Investigating the Effect of well Inclination Angle on Wellbore Stability using Under Balance Drilling in Parsi Oil Field

Investigating the Effect of well Inclination Angle on Wellbore Stability using Under Balance Drilling in Parsi Oil Field

Wellbore instability is one of the main problems in drilling oil and gas wells. This problem can be alleviated by determining of appropriate mud weight window. Geo mechanical properties of formations with amount of pore pressure, magnification and direction of in-situ stress are necessary parameters for wellbore stability analysis and determining of safe mud weight window. The objective of this project is to determine of safe mud weight window for vertical and directional well bores using under balance drilling technique in a carbonate formation by using numerical modeling and also investigating the rate of well inclination effect on well bore stability by FLAC. Well number A is a represents of a carbonate formation located at south west of Iran selected to conduct the study. To compare the result of numerical method with analytical method, Mohr-coulomb criterion is used. The results of this study indicated that Mohr-Coulomb criterion estimates mud window required to stabilize the wellbore close to result of numerical modeling. Furthermore, the results show that the wellbore inclination angle has a significant role in wellbore stability during drilling. According to the conducted analysis, increasing in wellbore inclination in Parsi oilfield, causes more unstable wellbores. Presented numerical model in this project can be used for easy and reliable determination of safe mud weight and wellbore trajectory required to maintain stability of wellbore. In this research for determine the range of mud weight for this well, poro-elastic theory is combined with finite differences codes