Gas hydrate and free gas saturations using rock physics modelling at site NGHP-01-05 and 07 in the Krishna–Godavari Basin, eastern Indian margin

Several approaches exist for the estimation of gas hydrate and free gas depending on the nature and distribution of gas hydrate into the sediments. Here, we apply various rock physics models to the P-wave sonic velocity logs that were collected during the Indian National Gas Hydrate Program (NGHP) Expedition 01 at sites NGHP-01-05 and NGHP-01-07 for the resource estimate of gas hydrate. Using the weighted equation, it is found that maximum up to13% and 12% volumes of the pores of regional sediments above bottom simulating reflector (BSR) of sites NGHP-01-05 and NGHP-01-07 respectively are occupied by gas hydrates. Alternatively, gas hydrate saturations computed for these sites using effective medium models are found maximum up to 16% and 22%. We have further used the velocity porosity transforms to estimate the free gas saturations below the BSRs for both the sites. The saturation of free gas in the sediments at both the sites is found in the range of 0.5–2.2%.