issues fracture gradients may be projected based on fracturing measurements made on offset wells or at depths less that the depths of interest such fracturing measurements may come from leakoff tests and formation integrity tests formation fracture gradients may also depend on well deviation and trajectories that are different than those where the measurements were taken wellbore stability models extrapolate data to predict look ahead scenarios based on these differences and any available well testing or drilling event data various wellbore stability models may be used the wbs engine 140 may use a linear elastic model that addresses deviated wellbores under anisotropic stresses the linear elastic model addresses many of the drilling events observed at the wellsite such as fracturing loses of mud tight holes and cavings the wbs engine 140 may also use the modified lade failure criterion the modified lade criterion is a three dimensional failure criterion that uses two empirical constants which may be determined from triaxial tests a component of the process is the capturing and archiving of wellbore stability related events and observations made by the drilling fluid engineer and the subsequent use of the events and observations to calibrate wellbore stability model parameters for the analyses this near real time update to the geomechanics model elevates the process beyond traditional approaches where geomechanics experts often do not participate in wellsite activities or interact with wellsite personnel during the drilling phase the archived events and observations can be presented daily or on demand to wellsite personnel and can also be used for end of well analyses and planning of subsequent wells drilled in the region examples of wellbore stability related events captured in the wbs engine 140 include lost circulation tight hole washout hole collapse.