OS034-01
Prospecting for gas hydrate using public geophysical data in the northern Gulf of Mexico
Prospecting for gas hydrate using public geophysical data in the northern Gulf of Mexico
Friday, 11 December 2020: 17:32
Virtual
Abstract:
We present the first basin-wide gas hydrate prospecting in the northern Gulf of Mexico since early-2010, when Bureau of Ocean Energy Management released its BSR mapping and preliminary resource evaluation studies. We discover new gas hydrate accumulations using 3D seismic data over the area of ~18,000 km2, which is comparable with the area of New Jersey. These seismic data were released after a 25-year proprietary term and now available to the public. We use seismic attribute analyses in five Project Areas to identify hydrate induced amplitude anomalies at the predicted base of gas hydrate stability zone (GHSZ), and where data quality allows, provide detailed characterization of the most promising gas hydrate prospects. Where available, we also use well log data to identify lithology of potential hydrate-bearing units from gamma ray and electrical resistivity logs.
We identified phase reversals and multiple bottom simulating reflections (BSRs) within channel systems, over salt domes and at the feather edge of GHSZ in water depths ~500-2200 m (~0 to 500 m subseaflor depth). We found that both channel deposits and salt tectonics are important prerequisites for the most prominent BSRs, suggesting that high-saturation gas hydrate tend to form in coarse-grained depositional systems in salt cored anticlines and domes. Associated salt-induced faulting could provide routes for thermogenic gas for some of the gas hydrate accumulations, however we also identified gas hydrate in systems without evidence of advection. The area of BSRs mapped in all Project Areas exceeds 250 km2. We also compiled a database of BSR-derived geothermal gradients that vary from 23 to 60 °C/km over the study area. Our study provides a collection of potential gas hydrate accumulations that can be used for more detailed hydrate resource estimates, as well as guide further reservoir scale analyses and drilling site selection.
We identified phase reversals and multiple bottom simulating reflections (BSRs) within channel systems, over salt domes and at the feather edge of GHSZ in water depths ~500-2200 m (~0 to 500 m subseaflor depth). We found that both channel deposits and salt tectonics are important prerequisites for the most prominent BSRs, suggesting that high-saturation gas hydrate tend to form in coarse-grained depositional systems in salt cored anticlines and domes. Associated salt-induced faulting could provide routes for thermogenic gas for some of the gas hydrate accumulations, however we also identified gas hydrate in systems without evidence of advection. The area of BSRs mapped in all Project Areas exceeds 250 km2. We also compiled a database of BSR-derived geothermal gradients that vary from 23 to 60 °C/km over the study area. Our study provides a collection of potential gas hydrate accumulations that can be used for more detailed hydrate resource estimates, as well as guide further reservoir scale analyses and drilling site selection.