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Modeling Shale Seismic Attributes At Effective Pressures Up to 60 MPa As a Function of Pore Pressure, Using a Genetic Annealing Algorithm (GAN)

1. Summary We propose a new method of calculating the shale seismic attributes from a restricted set of experimental data. A genetic annealing algorithm (GAN) is used to predict shale velocity values at different effective pressures and the results are verified against a full data set obtained experimentally. The model is tested for a chosen wave propagation direction at a known angle t o the foliation plane. Particular emphasis is placed on the effect of pore pressure on seismic velocity. Several fully saturated North Sea shale cores were tested under very high pore pressures (up to 40 MPa) and confining pressures up to 65 MPa. Conditions of overpressure known to occur at the in-situ depth of the samples were reproduced in a pressure vessel in the laboratory. The difference between the known laboratory data and the GAN model-derived data is shown to be within acceptable error limits.