Quantification of Gas Hydrates in Fractured Marine Sediments, Krishna Godavari Basin, India

Abstract

An effective medium theory for modeling elastic velocities in unconsolidated sediments with hydrate-saturated, random fractures was developed. In this model, elastic velocities are not sensitive to the size or orientation of fractures but only to their density and interconnectivity (the two extreme cases being fully disconnected and fully connected fractures). Comparing hydrates in fractures with other familiar states of hydrates suggest that elastic velocities increase due to hydrate-saturated fractures are more rapid than hydrates in pore-filling and load-bearing states. However, the increment is dependent on the mode of fractures; interconnected fractures show the highest velocity response. In Krishna Godavari (KG) Basin at NGHP 01-10 site, VP, VS, and hydrate saturation can be explained by simultaneously assuming two growth styles of hydrates- in matrix as load-bearing phase as well as in fractures. Although occurrence of fractures; both connected and disconnected show high fractures hydrates saturation (above 50% of fractures porosity), these zones are also associated with background matrix of low hydrates saturations and overall less total saturations.