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M. Simhadri Naidu ¹, P. Prasada Rao ¹, B. Ashalatha ¹, N. K. Thakur ¹

Affiliations
1 National Geophysical Research Institute, Uppal Road, Hyderabad - 500 007, IN

Abstract

The Kerala-Konkan Basin on the Western continental margin of India (WCMI) with 2 to 3 km maximum sediment thickness and suitable percentage of Total Organic Content (TOC) provides an interesting avenue for the exploration of gas hydrates. The identification of characteristic feature i.e. Bottom Simulating Reflectors (BSRs) in the multi-channel seismic data provides the inference about the presence of gas hydrates in a region. However, in absence of one of the main characteristics of BSR (i.e. cross-cutting with the geological strata) in the Kerala-Konkan Basin, we have examined other evidences such as venting, pockmarks, faulting, blanking and diapirs. The seismic sections show several deep faults which can be traced up to the seafloor in a few locations. Shallow faults within the sediments in the vicinity of deep faults have been observed. The presence of several deep and shallow faults provides channels for vertical gas-fluid migration contributing to the methane in the shallow sediments. The region is characterized by compression related diapiric structures bounded by faults. The columnar fractures occurring below the seafloor and depressions are interpreted as fluid/ gas escape features. Over-pressured sediment structures, large amplitude reflections within the sand layer indicate that gas is probably abundant in this area. The present study deals with analysis of geological and tectonic processes and the structural controls derived from the re-interpretation of seismic reflection sections for understanding the formation of gas hydrates in the Kerala-Konkan Basin.

Keywords

Gas Hydrate, Faults, Fluid/Gas Migration, Kerala-Konkan Basin.

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B. Ashalatha ¹, R. N. Singh ²

Affiliations
1 National Geophysical Research Institute, Hyderabad - 500007, IN
2 National Environmental Engineering Research Institute, Nehru Marg, Nagpur - 440 020, IN

Abstract

The thermal structure of Carlsberg Ridge in the northwest Indian Qcean is discussed using the plate model with realistic thermal boundary condition at the ridge axis, which includes the effects of adiabatic cooling, magmatic crystallization and solidification. The elastic and brittle layer boundaries as predicted by the model are shallower when compared with results from earlier studies using gravity-bathymetry data across the ridge and seismicity at the axis of the ridge. In order to explain the observed anomalous structure, we consider hydrothermal circulation as resulting in additional heat loss. This is incorporated in the thermal model by presenting lower temperature in the shallow regions at the axis where fluid flows could occur. The resulting thermal structure explains the observed elastic thickness and brittle layer thickness.

Keywords

Carlsberg Ridge, Elastic Thickness, Thermal Structure, Plate Model, Hydrothermal Circulation.

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