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 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.