Recent HPHT campaigns have successfully tested deep seated overpressures plays at depths over 4500m below mudline and subsurface pressure more than 14000psi/96.5MPa. Regional overpressure model identified under-compaction as the predominant overpressure mechanism within this region. Furthermore, inflationary overpressures are also inferred in some wells where significant overpressure increases are observed beyond the under-compaction trend. A primary concern during pre-drill was the possibility of encountering inflationary overpressures (also termed late overpressures) where prediction is difficult. Wells that have encountered inflationary overpressure are characterized by a lack of clear inversion in sonic and resistivity log profiles, with abrupt pressure increase, however with considerable variation in magnitude. This rapid pressure increase has resulted in early TD of previous wells. Successful development of alternative way in incorporating all available well and seismic data has proved to underpin the prediction of overpressures in exploration prospects. Utilizing pre-drill pore pressure prediction result from this method has successfully helped drilled both wells safely. Throughout these HPHT campaign, monitoring various gas trends was found to be a reliable key indicator for real-time pore pressure estimation. Small increases in event gas peak amplitudes were flagged and interpreted to signal increased pore pressure, with mud weights raise accordingly.


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