Methods of using a particle impact drilling system for removing near-borehole damage, milling objects in a wellbore, under reaming, coring, perforating, assisting annular flow, and associated methods
A particle impact drilling system and method are described. In several exemplary embodiments, the system and method may be a part of, and/or used with, an apparatus or system, methods, to excavate a subterranean formation. The system can including, for example, removing near-borehole damage, casing, window milling, fishing, drilling with casing, under reaming, coring, perforating, effective circulatory density management, assisted annular flow, and directional control. Embodiments of associated systems and methods are also included.
1. A wellbore under reamer apparatus comprising:
a) a drill string;
b) a bit in fluid communication with the drill string wherein an annulus is defined between the well bore and an exterior surface of the drill string and the bit above a terminal end of the bit that is substantially uninterrupted along an extent of the drill string and the bit;
c) at least one nozzle in fluid communication with the drill string;
d) a mixture of a pressurized circulating fluid and a plurality of impactors flowing through the drill string and being discharged directly into the annulus from a nozzle exit that is oriented so that when the drill string and nozzle are disposed in a wellbore a portion of the plurality of impactors are discharged from the nozzle exit directly into the annulus to intersect and contact a formation with sufficient velocity to structurally alter the formation and increase the wellbore diameter.
2. A wellbore under reamer as defined in claim 1 , wherein the at least one nozzle is disposed on a location selected from a list consisting of the bit and the drill string.
3. A method of increasing the diameter of a borehole that intersects a formation, the method comprising:
a) deploying in the borehole a drill string, a bit connected to a lower end of the drill string and a nozzle wherein the bit and the nozzle are in fluid communication with the drill string and an annulus is defined above a terminal and of the bit between a circumference of the borehole and an exterior surface of the drill string and the bit that is substantially uninterrupted along an extent of the drill string and the bit; and
b) flowing a mixture of impactors and pressurized circulating fluid through the drill string and to the nozzle so that a portion of the impactors are discharged from the nozzle directly into the annulus and contact the borehole circumference with sufficient energy to compress and structurally alter the formation thereby eroding the formation at the borehole circumference to widen the borehole.
4. A method as defined in claim 3 , further comprising orienting the nozzle so that the impactors exiting the nozzle travel in a line oblique to the drill string.