Title:
Packer washout assembly
Kind Code:
A1


Abstract:
A packer washout assembly for removing debris from a well bore is disclosed. The packer washout assembly includes a tubing string positioned in the well bore and forming an annulus with the well bore. A packer is interposed in the tubing string and is sealable against the interior of the well bore. A packer washout sub is connected to an upper end of the packer. The packer washout sub includes a mandrel having at least one fluid flow port extending through a sidewall and a rupture disk positioned in the fluid flow port of the mandrel. The rupture disk is adapted to rupture upon the application of a predetermined pressure within the fluid passage of the mandrel so as to place the fluid passage in fluid communication with the annulus to permit fluid to pass through the fluid port from the mandrel to the annulus and thereby circulate fluid over the top of the packer so as to wash debris from the top of the packer.



Inventors:
Witcher, Harold L. (Atoka, OK, US)
Application Number:
11/229781
Publication Date:
03/22/2007
Filing Date:
09/16/2005
Primary Class:
Other Classes:
166/312
International Classes:
E21B37/00
View Patent Images:
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Primary Examiner:
ANDREWS, DAVID L
Attorney, Agent or Firm:
DUNLAP CODDING, P.C. (PO BOX 16370, OKLAHOMA CITY, OK, 73113, US)
Claims:
What is claimed is:

1. A packer washout assembly for removing debris from a well bore, comprising: a tubing string positioned in the well bore and forming an annulus with the well bore; a packer interposed in the tubing string and sealable against the interior of the well bore, the packer having an upper end and a lower end; a packer washout sub comprising: a mandrel having an upper end connected to the tubing string, a lower end connected to the upper end of the packer, and a sidewall extending from the upper end to the lower end, the sidewall defining a fluid passage extending from the upper end to the lower end, the mandrel having at least one fluid flow port extending through the sidewall; and a closure member positioned in the fluid flow port of the mandrel, the closure member adapted to open upon the application of a predetermined pressure within the fluid passage of the mandrel so as to place the fluid passage in fluid communication with the annulus to permit fluid to pass through the fluid port from the mandrel to the annulus and thereby circulate fluid over the top of the packer so as to wash debris from the top of the packer.

2. The packer washout assembly of claim 1 wherein the mandrel includes a plurality of fluid ports, each fluid port has a closure member positioned therein.

3. The packer washout assembly of claim 1 wherein the mandrel includes a plurality of fluid flow ports extending through the sidewall, the fluid ports longitudinally axially aligned from the lower end to the upper end of the mandrel, each fluid flow port having a closure member positioned therein.

4. The packer washout assembly of claim 1 wherein the mandrel includes a plurality of fluid flow ports extending through the sidewall, the fluid ports arranged in a helical pattern about the sidewall of the mandrel, each fluid flow port having a closure member positioned therein.

5. The packer washout assembly of claim 1 wherein the mandrel includes a plurality of fluid flow ports extending through the sidewall, the fluid ports circumferentially spaced an equal distance about the mandrel, each fluid flow port having a closure member positioned therein.

6. A packer washout assembly for removing debris from a well bore, comprising: a tubing string positioned in the well bore and forming an annulus with the well bore; a packer interposed in the tubing string and sealable against the interior of the well bore, the packer having an upper end and a lower end; a packer washout sub comprising: a mandrel having an upper end connected to the tubing string, a lower end connected to the upper end of the packer, and a sidewall extending from the upper end to the lower end, the sidewall defining a fluid passage extending from the upper end to the lower end, the mandrel having at least one fluid flow port extending through the sidewall; and a rupture disk positioned in the fluid flow port of the mandrel, the rupture disk adapted to open upon the application of a predetermined pressure within the fluid passage of the mandrel so as to place the fluid passage in fluid communication with the annulus to permit fluid to pass through the fluid port from the mandrel to the annulus and thereby circulate fluid over the top of the packer so as to wash debris from the top of the packer.

7. The packer washout assembly of claim 6 wherein the mandrel includes a plurality of fluid ports, each fluid port having a rupture disk positioned therein.

8. The packer washout assembly of claim 6 wherein the mandrel includes a plurality of fluid flow ports extending through the sidewall, the fluid ports longitudinally axially aligned from the lower end to the upper end of the mandrel, each fluid flow port having a rupture disk positioned therein.

9. The packer washout assembly of claim 6 wherein the mandrel includes a plurality of fluid flow ports extending through the sidewall, the fluid ports arranged in a helical pattern about the sidewall of the mandrel, each fluid flow port having a rupture disk positioned therein.

10. The packer washout assembly of claim 6 wherein the mandrel includes a plurality of fluid flow ports extending through the sidewall, the fluid ports circumferentially spaced an equal distance about the mandrel, each fluid flow port having a rupture disk positioned therein.

11. A method for removing debris from the top of a packer sealed against a well bore, comprising: producing fluid through a tubing string positioned in the well bore, the tubing string forming an annulus with the well bore, the tubing string having a packer interposed therein, the packer sealed against the interior of the well bore and the packer having an upper end and a lower end, the tubing string further having a packer washout sub, the packer washout sub comprising: a mandrel having an upper end connected to the tubing string, a lower end connected to the upper end of the packer, and a sidewall extending from the upper end to the lower end, the sidewall defining a fluid passage extending from the upper end to the lower end, the mandrel having at least one fluid flow port extending through the sidewall; and a rupture disk positioned in the fluid flow port of the mandrel; sealing the tubing string; and pressurizing the tubing string to a sufficient pressure to rupture the rupture disk of the packer washout sub so as to place the fluid passage of the mandrel in fluid communication with the annulus to permit fluid to pass through the fluid port from the mandrel to the annulus and thereby circulate fluid over the top of the packer so as to wash debris from the top of the packer.

12. A method for removing debris from the top of a packer sealed against a well bore, comprising: providing a tubing string in the well bore so that the tubing string forms an annulus with the well bore, the tubing string having a packer interposed therein, the packer sealed against the interior of the well bore and the packer having an upper end and a lower end, the tubing string further having a packer washout sub, the packer washout sub comprising: a mandrel having an upper end connected to the tubing string, a lower end connected to the upper end of the packer, and a sidewall extending from the upper end to the lower end, the sidewall defining a fluid passage extending from the upper end to the lower end, the mandrel having at least one fluid flow port extending through the sidewall; and a rupture disk positioned in the fluid flow port of the mandrel; sealing the tubing string; and pressurizing the tubing string to a sufficient pressure to rupture the rupture disk of the packer washout sub so as to place the fluid passage of the mandrel in fluid communication with the annulus to permit fluid to pass through the fluid port from the mandrel to the annulus and thereby circulate fluid over the top of the packer so as to wash debris from the top of the packer.

Description:

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to an apparatus for washing debris from a well bore, and more particularly, but not by way of limitation, to an apparatus and method for washing debris from a packer set in a well bore to permit the packer to be released.

2. Brief Description of Related Art

Packers are downhole tools widely used in the completion of oil and gas wells to isolate and control producing and injected fluids. A variety of packers are known. Packers are often classified as either permanent or retrievable. A permanent packer is recovered from the well bore by using milling tools, while a retrievable packer is designed to be released and retrieved on the production tubing or on a workstring.

A concern of well operators when setting a retrievable packer is the possibility of debris, such as sand, shale, or rust, settling on top of the packer and prohibiting the release of the packer. When this occurs one of several things may be attempted to retrieve the packer from the well bore. First, the tubing may be shot off just above the packer thereby permitting the majority of the tubing to be removed from the well bore. Next, an operator may fish back on the tubing in attempt to release the packer. Finally, if all the above fail, then the packer is milled out, or the well may be abandoned.

Each of these procedures is time consuming and expensive. As such, a need exists for a tool that may be used with a packer to allow debris to be selectively removed from the packer when required. However, such an improved tool must also be cost efficient and substantially maintenance-free. It is to such a tool and method of use that the present invention is directed.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

FIG. 1 is a schematic illustration, partially in cross section, of a packer washout assembly constructed in accordance with the present invention.

FIG. 2 is a cross sectional view of a packer washout sub.

FIG. 3 is a cross sectional view of another embodiment of a packer washout sub constructed in accordance with the present invention.

FIG. 4 is a cross sectional view of another embodiment of a packer washout sub constructed in accordance with the present invention.

FIG. 5 is a schematic illustration, partially in cross section, of another embodiment of a packer wash out assembly constructed in accordance with the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Referring now to FIG. 1, a packer washout assembly 10 constructed in accordance with the present invention for removing debris, such as sand, silt, shale, and rust, from the top of a packer 20 to permit the packer to be released is schematically illustrated. A well bore 12 is shown to be lined with a casing 14 extending down from a wellhead 15. The casing 14 provides a permanent borehole through which production operations may be conducted. The casing 14 is affixed in the well bore 12 in a conventional manner, such as by cement (not shown), and is provided with perforations 16 open to a producing subterranean formation 17.

The packer washout assembly 10 includes a tubing string 18, a packer 20, and a packerwashout sub 22. The tubing string 18 provides fluid communication between the producing subterranean formation 17 and a surface 24 such that a reservoir fluid (not shown), for example oil and/or natural gas, is produced through the tubing string 18. The casing 14 and the tubing string 18 define an annulus 26 which also provides fluid communication through the well bore 12.

The packer 20 is interposed in the tubing string 18 in a manner well known in the art. The packer 20 is commonly known as a retrievable packer in that it is designed to be inserted in the casing 14 when in a deflated or relaxed condition, set so as to seal against the interior wall of the well bore 12, and then released when it is desired to remove the tubing string 18 and the packer 20 from the well bore 12. As mentioned above, release of the packer 20 may be hindered by the accumulation of debris on top of the packer 20.

The packer washout sub 22 is interposed in the tubing string 18 by connecting the packer washout sub 22 to the top of the packer 20. As best shown in FIG. 2, the packer washout sub 22 includes a mandrel 30 having an upper end 32 adapted to be threadingly coupled to the tubing string 18, a lower end 34 adapted to be threadingly coupled to the upper end 32 of the packer 20, and a sidewall 36 extending from the upper end 32 to the lower end 34. The sidewall 36 defines a fluid passage 38 extending from the upper end 32 to the lower end 34 so as to permit fluid flow between the tubing string 18 and the packer 20. The mandrel 30 has at least one fluid port 40 extending through the sidewall 36; however, preferably, the mandrel 30 has a plurality of fluid ports 40. FIG. 2 shows one version where three fluid ports 40 are longitudinally aligned from the lower end 34 to the upper end 32 of the mandrel 30 along one side of the mandrel 30.

To close the fluid ports 40, a closure member 42 is positioned in each of the fluid ports 40 of the mandrel 30 to close the fluid ports 40 during normal well operations. The closure members 42 are illustrated as being rupture disks that are screwed into the fluid ports 40 or otherwise secured in the fluid ports 40. The rupture disks 42 are adapted to rupture upon the application of a predetermined pressure within the fluid passage 38 of the mandrel 30 so as place the fluid passage 38 in fluid communication with the annulus 26 to permit fluid to pass through the fluid port 40 from the mandrel 30 to the annulus 26 and thereby circulate fluid over the top of the packer 20 so as to wash debris from the top of the packer 20.

The rupture disks 42 selected to be positioned in the fluid ports 40 must maintain their integrity under normal fluid production or injection operations. For example, if the tubing string 18 will be subject to 1000 psi during production operations, a rupture disk rated to rupture at 2,500 psi may be selected. On the other hand, if the tubing string 18 is being used for the injecting fluid into a formation, the tubing string 18 may be subject to 5,000 psi. In this case, a rupture disk rated to rupture at 10,000 psi may be selected.

FIGS. 3 and 4 illustrate other embodiments of a packer washout sub 22a and 22b, respectively. FIG. 3 shows the packer washout sub 22a having four fluid ports 40a arranged in a helical pattern about the sidewall 36 of the mandrel 30a. A rupture disk 42a is positioned in each of the fluid ports 40a. FIG. 4 shows the packer washout sub 22b having four fluid ports 40b that are circumferentially spaced an equal distance about the mandrel 30b. A rupture disk 42b is positioned in each of the fluid ports 40b.

The packer washout sub 22 is used in the event that the packer 20 fails to release due to the accumulation of debris (depicted in FIG. 1 by the reference numeral 48) such as sand, shale, silt, or rust, on top of the packer 20. Upon determining that the packer 20 is stuck, a standing valve 46 is landed on a seating nipple (not shown) to close off the tubing string 18 from below the packer washout sub 22. Next, the tubing string 18 is pressurized with fluid, such as water, to a pressure sufficient to rupture the rupture disks 42. Upon the rupture disk 42 rupturing, fluid communication between the fluid passage 38 of the mandrel 30 and the annulus 26 is established to permit fluid to pass from the mandrel 30 through the fluid port 40 and into the annulus 26. In the annulus 26, fluid is circulated through the debris, over the top of the packer 20, and finally to the surface 24 so as to carry the debris to the surface 24 and thereby wash the debris from the top of the packer 20. After the debris has been washed from the top of the packer 20, the packer is released and the tubing string 18, along with the packer washout sub 22 and the packer 20, is withdrawn from the well bore 12.

FIG. 5 illustrates the use of a packer washout sub 22 in a tubing string 18a. The tubing string 18a includes a packer 20a and a plug 48. The tubing string 18 provides fluid communication between producing subterranean formation 50 and a surface 52 such that a reservoir fluid (not shown), for example oil and/or natural gas, is produced through the tubing string 18a. A casing 14a is affixed in a well bore 12a in a conventional manner, such as by cement (not shown), and is provided with perforations 54 open to the producing subterranean formation 50. It will be noted that the producing subterranean formation 50 is above the packer 20a. As such, the tubing string 18a is provided with perforations 56 to permit fluid passing from the formation 50 to pass into the tubing string 18a.

In the situation where the packer 20a fails to release and the tubing string 18a is perforated above the packer 20a, the perforations 56 are first sealed prior to pressuring the tubing string 18a for the purpose of rupturing the rupture disks 42. The perforations 56 may be sealed by inserting balls 58 into a stream of fluid injected into the tubing string 18a at the surface 52. The balls 58 will lodge in the perforations 56 and thereby seal the perforations 56. Upon determining that the perforations 56 are sealed by an increase in fluid pressure, the fluid pressure in the tubing string 18a is further increased to a pressure sufficient to rupture the rupture disks 42. Upon the rupturing of the rupture disks 42, fluid is circulated through the debris (depicted in FIG. 5 by the reference numeral 60), over the top of the packer 20a, and finally to the surface 52 so as to carry the debris to the surface 52 and thereby wash the debris from the top of the packer 20a. After the debris has been washed from the top of the packer 20a, the packer 20a is released and the tubing string 18a, along with the packer washout sub 22 and the packer 20a, is withdrawn from the well bore 12a.

From the above description it is clear that the present invention is well adapted to carry out the objects and to attain the advantages mentioned herein as well as those inherent in the invention. While presently preferred embodiments of the invention have been described for purposes of this disclosure, it will be understood that numerous changes may be made which will readily suggest themselves to those skilled in the art and which are accomplished within the spirit of the invention disclosed and as defined in the appended claims.