A process and program for characterising evolution of an oil reservoir over time

摘要

Evolution of an oil reservoir in the process of producing is carried out by co-analyzing the changes in the propagation times and seismic amplitudes of a seismic wavelet along propagation paths in the ground. A base survey of the reservoir is provided, with a set of seismic traces at a first time T associated to a first velocity field V b ; a monitor survey of the reservoir is provided, the monitor survey being taken at a second time T + ”T, with a set of seismic traces associated to the same positions as in the base survey; the monitor survey is associated to a second velocity field V m . For a set of points i in the base survey, one computes over the points of the set the sum S of a norm of the difference between - the amplitude b i of the seismic trace in the base survey at each point i and - the sum of the amplitude m i' of the seismic trace at a time-corresponding point i' in the monitor survey and the amplitude due to the reflectivity change local to the time-corresponding point i ' induced by the difference between the first velocity field V b and the second velocity field V m ; the time-corresponding point i ' being shifted in time by a time-shift derived from the velocity changes along the propagation path from the surface to time-corresponding point i '. This sum is minimized to characterize the evolution of the oil reservoir and derive the velocity changes from the base survey to the monitor survey.