ROTATING BACKUP SYSTEM FOR PACKER ELEMENTS USED IN NON-RETRIEVABLE APPLICATIONS

Abstract

A packer element assembly includes an annular sealing element having inner and outer sides, wherein the sealing element is axially compressible from a first position to a set position, and first and second backup rings located on opposite ends of the sealing element. When the sealing element is axially compressed to the set position, the sealing element expands radially, and the backup rings rotate relative to the sealing element. A setting method may include locating the packer element assembly within a well casing bore, and axially compressing the packer element assembly to the set position. The sealing element expands radially such that the outer side of the sealing element expands against the well casing bore and the backup rings are rotated relative to the sealing element to eliminate a gap between a mandrel and the sealing element, thereby preventing extrusion of the sealing element along both inner and outer sides.

Description

FIELD OF INVENTION

The present invention relates to packer elements used in sealing segments of drilling operations, such as down hole seals used in oil and gas hydraulic fracturing systems, and more particularly to backup components for such sealing assemblies.

BACKGROUND OF THE INVENTION

In oil and gas drilling operations, a variety of down hole tools are used for the manufacturing, operation, and maintenance of such drilling systems. One example of a down hole tool is a plug seal or packer element assembly, which can be used to seal and isolate certain portions of a drilled well from other portions of the well. A sealing plug that fully isolates one well portion (e.g., a down hole portion) from another well portion (e.g., an up hole portion), wholly blocking flow between the two portions, is commonly referred to as a bridge plug. Other types of plug seals may allow flow in a particular direction (e.g., downstream), but block flow in other directions (e.g., upstream). Plug seals may be permanent, or may be non-permanent dissolving or otherwise removable plug seals.

Hydraulic fracturing (commonly referred to as “fraccing” or “Tracking”) is becoming a common method of oil and gas drilling, which may employ packer element assemblies or plug seals to isolate different portions of a well. For example, a plug seal or packer element assembly may be located within an outer well casing so as to isolate a down hole portion of a well from an up hole portion of the well. In the up hole portion, the well casing may include a plurality of transverse holes that open into a surrounding rock formation. In the hydraulic fracturing process, pressurized fluid is pumped down into the well. At the packer element assembly, flow is blocked from proceeding from the up hole portion into the down hole portion, pressurizing the well. Under such pressure, the fluid is forced through the holes in the up hole well casing into the adjacent rock formation. The pressurized flow into the rock formation in turn creates cracks through which oil and gas may be extracted.

Conventional packer element assemblies, however, have proven to be deficient in certain respects. In typical assembly configurations, an inner mandrel operates to isolate segments of the drilling operation within a bore defined by an outer well casing. A packer element assembly includes a rubber-type sealing element, which expands under an axial setting pressure to provide a seal between the mandrel and the well casing. Under the high pressure, the sealing material of the packer element assembly can extrude along the well casing, and/or along the mandrel, which can damage the seal material and undermine the sealing efficacy. Accordingly, backup systems are provided to prevent extrusion of the sealing material. It has proven difficult, however, to provide a backup system that functions effectively under the extreme conditions of high pressure drilling operations.

SUMMARY OF THE INVENTION

The present invention generally is directed to a backup system to resist extrusion of a packer element assembly. Packer element assemblies typically may be configured as cylindrical assemblies that are used for down hole isolation, and typically include one or multiple rubber elements that expand to seal the annulus between the packer mandrel and the well bore of the well casing. This expansion occurs during the axial setting of the packer element assembly. Pressure from hydraulic fracturing can then occur. For higher pressure applications, backup rings may be installed on both ends of the sealing element to resist rubber extrusion due to high pressures. The ultimate goal of a backup ring is to fully close the annulus gap between the mandrel and the well bore so that no rubber of the sealing element can extrude through the annulus. The present invention thus provides a continuous, semi-rigid backup ring system that is able to rotate during the packer setting process, and once set substantially precludes extrusion of the sealing element.

More particularly, once set, the backup system will completely fill the annulus gap between the mandrel and the well bore, including gap portions of the annulus both along the well casing and along the mandrel. This is performed via a specifically configured geometry that once rotated, prevents sealing element extrusion both over and under the backup ring, thus completely encasing the sealing element. The backup ring material generally should be relatively soft enough to fully rotate, yet sufficiently rigid and strong enough to hold and perform the backup function under high temperatures and pressures. To achieve such characteristics, the backup ring may be manufactured from numerous thermoplastsic materials including polyaryletherketones (e.g., PEEK or PAEK), polytetrafluoroethylne (PTFE), polyamide-imide (PAI), and like materials. Softer metals may also be used, including brass, bronze, aluminum, and like materials.

An aspect of the invention is a packer element assembly. In exemplary embodiments, the packer element assembly may include an annular sealing element having an inner side and an outer side, wherein the sealing element is axially compressible from a first position to a set position, and first and second backup rings located on opposite ends of the sealing element. When the sealing element is axially compressed from the first position to the set position, the sealing element expands radially, and the backup rings rotate relative to the sealing element to prevent axial extrusion of the sealing element at both the inner side and the outer side in the set position. Each backup ring may have a cross-sectional face such that when the first and second backup rings rotate to the set position, the cross-sectional face is configured to prevent axial extrusion of the sealing element at both the inner side and the outer side.

Another aspect of the invention is a method of setting a packer element assembly. In exemplary embodiments, the setting method may include the steps of: locating a packer element assembly at a desired position within a well casing bore, the packer element assembly comprising an annular sealing element having an inner side and an outer side, and first and second backup rings located on opposite ends of the sealing element; axially compressing the packer element assembly to a set position, wherein the sealing element expands radially such that the outer side of the sealing element expands against the well casing bore; and wherein upon axially compressing the sealing element to the set position, the backup rings rotate relative to the sealing element to eliminate a first gap between the well casing and the outer side of the sealing element and a second gap between the mandrel and the inner side of the sealing element, thereby preventing extrusion of the sealing element along the well casing and mandrel.

These and further features of the present invention will be apparent with reference to the following description and attached drawings. In the description and drawings, particular embodiments of the invention have been disclosed in detail as being indicative of some of the ways in which the principles of the invention may be employed, but it is understood that the invention is not limited correspondingly in scope. Rather, the invention includes all changes, modifications and equivalents coming within the spirit and terms of the claims appended hereto. Features that are described and/or illustrated with respect to one embodiment may be used in the same way or in a similar way in one or more other embodiments and/or in combination with or instead of the features of the other embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a drawing depicting a side view of a packer element assembly in accordance with embodiments of the present invention.

FIG. 2 is a drawing depicting a cross-sectional view of the packer element assembly of FIG. 1.

FIGS. 3 is a drawing depicting a top view of one of the backup rings for use in a packer element assembly in accordance with embodiments of the present invention.

FIG. 4 is a drawing depicting a cross-sectional view of the backup ring of FIG. 3.

FIG. 5 is a drawing depicting a close-up view of the cross-section of the backup ring of FIGS. 3 and 4.

FIG. 6 is a drawing depicting a side view of an exemplary packer element assembly in the unset position relative to a well casing and mandrel in accordance with embodiments of the present position.

FIG. 7 is a drawing depicting a side view of the packer element assembly of FIG. 6 in the set position.

FIG. 8 is a drawing depicting an isometric view of an exemplary packer element assembly in the unset position.

FIG. 9 is a drawing depicting an isometric view of the packer element assembly of FIG. 8 in the set position.

DETAILED DESCRIPTION

Embodiments of the present invention will now be described with reference to the drawings, wherein like reference numerals are used to refer to like elements throughout. It will be understood that the figures are not necessarily to scale.

FIG. 1 is a drawing depicting a packer element assembly 10 in accordance with embodiments of the present invention, and FIG. 2 is a cross-sectional view of the packer element assembly 10 of FIG. 1. In these figures, the packer element assembly 10 is depicted in the unset configuration. The packer element assembly may have a generally cylindrical configuration so as to act as a plug seal to isolate different portions of an oil or gas well, and thus the packer element assembly may be positioned within commensurately cylindrical portions of a well casing. Generally, the packer element assembly may include an annular sealing element having an inner side and an outer side, and the sealing element is axially compressible from a first (unset) position to a set position, and first and second backup rings located on opposite ends of the sealing element. As further detailed below, when the sealing element is axially compressed from the first position to the set position, the sealing element expands radially, and the backup rings rotate relative to the sealing element to prevent axial extrusion of the sealing element at both the inner side and the outer side in the set position.

Referring to the example of FIGS. 1 and 2, the packer element assembly 10 may include an annular packer sealing element 12 that acts as an elastomeric sealing element between a mandrel and a well casing bore (not shown in these figures), and thus is made of a rubber-like, elastomeric material as are known in the art for sealing in down hole drilling operations. The sealing element has an inner side 11, which is the inner surface shown in the cross-sectional view of FIG. 2, that interfaces with an outer diameter of a mandrel. The sealing element further has an outer side 13, which is the outer surface shown in the side view of FIG. 1, that interfaces with the inner diameter of a well casing. The packer element assembly 10 further includes opposing backup rings 14 and 15 on opposite ends of the sealing element, which provide the backup function that prevents the packer element sealing material from extruding along the well casing or along the mandrel when the packer element assembly is in the set position.

FIGS. 3-5 are schematic diagrams depicting various views of one of the backup rings 14 (or 15) in accordance with embodiments of the present invention. FIG. 3 is a drawing depicting a top view of one of such backup rings. As seen in the view of FIG. 3, the backup ring 14 has a ring configuration so as to encircle an end of the sealing element as seen in FIGS. 1 and 2. It will be appreciated that the second backup ring 15 would be configured with a comparable ring structure as the first backup ring 14.

FIG. 4 is a drawing depicting a cross-sectional view of the backup ring 14 of FIG. 3, and FIG. 5 is a drawing depicting a close-up view of an end portion of the backup ring. FIG. 4, and more particularly the close-up view of FIG. 5, illustrate the geometry of an exemplary backup ring cross-section 16. It similarly will be appreciated that the second backup ring 15 would be configured with a comparable cross-sectional configuration as the first backup ring 14. Generally, each backup ring may have a cross-sectional face such that when the first and second backup rings rotate to the set position, the cross-sectional face is configured to prevent axial extrusion of the sealing element at both the inner side and the outer side. The backup ring material generally should be relatively soft enough to fully rotate, yet sufficiently rigid and strong enough to hold and perform the backup function under high temperatures and pressures. To achieve such characteristics, the backup ring may be manufactured from any of numerous thermoplastsic materials including polyaryletherketones (e.g., PEEK or PAEK), polytetrafluoroethylne (PTFE), polyamide-imide (PAI), and like materials. Softer metals may also be used, including brass, bronze, aluminum, and like materials.

Referring most readily to FIG. 5, the geometry of the cross-section 16 may include an upper side 18, and a first slope 20 that is sloped with a first angle A relative to the upper side 18, and a second slope 22 that is sloped with a second angle B relative to the upper side 18. In exemplary embodiments, the first angle A of the first slope is greater than the second angle B of the second slope. The slopes are configured to define a chamfered end 24 opposite from the upper side 18, and specifically having a chamfer 26. As further explained below, the geometry of the backup ring cross-section is configured to permit the backup ring 14 to rotate relative to the packer sealing element 12 during setting to provide an effective backup function to enhance the efficacy of the seal. In the set position, the chamfer 26 of each chamfered end 24 of the backup rings compresses against the sealing element adjacent the inner side of the sealing element. The direction of rotation of opposing backup rings is shown in the arrows of FIGS. 4 and 5.

FIG. 6 is a drawing depicting a side view of an exemplary packer element assembly 10 in a first or unset position relative to a well casing 28 in accordance with embodiments of the present position. Reference numeral 30 represents the inner surface of the well casing 28 that defines the bore in which the packer element assembly 10 is utilized. Opposite to the well casing 28, the packer assembly 10 interacts against a mandrel 31. Reference numeral 32 represents an outer face of the mandrel 31 used with the packer element assembly 10.

Elements 34 and 36 represent opposing setting tool elements, such as opposing first and second setting cones that may be used to set the packer element assembly 10. The first setting cone 34 and the second setting cone 36 are generally ring structures that are located in the space 37 between the mandrel and the well casing comparably as the packer element assembly, and the setting cones particularly may be located around and against the mandrel spaced inwardly from the inner surface of the well casing. For example the first setting cone 34 may be located around the mandrel on a down hole side of the sealing element, and the second setting cone nay be located around the mandrel on an up hole side of the setting element. As further detailed below, the second setting cone may be moveable from the up hole side toward the down hole side to axially compress the sealing element from the first or unset position to the set position. In addition, as seen in FIG. 5, in the first/unset position there is a first annulus or gap 38 between the packer sealing element 12 and the well casing inner surface 30, and a second annulus or gap 40 between the backup rings 14 and 15 and the mandrel outer surface 32. During setting, the backup rings 14 and 15 rotate in the direction of the arrows depicted in FIG. 6. The rotation of the backup rings closes the gaps 38 and 40 as shown in FIG. 7.

FIG. 7 is a drawing thus depicting a side view of the packer element assembly 10 in the set position relative to the well casing 28 and mandrel 31. As indicated in FIG. 7, in exemplary embodiments the packer element assembly 10 is set from the up hole side 42 (the right side in the depiction of FIGS. 6 and 7 as oriented) by compression of the packer assembly towards the down hole side 44 (the left side in the depiction of FIGS. 6 and 7 as oriented). In other words, the setting cone 36 is moved down hole towards setting cone 34, which compresses the packer element assembly 10 in the axial direction. The axial compression causes the packer sealing element 12 to expand radially against the well casing. In addition, the backup rings 14 and 15 rotate in the directions shown by the arrows in FIG. 6 relative to the sealing element to the set position shown in FIG. 7, which prevents axial extrusion of the sealing material at either the inner side or outer side of the sealing element 12. In particular, as a result of the rotation, the closing of the gap 38 includes elimination of such gap between the well casing and the backup rings. In addition, the rotation at the chamfered ends 24 results in the chamfer 26 pressing against and compressing the sealing element 12. The result is a further closing of the gap 40 between the backup rings and the mandrel. With such a gapless configuration upon setting on both sides of the sealing element, an effective seal is maintained with enhanced backup functioning that prevents the material of the sealing element 12 from extruding along either the well casing or the mandrel. More specifically, such axial extrusion is precluded both along the well casing at the outer side of the sealing element, and along the mandrel at the inner side of the sealing element, as the rings 14 and 15 have rotated to close both gaps as between the backup rings and the mandrel and well casing.

FIGS. 8 and 9 are drawings that depict additional isometric views of the packer element assembly 10 in the unset (FIG. 8) and set (FIG. 9) positions. The well casing has been removed from FIGS. 8 and 9 for an enhanced view of the packer assembly as the packer assembly is moved between the set and unset positions. FIGS. 8 and 9 further illustrate a method of setting a packer element assembly in accordance with embodiments of the present invention. The setting method generally may include locating the packer element assembly within a well casing bore, and axially compressing the packer element assembly from the first/unset position to the set position. During such compression, the sealing element expands radially such that the outer side of the sealing element expands against the well casing bore to eliminate the first gap between the sealing element and the well casing bore, and the backup rings are rotated relative to the sealing element to eliminate the second gap between the mandrel and the sealing element. In this manner, the setting of the packer element assembly prevents extrusion of the sealing element along both the inner side against the mandrel and the outer side against the well casing bore.

The progression of FIG. 8 to FIG. 9 shows the setting of the packer element assembly 10 between the first and second setting cones 34 and 36. As referenced above, setting typically is performed by axial compression from the up hole side (the top in the depiction of FIGS. 8 and 9 as oriented) by compression of the packer assembly towards the down hole side 44 (the bottom in the depiction of FIGS. 8 and 9 as oriented). FIG. 9 further shows how the backup rings 14 and 15 have rotated relative to the sealing element 12. Once the packer element assembly is set, the setting cones typically will remain down hole in such set positions. An optional ratchet mechanism may be employed to prevent the setting cones from sliding out from the set position.

With the configuration of the present invention, the backup rings may be singular, continuous, and homogeneous. There is no need to provide notches, segments, grooves, or like structures in the backup rings as are typical in conventional backup systems, and thus the backup rings of the present invention are less complex to manufacture. In addition, the thermoplastic materials of the backup rings are less costly and easier to manufacture as compared to conventional backup rings, and the materials are highly millable as compared to conventional backup ring materials which can provide for easier removal should removal become necessary. The backup ring positioning once set is highly stable and gapless on both the well casing and mandrel sides to prevent any axial extrusion of the sealing element material. In addition, the rotation provides effective backup performance, but the slight nature of the rotation is such that the seal is energized with less stress on the assembly components as compared to conventional configurations. This reduction of stress may prolong the useful life the sealing element material.

An aspect of the invention, therefore, is a packer element assembly. In exemplary embodiments, the packer element assembly includes an annular sealing element having an inner side and an outer side, and the sealing element is axially compressible from a first position to a set position, and first and second backup rings located on opposite ends of the sealing element. When the sealing element is axially compressed from the first position to the set position, the sealing element expands radially, and the backup rings rotate relative to the sealing element to prevent axial extrusion of the sealing element at both the inner side and the outer side in the set position. The packer element assembly may include one or more of the following features, either individually or in combination.

In an exemplary embodiment of the packer element assembly, each backup ring has a cross-sectional face such that when the first and second backup rings rotate to the set position, the cross-sectional face is configured to prevent axial extrusion of the sealing element at both the inner side and the outer side.

In an exemplary embodiment of the packer element assembly, the cross-sectional face comprises an upper side, a first slope that is sloped with a first angle relative to the upper side, a second slope that is sloped with a second angle relative to the upper side, and a chamfered end opposite the upper side.

In an exemplary embodiment of the packer element assembly, the first angle of the first slope is greater than the second angle of the second slope.

In an exemplary embodiment of the packer element assembly, in the set position, a chamfer of each chamfered end compresses against the sealing element adjacent the inner side of the sealing element.

In an exemplary embodiment of the packer element assembly, the backup rings are made of a thermoplastic material.

In an exemplary embodiment of the packer element assembly, the backup rings are made of one of a polyaryletherketone, polytetrafluoroethylne, or polyamide-imide material.

In an exemplary embodiment of the packer element assembly, the backup rings are made of one of brass, bronze, or aluminum.

In an exemplary embodiment of the packer element assembly, the sealing element is made of an elastomeric material.

In an exemplary embodiment of the packer element assembly, the assembly further includes a mandrel positioned on the inner side of the sealing element.

In an exemplary embodiment of the packer element assembly, the assembly further includes a first setting cone located around the mandrel on a down hole side of the sealing element, and a second setting cone located around the mandrel on an up hole side of the setting element, wherein the second setting cone is moveable from the up hole side toward the down hole side to axially compress the sealing element from the first position to the set position.

Another aspect of the invention is a method of setting a packer element assembly. In exemplary embodiments, the setting method includes the steps of: locating a packer element assembly at a desired position within a well casing bore, the packer element assembly comprising an annular sealing element having an inner side and an outer side, and first and second backup rings located on opposite ends of the sealing element; axially compressing the packer element assembly to a set position, wherein the sealing element expands radially such that the outer side of the sealing element expands against the well casing bore; and wherein upon axially compressing the sealing element to the set position, the backup rings rotate relative to the sealing element to eliminate a first gap between the well casing and the outer side of the sealing element, thereby preventing extrusion of the sealing element along the well casing. The setting method may include one or more of the following features, either individually or in combination.

In an exemplary embodiment of the setting method, the packer element assembly further comprises a mandrel positioned on the inner side of the sealing element, wherein upon axially compressing the sealing element, the rotating of the backup rings relative to the sealing element further eliminates a second gap between the mandrel and the inner side of the sealing element, thereby preventing extrusion of the sealing element along the mandrel.

In an exemplary embodiment of the setting method, the packer element assembly further comprises a first setting cone located around the mandrel on a down hole side of the sealing element, and a second setting cone located around the mandrel on an up hole side of the setting element; and the setting method further comprising moving the second setting cone from the up hole side toward the down hole side to axially compress the sealing element from the first position to the set position.

In an exemplary embodiment of the setting method, the packer element assembly is compressed from an up hole side of the well casing toward a down hole side of the well casing.

In an exemplary embodiment of the setting method, the backup rings each has a chamfered end, and when the backup rings rotate a chamfer of each chamfered end compresses against the sealing element adjacent the inner side of sealing element.

Although the invention has been shown and described with respect to a certain embodiment or embodiments, it is obvious that equivalent alterations and modifications will occur to others skilled in the art upon the reading and understanding of this specification and the annexed drawings. In particular regard to the various functions performed by the above described elements (components, assemblies, devices, compositions, etc.), the terms (including a reference to a “means”) used to describe such elements are intended to correspond, unless otherwise indicated, to any element which performs the specified function of the described element (i.e., that is functionally equivalent), even though not structurally equivalent to the disclosed structure which performs the function in the herein illustrated exemplary embodiment or embodiments of the invention. In addition, while a particular feature of the invention may have been described above with respect to only one or more of several illustrated embodiments, such feature may be combined with one or more other features of the other embodiments, as may be desired and advantageous for any given or particular application.

Claims

1. A packer element assembly comprising:

an annular sealing element having an inner side and an outer side, and the sealing element is axially compressible from a first position to a set position; and

first and second backup rings located on opposite ends of the sealing element;

wherein, when the sealing element is axially compressed from the first position to the set position, the sealing element expands radially, and the backup rings rotate relative to the sealing element to prevent axial extrusion of the sealing element at both the inner side and the outer side in the set position.

2. The packer element assembly of claim 1, wherein each backup ring has a cross-sectional face such that when the first and second backup rings rotate to the set position, the cross-sectional face is configured to prevent axial extrusion of the sealing element at both the inner side and the outer side.

3. The packer element assembly of claim 2, wherein the cross-sectional face comprises an upper side, a first slope that is sloped with a first angle relative to the upper side, a second slope that is sloped with a second angle relative to the upper side, and a chamfered end opposite the upper side.

4. The packer element assembly of claim 3, wherein the first angle of the first slope is greater than the second angle of the second slope.

5. The packer element assembly of claim 3, wherein in the set position, a chamfer of each chamfered end compresses against the sealing element adjacent the inner side of the sealing element.

6. The packer element assembly of claim 1, wherein the backup rings are made of a thermoplastic material.

7. The packer element assembly of claim 6, wherein the backup rings are made of one of a polyaryletherketone, polytetrafluoroethylne, or polyamide-imide material.

8. The packer element assembly of claim 1, wherein the backup rings are made of one of brass, bronze, or aluminum.

9. The packer element assembly of claim 1, wherein the sealing element is made of an elastomeric material.

10. The packer element assembly of claim 1, further comprising a mandrel positioned on the inner side of the sealing element.

11. The packer element assembly of claims 10, further comprising a first setting cone located around the mandrel on a down hole side of the sealing element, and a second setting cone located around the mandrel on an up hole side of the setting element, wherein the second setting cone is moveable from the up hole side toward the down hole side to axially compress the sealing element from the first position to the set position.

12. A method of setting a packer element assembly comprising the steps of:

locating a packer element assembly at a desired position within a well casing bore, the packer element assembly comprising an annular sealing element having an inner side and an outer side, and first and second backup rings located on opposite ends of the sealing element;

axially compressing the packer element assembly to a set position, wherein the sealing element expands radially such that the outer side of the sealing element expands against the well casing bore; and

wherein upon axially compressing the sealing element to the set position, the backup rings rotate relative to the sealing element to eliminate a first gap between the well casing and the outer side of the sealing element, thereby preventing extrusion of the sealing element along the well casing.

13. The setting method of claim 12, wherein the packer element assembly further comprises a mandrel positioned on the inner side of the sealing element,

wherein upon axially compressing the sealing element, the rotating of the backup rings relative to the sealing element further eliminates a second gap between the mandrel and the inner side of the sealing element, thereby preventing extrusion of the sealing element along the mandrel.

14. The setting method of claim 13, wherein the packer element assembly further comprises a first setting cone located around the mandrel on a down hole side of the sealing element, and a second setting cone located around the mandrel on an up hole side of the setting element; and

the setting method further comprising moving the second setting cone from the up hole side toward the down hole side to axially compress the sealing element from the first position to the set position.

15. The setting method of claim 12, wherein the packer element assembly is compressed from an up hole side of the well casing toward a down hole side of the well casing.

16. The setting method of claim 12, wherein the backup rings each has a chamfered end, and when the backup rings rotate a chamfer of each chamfered end compresses against the sealing element adjacent the inner side of sealing element.