Multiple Plug Release System

Abstract

This invention relates to liner plugs used in oil and gas well cement operations. More particularly, the invention is concerned with a locking device within the plugs which permits two or more plugs to be suspended in the well bore and released individually as required.

Parent Case Text

CROSSREFERENCES TO RELATED APPLICATIONS

This application is a continuation-in-part of an original application for "Multiple Plug Release System for Cementing Operations" Ser. No. 64,522, by B. Jack Bradley, filed Aug. 10, 1970, and now abandoned.

Description

BACKGROUND OF THE INVENTION

When a liner is being cemented in a well, various size pipes are involved: the drill pipe having one I.D. (internal diameter); the liner setting tool or casing hanger having another size I.D.; and the liner, suspended from the setting tool or hanger, having yet another size I.D. The liner setting tool stinger positioned at the top of the liner may also have an I.D. different from the other pipes. If a multiple stage cementing tool, such as disclosed in U.S. Pat. No. 3,247,905, is made an integral part of the string of liner pipe, the two seats therein have different I.D.s. The different size pipes present a problem during the cementing operations in that a wiper plug small enough to be pumped through the stinger and the drill pipe will be too small to wipe the larger size liner. To overcome this problem, a single hollow plug, having wipers large enough to wipe the liner, is lowered into the well along with the liner pipe prior to cementing operations. The plug is suspended from the stinger, attachement thereto being by means of shear pins positioned through the stinger and the upper end of the plug. At the appropriate time during the cementing operations a small solid plug is pumped down the drill pipe and landed in the liner plug. Pressure acting on the plug shears the pins and pushes the plug downward. This action disengages the liner plug from the stinger, thus permitting the plug to be pumped down the liner. Where the cementing operation is completed in one step, the liner plug is pumped down to the bottom of the liner pipe following the cement so as to wipe the liner free of cement.

In a cementing operation which requires two stages, the single liner plug must be expended to close ports in the multiple stage cement tool. Thus, the first stage of cement must be displaced without plugs. This results in inexact placement and contamination of the cement, excessive and costly drill out operations and so forth.

Another solution to the problem that exists is a two-plug system. Here, a bottom liner plug is attached to a top liner plug by shear pins of a given strength. The top liner plug is attached to a hanger or stinger by upper pins having greater shear strength than the lower pins. The bottom plug is released in front of the cement by pumping a solid rubber ball down the drill pipe into a seat in that plug. Increased pump pressure shears the pins holding the two liner plugs together and the bottom plug is free to be pumped to the bottom of the well. Following the cementing, the top liner plug is released in the same manner; i.e., a ball or dart is dropped from the surface into the plug. Increased pump pressure shears the pins holding the top liner plug to the stinger.

The two-plug system represents an improved method in liner pipe cementing operations. However, the effectiveness and reliability of this sytem is totally dependent on the lower pins shearing off before the upper pins.

It is believed that no system has heretofore been devised which would allow the suspending and sequential releasing of three or more liner plugs.

SUMMARY OF INVENTION

The present system provides a hollow liner plug system for sequentially releasing three or more hollow liner plugs one at a time and comprises an upper liner plug, one or more intermediate liner plugs, and a lower liner plug, wherein the liner plugs generally comprise a hollow tubular housing containing a releasing sleeve and a locking sleeve with the releasing sleeve held in place by shear pins and each liner plug held to the next upper adjacent plug by spherical means located in apertures in the tubular housing, and each liner plug adapted to prohibit its release until after the release of all liner plugs below it.

In order to more fully describe the present invention, reference is made to the accompanying drawings wherein:

FIG. 1 is a schematic diagram showing a plurality of liner plugs carried on the lower end of a stinger in position within a well casing;

FIG. 2 is a sectional view of a liner plug of FIG. 1 constructed in accordance with the invention;

FIG. 2a is a cross section taken along line 2a--2a of FIG. 2;

FIG. 3 is a sectional view of two of the liner plugs of FIG. 1 showing the attachment of one liner plug to another;

FIG. 4 is a sectional view of the liner plug of FIG. 1 after it has been released from attachment to another liner plug or stinger;

FIG. 5 is a sectional view of an alternate embodiment of the bottom liner plug of FIG. 1.

DETAILED DESCRIPTION

Three hollow liner plugs numbered 11a, 11b, and 11c are shown suspended from liner setting tool stinger 12 in FIG. 1. Each liner plug 11 may be of similar construction but of different dimensions; internal dimensions vary so as to receive the correct drill pipe plug (not shown); external dimensions vary so as to fit into the correct seats (not shown) in float shoe 18 and multiple stage cementing tool 17. Stinger 12 is in turn attached to liner setting tool 13. Liner pipe 14 extends from an anchor (not shown), set adjacent to casing 15 which had previously been cemented-in, to the bottom of well 16. Incorporated in the liner string 14 is a multiple stage cementing tool 17 and float shoe 18. Completing the conduit to the surface is drill pipe (not shown), extending above setting tool 13. In this and subsequent FIGURES, the nose or front end of plugs 11a, 11b, 11c, or 111, as the case may be, point downward toward the bottom of the page. It is this position in which plugs 11a, 11b, 11c, and 111 are placed when suspended in well 16 from stinger 12.

Referring now to FIG. 2 and 2a, attention is drawn to the internal construction of liner plug 11b. The cylndrical tubular body 25 has a series of wipers 26 positioned circumferentially thereon. At the upper end of body 25 is collar 27 having internal threads 28, and shoulder 29. Collar 27 can be threadedly attached to a liner plug positioned above, such as plug 11a shown in FIG. 1; collar 27 which otherwise would be threadedly attached to plug 11b at its lower end and would be a part of plug 11c has been omitted. Slidably mounted within body 25 is collar releasing sleeve 30. Holding sleeve 30 in the position shown is shear pin 31. Positioned around sleeve 30 and in recess 32, is expanding lock ring 33. A series of holes 35 are located about the upper end of body 25 and pass through the side of body 25. Balls 36, placed one in each hole 35, are pressed outwardly onto shoulder 29 of collar 27 by sleeve 30. Until balls 36 are removed therefrom collar 27 is secured to body 25. Located in the interior wall 37 of body 25, and positioned below holes 35, is recess 38. Recess 38 receives expanding lock ring 33 as sleeve 30 slides down within body 25. Slidably mounted within body 25 and immediately below sleeve 30 is locking sleeve 40. Until locking sleeve 40 moves downward, sleeve 30 and balls 36 are locked in the position shown. Locking sleeve 40 extends down beyond the lower end of body 25. Shoulder means 41 is attached to locking sleeve 40 and may consist of an integral shoulder or a threaded nut located at the lower end of locking sleeve 40, with said nut being attached to the locking sleeve 40 by companion threads 42. Exterior threads 43, positioned about body 25 at its lower end, receive collar 27 as described above.

FIG. 3 illustrates how liner plugs 11 are attached to each other or to stinger 12 (FIG. 1). Using for illustration liner plugs 11a and 11b, attachment is accomplished by threading locking collar 27 onto liner plug 11a. Collar 27 is attached to liner plug 11b via balls 36 of liner plug 11b. Attention is specifically drawn to the abutting relationship existing between locking sleeve 40 of plug 11a and plug 11b. As long as plug 11b remains attached to plug 11a, locking sleeve 40 cannot slide downward unlocking sleeve 30 (FIG. 2).

FIG. 4 illustrates how liner plugs 11 are disengaged from each other or from stinger 12 (FIG. 1). Using for illustration liner plug 11b and assuming liner plug 11c has already been disengaged, a drill pipe plug 50, shown in broken lines, has been landed in plug 11b. Pump pressure thereon has caused the shearing of pin 31, allowing collar releasing sleeve 30 to slide downward. Recess 38, located on interior wall 37 of body 25, receives lock ring 33. Expansion of ring 33 within recess 38 prevents upward movement of drill pipe plug 50 and collar releasing sleeve 30. Note that locking sleeve 40 has permitted the above action by being able to also travel downward. Having liner plug 11b attached to plug 11a prevents downward movement of 11a by the abutting position of liner plug 11b (FIG. 3), with sleeve 40 as described above. The downward movement of releasing sleeve 30 lets balls 36 roll inward out of contact with shoulder 29 of collar 27, shown in broken lines. Liner plug 11b is now disengaged and is free to be pumped down liner 14 (FIG. 1). Note that downward movement of locking sleeve 40 has been arrested by the abutting of locking sleeve nut 41 against shoulder 29 positioned within collar 27.

FIG. 5 depicts an alternate lower liner plug 111 which may be advantageously utilized in place of 11c in the lowermost position in the liner plug system. In 111 the locking sleeve 40 and lower collar 27 of FIGS. 3 and 4 have been made an integral part of the tubular housing 25 of liner plug 11b. The result is a solid tubular housing 125 having upper shoulder 101, lower shoulder 102, apertures 103, a circumferential wiper sleeve 146 with radially extending wipers 126, annular recesses 121 and 122 of differing diameters and an upper end with inner diameter 123 larger than that below annular recess 121. A collar releasing sleeve 130 is located snugly within the enlarged diameter 123 of housing 125, and apertures 135 located in the housing open into the enlared diameter 123. Shear pins 131 hold the releasing sleeve 130 to the housing 125 and expanding lock ring 133 located in recess 132 in the releasing sleeve 130 serves to prevent any movement upwards by the releasing sleeve once it has been moved to its lowermost position in abutment with shoulder 124 of annular recess 121. Lock ring 133 prevents upward movement of releasing sleeve 130 by partially expanding into annular recess 122. O-ring seals 155 are used to provide a fluid tight seal between sleeve 130 and housing 125 as well as between collar 127 and housing 125.

Spherical balls 136 located in apertues 135 abut with the releasing sleeve 130 on the inside and extend out of the housing 125 far enough to abut shoulder 129 of collar 127. Liner plug 111 can be released from the system by pumping a drill pipe plug (not shown) down the center of the system, which plug will seat in the beveled shoulder 144 of releasing sleeve 130. Fluid pressure is then applied to the system and shear pins 131 are sheared allowing the releasing sleeve 130 and drill pipe plug to slide down into the recessed areas 121 and 122, to abut with shoulder 124 thereby ending the downward movement of the releasing sleeve.

The downward movement of the releasing sleeve 130 allows balls 136 to be pushed inward by the wedging action of shoulder 129 on them. With this hindrance removed, fluid pressure which is still acting through the plug and a releasing sleeve and onto the housing pushes the housing down and out of collar 127, freeing the liner plug 111 to perform its function lower down the liner.

In actual operation, where liner 14 is cemented into well 16 via two stages, plugs 11a, 11b, and 11c or 111 are lowered into the well bore to a position near the top of liner 14 (FIG. 1). The first stage cement, from the surface, is pumped down through the drill pipe (not shown), through liner 14 to the bottom of well 16 and back up around the annular space outside of liner 14 to a point immediately above tool 17. Liner plug 11c is then released via drill pipe plug 50 (FIG. 4), and pumped to bottom cleaning the liner of all cement therein. Liner plug 111 could be used in place of plug 11c. Liner plug 11b is next released via a second drill pipe plug 50 (FIG. 4) and landed in tool 17 (FIG. 1), opening ports (not shown) therein, and also plugging off the lower part of liner 14. The second stage cementing operation is then commenced. Cement is pumped down the drill pipe and liner 14 and out the ports (not shown) of tool 17 filling the remaining annular space up past the bottom of casing 15 (FIG. 1). Liner plug 11a is then released via a third drill pipe plug 50 (FIG. 4) and pumped down liner 14 (FIG. 1), cleaning cement from liner 14 and pushing it out the ports (not shown). Landing in tool 17, liner plug 11a closes the ports. This concludes the cementing operation and all that is now required to prepare the well for production is the relatively simple task of drilling out the liner plugs and perforating liner 14 opposite the oil and/or gas bearing formation.

Whereas three liner plugs are shown (FIG. 1), any number can be attached with assurance that only the lowest of plugs remaining suspended from stinger 12 can be detached.

The present invention has been disclosed in the light of performing a series of functions during a multiple stage cement operation. This has been so done only for purposes of illustration and is not to be construed as limiting the function of the invention. For example, a stinger loaded with two liner plugs can be provided for single stage cementing. The first or lowest plug precedes the cement, wiping mud from the liner's walls. The second or upper plug follows the cement displacing it from the liner out into the annulus. Other and equally important areas, both within and without the oil industry, will find this invention applicable. One such use is where a number of tools located down the well need to be actuated serially. With the present invention, the proper actuating sequence can be obtained with certainty.

It will be understood that other and further forms of the invention may be devised without departing from the spirit and scope of the appended claims.

Claims

What is claimed is:

1. A liner plug used in oil well cementing operations, said plug comprising:

a. a tubular body having an upper and a lower end, at least one hole passing through a side thereof located at the upper end, and a plurality of wipers disposed circumferentially in spaced relation along the exterior length thereof;

b. a collar having an internal annular shoulder slidably located about the upper end of said body;

c. at least one ball positioned in said hole in said body,

d. an annular collar releasing sleeve slidably mounted within said body, said sleeve positioned so that said ball is pressed outwardly through said hole in said body against the internal annular shoulder of said collar until said sleeve is slid downwardly thereby permitting said ball to move inwardly; and

e. an annular locking sleeve slidably mounted within said body in abutting position with said collar releasing sleeve so that movement of said collar releasing sleeve is permitted only with movement of said locking sleeve.

2. A liner plug as in claim 1 wherein said locking sleeve further comprises a tubular sleeve having shoulder means at its lower end for preventing said tubular sleeve from sliding out of said liner plug.

3. A bottom liner plug used in oil well liners and adapted to be used at the bottom of a multiple plug string, said bottom liner plug comprising:

a. a tubular housing containing upper and lower external shoulders, spaced apart circumferential apertures, and an internal annular recess;

b. a circumferential wiper sleeve attached to the exterior of said housing between said upper and lower shoulders and having a plurality of radially extending wipers;

c. a collar releasing sleeve located concentrically within said tubular housing adapted to slide downward in said housing into abutting relationship with the lower edge of said annular recess;

d. shear pin means connecting said collar releasing sleeve to said tubular housing so that said sleeve internally covers said apertures in said housing;

e. a connector collar slidably located about the upper end of said tubular housing for connecting said liner plug to the next upper liner plug or tool and containing an inner circumferential shoulder facing inward and upward; and

f. spherical means located in said apertures between said releasing sleeve and said connector collar and abutting said inner circumferential shoulder thereby preventing downward movement of said tubular housing until said shear pin means is sheared and said releasing sleeve is moved downward.

4. A multiple liner plug release system for attaching to a liner setting tool stinger and for systematically and sequentially releasing three or more hollow liner plugs one at a time during operations in a liner in a well bore, said system comprising:

three or more liner plugs connected together and connected to said liner setting tool stinger at the top of said liner, each of said liner plugs comprising:

a. a tubular body having an upper and lower end, at least one hole passing through a side thereof located at the upper end, and a plurality of wipers disposed circumferentially in spaced relation along the exterior length thereof;

b. a collar having an internal annular shoulder slidably located about the upper end of said body;

c. at least one ball positioned in said hole in said body;

d. an annular collar releasing sleeve slidably mounted within said body, said sleeve positioned so that said ball is pressed outwardly through said hole in said body against the internal annular shoulder of said collar until said sleeve is slid downwardly thereby permitting said ball to move inwardly; and

e. an annular locking sleeve slidably mounted within said body in abutting position with said collar releasing sleeve so that movement of said collar releasing sleeve is permitted only with movement of said locking sleeve; and

means for moving the annular collar releasing sleeve of each of said liner plugs downwardly so that each of said liner plugs is released, the lowermost liner plug being released first and the remaining liner plugs being released sequentially one at a time.

5. The multiple liner plug release system of claim 4 wherein said means for moving the annular collar releasing sleeves of each of said liner plugs downwardly so that said liner plugs are released sequentially comprises:

each of said collar releasing sleeves including an annular plug seat at the top thereof adapted to receive and sealingly engage a drill pipe plug whereby the inner passage of said collar releasing sleeve is fluidically sealed when a drill pipe plug is positioned against said seat, each of said collar releasing sleeves being of progressively smaller inner diameter than the inner diameter of the next adjacent tool above; and

shear pin means connecting said collar releasing sleeve to said tubular body and adapted to shear at a given fluidic pressure level.

6. The multiple liner plug release system of claim 5 wherein said lower liner plug comprises:

a. a tubular housing with upper and lower exterior circumferential shoulders, a plurality of apertures near the top, and an inner annular shoulder;

b. a circumferential wiper sleeve attached externally to said tubular housing and located between said upper and lower shoulders and having radially extended wipers;

c. a cylindrical tubular collar releasing sleeve with an outer diameter substantially equal to the inner diameter of said housing, located concentrically within said housing near its upper end, and having two or more circumferential recesses located in the outer wall for receiving a lock ring and sealing means; and

d. a connector collar slidably connected to the upper end of said tubular housing.

7. An oil well tool comprising:

a. a tubular body;

b. an upper collar slidably connected to said body;

c. an inner releasing sleeve concentrically located within said body;

d. shear means holding said releasing sleeve to said body;

e. locking sleeve means located within said body in abutting relationship with said releasing sleeve; and,

f. releasing means located between said body and said collar for selectively releasing said body from said collar at a predetermined instant.

8. The oil well tool of claim 7 wherein said releasing means comprises: apertures in said tubular body; spherical balls within said apertures abutting the exterior wall of said inner releasing sleeve; and projecting out of said apertures toward said collar; and a lower interior annular shoulder in said collar adapted to abut said spherical balls projecting outward and prevent said tubular body from moving downward until said releasing sleeve is moved downward allowing said balls to be wedged inward.