Single trip perforation/packing method

A method for performing single trip perforation and packing operations via a downhole assembly in a cased well bore is described. The assembly is provided with an upper packer and a lower packer and has fluid communication established therethrough. The upper packer of the assembly is set to isolate a perforated production zone by introducing pressurized fluid through the assembly and against the casing below the lower packer of the assembly.

BACKGROUND

Downhole packers are commonly used in many oilfield applications for the purpose of sealing against the flow of fluid to isolate one or more portions of a well bore for the purposes of testing, treating or producing the well. The packers are suspended in the well bore, or in a casing in the well bore, from a work string, or the like, and are activated, or set, so that one or more packer elements engage the inner surface of the well bore or casing to isolate various zones in the well bore.

Sand control methods are often used to prevent production of formation sand during downhole operations. According to one of these methods, a single trip process may be employed wherein perforation of a hydrocarbon interval (production zone) and setting of packing elements may be accomplished in one trip down the well bore. In a single trip perforation and packing process, a production screen is placed in the well bore, usually between an upper and lower packer. The packers are set and the annulus surrounding the production screen is then packed with a prepared sand/gravel slurry of a specific size designed to prevent the passage of formation sand. This also stabilizes the formation while causing minimal impairment to well productivity.

Conventional single trip sand control methods require a plugging device to be inserted into the above system to set the upper packer. To prevent the various tools and seals associated with the above-described assembly from becoming hydraulically locked after setting of the upper packer, a mechanical or hydraulic-operated venting device is typically inserted into the assembly to prevent hydraulic locking. However, this operation adds to the cost and time of the single trip sand control method.

Therefore, what is needed is an improved method for performing single trip perforating and packing operations within a well bore while eliminating the need to insert a plugging device to set the upper packer, thereby avoiding the problem of

DETAILED DESCRIPTION

Referring toFIGS. 1 and 2, an assembly for performing single trip perforation and packing operations is referred to, in general, by the reference numeral10and is shown installed in a casing12disposed in a well bore. The assembly10includes a tubular conduit14, such as a work string, which is lowered from a ground surface (not depicted) to a predetermined depth in the casing12. The work string14and the casing12cooperate to define an annulus15between the work string and the casing.

The work string14is connected to an upper packer16having a longitudinal flow passage (not depicted) disposed therethrough such that fluid communication is established from the surface, through the work string, and to and through the upper packer. The upper packer16will be further described with respect to the operation.

A gravel pack assembly18is connected below the upper packer16and includes a tubular housing20for housing various components of the gravel pack assembly as will be described. The gravel pack assembly18and the casing12cooperate to define an annulus21.

The gravel pack assembly18includes a service tool22, a portion of which is depicted inFIG. 1, which is disposed within the housing20and operates to provide sand control operations as will be further described. The service tool22is of any hydraulic and/or mechanical design and, as such, will not be described in detail. One service tool22that may be used with the current method is disclosed in U.S. Pat. No. 4,372,384 and is incorporated herein by reference.

The service tool22includes a conduit23disposed concentrically with the housing20such that fluid communication is continued from the upper packer16to and through the service tool22. A plurality of flow ports24are formed radially through the housing20, and as shown inFIG. 1, do not initially fluidly communicate with the conduit23. A pair of longitudinally-spaced, annular screen sections26are wrapped around corresponding sections of the housing20to aid in sand control operations during production of a production zone28as will be described.

A wash pipe30, of which the downstream end is depicted inFIG. 1, is connected to the downstream end of the service tool22and extends through the section of housing20receiving the screen sections26. The wash pipe30is connected to a tubular seal assembly32, which is initially sealed into the housing20. The seal assembly32includes a plurality of seals34for forming a sliding seal arrangement with the housing20. The above-described arrangement allows for fluid communication to be established from the conduit23to and through the wash pipe30and the seal assembly32.

A lower packer36is connected to the downstream end of the housing20via any conventional means. The lower packer36is a conventional packer which is set, or activated, causing it to engage the inner surface of the casing12to seal against the annular flow of fluids and permit hydraulic isolation of the production zone28. The lower packer36, like the upper packer16, includes a longitudinal flow passage (not depicted) disposed therethrough such that fluid communication is continued from the tubular seal assembly32to and through the lower packer.

A section of tubing38connects to the downstream end of the lower packer36and extends therefrom. The tubing38and the casing12cooperate to define an annulus39. A plurality of vent ports40are formed radially through the tubing38such that fluid communication is established from the lower packer36, through the tubing38, and into the annulus39. Thus, fluid communication is established from the ground surface (not depicted), through the assembly10, and to the vent ports40.

A perforating gun assembly42is connected to the downstream end of the tubing38and is adapted to perforate the casing12to permit the flow of fluids into and from the casing. The gun assembly42is of a conventional design and, as such, comprises perforating guns and gun carriers and a mechanically or hydraulically operated firing head device with a ported sub. Since these components are all conventional they are not shown, nor will they be described, in detail. A plugging device44is disposed below the assembly10for reasons to be described with respect to the operation.

Referring toFIG. 2, a portion of the assembly10is shown lowered further into the well bore to a position where the screen sections26are placed adjacent the production zone28.

In operation, referring toFIG. 1, the single trip assembly10is lowered, via the work string14, into the well bore to position the gun assembly42adjacent the production zone28. The lower packer36is set to isolate the production zone28during perforation. The perforating guns associated with the gun assembly42are then mechanically or hydraulically fired to perforate the casing12as shown.

Referring toFIG. 2, after the perforation is completed, the lower packer36and the gun assembly42(not depicted) are released and the work string14is positioned lower into the well bore, which positions the screen sections26adjacent the previously perforated production zone28. The lower packer36is then set to seal off the annulus39from the annulus21.

The lower packer36is then pressure tested by introducing pressurized fluid down and through the assembly10and against the casing12via the vent ports40. The tubing38is closed off via any conventional means below the vent ports40to allow for the above-described fluid path. The plugging device44(FIG. 1) provides for the hydraulic integrity needed to conduct such a pressure test. The pressure test confirms whether or not the screen sections26, and therefore the production zone28, are hydraulically isolated above the lower packer36. This is advantageous as pressure testing of the lower packer36is not possible with conventional sand control methods as such methods require a plugging device to be inserted into the assembly10, thereby preventing fluid flow beyond the plugging device.

Upon sealing below the screen sections26, the pressure of the pressurized fluid is increased and maintained through the assembly10and against the casing12below the lower packer36to cause setting of the upper packer16. While passing through the service tool22, the pressurized fluid exerts a hydraulic force on a hydraulic setting piston (not depicted) of the service tool22. The setting piston converts the hydraulic force into a mechanical force, which the service tool22utilizes to set the upper packer16. Thus, setting of the upper packer16is simplified as it is accomplished with the same method used to pressure test the lower packer36, albeit using pressurized fluid having an increased pressure.

Upon setting of the upper packer16, the upper packer is pressure tested by introducing pressurized fluid down the annulus15against the upstream end of the upper packer to ensure that the upper packer is properly set and the production zone28is properly isolated.

After setting and testing the upper packer16, the service tool22is released and lifted from the housing20by hydraulic or mechanical means. By releasing and lifting the service tool22, the seal assembly32, which is connected to the service tool via the wash pipe30, is disengaged from the housing20. The problem of hydraulic locking of the service tool22, the wash pipe30, and the seal assembly32is eliminated as no plugging device was inserted into the assembly10to set the upper packer16.

The service tool22, via the flow ports24, now serves as a pathway for pumping sand control treatment during production. As such, sand control operations commence in a conventional manner.

The above method mitigates against the possibility of hydraulic locking of the service tool22and the seal assembly32by eliminating the use of a plugging device, such as a packer setting ball, for setting the upper packer16. Furthermore, additional tools, such as venting devices, do not need to be inserted into the assembly10to prevent hydraulic locking. Rather, the service tool22, with the wash pipe30and seal assembly32attached thereto, are released and lifted without the problem of hydraulic locking. Thus, setting time of the assembly10is reduced and associated problems of placing a plugging device in the assembly to set the upper packer16are eliminated.

It is understood by those skilled in the art that various changes in form and detail may be made therein without departing from the spirit and scope of the invention. For example, a variety of service tools22may be used to implement the described method. Furthermore, a variety of seal assemblies32may be used to achieve a sliding seal arrangement with the housing20. For example, the seal assembly32may employ radially compressed molded seals. Moreover, the number of screen sections26is variable and is not limited to the arrangement of two screen sections as described. Furthermore, the plugging device44may be any of a variety of plugging devices such as a bridge plug.

Still further, the invention is not limited to the perforating process as described, but is equally applicable to other perforating methods. Moreover, a variety of additional tools may be used with the described method to accomplish various other downhole operations. Since other modifications, changes, and substitutions are intended in the foregoing disclosure, it is appropriate that the appended claims be construed broadly and in a manner consistent with the scope of the invention.