l l o w e d t o e s t i m a t e t e m p e r a t u r e s a t d e p t h a n d t o p r o v i d e a p r e l i m i n a r y a s s e s s m e n t o f t h e g e o t h e r m a l r e s o u r c e s . T h e t h e r m a l c o n d u c t i v i t y w a s m e a s u r e d i n 6 2 r o c k s s a m p l e s c o l l e c t e d f r o m t h e n o r t h a n d w e s t e r n fl a n k o f N e v a d o d e l R u i z Vo l c a n o , u s i n g t h e t h e r m a l p r o p e r t i e s a n a l y z e r, K D 2 P r o ( F i g u r e s 4 a n d 5 ) . T h e p r o b e c o n s i s t s o f a n e e d l e w i t h a h e a t e r a n d a t e m p e r a t u r e s e n s o r i n s i d e . E l e c t r i c c u r r e n t i s p a s s e d t h r o u g h t h e h e a t e r a n d t h e t e m p e r a t u r e o f t h e p r o b e i s m o n i t o r e d o v e r t i m e . A n a n a l y s i s o f t h e p r o b e t e m p e r a t u r e i s u s e d t o d e t e r m i n e t h e r m a l c o n d u c t i v i t y ( D e c a g o n D e v i c e s I n c . , 2 0 0 8 ) . T h e s p e c i fi c h e a t o f r o c k s a m p l e s w a s e s t i m a t e d f r o m v a l u e s p u b l i s h e d b y W a p l e s a n d W a p l e s ( 2 0 0 4 ) , f o r d i ff e r e n t t y p e s o f r o c k s . T h e t h e r m a l c o n d u c t i v i t y v a l u e s o b t a i n e d f o r t h e d i ff e r e n t f o r m a t i o n s d i d n o t s h o w a l a r g e v a r i a t i o n : - 1 - 1 m o s t o f t h e s e v a l u e s w e r e c l o s e t o 2 . 0 W m K . O n l y t h e C a j a m a r c a c o m p l e x s h o w e d a g r e a t e r v a l u e o f - 1 - 1 2 . 9 W m K ( F i g u r e 4 ) . T h e h e a t c a p a c i t y r a n g e d - 1 - 1 b e t w e e n 8 1 5 a n d 11 4 0 J K g K , w i t h a n a v e r a g e - 1 -v a l u e o f 9 1 6 J K g K 1 .The geothermal potential was estimated according to a recovery factor since it is not possible to extract the total heat content of the underground. This recovery factor is defined by the ratio between the utilizable energy versus the available energy (Calcagano et al., 2014) and it depends on the porosity and permeability of the reservoir formation (Walsh, 2013).
In this study, a recovery factor (R) of 2.4% has been used, this value is reported by Calcagano et al., (2014) as the minimum recovery factor for fractured aquifers. The power generation potential (Table 1; Gp (MW)) was calculated according to the next equation:
Gp=R*(Q /t)*hr
assuming an exploitation period (t) of 30 years and a reservoir width (h) of 5 Km.
The resource assessment was made in the region with temperatures over 216 °C, nevertheless a large portion of this area belongs to the Los Nevados Natural National Park (NNP) and it cannot be exploited. Therefore the evaluation focused on the area outside the NNP (figure 7), and finally on a smaller area where exploitation of geothermal resources can be economical and environmental feasible.
A geothermal resource assessment was carried out to establish the amount of heat that is available underground to produce electricity or some other form of work.
The heat content was initially determined with:
Q =ρ*C*A*(T -T )r r o
-1
Q : heat available in the reservoir (J m )r
-3
ρ: density of the reservoir rock (Kg m )
-1 -1
C: heat capacity of the reservoir rock (J Kg K )
2
A: area of the reservoir (m ) T : reservoir temperature (K)r T : surface temperature (K)o
The reservoir width was difficult to determine for the study area; therefore the amount of heat available in the reservoir was estimated by unit length (MJ/m).
CONCLUSIONS
Alfaro, C., Bernal, N., Ramírez, G., & Escovar, R. (2000). Colombia, Country Update. Paper presented at the Proceedings World Geothermal Congress Kyushu - Tohoku, Japan.
Calcagno, P., Baujard, C., Guillou-Frottier, L., Dagallier, A., & Genter, A. (2014). Estimation of the deep geothermal potential within the Tertiary Limagne basin (French Massif Central): An integrated 3D geological and thermal approach. Geothermics, 51(0), 496-508. doi: http://dx.doi.org/10.1016/j.geothermics.2014.02.002
Decagon Devices Inc. (2008). KD2 Pro Thermal Properties Analyzer Operator's Manual Version 12 (pp. 72): Decagon Devices, Inc.
Forero, J. A. (2012). Caracterización de las alteraciones hidrotermales en el flanco Noroccidental del Volcán Nevado del Ruiz, Colombia. (Master’s Thesis), Universidad Nacional de Colombia, Bogotá D.C.
Mejía , E. (2012). Características Cinemáticas y Condiciones de Deformación de un Segmento de la Falla Palestina al NE del Volcán Nevado del Ruíz. (Master’s Thesis), Universidad Nacional de Colombia, Bogotá.
Mejía, E., Rayo, L., Méndez, J., & Echeverri, J. (2014). Geothermal Development in Colombia Paper presented at the Short Course VI on Utilization of Low- and Medium-Enthalpy Geothermal Resources and Financial Aspects of Utilization, Santa Tecla, El Salvador.
Mejía, E., Velandia, F., Zuluaga, C. A., López, J. A., & Cramer, T. (2012). Análisis estructural al noreste del Volcán Nevado de Ruíz Colombia – Aporte a la Exploración Geotérmica. Boletín de Geologia, 34(1), 15.
Rayo, L. (2012). Evolución Geoquímica y Térmica del Volcán Nevado del Ruíz, Colombia. (Master’s Thesis), Universidad Nacional de Colombia, Bogotá D.C, Colombia.
Rojas, O. E. (2012). Contribución al modelo geotérmico asociado al sistema volcánico Nevado del Ruiz-Colombia, por medio del análisis de la relación entre la susceptibilidad magnética, conductividad eléctrica y térmica del sistema. Universidad Nacional de Colombia, Bogotá
Servicio Geologico Colombian. (2014) Nevado del Ruiz.
h t t p : / / w w w. s g c . g o v. c o / M a n i z a l e s / Vo l c a n e s / N e v a d o d e l r u i z / G a l e r i a d e -fotos/Generales/2014/Septiembre/23-de-Septiembre.aspx.
Walsh, W. (2013). Geothermal resource assessment of the Clarke Lake Gas Field, Fort Nelson, British Columbia. Bulletin of Canadian Petroleum Geology, 61(3), 241-251.
Waples, D., & Waples, J. (2004). A Review and Evaluation of Specific Heat Capacities of Rocks, Minerals, and Subsurface Fluids. Part 1: Minerals and Nonporous Rocks. Natural Resources Research, 13(2), 97-122. doi: 10.1023/B:NARR.0000032647.41046.e7
Metamorphic and igneous formations with different deformation degrees dominate the sector (Figure 3) (Mejia et al., 2012).
Pes (Cajamarca complex): ensemble of metamorphic
rocks.
Kvc – Ksc (Quebrada Grande complex): group of
volcanic and sedimentary rocks.
Kpgcdm (Manizales stock): granitoids rock with an
intense jointing.
NgQa (Andesitic lava flows): thick layer of extrusive
rocks
Also there are several superficial deposits, product of the volcanic activity in the quaternary period:
Qto: pyroclastic rocks
Qfl: volcanic mud flow deposits Qg: glacial deposits
Qar: recent alluvial deposits
REFERENCES
Area with T>216 °C Area outside NNP
Area closer to surface
Power generation
potential (MW) 2958 517 50
Table 1. Estimation of the power generation potential
Figure 5. KD2 Pro probe during a measurement of thermal conductivity of a rock sample
Figure 2. Nevado del Ruiz from Servicio Geológico Colombiano (2014).
Figure1. Geothermal development in Colombia from Mejia et al., 2014
TEMPERATURE AT DEPTH
The temperature estimated at depth allowed to identify an area
2
of 25.9 Km with temperatures between 216 and 459 °C, ranging from 2200 to 5300 meters below the surface. These temperatures occur in the andesitic lava flows (NgQa) and Cajamarca complex (Pes) formations. A large part of the area is located inside Los Nevados Natural National Park, therefore
2
only an area of about 6.3 km can be considered like a potential geothermal reservoir.
Currently, the main source of power generation in the region is hydropower. This area has 3 main hydroelectric power plants:
San Francisco (135 MW), Esmeralda (30 MW) and Insula (20 MW). Considering the above information, the estimated geothermal potential (50 MW), constitute a significant contribution to the diversification of the power generation sources in the region.
Geothermal resource assessment depends on reservoir volume and recovery factor; in consequence, an improved estimation of Nevado del Ruiz geothermal potential will require further studies to determine reservoir volume and to provide a better estimation of the recovery factor.
Figure 4. Results of thermal conductivity and heat capacity analysis
Figure 3. Interpreted lithological profile
Figure 7. Preliminary geothermal resource assessment Figure 7. Preliminary geothermal resource assessment
