Seismic pore pressure prediction with uncertainty using a probabilistic mechanical earth model

We propose a methodology to propagate uncertainties in seismic pore pressure prediction using a 3-D Probabilistic Mechanical Earth Model (P-MEM). An extended form of Bowers formula is used to link pore pressure to seismic velocity, overburden stress, porosity and clay volume. Probability Distribution Functions (PDFs) for all input variables are stored as attributes in the 3-D MEM. An output PDF for pore pressure is then calculated point by point in the 3-D model, using either a linearized Gaussian approximation or a sequential stochastic simulation approach that fully accounts for nonlinearities in the velocity to pore pressure transform and spatial correlation between the different input variables. The linearized and stochastic approaches are compared in the context of a seismic pore pressure prediction study involving overpressured reservoir sands.