US3424478A - Wellhead apparatus - Google Patents

Description

Jan. 28, 1969 c. R. HUTCHINSON 3,424,478

WELLHEAD APPARATUS Filed June 27, 1966 :Sheet 1 of 5 INVENTOR cam. R. HUTGHINSON BY (d W Y ATTORNEY Jan. 28, 1969 .c. R. HUTCHINSON WELLHEAD APPARATUS :Sheet Filed June 27, 1966 Rm mm Am 9 mm Amm I R. w. A m mm E c Q ATTORNEY -28, 1969 C.R.HUTCHIN 3,424,478

FIE] INVENTOR CARL R. HUTCHINSON M a/ W A ORNEY United States Patent ()ftice Patented Jan. 28, 1969 3,424,478 WELLHEAD APPARATUS Carl R. Hutchinson, Houston, Tex., assignor to FMC Corporation, San Jose, Calif., a corporation of Delaware Filed June 27, 1966, Ser. No. 560,539 U.S. Cl. 285-90 8 Claims Int. Cl. F16j /00; F161 21/08, 19/00 ABSTRACT OF THE DISCLOSURE A well completion apparatus including a combined pipe hanger bushing and packoff with a system for locking a pipe hanger to the bushing and the bushing to a wellhead, and a sealing system for providing a fluid seal between the hanger and wellhead, the two systems interrelated such that locking the bushing to the wellhead establishes the fluid seal and locks the hanger to the bushing.

Down well pressures in an oil well are on occasion extremely great and are sometimes sufiicient, when acting against the underside of a pipe hanger, to overcome the weight of the pipe supported by the hanger. In such a case the pipe and hanger may be blown out of the wellhead causing extensive damage.

It is customary when installing the production piping in a well to employ a blowout preventer over the wellhead. The blowout preventer has a vertical passage with an inside diameter equal to or larger than the inside diameter of the vertical passage in the wellhead to allow the pipe supporting equipment to be landed therethrough. When the well is reworked, a blowout preventer having a passage of smaller inside diameter is used because the reworking equipment cannot handle a large blowout preventer and a smaller blowout preventer is much less expensive than a large one.

Because of the use of a smaller blowout preventer, a pipe hanger which is formed on one piece and which extends across the entire diameter of the wellheadcannot be employed since it would not pass through the vertical passage of the smaller blowout preventer. However, the use of hanger with an outside diameter permitting its passage through the smaller preventer generally requires an additional element, such as a sleeve or bushing, between the hanger and wellhead, but this type of system presents problems both in locking the hanger in the wellhead and in providing an effective seal between the wellhead and hanger.

Each of the foregoing problems has been overcome by the present invention which, briefly summarized involves a pipe hanger bushing with a system of locking elements or dogs to secure an inner pipe hanger to the bushing, and an annular resilient deformable packing member which, upon axial compression, expands radially to fill the space between the wellhead and the pipe hanger and simultaneously to move the locking dogs radially inward toward the pipe hanger. The packing member is compressed by longitudinal axial movement of a force transmitting element which also serves as a positive abutment for the locking dogs, this element moving axially in response to pressure exerted on it by a single set of lockdown screws extending through the wellhead wall. The locking dogs enter a recess formed in the pipe hanger, and when in that recess prevent the pipe hanger from raising in response to the pressures from below.

It is an object, therefore, of this invention to provide an improved wellhead apparatus.

It is another object of this invention to provide an improved lockdown and sealing assembly for use in a wellhead.

Another object of this invention is to provide a locking element which is movable into an operative position and retractable to an inoperative position by means remote from the locking element itself.

It is another object of this invention to provide a locking element that is actuated by expansion of a packing member which simultaneously serves as a seal.

It is another object to provide a lockdown and sealing assembly for pipe hangers which may be utilized with blowout preventers of various sizes.

Another object of the invention is to provide a lockdown and sealing assembly wherein a single set of lockdown screws may be used to lock the hanger in the wellhead as Well as to energize the sealing unember.

Other objects and advantages will become apparent from the following description and the accompanying drawings, in which:

FIGURE 1 is a longitudinal section of a wellhead embodying the subject invention.

FIGURE 2 is an enlarged, fragmentary, longitudinal section showing the invention in an unlocked and unsealed position.

FIGURE 3 is an enlarged, fragmentary, longitudinal section showing the invention in a locked and sealed position.

FIGURE 4 is an enlarged diametrical section taken generally along the line 4-4 of FIGURE 1.

In general, the invention is best understood by referring to FIGURE 1 wherein is shown a wellhead 10 which is supported above the ground in a manner conventional in the art. The well-head is provided with a seat 11 on which is supported a bushing 12. The bushing in turn supports a pipe hanger 13. The pipe hanger supports a pipe mandrel 14 and pipes 15 connected by the mandrel. A lockdown and sealing assembly 16 is positioned on the bushing 12 between the pipe hanger and the inner wall of the Wellhead. A force transmitting element or ring 17 rests on the lockdown and sealing assembly and is moved downward in the wellhead by a lockdown screw 18. Mounted on the top of the wellhead by a conventional clamp 19 is a small blowout preventer 20. A large blowout preventer 21 is shown in phantom lines.

The bushing 12 is provided with a bore 22 and is oounterbored to provide a seat 23 for supporting the pipe hanger 13. A plurality of equally spaced threaded holes 24 are provided in the top of the bushing for a purpose to be later described. The outside diameter of the bushing 12 is greater than the inside diameter of the small blowout preventer 20 but is smaller than the inside diameter of the large blowout preventer 21.

The pipe hanger 13 is provided with an inner bore 25 and is counter bored to provide a seat 26 for the pipe mandrel 14. The pipe hanger also has a lower chamfered edge 33 that engages the seat 23 of the bushing 12, and it is to noted that the outside diameter of the pipe hanger is less than the inside diameters of both blowout preventers.

The pipe mandrel 14 has internal threads at its upper and lower ends 27 and 28, respectively, to receive sections of the pipe 15. Conventional O-ring seals 29 are interposed between the pipe mandrel and the hanger and rest in grooves 30 in the coupling provided for that purpose. As best shown in FIGURES 2 and 3, the pipe hanger is also provided with a circumferential recess 31 having upper and lower edges 31a and 31b, respectively, and an inner face 310 which joins the upper and lower edges.

The lockdown and sealing assembly 16 comprises a one-piece circular sealing or packing member 35 which is made of a resilient deformable material, such as rubber. The packing member has an inner portion removed to form a cylindrical recess 36. The lower end 35a of the packing member is approximately of the same thickness as the bushing 12 and is provided with eight equally spaced holes 35b. An annular support ring 37, preferably made of metal or other hard material, is mounted in the recess; Resting on the top of the support ring are a plurality of locking segments or dogs 38 which, as seen in FIGURE 4, are formed as segments of a circle. The upper and lower inner edges 38a and 3811, respectively, of the dogsvare chamfered to provide camming surfaces. Each of the dogs is also provided with a generally centrally located hole 39 (FIG. 4). A small cylindrical sealing insert 40 is positioned in each hole. Interposed between the inside face of the wall defining the recess 36 of the packing member 35 and the outside surface of the dogs is a split-ring 42 (FIG. 4). The split-ring is comprised of two sections 42a and 42b having their ends spaced from one another as indicated by reference numerals 43. The gaps allow for sufficient inward movement of the split-ring to move the locking dogs against the inner face of the recess in the pipe hanger.

It is an inherent quality of the resilient packing member 35 that upon being compressed in one direction it will expand in the path of least resistance. In this case, when the packing member is compressed axially, it will expand radially in the area above the support ring 37 and will press against the split-ring 42. Consequently, the split-ring will move inwardly, sliding the locking dogs 38 into the circumferential recess 31 of the pipe hanger 13. Furthermore, the radial expansion of the lower end 35a of the packing member will create a tight seal between the outside surface of the hanger and inside surface of the wellhead.

In order to axially compress the packing member 35 to effect expansion thereof and movement of the locking dogs 38, a force transmitting element or ring 47 is provided. The force transmitting element has a chamfered edge 48 which provides a smooth sliding surface for the inner end of the lockdown screws 18. Each lockdown screw is conventional and is provided with a body 49 which is threaded at its inner end 50 into a threaded bore 51 in the wellhead 10. The body is circumscribed at its outer end by a plug '52 which is threaded into a bore 53 in the outside of the wellhead. A conventional O-ring sealing member 54 is interposed between the inner wall of the threaded bore 53 and the inner surface of the plug and provides a seal 'between the lockdown screw and the wellhead. The innermost end of the lockdown screw is provided with a conical point 55 which is adapted to engage the chamfered edge of the force transmitting element 47 and move it axially in the wellhead. The force transmitting element is also apertured with eight equidistantly spaced holes 56 each of which receives a long bolt 57. The bolts pass through the cylindrical sealing inserts 40 in the locking dogs 38, through the support ring 37, and through the holes 35b in the lower end of the packing member 35, and are threaded into the holes 24 in the bushing 12. The bolts are utilized to connect these various elements as a single unit, greatly facilitating handling thereof.

In the operation of the device, the bushing 12, lockdown and sealing assembly 16, and the force transmitting element 47 are all landed in the wellhead through the large blowout preventer 21 with the bushing resting on the seat 11. Next the pipe hanger is landed on the seat 23 of the bushing. At this time, of course, the lockdown screws 18 are in a retracted position and the locking dogs 38 likewise are retracted. Should the locking dogs per chance still extend slightly into the path of the pipe hanger while it is being landed the bottom chamfer 33 of the hanger will strike the upper edges 38a of the locking dogs and 'force them outwardly out of the path. Once the pipe hanger is landed, the pipe coupling 14 and the pipes are landed in the pipe hanger.

The initial position of the equipment with the locking dogs 38 and lockdown screws 18 retracted is shown in FIGURE 2. When it is desired to lock the pipe hanger 13 in the head, the lockdown screws 18 are rotated moving the conical points 55 thereof inwardly against the chamfered edge 48 of the force transmitting element 47 as shown in FIGURE 3. The force transmitting element is thus moved downwardly, compressing the packing member 35 against the top surface of the bushing 12. As the packing member is compressed, it expands radially inwardly pushing the split-ring 42 against the dogs and sliding them across the annular support ring 37 and intothe recess 31 on the hanger. Also, the lower end 35a of the packing member is pressed tightly against the pipe hanger and the inside surface of the wellhead to form a firm seal.

Should. the hanger 'be raised from below, it will be readily seen that the lower edge 31b of the recess 31 will engage the chamfered lower edges 38b of the locking dogs 38. Since the upper surfaces of the locking dogs abut against the lower surface of the force transmitting element 47 which is held by the lockdown screws, the pipe hanger is precluded from being moved upwardly beyond this point of engagement. When it is desired that the pipe and pipe hanger be removed, as for example, when the well is being reworked, and with a small blowout preventer 20 in place, the lockdown screws 18 are retracted allowing the packing member 35 to expand axially and urge the force transmitting element 47 upward. As the packing member returns to its original shape, the inwardly directed pressure on the locking dogs is removed, permitting them to move radially outwardly and release themselves from the recess 31 on the pipe hanger. Should the locking dogs still extend into the path of the pipe hanger as it is being removed, the lower chamfered edge 31b of the recess 31 will engage the lower chamfered edges 38]; of the locking dogs and force them outwardly out of the path of the hanger. Thus, as can be readily seen, the subject invention provides an extremely simple and effective assembly for simultaneously locking a pipe hanger in a wellhead while simultaneously sealing the area between the pipe hanger and the wellhead. A second advantage is that smaller, less expensive blowout preventers may be used during subsequent operations on the well, such as, reworking the well. Still another advantage is that a single set of lockdown screws performs a locking and seal engaging function saving substantial machining costs in the wellheads.

Although the preferred apparatus for carrying out the invention has been shown and described, it will be understood that it is capable of modification and variation while still operating according to the principles of the invention. It is to be understood, therefore, that the scope of the invention is limited only by the claims appended hereto.

Having thus described the invention, that which is believed to be new and for which the protection by Letters Patent is desired is:

1. Wellhead apparatus comprising a wellhead; a sent within said wellhead; a bushing member resting on said seat, said bushing member having a seat thereon; a pipe hanger slidably received in said bushing member and resting on said bushing seat; a resilient packing member circumscribing said pipe hanger; locking means mounted in engagement with said packing member for slidable movement radially thereof, said locking means including a plurality of locking segments and a split-ring interposed radially between said locking segments and said packing member; an annular support ring interposed axially between said locking segments and split-ring and said member, said locking segments being in direct engagement with said annular support ring during at least part of said radial movement of said locking means, said pipe hanger having a recess con-fronting said locking means whereby inward radial movement of said locking means will effect movement of said locking segments into said recess; a force transmitting element resting on said packing member and adapted to move axially of said wellhead; and means applying an axial force on said force transmitting element thereby causing said packing member to expand radially forming a seal and to move said locking segments into said pipe hanger recess whereby said pipe hanger is locked against axial movement and said packing means eifectively seals the area between said pipe hanger and said wellhead, said locking means being in direct engagement with said force transmitting element during said radial movement and when said locking segments are fully seated in said recess.

2. The wellhead apparatus defined in claim 1 further including retainer means for connecting said force transmitting element, locking means, packing member and bushing into a unit to facilitate handling.

3. The wellhead apparatus defined by claim 1 wherein said force applying means includes a lockdown screw.

4. The wellhead apparatus defined by claim 1 further including a blowout preventer mounted on said wellhead and having an inside diameter less than the inside diameter of said wellhead, and wherein said bushing member has an outside diameter larger than said inside diameter of said blowout preventer whereby said blowout preventer precludes removal of said bushing member.

5. An apparatus for locking and sealing a cylindrical tool having a circumferential recess into a wellhead, comprising an annular bushing having upper and lower end surfaces with said lower end surface adapted for supporting the bushing in a wellhead; an annular resilient packing member adjacent the upper end surface of the bushing; locking means mounted in engagement with said packing member for slidable movement radially thereof, said locking means including a plurality of locking segments and a split-ring interposed radially between said locking segments and said packing member; an annular support ring interposed axially between said locking seg ments and split-ring and said packing member, said locking segments being in direct engagement with said annular support ring during at least part of said radial movement of said locking means; and :a force transmitting element resting on said packing member and adapted to move axially of said bushing to compress said packing member thereby causing it to expand radially and to move the locking means radially, whereby when said apparatus is in place between said cylindrical tool and said wellhead said compressed packing member forms a seal between said tool and wellhead and said locking segments extend into said recess to lock said tool against axial movement with respect to said apparatus, said locking means being in direct engagement with said force transmitting element during said radial movement and when said locking segments are fully seated in said recess.

6. The apparatus defined by claim 5 further including retainer means for connecting said force transmitting element, locking means, packing member and bushing into a unit to facilitate handling.

7. The apparatus defined by claim 5 wherein said locking segments are formed as segments of a circle and have chamfered upper and lower inner edges providing camming surfaces.

8. The apparatus defined by claim 5 wherein each of said locking segments contains a sealing insert positioned in a generally centrally located passageway extending between opposite upper and lower surfaces of said segments.

References Cited UNITED STATES PATENTS 2,023,033 12/1935 Spalding 285-144 2,047,569 7/1936 Loomis 285-146 X 2,118,094 5/1938 McDonough et al. 285-133 X 2,187,839 1/1940 Penick et al 285-348 X 2,230,725 2/1941 Nathan 285-340 X 2,394,351 2/ 1946 Wurzburger 285-348 X 3,097,695 7/1963 Le Rouax et :al. 285- X 3,188,118 6/1965 Jones 285-133 X 3,194,592 7/1965 Boughton 285-348 X 3,287,035 11/1966 Greenwood 285-147 3,219,751 11/1965 Pfendler et a1 285-340 X FOREIGN PATENTS 1,008,020 2/ 1952 France.

CARL W. TOMLIN, Primary Examiner.

DAVE W. AROLA, Assistant Examiner.

US. Cl. X.R. 285-143, 348

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