Patent Publication Number: US-6712147-B2

Title: Spool for pressure containment used in rigless well completion, re-completion, servicing or workover

Description:
FIELD OF THE INVENTION 
     The present invention relates in general to methods and apparatus for well completion, re-completion, servicing or workover, and in particular to methods and apparatus for well completion, re-completion, servicing or workover without the assistance of a service rig. 
     BACKGROUND OF THE INVENTION 
     Subterranean wells that are drilled to produce oil or gas must be prepared for production and reworked or serviced from time to time. Wells may require reworking or service for a number of reasons. 
     The preparation of subterranean wells for the production of oil and gas is a complex process which requires specialized equipment that is expensive to purchase, operate and maintain. Because many wells are now drilled in marginal bearing formations, the wells may require fracturing or some other form of stimulation treatment before production becomes economical. The preparation of a new well for production is called well completion. Well completion generally involves wellhead installation, casing perforation, production tubing installation, etc. If the well is in a marginal production zone, the well may require stimulation after casing perforation. Traditionally, after a well was stimulated, it was “killed” by pumping in overbearing fluids such as drilling mud to permit a wellhead to be put on the casing. This practice is losing favor, however, as it has been observed that killing a well may reverse much of the benefit gained by the stimulation process. 
     It is also common practice now to re-complete hydrocarbon wells to extend production. Hydrocarbon wells are re-completed using drilling and/or production stimulation techniques well known in the art. Re-completion generally requires the same tools and equipment required for well completion. 
     Well workover generally entails well treatments to stimulate hydrocarbon production in wells in which production has dropped below an economically viable level. Such treatments may include high pressure fracturing and/or acidizing. During well stimulation it is common knowledge that it is preferable to introduce stimulation fluids into the well at the highest possible transfer rate. Consequently, it is now common practice to remove the wellhead and pump stimulation fluids through the blowout preventers and into the casing. In order to protect the blowout preventers from washout, blowout preventer protectors have been invented, as described, for example, in Applicant&#39;s U.S. Pat. No. 5,819,851 which issued on Oct. 13, 1998, the specification of which is incorporated herein by reference. 
     Generally, when a well completion, re-completion or workover is required a service rig is brought in and set up to remove the wellhead components, shift or remove production tubing, etc. Such rigs have a derrick or mast that supports pulleys or block and tackle arrangements operable to pull the wellhead from the well, shift the production tubing string or remove it from the well bore, run a production tubing string or other tools into the well bore, unseat and reseat the packers and/or anchors in the well bore, etc. 
     Although rigs are very useful and adapted to perform any job associated with manipulating well components during a well completion, re-completion, or workover, they are complex assemblies of equipment that are expensive to construct and maintain. Besides, they generally require a crew of four, so they are expensive to operate. Rigs are also usually only intermittently during a well completion, re-completion, servicing or workover operation. Consequently, there is normally considerable idle time on such rigs. This is uneconomical and contributes to the cost of production. 
     Wells may require service to replace worn or faulty valves, replace or renew seals, to remove a flange from the wellhead, or insert a new flange into the wellhead. Many of these operations are relatively simple and do not require much time. It is therefore uneconomical to bring in and set up a service rig to perform the well service operation. 
     There is therefore a need for a method and an apparatus that is adapted to provide the functionality required for most well completion, re-completion, servicing and workover jobs, without the requirement of a service rig. 
     SUMMARY OF THE INVENTION 
     It is therefore an object of the invention to provide an apparatus that is adapted to perform a variety of operations associated with subterranean well completion, re-completion, servicing or workover without the use of a service rig. 
     It is another object of the invention to provide a wellhead spool for pressure containment that may be used for rigless completion, re-completion, servicing or workover a subterranean well. 
     It is a further object of the invention to provide methods for rigless completion, re-completion, servicing or workover of a subterranean well. 
     The invention therefore provides an apparatus that includes a spool for pressure containment that can be mounted to a tubing head spool to permit a well to be completed, re-completed, serviced or worked over without the use of a service rig. The spool supports prime movers, such as hydraulic cylinders, ball jacks or screw jacks, used to insert tubulars, tools or wellhead components into or remove them from the well bore. The spool may be a blowout preventer (BOP) or a high pressure valve. The prime movers may be supported in bores that extend through a body of the spool, or by brackets welded to sidewalls of the spool. 
     The apparatus in accordance with the invention permits most well completion, re-completion, service and workover operations to be performed without the use of a service rig. Considerable savings are therefore realized. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Having thus generally described the nature of the present invention, reference will now be made to the accompanying drawings, showing by way of illustration the preferred embodiments thereof, in which: 
     FIG. 1 is a side elevational view, partially in cross-section, of a spool for pressure containment in accordance with an embodiment of the invention; 
     FIG. 2 is a top plan view of the spool shown in FIG. 1; 
     FIG. 3 is a side elevational view, partially in cross-section of a spool for pressure containment in accordance with another embodiment of the invention; 
     FIGS. 4 a  through  4   d  illustrate alternative arrangements of securing prime movers to the spool shown in FIG. 1, or the spool shown in FIG. 2, in which FIGS. 4 a  and  4   b  are respectively partial side elevational and partial top plan views of a prime mover with its securing mechanism incorporated into spools, and FIGS. 4 c  and  4   d  are, respectively, a top plan and a cross-sectional view of a clamp used for securing the prime mover; 
     FIG. 4 e  is a partial cross-sectional view of the prime mover, showing an alternative configuration thereof; 
     FIG. 5 is a block diagram illustrating hydraulic circuits for supplying pressurized hydraulic fluid to hydraulic cylinders, when the hydraulic cylinders are used as prime movers; 
     FIG. 6 is a partial cross-sectional view of FIG. 1 or FIG. 2, according to a further embodiment of the present invention, showing a Bowen union mounted to a top of the spools and protected by a protective bonnet; 
     FIG. 7 is a top plan view of the protective bonnet shown in FIG. 6; 
     FIG. 8 is a partial side elevational view of the spool shown in FIG. 1 or the spool shown in FIG. 2, further including a hydraulic crane mounted thereon in accordance with a further embodiment of the invention; 
     FIG. 9 is a side view of the hydraulic crane shown in FIG. 8; 
     FIG. 10 a  is a cross-sectional view of a wellhead equipped with a spool in accordance with one embodiment of the invention, illustrating the insertion of a mandrel of a blowout preventer protector with a sealing assembly for pack-off in a casing of a well to be stimulated during a well workover procedure; 
     FIG. 10 b  is a top plan view of a work platform used with the spool shown in FIG. 10 a;    
     FIG. 10 c  is a cross-sectional view of the work platform shown in FIG. 10 b;    
     FIG. 10 d  is a partial cross-sectional view of an annular adapter for use with the Bowen union shown in FIG. 10 a , illustrating the details thereof; 
     FIG. 11 is a cross-sectional view of a wellhead equipped with an embodiment of the invention, for inserting a mandrel of a blowout preventer protector having an annular sealing body for sealing engagement with a bit guide that protects a top of a casing of the well, while supporting a tubing string in the well bore; 
     FIG. 12 is a cross-sectional view of a wellhead equipped with an embodiment of the invention, for inserting a tubing hanger with the tubing string into a tubing head spool in a live well; 
     FIG. 13 is a cross-sectional view of a wellhead equipped with an embodiment of the invention for running a coil tubing string into and out of the well after a blowout preventer protector is inserted through the wellhead; and 
     FIGS. 14 a  and  14   b  are partial cross-sectional views of configurations in accordance with the invention for connecting a prime mover to a base plate used to set tools on a live well. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The invention provides an apparatus and methods for completing, re-completing or performing a workover on a well bore without using a service rig. The apparatus and methods can be used in completing any well in which coil tubing is to be used for production. The method and apparatus can also be used for re-working substantially any well in which tubing is already installed. The apparatus is also useful during well re-completion or servicing procedures, and permits tool insertion and other operations to be performed without the expense of a service rig. 
     FIG. 1 shows an apparatus, partially in a cross-sectional view in accordance with one embodiment of the present invention, generally indicated by reference numeral  20 . The apparatus  20  includes a spool for pressure containment  22  having at least one flow control mechanism  24 ,  26 . In this example, the spool for pressure containment is a blowout preventer (BOP)  22  having opposed tubing rams  24  used to close an annulus of the well bore (not shown) around a production tubing (not shown) of a known diameter, and a set of opposed blind rams  26 , which are used to completely seal the well bore. The construction of the tubing rams and blind rams of a BOP is well known in the art and will not be further described. 
     A pair of bi-directional prime movers  28  are secured to the BOP  22  at opposed sides thereof. The prime movers  28  may be screw jacks, ball jacks or, as illustrated in FIG. 1, hydraulic cylinders. The prime movers  28  are substantially vertically oriented and are received or secured by mechanisms integrated with the BOP  22 . In this embodiment of the invention, the BOP  22  includes a pair of bores  30  that are oriented in a substantially parallel relationship to a central bore  32  of the BOP  22 . The prime movers  28  are received in the respective bores  30  and extend therethrough. In order to provide a sufficient length of stroke, each prime mover  28  is longer than the bore  30  so that a lower end of the prime mover  28  projects downwardly from a bottom  34  of the BOP  22  when the top end of the prime mover  28  is secured to a top  36  of the BOP  22 . As will be understood by persons skilled in the art, the prime movers  28  can also be arranged to extend above, rather than below, the BOP  22 . 
     A cylinder cap  37  having a larger diameter than the prime mover  28 , serves as a stop to restrain downward movement of the prime mover  28  relative to the BOP  22 . A lock ring  38  secured to the prime mover  28  by set screws  40  restrains the prime mover  28  from upward movement relative to the BOP  22 . The set screws  40  engage an annular groove  42  formed around the prime mover  28  just below the bottom  34  of the BOP  22 . Hydraulic connectors  44  are provided at opposite ends of the prime mover  28  to permit hydraulic fluid to be injected into or withdrawn from either end of the prime mover  28 , in order to achieve a double acting functionality. The piston ram  46  of each prime mover  28  is provided with a bore  48  at its top end for connecting a workload or an extension rod, as will be further described below. 
     The BOP  22  is provided with a plurality of threaded bores  50  in the bottom flange  34  and top flange  36  to permit the BOP  22  to be secured to other spools of a wellhead. 
     FIG. 2 shows a top plan view of the BOP  22  shown in FIG. 1, without the prime movers  28 . Four cylindrical bores  52  are machined into the top  36  of the BOP  22 , adjacent to a periphery thereof. The bores  52  receive and support support beams for a hydraulic crane, which will be further described with reference to FIGS. 8 and 9. Set screws  54  are used to lock the support beams in the bores  52 . 
     FIG. 3 shows an apparatus  20 ′ in accordance with another embodiment of the invention. The spool for pressure containment  20 ′ is a high pressure valve  22 ′ having at least one flow control mechanism  24 ′, which is a high pressure valve used for containment of pressurized fluid within a well bore, and is well known in the art. As described above with reference to FIG. 1, high pressure valve  22 ′ includes a pair of parallel bores. The bores in this example support prime movers that are screw or ball jacks  27 , which include a power transfer case  39  having a drive shaft  41  with a connector end  43  adapted to be connected to a hydraulic motor (not shown), or some other drive power source. The power transfer case translates rotational movement of the drive shaft  41  into vertical movement of a threaded shaft  45 , in a manner well known in the art. The top end of the threaded shaft  45  includes a bore  47  for connection of an extension or other tool, as will be explained below in more detail. Other structural features of the apparatus  20 ′ are similar to those described with reference to the apparatus  20  shown in FIG.  1 . The top  36  of the high pressure valve  22 ′ has a layout similar to that of the BOP  22  described above with reference to FIG.  2 . 
     FIGS. 4 a  and  4   b  show an alternative configuration for securing the prime movers&#39; hydraulic cylinders  28  or jacks  27  to the BOP  22 . Instead of the bores  30  through the BOP  22  shown in FIG. 1, the BOP  22 , partially shown in FIGS. 4 a  and  4   b , includes a pair of brackets  56  at opposite sides of the top  36  thereof and a pair of brackets  58  at the opposite sides of the bottom  34 . The pair of brackets  56  are spaced apart slightly more than an external diameter of the prime movers  27 ,  28  and a groove  60  is formed in a top flange  62  of the BOP  22 . Similarly, the pair of brackets  58  are spaced apart slightly more than the external diameter of the prime mover  27 ,  28  and a groove  64  is formed in a bottom flange  66  between the brackets  58 . Thus, one of the prime movers  27 ,  28  is received in the respective grooves  60 ,  64  and between the brackets  56 ,  58 , and is locked in position by bolts  68 . 
     FIGS. 4 c  and  4   c  show an alternative to the lock ring  38 , which can be replaced with a clamp  70 . The clamp  70  is made in two parts that form a hollow cylinder with a radially inwardly projecting annular shoulder  72  and radially outwardly protruding ears  74  which can be secured together by lock screws  76 . The two parts of the clamp  70  are placed around the prime mover  27 ,  28 , similarly to the lock ring  38  shown in FIG. 1, while inserting the radially inwardly projecting annular shoulder  72  of the clamp  70  into the annular groove  42  of the prime mover  28 . The two halves of the clamp  70  are then secured together by lock screws  76 , which are inserted through bores in the lock ears  74 . 
     In a further embodiment of the invention, the prime mover  28  is secured to the BOP  22  by a bottom end cap  78 , as shown in FIG. 4 e . The bottom end cap  78  includes an extended side wall  80  that extends upwardly over the lower section of the prime mover  28 , so that the bottom end cap  78  inhibits the prime mover  28  from upward movement relative to the BOP  22 . The locking arrangement illustrated in FIGS. 4 c ,  4   d  and  4   e  may be used in conjunction with either bores  30  shown in FIG. 1 or brackets  56 ,  58  shown in FIGS. 4 a  and  4   b . The locking mechanisms illustrated in FIGS. 4 a  through  4   e  may be used to secure prime movers to BOP  22  or the high pressure valve  22 ′. 
     FIG. 5 illustrates a hydraulic circuit for supplying pressurized fluid to actuate the prime movers  28 . The hydraulic circuit, generally indicated by reference numeral  82 , includes a motor  84  coupled to a pump  86 . The pump  86  pumps hydraulic fluid from a reservoir (not shown) into an accumulator  88 , which generally includes a bladder to ensure that the hydraulic pressure is maintained in the hydraulic circuit  82  in case the pump  86  or motor  84  fail. The pressurized hydraulic fluid from the accumulator  88  is distributed by two valves  90 , so that the prime movers  28  can be controllably actuated to extend or retract. When hydraulic fluid is introduced into one end of the prime movers  28  the exhausted hydraulic fluid drains from the other end of the prime movers  28  into the reservoir (not shown). 
     FIG. 6 illustrates the apparatus  20  shown in FIG. 1 further including a threaded connector  92 , commonly called a Bowen connector. The threaded connector  92  includes a base flange  94  and a cylindrical fitting  96 , with a central bore  98  that extends therethrough. The central bore  98  has a diameter substantially the same size as the central bore  32  of the BOP  22 . A landing bore  100  has a larger diameter than the central bore  98 . External threads  102  are provided at the top of the fitting  96 . The treaded connector  92  is mounted to the top  36  of the BOP  22  by a plurality bolts  104 , which extend through bores in the base flange  94  and are received in the threaded bores  50  in the top  36  of the BOP  22 . 
     A protective bonnet  106  is selectively placed over the threaded connector  92 . The bonnet  106  includes a cylindrical side wall  108  and a top wall  110  with a central bore  112  therethrough. As more clearly shown in FIG. 7, the bonnet  106  is assembled from two parts  114  and  116 , which are pivotally connected together on one side by a hinge pin  118  to permit the bonnet  106  to be opened and closed. A locking device  120  is provided on the opposite sides of the two parts  114 ,  116  to lock the two parts  114 ,  116  together. A pair of lifting ears  122  with bores  125  therethrough (see FIG. 6) are provided on the respective parts  114 ,  116  to permit the bonnet  106  to be lifted as required. 
     FIG. 8 illustrates the apparatus  20  shown in FIG. 1, further including a hydraulic crane  124  which is removably mounted to the top  36  of the BOP  22 . The hydraulic crane  124  is supported by four support beams  126 , a top end of each being inserted into a corresponding socket  128  of the hydraulic crane  124  and locked by set screws  130 . The bottom end of each support beam  126  is received in one of the bores  52  (see FIG. 2) in the top  36  of the BOP  22  and secured by the set screws  54 , as described above. 
     FIG. 9, which appears on sheet six of the drawings, shows the hydraulic crane  124  in more detail. The hydraulic crane  124  includes a base  132  which can be a plate, a cylindrical box structure, a beam, or the like. A bracket member  134  is rotatably coupled to the base  132 . The bracket member  134  includes a downwardly extending arm  136 . A lower end of the arm  136  is connected to a telescoping boom  138  by a pivot pin  140 . A hydraulic cylinder  142  interconnects a base section  144  of the telescoping boom  138  and the bracket member  134 , so that the telescoping boom  138  can be pivoted by the hydraulic cylinder  142  about the pivot pin  140  from a substantially horizontal position to a substantially vertical position, as shown by the arrow  146 . An extension  148  of the telescoping boom  138  can be extended or retracted by another hydraulic cylinder, or as shown in FIG. 9, by pressurized hydraulic fluid introduced into an inner chamber of the base section  144 , which exerts hydraulic pressure on the piston  150  of the extension  148 . A cable  152  is wound around a drum  154  which is rotatably mounted to the arm  136  and is driven by a hydraulic motor (not shown). The cable  152  extends along the length of the telescoping boom  138  and around a pulley  156  which is rotatably mounted to a free end of the extension section  148 , and is connected at its free end to a lifting hook  158 , for example. The bracket member  134  with the telescoping boom  138  is rotatable about a vertical axis relative to the base  132  in a range of about 360° when the telescoping boom  138  is in a retracted or a downwardly pivoted position. When the telescoping boom  138  is extended and horizontally oriented as shown in FIG. 9, the rotation of the bracket member  134  with the telescoping boom  138  is limited to a space between two adjacent supporting beams  126  shown in FIG. 8. A hydraulic motor  159  is preferably provided on the top of the base  132  to rotate the bracket member  134 . 
     The prime movers  28  shown in FIG. 1 are used to support a heavy workload, such as the weight of an entire tubing string suspended in a well bore, or the high fluid pressure acting on tools to be inserted into the well bore. The hydraulic crane, however, is used for different purposes and can be used in an area surrounding the wellhead, but can only support a limited workload. For example, the hydraulic crane  124  in accordance with this embodiment has a limited lifting capacity of about three tons. During a well completion, re-completion, servicing or workover, various tools or equipment need to be hoisted to the top of the wellhead or suspended above the wellhead for assembly before the tools or equipment are connected to a tubing string and/or the prime movers  28  which then perform the lifting and inserting functions under a full workload. Conventionally, these lifting functions are performed by a service rig and/or a boom truck. With the hydraulic crane  124 , the apparatus  20  is enabled to provide all of the services required for a rigless well completion, re-completion, servicing or workover. A few examples of applications using the apparatus  20  in well completion, re-completion, servicing or workover are described below. 
     FIG. 10 a  illustrates an example of using the apparatus  20  to insert a mandrel  160  of a BOP protector into a wellhead  162 . The mandrel  160  has a seal assembly  164  mounted to its bottom end for pack-off inside a casing  166  of the well to be stimulated. Mounted to the top of the wellhead  162  is the BOP  22  with the two prime movers  27 ,  28 . The installation of the BOP  22  is accomplished by a boom truck (not illustrated) for example, used to hoist the BOP  22  from a transportation deck (not shown). The deck, preferably includes bores for receiving the two prime movers  27 ,  28  that project downwardly from the BOP  22 , so that they do not have to be removed from the BOP  22  for transportation. The hydraulic crane  124 , as shown in FIG. 8 is then mounted to the top of the BOP  22 . In order to more clearly illustrate other parts of the apparatus  20 , the hydraulic crane  124  is not shown in FIG. 10 a . After the BOP  22  with prime movers  27 ,  28  and the hydraulic crane  124  are mounted to the wellhead  162 , the boom truck is no longer required. If the boom truck is kept on site, the hydraulic crane  124  is not required. 
     The threaded connector  92  is hoisted by the hydraulic crane  124  (see FIG.  8 ), for example, to the top of the BOP  22  and is secured thereto if the threaded connector  92  has not been previously connected to the BOP  22 . The mandrel  160  with its sealing assembly  164  is equipped with an annular adapter  168 . The annular adapter  168 , more clearly shown in FIG. 10 d  includes a cylindrical side wall  170  and a bottom wall  172  with a central bore  174 , which has the same diameter as the central bore  98  of the threaded connector  92  (see FIG.  6 ). An external shoulder  176  protrudes from the cylindrical side wall  170 . Packing rings  178  constructed of brass, rubber and fabric are disposed within the cylindrical side wall  170  and are secured between the bottom wall  172  and a gland nut  180 , which has external threads  182  that engage corresponding internal threads  184  in the cylindrical side wall  170 . The packing rings  178  and the gland nut  180  define a vertical passage  186  of a same diameter as a periphery of the mandrel  160 , to provide a fluid seal between the mandrel  160  and the annular adapter  168 , as shown in FIG. 10 a . The annular adapter  168  further includes two high-pressure O-rings  188  engaged in grooves around the periphery of the cylindrical side wall  170  below the external shoulder  176 . The O-rings  188  provide a fluid tight seal between the annular adapter  168  and the threaded connector  92  when the annular adapter  168  is seated within the threaded connector  92 , as shown in FIG. 10 a . A lock nut  190  engages the external shoulder  176  and includes internal threads that are threadedly engaged with the threaded connector  92  when the annular adapter  168  is seated within the threaded connector  92 . 
     The mandrel  160 , which is surrounded by the annular adapter  168  is connected at its top end to a connector  192  that includes a base plate  194 . The connection of the top end of the mandrel  160  to the connector  192  is described in detail in Applicant&#39;s issued patents. The connector  192  further includes a lock nut  196  for engagement with the external threads  198  of the annular adapter  168  (see FIG. 10 d ). 
     The combination of the mandrel  160  with the base plate  194  and the annular adapter  168  is hoisted by the hydraulic crane  124  (see FIG. 8) and is positioned above the top  36  of the BOP  22 . The combination is lowered by the hydraulic crane  124 , or a crane truck (not shown), until the seal assembly  164  of the mandrel  160  is inserted into the central bore of the threaded connector  92 , or further down into the central bore of the BOP  22  above the blind rams  26  (see FIG.  1 ), which are closed. 
     During this operation, the annular adapter  168  can be suspended on the mandrel  160  by a frictional force between the packing rings  178  and the periphery of the mandrel  160 , or can be suspended from the lock nut  196 . When the mandrel  160  is maneuvered to this position, the annular adapter  168  is pushed down and seated within the threaded connector  92 , and is locked down using the lock nut  190 . FIG. 10 a  specifically illustrates this stage. 
     A pair of extension rods  204 , which are inserted through bores  206  of the base plate  194 , are connected to the extended piston rams  46  of the prime movers  28 . A high pressure valve  200  is then connected to a top of the base plate  194 , in order to controllably close the fluid passage defined by the central bore  202  of the base plate  194 . Thus, the mandrel  160  is ready to be inserted into the wellhead  162  against well fluid pressure. The blind rams  26  of the BOP  22  (see FIG. 1) are opened and the mandrel  160  is subjected to the well fluid pressure. The pressure is preferably balanced between the mandrel  160  and the well bore before the blind rams are opened, using methods well known in the art. An upward force exerted by the well fluid pressure on the mandrel  160 , is transferred by means of the base plate  194  and the extension rods  104 , to the piston rams  46  of the prime movers  27   28 , which are hydraulically locked. The prime movers  27 ,  28  are then actuated to lower the base plate  194  and thereby insert the mandrel  160  through the packing rings  178  of the annular adapter  168  and into the wellhead  162  until the seal assembly  164  of the mandrel  160  is packed off within the casing  166 . The lock nut  196  of the connector  192  is then threadedly engaged with the annular adapter  168 . 
     The well is now ready for a well stimulation procedure, which is well known in the art and will not be further described. 
     A work platform  208  (more clearly shown in FIGS. 10 b  and  10   c ) is optionally provided so that operators have a place to stand for working over the wellhead  162 . The work platform  208  has a central aperture  209  and a plurality of openings  211  and  213 . The work platform  208  is substantially horizontally disposed at a level not lower than the top  36  of the BOP  22  (see FIG. 10 a ), and is preferably placed on the top  36  of the BOP  22 , while being supported by legs  215  which rest on the ground. The legs  215  include height adjustment mechanisms that include pressure feet  207  rotatably connected to threaded extension legs  205 . When the work platform  208  is set as shown in FIG. 10 a , the central opening  209  receives the threaded connector  92  and the openings  211 ,  213  permit the respective piston rams  46  of the prime movers  27 ,  28  and the supporting beams  126  of the hydraulic crane  124  (see FIG. 8) to pass therethrough. 
     Another example of using the apparatus  20  in a rigless well completion, re-completion, servicing or workover is illustrated in FIG. 11. A mandrel  210  of a BOP protector having a pack-off assembly  212  at a bottom end thereof, is to be inserted through a wellhead  214  from which a tubing string is suspended. The tubing string is supported by, for example, slips  218  or some other support mechanism, at the top of the wellhead  214 . The BOP  22  of the present invention is mounted to a tubing head spool  220 . The tubing string  216  is normally supported by a tubing hanger inside the tubing head spool  220 , but the tubing hanger has been pulled out of the well using the prime movers  27 ,  28 , for example, to an extent that a length of the tubing string  216  that extends above the wellhead  214  is greater than a length of the BOP  22 . The tubing string  216  is then supported on the top of the protective bonnet  106  using slips  218 , for example, before the mandrel insertion procedure begins. The process of using prime movers  27 ,  28  to install a tubing hanger (not shown) in the tubing head spool  220  or to remove the tubing hanger from same will be further described with reference to FIG.  12 . 
     A fracturing head  222  having a central passage  224  and at least two radial passages  226 ,  228  is mounted to the top of the base plate  194 , before the combination of the mandrel  210 , the base plate  194  and the annular adapter  168  is hoisted above the wellhead  214 . Two high pressure valves  230 ,  232  are also mounted to the fracturing head  222  to close the radial passages  226 ,  228 , respectively. The mandrel  210  is aligned with the tubing string  216  and is lowered over the tubing string  216  until the top end  234  of the tubing string  216  extends above the top end of the fracturing head  222 . A tubing adapter  236  is then connected to the top end  234  of the tubing string  216 . The tubing adapter  236  is also connected to the top of the fracturing head  222 . The extension rods  204  are then connected to the piston ram  46  of the prime movers  27 ,  28  which are in the extended position, and to the base plate  194 . 
     After the base plate  194  is connected to the prime movers  27 ,  28 , the hydraulic crane  124  (see FIG. 8) can be used to hoist a high pressure valve  200  (partially shown) to the top of the tubing adapter  236 . The high pressure valve  200  is then mounted to the top of the tubing adapter  236 . 
     The tubing string  216  and the mandrel  210  are supported by the prime movers  27 ,  28  so that the slips  218  and the cylindrical protector  106  can be removed in order to clear the passage for insertion of the mandrel  210 . The prime movers  27 ,  28  are actuated to lower the tubing string  216  and the mandrel  210  onto the top of the BOP  22  so that the annular adapter  168  can be pushed down over the mandrel  210  and connected to the threaded connector  92 , similarly to the position illustrated in FIG. 10 a . The mandrel  210  is inserted into the threaded connector  92  and the BOP  22 , but remains above the BOP tubing rams  24  (FIG.  1 ). Persons skilled in the art will understand that in a high pressure well bore, the tubing string  216  is plugged and the tubing rams  24  of the BOP are closed around the tubing string  216  before the installation procedure begins. Thus, the fluids under pressure inside the well bore are not permitted to escape from the tubing string  216 , or from the annulus between the tubing string  216  and the wellhead  214 . 
     In order to open the tubing rams  24  of the BOP  22  and further insert the mandrel  210  down through the wellhead  214 , the high pressure valves  230 ,  232  and  200  must be closed and the annular adapter  168  must be sealingly connected to the threaded connector  92 . The packing rings  178  and all other seals between interfaces of the connected parts seal the central passage of the mandrel  210  against pressure leaks. The tubing rams  24  of the BOP  22  are opened after pressure is balanced across the BOP tubing rams  24 . This procedure is well known in the art. After the BOP tubing rams  24  are opened, the prime movers  27 ,  28  are operated to lower the mandrel  210  down through the BOP  22 . When the mandrel  210  is in an operating position, the bottom end of the pack-off assembly  212  is in sealing contact with a bit guide  246  connected to a top of the casing  166 . The bit guide  246  caps the casing  166  to protect the top end of the casing  166  and provides a seal between the casing  166  and the tubing head spool  220 , in a manner well known in the art. The mandrel  210  has optional and variable lengths of extension sections. Thus, the assembled mandrel  210  including the pack-off assembly  212 , is pre-adjusted in length to ensure that the lock nut  196  is able to be threadedly engaged with the annular adapter  168  when the pack-off assembly  212  is seated against the bit guide  246 . The prime movers  27 ,  28  are preferably hydraulically locked during the well stimulation procedure that follows, in order to support the weight of the tubing string  216 , including the equipment and tools attached thereto. 
     FIG. 12 illustrates a procedure for using an apparatus  20 ″, in accordance with a further embodiment of the invention, to install a tubing hanger  248  into the tubing head spool  220  or remove it from the tubing head spool  202 . It is well know in the art that the tubing hanger  248  must be set in the tubing head spool  220  in order to suspend the production tubing string  216  in the well after the production tubing string  216  has been run into the well. The tubing hanger  248  is connected to a top end of the tubing string  216 , and conventionally, special equipment is required to run the tubing hanger  248  into the tubing spool  220 . It is also well known that the tubing hanger  248  must be removed from the tubing head spool when a mandrel  210  of a BOP protector is to be inserted into the wellhead  214 , as illustrated in FIG.  11 . 
     The apparatus  20 ″ permits the tubing hanger  248  to be rapidly and safely inserted into or removed from the tubing head spool  220  of a “live” well without use of an additional BOP. The apparatus  20 ″ is similar to the apparatus  20  and  20 ′ illustrated in FIGS. 10 a  and  11 , and similar parts are indicated by the same reference numerals and are not described. However, an annular adapter  250 , described in Applicant&#39;s copending U.S. patent application Ser. No. 09/791,980 filed Feb. 23, 2001, the specification of which is incorporated herein by reference, replaces the annular adapter  168  of the apparatus  20  described above. A landing joint  252  which is rotatably suspended from and supported by a base plate  194  and is adapted to be connected to the tubing hanger  248 , replaces the connector  192  of the apparatus  20 , which connects the annular adapter  168  to the base plate  194  as illustrated in FIG. 10 a . The landing joint  252  is inserted through a passage  254  of the annular adapter  250 . The passage  254  includes a packing cavity at a top thereof, which retains a steel packing washer  256 . A high pressure packing  258 , such as a chevron packing, is retained above the steel packing washer  256 . The high pressure packing  258  closely surrounds and provides a high pressure seal around the landing joint  252  to ensure that well fluids do not escape to the atmosphere when the tubing hanger  248  is inserted into, or removed from, the tubing head spool  220 . The high pressure packing  258  is retained by a gland nut  260 . A safety nut  262  threadedly engages a spiral thread on an outer periphery of the top end of the annular adapter  250 . A top wall of the safety nut  262  projects inwardly to cover the gland nut  262  in order to ensure that the gland nut  262  is not stripped by fluid pressures exerted on the high pressure packing  258 . 
     A side wall of the annular adapter  250  includes at least two eyes or hooks  264  which receive chain or cable  266  that is connected to the hydraulic crane  124  (see FIG. 8) in order to suspend the annular adapter  250 , while the landing joint  252  is connected to a top end of the tubing hanger  248 . The annular adapter  250  is also suspended while slips  218  (see FIG. 11) that suspend the production tubing string  216  are removed to permit the tubing hanger  248  to be inserted down through the BOP  22 . 
     After the landing joint  252  is connected to a top end of the tubing hanger  248 , the extension rods  204  are connected to the piston rams  46  of the prime movers  28 , which are in their extended condition and are hydraulically locked. The slips  218  (see FIG. 11) are then removed and the weight of the production tubing string  216  is therefore transferred to the prime movers  28 . Thereafter, the landing joint  252  is lowered to move the tubing hanger  248  down into the threaded connector  92  and the BOP  22 , but support it above the closed tubing rams  24  of the BOP  22 . A retrievable plug  268  which seals a bottom of the production tubing string  216 , seals the well fluids within the well. After the slips  218  and the protective bonnet  106  (see FIG. 11) are removed and the tubing hanger  248  is lowered by the prime movers  28 , the annular adapter  250 , which is suspended from the cables  266  by the hydraulic crane  124  (see FIG.  8 ), is lowered so that the lock nut  190  of the annular adapter  250  can be threadedly engaged with the threaded connector  92 . The O-rings  188  around the annular adapter  250  seal the interface between the annular adapter  250  and the threaded connector  92 . 
     After the annular adapter  250  is mounted to the BOP  22 , pressure is equalized between an annulus of the live well and the annular adapter  250  using a bleed hose (not shown) connected between the pressure bleed ports  270  on the annular adapter  250  and corresponding ports or valves  272  of the tubing head spool  220 . After the respective valves are closed and the bleed hose is removed, the tubing rams  24  (FIG. 1) of the BOP  22  are opened in order to permit the tubing hanger  248  to be lowered into the tubing head spool  220  by operating the prime movers  28 . Once the tubing hanger  248  is seated in the tubing head spool  220 , lock bolts  274  in the tubing head spool  220  are adjusted to lock the tubing hanger  248  in the tubing head spool  220 . 
     The landing joint  252  is then rotated, preferably by a hydraulic motor  276 , to disconnect the landing joint  252  from the tubing hanger  248 , and the landing joint  252  is raised with the base plate  194  by operating the prime movers  28  until the landing joint  252  is above the blind rams  26  (FIG. 1) of the BOP  22 . After the blind rams  26  of the BOP  22  are closed, pressure is vented from the annular adapter  250  by, for example, opening the pressure bleed ports  270 . Subsequently, the annular adapter  250  is removed by the hydraulic crane  124  (see FIG.  8 ). 
     The steps required to remove the tubing hanger  248  from the tubing head spool  220  are a reverse of the above-described process. 
     As a further example of using the apparatus  20  for rigless well completion, re-completion, servicing or workover, FIG. 13 illustrates a method of installing the mandrel  160  of a BOP protector to permit the tubing string  216  to be run into or out of the well while protecting the BOP  22  on the wellhead during a well stimulation treatment. In much the same way as described above with reference to FIG. 10 a , the mandrel  160  with the annular adapter  168  and the fracturing head  222  are assembled to the base plate  194 , and a second BOP  278  is mounted to a top of a tubing adapter  280 . A blast joint  282  is threadedly engaged with the tubing adapter  280  so that the blast joint  282  is suspended from the tubing adapter  280 . The blast joint  282  has an inner diameter large enough to permit the coil tubing string  216  to be run in and out therethrough. The blast joint  282  protects the coil tubing string  216  from erosion when abrasive fluids are pumped through the radial passage  226 ,  228  in the fracturing head  222 , after the coil tubing string  216  is run into the well and a well stimulation treatment is begun. 
     When the combination of the mandrel  160 , the annular adapter  168 , the base plate  194 , the fracturing head  222 , which also includes the high pressure valves  230 ,  232 , and the second BOP  278  is assembled, the combination is hoisted by the hydraulic crane (see FIG.  8 ), to a position over the wellhead  214 . As will be well understood, the second BOP  278  may be mounted to the fracturing head  222  after it is connected to the extension rods  204 . The procedure then follows the steps described with reference to FIG. 10 a  until the mandrel  160  is inserted into the wellhead  214  in the operative position as shown in FIG. 13, and is locked into position by the lock nuts  190 ,  196 . 
     As further illustrated in FIG. 13, a coil tubing injector  284  is hoisted by a boom truck (not shown) or the hydraulic crane  124  (see FIG. 8) above the second BOP  278 , and is mounted to a top of the BOP  278 . The coil tubing string  216  can then be run into, and out of, the well without removing the apparatus  20  from the wellhead  214 . The tubing string  126  can also be moved up or down in the well while stimulation fluids are being pumped into the well. 
     The connection of the extension rods  204  to the base plate  194  is more clearly illustrated in FIGS. 14 a  and  14   b . The extension rod  204  includes a hex head  238 , which may include a threaded bore  240  in a top thereof. A connector  242  is provided at a lower end of the extension rod  204  for connection to the piston ram  46  (see FIG. 1) of a prime mover  27 ,  28 , or to another extension rod. When the apparatus  20  is used to install tools in the wellhead under well fluid pressure, which acts on the tools and offsets a weight of the tools, as illustrated in FIG. 10 a , the extension rod  204  is inserted through the bore  206  from a top of the base plate  194 , as shown in FIG. 14, to resist an upward force during insertion of the tools. If a tubing string is supported, as shown in FIG. 11, the workload is generally a downward force due to the weight of the combination of the tools and the tubing string, regardless of well fluid pressure. In such cases, the extension rod  204  is connected to the base plate  194  by an extension rod connector  244 , as shown in FIG. 14 b  and FIG. 11, so that the prime movers  28  can resist both upward and downward forces. 
     The apparatus of the present invention can be used in various other operations required for well completion, re-completion, servicing or workover without requiring a service rig. Under normal conditions, the service rig can be released as soon as drilling is complete, which represents a considerable savings for well owners and operators. 
     Although the embodiments of the invention described above show two prime movers  27 ,  28 , it should be understood by those skilled in the art that three or more can be used. Other modifications and improvements to the above-described embodiments of the present invention may become apparent to those skilled in the art. The foregoing description is intended to be exemplary rather than limiting. The scope of the invention is therefore intended to be limited solely by the scope of the appended claims.