Wells – Central chamber sealed with respect to prepositioned...
Reexamination Certificate
1998-10-07
2001-03-20
Dang, Hoang (Department: 3672)
Wells
Central chamber sealed with respect to prepositioned...
C166S125000, C166S208000, C166S075140
Reexamination Certificate
active
06202745
ABSTRACT:
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.
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Search Report under Section 17 regarding Application No. GB 9923304.1 dated Apr. 12, 2000 conducted by Examiner Matthew Parker.
Reimert Larry E.
Robinson Charles E.
Browning Bushman
Dang Hoang
Dril-Quip, Inc
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