India is the second most populated country in the world and is known for its rich culture, its variety of spices, and amazing food. It is also home to more than 300 hot springs often associated with mythological beliefs and places of worship. These hot springs are known to have medicinal and therapeutic purposes and are enjoyed by locals and tourists alike. Waters from geothermal areas associated with these springs have been used a wide variety of agricultural and manufacturing applications such as cocoon boiling for extraction of silk and curing of cement slabs.
Due to its geological history, India has a variety of rock masses and natural resources (mineral deposits, coal, and oil and geothermal resources). With this variety of rock masses, India is said to have rocks of almost all ages of the geological timescale.
Figure 1: Geothermal provinces in India (Gupta et al. 2010)
The Geological Society of India (GSI) identified ~400 hot springs that have been used to estimate the heat flow and geothermal gradients throughout India. Several geothermal provinces have been identified and are described below.
Himalaya geothermal province: Heat flows throughout the province are>100 mW/m2 and is due to mountain building processes. The main geothermal fields are summarized in the table below.
Table 1: Geothermal fields in the Himalayan Geothermal province, India. Estimated reservoirs temperatures calculated using various methods from references.
Sohana geothermal province: Hot springs have temperatures of 28 to 47 °C. The GSI estimated a geothermal gradient of 41 ± 10 °C/km and a heat flow of 100 ± 25mW/m2. Several boreholes ( up to 547 m) drilled yielded hot water of 44°C to 55°C.
West coast geothermal province: Hot springs located have temperatures from 34 to 72 °C. The geothermal gradient calculated from borehole surveys varies from 36°C to 78°C/km. Using geothermometry subsurface temperatures were estimated at 110 to 150 °C. The Unhavre Khed geothermal field has 6 geothermal wells and geophysical surveys (Resistivity) were carried out.
Gujarat-Rajasthan geothermal province: Gujarat – Hot springs have surface temperatures varying from 35 to 93 °C. High hot spring temperatures (93 °C) are close to igneous rock intrusions. At Rajasthan, hot spring temperatures are between 31 – 50 °C and the estimated reservoir temperatures vary from 120 to 150 °C. The maximum recorded heat flow value in the area is 205 mW/m2.
Cambay Basin: Boreholes drilled for oil exploration identified areas with high thermal anomalies. A thermal gradient of 70°C/km and a heat flow of 83mW/m2 were reported in the boreholes. Surface temperatures of 40- 90°C. are observer and reservoir temperatures are estimated 150 – 175°C.
Godavari geothermal province: Hot springs in this province have temperatures ranging from 30 to 62 °C. Estimated reservoir temperatures 175- 215 deg C. An estimated temperature gradient is about 45 °C/km. The maximum recorded heat flow in the area is 104 mW/m2.
Mahanadi geothermal province – Hot springs are reported along fractured rocks reaching temperatures of up to 96 deg c. Geothermometery studies on 8 geothermal springs estimated reservoir temperatures of 180 °C.
SONATA geothermal province
Tattapani geothermal area: Located in the Sarguja and Chhattisgarh region. The surface temperatures of the geothermal waters range from 30 to 97 °C. There are 26 known geothermal wells reaching depths of up to 620 m. The indicated reservoir temperature is 160°C to 190°C. From detailed geochemical studies, estimated a reservoir temperature of 205 to 217 °C. Several geophysical studies were carried out including gravity, magnetic-and self-potential.
Other thermal springs identified in this province include
Granites: Granites with high heat-generating capacity are found throughout the Indian continent. The geothermal provinces identified above have high heat flow values ranging from 75 > 200 mW/m2. Temperatures at a depth of about 1.5 km are in the range of 150 to 180 °C and increase to more than 220 °C at a depth of 4 km.
India has the potential to produce geothermal energy at a cost of USȼ 4.75/kWh. Additionally, in those areas where thermal gases are enriched in helium (He), commercial production of He can be planned. In Bakereswar and Tantloi geothermal areas, a pilot plant to extract and purify He from thermal gases is already in operation.
A 5KW geothermal power plant was installed in Manikaran that is now abandoned after a landslide destroyed the plant. India drafted a national policy, which aims to make India a global leader in the Geothermal power sector, by generating 1,000 MW in its primary phase by the year 2022.
Many direct use applications are in operation throughout India including industrial, agriculture, food processing, and tourism (spa, swimming, and bathing). See Table.
Table 2: Direct uses in geothermal areas India (adapted from Puppala and Jha, 2018)
The Ministry of New and Renewable Energy (MNRE) drafted a national policy for the development of geothermal resources in India. The goal is to develop 1,000 MW (thermal) and 20 MW (electricity) of geothermal energy capacity by 2022 and 10,000 MW(thermal) and 1000 MW(electricity) by 2030.
This concludes another Geothermal Country Overview as part of our larger #GeothermalFactsandStats blog series. A special thank you to our Guest Author, Jason Fisher for all his work that went into this piece. Please follow us on LinkedIn, Facebook, Twitter, and Instagram for more updates and stories promoting the geothermal potential around the world.
Geological Survey of India. http://www.indiaenergyportal.org/subthemes_link.php?text=geothermal&themeid=13
Government of India Ministry of New & Renewable Energy Draft National Policy on Geo-Thermal Energy. http://re.indiaenvironmentportal.org.in/files/file/Draft-National-Policy-on-Geothermal-Energy_0.pdf
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Sarolkar, P.B., 2018, February. Geothermal energy in India: poised for development. In Proceedings of 43rd Workshop on Geothermal Reservoir Engineering.
The USGS, the Himalayas: Two continents collide. https://pubs.usgs.gov/gip/dynamic/himalaya.html
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