Calculating borehole stability index for drilling operations

Abstract

A borehole stability index can be determined by using received user inputs and received subterranean formation characteristics. The portion of the subterranean formation characteristics that represent the rock stresses can be transformed to a coordinate system, such as a cylindrical system. Subterranean formation parameters can be calculated from the transformed characteristics. A lithology-specific algorithm can be applied to the subterranean formation parameters to generate a borehole stability index. The borehole stability analysis can then be performed using the subterranean formation parameters. The borehole stability analysis can be performed at incremental radial distance layers into the subterrane formation from a borehole wall. The borehole stability analysis can be performed at various measured depth layers within a measured depth interval of the borehole where the borehole stability index is the algorithmic combination of the individual calculated borehole stability indexes at each measured depth layer.