Patent Publication Number: US-6986394-B2

Title: Reciprocable impact hammer

Description:
DESCRIPTION OF THE INVENTION 
   Background of the Invention 
   The invention relates to a reciprocable impact hammer and more particularly to an impact hammer the tool support member of which is rotatable while under load. 
   Such a hammer is useable in operations aimed at creating, enlarging or otherwise working on a borehole. 
   Most commonly the need to carry out such operations arises in the oil and gas industries. In these industries it is very common to sink many boreholes, for purposes including but not limited to:
         geological and formation fluid sample acquisition;   downhole data logging and/or processing; and   oil and/or gas production.       

   Boreholes are also commonly sunk in other industries. Examples include but are not limited to:
         the acquisition of subterranean mineral samples in e.g. coal and other mining industries;   downhole data logging in non-hydrocarbon bearing formations such as coal fields; and   the testing and/or productionisation of water wells and aquifiers.       

   The invention is broadly applicable in all such industries as aforesaid; although it is of particular utility in the oil and gas exploration and production industries. 
   Impact hammers are used for cleaning out, re-shaping or reaming well conduits, or for making a new hole in a well. Various designs exist, all of which operate by driving a heavy downhole member against a force; and subsequently releasing the member so that the force drives it rapidly to strike a further member. The resulting impulse may cause a range of desired effects at a downhole location. 
   The heavy member typically is arranged to reciprocate so as to provide repeated impulses. 
   In oil drilling and other well operations, operators may use coiled tubing for raising and lowering tools into a well bore. The operators attach a tool/work string to the end of a reel of coiled tubing coiled around a large diameter reel at a surface location. By paying out the coiled tubing from the reel the operators can insert the tool/work string to a desired depth in the well which may be tens of thousands of feet from the surface location. By retracting the coiled tubing the operators remove the tool/work string from the well supported on the coiled tubing. 
   Coiled tubing is hollow along its entire length. Therefore through the use of coiled tubing it is possible to supply pressurised fluids to downhole locations. This can be for various purposes, one of which is to provide fluid to actuate or power any of various tools forming part of the tool string. 
   It is also known to use other types of fluid supply lines, e.g. jointed tubing in a wellbore. 
   Conventional drill bits and other rotary tools are not suitable for use with either coiled or jointed tubing. This is because in use such tools create torsional stresses that might damage or disconnect the tubing. Also it is impractical to rotate a string formed from many thousands of feet of coiled or jointed tubing. 
   Consequently the reciprocal, percussion-type tools as described above, that are powered by pressurized fluids supplied via the supply line, have been developed. 
   U.S. Pat. No. 5,156,223 discloses an impact hammer arrangement in which a drill bit rotates between impacts. The U.S. Pat. No. 5,156,223 arrangement utilizes the weight of the tool string to rotate the drill bit via a pin and helical track arrangement. Rotation of the tool takes place while the drill bit is unloaded. 
   The purpose of the rotation in the U.S. Pat. No. 5,156,223 arrangement is to prevent imprinting on the drilling surface. 
   The arrangement disclosed in U.S. Pat. No. 5,156,223 is not intended to rotate the drill bit while it is under load. 
   U.S. Pat. No. 3,946,819, U.S. Pat. No. 5,803,182 and U.S. Pat. No. 6,164,393 each disclose a reciprocal, percussion-type hammer tool that operates in response to fluid pressure communicated through a fluid supply line. Neither U.S. Pat. No. 3,946,819, U.S. Pat. No. 5,803,182 or U.S. Pat. No. 6,164,393 mention rotation of a hammer member or drill bit. 
   SUMMARY OF THE INVENTION 
   According to the invention there is provided a reciprocal impact hammer for use in a downhole location comprising:
         a tool support member;   a hammer member;   a jack mechanism;   a connector member; and   a transmission,   wherein the tool support member and the connector member are in spaced apart relation from one another and secured to the hammer member;   the tool support member and the hammer member are moveably captive one relative to the other;   the jack mechanism operatively interconnects the tool support member and the hammer member whereby operation of the jack mechanism causes limited separation of the hammer member and the tool support member one relative to the other;   the jack mechanism is reversible to permit subsequent collapsing of the hammer member and the tool support member together;   the connector member and the hammer member are moveably captive one relative to the other;   the transmission operatively interconnects the connector member and the hammer member; and   the transmission converts linear motion of the connector member to rotary motion of the hammer member whereby when a force acts on the connector member via the hammer member and the tool support member operation of the jack mechanism causes initial elongation of the impact hammer followed in succession by:   (i) collapsing of the hammer member and the tool support member together such that the hammer member separates from the connector member and imparts an impulse to the tool support member; and   (ii) movement of the connector member towards the hammer member under the influence of the force whereby the transmission causes rotation of the remainder of the impact hammer.       

   According to a preferred embodiment of the invention the jack mechanism includes:
         a piston;   a hollow cavity;   a valve member; and   a control member,   the piston being located at an in-use uphole end of the tool support member;   the hollow cavity being located within the hammer member;   the valve member being located adjacent to an in-use uphole end of the hollow cavity; and   the control member being moveable within the hollow cavity between a first position in engagement with the piston and a second position in engagement with the valve member, whereby to control the flow of fluid through the hammer member.       

   Conveniently the hammer member includes a resilient biasing member for moving the control member towards the second position. 
   The valve member preferably is or includes a tappet valve. 
   Conveniently the impact hammer is or includes a fluted dart. 
   Preferably the hammer member includes an impact cap, the impact cap being located adjacent to an in-use downhole end of the hammer member. 
   In an alternative embodiment the hammer member includes a threaded portion adjacent to an in-use uphole end thereof. 
   In a further preferred embodiment the transmission includes:
         a transmission body;   a first transfer member; and   a second transfer member,   the first and second transfer members being moveably captive one relative to the other at least partially within the transmission body;   the first transfer member converting the linear motion of the connector member to rotary motion of the second transfer member.       

   Conveniently, the first transfer member includes a pair of mutually engaged helical splines for converting the linear motion of the connector member to rotary motion of the second transfer member. 
   Preferably the second transfer member includes at least one of a freewheel clutch and a cone clutch, at least one of which operatively interconnects the first and second transfer members. 
   In another preferred embodiment of the invention the transmission body includes a thrust bearing interposed between the transmission body and the second transfer member. 
   Conveniently, the second transfer member includes a threaded portion that corresponds to the threaded portion of the hammer member, the corresponding threaded portions removably securing the hammer member and the transmission one to the other. 
   Preferably the connector member includes an engagement portion for connecting the impact hammer to an in-use downhole end of a fluid supply line. 
   Advantageously the tool support member includes a tool removeably secured to an in-use downhole end thereof. 
   It is an advantage of the invention to provide a reciprocable impact hammer that is capable of transmitting rotational torque to a tool support member while that tool support member is under load. 
   It is a further advantage of the invention that transmission of the torque takes place efficiently and without excessive wear of the hammer. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIGS. 1A to 1E  show a schematic representation of the operating sequence of an impact hammer according to an embodiment of the invention. 
       FIG. 2  is a part-sectional, elevational view of a hammer member and a tool support member according to an embodiment of the invention. 
       FIG. 3  is a plan view from a first end of a tool support member and a portion of a hammer member according to an embodiment of the invention. 
       FIG. 4  is a sectional, elevation view of the tool support member and the portion of a hammer member shown in  FIG. 3 . 
       FIG. 5  is a sectional, elevational view of a connector member and transmission according to an embodiment of the invention. 
       FIGS. 6A to 6D  show the operating sequence of the hammer member and the tool support member shown in  FIG. 2 . 
   

   DESCRIPTION OF THE EMBODIMENTS 
   Referring to the drawings, a reciprocable impact hammer according to the invention is designated by the reference numeral  10 . The impact hammer  10  includes a tool support member  11 ; a hammer member  12 ; a jack mechanism  13 ; a connector member  14 ; and a transmission  16  ( FIG. 1A ). 
     FIG. 2  shows the tool support member  11 , hammer member  12 , and jack mechanism  13  in more detail. 
   The tool support member  11  and the hammer member  12  are moveably captive one relative to the other. The jack mechanism  13  operatively interconnects the tool support member  11  and the hammer member  12 . 
   The tool support member  11  includes an impact shaft  17  that has a substantially circular cross-sectional profile. An uphole end of the tool support member  11  defines a piston  18 . A tool, e.g. a drill bit  19 , is removeably connected to a downhole end of the impact shaft  17 . Other types of tool may also be used. 
   The impact shaft  17 , piston  18  and drill bit  19  each include a central, hollow cavity  21 ,  22 ,  23 . The cavities  22 ,  23  of the piston  18  and the drill bit  19  are formed in communication with the cavity  21  of the impact shaft  17 . The cavities  21 ,  22 ,  23  allow for the transmission of pressurized fluids through the impact hammer  10 . 
   The hammer member  12  includes an elongate, hollow hammer body  24 . The hammer body  24  has a substantially circular cross-sectional profile. A downhole end of the hammer body  24  has an impact cap  26  removeably secured thereto. The impact cap  26  retains the piston  18 . In addition the impact cap  26  prevents the impact shaft  17  from rotating about its longitudinal axis. 
   An uphole end of the hammer member  12  includes a threaded portion  27 . 
   The hammer member  12  further includes a hollow cavity  28  located therein. The hollow cavity  28  is formed in communication with the uphole end of the hammer member  12  and the piston  18  of the tool support member  11 . 
   A tappet valve  29  is located within the hollow cavity  28 , adjacent to the threaded portion  27 . 
   A control member  31  is moveably captive within the hollow cavity  28 . In the preferred embodiment the control member  31  is a fluted dart. Other types of control member are also possible. 
   The control member  31  includes an uphole end  32  and an downhole end  33 . 
   The control member  31  is moveable between a first position in contact with the piston  18  ( FIGS. 2 and 6A ), and a second position in contact with the tappet valve  29  ( FIG. 6D ). 
   The hammer member  12  includes at least one resilient biasing member. In the preferred embodiment the hammer member  12  includes a first coil spring  34  and a second coil spring  35 . 
   Other types of hammer member as will be known to those of skill in the art, are also possible within the scope of the invention. 
   In a preferred embodiment of the impact hammer  10  the impact shaft  17  and the impact cap  26  include mutually opposable flat portions  36 A,  36 B ( FIGS. 3 and 4 ). 
     FIG. 5  shows the connector member  14  and the transmission  16  in more detail. 
   The connector member  14  and the transmission  16  are moveably captive one relative to the other. 
   The connector member  14  includes a threaded portion  37  for removeably connecting the impact hammer  10  to an in-use downhole end of a fluid supply line. 
   The connector member also includes a first mandrel  38  having a generally circular cross-sectional profile. The first mandrel  38  is moveable within an uphole end of the transmission  16 . 
   The transmission  16  includes a transmission body  39 . The transmission body  39  has a hollow, elongate, generally tubular form. 
   The transmission  16  further includes a first transmission member  41  and a second transmission member  42 . The first and second transmission members  41 ,  42  are moveably captive one relative to the other at least partially within the transmission body  39 . 
   The first transfer member  41  includes a pair of mutually engaged helical splines  43 ,  44 . 
   In the preferred embodiment the second transfer member  42  includes a first free wheel clutch  46  and a cone clutch  47  which operatively interconnect the first and second transfer members  41 ,  42 . 
   The preferred embodiment also includes a second freewheel clutch  48  interposed between the transmission body  39  and the second transfer member  42 . 
   Other types and combinations of clutch are also possible. 
   The transmission includes a thrust bearing  49  interposed between the transmission body  39  and the second transfer member  42 . A split ring  51 ,  52  is arranged adjacent to each side of the thrust bearing  49 . The split rings  51 ,  52  hold the second transfer member moveably captive. 
   The in-use downhole end of the second transfer member  42  includes a threaded portion  53 . The threaded portion  53  connects the transmission  16  to the hammer member  12  via the corresponding threaded portion  27  of the hammer member  12 . 
   Both the connector member  14  and the transmission  16  include a hollow, central cavity  54 ,  55  formed in communication one with the other. The cavities  54 ,  55  permit the supply of pressurized fluids to the hammer member  12 . 
   In use the impact hammer  10  of the invention operates as described below. 
     FIGS. 6A to 6D  show the operating sequence of the tool support member  11 ; the hammer member  12 ; and the jack mechanism  13 . 
   To initiate operation of the jack mechanism  13  an operator applies a so-called “set down weight” to the hammer member  12 . The set down weight may typically lie in the range 500 lbs to 2,850 lbs. 
   Simultaneously the operator applies a fluid pressure of typically between 500 psi and 2,500 psi to the impact hammer  10  via the fluid supply line. The fluid pressure is transmitted to the control member  31  via the hollow cavity  54  in the connector member; the hollow cavity  55  in the transmission  16 ; and the hollow cavity  28  in the hammer member  12 . 
   The combination of set down weight and fluid pressure causes the downhole end  33  of the control member  31  to seat against the piston  18 . The seating of the control member  31  against the piston  18  prevents the discharge of fluid via the remainder of the tool support member  11 , i.e. cavities  21 ,  22  and  23 . 
   Consequently there is a build up of pressure in the hollow cavity  28  of the hammer member  12 . This pressure increase causes limited separation of the hammer member  12  and the tool support member  11  one relative to the other. 
   Since the downhole end of the tool support member  11  is restrained by the bottom of the borehole, or other obstruction, the limited separation of the hammer member and the tool support member  11  has the effect of lifting the hammer member  12  in an uphole direction ( FIG. 6B ). 
   Movement of the hammer member  12  results in the compression of the first and second springs  34 ,  35 . When the first and second springs  34 ,  35  are fully compressed subsequent movement of the hammer body  12  lifts the control member  31  away from the piston  18  ( FIG. 6C ). 
   Movement of the control member  31  relative to the piston  18  breaks the seal therebetween. This allows the discharge of fluid via the cavities  21 ,  22 ,  23  in the tool support member  11 . As a result the fluid pressure within the hollow cavity  28  falls. 
   This reversing of the jack mechanism  13  permits the collapsing of the hammer member  12  and the tool support member  11  together ( FIG. 6D ). The collapsing occurs because of the absence of fluid pressure to lift the hammer member  12 . The weight of the hammer member  12  and the transmission connected thereto causes the hammer member  12  to collapse towards the tool support member  11 . 
   When the hammer member  12  and the tool support member  11  collapse together the hammer member  12  imparts an impulse to the tool support member  11 . The impulse is transmitted via the impact cap  26  to the impact shaft  17 . 
   The impulse drives the drill bit  19  into the drilling surface, thereby loading the drill bit  19  and the tool support member  11 . 
   Once the control member  31  moves away from the piston  18 , the first and second springs  34 ,  35  continue to move the control member  31  towards its second position, i.e., the tappet valve  29 . When the uphole end  32  of the control member  31  engages the tappet valve  29  it closes the valve. This interrupts the flow of fluid through the hammer member  12 . The resulting fall in fluid pressure in the hollow cavity  28  permits the control member  31  to return to its first position ( FIG. 6A ). The operating cycle then repeats. 
     FIGS. 1A to 1E  show in schematic form the operation of a reciprocable impact hammer according to the invention in combination with a known fluid supply line  56 . 
     FIG. 1A  indicates the condition of the impact hammer  10  following the application of a set down weight to the tool support member  11 . 
   The control member  31  becomes seated against the piston  18 . The increase in fluid pressure within the hammer member  12  causes limited separation of the hammer member  12  and the tool support member  11  one relative to the other ( FIG. 1B ). 
   The separation of the hammer member  12  and the tool support member  11  has the effect of lifting the remainder of the impact hammer  10  and the fluid supply line  56  in an uphole direction. 
   When the control member  31  is moved away from its seated position adjacent to the piston  18  the fluid pressure in the hammer member  12  falls. The hammer member  12  and the transmission  16  then collapse towards the tool support member  11  under their own weight. The collapsing together of the hammer member  12  and the tool support member  11  imparts an impulse to the tool support member  11 . The impulse drives the drill bit  19  into the drilling surface. 
   The drill bit  19  and tool support member  11  are now under load. 
   As the hammer member  12  and the transmission  16  collapse towards the tool support member  11 , inertia in the fluid supply line  56  results in the hammer member  12  and transmission  16  separating from the connector member  14  ( FIG. 1D ). 
   Once the hammer member  12  and the tool support member  11  have collapsed together ( FIG. 1D ) the set down weight forces the fluid supply line  56  and connector member  14  secured thereto to move towards the hammer member  12 . This movement causes the transmission  16  to rotate the remainder of the impact hammer  10 . 
   In the preferred embodiment the transmission  16  operates as follows. 
   Linear movement of the connector member  14  towards the hammer member  12  results in the linear movement of the first mandrel  38  relative to the transmission body  39  ( FIG. 5 ). 
   The mutually engaged helical splines  43 ,  44  convert this linear motion to rotary motion of the first transfer member  41 . The mutually engaged helical splines are more robust than, e.g. a pin a helical track arrangement. In addition, the compressive and torsional loads are evenly distributed when using a pair of splines, thereby reducing the amount of wear and damage that occurs. 
   The first freewheel clutch  46  and the cone clutch  47  transmit the rotary motion of the first transfer member  41  to the second transfer member  42 . 
   The first freewheel clutch  46  and the cone clutch  47  transmit rotary motion in one direction only. In the embodiment shown this direction is clockwise when viewed from the in-use uphole end of the impact hammer  10 . 
   When the hammer member  12  and transmission  16  separate from the connector member  14  ( FIG. 1D ) the first freewheel clutch  47  freewheels and the cone clutch  47  disengages. As a result rotary motion of the first transfer member  41  is not transmitted to the secondary member  42 , thereby helping to prevent the transmission of so-called “back-torque” to the tool support member  11 . 
   During use of the impact hammer  10  the thrust bearing  49  transmits axial load between the second transfer member  42  and the transmission body  39 . This limits the friction force acting on the second transfer member  42  during operation of the hammer  10 . 
   A second freewheel clutch  48  is interposed between the second transfer member  42  and the transmission body  39 . This helps to further reduce the transmission of back-torque to the tool support member  11 . 
   The second transfer member  42  is removeably secured to the hammer member  12  via corresponding threaded portions  53 ,  27 . Therefore rotary motion of the second transfer member is transmitted to the hammer member  12 . 
   The mutually opposable flat portions  36 A,  36 B( FIG. 4 ) prevent rotation of the tool support member  11  and the hammer member  12  one relative to the other. Consequently, as the hammer member  12  rotates the tool support member  11  and the drill bit  19  rotate. 
   Rotation of the tool support member  11  occurs while it and the drill bit  19  are under load, thereby enabling the tool operator to control the hammer action. The tool operator controls the hammer action by during the drilling operation setting down or laying off weight on the drilling bit, as necessary.