Patent ID: 7980326

Claim:
A method of subterranean excavating comprising: (a) providing an excavation system in a borehole, the excavation system having, a rig, a tubular string suspended in the borehole from the rig and held with a support force from the rig, the string having an axial bore, an excavating member on an end of the string, a nozzle on the member in fluid communication with the string bore; (b) pumping a fluid into the string bore, so that when the fluid forms a continuous flow through the string bore to the excavating member where it exits the nozzle and courses through an annulus formed between the borehole and the string; (c) identifying a target WOB; (d) estimating a realized WOB based on a flow density; and (e) applying a compensating force to the string so that the realized WOB is approximately the same as the target WOB.