4D seismic or time-lapse seismic is the process of repeating3D seismic surveys over a producing reservoir to monitorchanges in saturation and pressure. Repetition ofmeasurements makes it possible to eliminate the effects ofunknown static reservoir properties to focus on the dynamicchanges in production related properties.While there are many simple and direct methods of usingtime-lapse seismic data based on the study of rock propertiesalone, these tend to ignore constraints on saturation andpressure imposed by mass conservation and flowrelationships. In contrast to other research work, this papergives a way to use seismic impedance change data in anautomatic history matching procedure. We use a finitedifference,black-oil reservoir simulator, with rock physicsincluded, to predict seismic impedance as a function ofsaturation and physics. The adjoint method for computingderivatives is used with a quasi-Newton minimization methodto efficiently minimize the difference between observedimpedance changes and the impedance changes predictedusing the reservoir simulator. The permeability and porosity ofsimulator grid-cells are adjusted iteratively during theminimization process. The feasibility of this method ofutilizing time-lapse seismic data is illustrated with anapplication to a semi-synthetic model created from a largemiddle-eastern oil field. A primary conclusion is that thespatial distribution of seismic impedance change data ishelpful in reducing the uncertainty of the estimates ofreservoir parameters.
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