US20100263873A1

US20100263873A1 - Method and apparatus for use in selectively fracing a well

Info

Publication number: US20100263873A1
Application number: US12/579,358
Authority: US
Inventors: Don Turner; Steve Winkler
Original assignee: Source Energy Tool Services Inc
Current assignee: LOGAN COMPLETION SYSTEMS Inc
Priority date: 2008-10-14
Filing date: 2009-10-14
Publication date: 2010-10-21
Also published as: CA2682621A1; CA2641778A1

Abstract

An apparatus for selectively fracing a well includes a tubular body having an exterior surface, and an interior surface that defines an interior bore. An annular flow area that has at least one fluid flow port extends radially through the tubular body to permit fluids from the interior bore to pass through the at least one fluid flow port into a surrounding earth formation. An external sealing sleeve selectively covers the annular flow area. There is a pressure actuated sleeve shifting mechanism, where increasing pressure tending to cause axial movement of the external sealing sleeve. The axial movement is resisted until a pre-selected pressure threshold is reached to permit movement of the external sealing sleeve to open the at least one fluid flow port.

Description

FIELD

There is disclosed a method and apparatus for placing multiple fractures at spaced locations along a well bore.

BACKGROUND

U.S. Pat. No. 7,267,172 (Hofman) entitled “Cemented Open Hole Selective Fracing System” teaches selectively opening holes in production tubing of a hydrocarbon producing well by using sliding valves which can be selectively opened by a shifting tool. U.S. Pat. No. 7,096,954 (Weng et al.) entitled “Method and Apparatus for Placement of Multiple Fractures in Open Hole Wells” teaches using a plurality of burst disk assemblies, each having an independent burst pressure. The present method provides an alternative method of selectively opening holes in production tubing.

SUMMARY

There is provided an apparatus for use in selectively fracing a well. The apparatus comprises a tubular body having an exterior surface, and an interior surface that defines an interior bore. An annular flow area that has at least one fluid flow port extends radially through the tubular body from the interior surface to the exterior surface to permit fluids from the interior bore to pass through the at least one fluid flow port into a surrounding earth formation. An external sealing sleeve is detachably secured to the exterior surface of the tubular body to selectively cover the annular flow area and close the at least one fluid flow port. There is a pressure actuated sleeve shifting mechanism, with increasing pressure tending to cause axial movement of the external sealing sleeve. Axial movement is resisted until a pre-selected pressure threshold is reached to permit movement of the external sealing sleeve to open the at least one fluid flow port.
There is also provided a method for use in selectively fracing a well comprising the following steps: (a) providing a plurality of apparatus as described above; (b) deploying the apparatuses along a production tubing string in a well with packers being positioned between the apparatuses to isolate production areas, the pre-selected pressure threshold for each production area increasing from a toe of the well toward a heel of the well; (c) pumping fluids down the production tubing at pressures just sufficient to selectively shift the external sealing sleeve of the apparatus having a lowest shifting pressure to an open position without shifting the external sealing sleeve of others of the apparatus having higher shifting pressures; (d) continuing to pump fluids down the production tubing to pump fluids into the earth formation through the apparatus that has had its external sealing sleeve moved to the open position; (e) pumping balls down the production tubing until the balls seat on and close the at least one fluid flow port on the apparatus that has had its external sealing sleeve moved to the open position; (f) using fluid pressure to maintain the balls seated on the at least one fluid flow port while other of the external sealing sleeves in the production tubing are selectively moved to the open position; and (g) repeating steps (c), (d), (e) and (f) to selectively open the external sealing sleeve in apparatus in the production tubing in stages.
There is also provided an isolation tool for selectively applying pressure to an outer tubular body. The isolation tool comprises a tubular body carrying a first sealing element and a second sealing element. The tubular body has a fluid inlet and a fluid outlet. The tubular body is movable within the outer tubular body. A pressure cavity is defined by an outer surface of the tubular body, an inner surface of the outer tubular body, and the first and second sealing elements. The fluid outlet of the tubular body is in fluid communication with the pressure cavity. The first sealing element and the second sealing element permit fluid flow into the pressure cavity and sealing against fluid flow out of the pressure cavity.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features will become more apparent from the following description in which reference is made to the appended drawings, the drawings are for the purpose of illustration only and are not intended to be in any way limiting, wherein:

FIG. 1 is a side elevation view in section of an apparatus for selectively fracing a well.

FIG. 2 is an end elevation view in section of a sealing sleeve of the apparatus depicted in FIG. 1.

FIG. 3 is a detailed side elevation view of the sealing cavity of the fluid cavity of FIG. 1.

FIG. 4 is a side elevation view in section of the sealing sleeve in the open position.

FIG. 5 is a side elevation view in section of the flow ports plugged with balls.

FIG. 6 is a side elevation view of the apparatus depicted in FIG. 1 installed in a tubing string and inserted into a well.

FIG. 7 is a side elevation view in section of an alternative tubular body.

FIG. 8 is a side elevation view in partial section of an isolation tool.

FIG. 9 is a side elevation view in partial section of the isolation tool adjacent to the apparatus depicted in FIG. 1.

FIG. 10 is a side elevation view in section of an alternative apparatus.

DETAILED DESCRIPTION

An apparatus for use in selectively fracing a well generally identified by reference numeral 10, will now be described with reference to FIG. 1 through 4. The use and operation of the apparatus will then be discussed with reference to FIG. 1 through 6, 8 and 9. An alternative tubular body will be described with reference to FIGS. 7 and 10.

Structure and Relationship of Parts:

Referring to FIG. 1, apparatus 10 includes a tubular body 12 that has an exterior surface 14 and an interior bore 16 defined by an interior surface 17. An annular flow area 18 has one or more fluid flow ports 20 extending radially through tubular body 12 from interior surface 17 to exterior surface 14. In FIG. 1, three flow ports 20 are included and in FIG. 2, the sealing sleeve 24 is designed to cover three. It will be understood that the number may be varied during construction of apparatus 10, according to the preferences of the user or manufacturer. Fluid flow ports 20 permit fluids from interior bore 16 to pass through fluid flow ports 20 into a surrounding earth formation.
Referring to FIGS. 1 and 2, an external sealing sleeve 24 is detachably secured to exterior surface 14 of tubular body 12 to selectively cover annular flow area 18 and close fluid flow ports 20. External sleeve 24 has a first end 26 with a first internal diameter that engages a first sealing area 28 on exterior surface 14 of tubular body 12 on a first side 30 of annular flow area 18. External sleeve has a second end 32 with a second internal diameter that engages a second sealing area 34 on exterior surface 14 of tubular body 12 on a second side 36 of annular flow area 18. In the depicted embodiment, first sealing area 28 and second sealing area 34 have first and second seal grooves 38 and 40 in which are positioned first and second O- ring seals 42 and 44, respectively. A locking engagement is preferably provided between external sealing sleeve 24 and exterior surface 14 of tubular body 12 to lock external sealing sleeve 24 in the open position as shown in FIG. 4. For example, as depicted in FIG. 3, several resilient fingers 52 may be carried by external sealing sleeve 24. Resilient fingers 52 would then engage an engagement profile 54 on exterior surface 14 of tubular body 12 to maintain external sealing sleeve 24 in the open position.
Preferably, external sealing sleeve 24 is detachably secured to exterior surface 14 of tubular body 12 by shear pins 46 in shear pin apertures 47. Exterior surface 14 of tubular body 12 has a circumferential shear pin groove 48 to accommodate shear pins 46. Shear pins 46 are designed to shear and permit external sealing sleeve 24 to move as pressure builds within annular flow area 18 and reaches a predetermined pressure threshold. In a preferred embodiment, the number of shear pins 46 is adjustable, which permits a user to select a pre-selected pressure threshold at which the external sealing sleeve 24 is able to move by using a greater number or fewer number of shear pins 46.
External sealing sleeve 24 is moved by applying pressure to a pressure actuated sleeve shifting mechanism. For example, as shown in FIG. 3, external sealing sleeve 24 is shifted by applying pressure within a fluid cavity 50 that is formed between external sealing sleeve 24 and exterior surface 14 of tubular body 12. Fluid cavity 50 is asymmetrical to provide an asymmetrical pressure distribution, so that increasing pressure within fluid cavity 50 tends to cause axial movement of external sealing sleeve 24. In another example shown in FIG. 9, external sealing sleeve 24 may also be shifted by applying pressure to an inclined plane 51 located at the end of fluid flow port 20. As pressure builds within this fluid flow port extension 50, pressure acts against tapered wall 51 and pushes sealing sleeve 24 axially along apparatus 10. In either example, axial movement is resisted until a pre-selected pressure threshold is reached, such as by using shear pins 46 as described above. Once the pre-selected pressure threshold is reached, movement of external sealing sleeve 24 is permitted to open fluid flow ports 20.
It will be understood that other pressure actuated sleeve shifting mechanisms may be used, including different release mechanisms. For example, sleeve 24 may be biased to the shifted, open position, and a pressure increase may release a catch that allows sleeve 24 to shift.

Operation:

Referring to FIG. 6, apparatuses 10 are deployed along a production tubing string 53 with packers 55, such as hydraulically set dual element open hole packers. The type of packer used will be selected based on the conditions and preferences of the user. As apparatuses 10 are intended to be used downhole, they may be hard coated with carbide seats to improve durability. Referring to FIG. 1, each apparatus 10 is prepared by positioning external sealing sleeve 24 over annular flow area 18 such that flow ports 20 are blocked. External sealing sleeve 24 is then locked into the closed position by inserting a certain number of shear pins 46 that engage shear pin groove 48. The number of shear pins 46 sets the pressure at which external sealing sleeve 24 will move, such that, by increasing the number of shear pins 46, the pre-determined pressure also increases. Referring again to FIG. 6, packers 55 are positioned between apparatuses 10 to isolate the desired production areas. Tubing string 53 is then inserted into the casing 56 of a wellbore 58, in this case, a horizontal wellbore, such that each apparatus 10 is aligned with the portion of the formation to be fraced.
Once tubing string 53 is positioned with packers 55 set, fluids are pumped down tubing string 53 at pressures just sufficient to selectively shift external sealing sleeve 24 of apparatus 10 having the lowest pre-determined shifting pressure to an open position as shown in FIG. 3, such that fingers 52 engage profile 54, without shifting other external sealing sleeves 24 that have higher shifting pressures. Fluids are continued to be pumped down production tubing 53 to pump fluids into the earth formation through apparatus 10 that has had its external sealing sleeve 24 moved to the open position to treat the formation. Once treated, balls 60 are then pumped down tubing 53 until balls 60 seat on, and close fluid flow ports 20 on the open apparatus 10 as shown in FIG. 5. Fluid pressure is maintained to keep balls 60 seated on fluid flow ports 20. Fluid pressure is then increased until the next pre-determined pressure threshold is met to move the desired external sealing sleeve 24 to the open position. These steps are repeated to selectively open the desired external sealing sleeves 24 in the desired order, generally by starting toward the toe 62 and working toward the heel 64 if the well is a horizontal wellbore, or from the end of the wellbore and working backward.
The operation steps above are based on using differential pressures to open selected sealing sleeves 24. It has been found that in some circumstances, the flow ports 20 closest to the wellhead may become washed out by the abrasives, and become unusable. It will be understood other methods may also be employed, and may be preferable in some circumstances. For example, referring to FIG. 8, an isolation tool 70 may be used to apply pressure to a specific portion of tubing string 53 shown in FIG. 6. Isolation tool 70 may be a cup frac tool, which is used to selectively frac a portion of a formation. Isolation tool 70 has an input 72 in fluid communication with an output or fluid flow ports 74, with sealing elements 76 positioned on either side of fluid flow ports 74. Input 72 is connected to another tubing string (not shown) that extends to the surface, such that fluid pressure may be applied by pumping fluid through the tubing string and out outputs 74, as shown by arrows 78. Isolation tool 70 is inserted into tubing string 53 until fluid flow ports 20 of a selected apparatus 10 are positioned between sealing elements 76. Referring to FIG. 9, sealing elements 76 engage interior surface 17 such that the fluid pressure is applied to the selected fluid flow ports 20. Once the fluid pressure causes external sealing sleeve 24 to shift as described above, pressure is continued to be applied to frac the portion of the formation corresponding to those ports 20. This method negates the need for providing increasing opening pressures for each apparatus 10, as well as the need to pump balls down tubing string 53 to plug the opened fluid flow ports 20. It also reduces the risk of ports 20 becoming prematurely washed out. Once the frac is complete for that section, isolation tool 70 is repositioned at the next set of fluid flow ports, and the process is repeated. This also leaves a full bore access as the internal components used to shift sleeve 24 are removed.
Isolation tool
In the example described above, an isolation tool 70 is used to apply pressure to a specific portion of outer tubular member, or tubing string 53. It will be understood that this particular tool may be used for other tools aside from a sealing sleeve 24. For example, the isolated pressure may be used to open various types of pressure-actuated openings, such as rupture discs, removable plugs, shifting sleeves, etc. as are known in the art.
Referring to FIG. 8, isolation tool 70 has sealing elements 76 that are in constant contact with the inner surface of an outer tubular body, such as tubing string 53, during installation. To prevent a fluid block, isolation tool 70 has an equalization valve 86 that is open when tool 70 is being run in, and closes when pressure is applied within the pressure cavity 88 that is defined by sealing elements 76, the outer surface of tubular member 12, and As sealing elements 76 are cup-shaped, they permit fluid to flow past in one direction, but create a seal when a force is applied in the other directions. Thus, as tool 70 is being run in, fluid flows past the lower sealing element 76 and through equalization valve 86. As tool 70 is being pulled out, fluid above tool 70 passes over the upper sealing element 76 and through equalization valve 86. Equalization valve 86 is preferably adjustable such that the pressure at which it closes is adjustable. Once positioned, fluid pressure is applied between sealing elements 76 and as pressure builds within pressure cavity 88, sealing elements 76 are sealed against the inner surface of outer tubular body 53. Preferably, sealing elements 76 are biased into sealing contact with tubular body 53, otherwise the pressurized fluid may flow around elements 76 and out of pressure cavity 88.

Variations

FIG. 7 shows a slightly modified tubular body 12. Compared with FIG. 1, tubular body 12 has been lengthened. This has the effect of locking external sealing sleeve 24 (not shown) further from flow ports 20. In addition, instead of a shoulder that is engaged, profile 54 is a groove. This allows tubular body 12 to have a thicker sidewall past profile 54. Finally, tubular body has a slightly angled surface 66 between seal groove 40 and shear pin groove 48. While not shown, external sealing sleeve 24 will also have a corresponding angled surface 66.
FIG. 10 shows another modification, where, instead of finger 52 engaging shoulder 54, a ratcheting system is provided, where a profiled element 80 engages a profiled surface 82 on tubular body 12. The top surface of element 80 is sloped and engages a sloped surface within external sealing sleeve 24, such that any reverse movement is discouraged by the engagement between element 80 and surface 82, which increases due to the sloped surfaced as any reverse force increases. Preferably, element 80 is enclosed within a resilient portion of sleeve 24, such as a split ring-type design, such that sleeve 24 is able to flex, but still applies pressure to element 80. Also shown in FIG. 10 is an inner sleeve 84 that can be shifted back to close off ports 20 if desired.
In this patent document, the word “comprising” is used in its non-limiting sense to mean that items following the word are included, but items not specifically mentioned are not excluded. A reference to an element by the indefinite article “a” does not exclude the possibility that more than one of the element is present, unless the context clearly requires that there be one and only one of the elements.
The following claims are to be understood to include what is specifically illustrated and described above, what is conceptually equivalent, and what can be obviously substituted. Those skilled in the art will appreciate that various adaptations and modifications of the described embodiments can be configured without departing from the scope of the claims. The illustrated embodiments have been set forth only as examples and should not be taken as limiting the invention. It is to be understood that, within the scope of the following claims, the invention may be practiced other than as specifically illustrated and described.

Claims

1. An apparatus for use in selectively fracing a well, comprising:

a tubular body having an exterior surface, and an interior surface that defines an interior bore;

an annular flow area having at least one fluid flow port extending radially through the tubular body from the interior surface to the exterior surface to permit fluids from the interior bore to pass through the at least one fluid flow port into a surrounding earth formation;

an external sealing sleeve detachably secured to the exterior surface of the tubular body to selectively cover the annular flow area and close the at least one fluid flow port;

a pressure actuated sleeve shifting mechanism, where increasing pressure tending to cause axial movement of the external sealing sleeve, such axial movement being resisted until a pre-selected pressure threshold is reached to permit movement of the external sealing sleeve to open the at least one fluid flow port.

2. The apparatus of claim 1, wherein the pressure actuated sleeve shifting mechanism is a fluid cavity formed between the external sealing sleeve and the exterior surface of the tubular body, the fluid cavity being asymmetrical to provide an asymmetrical pressure distribution so that increasing pressure within the fluid cavity tends to cause axial movement of the external sealing sleeve.

3. The apparatus of claim 1, wherein the pressure actuated sleeve shifting mechanism is an inclined plane in fluid pressure communication with at least one fluid flow port.

4. The apparatus of claim 1, wherein the external sleeve has a first end with a first internal diameter that engages a first sealing area on the exterior surface of the tubular body on a first side of the annular flow area and the external sleeve has a second end with a second internal diameter that engages a second sealing area on the exterior surface of the tubular body on a second side of the annular flow area.

5. The apparatus of claim 4, wherein the first sealing area has a first seal groove in which is positioned a first O-ring seal and the second sealing area has a second seal groove in which is positioned a second O-ring seal.

6. The apparatus of claim 1, wherein a locking engagement is provided between the external sealing sleeve and the exterior surface of the tubular body to lock the external sealing sleeve in the open position.

7. The apparatus of claim 6, wherein several resilient fingers are carried by the external sealing sleeve and the exterior surface of the tubular body has an engagement profile that the resilient fingers engage to maintain the external sealing sleeve in the open position.

8. The apparatus of claim 1, wherein the external sealing sleeve is detachably secured to the exterior surface of the tubular body by shear pins.

9. The apparatus of claim 8, wherein one selects the pre-selected pressure threshold at which the external sealing sleeve moves by using a greater number or fewer number of shear pins.

10. The apparatus of claim 8, wherein the exterior surface of the tubular body has a circumferential shear pin groove to accommodate the shear pins.

11. A method for use in selectively fracing a well, comprising:

(a) providing a plurality of apparatus, each apparatus comprising:

a pressure actuated sleeve shifting mechanism, where increasing pressure tending to cause axial movement of the external sealing sleeve, such axial movement being resisted until a pre-selected pressure threshold is reached to permit movement of the external sealing sleeve to open the at least one fluid flow port;

(b) deploying the apparatuses along a production tubing string in a well with packers being positioned between the apparatuses to isolate production areas, the pre-selected pressure threshold for each production area increasing from a toe of the well toward a heel of the well;

(c) selectively shifting an external sealing sleeve to an open position by applying fluid pressure to the pressure actuated sleeve shifting mechanism;

(d) continuing to apply fluid pressure to pump fluids into the earth formation through the apparatus that has had its external sealing sleeve moved to the open position;

(e) preventing additional flow through the apparatus that has had its external sealing sleeve moved to the open position;

(f) repeating steps (c), (d), and (e) to selectively open the external sealing sleeve in apparatus in the production tubing in stages working toward a wellhead of the well from a remote end of the well.

12. The method of claim 11, wherein the pressure actuated sleeve shifting mechanism is a fluid cavity formed between the external sealing sleeve and the exterior surface of the tubular body, the fluid cavity being asymmetrical to provide an asymmetrical pressure distribution so that increasing pressure within the fluid cavity tends to cause axial movement of the external sealing sleeve.

13. The method of claim 11, wherein the pressure actuated sleeve shifting mechanism is an inclined plane in fluid pressure communication with at least one fluid flow port.

14. The method of claim 11, wherein selectively shifting the external sealing sleeve to the open position comprises using an isolation tool inserted into the tubular body, the isolation tool isolating fluid pressure to a desired portion of the interior surface of the tubular body.

15. The method of claim 11, wherein selectively shifting the external sealing sleve to the open position comprises pumping fluids down the production tubing at pressures just sufficient to selectively shift the external sealing sleeve of the apparatus having a lowest shifting pressure to an open position without shifting the external sealing sleeve of others of the apparatus having higher shifting pressures.

16. The method of claim 11, wherein preventing additional flow comprises:

pumping balls down the production tubing until the balls seat on and close the at least one fluid flow port on the apparatus that has had its external sealing sleeve moved to the open position; and

using fluid pressure to maintain the balls seated on the at least one fluid flow port while other of the external sealing sleeves in the production tubing are selectively moved to the open position.

17. In combination:

a production tubing string having a plurality of apparatuses for use in selectively fracing a well and an isolation tool, each apparatus for use in selectively fracing a well comprising:

an external sealing sleeve detachably secured to the exterior surface of the tubular body to selectively cover the annular flow area and close the at least one fluid flow port; and

a pressure actuated sleeve shifting mechanism, where increasing pressure tending to cause axial movement of the external sealing sleeve, such axial movement being resisted until a pre-selected pressure threshold is reached to permit movement of the external sealing sleeve to open the at least one fluid flow port; and

an isolation tool at least partially extended into the production tubing string, comprising:

a tubular body having a fluid input in fluid communication with a fluid output;

seals positioned on either side of the fluid output, the seals being adapted to seal against the interior surface of the tubular body such that fluid flowing from the output is isolated to a desired portion of the interior surface of the tubular body.

18. An isolation tool for selectively applying pressure to a pressure actuated opening of an outer tubular body, the isolation tool comprising:

a tubular body carrying a first sealing element and a second sealing element, the tubular body having a fluid inlet and a fluid outlet, the tubular body being movable within the outer tubular body;

a pressure cavity defined by an outer surface of the tubular body, the inner surface of the outer tubular body, and the first and second sealing elements, the fluid outlet of the tubular body being in fluid communication with the pressure cavity;

the first sealing element and the second sealing element permitting fluid flow into the pressure cavity and sealing against fluid flow out of the pressure cavity.

19. The isolation tool of claim 18, further comprising an equalizing valve that is open when the isolation tool is being run into the outer tubular body and closes upon application of the fluid pressure within the pressure cavity.