GB2483856A - Inflatable packer - Google Patents

Abstract

An external casing packer (ECP) for oil and gas wells uses a deformable sheath 7, preferably of metallic construction but possibly composite or laminate, to conform to the open hole or casing to provide a seal that does not rely on elastomers. The sheath is mounted on a pipe by a fixed end adapter 5 and an axially slidable end adapter 6 and is radially expandable in a controlled manner under application of internal pressure within the pipe via non-return check valves 9 in the fixed end adapter 5 and/or by mechanical loading. The outer surface of sheath 7 contains tooth features 8 in the form of sharp edged ring protrusions to prevent axial movement.

Description

1 Inflatable packer

3 This invention relates to an inflatable packer assembly 4 for use in oil and water/gas well applications.

6 Inflatable packers or external casing packers (FOPS) are 7 known in the industry. FOPs are used to form an annular 8 seal between the well bore and a tubing string inserted 9 into the wellbore. The basic construction of an FOP is a hollow central mandrel or core, on which is mounted a 11 bladder assembly. Via various porting devices, and 12 accessory tools, the bladder is inflated is situ. As the 13 bladder inflates, it comes into contact with the welibore 14 wall, forming a pressure seal. It is also understood that the FOP is also prevented from moving axially in the 16 weilbore, primarily due to the contact friction between 17 the bladder and the wellbore.

19 The construction of the bladder assembly as currently known in the industry is of a rubber or elastomeric 21 sheath, strengthened by metal ribs. The elastomeric 22 sheath is normally moulded onto the rib support 23 structure. The construction is akin to a radial or cross- 24 ply automotive tyre.

26 The limitations to the current state of the art are 27 known. As FOPs known in the industry use an elastomeric 1 sheath, the sheath itself can be susceptible to chemical 2 attack, age hardening due to the down hole environment, 3 creep or extrusion due to applied pressure differential 4 across the bladder.

6 An invention is disclosed which mitigates against the 7 limitations of the current state of the art.

9 The bladder assembly consists of a solid metal sheath, which is deformabie by applied pressure. The deformation 11 is controlled by the geometry of the metal sheath and 12 applied pressure and mechanical loading, which allows the 13 sheath to expand in a controlled manner to contact the 14 wellbore.

16 Preferably the sheath is of metallic construction, 17 although metal, composite and laminate structures are 18 possible.

Preferably the sheath radially expands in a controlled 21 manner, under application of internal pressure and/or 22 mechanical loading.

24 Preferably the sheath is mounted on a mandrel or core, which forms part of a down hole tubing string.

1 Preferably the bladder formed by the oore and sheath 2 contains a non-return valve to maintain applied pressure 3 to keep the sheath expanded against the wellbore wall.

A particular embodiment of the invention will now be 6 described with reference to the accompanying drawings 7 in which: 9 Figure lA shows the ECP within the wellbore in the "run-in" position.

12 Figure lB shows the ECP with the bladder inflated.

14 Figure 2 shows a preferred construction of the sheath and key features.

17 In figure 1A, the FCP 3A is installed on a tubing string 18 2 into a well bore 1 at the required position. Pressure 19 is applied inside the tubing string 2 which passes through a non-return valve 9 filling the bladder formed 21 by the core 4 and the sheath 7, ECP 2. The pressure 22 differential formed across the sheath causes the sheath 23 the plastically deform, ballooning the sheath until it 24 comes into contact with the well bore 1.

26 Figure 2 shows a schematic of the preferred construction 27 of the ECP. On the core 4, is mounted a fabricated 28 assembly, consisting of an upper gauge ring assembly 5, 1 sheath 7 lower gauge ring assembly 6. Preferably the 2 upper gauge ring assembly contains a fluid access path 3 and non-return valve or valves 9, used to inflate the 4 ECP. Preferably, the lower gauge ring 6 allows for axial movement, to accommodate shortening of the unit as the 6 sheath radially expands. It also contains a seal such as 7 an c-ring 10 with maintains the integrity of the bladder 8 assembly.

The cuter surface of the sheath 7, contains tooth 11 features 8, which are used tc prevent axial movement of 12 the ECP when the sheath is expanded. The form of the 13 tooth is preferably a plurality of sharp edged 14 prctrusicns in rings around the outer surface cf the sheath.

17 In can be seen to these skilled in the art that various 18 changes may be made to the features within these 19 embodiments, without departing from the spirit of the invention.