The present disclosure relates to an underreamer. In one aspect, the underreamer comprises a body, the body comprising at least one pocket therein, the underreamer further comprising at least one cutter secured with respect to the body, at least one actuating mechanism for moving the cutter between a retracted position in the pocket, and an extended position in which only the cutter projects from the body. In one aspect, the or each actuating mechanism comprises a piston for driving extension of the cutter, and a linkage to a cutter arm with respect to which the cutter is mounted, and a return spring for biasing the cutter to the retracted position.

A retractable and extendable roller reamer is positioned on a string. The retractable and extendable roller reamer is configured to support and centralize the string within the wellbore. An extension and retraction mechanism is configured to extend and retract the roller reamer. A hydraulic power unit is configured to control the extension and retraction mechanism. Sensors positioned on or within the roller reamer. The sensors are configured to detect parameters of the well-string stabilizing system. A controller is operatively coupled to the hydraulic power unit and the plurality of sensors. The controller is configured to be positioned in a wellbore. The controller is configured to receive signals from the sensors. The signals represent the parameters detected by the sensors. The controller is configured to identify the parameters represented by the signals. The controller is configured to adjust a well-string stabilizing operation in response to the received signals.

A retractable and extendable cone-type reamer is positioned on a drill string. An extension and retraction mechanism is configured to extend and retract the cone-type reamer. A hydraulic power unit is configured to control the extension and retraction mechanism. Sensors are positioned on or within the cone-type reamer. The sensors are configured to detect parameters of the wellbore-type hole opening system. A controller is operatively coupled to the hydraulic power unit and the sensors. The controller is configured to be positioned in a wellbore. The controller is configured to receive signals from the sensors. The signals represent the parameters detected by the sensors. The controller is configured to identify the parameters represented by the signals. The controller is configured to adjust a parameter of a wellbore-type hole opening operation in response to the received signals.

A perforating tool usable in a well casing to perforate the well casing is described. Perforating tool includes an activation member disposed in body wherein the activation member is moveable relative to the body to move at least one working member between and inwardly retracted condition an outwardly deployed condition relative to the body. A plurality of pistons is arranged to move the activation member relative to the body, each piston being disposed in a respective pressure chamber arranged to be filled with fluid in response to an increase in fluid pressure in the body.

A wellbore reamer assembly positionable on a drill string in a wellbore includes a reamer body having an internal cavity and multiple radial openings, multiple cutting structures each positioned in one of the radial openings in the reamer body, and a fluid-activated expandable support element positioned in the internal cavity of the reamer body adjacent the cutting structures. The cutting structures are extendable radially away from a central longitudinal axis of the reamer body through respective radial openings and retractable toward the central longitudinal axis of the reamer body.

A retractable and extendable roller reamer is positioned on a string. The retractable and extendable roller reamer is configured to support and centralize the string within the wellbore. An extension and retraction mechanism is configured to extend and retract the roller reamer. A hydraulic power unit is configured to control the extension and retraction mechanism. Sensors positioned on or within the roller reamer. The sensors are configured to detect parameters of the well-string stabilizing system. A controller is operatively coupled to the hydraulic power unit and the plurality of sensors. The controller is configured to be positioned in a wellbore. The controller is configured to receive signals from the sensors. The signals represent the parameters detected by the sensors. The controller is configured to identify the parameters represented by the signals. The controller is configured to adjust a well-string stabilizing operation in response to the received signals.

A retractable and extendable cone-type reamer is positioned on a drill string. An extension and retraction mechanism is configured to extend and retract the cone-type reamer. A hydraulic power unit is configured to control the extension and retraction mechanism. Sensors are positioned on or within the cone-type reamer. The sensors are configured to detect parameters of the wellbore-type hole opening system. A controller is operatively coupled to the hydraulic power unit and the sensors. The controller is configured to be positioned in a wellbore. The controller is configured to receive signals from the sensors. The signals represent the parameters detected by the sensors. The controller is configured to identify the parameters represented by the signals. The controller is configured to adjust a parameter of a wellbore-type hole opening operation in response to the received signals.

An apparatus and method for alleviating spiraling in boreholes is disclosed. The apparatus includes a sub, which adjusts the length of the bottom-hole assembly in response to tension/compression, flexural bending and/or torque measurements made above and below the reamer so that the drill bit and the reamer cut at the same depth rate. The sub is connected between the drill bit and the reamer. The apparatus further includes measurement devices disposed on the bottom-hole assembly above and below the reamer, which are capable of measuring the tension/compression, flexural bending and torque in the bottom-hole assembly. The method includes use of a data processor, which determines which operational output signals to supply to the sub in order to adjust its length and thereby accomplish the desired drilling rates.

This cutting assembly provides a radially grooved body insert upon which cutter arms with complementary radial grooves may translate to extend the cutter arms in a radial fashion from a body of a downhole drilling assembly. This improved cutting assembly design can be incorporated into an underreamer, hole opener, drill bit, or section mill.

Using a rock crushing system for widening a pilot hole on rocky terrain includes taking a plurality of crushing elements, for example roller bits and/or cutter discs, pressing the crushing elements against the lateral wall of the pilot hole and at the same time rolling the crushing elements along a cylindrical portion of the lateral wall, widening the pilot hole. The crushing elements, free to rotate with respect to an axis thereof, are radially pushed by hydraulic cylinders. Stabilising means exemplarily include a basket abutting the lateral wall to keep a main body bearing the hydraulic cylinders centered with respect to an axis of the pilot hole during the rock crushing.