13-10-2010, 02:29 PM
This article is presented by:
D. Chandrasekharam
Department of Earth Sciences
Indian Institute of Technology
Bombay 400076, India
GEOTHERMAL ENERGY RESOURCES OF INDIA: COUNTRY UPDATE
ABSTRACT
All the geothermal provinces of India are located in areas with high heat flow and geothermal gradients. The heat flow and thermal gradient values vary from 75–468 mW/m2 and 59–234°C respectively. Additional exploration studies and reservoir modelling have been carried out between 1995 and 1998 to understand the reservoir characteristics. Thermal gas discharges from several thermal provinces recorded high helium concentration varying from 0.5–6.9%. Gas data, together with heat flow and thermal gradient data, suggests the presence of granites and related intrusives with high U concentration (0.19–10.7%) in these provinces. Many such provinces are also best suited for HDR projects. High 4He content in the thermal gases is obliterating the presence of primordial helium. Pilot power plants, commissioned at certain thermal discharge sites, proved the power generating capacity of these provinces. The estimated power generating capacity of the thermal discharges is about 10,600 MW. The available geophysical and geochemical data are sufficient to identify sites for undertaking deep drilling projects, and to commission binary power plants. Many independent power producers are keen to collaborate with foreign financial institutions to develop geothermal energy sources in rural India. With the existing environmental problems associated with coal based mega power projects, and with incentives given to develop non-conventional energy sources, the future of the Indian geothermal energy program is bright.
INTRODUCTION
The seven major geothermal provinces of India, enclosing nearly 400 thermal springs, are associated with midcontinental rifts, subduction, sedimentary basins and Cretaceous-Tertiary volcanism (Fig. 1). These provinces include i) The Himalayas, ii) Sohana, iii) Cambay, iv) Son- Narmada-Tapi rift zone (SONATA), v) West coast, vi) Godavari, and vii) Mahanadi. With the recent volcanic eruption, the Barren island has become one the most important geothermal provinces in the Indian subcontinent. The estimated energy from one third of these springs is of the order of 40.9x1018 calories. This is equivalent to the energy that can be obtained from 5.7 billion tonnes of coal or 28 million barrels of oil. If these energy resources are developed for a medium to low temperature application it will substitute about 10,600 MW of power (Ravi Shanker, 1996). The estimated power shortfall in India at present is about 5000 MW and it could rise to about 43,000 MW in the next five years. To decrease this supply-demand gap, renewable energy sources have been given increased importance during the last few years. Thus, wind energy is expected to generate about 1000 MW, biomass about 140 MW, small hydro power about 172 MW and solar about 810 MW of power.
Though geothermal energy sources can potentially generate 10,600 MW of power, they have not been exploited to date. Additional exploration studies on thermal gases from these geothermal provinces have been carried out since 1996 in order to understand the reservoir characteristics. In addition, Deep Seismic Sounding (DSS) profiles were carried out across several geothermal provinces (Son-Narmada-Tapi; West coast and Cambay ) to understand the crustal structure below these thermal provinces. Several potential sites were identified for further exploration through deep drilling. Private power producers are keen to develop this source with financial partners from other countries.
EXPLORATION ACTIVITIES
Exploration activities in terms of geochemical studies on thermal gases, computer simulations and geophysical data acquisition, are being carried out in some of the most promising geothermal fields, like the Puga, Manikaran, Tattapani, Cambay, and the West coast. Work on other thermal provinces is yet to make a beginning.
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