Wellhead apparatus

Wellhead apparatus is shown to comprise a casing hanger releasably latched to a running tool for lowering, landing and locking within the bore of a housing so as to suspend an inner casing which is suspended from the hanger within an outer casing string to which the housing is connected. The hanger includes a mandrel carrying a lock ring for locking in a recess in the housing bore, and a seal sleeve is carried by the mandrel for movement between an upper position to permit cement to be circulated through a space between the mandrel and a lower position closing the space. The tool includes a body carrying a latch ring which is held within a groove in the bore of the mandrel as the hanger is lowered and locked within the housing bore, and which may be actuated to lower the sleeve into sealed position and release the latch ring for retrieval of the tool, from the hanger within the well bore.

This invention relates generally to wellhead apparatus for use in
 suspending a casing string within another casing string or other well
 conduit suspended within the bore of an oil or gas well. More
 particularly, it relates to improvements in apparatus of this type
 wherein, during the drilling and completion of the well, a hanger
 connected to the upper end of an inner casing string is lowered into and
 landed and locked within the bore of a housing of the other hanger which
 is connected to the upper end of the outer string, whereby cement may be
 circulated upwardly through an annular space between the casing strings
 and hangers to anchor the inner casing within the well bore, and the space
 is closed by a seal assembly and the closure and then tested by means of
 test pressure above it. In another of its aspects, it relates to
 improvements in the tool or tools on which the hanger mandrel and seal
 assembly carried thereby are run into, landed, and locked within the well
 bore, and the seal assembly lowered to seal off the space, and the tool
 released from the hanger mandrel to permit testing of the seal retrieval
 of the tool from the well bore.
 In order to minimize the cost of drilling and completing the well, the
 diameters of the well bore, and those of the casing strings, are as small
 as possible. Hence, it is important that the inner casing hanger, and its
 associated seal assembly, be of minimum radial thickness while
 nevertheless being able to support the load of the casing as well as
 pressure testing. This is a special challenge where it is necessary to
 support not only the weight of the casing string suspended from the
 hanger, but also the weight of another casing to be suspended within it,
 and it is the primary object if the inventor to provide apparatus which
 accomplish these purposes.
 It is a further object to provide such apparatus which includes a running
 tool which enables the hanger to be landed and locked within the bore of
 the housing and the seal assembly installed within the space in only one
 trip.
 These and other objects are accomplished, in accordance with the
 illustrated embodiment of the present invention, by wellhead apparatus
 which comprises a housing having a bore therethrough and a lower end
 connectible to an outer casing string for suspension within a well bore,
 an upwardly facing shoulder in the bore, a locking groove in the bore
 above the shoulder and having an upwardly facing load surface, and first
 fluid bypass means connecting with the bore above and below the groove. It
 further comprises a casing hanger which includes a mandrel having a bore
 therethrough and a lower end connectible to an inner casing string for
 suspension within the outer casing string, and a radially expandable and
 contractible locking ring carried about mandrel in a contracted position.
 A downwardly facing cam surface is formed on the mandrel above the recess,
 and a sleeve is connected within the bore of the mandrel so as to land on
 the shoulder in the housing bore in order to initially locate the locking
 ring opposite the locking groove therein. The connection is releasable in
 response to downward movement of the mandrel and locking ring with respect
 to the housing to expand the ring into and hold it within the groove,
 whereby the load of the casing is transmitted through the hanger mandrel,
 to the locking ring, and from the locking ring to the housing.
 The housing bore and mandrel form an annular space between cylindrical seal
 surfaces thereon which is an upward continuation of the first bypass
 means, and a sleeve carrying a aseal ring is connected about the hanger
 mandrel for vertical movement closely within the housing bore, in response
 to rotation of the sleeve, between an upper position in which the seal
 ring is above the annular space to permit circulation therethrough, and a
 lower position in which the ring is in sealing engagement with the seal
 surfaces to close the space. The bore of the housing also has second fluid
 bypass means outside the sleeve to form an upward continuation of the
 annular space, thus cooperating with the first fluid bypass means and
 space to provide a flow path for cement which is outside the hanger
 mandrel, whereby the hanger may be of minimal thickness, but nevertheless
 of such construction as to carry the loads to be described.
 In accordance with one novel aspect of the invention, the hanger and
 running tool are of such construction as to enable the mandrel to be
 landed within and locked to the housing bore in only one run, and, for
 this purpose, the tool includes a body adapted to be suspended from a pipe
 string for rotation and vertical movement therewith within the well bore,
 and having a downwardly facing load surface for seating on the upwardly
 facing load surface of the mandrel. A radially expandable and contractible
 latch ring carried within a recess about the body has an upwardly facing
 load surface, and an expander is threadedly connected about the body and
 guidably movable within a slot in the hanger mandrel to cause the expander
 to be moved vertically, in response to rotation of the body, between an
 upper position in which the latch ring may contract and a lower position
 in which the latch ring is expanded and held within the groove.
 In this position, an upwardly facing surface on the latch ring is
 engageable by a downwardly facing surface on the mandrel groove so as to
 carry the load of the casing string as it is lowered into the well with
 the tool. On the other hand, the tolerance of the latch ring and mandrel
 groove are such as to not transmit downward load to the hanger when the
 annular space is closed to permit pressure testing, as will be described
 to follow.
 In accordance with another aspect of the present invention, the sleeve has
 a slot in its inner diameter to slidably guide a key carried by the tool
 body for rotation and vertical movement with it to lower the sleeve which
 is threadedly connected to the hanger mandrel. In the preferred and
 illustrated embodiment, the key is mounted on a collar which is carried on
 the tool body and on the lower end of which the downwardly facing load
 surface of the tool body is formed to seat on the upper end of the
 mandrel. As above noted, with the expander guidably slidable vertically
 within a slot in the inner diameter of the hanger mandrel, the expander is
 confined for vertical movement with respect to the tool body to enable the
 tool to both lock the hanger mandrel to the housing bore and lower the
 seal ring to close the space in one run.

With reference now to details of the above described drawings, the housing,
 indicated in its entirety by reference character 20, is connected to the
 upper end of an outer casing string 21 (FIG. 1) and has a bore 22
 therethrough in which a casing hanger 23 is installed to suspend an inner
 casing string 24 (FIG. 1) connected to its lower end within the outer
 casing string 21. There is annular space between the casing strings
 through which, as will be described to follow, cement may be circulated
 upwardly between the hanger and bore of the casing hanger to anchor the
 inner casing string within the outer casing string. The apparatus further
 includes a running tool, indicated in its entirety by reference character
 L to which the hanger is latched for lowering into a position in which it
 is landed and locked within the bore of-the housing.
 The housing, which is indicated by reference character 26, includes a main
 tubular member 27 and a tubular insert 28 threadedly connected at 29
 within a lower recess in the main tubular member 27. As shown, the outer
 diameter of the insert has vertical slots 30 formed therein which are open
 at their upper and lower ends so as to permit cement to be circulated
 through the lower bypass formed thereby. Locking groove 35 is formed in
 the inner diameter of housing insert 28 adjacent its upper end and above
 an upwardly facing shoulder 34 in the bore.
 As previously described, the hanger includes a mandrel 33 to which the
 upper end of the inner casing string 24 is connected, and an expandable
 and contractible split locking ring 36 carried about the hanger mandrel.
 In addition, a sleeve 38 is releasably connected by means of a shear pin
 39 to the outer diameter of the mandrel beneath the recess and thus
 beneath the lock ring 36 but above shoulder 34 so as to initially locate
 the lock ring opposite the groove. The hanger also carries a guide ring 40
 there about which fits closely within the bore of insert 28 to maintain it
 concentrically therein.
 The lock ring 36 is normally contracted into recess 36A so that the hanger
 is freely moveable downwardly into the position shown in FIG. 2. Upon
 reaching the FIG. 2 position, weight is imposed upon the hanger so as to
 shear the pin 39 and thus permit the locking mandrel and lock ring to move
 downwardly to the illustrated positions in which the lock ring may be
 forced out of groove 36A and into the lock groove 35 and then held it in
 such position. For this latter purpose, the hanger mandrel has a
 downwardly and inwardly tapered cam surface 40A, which, as the mandrel is
 moved further, forces the ring into locked position within the locking
 groove until a downwardly facing shoulder 41 on the mandrel above its
 recess lands on the upper end of the locking ring, as shown in FIG. 3.
 The locking groove has upwardly facing load surfaces which are engaged by
 the downwardly facing load surfaces of the lock ring whereby, as
 previously mentioned, the load of the hanger, and that to be imposed by
 test pressure, is transmitted from the hanger, through the lock ring and
 onto the housing bore. Ratchet teeth 42 and 43 are formed on the inner
 diameter of the locking ring and outer diameter of the mandrel beneath its
 surface 41 so as to prevent upward movement of the hanger from its locked
 position as well as to permit the operating string to impose tension on
 the running tool to test the lock. It will be understood of course that
 the locking ring has sufficient clearance in the groove and flexibility to
 permit the ratchet teeth to move into ratcheted position.
 As previously described, the hanger also includes a sleeve 45 which carries
 a elastomeric seal ring 46 and whose inner diameter is threadedly
 connected at 47 to the outer diameter of the hanger mandrel. When the
 mandrel is locked within the housing bore, the seal sleeve occupies an
 upper position in which the seal ring 46 is above an annular space S
 formed between oppositely facing annular seal surfaces 49 and 50 on the
 outer diameter of the mandrel and intermediate bore portion of the
 housing. As will be described to follow, upon manipulation of the running
 tool, the sleeve is lowered to move its seal ring 46 into the space for
 sealing between the seal surfaces.
 Preferably, the mandrel has an upwardly facing shoulder 51 above the lock
 ring in position to be engaged by the seal sleeve as it is lowered into
 the space, whereby continued lowering of the seal sleeve, following
 seating on the shoulder, will cause the seal ring to be compressed and
 thus sealably engaged with both sealing surfaces to close the space. As
 also illustrated, the seal ring 46 is disposed between upper and lower
 portions of the sleeve, and a downwardly and outwardly extending flared
 surface 52 (FIG. 2)is formed on the outer diameter of the hanger mandrel
 above its seal surface thereon so as to stretch the seal ring tightly over
 it, as it moves into the space, as best shown in FIG. 12. Also, the upper
 end of the sleeve comprises upper and lower parts connected in end-to-end
 relation by means of a ring 53 which permits them to rotate relative to
 one another, whereby the seal ring need not rotate with the upper end of
 the seal sleeve as it is moved into sealing position.
 Prior to lowering the seal ring, cement may be circulated upwardly through
 the bypass slots in the housing insert and into and through the annular
 space 5 and then upwardly within bypass slots 55 formed in the housing
 bore about the sleeve. As shown, the outer diameter of the hanger mandrel
 beneath the shoulder is slotted at 55A as to facilitate flow between the
 bypass formed by slots 30 and the annular space.
 The running tool T is shown to comprise a body 56 carried about a well pipe
 56A for rotation therewith and releasably connected to the mandrel hanger
 by means of a split latch ring 57 on the tool body engageable within a
 latch groove 58 in the bore of the hanger mandrel. As shown, the latch
 ring is carried about the running tool body for radial expansion and
 contraction between its latching position in which it may lower the hanger
 therewith and its released position of FIG. 12, which enables the tool to
 be inserted within or withdrawn from within the hanger for retrieval from
 the well bore, as shown in FIG. 5.
 The latch ring is held in latching position by means of a cylindrical
 expander 60 carried about the body of the tool for vertical movement
 between a lower position in which it fits between the body and the latch
 ring to hold the latch ring in latching position, and an upper position in
 which it permits the split latch ring to contract to and thus permit
 installation of the running tool. As the expander is moved downwardly from
 its releasing position, a downwardly and inwardly facing cam surface 61
 thereon engages a similarly tapered surface 62 on the upper end of the
 latch ring 57 to force the latch ring outwardly into the latch groove 58
 in the mandrel of the hanger and hold it in such position as a lower
 cylindrical end the expander moves into the cylindrical inner diameter of
 the ring. In this position, downwardly and inwardly tapered load surface
 63 thereon is engageable with the similarly tapered load surface 64 on the
 latch groove so as to support the hanger and inner casing string from the
 running tool.
 However, and as best shown in FIG. 11, the tolerances are such that, with
 the tool body supported on the upper end of the hanger, the downwardly
 facing surfaces on the inner side of the latch ring are spaced from the
 oppositely facing surfaces of the groove, so that downward load of the
 hanger and string, as well as the force of test pressure, are transmitted
 through the lock ring, as previously described.
 The inner diameter of the expander is threadedly connected at 69 to the
 outer diameter of the body of the running tool and has ribs 70 in its
 outer diameter at to fit closely within slots 71 formed in the inner
 diameter of the hanger mandrel. Thus, rotation of the running tool in one
 direction will move the expander downwardly to expanding position, and in
 the opposite direction will raise the expander from latching position. The
 expander is initially lowered to latch the tool to the hanger at the
 surface 50 that the hanger may be lowered therewith into the bore of the
 housing until the locating sleeve seats on the upper end of the shoulder
 34, whereby downward force may be applied through the running tool to
 shear the pin 39 and thus release the locating sleeve and permit the
 locking ring to be moved into locking position within the bore of the
 housing.
 The seal sleeve 45 is connected to the running tool for rotation therewith
 and vertical movement with respect thereto by means of keys 72 which are
 carried within guideways in a collar 75 which is connected to the tool
 body by a pin 76. The keys are yieldably urged (see FIG. 2) outwardly into
 slots 77 in the inner diameter of the seal sleeve to permit relative
 vertical movement between them. As previously described, the inner
 diameter of the seal sleeve is threadedly connected at 69 to the outer
 mandrel of the casing hanger mandrel generally opposite the upper bypass
 slots 55 in the bore of the housing so as to be m movable downwardly into
 the space by rotation of tool. As shown, the collar has a lower extension
 80 which, upon latching of the running tool to the hanger mandrel, engages
 the upper end 81 of the hanger mandrel, whereby keys are located opposite
 the latch groove about the casing mandrel.
 The threads connecting the expander 60 to the body of the running tool, and
 those connecting the seal sleeve to the mandrel, are so arranged that,
 upon installation of the hanger on the running tool, the seal sleeve is in
 its upper position above the space between the hanger mandrel and the
 housing bore, as shown in FIG. 2. This of course can be accomplished at
 the surface by the rotation of the body of the running tool in one
 rotational direction so as to simultaneously move the expander downwardly
 to force the latch ring 57 into the latch groove of the hanger mandrel
 while raising the seal sleeve to its raised position.
 With the mandrel lowered into and locked within the housing bore, reverse
 rotation of the running tool body will raise the expander 60 to release
 the latch ring 57 and move the seal sleeve downwardly toward sealing
 position within the space between the hanger mandrel and housing bore
 (FIG. 4). As best shown in FIG. 3A, the threaded connections are so
 arranged as to raise the expander to release the latch ring from the
 hanger mandrel before the seal sleeve is lowered to fully compress the
 seal ring, thus assuring that the running tool can be retrieved even
 though the space between the mandrel and the housing bore is not fully
 closed. At the same time, it enables the running tool to apply full torque
 to compress the seal ring.
 The body of the running tool is recessed about its lower end to carry a
 seal 85 for sealably engaging the bore of the mandrel when the, mandrel is
 assembled on the tool. This seal ring 85 is held in place by a retainer
 ring,86 threadedly connected to the lower end of the recess. Thus, the
 seal cooperates with the seal ring 46 to close off the annular space
 between the running string and housing bore 50 that it may be tested by
 pressure from above.
 Preferably, and as shown, the tool body is made up of a main upper portion
 87 which is mounted for rotation with the pipe string by means of keys 88,
 and a lower portion 89 of the body is supported on a shoulder 90 about the
 pipe string. The latch ring 57 and seal rings are supported on the lower
 end of a reduced diameter portion at the upper end of the lower body
 portion, and seal rings 91 on the pipe complete closure of the space.
 Thus, the pipe string and upper portion of the body of the running tool
 may be rotated without rotation of the latch ring and seal ring 85.
 From the foregoing it will be seen that this invention is one well adapted
 to attain all of the ends and objects herein above set forth, together
 with other advantages which are obvious and which are inherent to the
 apparatus.
 It will be understood that certain features and subcombinations are of
 utility and may be employed without reference to other features and
 subcombinations. This is contemplated by and is within the scope of the
 claims.
 As many possible embodiments may be made of the invention without departing
 from the scope thereof, it is to be understood that all matter herein set
 forth or shown in the accompanying drawings is to be interpreted as
 illustrative and not in a limiting sense.