Wells – Processes – Disassembling well part
Utility Patent
1998-04-30
2001-01-02
Suchfield, George (Department: 3672)
Wells
Processes
Disassembling well part
C166S151000, C166S181000, C166S182000, C166S324000, C166S387000
Utility Patent
active
06167970
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates generally to methods and apparatus for well completions and, more particularly, to methods and apparatus for setting and/or releasing from isolation tools within a well. Specifically, this invention relates to methods and apparatus for equalizing pressure differentials existing across the seals of a well isolation tool, such as a packer or bridge plug, during tool setting operations.
2. Description of Related Art
In well completions, it is often desirable to isolate one or more sections of a well from another. For example, one completion zone may be isolated from another so that only one completion zone is open for production or injection at a time. Such isolation may be accomplished by the placement of one or more isolation tools, such as packers and/or bridge plugs, in the wellbore on either or both sides of one or more completion zones. Isolation tools are typically annular in shape and configuration. The sequence of production from, or injection into, isolated completion zones formed by such tools and related well equipment is typically dictated by well and reservoir conditions. Such conditions may include different fluid loss characteristics from zone to zone, downhole well pressures which differ from zone to zone, and differing mineralogical conditions from zone to zone. In other cases, legal or regulatory requirements may dictate that individual zones be completed for production or injection individually. In still other cases, completion, workover and/or remedial operation concerns may dictate that individual zones be isolated and treated separately.
During well operations, an isolation tool may be set in a wellbore at a point below which no open perforations exist. This has the effect of creating a “closed volume” between the isolation tool and the bottom of the well. For example, a wireline or pipe-conveyed bridge plug may be set to form a plugback depth in order to eliminate unnecessary open wellbore at the bottom of the hole. In other cases, it may be desirable to position a wireline or pipe-conveyed packer prior to perforation and completion of wellbore intervals below the setting depth of the tool. Such completions are often made in relatively high or low pressure formations using pipe-conveyed perforating guns by setting a packer above the zone of interest with pipe conveyed perforating guns extending across the formation of interest. Once the packer is set, the zone of interest below the packer may be perforated with tubing or drill pipe in the hole so that the well casing above the packer is not exposed to the pressure of the formation. In other cases, a packer may be set above the zone of interest and through-pipe perforating guns may then be run out the end of the packer to perforate the formation. In still other cases, a sump packer may be first set between two zones of interest. A second packer and completion assembly may then be run and set above the upper zone of interest. In such cases, the completion assembly may include a seal assembly for location in the lower packer. This completion configuration allows the upper zone to be completed for production, treatment or injection first, while still allowing later completion in the lower zone through the sump packer. In still other cases, one or more zones of interest may be simultaneously completed in a similar manner and selectively produced using selective completion devices including, but not limited to, sliding sleeves and/or internal tubing plugs. The foregoing are just a few of the multitude of possible multiple and/or selective completion schemes that may be implemented using methods and apparatus known to those of skill in the art. In any of the aforementioned cases, it is typically necessary to retrieve a setting tool from a packer prior to adding perforations below the packer.
During gravel pack procedures, a region between two packers or between a bridge plug and packer may be gravel packed and isolated. In this method, a first isolation tool, such as a sump packer, may be set at a first location within a wellbore below the zone of interest and typically at a point below which no perforations exist. A gravel pack screen assembly may then be run into the wellbore on a second packer which may be positioned and set within the wellbore at a second location above the zone of interest. The zone of interest is typically perforated at some time prior to running the second packer. The zone may then be gravel packed using procedures known in the art. Using such a completion configuration, the gravel packed completion interval may be first produced while allowing for the possibility of future production of another zone located beneath the sump packer by, for example, later perforating a region below the sump packer with a through-pipe perforating gun. Another possible completion method may comprise selectively producing the region located between first and second packers and a region located below the first packer using isolation selective producing apparatus such as sliding sleeves, tubing plugs, etc. In still other cases, an upper completion interval may be gravel packed and isolated with, for example, a sliding sleeve and the lower completion interval then perforated through pipe and selectively produced as described above. In such completions, it is typically necessary to retrieve a setting tool from the first isolation tool under conditions in which a closed volume exists below the isolation tool.
During these and other types of wellbore operations, when a isolation tool such as a packer or bridge plug is set at a point in a wellbore having no perforations open below the setting point, a setting tool when pulled from the isolation tool may cause a vacuum or reduced pressure condition to exist below the isolation tool relative to the pressure existing above the isolation tool. Such a pressure differential typically acts on sealing elements or apparatus of the setting tool so that an unacceptably large amount of force may be required to pull the setting tool from is the isolation tool. When the force required to pull the setting tool from the isolation tool exceeds the maximum allowable pulling force, for example of tubing used to set the isolation tool, tubing failure may occur prior to the point where the setting tool becomes unseated from the isolation tool. In such cases, the setting tool may be referred to as being “differentially stuck” in the isolation tool. When such a condition exists, it may be necessary to perforate the tubing in order to equalize the pressure, or even to sever the tubing so that it may be retrieved from the hole. Perforating or severing the tubing is undesirable because it may damage downhole completion assemblies leaving the isolation tool and/or setting tool in unusable condition, and even potentially “junking” the well. In some cases, a sufficient pressure differential may be created during attempted pulling of a setting tool such that a collapse force is generated across the isolation tool components resulting in tool failure.
Undesirably high pressure differentials may also be created when pulling a setting tool out of an isolation tool even where open perforations exist below the isolation tool. Such a problem may exist, for example, where the perforations are of limited entry into the formation, where a formation is very tight (or has very low permeability), and/or where the permeability of a perforated formation is damaged.
SUMMARY OF THE INVENTION
The disclosed method and apparatus may be used for setting or retrieving an isolation tool in a well, particularly in situations in which a pressure differential exists across the seals of the tool. Such situations include those where a substantially closed volume exists below the isolation tool, for example, where no perforations, mechanical isolation, ineffective perforations or perforations into low permeability or damaged formations exist below the isolation tool. Advantageously, the disclosed method and apparatus provide for, among other thing
Matte James T.
Stout Gregg W.
B J Services Company
Howrey Simon Arnold & White , LLP
Suchfield George
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