Patent ID: 8590635

Claim:
A method for automated drilling of a borehole in a subsurface formation, comprising: (a) drilling the borehole using a set of drilling control variables assigned a set of values; (b) monitoring an automated drilling index of the drilling of step (a), the automated drilling index of the drilling of step (a) being a combination of a first index dependent on a rate of penetration of the drilling of step (a) and a second index dependent on a mechanical specific energy of the drilling of step (a); and having the form: ADI=(weight_ROP×ROPI)+(weight_MSE×MSEI), where ADI is the automated drilling index, ROPI is the first index dependent on rate of penetration, MSEI is second index dependent on the mechanical specific energy, and weight_ROP and weight_MSE are weights; and (c) selectively adjusting the set of values of step (a) at least once during step (a) based on the monitoring of step (b).