Wells – Processes – Graveling or filter forming
Reexamination Certificate
1999-05-14
2001-10-16
Neuder, William (Department: 3672)
Wells
Processes
Graveling or filter forming
C166S051000, C166S334400
Reexamination Certificate
active
06302208
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to the field of isolation systems and gravel pack assemblies for use in a wellbore. More particularly, the invention provides an improved system and method for zone isolation following gravel pack completions installed in a wellbore.
2. Description of the Prior Art
Typical prior art isolation systems involve intricate positioning of tools which are installed down-hole after the gravel pack. An example of this type of system is available from Baker. This system utilizes an anchor assembly which is run into the well bore after the gravel pack. The anchor assembly is released by a shearing action, and subsequently latched into position.
Certain disadvantages have been identified with these systems. For example, prior conventional isolation systems have had to be installed after the gravel pack, thus requiring greater time and extra trips to install the isolation assemblies. Also, prior systems have involved the use of fluid loss control pills after gravel pack installation, and have required the use of thru-tubing perforation or mechanical opening of a wireline sliding sleeve to access alternate or primary producing zones. Since multiple trips into the well are required for gravel pack and isolation, these systems are time consuming methods and provide less flexibility and reliability.
An example of an isolation washpipe for well completions is disclosed in U.S. Pat. No. 5,343,949, incorporated herein by reference. In this system, there is an expansion joint which is used to push a closing sleeve into a closed position over the production screen.
More recently, isolation systems have been developed which do not require the running of tailpipe and isolation tubing separately. Instead, the system uses the same pipe to serve both functions: as tailpipe for circulating-style treatments and as production/isolation tubing. An example of this type of isolation system is disclosed in U.S. Pat. No. 5,865,251, incorporated herein by reference. An isolation sleeve is installed inside the production screen at surface and placed in the wellbore simultaneously with the service tool. The isolation sleeve is thereafter controlled in the wellbore by means of the inner service string. This system is adapted for well control purposes and for well bore fluid loss control. It combines simplicity, reliability, safety and economy, while also affording flexibility in use.
However, '251 provides only small orifices for circulation of the gravel pack fluid through the isolation sleeve. Further, '251 allows debris to become trapped between the production screen and the isolation sleeve. Further, because the washpipe extends through the isolation sleeve during the gravel pack operation, there is the possibility that debris will become lodged between the isolation sleeve and the wash pipe. This debris could cause the washpipe to hang or jam upon withdrawal so that the entire service string is permanently lodged in the isolation sleeve. Therefore, there is a need for a system which allows the isolation sleeve to be closed without a washpipe extending through the isolation sleeve. Further, there is a need for an isolation sleeve which does not allow debris to become accumulated between the isolation sleeve and the production screen and which allows fluid to freely pass through the isolation sleeve during the gravel pack operation.
SUMMARY OF THE INVENTION
The present invention is a system and method for providing full fluid flow through the production screen during a gravel pack operation and which does not allow debris to accumulated between the isolation system and the production screen. Further, the isolation system is closeable immediately upon completion of the gravel pack operation by the service tool which performed the gravel pack. Closure of the isolation system may even be accomplished without a wash pipe extending through the isolation system. The system comprises an activation tool which allows the isolation system to operate between the open and closed positions.
According to one aspect of the invention, there is provided an isolation system having: an isolation string, wherein the isolation string has a packing assembly which secures the isolation string in a wellbore casino, wherein the isolation string has a production screen which allows production fluid to pass into the isolation string; an isolation sleeve which slides within the isolation string between open and closed positions; a locking device which locks and unlocks the isolation sleeve in an open position; and an activation tool which allows the isolation sleeve to move to a closed position, wherein the open position allows fluid communication between the production screen and an interior portion of the isolation string and the closed position prevents fluid communication between the production screen and an interior portion of the isolation string.
According to a further aspect of the invention, there is provided an isolation system having: an isolation string, wherein the isolation string has a packing assembly which secures the isolation string in a wellbore casing, wherein the isolation string has a production screen which allows production fluid to pass into the isolation string; an isolation sleeve which slides within the isolation string between open and closed positions, wherein the open position allows fluid communication between the production screen and an interior portion of the isolation string and the closed position prevents fluid communication between the production screen and an interior portion of the isolation string, wherein the isolation sleeve comprises at least one isolation valve which is coupled within the isolation sleeve, wherein the at least one isolation valve is movable between open and closed positions; a locking device which locks and unlocks the isolation sleeve in an open position, wherein the locking device comprises a trigger that secures the isolation sleeve to the isolation string before the trigger is activated and releases the isolation sleeve from the isolation string after the trigger is activated, wherein the trigger comprises: a piston collar having a solid cylindrical portion attached to the isolation sleeve and a finger portion having at least one finger, wherein the at least one finger has a head at a distal end; and at least one recess in the isolation string, wherein the head of the at least one finger is engaged in the at least one recess; a cylindrically shaped pop lock positioned adjacent the head of the at least one finger so that the head is between the pop lock and the recess, wherein the pop lock secures the head relative to the recess; and a latch attached to the service tool which couples with the pop lock, wherein the trigger is activated by removing the pop lock from the position adjacent the head; and an activation tool which allows the isolation sleeve to move to a closed position, wherein the activation tool is a piston driven by a hydrostatic chamber which comprises lower pressure within the hydrostatic chamber than without, and wherein the piston moves the isolation sleeve from the open to the closed position.
According to an even further aspect of the invention, there is provided a process for isolating a production zone within a well, the process having the steps of: installing an isolation string and a service tool simultaneously within the well adjacent the production zone, wherein the isolation string comprises an isolation sleeve; locking the isolation sleeve in an open position during the installing an isolation string, wherein the open position allows fluid communication between the production screen and an interior portion of the isolation string; unlocking the isolation sleeve with the service tool; and moving the isolation sleeve to a closed position, wherein the closed position prevents fluid communication between the production screen and an interior portion of the isolation string.
Other and further features and advantages will be apparent from the following descri
Richards William Mark
Walker David Joseph
Baker & Botts L.L.P.
Neuder William
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