Method for predicting the directional tendency of a drilling assembly in real-time

The invention uses the continuous inclination, direction and tool-face information supplied from either an MWD tool and/or a rotary steerable drilling system, and/or other downhole equipment, e.g., the at-bit inclination measurement (AIM), to give a prediction of the tendency of a rotary, steerable, or rotary steerable system. These measurements are used with a finite element mathematical model of the drilling process to continually calibrate in real-time the drilling parameters that are not obtainable from measurements, and to refine the subsequent tendency prediction in real-time. The continuous data will be used in conjunction with the accepted survey measurements (which occur less frequently than the continuous inclination and direction measurements) so that the optimum slide and rotation ratio between well sections can be selected, and drilling targets can be more accurately hit.