Abstract: A jarring tool can include a longitudinally displaceable piston, a first fluid chamber having a volume that decreases in response to displacement of the piston, a flow controller that controls flow of fluid between the first fluid chamber and a second fluid chamber, and a plug seat secured to the piston. A method of applying a jarring force can include applying a pressure differential across a plug in a jarring tool, the plug restricting flow from a first flow passage section to a second flow passage section, then increasing a flow rate of fluid from the first flow passage section. Another jarring tool can include an outer housing with a longitudinal flow passage and seal surfaces at opposite ends of the outer housing, and a flow obstruction, fluid flow through the flow passage being increased in response to application of a pressure differential across the obstruction.

Abstract: A mechanical jar including a housing, a piston disposed in the housing and responsive to applied fluid pressure to move in a first direction relative to the housing, a biasing arrangement disposed in the housing and configured to bias the piston in a second direction opposite the first direction, and a restraint configured to prevent movement of the piston in the second direction until a threshold force is applied to the restraint by the piston, whereafter the piston suddenly moves in the second direction.

Abstract: A wellbore assembly includes a cable configured to be disposed within a wellbore. The wellbore assembly also includes a housing attached to a downhole end of the cable. The housing defines a fluid outlet at a downhole end of the housing. The housing includes an anchor and a collapsible gate. The anchor engages a wall of the wellbore under increased tension in the cable, thereby anchoring the housing to the wellbore. The collapsible gate is disposed inside the housing between an uphole end of the housing and the fluid outlet. The housing temporarily stores a treatment fluid configured to treat an obstruction in the wellbore. The collapsible gate is configured to break, with the anchor engaged, under further tension applied by the cable, inside the housing to allow the treatment fluid to flow out of the housing through the fluid outlet toward the obstruction.

Abstract: A string guide comprising an upper mandrel, a lower muleshoe guide concentric to a lower portion of the upper mandrel, and an annular fastener internal to the lower muleshoe guide that fastens the lower muleshoe guide to the upper mandrel. When the guide encounters an obstruction (e.g., a packer bore or liner top), the weight of equipment above the lower muleshoe guide elastically deforms the annular fastener which drives the lower muleshoe guide up the upper mandrel. As the lower muleshoe guide travels up the upper mandrel, internal lugs of the muleshoe guide ride a spiral groove on the upper mandrel to rotate the lower muleshoe guide around the upper mandrel.

Abstract: An assembly disposed within a subterranean wellbore can include a first dislodging tool coupled to a bottom end of a tubing string, wherein the first dislodging tool, when enabled at a first time, performs a first action to free at least one service tool, disposed below the first dislodging tool in the subterranean wellbore, from being stuck.

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. The release lugs may be supported by an annular ring member.

Abstract: Tools and methods are described for removing a packer beyond a restriction in a casing of a wellbore. A packer milling tool includes: a milling body with an outer diameter; milling blocks positioned at intervals around a circumference of the milling body, each milling block pivotably attached to the milling body and pivotable between a running position and a milling position; and a wash pipe extending from a downhole end of the milling body. The milling blocks have a rotational circumference with a rotational diameter that is less than the outer diameter of the milling body when in the running position and the rotational diameter is more than the outer diameter of the milling body and less than the inner diameter of the casing when in the milling position.

Abstract: A method of freeing a stuck pipe in a wellbore includes positioning a pipe freeing tool within an annulus of the stuck pipe, the pipe freeing tool including a body and two or more arms coupled to and extending from the body, and activating the two or more arms of the pipe freeing tool to extend outwards from the body to apply a force to the stuck pipe. Another method of freeing a stuck pipe in a wellbore includes determining a stuck point along a drillstring comprising the stuck pipe, and activating a pipe freeing tool coupled to the stuck pipe to apply a force to the stuck pipe, wherein the force moves the stuck pipe away from a surface of the wellbore and towards a center of the wellbore, and the pipe freeing tool includes a plurality of expandable disc elements.

Abstract: A downhole valve has a valve body having at least one port and slidably receiving in a longitudinal bore thereof at least a first sliding sleeve for opening and closing the at least one port. The first sliding sleeve has a circumferential actuation groove. An actuation assembly is extendable into the first sliding sleeve and has an actuation housing axially movably receiving thereon a compressible sealing element and a slip assembly. The slip assembly has one or more slips radially outwardly extendable under a hydraulic pressure for engaging the circumferential actuation groove of the first sliding sleeve for opening the at least one port, and the actuation assembly is longitudinally extendable to position a portion thereof on an inner side of the one or more slips for supporting the one or more slips at a radially outwardly extended configuration.

Abstract: A jarring tool includes a spring and a hydraulic piston cylinder arrangement for controlling the release of a mandrel to initiate a jarring force. The tool includes an adjustment mechanism for adjusting the minimum amount of an upward pulling force required to release the mandrel. The adjustment mechanism includes an axially adjustable trigger sleeve that cooperates with a dog clutch surrounding the mandrel.

Abstract: A downhole valve has a valve body having at least one port and slidably receiving in a longitudinal bore thereof at least a first sliding sleeve for opening and closing the at least one port. The first sliding sleeve has a circumferential actuation groove. An actuation assembly is extendable into the first sliding sleeve and has an actuation housing axially movably receiving thereon a compressible sealing element and a slip assembly. The slip assembly has one or more slips radially outwardly extendable under a hydraulic pressure for engaging the circumferential actuation groove of the first sliding sleeve for opening the at least one port, and the actuation assembly is longitudinally extendable to position a portion thereof on an inner side of the one or more slips for supporting the one or more slips at a radially outwardly extended configuration.

Abstract: In certain embodiments, a downhole swivel sub includes a first swivel part configured to connect to a first section of a workstring, and a second swivel part configured to connect to a second section of the workstring. The second swivel part is rotatable relative to the first swivel part. The downhole swivel sub also includes a locking sleeve rotationally coupled with the first swivel part and movable axially between a locking position wherein the first swivel part and the second swivel part are rotationally coupled and an unlocking position wherein the first swivel part is rotatable relative to the second swivel part. The locking sleeve includes at least two first rows of teeth disposed at a same radial position and separated axially on the locking sleeve. The at least two first rows of teeth are configured to engage and disengage with at least two second rows of teeth located on the second swivel part.

Abstract: A tubular includes an outer surface and an inner surface defining a passage. A plug is arranged in the tubular blocking the passage. The plug is formed from a disintegrating on demand (DOD) material. An ignition device is coupled to the plug. An excitation mechanism is selectively operatively associated with the ignition device. The excitation mechanism selectively activates the ignition device to break apart the plug.

Abstract: An impact apparatus operable to be coupled along and impart an impact to a downhole tool string. The impact apparatus includes a housing, a first and second chambers within the housing, and a piston shaft assembly movable with respect to the housing. The piston shaft assembly includes a first piston slidably disposed within and dividing the first chamber into a first chamber portion and a second chamber portion, a first shaft connected with the first piston and axially movable into and out of the housing, a second piston slidably disposed within the second chamber, and a second shaft connecting the first and second pistons. The first chamber portion is open to a space external to the housing. The second chamber contains a fluid operable to maintain the piston shaft assembly and the housing in a predetermined relative position.

Abstract: A release device for a jarring tool includes a collet positioned between the mandrel of the jarring tool and a trigger sleeve. At least one end of the collet is in contact with a precompressed spring via a bushing. In order for the jarring tool to operate, a force greater than the precompressed force of the spring must be applied to the mandrel so that the collet can move in axial direction against the spring thereby releasing the mandrel.

Abstract: According to an aspect, a detonator positioning device is provided for use with a wireless detonator in a perforating gun assembly. The detonator positioning device includes a single mechanism for physical electrical connection, while the remaining electrical connections are made via electrically contactable components. A method of assembling the perforating gun assembly is also provided, including a detonator positioning device configured to receive and hold the wireless detonator.

Abstract: A jarring tool includes a spring and a hydraulic piston cylinder arrangement for controlling the release of a mandrel to initiate a jarring force. The tool includes an adjustment mechanism for adjusting the minimum amount of an upward pulling force required to release the mandrel. The adjustment mechanism includes an axially adjustable trigger sleeve that cooperates with a dog clutch surrounding the mandrel.

Abstract: An underreamer for increasing a diameter of a wellbore. The underreamer includes a body having an axial bore extending at least partially therethrough. A sleeve is arranged and designed to move a first axial distance within the body. A cutter block is movably coupled to the body. The cutter block is arranged and designed to move at least the first axial distance with respect to the body to contact the sleeve in response to hydraulic pressure in the bore. The cutter block moves from a first outer diameter to a second outer diameter as the cutter block moves the first axial distance.

Abstract: A jar includes the following: a mandrel; an outer housing slidably disposed about the mandrel; a low pressure chamber having a first port and formed between the mandrel and the outer housing; a high pressure chamber having a second port and formed between the mandrel and the outer housing; a fluid passage between the first and second port; and a valve disposed in the fluid passage.

Abstract: The invention is directed to a novel and useful fluid-tight, metal-to-metal, annular seal which can be repeatedly cycled in a high temperature, high pressure environment. More specifically, the invention provides a metal-to-metal, annular, seal on a radially expandable sliding sleeve which moves longitudinally from a reduced ID section of a bore to an enlarged section of the bore. The seal is disengaged at the enlarged bore section resulting in rapid fluid flow and pressure equalization which would destroy many traditional elastomer seals.

Abstract: A cable-operated jar comprising a releasable coupling is arranged for connection to a piece of downhole equipment, in which a mandrel is connected to a cable comprising a hammer section. The hammer section is arranged to strike, on the release of a mandrel coupling, against a shoulder section in a housing, and the mandrel is pre-tensioned in a releasable position with a spring arrangement. The spring arrangement includes an adjusting mechanism operated by the cable alternately being tensioned and relaxed.

Abstract: An impact apparatus conveyable in a tool string via conveyance means within a wellbore. The impact apparatus comprises a first portion, including a first interface coupled with a first tool string component, a first engagement feature, and a first impact feature. The impact apparatus also comprises a second portion, including a second interface coupled with a second tool string apparatus, a second engagement feature in selectable engagement with the first engagement feature, and a second impact feature positioned to impact the first impact feature in response to disengagement of the first and second engagement features and a tensile force applied across the tool string by the conveyance means. A release member positionable between first and second positions in response to a signal carried by the conveyance means prevents disengagement of the first and second engaging features when in the first position but not the second position.

Abstract: A jar comprises a housing including an anvil. In addition, the jar comprises a mandrel telescopically disposed within the housing and including a hammer. Further, the jar comprises an annular chamber radially positioned between the mandrel and the housing. Still further, the jar comprises an actuation assembly disposed in the annular chamber. The actuation assembly includes a first collet disposed about the mandrel, a first trigger sleeve disposed about the first collet and adapted to releasably engage the first collet, and a first biasing member adapted to exert an axial force on the mandrel. Moreover, the jar comprises a lock assembly disposed in the annular chamber. The lock assembly includes a second collet disposed about the mandrel, a second trigger sleeve disposed about the second collet and adapted to releasably engage the second collet, and a second biasing member adapted to exert an axial force on the mandrel.

Abstract: An impact apparatus conveyable in a tool string within a wellbore comprises a mandrel, a first impact feature, and a latch pin retainer encircling an end of the mandrel. A release sleeve encircles a portion of the latch pin retainer and includes a radial recess. Latch pins retained by the latch pin retainer are slidable into and out of the radial recess, and prevent disengagement of the mandrel end from the latch pin retainer when not extending into the radial recess. A release member electromagnetically causes relative translation of the latch pin retainer and the release sleeve, including aligning the latch pins with the radial recess and thereby permitting the disengagement. A second impact feature is positioned to impact the first impact feature in response to the disengagement when the impact apparatus is under tension.

Abstract: A hydraulic jar having multiple high pressure chambers includes a jar body comprising an inner body telescopically engaged by an outer body. There is a first contact surface carried by the inner body, and a second contact surface carried by the outer body that engage when the jar body is moved to the jarring position. A plurality of axially spaced pressure chambers are spaced axially along the jar body, with each pressure chamber having a hydraulic delay section and a jarring section. A piston separates the pressure chamber. A hydraulic delay is in fluid communication with a high pressure section and a low pressure section of each pressure chamber and permits movement of the piston toward the second end at a first speed. A jarring valve permits movement of the piston toward the second end at a second speed that is greater than the first speed when in a japing section.

Abstract: An apparatus configured to impart a force on a downhole component, having a piston configured to expand from a movement of a drilling fluid in a downhole environment, a weight configured to move from a first position to a second position, wherein the weight contacts the piston and the piston is configured to move the weight from the first position to the second position when the piston expands from movement of the drilling fluid, a spring configured to contact a bearing surface and the weight, wherein movement of the weight toward the second position compresses the spring, a return spring configured to impart a force on the weight to return the weight to the first position from the second position and a trigger mechanism configured to actuate a return of the weight from the second position to the first position by the return spring.

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: The present invention relates to hydraulic jars which include a jar body; a spindle axially movable within the jar body and coupled to the jar body by means of a helical splined coupling; the spindle being connectable to a pipe string and the stuck object; a cylinder concentrically placed within the jar body with a radial gap, and having chambers for filling with a work fluid, the chambers being separated by a piston and fluidly connected by a channel, wherein the channel is provided by a back valve. The piston is axially movable within the cylinder, and is connectable to the spindle by means of a tractive rod, and to the body by means of a compensative rod. The piston is further provided with elastic split compression rings having initial gaps equal or close to zero.

Abstract: A vibratory tool for use in a tubular string to prevent sticking or to release a stuck string features a fluid operated dart valve working in conjunction with an impact sleeve to deliver continuous axial jarring blows in opposed directions as long as flow is maintained. Movement of one of those components axially in opposed directions opens and closes access to opposed lateral ports so that a lateral vibration is also established as flow cyclically occurs and stops sequentially at opposed lateral outlets.

Abstract: A method for unseating a threaded connection of wellbore tubing within the wellbore. The method utilizes a back-off tool which consists of a tubular metal housing, a shaped charge and HNS detonating cord within the housing, and an explosive material attached to the housing. The back-off tool is detonated near the threaded connection, creating a shockwave that strikes the threaded connection with sufficient force to unseat the connection.

Abstract: A drilling system for drilling a lateral borehole from a main borehole comprises a tubular conduit through which a fluid can be pumped, and a drilling assembly connected to the tubular conduit so as to receive fluid pumped therethrough. The drilling assembly comprises a power conversion unit, through which the fluid flows and which operates to provide a downhole power output; a drilling unit including a drilling apparatus powered by the output of the power conversion unit and operable to drill a lateral borehole into the formation surrounding the main borehole, and a liner unit for storing one or more liners for installation into the lateral borehole; and an anchor unit operable to anchor the drilling assembly in the main borehole when the drilling unit operates to drill the lateral borehole.

Abstract: Disclosed are embodiments of an adjustable jar and accelerator system and methods of use thereof. One exemplary jarring system includes a jar having a first processor configured to determine a release point of the jar, an accelerator operatively coupled to the jar and having a second processor communicably coupled to the first processor via a communication line, the second processor being configured to determine a spring rate and stroke of the accelerator, and an impact recording device operatively coupled to the jar and having a third processor communicably coupled to one or both of the first and second processors.

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 downhole jarring tool includes a mandrel having a small diameter portion and a large diameter portion, a detent cylinder sealingly disposed around the mandrel forming an enclosure, a divider disposed in the enclosure between the mandrel and the detent cylinder, wherein the divider partitions the enclosure into a storage chamber and a metering chamber, and a metering system disposed around the mandrel. A method of applying an impact force using a downhole jarring tool includes moving a mandrel with respect to a detent cylinder by applying an axial force, positioning the mandrel such that a metering system disposed on the mandrel enters a reduced diameter portion of the detent cylinder, transmitting energy to an energy storing component disposed inside the detent cylinder, metering a fluid through the metering system, and accelerating the mandrel with respect to the detent cylinder.

Abstract: An impact apparatus conveyable in a tool string within a wellbore comprises a mandrel, a first impact feature, and a latch pin retainer encircling an end of the mandrel. A release sleeve encircles a portion of the latch pin retainer and includes a radial recess. Latch pins retained by the latch pin retainer are slidable into and out of the radial recess, and prevent disengagement of the mandrel end from the latch pin retainer when not extending into the radial recess. A release member electromagnetically causes relative translation of the latch pin retainer and the release sleeve, including aligning the latch pins with the radial recess and thereby permitting the disengagement. A second impact feature is positioned to impact the first impact feature in response to the disengagement when the impact apparatus is under tension.

Abstract: A jar comprises an outer housing; an inner mandrel within the outer housing to define a fluid chamber; a valve disposed within the fluid chamber with a restriction surface facing, during setting, a cooperating restriction surface on the outer housing and a pressure surface facing the inner mandrel, the valve movable between a seated position and an unseated position; the cooperating restriction surface cooperating with the restriction surface to set the jar for a jar in a first direction; the pressure surface being exposed to fluid within the fluid chamber when the jar is set and pressuring up for a jar in the first direction; the pressure surface being indented to cause uneven radial movement, in a plane perpendicular to a jar axis, of the restriction surface towards the cooperating restriction surface when the jar is set and pressuring up for a jar in the first direction; and jarring surfaces.

Abstract: A hydraulic jar for delivering impacts downhole. The jarring mechanism includes a cup-type piston that moves through a seal bore. The cup is deformable in response to fluid pressure so that it expands each time it moves through the seal bore to compensate for wear on the lip. Since only minimum interference is required between the piston and seal bore, less material may be used. This reduces the force required to reset the tool, which is particularly advantageous in horizontal wells. The seal bore may be slightly wider at the exit; the cup expands to this exit diameter, ensuring an interference fit as the cup travels back through the smaller diameter entry section. The entry end of the seal bore may include longitudinal grooves. This prevents the piston cup from rupturing by preventing a fluid seal around the lip until the most of cup is inside the seal bore.

Abstract: A downhole transport assembly (100, 101) having first and second members (10, 20) having a common longitudinal axis, at least one of the members (10, 20) being rotatable about the longitudinal axis and movable along the longitudinal axis relative to the other member, the rotatable member having at least one engaging member (60), the or each engaging member (60) being configured and/or disposed on the rotatable member so that rotation of the rotatable member about the longitudinal axis causes the first and second members (10, 20) to move with respect to each other in opposite directions along the longitudinal axis.

Abstract: A jar comprises a housing including an anvil. In addition, the jar comprises a mandrel telescopically disposed within the housing and including a hammer. Further, the jar comprises an annular chamber radially positioned between the mandrel and the housing. Still further, the jar comprises an actuation assembly disposed in the annular chamber. The actuation assembly includes a first collet disposed about the mandrel, a first trigger sleeve disposed about the first collet and adapted to releasably engage the first collet, and a first biasing member adapted to exert an axial force on the mandrel. Moreover, the jar comprises a lock assembly disposed in the annular chamber. The lock assembly includes a second collet disposed about the mandrel, a second trigger sleeve disposed about the second collet and adapted to releasably engage the second collet, and a second biasing member adapted to exert an axial force on the mandrel.

Abstract: This invention relates to a jar used to dislodge tools stuck in a well. The jar includes two housing portions movable with respect to each other. A release collet forms a portion of one of the housings. A release sleeve is carried by a mandrel and is located within the release collet. After a given amount of movement of the housing with respect to the mandrel, the release mechanism is activated and the two housing sections rapidly move with respect to each other. A hammer portion of the mandrel then strikes an anvil in the anvil housing, thus applying an upward force to the tool lodged in the well.

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 double-acting compounder comprises: an outer housing; an inner mandrel disposed telescopically within the outer housing to define a fluid chamber; an equalizer, such as an equalizer piston, between the fluid chamber and an exterior of the outer housing for equalizing pressure; a movable seal assembly within the fluid chamber with a first end defining an end of the fluid chamber; the inner mandrel having an outer shoulder for moving the movable seal assembly with the inner mandrel when the inner mandrel moves in a first direction relative to the outer housing to compresses fluid within the fluid chamber; and the outer housing having an inner shoulder for preventing the movable seal assembly from moving with the inner mandrel when the inner mandrel moves in a second direction relative to the outer housing to compresses fluid within the fluid chamber.

Abstract: A method of using jarring tool in a wellbore, where the jarring tool is electrically activated to apply an impact force transmitted to at least another tool in the well. The method may further comprise operating a hydraulic mechanism in response to electrical activation of the jarring tool to cause a first member of the jarring tool to be moved to collide with a second member of the jarring tool to apply the impact force. Also, the method may involve electrically activating the jarring tool by communicating at least one command over at least one electrical conductor to the jarring tool.

Abstract: A downhole assembly, including a downhole tool, a downhole force-creating device, and a shock damper. The shock damper includes a hollow housing including an annular shoulder near each end and extending radially inward from the housing. The damper also includes a mandrel located at least partially inside the housing to form an annulus between the mandrel and the housing, the mandrel including an annular shoulder near each end and extending radially outward from the mandrel. A spring is located in an annular cavity formed by the annulus and between both the housing shoulders and the mandrel shoulders. The mandrel is movable relative to the housing to an expanded position in one direction and to a compressed position in the other direction.

Abstract: A jarring device includes an outer housing which defines an axial flow path therethrough. An impact rotator is retained within the housing and is rotatable therewithin between a first rotational position and a second rotational position to create a jarring impact. A torsional spring biases the impact rotator toward the first rotational position. Fluid flow through the housing rotates the impact rotator from the first to the second rotational position.

Abstract: A jarring tool is disclosed. The tool has a segment of sub housing containing an upper stop proximate a first end thereof. An outer latch piece is connected to an upper end of the lower shaft inside the sub housing, and an upper shaft passes through the stop and connects on a first end thereof to an inner latch piece. A cap is on a second end of the upper shaft retaining a washer stack against the upper stop. A retainer is inside the sub housing and has an first piece providing a restraining region and an open region and a second piece attached to the sub housing. The retainer retains the inner and outer latch pieces in a latched position in the restraining region until the latch pieces are displaced toward the second end of the sub housing through the retainer to the open region as a result of a tensile force on the outer latch piece.

Abstract: A shock de-coupler for use with a perforating string can include perforating string connectors at opposite ends of the de-coupler, a longitudinal axis extending between the connectors, and a biasing device which resists displacement of one connector relative to the other connector in both opposite directions along the longitudinal axis, whereby the first connector is biased toward a predetermined position relative to the second connector. A perforating string can include a shock de-coupler interconnected longitudinally between components of the perforating string, with the shock de-coupler variably resisting displacement of one component away from a predetermined position relative to the other component in each longitudinal direction, and in which a compliance of the shock de-coupler substantially decreases in response to displacement of the first component a predetermined distance away from the predetermined position relative to the second component.

Abstract: A shock de-coupler for use with a perforating string can include perforating string connectors at opposite ends of the de-coupler, a longitudinal axis extending between the connectors, and a biasing device which resists displacement of one connector relative to the other connector in both opposite directions along the longitudinal axis, whereby the first connector is biased toward a predetermined position relative to the second connector. A perforating string can include a shock de-coupler interconnected longitudinally between components of the perforating string, with the shock de-coupler variably resisting displacement of one component away from a predetermined position relative to the other component in each longitudinal direction, and in which a compliance of the shock de-coupler substantially decreases in response to displacement of the first component a predetermined distance away from the predetermined position relative to the second component.

Abstract: Embodiments disclosed herein relate to a jar including the following: a mandrel; an outer housing slidably disposed about the mandrel; a ball stop housing disposed below the outer housing; a lower sub disposed below the ball stop housing; and a ball stop assembly disposed in the ball stop housing. The ball stop assembly includes a ball stop pivotally disposed in the ball stop assembly.

Abstract: A hydraulically powered fishing tool is provided for retrieving another tool or tubular stuck in a well. A tool housing is supported in a well on a work string, and the housing encloses a plurality of pistons (16, 28, 34) each movable in response to pressurized fluid transmitted through the work string. An anchor (52) axially fixes the position of the tool in the well, and a tool mandrel (40) is axially movable relative to tool housing when the anchor is set. A fishing device (82) engages the another tool or tubular, so that axial movement of the mandrel in response to the plurality of pistons dislodges the stuck tool or tubular.