Patent ID: 8485279

Claim:
A method of excavating a borehole through a subterranean formation comprising: (a) pumping a supply of drilling fluid with a pump to supply a pressurized drilling circulating fluid to a drill string; (b) adding impactors to the pressurized drilling circulating fluid downstream of the pump to form a pressurized impactor laden slurry; (c) providing a circulating flow for excavating the borehole by directing the pressurized impactor slurry to the drill string in the borehole that has a drill bit connected to a lower end of the drill string in fluid communication with the drill string; (d) rotating the drill bit about an axis; (e) discharging a first pressurized impactor slurry spray from a first nozzle on the drill bit that is in fluid communication with the drill string, obliquely angled in at least one plane with respect to the axis and orbits about the axis with drill bit rotation to trace a first path in the borehole; and (f) discharging a second pressurized impactor slurry spray from a second nozzle on the drill bit that is in fluid communication with the drill string, obliquely angled in at least one plane with respect to the axis and orbits about the axis with drill bit rotation to trace a second path in the borehole, wherein the first discharge crosses over a vertical projection of the second borehole path and the second discharge crosses over a vertical projection of the first borehole path when the drill bit is rotated, such that the second borehole path circumscribes the first borehole path.