Multiple lateral hydraulic drilling apparatus and method

Abstract

Hydraulic drilling apparatus and method in which a hole is formed with a series of drill heads and strings of successively smaller diameter. After each section of the hole is formed, the drill head is withdrawn back through the string, leaving the string in place in the hole to serve as a casing for the well. The next smaller size drill head and string are then introduced through the strings which have already been placed, and the process is repeated until the hole has reached the desired length. The course of the hole can be changed, e.g. from vertical to horizontal, without interruption of the drilling process by selective application of the drilling fluid to the nozzles in the drill head to steer the advancing string. Multiple laterals are formed by introducing a module having a plurality of extensible drilling tubes with drill heads at the distal ends thereof into the string and applying the pressurized drilling fluid to the module to advance the tubes from the string. The direction of the holes formed with the tubes is controlled by inclining the drill heads at oblique angles relative to the axes of the tubes. Once the laterals have been drilled, the module is withdrawn from the string, and the drilling tubes can either be withdrawn with the module or they can be cut off and left in the well. In one disclosed embodiment, the drill heads which form the laterals have a generally hemispherical nose with a plurality of vortex generators or nozzles distributed thereover. In another, the drill heads have a hemispherical button projecting from a forwardly facing planar surface, with forwardly directed nozzle openings toward the front of the button and laterally directed nozzle openings in the base of the button near the planar surface.