JANUARY 2016 LUNCHEON MEETING
Dr. Martin Cassidy
from the University of Houston
the Norphlet Desert and its Sand Dunes
11:30 AM Wednesday, January 20, 2016
at the Cascades
4511 Briarwood Road
Tyler, TX 75709
Dr. Martin Cassidy's
(click to read)
"Gulf of Mexico USA,
The Norphlet Desert and its Sand Dunes in a sub-aerial basin below Sea Level,
a SABSEL basin"
by Dr. Martin M. Cassidy, research scientist
Department of Earth and Atmospheric Sciences
University of Houston
In the late Triassic extension of Pangaea future Gulf of Mexico rifting began with a horst and graben terrain filled with clastic non-marine sediments. As extension and subsidence continued the ocean entered depositing evaporates ending with the Louann Salt formation. At that time the entrance from the Pacific Ocean closed but the area of the present Gulf of Mexico continued to subside well below sea level, the arid environment continued, and desert sand dunes were deposited in the Norphlet desert on top of the Louann salt.
Sands on the shores of the basin were swept into cross-bedded red sand dunes distributed throughout the basin by regional and adiabatic winds. When the barrier to the ocean finally broke the sea flooded in. Water rose like filling a bathtub. The dunes were not eroded but submerged by hundreds of feet of water. Deepwater black limestones (the Smackover) directly overly the dunes with no transitions.
The sandstones are good reservoirs even at 20,000 feet below sea level as seen in Mobil well 76-1 in Mobile bay, Alabama. The 412 feet of fine to medium grained sandstone gas column had an average porosity of 11.1%, 7.7 md permeability. At 11,240 psi formation pressure and BHT of 414 degrees Fahrenheit the well had an AOF of 37.3 MMCF/D. Chlorite coatings of grains prevent quartz overgrowths, preserving porosity and permeability to great depth. Norphlet reservoirs should exist in local areas throughout the Gulf of Mexico and be prospective of gas production where ever within drilling depth. Good seismic will help predict location of thick deposits. The distinctive shape of the large dunes can be seen on 2D seismic lines. The Norphlet Sandstone is the prospective reservoir immediately above the original Louann sale, where the salt used to be, or carried up on first generation salt domes. The laminated fine bedded dark limestone/dolomite of Smackover Brown dense formation is a marker of deep flooded basins and may mark areas prospective for underlying sand dunes of the Norphlet.
Cross-bedded Jurassic desert sandstones equivalent to the Norphlet are even found offshore Mexico west of the Yucatan and are reported to be productive from the E. K. Balam Field.
The Norphlet desert sand dunes are probably prospective in all the basins where the Louann salt is present.
Thanks are due to all the many oil companies that have published about the deep reservoirs of the Gulf of Mexico and especially to Exxon Mobile for their detailed presentations about Mobile Bay fields.