Patent Publication Number: US-2021164313-A1

Title: Fracturing trees with horizontally offset connections

Description:
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. 
     Hydraulic fracturing, commonly referred to as fracing, is a technique used to enhance and increase recovery of oil and natural gas from subterranean natural reservoirs. More specifically, fracing involves injecting a fracing fluid, e.g., a mixture of mostly water and sand, into an oil or gas well at high pressures. The fracing fluid is injected to increase the downhole pressure of the well to a level above the fracture gradient of the subterranean rock formation in which the well is drilled. The high pressure fracing fluid injection causes the subterranean rock formation to crack. Thereafter, the fracing fluid enters the cracks formed in the rock and causes the cracks to propagate and extend further into the rock formation. In this manner, the porosity and permeability of the subterranean rock formation is increased, thereby allowing oil and natural gas to flow more freely to the well. 
     A variety of equipment is used in the fracing process. For example, fracing fluid blenders, fracing units having high volume and high pressure pumps, fracing tanks, and so forth may be used in a fracing operation. Additionally, a fracing tree is generally coupled between the wellhead of a well and the fracing unit. The fracing tree has a variety of valves to control the flow of fracing fluid and production fluid through the fracing tree. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Various features, aspects, and advantages of the present invention will become better understood when the following detailed description is read with reference to the accompanying figures in which like characters represent like parts throughout the figures, wherein: 
         FIG. 1  is a schematic of a horizontal frac tree system coupled to a well head assembly in a surface application; 
         FIG. 2  is an embodiment of a horizontal frac tree system having a single horizontal branch; 
         FIG. 3  is an embodiment of a horizontal frac tree system having a unified block configuration and two horizontal branches; 
         FIG. 4  is an embodiment of a horizontal frac tree system mounted to a skid; 
         FIG. 5  is an embodiment of a horizontal frac tree system having two horizontal goathead connections; and 
         FIG. 6  is an embodiment of a horizontal frac tree system having a casing hangar with an access port for a horizontal bore. 
     
    
    
     DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS 
     One or more specific embodiments of the present invention will be described below. These described embodiments are only exemplary of the present invention. Additionally, in an effort to provide a concise description of these exemplary 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,” 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, 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. 
     Embodiments of the present disclosure include a frac tree having a horizontal configuration (e.g., a horizontal frac tree), which is configured to reduce the bending moments caused by vibrations, external loads (e.g., connected piping), and so forth. In particular, the horizontal frac tree is specifically designed for a surface application, e.g., land-based in an air environment. Accordingly, the horizontal frac tree may have a variety of mounts, supports, connectors, and other features designed for the surface application. The concepts described herein are not limited to frac trees. In fact, these concepts are also applicable to other flow control devices, such as production trees, workover trees, to name a few. 
     Hydraulic fracturing, or fracing, involves injecting a fracing fluid into a wellbore to create and propagate cracks in the subterranean rock formation beneath the wellhead. In this manner, the porosity and permeability of the rock formation is increased, leading to enhanced recovery of natural gas and oil from natural reservoirs beneath the earth&#39;s surface. The fracing fluid is introduced to the well through a frac tree connected to the wellhead. 
     As discussed in detail below, the disclosed embodiments provide a frac tree with a horizontal configuration. Specifically, the frac tree may have one or more arms or branches extending horizontally from a master valve of the frac tree. The branches of the frac tree include one or more piping connections (e.g., goathead connections) to enable connection with a fracing system. The horizontal configuration of the frac tree places the frac connections closer to ground level than frac trees with a vertical configuration. As a result, the frac tree may experience reduced external bending moments caused by excessive vibration and other loads experienced during the fracing process. 
       FIG. 1  is a schematic of a fracing system  10  having a horizontal frac tree  12  (e.g., a surface frac tree). As mentioned above, the fracing system  10  is used to pump a high pressure fracing fluid into a well  14  formed in a subterranean rock formation  16 . As will be appreciated, the well  14  may be a natural gas and/or oil well. The horizontal frac tree  12  is coupled to a wellhead  18  of the well  14 . As discussed above, a frac system  20  introduces a high pressure fracing fluid into the well  14  through the horizontal frac tree  12  coupled to the well head  18 . The frac system  20  may include a variety of high volume and high pressure pumps and monitoring units configured to supply the fracing fluid to the horizontal frac tree  12 . In certain embodiments, the fracing fluid may include water. In other embodiments, the fracing fluid may include other components such as chemical gels or foams, as well as gases such as air, nitrogen, and carbon dioxide. As will be appreciated, the particular contents of the fracing fluid may depend on different factors such as the type of rock formation  16 , the desired pressure of the fracing fluid, and so forth. 
     The fracing fluid passes through the horizontal frac tree  12  and the well head  18  into a well bore  22 . From the well bore  22 , the fracing fluid enters the well  14 , and the high pressure of the fracing fluid causes the subterranean rock formation  16  to crack and propagate. As cracks are formed and propagated in the rock formation  16 , additional natural gas and/or oil from the rock formation  16  is released and may flow into the well  14  to be recovered. 
     As shown, the horizontal frac tree  12  has a horizontal branch  24  that extends along a horizontal axis  26  from the well head  18 . The horizontal branch  24  includes at least one piping connection (e.g., goathead connection  28 , which may itself comprise multiple connections) to couple with the frac system  20 . As discussed in detail below, the horizontal branch  24  may include multiple goathead connections  28  in a variety of orientations. Moreover, the goathead connections  28  may include WECO union connectors, compression fit connectors, or other types of pipe connectors for coupling to the frac system  20 . In certain embodiments, the goathead connections  28  may have threaded or butt welded ends and may be configured to withstand pressures up to 5,000 psi, 10,000 psi, 15,000 psi, 20,000 psi, 25,000 psi, or more. Furthermore, as discussed below, the horizontal frac tree  12  includes a variety of valves to regulate the flow of the fracing fluid through the horizontal frac tree  12 . 
     As will be appreciated, the horizontal orientation of the horizontal frac tree  12  positions the goathead connections  28  closer to ground level. For example, the disclosed horizontal fracing system  10  has a vertical dimension or height  11  that is substantially less than that of a vertical fracing system, and a horizontal dimension or width  13  that is substantially greater than that of a vertical fracing system. In certain embodiments, the height  11  may be less than approximately 12, 18, 24, 30, 36, 42, or 48 inches. For example, the height  11  may be approximately 12 to 60, 18 to 48, or 24 to 36 inches. Furthermore, the width  13  may be approximately 1 to 20, 2 to 15, or 3 to 10 feet. In certain embodiments, a width/height ratio of the width  13  to the height  11  may be approximately 2:1 to 20:1, 3:1 to 15:1, or 4:1 to 10:1. By further example, the horizontal frac tree  12  (i.e., above the wellhead  18 ) may have a vertical dimension or height  15  that is substantially less than a vertical frac tree, and the horizontal dimension or width  13  that is substantially greater than a vertical frac tree. In certain embodiments, the height  15  may be less than approximately 12, 18, 24, 30, 36, 42, or 48 inches. For example, the height  15  may be approximately 12 to 48, 18 to 42, or 24 to 36 inches. Furthermore, the width  13  may be approximately 1 to 20, 2 to 15, or 3 to 10 feet. In certain embodiments, a width/height ratio of the width  13  to the height  15  may be approximately 2:1 to 20:1, 3:1 to 15:1, or 4:1 to 10:1. 
     As mentioned above, a frac tree may be subjected to vibrations and other forces that create a bending moment in the frac tree  12 . The horizontal frac tree  12  reduces the possibility of bending moments exceeding specified parameters at a connection  17  (e.g., a flanged connection) between the well head  18  and the horizontal frac tree  12  by positioning external loads (e.g., piping, valves, and other components) closer to the ground level. In other words, the external loads are vertically closer to the connection  17 , thereby substantially reducing any bending moment relative to the connection  17 . Specifically, the bending moment about a vertical axis  30  of the well  14  may be reduced with the illustrated horizontal frac tree  12 . Furthermore, the horizontal frac tree  12  may have a variety of mounts, connections, and supports to help retain the horizontal branch  24  in the horizontal orientation without subjecting the connection  17  to bending. The horizontal frac tree  12  also improves serviceability, because a technician can more easily inspect and repair the tree  12  at the ground level. As a result, operators of the fracing system  10  may not need an external lifting or raising apparatus (e.g., a ladder, hydraulic lift, or scaffolding) to reach the goathead connections  28 . Indeed, all components and connections of the horizontal frac tree  12  may be accessed from the ground level. 
     In addition to the goathead connections  28  that may be used for the fracing process, the horizontal frac tree  12  also includes a vertical access connection  32 . Consequently, a well operator may have separate access to the well  14 , while the frac system  20  is coupled to the horizontal frac tree  12 . As shown, the vertical access connection  32  is generally in line with the vertical axis  30  of the well  14 . The vertical access connection  32  may be used to access the well  14  in a variety of circumstances. For example, the vertical access connection  32  may be used for natural gas and/or oil recovery, fracing fluid recovery, insertion of a frac mandrel, and so forth. During the fracing process, the vertical access connection  32  may not be in use. In such circumstances, the vertical access connection  32  may be plugged or sealed in order to maintain a high pressure in the well  14 . More specifically, the vertical access connection  32  may be plugged with one or more of a variety of plugs  34 , such as metal or elastomer seals. For example, a one-way back pressure valve (BPV) plug  36  or a wireline set plug  38  may be used to plug the vertical access connection  32 . In certain embodiments, a lubricator  40  may be used to seal the vertical access connection  32 . As will be appreciated, one or more plugs  34  may be used in the vertical access connection  32  to isolate the well  14  and the wellbore  22 . Additionally, as discussed below, one or more plugs  34  may be used below a horizontal bore ( 72 ; see  FIG. 2 ) in the horizontal frac tree  12  to isolate any equipment coupled the vertical access connection  32  above the horizontal frac tree  12 . The vertical access connection  32  also may be used to insert a variety of tools and other equipment into the wellbore  22 . 
       FIG. 2  is a schematic of an embodiment of the fracing system  10 , illustrating the horizontal frac tree  12  having one branch  24  with three goathead connections  28 . In the illustrated embodiment, the horizontal frac tree  12  is coupled to a master valve block  60  having a master valve  62 . More specifically, in this embodiment, the horizontal frac tree  12  is coupled to the master valve block  60  by a flange  64 . In other embodiments, as discussed below, the master valve block  60  and the horizontal frac tree  12  may be part of a single unified block or may be coupled through a union nut assembly that draws the two components together. As will be appreciated, the master valve  62  regulates the flow through a main bore  66  coupled to the wellbore  22 . The flow through the main bore  66  may be a production fluid such as natural gas and/or oil or a fracing fluid supplied by the frac system  20 . The main bore  66  and a vertical bore  67  of the tree  12  may be sized to provide “full bore access”, such that tools may be inserted through the main and vertical bores  66  and  67  into the wellbore  22 , without restrictions from the main and vertical bores  66  and  67 . This can be accomplished by, for example, ensuring the main and vertical bores  66  and  67  have an internal diameter that is equal to or greater than the internal diameter of a production casing  69  within the wellbore  22 . In certain embodiments, the master valve  62  may be manually operated. In other embodiments, the master valve  62  may be hydraulically operated. Additionally, plugs  34  may be disposed in the main bore  66  to isolate a desired portion of the bore  66 . For example, a plug  68  may be disposed in the main bore  66  to isolate a flow of fracing fluid to the well bore  22 . Similarly, a plug  70  may be disposed in the main bore  66  to isolate equipment coupled to the vertical access connection  32 . Moreover, because the illustrated embodiment includes only one master valve  62 , a well operator may access the well bore  22  through the vertical access connection  32  without needing to go through multiple valves. 
     As shown, a horizontal bore  72  extends through the horizontal frac tree  12  along the horizontal axis  26  of the frac tree  12  (e.g., along horizontal branch  24 ), and is operatively connected to the main bore  66 . The horizontal frac tree  12  also includes valves  74  disposed along the horizontal bore  72 . The valves  74  are configured to control and regulate the flow of fracing fluid from the fracing system to the main bore  66  and the well bore  22 . As with the master valve  62 , the valves  74  of the horizontal frac tree  12  may be manually or hydraulically operated. The horizontal frac tree  12  also includes three goathead connections  28  at an end  76  of the branch  24  opposite the main bore  66 . More specifically, the frac tree  12  includes a horizontal goathead connection  78 , a top vertical goathead connection  80 , and a bottom vertical goathead connection  82 . While the illustrated embodiment includes three goathead connections  38 , other embodiments may include 1, 2, 4, 5, 6, or more goathead connections  28  or other types of piping connections. Each goathead connection  28  is operatively connected to the horizontal bore  72 . As will be appreciated, each of the three goathead connections  28  may be connected to the frac system  20  by a pipe or other conduit configured to flow a fracing fluid. Furthermore, in the illustrated embodiment, the horizontal frac tree  12  is supported by a brace  84  extending from the frac tree  12  to the master valve block  60 . For example, the brace  84  may be mechanically coupled (e.g., bolted) or welded between the frac tree  12  and the block  60 . In other embodiments, as discussed below, the horizontal frac tree  12  may be supported by a post or brace mounted to a skid. The brace  84  helps to retain the horizontal branch  24  in the horizontal orientation, thereby reducing the possibility of any bending or pivoting of the horizontal branch  24  relative to the block  60 , well head  18 , or various connections (e.g., flange  64 ). 
       FIG. 3  is a schematic of an embodiment of the fracing system  10 , illustrating the horizontal frac tree  12  having two horizontal branches  24 . The illustrated embodiment includes similar elements and element numbers as the embodiment shown in  FIG. 2 . Both horizontal branches  24  extend from the main bore  66  along the horizontal axis  26 . Additionally, the horizontal branches  24  of the frac tree  12  extend in opposite horizontal directions. In other words, a first branch  100  extends in a first direction  102  horizontally away from the well head  18 , a second branch  104  extends in a second direction  106  horizontally away from the well head  18 , and the first and second directions  102  and  106  are approximately 180 degrees apart. In other embodiments, the first and second directions  102  and  106  may be 1 to 179, 2 to 150, 3 to 100, 4 to 50, or 5 to 25 degrees apart. Similarly, other embodiments of the horizontal frac tree  12  may include three or more horizontal branches  24 . For example, the branches  24  of the horizontal frac tree  12  may be configured in a symmetrical arrangement (e.g., two branches  24  at 180 degrees apart, three branches  24  at 120 degrees apart, four branches at 90 degrees apart, five branches  24  at 72 degrees apart, or six branches  24  at 60 degrees apart) about the well head  18 , thereby reducing the possibility of any bending or pivoting relative to the well head  18 , block  60 , and associated connections (e.g., flange  64 ). The symmetrical arrangement of branches  24  may include substantially equal lengths, diameters, and/or weights to help distribute the loads symmetrically about the well head  18 . In other embodiments, the branches  24  may not be in a symmetrical arrangement about the well head  18 . 
     As shown, the horizontal bore  72  of each of the first and second branches  100  and  104  of the horizontal frac tree  12  is operatively connected to the main bore  66 . As a result, two flows of fracing fluid may enter the main bore  66  during a fracing operation, as indicated by arrows  103 . Additionally, both horizontal branches  100  and  104  have three goathead connections  28 , wherein each goathead connection  28  is operatively connected to the respective horizontal bore  72  of the first and second branches  100  and  104 . As discussed above, the horizontal branches  24  may have other numbers of goathead connections  28 , such as 1, 2, 4, 5, 6, or more goathead connections  28 . 
     In the illustrated embodiment, the first and second horizontal branches  100  and  104  and the master valve block  60  form a single, continuous block  108 . In other words, the first and second horizontal branches  100  and  104  and the master valve block  60  may be a single piece, and are not coupled to one another by the flange  64 . For example, a single block of metal may be used to form the branches  100  and  104  and the block  60 , rather than connecting separate metal components together. In other embodiments, the first and second horizontal branches  100  and  104  and the master valve block  60  may be fixedly coupled together via welded joints or other permanent connections. In this manner, the number of flanges  64  and other removable connections in the fracing system  10  is reduced, thereby increasing the structural integrity in the fracing system  10  and reducing the effects of bending moments on the fracing system  10 . 
       FIG. 4  is a schematic of an embodiment of the fracing system  10 , illustrating the horizontal frac tree  12  mounted to a skid  120 . The illustrated embodiment includes similar elements and element numbers as the embodiment shown in  FIG. 2 . As shown, the skid  120  is disposed about the wellhead  18  and supports the horizontal frac tree  12 . In certain embodiments, the skid  120  may include a central opening that is completely surrounded by structural elements (e.g. beams and framework), such that the well head  18  fits in the central opening and is completely surrounded by the structural elements. Accordingly, the horizontal frac tree  12  may be installed by moving the skid  120  to a position above the well head  18 , and then gradually lowering the skid  120  downward such that the well head  18  fits within the central opening. In other embodiments, the skid  120  may include an opening or slot that extends horizontally from an edge of the skid  120  to a central portion of the skid  120 . Accordingly, the horizontal frac tree  12  may be installed by moving the skid  120  horizontally toward the well head  18 , such that the well head gradually moves along the slot until the tree  12  is in the proper position. In either embodiment, the skid  120  helps to support, level, and generally align the tree  12  during and after the installation of the tree  12 . In addition, the horizontal frac tree  12  is supported by braces  122 , which extend between the horizontal frac tree  12  and the skid  120 . In certain embodiments, the braces  122  may be mechanically secured (e.g., bolted) or welded between the horizontal frac tree  12  and the skid  120 . The skid  120  is secured to the ground by anchored posts  124 . For example, the anchored posts  124  may be secured to the ground by concrete or other anchoring material. 
     Additionally, the skid  120  includes adjustment legs  126 . The adjustment legs  126  enable height adjustability of a height  128  of the skid  120  from the ground. For example, the adjustment legs  126  may be pneumatically-driven legs, hydraulically-driven legs, motorized legs, threaded legs, or any combination thereof. Furthermore, the adjustment legs  126  may be manually adjusted by an operator, or the adjustment legs  126  may be automatically adjusted by a controller that incorporates sensor feedback, user input, and various models (e.g., a CAD model of the tree  12 , a model of the landscape, and so forth. 
     As the height  128  of the skid  120  is adjusted, the height of the horizontal frac tree  12  is adjusted. The adjustment legs  126  may be used to provide additional vertical support to hold the horizontal frac tree  12  in place, thereby blocking any undesired movement of the tree  12 . The adjustment legs  126  also may be used to level the tree  12  relative to the ground and/or align the tree  12  relative to the well head  18 . For example, the rightward adjustment leg(s)  126  may be used to raise or lower the right portion of the skid  120 , and thus the horizontal frac tree  12 . Likewise, the leftward adjustment leg(s)  126  may be used to raise or lower the left portion of the skid  120 , and thus the horizontal frac tree  12 . 
       FIG. 5  is a schematic of an embodiment of the fracing system  10 , illustrating a horizontal frac tree  12  having two horizontal goathead connections  28 . The illustrated embodiment includes similar elements and element numbers as the embodiment shown in  FIG. 2 . As shown, the end  76  of the branch  24  of the frac tree  12  includes two goathead connections  28 . More specifically, each goathead connection  28  extends horizontally from the end  76  of the branch  24 . In other words, each of the goathead connections  28  extends from the end  76  along the horizontal axis  26  of the horizontal frac tree  12 . As discussed above, each goathead connection  28  is operatively connected to the horizontal bore  72 . 
       FIG. 6  is an embodiment of the fracing system  10 , illustrating the wellhead  18  having a casing hanger  140  with an access port  142  for the horizontal bore  72 . The illustrated embodiment includes similar elements and element numbers as the embodiment shown in  FIG. 2 . As shown, the horizontal bore  72  extends through the access port  142  of the casing hanger  140  and is coupled to the main bore  66 . Additionally, in the illustrated embodiment, the master valve  62  is located on the horizontal frac tree  12  and along the horizontal bore  72 . As will be appreciated, the connection of the horizontal bore  72  to the main bore  66  through the access port  142  of the casing hanger  140  enables an operator to access the casing hanger  140  (e.g., through the vertical access  32 ) without needing to move the horizontal frac tree  12 . Similarly, an operator may access the main bore  66  and the wellbore  22  without removing the horizontal frac tree  12  from the wellhead  18 . 
     While the invention 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. However, 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.