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AAPG Asia Pacific Region GTW, Pore Pressure & Geomechanics: From Exploration to Abandonment

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An example when not to rely on seismic velocities for a pre-Previous HitdrillNext Hit pore pressure prediction

Abstract

Pre-Stack Depth Migrated (PSDM) seismic velocities are routinely used for pre-Previous HitdrillNext Hit pore pressure predictions (PPP) in frontier-to-emerging basins where there is little or no available/relevant offset well data to aid well design for safe drilling operations. In a basin with considerable lateral heterogeneity indicative of a complex lithological depositional environment, we show an example where seismic velocities were treated with caution and ultimately not used for a pre-Previous HitdrillNext Hit PPP at a proposed well location, despite previous success for other drilled wells. Instead, a regional pore pressure-depth trend forward model that was calibrated to the key offset well was favoured for the pre-Previous HitdrillNext Hit PPP, which was further complemented by more resolute Full Waveform Inversion (FWI) seismic velocities. Following drilling at the proposed well location, the actual measured well velocities indicated the use of the regional Pressure-Depth trend forward model for the pre-Previous HitdrillTop PPP was justified rather than relying on the PSDM seismic velocities.