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Abstract: Previous HitPredictingNext Hit Previous HitPorosityNext Hit in a Saudi Arabian Carbonate Previous HitReservoirNext Hit Using Geologic Constraints Integrated With 3-D Seismic and Well Data

Robert Jeffery, Mark Thomsen

A method for Previous HitpredictingNext Hit lateral changes in Previous HitreservoirNext Hit Previous HitporosityNext Hit using 3-D seismic amplitudes, calibrated against the amplitude response versus Previous HitporosityNext Hit measured at a select number of wells, was implemented and applied to produce a Previous HitporosityNext Hit map of a Saudi Arabian carbonate Previous HitreservoirNext Hit. The technique relies on the uniform lithologic seismic response of an overlying anhydrite, and thus assigns variations in amplitudes at the Previous HitreservoirNext Hit level to changes in Previous HitreservoirNext Hit average Previous HitporosityNext Hit.

Throughout the study area, Previous HitreservoirNext Hit Previous HitporosityNext Hit and acoustic impedance logs exhibit a firm linear relationship. As Previous HitreservoirNext Hit Previous HitporosityNext Hit increases, its acoustic impedance decreases, and the greater contrast with the overlying anhydrite translates into larger seismic amplitudes. Thus, we expect the Previous Hitreservoir'sNext Hit relative amplitude response to also increase linearly with increasing Previous HitporosityNext Hit. A check on this hypothesis was provided by computing synthetic seismograms at several wells, and measuring the Previous Hitreservoir'sNext Hit theoretical amplitude response versus Previous HitporosityNext Hit averaged over the producing zone within the Previous HitreservoirNext Hit. This trend supported a linear seismic amplitude to Previous HitporosityNext Hit transform.

Upon verification of the technique's applicability, the Previous Hitreservoir'sNext Hit amplitude response was extracted from the 3-D seismic volume in the vicinity of several wells. These were used in conjunction with porosities averaged over the Previous HitreservoirNext Hit to derive the amplitude to Previous HitporosityNext Hit transform. This transform was used in converting the mapped Previous HitreservoirNext Hit amplitudes into variations in average porosities. The success ratio for Previous HitpredictingTop porosities in wells not used in the analysis was nearly perfect, and the map continues to correctly predict porosities in subsequently drilled wells.

AAPG Search and Discovery Article #90956©1995 AAPG International Convention and Exposition Meeting, Nice, France