Characterising the evolution of a reservoir over time from seismic surveys, making allowance for actual propagation paths through non-horizontal layers

摘要

Disclosed is a process for characterising the evolution of a reservoir that comprises non-horizontal layers, by analyzing the changes of at least the seismic amplitudes of seismic reflections. The process comprises the steps of providing a base survey of the reservoir with a set of seismic traces at a first time and providing a monitor survey of the reservoir, taken at a second time, with a set of seismic traces associated to the same positions as in the base survey. The sets of seismic traces from the base and monitor surveys are then inverted to obtain an estimate of the changes having occurred in the time interval between base and monitor surveys, the inversion being performed using seismic traces for which allowance is made for the actual propagation paths through the non-horizontal layers of the reservoir. The base and monitor surveys may be transformed to a 1D space in order to make said allowance, and the inversion is then performed on the transformed traces. The transforms may rotate the surveys such that the layers are substantially horizontal.