Geological Controls and Evidence for Gas Hydrate Occurrences in the Kerala-Konkan Basin on the Western Continental Margin of India

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.