US3168337A

US3168337A - Wellhead assembly

Info

Publication number: US3168337A
Application number: US72168A
Authority: US
Inventors: Glenn D Johnson; Bruce J Watkins
Original assignee: Shell Oil Co
Current assignee: Shell USA Inc
Priority date: 1960-11-28
Filing date: 1960-11-28
Publication date: 1965-02-02
Anticipated expiration: 1982-02-02
Also published as: GB932119A

Description

Feb. 1965 G. D. JOHNSON ETAL 3,158,337

WELLHEAD ASSEMBLY Filed Nov. 28. 1960 IN 1' r W l q: a

FIG. 2

ufl] INVENTORSZ I G. D. JOHNSON B. J. WATKINS BY: e /{1,4 0

THEIR AGENT United States Patent Office 3,lh8,337 Patented Feb. 2, 1965 3,168,337 WELLHEAD ASSEMBLY Glenn D. Johnson, Compton, and Bruce J. Watkins, West Covina, Calif., assignors to Shell (Bil Company, New York, FLY a corporation of Delaware Filed Nov. 28, 196i Ser. No. 72,168 8 laims. (Cl. 285-133) This invention relates to a wellhead assembly for closing the top of oil and gas wells and pertains more particularly to a Wellhead assembly especially adapted to be employed underwater at the top of a well at offshore locations for suspending tubing and casing within the well.

A recent development in the oil industry is the drilling and producing of offshore wells wherein the wellhead assembly and production fiowlines are positioned below the surface of the water, preferably on or near the ocean floor so as not to be subjected to the major wind and wave forces and to be out of the Way of boats that may navigate in that area. Most offshore well drilling operations of this type are conducted from a platform or anchored barge from which the various pieces of equipment, used in or on the well, are lowered through the water from the barge to their position near the ocean floor. When operating at water depths or at locations where a diver cannot be employed to assemble the equipment on the ocean floor, it is necessary to provide apparatus that may be lowered through the water from a remote station, and then aligned and connected to other pieces of equipment at the ocean floor.

When installing equipment at the top of an underwater well by the method described in copending application, Serial No. 24,558, filed April 25, 1960, now patent No. 3,099,316, it is preferred that the wellhead assembly be designed so that no fluid flowlines be connected to lateral discharge ports in the wellhead as this would interfere with the use of certain equipment used in installing or removing the wellhead from the top of the well. Wellheads have to be opened or removed at certain times in order to carry out workover operations within the well, or in order to replace a tubing or casing string therein. Presently known wellheads all employ at least one laterally directed flowline which would interfere with certain underwater operations carried out at the wellhead.

It is therefore a primary object of the present invention to provide a wellhead in which the flow from a plurality of pipe strings suspended therein is directed vertically out of the wellhead.

Another object of the present invention is to provide a Wellhead for underwater installations which permits a production tree to be stabbed into the top of a wellhead in a fluidtight manner.

A further object of the present invention is to provide a Wellhead wherein at least one production tubing string is nested within a casing in a concentric manner, with flow from the concentrically mounted tubing and easing strings leaving the top of the wellhead through parallelly-arranged flowlines that extend vertically from the top of the wellhead.

Still another object of the present invention is to provide a wellhead having a housing made up of a plurality of sections seated one on the other and secured together by substantially horizontally-directed connector elements.

Another object of the present invention is to provide a wellhead assembly for hanging a casing string and a tub ing string therein with means for holding down the tubing and casing string hangers in a fluidtight manner within the wellhead.

Still a further object of the present invention is to provide a multiple-section wellhead having aligning means for aligning one section with respect to the other.

These and other objects of this invention will be understood from the following description taken with reference to the drawing, wherein:

FIGURE 1 is a diagrammatic view of the wellhead of the present invention shown in partial longitudinal crosssection; and

FIGURE 2 is a schematic view of a drilling head adapted to replace the upper or bonnet section of the wellhead of FIGURE 1.

In FIGURE 1 of the drawing, numeral 11 represents a surface casing or conductor pipe which has been installed in a well in the ground and preferably cemented therein in a conventional manner. At the time the surface casing is positioned in place, a wellhead or casinghead inaccordance with the present invention has been fixedly secured to the top of the surface casing in any suitable manner such as by welding or by threading. In the particular arrangement of the wellhead shown in the drawing, the wellhead comprises lower, intermediate and

top sections

12, 13 and 14, respectively, of a housing which forms the wellhead of the present invention. The lower section 12 of the housing is preferably provided with a support base 15 which is fixedly secured to the lower section as by welding. The support base 15 in turn may rest on a cement foundation (not shown) or any other suitable foundation or base placed around the well.

The lower section 12 of the housing of the wellhead is provided with a sloping shoulder 16 adapted to seat and receive thereon a cooperating portion of a casing hanger 17 which is normally provided with suitable seals 18. The casing hanger 17 is employed to support a string of well casing 21 within the surface casing 11. The interior wall of the casing hanger 17 is provided with suitable means, for example, a left-hand thread by which the casing hanger 17 could be attached to the lower end of a pipe string (not shown) for lowering this element 17 and its depending casing string 21- into the Well from a suitable operational platform positioned above the well.

The lower and intermediate sections of the housing, 12 and 13 respectively, are provided with

seating surfaces

23 and 24, respectively, on the outer surfaces near the upper ends thereof which are adapted to seat thereon cooperating seating surfaces 25 and 26 formed on the inner surfaces near the lower ends of the intermediate and

upper housing sections

13 and 14, respectively. Seal means 27 and 28 are provided between the cooperating seating faces.

Lower locking screws or bolts 31 are horizontally positioned in a threaded manner within the lower end of the intermediate section of housing 13 and arranged to extend through the wall thereof and into cooperating recesses 32 formed in the wall of the lower housing section 12 near the top thereof. In a like manner, the top section 14 of the housing is provided with upper lock screws 33 adapted to seat in recesses 34 in the wall of the intermediate section 13 of housing near the top thereof. If desired or necessary, the

lock screws

31 and 33 may be provided with

fiuidtight seals

35 and 36. While it is preferred in accordance with the present invention to employ a wellhead having lower and intermediate sections of a

housing

12 and 13, respectively, it is quite ap parent that the intermediate and

lower sections

13 and 12 could be formed as a single element in which case the lower locking screws 31 could be eliminated. However, as a safety precaution in underwater wellhead structures, the housing employs lower and

intermediate sections

12 and 13 secured together by means of the lower locking screws 31 which are preferably made of an alloy carbon steel or other suitable material so that they can be drilled out in the event that the upper lock screws 33 become wedged or corroded in a manner so that they cannot be withdrawn from their seating position in order to remove the top section 14 of the housing from the wellhead.

Formed on the inner wall of the casing hanger 17 near the top thereof is a landing surface 37 adapted to receive and seat'thereon a tubing hanger 38. The outer surface of the tubing hanger 38 at the lower end thereof is provided with a tapered seating surface'41, preferably provided with seal means 42, such for example as any suitable type of packing'or O-rings. The tubing hanger 38 is adapted to be secured at its lower end to the top of 'a string of tubing 43, for example, byscrew threads. The tubing string 43 depending from the tubing hanger 38 is concentrically arranged within the well casing string 21.

Formed within the tubing hanger 38 are a pair of concentrically and vertically arranged and inwardly directed spaced

sealing surfaces

44 and 45 against which a pair of

concentric nipples

46 and 47 are adapted to seal. The lower ends of the

nipples

46 and 47 are provided with packing rings 48 and 49 in order to form a fiuidtight seal. Preferably, the portions of the tubing hanger at the top of the

sealing surfaces

44 and 45 are tapered as at 52 and 53 to facilitate entry of the lower ends of the nipples into the top'of the tubing hanger 38. One or more fluid flow passageways 54 extend vertically through the tubing hanger 38 in communication between the space between the

sealing surfaces

44 and 45 and the annulus 55 formed between the outer wall of the tubing'43 and the inner wall of the casing 21.

Formed in the top of the upper bonnet section 14, which forms the closure section of thehousing, is a chamber 56. The outer nipple 46 is fixedly secured at its'upper end inside the top section 14 of the housing in a manner such that the open top end of the nipple 46 is in open communication with 'the chamber '56 within the housing. chamber 56 are closed in any suitable manner by a suitable cover plate 57 which may form the lower flange of The top section, 14 of the housing and the 43, be removed and the apparatus would still function in the same way. A seal 73 is provided between the top cover plate 73 and its mating flange 74 at the top of the upper section of the housing.

A set of control screws 75 are threadedly mounted in a fluidtight manner within screw holders 76 which are in turn fixedly secured into the wall of the intermediate section 13 of the housing so that the inwardly-directed end of the screw 75 is adapted to engage a circumferential groove 77 formed in the outer wall of the tubing hanger 38 so as to hold the tubing hanger in the wellhead and prevent it from being raised off its seat 37 by means of well pressure. Similar lower control screws 80 mounted in holders 81 are provided whereby the screws80 can be extended toengage a circumferential groove 82 formed in the outer surface of the casing hanger 17.

Aligning means must be provided between the various sections of the

housing

12, 13 and 14 so that the lock screws 31 and 33 holding the sections together are in register with their respective recesses 32'and 34 at the time the lock screws engage the recesses. The recesses 32 and 34 are no larger than the tapered end of the lock a production tree (not shown) which is secured to the top of the well. The production tree may include a pair of How

conduits

60 and 61 having

valves

62 and 63 located therein, respectively. The cover plate 57'is conr nected in any suitable manner to the top-section 14 of the housing, as by bolts 63'and 64. Passing through the 7 cover plate 57 in communication with

thefiow conduits

60 and 61 are a pair of

flow passageways

66 and 67.

The flow passageway 67 is in communication between the flow conduit 61, and thence through chamber 56, annular space 69 and flow passageways 54, with the annular space 55 between the tubing string 43 and, the casing string 21. Thus, means are provided for measuring the casing pressure within the well or for extracting or injecting fluid into the annulus 55 between the tubing string 43 and the casing string 21. By providing concentric tubing and

casing strings

43 and 21, respectively,'below the wellhead, smaller diameter pipe may be employed than would be needed if two parallel tubing strings were run down the well. Additionally, the casingstring 21 has considerably more strength than a tubing string 43..

screws 31 and 33so that an area contact is established between the lock screws and the housing section in which they are positioned, thus substantially eliminating any plastic flow of metal as would take place in line contact between the two elements. 1

Any suitable means for aligningone section with respect to another may be employed. In the particular arrangement illustrated, the lower portion of the top or bonnet section of the housing 14 is provided with tapered slots 83 which align themselves on pins formed by the screw holder 76 mounted on the outside of the intermediate section 13 of the housing. In a like manner, the lower portion of the intermediate section 13 of the housing is provided with aligning slots 84 adapted to receive therein the screws holder 81 which is secured to the lower section 12 of the housing. If desired, the portions of the housing sections between the aligning slots may be interconnected by

ring members

85 and 86 to give more strength to the assembly. In using the wellhead of the present invention on an underwater well, the well is first drilled in the ocean floor and the lower section 12 of the housing being securely fastened to the surface casing 11 is lowered into place on the ocean floor in its position there when the surface casing is cemented in a conventional manner. The intermediate section 13 of the housing is also normally connected to the lower section 12 of the housing at this of the tubing hanger 38 provides straight through fluid- V tight communication between the tubing string 43 and the flow passageway 66 to the flow conduit-60 in the production tree on top of the wellhead. Toreduce the diameter of the equipment needed in the present wellhead, sealing surfaces 44 and 45-are preferably axially displaced one from the other as illustrated to give a larger flow passage between.

Secondary seals and 71 are provided between the top and intermediate sections and between the intermediate and lower sections of the housing, respectively. 'It is realized that with seals '28 and 70 being employed in the upper part of the housing, the outer nipple 46 could time, being secured together by :lock screws 31. The control screws and are carried by the intermediate and

lower sections

13 and 12, respectively, of thehousing with the screws being in a retracted position.

In running the lower section 12 and the intermediate section 13 of the housing to the ocean floor together with the surface casing 11 which is run into the well, a drilling bonnet 99 (FIGURE 2) replaces the top or bonnet section 14 (FIGURE 1) and is secured to the intermediate section 13 of the housing by means of a series of bolts 91 (FIGURE 2) which are identical to bolts 33 (FIGURE 1) and are positioned to seat within the same recesses 34. Drilling operations are continued with the drilling bonnet 91) in place on the top of the housing. The drilling bonnet 'may have conventional equipment secured thereto such as a blowout preventer 92, remotely-controlled connector apparatus 93 and a fluid conductor pipe 34 through which drill pipe or other pipe strings (not shown) may extend at diiierent periods during the drilling operations.

When the time has arrived in drilling operations to install the casing string 21, the casing suspension hanger 17 is connected to the top of the casing string 21 and the entire apparatus is lowered, as from an operational platform or barge on the surface of the water, in any suitable well known manner, as by means of a pipe string, down the intermediate and lower sections of the housing until the casing hanger 17 is seated on the shoulder 16 within the lower section 12 of the housing. Subsequently, at the desired time, the tubing hanger 38 is secured to the top of the tubing string 43 and run in the well in the same manner until the tubing hanger 38 is seated on the landing surface 37 at the top of the casing hanger. Hold down screws 86) are preferably caused to engage and secure the casing hanger 17 immediately after the latter has been landed. Likewise, hold-down screws 75 are caused to engage and secure the tubing hanger 38 after the latter has been landed in assembly.

It is of importance to note that under normal conditions lock screws 31 are not manipulated during the well completion operation inasmuch as their only function is to secure

parts

13 and 14 in assembly and these are preferably screwed together prior to being installed and are not disconnected during normal completion practices.

The upper section of bonnet 14 is then lowered, as by means of a detachable pipe string, onto the top of the intermediate section 13 and the

nipples

46 and 47 are stabbed into the tubing hanger 38 so as to form a fluidtight seal with the sealing surfaces 44 and 45, respectively. All of the lock screws 33 are then rotated in any suitable manner, as by means of the apparatus disclosed in copending patent application, Serial No. 24,558, filed April 25, 1960, in the event that the water is too deep to use divers. The screws are tightened until the components of a wellhead have been secured together in a fluidtight and pressuretight manner. At the time the bonnet 14 is lowered into place, the cover plate 57 and the production tree (not shown) including the

flow conduits

60 and 61 which have been previously attached to the top of the bonnet, are installed.

We claim as our invention:

1. A wellhead assembly for supporting a casing string and a tubing string disposed within said casing string, both of said strings extending into a well bore and depending from said wellhead assembly, said Wellhead assembly comprising a housing member having an open upper end,

landing surface means formed in said housing member for supporting a tubing hanger thereon with a tubing string depending from said tubing hanger,

closure means releasably connectible to said housing member for closing the upper end thereof, I

first passageway means defined by said wellhead assembly and extending through said closure means in communication between said tubing string depending within said housing member and the space above said closure means, portions of said first passageway means being defined by separable portions of said wellhead assembly,

first conduit means forming a portion of said separable portions of said wellhead assembly defining said first passageway means,

a connector means carried on one end of said first conduit means within said housing and engageable through vertically-directed motion by translation with a mating portion of said other separable portion, and

second passageway means defined by said wellhead assembly and extending through said closure means in communication between the space above the closure means and a space within said wellhead assembly formed between said tubing string and said casing string depending from said wellhead assembly.

2. The apparatus of claim 1 including the second conduit means spaced from said first conduit means and forming a portion of said second passageway means.

3. The apparatus of claim 1 wherein a portion of said first conduit means comprises downwardly-extending nipple means fixedly positioned within said housing mem her, the lower end of said nipple means being in axial alignment with the landing surface means in said housing for supporting a tubing hanger.

4. The apparatus of claim 1 wherein the outer surface of said housing member tapers inwardly and upwardly near the top thereof forming a tapered landing surface for said closure means, and wherein said closure means has a downwardly-extending portion adapted to fit down over the top of said housing member, there being formed on the inner surface of said downwardly-extending portion of said closure means an inwardly and upwardly tapering seating surface at an angle to cooperate with said landing surface of said housing member.

5. The apparatus of claim 4 including connecting means for securing said closure means to said housing member, wherein said connector means comprises a plurality of inwardly extending locking screws carried by said closure means around the periphery and adapted to extend through the wall of the downwardly-extending portion thereof and extendible into mating recesses formed in the adjacent outer wall of said housing member.

6. A wellhead assembly for supporting a casing string and a tubing string concentrically-disposed within said casing string, both of said strings extending into a well bore and depending from said wellhead assembly, said wellhead assembly comprising a housing member having an open upper end and defining a cross-over chamber formed therein when said housing member is closed,

unitary closure means having a pair of laterally dis-' placed ports therethrough and being releasably connectible to said housing member for closing the upper end thereof,

first nipple means carried by said wellhead assembly in communication between a tubing string depending from said housing member and through one of said ports in said closure means with the space thereabove,

second nipple means spaced apart from said first nipple means carried by said wellhead assembly in communication, through the cross-over chamber within said wellhead assembly and through the other of said ports in said closure means, between the space above the closure means and a space formed between a tubing string and a casing string depending from said housing member, and

said lower end of said unitary closure means and said lower end of said first nipple means being each engageable through vertically-directed motion by translation with a mating portion of said wellhead assembly.

7. A wellhead assembly for supporting a tubing string and a casing string within a well and providing vertical discharge connections from said tubing string and easing string, said wellhead assembly comprising a housing structure, said housing being formed in at least a lower section and a top unitary closure section, said lower section having seating means formed near the upper end thereof adapted to seat cooperating seating means of said closure section,

first support means carried by the lower section of said housing,

casing suspension means supported by said first support means of said housing,

second support means carried within said lower section of said housing,

tubing suspension means supported by said second support means,

casing means secured at one end to said casing suspension means,

tubing means secured at one end to said tubing suspension means and depending therefrom within said casing means,

connector means carried by one of said sections of said housing for securing said sections together,

said closure section defining at least two 'fiuid passageways,

first conduit means in said housing in communication between said tubing means and one of the fluid passageways in the closure section,

second conduit means in said housing in communication between said suspended casing means and a second'of said fluid passageways in the closure sec-, tion, and

said lower end of said unitary closure means and said lower ends of said first and second conduit means being each engageable through vertically-directed motion by translation with a correlative portion of said wellhead assembly.

8. A Wellhead assembly for supporting a tubing string said housing cross-over chamber being formed above said tubing suspension means,

nipple means having the upper end thereof secured to the closure section and extending downwardly through said chamber, the lower end of said nipple means being positioned through vertically-directed motion by translation in fluid communication with the top of said tubing means,

said closure section defining two vertical fluid passageways,

one of said passageways being in communication with the upper end of the nipple means and the other of said passageways being in communication with the cross-over chamber and conduit means in said housing.

and a casing string within a well and providing parallel vertical discharge connections from said tubing string and easing string, said wellhead assembly comprising a housing structure, said housing being formed in at least a lower section and a top closure section, said lower section having seating means formed near the References Cited by the Examiner UNITED STATES PATENTS upper end thereof adapted to seat cooperating seat- $333 u ing means 0f Said Closure Sectio Dean a first landing means for casing suspension means carried 1849374 3/32 M CEV 285 144 by the lower section of said housing, 1941467 1/34 Fwseky 285:137 casing suspension means supported on said first landing 1983938 v12/34 g 285 140 means 2,034,698 V 3/36 Hild. second landing means for tubing suspension means 2 082 413 6/37 Mu d1 V 285 A01 f i sa1d housmg 2,118,094 5/38 McDonough 2s5-140 tubing suspension means supported by sa1d second landoO- 2 134 200 10/38 Pivoto 166 86 ing means, casing means secured at one end to said casing suspeng zi g; t means 2,584,283 2/52 Oliver 285 4o4 ubing means secured at one end to said tublng suspen- 2 983 318 5/61 Baker 166 89 sion means, w said tubing suspension means having vertical fluid flow 3004778 10/61 Wflhams' passageway means in addition to the bore there- FOREIGN PATENTS through, i said housing defining a cross-over chamber and con- 480,817 3/38 Great Bmamduit means therein in communication with the flow 40 passageway means through said tubing suspension CARL W. TOMLIN, Primary Examiner.

7 means,

Claims

1. A WELLHEAD ASSEMBLY FOR SUPPORTING A CASING STRING AND A TUBING STRING DISPOSED WITHIN SAID CASING STRING, BOTH OF SAID STRINGS EXTENDING INTO A WELL BORE AND DEPENDING FROM SAID WELLHEAD ASSEMBLY, SAID WELLHEAD ASSEMBLY COMPRISING A HOUSING MEMBER HAVING AN OPEN UPPER END, LANDING SURFACE MEANS FORMED IN SAID HOUSING MEMBER FOR SUPPORTING A TUBING HANGER HTEREON WITH A TUBING STRING DEPENDING FROM SAID TUBING HANGER, CLOSURE MEANS RELEASABLY CONNECTIBLE TO SAID HOUSING MEMBER FOR CLOSING THE UPPER END THEREOF, FIRST PASSAGEWAY MEANS DEFINED BY SAID WELLHEAD ASSEMBLY AND EXTENDING THROUGH SAID CLOSURE MEANS IN COMMUNICATION BETWEEN SAID TUBING STRING DEPENDING WITHIN SAID HOUSING MEMBER AND THE SPACE ABOVE SAID CLOSURE MEANS, PORTIONS OF SAID FIRST PASSAGEWAY MEANS BEING DEFINED BY SEPARABLE PORTIONS OF SAID WELLHEAD ASSEMBLY, FIRST CONDUIT MEANS FORMING A PORTION OF SAID SEPARABLE PORTIONS OF SAID WELLHEAD ASSEMBLY DEFINING SAID FIRST PASSAGEWAY MEANS, A CONNECTOR MEANS CARRIED ON ONE END OF SAID FIRST CON-