Seismic characterization of hydrates in faulted, fine-grained sediments of Krishna-Godavari basin: Unified imaging
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A combination of diffusion and advection in fine grained sediments can create a patchy Bottom Simulating Reflector (BSR) which has little to no apparent correlation with the overlying hydrate distribution. Using 2D seismic data from faulted, clay-rich sediments in the Krishna-Godavari (KG) basin, we show both the hydrate distribution and the BSR structure are fault controlled. Our demonstration hinges upon a kinematically accurate P wave velocity (V sub(P)) model which is estimated using a composite traveltime-inversion, depth-migration method in an iterative manner. The flexibility of the method allows simultaneous usage of traveltimes from multiple, discontinuous reflectors. The application begins with a simple V sub(P) model from time processing which is reflective of a diffusive, continuous, hydrate– and free gas–bearing system. The application converges in three iterations yielding a final V sub(P) model which is suggestive of a patchy distribution of hydrates and free gas possibly developing through a combined diffusive-advective system. The depth image corresponding to the final V sub(P) model can be interpreted for faults that suggest ongoing tectonism. The BSR appears to be truncated at active faults zones. Both the final V sub(P) model and the corresponding depth image can be reconciled with the hydrate distribution and BSR depth at logging/coring sites located approx. 250 m away from the line by projecting the sites along the strike direction of the regional faults.
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