Rock Physics Models for Gas Hydrate Exploration - Where Are We?

Gas hydrate exploration technology has developed from an interpretation of Bottom Simulating Reflections (BSRs) on seismic data to more advanced target oriented acquisition of seismic and other geophysical data. The rock physics modeling also developed in parallel to keep up with a demand for interpreting the observed anomalies and also the joint inversion of geophysical data such as controlled source electromagnetic and seismic. The simplest models of using empirical methods have given way to more sophisticated methods of incorporating rock microstructure into the inversion to minimize the uncertainties involved in predicting gas and gas hydrate saturations associated with gas hydrate prospects. Models combining rock property measurements and host medium grain to grain interactions gave good control on background rock properties about the host medium and hydrate microstructure. Self consistent approximation - differential effective medium (SCA/DEM) approach gave an opportunity to incorporate the microstructure through statistical assumptions. Visco-elastic effects of fluid flow within the gas hydrate microstructure and frequency related interface properties on seismic attenuation is incorporated into a new rock physics model which can explain contrasting acoustic observations from gas hydrate zones from different geological settings.