The seismic response to overpressure: a modelling study based on laboratory, well and seismic data |
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| Authors: | José M Carcione Umberta Tinivella |
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| Institution: | Istituto Nazionale di Oceanografia e di Geofisica Sperimentale, Osservatorio Geofisico Sperimentale, Borgo Grotta Gigante 42C,
34010 Sgonico (Trieste), Italy |
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| Abstract: | We investigate the seismic detectability of an overpressured reservoir in the North Sea by computing synthetic seismograms for different pore-pressure conditions. The modelling procedure requires the construction of a geological model from seismic, well and laboratory data. Seismic inversion and AVO techniques are used to obtain the P-wave velocity with higher reliability than conventional velocity analysis. From laboratory experiments, we obtain the wave velocities of the reservoir units versus confining and pore pressures. Laboratory experiments yield an estimate of the relationship between wave velocities and effective pressure under in situ conditions. These measurements provide the basis for calibrating the pressure model. Overpressures are caused by different mechanisms. We do not consider processes such as gas generation and diagenesis, which imply changes in phase composition, but focus on the effects of pure pore-pressure variations. The results indicate that changes in pore pressure can be detected with seismic methods under circumstances such as those of moderately deep North Sea reservoirs. |
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