Determination of optimum drilling mud weight in Kangan and Upper-Dalan formations based on core data

Determination of optimum drilling mud weight in Kangan and Upper-Dalan formations based on core data

During the drilling, borehole breakouts and drilling induced fractures (breakdowns) are the two main instability problems, which may lead to stuck pipe, reaming operations, side tracking, and loss of circulation. These problems can be often addressed by selecting a suitable mud weight for drilling. To evaluate the stability of a wellbore, an accurate model is required to compute the stresses around the borehole. Linear elastic model assumes that after yield zone, rock is completely unable to endure strength, while in reality there is a residual strength in rock. A parameter is often used as a borehole instability risk indicator, which is the cross-sectional area of the yielded rock around the borehole divided by the area of the original borehole that is called NYZA (normalized yielded zone area). In this study, numerical simulations for wellbore stability analysis in an offshore well of Iran were performed in order to predict optimum drilling mud weight