AN ANALYTICAL METHOD FOR DETERMINING HORIZONTAL STRESS BOUNDS FROM WELLBORE DATA

Several issues including control of stress-induced wellbore instabilit y and design of deviated and horizontal wellbores require knowledge of the magnitude and orientation of the in-situ stressfield. An analytic al method has been developed to determine bounds to the in-situ horizo ntal stresses from wellbore data for cases where the explicit measurem ent of stresses is not available. The method has been used to determin e the anisotropic stress state at depths between 1500 m and 4000 m in the immediate region of the Cossack and Wanaea fields in the North Wes t Shelf of Australia The validity of the method is demonstrated by the satisfactory comparison of the determined stress bounds with the mino r and major horizontal stresses estimated directly from modified leak- off tests.