US 5,467,834 AGranted

Method and apparatus for short radius drilling of curved boreholes

AssigneeMaverick Tool Company

InventorsW. James Hughes, James W. McCabe, Owen L. Marks, Jr.

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Abstract

A method and apparatus for the drilling of the curved borehole portion of a horizontal or directional well. A tight radius of curvature is rotary drilled by use of flexible composite drilling pipe or other flexible pipe common to the industry which terminate within an eccentric collar on the final drill string section. The eccentric collar is equipped with a retractable and grooved compression pad which expands outwardly to hold the eccentric collar (which is also grooved on its opposite side) against the side of the well bore to prevent the eccentric collar from rotating during the rotary drilling process. The final drill string section connects to a lower drill bit collar and rotary drill bit through a driving ball and socket connection. The eccentric collar on the final drill string section that engages the well bore forces the deflection of the drill bit about the ball and socket connection and holds this orientation as the rotating drill proceeds forward. Such a technique can achieve a radius of curvature of less than twenty feet.

Claims16

Dependent claims

In a drilling assembly of interconnecting generally tubular elements descending in a flexible alignment;

the drilling assembly having a central opening descending therethrough capable of having fluid under pressure pumped therethrough during the drilling operation, the drilling assembly being capable of providing a rotatable torque for rotatably drilling a curved lateral borehole from an existing main borehole by means of a terminal drill bit,
a drilling tool for drilling a curved borehole comprising:
a drill pipe sub having an upper section and a lower section with a central opening descending therethrough, the upper section rotatably connected to the drilling assembly and the lower section having a horizontal port connected to the central opening,
an eccentric cylindrical collar rotatably and sealably mounted about the lower section of the drill pipe sub, the eccentric collar having a thick side and an opposite thin side, the thick side having a horizontal cylindrical piston bore communicating with the horizontal port in the lower section of the drill pipe sub, a piston mounted for sliding within the piston bore, a retractable compression pad mounted on the thick side over the piston and movable outwardly by the piston,
wherein the piston and compression pad are capable of being activated by fluid under pressure passing through the horizontal port opening into the piston bore so that the retractable compression pad is pushed outwardly by the piston against the borehole and wherein the thin side of the collar is pushed simultaneously against the opposite side of the borehole to secure the collar from rotating and
wherein the piston and compression pad are capable of being deactivated and of being retracted by decreasing the fluid pressure.

3 more elements

A method for drilling a curved lateral borehole from an existing main borehole by means of drilling assembly having a drill string transmitting rotational torque sequentially to a lower borehole drilling tool which in turn is connected by a flexible joint to a terminal drill bit and wherein fluid under pressure is pumped through a central opening in the drilling assembly during the drilling comprising:

providing a borehole drilling tool which includes an eccentric collar rotatably mounted circumferentially about a drill pipe sub and having a horizontal opening extending outwardly from the central opening, the horizontal opening being in sealed alignment with a piston activated radial extending and retractable compression pad on a cammed side of the eccentric collar,
drilling the curved borehole while pumping fluid under pressure through the central opening in the drilling assembly such that the fluid passes through the horizontal opening and engages the piston, thus forcing the compression pad outwardly against the borehole wall causing the drilling tool to be displaced to a side of the borehole, while simultaneously pressing a side of the eccentric collar opposite from the cammed side against a side of the borehole wall, thus preventing the eccentric collar from rotating during the rotational drilling,
thereafter reducing the fluid pressure, after a period of drilling, so as to disengage the compression pad from the borehole wall and retract the piston and compression pad into their deactivated positions, and then moving the drilling tool as required.

Dependencies are inferred from the claim text.