Controlled Source Seismics and Gas Hydrates

Controlled Source Seismic

The CSIR-National Geophysical Research Institute (CSIR-NGRI) initiated Controlled-Source Seismic (CSS) studies in 1972, originally adopting deep seismic sounding (DSS) techniques collaboration with former USSR. Over time, advancements in data acquisition and interpretation facilitated the development of a national program aimed at mapping the continental crust of India. Initially, the institute focused on seismic refraction and wide-angle reflection techniques, later incorporating deep seismic reflection methods in 1992 and wireless telemetry in 1998. The adoption of a hybrid approach integrating refraction and reflection techniques significantly enhanced structural imaging and velocity estimation.

Through extensive CSS investigations, CSIR-NGRI has mapped over 6000 line-km across diverse geological provinces, yielding critical insights into the crustal dynamics, composition, and evolutionary history of the Indian subcontinent.

The primary goal of this group is to study India's deep crustal structure, providing essential data for geodynamic and tectonic research, which supports hydrocarbon and mineral exploration.

First DSS study in Kavali-Udipi Profile, Dharwar Craton

Major Deep Seismic Sounding (DSS) Profiles in India.

Cratonic and Orogenic Regions: Kavali-Udupi (Dharwar Craton), Perur-Chikmagalur (Dharwar Craton), Aravalli-Delhi Fold Belt, Southern Granulite Terrain (SGT).
Sedimentary Basins: Cuddapah Basin, Cambay Basin, Kachchh Basin, Saurashtra Peninsula, East Coast Sedimentary Basins, West Bengal Basin, Mahanadi Basin, Pranahita-Godavari Rift Basin, Rewa Basin.
Seismically Active and Tectonic Regions: Central Indian Tectonic Zone, Koyna Region, Deccan Syncline, and Northwest Himalaya.

Deep Seismic Imaging of Kachchh Basin using Reflection study and CRS technique.

Velocity Model of Sinor-Valod Profile of Deccan Syneclise Region using Ray-Trace Inversion and Tomography.

Key Methodological Developments.

Refraction Data Interpretation: Statistical inversion methods solved hidden layer problems (Kaila & Narain, 1970).
Seismic Reflection Migration: Early computational techniques improved accuracy over conventional methods (Kaila & Krishna, 1979).
Low-Velocity Layer Solutions: New methods estimated LVL thickness using refraction and reflection data (Kaila et al., 1981; Sain et al., 1995).
Wide-Angle Reflection Analysis: Advanced inversion techniques refined crustal structure estimates (Sain & Kaila, 1994, 1996).
Velocity Inversion Challenges: Modeled seismic wave behavior in complex velocity structures (Tewari, 1998).
Reflection Seismic Theories: Established asymptotic behavior of time-offset power series in reflection seismic (Ghosh & Kumar, 2002).
New Estimation Approaches: Developed travel-time-based methods to determine layer thickness and velocity without prior velocity data (Kumar et al., 2003).

Gas Hydrates

Gas-hydrate is crystalline form of the methane and water and is a promising futuristic natural energy resource that occur under low temperature (<15o C), high-pressure (>5 MPa) conditions with sufficient methane concentration. In general, these conditions are existed in shallow sediments along the continental margins and permafrost regions. The schematic view of the seismic experiment and gas-hydrate stability zone are shown in following figures.

The real-time gas-hydrate samples and evaluated thickness of the gas-hydrates in Indian subcontinental region are shown in below.

Major achievements:

Proposed new approaches for delineation, characterization, quantification of gas-hydrates.
Delineated gas-hydrates in Krishna-Godavari (KG), Mahanadi and Andaman regions by identifying BSR (marker for gas-hydrates) and characterizing various seismic attributes.
Validated occurrences of gas-hydrates in eastern Indian margin by drilling and coring
Acquired 7500 line Km MCS and 880 line Km OBS data in KG and Mahanadi basins for detailed investigation of gas-hydrates, and identified new prospective zones.
Imaged gas-hydrates and free-gas bearing sediments by seismic travel time tomography.
Appraised 5-15% of gas-hydrates and 3.0-4.5% free-gas of pore volume at BSR along a seismic line in the Arabian Sea using AVO crossplot & rock physical modeling.
Estimated, for the first time, saturation (33-41%) of gas-hydrates in fractured shale in KG basin by indigenously developed method based on sophisticated effective medium theory.
Published more than 60 articles on Gas-hydrates in reputed journals.