US3087548A - Back pressure valve - Google Patents

Description

April 30, 1963 B. J. GRAHAM 3,087,548 K' BACK PRESSURE VALVE Filed Dec. 21. 1959 I' |3- 'i 6* l I4 3 -2 I I N I 4 l |5, I 24/1` w 23 l !l i l n2 5 -`2O l 6 li f/ l MI -u 9 8V "`50 lo y 22 19 l v l F|G.|

Blly J. Graham lnvenior Attorney United States Patent O 3,087,548 BACK PRESSURE VALVE Billy J. Graham, Midland, Tex., assignor to Jersey Production Research Company, a corporation of Deiaware Filed Dec. 21, 1959, Ser. No. 860,811 8 Claims. (Cl. 1166-127) The present invention is broadly concerned with yan improvide technique for cementing, particularly squeeze cementing in well boreholes. The invention is more speciiically concerned with `an improved low pressure, easily drillable retainer back pressure valve mechanism or assembly .by which the pressure on the cement may be retained ffor the desired time period until the cement has properly set. In essence the assembly comprises an upper retrievabl-e section and a lower non-retrievable section. The lower non-retrievable section is detached and may be readily removed by drilling. A particular feature Iof the present invention comprises a `i'rangible insert positioned at the lower end of the non-retrievable section which insert may lbe removed or broken by dropping a hollow bar or piece or" lead pipe or equivalent which permits a ball t seat in a valve seat thereby retaining the pressure on the cement.

In the drilling art it is Well known to use various methods and techniques rfor sealingo undesirable formations. For example, in a well in which casing has been set and in which there exists perforations into an oil-bearing formation at times oil will cease to produce and water will be produced through these perforations. Under these circumstances various techniques have been utilized for squeeze cementing through these perforations into the formation about the casing in order to prevent further entry of undesirable water or brine into the casing. One .problem in this type of operation is to maintain the desired pressure on the cement until the same has set in order to prevent the back ilowing of the cement into the casing which would result in an undesirable cementing operation.

The apparatus and process of the present invention may be readily understood by reference tothe drawing illustrating one embodiment of the same. Referring speciiically to the drawing, the squeeze cementing apparatus of the present invention is shown -attached to the lower end of ldrill pipe or tubing 1 by means of a suitable tool joint 13. Tool joint 13 is characterized by having a lower iiat surface or shoulder 16.

The apparatus is shown positioned within casing 2 near the bottom of the -borehole wherein perforations 19 provide communication from formation 18 to within casing 2. The .apparatus or assembly comprises an upper retrievable section comprising a hollow cylindrical mandrel 14 about which is positioned an expandable packing element 3 which may be made of rubber or other suitable packing material which will expand upon compression so as to seal off the vannular area between the assembly and the inner wall of the casing. The area within the hollow cylindrical mandrel 414 communicates to the `area within the pipe string 1 thus permitting the flow of iluid or cement downwardly. Positioned below packer .3 on the exterior of the mandrel is an expandable slip assembly 21, including slip cage 23, ring means 24 non-rotatably mounted in the interior of the slip cage, and springs 4 which extend outwardly from slip cage 2,3` and maintain tfrictional contact with the inner wall tot the casing. Serated or toothed latching lslips 15 are positioned on the outer surface of slip assembly 21 by conventional means. Tapered locking elements 17 are positioned on the outer surface of the mandrel and will function as hereinafter described. The lower end of the mandrel is connected to and communicates with the lower non-retrievable section. The non- 3,56%?,548 Patented Apr. 30, 1963 ICC retrievable section includes a short nipple section 20', the lower end of which comprises a downwardly facing shoulder which forms valve sea-t 7, and an outwardly Haring portion below the valve seat. A circular cup 30 is at-v tached to the lower edge of the outwardly flared portion of nipple section 20. The upper retrievable section and the lower non-retrievable section lare attached to one `21nother lby means of shear pins `Si. Ports 12 in the mandrel provide communication from within the tubing and mandrel to the outer annular area between the assembly and the easing.

As mentioned, the lower section of the assembly comprises the valve seat 7, the seal or cup-type packer 1&1, the slip k6 mounted on the .packer and nipple 2.0 in which the valve seat 7 is tformed, and also the cup attached to the bottomy of the outwardly flaring portion of nipple 20 below the valve seat 7, the frangible bottom 22 of the cup and the ball valve 9` and guides holding the ball oli its seat. This assembly lconstitutes the truste-conical valve structure. Frangible insert 22 is provided at the lower end of the cup 3i? which insert contains perforations 10. A sealing or valve shutoii ball 9 is positioned above the insert in a fixed position by means of upwardly extending guides 8.

In operation the assembly is lowered through the casing to the ydesired position which normally is immediately above the formation to be squeeze cemented oli. In lowering the assembly friction contact is maintained be` tween springs `4 and the inner surface of the casing. After the apparatus has .been lowered to the desired point the tubing is rotated thereby causing @slip cage 23 of assembly 211 to move upward, which fforces :slips 15 to expand outwardly. The toothed surface or edges engage the inner surface of the casing, thereby retarding downward movement of the same. In essence this upper section assembly of the present invention comprises a conventional hook wall packer assembly. After the toothed surface of slips 15 have engaged the inner surace of the casing the tubing is lowered thereby causing the shoulder 16 to exert comprissive thrust on the upper area of packer 3. This expands packer 3 so as to make contact between the assembly and the inner surface of the casing thereby preventing communication from below the packer to above the packer. Also tapered locking elements 17 exert a downward thrust on slips 15 thereby locking these latter elements against the casing.

At this point a hollow drill bar, a piece of lead pipe or other heavy material is dropped down within the drill stem which falls against insert 22 thereby shattering the same and removing it. It is to be noted that the up.- wardly extending guides 8 are attached only to the insert 22 and are thereby removed when 22 is broken' thereby permitting brall 9 free movement. lt is to be also noted that retaining guides 8 extend close enough to the surface of the seat `so that ball 9 will not be free until 22 is shattered.

The squeeze cementing is then` carried out by forcing the cement downwardly within the tubing through the assembly into the formationI 18 through perforations 19. During this operation it is .to be noted that there exists no differential pressure 'across the assembly :due to the pressure equalizing holes 12 in the running tool. After the squeeze cementing operation has been completed and the surface pressure released then the valve ball 9 which is preferably a Bakelite or other type of rubber material is set in the valve seat thereby preventing upward iiow of the cement. The upward pressure also expands the rub ber seal 1-1 and sets slips 6 against the casing which prevents upward movement of the lower section of the assembly. This maintains the desired pressure on the cement as it sets.

An upward thrust is exerted by the string which will shear ott shear pins 5 permitting the raising of the upper retrievable section of the assembly and retaining the lower non-retrievable section of the assembly in the borehole for maintaining the desired high pressure on the cement within the formation until the cement has properly set.

As pointed out heretofore, when the assembly is run in the hole the ball is retained away from the seat by the frangible insert and lby guides attached to the insert. At such time when the tool is run in to the desired depth a hollow drillable bar or piece of lead pipe is dropped. This bar shears loose the small insert in the junk pusher to which are fastened the guides. Both will fall to bottom and the lball is free to seat in the valve seat. The ball is of a plastic material lighter than oil and thus will float up against the seat at any time uid is not being pumped :through the tool. Thus it acts as a back pressure or check valve.

The slips 6 in the lower section are preferably molded into the rubber seal 11 `and fitted by tongue and groove into the top retainer piece which is preferably nia-de of brittle cast iron with hardened teeth. All the other parts of the lower section of the tool are preferably made of magnesium and rubber which are both easily drillable. All parts not having la pressure differential are preferably criss crossed with grooves so that these parts will readily break into small pieces and be circulated out of the hole while the tool is being drilled up. The easy drillability of this tool is a most important factor since it can be drilled in about one hour whereas conventional non-retrievable retainers take several hours and longer to remove, especially at shallow depths. The assembly of the present invention can also be used as a low pressure squeeze tool in conjunction with a rotating or reciprocating circulation control unit.

What is claimed is:

1. Improved assembly for positioning in a borehole to maintain back pressure in said borehole which comprises an outwardly and downwardly flared conical structure thus defining a frusto-conical valve structure, an opening in the upper area of said structure permitting communication from without said structure to within said structure, a circular cup attached to the bottom of said structure, the base of said cup being 1frangible, a guide extending upwardly from said base, and a ball positioned in the area deiined by said guide, said base and the walls of said cup whereby said ball is locked into a relatively fixed position, the density of said =ba1l .being less than the density of borehole uid, means for fracturing said base thereby permitting movement of said ball within said structure, whereby as fluid flows downwardly through said opening, free passage of the same is permitted; but, on back ow of lluid said ball seats in said structure thereby preventing back ow of said lluid.

2. Apparatus as delined by claim 1 wherein an expandable packing element is circumferentially positioned on the exterior of said conical structure.

3. Apparatus as delined :by claim 2 wherein a toothed slip is embedded in said packing element, the teeth of which are adapted to engage the wall surrounding the assembly and prevent vertical movement of the same.

4. An improved apparatus for positioning ina borehole casing to conduct a squeeze cementing operation` and to maintain back pressure in said hole until the cement has set which comprises an upper retrievable section and a lower non-retrievable section, said upper retrievable section being adapted to be attached to the lower end of a drill string by suitable means in a borehole adjacent the formation to be cemented, said upper retrievable section comprising a hollow mandrel having interior communication with the interior of said drill string, a packer element disposed circumferentially without said mandrel adapted to be expanded upon compression, slip means on said mandrel, including a slip cage, guide springs extending outwardly from said slip cage to maintain frictional contact with the inner wall of said casing through which the assembly is lowered, toothed slip means in said cage adapted to be expanded and extend outwardly from the exterior of said mandrel and to contact the interior of the casing thereby preventing vertical movement of the assembly, a lower non-retrievable section attached to said upper retrievable section by means of a pipe section connected by shear pins, said lower non-retrievable section comprising an outwardly and downwardly flared conical struct-ure defining a frusto-conical valve structure, an' opening in the upper area of said structure permitting communication from within said structure to within said pipe section to within said mandrel, a circular cup attached to the bottom of said structure, the base of said cup .being frangible, a guide affixed to said base extending upwardly from said base and `a ball positioned in the area delined by said guide, said base :and the walls of said cup whereby said ball is locked into position, the density of said ball being less than the density of said cement, means for passing a heavy object downwardly through said drill stem through said mandrel and into and through said structure to break said frangible base, thereby permitting movement of said ball within said structure, whereby as cement flows downwardly through said opening, free passage of the same is permitted; but, on back ow of cement said ball seats in said structure thereby preventing back llow of said cement.

5. Apparatus as delined by claim 4 wherein said frangible base contains perforations.

6. Apparatus as defined by claim 4 wherein said pipe section contains perforations thereby permitting comm-unication from within said pipe section to the yannular area about the apparatus and between the packer element disposed without said mandrel and the exterior area of said structure.

7. Apparatus as defined by claim 4 wherein an expandable packing element is circumferentially extended on the exterior of said structure.

8. Apparatus as dened by claim 7 wherein a toothed slip is embedded in said packing element, lthe teeth of which are adapted to engage the walls surrounding the assembly and prevent vertical movement of the same.

References Cited in the tile of this patent UNITED STATES PATENTS 2,187,482 Baker et al. Ian. 16, 1940 2,196,661 Grubb Apr. 9, 1940 2,313j178 Spang Mar. 9, 1943 2,598,512 Cypher May 27, 1952 2,672,199 McKenna Mar. 16, 1954 2,729,293 Cloud Ian. 3, 1956

Claims (1)

1. IMPROVED ASSEMBLY FOR POSITIONING IN A BOREHOLE TO MAINTAIN BACK PRESSURE IN SAID BOREHOLE WHICH COMPRISES AN OUTWARDLY AND DOWNWARDLY FLARED CONICAL STRUCTURE THUS DEFINING A FRUSTO-CONICAL VALVE STRUCTURE, AN OPENING IN THE UPPER AREA OF SAID STRUCTURE PERMITTING COMMUNICATION FROM WITHOUT SAID STRUCTURE TO WITHIN SAID STRUCTURE, A CIRCULAR CUP ATTACHED TO THE BOTTOM OF SAID STRUCTURE, THE BASE OF SAID CUP BEING FRANGIBLE, A GUIDE EXTENDING UPWARDLY FROM SAID BASE, AND A BALL POSITIONED IN THE AREA DEFINED BY SAID GUIDE, SAID BASE AND THE WALLS OF SAID CUP WHEREBY SAID BALL IS LOCKED INTO A RELATIVELY FIXED POSITION, THE DENSITY OF SAID BALL BEING LESS THAN THE DENSITY OF BOREHOLE FLUD, MEANS FOR FACTURING SAID BASE THEREBY PERMITTING MOVEMENT OF SAID BALL WITHIN SAID STRUCTURE, WHEREBY AS FLUID FLOWS DOWNWARDLY THROUGH SAID OPENING FREE PASSAGE OF THE SAME IS PERMITTED; BUT ON BACK FLOW OF FLUID SAID BALL SEATS IN SAID STRUCTURE THEREBY PREVENTING BACK FLOW OF SAID FLUID.

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