Mapping Gas Hydrates in the Gulf of Mexico Using Marine CSEM

Gas hydrates are a geohazard and a potential energy resource, yet the estimated global volume varies by over four orders of magnitude. This is because mapping hydrates with seismic methods alone is difficult, showing only the edges of the hydrate stability zone. Another technique, marine controlled source electromagnetic (CSEM) techniques, are more apt in estimating hydrate saturations than seismic methods. In 2008, an extensive CSEM data set was collected in the Gulf of Mexico (GoM) aimed at developing the CSEM technique to map marine gas hydrates. Preliminary 1D apparent resistivity pseudo-section results of the data show lateral variations in resistivity that may be attributed to gas hydrate, deeper salt bodies, carbonates, and water saturated channel sands. However, the exact resistivity values and geometries of hydrate emplacement within the surrounding sedimentary architecture requires 2D or even 3D modeling and inversion before final interpretations of the CSEM data and volume estimates of gas hydrate saturation can be made. Here we apply a newly developed parallel goal-oriented adaptive finite-element modeling algorithm (referred to as MARE2DEM) for efficient 2.5D imaging of the CSEM data and present preliminary inversion results for the GoM survey.