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CROSS-REFERENCE TO RELATED APPLICATIONS 
     This is a continuation-in-part of U.S. patent application Ser. No. 08/992,235 which was filed on Dec. 17, 1997 now U.S. Pat. No. 6,009,941. 
    
    
     TECHNICAL FIELD 
     This invention relates to the handling of downhole well tools and tubing strings, and in particular to an apparatus for axially displacing a downhole well tool or tubing string in a well bore equipped with a wellhead, the downhole well tool being supported by a tubing string in the well which includes a telescoping joint to permit the axial displacement of the downhole well tool and the tubing string. As well as any downhole operation in which well tubulars or downhole equipment is manipulated or downhole operations are performed in which pressure containment is necessary. 
     BACKGROUND OF THE INVENTION 
     Downhole operations and the handling of downhole well tools in completed wells has always presented a certain challenge, especially when working in wells having a natural pressure that exceeds atmospheric pressure, necessitating the containment of the well at all times. A further challenge has been the maintenance of well bores which pass through production zones that are not well suited to continuous production. For example, a production zone which yields both water and oil or gas or any combination thereof may require relatively frequent repositioning of a lower end of a production tubing in order to recover oil or gas efficiently. Production zones which produce crude oil high in waxy compounds or asphaltines, or laden with salts, which tend to plug casing perforations and therefore require frequent treatment to maintain an economic flow of hydrocarbon are further examples of such production zones. 
     To date, the maintenance of such wells has proven time-consuming and expensive. For example, in wells which produce both oil, water and gas and/or water and gas and have a mobile water/hydrocarbon interface, the production of hydrocarbon gradually decreases over time until only water or gas is produced from the well. Relocation of the bottom end of the production tubing string is then required to recommence oil production. The relocation of the tubing string has been a complex process which involved many time-consuming and expensive steps that are well known in the art. It is not difficult to appreciate that there is a need for a more efficient and less costly system for producing oil or gas from such wells. Such a system is described in applicant&#39;s copending patent application incorporated herein by reference. The apparatus described in that patent application eliminates many of the shortcomings of prior art procedures for selectively producing fluids from wells, performing barefoot completions of well bores in sensitive zones, and other downhole operations using production tubing and tools that require axial displacement within a limited range in a well bore. At the time of filing that patent application, it was considered that the apparatus described in U.S. Pat. No. 4,867,243 which issued on Sep. 19, 1989 to Garner et al. would be suitable for effecting the axial displacement of the downhole well tools. It has now been recognized that such prior art tools for inserting mandrels through wellheads is not necessarily adequate or optimal for performing the axial displacement of such downhole well tools. 
     There are several reasons why such prior art tools are not optimal tools for this purpose. First, they are designed for inserting wellhead isolation mandrels into wellheads and withdrawing them from the wellheads after the well is serviced. Since wellhead isolation mandrels are of inconsequential weight, they are stroked through a wellhead relatively easily. Moving a tubing string of 4,500′ (1,500 meters), which is not uncommonly encountered in handling downhole well tools, may require a force in excess of 50 tons. The force required is due not only to the considerable weight to be lifted but also to the extra force required to unseat anchors and/or packers supporting the tubing string. Such forces may subject the wellhead to potentially damaging stresses. Second, wellhead isolation tools provide no mechanism for rotating a downhole tubing string since rotation is not required for the insertion or withdrawal of a wellhead isolation mandrel. When manipulating a downhole tubing string, however, rotational movement is often required in order to release or set components such as packers, anchors, hangers and the like. Considerable rotational force may be required to accomplish the release of such components and it is therefore desirable to provide a mechanism for selectively rotating the downhole string as required. 
     It has also now been recognized that certain downhole operations can be more economically performed through the wellhead with pressure containment than performing those operations using a rig, for example. It is also known that certain near-surface operations such as the drilling out of permanent bridge plugs, cement plugs or any other obstruction in the casing column during re-entries require pressure containment in order to avoid the escape of hydrocarbons to atmosphere and potentially dangerous releases of contained pressure. There therefore exists a need for an apparatus which is adapted to provide pressure containment while enabling downhole manipulations to move production tubing, and remove near-surface obstructions with or without the use of a telescoping joint in a tubing string. 
     SUMMARY OF THE INVENTION 
     It is an object of the invention to provide an apparatus for axially displacing a downhole tool or tubing string in a well bore equipped with a wellhead which is robust enough to permit a lengthy tubing string to be displaced in the well bore. 
     It is a further object of the invention to provide an apparatus for axially displacing a downhole tool or tubing string in a well bore equipped with a wellhead which permits a tubing string alone or a tubing string supporting the downhole tool to be rotated, if required. 
     It is yet a further object of the invention to provide an apparatus for axially displacing a downhole tool or tubing string in a well bore equipped with a wellhead which is stabilized to reduce stress on the wellhead. 
     It is yet a further object of the invention to provide an apparatus for axially displacing a downhole tool or tubing string in a well bore equipped with a wellhead which is safe to use. 
     It is also an object of the invention to provide an apparatus for axially displacing a downhole tool or tubing string in a well bore equipped with a wellhead which is readily transported from one well bore to another. 
     It is a further object of the invention to provide an apparatus for performing downhole operations which require pressure containment at the wellhead. 
     These and other objects of the invention are realized in an apparatus for axially displacing a downhole tool or tubing string in a well bore equipped with a wellhead, the downhole tool being supported by a tubing string in the well which includes a telescoping joint to permit the axial displacement of the tool, comprising: 
     a lift rod string; 
     a tool entry spool adapted to be mounted to a top of the wellhead; 
     at least one annular seal for containing well pressure mounted above the tool entry spool, the annular seal providing a fluid seal around a periphery of the lift rod string; 
     means for axially displacing the lift rod string; 
     means for selectively rotating the lift rod string; and 
     a swivel joint for enabling free rotational movement in a link rod between the means for axially displacing the lift rod string and the means for selectively rotating the lift rod string. 
     The apparatus in accordance with the invention includes a lift rod string which is equipped with a releasable latch tool for connecting a free end of the lift rod string to a latch point in or near a telescoping joint described in applicant&#39;s copending patent application, or connected directly to a tubing string. The lift rod string is supported on its top end by a stem which is connected to the means for selectively rotating the lift rod string. The means for selectively rotating the lift rod string is preferably a motor. A hydraulic or an electric motor or a mechanical rotational device can be used. Attached to the stem for supporting the lift rod string is a link rod that includes a swivel joint for enabling free rotational movement between the stem for supporting the lift rod string and the means for axially displacing the lift rod string. The means for axially displacing the lift rod string is preferably a hydraulic cylinder or a mechanical jack, but any other hoisting mechanism may be used. 
     In preferred embodiments of the apparatus designed for use on deep wells, the apparatus is supported and stabilized by adjustably extendible support posts designed to rest on a ground surface surrounding the wellhead. The support posts help bear the weight of heavy tubing strings and stabilize the apparatus to reduce torsional stress on the wellhead. 
     The apparatus preferably includes a tool entry spool adapted to be mounted to a top of the wellhead. The tool entry spool provides a space for accommodating a latch tool such as a spear, key, collet, slip or friction type tool, attached to the bottom end of the lift rod string. Mounted above the tool entry spool is at least one annular seal for containment of well pressure. The annular seal may be a stuffing box, but it is preferably one or more blowout preventers. Desirably, a spool which includes at least one tool window is provided above the blowout preventer. The tool window provides access to the lift rod string with gripping or locking devices useful for inhibiting axial or rotational movement while lift rod joints are being inserted or removed. Alternatively, a pair of oppositely oriented well slip assemblies such as described in U.S. Pat. No. 3,846,877 which issued on Nov. 12, 1974 to Spiri, the entire specification of which is incorporated herein by reference, can be used in place of the tool access spool to selectively inhibit axial or rotational movement of the lift rod string. 
     Each joint of the lift rod string may include axial bores which permit fluid to be circulated or pumped straight through the lift rod string, if required. For example, conditions are sometimes encountered in wells such as gas wells where hydrating frequently occurs at or near the well surface. Such hydrates can prevent entry or retrieval, or foul or seize latch tools such as spears, keys, collets, slips type or friction type tools and prevent their release or proper functioning. If the lift rod string includes axial bores to permit the circulation of hot fluid, the string can be heated to melt ice or paraffins, etc. and free up the seized component to effect the desired release. One way of circulating fluid through the lift rod string is to use aligned bores that extend through the means for axially displacing the lift rod string so that a fluid connection can be made at the top of the apparatus. If a hydraulic cylinder is used for axially displacing the lift rod string, the hydraulic cylinder is provided with a polished rod that extends through a top of the cylinder. A free end of the polished rod is equipped with threaded connectors for the attachment of fluid circulation hoses which are in turn connected to a pump and a heated reservoir. It may also be desirable to pump fluid straight through a lift rod string. This can be advantageous for clearing hydrates or paraffin buildup from a production tubing. One way of accomplishing this is by modifying the spear, collet, slip or friction type tool to let fluid flow out a bottom end of the lift rod string, or to run in the lift rod string without a tool on its bottom end so that fluid can be pumped through one or both axial bores. 
     The apparatus in accordance with the invention may also be used to axially or rotationally displace tubulars in a well bore that are not equipped with telescoping joints. If slip or spear latch tools, for example, are used, a production tubing, or the like, can be repositioned in a well without killing the well or removing the wellhead. Depending on the downhole components associated with the tubing string, it is possible and practical to remove an entire production tubing string from a well without removing the wellhead. 
     The apparatus in accordance with the invention also enables downhole operations, in particular near-surface operations which require pressure containment. Such operations include the drilling out of permanent bridge plugs, cement plugs or any other obstruction in the casing column near the surface during re-entries to a well bore. 
     Although the apparatus in accordance with the invention is versatile and robust, it may be easily disassembled for transport to another well site. It can also be transported without disassembly, permitting well bores to be readily serviced at minimal cost. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention will now be explained by way of example only, and with reference to the following drawings wherein: 
     FIG. 1 is a cross-sectional view of a first preferred embodiment of the apparatus in accordance with the invention connected to a wellhead of a well bore; 
     FIG. 2 is an elevational view of the apparatus shown in FIG. 1; 
     FIG. 3 is an elevational view of a second preferred embodiment of an apparatus in accordance with the invention; 
     FIG. 3 a  is an enlarged cross-sectional view of a connection between a stem and a lift rod joint in accordance with the invention, showing the arrangement of fluid circulation bores in each; 
     FIG. 4 is an elevational view of another preferred embodiment of the apparatus in accordance with the invention; 
     FIG. 5 is an elevational view of yet a further preferred embodiment of the invention suitable for use in shallow wells where production tubing string weights are moderate; and 
     FIG. 6 is a cross-sectional view of the apparatus shown in FIG. 1 connected to a telescoping joint described in applicant&#39;s copending patent application. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     This invention relates to an apparatus for axially displacing a downhole tool or a tubing string in a well bore equipped with a wellhead, the downhole tool being supported by the tubing string in a well to permit axial displacement of the downhole tool or tubing string. The apparatus in accordance with the invention may also be used for performing downhole operations that require pressure containment to ensure that hydrocarbons are not released to atmosphere and concessive pressure releases do not occur during such operations. 
     FIG. 1 shows a cross-sectional view of a first preferred embodiment of an apparatus in accordance with the invention, generally indicated by the reference  10 . The apparatus is mounted to a top of a wellhead generally indicated by reference  12 . Typically, the wellhead  12  includes a surface spool  14  and a master valve spool  16 , the structure of each being well known in the art. Some wellheads do not include master valves. Mounted to a top of the master valve spool  16  or an uppermost part of the wellhead is a tool entry spool  18 , which is the lowermost component of the apparatus  10 . The tool entry spool  18  accommodates a latch tool  96  (see FIG. 6) for connecting a lift rod string  20  to a latch point  94  of a telescoping joint  90  or directly to a downhole tubular when the lift rod string  20  is run into the well bore, as well as when it is removed from the well bore, as will be explained in detail with reference to FIG.  6 . Mounted to a top flange  19  of the tool entry spool  18  is an annular seal for containing well pressure, such as a blowout preventer  22 . As will be understood by those skilled in the art, other annular seals for containing well pressure can be adapted for use with the apparatus  10 . For example, certain stuffing box structures or multiple ram type or annular preventers can be adapted for such use. The blowout preventer  22  is preferred, however, because of the ease of use and the security of the seal it provides. Preferably, the apparatus includes two blowout preventers  22  connected in sequence in order to increase the safety of the apparatus and to provide extra room between the master valve spool  16  and the uppermost blowout preventer  22  to accommodate latch tools  96  of different lengths. With two or more blowout preventers safety is increased because the preventers can be opened and closed in sequence at each lift rod joint connector in the lift rod string to prevent tears in sealing surfaces which can result from forcing rough surfaces at the connectors through a closed preventer. For this reason, it is preferable that the adjacent preventers be spaced about 10-13 cm (4″-5″) apart to accommodate a lift rod joint connector between them. 
     Mounted to a top of the uppermost blowout preventer  22  is a tool access spool  24  having at least one tool window  26  or an integral locking mechanism (not illustrated). The tool window  26  permits gripping or locking devices to be inserted for engaging the lift rod string. As will be explained below in some detail, the tool window  26  permits the lift rod string  20  to be gripped to permit joints to be added to, or removed from, the lift rod string  20 . It also permits the lift rod string  20  to be locked against axial movement when joints are being added to, or removed from, the lift rod string  20 . For example, the weight of the tubing string  94  can be supported at the tool window  26  in low pressure wells while lift rod string joints are being added, or removed. If wells with exceptionally high pressure are being worked, a lock inserted through the tool window  26  prevents the lift rod string  20  from being forced up out of the well bore while joints are being added to, or removed from, the lift rod string. 
     The tool access spool can be replaced by a pair of oppositely oriented well slip assemblies described in U.S. Pat. No. 3,846,877 to Spiri. Preferably, two oppositely oriented slip tools are mounted to a top of the uppermost blowout preventer  22 . They may be operated separately, or in unison, to control axial or rotational movement of the lift rod string  20 , as required by well and/or operating conditions. 
     Bolted to the top flange  25  of the tool access spool  24  is a lower support plate  28  which is preferably supported by a plurality of support posts  30 a to reduce compressive and torsional forces on the wellhead which may be induced by the lifting and manipulation of heavy production tubing strings. The number of support posts  30   a  is a matter of design choice. Preferably at least three are provided and four support posts  30   a  are considered more appropriate for supporting the lower support plate  28 . Located above the lower support plate  28  is an upper support plate  32  which is supported by support posts  30   b . The support posts  30   b  may be integral extensions of support posts  30   a  or may be separate posts which threadably engage threaded bores in the lower support plate  28 . For the sake of rigidity and optimal support, it is preferable that the support posts  30   a  and  30   b  be integral and that the support posts  30   a,b  pass through bores in the lower support plate  28 . The support posts  30   a,b  may be secured to the lower support plate  28  in any one of several ways well known in the art, such as pins, wedges, set screws or the like. 
     Reciprocally moveable between the lower support plate  28  and the upper support plate  32  is a travelling support plate  34 . The travelling support plate  34  includes bores  37  which receive the upper support posts  30   b  with adequate clearance to permit the travelling support plate  34  to move reciprocally between the upper support plate  32  and the lower support plate  28  without undue resistance. The support posts  30   b  stabilize the travelling support plate  34  and inhibit it from rotational movement when a motor  36  is operated to rotate the lift rod string  20 . Affixed to the travelling support plate  34  is the motor  36  for selectively rotating the lift rod string  20 . The stator  38  of the motor  36  is mounted to the travelling support plate  34  and the rotor  40  is attached to a link rod  42 . The link rod  42  connects the lift rod string  20  with a piston rod  44  of a hydraulic cylinder  46 , which provides the motive of force for axially displacing the lift rod string  20  and the tubing string  94  to which it is attached, as will be explained below in more detail with reference to FIG.  6 . The motor  36  may be a hydraulic motor or an electric motor, for example. A hydraulic motor such as the Bowen PS-60 Power Sub available from Bowen Tools, Inc., a division of IRI International Corporation, is suitable for most applications. An electric motor with equivalent torque can also be used. 
     Interconnecting the link rod  42  and the piston rod  44  is a swivel joint  48  which permits free rotation of the link rod  42  with respect to the piston rod  44  to permit the lift rod string  20  to be selectively rotated without causing damage or wear in the hydraulic cylinder  46 . The hydraulic cylinder  46  is mounted to a top surface  56  of the upper support plate  32  by one or more mounting brackets  50  in a manner well understood in the art. 
     FIG. 2 shows an elevational view of the apparatus  10  shown in FIG.  1 . As described above, four supports posts  30   a,b  preferably support the lower support plate  28 , the upper support plate  32  and stabilize the travelling support plate  34 . In plan view, the respective support plates  28 ,  32  and  34  may be square, circular, hexagonal or any other convenient shape. The travelling support plate  34  is shown in a position in which the piston rod  44  is nearing an end of its stroke. As described above, the travelling support plate  34  freely reciprocates between the lower support plate  28  and the upper support plate  32  with the extension and retraction of the piston rod  44 . The only other component of the apparatus shown in FIG. 2 which was not described above is a valve  52  preferably provided on the tool entry spool  18 . The valve  52  permits the release of well pressure after the lift rod string  20  has been withdrawn from a well and the master valve  16  has been closed but before the BOPs  22  are opened. Each BOP  22  also includes one or more of bleed off or equalization valves  54 , which are well known in the art. The operation of the apparatus shown in FIG. 2 will be described below with reference to FIG.  6 . 
     FIG. 3 shows an elevational view of another preferred embodiment of the apparatus in accordance with the invention. The apparatus shown in FIG. 3 is similar to that shown in FIGS. 1 and 2 with the exception that the travelling support plate  34  is eliminated and the stator  38  of the motor  36  is mounted to a top surface  56  of the upper support plate  32 . As shown in dotted lines, the upper support plate includes a guide roller assembly  58  through which a splined link rod  60  extends. The splined link rod meshes with a splined hub (not illustrated) of the rotor  40  (see FIG. 1) of the motor  36 . The splined link rod  60  reciprocates through the splined hub to permit the lift rod string  20  to be axially displaced. A swivel joint  48  connects the piston rod  44  to the splined link rod  60  as described above with reference to FIG.  1 . The mounting brackets  50  which support the hydraulic cylinder  46  are elongated to support the hydraulic cylinder about the length of its stroke above the upper support plate  32 . 
     The embodiment shown in FIG. 3 also illustrates a further feature of the invention which may be implemented in the embodiments shown in FIGS. 1,  4  or  5  as well. In the embodiment shown in FIG. 3, a polished rod  62  extends through a top end of the hydraulic cylinder  46 . The polished rod  62  is attached to the piston of the hydraulic cylinder  46  and reciprocates with the piston through seals in a top wall of the hydraulic cylinder  46  in a manner well known in the art. A top end of the polished rod  62  includes connectors  64  to which fluid circulation hoses may be attached. The fluid circulation hoses permit fluids to be circulated through axial bores in the polish rod  62 , the piston of the hydraulic cylinder  46 , the cylinder rod  44 , the swivel joint  48 , the splined link rod  60  and each joint of the lift rod string  20 . The fluid circulation bores are useful in certain instances where it is advantageous to circulate fluid through the lift rod string  20 . For example, in certain gas wells it is not unusual to have hydrate conditions near the top of the well bore in which ice accumulates on tools and connections. In oil wells, paraffins accumulate on tools and connectors. Under either of these conditions, it is possible for a latch tool  96  (FIG. 6) such as a spear, key, collet, friction or slip type connector to freeze or become clogged with hydrates or paraffins. If that happens, it may not be possible to release the latch tool  96  or move the lift rod string  20  unless the latch tool  96  can be heated to melt accumulated hydrate or paraffin deposits. It is therefore advantageous to circulate heated fluid such as heated oil through the lift rod string  20  when this occurs. 
     FIG. 3 a  shows an enlarged cross-sectional view of the connection between the lift rod string  20  and the splined link rod  60 . Joints in lift rod string  20  have similar connectors. A fluid circulation bore  66  is an axial bore which extends through each lift rod string joint  20  and the splined link rod  60  so that the ends of the bores are connected when the two are securely screwed together. A recirculation bore  68  is radially offset from the fluid circulation bore  66 . Since the recirculation bore  68  in one component may not align with the recirculation bore  68  in the other component when two joints are connected, a recirculation chamber  70  is machined in the bottom of each female component of the joint so that a fluid recirculation path is enabled even though the two recirculation bores  68  are not aligned when the components are securely connected. The swivel joint  48  is constructed in the same manner to permit the swivel joint to freely turn while ensuring that fluid circulation is not inhibited. 
     FIG. 3 a  also shows a further feature of the invention in which each joint of the lift rod string  20  includes opposed peripheral areas of reduced diameter to provide parallel tool gripping surfaces  72  that are adapted to be engaged by a clamping or securing device to permit joints to be added to, or removed from, the lift rod string  20  and to permit the lift rod string  20  to be secured to prevent axial movement when joints are added or removed. Clamping or securing devices used for this purpose are well known in the art and may include wrenches or hydraulic or mechanical clamps, all of which are commercially available. 
     FIG. 4 shows yet another embodiment of the apparatus  10  in accordance with the invention. The embodiment shown in FIG. 4 is identical to the embodiment shown in FIG. 1 with the exception that the hydraulic cylinder  46  is replaced with a mechanical jack  74  that has an axially displaceable jackpost  76 , such as a ball jack which is well known in the art. A lower end of the jackpost  76  is affixed to the swivel joint  48  which is in turn affixed to the link rod  42 . Reciprocal movement of the jackpost  76  is effected by rotation of a drive shaft  78 . The drive shaft  78  may be rotated by a hydraulic motor, an electric motor or the like, as appropriate. A mechanical jack such as the ball jack  74  is capable of securely moving significant loads and provides a safe mechanism for shifting the position of very long tubing strings in deep wells. 
     FIG. 5 shows another preferred embodiment of the invention principally intended for use on shallow wells where production tubing strings are of a weight that is safely supported directly by the wellhead. In this embodiment, support posts  80  are bolted directly to a top flange  25  of the tool access spool  24 . The number of support posts  80  is a matter of design choice but at least three are required and preferably at least four are used. The top end of the support posts  80  are bolted directly to a bottom flange  82  of a hydraulic cylinder  46  and supports the hydraulic cylinder  46  above the tool access spool  24 . A smaller version of the travelling support plate indicated by reference  84  reciprocates with movement of the piston rod  44  as explained above with reference to FIG.  1 . The stator  38  of the motor  36  is mounted to the travelling support plate  84 , as also explained with reference to FIG.  1 . In operation, the apparatus shown in FIG. 5 functions the same as the apparatus described above with reference to FIGS. 1-4. The apparatus is somewhat lighter and easier to handle, which makes it ideal for use in areas where there are an abundance of shallow wells that require service. 
     FIG. 6 is a cross-sectional view of the apparatus  10  described above with reference to FIGS. 1 and 2 mounted to a wellhead in which a production tubing  94  produces oil from a formation B that bears gas, oil and water. As is understood by those skilled in the art, such wells may require frequent service in order to maintain oil production as the gas/oil/water interface moves upwardly or downwardly with the production of hydrocarbons from the well. In certain areas, the gas/oil/water interface may move upwards several feet annually. In order to produce principally a selected fluid from such formations, the applicant has invented an apparatus generally indicated by reference  86  for isolating fluid zones in a casing  88  of a well bore. Periodically, the apparatus  86  must be repositioned within the casing  88 . This is accomplished using one of the preferred embodiments of the apparatus  10  in accordance with the invention. In an initial step in the process, the apparatus  10  is attached to the top of the wellhead  12  as described above with reference to FIGS. 1-5. If the well is a deep well, the apparatus is preferably one of those described with reference to FIGS. 1-4. If the well is a shallow well, any one of the apparatus shown in FIGS. 1-5 may be used. 
     After the apparatus  10  is bolted to a top of the wellhead  12 , the adjustable support pads  31  located respectively at the base of each support leg  30   a  are adjusted so that the apparatus  10  is level and the support legs  30   a  will share the load to be placed on the apparatus  10  when the lift rod string  20  supports the tubing string  94 . Once the apparatus  10  is properly set up, the lift rod string  20  is assembled using a plurality of joints which are interconnected. Attached to a free end of the first joint is a latch tool  96  for releasably connecting to a latch point  92  of a telescoping joint  90  described in applicant&#39;s copending patent application. The telescoping joint  90  permits the tubing string  94  and the apparatus for isolating fluid zones  86  to be axially displaced in the casing  88 . The latch point  92  is engaged by any one of a number of well known latch tools  96  which may include quick-disconnect threads, spears, keys, collets, friction or slip type tools, releasable packers or rotary taper taps, each of which is commercially available from several manufacturers and well known in the art. The latch tool  96  is shown in an engaged position with the latch point  92  at the bottom of the telescoping joint  90 . After the lift rod string  20  has been extended down through the telescoping joint  90  and a connection with the latch point  92  has been effected, the downhole tool  86  may be raised or lowered within the range of the telescoping joint  90 . This permits a variety of downhole tool manipulations to accomplish tasks such as those described in applicant&#39;s copending patent application without setting up a derrick or bringing in a crane, killing the well or performing many of the other steps required using prior art methods. 
     To run the lift rod string  20  into the well, a latch tool  96  is attached to a first joint of the lift rod string  20  and the joint is connected to the stem  41  at the end of the link rod  42 . The hydraulic cylinder is extended until the tool grip surfaces  72  are in the tool window  26  of the tool access spool  24 . The tool grip surfaces  72  are then engaged using a locking tool inserted through the tool window  26 , the motor  36  is operated to release the stem  41  from the first joint of the lift rod string  20 , the piston of the hydraulic cylinder is stroked back to the top of the cylinder  46  and another lift rod joint is added between the first joint and the stem  41 . The hydraulic motor  36  is operated to make the connection between the first and second joints of the lift rod string  20  and the stem  41 . The locking tool is then released from its grip on the tool grip surfaces  72  of the lift rod string  20 , the hydraulic cylinder  46  is stroked downwards until the tool grip surfaces  72  of the second joint appear in the tool window  26 , and the process is repeated until the latch tool  96  engages the latch point  92  of the telescoping joint  90 . After engagement of the latch tool  96  with the latch point  92 , the lift rod string  20  is tensioned to remove weight from compression anchors, hangers or packers  98  which support the tubing string  94  in the casing  88 , and the motor  36  is operated to rotate the tubing string  94  by rotation of the lift rod string  20  to release the anchors, hangers or packers  98 . A production packer  100  is released in the same way. Once the anchors, hangers or packers  98  and the production packer  100  are released, the tubing string may be raised or lowered in the casing  88  by adding or removing joints of the lift rod string  20  as described above. When the downhole tool  86  has been repositioned to a new location in the well bore, the motor  36  is operated to reset the anchors, hangers or packers  98  and the production packer  100 . 
     After the anchors, hangers or packers  98  and the production packer  100  are reset, the latch tool  96  may be released from the latch point  92  using methods well known in the art. For example, if the latch tool  96  is a releasing spear, release is accomplished using a “bump down” to break the attachment. The releasing spear is then rotated two or three times to the right. The rotation moves a releasing spear mandrel up through a grapple of the releasing spear, forcing the grapple against a release ring and putting the spear in the released position. A straight upward pull will then generally free the spear, however, it is recommended that the spear be rotated slowly to the right when coming out. The motor  36  is operated to accomplish the rotation. The lift rod string  20  is then disassembled in reverse order of the process described above for adding joints to the lift rod string  20 . After the latch tool  96  is withdrawn above the wellhead  12 , the master valve in master valve spool  16  (see FIGS. 1-4) is closed and well pressure is bled off through the release valve  52  in the tool entry spool  18 . The BOPs  22  are fully opened after the well pressure is bled off through the release valve  52 , the latch tool  96  is stroked up through the BOPs and the last joint of the lift rod string  20  is removed. The apparatus  10  may then be disconnected from the top of the wellhead  12  and the well may be put back into production. 
     As will be understood by persons skilled in the art, the apparatus in accordance with the invention may be used to displace tubulars in a well bore that are not equipped with a telescoping joint. Spears, friction or slip type tools may be used as latch tools to grip downhole tubulars for displacing the tubulars to add or remove joints, as required. Because of the structure of the apparatus in accordance with the invention, this can be accomplished while well pressure is contained, as is well understood in the art. 
     The apparatus in accordance with the invention can also be used for downhole operations which require pressure containment. Such operations include the drilling out of permanent bridge plugs, cement plugs or any other obstruction in the casing. Normally, such operations are required when abandoned well bores must be re-entered. Consequently, the permanent bridge plugs, cement plugs or other obstruction in the casing are generally near the surface. In order to re-enter an abandoned well, the apparatus  10  in accordance with the invention is connected to a wellhead of the abandoned well bore. If the well bore is not equipped with a wellhead, a wellhead is installed before re-entry operations are begun. 
     After the apparatus is set up, a hydraulically driven bit is connected to the bottom of the tubular which is ran down through the apparatus and fluids are pumped through the tubular to operate the bit while the BOPs  22  contain any potential pressure release from the re-entered well bore. Consequently, the removal of permanent bridge plugs, cement plugs, or any other obstruction in the casing can be safely and economically performed without danger of release of concessive pressures or hydrocarbons from the re-entered well bore. 
     Although only a few processes for the relocation of a downhole tool has been described, it will be understood by those skilled in the art that the apparatus in accordance with the invention can be used for any of the processes described in applicant&#39;s copending application as well as processes that have yet to be discovered. For example, it can also be used to accomplish such tasks as setting plugs, packers or subsurface safety control valves in a production tubing string using the lift rod string  20  for running those components into the tubing string. As will be understood by those skilled in the art, there is no practical limit to the length of a lift rod string  20 , so even deep well operations can be accomplished, if required. The light weight and versatility of the apparatus make it ideal for many operations now accomplished using much heavier rigs which are more expensive to construct and maintain. 
     Changes and modifications to the embodiments described above will no doubt become apparent to those skilled in the art. The scope of this invention is therefore intended to be limited solely by the scope of the appended claims.

Summary:
An apparatus for axially displacing a downhole tool or a tubular in a well bore equipped with a wellhead is described. The apparatus includes a lifting mechanism such as an hydraulic cylinder or a mechanical jack that is connected to a lift rod string. The lift rod string includes a latch for engaging the tubular or the downhole tool. The apparatus further preferably includes a motor for rotating the lift rod string to permit rotationally releasable downhole equipment to be released by rotational movement of the lift rod string. The apparatus is also useful for removing obstructions in a casing of the well bore, and for removing soluble solids from a tubular in the well bore. The advantage is a simple, light weight, lifting apparatus that is versatile, yet inexpensively manufactured and readily transported from one wellhead to another.