Modelling production caused changes in conductivity for a siliciclastic reservoir: A differential effective medium approach

Abstract

Marine controlled-source electromagnetic sounding is a rapidly growing exploration technique that complements the seismic method in case of pore fluid discrimination between water and oil. Further development of the method is foreseen to be within reservoir monitoring involving permanent instrumentation on both seafloor and within wells. Such advanced applications demand a good understanding and description of the electric Earth model to ensure accurate modelling of possible Earth responses as well as successful inversion of measurement data. Based on earlier works carried out within petrophysics and resistivity-logging, an extended effective-medium scheme is derived that can be applied to model reservoir production effects. This rock-physics model has the potential of taking into account the effect of important parameters like grain-shape distribution, grain alignment, shaliness, salinity, saturation, temperature and stress, based on a uniform formulation. It has been calibrated by employing various core sample measurements. The effective-medium scheme can easily be interfaced with an existing standard electromagnetic modelling program and several such examples are presented. © 2008 European Association of Geoscientists & Engineers.