Integrating Geomechanics and Geochemistry to Quickly Estimate Pore Pressure near Salt Diapirs

Traditional pore pressure prediction methods, which are based on seismic velocities, allow accounting for overpressure generated by compaction disequilibrium. Although several other sources of overpressure has been widely recognized, they are still poorly quantified. This abstract presents a workflow for quantifying the overpressure due to both the lateral strain exerted by a salt diapir and the clay diagenesis (smectite to illite transformation). The former is modelled using geomechanical analytical approach, based on the Geertsma method. The latter is instead derived from geochemical lab tests carried out on bottom-hole cores. The overpressures resulting from the three mechanisms (i.e., under-compaction, lateral strain and clay digenesis) have been superimposed to a post-drilling pore pressure interpretation. The sum of the calculated overpressure fits quite well with the pore pressure interpretation down to a certain depth, below which the considered mechanisms are not enough to fully justify the measured overpressures.