Title:
PLUG RETRIEVAL AND DEBRIS REMOVAL TOOL
Kind Code:
A1


Abstract:
An apparatus adapted for removing a plug (12) from a subsea Christmas tree (10) is disclosed which includes a housing (84), a distal end of the apparatus that is adapted to engage the plug (12) and a fluid passage (83) formed in the housing (84) for use in directing a stream of fluid toward the plug (12) to remove debris (90) from above the plug (12). Also disclosed is a method for removing debris (90) from a subsea Christmas tree (10) including connecting a marine riser and a blowout preventer (BOP) (60) to a subsea Christmas tree (10), lowering a plug removal tool (80) through the marine riser to the Christmas tree (10), the plug removal tool (80) having a fluid passage (83) formed therein, and forcing a fluid down the marine riser and through the fluid passage (83) in the plug removal tool (80) to wash out debris (90) in the Christmas tree (10).



Inventors:
Lawson, John E. (Todmorden, GB)
Application Number:
12/093387
Publication Date:
09/24/2009
Filing Date:
12/08/2006
Primary Class:
Other Classes:
166/335
International Classes:
E21B23/00; E21B23/04; E21B33/043; E21B
View Patent Images:
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Primary Examiner:
BUCK, MATTHEW R
Attorney, Agent or Firm:
WILLIAMS MORGAN, P.C. (HOUSTON, TX, US)
Claims:
What is claimed:

1. An apparatus adapted for removing a plug (12) from a subsea Christmas tree (10), comprising: a housing (84); a distal end of said apparatus that is adapted to engage said plug (12); and a fluid passage (83) formed in said housing (84) that is adapted for use in directing a stream of fluid toward said plug (12) to remove debris from above said plug (12).

2. The apparatus of claim 1, further comprising a tubing hanger running tool (70) having a bore (75) formed therein, wherein said housing (84) is moveably positioned within said bore (75).

3. The apparatus of claim 2, wherein said housing (84) sealingly engages said bore (75).

4. The apparatus of claim 2, wherein a seal is established between said housing (84) and said bore (75).

5. The apparatus of claim 2, wherein said tubing hanger running tool (70) further comprises a flow port (77) formed therein that defines a portion of a fluid flow passage that is adapted for removing said fluid introduced through said fluid passage (83) in said housing (84).

6. The apparatus of claim 5, wherein said flow port (77) in said tubing hanger running tool (70) is adapted to engage an external choke and kill line (62).

7. The apparatus of claim 1, wherein said apparatus further comprises a proximal end that is adapted to be coupled to a wireline device.

8. The apparatus of claim 1, wherein a distal end of said fluid passage defines a nozzle.

9. An apparatus adapted for removing a plug (12) from a subsea Christmas tree (10), comprising: a housing (84); a distal end of said apparatus that is adapted to engage said plug (12); a fluid passage (83) formed in said housing (84), the exit of which defines a nozzle that is adapted for use in directing a stream of fluid toward said plug (12) to remove debris from above said plug (12); and a tubing hanger running tool (70) having a bore (75) formed therein, wherein said housing (84) is moveably positioned within said bore (75).

10. The apparatus of claim 9, wherein said housing (84) sealingly engages said bore (75).

11. The apparatus of claim 9, wherein a seal is established between said housing (84) and said bore (75).

12. The apparatus of claim 9, wherein said tubing hanger running tool (70) further comprises a flow port (77) formed therein that defines a portion of a fluid flow passage that is adapted for removing said fluid introduced through said fluid passage (83) in said housing (84).

13. The apparatus of claim 12, wherein said flow port (77) in said tubing hanger running tool (70) is adapted to engage an external choke and kill line (62).

14. The apparatus of claim 9, wherein said apparatus further comprises a proximal end that is adapted to be coupled to a wireline device.

15. An apparatus for removing a plug (12) from a subsea Christmas tree (10), comprising: a tool housing (84) having a central passage (83) formed therethrough and a plug engaging means (86), said plug engaging means comprising a constricted nozzle adapted for washing out debris from above the plug (12); and a tubing hanger running tool (70).

16. The apparatus of claim 15, wherein said tubing hanger running tool (70) comprises a central passage (75), the tool housing (84) being movable but sealingly engaged within the passage (75).

17. The apparatus of claim 16, wherein said tubing hanger running tool (70) includes a shoulder (74).

18. The apparatus of claim 15, wherein said tubing hanger running tool (70) includes at least one flow port (77).

19. The apparatus of claim 18, wherein said apparatus includes a passage (73) connecting the flow port (77) with an external choke and kill line (62).

20. A method for removing debris (90) from a subsea Christmas tree (10), comprising: connecting a marine riser and a blowout preventer (BOP) (60) to said subsea Christmas tree (10); lowering a plug removal tool (80) through the marine riser to the Christmas tree (10), said plug removal tool (80) having a fluid passage (83) formed therein; and forcing a fluid down the marine riser and through said fluid passage (83) in said plug removal tool (80) to wash out debris (90) in said Christmas tree (10).

21. The method of claim 20, further comprising lowering a tubing hanger running tool (70) through the marine riser to the Christmas tree (10).

22. The method of claim 21, wherein said tubing hanger running tool (70) and said plug removal tool (80) are lowered at the same time.

23. The method of claim 21, wherein said tubing hanger running tool (70) and said plug removal tool (80) are lowered at different times.

24. The method of claim 21, wherein said tubing hanger running tool (70) comprises a flow port (77) formed therein, and wherein the method further comprises forcing said fluid through said flow port (77) in said tubing hanger running tool (70).

25. The method of claim 24, further comprising forcing fluid through a choke and kill line (62) of said Christmas tree (10).

26. A method for removing debris (90) from a subsea Christmas tree (10), comprising: connecting a marine riser and a blowout preventer (BOP) (60) to said subsea Christmas tree (10); lowering a running tool (70) through the marine riser to the Christmas tree (10); lowering a plug removal tool (80) towards engagement with the running tool (70); and forcing fluid down the riser, the fluid flowing through a passage (83) in the plug removal tool (80) to wash out debris (90) in the Christmas tree (10).

27. The method of claim 26, wherein the plug removal tool (80) is lowered together with the running tool (70).

Description:

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention is generally related to the field of subsea wells and tools, and more particularly, to methods and tools for retrieving wire line plugs from subsea wells, which allows debris to be removed from on top of the plugs and riser hydrostatic pressure effects to be overcome.

2. Description of the Related Art

A horizontal Christmas tree is a device that is commonly employed on many subsea wells. Such horizontal trees utilize wire line plugs. All suppliers of this type of tree have problems with debris accumulating on the plugs. A solution, which allowed the plugs to be pulled without preliminary debris clearing, and or under conditions where riser hydrostatic pressure is greater than wellhead pressure would be a significant completive advantage.

Debris from drilling and the completion riser systems accumulate on top of horizontal Christmas trees settling in the upper bore of the tubing hanger over the wire line plugs. The wire line plugs must be removed to allow access to the well bore. Removal of the debris is costly with current methods and increases in cost with water depth and rig rates, both of which are increasing. Furthermore, in deep water applications, the hydrostatic pressure in the completion riser is sometimes in excess of the wellhead pressure. This produces a downward load on the load on the wireline plug which can be larger than the wire tensile capacity. This prevents or complicates plug retrieval.

When clearing out debris from the wellhead or Christmas tree, the normal practice is to run a wire line bailer or pump to remove the debris. It is also possible to run coiled tubing into the well to wash out the debris before the wire line operations are performed. The use of coiled tubing allows a higher pulling load to be applied to the plug overcoming some of the riser-wellhead pressure balance problems. Special pulling tools may also be used to the same effect.

The current practice is an incomplete solution to the problem because the bailing tool must be run to establish if debris is present above the plug. It is then run repeatedly, which removes a limited amount of debris with each trip of the tool from the surface to the top of the debris, until it fails to retrieve debris, which indicates clearance. All of these trips cost additional time and money if the clearance can be accomplished without a separate wire line operation. Coiled tubing can be run into the well through the production riser to wash the debris from above the top of the plugs. This is considered to be a prohibitively expensive procedure due to extra equipment mobilization and the complexity of the operation. Special pulling tools, like the normal wireline pulling tools, cannot be used until the debris has been removed by separate operations.

The present invention is directed to an apparatus and methods for solving, or at least reducing the effects of, some or all of the aforementioned problems.

SUMMARY OF THE INVENTION

The following presents a simplified summary of the invention in order to provide a basic understanding of some aspects of the invention. This summary is not an exhaustive overview of the invention. It is not intended to identify key or critical elements of the invention or to delineate the scope of the invention. Its sole purpose is to present some concepts in a simplified form as a prelude to the more detailed description that is discussed later.

In one illustrative embodiment, an apparatus adapted for removing a plug from a subsea Christmas tree is disclosed which comprises a housing, a distal end of the apparatus that is adapted to engage the plug, and a fluid passage formed in the housing that is adapted for use in directing a stream of fluid toward the plug to remove debris from above the plug.

In another illustrative embodiment, an apparatus adapted for removing a plug from a subsea Christmas tree is disclosed which comprises a housing, a distal end of the apparatus that is adapted to engage the plug, a fluid passage formed in the housing, the exit of which defines a nozzle that is adapted for use in directing a stream of fluid toward the plug to remove debris from above the plug, and a tubing hanger running tool having a bore formed therein, wherein the housing is moveably positioned within the bore.

In yet another illustrative embodiment, the invention consists of a wire line plug pulling tool with a fluid path which begins above an enlarged outside diameter section and exits at or close to the end of the tool which engages the wire line plug. The tool's enlarged outer section interacts with a reduced internal bore of the completion riser assembly, which creates a fluid flow restriction past the outside of the tool. This restriction forces any fluid pumped down the production riser through the fluid path of the tool exiting at high velocity at the end of the tool, thereby washing debris away from the pulling tool and plug interface. Furthermore, fluid pressure applied by this restriction creates a net upward or pulling load on the tool when the central wash port is closed.

No known method or tool combines the ability to remove debris from the tool-plug interface with the tool that is used to pull the plug and/or produce a net upward or pulling load on the tool using pressure from the surface.

In one illustrative embodiment, a method for removing debris from a subsea Christmas tree is disclosed which comprises connecting a marine riser and a blowout preventer (BOP) to a subsea Christmas tree, lowering a plug removal tool through the marine riser to the Christmas tree, the plug removal tool having a fluid passage formed therein, and forcing a fluid down the marine riser and through the fluid passage in the plug removal tool to wash out debris in the Christmas tree.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention may be understood by reference to the following description taken in conjunction with the accompanying drawings, in which like reference numerals identify like elements, and in which:

FIG. 1 is a cross-sectional view showing a subsea test tree with a tubing hanger installation tool;

FIG. 2 is a cross-sectional view showing the tool suspended above the tubing hanger;

FIG. 3 is a cross-sectional view showing the tool latched to the wireline plug;

FIG. 4 is a cross-sectional view showing the tool in a second mode of operation;

FIG. 5 is a cross-sectional view showing the tool in a third mode of operation;

FIG. 6 is a cross-sectional view showing the tool in a fourth mode of operation;

FIG. 7 is a cross-sectional view showing a second embodiment of the invention; and

FIG. 8 is a cross-sectional view similar to FIG. 7 showing the plug removal operation.

While the invention is susceptible to various modifications and alternative forms, specific embodiments thereof have been shown by way of example in the drawings and are herein described in detail. It should be understood, however, that the description herein of specific embodiments is not intended to limit the invention to the particular forms disclosed, but on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention as defined by the appended claims.

DETAILED DESCRIPTION OF THE INVENTION

Illustrative embodiments of the invention are described below. In the interest of clarity, not all features of an actual implementation are described in this specification. It will of course be appreciated that in the development of any such actual embodiment, numerous implementation-specific decisions must be made to achieve the developers' specific goals, such as compliance with system-related and business-related constraints, which will vary from one implementation to another. Moreover, it will be appreciated that such a development effort might be complex and time-consuming, but would nevertheless be a routine undertaking for those of ordinary skill in the art having the benefit of this disclosure.

The present invention will now be described with reference to the attached figures. The words and phrases used herein should be understood and interpreted to have a meaning consistent with the understanding of those words and phrases by those skilled in the relevant art. No special definition of a term or phrase, i.e., a definition that is different from the ordinary and customary meaning as understood by those skilled in the art, is intended to be implied by consistent usage of the term or phrase herein. To the extent that a term or phrase is intended to have a special meaning, i.e., a meaning other than that understood by skilled artisans, such a special definition will be expressly set forth in the specification in a definitional manner that directly and unequivocally provides the special definition for the term or phrase.

Referring to FIG. 1, a flow completion assembly 10, commonly referred to as a horizontal tree completion, is shown in the installation or workover mode of operation. In either of these modes of operation, a blowout preventer (BOP) 60 is connected to the top of the tubing spool 14 and a tubing hanger running tool (THRT) 70 is attached to the top of the tubing hanger 18. A subsea test tree (SSTT) 63 is normally connected to the top of the THRT 70. The BOP includes an internal BOP bore 61, at least one set of rams 65 which is capable of sealing against the THRT 70, and at least one choke and kill line 62 for providing communication between the BOP bore 61 below the rams 65 and a surface vessel (not shown). At least two valves 64 are provided to secure any wellbore pressure from under the BOP rams 65. This combination of BOP functions and SSTT 63 provide the standard subsea safety package for the installation or workover mode of operation. The THRT 70 or the SSTT 63 includes a smooth, or seal, bore 75, which is larger than the wireline plugs 11, 12 and smaller in diameter than the riser-SSTT bore above and the THRT bore below. A landing shoulder 74 is provided above or below the reduced bore 75. In addition the THRT 70 comprises an internal bore 76 or production port, a production stab 71, which connects to the production bore 26 of the tubing hanger 18. This production stab may be removed, or constructed to move axially, to open a flow path from the production bore 26 of the tubing hanger 18 to flow ports 77 through the THRT 70 and out of the choke and kill line 62 of the BOP 60. Flow may also be possibly established between the outside diameter of the THRT 70 and the BOP bore 61. Alternatively or additionally, a sleeve valve 72, or other type of valve, may be included in the THRT 70 to allow flow from the production bore 26 through the THRT internal bore 76 and ports 73 to exit out of the choke and kill line 62 of the BOP 60. Either or both of these flow paths may be utilized to evacuate debris that has been washed from the well bore, in particular from on top of either of two closure members 11, 12. These closure members are normally wireline plugs. When the wireline plugs 11, 12 are removed, fluid flow, in the reverse direction, from the surface vessel (not shown) may be useful in balancing the well production bore pressure or killing the well. This capability is particularly important if the subsea test tree SSTT 63 has failed and fluid cannot be pumped down the production-completion riser system bore.

Referring to FIG. 2, a wireline plug pulling tool 80 is shown suspended on a shoulder 85 mating with the landing shoulder 74, which is part of the THRT 70. The plug pulling tool 80 is free to move vertically upward. The wireline plug pulling tool 80 may be run with the THRT, SSTT and completion riser (not shown) and not attached to the wireline unit during installation, alternatively the wireline plug pulling tool 80 may be installed with the wireline unit after the THRT, SSTT and completion riser (not shown). The plug pulling tool 80 is equipped with a wireline fishneck 81. This fishneck is used to connect to the wireline unit remotely in the well or manually at the surface. Debris 90 typical of that displaced from the drilling riser and BOP during the running of the THRT, SSTT and completion riser (not shown) is indicated on top of, and trapped between, the two wireline plugs 11, 12. The wireline plug pulling tool 80 includes a housing 84 having a diameter which co-acts with the reduced diameter smooth bore 75 to restrict flow of fluid between the outside diameter of the wireline plug pulling tool 80 and the completion riser assembly bore below the reduced diameter smooth bore 75. It is clear that this flow could be reduced to zero if required by the introduction of seal elements at this location. The wireline plug pulling tool 80 further includes a vertical flow port 83 which extends from, or near to, the bottom wireline plug latch mechanism 86 upward to intersect with horizontal flow ports 82 which exit into the bore of the completion riser assembly above the reduced diameter smooth bore 75. It can then be seen that pumping fluid down the completion riser assembly from a surface vessel (not shown) would produce a fluid jet downward from the bottom of the wireline plug pulling tool 80, and that this fluid jet could be used to wash debris from on top of the tubing hanger 18 and the wireline plugs 11, 12. The debris could be carried up and exit out of the choke and kill line 62 or other of the multiple choke and kill lines of BOP 60. It is clear that this washing could be conducted prior to the landing of the THRT 70 onto the tubing hanger 18. After the THRT 70 is connected to the tubing hanger and the production stab 71 and/or the sleeve valve 72 of the THRT 70 is shifted to the open position, debris washing may be continued, even though the BOP rams 65 have been closed, sealing the annulus between the THRT-SSTT assembly and the BOP bore 61, placing the well in a safe (controlled) condition before the wireline plugs 11, 12 are pulled. The production stab 71 and sleeve valve 72 may be hydraulically operated cylinders with seals positioned on each end. The stab 71 and/or sleeve 72 may move vertically to enter a mating counter bore to complete a sealed barrier between two cylindrical parts of the tubing hanger running tool 70, and the riser above the tool 80 in the upward direction and between the tubing hanger running tool 70 and the tubing hanger 18 in the lower direction. Such details regarding hydraulic cylinders are well known to those skilled in the art.

Referring to FIG. 3, a wireline plug pulling tool 80 is shown latched with the wireline plug latch mechanism 86 into the fishneck of the upper wireline plug 12, in the normal manner, after the obstructing debris has been washed away. The surface wireline unit latch mechanism 86 has been latched into the plug pulling tool fishneck 81 in a similar manner. Standard wireline jarring and pulling operations have been conducted to shift a valve closing the horizontal flow ports 82 of the wireline plug pulling tool 80. Clearly other valve devices such as a check valve could also be used. The completion riser system above the smooth, or seal, bore 75 is automatically filled with seawater, or other fluid such as fresh water, which is present in the drilling riser, as the completion riser system is run. The choke and kill line 62 provides communication between the BOP bore below the rams 65 and a surface vessel (not shown) are flushed clean and filled with completion fluid of the correct weight to balance the bottom hole pressure of the well. The two valves 64 are opened and the hydrostatic pressure of the completion fluid is seen from under the BOP rams 65 and the smooth, or seal, bore 75 and on top of the upper wireline plug 12. If the plug is free, not wedged or stuck in the bore of the tubing hanger 18, and the area under the plug can be vented or pressurized through the workover control system as intended, then the plug can be pulled using the surface wireline unit as normal. The hydrostatic pressure from the completion fluid in the choke and kill line 62 will be higher than the hydrostatic pressure from the completion riser. This pressure differential can be increased up to the limit of the system by increasing the pressure down the choke and kill line 62. Because the wireline plug pulling tool 80 includes a diameter 84 which co-acts with the reduced diameter smooth bore 75 and this diameter is larger than the outside diameter of the wireline plug 12, the pressure from the choke and kill line 62 will produce an upward load on the wireline plug pulling tool 80 and the wireline plug 12 attached to it. The higher specific gravity of the completion fluid in the choke and kill line is the less load is required from the surface wireline unit. This is exactly opposite to the normal situation and beneficial for deep-water applications with low wellhead pressures. The wireline plug pulling tool 80 and the upper wireline plug are retrieved to the surface vessel (not shown) using the surface wireline unit as normal. The wireline plug pulling tool 80, adjusted in length, is lowered back into position to wash the debris from on top of and retrieve the lower wireline plug 11 in the same procedure as used for the upper plug 12. After the plugs are retrieved, the production stab 71 and/or the sleeve valve 72 of the THRT 70 is shifted to the closed position and well completion or workover operations may be continued.

Referring to FIG. 4, a wireline plug pulling tool 80 is shown latched with the wireline plug latch mechanism 86 into the fishneck of the upper wireline plug 12, in the normal manner, after the obstructing debris has been washed away. The wireline plug pulling tool 80 is suspended on a shoulder 85 mating with the landing shoulder 74, which is part of the THRT 70, specifically incorporated into the sleeve valve 72 of the THRT. When configured in this manner, the wireline plug 12 is subject to the combined pulling loads of the surface wireline unit, the upward load on the wireline plug pulling tool 80 produced by the pressure from the choke and kill line 62 and the upward load from the sleeve valve 72 actuator mechanism. It is clear that his upward loading landing shoulder mechanism could be built into any component of the completion riser, SSTT or THRT.

Referring to FIG. 5, a wireline plug pulling tool 80 is shown latched with the wireline plug latch mechanism 86 into the fishneck of the upper wireline plug 12, in the normal manner, after the obstructing debris has been washed away. The wireline plug pulling tool 80 diameter 84, which co-acts with the reduced diameter smooth bore 75 to restrict or seal flow of fluid between the outside diameter of the wireline plug pulling tool, has been replaced in this variation of the invention by packer assembly 79 which increases in diameter to seal in the completion riser assembly bore. This allows the tool to wash debris and provides force to pull the plugs by supplying pressure from the choke and kill line 62. All other operations are as described above.

Referring to FIG. 6, a wireline plug pulling tool 80 is shown latched with the wireline plug latch mechanism 86 into the fishneck of the upper wireline plug 12, in the normal manner, after the obstructing debris has been washed away. The surface wireline unit has been replaced in this variation of the invention by a pipeline pigging element 87. The forces to pull the plugs are supplied by pressure from the choke and kill line 62. The standard wireline running and pulling functions may be replaced by flow from above or from below the pipeline pigging element 87, thus driving the wireline plug pulling tool 80, and when latched to it, the wireline plug, up and down the completion riser. All other operations are as described above.

Referring to FIG. 7, a wireline plug pulling tool 80 is shown latched with the wireline plug latch mechanism 86 into the fishneck of the upper wireline plug 12, in the normal manner, after the obstructing debris has been washed away. The completion riser, SSTT and THRT has been replaced in this variation of the invention by a drill pipe handling string attached to a simple tubular housing 40. The housing or the drill pipe handling string may include one or more valves as safety closure devices 47. This housing includes a smooth, or seal, bore 45, which is larger than the wireline plugs 11, 12 and smaller in diameter than the housing bore below the smooth, or seal, bore 45. A landing shoulder 44 is provided above or below the reduced bore 45. In addition, the tubular housing comprises an internal bore 46 or production port, and stab 41, which connects to the production bore 26 of the tubing hanger 18. The forces to pull the plugs are supplied by pressure from the choke and kill line 62 and an additional, or replacement, force by applying tension to the drill pipe handling string. The complete assembly, including the wireline plug 12 or 11 latched to the plug pulling tool 80, is retrieved using the drill pipe handling string through the drilling riser after the BOP rams 65 have been retracted. All other operations are as described above.

Referring to FIG. 8, a wireline plug pulling tool 80 is shown latched with the wireline plug latch mechanism 86 into the fishneck of the upper wireline plug 12, in the normal manner, after the obstructing debris has been washed away. The completion riser, SSTT and THRT has been replaced in this variation of the invention by a wireline plug pulling tool guide tubular housing 40. The housing, or assemblies attached to it, may include one or more valves as safety closure devices 47. This housing includes a smooth, or seal, bore 45, which is larger than the wireline plugs 11, 12 and smaller in diameter than the housing bore below the smooth, or seal, bore 45. A landing shoulder 44 is provided above or below the reduced bore 45. In addition, the tubular housing comprises an internal bore 46 or production port, and stab 41, which connects to the production bore 26 of the tubing hanger 18. The forces to pull the plugs are supplied by pressure from the choke and kill line 62 and an additional, or replacement, force by applying pressure from the choke and kill line 67 under BOP rams 69, or other sealing devices of the BOP. The diameter of the tubular housing 40 is larger at this position than the BOP ram 65 sealing position. The pressure from the choke and kill line 67 therefore produces an upward load on the tubular housing 40 which in turn is transmitted through landing shoulder 44 and plug pulling tool shoulder 85 to pull the wireline plug 12. The complete assembly, including the wireline plug 12 or 11 latched to the plug pulling tool 80, may be retrieved through the drilling riser, after the BOP rams 65 and 69 have been retracted, using a drill pipe handling string which connects to the tubular housing 40. Alternatively, the wireline plug pulling tool 80 including the wireline plug 12 or 11 latched to the plug pulling tool may be retrieved independently to the surface vessel (not shown) using the surface wireline unit as normal. All other operations are as described above.

It should be apparent to those skilled in the art that changes can be made without departing from the scope of the invention. For example, a variety of tubing hanger running tools may be employed.

The particular embodiments disclosed above are illustrative only, as the invention may be modified and practiced in different but equivalent manners apparent to those skilled in the art having the benefit of the teachings herein. For example, the process steps set forth above may be performed in a different order. Furthermore, no limitations are intended to the details of construction or design herein shown, other than as described in the claims below. It is therefore evident that the particular embodiments disclosed above may be altered or modified and all such variations are considered within the scope and spirit of the invention. Accordingly, the protection sought herein is as set forth in the claims below.