Device for use with a retrievable bridge plug

Details Device for use with a retrievable bridge plug Device for use with a retrievable bridge plug

1999-07-30

2001-05-22

Schoeppel, Roger (Department: 3672)

Wells

Packers or plugs

With expanding anchor

C166S134000

Reexamination Certificate

active

06234249

ABSTRACT:

CROSS-REFERENCE TO RELATED APPLICATIONS
This is the national stage of International Application No. PCT/NO98/00009 filed Jan. 12, 1998 which claims priority from Norwegian Patent Application No. 970561 filed Feb. 6, 1997.
BACKGROUND OF THE INVENTION
The present invention concerns generally retrievable bridge plugs, but more specifically a drawable mechanical barrier having a packer element, according to the introductory part of patent claim
1
.
Among other things, bridge plugs are used for oil- and gas wells. Such bridge plugs have a packer element which seals against fluid and pressure. The packer element is comprised mainly of an elastic rubber body sealing against the pressure, and mechanical barriers preventing extrusion of the rubber at pressure load. In oil and gas wells the bridge plug will, in many cases, have to pass restrictions such as, for example, valves and nipples, for subsequent location in a larger diameter. Known retrievable bridge plugs have a limited degree of expansion at a high pressure and a high temperature. The limitation in the degree of expansion is mainly caused by the construction of the drawable mechanical barrier.
SUMMARY OF THE INVENTION
It is thus an object with present invention to provide a drawable mechanical barrier, which stabilizes and prevents extrusion of the packer elements at high pressure/temperature and has a large degree of expansion.
The object of the invention is achieved by a device having features as stated in the characterizing part of patent claim
1
. Further features are stated in the dependent claims.
According to the invention, a mechanical barrier is developed, which through an axial movement is expanded and then drawn through an opposite movement.
In some oil and gas wells it is desirable that the bridge plug changes pressure direction from one side to the other side. In this case, two packer elements are installed, having a mechanical barrier inbetween. When the packer elements are expanded, the rubber will be forced out radially along the mechanical barrier, and up against the casing. In expanded position, the mechanical barrier has a wedge shape up against the casing. By applying pressure, the packer element will creep into the radial wedge shape, and seal. This wedge shape also has a positive effect to the sealing property of the packer element at increasing pressure load. If the bridge plug should seal against differential pressure from one side, a mechanical barrier with a packer element is installed at the pressure side.
Upon expansion of two packer elements with a mechanical barrier inbetween, a fluid volume will form between the packer elements. When one of the packer elements is pressurized, it will move and cause a pressure build-up on the enclosed volume. This pressure build-up will again cause a movement of the packer element at the non-pressure side. This involves an extra strain on the packer element at the non-pressure side, and is unfortunate, however. This is solved by draining unwanted fluid volume causing pressure build-up. Drainage is performed by way of U-shaped packers installed in a packer bracket at the non-pressure side. These U-shaped packers act as check valves, and are described below.
When setting the bridge plug in horizontal oil and gas wells, the mechanical barrier positions the mechanical bridge plug in the centre, and thus avoids the extra strain on the packer element from the bridge plug's own weight.
When drawing the bridge plug from the well, the mechanical barrier according to the present invention has a construction whereby it is possible to be actively drawn when running into restrictions. This is performed when the mechanical barrier is subjected to tension, which then leads to the link pairs rotating around their belonging bolts, thus forcing them against the centre of the bridge plug.
According to the present invention, the mechanical barrier has a construction making it functionally reliable during the aggregation of sand above the bridge plug. The mechanical barrier being situated between two packer elements is advantageous in this respect.


REFERENCES:
patent: 3706342 (1972-12-01), Woolley
patent: 4554973 (1985-11-01), Shonrock et al.
patent: 4588029 (1986-05-01), Blizzard
patent: 5010958 (1991-04-01), Meek et al.

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