High concentration methane hydrate in a silt reservoir from the deep-water Gulf of Mexico

We present results from 30 quantitative degassing experiments of pressure core sections collected during The University of Texas-Gulf of Mexico 2-1 (UT-GOM2-1) Hydrate Pressure Coring Expedition at Green Canyon Block 955 in the deep-water Gulf of Mexico as part of The University of Texas at Austin–US Department of Energy Deepwater Methane Hydrate Characterization and Scientific Assessment. The hydrate saturation (S_h), the volume fraction of the pore space occupied by hydrate, is 79% to 93% within sandy silt beds (centimeters to meters in thickness) between 413 and 442 m below seafloor in 2032 m water depth. Sandy silt intervals are characterized by high compressional wave velocity (V_p) (2515–3012 m s⁻¹) and are interbedded with clayey silt sections that have lower S_h (2%–35%) and lower V_p (1684–2023 m s⁻¹). Clayey silt intervals are composed of thin laminae of silts with high S_h within clay-rich intervals containing little to no hydrate. Degassing of single-lithofacies sections reveals higher-resolution variation in S_h than is possible to observe in well logs; however, the average S_h of 64% through the reservoir is similar to well log estimates. Gas recovered from the hydrates during these experiments is composed almost entirely of methane (99.99% CH₄,