US Patent 7987928 Injection system and method comprising an impactor motive device

An excavation system for forming a wellbore through a subterranean formation, the system employing pressurized drilling fluid with impactors mixed therein. The pressurized fluid with impactors is directed to a drill string having a drill bit with nozzles on its lower end. The fluid impactor mixture is discharged from the nozzles and against the formation, wherein the impactors contact, compress, and fracture the formation to excavate through the formation. The system includes an impactor injection system that injects impactors into a stream of pressurized drilling fluid to form the mixture. The injection system operates at substantially the same pressure as the pressurized drilling fluid.