ABSTRACT

There is much theoretical and laboratory evidence for fluid-related mechanisms causing attenuation in the seismic bandwidth; however, the number of measurements made from seismic reflection data is limited. We measured attenuation changes in a reservoir undergoing depletion and, in some locations, water injection. Two different applications of these measurements were then found. First, we used the measured attenuation changes to perform a time-lapse Q correction to improve 4D inversion results in an underlying reservoir. Second, we attempted to integrate the measured attenuation changes with changes in traveltime to try to separate gas and water saturations in the reservoir. We determined that large and coherent time-lapse attenuation measurements can occur in reservoirs undergoing production and that the nature of this attenuation when averaged across a region of the reservoir was consistent with a constant-Q hypothesis. Measurements were of good quality and were coherent with the geologic (such as channels) and dynamic characteristics (such as gas coming out of solution) of the reservoir. Finally, we evaluated the possible implications of such data sets upon enhancing our understanding of the underlying mechanisms controlling attenuation in the seismic bandwidth by providing favorable conditions for canceling spectral contamination and the fact that we have knowledge of the physical changes occurring within the reservoir.

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