Wellbore breakout analysis and the maximum horizontal stress determination using the thermo-poroelasticity model

Abstract

The accurate information about the magnitude and orientation of in-situ stress in depth contributes to the reasonable design of drilling fluid density and borehole trajectory for avoiding wellbore failure and the associated underground complexity. The technique of estimating the magnitude of the maximum horizontal stress using the wellbore breakout observed from imaging logging has been widely recognized, but the influence of thermo-poroelastic coupling of formation rock has always been neglected. In order to accurately determine the maximum horizontal stress in depth, the wellbore breakouts during drilling process are simulated and a calculation method of the maximum horizontal stress is provided by using the thermo-poroelastic rock mechanics theory and the Mogi-Coulomb criterion. The results show that the wellbore is more prone to shear failure due to thermo-poroelastic effect of rock, and the cooling effect of drilling fluid will reduce the degree of the wellbore breakout during drilling process. The comparison between the calculation result of the maximum horizontal stress and the actual data shows that the calculation method provided is correct and feasible. Considering the thermo-poroelastic effect of rock, the magnitude of the maximum horizontal stress determined by using wellbore breakout is smaller.