Methods of and apparatus for drilling, casing and/or completing a borehole wherein one or more portions of the borehole are drilled into a formation at a single diameter along the entire length or depth of the or each portion of the borehole. An expandable tubular member is then located within the or each portion of the borehole and radially expanded in the or each portion to line and/or case it or them. Optionally, a corrosion resistant member and/or a service string can be located in the borehole. An advantage of certain embodiments is that a single diameter borehole is formed along the entire length or depth thereof.

An apparatus for use in a wellbore. The apparatus includes a body and a blade assembly. The blade assembly is movable between a collapsed position whereby the expandable apparatus has a smaller outer diameter and an expanded position whereby the expandable apparatus has a larger outer diameter. The apparatus further includes a pressure activated member for selectively allowing the blade assembly to move from the closed position to the open position. A method for using the apparatus, wherein a drill string with an expandable bit at the end thereof is lowered into the wellbore. Thereafter, the pressure activated member is activated to allow the cutting members to move from the collapsed position to the expanded position. Subsequently, the expandable bit is rotated to form a portion of the wellbore. Next, the expandable bit is deactivated and the cutting members are moved from the expanded position to the collapsed position.

A borehole reamer which may be deployed to a desired depth in an existing uncased borehole or below existing casing and used to substantially expand the diameter of the borehole. The diameter may be expanded by an amount that ranges from a fraction to a multiple of the original diameter of the borehole. In this fashion, geological formations containing oil, gas or groundwater which were previously uneconomical to produce may be worked into a condition of economical production. In a preferred embodiment, the borehole reamer is formed as an elongated assembly having an outside diameter which is sized to fit within a diameter of a conventional borehole. The assembly is preferably attached to drill pipe and lowered into a borehole to an appropriate depth corresponding to a pay zone of interest. A lower portion of the assembly, which is located at the deeper depth in the borehole, is constructed in the form of a bellows which functions as a pilot/anchor for the assembly. A group of deployable cutting elements are disposed above the bellows and below a sliding power transfer unit which forms the upper portion of the assembly and attaches to a drill stem.

In one aspect of the invention, a drill bit assembly has a body portion intermediate a shank portion and a working portion, the working portion having at least one cutting element. The working portion also has an opening to an axial chamber disposed in the body portion of the assembly. The drill bit assembly also has an axial shaft rotationally isolated from the body portion, the shaft being at least partially disposed within the chamber, and partially protruding form the working portion. The shaft is also in communication with an energy adapter disposed within the drill but assembly and is adapted to use relative motion between the body portion and the shaft to provide power to at least one downhole device.

In one aspect of the present invention a drill bit assembly has a body portion intermediate a shank portion and a working portion. The working portion has at least one cutting element and the body portion has at least a portion of a jackleg apparatus. The jackleg apparatus has at least a portion of a shaft disposed within a chamber; the shaft has a distal end. The jackleg apparatus has a hydraulic compartment adapted to displace the distal end of the shaft relative to the working portion. The chamber also has an opening proximate the working portion of the assembly. The hydraulic compartment may be part of a hydraulic circuit which has a pump. The pump may have a first section with is rotationally fixed to the body portion and a second section rotationally isolated from the body portion.