Combination down hole tool

Abstract

A series of down hole tools are assembled from a common subassembly to which are added various specialty parts to make a flow back plug, a bridge plug or a plug with a disintegratable check valve. The subassembly may be used, as is, as a ball drop plug. The components may be added through either end of the subassembly without having to take the subassembly apart. The subassembly and specialty parts may be shipped to the customer so the end user may customize the subassembly to provide a plug operable to provide a variety of functions.

Description

This application is based on U.S. Provisional Application 61/214,347 filed Apr. 21, 2009priority of which is claimed.

This invention relates to a tool used in wells extending into the earth and, more particularly, to a series of down hole tools based on a common subassembly.

BACKGROUND OF THE INVENTION

This invention is a modification or improvement over the devices shown in U.S. patent application Ser. No. 12/317,497filed

December 23, 2008, the disclosure of which is incorporated herein by reference.

An important development in natural gas production in recent decades has been the drilling of horizontal legs of hydrocarbon wells in combination with improvements in hydraulic fracturing techniques for stimulating production from previously uneconomically tight formations. For some years, the fastest growing segment of gas production has been from shales or very silty zones that previously have not been considered economic. The current areas of increasing activity include the Barnett Shale, the Haynesville Shale, the Fayetteville Shale, the Marcellus Shale and other shale or shaley formations.

There are a variety of down hole tools used in the completion and/or production of hydrocarbon wells such as bridge plugs, flow back plugs, ball drop plugs and the like. In the past, these have all been tools specially designed for a single purpose.

It is no exaggeration to say that the future of natural gas production in the continental United States is from heretofore uneconomically tight gas bearing formations, many of which are shales or shaley silty zones. Accordingly, a development that allows effective frac jobs at overall lower costs is important.

SUMMARY OF THE INVENTION

As disclosed herein, there is provided a common subassembly that can easily be assembled with specialty parts to provide a bridge plug, a ball drop plug, or a plug having a disintegratable ball or plug check. In addition, the subassembly may be used, without any specialty parts, as a flow back plug. Thus, a variety of down hole tools or plugs may be assembled from a common subassembly and a few specialty parts that provide the special functions of different plugs. In one aspect, a supplier does not have to keep so much inventory because one always seems to receive orders for what is in short supply. Another major advantage of the disclosed device is that a subassembly and a package containing the specialty parts may be shipped to a supply store customer or to an operator customer. In some embodiments, the customer may use the shipped subassembly as a ball drop tool or may remove one end from the tool and insert one of the specialty parts in a recess at the end of the tool and thereby convert the subassembly to a bridge plug or a flow back plug.

An important advantage of the combination well tool disclosed herein is that the specialty parts may be incorporated into the subassembly without having to take the subassembly apart and then reassemble it. This is accomplished by adding the specialty parts through one end and leaving the opposite end of the subassembly intact.

The subassembly parts that are common to the down hole plugs disclosed herein are, in some embodiments, a mandrel, the elements of a slips/seal section, a mule shoe and a setting assembly that, when the plug is manipulated by a conventional setting tool, expands the slips/seal section into sealing engagement with the inside of a production or pipe string. An important advantage of this subassembly is that manipulating the tool to set the slips creates a passageway through the setting assembly and, in some embodiments, through the plug. This allows the assembly of a bridge plug, a flow back plug, a ball drop plug or a plug having a disintegratable valve simply by the addition of specialized parts.

In some embodiments, the common subassembly is a mandrel, the elements of a slips/seal section and a mule shoe. In these embodiments, the plug is expanded by pulling on the mandrel and/or pushing on the slips/seal section to expand the slips/seal section in a conventional manner. In application Ser. No. 12/317,497, the common assembly includes a separate setting device attached to the mandrel and a setting rod threaded into the setting device. Pulling sufficiently on the setting rod strips the threads and releases the setting rod thereby opening a passage through the mandrel thereby allowing separate components to be inserted into the passage to provide a bridge plug, a flow back plug, a ball drop plug and the like.

In some embodiments of this invention, the setting device comprises a threaded upper end of the mandrel and the setting rod comprises a threaded member received in the threaded upper end of the mandrel. In these embodiments, a portion of the mandrel spaced below the threads, i.e. distanced further from the surface of the earth, is of reduced thickness so pulling on the setting rod first causes the slips/seal section to expand into engagement with the inside of a production string and then causes the mandrel to fail thereby opening a passage, or increasing the internal passage, through the mandrel. This common subassembly allows additional elements to be added to create a bridge plug, a flow back plug, a ball drop plug and the like.

An important advantage of this invention is the specialty parts added to the common subassembly are conveniently added to one end of the common subassembly without having to take the subassembly apart. In some embodiments, the specialty parts may be added to a top of the subassembly and, in other embodiments, may be added to a bottom of the subassembly.

It is an object of this invention to provide an improved down hole well subassembly that is easily adapted to provide different functions.

Another object of this invention is to provide an improved down hole subassembly where specialty parts may be added to one end of the subassembly without having to take the subassembly apart.

A more specific object of this invention is to provide an improved down hole plug in which a setting rod is tensioned to set the plug on the inside of a production or pipe string and then pulled out of the plug.

Another object of this invention is to provide an improved method of distributing down hole well tools.

These and other objects and advantages of this invention will become more apparent as this description proceeds, reference being made to the accompanying drawings and appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view of a subassembly which is readily modified to act as a variety of tools and which also comprises a ball drop plug, illustrated in a running in or extended position;

FIG. 2 is a cross-sectional view of the ball drop plug of FIG. 1, illustrated in a set or collapsed position;

FIG. 3 is a cross-sectional view of a flow back plug illustrated in a running in or extended position;

FIG. 4 is an enlarged cross-sectional view of a bridge plug, illustrated in a running in or extended position;

FIG. 5 is a schematic view of a subassembly and a container having therein specialty parts for converting the subassembly to one of a variety of down hole tools; and

FIG. 6 is a cross-sectional view of another common subassembly or flow back plug.

DETAILED DESCRIPTION

The present invention relates to devices for use in hydrocarbon wells drilled into the earth and completed using a variety of techniques. The materials from which the tools are made are subject to considerable variation. Some of the components are made of metals and some are made of composite plastics. Any components left in the well are usually made of drillable materials. Various changes and adaptations may be made in the tools without departing from the spirit and scope of the invention, which is to be measured solely by the claims themselves.

Referring to FIGS. 1-2, there is illustrated a subassembly 10 which is usable, without modification, as a ball drop plug and which may have a few components added to it to provide a flow back plug 12 shown in FIG. 3 or a bridge plug 14 as shown in FIG. 4. The subassembly 10, the flow back plug 12 and the bridge plug 14 may comprise, as major components in some embodiments, mandrels 20, slips/seal sections or assemblies 22, setting assemblies 24 and mule shoes 26. Because it is often desired to drill out the plugs 10, 12, 14 the components left in the well are typically made of drillable materials, such as composite plastics, aluminum, bronze, cast iron or other drillable materials. Composite plastics are well known in the art and are of a variety of types, such as a fabric impregnated with a suitable resin and allowed to cure, a wound fiberglass filament resin impregnated material, a fiber molded injection impregnated material or the like.

The mandrel 20 may provide a central axial passage 28, a threaded section 30 intermediate the ends of the mandrel 20, a tapered or valve seat section 32 above the threads 30 and an upper threaded section 34. A retaining sleeve 37 may be attached to the upper end of the mandrel 20 in any suitable manner, as by threads, set screws, pins or the like. The words upper and lower are somewhat inaccurate because they refer to the position of the well tools as if they were in a vertical position while many, if not most, of the plugs disclosed herein will be used primarily in horizontal wells. The words upper and lower are used for purposes of convenience rather than the more accurate proximal and distal. The lower end 38 of the mandrel 20 is threaded for connection to the mule shoe 26 as will be more fully apparent hereinafter.

The slips/seal section 22 may be more-or-less conventional and provides one or more resilient seals 40 and one or more wedge shaped elements 42 which abut wedge shaped slips 44, 46 having wickers or teeth. The elements 42 are conveniently pinned to the mandrel 20 by set screws, plastic bolts or pins (not shown) so the seals 40 and elements 42 stay in place during handling. The set screws, plastic bolts or pins (not shown) are easily sheared during setting of the plugs 10, 12, 14. The upper slips 44 abut a ring 48 while the lower slips 46 abut a square shoulder provided by the mule shoe 26.

The setting assembly 24 includes a setting rod 50 connected to the mandrel 20 and may have a lower threaded end 52 received in the threads 34. The setting assembly 24 includes some mechanism to separate the setting rod 50 from the mandrel 20 and unblock or open the mandrel passage 28. This mechanism may be of any suitable type such as such as shear pins or shear screws extending through the mandrel 20 into the setting rod 50 or may comprise a reduced diameter, partible or necked down section 36 of the mandrel 20. Thus, in the vocabulary of Ser. No. 12/317,497, the threads 34 and partible neck 36 or the shear pins/screws comprise a setting device. Because the setting rod 50 is removed from the well, in most embodiments it is normally not made of a drillable material and is typically of steel. As is apparent, the setting device or threads 34 and/or necked down section 36 may provide a passage therethrough. The setting rod 50 may be solid, i.e. have no passage therethrough, or may be tubular having a passage therethrough. It will be seen that part of the necked down or partible section 36 may provide the tapered valve seat 32.

When setting the plugs 10, 12, 14 the setting tool (not shown) pulls on the setting rod 50 and/or pushes on the load ring 48, the slips/seal section 22 expands to set the seals 40 and the slips 44, 46 against a production or pipe string in the well. The rod 50 may be pulled completely out of the mandrel passage 28 and it is desirable that the rod 50 pull out of the mandrel 20 in response to a predictable force. To this end, the material of the mandrel 28 and the thickness of the necked down section 36 are selected to fail at a predictable tensile force.

The mule shoe 26 comprises the lower end of the subassembly 10 and differs from the device shown in application Ser. No. 12/317,497 because the function altering components are at the top or proximal end of the plugs 10, 12, 14 rather than at the bottom or distal end. The mule shoe includes a body 54 having a tapered lower end 56 and a passage 58 opening through the lower end 56. The mule shoe 26 includes an upper end 60 abutting the bottom of the lower slip 46 and a series of grooves 62 which allow completion fluids to pass more readily around the mule shoe 26 at appropriate times, for example when the plug is being pulled by a wireline upwardly in a liquid filled well. A pump down collar 64 slips over the lower end of the mule shoe 26 so the plug may be pumped into a horizontal leg of a well. In some embodiments, the mule shoe 26 may be pinned to the mandrel 20 so it won't become unthreaded.

No special components need to be added to the subassembly 10 to provide the ball drop plug. In other words, the ball drop plug and the subassembly 10 are identical. Thus, in one mode of operation, a ball check 66 is dropped into a production or pipe string (not shown) after the subassembly 10 is expanded against the production string to seat against the tapered inlet 32. Those skilled in the art will recognize that the ball drop plug 10 can be used in a situation where a series of zones are to be fraced. There are a number of ways that ball drop plugs are conventionally used, one of which is to frac a zone, run a ball drop plug 10 into the well above the fraced zone, drop a ball 66 into the production string and thereby isolate the lower zone so a higher zone may be fraced. In another mode of operation, the mandrel 20 may be lengthened above the necked down section 36 as suggested by the break lines in FIG. 1 to provide a recess to receive the ball check 66 which may be incorporated into the subassembly 10 before it is run into a well, as suggested by the break lines in FIG. 1. In the alternative, the setting rod 50 may provide a cavity 67 to receive a ball check 66 incorporated into the subassembly 10 before it is run into a well, as shown in dotted lines in FIG. 1.

In order to assemble the flow back plug 12 from the subassembly 10, it is necessary only to insert a ball check assembly 68 on the threads 30. This may be accomplished by removing the setting rod 50, if necessary, and inserting the ball check assembly 68 into the upper end of the mandrel 20. It will be apparent to those skilled in the art that the flow back plug 12 is often used in situations where a series of zones are to be fraced in a well. After a zone is fraced, the flow back plug 12 is run into the well and expanded against a production string. The ball check assembly 68 prevents flow through the plug 12 is a downward direction in a vertical well but allows the fraced zone to produce up the production string. The ball check assembly 68 comprises a housing 70 which may include threads 72 meshing with the threads 30 on the inside of the mandrel 20 or the housing 70 may be captivated in the mandrel 20 in any suitable manner. The housing 70 provides O-rings 74 sealing between the housing 70 and the mandrel 20 and a pin 76 or other restraint preventing a ball 78 from flowing upwardly out of the plug 12.

In order to assemble the bridge plug 14, it is necessary only to insert an obstruction 80 onto the threads 30. In some embodiments, the obstruction 80 includes an imperforate housing 82 having one or more O-rings or other seals 84 engaging the inside of the mandrel 20. Threads 86 may be provided for coupling with the threads 30 of the mandrel 20 or the housing 82 may be captivated inside the mandrel 20 in any suitable manner. It will be seen to those skilled in the art that the bridge plug 14 prevents flow, in either direction, through the plug 14 so the plug 14 is used in any situation where bridge plugs are commonly used.

It will be apparent that the ball check 66 or the ball check 78 may be made of a disintegratable material so the check valve action of these plugs is eliminated over time.

In use, the subassembly 10 and a package containing the ball check 66, the valve assembly 68 and the obstruction 80, and the setting rod 50 are shipped to a supply store or customer. The subassembly 10 may be shipped with the setting rod 50 assembled or in the package 88. Customizing the subassembly 10 may be done at any time simply by opening the package, retrieving the desired specialty component and/or the setting rod 50, inserting the desired specialty component in the mandrel passage 28 and installing setting rod 50. Thus, customizing the subassembly 10 may be done at a supply store, at a shop of the operator or service company, at the well location or at any other suitable time after receipt by the customer or its representative.

The plugs 10, 12, 14 are set in a conventional manner using a conventional setting tool (not shown) such as a Model 10, 20, E-4, or E-5 Setting Tool available from Baker Oil Tools, Inc., Houston, Tex., and appropriate connector subs are attached to the setting rod 50 of the plug being set and an annular member rides over the upper section end of the mandrel 20 to abut the load ring 48, which is the uppermost component of the slips/seat section 22. When this assembly has been lowered to the desired location in a vertical well or pumped to the desired location in a horizontal well, the setting tool is actuated to tension the rod 50 and/or compress the load ring 48. This shears off the plastic screws 86 so the slips 44, 46 slide toward each other on the exterior of the mandrel 20. This forces the resilient seals 40 outwardly to seal against the inside of the production string and expands the slips 44, 46 so the withers grip the inside of the production string and set the plug in place. Continued pulling on the rod 50 pulls the neck 32 of the mandrel 20 in two thereby releasing the rod 50 which is withdrawn from the mandrel 20. This may leave the passage 28 open through its maximum internal diameter through the mandrel 20. This allows the subassembly 10 to be used without modification as a ball drop plug, to be configured as the flow back plug 12 of FIG. 3 or the bridge plug 14 of FIG. 4. It will be evident that FIG. 2 is misleading in the sense that the setting assembly 50 has sheared off from the mandrel 20 but the slips/seal section 22 is not illustrated as being expanded. In fact, the slips/seal section 22 expands first and the setting rod 50 then shears off.

Although the function of the subassembly 10 is modified by inserting the specialty parts into the top of the tool, the same function can be accomplished by providing a cavity or recess between the bottom of the mandrel 20 and the mule shoe 26 for receiving a check valve assembly analogous to the assembly 68 and/or an obstruction analogous to the obstruction 80. In the embodiments previously described, the mule shoe 26 may be pinned or otherwise secured to prevent unthreading of the mule shoe 26 from the mandrel 20. In embodiments where the specialty parts are to be installed at the bottom of the subassembly 10, the mule shoe 26 is simply threaded onto the mandrel 20 and any pinning of the mule shoe 26, if desired, is accomplished after the specialty parts are installed.

As shown in FIG. 5, it will be apparent that the subassembly 10 may be shipped to a customer along with a container 88 having therein the ball check 66, the ball check assembly 68 and the obstruction 80 so the plug needed may be assembled in the field by a wire line operator. It will be apparent that the subassembly 10 and container 88 may be packaged together or shipped separately to a customer.

Referring to FIG. 6, there is illustrated another embodiment 90 which serves as a ball drop plug or subassembly for another family of bottom hole tools analogous to FIGS. 1-4. As illustrated, the subassembly 90 is a combination of some components from FIGS. 1-4 and some components from application Ser. No. 12/317,497. The subassembly 90 comprises, as major components, a mandrel 92, a slips/seal section 94, a setting assembly 96 and a mule shoe 98. The mandrel 92 includes an interior passage 100 having threads 102 at a suitable location to receive a ball check assembly analogous to the ball check assembly 68 or an obstruction analogous to the obstruction 80. The mandrel 92 includes an upper tapered ball seat surface 104 for sealably receiving a ball check analogous to the ball check 66. The mandrel 92 may also comprise a retaining sleeve 106 to keep the components of the slips/seal section 94 in assembled condition.

A substantial difference between the subassemblies 10 and 90 lies in a different technique for expanding the plug. More specifically, the setting assembly 96 comprises an elongate rod 108 which is pinned to the mandrel 92 or the mule shoe 98 by one or more shear pins 110 extending through openings 112 into a recess 114 in the rod 108. The shear pins 110 are selected to shear or fail at a predetermined load applied between the mandrel 92 and the rod 108 thereby expanding the slips/seal section 94.

It will be seen that the subassembly 90 includes a setting device comprising the connection between the mandrel 92 or mule shoe 98 and the setting rod 108.

The subassembly 90 is set in a conventional manner, i.e. a setting tool connects to the setting rod 96 and pushes on the upper load ring 116 and/or pulls on the mandrel 92 thereby expanding the slips/seal section 94 and ultimately shearing the pins 110. This releases the rod 108 which is pulled from the mandrel 92 thereby operating in much the same manner as the device of Ser. No. 12/317,497.

Although this down hole tool has been disclosed and described in its preferred forms with a certain degree of particularity, it is understood that the present disclosure of the preferred forms is only by way of example and that numerous changes in the details of operation and in the combination and arrangement of parts may be resorted to without departing from the spirit and scope of the invention as hereinafter claimed.

Claims

1. A down hole well tool comprising

a mandrel having an upper end, a lower end and a passage between the ends;

a slips/seal section movable on an exterior of the mandrel from a running in position to an expanded position for sealing against a production string;

a setting assembly assisting in moving the slips/seal section from the running in position to the expanded position, the setting assembly including a setting device rigid with the mandrel having a partible section adjacent an upper end of the mandrel and distant from the lower end of the mandrel for failing at a predetermined load to separate the setting device from the mandrel, and a setting rod connected to the setting device so that tensioning on the setting rod parts the setting device, expands the slips/seal section into sealing engagement with the production string and removes the setting rod from the mandrel, the arrangement of the setting device and setting rod being that removal of the setting rod from the tool unblocks the mandrel passage.

2. The down hole tool of claim 1 wherein the partible section includes a reduced thickness section of the mandrel.

3. The down hole tool of claim 2 wherein the reduced thickness section includes a tapered section on the mandrel acting as a seat for a ball check.

4. The down hole tool of claim 1 wherein the mandrel passage includes a cavity below the partible section and further comprising a ball check assembly captivated in the cavity allowing upward flow through the mandrel passageway and preventing downward flow therethrough.

5. The down hole tool of claim 1 wherein the mandrel passage provides a tapered section below the partible section acting as a seat for a ball check.

6. The down hole tool of claim 5 further comprising a ball check seated against the tapered section preventing downward flow into the production string.

7. The down hole tool of claim 1 wherein the mandrel passageway provides a cavity and further comprising an obstruction in the cavity below the partible section preventing upward flow through mandrel passage and preventing downward flow therethrough.

8. The down hole tool of claim 1 wherein the setting rod is a solid member having no passage therethrough.

9. The down hole tool of claim 1 wherein the mandrel passageway provides a cavity having threads and a threaded obstruction connected to the cavity threads converting the down hole tool to a bridge plug.

10. The down hole tool of claim 1 wherein the setting rod is removably attached to the mandrel and, upon removal from the mandrel, exposes a cavity having a check valve assembly therein.

11. The down hole tool of claim 1 wherein the setting rod is removably attached to the mandrel and, upon removal from the mandrel, exposes a cavity having an obstruction therein blocking the mandrel passage and converting the down hole tool into a bridge plug.

12. The down hole tool of claim 1 wherein the setting rod is removably attached to the mandrel and, upon removal from the mandrel, exposes a cavity having a ball check converting the down hole tool into a ball drop plug.

13. A method of distributing a combination down hole well tool having a plurality of functions, comprising

shipping to a customer a subassembly including a mandrel having an upper end, a lower end and a passage between the ends, a slips/seal section movable on an exterior of the mandrel from a running in position to an expanded position for sealing against a production string and a setting assembly assisting in moving the slips/seal section from the running in position to the expanded position;

shipping to the customer a container having therein specialty parts comprising a check valve assembly for converting the subassembly into a flow back plug and an obstruction for converting the subassembly into a bridge plug; and

after the subassembly and the container are shipped to the customer, customizing the subassembly by opening the container and retrieving one of the specialty parts and installing the specialty part in the subassembly.

14. The method of claim 13 wherein the subassembly and the container are shipped to the customer in a single package.

15. The method of claim 13 wherein the subassembly includes a setting rod for actuating the setting assembly, the setting rod being assembled on the subassembly when it is shipped to the customer.

16. The method of claim 13 wherein the container includes therein a setting rod for actuating the setting assembly, the setting rod being assembled on the subassembly after the container is opened.

17. The method of claim 13 wherein the container further comprises a ball check separate from the check valve assembly.

18. The method of claim 13 wherein the container further comprises a disintegratable check.