Identification of Takab geothermal system reservoir by using gravity method
Subject Areas :Mohammad Mohammadzadeh Moghaddam 1 , Javad Nouraliee 2 , Soheil Porkhial 3 , لیلا ابراهیمی 4 , Saba Moradalivand 5
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Keywords: Gravity Geothermal Takab Gravity derivatives 3D inversion Reservoir ,
Abstract :
The presence of hot springs, travertine outcrops, hydrothermal altered area and active tectonic in the north-east of Takab city in the West Azarbayjan province indicate that there is a geothermal system in the area. In order to characterize the geological structures associated to the geothermal system in the region, a gravity survey was carried out in 140 stations which covered an area about 600 km2. Necessary modifications such as Bouguer, topography and free air were applied over data to obtain complete Bouguer anomaly field. Then, residual gravity anomaly field was calculated by subtracting the regional gravity field from complete Bouguer field. The regional gravity field was calculated by fitting a three-order polynomials surface over the complete Bouguer field. The calculated residual gravity map shows two negative anomaly zones (A1 and A2) in the study area. In geothermal exploration, negative gravity anomalies are considered as probable reservoir of geothermal systems. The horizontal and vertical derivative maps show complicated fracture zones in the study area. To obtain more information, the depth estimation carried out using Euler method. Estimated depth for the top of negative anomaly source in zone 1 is between 1000 and 2000 m. Finally, 3D inversion of the data was performed using Li and Oldenburg algorithm to show an image of the reservoir in the depth. The results of 3D inversion show a significant negative density contrast that occurred only in zone 1. Therefore, the reservoir of the Takab geothermal system is located in the depths between 3000 and 5000 m in A1 anomaly zone.
نبوی، م. ح.، 1355. دیباچه¬ای بر زمین¬شناسی ایران.، سازمان زمین¬شناسی کشور، 109.
Abiye, T.A. and Haile T., 2008. Geophysical exploration of the Boku geothermal area, Central Ethiopian Rift. Geothermics, 37, 586–596.
Blakely, R.J., 1996. Potential Theory in Gravity and Magnetic Applications. Cambridge university press. 464.
Blakely, R.J. and Simpson, R.W., 1986. Approximating edges of source bodies from magnetic or gravity anomalies, Geophysics, 51, 1494-1498.
Cooper, G.R.J. and Cowan, D.R., 2004. Filtering using variable order vertical derivatives. Computer and Geosciences, 30, 455-459.
Gottsmann, J., Camacho, A.G., Martí, J.,Wooller, L., Fernández, J., García, A. and Rymer, H., 2008. Shallow structure beneath the Central Volcanic Complex of Tenerife from new gravity data: implications for its evolution and recent reactivation. Physics of the Earth and Planetary Interiors, 168, 212–230.
Kalateh A.N, and Kahoo, A.R., 2013. Estimation of 3D density distribution of chromite deposits using gravity data. Journal of Mining & Environment, 4, 97-104.
Keating, P. and Pilkington, M., 2004. Euler deconvolution of the analytic signal and its application to magnetic interpretation, Geophys. Prospect, 52, 165–182.
Li, Y. and Oldenburg, D.W., 1998a. 3D inversion of gravity data, Geophysics 63, 109–119.
Li, Y. and Oldenburg, D. W., 1998b, Separation of regional and residual magnetic field data, Geophysics, 63, 431-439.
Montesinos, F.G., Camacho, A.G., Nunes, J.C., Oliveira, C.S. and Vieira, R., 2003. A 3-D gravity model for a volcanic crater in Terceira Island (Azores), Geophysical Journal International, 154, 393–406.
Nabighian, M.N., 1972. The analytic signal of two-dimensional magnetic bodies with polygonal cross-section: Its properties and use for automated anomaly interpretation, Geophysics, 37, 507-517.
Nabighian, M.N., 1984. Toward a three-dimensional automatic interpretation of potential field data via generalized Hilbert transforms: fundamental relations, Geophysics, 49, 780–786.
Nouraliee, J., Porkhial, S., Ebrahimi, D. and Rahmani, M., 2014. Chemical studies on warm springs of West Azarbaijan province in the north west of Iran, Journal of Scientific Research and Studies, 1, 65-72.
Noualiee, J., Porkhial, S., Mohammadzadeh-Moghaddam, M., Mirzaei, S., Ebrahimi, D. and Rahmani, M., Accepted for publication. Investigation on density contrasts and geological structures around hot springs in Mahallat geothermal region using gravity method, Russian Geology and Geophysics.
Oldenburg, D. W. and D. A. Pratt, 2007. Geophysical inversion for mineral exploration - A decade of progress in theory and practice, in B. Milkereit, ed., Proceedings of Exploration 07, Fifth Decennial International Conference on Mineral Exploration, 61–95.
Reid, A.B., 1995. Euler deconvolution: past, present and future – a review. 65th SEG Meeting, Houston, USA, Expanded Abstracts, 272–273.
Represas, P., Santos, F.A. and Ribeiro, J., 2013. Interpretation of gravity data to delineate structural features connected to low-temperature geothermal resources at Northeastern Portugal, Applied Geophysics, 92, 30-38.
Saad, A.H., 2006. Understanding gravity gradients-a tutorial. The Leading Edge, 25, 942–949.
Salem, A., Furuya, S., Aboud, E., Elawadi, E., Jotaki, H. and Ushijima, K., 2005. Subsurface Structural Mapping Using Gravity Data of Hohi Geothermal Area, Central Kyushu, Japan, Proceedings World Geothermal Congress, Antalya, Turkey.
Schiavone, D. and Loddo, M., 2007. 3-D density model of Mt. Etna Volcano (Southern Italy), Journal of Volcanology and Geothermal Research, 164, 161–175.
Soengkono, S., 2011. Deep Interpretation of Gravity and Airborne Magnetic Data over the Central Taupo Volcanic Zone, New Zealand Geothermal Workshop.
Telford, W.M., Geldart, L.P., Sheriff, R.E. and Keys, D.A., 1990. Applied Geophysics, 2nd edition. Cambridge University Press.
Thompson, D.T., 1982. EULDPTH – a technique for making computer-assisted depth estimates from magnetic data, Geophysics, 47, 31–37.