Patent Publication Number: US-8540028-B1

Title: Autonomous junk collecting sleeve for a riser

Description:
CO-PENDING APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 12/054,362, filed Mar. 24, 2008 now U.S. Pat. No. 8,162,064, and claims priority from U.S. Provisional Application No. 60/896,786, filed Mar. 23, 2007, which is incorporated herein by reference as if set forth in full below. 
    
    
     BACKGROUND OF THE INVENTION 
     I. Field 
     The present invention relates to an oilfield tool and more particularly, to an autonomous junk collecting sleeve for a riser which is constructed and arranged to be independently lowered and seated above a subsea tree and, subsequently, raised and removed or cleaned. 
     II. Background 
     Various types of junk baskets have been devised for collecting debris from a wellbore during a cleaning operation. The junk basket has a basket dimensioned to collect debris flowing around and external to the basket. The top end of the junk basket is open and relies on free falling debris in the upward-flowing drilling fluid to fall into the opening of the junk basket where it remains until the junk basket is removed. However, the force of the upward-flowing drilling fluid carrying the debris impedes the collection of the debris by the junk basket. 
     Thus, some junk baskets are not able to collect a substantial portion of the debris in the wellbore, particularly when fluid circulates through the junk basket and upward through an annulus in the well as the basket is retrieved to the surface. Other junk baskets are complicated and are thus relatively expensive. 
       FIG. 1  illustrates a conventional junk basket  1  having a central mandrel  2  and a basket  4 . The annulus between the wellbore  3  and the basket  4  narrows. Thus, the upward-flowing fluid, denoted by ARROW A, has a first speed. The fluid, denoted by ARROW B, has a second speed faster than the first speed as a result of the narrower annulus. The fluid, denoted by ARROW C, continues upward toward the top of the wellbore  3  and is generally slower than the fluid, denoted by ARROW B. However, as the fluid, denoted by ARROW B, passes the upper end of the basket  4 , a portion of the fluid automatically travels, in the direction of ARROW E, toward the central mandrel  2  as the annulus is abruptly enlarged. This portion of the fluid flowing in the direction denoted by ARROW E forms small eddy currents created directly over the opening in the basket  4 . However, simultaneously, fluid flowing upward, in the direction of ARROW C, recaptures or carries away the debris. Thus, the deposit of debris in the basket  4  is impeded. 
     Most junk baskets are positioned at various locations in a work string. However, a significant amount of debris is still carried up to the top of the wellbore. The floating debris must be retrieved and removed from the drilling fluid. However, there is not an efficient or quick means of removing the debris near the top of the wellbore. 
     The slower moving fluid in the riser may not be able to suspend the heavier debris. Thus, the heavier debris floats downward. 
     Thus, there is a continuing need for an autonomous junk collecting sleeve for use in a riser which is constructed and arranged to be independently lowered and seated above a subsea tree section to collect debris in the riser and, subsequently, raised and removed independent of the work string. 
     SUMMARY OF THE INVENTION 
     The present invention contemplates an autonomous junk collecting sleeve for use in a riser comprising: a first outer cylindrical structure, a second inner cylindrical structure concentric to and shorter than the first cylindrical structure and which are joined together in spatial relation at a bottom end to form an interior J-channel basket, the J-channel basket being operable to collect debris traveling up through the bottom end and over the top of the second cylindrical structure for deposit therein. 
     An object of the present invention is to provide an autonomous junk collecting sleeve with a first cylindrical structure having at a top end, a brim operable to attach a tool thereto to lower and retrieve sleeve. 
     A further object of the present invention is to provide an autonomous junk collecting sleeve with a first cylindrical structure having a brim which protrudes from the first cylindrical structure toward a longitudinal axis of the first cylindrical structure a distance that approximates the spatial relationship between the first cylindrical structure and the second cylindrical structure. 
     A still further object of the present invention is to provide an autonomous junk collecting sleeve with a first cylindrical structure that is longer in length than the second cylindrical structure. A hollow interior cavity is formed above a top edge of the second cylindrical structure and below the brim. 
     A still further object of the present invention is to provide an autonomous junk collecting sleeve with an outer diameter of the first cylindrical structure being slightly smaller than an inner diameter of the riser. 
     A still further object of the present invention is to provide an autonomous junk collecting sleeve with a second cylindrical structure having an inner diameter which is the same as or larger than the inner diameter of the subsea tree section. 
     A still further object of the present invention is to provide an autonomous junk collecting sleeve having an inner diameter that allows the sleeve to be seated at a bottom of the riser and supported at a riser seat above a subsea tree section. 
     A still further object of the present invention is to provide an autonomous junk collecting sleeve with a first cylindrical structure having, at a top end, a brim operable to have attached thereto a fishing tool to autonomously retrieve the sleeve from a bottom of the riser. 
     The present invention further contemplates an autonomous junk collecting sleeve for a riser and which is independent of a work string. The sleeve comprises a cylindrically-shaped, J-channel basket having a junk collecting space and a hollow throughbore center with access directly into the junk collecting space. The J-channel basket is operable to collect debris traveling up through the bottom end of the hollow throughbore center and over the access for deposit of the debris in the junk collecting space. 
     The present invention further contemplates a method of cleaning a wellbore. The method comprises: cleaning a riser from an upper surface to a subsea tree section; lowering an autonomous junk collecting sleeve at a seat of the riser; installing a work string through the riser and the autonomous junk collecting sleeve to a depth of the wellbore, the work string being independent of the sleeve; cleaning a wellbore with the work string; and collecting debris from the wellbore in the autonomous junk collecting sleeve, simultaneously with the cleaning of the wellbore. 
     An advantage of the autonomous junk collecting sleeve is its autonomy from the work string. Thus, the autonomous junk collecting sleeve may be deployed, emptied and re-deployed independent of the work string. 
     A further advantage of the autonomous junk collecting sleeve is the increased junk collecting space provided in the J-channel basket to collect larger amounts of debris including heavy and larger size debris suspended in the riser. 
     The above and other objects and features of the present invention will become apparent from the drawings, the description given herein, and the appended claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
       For a further understanding of the nature and objects of the present invention, reference should be had to the following description taken in conjunction with the accompanying drawings in which like parts are given like reference numerals. 
         FIG. 1  illustrates a conventional junk basket installed in a wellbore below a riser. 
         FIG. 2  illustrates a perspective view of an autonomous junk collecting sleeve in accordance with the present invention with a portion removed. 
         FIG. 3  illustrates a cross-sectional view of the autonomous junk collecting sleeve installed in a riser above a subsea tree section in accordance with the present invention. 
         FIG. 4  illustrates a cross-sectional view of an alternate configuration of the autonomous junk collecting sleeve installed in a riser above a subsea tree section in accordance with the present invention. 
         FIG. 5  illustrates a cross-sectional view of a still further alternate configuration of the autonomous junk collecting sleeve installed in a riser above a subsea tree section in accordance with the present invention. 
     
    
    
     The images in the drawings are simplified for illustrative purposes and are not depicted to scale. To facilitate understanding, identical reference numerals have been used, where possible, to designate identical elements that are common to the Figures, except that suffixes may be added, when appropriate, to differentiate such elements. 
     The appended drawings illustrate exemplary configurations of the invention and, as such, should not be considered as limiting the scope of the invention that may admit to other equally effective configurations. It is contemplated that features of one configuration may be beneficially incorporated in other configurations without further recitation. 
     DETAILED DESCRIPTION 
     Referring now to the drawings and particularly  FIGS. 2-3 , an autonomous junk collecting sleeve is designated by the reference numeral  10 . The autonomous junk collecting sleeve  10  is operable to be positioned in a riser  16 , such as defined by the interior surface  14  of the riser  16 , to collect debris from a wellbore  12  such as during cleaning operations. The riser  16  is followed by a subsea tree section  22 . The subsea tree section  22  is followed by the casing wall  24  of the wellbore  12 . 
     Wellbores are cleaned after a hole is drilled and the casing wall  24  is set in place. In order to save time and money, operators generally prefer to run the cleaning work string into the wellbore just once if possible. It usually takes one to four days to clean a wellbore  12  of leftover drilling fluids, cement bits, iron debris and caked deposits on the casing wall  24 . For wells having risers (generally a temporary tube connecting the surface drilling operation to the sea floor which is typically a few hundred feet to several thousand feet long) are usually cleaned in two operations. In a first cleaning operation, a short string is used to clean from upper surface to the subsea tree section  22 . In a second cleaning operation, a long string is generally used to clean from the subsea tree section  22  to the wellbore depth. Very high fluid flow rates can be used to clean the riser  16  during the first cleaning operation. In one aspect, the autonomous junk collecting sleeve  10  may be used after the riser  16  is cleaned because it may be most efficient in trapping debris coming up from the wellbore  12 . Furthermore, the autonomous junk collecting sleeve  10  may remain in the riser  16  until the clean up operations are complete. 
     During cleaning operations, a work string  26  is lowered downhole in the wellbore  12  for cleaning operations. The interior surface of the casing wall  24  may be in fluid communication with a hydrocarbon formation. As best seen in  FIG. 3 , the riser  16  has an inner diameter ID which is larger than the ID of the subsea tree section  22  and/or the casing wall  24 . The transition between a larger riser ID to a smaller subsea tree ID creates a riser seat  20 . The subsea tree section  22  may have one or more sub-sections with varying IDs one of which may be dimensioned to coincide with the ID of the casing wall  24  immediately below the subsea tree section  22 . 
     In general, the autonomous junk collecting sleeve  10  is constructed and arranged to be independently lowered and seated above the subsea tree section  22  on the riser seat  20  and, subsequently, raised and removed independently of the work string  26 . For example, the junk collecting sleeve  10  may be fished from the riser  16 . Alternately, the junk collecting sleeve  10  may be raised with the work string  26 . The autonomous junk collecting sleeve  10  may be comprised of tough steel that may be easily welded, such as  4130 . 
       FIG. 2  illustrates a perspective view of an autonomous junk collecting sleeve  10  with a portion removed.  FIG. 3  illustrates a cross-sectional view of the autonomous junk collecting sleeve  10  installed in the riser  16  above a subsea tree section  22 . The autonomous junk collecting sleeve  10  comprises in general a first cylindrical structure  30 , a second cylindrical structure  32  concentric to the first cylindrical structure  30  and a bottom basket floor  34 . The second cylindrical structure  32  is shorter in length then the first cylindrical structure  30 . The bottom basket floor  34  joins the first and second cylindrical structures  30  and  32  together at a lower end thereof in spatial relation to form an interior J-channel basket  40 . The space relationship between the first and second cylindrical structures  30  and  32  creates a collecting space  41  to collect debris therein. 
     The larger diameter of the riser  16  enables the area of the collecting space  41  to be increased over other junk collecting spaces of other junk baskets dimensioned for use in the casing wall  24  below the subsea tree  22 . Thus, the junk collecting sleeve  10  allows the larger size and/or heavier debris to be collected near the bottom of the riser  16 . Furthermore, the outer diameter OD of the first cylindrical structure  30  is slightly smaller than the ID of the riser  16  to provide sufficient clearance between the first cylindrical structure  30  and the interior surface  14  of the riser  16  so that the sleeve  10  may be installed and removed without hindrance. 
     The longitudinal centers of the first and second cylindrical structures  30  and  32  are hollow. Thus, the upper portion of the first cylindrical structure  30  creates a first central hollow throughbore section  42   a  above the top edge  33  of the second cylindrical structure  32 . The second cylindrical structure  32  creates a second central hollow throughbore section  42   b  having an inner diameter ID which is smaller than the ID of the first central hollow throughbore section  42   a.    
     The first cylindrical structure  30  further includes a top side or edge  45  having brim  47 . The brim  47  narrows the opening  49  at the top side or edge  45  of the first cylindrical structure  30 . The opening  49  has an ID which is larger than the OD of a work string  26 . The brim  47  is also constructed and arranged to allow the autonomous junk collecting sleeve  10  to be lowered to and fished out from the riser independently of the work string  26 . The brim  47  may serve as a fish neck for attachment of a tool to lower, set and retrieve the sleeve  10 . 
     In one configuration, the brim  47  is a solid structure contoured with a lower edge  48   a  extending a small distance from the inner surface of the first cylindrical structure  30 . The distal end of the lower edge  48   a  away from the first cylindrical structure  30  curves or transitions upward and becomes essentially vertical to form a vertical surface  48   b  (curving in the direction toward the upper distal end of the first cylindrical structure  32 ). An upper portion  48   c  of the vertical surface  48   b  tapers, slopes or flares slightly back toward the first cylindrical structure  30  such that the ID of the opening  49  is slightly flared or increased. 
     The brim  47  may protrude a distance toward the second cylindrical structure  32  such that the distance approximates the distance between the first and second cylindrical structures  30  and  32 . The brim  47  may be used as a guide. 
     The bottom end (coinciding with the plane of the bottom basket floor  34 ) of the central hollow throughbore section  42   b  of the second cylindrical structure  32  serves both as an inlet and outlet. Likewise, the opening  49  of the first cylindrical structure  30  provide both an inlet and an outlet. For example, as the work string  26  is lowered downhole, the work string  26  passes through and into opening  49  and, subsequently, out of the bottom end of the central hollow throughbore section  42   b . Also, reverse fluid traveling upward to the top of the riser  16  in the direction of ARROWS A 1  and A 2 , travels up through the bottom end of the central hollow throughbore section  42   b.    
     The second central hollow throughbore section  42   b  has an inner diameter ID which is intended to be larger than the OD of the work string  26 . Thus, an annulus  50   b  is defined between work string  26  and the interior circumferential surface of the second cylindrical structure  32 . Likewise, an annulus  50   a  is defined between work string  26  and the interior circumferential surface of the first cylindrical structure  30 . Annulus  50   b  is smaller than the annulus  50   a . The enlarged annulus  50   a  followed by a narrowing about opening  49  promotes deflection of a portion of the reverse drilling fluid in the direction of ARROW B, the narrowing being generated by the protrusion of the brim  47 . The placement of brim  47  allows fluid to slow and swirl thereunder. Thus, any debris or other heavy debris collecting in the interior annulus  50   a  promotes deposit of the debris within the interior J-channel basket  40 . The upper portion  48   c  is sloped in a direction to promote feeding the reverse fluid out of opening  49  in the direction of ARROW C. 
     In one mode of operation, to install the autonomous junk collecting sleeve  10 , the sleeve  10  is lowered to the bottom of riser  16  to rest on riser seat  20 . A work string  26  may be installed downhole in the wellbore  12 . Fluid flows downward in the direction of ARROWS E in the throughbore of the work string  26 . During, cleaning operations, the fluid flowing in the direction of ARROWS E are emitted into the wellbore  12 . The fluid carries debris in a reverse flow up to the top of the wellbore  12  and into the riser  16 . This fluid passes into the annulus  50   b  and up to the enlarged annulus  50   a  to create eddy currents to deposit debris in the interior J-channel basket  40 . After a predetermined period or at the end of a cleaning cycle, the autonomous junk collecting sleeve  10  is fished from the bottom of the riser  16  so that the interior J-channel basket  40  can be cleaned. 
     In one aspect, the autonomous junk collecting sleeve  10  remains in the riser  16  until cleaning operations are complete. In another aspect, the autonomous junk collecting sleeve  10  may be deployed, raised and re-deployed with or without the work string  26  downhole. 
     The wellbore cleaning operation preferably entails additional cleaning tools for liberating debris within the wellbore  12  such as may be accumulated along the interior surface of the casing wall  24 . For example, a brush or scraper type tool may be positioned along the upper string, and/or a hydraulically powered jetting or circulating tool positioned below the junk basket. 
     During the wellbore cleaning operation, the cleaning tools may be used to liberate debris prior to and/or concurrently with passing fluid through the work string  26 , then upward through the casing wall past the subsea tree section  22  and into the riser  16 . Fluid is thus passed from the work string  26 , downward through its center into the wellbore  12 . Fluid passing into the wellbore  12  may gather and carry formation debris present within the wellbore  12 . The fluid passes from the wellbore  12  upward to the riser  16  and through the annulus  50   b  or  50   a , possibly carrying with it debris from the wellbore  12 . Debris may be liberated using brushes, scrapers or a combination of brushes and scrapers. Furthermore, high velocity jets directed toward the casing wall may be used in combination with the brushes and/or scrapers. 
     Upon completion of the wellbore cleaning operation or drilling operations, the work string  26  may be moved upward from the wellbore  12 . The autonomous junk collecting sleeve  10  may then be emptied into an appropriate waste receptacle and used again in subsequent wellbore cleaning operations. 
       FIG. 4  illustrates a cross-sectional view of an alternate configuration of the autonomous junk collecting sleeve  100  installed in a riser  116  above a subsea tree section  122  in accordance with the present invention. The autonomous junk collecting sleeve  100  has a longer length then the autonomous junk collecting sleeve  10 . The longer length increases the length of the first and second cylindrical structures  130  and  132  to create a larger collecting space  141  to collect debris therein. Since, the autonomous junk collecting sleeve  100  is independent of the work string  126 , the sleeve  100  may take advantage of the depth of the riser  116  to maximize the collecting space  141 . The configuration of autonomous junk collecting sleeve  100  provides a smaller brim  147  which creates a smaller protrusion into the reverse fluid flow. Thus, any heavy debris carried away and out of opening  149  at the top of autonomous junk collecting sleeve  100 , may float back down into the opening  149 . The brim  147  may still be sufficient to attach a tool for lowering, setting and retrieving the autonomous junk collecting sleeve  100 . 
       FIG. 5  illustrates a cross-sectional view of a still further alternate configuration of the autonomous junk collecting sleeve  200  installed in a riser  216  above a subsea tree section  222  in accordance with the present invention. The autonomous junk collecting sleeve  200  has a longer length then both the autonomous junk collecting sleeves  10  and  100 . The longer length increases the length of the first and second cylindrical structures  230  and  232  to create a larger collecting space  241  to collect debris therein. Since the autonomous junk collecting sleeve  200  is independent of the work string  226 , the sleeve  200  may take advantage of the depth of the riser  216  to maximize collecting space  241 . The configuration of autonomous junk collecting sleeve  200  provides a triangularly shaped brim  247 . The brim  247  may protrude a distance toward the second cylindrical structure  232  such that the distance approximates the distance between the first and second cylindrical structures  230  and  232 . The brim  247  may be used to attach a tool for lowering, setting and retrieving the autonomous junk collecting sleeve  200 . 
     In this configuration, the increase in length of the first cylindrical structure  230  increases the length of the annulus  250   a  above the second cylindrical structure  232  to the brim  247 . This added length may promote deposit of debris into the interior J-channel basket  240 . 
     The autonomous junk collecting sleeve  200  further comprises a soft seal  260  around the outer perimeter of the first cylindrical structure  230  to buffer or protect the interior surface  214  of the riser  216  and the first cylindrical structure  230  during deployment and retrieval of the autonomous junk collecting sleeve  200 . The soft seal  260  may comprise Neoprene Shore A 70. 
     To those skilled in the art to which the invention relates, many changes in construction and widely differing embodiments and applications of the invention will suggest themselves without departing from the scope of the invention as defined in the appended claims. The disclosures and the descriptions herein are purely illustrative and are not intended to be in any sense limiting.