Process and program for characterising evolution of an oil reservoir over time

• Main Authors: SEXTON PAUL, WILLIAMSON PAUL, CHERRETT ADAM JOHN
• Format: Patent
• Language: English
• Published: 18.08.2009
• Subjects: DETECTING MASSES OR OBJECTS; GEOPHYSICS; GRAVITATIONAL MEASUREMENTS; MEASURING; PHYSICS; TESTING

Evolution of an hydrocarbon 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 Vb; a monitor survey of the reservoir is provided, the monitor survey being taken at a second time T+DeltaT, 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 Vm. 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 bi of the seismic trace in the base survey at each point i and the sum of the amplitude mi' 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 Vb and the second velocity field Vm; 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 hydrocarbon reservoir and derive the velocity changes from the base survey to the monitor survey.