Patent Publication Number: US-10316609-B2

Title: Ball launcher with pilot ball

Description:
BACKGROUND 
     This section is intended to introduce the reader to various aspects of art that may be related to various aspects of the presently described embodiments. 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 embodiments. Accordingly, it should be understood that these statements are to be read in this light, and not as admissions of prior art. 
     In order to meet consumer and industrial demand for natural resources, companies often invest significant amounts of time and money in finding and extracting oil, natural gas, and other subterranean resources from the earth. Particularly, once a desired subterranean resource such as oil or natural gas is discovered, drilling and production systems are often employed to access and extract the resource. These systems may be located onshore or offshore depending on the location of a desired resource. Further, such systems generally include a wellhead assembly through which the resource is accessed or extracted. These wellhead assemblies may include a wide variety of components, such as casing heads, tubing heads, valves, and other connected components, that facilitate drilling or extraction operations. 
     In some instances, balls (e.g., frac balls used for fracturing operations) are used in wells to actuate downhole components, to seal the wells, or to carry out other functions. These balls are often pumped down wells with pressurized fluids (e.g., fracturing fluid) to perform their intended functions. Pressure at the wellhead can then be lowered so that pressurized fluid in the wellbore returns the balls to the surface. 
     SUMMARY 
     Certain aspects of some embodiments disclosed herein are set forth below. It should be understood that these aspects are presented merely to provide the reader with a brief summary of certain forms the invention might take and that these aspects are not intended to limit the scope of the invention. Indeed, the invention may encompass a variety of aspects that may not be set forth below. 
     Some embodiments of the present disclosure generally relate to systems for introducing balls into wells. Such systems can include a ball launcher coupled to a wellhead assembly, and balls can be loaded into the ball launcher and then introduced into a well through the wellhead assembly. In certain embodiments, the ball launcher includes a fluid conduit that extends laterally away from a wellhead assembly and a pilot ball positioned in the fluid conduit. A drop ball smaller than the pilot ball can be inserted into the fluid conduit at a location between the wellhead assembly and the pilot ball. Pressurized fluid can then be routed into the fluid conduit to push the pilot ball toward the wellhead assembly, causing the pilot ball to drive the smaller drop ball toward the wellhead assembly as well. A stop or other obstruction along the travel path of the drop ball prevents the pilot ball from falling into a central bore of the wellhead assembly, while allowing forward momentum of the smaller drop ball to carry it into the central bore of the wellhead assembly. The pilot ball can then be returned away from the stop through the fluid conduit to prepare for launch of an additional drop ball. Further, in some embodiments the drop ball is inserted into the fluid conduit of the ball launcher at a lower elevation (e.g., by an operator standing at ground level) than the point at which the drop ball is routed into the wellhead assembly. 
     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. Again, the brief summary presented above is intended only to familiarize the reader with certain aspects and contexts of the some embodiments without limitation to the claimed subject matter. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       These and other features, aspects, and advantages of certain embodiments 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 representing an apparatus including a ball launcher connected to a wellhead assembly in accordance with an embodiment of the present disclosure; 
         FIG. 2  schematically depicts the use of balls dropped into a well to seal portions of the well in accordance with one embodiment; 
         FIG. 3  is an elevational view of a ball launcher coupled to a wellhead assembly, the ball launcher including a fluid conduit for routing drop balls into the wellhead assembly, in accordance with one embodiment; 
         FIG. 4  generally depicts introduction of a drop ball into the fluid conduit of the ball launcher of  FIG. 3  and a pilot ball for driving the drop ball through the fluid conduit toward the wellhead assembly in accordance with one embodiment; 
         FIG. 5  depicts an end of the fluid conduit of  FIG. 3  coupled to a fracturing tree of the wellhead assembly in accordance with one embodiment; 
         FIG. 6  is a cross-section of a portion of the apparatus depicted in  FIG. 5  and shows an obstruction in the fluid conduit that stops movement of the pilot ball of  FIG. 3  while allowing a drop ball to pass and enter into a central bore of the wellhead assembly; and 
         FIG. 7  depicts a pair of ball catchers for receiving, through a fluid conduit of a ball launcher, drop balls returning from a well in accordance with one embodiment. 
     
    
    
     DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS 
     One or more specific embodiments of the present disclosure 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, the articles “a,” “an,” “the,” and “said” are intended to mean that there are one or more of the elements. The terms “comprising,” “including,” and “having” are intended to be inclusive and mean that there may be additional elements other than the listed elements. Moreover, any use of “top,” “bottom,” “above,” “below,” other directional terms, and variations of these terms is made for convenience, but does not require any particular orientation of the components. 
     Turning now to the present figures, a well system  10  is generally depicted in  FIG. 1  in accordance with one embodiment. Notably, the system  10  facilitates production of a resource, such as oil or natural gas, from a well  12 . As depicted, the system  10  includes a wellhead assembly having a wellhead  14  installed at the well  12 . The wellhead  14  can include various components, such as one or more casing heads or tubing heads installed above various casing or tubing in the well  12 . In certain embodiments, the well  12  is a surface well accessed through equipment of wellhead  14  installed at surface level (e.g., on the ground). But the well  12  could take other forms, such as an offshore platform well. 
     The wellhead assembly also includes a fracturing tree  16  coupled to the wellhead  14  for fracturing the well  12  and enhancing production. By way of example, resources such as oil and natural gas are generally extracted from fissures or other cavities formed in various subterranean formations. The well  12  can penetrate a resource-bearing formation and be subjected to a fracturing process that creates man-made fractures in the formation. This facilitates coupling of pre-existing fissures and cavities, allowing fluids in the formation to flow into the well  12 . For instance, in hydraulic fracturing, a fracturing fluid (e.g., a slurry including sand and water) can be pumped into the well  12  through the fracturing tree  16  and the wellhead  14  to increase the pressure inside the well  12  and form the man-made fractures noted above. Such fracturing often increases both the rate of production from the well and its total production. 
     The system  10  also includes a ball launcher  18  for introducing balls into the well  12 . In some embodiments, the ball launcher  18  can be used to drop frac balls into the well  12 , as described below with respect to  FIG. 2 . But it is noted that the ball launcher  18  could also be used to drop other balls into a well, such as balls that actuate downhole tools or other components, or balls that seal a portion of the well for purposes other than fracturing. The system  10  further includes a fluid source  20  coupled to the ball launcher  18 . In at least some embodiments, such as that depicted in  FIG. 1 , the fluid source  20  is coupled to the ball launcher  18  by a manifold  22 . The manifold  22  can be used to connect the fluid source  20  to ball launchers  18  for multiple wellhead assemblies. But in other embodiments, the fluid source  20  can be coupled directly to a single ball launcher  18  without a manifold  22 . As described in greater detail below, fluid from the source  20  can be routed into a conduit of the ball launcher  18  to facilitate injection of a ball into the well  12  through the wellhead  14 . 
     One example of the use of balls in the well  12  for fracturing is generally illustrated in  FIG. 2 . In this embodiment, the well  12  includes a casing  24 . The well  12  is depicted as having zones or sections  26 ,  28 , and  30 . Each of these sections of the well  12  can be isolated from another portion further downhole in the well through the use of frac balls introduced into the well. As presently shown, the casing  24  includes baffles or packers  34  with openings for allowing fluid flow and for receiving balls  36 . Although three balls  36  (with three corresponding packers  34 ) are shown in  FIG. 2  for explanatory purposes, it will be appreciated that the well  12  can include any number of desired zones that can be isolated with respective sets of packers  34  and balls  36 . Further, the packers  34  may be provided as part of sliding sleeve assemblies in which the balls  36  can be seated on the packers  34  such that pressure on the balls  36  cause sliding sleeves to move to expose ports in the casing  24 . In this manner, the balls  36  can be used to selectively open the sleeves to facilitate access to a formation through the ports (e.g., to enable fracturing of the formation via the ports). 
     In the depicted embodiment, the packers  34  are designed to receive balls  36  of different sizes. More specifically, the packer  34  furthest from the surface in the well  12  has the smallest opening and receives the smallest ball  36 . Moving up the well  12  from that packer  34 , additional packers  34  have openings to receive balls  36  of increasing size. That is, the closer the packer  34  is to the surface, the larger the ball  36  it is intended to receive. 
     By way of example, during a fracturing operation, the smallest ball  36  can be introduced into the well (e.g., along with fracturing fluid) and that ball  36  can pass through openings of diminishing size in the other packers  34  until it reaches the packer  34  furthest from the surface (corresponding to zone  30  in  FIG. 2 ). Fracturing fluid can be pumped through ports  40  in the casing  24  in zone  30  to fracture the surrounding formation. The ports  40  may be formed in any suitable manner. For example, the ports  40  can be formed in the casing  24  before installation, or they can be formed by perforating the casing  24  after it is installed in the well  12 . The next ball  36  can then be introduced (e.g., to engage the next packer  34  that isolates zone  28  from zone  30 ) and fracturing of zone  28  may also be performed. 
     The process of dropping a ball  36  to engage a packer and fracturing the zone above the packer (e.g., through ports  40 ) can be repeated with frac balls of increasing size (that is, from smallest to largest). In at least some embodiments, all of the balls  36  can be returned to the surface together (e.g., by wellbore pressure) after fracturing of the well  12  is completed. But in other embodiments, each ball  36  can be returned after fracturing a respective zone of the well  12 , or groups of balls  36  can be returned together after fracturing multiple zones. In other instances, the balls  36  could be left in the well  12  (e.g., to be drilled out later or, for balls of certain materials, to dissolve on their own). 
     An example of an apparatus  50  including a wellhead assembly  52  and a ball injection assembly  62  for introducing balls into a well through the wellhead assembly  52  is generally shown in  FIG. 3 . The wellhead assembly  52  is positioned over the well  12  and includes a casing head  56 , a tubing head  58 , and a fracturing tree  60 . The ball injection assembly  62  (also referred to herein as ball launcher  62 ) includes a fluid conduit  64  coupled to, and extending laterally away from, the wellhead assembly  52 . The conduit  64  is in fluid communication with a central bore of the wellhead assembly  52 , and can include any suitable, hollow components that allow a ball to be conveyed through the conduit  64  into the wellhead assembly. In the embodiment shown in  FIG. 3 , the fluid conduit  64  includes pipes, connection blocks, valves, and spools. 
     The depicted ball launcher  62  includes an entry valve  68  (e.g., a gate valve) for introducing balls into the fluid conduit  64 . The entry valve  68  can be opened when the fluid conduit  64  is unpressurized to allow an operator to insert a ball into the conduit  64  via a ball injection port  72  ( FIG. 4 ) and then closed to seal the ball within the conduit. In other embodiments, the valve  68  can be omitted and balls can be introduced into the fluid conduit  64  in some other way, such as through a ball injection port  72  with a removable cap. 
     The apparatus  50  can also include a ball catcher  70  for receiving balls returning to the surface from the well  12  during a flowback operation. The ball catcher  70  of  FIG. 3  is coupled to an end of the fluid conduit  64  apart from the wellhead assembly  52 , which allows returning balls to be routed through the fluid conduit  64  and into the catcher  70 . As shown in  FIG. 4 , the fluid conduit of the ball launcher  62  includes a connection block  76  coupled to a fluid pipe  78  and to the entry valve  68 . The ball catcher  70  is also coupled to the connection block  76  via a spool  80  and a valve  84  (e.g., a gate valve) of the conduit  64 . 
     A fluid pipe  86  is connected to the ball catcher  70  for routing fluid (e.g., pumped from the fluid source  20 ) into the fluid conduit  64  through the ball catcher  70  to launch balls into a well. More specifically, the ball launcher  62  includes a pilot ball  92  that can be pushed through the fluid conduit  64  toward the wellhead assembly  52 . In at least some embodiments, an operator inserts a ball  94  that is to be dropped into the well  12  (i.e., a drop ball) through the ball injection port  72  and the open valve  68  so that the ball  94  is positioned inside the conduit between the wellhead assembly  52  and the pilot ball  92 . After closing the valve  68 , pressurized fluid is routed through the pipe  86  and the ball catcher  70  to the pilot ball  92  (e.g., by opening valve  84 ). The pressurized fluid pushes the pilot ball  92  through the fluid conduit  64  toward the wellhead assembly  52 , causing the pilot ball  92  to drive the drop ball  94  through the conduit toward the wellhead assembly. 
     In one embodiment, the fluid conduit  64  of the ball launcher  62  is coupled to the fracturing tree  60  of the wellhead assembly  52  as shown in  FIG. 5 . The depicted fluid conduit  64  includes a connection block  102 , wing valves  104 , and an adapter spool  106  that is connected to a connection block  108  of the fracturing tree  60 . Valves  104  can be opened to allow passage of drop balls  94  and closed to isolate the majority of the fluid conduit  64  from fluid in the central bore through the fracturing tree  60  (e.g., during fracturing). 
     The fracturing tree  60  can have any suitable configuration, but in  FIG. 5  is shown to include master valves  110  that can be selectively opened to allow passage of fluid or items (e.g., fracturing fluid or drop balls  94 ) through lower components of the wellhead assembly  52  and into the well  12 . Fracturing fluid can be pumped into the fracturing tree  60  through valves  114  coupled to connection block  116 . The fracturing tree  60  also includes valves  118  and  120  along its central axis. Valve  118  can be closed to isolate the connection block  116  from the connection block  108 , and valve  120  can be opened to access the bore of the tree  60 . Further, a kill line can be coupled to the fracturing tree  60  via valves  122 . The various valves depicted in  FIG. 5  can be provided as gate valves or in some other form. Further, the various valves could be operated in any suitable manner, such as manually or hydraulically. 
     In at least some embodiments, including that depicted in  FIGS. 3-5 , the ball launcher is configured so that a ball to be launched into the well  12  is inserted into the fluid conduit  64  at a lower elevation than that at which the ball enters the wellhead assembly  52 . For instance, as generally shown in  FIG. 3 , a portion of the fluid conduit  64  runs along the ground at an elevation that allows an operator standing on the ground to manually insert a ball into the conduit  64  via the ball injection port  72 . This ground-based portion of the fluid conduit  64  and the ball injection port  72  can be positioned less than eight feet (approximately 2.4 meters) above the ground to facilitate insertion of balls into the fluid conduit  64  by an operator. For convenience, the ground-based portion of the fluid conduit  64  and the ball injection port  72  could be positioned even lower in some embodiments, such as less than six feet (approximately 1.8 meters) above the ground. A ball inserted into the fluid conduit  64  can then be driven through the conduit  64  to enter the wellhead assembly  52  at a higher elevation. In contrast to tree-mounted ball launching systems positioned vertically above a wellhead, the position of the ball injection port  72  at ground level remote from the wellhead assembly in some embodiments allows an operator to insert balls into the ball launcher  62  at an appropriate distance from the high-pressure area of the wellhead and at a lower elevation that does not require the operator to climb scaffolding or ladders. Although the fluid conduit  64  is depicted in  FIG. 3  as having two horizontal portions (one at the wellhead assembly, the other located at ground level apart from the wellhead assembly) joined by a vertical portion, the fluid conduit  64  could take other forms. For example, the fluid conduit  64  could have an inclined pipe that causes the driven ball to move upward while moving laterally closer to the wellhead assembly. 
     As noted above, the pilot ball  92  can be used to drive the drop ball  94  through the fluid conduit  64  and into the wellhead assembly  52 . The apparatus  50  includes a stop or some other obstruction along the travel path of the drop ball  94 . This obstruction prevents the pilot ball  92  from falling from the fluid conduit  64  into the central bore of the wellhead assembly  52 , while still allowing drop balls  94  to be routed through the fluid conduit  64 , past the obstruction, and into the bore of the wellhead assembly  52 . 
     One example of such an obstruction is depicted in  FIG. 6  as a stop shoulder  130  at an end of a bore  126  of the fluid conduit  64 . In a ball launch operation, the fluid conduit  64  is pressurized behind the pilot ball  92  to drive the pilot ball  92  and the drop ball  94  through the bore  126  toward the wellhead assembly  52  (e.g., to the fracturing tree  60 ). While drop balls  94  are smaller than the pilot ball  92  and can freely pass the stop shoulder  130  to enter a central bore  132  of the wellhead assembly  52 , the stop shoulder  130  prevents passage of the larger pilot ball  92  and retains it within the bore  126  of the fluid conduit  64 . In response to pressure, the pilot ball  92  drives the drop ball  94  toward the central bore  132  until the pilot ball  92  reaches the stop shoulder  130 . The stop shoulder  130  prevents further movement of the pilot ball  92  toward the central bore  132 , but the forward momentum of the drop ball  94  carries it into the central bore  132  so that the ball  94  can fall down the bore  132  (as generally indicated by arrow  134 ) and into the well  12 . 
     In at least some embodiments, pressure within the bore  126  can be monitored to verify launch of the drop ball  94  into the central bore  132 . For example, a pressure sensor can be coupled to the fluid conduit  64  (e.g., at the adapter spool  106 ) to detect fluid pressure in the bore  126 . When the pilot ball  92  engages the stop shoulder  130  as shown in  FIG. 6 , pressure in the bore  126  behind the pilot ball  92  will increase. The position of the pilot ball  92  against the stop shoulder  130  can be determined from this pressure increase. And with the stop shoulder  130  positioned near the central bore  132 , the detected position of the pilot ball  92  against the shoulder  130  is indicative of passage of the drop ball  94  past the shoulder  130  and into the central bore  132 . 
     The stop shoulder  130  is shown in  FIG. 6  as positioned at an end of the adapter spool  106 , but the shoulder  130  could be provided elsewhere in the bore  126  or in the wellhead assembly itself (e.g., at the port of the connecting block  108  to which the fluid conduit  64  is coupled). Further, although the shoulder  130  is provided as one example of an obstruction for preventing the pilot ball  92  from falling down the central bore  132 , other obstructions could also or instead be used. For instance, the interior of the adapter spool  106  could have a conical profile with an inner diameter at some portion of the spool smaller than the diameter of the pilot ball  92 , or the port of the connection block  108  to which the fluid conduit  64  is coupled could have a smaller diameter than that of the pilot ball  92 . 
     After the drop ball  94  is pushed into the central bore  132 , the pilot ball  92  can be returned through the fluid conduit  64  past the ball injection port  72  (e.g., to the position shown in  FIG. 4 ). In some instances, a fracturing operation is performed after the drop ball  94  is dropped into the well  12  and fracturing fluid pressure in the bore  132  pushes the pilot ball  92  through the conduit  64  away from the wellhead assembly  52 . Once the pilot ball  92  is positioned remote from the wellhead assembly  52  beyond the ball injection port  72 , another drop ball  94  can be inserted into the fluid conduit  64  for launch into the well. Further, the process described above can be repeated for launching additional drop balls  94  into the well  12 . For instance, dozens of drop balls  94  can be individually loaded into the fluid conduit  64  and driven by the pilot ball  92  for introduction to the well  12 . In one embodiment, the dozens of drop balls  94  are loaded into the conduit  64  and launched into the well  12  in sequence from smallest to largest (e.g., with diameters of the balls  94  increasing by one-eighth-inch (approximately 3.2 mm) intervals). Additionally, an operator can individually verify the size of each of the drop balls  94  before loading the ball  94  into the fluid conduit  64  for launch into the well  12 . 
     In at least some embodiments, multiple ball catchers  70  are coupled to the ball launcher  62  for receiving the drop balls  94  returned to the surface. As shown by way of example in  FIG. 7 , two ball catchers  70  are coupled, in parallel, to the ball launcher  62  via connection blocks  138  and valves  84 . A valve  140  between the connection blocks  138  allows an operator to control travel of the returning balls  94  into the catchers  70 . If one of the ball catchers  70  becomes clogged (e.g., from the balls, sand, and debris in the flowback fluid), the valves  84  and  140  could be operated to route the returning fluid through the other ball catcher  70  while isolating the clogged ball catcher  70 . The depicted apparatus also includes a manifold  144  having valves  142  that can be used to control fluid flow through the catchers  70 . Pressurized fluid can be supplied through the manifold  144  to the fluid conduit  64  (via either or both of the ball catchers  70 ) for pushing the pilot ball  92  and launching drop balls  94  into the well  12 . The manifold  144  could also or instead be used during a flowback process to route returning fluid from the catchers  70 . 
     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.