Pore pressure prediction and geomechanical modelling play a very important role in well planning. The exploration focus worldwide is moving more and more into the challenging environments. Well planning and design in high pressure high temperature (HPHT) environments comprise numerous challenges such as play identification and prospect de-risking to drillability and development to production. Overpressure prediction is one of the principal challenges facing the oil industry today, as exploration focus worldwide moves further into the HPHT environments. Pressure related problems in HPHT wells include well control incidents, lost circulation, formation breathing, differential sticking, reduced rates of penetration, and reservoir damage, many which can potentially lead to expensive sidetracks, well abandonments and underground blowouts. A better understanding of the prevalent pore pressure regimes including generating mechanisms, pressure maintenance and dissipation through geologic time enables invaluable insight into these challenges and the ability to mitigate or minimize them. It is important to analyse the challenges prior to drilling so that various plans and systems can be established. Once the pore pressure regime is well understood, the next step is to understand the stress regime. Thus building a geomechanical model is the next key element for well design. The stress model can be used for wellbore stability analysis to understand wellbore failures and help in thedesignof optimum mud weights. Additionally in HPHT environments, thermal-induced stresses and their impacts on stability must also be considered. This understanding helps in modelling wellbore failures due to heating and cooling arising from mud circulation. Other considerations including drilling through faults can set another aspect of wellbore failure which could further complicate the already difficult drilling situation.
This paper presents a case study on using geomechanical evaluations to reduce drilling risks and costs in a high-pressure/high-temperature (HP/HT) well located in offshore Asia Pacific. The major risk anticipated for this well, which was drilled to explore a deep-play (>3.5 Km), was high-pressure (>10,000 psi) and high-temperature (>2000C) with narrow margin drilling conditions. The geomechanical study provided inputs for an effective well design.