oa Pore Pressure Prediction for Exploration Drilling in DW Sabah

The North West Borneo deepwater fold and thrust belt still holds significant potential<br>for successful hydrocarbon exploration. Top seal analysis is a critical success factor, and seismic velocity based pore pressure prediction is a key ingredient of an integrated workflow<br>to study trap integrity and retention risk. Moreover, drilling high-pressure, high-temperature (HPHT), low drilling margin wells in a deepwater setting poses substantial HSE risks and significant financial exposure. Accurate pre-drill pore pressure and fracture gradient<br>evaluation combined with in-depth shallow hazards analysis leads to appropriate and costeffective well-design. Inflationary overpressures at crestal locations on ridges with little overburden, but potentially long connectivity into the basins pose a special challenge. A well<br>established procedure using results of regional rock property studies converts acoustic<br>velocities to vertical effective stress. Seismic interval velocities corrected for shale-related anisotropy effects and calibrated to check-shot velocities from the entire deepwater area yield<br>an initial idea about overpressure. Pressure sampling from past drilling activity shows that reservoirs on high-relief structures are often inflated relative to seismic-derived pressures, which is corrected for using the centroid approximation. During drilling, real-time monitoring and pressure prediction ahead of the bit contributes to timely adjustment of casing schemes and mud weights, whereas continued updates of pressure-vs-depth plots facilitates early<br>understanding of hydrocarbon column heights and volumetric scenario modeling. Case studies from recently drilled prospects in deepwater Sabah will be used to illustrate the concepts and workflows.