Patent Publication Number: US-10316626-B2

Title: Buoyancy assist tool

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims benefit of U.S. Provisional Patent Application Ser. No. 62/162,358, filed May 15, 2015, which is herein incorporated by reference. 
    
    
     BACKGROUND 
     Hydrocarbon fluids, such as oil and natural gas, may be obtained from a hydrocarbon-bearing subterranean geologic formation by drilling a well that penetrates the formation. Once a wellbore is drilled, various forms of well completion components may be installed in order to control and enhance the efficiency of producing the fluids. 
     SUMMARY 
     The summary is provided to introduce a selection of concepts that are further described below in the detailed description. This summary is not intended to identify key or essential features of the claimed subject matter, nor is it intended to be used as an aid in limiting the scope of the claimed subject matter. 
     In accordance with an example implementation, a method includes running a tubing string that includes a tool inside a wellbore. The tool includes a wiper plug assembly and is configured to form a fluid barrier inside a central passageway of the tubing string. The technique includes using a degradable material to secure the wiper plug assembly to a body of the tool; pressurizing the tubing string to breach the fluid barrier; communicating a cement slurry into the tubing string and through the breached fluid barrier; and communicating another plug assembly into the tubing string behind the cement slurry to engage the wiper plug assembly and release the wiper plug assembly from the tool. 
     In accordance with another example implementation, an apparatus that is usable with a well includes a tubular body, a wiper plug assembly, and a degradable member. The wiper plug assembly is disposed inside the central passageway of the tubular body, and the degradable member retains the wiper plug assembly to the tubular body. 
     In accordance with another example implementation, a system includes a casing string and a buoyancy assist tool that is disposed in the casing string. The buoyancy assist tool includes a tubular body, a wiper plug assembly, and a degradable member. The wiper plug assembly is disposed inside the central passageway of the tubular body, and the degradable member retains the wiper plug assembly to the tubular body. 
     In accordance with yet another example implementation, a technique includes running a casing string including a buoyancy assist tool inside a wellbore. The buoyancy assist tool includes a wiper plug assembly retained in place inside the buoyancy assist tool by a degradable sleeve and shear pins attaching the wiper plug assembly to the degradable sleeve; and the wiper plug assembly includes a central passageway that is blocked by a first fluid barrier. The technique includes pressurizing the tubing string to breach the first fluid barrier; communicating a completion fluid downhole inside the casing string to cause the fluid to circulate through the casing string and into an annulus between the casing string and the wellbore; communicating a predetermined volume of a cement into the tubing string; communicating a fluid inside the tubing string following the cement, including communicating a cementing plug assembly to land the cementing plug assembly inside the central passageway of the wiper plug assembly; pressurizing the tubing string to shear the shear pins to cause the wiper plug assembly to be released from the buoyancy assist tool; and using the wiper plug assembly to follow the cement through a central passageway of the casing string until the wiper plug assembly lands in a landing collar of the casing string. 
     Advantages and other features will become apparent from the following drawings, description and claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIGS. 1, 3, 5, and 7  are schematic diagrams of a well illustrating operations related to installing a casing string in a laterally-extending wellbore according to an example implementation. 
         FIGS. 2, 4, 6, 8 and 9  are cross-sectional views of a buoyancy assist tool of the casing string in different states associated with the installation of the casing string according to an example implementation. 
         FIGS. 10 and 11  are flow diagrams depicting techniques to install a casing string in a well according to example implementations. 
     
    
    
     DETAILED DESCRIPTION 
     In the following description, numerous specific details are set forth but implementations may be practiced without these specific details. Well-known circuits, structures and techniques have not been shown in detail to avoid obscuring an understanding of this description. “An implementation,” “example implementation,” “various implementations” and the like indicate implementation(s) so described may include particular features, structures, or characteristics, but not every implementation necessarily includes the particular features, structures, or characteristics. Some implementations may have some, all, or none of the features described for other implementations. “First”, “second”, “third” and the like describe a common object and indicate different instances of like objects are being referred to. Such adjectives do not imply objects so described must be in a given sequence, either temporally, spatially, in ranking, or in any other manner. “Coupled” and “connected” and their derivatives are not synonyms. “Connected” may indicate elements are in direct physical or electrical contact with each other and “coupled” may indicate elements co-operate or interact with each other, but they may or may not be in direct physical or electrical contact. Also, while similar or same numbers may be used to designate same or similar parts in different figures, doing so does not mean all figures including similar or same numbers constitute a single or same implementation. Although terms of directional or orientation, such as “up,” “down,” “upper,” “lower,” “uphole,” “downhole,” and the like, may be used herein for purposes of simplifying the discussion of certain implementations, it is understood that these orientations and directions may not be used in accordance with further example implementations. 
     In accordance with example implementations, casing string may be installed in a horizontal, or laterally extending wellbore, using a buoyancy assist tool. The buoyancy assist tool is part of the casing string and, as its name implies, is used to increase the buoyancy of the casing string during the string&#39;s installation. In this manner, the buoyancy assist tool is used to retain air inside a segment of the casing string that is being run into a laterally extending wellbore so that the segment is buoyant, or “floats,” and thereby experiences less drag. The buoyancy assist tool may be used to form a fluid barrier at the uphole end of the lateral casing segment, with a cementing float shoe of the lateral casing segment forming a fluid barrier at the downhole end of the segment. The central passageway of the casing string segment is filled with air between these fluid barriers. After being run into the wellbore, a completion fluid may be pressurized in the column above the buoyancy assist tool to remove the fluid barrier imposed by the tool and allow the completion fluid to be circulated through the lateral segment of the casing string and return through the annulus, thereby displacing any drilling fluid (and water above the drilling fluid). A predetermined volume of cement may then be communicated downhole into the central passageway of the casing through the now opened, buoyancy assist tool. The cement may be followed, or chased, by a cementing plug assembly, which is pumped downhole using additional completion fluid. The cementing plug assembly lands in a passageway of a liner wiper plug assembly, which is initially retained inside the buoyancy assist tool. The landed cementing plug assembly forms a fluid barrier inside the casing string; and by pressuring the completion fluid (using this fluid barrier), the wiper plug assembly is released from the tool. After being released, the wiper plug assembly may then travel downhole due to the pumping of the completion fluid to swab the inside of the lateral casing string segment and aid in displacing the cement into the surrounding annulus. At the far, or distal, end (i.e., the toe end) of the casing segment, the wiper plug assembly lands in a landing collar that is disposed near the float shoe near the end of the lateral casing segment. 
     One way to initially secure the wiper plug assembly to a buoyancy assist tool is to use shear pins that extend between a tubular body of the assembly and into the tubular body of the tool, which forms part of the casing string wall. In this manner, by plugging the wiper plug assembly with the cementing plug assembly and pressuring the column of completion fluid above the wiper plug assembly, the shear pins shear to release the wiper plug assembly. A particular challenge associated with retaining the wiper plug assembly to the buoyancy assist tool in the above-described manner is that the outer diameter (O.D.) of the wiper plug assembly is close in size to the inner diameter (I.D.) of the buoyancy tool&#39;s tubular body. This relationship, in turn, constrains the I.D. of any component of the casing string downhole from the buoyancy assist tool to be near the I.D. of the buoyancy tool&#39;s tubular body. 
     In accordance with example implementations that are described herein, the buoyancy assist tool retains a wiper plug assembly in a manner that allows the wiper plug assembly to have a decreased O.D., as compared to conventional buoyancy assist tools. Consequently, components of the casing string that are disposed downhole from the buoyancy assist tool may have relatively smaller IDs. More specifically, in accordance with example implementations, the buoyancy assist tool includes a degradable member to which the wiper plug assembly is initially secured (by one or multiple shear pins, for example). The degradable member, in accordance with example implementations, is a degradable sleeve that circumscribes the wiper plug assembly and is retained inside a tubular body of the buoyancy assist tool. The annular space that is occupied by the degradable sleeve allows the wiper plug assembly to have a reduced OD, thereby resulting in reduced IDs for components of the casing string downhole of the buoyancy assist tool. 
     When the column of completion fluid is pressurized uphole of the buoyancy assist tool to release the wiper plug assembly from the buoyancy assist tool, the shear member(s) shear, thereby leaving the degradable sleeve in place inside the buoyancy assist tool. The degradable member is constructed to deteriorate, dissolve, or degrade, in a relatively short interval of time (a time of a few weeks or a few months, depending on the particular implementation). Therefore, the space inside the body of the buoyancy assist tool increases with the removal of the degradable sleeve, and moreover, the degrading of the sleeve leaves little to no debris in the lateral casing segment, in accordance with example implementations. 
     Referring to  FIG. 1 , as a more specific example, a well  100  may include a laterally extending wellbore  122 , which may, extend from a relatively more vertically extending wellbore  120  of the well  100 . The laterally extending wellbore segment  122  may traverse one or more hydrocarbon-bearing formations.  FIG. 1  depicts the initial installation of a casing string  130 , a tubing string inside the well, and more specifically, the casing string  130  has a segment  131  that extends into the laterally extending wellbore  122 . In this state, an annulus  170  of the casing string segment  131  is surrounded by drilling fluid, and water may be present above the drilling fluid. As depicted in  FIG. 1 , the lateral casing string segment  131  extends from a heel end  141  to a toe end  143  of the laterally extending wellbore  122 , in accordance with example implementations. 
     For purposes of cementing the lateral casing string segment  131  in place inside the laterally extending wellbore  122 , the casing string  130  includes a buoyancy assist tool  156 , which is disposed near the heel end  141  of the wellbore  122  after the casing string segment  122  has been run into position. The buoyancy assist tool  156  is run downhole in a state in which the tool  156  initially blocks fluid communication through the central passageway of the lateral casing string segment  131 . In other words, initially, the buoyancy assist tool  156  forms a fluid obstruction, or barrier, inside a central passageway  150  of the casing string  130 , so that the casing string segment  131  downhole of the buoyancy assist tool  156  is isolated from the central passageway of the tubing string uphole of the tool  156  (and a column of completion fluid  160  uphole of the tool  156 , for example). Moreover, a cementing float shoe, a one way valve, maintains the isolation at the downhole end of the casing string segment  131 . Due to this isolation, the interior space of the casing string segment  131  is kept free of the drilling fluid and other liquids during the running of the casing string  130  downhole, which facilitates installation of the string due to the string&#39;s increased buoyancy and lowered weight. 
     In accordance with example implementations, the casing string segment  131  may be initially filled with air or another gas. As depicted in  FIG. 1 , the casing string  130  may further includes a landing collar  180 , which is used, as further described herein. 
     It is noted that although  FIG. 1  and other figures that are described herein depict a laterally extending wellbore, the techniques and systems that are disclosed herein may likewise be applied to more vertically extending wellbores. Moreover, in accordance with example implementations, the well  100  may contain multiple wellbores, which contain tubing strings that are similar to the illustrated tubing string  130  of  FIG. 1 . The well  100  may be a subsea well or may be a terrestrial well, depending on the particular implementation. Additionally, the well  100  may be an injection well or may be a production well. Thus, many implementations are contemplated, which are within the scope of the appended claims. 
       FIG. 2  depicts the buoyancy assist tool  156 , in accordance with an example implementation. In particular,  FIG. 2  depicts the buoyancy assist tool  156  in its initial, or run-in hole, state. Referring to  FIG. 2  in conjunction with  FIG. 1 , the buoyancy assist tool  156  includes a tubular housing, or body  210 , which, in general, circumscribes a longitudinal axis  201  of the tool  156  (and nearby portion of the lateral casing string segment  131 ). As depicted in  FIG. 2 , in its run-in hole state, the buoyancy assist tool  156  includes a liner wiper plug assembly  230 , which is disposed inside a central passageway of the tool  156 . Moreover, in the run-in hole state of the buoyancy assist tool  156 , the wiper plug assembly  230  is secured in place by a degradable sleeve  220  (that circumscribes a tubular member  231  of the wiper plug assembly  230 ) and one or multiple shear pins  224  that attach the tubular member  231  to the sleeve  220 . 
     More particularly, in accordance with example implementations, the degradable sleeve  220  circumscribes the longitudinal axis  201  and is circumscribed by the body  210  of the buoyancy assist tool  156 . As an example, the body  210  may form part of the wall of the casing string  130 . In accordance with some implementations, the degradable sleeve  220  rests in a restriction that is formed inside the tubular body  210  by an uphole and inwardly facing inclined annular surface  211  of the tubular body  210 . In this manner, as shown in  FIG. 2 , a corresponding downhole and outwardly facing inclined annular surface  226  of the degradable sleeve  220  may contact the surface  211 . On its uphole end, the degradable sleeve  220  may be held in place inside the tubular body  210  by a retaining device, such as a lock ring  214 . As an example, the lock ring  214  may be installed inside the tubular body  210  and have outer threads  215  that engage corresponding inner threads  217  of the tubular body  210 , in accordance with example implementations. As also shown in  FIG. 2 , in accordance with some implementations, the tubular member  231  of the wiper plug assembly  230  may be secured to the degradable sleeve  220  by one or multiple shear pins  224 , thereby initially securing the wiper plug assembly  230  inside the buoyancy assist tool  156 . 
     In general, the wiper plug assembly  230  has swabbing wipers, or cups  234  (rubber or elastomer cups, for example) that annularly extend about the tubular member  231  for purposes of swabbing the interior surface of the lateral casing string segment  131  after the wiper plug assembly  230  has been released from the buoyancy assist tool  156 , as further described below. The wiper plug assembly  230  forms an interior fluid barrier inside the buoyancy assist tool  156 , which inhibits, or prevents, fluid communication through the wiper plug assembly  230  for purposes of initially created the air filled zone in the lateral casing string segment  131 . In this manner, in the run-in-hole states of the buoyancy assist tool  156 , the outer swabbing cups  234  may be energized to form an annular fluid seal between the tubing member  231  and the tubular body  210 ; one or multiple o-rings  228  may form fluid seals between the tubing member  231  and the degradable sleeve  220 ; and a removable fluid barrier  240  prevents fluid communication through the central passageway of the tubular member  231  of the wiper plug assembly  230 . In accordance with example implementations, the fluid barrier inside the tubing member  231  may be formed from a rupture disc, which is constructed to rupture at a pressure above a certain threshold, which allows a pressurized fluid column above the buoyancy assist tool  156  to be used to remove the initial fluid barrier that is created by the tool  136 , so that completion fluid may be circulated through the central passageway of the lateral casing string segment  131  and into the surrounding annulus  170 . 
     Among its other features, the buoyancy assist tool  156  may include couplers to couple, or connect, the buoyancy assist tool  156  in line with the casing string  130 . For example, in accordance with some implementations, the buoyancy assist tool  156  may include a box end coupler  204  at its far uphole end and a pin end coupler  206  at its far downhole end. Other connectors may be used to couple the buoyancy assist tool  156  in line with the casing string  130 , in accordance with further example implementations. 
     As also depicted in  FIG. 2 , in accordance with some implementations, the wiper plug assembly  230  may include outer ratcheting teeth  244  near the downhole end of the tubing member  231  to lock the assembly  230  in place after landing in the landing collar  180 . Moreover, as shown in  FIG. 2 , uphole form the ratcheting teeth  244 , the wiper plug assembly  230  may include a stop collar  246 , which circumscribes the tubing member  231  for purposes for purposes of limiting downhole travel of the wiper plug assembly  230  into the landing collar  180 . 
       FIG. 3  depicts an illustration  300  of the well after completion fluid  160  has been pumped into the casing string  130  such that the fluid column above the buoyancy assist tool  156  has been pressurized above the rupturing threshold of the rupture disc  240  ( FIG. 2 ). In this manner, referring to  FIG. 4  in conjunction with  FIG. 3 , the pressurized fluid opens, or ruptures, the rupture disc  240  to allow fluid communication through central passageway of the tubing member  231  (i.e., allow fluid communication through the buoyancy assist tool  156 ). The completion fluid may then be circulated through the float shoe  182  of the casing string  130  and into the annulus  170 , as depicted by arrows  302  and  304  in  FIG. 3 . It is noted that the wiper plug assembly  230 , for this state, remains inside the buoyancy assist tool  156 . 
     Referring to  FIG. 5  (an illustration  500  of the next state of the well  100 ) and  FIG. 6  (an illustration  600  of the corresponding state of the buoyancy assist tool  156 ), a predetermined volume of cement  502  ( FIG. 5 ) may be communicated downhole through the central passageway of the casing string  130 , and the pumping of the cement  502  may be followed, or chased, by a cementing plug assembly  510 , which, in turn, is followed by a column of completion fluid (as depicted at reference numeral  514  of  FIG. 5 ). The plug assembly  510  enters the inner tubing member  231  of the plug assembly  230  for purposes of forming a corresponding fluid barrier inside the tubing member  231 . By increasing the pressure of the completion fluid column on the buoyancy assist tool  156 , an axial force is exerted on the tool  156  to cause the shear pin(s)  224  to shear, thereby releasing the wiper plug assembly  230  from the buoyancy assist tool  156 , as depicted by an illustration  800  of  FIG. 8 . In this manner, the wiper plug assembly  230  exits the buoyancy assist tool  156  and travels in a downhole direction  810  as shown in  FIG. 8 . Referring to an illustration  700  in  FIG. 7  showing the landing of the wiper plug assembly  230  in the landing collar  180 , for this state, the cement has been displaced in the annulus  170 , thereby completing the cementing operation. 
     Referring back to  FIG. 8 , after the wiper plug assembly exits the buoyancy assist tool  156 , the degradable sleeve  220  remains. After a relatively short interval of time (a few weeks, or months, depending on the particular implementation), the degradable material degrades to the extent that the degradable sleeve  220  falls, or is otherwise removed from the buoyancy assist tool  156 , as depicted in illustration  900  of  FIG. 9 . 
     In accordance with example implementations, one or more components of the buoyancy assist tool  156  (such as the degradable sleeve  220 ) may contain a material or materials, which allow at least part of the object to degrade (dissolve, structurally deteriorate, and so forth) by well fluid or another fluid, which is introduced into the tubing string passageway. As an example, the material(s) for the object may be the same or similar to the materials disclosed in the following patents, which have an assignee in common with the present application and are hereby each incorporated by reference: U.S. Pat. No. 7,775,279, entitled, “DEBRIS-FREE PERFORATING APPARATUS AND TECHNIQUE,” which issued on Aug. 17, 2010; and U.S. Pat. No. 8,211,247, entitled, “DEGRADABLE COMPOSITIONS, APPARATUS COMPOSITIONS COMPRISING SAME, AND METHOD OF USE,” which issued on Jul. 3, 2012. 
     In this context, a degradable material is a material that degrades at a significantly faster rate than other materials or components (the casing string  130 , for example) of the downhole well equipment. For example, in accordance with some implementations, dissolvable or degradable material(s) may degrade at sufficiently fast rate to allow the fluid barrier to disappear (due to the material degradation) after a relatively short period of time (a period less than one year, a period less than six months, or a period of less than ten weeks, as just a few examples). In this manner, in accordance with example implementations, the degradable sleeve of the buoyancy assist tool maintains its structural integrity for a sufficient time to allow the cementing operation(s) that rely on the buoyancy assist tool  156  to be performed, while disappearing shortly thereafter to remove any obstruction presented by the member to allow other operations to proceed in the well, which rely on access through the portion of the casing string, which contained the fluid barrier. 
     Thus, in general, a technique  1000  ( FIG. 10 ) may be performed in accordance with example implementations. Pursuant to the technique  1000  a tubing string is run (block  1002 ) inside a wellbore, where the tool forms fluid barrier inside central passageway of the tubing string. Pursuant to block  1004 , a degradable material is used to secure a wiper plug assembly of the tool to a body of the tool. The tubing string may be pressurized (block  1006 ) to breach a fluid barrier that is formed inside a central passageway of the tubing string by the tool. Cement may then be communicated (block  1008 ) into the tubing string and through the breached, fluid barrier. Another plug assembly may then be communicated into the tubing string behind the cement slurry to engage the wiper plug assembly to form a fluid barrier, and fluid uphole of the tool may be pressurized using the fluid barrier to release the wiper plug assembly from the tool, pursuant to block  1010 . 
     More specifically, referring to  FIG. 11 , in accordance with some implementations, a technique  1100  includes running (block  1102 ) a casing string that includes a buoyancy assist tool inside a wellbore. The buoyancy assist tool includes a wiper plug assembly that is retained in place inside the buoyancy assist tool by a degradable sleeve and shear pins that attach the assembly to the sleeve; and the wiper plug assembly includes a central passageway that is initially blocked by the fluid barrier. Pursuant to block  1104 , the tubing string may then be pressurized to breach the fluid barrier in the central passageway. Completion fluid may then be communicated (block  1106 ) downhole inside the casing string to cause the fluid to circulate through the casing string and into the annulus between the casing string and the wellbore. A predetermined volume of cement may then be communicated into the casing string, pursuant to block  1108 . The technique  1100  next includes communicating (block  1110 ) fluid inside the casing string following the cement, including communicating a cementing plug assembly to land the cementing plug assembly inside a central passageway of the wiper plug assembly. The tubing string may then be pressurized (block  1112 ) to shear the shear pins to cause the wiper plug assembly to be released from the buoyancy assist tool. The wiper assembly is then used (block  1114 ) to follow the cement through the central passageway of the casing string until the wiper plug assembly lands in a landing collar of the casing string. 
     While the present techniques have been described with respect to a number of embodiments, it will be appreciated that numerous modifications and variations may be applicable therefrom. It is intended that the appended claims cover all such modifications and variations as fall within the scope of the present techniques.