Patent ID: 7136795

Claim:
A method of predicting the operation of a steerable drilling system comprising the steps of: calculating an ideal reachability ellipse using the equations: Build = W build * [ WOB - meanWOB meanWOB ] + R build * [ ROP - meanROP meanROP ] + P build * [ Pressure - meanPressure meanPressure ] + F build * [ Flow - meanFlow meanFlow ] + M build * [ RPM - meanRPM meanRPM ] + T build * [ Torque - meanTorque meanTorque ] + I build * [ sin ⁢ ⁢ Inc - mean ⁢ ⁢ sin ⁢ ⁢ Inc mean ⁢ ⁢ sin ⁢ ⁢ Inc ] + K B * [ BuildDemand ⁢ % ] + C BT * [ TurnDemand ⁢ % ] + build bias and Turn = W turn * [ WOB - meanWOB meanWOB ] + R turn * [ ROP - meanROP meanROP ] + P turn * [ Pressure - meanPressure meanPressure ] + F turn * [ Flow - meanFlow meanFlow ] + M turn * [ RPM - meanRPM meanRPM ] + T turn * [ Torque - meanTorque meanTorque ] + I turn * [ sin ⁢ ⁢ Inc - mean ⁢ ⁢ sin ⁢ ⁢ Inc mean ⁢ ⁢ sin ⁢ ⁢ Inc ] + K T * [ TurnDemand ⁢ % ] + C TB * [ BuildDemand ⁢ % ] + turn bias inputting data representative of actual drilling conditions into a parametric model; calculating predicted build and turn gain, cross-coupling and bias values to derive build and turn responsiveness values attainable under given operating conditions from the parametric model to produce a predicted reachability ellipse; plotting the predicted reachability ellipse and ideal reachability ellipse on a diagram to compare the predicted build and turn responsiveness to the ideal response for one or more sets of operating conditions.