Migration of methane at the diapiric structure of the western continental margin of India — insights from seismic data

Investigations are being carried out to locate the indirect evidences of gas occurrences in the Indian Continental Margins by identifying features like pockmarks, shale diapirs, venting as well as bottom simulating reflectors (BSR). We investigate one such case of a shale diapirs. Occurrence of free gas and gas hydrates is reported using a complex trace analysis to study the variation of reflection strength and instantaneous frequency along individual reflections. A frequency analysis over the flank of the shale diapir indicates attenuation of high frequencies, possibly representing the migration of fluids (probably methane) along the fault pathways. Similarly a plot of reflection strength along an individual reflector shows the migration pathways and significant blanking.