A method of calculating an optimum continuous stress solution along a wellbore into a subterranean formation, comprising the steps of: a) estimating, from existing log data, a vertical stress and sub-surface rock properties comprising uniaxial compressive strength, Young's modulus, Poisson's ration, and frictional strength; b) at locations in the borehole where no compressive/tensile borehole failure occurs, performing continuous elastic stress solution based on plain-strain elastic solution using sonic logs obtained previously from said wellbore; c) at locations in the borehole where compressive/tensile borehole failure occurs, performing a stationed frictional equilibrium solution; d) determining continuous stress solutions by iteratively performing the solution between defining polynomial functions based on co-existing solutions from steps (b) and (c), and a solution defining uniaxial compressive strength functions based on co-existing solutions from steps (b) and (c); and e) comparing results from step d) with existing data from already acquired sample points, and if the difference is greater than a cut-off, determining that the continuous stress solution is not optimal and returning to step d) and further optimising the solutions by modifying the polynomial functions or the uniaxial compressive strength functions; or if the difference is less that the cut-off, determining that the optimum continuous stress solution has been reached; the method further including the steps of using the optimum continuous stress solution to plan a hydraulic stimulation operation, and executing the hydraulic stimulation operation. a) estimating, from existing log data, a vertical stress and sub-surface rock properties comprising uniaxial compressive strength, Young's modulus, Poisson's ration, and frictional strength; b) at locations in the borehole where no compressive/tensile borehole failure occurs, performing continuous elastic stress solution based on plain-strain elastic solution using sonic logs obtained previously from said wellbore; c) at locations in the borehole where compressive/tensile borehole failure occurs, performing a stationed frictional equilibrium solution; d) determining continuous stress solutions by iteratively performing the solution between defining polynomial functions based on co-existing solutions from steps (b) and (c), and a solution defining uniaxial compressive strength functions based on co-existing solutions from steps (b) and (c); and e) comparing results from step d) with existing data from already acquired sample points, and if the difference is greater than a cut-off, determining that the continuous stress solution is not optimal and returning to step d) and further optimising the solutions by modifying the polynomial functions or the uniaxial compressive strength functions; or if the difference is less that the cut-off, determining that the optimum continuous stress solution has been reached; if the difference is greater than a cut-off, determining that the continuous stress solution is not optimal and returning to step d) and further optimising the solutions by modifying the polynomial functions or the uniaxial compressive strength functions; or if the difference is less that the cut-off, determining that the optimum continuous stress solution has been reached; using the optimum continuous stress solution to plan a hydraulic stimulation operation, and executing the hydraulic stimulation operation.