Method and apparatus for inducing under balanced drilling conditions using an injection tool attached to a concentric string of casing

Abstract

A method and apparatus for under balanced drilling comprising a production casing extending vertically from the ground to the area where the drilling is taking place, a concentric casing mounted within the production casing and forming therewith an outer annulus, a concentric casing connecting at its lower end with an upper end of an injection tool, the injection tool having a lower end connecting with a packer assembly which includes a packer and slips, and a drill string having a drill bit at the lower end thereof extending downwardly through the concentric casing, the injection tool, and packer assembly to the area where the drilling is taking place, the injection tool having a generally cylindrical body and a plurality of spaced spiral flutes extending outwardly from the cylindrical body to the inner wall of the production casing and forming therebetween spiral openings through which fluid may be forced downwardly through the outer annulus and against the packer, each flute having an upwardly directed spiral passageway, the space between the drill pipe and the concentric casing forming an inner annulus for the return of drilling fluid, gas, oil, water, mud and cuttings from the drilling area upwardly to the ground, the fluid material coming down through the outer annulus going upwardly through the spiral passageways and generating a vortex where the passageways merge with the inner annulus so as to force the drilling mud, oil, gas, water and cuttings upwardly through the inner annulus, drilling mud being provided through a central bore in the drilling pipe to go downwardly into the area where the drilling is taking place.