October, 2014

October, 2014   ||  Volume 18 No.4



An anomalous high conductivity upper crustal body detected underneath the Surajkund hot spring area from a magnetotellric study

S. Prabhakar Eknath Rao1*, G. Dhanunjaya Naidu 2, T. Harinarayana 3, S V S Sarma1 and A.K. Gupta1

1CSIR-National Geophysical Research Institute, Hyderabad- 500 606, India.
2 Central Water and Power Research Station (CWPRS), Pune, Ministry of Water Resources, India-411024.
3 Gujarat Energy Research and Management Institute (GERMI) Research Center, Gandhinagar, Gujarat, India-382007.
*Corresponding author: pesatdive@gmail.com


Surajkund geothermal area in Jharkhand state is considered to be an important geothermal region after Tatapani hot spring area of Chhattisgarh state, in the Narmada-Son Lineament (NSL) zone, India. It lies within the Proterozoic metamorphites with highly fractured migmatites/gneisses associated with chert. With a view to understand the subsurface electrical structure of the hot spring area and to examine its relation to the origin of hot springs, a magnetotelluric (MT) survey covering a total of 21 stations was conducted in and around the Surajkund hot spring area. Among these stations, a subset of 12 MT soundings, which fall on NW-SE trending profile passing through the hot spring location have been selected for the present study. The 2D modeling results of the MT profile brought out an anomalous, 10 km thick horizontal crustal conductor (5-10 Ohm.m) underneath the Surajkund hot spring area in the depth range of 5-15 km. The anomalous high conductive feature in this tectonically active NSL zone is inferred to be magmatic material originated from upper mantle depths and emplaced in the upper crust. This feature is suggested to be closely related to the geothermal conditions of the area and the low resistivities are attributed to partial melts and the associated fluids. Inversion results also indicate another feature, a moderately resistive (~100 Ohm.m) narrow vertical feature at shallow crustal depths (<5 km.), close to the hot spring. This feature, which falls over a fault/shear zone indicated from surface geology is inferred to be a fault zone connected to the horizontal high conductive body and possibly provides pathways for upward transportation of fluids from deeper levels.


Coping groundwater depletion through scientific agronomical practices in Hard-rock areas of Nalgonda District, Telangana

*Rajesh Rekapalli1,2, R.K.Tiwari1,2,M.J.Nandan2 and T.Balaji2

1AcSIR-NGRI, Hyderabad, India
2CSIR-NGRI, Hyderabad, India
*Corresponding Author: rekapalli@gmail.com

The Mandollagudem TECHVIL Cluster located in Nalgonda District, Telangana falls under drought prone area as it receives an average rainfall of 620 mm. The region is characterised by low infiltration of surface water and poor connectivity between the aquifers. Groundwater levels dropped significantly during the past decade due to the over exploitation of ground water induced by the shifting of crop pattern from Castor/Cotton to paddy cultivation in addition to the exogenous processes. Since it is very difficult to suddenly shift to new crop, we suggest that the adoption of the System of Rice Intensification (SRI) method along with Alternate Wetting and Drying (AWD) and Direct Seeding (DS) methods will reduce the consumption of water up to 30 percent with more grain productivity compared to continuous uncontrolled flooded field methods. From the statistical analysis of various data sets, it is concluded that the adoption of low water consuming crops and scientific irrigation practices are the most recommended solutions to mitigate the drastic depletion of groundwater levels.


Gas Hydrate occurrences in the Andaman offshore, India – Seismic Inferences
N. Satyavani*, Kalachand Sain and V. Jyothi
CSIR-National Geophysical Research Institute, Uppal Road, Hyderabad - 500007
*Corresponding author: satyavani_nittala@yahoo.com

Multi-Channel Seismic (MCS) data in Andaman offshore shows a prominent bottom simulating reflector (BSR) at a depth of ~575 meters below the seafloor (mbsf), indicating the presence of gas hydrates/free gas in the region. Based on AVO modeling and attenuation (Q-1), an attempt has been made to qualify if the BSR is related to gas-hydrates underlain by free gas. The travel time tomography of identifiable seismic phases has also been carried out to delineate the general distribution of gas hydrates and/or free gas along the seismic line. The increase in seismic amplitudes at BSR, almost double to that of the seafloor, indicates the presence of free gas below the BSR and the study of Q made at two locations (with and without BSR) indicates the presence of gas hydrates above the BSR. These observations are further confirmed by the results of travel time tomography where a ~200m free gas zone with a velocity of 1.4-1.7km/s is found to be overlain by ~400m thick gas hydrate zone with a velocity of 1.8-2.2km/s.

Detecting oil contamination by Ground Penetrating Radar around an oil storage facility in Dhanbad, Jharkhand, India
Subba Rao Ch* and Chandrashekhar V
Central Water and Power Research Station, Pune 411024, India
Tel.9120-24103484 Fax. 9120-24381004
Corresponding author: chilukuri3_2000@yahoo.com

The subsoil and groundwater were suspected to be polluted by leakage from underground tanks around the oil storage facility in Dhanbad, Jharkhand, India. To delineate the seepage zone, integrated geophysical methods comprising Ground Penetrating Radar (GPR) and 2D Electrical Resistivity Imaging (ERI) methods were employed over the suspected zone and in the close vicinity. The studies were conducted over eight underground storage tanks containing petrol and kerosene. GPR system with antennas operating at frequencies of 250 MHz and 800 MHz were deployed. The GPR survey delineated a hydrocarbon contaminated soil and/or groundwater zone as deciphered from the amplitude shadow zones within 0.7- 1.0 m depth from the surface. Limited Electrical Resistivity Imaging (ERI) study was conducted over one traverse using a 2D multi electrode imaging system employing ‘Wenner-Schlumberger’ configuration in the area where GPR anomalies were located. Relatively lower resistivities ranging from 0.5 ohm-m to 9.5 ohm-m were found at the locations where GPR anomalies indicated hydrocarbon seepage. The results from the ERI study revealed a good match with the findings from GPR study.

Multi-litho Attribute based Inversion for Reservoir Classification in Kalol Reservoir, Cambay Basin, India
Surajit Gorain
Prize Petroleum Company Limited, 3rd floor UCO Bank Building, Sansad Marg, New Delhi
Email-ID: sgorain@gmail.com, Phone no:+919999981246, Fax no: +91-1123737898

Kalol Field, Cambay Basin India, was discovered in June 1961 and put on production in 1964. But the production history reveals that oil recovery remained hardly around 10% (Jena, 2008). Most often, the contributing factor for this low recovery is poor reservoir facies (tight silts) within the major producing sequences like Kalol IX and Kalol X. Identifying areas of better reservoir facies remained a challenging task before the geo-scientists.
To tackle the above challenge, geo-scientists evolved seismic inversion. Inversion through sonic log has been a trend for many years as a litho-prediction tool. But it is often observed that sonic log alone is not fully effective in resolving the subtle differences between clastic facies like Silty Sand and Silty Shale.
Conventional seismic inversion approach has been modified and a “Multi-litho Attribute based Inversion” has been developed to overcome this challenge of reservoir classification in which 3D attribute volume of petrophysical properties are calculated through Genetic Inversion algorithm using a correlation between seismic property and log property. Calculated 3D attribute volume of petrophysical properties are utilized for reservoir classification.
It is known that Gamma Ray log is very effective in differentiating subtle vertical variations in clastic litho-facies in wells, whereas resistivity gives the idea of porosity. Keeping this in view, an attempt is made to develop a correlation between log property (Gamma Ray, Resistivity) and seismic property (seismic envelope) against the reservoir section in Kalol Pay and developed a “Multi-litho Attribute based Inversion” method to identify the areas of better reservoir facies within the productive sequences in the field. This approach is operative even if the reservoir is very thin beyond seismic resolution and can provide a probability distribution map of reservoir. This approach is also effective in determining the reservoir geometry and quality of reservoir, which may help in planning future drilling locations.

Efficacy of Kumarswamy method in determining Aquifer Parameters of Large-Diameter Dugwells in Deccan Trap Region, Nagpur District, Maharashtra
*Abhay M. Varade1, Rahul Shende2, Bhushan Lamsoge2, Kartik Dongre2 and Amit Rajput1
1 Post Graduate Department of Geology, RTM Nagpur University, Nagpur (MS)-440001
2 Central Ground Water Board (CGWB) Central Region, Civil Lines, Nagpur (MS)-444001
*Correspondinfg Author: varade2010@gmail.com

Since ancient times, withdrawal of groundwater in India is carried out from shallow level phreatic aquifers by the means of dugwells. These shallow unconfined/anisotropic aquifers, generally comprising weathered material, are tapped by the dugwells of large diameter. Such wells, specially penetrating the crystalline and basaltic terrain ensure large storage of groundwater in low permeability aquifer conditions. Therefore, proper understanding of the characteristics and behaviour of this almost omnipresent phreatic aquifer, being tapped by vast number of large diameter dugwells becomes imperative. In view of this, an attempt has been made here to analyze the pumping test data of ten (10) large diameter dugwells, falling under micro-watershed of WGKKC-2 of Kalmeshwar Tehsil, Nagpur district, Maharashtra. The drawdown and recovery data, generated through pumping tests were analyzed by the empirical formula given by Kumarswamy (1973). The transmissivity (T) and specific yield (Sy) values for the large diameter dugwells, tapping the phreatic aquifer of study area were found in between 22.43-385.60 m2/day and 0.028-0.127 (fractions), respectively. The permeability (K) and specific capacity (C) values range in between 0.99-82.96 m/day and 68.45-526.37 lpm/m, respectively. Subsequently, these results were compared with ‘T’ and ‘Sy’ values, reported by various workers/departments elsewhere in the basaltic terrain of Maharashtra. The range of observed values of ‘Sy’ and ‘T’ of present study confirms to those values reported earlier by the previous workers. The overall study indicates the efficacy of Kumarswamy (1973) method in determining the aquifer parameters of large-diameter dugwells tapping the basaltic aquifers.

Applications of heat conduction equation based models in Indian geology
R N Singh
CSIR-National Geophysical Research Institute, Hyderabad 500 007
Corresponding Author: rnsingh@ngri.res.in

Active Seismograph for Early Detection of Earthquake
D.N. Avasthi
SPS Consultants, New Delhi

Passive seismographs can detect impending earthquakes only a few minutes before the occurrence of an earthquake. In contrast, active seismographs can detect impending earthquakes months in advance. As such they are better suited to issue necessary warning with sufficient time in hand to meet the disaster that the impending earthquake may bring about. Apart from activating the disaster management to get prepared to meet the eventuality by taking steps to minimise the risks to local population, civil constructions, buildings, water and power supplies, active seismographs are found most useful for shutting off operating nuclear power plants. Such an operation in time, in the region of impending earthquake helps to ward of any catastrophic situation due to uncontrolled nuclear radiations.
Active seismographs measure the response of subsurface geologic and tectonic features, which include changes in the rock properties under stress generated due to progressive increase in destabilising geologic forces.
A simple, yet effective, system of active seismograph is described, which can conveniently be set up and monitored.

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