Publications

Foreknowledge of upcoming drilling challenges in an HPHT environment is the best way to optimize drilling. Compounded with drilling high angle wells in such environment with narrow drilling margin necessitates a geomechanics study. Such study should present before drillers the drilling risk associated with drilling these wells and should be able to predict formation sensitivity to variation in drilling trajectory and mud weights. This paper describes one such geomechanics study which aided 2009 HPHT drilling campaign by MEDCO E&P Indonesia, one of the largest oil and gas operators in Indonesia.In this campaign, two HPHT wells - high angle and horizontal were to be drilled through overpressured Gumai shales and landed in overpressured Baturaja formation - a naturally fractured carbonate reservoir, in South Sumatra. Under this study, two vertical wells drilled about 10 years ago were reviewed and several NPT events - pack-offs, losses and high gasses due to low overbalance, were observed. Hence, managing the wellbore instability in high pressure wells, with limited drilling margin and high inclination, by means of optimizing the wellbore annulus pressure as well as the well trajectory was the main concern.A fit-for-purpose Mechanical Earth Model was generated using limited available data. This served as an input for predrill wellbore stability analysis which identified drilling hazards in plan wells. Suitable recommendations were made to optimize drilling plan to reduce the drilling risks.The wells were drilled successfully without significant NPT related to formation pressure and hole instability. Postdrill analysis confirmed drilling events observed were as per studys prediction. The study was updated with data recorded this campaign and the analysis was updated for drilling drain hole of one of the plan wells. The overall benefit recognized by Medco is efficient drilling complimented with better production and hence achieving the campaigns objectives.