Analytical investigation of the drilling orientation effect on wellbore stability

Analytical investigation of the drilling orientation effect on wellbore stability

Wellbore stability problems are always one of major concerns and difficulties of petroleum industry before, during and after drilling. Analysis of the induced stress field around the wellbore and its effect on the wellbore stability is one of the aims of this study that is become more important by development of drilling industry, especially drilling of deviated wells. Because in deviated wells unlike the vertical wells, the principal stresses acting in the vicinity of the wellbore wall are generally not aligned with the wellbore axis. For analysis of the induced stress field around deviated wells, coordinate transformation is usually used. In this study, analysis of the effect of well orientation on the change of induced stress field, and finally, on wellbore instability in arbitrary orientation is carried out. Thus, one of wells of Iranian oil fields is chosen and by assuming that the specified in-situ stress field corresponds to one of normal, strike-slip and reverse faulting stress regimes, the analysis is, then, made. The tendency for the initiation of tensile fractures to form in the wells of different orientations is investigated in this paper by the use of Kirsch analytical equations and Mohr-Coulumb failure criterion