Patent Publication Number: US-11028665-B2

Title: Method and apparatus for hydraulic fracturing

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. application Ser. No. 15/476,561, filed Mar. 31, 2017, entitled “METHOD AND APPARATUS FOR HYDRAULIC FRACTURING,” which is a continuation-in-part of U.S. application Ser. No. 15/152,370, filed May 11, 2016, entitled “FRAC HEAD SYSTEM,” which claims the benefit of U.S. Provisional Application No. 62/188,621, filed Jul. 3, 2015, entitled “FRAC HEAD SYSTEM.” U.S. application Ser. No. 15/476,561 also claims the benefit of U.S. Provisional Application No. 62/317,094, filed Apr. 1, 2016, entitled “METHOD AND APPARATUS FOR HYDRAULIC FRACTURING.” U.S. application Ser. No. 15/476,561, U.S. application Ser. No. 15/152,370, U.S. Provisional Application No. 62/188,621, and U.S. Provisional Application No. 62/317,094 are hereby incorporated by reference in their entirety for all purposes. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates generally to frac heads. 
     BACKGROUND 
     This section is intended to introduce the reader to various aspects of art that may be related to various aspects of the present invention, which are described and/or claimed below. This discussion is believed to be helpful in providing the reader with background information to facilitate a better understanding of the various aspects of the present invention. Accordingly, it should be understood that these statements are to be read in this light, and not as admissions of prior art. 
     Wells are frequently used to extract resources, such as oil and gas, from subterranean reserves. These resources, however, can be difficult to extract because they may flow relatively slowly to the well bore. Frequently, a substantial portion of the resources is separated from the well by bodies of rock and other solid materials. These solid formations impede fluid flow to the well and tend to reduce the well&#39;s rate of production. 
     In order to release more oil and gas from the formation, the well may be hydraulic fractured. Hydraulic fracturing involves pumping a frac fluid that contains a combination of water, chemicals, and proppant (e.g., sand, ceramics) into a well at high pressures. The high pressures of the fluid increases crack size and crack propagation through the rock formation, which releases more oil and gas, while the proppant prevents the cracks from closing once the fluid is depressurized. Unfortunately, the high-pressures and abrasive nature of the frac fluid may wear components. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       These and other features, aspects, and advantages of the present invention will become better understood when the following detailed description is read with reference to the accompanying drawings in which like characters represent like parts throughout the drawings, wherein: 
         FIG. 1  is a block diagram of an embodiment of a hydrocarbon extraction system; 
         FIG. 2  is a cross-sectional view of an embodiment of a frac head system; 
         FIG. 3  is a cross-sectional view of an embodiment of a frac head system; 
         FIG. 4  is a cross-sectional view of an embodiment of an isolation sleeve along line  4 - 4  of  FIG. 3 ; 
         FIG. 5  is a cross-sectional view of an embodiment of an isolation sleeve; 
         FIG. 6  is a cross-sectional view of an embodiment of an isolation sleeve; 
         FIG. 7  is a front view of an embodiment of an isolation sleeve; 
         FIG. 8  is a front view of an embodiment of an isolation sleeve; 
         FIG. 9  is a cross-sectional view of an embodiment of a frac head system; 
         FIG. 10  is a cross-sectional view of an embodiment of a frac head system; 
         FIG. 11  is a cross-sectional view of an embodiment of a frac head system; 
         FIG. 12  is a schematic diagram showing insertion of a tool during a multi-stage fracking operation, in accordance with one embodiment of the present disclosure; 
         FIG. 13  is a schematic diagram showing withdrawal of the tool of  FIG. 1  during the multi-stage fracking operation, in accordance with one embodiment of the present disclosure; and 
         FIG. 14  is a cross-sectional schematic of an isolation sleeve inserted within a goathead to at least partially protect a wireline, in accordance with one embodiment of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS 
     One or more specific embodiments of the present invention will be described below. In an effort to provide a concise description of these embodiments, all features of an actual implementation may not be described in the specification. It should be appreciated that in the development of any such actual implementation, as in any engineering or design project, numerous implementation-specific decisions must be made to achieve the developers&#39; specific goals, such as compliance with system-related and business-related constraints, which may vary from one implementation to another. Moreover, it should be appreciated that such a development effort might be complex and time consuming, but would nevertheless be a routine undertaking of design, fabrication, and manufacture for those of ordinary skill having the benefit of this disclosure. 
     When introducing elements of various embodiments of the present invention, the articles “a,” “an,” “the,” “said,” and the like, are intended to mean that there are one or more of the elements. The terms “comprising,” “including,” “having,” and the like are intended to be inclusive and mean that there may be additional elements other than the listed elements. Moreover, the use of “top,” “bottom,” “above,” “below,” and variations of these terms is made for convenience, but does not require any particular orientation of the components. 
     The present embodiments disclose a frac head system with an isolation sleeve that protects a tubing during hydraulic fracturing operations. As will be explained below, some hydraulic fracturing operation may use a downhole tool controlled by a tubing that aligns the downhole tool with a natural resource formation. For example, the tubing may push and/or pull the downhole tool through a wellbore. Once the downhole tool is aligned with the formation, the downhole tool plugs the wellbore and cuts through a casing that lines the wellbore. Frac fluid may then be pumped into the wellbore to hydraulically fracture the formation. As frac fluid is pumped into the frac head it may flow at high velocities. As explained above, frac fluid contains abrasive materials that can wear components. In order to protect the tubing from frac fluid moving at high velocities, the frac head system includes an isolation sleeve in a frac head. As will be explained below, the isolation sleeve may have wear resistant features that increase the durability of the isolation sleeve. Furthermore, in the event that a portion of the isolation sleeve separates from the rest of the isolation sleeve, the isolation sleeve and frac head may block those portions that separate from entering the wellbore. 
       FIG. 1  is a block diagram that illustrates an embodiment of a hydrocarbon extraction system  10  capable of hydraulically fracturing a well  12  to extract various minerals and natural resources (e.g., oil and/or natural gas). The system  10  includes a frac tree  14  coupled to the well  12  via a wellhead hub  16 . The wellhead hub  16  generally includes a large diameter hub disposed at the termination of a well bore  18  and is designed to connect the frac tree  14  to the well  12 . The frac tree  14  may include multiple components such as valves  20  and a frac head system  22  that enable and control fluid flow into and out of the well  12 . For example, the frac tree  14  may route oil and natural gas from the well  12 , regulate pressure in the well  12 , and inject chemicals into the well  12 . 
     As illustrated, the well  12  may have multiple formations  24  at different points. In order to access each of these formations (e.g., hydraulically fracture) in a single run, the hydrocarbon extraction system may use a downhole tool  26  coupled to a tubing  28  (e.g., coiled tubing, conveyance tubing). In operation, the tubing  28  pushes and pulls the downhole tool  26  through the well  12  to align the downhole tool  26  with each of the formations  24 . Once the tool  26  is in position, the tool  26  prepares the formation to be hydraulically fractured by plugging the well  12  and boring through the casing  30 . For example, the tubing  28  may carry a pressurized cutting fluid  27  that exits the downhole tool  26  through cutting ports  29 . After boring through the casing  30 , the hydrocarbon extraction system  10  pumps frac fluid  31  (e.g., a combination of water, proppant, and chemicals) through conduits  32  and into the frac head system  22 . The frac head system  22  guides the frac fluid  31  into a bore  34  in the frac tree  14 , which then conduits the frac fluid  31  into the well bore  18 . As will be explained in detail below, the frac head system  22  protects (e.g., reduces wear) the tubing  28  from the frac fluid  31  as it enters the bore  34 . 
     As the frac fluid  31  pressurizes the well  12 , above the downhole tool  26 , the frac fluid  31  fractures the formations  24  releasing oil and/or natural gas by propagating and increasing the size of cracks  36 . Once the formation  24  is hydraulically fractured, the hydrocarbon extraction system  10  depressurizes the well  12  by reducing the pressure of the frac fluid  31  and/or releasing frac fluid  31  through some of the valves  20  (e.g., wing valves). For example, the valves  20  may open enabling frac fluid  31  to exit the frac tree  14  through the conduits  38 . The hydrocarbon extraction system  10  may then repeat the process by moving the downhole tool  26  to the next formation  24  with the tubing  28 . 
       FIG. 2  is a cross-sectional view of an embodiment of a frac head system  22 . In some embodiments, the frac head system  22  includes a frac head  60  (colloquially called a goat&#39;s head), an isolation sleeve  62 , and an adapter spool  64 . As illustrated, the isolation sleeve  62  rests within a bore  66  of the frac head  60 . The bore  66  forms part of the bore  34  that enables the tubing  28  to extend through the frac tree  14  and into the well  12 . The bore  66  in turn fluidly communicates with one or more frac passages  68  (e.g., 1, 2, 3, 4, or more) that enable frac fluid  31  to be pumped into the frac head  60  through connectors  70 . The connectors  70  in turn couple to the conduits  32 , seen in  FIG. 1 , that carry frac fluid  31  from a frac source. As the frac fluid  31  passes through the frac passages  68  and enters the bore  66 , the frac fluid  31  may increase in velocity because of the pressure differential between the pressure of the frac fluid  31  in the frac passages  68  and the pressure in the bore  66 . For example, there may limited space  72  between the tubing  28  and the outlets  76  of the frac passages  68 . Accordingly, the frac head system  22  includes the isolation sleeve  62  to protect the tubing  28  from wear caused by frac fluid  31  entering the bore  66 . 
     As illustrated, the isolation sleeve  62  rests in the bore  66  and includes a passage  78  (e.g., tubing bore) that enables the tubing  28  to pass through the frac head system  22 . The isolation sleeve  62  may be held in place using threads, bolts, and/or a flange  80 . For example, the flange  80  may extend over a top surface  82  of the frac head  60  blocking axial movement of the isolation sleeve  62  in direction  64 . In order to block axial movement in direction  86 , the frac head system  22  may include the adapter spool  64  that bolts to the frac head  60 . The adapter spool  64  includes a counterbore  88  that receives the flange  80  and blocks axial movement of the isolation sleeve  62  in axial direction  86 . In some embodiments, the isolation sleeve  62  may include threads  90  in a top portion  94  that couple to threads  96  in the adapter spool  64 . In addition to retaining the isolation sleeve  62  in the frac head  60 , the adapter spool  64  enables additional components of the hydrocarbon extraction system  10  to couple to the frac tree  14 . For example, the adapter spool  64  may enable a blowout preventer (BOP), gate valve, lubricator, crossover, side door stripper, and injector head to couple to the frac tree  14 . 
     In operation, the isolation sleeve  62  blocks wear of the tubing  28  by extending over a portion of the tubing  28 . More specifically, the isolation sleeve  62  includes a portion  98  (e.g., protection portion) that extends over the outlets  76  of the frac passages  68 . The portion  98  blocks direct contact between the frac fluid  31  and the tubing  28  as the frac fluid  31  exits the frac passages  68 . In this way, the isolation sleeve  62  reduces wear of the tubing  28  during hydraulic fracturing operations. Furthermore, the portion  98  may have a uniform thickness  100 ; instead of being tapered. By including a uniform thickness instead a tapered thickness the isolation sleeve  62  blocks or reduces opportunities for parts of the isolation sleeve  62  to wear and separate from the isolation sleeve  62 . 
       FIG. 3  is a cross-sectional view of an embodiment of a frac head system  22  with an isolation sleeve  62 . The isolation sleeve  62  includes a first portion  110 , a middle or second portion  112  (e.g., protection portion), and a third portion  114 . As illustrated, the middle portion  112  extends over the outlets  76  of the frac passages  68  to block direct contact between the frac fluid  31  and the tubing  28  as the frac fluid  31  exits the frac passages  68 . In this way, the isolation sleeve  62  reduces wear on the tubing  28  during hydraulic fracturing operations. However, overtime the frac fluid  31  may wear the middle portion  112  of the isolation sleeve  62  enabling frac fluid  31  to pass through the isolation sleeve  62  and/or enabling the first portion  110  to separate from the rest of the isolation sleeve  62 . In order to monitor wear of the middle portion  112 , the middle portion  112  may include one or more wear indicators  116  (e.g., grooves). The wear indicator  116  enables a user to monitor wear and thus replace the isolation sleeve  62  when the isolation sleeve  62  reaches a wear threshold. Moreover, in some embodiments, the isolation sleeve  62  may include one or more protrusions  118  (e.g., 1, 2, 3, 4, or more) that extend radially from the first portion  110 . These protrusions  118  may rest on corresponding ledges  120  (e.g., landings, circumferential lip) of the frac head  60  that extend radially inward into the bore  66 . In operation, the ledges or landings  120  may act as a failsafe that blocks the lower portion  110  from falling into the well  12  if the lower portion  110  separates from the middle portion  112  during use. 
     As illustrated, the isolation sleeve  62  may couple to the frac head  60  with the third portion  114 . For example, the third portion  114  may include threads  122  that threadingly engage threads  124  on the frac head  124 . In some embodiments, the third portion  114  may include a lip  126  (e.g., circumferential) that rests on a landing  128  (e.g., circumferential) of the frac head  60  to block axial movement of the isolation sleeve  62  in axial direction  84 . In still other embodiments, the isolation sleeve  62  may include both the threads  122  and the lip  162 . In order to block fluid flow around the isolation sleeve  62  in axial direction  86 , the isolation sleeve  62  and/or frac head  60  may include seals  134  (e.g., circumferential) that rest within grooves  136  (e.g., circumferential). 
       FIG. 4  is a cross-sectional view of an embodiment of an isolation sleeve along line  4 - 4  of  FIG. 3 . As illustrated, the isolation sleeve  62  includes multiple protrusions  118  that extend radially outward to form flutes or passages  160  that enable frac fluid  31  to flow between the frac head  60  and an outer surface  162  of the isolation sleeve. As explained above, the isolation sleeve  62  may include one or more of these protrusions  118  (e.g., 1, 2, 3, 4, or more). For example, the frac head  60  may include multiple frac fluid passages  68 , and each of these frac fluid passages  68  may direct fluid flow into a respective flute  160 . Moreover, in order to monitor wear from frac fluid  31  flowing through separate frac fluid passages  68 , the isolation sleeve  62  may have a corresponding wear indicator  116 . The different wear indicators  116  may enable detection of varying wear of the isolation sleeve  62  about the circumference  164 . This information may enable adjustment of the hydrocarbon extraction system  10  ensuring that the frac fluid  31  is pumped through each of the frac passages  68  in substantially equal amounts and with substantially equal pressures. 
       FIG. 5  is a cross-sectional view of an embodiment of an isolation sleeve  62 . In some embodiments, the isolation sleeve  62  may include coatings that reduce wear and friction during fracing operations. For example, the outer surface  162  of the isolation sleeve  62  may include a wear resistant coating (e.g., tungsten carbide) and/or be treated with a surface treatment  180  (e.g., shot peening). In operation, the wear resistance coating and/or treatment  180  (e.g., wear resistance feature) increases the wear resistance of the isolation sleeve  62  against the flow of frac fluid  31 . In some embodiments, the interior surface  182  may also include a coating  184  (e.g., coating and/or surface treatment). However, instead of a wear resistance coating or treatment the interior coating  184  may be a friction reducing coating and/or treatment that facilitates movement of the tubing  28  through the passage  78 . The interior surface  182  may also include a curved or angled edge  186  (e.g., circumferential) that guides the tubing  28  into and through the passage  78 . 
     In some embodiments, the isolation sleeve  62  may enable coupling to the frac head  60  using fasteners (e.g., bolts, screws, etc.). For example, the isolation sleeve  62  may include radial apertures  188  in the first portion  110  that enable the first portion  110  to couple to the frac head  60  or another component in the frac tree  14  (e.g., a spool, valve, etc,) with fasteners. In order to protect the fasteners from frac fluid  31 , the first portion  110  may include seals  192  that rest in grooves  190  that extend circumferentially about apertures  188 . In some embodiments, the apertures  188  may include a retaining ring groove  194  that receives a retaining ring (e.g., snap ring, c-ring). In operation, the retaining rings block removal of the fasteners. Similarly, the third portion  114  may include apertures  188  that enable the isolation sleeve  62  to couple to the frac head  60  or another component in the frac tree  14  (e.g., a spool, valve, etc,). Accordingly, the isolation sleeve  60  may be secured to the frac head  60  and/or other components of the frac tree  14  using the first portion  110  and/or the third portion  114 . 
       FIG. 6  is a cross-sectional view of an embodiment of an isolation sleeve  62 . As explained above, the frac fluid  31  exits the frac passages  68  and directly contacts the second portion  112  of the isolation sleeve  62 . In this way, the second portion  112  may experience the greatest wear of the three portions  110 ,  112 , and  114 . To compensate for this wear, the second or middle portion  112  may include a frac fluid  31  contact portion  210  (e.g., wear resistance feature) that has a width  212  that is greater than a width  214  of the remaining second portion  114 . Accordingly, the portion  210  may increase the life of the isolation sleeve  62  during fracing operations. In some embodiments, the frac fluid  31  contact portion  210  may include wear indicators  116  (e.g., grooves) that enable a user to visually determine the amount of wear experienced by the isolation sleeve  62 . 
       FIG. 7  is a front view of an embodiment of an isolation sleeve  62 . As illustrated, the second portion  112  of the isolation sleeve  62  may include a flow feature  230  (e.g., wear resistance feature). The flow feature  230  may include helical grooves and/or helical protrusions  232  that wrap around the second portion  112 . In operation, the flow feature  230  may increase wear resistance by channeling (e.g., swirling) the frac fluid  31  around the isolation sleeve  62  to reduce direct impact between the frac fluid  31  and the isolation sleeve  62 . 
       FIG. 8  is a front view of an embodiment of an isolation sleeve  62 . As illustrated, the isolation sleeve  62  may include a plurality of apertures  240  that enable frac fluid  31  to flow through the isolation sleeve  62  and into the passage  78 . As frac fluid  31  enters the passage  78  and more quickly fills the annular space between the tubing  28  and the isolation sleeve  62 , the isolation sleeve  62  may reduce the boost pressure (e.g., stress) acting on the second and third portions  112  of the isolation sleeve  62 . 
       FIG. 9  is a cross-sectional view of an embodiment of a frac head system  22 . As illustrated, the frac head  60  and isolation sleeve  62  are one-piece (e.g., integral or formed into a single integral, gaplessly continuous piece). For example, the frac head  60  may be cast as one-piece, machined as one-piece, and/or produced using additive manufacturing processes. By producing the frac head system  22  as one piece, the frac head system  22  may avoid connecting and sealing issues between the isolation sleeve  62  and the frac head  60 . As shown, one or more seal grooves  242  (e.g., circumferential) are provided in the one-piece frac head  60  and isolation sleeve  62 . For example, the seal grooves  242  may circumferentially surround apertures of the one or more frac passages  68  and may be configured to receive a seal (e.g., circumferential). In the illustrated embodiment, a portion  244  (e.g., a lower portion) of the isolation sleeve  62  is positioned within the corresponding seal groove  242 . 
       FIG. 10  is a cross-sectional view of an embodiment of a frac head system  22  with an isolation sleeve  62 . In the illustrated embodiment, the frac passages  68  are generally orthogonal to the bore  66  of the frac head  60  and the tubing  28 . As shown, the middle portion  112  of the isolation sleeve  62  extends over the outlets  76  of the frac passages  68  to block direct contact between the frac fluid  31  and the tubing  28  as the frac fluid  31  exits the frac passages  68 . 
       FIG. 11  is a cross-sectional view of an embodiment of a frac head system  22 . As illustrated, the frac head  60  and isolation sleeve  62  are one-piece, and the frac passages  68  are generally orthogonal to the bore  66  of the frac head  60  and the tubing  28 . The various features disclosed herein may be combined in any suitable manner. For example, the frac head systems  22  illustrated in  FIGS. 10 and 11  may include any of the features described above with respect to  FIGS. 1-9 . 
     As noted above, to meet consumer and industrial demand for natural resources, companies often invest significant amounts of time and money in finding and extracting hydrocarbons (like oil and natural gas) and other subterranean resources from the earth. Particularly, once a desired subterranean reservoir containing hydrocarbons is discovered, drilling and production systems are often employed to drill and complete a well and to access and extract those hydrocarbons, which are typically found within a particular strata or layer of the earth&#39;s surface. These systems may be located onshore or offshore depending on the hydrocarbon reservoir&#39;s location. 
     As noted above, fracking is a process for improving reservoir yield. In short, fracking comprises injecting a stimulant (often a water and sand proppant slurry) at high pressure into the well and reservoir. The pressurized proppant creates fissures (fractures) within the formation defining the reservoir, stimulating the flow of subterranean hydrocarbons up through the well and, ultimately, to the surface for collection. 
     As noted above, a single well may be “fracked” at multiple locations or stages. One type of multi-stage fracking is called “plug-and-perf” fracking—in which a series of consecutively installed plugs segregate the well into isolated zones, and a perforating gun perforates the well in each zone, giving the well access to the reservoir. For example, once a well is drilled and the production casing is cemented in place, a perforating gun carrying a plug is lowered into the well via a wireline. Firing the gun sets the plug in the well and then perforates the production casing and surrounding cement, providing a flow path from the reservoir into the well. The wireline and perforating gun are then completely removed from the well. Following that, fracking proppant pumped down at high pressure into the well flows into the reservoir through the perforations punched into the well, to fracture the reservoir. Once fracking of a stage is complete, the process is repeated by plugging and perforating the next stage, which is at a higher location in the well. Installation and complete removal of the perforating gun can be a time consuming process, both of which are completed before the introduction of proppant for each stage begins. 
     Certain embodiments of the present disclosure generally relate to apparatus and methods for retrieving a downhole tool via a conveyance string during a fracking operation. For example, in one embodiment, a plug-and-perf assembly may be retrieved via a conveyance string (e.g., a wireline, coiled tubing, segmented tubing, coated wireline, or the like) concurrently with the fracking proppant (e.g., a fluid, which may include water, chemicals, and/or a proppant, such as sand or ceramics) being pumped into the well. The conveyance string may be partially shielded from the proppant by a sleeve (e.g., annular sleeve) disposed inside a goathead (e.g., frac head) receiving the pressurized proppant. That is, the conveyance string extending vertically through the goathead may be damaged by proppant entering the goathead in at least a partial horizontal direction. The sleeve, however, shields the conveyance string from this pressurized proppant, limiting damage to the conveyance string while it remains in the well as the proppant is injected. Advantageously, this is believed to reduce the operating time for performing a fracking operation (e.g., multi-stage or single-stage fracking operation), as the proppant can be injected while the perforating gun and conveyance string are being “pulled-out-of-hole” and/or reset for the next stage. 
     While certain embodiments are discussed with reference to a fracking proppant to facilitate discussion, as noted above, it should be appreciated that the system and method may be used with any type of fluid, including any suitable well stimulation fluid with or without proppant, such as water, water with a gel or lubricant, or an acidic fluid (e.g., corrosive fluid that may increase porosity and/or permeability of rock). For example, the sleeve may shield the conveyance string from an acidic fluid that is provided through the goathead to a location below a reservoir rock fracture gradient to avoid fracture of the rock or to a location above the reservoir rock fracture gradient to create fractures to facilitate hydrocarbon flow and extraction. For example, the sleeve may shield the conveyance string from a chemical diverter or diverting agent that may be provided through the goathead to plug or seal (e.g., temporarily block fluid flow through) existing perforations in the casing. The chemical diverter may include any suitable material that is configured to plug the existing perforations and then to degrade over time and/or due to temperature and/or to dissolve in water and/or during oil production, for example. Furthermore, while certain embodiments are discussed with reference to a wireline to facilitate discussion, as noted above, it should be appreciated that the system and method may be used with any suitable conveyance string, including a wireline, a coiled tubing, a segmented tubular, a wireline coated in a friction-reducing material (e.g., having a polytetrafluoroethylene [PTFE] sheath), or the like. Furthermore, while certain embodiments are discussed with reference to multi-stage fracking to facilitate discussion, as noted above, it should be appreciated that the system and method may be used in single-stage fracking operations. Furthermore, while certain embodiments are discussed with reference to a downhole tool that includes a perforating gun to facilitate discussion, it should be appreciated that the system and method may be used with any suitable downhole tool, including sensors configured to monitor conditions within the well (e.g., pressure sensors configured to monitor pressure, temperature sensors configured to monitor temperature, image sensors configured to obtain an image of the well, and/or any of a variety of sensors [e.g., chemical, acoustic, optical, capacitive, or the like) configured to monitor characteristics [e.g., chemical composition, density, or the like) of fluid within the well, or the like). Thus, the disclosed system and method may use the sleeve to shield any of a variety of conveyance strings supporting any of a variety of downhole tools from any fluid that is provided through the goathead, thereby enabling use and/or movement (e.g., insertion or withdrawal) of the downhole tool as the fluid is provided through the goathead, such as during multi-stage or single-stage fracking operations, for example. 
     Turning now to the present figures,  FIGS. 12 and 13  illustrate a fracking system  300  for a well  312 , in accordance with one embodiment. In particular,  FIG. 12  is a schematic diagram showing insertion of a tool  310  (e.g., downhole tool or tool assembly having a perforating gun, plug, sensors, or the like) during a multi-stage fracking operation, and  FIG. 13  is a schematic diagram showing withdrawal of the tool  310  during a multi-stage fracking operation. As shown, the well  312  has a vertical leg  314  that extends to a subterranean reservoir  316  that, as illustrated, has a much greater horizontal length than vertical depth. To maximize reservoir yield, the well  312  also has a horizontal leg  318 , which may extend for thousands of feet. Indeed, the well  312  may have any number of constructions, including the construction shown in  FIG. 1 , for example, depending on the geological formation, and need not be limited to directly vertical, horizontal, or linear legs. 
     The illustrated well  312  may be formed by drilling a wellbore and then lining that wellbore with a production casing  320  (e.g., annular casing). A layer of cement  322  is then added to seal the annular space between the exterior surface of the production casing  320  and the earthen walls of the wellbore. 
     At the surface, an exemplary wellhead assembly  324  facilitates and controls ingress and egress to the well  312 . In the illustrated embodiment, one or more spool bodies  326  (e.g., a casing head, tubing head, casing spool, or tubing spool) are provided to support various casing or tubing strings that may extend into the well  312 . 
     The wellhead assembly  324  includes a number of components to control the insertion of fracking proppant (e.g., a fluid, which may include water, chemicals, and/or a proppant, such as sand or ceramics) into the well  312 , the components and spool bodies  326  cooperating to form a wellhead bore  325  that aligns with the entrance of the well  312 . For example, a frac valve  328 —which may be any number of types of valves, including ball valves, gate valves, for example—is coupled to the spool bodies  326  and can be used to isolate the well  312  from a pressurized-proppant source  329 , and vice versa. The wellhead assembly  324  also includes a goathead  330  (e.g., a frac head) that can be used to merge pressurized proppant from multiple sources  329  and direct the pressurized proppant into the wellhead bore  325  and the well  312 . 
     However, before the proppant is injected into the well  312 , the well  312  may be perforated. As shown in  FIG. 13 , perforations  332  (e.g., holes) are punched into the casing  320  and surrounding cement  322 , creating a fluid pathway between the well  312  and the reservoir  316 . This can be accomplished, for example, with the tool  310 , which may have a perforating gun  333  carried by a setting tool  334  and a wireline  336  (e.g., conveyance string). In the illustrated embodiment, a wireline source  338  feeds wireline  336 , which may be thousands of feet long, into the well  312 . The wireline  336  is a conveyance tool that can send electrical, acoustic, optical or mechanical signals to activate/operate the attached setting tool  334  and perforating gun  333 , for example. The system  300  may include a supported pulley  340  that guides the wireline  336  through a top valve  342  of the wellhead assembly  324 . 
     In operation, the tool  310  may be lowered into the well  312 , as shown by arrow  337  in  FIG. 12 . In some embodiments, to drive the setting tool  334  downhole into the well  312 , fluid, generally just above wellbore pressure is pumped into the well  312 . This carries the setting tool  334  down to a desired location in the well  312 . Once the desired location is reached, the wireline  336  is prevented (e.g., blocked) from further unspooling, fixing the location of the setting tool  334  within the well  312 . 
     At this point, a signal providing operating instructions is sent from the surface to the setting tool  334  via the wireline  336 . By way of example, the signal may instruct a plug  344  (e.g., radially-expandable plug) coupled to the setting tool  334  to expand and set to seal off the well  312  below it (e.g., downstream of the plug  344 ). The signal may also trigger the perforating gun  333 , causing explosively charged projectiles to puncture or punch through the casing  320  and surrounding cement  322 , creating the perforations  332  that permit fluid to flow between the reservoir  316  and the well  312 , as shown in  FIG. 13 . 
     In certain traditional systems, the wireline  336  and the setting tool  334  undergo a “pull-out-of-hole” operation—i.e., the wireline  336  and setting tool  334  are retrieved (e.g., fully removed or withdrawn) out of the well  312 —after formation of the perforations  332  and before fracking proppant is introduced into the well  312 . But retrieval can be a time consuming process, as there may be thousands of feet of wireline  336  in the well  312 . In such traditional systems, once the wireline  336  and setting tool  334  are retrieved, fracking proppant is pressurized at the source  329 , sent to the goathead  330 , and directed into the well  312  and through the perforations  332  to create fissures  346  in the formation. In such traditional systems, the process (i.e., inserting the tool  310 , placing the plug  344 , creating the perforations  332 , completely retrieving the tool  310 , and subsequently providing the proppant) may then be repeated for each stage (e.g., location within the well  312 )  334 . However, the plug  344  is set and perforations  332  are punched at a higher point in the well  312  each time—the more recently set plug  344  isolating the previously fracked section or stage below it. 
     The exemplary embodiment, however, facilitates withdrawal or retrieval of the wireline  336  and the setting tool  334 , as shown by arrow  345  in  FIG. 13 , concurrently (e.g., simultaneously or at the same time) with injection of fracking proppant into the well  312 , as shown by arrow  347  in  FIG. 13 . For example, the wireline  336  and the setting tool  334  are pumped (e.g., driven), typically at a relatively low pressure, down to the desired location, and a signal is sent to fire the perforating gun  333  and to set the plug  344 . However, the fracking proppant may be injected into the well  312  before the pull-out-of-hole operation for the wireline  336  and the setting tool  334  is complete—that is, while the setting tool  334  and the wireline  336  are still in the well  312  (e.g., positioned within and/or moving within the well  312 ). In some embodiments, as shown in  FIG. 13 , respective plugs  344  may be set and respective perforations  332  may be created at multiple stages using the disclosed techniques. This is believed to save considerable time and reduce the cost of operating equipment and/or personnel necessary to complete the fracking operation (e.g., single-stage or multi-stage fracking operation). 
       FIG. 14  illustrates an exemplary device that facilitates this concurrent operation. Specifically,  FIG. 14  illustrates an embodiment of a goathead assembly  31  (e.g., frac head system) having the goathead  330  with a series of inlets  348  that receive pressurized proppant from the proppant source  329 . The illustrated inlets  348  are arranged at a 45 degree angle (e.g., relative to a central or axial axis of the wellhead bore  325 ), but other arrangements, including completely horizontal arrangements (e.g., perpendicular to a central or axial axis of the wellhead bore  325 ), are envisaged. The inlets  348  provide passageways for the pressurized proppant to enter the wellhead bore  325  of the wellhead assembly  324 . As shown, the goathead assembly  331  also includes an adapter spool  227  and connectors  335  that are configured to couple to conduits that extend to the proppant source  329 . 
     Pressurized proppant exiting the inlets  348  to go downhole into the well  312  impact an isolation sleeve  350  (e.g., annular sleeve) surrounding (e.g., circumferentially surrounding) at least a portion of the wireline  336 . This protects the wireline  336  from the abrasive turbulence caused by the insertion of the proppant into the goathead  330 —abrasive turbulence which increases the chances of shearing or otherwise damaging the wireline  336 . The wireline  336  is exposed to the proppant below this isolation sleeve  350 ; however, it is believed that this proppant will have a more laminar flow and, thus, be less likely to damage the wireline  336 . Indeed, the proppant exiting the inlets  348  is at a relatively high-velocity. By shielding the wireline  336  from the proppant as it introduced into the wellhead bore  325 , the wireline  336  can remain in the well  312  and be retrieved while fracking proppant is injected into the well  312 . 
     Retrieval of the wireline  336  concurrent with injecting of fracking proppant is believed to provide a number of advantages. For example, it reduces the time between when the perforations  332  are made and fracking proppant is injected into the well  312 , decreasing the likelihood of unwanted perforation closure that could damage the well  312 . It also increases the number of fracking stages that can be completed in a day, which can reduce the number of days necessary for the fracking operations and, in turn, reduce the operating costs for performing the fracking. Put simply, it allows the injection of fracking proppant into the well  312  at a relatively short time after a given stage of the well  312  has been plugged and perforated. 
     The isolation sleeve  350  may be a separate, retrievable piece (e.g., coupled to and/or held in place relative to the goathead  330  via fasteners, threads, flanges, or the like), or it may be integrated into the goathead  330  (e.g., integrally formed with the goathead  330 , thereby forming a one-piece structure), or other spool body that is the inlet for the fracking proppant. It should be appreciated that the isolation sleeve  350  and the goathead  330  may have any of a variety of configurations that enable the isolation sleeve  350  to block contact between the proppant flowing into the wellhead bore  325  and the wireline  336  and/or to facilitate injection of fluid to drive the downhole tool  310  into the well  312  and/or injection of the proppant while the wireline  336  is positioned within and/or moves through the wellhead bore  325 . 
     Various refinements of the features noted above may exist in relation to various aspects of the present embodiments. Further features may also be incorporated in these various aspects as well. These refinements and additional features may exist individually or in any combination. For instance, various features discussed below in relation to one or more of the illustrated embodiments may be incorporated into any of the above-described aspects of the present disclosure alone or in any combination. For example, the frac head  60  and the isolation sleeve  62 , as well as any other components shown and described with respect to  FIGS. 1-11 , may be utilized in combination with the components and the techniques described with respect to  FIGS. 12-14 . For example, it should be understood that the goathead assembly  31  may have any of the features of the frac head system  22  illustrated in  FIGS. 1-11 , and the sleeve  350  illustrated in  FIGS. 12-14  may have any of the features of the isolation sleeve  62  illustrated in  FIGS. 2-11 . Again, the brief summary presented above is intended only to familiarize the reader with certain aspects and contexts of some embodiments without limitation to the claimed subject matter. 
     While the aspects of the present disclosure may be susceptible to various modifications and alternative forms, specific embodiments have been shown by way of example in the drawings and have been described in detail herein. But it should be understood that the invention is not intended to be limited to the particular forms disclosed. Rather, the invention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention as defined by the following appended claims.