Calibration of the petro-elastic model (PEM) for 4D seismic studies in multi-mineral rocks

We propose a method to calibrate the petro-elastic model in a multi-well fashion, applicable to multimineral,multi-fluid rocks. We use a model that combines Gassmann’s equations (1951) with the modified MacBeth (2004) rock stress sensitivity model (Alvarez & MacBeth, 2013) through a linear search optimisation algorithm, which allows modelling of the variations of the dry-frame elastic moduli with changes in porosity and mineralogy. The importance of the rock framework characterisation on PEM predictions is highlighted, and it is concluded that an over-simplification of the dry-frame characterisation in 4D seismic-related studies can lead to errors of the same magnitude as the 4D seismic signal and therefore these effects cannot be ignored.