METHOD AND APPARATUS FOR RADIALLY DRILLING THROUGH WELL CASING AND FORMATION

摘要

An apparatus for drilling holes in the steel casing of an a oil or gas well, and drilling into the surrounding earth, includes a number of components controlled by hydraulic fluid. A first hydraulic motor drives a steel milling assembly and a second hydraulic motor drives a rock drilling assembly. All assemblies are supporte d in a housing that is conveyed by conventional jointed pipe or coiled tubing down the well casing. Control components cause a carriage carrying the milling assembly to be indexed up a predetermined distance relative to the well casing, and then extend a mill b it gradually into contact with the well casing while being rotated by a hydraulic motor. After the mill bit completes a hole through the well casing, the hydraulic components retract t he mill bit and index the carriage back down to its starting position to align a rock drilling bit with the hole that was just drilled in the casing. The rock drilling bit is provided on the outer end of a flexible drillstem to enable the rock bit to extend while drilling radially from the wellbore, through the hole in the casing, as it is rotated by the second hydraulic motor. The apparatus makes it possible to radially drill multiple holes through the metal casing and multiple corresponding long tunnels through surrounding earth, without having to be raised to the surface and re-lowered between operations.