Proceedings World Geothermal Congress 2010 Bali, Indonesia, 25-29 April 2010 Exploration Strategy for Hot Springs Associated with Gondwana Coalfields in India P.B. Sarolkar Geological Survey of India, Seminary Hills, Nagpur [email protected] Keywords: Strategy, Gondwana Coalfield, Geothermal, 2. GONDWANA BASINS IN INDIA Hotsprings The Gondwana basins of Peninsular India are restricted to the eastern and central parts of country and are dispersed in ABSTRACT linear belts along major river valleys, including the Damodar The Gondwana coalfields in India are a warehouse of fossil Koel, Son-Mahanadi, Narmada (Satpura area) and Pranhita- fuel energy sources. The coal bearing formations are Godavari basins. The present day basins are likely to be the deposited in deep subsiding basinal structures confined to faulted and eroded remnants of past ones (Dy. Director half-grabens. The Talchir, Barakar, Barren Measures and General, 2007). The Gondwana Coalfields in India are Raniganj formations were deposited in this subsiding basin scattered in the states of West Bengal, Jharkhand, Bihar, with basement rocks separated by faulted margins. The Chhattisgarh, Madhya Pradesh, Maharashtra and Andhra contact of Gondwana rocks with the basement is marked by Pradesh. The important coal fields are shown in Figure 1. faulted margins, while the downthrown side represents a basin of deposition where a huge pile of sediments were All these coalfields have basements with faulted margins, deposited. The cumulative thickness of the sedimentary pile along which Gondwana sedimentation took place. The in the basins varies from 1200 m to 3000 m, depending on Gondwana supergroup of formations hosts coal, coal bed the Gondwana formations deposited. Sedimentary rocks are methane, and number of hot springs. Some promising mostly permeable, facilitating deep percolation and lateral geothermal areas in Central India are associated with the movement of groundwater. The water percolating to deeper Gondwana Formations. The important geothermal resources levels collects heat during the subsurface movement and in India reported along the Gondwana margins are the follows the conduit provided by fault zones for upward Tatapani Geothermal field in the Surguja district, the movement toward the surface, giving rise to hot springs Anhoni-Samoni hot springs in the Hoshangabad district, and along Gondwana margins. The hot springs at Tatapani in the the Salbardi hot springs in the Betul and Amaravati districts. Surguja district (52°C –97°C), Anhoni Samoni in the U.L. Pitale et al. (1994) described the importance of Hoshangabad district (45°C –54°C), and Managuru (40°C- Gondwana margins in the location of hot springs in Central 42°C) in the Khammam district are located along the fault India. In addition to the abovementioned hot spring areas, controlled Gondwana margins. During drilling, hot water the Geological Survey of India has reported artesian flow of was encountered in the Mand –Raigarh coalfield in the hot water from boreholes drilled in the Gadghora coal belt in Raigarh district and the Kothagudem coalfield in the the Raigarh, Chhattisgarh, and Birbhum districts of West Khammam district. These hot springs are of intermediate Bengal. The properties of hot springs reported along enthalpy and may be utilized for direct heat schemes, Gondwana Coalfields are summarized in Table 1. particularly during winter months. The need to explore the Gondwana coalfields for geothermal energy resources for 2.1 Tatapani Geothermal field, Surguja district site specific direct use and electricity generation is The Tatapani -Jhor geothermal field in the Surguja district is emphasized in this paper. The fault margins of the located in the Son valley along the margin of the Tatapani- Gondwana basins form a suitable locus for exploration. Ramkola coalfield. The geological work carried out here has Geophysical surveys associated with drilling along the determined a sizeable geothermal anomaly. The geothermal intersecting lineaments are possible sites for geothermal 2 anomaly is intense over an area of 0.5 km , with hot springs exploration. discharging water at up to 97°C (Ravishanker 1987). The hot springs at Tatapani are spread over an area of 0.05 km2. 1. INTRODUCTION along the Gondwana-Proterozoic contact. The hot springs Geothermal resources all over the world show affinity to discharge water at 52°C to 97°C. A total of 26 boreholes structural features and tectonic blocks. Most geothermal were drilled in this field, 5 of which produce hot water at fields are located along plate margins or fault zones. The >100°C on the surface. These 5 wells produced hot water Gondwana Coalfields are deposited in fault controlled with a cumulative discharge of 1200 lpm to 1800 lpm. The subsiding basins or half-grabens. The huge amount of geological mapping of the area revealed a basement of sedimentation in Gondwana basins makes a good storage Proterozoic rocks and pink felspathic, granite gneiss. These area for groundwater due to good porosity and permeability. metamorphic rocks acted as a basement, over which the Gondwana sediments were deposited (Raja Rao 1983). A Interbasinal faulting and formational contacts provide easy thick pile of Gondwana sediments was observed resting passage for the movement of subsurface water. Additionally, unconformably over the basement. Three sets of faults have the inherent porosity and leaching cavities in sandstone been reported in these coalfields, and their interference has provide sufficient porosity forming sandstones to store resulted in the development of a number of horst/graben groundwater. The groundwater with deep circulation collects structures (D.K. Das et al 2007). The southern boundary of heat from the deeper part of reservoir, which forms hot the geothermal field is confined to the Tatapani fault springs if a suitable conduit to surface is available. Thus, the trending ENE-WSW with dip of 78°C toward the north Gondwana basin is a suitable locale for formation of the host (Thussu et al., 1987) and crosses faults trending NNE-SSW springs. that demarcate the E-W extent of geothermal field. 1 Sarolkar Overlying Gondwana rocks with high porosity and The Gondwana sediments comprise mostly the Talchir permeability act a very good transmission zone for Formation of greenish grey splintery shale, fine grained downward percolation of meteoric water (Pitale et al 1996). sandstone, and rhythmite. This formation trends N60°W- The downhole well testing of these production wells has S60°E to E-W with moderate dips toward the south. The indicated a maximum temperature of 112.5°C. The Bagra Formation, comprising coarse conglomerate and silty geothermal anomalous zone extends over an area of 1.26 brick red clay, is brought in juxtaposition with the Talchir km2 for the isotherm of 100°C at a depth of 300 m. The heat Formation and Proterozoic rocks due to ENE-WSW trending flow values calculated from the borehole data are 241.4 faults and numerous sympathetic minor faults trending mW/m2, with a temperature gradient of 0.08° to 0.1°C/m N50°W-S50°E which act as conduits for upflow of thermal (Ravi Shanker, 1987). water. 2.2 Anhoni- Samoni hot springs, Hoshangabad district Free flow of thermal water was encountered in borehole ANH-1 at a depth of 585 m with well-head temperature of The Anhoni-Samoni Geothermal field is located in the 50°C and in borehole ANH-2 at a wellhead temperature of foothills of Pachamarhi, in the southern part of the Narmada 53°C and a flowrate of 130 lpm. The thermal gradient varies lineament zone, near the Gondwana contact with basic sill in from 0.058°C/m to 0.109°C/m in this area. Chhindwara district. The geothermal manifestations are in the form of isolated hot springs and clusters of hot springs with sporadic gaseous activity located along a nala. The temperatures of the hot springs range from 30°C to 43°C. 68 ° 72° 76° 80 ° 84 ° 88° 92° 96 ° m m m m m m m m 36° m36° COALFIELDSCOALFIELDS ANDAND LIGNITELIG NITE OCCURRENCESOCCURRENCES OFOF INDIA 1 %Sri nagar 2 3 4 500 0 500km Kilomet 79 32° m32 ° Simla % Chandigarh% 28° m28 ° New De%lhi 8 5 23 6 10 12 1 7 2 13 18 3 14 17 4 9 16 15 11 24 Ga n g t o k 25 19 21 % % Itan agar 5 2 Jaip ur 6 24 20 26 7 % 8 23 Lucknow 25 % 30 28 27 31 26 29 Di s pu r 32 % 9 10 33 35 Kohima 34 % 2 Shillo ng 36 20 % Patn a 19 14 15 1 % 12 21 17 13 18 Imphal 24° 16 % m24° 37 38 39 32 27 33 31 41 44 51 34 44 30 40 47 43 Aizawl 46 % Agartala 39 28 % 48345 41 8 45 49 29 49 52 464037 # 42 35 70 42 50 50 4748 43 Bhopal 53 56 36 51 Gandhin agar 5457 % 62 % 55 61 59 78 60 58 63 64 Cal cutta 7 66 % 65 75 76 53 52 54 67 74 68 20° Tertiary Coalfields 73 1. Mi ao-bum m20 ° 72 Bhu baneswar % 2. N amchik - Namp huk 71 3. Makum 4. Dilli - Jey pore # 5. Ti ru # Lign it e Occur renc es % Mumbai 6. Borjan 1. Nicha# hom Baramula 36. Jalipa # 7. Tu en Sang 69 2. Na#gbal 37. Lakhpat 8. Jh anzi-Disai 3,4. Firozpu# r Shalig anga 38. Dhed adi Gondwana Coalfields # 5. Khari 39. Pranpur Hy derabad 70 9. K oilajan # % 22. Singrimari 52. Korar 6. Gangashahr 40. Kaiyari 55 10. Diphu 16° # 23. Abor Hills 53. Umaria # 69 68 # # 7,8. Sarup# Desar 41. Pana ndhro 11. Bapu ng 67 24. Daph la Hi lls 54. Johilla 16° 9. Ko#layat 42. Akhr imota # # m # 25. Aka Hills 55. Soha gp ur 12.