Estimation of Gas Hydrate Saturation Using Rock Physics Modelling - A Case Study in the Krishna-Godavari Region

The NGHP Expedition 01 confirmed the presence of gas hydrate in the Krishna Godavari basin region. We have used the LWD sonic log of the NGHP-01-05 site obtained during this expedition and determined the hydrate reservoir properties using two different rock physics modelling approaches. We applied the ant colony global optimization technique to invert the acoustic properties into reservoir properties. The initial models used during the inversion were generated using rock physics equations. The region lying above the BSR was subjected to determination of gas hydrate saturation while the one below BSR was analyzed for free gas. The saturations of hydrate and free gas and also the porosity of the sediments were mapped for the NHGP-01-05 well. It was found that the sediments at the site are saturated with about 12-20% gas hydrate and 0.5-1.5% free gas.