1. A method for controlling drilling of a current well into a geological region to avoid sticking of a drill string in the well, the method comprising the steps of: (a) determining a plurality of field parameters and values thereof from at least two historical wells in the geological region for drilling a borehole wherein drill strings became stuck and from at least two historical wells in the geological region wherein drill strings remained unstuck; (b) deriving with aid of a computer from the field parameters a plurality of engineering parameters and values for the engineering parameters, the engineering parameters being substantially independent of one another and being statistically significant in discriminating physical mechanisms associated respectively with the drill strings becoming stuck and remaining unstuck; (c) determining field parameter values for the current well using the same field parameters of step (a); (d) deriving values of the engineering parameters for the current well; (e) comparing the engineering parameter values for the current well with the engineering parameter values for the historical wells to determine the probability of the drill string becoming stuck in the current well; and (f) if such comparison indicates an unacceptably high probability of the drill string becoming stuck in the current well, modifying at least one field parameter value of the current well to decrease such probability to an acceptable level.