Pore pressure prediction and geomechanical modelling play a very important role in well planning and is one of the many challenges facing the oil industry today, as exploration focus worldwide is moving more and more into the deep-water environment. Pressure related problems in deepwater wells are mainly associated with narrow operating window resulting in severe well control incidents, sometimes even leading to early abandonment. A better understanding of the prevalent pore pressure regimes in terms of generating mechanisms along with pressure maintenance and dissipation through geologic time offers invaluable insight and perception about these challenges and also on our ability to predict and mitigate or minimize them. Borehole instability related problems like excessive wellbore breakout can result hole cleaning issues, stuck pipe, setting casing earlier or potentially losing the wellbore. It is important to analyze these challenges and develop an understanding of the same, prior to drilling so that, various plans and mitigation systems can be put in place. A substantial amount of non-productive time (NPT) was associated during the initial phases of drilling campaigns in the Brunei deepwater. Accurate mud weight window prediction using regional scale pore pressure prediction and geomechanical modeling clearly demonstrated a significant reduction in nonproductive times over the different phases of drilling campaigns till date. This also includes a regular update or refinement of the model as soon as new data or information becomes available. This paper presents some of the methodologies used during well planning and construction of deepwater and ultra-deepwater wells. It also discusses the work refinement throughout each drilling campaigns, which resulted in improvement on geological and geomechanical model. It is imperative to note that the intent is to document and share experiences and lessons learned in Brunei deepwater wells within the industry. This would enable the execution workflow and well design to be continuously improved for a safe and cost- efficient delivery of the wells.
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