A method is presented for determining porosity, specific surface area and permeability of shales by means of pulsed Nuclear Magnetic Resonance pulsed Nuclear Magnetic Resonance (NMR). The method is applied to drilling chips collected from a Gulf Coast well. Combining well data on pressure and temperature with the NM pressure and temperature with the NM determination of permeability, a calculation of vertical flux is made. An analysis of the behavior of the flux with depth suggests that clay diagenesis is responsible for the supernormal pressure. All other observed properties can be explained on this basis.
There are many hypotheses for the cause and present day characteristics of supernormally pressured sediments. In general we do not have enough information to validate a given hypothesis. The purpose of this report is to present a method for determining the permeability to fluid flow of the shales in the supernormally pressured section. These permeabilities can be combined with permeabilities can be combined with pressure data on adjacent sands and pressure data on adjacent sands and yield the present day flux of water through the shales. A knowledge of the variation of water flux with depth will aid in understanding the cause.