Patent Publication Number: US-11041355-B2

Title: Lubricator system and method of use

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. application Ser. No. 16/549,041, filed Aug. 23, 2019, the entire disclosure of which is hereby incorporated herein by reference. 
     U.S. application Ser. No. 16/549,041 is a continuation of U.S. application Ser. No. 16/044,061, filed Jul. 24, 2018, the entire disclosure of which is hereby incorporated herein by reference. 
     U.S. application Ser. No. 16/044,061 claims the benefit of the filing date of, and priority to, U.S. Application No. 62/563,855, filed Sep. 27, 2017, the entire disclosure of which is hereby incorporated herein by reference. 
    
    
     TECHNICAL FIELD 
     The present disclosure relates generally to oil and gas exploration and production operations, and, more particularly, to a lubricator system used during, for example, “plug-and-perf” completions operations. 
     BACKGROUND 
     In oil or gas exploration and production operations, a lubricator system may be connected to a wellhead at the top or head of a wellbore that traverses one or more subterranean formations. The lubricator system facilitates rapid access to a vertical, inclined, or horizontal portion of the wellbore using a downhole tool at the end of a wireline. The wireline extends from a wireline truck at the surface and into a lubricator connected to the wellhead, which lubricator is adapted to seal around the wireline to hold backpressure as fluid is communicated into the lubricator behind the downhole tool. The fluid communicated into the lubricator propels the downhole tool to the vertical, inclined, or horizontal portion of the wellbore. In many cases, the lubricator extends vertically along a straight path far above the wellhead, and may require a crane to support the lubricator in position. However, it is difficult and costly to properly set up the crane and to suspend the lubricator in position above the wellhead. Frequently, operations cannot begin, or must be stopped, so that the crane may be lowered as a safety precaution, especially if the wind exceeds certain windspeed limits. Therefore, what is needed is an apparatus, system, or method to address one or more of the foregoing issues, and/or one or more other issues. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a diagrammatic illustration of a lubricator system including a lubricator, a downhole tool, and lubricator pumps, the lubricator system being connected to a fracturing tree, which is connected to a wellhead located at the top or head of an oil and gas wellbore, according to one or more embodiments of the present disclosure. 
         FIG. 2  is a schematic view of an embodiment of the downhole tool of  FIG. 1 , the downhole tool including a perforating gun, a setting tool, and a plug, according to one or more embodiments of the present disclosure. 
         FIG. 3  is an elevational/schematic view of the fracturing tree, the wellhead, and an embodiment of the lubricator of  FIG. 1 , the lubricator including a downwardly concave section and an upwardly concave section, according to one or more embodiments of the present disclosure. 
         FIG. 4  is a diagrammatic illustration of the lubricator system of  FIG. 1  in a first operational state in which the downhole tool extends within the lubricator, according to one or more embodiments of the present disclosure. 
         FIGS. 5( a ) and ( b )  are elevational/schematic views in partial cross section of an embodiment of the first operational state illustrated in  FIG. 4  in which  FIG. 2 &#39;s downhole tool extends within  FIG. 3 &#39;s lubricator, according to one or more embodiments of the present disclosure. 
         FIGS. 6( a )-( d )  are schematic views of consecutive steps for loading  FIG. 2 &#39;s downhole tool into  FIG. 4 &#39;s lubricator, according to one or more embodiments of the present disclosure. 
         FIG. 7  is a diagrammatic illustration of the lubricator system of  FIG. 1  in a second operational state in which the downhole tool extends within the lubricator and the fracturing tree, according to one or more embodiments of the present disclosure. 
         FIG. 8  is an elevational/schematic view in partial cross section of an embodiment of the second operational state illustrated in  FIG. 7 , according to one or more embodiments of the present disclosure. 
         FIG. 9  is a diagrammatic illustration of the lubricator system of  FIG. 1  in a third operational state in which the downhole tool extends within the wellbore, according to one or more embodiments of the present disclosure. 
         FIGS. 10( a )-( c )  are elevational/schematic views in partial cross section of an embodiment of the third operational state illustrated in  FIG. 9 , according to one or more embodiments of the present disclosure. 
         FIG. 11  is an elevational/schematic view in partial cross section of an embodiment of a portion of the lubricator system of  FIG. 1 , the wellhead including an orienting device, according to one or more embodiments of the present disclosure. 
         FIGS. 12( a ) and ( b )  are schematic views of the orienting device of  FIG. 11 , according to one or more embodiments of the present disclosure. 
         FIG. 13  is a diagrammatic illustration of a lubricator system including a lubricator, a downhole tool, a pushrod actuator, and a pushrod, the lubricator system being connected to a fracturing tree, which is connected to a wellhead located at the top or head of an oil and gas wellbore, according to one or more embodiments of the present disclosure. 
         FIG. 14  is a schematic view of an embodiment of the pushrod of  FIG. 13 , the pushrod including a solid portion and a segmented portion, according to one or more embodiments of the present disclosure. 
         FIG. 15  is a diagrammatic illustration of the lubricator system of  FIG. 13  in a first operational state in which the downhole tool extends within the lubricator, according to one or more embodiments of the present disclosure. 
         FIGS. 16( a ) and ( b )  are elevational/schematic views in partial cross section of an embodiment of the first operational state illustrated in  FIG. 15 , according to one or more embodiments of the present disclosure. 
         FIG. 17  is a diagrammatic illustration of the lubricator system of  FIG. 13  in a second operational state in which the downhole tool extends within the lubricator and the fracturing tree, according to one or more embodiments of the present disclosure. 
         FIG. 18  is an elevational/schematic view in partial cross section of an embodiment of the second operational state illustrated in  FIG. 17 , according to one or more embodiments of the present disclosure. 
         FIG. 19  is a diagrammatic illustration of the lubricator system of  FIG. 13  in a third operational state in which the downhole tool extends within the wellbore, according to one or more embodiments of the present disclosure. 
         FIG. 20  is a diagrammatic illustration of a lubricator system including a lubricator, a downhole tool, and an injector, the lubricator system being connected to a fracturing tree, which is connected to a wellhead located at the top or head of an oil and gas wellbore, according to one or more embodiments of the present disclosure. 
         FIG. 21  is an elevational/schematic view of the fracturing tree, the wellhead, and an embodiment of the lubricator of  FIG. 20 , the lubricator including downwardly concave section, upwardly concave section, a tubular part, and an open part, according to one or more embodiments of the present disclosure. 
         FIG. 22  is a diagrammatic illustration of the lubricator system of  FIG. 20  in a first operational state in which the downhole tool extends within the lubricator, according to one or more embodiments of the present disclosure. 
         FIG. 23  is an elevational/schematic view in partial cross section of an embodiment of the first operational state illustrated in  FIG. 22 , according to one or more embodiments of the present disclosure. 
         FIG. 24  is a diagrammatic illustration of the lubricator system of  FIG. 20  in a second operational state in which the downhole tool extends within the lubricator and the fracturing tree, according to one or more embodiments of the present disclosure. 
         FIG. 25  is an elevational/schematic view in partial cross section of an embodiment of the second operational state illustrated in  FIG. 24 , according to one or more embodiments of the present disclosure. 
         FIG. 26  is a diagrammatic illustration of the lubricator system of  FIG. 20  in a third operational state in which the downhole tool extends within the wellbore, according to one or more embodiments of the present disclosure. 
         FIG. 27  is a flowchart illustration of a method of using a lubricator system, according to one or more embodiments of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     Referring to  FIGS. 1-3 , a lubricator system is generally referred to by the reference numeral  10  and includes a conveyance truck  12 , a downhole tool  14 , a lubricator  16 , and lubricator pumps  18 —the lubricator system  10  is shown diagrammatically in  FIG. 1 . The lubricator  16  is connected to a fracturing (or “frac”) tree  20 . The frac tree  20  is connected to a wellhead  22  opposite the lubricator  16 . In some embodiments, the frac tree  20  is, includes, or is part of the wellhead  22 . The wellhead  22  is located at the top or head of an oil and gas wellbore  24  that penetrates one or more subterranean formations and is used in oil and gas exploration and production operations. The lubricator  16  is connected to, and adapted to be in fluid communication with, the lubricator pump(s)  18 . Similarly, the frac tree  20  is connected to, and adapted to be in fluid communication with, frac pump(s)  26 . The conveyance truck  12  includes a reel  28  on which a conveyance string  30  is coiled. The conveyance string  30  may be any type of conveyance string capable of being connected to the downhole tool  14  and conveyed together therewith through the lubricator  16  to the wellbore  24 —such conveyance strings may include, but are not limited to, casing, drill pipe, coiled tubing, production tubing, other types of pipe or tubing strings, and/or other types of conveyance strings, such as wireline, slickline, or the like. For example, in some embodiments, the conveyance string  30  is wireline and the conveyance truck  12  is a wireline truck. For another example, in some embodiments, the conveyance string  30  is coiled tubing and the conveyance truck  12  is a coiled tubing tuck. 
     The conveyance string  30  is connected to the downhole tool  14  opposite the reel  28 . The downhole tool  14  includes a perforating gun  32 , a setting tool  34  connected to the perforating gun  32 , and a plug  36  connected to the setting tool  34 . The downhole tool  14  is adapted to traverse the lubricator  16 , the frac tree  20 , the wellhead  22 , and the wellbore  24  to perform a “plug-and-perf” operation, as will be described in further detail below. However, although described herein as including the perforating gun  32 , the setting tool  34 , and the plug  36  for use during a “plug-and-perf” operation, the downhole tool  14  may instead be another type of downhole tool for use in connection with another lubricator application—such an application may include, but is not limited to, drilling, completions, measurement, logging, or the like. 
     Turning to  FIG. 2 , an embodiment of the downhole tool  14  is shown in which the perforating gun  32  includes interconnected perforator segments  38  and pivot joints  40  extending along a longitudinal axis  42 . The perforator segments  38  include explosive charges (not shown) adapted to perforate the wellbore  24  as part of the “plug-and-perf” operation, as will be described in further detail below. In addition to, or instead of, the explosive charges, the perforator segments  38  may include other components adapted to perforate the wellbore  24 , such as, for example, hydraulic jets or the like. Before the wellbore  24  is perforated by the perforating gun  32 , the setting tool  34  is adapted to set the plug  36  in the wellbore  24  as part of the “plug-and-perf” operation, as will be described in further detail below. Most of the pivot joints  40  are interposed between respective ones of the perforating gun  32 &#39;s perforator segments  38 —but at least one of the pivot joints  40  is interposed between the perforating gun  32  and the setting tool  34 . 
     The pivot joints  40  permit pivoting of the perforator segments  38  relative to one another, and pivoting of the setting tool  34  relative to the perforating gun  32 . More particularly, the pivot joints  40  each permit pivoting about a pair of axes  44  and  46 , as indicated by curvilinear arrows  48  and  50 , respectively. The axes  44  and  46  are spaced in a substantially perpendicular relation with one another. Moreover, the longitudinal axis  42  extends in a substantially perpendicular relation to the axes  44  and  46 . In addition to, or instead of, permitting pivoting about the axes  44  and  46 , the pivot joints  40  may be adapted to permit pivoting about one or more additional axes perpendicular to the longitudinal axis  42 , and/or about the longitudinal axis  42  itself. In those embodiments in which the downhole tool  14  is omitted in favor of another downhole tool, pivot joints analogous to the pivot joints  40  may be incorporated into such a downhole tool to enable similar pivotability. Moreover, although described herein as including pivot joints, other downhole tools are contemplated that include flexible portions instead (or in addition) to enable similar pivotability. In some embodiments, the downhole tool  14  (or another downhole tool) includes other components, such as, for example, a collar counter, a measurement tool, a logging tool, or the like. 
     Turning to  FIG. 3 , an embodiment of the lubricator  16  is shown in which the lubricator  16  is a tubular member defining an internal passage  51  and including a downwardly concave section  52  and an upwardly concave section  54 . The downwardly concave section  52  extends along a curvilinear axis  56  defining a radius R 1 , and the upwardly concave section  54  extends along a curvilinear axis  58  defining a radius R 2 . In some embodiments, the radius R 2  is substantially equal to the radius R 1 . In some embodiments, the curvilinear axes  56  and  58  each extend within a single plane. In some embodiments, the curvilinear axes  56  and  58  are co-planar. In some embodiments, the axis  56  at least partially forms or defines a curvilinear path along which the internal passage  51  of the lubricator extends. In some embodiments, the axis  58  at least partially forms or defines the curvilinear path along which the internal passage  51  of the lubricator  16  extends. In some embodiments, the axes  56  and  58  at least partially form or define the curvilinear path along which the internal passage  51  of the lubricator  16  extends. The term “curvilinear path,” as used herein, refers to any path whose traversal produces both vertical and horizontal movement, including, for example, a path having a plurality of straight segments angled relative to one another. 
     The downwardly concave section  52  is connected to the frac tree  20 . The upwardly concave section  54  is connected to the downwardly concave section  52  opposite the frac tree  20 . The lubricator pump(s)  18  are connected to, and adapted to be in fluid communication with, an end portion  60  of the lubricator  16  opposite the frac tree  20 , as indicated by arrow  62 . However, rather than being connected to the end portion  60  of the lubricator  16 , the lubricator pump(s)  18  may be connected elsewhere to the lubricator  16 . Moreover, although described herein as including the radii R 1  and R 2 , the curvilinear axes  56  and  58  of the lubricator  16  may instead extend along another curvilinear path—such a path need not be limited to an arc or any other similarly curved shape. In some embodiments, the curvilinear axis  58  may be omitted in favor of another axis such as, for example, a horizontally-extending linear axis so that the curvilinear path extends along the linear axis and the curvilinear axis  56 ; in some embodiments, this linear axis and the curvilinear axis  56  at least partially form or define the curvilinear path along which the internal passage  51  of the lubricator  16  extends. 
     The frac tree  20  includes a goat head  64  and a swab valve  66 . The goat head  64  is connected to the wellhead  22 . The swab valve  66  is connected to the goat head  64  opposite the wellhead  22 . The wellhead  22  is connected to a casing string  68  that traverses at least part of the wellbore  24 . The frac pump(s)  26  are connected to, and adapted to be in fluid communication with, the goat head  64 , as indicated by arrows  70 . The frac tree  20  has a maximum height H 1  measured from the ground to the top of the swab valve  66 . The lubricator  16  has a maximum height H 2  measured from the ground to the top of the downwardly concave section  52 . In some embodiments, the height H 2  is equal to, or less than, double the height H 1 . In some embodiments, a lubricator support rod  72  engages the downwardly concave section  52  to support the lubricator  16  at the maximum height H 2 . The lubricator support rod  72  is stabilized by guide wires  74 . However, other types of supports are contemplated to support the lubricator  16  at the maximum height H 2 , such as, for example, scaffolding or the like. 
     Referring to  FIGS. 4, 5 ( a ), and  5 ( b ), the lubricator system  10  is illustrated in a first operational state in which the downhole tool  14  is positioned within the lubricator  16 —the first operational state is shown diagrammatically in  FIG. 4 . The conveyance string  30  is connected to the downhole tool  14  and extends out of the lubricator  16  to the reel  28  on the conveyance truck  12 . In the first operational state of the lubricator system  10 , the lubricator pump(s)  18  are adapted to pump fluid into the lubricator  16  behind the plug  36  to thereby create a pressure differential across the plug  36 . The pressure differential across the plug  36  urges the downhole tool  14  through the lubricator  16  like a piston so that, as the conveyance string  30  is unwound from the reel  28 , the downhole tool  14  moves through the lubricator  16  toward the frac tree  20 . 
     Turning to  FIGS. 5( a ) and ( b ) , an embodiment of the first operational state of the lubricator system  10  is shown in which the downhole tool  14  extends within, or at least immediately upstream of, the downwardly concave section  52 , and further extends within the upwardly concave section  54  and the end portion  60  of the lubricator  16 . To enable the extension of the downhole tool  14  within the upwardly concave section  54  and the downwardly concave section  52  of the lubricator  16 , the downhole tool  14  pivots about the axes  44  and  46  (shown in  FIG. 2 ) via the pivot joints  40 —such pivoting generally aligns the downhole tool  14  with the curvilinear axes  56  and  58  (shown in  FIG. 3 ) of the lubricator  16 . The end portion  60  of the lubricator  16  is sealingly engaged (e.g., threadably) by a sealing cap  76  through which the conveyance string  30  extends. The conveyance string  30  is guided via pulleys  78  to the reel  28  on the conveyance truck  12  (shown in  FIG. 4 ). The sealing cap  76  sealingly engages the conveyance string  30  to prevent, or at least reduce, leakage of fluid from inside the lubricator  16  to atmosphere. 
     The lubricator pump(s)  18  are connected to the lubricator  16  and adapted to pump fluid into the lubricator  16  behind the plug  36  to thereby create the pressure differential across the plug  36 , as indicated by the arrow  62  (also shown in  FIG. 3 ). The radial clearance between the plug  36  and the lubricator  16  is less than the radial clearance between the setting tool  34  and the lubricator  16 , and is less than the radial clearance between the perforating gun  32  and the lubricator  16 —this reduced clearance enables the pressure differential to be created across the plug  36 . Additionally, the sealing engagement of the sealing cap  76  with both the conveyance string  30  and the end portion  60  of the lubricator  16  holds backpressure caused by the pumping of the fluid into the lubricator  16  by the lubricator pump(s)  18 , thereby enabling the pressure differential to be created across the plug  36 . The pressure differential across the plug  36  urges the downhole tool  14  through the lubricator  16  like a piston so that, as the conveyance string  30  is unwound from the reel  28 , the downhole tool  14  moves through the lubricator  16  toward the frac tree  20 . 
     Turning to  FIGS. 6( a )-( d )  with continuing reference to  FIGS. 5( a ) and ( b ) , the manner in which the downhole tool  14  is loaded into the lubricator  16  is illustrated. As shown in  FIG. 6( a ) , before the sealing cap  76  is sealingly engaged with the end portion  60  of the lubricator  16 , the downhole tool  14  is inserted into the lubricator  16  via the end portion  60  thereof. The conveyance string  30  extends through the sealing cap  76  and is connected to the downhole tool  14 . The end portion  60  of the lubricator  16  includes a pin-hole  80 . The downhole tool  14  includes a pin-hole  82  adapted to be aligned with the pin-hole  80  of the lubricator  16 . As shown in  FIG. 6( b ) , after the downhole tool  14  is inserted into the lubricator  16  via the end portion  60  thereof, the respective pin-holes  80  and  82  of the downhole tool  14  and the lubricator  16  are aligned—once so aligned, a pin  84  is inserted into the pin-holes  80  and  82 . The pin  84  retains the downhole tool  14  within the lubricator  16  so that the sealing cap  76  may be connected to the end portion  60  of the lubricator  16  (i.e., the pin  84  prevents gravity from ejecting the downhole tool  14 , due to the curved shape of the lubricator  16 , before the sealing cap  76  is connected). As shown in  FIG. 6( c ) , after the pin  84  is inserted into the pin-holes  80  and  82  to retain the downhole tool  14  within the lubricator  16 , the sealing cap  76  is partially connected to the end portion  60  of the lubricator  16 . This partial connection of the sealing cap  76  to the end portion  60  of the lubricator  16  holds the downhole tool  14  within the lubricator  16  regardless of whether or not the pin  84  in inserted into the pin-holes  80  and  82 , thereby enabling removal of the pin  84  from the pin-holes  80  and  82 . As shown in  FIG. 6( d ) , after the pin  84  is removed from the pin-holes  80  and  82 , the sealing cap  76  is fully connected to the end portion  60  of the lubricator  16 —once so fully connected, the sealing cap  76  covers the pin-hole  80  and sealingly engages the conveyance string  30  to prevent, or at least reduce, leakage of fluid (e.g., fluid pumped from the lubricator pump(s)  18 ) from inside the lubricator  16  to atmosphere. 
     Referring to  FIGS. 7 and 8 , the lubricator system  10  is illustrated in a second operational state in which part of the downhole tool  14  extends within the frac tree  20 —the second operational state of the lubricator system  10  is shown diagrammatically in  FIG. 7 . To actuate the lubricator system  10  from the first operational state to the second operational state, the lubricator pump(s)  18  pump fluid into the lubricator  16  behind the plug  36 , causing the downhole tool  14  to move through the lubricator  16  toward the frac tree  20 , as described above. In the second operational state of the lubricator system  10 , the frac pump(s)  26  are adapted to pump fluid into the frac tree  20  behind the plug  36  to thereby create a pressure differential across the plug  36 . When the frac pump(s)  26  pump fluid into the frac tree  20 , the lubricator pump(s)  18  may or may not continue to pump fluid into the lubricator  16  to thereby contribute to the pressure differential across the plug  36 . The pressure differential across the plug  36  urges the downhole tool  14  through the frac tree  20  and the wellhead  22  like a piston so that, as the conveyance string  30  is unwound from the reel  28 , the downhole tool  14  moves through the frac tree  20  and the wellhead  22  toward the wellbore  24 . 
     Turning to  FIG. 8 , an embodiment of the second operational state of the lubricator system  10  is shown in which the frac pump(s)  26  are connected to the goat head  64  and adapted to pump fluid into the frac tree  20  behind the plug  36  to thereby create the pressure differential across the plug  36 , as indicated by the arrows  70  (also shown in  FIG. 3 ). When the frac pump(s)  26  pump fluid into the frac tree  20 , the lubricator pump(s)  18  may or may not continue to pump fluid into the lubricator  16  (as indicated by the arrow  62  in  FIG. 5( b ) ) to thereby contribute to the pressure differential across the plug  36 . The radial clearance between the plug  36  and the respective interiors of the frac tree  20  and the wellhead  22  is less than the radial clearance between the setting tool  34  and the lubricator  16 , and is less than the radial clearance between the perforating gun  32  and the lubricator  16 —this reduced clearance enables the pressure differential to be created across the plug  36 . Additionally, the sealing engagement of the sealing cap  76  with both the conveyance string  30  and the end portion  60  of the lubricator  16  holds backpressure caused by the pumping of the fluid into the frac tree  20  by the frac pump(s)  26  (and, optionally, by the pumping of the fluid into the lubricator  16  by the lubricator pump(s)  18 ), thereby enabling the pressure differential to be created across the plug  36 . The pressure differential across the plug  36  urges the downhole tool  14  through the frac tree  20  and the wellhead  22  like a piston so that, as the conveyance string  30  is unwound from the reel  28 , the downhole tool  14  moves through the frac tree  20  and the wellhead  22  toward the wellbore  24 . 
     Referring to  FIGS. 9 and 10 ( a )-( c ), the lubricator system  10  is illustrated in a third operational state in which the downhole tool  14  is positioned within the wellbore  24 —the third operational state of the lubricator system  10  is shown diagrammatically in  FIG. 9 . The conveyance string  30  extends from the reel  28  on the conveyance truck  12 , through the lubricator  16 , the frac tree  20 , the wellhead  22 , and the wellbore  24 , and to the downhole tool  14 . To actuate the lubricator system  10  from the second operational state to the third operational state, the frac pump(s)  26  pump fluid into the frac tree  20  behind the plug  36 , causing the downhole tool  14  to move through the frac tree  20  and the wellhead  22  toward the wellbore  24 , as described above. Moreover, as described above, the lubricator pump(s)  18  may or may not continue to pump fluid into the lubricator  16  to thereby contribute to the actuation of the lubricator system  10  from the second operational state to the third operational state. In the third operational state of the lubricator system  10 , the downhole tool  14  is adapted to perform the “plug-and-perf” operation, as will be described in further detail below. 
     Turning to  FIGS. 10( a )-( c ) , an embodiment of the third operational state of the lubricator system  10  is shown in which the wellbore  24  includes a curved section  86  and a horizontal or inclined section  88 . The curved section  86  defines a radius R 3 . The radius R 3  is substantially equal to, or greater than, the radii R 1  and R 2  of the lubricator  16 . In some embodiments, the radius R 3  of the wellbore  24  may be significantly less than that of conventional wellbores due to the pivotability of the downhole tool  14 , thus facilitating greater exploitation of a given subterranean zone. To enable the lowering of the downhole tool  14  through the curved section  86  and into the horizontal or inclined section  88 , the downhole tool  14  pivots about the axes  44  and  46  (shown in  FIG. 2 ) via the pivot joints  40 . The lowering of the downhole tool  14  into the wellbore  24  is made possible by gravity and the continued pumping of fluid into the frac tree  20  by the frac pump(s)  26 .  FIG. 10( a )  shows the setting tool  34  setting the plug  36  in the horizontal or inclined section  88  of the wellbore  24  as part of the “plug-and-perf” operation.  FIG. 10( b )  shows the perforating gun  32  perforating the wellbore  24  by exploding the explosive charges in the perforator segments  38  as part of the “plug-and-perf” operation. Finally,  FIG. 10( c )  shows the perforating gun  32  and the setting tool  34  being retrieved from the wellbore  24 . In some embodiments, the perforating gun  32  and the setting tool  34  are retrieved from the wellbore  24  by winding the conveyance string  30  onto the reel  28  of the conveyance truck  12 . The plug  36  remains in the wellbore  24  to enable the execution of a fracturing operation on the perforated section of the wellbore  24 . 
     Referring to  FIGS. 11, 12 ( a ), and  12 ( b ), in some embodiments, the lubricator system  10  includes an orienting device  90  adapted to ensure proper orientation of the downhole tool  14  relative to the lubricator  16  upon the re-entry of the downhole tool  14  into the lubricator  16  from the wellbore  24 . The orienting device  90  is connected to the frac tree  20  opposite the wellhead  22 , as shown in  FIG. 11 . However, rather than being connected to the frac tree  20  opposite the wellhead  22 , in some embodiments, the orienting device  90  may be connected between the frac tree  20  and the wellhead  22 , between the wellhead  22  and the casing string  68 , or elsewhere in the lubricator system  10 . As the downhole tool  14  passes through the orienting device  90  in an upward direction, the orienting device  90  is adapted to rotate the downhole tool  14  so that pivoting of the pivot joints  40  about the axes  44  and  46  (shown in  FIG. 2 ) is permitted when the downhole tool  14  re-enters the lubricator  16 . 
     Turning to  FIGS. 12( a ) and ( b ) , the manner in which the orienting device  90  rotates the downhole tool  14  into the proper orientation is illustrated. The orienting device  90  includes an internal passage  92 , a profile surface  94 , and a longitudinally-extending slot  96 —for clarity, other parts of the orienting device  90  are omitted from view in  FIGS. 12( a ) and ( b ) . The internal passage  92  of the orienting device  90  receives the downhole tool  14  from the wellbore  24 . The profile surface  94  of the orienting device  90  extends about the internal passage  92  and slopes toward the longitudinally-extending slot  96 . The downhole tool  14  includes an orienting key  98  adapted engage the profile surface  94  of the orienting device  90  as the downhole tool  14  passes through the orienting device  90  in the upward direction. The engagement of the orienting key  98  with the profile surface  94  as the downhole tool  14  moves in the upward direction causes the downhole tool  14  to rotate until the orienting key  98  is received within the longitudinally-extending slot  96 . The longitudinally-extending slot  96  is positioned to ensure proper orientation of the downhole tool  14  as the downhole tool  14  enters the lubricator  16 . In some embodiments, the downhole tool  14  includes one or more longitudinally-spaced orienting keys each of which is substantially identical to the orienting key  98 . 
     Referring to  FIGS. 13 and 14 , a lubricator system is generally referred to by the reference numeral  100 —the lubricator system  100  is substantially identical to the lubricator system  10 , except that, instead of the lubricator  16  and the lubricator pump(s)  18 , the lubricator system  100  includes a lubricator  102 , a pushrod  104 , and a pushrod actuator  106 . Therefore, in connection with  FIGS. 13-15, 16 ( a ),  16 ( b ), and  17 - 19 , parts of the lubricator system  100  that are substantially identical to corresponding parts of the lubricator system  10  are given the same reference numerals. Thus, the lubricator system  100  includes the conveyance truck  12 , the downhole tool  14 , the lubricator  102 , the pushrod  104 , and the pushrod actuator  106 —the lubricator system  100  is shown diagrammatically in  FIG. 13 . The lubricator  102  is connected to the frac tree  20 . The frac tree  20  is connected to the wellhead  22  opposite the lubricator  102 . The frac pump(s)  26  are connected to, and adapted to be in fluid communication with, the frac tree  20 . The conveyance truck  12  includes the reel  28  on which the conveyance string  30  is coiled. The conveyance string  30  is connected to the downhole tool  14  opposite the reel  28 . The pushrod actuator  106  is connected to the pushrod  104 , which pushrod, in turn, is adapted to engage the downhole tool  14 . 
     Turning to  FIG. 14 , an embodiment of the pushrod  104  is shown including a solid portion  108  and a segmented portion  110 . The segmented portion  110  includes pusher segments  112  and pivot joints  114  extending along a longitudinal axis  116 . Most of the pivot joints  114  are interposed between respective ones of the pushrod  104 &#39;s pusher segments  112 —but at least one of the pivot joints  114  is interposed between the segmented portion  110  and the solid portion  108  of the pushrod  104 . The pivot joints  114  permit pivoting of the pusher segments  112  relative to one another, and pivoting of the segmented portion  110  relative to the solid portion  108  of the pushrod  104 . More particularly, the pivot joints  114  each permit pivoting about a pair of axes  118  and  120 , as indicated by curvilinear arrows  122  and  124 , respectively. The axes  118  and  120  are spaced in a substantially perpendicular relation with one another. Moreover, the longitudinal axis  116  is spaced in a substantially perpendicular relation with the axes  118  and  120 . The pushrod  104  includes eyelets  126  connected to the segmented portion  110  of the pushrod  104  and spaced therealong to accommodate the conveyance string  30 , as will be described in further detail below. In addition to, or instead of, permitting pivoting about the axes  118  and  120 , the pivot joints  114  may be adapted to permit pivoting about one or more additional axes perpendicular to the longitudinal axis  116 , and/or about the longitudinal axis  116  itself. Moreover, although described herein as including pivot joints, other pushrods are contemplated that include flexible portions instead (or in addition) to enable similar pivotability. 
     Referring to  FIGS. 15, 16 ( a ), and  16 ( b ), the lubricator system  100  is illustrated in a first operational state in which the downhole tool  14  and part of the pushrod  104  are positioned within the lubricator  102 —the first operational state of the lubricator system  100  is shown diagrammatically in  FIG. 15 . The conveyance string  30  is connected to the downhole tool  14  and extends out of the lubricator  102  to the reel  28  on the conveyance truck  12 . The pushrod  104  engages the downhole tool  14  and extends out of the lubricator  102  to the pushrod actuator  106 . In the first operational state of the lubricator system  100 , the pushrod actuator  106  is adapted to actuate the pushrod  104  in a manner that causes the pushrod  104  to engage the downhole tool  14  so that the downhole tool  14  moves through the lubricator  102  toward the frac tree  20 . 
     Turning to  FIGS. 16( a ) and ( b ) , an embodiment of the first operational state of the lubricator system  100  is shown in which the lubricator  102  is substantially identical to the lubricator  16 , except that, instead of the end portion  60 , the lubricator  102  includes an end portion  128  adapted to accommodate the pushrod  104 . Therefore, in connection with  FIGS. 16( a ), 16( b ) , and  18 , parts of the lubricator  102  that are substantially identical to corresponding parts of the lubricator  16  are given the same reference numerals. As a result, in the first operational state of the lubricator system  100 , the downhole tool  14  extends within the downwardly concave section  52 , the upwardly concave section  54 , and the end portion  128  of the lubricator  102 . To enable the extension of the downhole tool  14  within the upwardly concave section  54  and the downwardly concave section  52  of the lubricator  102 , the downhole tool  14  pivots about the axes  44  and  46  (shown in  FIG. 2 ) via the pivot joints  40 —such pivoting generally aligns the downhole tool  14  with the curvilinear axes  56  and  58  of the lubricator  102 . 
     The end portion  128  of the lubricator  102  is sealingly engaged (e.g., threadably) by a sealing cap  130  through which the conveyance string  30  and the pushrod  104  extend. The sealing cap  130  sealingly engages the conveyance string  30  and the pushrod  104  to prevent, or at least reduce, leakage of fluid from inside the lubricator  102  to atmosphere. The eyelets  126  spaced along the segmented portion  110  of the pushrod  104  accommodate the conveyance string  30  to prevent, or at least reduce, entanglement of the conveyance string  30  and the pushrod  104  within the lubricator  102 . The pushrod actuator  106  (not shown in  FIG. 16( b ) ) is adapted to actuate the solid portion  108  of the pushrod  104  through the sealing cap  130  in a manner that causes the segmented portion  110  of the pushrod  104  to engage the downhole tool  14  so that, as the conveyance string  30  is unwound from the reel  28 , the downhole tool  14  moves through the lubricator  102  toward the frac tree  20 . In some embodiments, the pushrod  104  is also adapted to assist in the retrieval of the downhole tool  14  from the wellbore  24  and/or the wellhead  22  upon completion of, for example, the “plug-and-perf” operation. 
     Referring to  FIGS. 17 and 18 , the lubricator system  100  is illustrated in a second operational state in which part of the pushrod  104  extends within the lubricator  102  and part of the downhole tool  14  extends within the frac tree  20 —the second operational state of the lubricator system  100  is illustrated diagrammatically in  FIG. 17 . To actuate the lubricator system  100  from the first operational state to the second operational state, the pushrod actuator  106  actuates the pushrod  104  in a manner that causes the pushrod  104  to engage the downhole tool  14  so that the downhole tool  14  moves through the lubricator  102  toward the frac tree  20 , as described above. In the second operational state of the lubricator system  100 , the frac pump(s)  26  are adapted to pump fluid into the frac tree  20  behind the plug  36  to thereby create a pressure differential across the plug  36 . The pressure differential across the plug  36  urges the downhole tool  14  through the frac tree  20  and the wellhead  22  like a piston so that, as the conveyance string  30  is unwound from the reel  28 , the downhole tool  14  disengages from the pushrod  104  and moves through the frac tree  20  and the wellhead  22  toward the wellbore  24 . 
     Turning to  FIG. 18 , an embodiment of the second operational state of the lubricator system  100  is shown in which the frac pump(s)  26  are connected to the goat head  64  and adapted to pump fluid into the frac tree  20  behind the plug  36  to thereby create the pressure differential across the plug  36 , as indicated by arrows  132 . The radial clearance between the plug  36  and the lubricator  102  is less than the radial clearance between the setting tool  34  and the lubricator  102 , and is less than the radial clearance between the perforating gun  32  and the lubricator  102 —this reduced clearance enables the pressure differential to be created across the plug  36 . Additionally, the sealing engagement of the sealing cap  130  with the conveyance string  30 , the pushrod  104 , and the end portion  128  of the lubricator  102  holds backpressure caused by the pumping of the fluid into the frac tree  20  by the frac pump(s)  26 , thereby enabling the pressure differential to be created across the plug  36 . The pressure differential across the plug  36  urges the downhole tool  14  through the frac tree  20  and the wellhead  22  like a piston so that, as the conveyance string  30  is unwound from the reel  28 , the downhole tool disengages from the pushrod  104  and moves through the frac tree  20  and the wellhead  22  toward the wellbore  24 . As the downhole tool disengages from the pushrod  104  and moves through the frac tree  20  toward the wellbore  24 , the eyelets  126  spaced along the segmented portion  110  of the pushrod  104  accommodate the conveyance string  30  to prevent, or at least reduce, entanglement of the conveyance string  30  and the pushrod  104  within the lubricator  102 . The accommodation of the conveyance string  30  within the eyelets  126  prevents, or at least reduces, wear or erosion that might otherwise be cause by contact between the conveyance string  30  and the interior of the lubricator  102 . 
     Referring to  FIG. 19 , the lubricator system  100  is illustrated in a third operational state in which part of the pushrod  104  extends within the lubricator  102  and the downhole tool  14  is positioned within the wellbore  24 —the third operational state of the lubricator system  100  is shown diagrammatically in  FIG. 19 . The downhole tool  14  is disengaged from the pushrod  104 , which pushrod, in turn, remains at least partially positioned within the lubricator  102 . The conveyance string  30  extends from the reel  28  on the conveyance truck  12 , through the lubricator  102 , the frac tree  20 , the wellhead  22 , and the wellbore  24 , and to the downhole tool  14 . To actuate the lubricator system  100  from the second operational state to the third operational state, the frac pump(s)  26  pump fluid into the frac tree  20  behind the plug  36  so that, as the conveyance string  30  is unwound from the reel  28 , the downhole tool  14  disengages from the pushrod  104  and moves through the frac tree  20  and the wellhead  22  toward the wellbore  24 , as described above. Many aspects of the third operational state of the lubricator system  100  are substantially identical to the third operational state of the lubricator system  10 —at least some of these substantially identical aspects can be seen by referring again to  FIGS. 10( a )-( c ) . Therefore, the third operational state of the lubricator system  100  will not be described in further detail. Moreover, in some embodiments, the lubricator system  100  includes the orienting device  90  adapted to ensure proper orientation of the downhole tool  14  relative to the lubricator  102  upon re-entry of the downhole tool  14  into the lubricator  102  from the wellbore  24 . The orienting device  90  is described above in connection with  FIGS. 11, 12 ( a ), and  12 ( b ), and, therefore, will not be described in further detail. 
     Referring to  FIGS. 20 and 21 , a lubricator system is generally referred to by the reference numeral  134 —the lubricator system  134  is substantially identical to the lubricator system  10 , except that, instead of the lubricator  16  and the lubricator pump(s)  18 , the lubricator system  134  includes a lubricator  136  and an injector  138 . Therefore, in connection with  FIGS. 20-25 , parts of the lubricator system  134  that are substantially identical to corresponding parts of the lubricator system  10  are given the same reference numerals. Thus, the lubricator system  134  includes the conveyance truck  12 , the downhole tool  14 , the lubricator  136 , and the injector  138 —the lubricator system  134  is shown diagrammatically in  FIG. 20 . The lubricator  136  is connected to the frac tree  20 . The frac tree  20  is connected to the wellhead  22  opposite the lubricator  136 . The frac pump(s)  26  are connected to, and adapted to be in fluid communication with, the frac tree  20 . The conveyance truck  12  includes the reel  28  on which the conveyance string  30  is coiled. The conveyance string  30  is connected to the downhole tool  14  opposite the reel  28 . The injector  138  is connected to the lubricator  136  and adapted to engage the downhole tool  14 , as will be described in further detail below. In some embodiments, the injector  138  is, or is adapted from, a coiled tubing type injector head. 
     Turning to  FIG. 21 , an embodiment of the lubricator system  134  is shown in which the lubricator  136  is substantially identical to the lubricator  16 , except that, instead of the downwardly concave section  52 , the upwardly concave section  54 , and the end portion  60 , the lubricator  136  includes a downwardly concave section  140 , an upwardly concave section  142 , and a sealing cap  144 . In many respects, the downwardly concave section  140  and the upwardly concave section  142  are substantially identical to the downwardly concave section  52  and the upwardly concave section  54 , respectively, and, therefore, in connection with  FIGS. 21, 23, and 25 , parts of the downwardly concave section  140  and the upwardly concave section  142  that are substantially identical to corresponding parts of the downwardly concave section  52  and the upwardly concave section  54  are given the same reference numerals. Thus, in some embodiments, the downwardly concave section  140  extends along the curvilinear axis  56  defining the radius R 1 , and the upwardly concave section  142  extends along the curvilinear axis  58  defining the radius R 2 . However, instead of being tubular along its entire length in a manner similar to the lubricator  16 , the lubricator  136  includes a tubular part  146  and an open part  148  exposed to atmosphere. 
     The tubular part  146  of the lubricator  136  includes at least part of the downwardly concave section  140 , and defines the internal passage  51 . In some embodiments, the axis  56  of the downwardly concave section  140  at least partially forms or defines the curvilinear path along which the internal passage  51  of the lubricator  136  extends. The open part  148  of the lubricator  136  includes at least part of the upwardly concave section  142 . The tubular part  146  of the lubricator  136  is adapted to be sealingly engaged by the sealing cap  144 , as will be described in further detail below. The injector  138  is connected to the lubricator  136  adjacent the sealing cap  144  and adapted to inject the downhole tool  14  into the tubular part  146  via, for example, a pair of rollers  150 . In some embodiments, the rollers  150  are also adapted to assist in the retrieval of the downhole tool  14  from the wellbore  24  and/or the wellhead  22  upon completion of, for example, the “plug-and-perf” operation. 
     Referring to  FIGS. 22 and 23 , the lubricator system  134  is illustrated in a first operational state in which the downhole tool  14  is positioned within the lubricator  136 —the first operational state of the lubricator system  134  is shown diagrammatically in  FIG. 22 . The conveyance string  30  is connected to the downhole tool  14  and extends out of the lubricator  136  to the reel  28  on the conveyance truck  12 . The injector  138  engages the downhole tool  14 . In the first operational state of the lubricator system  134 , the injector  138  is adapted to engage the downhole tool  14  in a manner that causes the downhole tool  14  to move through the lubricator  136  toward the frac tree  20 . 
     Turning to  FIG. 23 , an embodiment of the first operational state of the lubricator system  134  is shown in which part of the downhole tool  14  extends within the tubular part  146  of the lubricator  136  and part of the downhole tool  14  is supported along the open part  148  of the lubricator  136 . As a result, in the first operational state of the lubricator system  134 , the downhole tool  14  extends along the downwardly concave section  140  and the upwardly concave section  142  of the lubricator  136 . To enable the extension of the downhole tool  14  along the downwardly concave section  140  and the upwardly concave section  142  of the lubricator  136 , the downhole tool  14  pivots about the axes  44  and  46  (shown in  FIG. 2 ) via the pivot joints  40 —such pivoting generally aligns the downhole tool  14  with the curvilinear axes  56  and  58  of the lubricator  136 . In the first operational state of the lubricator system  134 , the sealing cap  144  is not sealingly engaged with the tubular part  146  of the lubricator  136 , but is rather disengaged so as to allow passage of the downhole tool  14  into the tubular part  146  of the lubricator  136 . Moreover, the rollers  150  of the injector  138  are adapted to engage the downhole tool  14 , as indicated by curvilinear arrows  152 , in a manner that causes the downhole tool  14  to move through the lubricator  136  toward the frac tree  20 . 
     Referring to  FIGS. 24 and 25 , the lubricator system  134  is illustrated in a second operational state in which part of the downhole tool  14  extends within the frac tree  20 —the second operational state of the lubricator system  134  is illustrated diagrammatically in  FIG. 24 . To actuate the lubricator system  134  from the first operational state to the second operational state, the injector  138  engages the downhole tool  14  in a manner that causes the downhole tool  14  to move through the lubricator  136  toward the frac tree  20 , as described above. In the second operational state of the lubricator system  134 , the frac pump(s)  26  are adapted to pump fluid into the frac tree  20  behind the plug  36  to thereby create a pressure differential across the plug  36 . The pressure differential across the plug  36  urges the downhole tool  14  through the frac tree  20  and the wellhead  22  like a piston so that, as the conveyance string  30  is unwound from the reel  28 , the downhole tool  14  moves through the frac tree  20  and the wellhead  22  toward the wellbore  24 . 
     Turning to  FIG. 25 , an embodiment of the second operational state of the lubricator system  134  is shown in which the frac pump(s)  26  are connected to the goat head  64  and adapted to pump fluid into the frac tree  20  behind the plug  36  to thereby create the pressure differential across the plug  36 , as indicated by arrows  154 . The downhole tool  14  extends within the tubular part  146  of the lubricator  136 , but not within the open part  148  of the lubricator  136 . As a result, the downhole tool  14  extends along the downwardly concave section  140  of the lubricator  136 . The sealing cap  144  is sealingly engaged with the tubular part  146  of the lubricator  136 , as indicated by arrows  156 —when so sealingly engaged with the tubular part  146  of the lubricator  136 , the sealing cap  144  also sealingly engages the conveyance string  30  to prevent, or at least reduce, leakage of fluid from inside the tubular part  146  of the lubricator  136  to atmosphere. The radial clearance between the plug  36  and the lubricator  136  is less than the radial clearance between the setting tool  34  and the lubricator  136 , and is less than the radial clearance between the perforating gun  32  and the lubricator  136 —this reduced clearance enables the pressure differential to be created across the plug  36 . The sealing engagement of the sealing cap  144  with conveyance string  30  and the tubular part  146  of the lubricator  136  holds backpressure caused by the pumping of fluid into the goat head  64  by the frac pump(s)  26 , thereby enabling the pressure differential to be created across the plug  36 . The pressure differential across the plug  36  urges the downhole tool  14  through the frac tree  20  and the wellhead  22  like a piston so that, as the conveyance string  30  is unwound from the reel  28 , the downhole tool  14  moves through the frac tree  20  and the wellhead  22  toward the wellbore  24 . 
     Referring to  FIG. 26 , the lubricator system  134  is illustrated in a third operational state in which the downhole tool  14  is positioned within the wellbore  24 —the third operational state of the lubricator system  134  is shown diagrammatically in  FIG. 26 . The conveyance string  30  is connected to the downhole tool  14  and extends through the wellbore  24 , the wellhead  22 , the frac tree  20 , and the lubricator  136  to the reel  28  on the conveyance string  30  truck. To actuate the lubricator system  134  from the second operational state to the third operational state, the frac pump(s)  26  pump fluid into the frac tree  20  behind the plug  36  so that, as the conveyance string  30  is unwound from the reel  28 , the downhole tool  14  moves through the frac tree  20  and the wellhead  22  toward the wellbore  24 , as described above. Many aspects of the third operational state of the lubricator system  134  are substantially identical to the third operational state of the lubricator system  10 —at least some of these substantially identical aspects can be seen by referring again to  FIGS. 10( a )-( c ) . Therefore, the third operational state of the lubricator system  134  will not be described in further detail. Moreover, in some embodiments, the lubricator system  134  includes the orienting device  90  adapted to ensure proper orientation of the downhole tool  14  relative to the lubricator  136  upon re-entry of the downhole tool  14  into the lubricator  136  from the wellbore  24 . The orienting device  90  is described above in connection with  FIGS. 11, 12 ( a ), and  12 ( b ), and, therefore, will not be described in further detail. 
     Referring to  FIG. 27 , a method of using the lubricator system (e.g.,  10 ,  100 , or  134 ) is generally referred to by the reference numeral  158 . The method  158  includes connecting a lubricator (e.g.,  16 ,  102 , or  136 ) to the wellhead  22  at the top or head of the oil and gas wellbore  24  at a step  160 , the lubricator defining an internal passage extending along a curvilinear path. In some embodiments, the lubricator (e.g.,  16 ,  102 , or  136 ) includes a downwardly concave section (e.g.,  52  or  140 ) extending along the curvilinear axis  56  and an upwardly concave section (e.g.,  54  or  142 ) extending along the curvilinear axis  58 . The method  158  also includes actuating the lubricator system (e.g.,  10 ,  100 , or  134 ) to a first operational state in which the downhole tool  14  extends within the lubricator (e.g.,  16 ,  102 , or  136 ) at a step  162 . In some embodiments, the step  162  of actuating the lubricator system (e.g.,  10 ,  100 , or  134 ) to a first operational state includes generally aligning the downhole tool  14  with the curvilinear axes (e.g.,  52  and  54 , or  140  and  142 ) using the pivot joints (e.g.,  40 ), the pivot joints being interposed between respective portions of the downhole tool  14 . After the lubricator system (e.g.,  10 ,  100 , or  134 ) is actuated to the first operational state at the step  162 , the method  158  includes one of the following: pumping fluid into the lubricator (e.g.,  16 ,  102 , or  136 ) to urge the downhole tool  14  through the lubricator toward the wellhead  22  at a step  164 ; engaging the downhole tool  14  with the pushrod  104  to urge the downhole tool  14  through the lubricator (e.g.,  16 ,  102 , or  136 ) toward the wellhead  22  at a step  166 ; or engaging the downhole tool  14  with the rollers  150  of the injector  138  to urge the downhole tool  14  through the lubricator (e.g.,  16 ,  102 , or  136 ) toward the wellhead  22  at a step  168 . 
     In addition, the method  158  also includes actuating the lubricator system (e.g.,  10 ,  100 , or  134 ) to a second operational state in which the downhole tool  14  extends within the wellhead  22  at a step  170 , and, after the lubricator system (e.g.,  10 ,  100 , or  134 ) is actuated to the second operational state, pumping fluid into the wellhead  22  to urge the downhole tool  14  through the wellhead  22  toward the wellbore  24  at a step  172 . In some embodiments, the step  170  of actuating the lubricator system (e.g.,  10 ,  100 , or  134 ) to the second operational state includes connecting the conveyance string  30  to the downhole tool  14  so that the conveyance string  30  extends out of the lubricator (e.g.,  16 ,  102 , or  136 ), and sealingly engaging the conveyance string  30  with the sealing cap (e.g.,  76 ,  130 , or  144 ) so that, when the fluid is pumped into the wellhead  22 , the sealing cap holds backpressure of the pumped fluid in the lubricator (e.g.,  16 ,  102 , or  136 ). Finally, the method  158  includes actuating the lubricator system (e.g.,  10 ,  100 , or  134 ) to a third operational state in which the downhole tool  14  extends within the wellbore  24  at a step  174 . 
     In some embodiments, the lubricator system  10 ,  100 , or  134  eliminates the need for a crane to suspend the lubricator (e.g.,  16 ,  102 , or  136 ), thereby decreasing cost, increasing safety, and eliminating downtime usually caused by wind conditions. 
     The present disclosure introduces a method, including connecting a lubricator to a wellhead at the top or head of an oil and gas wellbore, the lubricator defining an internal passage extending along a curvilinear path; and conveying, through the internal passage of the lubricator and along the curvilinear path, a downhole tool in combination with a conveyance string connected to the downhole tool; wherein the lubricator includes a downwardly concave section extending along a first curvilinear axis, the downwardly concave section defining a first portion of the internal passage, and the first curvilinear axis at least partially forming or defining the curvilinear path along which the internal passage extends. In some embodiments, the lubricator further includes an upwardly concave section extending along a second curvilinear axis, the upwardly concave section defining a second portion of the internal passage; and the first and second curvilinear axes at least partially form or define the curvilinear path along which the internal passage extends. In some embodiments, the first curvilinear axis defines a first radius and the second curvilinear axis defines a second radius, the second radius being substantially equal to the first radius. In some embodiments, conveying, through the internal passage of the lubricator and along the curvilinear path, the downhole tool and the conveyance string connected to the downhole tool includes generally aligning the downhole tool with the first curvilinear axis using pivot joints, the pivot joints being interposed between respective portions of the downhole tool. In some embodiments, conveying, through the internal passage of the lubricator and along the curvilinear path, the downhole tool and the conveyance string connected to the downhole tool includes conveying the downhole tool and the conveyance string connected to the downhole tool so that the downhole tool extends within the lubricator. In some embodiments, conveying, through the internal passage of the lubricator and along the curvilinear path, the downhole tool and the conveyance string connected to the downhole tool further includes during or after conveying the downhole tool and the conveyance string connected to the downhole tool so that the downhole tool extends within the lubricator, pumping fluid into the lubricator to urge the downhole tool through the lubricator toward the wellhead. In some embodiments, conveying, through the internal passage of the lubricator and along the curvilinear path, the downhole tool and the conveyance string connected to the downhole tool further includes during or after conveying the downhole tool and the conveyance string connected to the downhole tool so that the downhole tool extends within the lubricator, engaging the downhole tool with a pushrod to urge the downhole tool through the lubricator toward the wellhead. In some embodiments, conveying, through the internal passage of the lubricator and along the curvilinear path, the downhole tool and the conveyance string connected to the downhole tool further includes during or after conveying the downhole tool and the conveyance string connected to the downhole tool so that the downhole tool extends within the lubricator, engaging the downhole tool with one or more rollers of an injector to urge the downhole tool through the lubricator toward the wellhead. In some embodiments, conveying, through the internal passage of the lubricator and along the curvilinear path, the downhole tool and the conveyance string connected to the downhole tool further includes conveying the downhole tool and the conveyance string connected to the downhole tool so that the downhole tool extends within the wellhead; and during or after conveying the downhole tool and the conveyance string connected to the downhole tool so that the downhole tool extends within the wellhead, pumping fluid into the wellhead to urge the downhole tool through the wellhead toward the wellbore. In some embodiments, conveying, through the internal passage of the lubricator and along the curvilinear path, the downhole tool and the conveyance string connected to the downhole tool further includes during or after conveying the downhole tool and the conveyance string connected to the downhole tool so that the downhole tool extends within the wellhead, pumping fluid into the wellhead to urge the downhole tool through the wellhead toward the wellbore. In some embodiments, conveying, through the internal passage of the lubricator and along the curvilinear path, the downhole tool and the conveyance string connected to the downhole tool further includes sealingly engaging the conveyance string with a sealing cap so that, when the fluid is pumped into the wellhead, the sealing cap holds backpressure of the pumped fluid in the lubricator. In some embodiments, conveying, through the internal passage of the lubricator and along the curvilinear path, the downhole tool and the conveyance string connected to the downhole tool further includes conveying the downhole tool and the conveyance string connected to the downhole tool so that the downhole tool extends within the wellbore. In some embodiments, the downhole tool includes: a plug; a setting tool connected to the plug; and a perforating gun connected to the setting tool, the perforating gun including a plurality of perforator segments; a plurality of first pivot joints, each of the first pivot joints being interposed between respective ones of the perforator segments; and a second pivot joint interposed between the setting tool and one of the perforator segments; and wherein conveying, through the internal passage of the lubricator and along the curvilinear path, the downhole tool and the conveyance string connected to the downhole tool includes generally aligning the downhole tool with the first curvilinear axis using the second pivot joint and the plurality of first pivot joints. 
     The present disclosure also introduces a lubricator system, including a lubricator defining an internal passage extending along a curvilinear path, the lubricator being configured to be connected to a wellhead at the top or head of an oil and gas wellbore; a downhole tool; and a conveyance string configured to be connected to the downhole tool; wherein the downhole tool and the conveyance string, in combination, are configured to be conveyed through the internal passage of the lubricator and along the curvilinear path; and wherein the lubricator includes a downwardly concave section extending along a first curvilinear axis, the downwardly concave section defining a first portion of the internal passage, and the first curvilinear axis at least partially forming or defining the curvilinear path along which the internal passage extends. In some embodiments, the lubricator further includes an upwardly concave section extending along a second curvilinear axis, the upwardly concave section defining a second portion of the internal passage; and the first and second curvilinear axes at least partially form or define the curvilinear path along which the internal passage extends. In some embodiments, the first curvilinear axis defines a first radius and the second curvilinear axis defines a second radius, the second radius being substantially equal to the first radius. In some embodiments, the downhole tool includes pivot joints interposed between respective portions thereof to enable general alignment of the downhole tool with the first curvilinear axis when the downhole tool and the conveyance string, in combination, are conveyed through the internal passage of the lubricator and along the curvilinear path. In some embodiments, the lubricator system is actuable to a first operational state in which the downhole tool extends within the lubricator. In some embodiments, in the first operational state, fluid is configured to be pumped into the lubricator to urge the downhole tool through the lubricator toward the wellhead. In some embodiments, in the first operational state, a pushrod is configured to engage the downhole tool to urge the downhole tool through the lubricator toward the wellhead. In some embodiments, the lubricator system further includes an injector, the injector including one or more rollers; wherein, in the first operational state, each of the one or more rollers is configured to engage the downhole tool to urge the downhole tool through the lubricator toward the wellhead. In some embodiments, the lubricator system is actuable to a second operational state in which the downhole tool extends within the wellhead; and the lubricator system is actuable to a third operational state in which the downhole tool extends within the wellbore. In some embodiments, in the second operational state: fluid is configured to be pumped into the wellhead to urge the downhole tool through the wellhead toward the wellbore; and the conveyance string is connected to the downhole tool and extends out of the lubricator, and a sealing cap sealingly engages the conveyance string so that, when the fluid is pumped into the wellhead, the sealing cap holds backpressure of the pumped fluid in the lubricator. In some embodiments, the downhole tool includes: a plug; a setting tool connected to the plug; and a perforating gun connected to the setting tool, the perforating gun including a plurality of perforator segments, a plurality of first pivot joints, each of the first pivot joints being interposed between respective ones of the perforator segments, and a second pivot joint interposed between the setting tool and one of the perforator segments; wherein the second pivot joint and the plurality of first pivot joints are configured to generally align the downhole tool with the first curvilinear axis so that the downhole tool, in combination with the conveyance string, is permitted to be conveyed through the internal passage of the lubricator and along the curvilinear path. 
     The present disclosure also introduces a lubricator system, including a lubricator defining an internal passage extending along a curvilinear path, the lubricator being adapted to be connected to a wellhead at the top or head of an oil and gas wellbore; wherein the lubricator includes a downwardly concave section extending along a first curvilinear axis, the downwardly concave section defining a first portion of the internal passage; wherein the lubricator system is actuable to a first operational state in which a downhole tool and a conveyance string connected thereto extend within the downwardly concave section of the lubricator; and wherein the first portion of the internal passage of the lubricator is configured to permit the downhole tool and the conveyance string connected thereto to extend within the downwardly concave section of the lubricator when the lubricator system is in the first operational state. In some embodiments, the lubricator further includes an upwardly concave section extending along a second curvilinear axis, the upwardly concave section defining a second portion of the internal passage. In some embodiments, in the first operational state: (a) fluid is adapted to be pumped into the lubricator to urge the downhole tool through the lubricator toward the wellhead; (b) a pushrod is adapted to engage the downhole tool to urge the downhole tool through the lubricator toward the wellhead; (c) an injector including one or more rollers is adapted to engage the downhole tool to urge the downhole tool through the lubricator toward the wellhead; or any combination of (a), (b), and (c). In some embodiments, the lubricator system is actuable to: a second operational state in which the downhole tool extends within the wellhead; and a third operational state in which the downhole tool extends within the wellbore. In some embodiments, the lubricator system further includes the downhole tool and the conveyance string connected thereto. In some embodiments, the conveyance string is, or includes, a wireline; wherein the lubricator system further includes a sealing cap adapted to sealingly engage the wireline; and wherein, in the second operational state: fluid is adapted to be pumped into the wellhead to urge the downhole tool through the wellhead toward the wellbore, the wireline extends out of the lubricator, and the sealing cap sealingly engages the wireline so that, when the fluid is pumped into the wellhead, the sealing cap holds backpressure of the pumped fluid in the lubricator. 
     It is understood that variations may be made in the foregoing without departing from the scope of the present disclosure. 
     In some embodiments, the elements and teachings of the various embodiments may be combined in whole or in part in some or all of the embodiments. In addition, one or more of the elements and teachings of the various embodiments may be omitted, at least in part, and/or combined, at least in part, with one or more of the other elements and teachings of the various embodiments. 
     Any spatial references, such as, for example, “upper,” “lower,” “above,” “below,” “between,” “bottom,” “vertical,” “horizontal,” “angular,” “upwards,” “downwards,” “side-to-side,” “left-to-right,” “right-to-left,” “top-to-bottom,” “bottom-to-top,” “top,” “bottom,” “bottom-up,” “top-down,” etc., are for the purpose of illustration only and do not limit the specific orientation or location of the structure described above. 
     In some embodiments, while different steps, processes, and procedures are described as appearing as distinct acts, one or more of the steps, one or more of the processes, and/or one or more of the procedures may also be performed in different orders, simultaneously and/or sequentially. In some embodiments, the steps, processes, and/or procedures may be merged into one or more steps, processes and/or procedures. 
     In some embodiments, one or more of the operational steps in each embodiment may be omitted. Moreover, in some instances, some features of the present disclosure may be employed without a corresponding use of the other features. Moreover, one or more of the above-described embodiments and/or variations may be combined in whole or in part with any one or more of the other above-described embodiments and/or variations. 
     Although some embodiments have been described in detail above, the embodiments described are illustrative only and are not limiting, and those skilled in the art will readily appreciate that many other modifications, changes and/or substitutions are possible in the embodiments without materially departing from the novel teachings and advantages of the present disclosure. Accordingly, all such modifications, changes, and/or substitutions are intended to be included within the scope of this disclosure as defined in the following claims. In the claims, any means-plus-function clauses are intended to cover the structures described herein as performing the recited function and not only structural equivalents, but also equivalent structures. Moreover, it is the express intention of the applicant not to invoke 35 U.S.C. § 112, paragraph 6 for any limitations of any of the claims herein, except for those in which the claim expressly uses the word “means” together with an associated function.