Patent Publication Number: US-2017356268-A1

Title: Apparatus and Method for Sealing a Tubular Section

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims priority to U.S. Provisional Patent Application Ser. No. 62/349,177, filed on Jun. 13, 2016, and U.S. Provisional Patent Application Ser. No. 62/397,041, filed on Sep. 20, 2016. These applications are hereby incorporated by reference in their entirety into the present application to the extent consistent with the present application. 
    
    
     BACKGROUND 
     In oil and gas production, it is sometimes beneficial to stimulate a reservoir by pumping in high pressure fluids and particulates, such as sand. In order to do this, portions of the well are isolated and then re-opened so the well can be produced. Some current isolation methods use a frac plug and sealing ball. A frac plug is a hollow, cylindrical plug that can be installed in the tubular to selectively isolate portions of the well. The sealing ball is then pumped down the well until it seats on a sealing element in the frac plug. 
     Seating the ball stops fluid flow through the bore of the frac plug. There is also a seal between the outer diameter of the frac plug and the tubular. Thus, hydrocarbons from the reservoir cannot flow through the bore of the frac plug and cannot divert around the outside of the frac plug. This isolates the selected portions of the well by preventing fluid flow from the surface to the reservoir and vice versa. 
     Frac plugs are usually built around a central mandrel. Typically, the central mandrel is then positioned in the wellbore and held in place using upper and lower slips. However, the frac plugs can decrease the inner diameter of the tubular where they are installed and may restrict flow after stimulating the reservoir. 
     Additionally, the sealing element of the frac plug on which the ball seats is positioned between the slips. This arrangement may prevent the sealing element from fully compressing if the slips become fully engaged prior to full compression of the sealing element. This, in turn, allows fluids to leak past the frac plug and defeat the isolation. Further, sometimes a portion of the wellbore is horizontal and it can be difficult to position the sealing ball in the horizontal portion. 
     What is needed, therefore, is an apparatus that does not significantly decrease the inner diameter of the tubular, ensures that the tubular is sealed for isolation, and includes a bore-sealing element that can be easily positioned within a horizontal tubular section. 
     SUMMARY 
     Embodiments of the disclosure may provide a retainer. The retainer may include an annular body and a slip. The annular body may have a first outer surface and include a first taper that extends along at least a portion of the first outer surface. The slip may be circumferentially disposed about the annular body and have a first axial end, a second axial end, an inner surface, a second outer surface, and an axial length extending between the first axial end and the second axial end. The slip may also include a second taper that extends along the inner surface and engages with the first taper. The slip may further include a left-hand thread pattern defined by the second outer surface that extends from the first axial end along a first portion of the axial length. Each thread the left-hand thread pattern may have a crest that is angled towards the first axial end. 
     Embodiments of the disclosure may further provide a dart. The dart may include a cap defining a vented cavity, a sealing element, and an engagement member that extends from the sealing element and that is slidably engaged with the cap. The sealing element may include a body that expands radially as it is compressed. The sealing element may further include a plurality of fins extending radially from the body. The plurality of fins may include a first fin that seals against the cap as the body is compressed. 
     Embodiments of the disclosure may further provide an apparatus for sealing a tubular section. The apparatus may include a retainer and a dart. The retainer may include an annular body and a means for mechanically engaging the tubular section. The dart may include a cap, a sealing element, and an engagement member. The cap may define a vented cavity and seat against the annular body of the retainer when positioned within the tubular section. The sealing element may seal the tubular section as it is compressed against the cap. The engagement member may extend from the sealing element and engage with the cap through the vented cavity. 
     Embodiments of the disclosure may further provide a retainer. The retainer may include an annular body and a plurality of fasteners. The annular body may define a plurality of holes. The plurality of fasteners may be configured to couple the annular body to a tubular section. Each fastener of the plurality of fasteners may be disposed within a respective hole of the plurality of holes. 
     Embodiments of the disclosure may further provide a method for sealing a tubular section of a wellbore. The method may include engaging a retainer with the inner diameter of the tubular section without sealing the tubular section. The method may also include pumping a dart including a sealing element down the wellbore to seat at least a portion of the sealing element in a cap and to seat the cap against the retainer. The method may further include compressing the sealing element of the dart against the cap to seal the tubular section. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present disclosure is best understood from the following detailed description when read with the accompanying drawings. It is emphasized that, in accordance with the standard practice in the industry, various features are not drawn to scale. In fact, the dimensions of the various features may be arbitrarily increased or reduced for clarity of discussion. 
         FIG. 1  illustrates a cross-sectional view of an exemplary tubular sealing apparatus, according to one or more embodiments disclosed. 
         FIG. 2A  illustrates a cross-sectional view of the retainer of  FIG. 1 . 
         FIG. 2B  illustrates an enlarged view of the portion of the retainer of  FIG. 2A  indicated by the detail labeled  2 B of  FIG. 2A . 
         FIG. 3  illustrates a cross-sectional view of the dart of  FIG. 1 , according to one or more embodiments disclosed. 
         FIG. 4  illustrates the retainer of  FIG. 1  set within a wellbore. 
         FIG. 5  illustrates the retainer of  FIG. 4  and the dart of  FIG. 1  in relation to the retainer. 
         FIG. 6  illustrates the dart of  FIG. 5  compressed against the retainer of  FIG. 4 . 
         FIG. 7  illustrates a cross-sectional view of an exemplary tubular sealing apparatus, according to one or more embodiments disclosed. 
         FIG. 8  illustrates a cross-sectional view of the retainer of  FIG. 7 . 
         FIG. 9  illustrates the retainer of  FIG. 7  positioned within a wellbore. 
         FIG. 10  illustrates the retainer of  FIG. 9  expanded within the wellbore. 
         FIG. 11  illustrates the retainer of  FIG. 7  fixed to a tubular section within a wellbore. 
         FIG. 12  illustrates the retainer of  FIG. 11  and the dart of  FIG. 7 . 
         FIG. 13  illustrates the dart of  FIG. 12  compressed against the retainer of  FIG. 11 . 
         FIG. 14  illustrates a flow chart of an exemplary method for sealing a tubular section of a wellbore. 
     
    
    
     DETAILED DESCRIPTION 
     It is to be understood that the following disclosure describes several exemplary embodiments for implementing different features, structures, or functions of the invention. Exemplary embodiments of components, arrangements, and configurations are described below to simplify the present disclosure; however, these exemplary embodiments are provided merely as examples and are not intended to limit the scope of the invention. Additionally, the present disclosure may repeat reference numerals and/or letters in the various exemplary embodiments and across the drawings provided herein. This repetition is for the purpose of simplicity and clarity and does not in itself dictate a relationship between the various exemplary embodiments and/or configurations discussed in the various drawings. Moreover, the formation of a first feature over or on a second feature in the description that follows may include embodiments in which the first and second features are formed in direct contact, and may also include embodiments in which additional features may be formed interposing the first and second features, such that the first and second features may not be in direct contact. Finally, the exemplary embodiments presented below may be combined in any combination of ways, i.e., any element from one exemplary embodiment may be used in any other exemplary embodiment, without departing from the scope of the disclosure. 
     Additionally, certain terms are used throughout the following description and claims to refer to particular components. As one skilled in the art will appreciate, various entities may refer to the same component by different names, and as such, the naming convention for the elements described herein is not intended to limit the scope of the invention, unless otherwise specifically defined herein. Further, the naming convention used herein is not intended to distinguish between components that differ in name but not function. Additionally, in the following discussion and in the claims, the terms “including” and “comprising” are used in an open-ended fashion, and thus should be interpreted to mean “including, but not limited to.” All numerical values in this disclosure may be exact or approximate values unless otherwise specifically stated. Accordingly, various embodiments of the disclosure may deviate from the numbers, values, and ranges disclosed herein without departing from the intended scope. Furthermore, as it is used in the claims or specification, the term “or” is intended to encompass both exclusive and inclusive cases, i.e., “A or B” is intended to be synonymous with “at least one of A and B,” unless otherwise expressly specified herein. 
       FIG. 1  illustrates an exemplary tubular sealing apparatus  100 , according to one or more embodiments disclosed. The uphole and downhole directions of the tubular sealing apparatus  100  are indicated by the arrows  101  and  103 , respectively. Those in the art having the benefit of this disclosure will appreciate that these terms are defined relative to the direction of the tubular sealing apparatus  100  when installed in a tubular section (not shown) for the intended use as is customary in the art. 
     The tubular sealing apparatus  100  may include a retainer  102  and a dart  104 . The retainer  102  may include an annular body  106  having an uphole axial end portion  110  that defines a seat  112  for a cap  114  of the dart  104 . Other embodiments of the retainer (not shown) may omit the seat  112 . The retainer  102  may further include a slip  116  coupled to the downhole side  117  of the annular body  106 . As shown in the exemplary embodiment, the slip  116  may define a left-hand thread profile  120 . 
     The dart  104  may include a sealing element  122  coupled to the cap  114  though an engagement member  124 , as shown in  FIG. 1 . A primary fin  126  and a plurality of secondary fins  128  may extend radially outward from a body  130  of the sealing element  122 . Additionally, at least one the fins  126 ,  128  may be angled uphole  101 , as shown in the exemplary embodiment. Other embodiments of the dart may include one or more fins (not shown) that are perpendicular to the sealing element  122 . 
       FIG. 2A  illustrates the retainer  102  of  FIG. 1 . In at least one embodiment, the annular body  106  may include a tapered portion  202  extending along at least a portion of the outer surface  204 . The annular body  106  may also include serrations  206  defined in the tapered portion  202  of the outer surface  204 . Other embodiments of the annular body  106  may replace the serrations  206  with a thread profile (not shown), or the serrations  206  may be omitted. 
       FIG. 2B  illustrates an enlarged view of the portion of the retainer  102  indicated by the detail labeled  2 B of  FIG. 2A . In the exemplary embodiment, each thread  208  (only one indicated) of the left-hand thread profile  120  may include a first flank  210  that is longer than a second flank  212 , angling the crest  214  of each thread  208  downhole  103 . As shown in  FIG. 2B , a portion  216  of the slip  116  adjacent to the annular body  106  may define one or more threads  218  (only one indicated) having a first flank  220  that is shorter than a second flank  222 , angling the crest  224  of each thread  218  uphole  101 . 
     In this particular embodiment of the slip  116 , a second thread  226  may have a larger pitch, a larger pitch diameter, or both a larger pitch and a larger pitch diameter than the other threads  218  that have crests  224  angled uphole  101 . Other embodiments of the slip  116  may include threads  218  that all have a pitch and a pitch diameter that are the same size, or a different thread (not shown) may have a larger pitch, a larger pitch diameter, or both a larger pitch and a larger pitch diameter than the other threads  218 . In another embodiment, the threads  218  may be replaced by teeth (not shown) that have points (not shown) angled uphole  101 . Further embodiments of the slip  116  may include a left-hand thread profile  120 , threads  218 , or both a left-hand thread profile  120  and threads  218  that have crests  214 ,  224  that are generally perpendicular to the slip  116 . 
     Returning to  FIG. 2A , the slip  116  may further include a plurality of longitudinal grooves (not shown). The grooves may extend along a portion of the axial length of the slip  116 . In one embodiment, adjacent grooves extend from alternating axial end portions  228 ,  230  of the slip  116 . In another embodiment, the grooves may extend from only one axial end portion  228 ,  230  of the slip  116 . Other embodiments of the slip  116  may include two or more adjacent grooves that extend from the same axial end portion  228 ,  230  of the slip  116 , include grooves that extend axially through the slip  116  without interfacing with either axial end portion  228 ,  230 , or omit the grooves. 
     An inner surface  232  of the slip  116  may be radially tapered in an outward direction as it moves from the axial end portion  230  toward the axial end portion  228 , as shown in the exemplary embodiment. The slip  116  may further include a thread profile  234  defined in the inner surface  232  that engages with the serrations  206  of the annular body  106  to couple the slip  116  to the annular body  106 . Other embodiments of the slip  116  may include a plurality of radial grooves (not shown) instead of a thread profile  234 . 
     In the exemplary embodiment, the annular body  106  and the slip  116  are made of a high-yield aluminum. Other embodiments of the annular body  106  and the slip  116  may be made of steel, a high-yield cast metal, a high-yield powdered metal, or a composite material. In at least one embodiment, the annular body  106  and the slip  116  are made of different materials, such as, for example, a high-yield aluminum annular body  106  and a powdered metal slip  116 , a steel annular body  106  and a cast metal slip  116 , or any other possible combination of annular body  106  material and slip  116  material. 
       FIG. 3  illustrates the dart  104  of  FIG. 1 . The cap  114  may be a cylindrical body  302  that defines a cavity  304 . The cap  114  may further define a vent  306  for the cavity  304 . In another embodiment, the cap  114  may include multiple cavities (not shown) and multiple vents (not shown), each vent extending through the cap  114  into a respective cavity. Other embodiments of the cap  114  may include a vent (not shown) extending radially through the cap  114  to reach the cavity  304 , or a vent (not shown) that extends into the cavity  304  at an angle relative to a longitudinal centerline  308 . 
     With reference to the sealing element  122 , the primary fin  126  may be wider than the secondary fins  128 . The primary fin  126  may include a tapered outer surface  310  and define a recess  312  that is adjacent to the cap  114 , as shown in the exemplary embodiment. Other embodiments of the primary fin  126  may omit the taper  310 , the recess  312 , or both. Although the exemplary embodiment includes two secondary fins  128 , other embodiments of the sealing element  122  may include one, three, or more secondary fins  128 . 
     The sealing element  122  is configured to compress against an uphole end  313  of the cap  114 . The recess  312  and a tapered inner surface  314  of the primary fin  126  mirror a tapered surface  316  on the uphole end  313  of the cap  114 . Thus, and more particularly, the downhole end  315  of the primary fin  126  mirrors in structure the uphole end  313  of the cap  114  such that, under pressure as described below, the primary fin  126  will compress against the tapered surface  316  of the cap  114 . 
     The engagement member  124  may extend from the sealing element  122  and engage the sealing element  122  with the cap  114  as shown in  FIG. 3 . The engagement member  124  may include a neck  318  that extends into the cavity  304  of the cap  114 . The neck  318  may include a flange  320  that is retained within the cavity  304  by a lip  322  extending from the cap  114 . Other embodiments of the dart  104  may include multiple engagement members (not shown) that engage with respective vented cavities (not shown) defined by the cap  114 . 
     In the exemplary embodiment, the sealing element  122  and the cap  114  are made of a dissolvable rubber. Other embodiments of the sealing element  122 , the cap  114 , or both may be made of another dissolvable material know in the industry. Further embodiments of the sealing element  122  and the cap  114  may use different types of dissolvable rubber. In at least one embodiment, the sealing element  122 , the cap  114 , or both are made from a material that is not dissolvable. 
       FIGS. 4-6  illustrate the installation of the tubular sealing apparatus  100  of  FIG. 1  within a tubular section  402 . The tubular section  402  is, in the illustrated embodiment, a section of the casing, but may be any type of tubular that is set in a wellbore, as known to the art. The retainer  102  is positioned within the tubular section  402  by a running tool (not shown) that extends through the retainer  102 . The retainer  102  is held on the running tool by a shear ring (not shown) configured to break at a predetermined load and a cylindrical retainer (not shown). The shear ring may be positioned adjacent to the slip  116  and the cylindrical retainer may be positioned adjacent to the annular body  106 . 
     Once the retainer  102  reaches the desired location, the running tool begins to compress the retainer  102  by pulling the slip  116  towards the annular body  106 , and pushing the annular body  106  towards the slip  116 . The slip  116  expands as it travels uphole  101  over the tapered portion  202  of the annular body  106 . In some embodiments, this expansion may cause the slip  116  to fracture along grooves (not shown), creating a plurality of slip segments (not shown). In other embodiments, grooves in the slip  116  may allow the slip  116  to expand without fracturing. Another embodiment of the slip  116  may expand along the tapered portion  202  of the annular body  106  without the use of grooves. 
     As the retainer  102  is set, the threads  218  having crests  224  that are angled uphole  101 , shown in  FIG. 2B , contact the tubular section  402 , as show in  FIG. 4 . The threads  218 , and, in particular, the larger thread  226 , may engage or “bite into” the inner diameter of tubular section  402 , preventing further movement of the slip  116  towards the annular body  106 . Since the retainer  102  is being compressed by the running tool, the running tool will continue to push the annular body  106  towards the slip  116 . This movement further expands the slip  116  along the tapered portion  202  of the annular body  106 . The continued expansion of the slip  116  allows the left-hand thread profile  120  of the slip  116  to engage with the tubular section  402 , preventing movement of the slip  116  away from the annular body  106  and further holding the retainer  102  in position. 
     The interface  404  between the serrations  206  of the annular body  106  and the thread profile  234  of the slip  116  may also have a ratcheting effect. The ratcheting effect allows the thread profile  234  of the slip  116  to slide over the serrations  206  of the annular body  106  in one direction, but restricts movement of the serrations  206  in the opposite direction. Accordingly, the ratcheting effect may prevent movement of the annular body  106  away from the slip  116 . 
     Once the retainer  102  has been set within the tubular section  402 , a dart  104  may be pumped down the tubular section  402 . As shown in  FIG. 5 , the cap  114  of the dart  104  may contact the annular body  106  of the retainer  102 , preventing further downhole  103  movement of the dart  104 . The force of the cap  114  against the annular body  106  of the retainer  102  may further secure the retainer  102  in place by shifting the slip  116  further along the tapered portion  202  of the annular body  106 . 
     After the dart  104  contacts the retainer  102 , pressure uphole  101  of the dart  104  compresses the sealing element  122  against the cap  114 , as shown in  FIG. 6 . The vent  306  prevents pressure from building within the cavity  304  of the cap  114 , allowing the engagement member  124  to shift within the cavity  304 . This movement presses the primary fin  126  against the cap  114  to seal the tubular section  402 . The secondary fins  128  are also forced against the tubular section  402  by an outer diameter slightly larger than the inner diameter of the tubular section  402 , creating additional seals within the tubular section. 
       FIG. 7  illustrates a cross-sectional view of an exemplary tubular sealing apparatus  700 , according to one or more embodiments. The tubular sealing apparatus  700  illustrated in  FIG. 7  may include a retainer  702  and the dart  104  describe above with respect to the tubular sealing apparatus  100  and shown in  FIGS. 1, 3, 5, and 6 . Accordingly, the tubular sealing apparatus  700  may be best understood with reference to the tubular sealing apparatus  100 , where like numerals indicate like elements and therefore will not be described again in detail. 
     The retainer  702  may be made of a high-yield aluminum. Other embodiments of the retainer  702  may be made of steel, a high-yield cast metal, a high-yield powdered metal, or a composite material. As shown in  FIG. 8 , the retainer  702  may include an annular body  704 . The annular body  704  may define a plurality of holes  706  that extend through the thickness of the annular body  704 . In the exemplary embodiment, the holes  706  are unthreaded and similar in size. Other embodiments may include threaded holes (not shown), holes (not shown) that are different sizes, or any combination thereof. Further embodiments of the retainer  702  may include holes (not shown) that extend only partially through the annular body  704  or omit the holes  706 . 
     The annular body  704  may also include a plurality of grooves  708  extending along a portion of an axial length of the annular body  704 . The grooves  708  may be angled with respect to a center axis  710 , as shown in  FIG. 8 . Other embodiments may include grooves  708  that are parallel to the center axis  710 . In at least one embodiment, the grooves  708  may be omitted and the retainer  702  may include a plurality of separate arcuate sections (not shown) that each define a plurality of holes  706 . 
       FIGS. 9-13  illustrate the installation of the tubular sealing apparatus  700  of  FIG. 7 . The retainer  702  is positioned within the tubular section  402  by a running tool (not shown) that extends into the retainer  702 . Once the retainer  702  reaches the desired location, the running tool expands the retainer  702 , causing the outer surface  1002  of the retainer  702  to contact the tubular section  402  as shown in  FIG. 10 . The grooves  708  in the retainer  702  may allow the retainer  702  to expand without fracturing. Other embodiments of the retainer  702  may fracture along the grooves  708  when expanded, forming multiple arcuate segments (not shown), or the running tool may position a retainer  702  made up of a plurality of separate arcuate segments (not shown) against the tubular section  402 . 
     After expanding or otherwise positioning the retainer  702  against the tubular section  402 , the running tool installs a plurality of fasteners  1102  that couple the retainer  702  to the tubular section  402  and hold the retainer  702  in position within the tubular section  402 . As shown in  FIG. 11 , the fasteners  1102  may extend through the plurality of holes  706  defined by the annular body  704  of the retainer  702 . In the exemplary embodiment, the fasteners  1102  are bolts that are fired through the tubular section  402 . Other embodiments of the retainer  702  may include screws (not shown) that extend into or through the tubular section  402 , or pins (not shown) that utilize an interference fit to secure the retainer  702  in position within the tubular section  402 . After setting the retainer  702 , the running tool is withdrawn from the wellbore and the dart  104  may be pumped down to seal the tubular section  402  as describe above and shown in  FIGS. 13 and 14 . 
     In light of the foregoing disclosure,  FIG. 14  illustrates a flow chart  1400  of an exemplary method for sealing a tubular section  402  of a wellbore. The method may include engaging a retainer  102 ,  702  with an inner diameter of a tubular section  402  without sealing the tubular section  402 , as shown at  1402 . The method may also include pumping a dart  104  including a sealing element  122  down a wellbore to seat at least a portion of the sealing element  122  in a cap  114  and seat the cap  114  against the retainer  102 ,  702 , as shown at  1404 . The method may further include compressing the sealing element  122  of the dart  104  against the cap  114  to seal the tubular section  402 , as shown at  1406 . 
     In addition to the embodiments described above, U.S. Provisional Patent Application Ser. Nos. 62/349,177, and 62/397,041 incorporated by reference above disclose additional embodiments differing from embodiments described herein in various ways. Although not expressly disclosed herein, these embodiments disclosed in the aforementioned provisional applications are, as previously stated, incorporated by reference into the present application to the extent consistent with the present application. It is to be understood that the lack of an express disclosure herein does not disclaim such embodiments. Those incorporated embodiments are, through their incorporation, a part of this disclosure as if expressly set forth herein. They, therefore, are within the scope of the subject matter claimed below. 
     As previously noted, the embodiments disclosed in the above provisional applications differ from the embodiments disclosed herein. For example, one embodiment disclosed in Provisional Applications 62/349,177 and 62/397,041 includes a plurality of arcuate segments (not shown) that are coupled to the tubular section  402  through welding, bolting, or other similar means. Two such means are illustrated herein and discussed above-namely, a threaded engagement of a slip and bolting. However, these are, by way of example and illustration, but two means by which this may be achieved. Still other means performing this function through equivalent structure and use may become apparent to those skilled in the art having the benefit of this disclosure. Any such means may be used in various embodiments. 
     An additional embodiment of the retainer (not shown) disclosed in Provisional application Provisional Applications 62/349,177 and 62/397,041 includes a single rectangular body (not shown) that may be retained within the tubular section  402  using an interference fit. Provisional application Provisional Applications 62/349,177 and 62/397,041 further disclose a sealing dart (not shown) that includes a plurality of annular seals (not shown) coupled to a dart body (not shown). 
     The foregoing has outlined features of several embodiments so that those skilled in the art may better understand the present disclosure. Those skilled in the art should appreciate that they may readily use the present disclosure as a basis for designing or modifying other processes and structures for carrying out the same purposes and/or achieving the same advantages of the embodiments introduced herein. Those skilled in the art should also realize that such equivalent constructions do not depart from the spirit and scope of the present disclosure, and that they may make various changes, substitutions, and alterations herein without departing from the spirit and scope of the present disclosure.