Abstract:
A locating and locking mandrel and associated nipple provide for positioning an item of equipment in large bore and high weight conditions. In a described embodiment, a locating and locking mandrel includes at least one collect which is configured to cooperatively engage an internal profile of a nipple. The collect is capable of supporting the weight of the item of equipment until at least one locking member of the mandrel is engaged with another internal profile of the nipple. A seal of the mandrel is received in a seal bore of the nipple prior to insertion of the locating member or locking member into the seal bore, thereby preventing damage to the seal bore.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates generally to positioning items of equipment within a subterranean well and, in an embodiment described herein, more particularly provides a locating and locking mandrel system. 
     When positioning an item of equipment, such as a wireline-conveyed subsurface safety valve, within a tubing string installed in a subterranean well, it is common practice to attach a lock mandrel to the valve and then convey the valve and lock mandrel into the string. The lock mandrel is then operatively engaged with a nipple interconnected in the string. Typically, the engagement between the mandrel and the nipple anchors the valve in position in the string and seals the valve to the string, so that flow through the string is constrained to pass through the valve. 
     When initially positioned in the nipple, it is typical for the weight of the valve to be supported by a no-go member of the mandrel. The no-go member may be a cylindrical member or ring having an outer diameter somewhat greater than an inner no-go diameter of the nipple. In this manner, engagement between the no-go member and the no-go diameter prevents the mandrel from passing through the nipple and thereby supports the weight of the valve on the no-go diameter. After the no-go member has engaged the no-go diameter, a locking member, such as a radially extendable dog or lug, is engaged with an internal profile of the nipple, in order to lock or anchor the mandrel in position relative to the nipple. 
     However, it has become increasingly prevalent to utilize large diameter tubing strings with large seal bores in wells, in order to maximize fluid flow therethrough. In designing tools for use in such large diameter tubing strings, the tool designer is faced with several problems. Larger diameter tools tend to have increased weight and, thus, in the typical lock mandrel and nipple system, increased weight must be borne by the no-go diameter of the nipple when engaged by the no-go member. Additionally, in order to provide a larger bore, the wall thickness of the nipple may be decreased, so that only a small area is available to support the weight of the valve. 
     Furthermore, lock mandrels and nipples have in the past required that a radially outwardly extending or biased locating and/or locking member of the mandrel, such as the lugs or dogs mentioned above, pass through a seal bore of the nipple before a seal of the mandrel sealingly engages the seal bore. It will be readily appreciated that this situation may cause damage to the seal bore by the locating and/or locking member, so that the seal cannot effectively engage the seal bore. 
     From the foregoing, it may be seen that it would be highly advantageous to provide a locating and locking mandrel system which is specially adapted for use in situations in which it is undesirable to support the weight of an item of equipment on a no-go diameter of a nipple. Additionally, it would be advantageous to provide a locating and locking mandrel system in which a seal surface of a nipple is protected from damage due to contact with a locating and/or locking member of the mandrel. 
     SUMMARY OF THE INVENTION 
     In carrying out the principles of the present invention, in accordance with an embodiment thereof, a locating and locking mandrel system is provided which does not require supporting the weight of an item of equipment on a no-go diameter of a nipple. The system also does not require that a locating or locking member of the nipple pass through a seal surface of the nipple. 
     In one aspect of the present invention, a locating and locking mandrel includes colleted locating members which engage an internal profile of a nipple. When engaged with the internal profile, the locating members are capable of supporting the weight of an item of equipment attached to the mandrel. With the weight supported by the locating members, separate locking members of the mandrel may then be operatively engaged with another internal profile of the nipple to thereby anchor the item of equipment relative to the nipple. 
     In another aspect of the present invention, the mandrel also includes a seal configured for sealing engagement with a seal surface of the nipple. The seal is downwardly disposed on the mandrel relative to the locating and locking members. In this manner, the seal engages the seal surface without the locating or locking members passing through or engaging the seal surface. 
     In yet another aspect of the present invention, the mandrel may include a backup no-go member, for use in the event that the locating members do not operatively engage the internal profile of the nipple. However, in the described embodiments, the no-go member does not contact a no-go diameter of the nipple in normal operation of the mandrel system. 
     In still another aspect of the present invention, the mandrel is constructed in a compact and efficient manner, with portions thereof positioned and configured for enhanced effectiveness, reduction of cost and reliable operation. For example, the mandrel is constructed with reduced moving parts, a reduced number of parts, a reduced number of threaded joints and with features that increase its reliability in operation. 
     These and other features, advantages, benefits and objects of the present invention will become apparent to one of ordinary skill in the art upon careful consideration of the detailed description of representative embodiments of the invention hereinbelow and the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a cross-sectional view of a first locating and locking mandrel system embodying principles of the present invention, a mandrel of the mandrel system being shown in a configuration in which it is conveyed into a nipple; 
     FIG. 2 is an enlarged scale cross-sectional view of a portion of the mandrel system of FIG. 1; 
     FIG. 3 is a cross-sectional view of the mandrel system of FIG. 1, the mandrel being shown in a configuration in which it is locked in position relative to the nipple; 
     FIG. 4 is a cross-sectional view of a second locating and locking mandrel system embodying principles of the present invention, a mandrel of the mandrel system being shown in a configuration in which it is conveyed into a nipple; and 
     FIG. 5 is a cross-sectional view of the mandrel system of FIG. 4, the mandrel being shown in a configuration in which it is locked in position relative to the nipple. 
    
    
     DETAILED DESCRIPTION 
     Representatively illustrated in FIG. 1 is a locating and locking mandrel system  10  which embodies principles of the present invention. In the following description of the mandrel system  10  and other apparatus and methods described herein, directional terms, such as “above”, “below”, “upper”, “lower”, etc., are used for convenience in referring to the accompanying drawings. Additionally, it is to be understood that the various embodiments of the present invention described herein may be utilized in various orientations, such as inclined, inverted, horizontal, vertical, etc., without departing from the principles of the present invention. 
     The mandrel system  10  includes a locating and locking mandrel  12  and a nipple  14 . The nipple  14  is configured for interconnection in a tubular string  16  installed in a subterranean well. The nipple  14  includes an upper internal circumferential recess or locking profile  18 , a middle internal circumferential recess or locating profile  20  and an inner seal surface or seal bore  22 . Note that the seal bore  22  is positioned below the locking and locating profiles  18 ,  20 . 
     The mandrel  12  is configured for positioning an item of equipment attached thereto, such as a subsurface safety valve  24 , relative to the nipple  14 . The mandrel  12  includes a seal or seals  26 , such as packing, a series of circumferentially spaced apart locating members or collets  28 , a series of circumferentially spaced apart locking members or keys  30  (only one of which is visible in FIG. 1) and an upper running/retrieving head  32 . 
     A key retainer sleeve  34  secures the keys  30  relative to a tubular housing  36  of the mandrel  12 . The retainer sleeve  34  permits the keys  30  to displace radially relative to the housing  36 , but prevents axial displacement of the keys relative to the housing. 
     A locking sleeve  38  is attached to the head  32  and is axially slidably received between the retainer sleeve  34  and the housing  36 . When in its upwardly disposed position relative to the keys  30  as shown in FIG. 1, the keys are permitted to displace radially inward. However, when the locking sleeve  38  is displaced downwardly, it maintains the keys  30  in a radially outwardly disposed position as shown in FIG.  3 . Each of the keys  30  has an external profile  40  formed thereon which is cooperatively shaped relative to the locking profile  18  of the nipple  14 , so that when the mandrel  12  is operatively positioned within the nipple and the locking sleeve  38  is downwardly displaced, the key profiles engage the locking profile and thereby prevent displacement of the mandrel and the valve  24  relative to the nipple and the tubing string  16 . Such downward displacement of the locking sleeve  38  may be accomplished by applying set down weight to the head  32  via a conventional running tool engaged with the head, in a manner well known to those skilled in the art. 
     Each of the locating collets  28  has an external profile  42  formed thereon. The profiles  42  are configured to cooperatively engage the locating profile  20  of the nipple  14  and prevent downward displacement of the mandrel  12  through the nipple. The collets  28  are resilient and radially inwardly displaceable so that, as the mandrel  12  is lowered through the tubing string  16 , the collets “seek” the cooperatively configured profile  20 . The profiles  20 ,  42  may be only one set out of multiple sets of differently configured profiles, so that the collets  28  will only cooperatively engage a particular profile formed in the nipple  14  out of perhaps multiple differently configured profiles in the tubing string  16 . In this manner, the collets  28  may be “selective” in that they will only cooperatively engage one or more of multiple nipple profiles in order to locate the mandrel  12  in an appropriate desired nipple. 
     When the collet profiles  42  engage the nipple profile  20 , the engagement between the profiles stops the downward displacement of the mandrel  12 , thereby locating the mandrel within the nipple. Such engagement between the collets  28  and the nipple  14  also supports the weight of the mandrel and valve  24 . 
     The seal  26  is positioned on the mandrel  12  below the keys  30  and the collets  28 . The seal  26  accordingly engages the seal bore  22  below the profiles  18 ,  20  in the nipple  14 . Thus, neither the keys  30  nor the collets  28  pass through the seal bore  22 , and there is no danger that the keys or collets will damage the seal bore. In the embodiment shown in FIGS. 1-3, the seal  26  sealingly engages the seal bore  22  prior to the collets  28  engaging the profile  20  or the keys  30  engaging the profile  18 . 
     The mandrel system  10  is shown in FIG. 1 with the mandrel  12  in its configuration as it is lowered through the tubing string  16 . When the collets  28  engage the profile  20 , the mandrel  12  cannot displace further downwardly relative to the nipple  14 . Thereafter, when it is desired to lock the mandrel  12  in position relative to the nipple  14 , the head  32  and locking sleeve  38  are displaced downwardly relative to the housing  36 , thereby forcing the keys  30  radially outward into engagement with the profile  18 . FIG. 3 shows the mandrel system  10  after the head  32  and locking sleeve  38  have been displaced downwardly. 
     Referring additionally now to FIG. 2, an enlarged view is shown of a portion of the mandrel system  10  encircled and indicated by the reference number  2  in FIG.  1 . In this view, it may be seen that a relatively small no-go shoulder  44  is formed internally on the nipple  14 . The mandrel  12  includes a no-go member or retainer ring  46  which is utilized to retain the collets  28  on the housing  36 . 
     The no-go ring  46  has an outer diameter which is greater than the inner diameter of the no-go shoulder  44 . Thus, engagement between the no-go ring  46  and the shoulder  44  may be utilized to prevent downward displacement of the mandrel  12  relative to the nipple  14 . However, note that there is a gap between the no-go ring and the shoulder  44 , due to the collets  28  being engaged with the profile  20 . The no-go ring  46 , therefore, acts as a secondary locating device, in the event that the collets  28  do not operatively engage the profile  20 . If the collets  28  do not engage the profile  20  and the mandrel  12  is permitted to displace downward far enough for the no-go ring  46  to contact the shoulder  44 , the mandrel will still be operatively positioned within the nipple  14  so that the keys  30  may be radially outwardly extended into engagement with the profile  18 . 
     Referring additionally now to FIGS. 4 &amp; 5, another locating and locking mandrel system  50  embodying principles of the present invention is representatively illustrated. The mandrel system  50  is very similar in many respects to the mandrel system  10  described above, differing mainly in the manner in which locking keys  52  are radially outwardly extended. Therefore, elements shown in FIGS. 4 &amp; 5 which are the same as, or similar to, elements shown in FIGS. 1,  2  &amp;  3  are indicated using the same reference numbers. 
     The mandrel system  50  includes a mandrel  54  in which, instead of displacing one or more members, such as the head  32  and locking sleeve  38 , downward to bring keys  30  into locking engagement with the profile  18 , a locking sleeve  56  is displaced upward to radially outwardly engage the keys  52  with the profile. Additionally, a head  58  of the mandrel  54  is attached to a housing  60  of the mandrel, and does not displace with the locking sleeve  56 . Note that the mandrel  54  does not include a separate key retainer, since the housing  60  also performs the function of retaining the keys  52 . 
     In FIG. 4 the mandrel  54  is shown in a configuration in which it is conveyed into a tubular string, such as the string  16 , with the collets  28  engaged with the profile  20  and supporting the weight of any item of equipment, such as the valve  24 , which may be attached to the mandrel. Note that in this configuration the keys  52  are not radially outwardly supported by the locking sleeve  56 . In FIG. 5, the mandrel  54  is shown in a configuration in which the locking sleeve  56  has been upwardly displaced and now radially outwardly supports the keys  52  in engagement with the profile  18 . 
     A generally C-shaped snap ring or C-ring  62  releasably maintains the locking sleeve  56  in either its upwardly or downwardly disposed position relative to the housing  60 . The locking sleeve  56  may be displaced between its upwardly and downwardly disposed positions by utilizing a conventional shifting tool or running/retrieving tool well known to those skilled in the art. 
     Retrieval of either the mandrel  12  or the mandrel  54 , with attached valve  24  or other item of equipment, is accomplished by displacing the locking sleeve  38  upwardly or by displacing the locking sleeve  56  downwardly, respectively, and applying an upward force to the head  32  or to the head  58 , respectively. With the keys  30  or  52  no longer radially outwardly supported in locking engagement with the profile  18 , the keys will displace radially inward, due to cooperating inclined surfaces formed on the keys and the profile. The collets  28  will not prevent upward displacement of the mandrel  12  or  54 , since the profiles  20 ,  42  are configured to prevent downward displacement of the collets relative to the nipple  14  when the profiles are engaged, but are not configured to prevent upward displacement of the collets relative to the nipple. The upper ends of the collets  28  will be radially inwardly displaced out of engagement with the profile  20  by cooperating inclined surfaces formed on the profiles  20 ,  42  when the collets displace upwardly relative to the profile  20 . 
     Thus have been described the mandrel systems  10  and  50  which solve the problems presented by use of large diameter tubing strings having large bores and minimum wall thickness for provision of no-go surfaces. The mandrel systems  10  and  50  also provide simplicity and economy of manufacture, and convenience and reliability in operation. 
     Of course, a person skilled in the art would, upon a careful consideration of the above description of representative embodiments of the invention, readily appreciate that many modifications, additions, substitutions, deletions, and other changes may be made to these specific embodiments, and such changes are contemplated by the principles of the present invention. Accordingly, the foregoing detailed description is to be clearly understood as being given by way of illustration and example only, the spirit and scope of the present invention being limited solely by the appended claims.