Integrated Geophysical Analysis for the presence of Gas Hydrates in Blake Ridge, Offshore, South Carolina, USA

Abstract

Gas hydrates contain a major untapped source of energy and are of potential economic importance. The Blake Ridge is one of the largest passive margins of gas hydrate provinces on Earth. The Blake Ridge Diapir is the southernmost of a line of salt diapirs along the Carolina trough. Gas hydrates are supposed to be present on the crest of the Blake Ridge. Identification and quantification of gas-hydrate and free-gas reservoirs in unconsolidated sediments using seismic data are important because the seismic method is the most promising remote sensing technique for the delineation of such prospects. Analysis of three-dimensional (3D) seismic data has led to significant advances in our understanding of the distribution of gas hydrates on the Blake Ridge. The most significant observation is a thick zone of gas hydrates. Bottom-simulating reflector (BSR) is observed as the base of the Gas Hydrates Stability Zone (GHSZ). BSR is not continuous throughout, and that can be explained by low methane supply rates or gas seeps. Seismic attribute analysis, seismic interpretation, petrophysics, inversion, Lambda-Mu-Rho (LMR) inversion, porosity section, and saturation results support the presence of gas hydrates. Amplitude blanking is also observed above BSR, which is a typical indication of gas hydrates. The porosity section was calculated using the cross-plot method, while saturation was derived from probabilistic neural network (PNN).