Patent attributes
Operation of a multi-variable drilling-rig is carried out within an envelope defined by convex hulls (TC,BC) that are derived from sets of historical values for the variables accumulated in a store (3) from previous operations. A display unit (5) shows the real-time values (Q01–Q10) of the variables on parallel axes (X01–X10) together with upper and lower limits (Up01–Up10, Lp01–Lp10) of the viable ranges for each variable to remain within the envelope, taking into account the current value of each other variable. The adjustment of the value of a variable (Q03) required to correct for a variable (Q08) found to be outside its viable range, is determined tentatively before implementation, by adjusting that value in the display to bring about re-calculation and display of the changes in viable ranges that would result from such adjustment.
