WELLBORE COMPOSITE PLUG ASSEMBLY

Abstract

A down hole tool assembly can be installed at a desired location within a subterranean wellbore that is capable of isolating one portion of the wellbore from another, while sealing fluid pressure within the wellbore from at least one direction. The plug assembly can include components constructed of non-metallic material that can be drilled, milled or mechanically broken up more quickly and efficiently than conventional wellbore plugs.

Description

CROSS REFERENCES TO RELATED APPLICATION

Priority of U.S. Provisional Patent Application Ser. No. 61/838,524, filed Jun. 24, 2013, and U.S. Provisional Patent Application Ser. No. 61/904,077, filed Nov. 14, 2013, both incorporated herein by reference, is hereby claimed.

STATEMENTS AS TO THE RIGHTS TO THE INVENTION MADE UNDER FEDERALLY SPONSORED RESEARCH AND DEVELOPMENT

None

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention pertains to a down hole assembly such as, but not limited to, a drillable bridge plug that can be installed at a desired location within a subterranean wellbore. More particularly, a preferred embodiment of the present invention pertains to a bridge plug assembly capable of sealing fluid pressure within a wellbore from at least one direction. More particularly still, the present invention pertains to a plug assembly that can be drilled, milled or mechanically broken up more efficiently than conventional wellbore plugs.

2. Brief Description of the Prior Art

It is frequently desirable to set at least one bridge plug or other anchoring, sealing device within a wellbore. In some cases, such assemblies are installed to isolate one portion of a wellbore from another, prevent fluid flow from one portion of a wellbore to another, and/or provide a fluid pressure sealing barrier within said wellbore. Such down hole bridge plugs or other anchoring, sealing devices are frequently set within the bore of a casing or tubing string, and both grip and provide a fluid pressure seal against the inner wall of such pipe; however, it is to be observed that in certain applications such plugs can also be installed within a section of drilled “open hole”.

Conventional bridge plugs used to isolate a portion of a wellbore from another portion of said wellbore typically comprise a sealing system or packing element incorporated into to the design, an anchoring system that grips the inner surface of the surrounding wellbore, as well as an additional internal force storing mechanisms. With such conventional plugs, a force is required to energize said packing element and actuate said anchoring system. In certain assemblies, such force or load is supplied by pipe weight situated above the plug, or by tensile loading applied from the wellbore surface. Such conventional plugs generally must be continually attached to a pipe string during the setting process in order to receive the force required to actuate said anchor system and energize said sealing mechanism and to continue to energize such system.

Certain conventional bridge plugs internally store setting forces supplied by an attached tubular, electrically actuated setting tool or hydraulic setting tool and are made to operate alone without any attachment to said devices. These conventional tools anchor and seal remotely of the said devices and are capable of storing forces transmitted by such setting devices to remain anchored and sealing.

Of the conventional bridge plugs that internally store setting forces, a portion are made to be drilled with a bit, hammer or mill drilling device to be removed from the wellbore when isolation of a portion of the wellbore is no longer desired. These conventional drillable bridge plugs are typically constructed of either drillable cast iron, aluminum, resin impregnated fiber or a combination. Such plugs generally comprise a mandrel, an upper slip support, upper slips, upper cone, upper element back up system, packing (sealing) element, lower element back up system, lower cone, lower slips, lower slip support and an enclosed locking ring located between the upper cone or upper slip support and the mandrel.

When such a conventional plug is set, the mandrel with the attached lower slip support and/or lower cone move relative to the upper slip assembly causing the upper and lower slip assemblies, to come together and contact the cones. The slip assemblies then are forced to extend radially outward toward the inner surface of a surrounding wellbore. Simultaneously, said packing element, typically located between the slip assemblies, compresses as the slip assemblies and cones come together; the packing member extends radially outward along and around the midpoint of the element toward the inner surface of the surrounding wellbore. Said opposing slip assemblies move toward each other, but once in contact with the inner surface of the surrounding wellbore said slip assemblies cannot move apart. Thus the slip assemblies lock in place to anchor the tool within the wellbore.

As the above sequence occurs, the mandrel moves through the upper slip support and for the upper cone as stated. A split lock ring internal to the upper slip support and for upper cone allows the mandrel to move through it in one direction only. The lock ring typically has small teeth machined on its inside surface and the mandrel has opposing teeth machined on its outside surface. As a result, said mandrel can move only in one direction through the lock ring. When a predetermined total setting force has been applied, the mandrel and lock ring engage, storing all of the setting force between the upper and lower cone and further anchoring the plug within the wellbore.

Such conventional drillable metallic plugs are generally highly reliable in operation, but are frequently too difficult and time consuming (and thus, too expensive) to drill out, mill up or otherwise mechanically break apart. In certain applications, multiple drillable plugs are installed within a single wellbore, thus compounding the time and cost of drilling, milling or otherwise removing said plugs. By way of example, but not limitation, the use of multiple plugs has become very common in both vertical and horizontal wells; frequently, multiple drillable plugs are installed in a single well completion.

Certain conventional plugs include components that are constructed from non-metallic materials such as, for example, composite materials. Such conventional plugs can generally be drilled or milled faster and more efficiently than plugs that are constructed from metallic components.

Such plugs are general designed exactly or substantially the same as drillable cast iron plugs, except that composite materials are substituted for the mandrel, upper slip support, upper cone, upper element back up system, lower element back up system, lower cone and lower slip support, or various combinations thereof.

One mechanism that has not been reliably replicated by such conventional composite plug devices is the lock ring system that prevents the mandrel from moving and unseating the plug when exposed to certain forces. Without a reliable locking mechanism, these composite plugs rely solely on the energy of the slips and packing element to store the energy require to anchor and seal. The mandrels of such conventional composite plugs are held only by friction forces and are able to move in relation to the slips and packing element when the plug is exposed to a significant pressure differential. Movement of such mandrel can cause a jarring effect on the plug, which has the ability to decrease the force stored in the slips and allow some or all of the setting force to dissipate resulting in the failure of the bridge plug to hold pressure and anchor.

Thus there is a need for a composite plug that securely locks in place after a setting sequence to store setting energy applied to said plug. Said plug assembly can be at least partially constructed of non-metallic components. When desired, said plug assembly should be capable of being drilled, milled or otherwise mechanically broken apart more easily and efficiently than conventional composite plugs, while more securely anchoring and providing a fluid pressure seal within a wellbore.

SUMMARY OF THE INVENTION

In a preferred embodiment, the present invention comprises a plug assembly for down hole use in wellbores such as, for example, in oil or gas wells penetrating subterranean formations. In a preferred embodiment, certain components of the plug assembly of the present invention can be beneficially constructed from at least one material that can be relatively easily milled or drilled, such as, for example, composite resin impregnated fiber or other material exhibiting similar qualities and characteristics.

Said plug assembly of the present invention comprises a fully sealing assembly, as well as a single slip assembly located either below or above the sealing assembly. In operation, the plug assembly of the present invention can be attached to a setting tool and conveyed into a well to a desired depth via continuous wire (such as, for example, electric line, slick line or braided line), coiled tubing or jointed pipe.

Once said plug assembly of the present invention is positioned at a desired location, said setting tool can be actuated. Upon actuation of said setting tool, certain outer components of said plug assembly are axially shifted relative to a central mandrel member of said plug assembly that remains substantially in place.

Concurrent to the movement of the setting tool causing the relative movement between the central mandrel (with an attached mule shoe cone) and the setting cylinder, incompressible fluid located in a first fluid chamber is displaced through a unidirectional seal assembly into a second fluid chamber. Once said fluid is displaced into said second fluid chamber, the unidirectional seal assembly traps the fluid in the second chamber thereby preventing any additional mandrel movement.

Concurrent to the action stated above, said setting cylinder forces the upper end of a cup forming sealing element to extend radially outward until contacting the inner surface wall of a surrounding wellbore. Continued movement of said mandrel further compresses said sealing element into the inner surface of the surrounding wellbore.

Additionally, the upper cone and the mule shoe cone come together, thereby forcing the independent bidirectional slips simultaneously radially outward to contact the inner surface of the surrounding wellbore. As setting force continues to a predetermined shearing force of shear pins, resultant force is distributed into the slip assembly and sealing element. Once a predetermined shear force is reached, said shear pins will break releasing the setting tool from the plug assembly of the present invention.

The plug assembly of the present invention can be installed down hole within a wellbore in order to isolate one portion of a wellbore from another, prevent fluid flow from one portion of a wellbore to another and provide a fluid pressure sealing barrier within said wellbore. Unlike conventional composite bridge plugs, the plug assembly of the present invention locks the mandrel in place by hydraulically storing setting forces within the plug assembly. Said plug assembly can be at least partially constructed of non-metallic components, and is capable of being drilled, milled or otherwise mechanically broken apart more easily and efficiently than conventional composite bridge plugs.

BRIEF DESCRIPTION OF DRAWINGS/FIGURES

The foregoing summary, as well as any detailed description of the preferred embodiments, is better understood when read in conjunction with the drawings and figures contained herein. For the purpose of illustrating the invention, the drawings and figures show certain preferred embodiments. It is understood, however, that the invention is not limited to the specific methods and devices disclosed in such drawings or figures.

FIG. 1 depicts a side sectional view of a preferred embodiment of a composite plug assembly of the present invention.

FIG. 2 depicts a side sectional detailed view of the highlighted area depicted in FIG. 1.

FIG. 3 depicts a side sectional view of the plug assembly of the present invention during the process of being run in a wellbore.

FIG. 4 depicts a side sectional view of the plug assembly of the present invention during the plug setting process.

FIG. 5 depicts a side sectional view of the plug assembly of the present invention after it has been installed and set in a wellbore.

FIG. 6 depicts a side perspective view of a unidirectional seal assembly of the present invention.

FIG. 7 depicts a side sectional view of a unidirectional seal assembly of the present invention.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT

The present invention comprises a plug assembly for down hole use in wellbores such as, for example, in oil or gas wells that penetrate subterranean formations. In a preferred embodiment, certain components of the plug assembly of the present invention can be beneficially manufactured from at least one material that can be relatively quickly and efficiently milled, drilled or otherwise mechanically broken apart such as, for example, composite resin impregnated fiber or other material exhibiting similar characteristics.

The plug assembly of the present invention can be installed to selectively isolate one portion of a wellbore from another, to prevent fluid flow from one portion of a wellbore to another and/or to provide a fluid pressure sealing barrier at a desired location within a wellbore. The plug assembly of the present invention can be beneficially set within the internal bore of a string of casing, production tubing or other tubular. However, it is to be observed that in certain applications or down hole environments, the plug assembly of the present invention can also be installed within an “open hole” section of a wellbore.

Said plug assembly of the present invention comprises a fluid pressure sealing assembly, as well as a slip assembly having independently operating gripping slip members. Although other relative positioning can be employed without departing from the scope of the present invention, said slips are typically disposed below said sealing assembly. Moreover, in a preferred embodiment, only a single slip assembly is required to anchor the plug assembly of the present invention within a wellbore, unlike conventional plug assemblies that typically require two or more sets of slip assemblies for this purpose; use of a single slip assembly makes the plug assembly of the present invention easier to drill, mill or otherwise mechanically break apart then conventional multi-slip plugs.

In operation, the plug assembly of the present invention can be attached to a setting tool and conveyed into a well to a desired depth via continuous wire (such as, for example, electric line, slick line or braided line), continuous or coiled tubing, or jointed pipe. Once said plug assembly is positioned at a desired location within a wellbore—that is, the depth at which setting of the plug assembly is desired—said setting tool can be actuated in order to anchor said plug assembly in place and energize said seal assembly of said plug assembly.

Referring to the drawings, FIG. 1 depicts a side sectional view of plug assembly 100 of the present invention. Plug assembly 100 comprises setting cylinder 20 having central through bore 21, upper cone member 40 having central through bore 41, setting ring 30 having central through bore 31 and lower cone member 50 having central through bore 51; said central through bores are substantially axially aligned.

Elongate inner mandrel 10, having central through bore 11 extending through said inner mandrel 10, is internally received within said substantially aligned central through bores 21, 31, 41 and 51. Put another way, setting cylinder 20, upper cone member 40, spacer sleeve 30 and lower cone member 50 are disposed along the outer surface of said inner mandrel 10. Lower cone member 50 can have bottom mule shoe configuration 90, and is beneficially attached to mandrel 10 using fiber pins 91 that extend through aligned transverse bores in mandrel 10 and lower cone member 50.

Sealing member 60 having central through bore 61 is disposed between setting cylinder 20 and upper cone member 40; in a preferred embodiment, said sealing member 60 comprises an elastomeric material that is capable of deforming in response to axial compression forces to extend radially outward and create a fluid pressure seal between plug assembly 100 and an inner surface of a surrounding wellbore (not depicted in FIG. 1).

Similarly, at least one slip assembly 70 is disposed along the outer surface of mandrel 10 between upper cone member 40 and lower cone member 50. Said at least one slip assembly 70 comprises a plurality of slip members 74 having gripping teeth 71 beneficially disposed along the outer surface of said slip members 74. The gripping teeth 71 of slip members 74 individually may be oriented opposite of one another, such that the gripping direction of said slip members is opposite from each other. At least one retaining ring 73 can be disposed around said slip members 74; said retaining ring 73 can hold said slip members 74 in place, but can break or shear when exposed to predetermined forces imparted by slip members 74 in a radially outward direction.

Still referring to FIG. 1, a first void space or lower chamber 22 is formed between an outer surface of mandrel 10, an inner surface of central through bore 21 of setting cylinder 20, and setting ring 30. O-rings 25 provide a fluid pressure seal between central mandrel 10 and setting ring 30. Similarly, O-rings 26 provide a fluid pressure seal between setting ring 30 and setting cylinder 20.

Similarly, a second void space or upper chamber 23 is formed between an outer surface of mandrel 10 and an inner surface of central through bore 21 of setting cylinder 20. A fluid channel 24 extends between lower chamber 22 and upper chamber 23; a unidirectional seal member 80 is disposed within said fluid channel 24 between said lower chamber 22 and upper chamber 23. O-rings 27 provide a fluid pressure seal between the outer surface of central mandrel 10 and an inner surface of setting cylinder 20, and prevent fluid entering said second chamber 23 from flowing between said surfaces.

Still referring to FIG. 1, a ball 5 is either run in place, gravity fed from the surface or pumped down a surrounding wellbore to plug assembly 100, can seat on upper seating surface 13 of central mandrel 10 to stop fluid flow from the surface direction through bore 11 extending through said inner mandrel 10. In a preferred embodiment, ball 5 can be constructed from resin impregnated fiber or materials with similar characteristics. In the view depicted in FIG. 1, shear pins 14 can extend through aligned transverse bores in central mandrel 10 and setting cylinder 20; said shear pins 14 can be set to break in response to a predetermined axial shear force acting on said pins 14.

FIG. 2 depicts a side sectional detailed view of the highlighted area depicted in FIG. 1. Fluid channel 24 extends between lower first chamber 22 and upper second chamber 23. Unidirectional seal member 80 is disposed within said fluid channel 24 between said chamber 22 and chamber 23. As described in detail below, said unidirectional seal member 80 allows fluid to flow from chamber 22 into chamber 23. However, said seal member 80 forms a fluid pressure seal that prevents fluid flow in the opposite direction—that is, from chamber 23 into chamber 22. As such, it is to be observed that any fluid that flows from lower first chamber 22 into upper second chamber 23 effectively becomes trapped within said chamber 23, and cannot flow in a reverse direction past unidirectional seal member 80 back into said lower first chamber 22.

FIG. 3 depicts a side sectional view of plug assembly 100 of the present invention during the process of being conveyed within wellbore 300 having inner wall surface 301. In normal operation, plug assembly 100 of the present invention is attached to a conventional wireline setting tool 200 and conveyed into wellbore 300 via continuous wireline to a desired depth; however, as noted above, plug assembly 100 can also be conveyed into a wellbore via continuous or coiled tubing, or jointed pipe. It is to observed that plug assembly 100 is partially rotated about its longitudinal axis in FIGS. 3 through 5, compared to the view depicted in FIG. 1; as a result, certain components, such as shear pins 14, are depicted in FIG. 1 but are not visible in FIGS. 3 through 5.

Wireline setting tools are well known to those having skill in the art and can have many different configurations. As depicted in FIG. 3, wireline setting tool 200 comprises outer sleeve 201 and inner tension mandrel 202. Further, said wireline setting tool 200 can be connected to mandrel 10 of plug assembly 100 using shear screws 12 that are capable of shearing when exposed to predetermined shear forces. Notwithstanding the foregoing, it is to be observed that plug assembly 100 of the present invention can be set using a conventional plug setting tool well known to those having skill in the art.

FIG. 4 depicts a side sectional view of plug assembly 100 of the present invention during the plug setting process. Once plug assembly 100 is positioned at a desired location within a wellbore, setting tool 200 is actuated, causing outer sleeve 201 to be axially shifted relative to mandrel 10. Specifically, outer sleeve 201 of setting tool 200 is axially shifted toward the distal end of plug assembly 100 (that is, substantially in a direction toward mule shoe 90). However, wireline tension mandrel 202 (and the attached wireline) prevents downward travel of central mandrel 10; thus, mandrel 10 remains substantially stationary relative to outer sleeve 201.

Still referring to FIG. 4, as outer sleeve 201 moves axially toward the distal end of plug assembly 100, said outer sleeve 201 imparts axial force on setting cylinder 20 while (as noted above) inner mandrel 10 remains substantially stationary relative to setting cylinder 20. Said setting cylinder 20, in turn, applies axial forces on sealing member 60, which is axially compressed between setting cylinder 20 and upper cone member 40. Such compressive forces cause said sealing member 60 to deform and extend radially outward, thereby forcing and compressing said sealing member 60 against inside surface 301 of the surrounding wellbore 300.

When a predetermined axial force is met, shear screws 12 that are used to attach plug assembly 100 to setting tool 200 break, thereby releasing plug assembly 100 from said setting tool 200 from said plug assembly 100. Thereafter, said setting tool 200 can be retrieved from the wellbore via wireline (or other means used to convey it in said wellbore).

FIG. 5 depicts a side sectional view of plug assembly 100 of the present invention after it has been installed and set within wellbore 300, and after setting tool 200 has been removed. As part of the setting process described above, axial forces are conveyed through sealing member 60 to upper cone member 40 which, in turn, acts on slip assembly 70. As individual slip members 74 of slip assembly 70 are exposed to compressive forces between lower cone member 50 and upper cone member 40, tapered surfaces 72 of slip members 74 ride on corresponding tapered surfaces 52 of lower cone member 50, thereby causing said slip members 74 to extend radially outward. Such compressive forces drive slip members 74 radially outward, breaking any retaining ring(s) 73 (not depicted in FIG. 5, but visible in FIG. 3) disposed around said slip members 74 and forcing gripping teeth 71 of slip members 74 toward inner surface 301 of the surrounding wellbore 300.

Said gripping teeth 71 of slip members 74 can partially embed within the inner surface 301 of surrounding wellbore 300, thereby increasing frictional forces acting between said plug assembly 100 and said surrounding wellbore 300. When deployed radially outward, said slip members 74 serve to anchor said plug assembly 100 in place within wellbore 300 and resist axial displacement of said plug assembly 100 within said surrounding wellbore 300, even when said plug assembly 100 is exposed to a fluid pressure differential across said plug assembly 100. In a preferred embodiment, certain of said slip members 74 and gripping teeth thereof can be oriented bi-directionally, in opposing axial directions. As such, when engaged against an inner surface of a wellbore, certain of said slip members 74 act to resist movement in one axial direction (for example, upward within said wellbore), while certain other of said slip members 74 act to resist movement in an opposite axial direction (for example, downward within said wellbore).

Still referring to FIG. 5, in a preferred embodiment sealing member 60 of the present invention comprises at least one cup-type sealing element profile 62, which can be constructed of completely elastomeric material requiring no backup sealing system of any kind (such as a metal support ring, composite support ring or elastomer support ring or base). As fluid pressure is applied to said sealing element 60, such pressure forces said cup-type sealing element profile(s) 62 radially outward to contact against inner surface 301 of surrounding wellbore 301 (typically the inner surface of a casing string) and form a fluid pressure seal. Generally, the greater the pressure, the greater the outward (sealing) force on said cup-type sealing element(s).

When plug assembly 100 will only be exposed to pressure from one axial direction (such as, for example, so-called “frac plugs” that are exposed to pressure only from above), said plug assembly 100 can beneficially employ a single cup-type sealing element. By contrast, plug assemblies that are exposed to pressure from opposing axial directions (such as, for example, bridge plugs that must seal from above and below said plug) can have at least two (2) opposing cup-type sealing elements that are oriented in opposite axial directions.

As noted previously, ball 5 is either run in place, gravity fed from the surface or pumped down a surrounding wellbore to plug assembly 100, can seat on upper seating surface 13 of central mandrel 10 to stop fluid flow from the surface direction through bore 11 extending through said inner mandrel 10. In a preferred embodiment, ball 5 can be constructed from resin impregnated fiber or materials with similar characteristics.

In a preferred embodiment, slip assembly 70 of plug assembly 100 is beneficially located below said sealing member 60 (that is, between sealing member 60 and mule shoe 90). As a result, when plug assembly 100 of the present invention is milled, drilled or otherwise mechanically broken apart (such as, for example, at the end of its useful life) from the upper opening of a wellbore, the sealing element(s) of sealing member 60 can be fully removed (i.e., drilled, milled or otherwise mechanically broken apart), thereby allowing any fluid pressure differential across said plug assembly 100 to equalize and become balanced across said plug assembly 100 before said slip assembly 70 is milled/drilled and plug assembly 100 is released from its grip within wellbore 300. Such pressure equalization will typically result in such drilling/milling operation being safer and more efficient.

Referring back to FIG. 2, during the setting sequence described herein setting cylinder 20 moves in an axial direction toward the distal end of plug assembly 100, forcing an incompressible fluid to flow from lower first fluid chamber 22 through fluid channel 24 and unidirectional seal member 80, and into upper second fluid chamber 23 (the volume of which increases due to said relative movement between setting cylinder 20 and central mandrel 10). Said unidirectional seal member 80 allows said incompressible fluid to pass in one direction only; once said incompressible fluid is in upper second fluid chamber 23, said unidirectional seal member 80 prevents said fluid from flowing or transferring back to said lower first chamber 22, thereby hydraulically storing such setting forces and locking central mandrel 10 in place. Referring to FIG. 1, it is to be observed the O-rings 27 further prevent such fluid in upper second fluid chamber 23 from escaping through any gap or channel formed between setting cylinder 20 and inner mandrel 10.

While this setting/locking technology of the present invention is advantageously used in tools made with composite materials like plug assembly 100 for facilitating drill ability, such setting technology can also be applied to plug assemblies and other tools constructed of other non-composite materials (such as, for example, cast iron or steel) when such.

FIG. 6 depicts a side perspective view of a unidirectional seal assembly 80 of the present invention. Unidirectional fluid pressure seal assembly 80 permits fluid to flow through said seal assembly 80 in one direction, while forming a fluid pressure seal or closure when said fluid attempts to flow through said seal assembly 80 in an opposite or reverse direction. Although other applications can be envisioned without departing from the scope of the present invention, as discussed herein said seal assembly 80 of the present invention can be beneficially used to provide a unidirectional fluid pressure seal within an annular space formed between cylindrical members (see, for example, FIG. 2 hereof).

Still referring to FIG. 6, seal assembly 80 generally comprises ring-like circular body member 81 defining an inner surface 82 having a diameter. FIG. 7 depicts a side sectional view of said a unidirectional seal assembly 80 of the present invention. In a preferred embodiment, said seal assembly 80 of the present invention comprises a substantially circular ring-like body member 81. One side of body member 81 defines a substantially “Y” shape having substantially parallel finger members 83 and central vertex section 84.

Said “Y”-shape or cup forms a pressure containing side of seal assembly 80. Seal assembly 80 of the present invention also contains a non-pressure containing side, or a backside surface 85, that defines a substantially rectangular surface. A plurality—typically eight (8)—of cut-outs 86 are formed in non-sealing surface 85 and extend to inner surface 82. In a preferred embodiment, said cut-outs 86 can be substantially semi-circular or scalloped in shape and equidistantly spaced around the inner diameter of circular ring-like body member 81 of seal assembly 80 of the present invention.

In a preferred embodiment, inner surface 82 of the seal member forms an interference fit with an outer surface of a smaller cylinder that is to be sealed to the present invention, thereby comprising a match in size and shape between the seal and the smaller cylinder. Additionally, said seal assembly 80 beneficially sits in a pocket or recess formed within a larger diameter cylinder; the outer diameter of seal assembly 80 and the inner diameter of said pocket or recess being substantially equal, such that said pocket or recess holds seal assembly 80 of the present invention in place.

In a preferred embodiment, by way of illustration, but not limitation, seal assembly 80 can be manufactured from Hydrogenated Nitrile Butadiene Rubber (HNBR) with a 90 Duro A Shore Hardness; however, other types of materials or elastomers may be used. Dimensions of seal assembly 80 and the pocket of the present invention will be determined by the size of the cylinders, and the resulting annular space, where said seal assembly 80 is to be used.

Referring back to FIG. 2, unidirectional seal member 80 is disposed in a pocket or seat within fluid channel 24 positioned between chamber 22 and chamber 23. Ring-like body member 81 is disposed around the outer surface of central mandrel 10, with surface 85 oriented generally in the direction of first chamber 22, while substantially “Y”-shaped section, having substantially parallel finger members 83 and central vertex section 84, is oriented generally in the direction of second chamber 23.

Said unidirectional seal member 80 allows fluid to flow from chamber 22 into chamber 23. However, said seal member 80 forms a fluid pressure seal that prevents fluid flow in the opposite direction—that is, from chamber 23 into chamber 22. As such, it is to be observed that any fluid that flows from lower first chamber 22 into upper second chamber 23 effectively becomes trapped within said chamber 23, and cannot flow in a reverse direction past unidirectional seal member 80 back into said lower first chamber 22.

The above-described invention has a number of particular features that should preferably be employed in combination, although each is useful separately without departure from the scope of the invention. While the preferred embodiment of the present invention is shown and described herein, it will be understood that the invention may be embodied otherwise than herein specifically illustrated or described, and that certain changes in form and arrangement of parts and the specific manner of practicing the invention may be made within the underlying idea or principles of the invention.

Claims

1. A down hole tool assembly for installation in a wellbore comprising:

a) a mandrel having a proximate end, a distal end, an outer surface and a central through bore;

b) a lower body member affixed to said distal end of said mandrel, wherein said lower body member has a larger outer diameter than said mandrel;

c) a setting cylinder having a central bore, wherein said mandrel is slidably disposed within said central bore of said setting cylinder;

d) a slip assembly disposed between said setting cylinder and lower body member;

e) a seal assembly disposed between said setting cylinder and said body member;

f) a first chamber formed between said mandrel and said setting cylinder;

g) a second chamber formed between said mandrel and said setting cylinder, wherein said first and second chambers are in fluid communication with each other; and

h) a unidirectional seal member disposed between said first and second chambers, wherein said seal member permits fluid to flow from said first chamber to said second chamber, but not from said second chamber to said first chamber.

2. The down hole tool assembly of claim 1, wherein said slip assembly extends radially outward to grip an inner surface of said wellbore.

3. The down hole tool assembly of claim 1, wherein said slip assembly is located either above or below said seal assembly.

4. The down hole tool assembly of claim 1, wherein said slip assembly comprises a plurality of slip members.

5. The down hole tool assembly of claim 4, wherein said slip members can be oriented bi-directionally.

6. The down hole tool assembly of claim 1, wherein said seal assembly extends radially outward to create a fluid pressure seal against the inner surface of said wellbore.

7. The down hole tool assembly of claim 1, further comprising incompressible fluid in said first and second chambers.

8. The down hole tool assembly of claim 1, wherein axial movement of said setting cylinder toward said distal end of said mandrel creates a reduction in volume of said first chamber and increases volume of second chamber.

9. The down hole tool assembly of claim 8, wherein said reduction in volume of said first chamber forces incompressible fluid from said first chamber to said second chamber.

10. The down hole tool assembly of claim 1, wherein said unidirectional seal allows said incompressible fluid to flow from said first chamber to said second chamber, but prevents said incompressible fluid from flowing from said second chamber to said first chamber.

11. The down hole tool assembly of claim 1, wherein said seal assembly is constructed entirely of elastomeric material.

12. The down hole tool assembly of claim wherein said lower body member further comprises a muleshoe.

13. The down hole tool assembly of claim 1 further comprising a setting tool.

14. The down hole tool assembly of claim 13, wherein said setting tool is adapted to apply force to said setting cylinder in a first axial direction and said central mandrel in an opposite axial direction.

15. The down hole tool assembly of claim 14, wherein said setting tool can be selectively removed from a wellbore following anchoring of said down hole tool assembly in said wellbore.