US2145884A

US2145884A - Stripper

Info

Publication number: US2145884A
Application number: US61462A
Authority: US
Inventors: Arthur L Leman
Original assignee: Nat Supply Co
Current assignee: National Supply Co
Priority date: 1936-01-30
Filing date: 1936-01-30
Publication date: 1939-02-07
Anticipated expiration: 1956-02-07

Description

I Feb. 7, 1939.

A. L. LEMAN STRIPPER Filed Jan. 30, 1936 2 Sheets-Sheet 1 IN VENTOR. A I BY 4Mzz/ c.

40% ATTORNEY.

. AQL. LEMAN Feb. 7, 1939.

STRIPPER Filed Jan. 30, 19:56

2 Sheets-Sheet 2 Patented Feb. 7, 1939 UNITED STATES STRIPPEB ArthurLLeman, Houston, Tex, adgnorto The National Supply Company, Pittsburgh, Pa, a

corporation of Pennsylv Application January :0, 193s, sci-m No. 01,402

2 Claims. (01. ass-1) My invention relates generally to casing heads and more specifically to casing heads having embodied therein a tubing stripper arranged to seal an inner concentric string of tubing in a casing head.

This invention may be conveniently applied to casing heads for use in the oil well art and is more particularly adapted to seal ofl an inner concentric string of tubing which is suspended from within the casing head from a point thereabove.

A tubing stripper in the casing head art comprises an annular flexible member held in position within the casing head, or similar member, in such a manner as to prevent the passage of fluid therebetween. This annular flexible member depends inwardly and downwardly, contacting the outer surface of the inner string of casing. By reason of its shape the stripper provides an inherent initial pressure against the tubing which aids in effecting a seal therebetween. Again any fluid well pressure acting upon the lower surface of the stripper increases the pressure engagement between the stripper and the tubing, thereby developing a greater sealing engagement in proportion to the existing pressure.

The stripper is purposely made of flexible material to provide for the passage of the tubing therethrough which prevents the escape of the fluid within the well even though couplings of enlarged diameter connecting the sections of tubing must pass through the stripper.

The principal object ofthis invention is the provision of a flexible stripper that will withstand the repeated passage of enlarged coupling members and the like without endangering the emciericy of the seal thereof. This advantage is gained by the particular design of the stripper member and the manner in which'it is incorporated into the casing head structure.

The specific objects of this invention deal with the manner in which the stripper is formed, the manner in which it is locked in place, the manner of forming the annular flexible hinge, the manner of supporting the hinged portion and the mode of backing the hinged portion to give it inherent rigidity without endangering its flexibility. 7

Other objects and advantages will appear in the following specification.

In the accompanying drawings wherein I have shown a practical embodiment ofthe principles of my invention, v

Fig. 1 is a vertical sectional view of a casing head having the stripper assembled therein.

Fig. 2 is an inverted plan view of the stripper.

Fig. 3 is an enlarged sectional view of the stripper showing its contour as a free body.

Fig. 4 is a vertical sectional view of a stripper in sealing engagement with an inner string of tubing with parts of the casing head broken away.

Fig.5isaviewsimiiartoFig.3showinga tubing coupling of enlarged diameter in sealing engagement with the stripper.

Referring to the drawings and more particularly to Fig. 1, ll represents a casing head or casing head attachment, arranged to be secured to the well casing, or associated member, as by the threads II at the bottom thereof. The casing head member comprises a tubular member having a series of bores arranged to seat or support the several elements necessary to complete the justed provide the proper compressive force on the annular gland member I 9 for compressing the packing ring I, thereby sealing the bore i2 of the casing head with the ring it.

Radially inward of the bolts II the upper portion of the ring it is provided with a plurality of upwardly extending stud-bolts 20, the positions of which are alternate with respect to the bolts it. These stud bolts are arranged to receive the inner gland member 2| which compressesthe inner packing member l5, forming a seal between the tubing l6 and the ring l3.

It should be noted that the ring l3 provides the packing seats and packing chambers, utilizing the walls of the adjacent members without their being preformed for that speciflc purpose. Again the ring I! furnishes the pressure means for both pecking members.

The bore 22, which is directly below the bore I! of the casing head, is tapered to receive and hold the slim 23, the function of which is to support the inner concentric tubing IS in the well known manner. The next succeeding

bores

24 and 25 are for the purpose of supporting and securing the flexible stripper 28 which is preferably made of rubber or the like. The bore 25 isof smaller diameter of, which merges into the bore 29 of the lower portion of the casing head body. The bore 24 is provided with detachable securing means for holding the stripper abutment ring 38.

3| represents a casing head vent which opens into the tubular member in the vicinity of the bore 29. This vent is employed to convey the fluid from the well to places where such products may be used or diverted. The lower bore 29 may extend to the lower end of the casing head and the casing securing means, such as the threads Il, may be cut in the face thereof. As shown herein the lower bore 29 is provided with the inner extending portion 32 which acts as a guide for the tubing l6 and also provides reenforcement for the externally threaded section II.

The casing head member is provided with the elevator lugs 33, one of which is shown at the right in Fig. 1.-

Referring specifically to the

stripper

26, 34 represents the lower annular flange which is arranged to snugly fit in the pocket 21 of the casing head. The upper annular flange 35 fits within the recess 36 of the stripper abutment ring 38. 31 represents castellations in the upper surface of the abutment ring 38 which are arranged to receive a tool for turning the ring 30 to compress and hold the stripper in its proper position. In Fig. 3, the stripper 26 is shown as a free bodyin full lines, the' dotted lines indicate the position it assumes when held in position as shown in Fig. 1. The stripper may or may not be formed in the shape indicated in Fig. 3, but however when assembled the body of the stripper between the annular shoulder 38 and the axis of pivotal movement 39 is compressed by the abutment ring 38. This initial compression will prevent or retard the separation of the shoulder 38 from the adjacent surface of the abutment ring 30 when the skirt of the stripper is flexed downwardly and outwardly. Again, the initial compression of the body and the stripper does not affect the shape or operation of the skirt when the latter is required to perform its function.

The upper surface 40 of the stripper between the annular flange 35 and the shoulder 38 is formed as a mating surface to the adjacent wall 40a of the abutment ring. This surface is preferably conical and appears as a tapered surface in the drawings. This particular shape of the surface 40 provides several advantages. It permits the body of the stripper and the abutment ring 30 to be of uniform thickness, thereby providing uniform distribution of compressive and. reactive forces. Again it enhances the hinging qualities of the stripper skirt. When the skirt is forced downwardly and outwardly, hinging on the pivot point 33, the conical surface 40 does not have the tendency to abruptly leave its complementary surface of the abutment ring 30. If the casing head is of the multiple type wherein a second string of tubing is vented from above the stripper, any sand or grit will be unable to seek its way between these mating surfaces. This is especially true if an initial compression of the stripper body is employed, as described above, for this section of the stripper must be completely free from compression before it has any tendency to leave its matng surface on the abutment ring.

A further important advantage of the surface 48 lies in its capability of retaining the upper portion of the stripper, thereby aiding or relieving the load on the large annular shoulder 35. v

The skirt of the stripper is designated generally by the numeral 4|. It comprises a portion of the body section as designated at 42, the annular depending section 43, the sealing contact portion 44, and the flaring nose or rim portion 45.

The zone of greatest flexibility is in the section 43 and the effective pivotal point for hinging is at 39. The zone or body section 42 contributes little to the hinging action but if the skirt is flexed to the limit there will be a tendency for the shoulder 38 to move away from the abutment ring 30 unless this portion of the stripper is under initial compression as described above. The section 44 obviously contributes little to the hinging action. This section must be maintained relatively rigid to perform the sealing function. Thus the forces created by the hinging action must be transmitted to this zone to enhance the sealing effect.

46 represents a plurality of web or bracing members which are preferably integral with the stripper and extend from the pivotal point 39 to the tip of the nose portion 45. They may be positioned around the stripper to provide a uniform transmission and distribution of the hinging forces from the section 43 to the section 44. Their number and relative thickness depends upon the size of the stripper and the degree of flexibility required to seal the varying dimensions of the tubular members inserted in the well. To be effective these webs must support part of the zone of greatest flexibility or the section 43. However it should be noted that they are maintained relatively shallow through this section by reason of the fact that the walls' of section 43 converge to section 44 from whence they are maintained substantially uniform. The deepest sections of these webs occur opposite the tubular sealing zone or section 45 where they become most effective. These webs function to interconnect sections 43 and 44 and are not permitted to contact the bore of the casing head. .Their function is confined solely in bracing these two sections.

Figs. 3, 4 and 5 illustrate the varying degrees of stressed condition which the stripper undergoes from that of a free body to its application in effecting a seal against the coupler '41. The contour of the outer edge of the web 46 in Fig. 5 is slightly curved owing to the extreme flexure of the stripper as the coupler 41 passes therethrough. In such instances the hinging action is effective along the webs from the point 39, causing the outer edges of the webs to assume a slight arcuate contour.

When the well contains fluid under pressure between the casing and the tubing string [6, this pressure is effective against the back of the skirt 4| forcing it into tighter sealing engagement with the tubing l6 and preventing the passage of the fluid therebetween. The fluid pressure is effective against a greater area than that of the contacting sealing surface. This produces a concentrated sealing pressure and by reason of the tapered section 43 and the webs 46, which are efiective in substantially an indirect proportion because of their relative position and shape, the skirt is not permitted to collapse in the zone of greatest flexibility and the same sealing section is maintained. A skirt not having these characteristics would collapse under high pressure, causing the rim thereof to curl outwardly, thereby losing the effective sealing contact area, permitting an escape of the fluid until the pressure is released and it is permitted to assume its normal shape. Under high pressures such askirt may collapse and regain -its normal shape with great rapidity until it has been flexed to such an extent that it fails completely and is torn from its socket. v

I have thus provided a stripper of relatively light cross section which permits repeated passage of enlarged tubing members without becoming ruptured or permanently deformed and I am enabled to maintain an eflicient seal by reason of the force transmitting or bracing webs which prevent collapse of the skirt.

'It is .evident that the fluid well pressure is effective against the entire perimetral surface of the stripper 26, including the webs l6, and thus a uniform force is effective to produce a sealing engagement for the complete circumference of the tubing member. This is very important.

, I claim:-

1. In a well casing head structure having a tubing string disposed axially therethrough, a flexible tubing stripper foreflecting a fluid tight seal between the head and the tubing which comprises an annular base portion arranged to be secured in fluid tight engagement in the bore of the casing head structure, an annular body portion extending radially inwardly and having a bore in spaced relation with the tubing, an anible tubing stripper for effecting a fluid tight seal between the head and the tubing which comprises an annular base portion arranged to be secured in fluid tight engagement in the bore of the easing head structure, an annular body portion ex-' tending radially inwardly and having a bore in spaced relation with the tubing, an annular skirt portion extending downwardly and inwardlly of the body portion and in spaced relation with the bore of the casing head structure and the tubing, an annular sealing portion adjacent the lower end of said skirt portion for yieldably engaging the tubing string, and a plurality of vertically disposed and circumferentially spaced ribs integral with the exterior of said skirt and sealing portions for reenforcing them as they are flexed during the passage of members of enlarged diameter to maintain a fluid under pressure within the casing head structure.

' AR'I'HUR. L. LEMAN.