Gas Hydrates Potential of Makran Area, Offshore Pakistan

Abstract

Gas hydrates are part of the unconventional energy resources called the gas clathrates. The present work focused on the assessment of gas hydrates potential of Makran area, Offshore, Pakistan. The presence of a clear bottom simulating reflector (BSR) is primary indicator for the occurrence of gas hydrates and generally referred to as base of gas hydrates stability zone. The gas hydrates zone in the study area was identified by the application of seismic attributes (sweetness, relative acoustic impedance and normalized apparent polarity) using major characteristics of BSR i.e. amplitude blanking, adopting the shape of seafloor, cross cutting the sedimentary structures and opposite polarity to seafloor. A low velocity layer was also interpreted beneath the hydrates layer due to the existence of free gas. Rock physics modelling for the two different geometrical distribution of hydrates was also applied to obtain effective elastic properties. The results of rock physics modelling showed that the hydrates as part of sediments have higher elastic properties compared to hydrates in pore spaces, and these properties were controlled by saturation of gas hydrates. Using the effective elastic properties, amplitude versus offset (AVO) forward modelling (Exact Zoeppritz + ray tracing) for different scenarios was performed to characterize the presence of BSR more efficiently.