Patent ID: 9027671
Filing Date: 2015-05-12
Classification: E21B

Abstract:
1. A method for automated drilling of a borehole in a subsurface formation, comprising: selecting at least one control variable; defining a drilling performance objective having a value that is influenced by drilling of the borehole using the at least one control variable; drilling a first interval of the borehole maintaining the at least one control variable at a first value; drilling a second interval of the borehole maintaining the at least one control variable at a second value; and drilling a third interval of the borehole maintaining the at least one control variable at a third value, the third value being selected by applying an offset to one of the first value and the second value, a direction of the offset selected based on a comparison of the value of the drilling performance objective while drilling the first interval and the value of the drilling performance objective while drilling the second interval to a predetermined optimal value of the drilling performance objective; selecting, for each of the first, second, and third interval, the value of the at least one control variable by applying a near search offset value to the value of the at least one control variable applied for a previously drilled interval; determining whether the value of the drilling performance objective has changed over the first second and third intervals; drilling a fourth interval of the borehole, and selecting, responsive to the determining, for the fourth interval of the borehole, a value of the at least one control variable by applying a far search offset value to the value of the at least one control variable based on the drilling performance objective not having changed over the first, second, and third intervals of the borehole; wherein a magnitude of the far search offset value is greater than a magnitude of the near search offset value.