Exploration for Gas Hydrates Based on Seismic Information – With Examples from Northern Gulf of Mexico

摘要

A five-step, integrated workflow is developed to delineate shallow gas hydrates using seismic information. We applied the workflow and estimated gas hydrate saturations in two study areas in the northern deepwater Gulf of Mexico. Due to lack of hard data (well control) for the shallow seismic data, our predictions used analogue models based on geologic interpretation, seismic inversion, and the basic principles of rock physics. To examine our predictions, we analyzed the hydrate from the wells that were drilled afterward and compared the “ground-breaking” truth from drilling with our pre-drill predictions. The comparison indicates that our pre-drill seismic predictions for gas hydrate saturations are in agreement with the log-based estimates (resistivity and sonic), as well as core data, especially when the hydrate concentrations are high. However, some uncertainties do exist regarding the current seismic detection method. These are mostly due to lack of constraints on the shallow rock model and seismic inv ersion during the pre-drill phase. Despite these uncertainties, our seismic-based methodology did provide valuable pre-drill information for selecting potential drill sites and to further characterize gas hydrate- bearing sediments. This technique could be used elsewhere, both onshore and offshore.