The overpressures in all of the Moore-Sams and some of the Morganza fields wells follow a local hydrostatic gradient with increasing depth indicating that pore fluids below the pressure seal are in communication, and demonstrating that sandstone connectivity occurs below the pressure seal as well as above. In the remaining Morganza wells, overpressure increases with depth in a stair-step manner that may comprise offset local hydrostatic gradients, to magnitudes of 117 MPa at depths of 5.9 km. The occurrence of the pressure seal within interbedded sandstones and shales, where high sandstone connectivity is expected, suggests that the sandstones of the seal zone are unusually tight.

The above observations coupled with a petrographic study of sandstones from the vicinity of the pressure seal suggest that extreme compaction of the sandstones after dissolution of carbonate cements may have contributed to the low permeability indicated by the pressure data, and that the seal formed a kilometer or more shallower than it is today.