US3289765A

US3289765A - Method and apparatus for completing wells

Info

Publication number: US3289765A
Application number: US249796A
Authority: US
Inventors: Joseph H Hynes
Original assignee: Gray Tool Co
Current assignee: Vetco Gray LLC
Priority date: 1963-01-07
Filing date: 1963-01-07
Publication date: 1966-12-06
Anticipated expiration: 1983-12-06
Also published as: GB1074942A; GB1074943A

Description

Dec. 6, 1966 J. H. HYNES 3,289,765

METHOD AND APPARATUS FOR COMPLETING WELLS Filed Jan. '7, 1963 5 Sheets-Sheet 1 FIG].

NI; I. 26 IHII1 6 22 2e & I [2 we 14 v Zr INVENTOR JOSEPH H. HYN ES Dec. 6, 1966 J. H. HYNES METHOD AND APPARATUS FOR COMPLETING WELLS 5 Sheets-Sheet 2 Filed Jan. '7, 1963 ATTORNEYS Dec. 6, 1966 J. H. HYNES METHOD AND APPARATUS FOR COMPLETING WELLS 5 Sheets-Sheet 5 Filed Jan. 7, 1963 ATTORNEY5 Dec. 6, 1966 J. H. HYNES 3,239,765

METHOD AND APPARATUS FOR COMPLETING WELLS Filed Jan. '7, 1963 5 Sheets-Sheet 4= FIG.7.

INVENTOR JOSEPH H. HYNEIS lay KW 1 5M) 6 ATTORNEYS Dec. 6, 1966 J. H. HYNES 3,289,765

METHOD AND APPARATUS FOR COMPLETING wELLs Filed Jan. 7, 1965 5 Sheets-Sheet 5 FIG..9.

INVENTOR.

JOSEPH H. HYNES United States Patent Q 3,289,765 METHOD AND APPARATUS FOR COMPLETING WELLS Joseph H. Hynes, Sugar Land, Tex., assignor to Gray Tool Company, Houston, Tex., a corporation of Texas Filed Jan. 7, 1963, Ser. No. 249,796 19 Claims. (Cl. 166-46) This invention has reference to new and improved oil well completion equipment and methods and apparatus for setting the casing head.

vWhen a rotary table is initially used for Well drilling purposes, it is the customary practice to set it aside after initial drilling operations in order to move the casing head into position for assembly to the top of the drive pipe or other previously set casing. The rotary table is then positioned back above the well after the casing head has been set, for further drilling purposes. This procedure is necessarily time-consuming and otherwise delays the completion of the well due to the labor requirernents for moving the rotary table in view of the cumbersome size of such a structure. For example, it is not unusual for a rotary table and associated equipment to weigh perhaps six tons or more.

Moreover, further delay in completing the well re sults in removing the mud riser or other control equipment prior to going forward with the next step of setting the casing head. When these steps are carried out in sequence, one after the other, the speed and efliciency with which the Well can be completed is reduced accordingly.

The principal object of the present invention is to prowide apparatus and procedure for completing the well in a more rapid and efficient manner than heretofore known in the art.

According to one feature of this invention, the casing head and associated equip-ment are constructed and arranged so that they can be passed through the rotary table. The casing head and associated parts are of special construction so that it can form a connected part of a unitary lowering assembly comprising the casing string and a lowering casing nipple joined by the casing head itself, so that the casing head may be lowered through the rotary table and control equipment or mud riser to its landed position. The casing head is sealed to both the casing string and the lowering nipple so that cementing operations can be commenced as soon as the casing head is landed. By virtue of this arrangement, the rotary table need not be removed from above the well when the casing head is to be set. The casing head is constructed and arranged to be of a size less than the mud riser or other control equipment temporarily mounted on the drive pipe so that the casing and the casing head can be lowered through the mud riser and the casing immediately cemented, the mud riser then being removed While the cement is setting. The next casing or tubing head can then be attached above the first-mentioned casing head but after drilling operations under pressure have been performed through control equipment which was attached to the first-mentioned casing head, and which, as customary, would then be removed after the drilling operations are performed, and prior to attachment of the next casing head as referred to. The invention contemplates a new and improved method and apparatus for mounting the casing head on the drive pipe and connecting it to the lowering nipple in sealed relation.

A further object of this invention is to provide a new and improved method for assembling the casing head directly to and between the casing and the lowering nipp'le. In this regard the casing head is adapted to receive a lowering bushing of new and improved construction,

3,289,765 Patented Dec. 6, 1966 this bushing being adapted to receive the casing head at its lower end, preferably by a left-handed thread connection. The upper end of this bushing is adapted to receive, as by a threaded joint, a suitable lowering nipple so that the united combination of casing, bushing and lowering nipple can be passed through the rotary table.

These and still further objects, advantages, and novel features of the present invention will become evident in the specification and claims, taken in connection with the accompanying drawings. It will be understood that the invention is intended to be used in association with the equipment and following the practices and procedures described and referred to in the Watts and Hill Patent 2,766,829.

In the drawings:

FIGURE 1 is an elevation view, generally in section, showing an initial phase of the well completion with the mud riser set on the drive pipe and drilling operations about to commence;

FIGURE 2 is a View similar to FIGURE 1 showing the casing head being lowered through a rotary table for support on top of the drive pipe;

FIGURE 3 is a sectional view of the casing head positioned on top of the drive pipe with the mud riser in place during cementing operations;

FIGURE 4 is a diagrammaticview similar to FIG- URE 3, but showing the mud riser and the lowering hanger removed in preparation for subsequent drilling operations;

FIGURE 5 is an elevation view partially broken out, of the completed assembly with the tubing head attached;

FIGURE 6 is an elevational section view of the casing head;

FIGURE 7 is an elevational section view of the lowering bushing;

FIGURE 8 is an enlarged, detail section view of a portion of the lowering bushing of FIGURE 7; and

FIGURE 9 is a partial sectional view of a modified embodiment of this invention.

Referring now to FIGURE 1, there is shown a drive pipe 10 which has been mounted in place in the well. A supporting hub 12 is joined to the top of the drive pipe 10. The supporting hub 12 includes a peripherally depending skirt 14 which surrounds the drive pipe and is Welded thereto. The supporting hub 12 has an outwardly extending flange 16 at its upper end. Moreover, the supporting hub 12 has an inwardly extending flange 18 with an inner peripherally tapered surface 20 at its upper end, together with vertically spaced apart passages 22 to allow passage of cement therethrough during cementing operations.

A mud riser or other control equipment 24 is positioned with its lower flange 26 on the flange 16 of the supporting hub so that the latter supports the control equipment 24. This joint includes a sealing ring and clamp as indicated at 28, as disclosed in the US. patents to Watts et al., 2,766,829 and 2,766,999.

A rotary table 30 is positioned immediately above the axis of the drive pipe 10 and the control equipment 24, this table 30 being supported at the derrick floor level by any suitable means well known in the art. It will be understood that the present invention has distinct applicability to under water drilling, in which case the mud riser 24 can extend to the surface of the water where it would be provided with suitable outlets and connections, as known in the art. The rotary table is driven in a conventional fashion through a drive train and prime mover (not shown) as is well known in the art. The rotary table 30 has a central circular passage 32 with an enlarged square upper end 34 defining there by a radial supporting shoulder 36 of square configuration. A master bushing 38 is supported in the central passage 32 of the rotary table 30 by an external square flange 40 at its upper end which rests on the supporting shoulder 36 of the rotary table 30. The master bushing 38 has a central, longitudinally tapered passage 42 which receives a drive bushing 44 at its upper end as by an annular recess 46, upon which the drive bushing 44 rests. A kelly 48 passes through the drive bushing 44 and is driven in the usual manner. The drilling equipment includes a drill pipe and collars 50 having a drill bit 52 at its lower end. With this arrangement, the initial drilling of the well through the drive pipe takes place in the usual manner.

After this initial drilling has been completed, the drilling equipment is raised from the well and the master bushing 38 and drive bushing 44 are removed from the rotary table 30, as best shown in FIGURE 2.

Next, a casing 54 is lowered into the drilled well through the central passage 32 of the rotary table 30 to the predetermined depth. The uppermost end of the casing 54 slidably receives a support plate 56 which has a bottom tapered surface 57 for nesting engagement on the tapered surface of the supporting hub 12 so that the hub passages 22 are not completely blocked. The support plate 56 is operative .to support a special casing head 58 of reduced outside diameter which has been joined to the uppermost end of the casing 54. In this regard, the lowering operation takes place with a lowering bushing 60, removably connected into the upper end of the casing head 58, this entire structure passing through the rotary table so that the same need not be removed from its aligned position for this purpose. This casing head 58 and the supporting plate 56 are adapted to be passed through the mud riser or other control equipment 24 so that the completion need not be delayed until the control equipment 24 has been removed from the supporting hub 12. A landing joint 61 is connected to the upper end of the lowering bushing 60. The supporting plate 56 may be of a two part hinged type so that it could be placed and locked around the casing 54 below the rotary table, if desired.

FIGURE 6 shows the construction of the casing head 58. There is here provided a central passage 62 which is interiorly threaded at its lower end with right-handed threads 64 for engagement with the cooperative threads 65 at the upper end of the casing pipe 54. The central passage 62, continuing upwardly, has a minimum diameter 66 at its central portion, then flares upwardly and outwardly at 68 forming a hanger seat, merging with a cylindrical portion 70. The passage 62 then flares upwardly and outwardly at 72 while another long cylindrical portion 74 merges therewith, the upper end of this latter cylindrical portion 74 then flaring upwardly and outwardly again at 76 where the passage 62 is interiorly threaded at 78 with left-handed threads. A further outward and upward flaring portion 80 is provided in the passage 62 at the upper end of the threads 78, the upper end of this latter flaring portion 80 merging with a curved annular recess 82. The upper end of this annular recess 82 terminates in a cylindrical portion v 84, the passage 62 then communicating with the upper end of the casing head 58 with an outwardly extending flaring portion 86. This casing head 58 in FIGURE 6 is shown to have

side outlet bosses

88 and 90 constructed and arranged to receive plugs (FIGURE 3), and a top flange 91.

The lowering bushing 60 in FIGURES 7 and 8 is adapted to be engaged with the left-handed threads 78 in the upper region of the central passages 62 in the easing head 58. This lowering bushing 60 has a dove-tailed recess at its lowermost end receiving an O-ring 92 which is adapted to seal against the interior of the casing head passage 62. Cooperative exterior left-handed threads 94 are carried about the lowering bushing 60 for engagement with the left-handed threads 78 in the casing head 58.

Above the upper end of these threads 94 there is an annular peripheral recess 96 which, when the bushing 60 is engaged with the casing head 58, aligns itself with the annular recess 82 so that an annular chamber is formed between these two structures (FIGURE 6). An outwardly flared surface 98 extends from the upper end of the recess 96 and here carries an O-ring 100 in a dovetailed recess for sealing engagement with the tapered surface 86 in the casing head 58. This surface 98 thence merges into an outwardly extending flange-like portion 102 of inverted U-shaped configuration, which is adapted to rest on the top of the casing head 58 when the lowering bushing 60 is joined thereto. Next, there is an in wardly and upwardly tapering portion 104 at the upper end of the flange portion 102, there being provided axially inclined bores 106 which are threaded along the outer part of its length at 108 for receiving a threaded plug 110. This bore 106 then communicates with another bore 112, the bore 112 providing communication with this annular chamber defined by the aligned peripheral recess 96 in the lowering hanger 60 and the annular recess 82 in the casing head 58. This arrangement of the

bores

106 and 112 thereby allows pressure-testing and the like, as is necessary to ensure a tight seal. The lowering bushing 60 has an axial passage 114 outwardly and downwardly flared at its lower end at 116 and interiorly threaded at its upper end at 118 with right-handed threads. This threaded portion 118 thus receives the landing joint 61 or other lowering equipment so that when the elements are connected, the casing head 58 can be lowered through the rotary table 30 in the manner shown in FIGURE 2.

Referring now to FIGURE 3, the casing head 58 is connected to the lowering bushing 60 whereby the elements are lowered to the supporting hub 12. The mud riser 24 is still attached to the supporting hub 12 but this View shows the mud riser threaded to the flange 26 rather than integral therewith. The side outlet bosses 88 and are equipped with removable plugs 122, so that the head is completely sealed to permit the pressure cementing operations as now referred to.

When the elements are positioned as shown in FIGURE 3, the cementing operations can be commenced immediately. With the landing joint 61 threaded onto the upper end of the bushing 60, cementing equipment (not shown) is mounted at the top of the lowering nipple. Cement is then introduced through the landing joint pipe 61 and on down into the casing 54- through the pressure tight bushing 60 and casing head 58. The cement flows out from the bottom end of the casing 54 in the usual fashion and upwardly between the exterior of the casing and the drive pipe 10. The passages 22 in the supporting hub 12 allow mud or water to escape, and depending upon the amount of cementing to be done, the cement blockade can be formed clear up to the top of the drive pipe 10. If the mud riser 24 or other control equipment has been removed, the mud displaced by the cement may simply flow outwardly to the pits or in the surrounding water (in submarine drilling) or it may flow upwardly through any control equipment which remains attached to discharge through suitable outlets at the top thereof.

While the cement is setting not only can the mud riser 24 be removed but also appropriate sized control equipment can be attached to the casing head 58 as is well known in the art, and drilling operations can proceed under pressure through this control equipment as is well known in the art. Thus, delays in completing the well are eliminated, as one step need not be delayed until the prior step is fully completed.

In FIGURE 4, the lowering bushing 60, and the mud riser 24 have been removed with the rotary table 30 still in place, and the cementing operations have been completed. Operations can begin immediately to flange on the appropriate control equipment (not shown).

Bushings

38 and 44 can be replaced in the rotary table 30 and subsequent drilling operations can begin, using necessary control equipment all as described or referred to in Watts and Hill Patent 2,766,829.

After the drilling has been completed, the Christmas tree is then completed as shown in FIGURE 5. A second casing 137 is sealed and supported in the casing head 58 by a suitable casing hanger 138, as is Well known in the art. The tubing head 130 is connected to the upper end of the casing head 58 by a sealing ring 132 which is formed of rigid but deflectable material and is operative for transverse deflection into stressed sealing engagement with the tapered surface 86 in the casing head 58 and a similarly tapered surface 134 in the bottom of the tubing head 130. A clamp 136 joins the flanged ends of the casing head and tubing head, this joint and the procedure involved being described in detail in the Watts et al Patents 2,766,829 and 2,766,999. The tubing 140 is mounted within the casing 54 using a suitable tubing hanger seal 142, and a Christmas tree bonnet 144 is connected to the upper end of the tubing head 140 by a like sealing ring 132 and clamp 136 as previously described. The Christmas tree valves and fittings will be supported on the bonnet 144 as is known in the art.

As previously described, the arrangement of elements, particularly the casing head 58 and the supporting plate 56 are such that the same may be passed through both the rotary table 30 and the mud riser 24- or other control equipment 24. The maximum diameter of these elements may vary depending on the particular conditions. For instance, the

bosses

88 and 90 in the casing head 58 determine these size relationships or the upper flange 91 in the casing head under some circumstances may conform to the size relationship. The supporting plate 56 may be very close to the inside diameter of the mud riser 24 and act as a guide for the elements as they are lowered into place. Moreover, the casing head 58 may be constructed so that the upper threads 78 in the passage 62 may extend downwardly relative to the

bosses

88 and 90 so that the outlets (FIGURE 3) are blocked by the lower end of the bushing 60, thereby precluding the need for plugs 122 to block these bosses during the cementing operation. V

The supporting plate 56 may be attached as by welding to the underside of the casing head 58 or remain separately movable along the casing pipe 54, as desired. A significant feature of this arrangement is the ease and flexibility of assembly with a minimum of lost time. The method may also take place in underwater operations as well as dual or multiple tubing string operations, as is apparent.

Referring now to FIGURE 9, the bushing 60' is shown to have a depending skirt 146 with an exterior O-ring 148 carried at its lower end. The interior wall 74 of the casing head bore is continuous and of substantial length so that the same is adapted to be sealed with the bushing 60 below the side outlets. The exterior surface of the casing head 58 is of smooth configuration having no bosses for the side outlets, the upper flange 91 thereby constituting the largest radial size which must pass through the control equipment. The casing head 58 has opposed boss-receiving surfaces 150 surrounding the side outlets with threaded machine bolt holes 152, and an annular sealing ring receiving recess 154. Thus, after initial land has been completed through the control equipment, as described and cementing operations have been completed, the

bosses

88 and 90 may be bolted to the surfaces 150 by machine bolts 156, with a sealing ring 158 carried in the recess 154.

From the foregoing description of the various embodiments of this invention, it is evident that the objects of this invention, together with many practical advantages are successfully achieved. While preferred embodiments of my invention have been described, numerous further modifications may be made without departing from the scope of this invention.

Therefore, it is to be understood that all matters herein set forth or shown in the accompanying drawings are to be interpreted in an illustrative and not in a limiting sense.

What is claimed is:

1. Method of rapid well completion comprising the steps of: setting a well drive pipe; positioning a rotary table axially above the drive pipe and commencing drilling operations with drilling equipment driven from said rotary table lifting the drilling equipment from the well through the rotary t-able; passing a well casing into the well through the rotary table; connecting a casing head to the upper end of the well casing; connecting a lowering bushing to the casing head and lowering this assembly through the rotary table to support the casing head on the drive pipe.

2. Method defined in claim 1 including the step of connecting the lowering bushing to the casing by rotation with a reverse thread connection.

3. Method defined in claim 1 including the step of supporting the casing head on the drive pipe by mounting a supporting hub to the top of the drive pipe and supporting the casing head on the supporting hub.

4. Method defined in claim 3 including the step of mounting control equipment to the supporting hub and lowering said assembly through the control equipment when so positioned.

5. Method defined in claim 1 including the step of mounting a mud riser to the drive pipe in axial alignment therewith and lowering said assembly through both the rotary table and the mud riser.

6. Well completion equipment comprising: a casing head having a central passage therethrough and including means at its lower end for receiving the upper end of a casing; a lowering bushing, means for removably joining the lower end of said bushing to the upper end of said casing \head; and means carried by the upper end of said lowering bushing for removably receiving lowering equipment; a drive pipe; a supporting hub for mounting on said drive pipe, a casing secured at its upper end to said casing head at the lower end thereof, a support plate surrounding said casing below said casing head to support the same on said supporting hub when lowered thereon, wherein said supporting hub includes a depending skirt at its lower end for engagement with said drive pipe, an outer flange at its upper end and an inwardly extending flange portion for receiving said supporting plate, and wherein said inwardly extending flange includes a tapered portion and said supporting plate includes a peripherally tapered portion for engagement therewith, said inwardly extending flange also having passages therethrough which are unobstructed by said supporting plate when the latter is positioned thereon.

7. In well completion equipment: a casing head having an interiorly threaded passage; a generally cylindrical lowering bushing, means on said bushing for removably engaging said bushing with said casing head, said lowering bushing being threaded about its exterior surface for engagement with said interior threads; means defining a circumferentially extending peripheral groove in said lowering bushing exterior surface above said threads, flange means extending laterally of said exterior surface adjacent said peripheral groove for support on the top of said casing head; means in said bushing defining passage means providing cornmunication between said peripheral groove and the exterior surface of said lowering bushing at said flange means; annular sealing means carried about the exterior surface of said lowering bushing in said flange means above said peripheral groove; another portion of said lowering bushing being constructed and arranged to receive lowering equipment and the like.

8. Well completion equipment defined in claim 7 wherein said casing head has an annular recessed groove in alignment with said peripheral groove when joined to said lowering bushing to define therewith an annular chamber.

9. Well completion equipment defined in claim 7 wherein said passage means includes a first bore extend ing inwardly from said lateral flange and a second bore angularly intersecting said first bore at its one end and said peripheral groove at its other end; and plug means removably carried in said first bore.

10. Well completion equipment defined in claim 7 wherein said lateral flange is of inverted U-shaped configuration in longitudinal section.

11. Well completion equipment defined in claim 7 wherein said threads are left-handed.

12. Well completion equipment defined in claim 7 wherein said lowering bushing has a tapered surface below said lateral flange, and said casing head has a tapered interior surface at its upper end for engagement therewith, said peripheral groove being positioned below said tapered surface and said sealing means including an O-ring carried in the tapered surface of said lowering bushing.

13. Well completion equipment defined in claim 12 wherein said sealing means includes a second O-ring carried by said lowering hanger below said exterior threads, said casing head having an aligned flat surface for sealing engagement with said second O-ring.

14. Well completion equipment defined in claim 7 where said lowering hanger is oppositely threaded along a portion thereof relative to said exterior threads for receiving said lowering equipment.

15. Well completion equipment comprising: a casing head having side outlets: plug means for removably sealing said side outlets; a casing string joined to the lower end of said casing head; and a lowering nipple operatively joined to the upper end of said casing head in sealed relationship therewith whereby cementing operations can commence immediately after lowering the equipment via said lowering nipple.

16. Well completion equipment defined in claim 15 including a bushing removably joined to said casing head at its lower end and joined to said lowering nipple at its upper end.

17. Well completion equipment comprising a first casing head for attachment to the upper end of an outer string of casing, said casing head having means for supporting a second casing head equipped for attachment to an inner string of easing, control equipment having means for attachment above said first casing head, said second casing head having, at its upper end a circumferentially extending generally radially outwardly directed flange, said flange including a clamp receiving circumferentially extending downwardly and inwardly tapering wedging surface thereon and having no other part or surface of lateral dimension greater than said flange means defining a central longitudinally directed bore through said second casing head, means defining generally laterally directed side outlets in said second casing communicating with said bore; and means defining a lowering bushing adapted for sealing engagement with the upper end of said second casing head, said bushing including a depending skirt receivable in said bore for sealing engagement with the peripheral surface of said bore below said side outlets, whereby said second casing head may be lowered and landed through the control equipment and its casing immediately cemented.

18. The method of completing wells which comprises drilling and landing an outer string of casing and mounting a casing head thereon, providing for mechanical control of the well by mounting control equipment on said first casing head and drilling through and below said outer casing string in order to land a second casing string, attaching a second casing head to said second string of casing and lowering it through the control equipment to a point of suspension above said first casing head.

19. Well completion equipment comprising a first casing head for attachment to the upper end of an outer string of casing, said casing head having means associated therewith for supporting a second casing head equipped for attaching an inner string of casing, control equipment having means for attachment on said first casing head and having means defining a throughbore therethrough, a second casing head having means for attachment to said inner string of casing, the interior diameter of said control equipment and the exterior diameter of said second head being such that said second casing head is capable of being passed through said throughbore of said control equipment and landed on said first casing head, whereby said inner string of casing may be immediately cemented after said second casing head is landed.

References Cited by the Examiner UNITED STATES PATENTS 2,207,255 8/1940 Jesson et al 166-88 2,504,025 4/1950 Humason 166-88 2,747,840 5/1956 Miles 166-665 2,748,869 6/1956 Hager 166-75 2,766,829 10/1956 Watts et al. 106-75 2,766,830 10/1956 Church 166-86 3,050,117 8/1962 Haber et al. 166-665 X OTHER REFERENCES Composite Catalog of Oil Field Equipment, 1962-63, pp. 2732, 2733 and 3484.

CHARLES E OCONNELL, Primary Examiner.

C. D. JOHNSON, J. A. LEPPINK,

' Assistant Examiners.

Claims

1. METHOD OF RAPID WELL COMPLETION COMPRISING THE STEPS OF: SETTING A WELL DRIVE PIPE; POSITIONING A ROTARY TABLE AXIALLY ABOVE THE DRIVE PIPE AND COMMENCING DRILLING OPERATIONS WITH DRILLING EQUIPMENT DRIVEN FROM SAID ROTARY TABLE LIFTING THE DRILLING EQUIPMENT FROM THE WELL THROUGH THE ROTARY TABLE; PASSING A WELL CASING INTO THE WELL THROUGH THE ROTARY TABLE; CONNECTING A CASING HEAD TO THE UPPER END OF THE WELL CASING; CONNECTING A LOWERING BUSHING TO THE CASING HEAD AND LOWERING THIS ASSEMBLY THROUGH THE ROTARY TABLE TO SUPPORT THE CASING HEAD ON THE DRIVE PIPE.

6. WELL COMPLETION EQUIPMENT COMPRISING: A CASING HEAD HAVING A CENTRAL PASSAGE THERETHROUGH AND INCLUDING MEANS AT ITS LOWER END FOR RECEIVING THE UPPER END OF A CASING; A LOWERING BUSHING, MEANS FOR REMOVABLY JOINING THE LOWER END OF SAID BUSHING TO THE UPPER END OF SAID CASING HEAD; AND MEANS CARRIED BY THE UPPER END OF SAID LOWERING BUSHING FOR REMOVABLY RECEIVING LOWERING EQUIPMENT; A DRIVE PIPE; A SUPPORTING HUB FOR MOUNTING ON SAID DRIVE PIPE, A CASING SECURED AT ITS UPPER END TO SAID CASING