Abstract: A method for dissipating force within a tubing string including providing a severing device to a desired location within a tubing string; a cut zone along the length of the tubing, and a housing disposed along the length of tubing and sized to enclose the cut zone therein, wherein the housing includes a first end and a second end each forming a housing shoulder, severing the tubing at the cut zone using the severing device creating a first tubing section and a second tubing section; wherein the first tubing section and the second tubing section slide apart within the housing.

Abstract: A pressurized fluid flow system for a down the hole drill hammer has main and auxiliary chambers that exert work on the piston. The auxiliary chambers are formed around respective waists on the piston and externally delimited by respective cylinders which are arranged longitudinally in series. A set of supply chambers filled with the pressurized fluid are defined by annular recesses in the external surface of the piston for supplying said fluid to the chambers. Supply channels and discharge channels are formed in between the outer casing and the cylinders for respectively supply pressurized fluid through exit ports in the cylinders to the supply chambers and emptying the chambers through discharge ports in the cylinders. The supply and discharge of the chambers is controlled in a cooperative way by the piston and the cylinders. A normal circulation drill hammers is provided having this system.

Abstract: A backhead assembly system for a Down The Hole (DTH) hammer operated by a supply of compressed fluid, that comprises mainly a backhead, said backhead having a central hole capable of transporting the pressurized air to the hammer and an inner cylinder, coaxially disposed and coupled with releasable holding mediums to the backhead, were said backhead has an interior frontal cavity and said releasable holding mediums are in the mentioned frontal cavity. The hammer also comprises a wear sleeve, coaxially disposed to the backhead and inner cylinder, in which the backhead is coupled to the rear side of the wear sleeve. In both embodiments of the present invention, the inner sleeve has a rear section of less diameter and a front side of larger diameter; both sections joined through a portion of generally increasing diameter.

Abstract: Systems and methods for moving a tubular string within a subterranean well include a downhole assembly. The downhole assembly includes a torque disconnecting member and a shock generating member. During normal drilling activities, both components are inactive. When a stuck pipe event occurs, first the torque disconnecting member is activated while the shock generating member is still inactive. Once the torque disconnecting member is activated, then the shock generating member is activated. A laterally-protruding shock pad of the activated shock generating member produces shocks against the proximate side of a wellbore wall while the shock generating member is rotating. Systems and methods for moving a tubular string within a subterranean well include a fishing assembly. The fishing assembly includes a fishing member, a swivel member, and an imbalanced member.

Abstract: A release mechanism for a jarring tool is formed by a plurality of segmented release lugs. Each lug includes a plurality of axial spaced projections on an inner surface and a plurality of grooves on an outer surface. The projections have either different widths or are separated by varying distances and releaseably engage corresponding grooves in a mandrel located within a housing of the tool. The release lugs are positioned between a trigger sleeve and the mandrel.

Abstract: A valve of a hydraulically striking device having a housing, the housing comprising a moving member being seated inside the housing to move in a reciprocating manner by means of a hydraulic fluid. The moving member has an inner space, the valve has a return space and a pressure space provided, in the axial direction, at a distance from one another on the inner surface of the housing facing the moving member, wherein the rest of the inner surface of the housing in the same axial positions of the return space and the pressure space forms guide surfaces that are concentric with the moving member and against the moving member for centering the moving member.

Abstract: A system for harvesting energy from the operation of a downhole jar is disclosed. The system converts the kinetic energy associated with the operation of the jar to electrical energy by associating the relative movement between a magnet and a coil to the relative movement between a movable member and a stationary member in the jar. Electrical energy is generated in the coil as a result of the relative motion between the magnets and the coil. This electrical energy may be stored in an electrical energy storage subsystem and provided to a downhole tool for use in the wellbore. The downhole tool may be used to power other tools, to take measurements, to communicate with other devices, to actuate other devices, and to otherwise control such other devices.

Abstract: A system and method of fabricating a percussion tool that includes one or more surfaces modified using the ferritic nitrocarburization process. The percussion tool includes a piston positioned in sliding contact within a casing. The piston includes an inner wall and an outer wall, where the inner wall defines a passageway extending longitudinally therethrough. The outer wall is positioned in close fitting relationship with an internal surface of the casing. One or more surfaces of at least one of the casing's internal surface and/or the piston's outer wall are modified using the ferritic nitrocarburization process.

Abstract: An underreamer for increasing the diameter of a bore. The underreamer includes a substantially cylindrical body having an axial bore therein. A mandrel may extend axially through the axial bore. One or more cutter blocks are movably coupled to the body. A ratio of a height of the cutter block to a diameter of the body is between about 0.35:1 and about 0.50:1.

Abstract: An underreamer for increasing the diameter of a bore. The underreamer includes a substantially cylindrical body. A mandrel may extend axially through the body. One or more cutter blocks are movably coupled to the body. A ratio of a height of the cutter block to a diameter of the body is between about 0.35:1 and about 0.50:1.

Abstract: A jar assembly for use downhole includes a housing, a piston assembly slidable within and selectively coupled to the housing, a mandrel assembly coupled on a lower end of the piston assembly, and an anvil coupled to an end of the mandrel assembly opposite the piston assembly. The jar assembly is deployed in a wellbore by a conveyance means that couples with the housing. A hydraulic circuit in the piston assembly activates a latch for decoupling the piston assembly from the housing; when decoupled, the housing slides downward and impacts the anvil to generate a jarring force. The jar assembly is re-cocked by raising it with the conveyance means.

Abstract: A shock assembly for use with a motion tool deployable into a wellbore by a conveyance. The motion tool includes a mandrel operatively connectable to the conveyance or the motion tool, a housing operatively connectable to the motion tool or the conveyance (the housing having an opening to slidingly receive the mandrel and including a first and a second spring portion), a first spring slidably positionable in the first spring portion and having a first spring stiffness, and a second spring slidably positionable in the second spring portion having a second spring stiffness. The second spring stiffness being less than the first spring stiffness such that the first and second springs selectively engage as the housing slidingly moves about the mandrel in response to forces applied to the system to selectively restrict movement between the mandrel and the housing whereby the motion tool is vibrated.

Abstract: A choke assembly for controlling air flow into a piston of a percussion tool for downhole drilling includes a choke and a choke adapter. The choke comprises a choke body and a choke opening in the choke body for fluid to flow therethrough. The choke further includes one or more arm slots formed into the choke body between an inner wall of the choke body and an outer wall of the choke body. The one or more arm slots are designed to receive one or more arms of a choke change tool. The choke adapter has an adapter opening extending through the choke adapter. The choke is sized to fit in the adapter opening. The choke is removable from the choke adapter after the choke is inserted into the adapter opening.

Abstract: A resettable downhole tool actuator comprises a housing, a collet slidable within the housing and defining a seating with which a ball is engageable, in use, the collet being mounted upon a moveable support including a piston and arranged such that, when the bail engages the seating, fluid flow through an axially extending passage provided in the support is restricted, the housing including an increased diameter region arranged such that, when the seating is aligned with the increased diameter region, outward deflection of the collet permits the ball to pass through the seating and through the axially extending passage.

Abstract: A hammer bit is herein described with tapered lateral sides and a modified face section. The tapered lateral sides taper inward towards a rear portion of the hammer bit. The modified face section includes a gauge portion and a larger angled or heel portion. The hammer bit provides improved penetration and directional control for drilling into the earth.

Abstract: An apparatus for drilling annulus ring hole, comprising: a down-the-hole (DTH) percussion hammer assembly, the DTH percussion hammer assembly comprising one or more DTH percussion hammers, an annulus ring structural housing having an outer diameter (OD) and an inner diameter (ID) for accommodating the DTH percussion hammers within space between the OD and the ID of the annulus ring structural housing; one or more drill pipes being connected serially with each other forming a string of drill pipes, the string of serially connected drill pipes being connected to the DTH percussion hammer assembly; a top pipe with one or more exhaust openings being connected to the string of serially connected drill pipes; an air or fluid distributor being connected to the top pipe; and a rotary head providing rotational turning motion for the apparatus, and the rotary head being connected to the air distributor.

Abstract: A percussion mole for inserting a ground-loop for a geothermal heat-pump apparatus. The ground-loop includes a first pipe and a second pipe. The mole comprises: a percussive drive mechanism; a first passage connectable to the first pipe, for receiving a driving fluid via the first pipe and delivering it to the drive mechanism, during insertion of the ground-loop; a second passage connectable to the second pipe, for exhausting the driving fluid from the drive mechanism via the second pipe, during insertion of the ground-loop; and a connection connecting the first passage with the second passage. The connection includes a non-return valve arranged to restrict flow of the driving fluid from the first passage to the second passage during insertion of the ground-loop but permit flow in the opposite direction, whereby after insertion, when the heat pump apparatus is in use, the ground-loop comprises the first and second pipes; the first and second passages; and the connection.

Abstract: A system and method of fabricating a percussion tool that includes one or more coatings applied onto a piston, casing, and/or flow tube. The percussion tool includes a piston positioned in sliding contact within a casing. The piston includes an inner wall and an outer wall, where the inner wall defines a passageway extending longitudinally therethrough. The outer wall is positioned in close fitting relationship with an internal surface of the casing. One or more coatings are disposed on at least one of the casing's internal surface and/or the piston's outer wall. A flow tube may be placed through the passageway such that an outer wall of the flow tube is in a close fitting relationship with the piston's inner wall. One or more coatings can be disposed on at least one of the piston's inner wall and/or the flow tube's outer wall.

Abstract: A choke assembly for controlling air flow into a piston of a percussion tool for downhole drilling includes a choke and a choke adapter. The choke comprises a choke body and a choke opening in the choke body for fluid to flow therethrough. The choke further includes one or more arm slots formed into the choke body between an inner wall of the choke body and an outer wall of the choke body. The one or more arm slots are designed to receive one or more arms of a choke change tool. The choke adapter has an adapter opening extending through the choke adapter. The choke is sized to fit in the adapter opening. The choke is removable from the choke adapter after the choke is inserted into the adapter opening.

Abstract: An apparatus, system, and method of fabricating a percussion tool that includes a flow tube. The flow tube includes upper and lower portions, inner and outer walls, and at least one opening formed in the outer wall. The upper portion extends from a top end towards a bottom end. The lower portion extends from the upper portion to the bottom end. The inner wall extends from the top end to the bottom end and defines a central channel therein. The outer wall extends from the top end towards the bottom end, surrounds a portion of the inner wall and defines an outer channel with the inner wall. The opening is fluidly communicable with a first conduit formed within a piston, which surrounds a portion of the flow tube, when in an up position and is fluidly communicable with a second conduit formed within the piston when in a down position.

Abstract: A system and method of fabricating a percussion tool that includes a choke valve that is replaceable and/or maintainable without disassembly of the percussion tool. The flow tube includes inner and outer walls and at least one opening formed in the outer wall. The inner wall extends from a top end of the flow tube to a bottom end of the flow tube and defines a central channel therein. The outer wall extends from the top end towards the bottom end, surrounds a portion of the inner wall, and defines an outer channel with the inner wall. The choke is positioned at the top end over the central channel and regulate a fluid flow therethrough. A check valve is positioned in fluid communication with the choke.

Abstract: A pressurized fluid flow system for a down the hole drill hammer has a plurality of chambers that exert work, namely one or more auxiliary drive and lifting chambers besides two main chambers located at opposite ends of the piston, the auxiliary chambers each formed around respective waists on the piston and externally delimited by respective cylinders which are arranged longitudinally in series. Two or more internal chambers filled with the pressurized fluid are defined by recesses in the inner surfaces of the piston for supplying said fluid to the work chambers, controlled in a cooperative way by the piston and a control tube coaxially arranged within a central bore of the piston. One or more discharge chambers are formed in between the outer casing and the cylinders for emptying the work chambers through discharge ports in the cylinders. Reverse and normal circulation drill hammers are provided having this system.

Abstract: A pressurized fluid flow system for a reverse circulation down-the-hole hammer includes a cylinder and a cylindrical control tube that are respectively coaxially disposed in between the outer casing and the piston of the hammer and in between the piston and the sample tube. Two chambers help to respectively supply and discharge pressurized fluid into and out of the front and rear chambers that exert work on the piston: an internal chamber, defined by a central recess in the inner surfaces of the piston and permanently connected to the source of pressurized fluid, and a discharge chamber, defined by one or more recesses in the inner surface of the outer casing and permanently communicated with the bottom of the hole. A hammer provided with this system has one or more end discharge ports connected to respective longitudinal discharge channels formed on the outer surface of the outer casing.

Abstract: A pressure pulse generating method and apparatus for use with a drill string includes a top and bottom subs for attaching the apparatus within the drill string; a power section comprising a rotor/stator; a drive assembly; and a nozzle sub which includes a nozzle assembly comprising a nozzle holder and a replaceable nozzle; and a nozzle housing having pulse openings. The nozzle holder has fluid ports which periodically align with the pulse openings as the nozzle holder rotates within the nozzle housing to achieve a desired pulse amplitude, frequency and waveform.

Abstract: An apparatus for inserting a ground-loop for a geothermal heat-pump system comprises: a percussion mole (4); a first fluid pipe (5), connected to the mole (4), for conveying a heat-exchange fluid from the heat-pump system into the ground; and a second fluid pipe (6), connected to the mole (4), for returning the heat-exchange fluid to the heat-pump system. One of the first and second fluid pipes (5, 6) comprises an intake pipe for delivering a driving fluid to the mole (4) during insertion of the ground-loop and the other fluid pipe comprises an exhaust pipe for the driving fluid.

Abstract: A down-the-hole drill hammer is provided that includes a housing, a piston mounted within the housing, a drill bit mounted below the housing, and a drive coupling operatively engaged with the housing and drill bit. The drive coupling can be configured with a plurality of lugs circumferentially disposed about the drill bit and coupled with the casing for providing rotation thereof. Alternatively, the drive coupling can be configured with segmented lugs configured to circumscribe the drill bit, or as a cylindrical chuck formed out of arch-shaped chuck segments which radially assemble onto the shank of the drill bit.

Abstract: A down-the-hole drill hammer for optimizing air consumption. The down-the-hole drill hammer includes a housing, a backhead connected to the housing, and a pressure control check valve assembly mounted within the housing. The pressure control check valve assembly includes a first check valve and a second check valve. The first check valve controls a flow of working fluid through the backhead. The second check valve is mounted to the first check valve and controls a flow of working fluid through the first check valve.

Abstract: A drilling tool assembly may include a housing, a piston disposed in the housing, and a clutch assembly coupled to the housing and the piston. The clutch assembly may be configured to facilitate rotation of the piston relative to the housing. A cutting assembly may be coupled to the piston in a manner that it is rotatable relative to the piston. A method of forming a wellbore may include positioning a drilling tool in the wellbore, the drilling tool comprising a housing, a piston, a clutch assembly, and a drill head. The method may further include reciprocating the piston axially within the housing, rotating the piston relative to the housing the clutch assembly, rotating the drill head relative to the housing and the piston, and forming the wellbore.

Abstract: A drilling apparatus including a hydraulically powered hammer having a piston to impact a drill bit; a shuttle valve to control reciprocation of the piston; and an accumulator for hydraulic fluid; at least one drill rod having a first connection valve for connection of the drill rod to the connection valve of the hammer; and a second connection valve for connection of the drill rod to the first connection valve of a like drill rod or to a rotation device. The piston and shuttle valve are positioned substantially in-line to the axis of movement of the hammer. The accumulator is positioned proximate to the shuttle valve; and the first connection valve, and second connection valve having at least one poppet valve positioned proximate to a corresponding valve seat.

Abstract: A drilling apparatus including a hydraulically powered hammer having a piston to impact a drill bit; a shuttle valve to control reciprocation of the piston; and an accumulator for hydraulic fluid; at least one drill rod having a first connection valve for connection of the drill rod to the connection valve of the hammer; and a second connection valve for connection of the drill rod to the first connection valve of a like drill rod or to a rotation device. The piston and shuttle valve are positioned substantially in-line to the axis of movement of the hammer. The accumulator is positioned proximate to the shuttle valve; and the first connection valve, and second connection valve having at least one poppet valve positioned proximate to a corresponding valve seat.

Abstract: Apparatus, methods and uses that allow extended reach drilling by virtue of the provision in the drillstring and to downhole tools collective vibrations, not tuned specifically to a single resonant frequency, from a hammer assembly that provides vibrations of different frequency ranges.

Abstract: A downhole tool having a progressive cavity mud motor with an impact generator disposed within the mud motor rotor or bearing assembly. In one embodiment, the impact generator includes a mud turbine connected to a eccentric ring that encircles and periodically strikes an anvil surface of a percussion shaft. The eccentric ring is pivotable between an engaged striking position and a disengaged non-striking position. The percussion shaft is coupled to a drill bit though a splined connector that provides limited slip for transmitting rotation of the mud motor rotor to the drill bit and for transmitting percussion strikes against the anvil to the drill bit without the need to accelerate the entire drill string.

Abstract: A down-the-hole drill hammer is provided that includes a housing, a solid core piston mounted within the housing, a seal located between the solid core piston and the housing, and a backhead configured to exhaust working fluid volumes about a proximal end of the DHD hammer. The backhead includes a check valve assembly having a plug seal that can be moved to a closed seal position by gravity. A DHD hammer having a segmented chuck assembly is also provided. The segmented chuck assembly includes a plurality of chuck segments forming a cylindrical chuck assembly.

Abstract: Apparatus and method for adjusting spring preloading in a downhole tool. In an apparatus, a mechanism includes a nut and a piston. The nut is configured to axially compress a spring in the downhole tool. The piston is coupled to the nut. Extension of the piston causes the nut to rotate and compress the spring. The nut is configured to maintain compression of the spring after the piston retracts.

Abstract: A hammer assembly is actuated to drive an earth bit through a formation. The hammer assembly includes a piston, and a flow control tube which extends through the piston. The flow control tube includes drive and return guide ports. The piston is repeatably moveable relative to the drive and return guide ports in response to a fluid flow through the flow control tube. In this way, the hammer assembly is actuated.

Abstract: A horizontal direction drilling system comprises a power pack coupled to a source of compressed air and a water reservoir and forms a mixture of compressed air, water, and oil. The horizontal direction drilling system further comprises a steerable horizontal drill. The steerable horizontal drill includes an air powered reciprocating hammer, and a drill head. The steerable horizontal drill receives the mixture to power the reciprocating hammer. The drill head includes a drill face and the mixture exits the steerable horizontal drill through the drill face.

Abstract: A percussion adapter that is driven to generate a percussive axial motion on a wellbore structure. One percussion adapter includes a drive connection to mechanically convert rotational drive to axially directed percussive motion. Another percussion adapter employs a valve that creates back pressure causing axially directed percussive motion. A wellbore tubular connection transitions torque to resist back off when left hand or right hand torque is applied.

Abstract: A hydraulic percussive apparatus is disclosed for generating vibrating forces to a pipe string. The apparatus is attached to the pipe string a central bore through which fluid may be introduced into the apparatus. The apparatus has a tubular housing, an anvil surface with an irregularly profiled surface, and a rotor with an irregularly profiled hammer surface that is urged to move axially toward and away from the anvil surface. The rotor has a longitudinally extending fluid bore and a tangentially oriented fluid port in communication with the longitudinal fluid bore of the rotor. Fluid entering the rotor's fluid bore and exiting the rotor's tangentially oriented fluid port rotates the rotor, and thus the irregularly profiled hammer surface on the irregularly profiled anvil surface, moving the hammer surface toward and away from the anvil producing intermittent impact forces.

Abstract: A directional drilling system, a drilling hammer and a fluid flow telemetry modulator use a plurality of magnets arranged to convert rotational motion into reciprocating linear motion. Various types of motor can provide rotational motion to a part of the magnets and various linkages and other devices can cause steering or operation of a modulator valve. A torsional drilling hammer uses a plurality of magnets arranged to convert reciprocating linear motion into reciprocating rotational motion. A motor and linkage drives the linearly moving part of the magnets, and the rotating part provides torsional impact be striking the linearly moving part of the magnets.

Abstract: A pressurized fluid flow system for a down the hole drill hammer has a plurality of chambers that exert work, namely one or more auxiliary drive and lifting chambers besides two main chambers located at opposite ends of the piston, the auxiliary chambers each formed around respective waists on the piston and externally delimited by respective cylinders which are arranged longitudinally in series. Two or more internal chambers filled with the pressurized fluid are defined by recesses in the inner surfaces of the piston for supplying said fluid to the work chambers, controlled in a cooperative way by the piston and a control tube coaxially arranged within a central bore of the piston. One or more discharge chambers are formed in between the outer casing and the cylinders for emptying the work chambers through discharge ports in the cylinders. Reverse and normal circulation drill hammers are provided having this system.

Abstract: A drilling system, including: a drill bit; and a thruster to apply a force to the drill bit. The thruster may include: an inner tubular member disposed within and configured to axially move within an outer tubular member; a thrust piston to transmit a hydraulic force to the inner tubular member, the thrust piston separating an upstream fluid chamber and a downstream fluid chamber between the inner and outer tubular members; at least one pressure switch fluidly connected to the downstream fluid chamber to control flow of a fluid to and from the downstream fluid chamber via at least one fluid inlet and at least one fluid outlet.

Abstract: A percussion drilling assembly includes an outer tubular, an inner tubular coupled within the outer tubular at a threaded region, a drill bit slideably disposed within the inner tubular, and a locking system located proximate the threaded region. The locking system is actuatable by translation of the drill bit relative to the locking system, whereby the locking system is configured to prevent rotation of the inner tubular relative to the outer tubular in at least a first direction.

Abstract: A percussion drilling assembly for boring into the earth is disclosed. The percussion drilling assembly includes a top sub, a casing coupled to the top sub, and a feed tube assembly disposed within the top sub and the casing. The feed tube assembly includes a non-rigid coupling having a throughbore and a tubular body disposed therein. The tubular body is translatable in the radial position and/or rotatable relative to a longitudinal centerline extending through the non-rigid coupling.

Abstract: A pressurized fluid flow system for a normal circulation down-the-hole hammer comprises a cylinder coaxially disposed in between an outer casing and a piston which reciprocates due to changes in pressure of pressurized fluid contained inside a front chamber and rear chamber located at opposites sides of the piston, supply/discharge of fluid to/from these chambers being conducted through a supply chamber and a discharge chamber defined by recesses on the inner surface of the casing and separated by a dividing wall, the front/rear chambers' in/out fluid flow being controlled solely by the overlap of the piston and the cylinder. A hammer having this system comprises a drill bit with one or more flushing passages which extend from channels cooperatively formed between splines on the inner surface of the driver sub and on the outer surface of the drill bit shank up to the front face of the drill bit.

Abstract: A pressure reversing valve for a down-the-hole percussive drilling (“DHD”) apparatus has a first valve pressure surface, a second valve pressure surface and a third valve pressure surface. The first valve pressure surface engages an internal surface of a housing of the DHD hammer. The second valve pressure surface is in communication with a high pressure port of the DHD hammer. The third valve pressure surface is in communication with a passageway that extends through a distributor within the DHD hammer. The valve also includes a valve passageway that extends through the valve and which is in communication with a first volume of the DHD hammer. The first volume is formed by surfaces of the distributor and the third valve pressure surface.

Abstract: A method of boring through a formation includes providing a drilling machine and drill string and operatively coupling an earth bit to the drilling machine through the drill string. An air flow is provided through the drill string at an air pressure less than about one-hundred pounds per square inch (100 psi) and an overstrike force is applied to the earth bit, wherein the overstrike force is less than about five foot-pounds per square inch (5 ft-lb/in2).

Abstract: A down-the-hole drill hammer having a housing, a backhead and a tubular sliding check valve assembly that includes a distal end, a threaded male proximal end, a supply inlet and an exhaust port. The exhaust port communicates between an interior of the backhead and an exterior of the backhead. The tubular sliding check valve assembly includes a distributor, a sliding valve, and a biasing member. The distributor has a central opening extending through the distributor, an aperture extending through the distributor, and an exhaust gallery. The sliding valve is slidable along the central opening. The biasing member biases the sliding valve to a closed position.

Abstract: A downhole tool having a progressive cavity mud motor with an impact generator disposed within the mud motor rotor or bearing assembly. In one embodiment, the impact generator includes a mud turbine connected to a eccentric ring that encircles and periodically strikes an anvil surface of a percussion shaft. The eccentric ring is pivotable between an engaged striking position and a disengaged non-striking position. The percussion shaft is coupled to a drill bit though a splined connector that provides limited slip for transmitting rotation of the mud motor rotor to the drill bit and for transmitting percussion strikes against the anvil to the drill bit without the need to accelerate the entire drill string.

Abstract: A method and apparatus for delivering repetitive jarring impacts to a stuck object downhole. The jarring tool is deployed on coiled tubing or other tubular well conduit, and fluid pressure is used to cycle the jar without reciprocating the well conduit at the wellhead. The tool includes a hydraulic reset assembly. The hydraulic chamber is in fluid communication with the flow path through the tool. Thus, when the internal fluid pressure inside the tool exceeds the external pressure in the well, the fluid pressure drives the piston in the hydraulic chamber to urge the tool toward the contracted position. In this way, the reset assembly can overcome the tendency of fluid pressure to extend the tool. The reset assembly can be configured to balance or equalize the extension pressure, to prevent undesired cocking of the tool, or to overcome the extension pressure to contract the tool for recocking the jar mechanism.

Abstract: A fluid-actuated percussive impact tool includes a drill bit disposed partially within a casing for respective longitudinal movement between extended and retracted positions. A bearing having a bore is fixedly disposed within the casing. A piston is located in the chamber and a second end thereof is configured to selectively enter the bore of the bearing through the first end to impact the first end of the drill bit. At least one groove is formed in an exterior surface of the piston proximate the second end thereof. The tool has a sealed position when the drill bit is in the extended position wherein a water seal is formed between an interior surface of the bearing and a portion of the exterior surface of the piston between the first end of the piston and the first end of the at least one groove.