Abstract: A drilling fluid delivery system for use in drilling boreholes with a drill bit, the system comprising: a primary flow circuit having a relatively high flow rate for transferring drilling fluid to and from the drill bit; a secondary flow circuit having a relatively low flow rate for transferring drilling fluid to and from the primary flow circuit; and a cuttings transfer system, such as a hydrocyclone or a rotating filter, between the primary and secondary flow circuits which, in use, receives fluid containing cuttings from the primary circuit, separates the fluid into a first stream that contains substantially no cuttings and a second stream containing cuttings, the first stream being returned to the primary flow circuit and the second stream being directed to the secondary flow circuit.

Abstract: A method of removing cuttings includes the steps of disposing a pipe string in a high-angle wellbore, circulating mud through the wellbore and creating a viscous coupling layer of mud spiraling about a section of the pipe string. Wherein the wellbore may be deviated from vertical thirty degrees or greater. The viscous coupling layer desirably extends outwardly beyond the outside diameter of the tooljoint upsets in the section of the pipe string. A pipe joint for creating a viscous coupling layer of drilling fluid spiraling about the pipe to remove cuttings from high angle wells includes an elongated tubular having an outer surface extending between opposing tooljoints, tooljoint upsets and projections provided on substantially the entire outer surface.

Abstract: A fluid driven drilling motor and system includes a flex shaft between the rotor and a cylindrical flow collar. The end of the flow collar opposite from the flex shaft has a bore in fluid communication with a drill bit. Ramped apertures are formed in the side wall of the flow collar. The ramped apertures are in fluid communication with the bore. Drilling fluid flowing under pressure down past the flex shaft is directed and drawn into the ramped apertures along a fluid flow path which spirals downwardly and radially inwardly of the flow collar so as to then flow into the bore. The pressure loss associated with drawing the drilling fluid down to the drill bit is thereby minimized.

Abstract: A method and system for drilling a wellbore is described. The system includes a wellbore with a variable density drilling mud, drilling pipe, a bottom hole assembly disposed in the wellbore and a drilling mud processing unit in fluid communication with the wellbore. The variable density drilling mud has compressible particles and drilling fluid. The bottom hole assembly is coupled to the drilling pipe while the drilling mud processing unit is configured to separate the compressible particles from the variable density drilling mud. The compressible particles in this embodiment may include compressible hollow objects filled with pressurized gas an configured to maintain the mud weight between the fracture pressure gradient and the pore pressure gradient. In addition, the system and method may also manage the use of compressible particles having different characteristics, such as size, during the drilling operations.

Abstract: In one embodiment of the invention, a downhole tool string component comprising a through bore running there through formed to accept drilling fluid. At least one mechanical actuation device is also disposed within the through bore. A guide channel is disposed within the through bore and comprises a geometry shaped to conduct the at least one mechanical actuation device. A switch is disposed within the guide channel in an original position and actuatable by the at least one mechanical actuation device to a subsequent position. A resettable mechanism is in contact with the switch wherein the resettable mechanism returns the switch to its original position. A receptacle may also be disposed within the through bore comprising a geometry shaped to accept the at least one mechanical actuation device.

Abstract: A technique is presented for providing a double-barrier to formation fluids during drilling operations with a concentric drill string having an inner bore and an annulus. A primary flow control system is used to provide a first barrier to formation fluids in the inner bore and annulus of the drill string. A backup flow control system is used to provide a second barrier to formation fluids. The backup flow control system comprises a backup inner bore shutoff valve and a backup annulus shutoff valve. The backup inner bore shutoff valve is dropped from the surface through the inner bore of the drill string. The backup inner bore shutoff valve has spring-biased tabs that are configured to extend outward to contact an inner surface profile of the inner bore of the drill string. The backup annulus shutoff valve may be provided with the profile to receive the spring-biased tabs from the backup inner bore shutoff valve.

Abstract: A technique that is usable with a well includes running string that includes a tool and a flowable object that is held in a retained position within the string downhole in the well. After the string is run downhole in the well, the flowable object is released to permit the object to flow in and subsequently seat in a flow path of the string to impede fluid communication so that the tool may be actuated in response to the impeded fluid communication.

Abstract: In one aspect of the present invention, a drilling assembly has a string of downhole tools connected to a drill bit with a bit body intermediate a shank and a working face. The drill bit is connected to the string of tools at the shank. A continuous fluid passageway is formed within the bit body and the string of tools. A valve mechanism disposed within the fluid passageway is adapted to substantially cyclically build-up and release pressure within the fluid passageway such that a pressure build-up results in radial expansion of at least a portion of the fluid passageway and wherein a pressure release results in a contraction of the portion of the fluid passageway. The expansion and contraction of the portion of the fluid passageway varies a weight loaded to the drill bit.

Abstract: The invention relates to a connection device for forming a fluid supply to a rotating tool, comprising a rotary feedthrough which has a rotor and a stator, the rotor being supported in a rotating manner relative to the stator. Furthermore, a torque support is provided, which is connected in a rotationally fixed manner to the stator and has at least one contact element. In accordance with the invention the at least one contact element can be displaced between a retracted position and a protruding position, in which the contact element is extended compared to the retracted position for the purpose of torque support.

Abstract: A drilling unit containing a combined pilot bit and reamer. The drilling unit includes a housing containing a mud motor and a pilot bit extending from its distal end. A reamer is mounted to the housing. The mud motor turns the pilot bit while the reamer is turned either by the mud motor or as the drill string is rotated from the surface. The well bore is drilled and reamed in one pass. By positioning the reamer between the pilot bit and the mud motor, the mud motor must only pass through the larger reamer bore rather than the smaller pilot hole. This will allow larger mud motors to be used than would otherwise be possible. In one embodiment, the pilot bit is offset relative to the center of the end of the drill housing, providing increased tangential speed at the point of impact between the pilot bit and formation.

Abstract: An improved vacuum drilling system and drill bit includes a generally hollow vacuum drill bit with one or more chip inlets arranged proximate to one or more cutting surfaces. The drill bit also includes grooves along its exterior. When the drill bit is guided by a bushing or guide hole, the grooves serve to reduce the friction therebetween. The grooves can also convey air for cooling and improved chip collection.

Abstract: A downhole impeller device for use within a well, comprising: a body connectable to a drill string and having an external diameter smaller than the well diameter so as to form an annulus between the body and the well; and one or more impeller members extending from the outer surface of the body such that rotation of the or each impeller member impels drilling fluid within the annulus.

Abstract: In one aspect of the present invention a tool string comprises a jack element substantially coaxial with an axis of rotation. The jack element is housed within a bore of the tool string and has a distal end extending beyond a working face of the tool string. A rotary valve is disposed within the bore of the tool string. The rotary valve has a first disc attached to a driving mechanism and a second disc axially aligned with and contacting the first disc along a flat surface. As the discs rotate relative to one another at least one port formed in the first disc aligns with another port in the second disc. Fluid passed through the ports is adapted to displace an element in mechanical communication with the jack element.

Abstract: An assembly for use in drilling in earth borehole using a drill string including a drill bit comprising a first downhole motor having a rotor operatively connected to said drill bit, a second downhole motor distal said first downhole motor, said second downhole motor having a rotor with a passageway therethrough and a bypass valve operatively connected to the second downhole motor, the bypass valve having a first position permitting drilling fluid to flow through said passageway and a second position wherein drilling fluid is prevented from flowing through said passageway.

Abstract: A down hole air diverter having a first opening in communication with the central passageway of a drillstring; a second opening in communication with the well bore annulus; and a means to control the flow of pneumatic fluid between the first opening and the second opening. The means to control the flow further includes a first sealing means and a first biasing means to control the first sealing means. The first sealing means allows communication with the well bore annulus when the well bore annulus pressure exceeds the first biasing means pressure and prevents communication when the bias pressure exceeds the bore annulus pressure. A second sealing means prevents communication with the drillstring when the pressure from the second sealing means chamber exceeds the first opening pressure and allowing communication when the first opening pressure exceeds the chamber pressure.

Abstract: A downhole tool (10) for use in oil and/or gas well bores. The tool has a tubular body (20) and a sleeve (22) including stabilizer blades (30). The tool is ball (76), activated, weight activated or hydraulically activated to selectively jet fluid from the body through jetting ports (44A, 44B, 44C) on the blades. Thus the tool provides the features of a stabilizer, cleaning tool and circulation tool in-one.

Abstract: An active differential pressure device (APD device) in fluid communication with a returning fluid creates a differential pressure across the device, which controls pressure below the APD Device. In embodiments, a control unit controls the APD Device to provide a selected pressure differential at a wellbore bottom, adjacent a casing shoe, in an intermediate wellbore location, or in a casing. In one arrangement, the control system is pre-set at the surface such that the APD Device provides a substantially constant pressure differential. In other arrangements, the control system adjusts an operating parameter of the APD Device to provide a desired pressure differential in response to one or more measured parameters. Devices such as an adjustable bypass can be used to control the APD Device. In other embodiments, one or more flow control devices coupled to the return fluid reduce the effective pressure differential provided by the APD Device.

Abstract: A downhole tool for use within a well comprising a body having an external diameter smaller than the diameter of the well so as to form an annular gap between the body and the interior surface of the well. A first downhole fluid passage having an upper inlet and a lower outlet is provided in the body. At least one secondary fluid passage extending between the first downhole fluid passage and the annular gap is provided at the body. A sleeve member is provided at the body and adapted to move between a first position in which said at least one secondary fluid passage is closed and a second position in which said at least one secondary fluid passage is open. The sleeve member is maintained at one or both of the first and second positions upon rotation of the body within the well.

Abstract: A technique that is usable with a well includes running a motor into the well and actuating the motor to turn a drill bit. The motor is used to pump well fluid from the well.

Abstract: The present invention relates methods and apparatus for lining a wellbore. In one aspect, a drilling assembly having an earth removal member and a wellbore lining conduit is manipulated to advance into the earth. The drilling assembly includes a first fluid flow path and a second fluid flow path. Fluid is flowed through the first fluid flow path, and at least a portion of which may return through the second fluid flow path. In one embodiment, the drilling assembly is provided with a third fluid flow path. After drilling has been completed, wellbore lining conduit may be cemented in the wellbore.

Abstract: The present invention comprises a drilling tool assembly for drilling oil comprising a bit release subassembly, a test sleeve that is removable to open and close flow ports, and a profile nipple.

Abstract: A method and system for introducing a fluid into a borehole, in which there is arranged a tubular drill string including a drill bit, wherein the drill bit is provided with a passageway between the interior of the drill string and the borehole, and with a removable closure element for selectively closing the passageway in a closing position, and wherein there is further provided a fluid injection tool comprising a tool inlet and a tool outlet, the method comprising passing the fluid injection tool through the drill string to the closure element, and using it to remove the closure element from the closing position, passing the fluid injection tool outlet through the passageway, and introducing the fluid into the borehole from the interior of the drill string through fluid injection tool into the borehole.

Abstract: A drilling assembly for drilling a borehole into geological formations. The assembly comprises a drilling shaft and a pump device, both placable in the borehole. The drilling shaft comprises a drilling head, and the pump device comprises a sealing device for sealing a first borehole part below the sealing device from a second borehole part above the sealing device. The pump device is enabled to pump a fluid from the first borehole part to the second borehole part.

Abstract: Method and apparatus for drilling a directional or horizontal wellbore in a hydrocarbon formation using concentric drill string having an inner pipe and an outer pipe defining an annulus there between. A bottomhole assembly comprising a directional drilling means such as an air hammer or a rotary drill bit and driving system is provide at the lower end of the concentric drill string and drilling medium is delivered through the annulus or inner pipe for operating the directional drilling means to form a borehole. Exhaust drilling medium, drilling cutting and hydrocarbon are removed from the wellbore by extracting the exhaust drilling medium, drilling cutting and hydrocarbon through the other of the annulus or inner pipe.

Abstract: Methods and control systems are provided for a wellbore drilling system having an active differential pressure device (APD device) in fluid communication with a returning fluid. The APD Device creates a differential pressure across the device, which reduces the pressure below or downhole of the device. In embodiments, a control unit controls the APD Device to provide a selected pressure differential at a wellbore bottom, adjacent a casing shoe, in an intermediate wellbore location, or in a casing. In one arrangement, the control system is pre-set at the surface such that the APD Device provides a substantially constant pressure differential. In other arrangements, the control system measures one or more parameters (e.g., wellbore pressure, formation parameters, BHA parameters, etc.) and adjusts an operating parameter of the APD Device to provide a desired pressure differential. Devices such as an adjustable bypass can be used to control the APD Device.

Abstract: A wellbore drilling system has an umbilical that carries a drill bit in a wellbore. Drilling fluid pumped into the umbilical discharges at the drill bit bottom and returns through an annulus between the umbilical and the wellbore carrying entrained drill cuttings. An active differential pressure device (APD device), such as a jet pump, turbine or centrifugal pump, in fluid communication with the returning fluid creates a differential pressure across the device, which alters the pressure below or downhole of the device. The APD device can be driven by a positive displacement motor, a turbine, an electric motor, or a hydraulic motor. A controller controls the operation of the APD device in response to programmed instructions and/or one or more parameters of interest detected by one or more sensors. A preferred system is a closed loop system that maintains the wellbore at under-balance condition, at-balance condition or over-balance condition.

Abstract: A method for drilling a borehole includes; providing a drill string of drill pipe including a center bore, a distal end, a bit assembly at the distal end; hanging a liner from the drill string, thereby forming an annular space between the drill string and the liner and with the bit assembly extending from a lower end of the liner; positioning the drill string with the liner attached thereto in a borehole such that a second annular space is formed between the liner and the borehole wall; operating the bit assembly to proceed with drilling the borehole; and circulating drilling fluid down through the center bore of the drill string out through the bit assembly and down through the second annular space between the liner and the borehole wall, the drilling fluid returning up through the annular space between the drill string and the liner.

Abstract: The invention relates to a drilling assembly for drilling a borehole into geological formations which assembly comprises: a drilling shaft placable in the borehole, which shaft has a drilling head; and a pump device placable in the borehole, wherein the pump device has sealing means for sealing a first borehole part below the sealing means from a second borehole part above the sealing means, and wherein the pump device is enabled to pump a fluid from the first borehole part to the second borehole part.

Abstract: The present invention provides an apparatus and methods to reduce ECD and pressure associated therewith while drilling with casing. In one aspect, the invention provides an energy transfer assembly locatable at a predetermined location in a casing string. The assembly includes an impeller portion in the interior of the casing to be acted upon by the downward moving fluid in the casing and a pump portion disposed outwardly of the impeller portion and arranged in fluid communication with the upward moving fluid in the annulus between the casing and the borehole, adding energy thereto and reducing pressure in the annulus therebelow. In another aspect, the energy transfer assembly is retrievable to the surface of the wellbore prior to cementing. In a further aspect, fluid ports between the interior and exterior of the casing are remotely sealable prior to cementing.

Abstract: A drive steel member for driving engagement with a rotary drilling machine, including a chuck adapter having main body and chuck seating means and being constructed and arranged in fixed, sealed relation on one end of the drive steel member.

Abstract: A valve assembly connects into a drill string for opening and closing the inner passage within the drill string. The valve member moves between the open and closed positions in response to axial movement of the drill string. The valve member has an upper portion and a lower portion. A valve member and valve sleeve are located within an inner passage. Lifting the drill string causes the upper portion to move upward relative to the lower portion, bringing along with it the valve member, while the valve sleeve remains stationary with the lower portion, opening the valve.

Abstract: The present invention provides an apparatus and methods to reduce ECD and pressure associated therewith while drilling with casing. In one aspect, the invention provides an energy transfer assembly locatable at a predetermined location in a casing string. The assembly includes an impeller portion in the interior of the casing to be acted upon by the downward moving fluid in the casing and a pump portion disposed outwardly of the impeller portion and arranged in fluid communication with the upward moving fluid in the annulus between the casing and the borehole, adding energy thereto and reducing pressure in the annulus therebelow. In another aspect, the energy transfer assembly is retrievable to the surface of the wellbore prior to cementing. In a further aspect, fluid ports between the interior and exterior of the casing are remotely sealable prior to cementing.

Abstract: A Down Hole Drilling Assembly (DHDA) that induces artificial lift to remove the drilling fluid from a well bore using a jet pump attached to a casing string. The DHDA includes a drill string that passes through the jet pump assembly. The power fluid is separated from the drilling fluid until after it has passed through the nozzle of the jet pump. The jet pump assembly is joined to a concentric casing string. The jet pump also contains a bladder element that expands to redirect the flow of the drilling fluid from the inner annulus into the jet pump assembly. The jet pump assembly lifts the drilling fluid, lowering the fluid level within a well bore to a point where the hydrostatic pressure near the bottom of the well is lower than the pore pressure of the formation being drilled thereby creating under balanced conditions.

Abstract: A fluid flow switching device for a drill string comprises a tubular member having a port (4). A sleeve member is slidable within the tubular member between a first position in which a port (3) thereof is in alignment with the port (4) and a second position in which the port (4) is obstructed. A plurality of fingers are connected to the sleeve member (2). Each finger defines one segment of a closure member that is closed when the fingers are pivoted inwardly and open when the fingers are pivoted outwardly. An operating surface is positioned within the tubular member, and the fingers are axially slidable thereover as the sleeve member is moved between the first and second positions to close and open the segmented closure.

Abstract: A method and system for introducing a fluid into a borehole, in which there is arranged a tubular drill string including a drill bit, wherein the drill bit is provided with a passageway between the interior of the drill string and the borehole, and with a removable closure element for selectively closing the passageway in a closing position, and wherein there is further provided a fluid injection tool comprising a tool inlet and a tool outlet, the method comprising passing the fluid injection tool through the drill string to the closure element, and using it to remove the closure element from the closing position; passing the fluid injection tool outlet through the passageway, and introducing the fluid into the borehole from the interior of the drill string through fluid injection tool into the borehole.

Abstract: The present invention relates to a chassis for a downhole drilling tool. The chassis is positionable in a drill collar of a downhole tool and includes a first portion and a second portion. The first portion defines a passage for the flow of drilling fluid through the drill collar. The first portion is made of a high machinable material and has at least one cavity therein for housing instrumentation. The second portion is positioned about the first portion such that the first portion is isolated from the drilling fluid. The second portion is made of a high strength and/or an erosion resistant material. A HIP process may be used to metallurgically bond the materials together to from the chassis.

Abstract: A wellbore drilling system has an umbilical that carries a drill bit in a wellbore. Drilling fluid pumped into the umbilical discharges at the drill bit bottom and returns through an annulus between the umbilical and the wellbore carrying entrained drill cuttings. An active differential pressure device (APD device), such as a jet pump, turbine or centrifugal pump, in fluid communication with the returning fluid creates a differential pressure across the device, which alters the pressure below or downhole of the device. The APD device can be driven by a positive displacement motor, a turbine, an electric motor, or a hydraulic motor. A controller controls the operation of the APD device in response to programmed instructions and/or one or more parameters of interest detected by one or more sensors. A preferred system is a closed loop system that maintains the wellbore at under-balance condition, at-balance condition or over-balance condition.

Abstract: The present invention relates to downhole apparatus and particularly but not exclusively, to multi-cycle circulating subs used during downhole drilling operations. Apparatus is provided comprising a piston (42) slidably mounted in a body (4) between positions in which at least one aperture (40) in the body is opened and closed. Movement of the piston (42) is controlled by a pin (86) secured to one of the body and a control member, and a control groove (52) in which a portion of the pin is received formed in the other of the body and control member. An arrangement of elements (32, 76) respectively connected to the control member and body is such that, as the control member moves axially, increasing lengths of said elements locate adjacent one another so as to provide resistance to relative rotation in at least one direction of the control member and body. The relative rotation is rotation which presses the control member against the control groove.

Abstract: A method and apparatus for under balanced drilling comprising a production casing extending vertically from the ground to the area where the drilling is taking place, a concentric casing mounted within the production casing and forming therewith an outer annulus, a concentric casing connecting at its lower end with an upper end of an injection tool, the injection tool having a lower end connecting with a packer assembly which includes a packer and slips, and a drill string having a drill bit at the lower end thereof extending downwardly through the concentric casing, the injection tool, and packer assembly to the area where the drilling is taking place, the injection tool having a generally cylindrical body and a plurality of spaced spiral flutes extending outwardly from the cylindrical body to the inner wall of the production casing and forming therebetween spiral openings through which fluid may be forced downwardly through the outer annulus and against the packer, each flute having an upwardly directed spi

Abstract: A drilling system and method for drilling a borehole into an earth formation is provided. The drilling system comprises a drill string (1) having a lower section provided with a sleeve (7) which is radially expandable from a retracted mode in which the sleeve extends around said lower drill string section and is releasably connected thereto, to an expanded mode in which the sleeve is released from the lower drill string section and is expanded against the borehole wall. The drilling system further comprises control means (10) for selectively releasing the sleeve (7) from the lower drill string section and expanding the sleeve against the borehole wall.

Abstract: A valve assembly connects into a drill string for opening and closing at least one inner passage within the drill string of the drill string. The valve assembly includes an annular valve assembly carried in an annular passage that moves between the open and closed positions in response to downward fluid pressure from the surface through the annular passage. The valve assembly also includes an inner valve assembly carried in an inner passage of the drill string. The inner valve assembly is a two-way valve that is actuated between open and closed positions by pressure pulses from the surface through the inner passage. The valve assembly can be used within coiled tubing.

Abstract: A valve assembly connects into a drill string for opening and closing a passage within the drill string. The valve assembly has an inner valve member for opening and closing an inner passage of the drill string. The valve member moves between the open and closed positions in response to axial movement of the drill string. Lifting the drill string causes the upper portion to move upward relative to the lower portion, bringing along with it the valve member, while the valve sleeve remains stationary with the lower portion, opening the valve. The valve assembly can include an annular valve assembly for opening and closing an annular passage located around the inner passage. The annular valve assembly is opened and closed by increasing the pressure in the annular passage above the annular valve assembly.

Abstract: A downhole tool (10) for selectively circulating fluid in a borehole is disclosed. The tool operates via the use of a combination of deformable drop balls (36) and smaller hard drop balls (40). In use a deformable drop ball (36) moves a sleeve (20) exposing a radial port (30,32) to provide fluid circulation radially from the tool. The smaller drop ball (40) can then obstruct the radial port (32,30) and by the increased pressure the deformable drop ball (36) is extruded through the tool. The resulting pressure differential as the drop ball (36) moves causes the sleeve (20) to rise, releasing the smaller drop (40) ball and closing the radial port (32,30). The process can be repeated to selectively circulate fluid through the tool.

Abstract: Method and apparatus for underground drilling and enlarging of holes, in particular in hard rock, by using a water-driven motor as drive unit.

Abstract: The invention relates to a device for drilling, especially percussion drilling or rotary percussion drilling, holes (2), comprising a drill bit (3) with a drilling or breaking surface (14), a drill rod (4) for introducing a rotary or percussive force and for introducing a rinsing or cooling fluid into the drill bit (3) and a sheath pipe (5) which defines a hollow space (6) between the drill rod (4) and the inside of the sheath pipe (5) and which is supported on the drill rod (4) or which can be connected to the drill bit (3).

Abstract: A rotary steering apparatus including a drill string, a drill bit, a main body connected at one end to the drill string and at another end to the drill bit, a sleeve extending around the main body such that the main body is freely rotatable within the sleeve, and a locking member affixed to the main body and interactive with the sleeve. The sleeve has at least one protruding pad extending outwardly therefrom so as to bear against a well bore. The locking member serves to lock the sleeve relative to the main body such that the sleeve rotates correspondingly with a rotation of the main body. The locking member locks the sleeve onto the main body relative to an increased flow rate of fluid through the interior passageway of the main body. The locking member includes a flipper pivotally connected to the main body so as to extend into the longitudinal passageway and a spring resiliently connected to the flipper so as to urge the flipper into the interior passageway with a desired spring rate.

Abstract: A drilling fluid powered rotary drilling motor is mounted on the downhole end of a non-rotating fluid conducting drill string has a drill bit on its distal end and a plurality of fluid engaging, rotating elements coupled to at least one speed reducing planetary gear stage that converts the kinetic and pressure energies of the drilling fluid to mechanical power for rotating the drill bit. The drilling motor includes a lubricator, a drilling fluid filter, a pressure relief valve, a bypass valve and a check valve and is mounted with an output isolation coupling and a bearing package sized to withstand drilling load conditions.

Abstract: A down-hole tool comprises a generally tubular body for connection in a drill string, the body typically having an upper tubular member and a lower tubular member interconnected to be axially secured and relatively rotatable, and a frangible element securing the upper and lower members together rotationally and adapted to rupture at a predetermined load

Abstract: The diverter valve is carried in a housing that serves as a length of drill string. A selector valve is actuated by selective mud flow control signals from the surface and can close to build internal pressure to move a poppet to open a by-pass channel. Positive resilient seals are carried inside a protective sleeve until the principal openings are closed, then the seal is deployed to stop leakage.

Abstract: A rock drilling tool including a tip (3) formed of a hard material and provided at one end of the tool stem and a shank (4) provided at an opposite end of the stem (2) and having a plurality of entrain grooves (5) extending up to a free end surface of the shank (4), with an entire recessed surface (11) of an entrain groove (5) being larger than an entire outer surface (10) of a groove-forming rest web (6), and with a mean rest cross-sectional area (A′), which is measured within an axial section of the drilling tool having a length at least equal to a product of a natural logarithm base and a stem diameter (e×D), deviating from a mean rest cross sectional area (A) along the entire tool length maximum by 20%.