Gulf of Mexico Geological
The Gulf of Mexico basin, east of the United State, is a major source of natural resources contributing to 95% of North America’s Offshore Continental Shelf supply.
The basin’s geological history makes it uniquely poised to host natural resources like oil and gas which form from the fossils of deceased marine organisms lying flat on the seabed.
During periods of intense sediment deposition, fossils are buried, compacted and isolated from oxygen. This change in the chemistry of the environment causes the organisms to convert into kerogen. Over hundreds of thousands of years, and under increased temperature, kerogen converts into oil and natural gas.
Pressure from overlying rocks squeezes fluids like natural gas upwards through the natural pore space in rocks until the fluids reach an impermeable layer like salt.
To understand the large abundance of resources in the Gulf, we must understand the history of sedimentation. During the last super continental cycle Pangea, present day Eastern North America and West Africa were sandwiched together. The break-up of Pangea, due to a hot plume that under Iceland today, resulted in the inflow of oceanic water and the birth of the Gulf of Mexico about 200 million years ago in the Lower Jurassic.
Over the next 70 million years throughout the Jurassic, periodic sea level changes resulted in periods of water evaporation in the basin leaving behind huge deposits of salt, like the Bonneville salt flats in Utah.
Salt is like other sedimentary rocks and forms horizontal layers but has a low density of 2 grams per cubic centimetre and a low viscosity 1017 Pas which allows salt to flow like a fluid over long timescales.
100 million years ago during the Cretaceous, global sea level rise and warm water temperatures promoted the grown of coral reefs in the Gulf, and the deposition of limestone and chalk. About 80 million years ago, the growth of mountain ranges during the Laramide Orogeny in Central and North-Western North America resulted in the growth of expansive river basins like the Missouri and the Mississippi, which flowed out to south-east America and depositing huge volumes of sediments at the Mississippi delta.
The deposition of massive dense sediments on top of ancient fossils and salt layers caused compaction and overpressure of the salt, and upwards flow. This upwards flow fractured and faulted the overlying rocks, and the combination of impermeable salt with structural traps immobilise fluid migration meaning the oil and gas moving upwards through pore space concentrate where faults intersect salt.
Salt is like other sedimentary rocks and forms horizontal layers but has a low density of 2 grams per cubic centimetre and a low viscosity 1017 Pas which allows salt to flow like a fluid over long timescales.
100 million years ago during the Cretaceous, global sea level rise and warm water temperatures promoted the grown of coral reefs in the Gulf, and the deposition of limestone and chalk. About 80 million years ago, the growth of mountain ranges during the Laramide Orogeny in Central and North-Western North America resulted in the growth of expansive river basins like the Missouri and the Mississippi, which flowed out to south-east America and depositing huge volumes of sediments at the Mississippi delta.
The deposition of massive dense sediments on top of ancient fossils and salt layers caused compaction and overpressure of the salt, and upwards flow. This upwards flow fractured and faulted the overlying rocks, and the combination of impermeable salt with structural traps immobilise fluid migration meaning the oil and gas moving upwards through pore space concentrate where faults intersect salt.
The goal of exploration is to characterise the micro-scale feature of salt and sub-salt reservoirs to best guide drilling. Research institutions like Texas A&M’s Geochemistry and Environmental Research Group supplement industrial surveying with their own studies.
The Walker Ridge hosts 231 academic drilling cores and an abundance of experimental data on gas chromatography, carbon 1-4 headspace studies, and scanning fluorescence. These experimental techniques characterise the quality and concentration of natural resources.
Locations with available drill logs are found all throughout the official protractions and can supplement information that S-Cube yield from creating sub-surface models out of seismic data.
Read more about S-Cube’s work characterising sites within the Walker Ridge here at the Leading Edge Journal @ (https://library.seg.org/doi/full/10.1190/tle42030196.1 )
Keywords:
BOEM, Protractions, Salt, Gas chromatography