A casing mill including a first milling configuration having a first blade for milling a first casing section, and a second milling configuration having a second blade, the second blade being an ultra-high expansion blade for milling a second casing section. A wellbore system including a borehole in a subsurface formation, two nested casings disposed within the borehole, a string disposed within the casings, a casing mill disposed within or as a part of the string and including a first milling configuration having a first blade for milling a first casing section, and a second milling configuration having a second blade, the second blade being an ultra-high expansion blade for milling a second casing section, the second casing section being radially outwardly disposed of the first casing section, and a stroking tool disposed between the first milling configuration and the second milling configuration.

A mill for a single casing string including a housing, a first blade section having a blade of a first profile disposed in the housing and positionable to axially mill the single casing string, a second blade section having a blade of a second profile disposed in the housing and positionable to axially mill the single casing string, the first and second blades deployable simultaneously, the second blade configured to ride on an inside diameter surface of the single casing string while the second blade in the deployed position.

Bottom hole assemblies with a combined roller-underreamer assembly can include: a body configured to be attached to a drill pipe; an uphole ring attached to the body; a downhole ring attached to the body between the uphole ring and the downhole end of the body; a sliding ring mounted around the body between the uphole ring and the downhole ring; a set tube slidably mounted around the body between the uphole ring and the sliding ring; a reamer assembly with at least one first articulated arm with extending between the uphole ring and the downhole end of the set tube; and a roller assembly with: at least one second articulated arm extending between the uphole end of the set tube and the sliding ring; and a rolling positioned at a joint of each second articulated arm.

Bottom hole assemblies with a combined roller-underreamer assembly can include: a body configured to be attached to a drill pipe; an uphole ring attached to the body; a downhole ring attached to the body between the uphole ring and the downhole end of the body; a sliding ring mounted around the body between the uphole ring and the downhole ring; a set tube slidably mounted around the body between the uphole ring and the sliding ring; a reamer assembly with at least one first articulated arm with extending between the uphole ring and the downhole end of the set tube; and a roller assembly with: at least one second articulated arm extending between the uphole end of the set tube and the sliding ring; and a rolling positioned at a joint of each second articulated arm.

A reamer includes a housing, a flow tube extending along a longitudinal axis of the housing, and a plurality of reamer blocks arranged radially around the flow tube and configured to extend and retract relative to the housing. The reamer has a reamer ratio between 1.8 and 2.5. The reamer ratio is a ratio between an expanded diameter of the reamer when the plurality of reamer blocks is extended and a retracted diameter of the reamer when the plurality of reamer blocks is retracted.

A section mill including a housing, a cutter pivotally connected to the housing, a drive piston operably connected to the cutter to radially expand or retract the cutter depending upon longitudinal position of the drive piston relative to the housing, and a limit configuration in operable contact with the drive piston to limit drive piston stroke responsive to hydraulic pressure on the drive piston. A method for cutting casing including determining condition of a structure radially outward of a casing to be cut, selecting an amount of expansion of a cutter based upon the determining, and cutting the casing. A borehole system including a borehole in a subsurface formation, a string in the borehole, and a section mill as in any prior embodiment disposed in the borehole.

A section mill including a housing, a cutter pivotally connected to the housing, a drive piston operably connected to the cutter to radially expand or retract the cutter depending upon longitudinal position of the drive piston relative to the housing, and a limit configuration in operable contact with the drive piston to limit drive piston stroke responsive to hydraulic pressure on the drive piston. A method for cutting casing including determining condition of a structure radially outward of a casing to be cut, selecting an amount of expansion of a cutter based upon the determining, and cutting the casing. A borehole system including a borehole in a subsurface formation, a string in the borehole, and a section mill as in any prior embodiment disposed in the borehole.

The present invention relates to a downhole operational tool for moving a tool part between a retracted position and a projected position in a well. The downhole operational tool comprises a tool body having an axial extension; the tool part being movable perpendicularly to the axial extension between the retracted position and the projected position; a projection actuator configured to project the tool part from the tool body by means of hydraulics, the projection actuator comprising an actuator housing and a projection piston configured to slide inside the actuator housing, the tool part being connected with the projection piston; and a retraction actuator comprising a spring element configured to retract the tool part into the tool body, the retraction actuator being connected with the projection piston so that when the projection actuator projects the tool part, the spring element is compressed. The spring element is arranged outside the actuator housing.

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 lateral wellbore is formed from a high side of a horizontal portion of a primary wellbore with a drill bit assembly that has a selectively extendable pilot bit. The drill bit assembly is mounted on a lower end of a drill string. A bit guide is disposed adjacent the drill bit assembly for urging the drill bit assembly in a lateral direction against the high side of the primary wellbore. Rotating the drill bit assembly while urging the drill bit assembly upward creates a groove in a subterranean formation adjacent the primary wellbore. This forms a ledge at a far end of the groove. The drill string is then drawn back from the groove, and the pilot bit is deployed. Urging the drill bit assembly forward engages the pilot bit with the ledge, providing leverage for retaining the drill bit assembly in an orientation for excavating the lateral wellbore.