Valve method for drilling with casing using pressurized drilling fluid

A method for manipulating a drill string when using a drill string axial and rotational drive mechanism and a compressed fluid as the drilling fluid, the drill string having an inner wall and an upper end, and the method comprising:

• providing a valve insertable into a drill string inner diameter to seal against fluid passage therepast except through the valve and selected to maintain fluid pressure in the drill string when the upper end of the drill string is open to atmosphere and capable of being releasably engaged to the drive mechanism to be slidably moved within the drill string, as driven by the drive mechanism, but releasable from the drive mechanism, when the drive mechanism is removed from the drill string;
• positioning the valve in the drill string inner diameter adjacent an upper end thereof;
• engaging the valve with the drive mechanism to move therewith to be drawn adjacent the upper end of the drill string as pipe connections are made thereto;
• and injecting fluid as the drilling fluid to the drill string through the valve.

A valve assembly for sealing a pressurized fluid within a drill string during drilling using a drill string axial and rotational drive mechanism and a compressed fluid as the drilling fluid, the drill string having an inner wall and an upper end and the valve assembly comprising:

• a valve body having a bore therethrough from its upper end to its lower end;
• a seal about the valve body, to seal between the valve body and the drill string inner wall but permitting the valve to be positionable in and slidable through the drill string;
• a one-way valve in the bore permitting fluid flow through the bore from the upper end to the lower end but sealing against reverse flow therethrough, and a portion for releasable engagement with the drive mechanism such that the valve is drivable by the drive mechanism through an upper portion of the drill string, but releasable therefrom to remain in the drill string when the drive mechanism is removed therefrom;
• and a valve-retaining clamp for securing over the upper end of the drill sting to retain the valve in the drill string when the drive mechanism is removed therefrom.