Wells – Processes – Placing or shifting well part
Reexamination Certificate
2001-06-27
2004-03-30
Bagnell, David (Department: 3672)
Wells
Processes
Placing or shifting well part
C166S382000, C166S118000, C166S120000, C166S134000, C166S138000
Reexamination Certificate
active
06712153
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a downhole non-metallic sealing element system. More particularly, the present invention relates to downhole tools such as bridge plugs, frac-plugs, and packers having a non-metallic sealing element system.
2. Background of the Related Art
An oil or gas well includes a wellbore extending into a well to some depth below the surface. Typically, the wellbore is lined with tubulars or casing to strengthen the walls of the borehole. To further strengthen the walls of the borehole, the annular area formed between the casing and the borehole is typically filled with cement to permanently set the casing in the wellbore. The casing is then perforated to allow production fluid to enter the wellbore and be retrieved at the surface of the well.
Downhole tools with sealing elements are placed within the wellbore to isolate the production fluid or to manage production fluid flow through the well. The tools, such as plugs or packers for example, are usually constructed of cast iron, aluminum, or other alloyed metals, but have a malleable, synthetic element system. An element system is typically made of a composite or synthetic rubber material which seals off an annulus within the wellbore to prevent the passage of fluids. The element system is compressed, thereby expanding radially outward from the tool to sealingly engage a surrounding tubular. For example, a bridge plug or frac-plug is placed within the wellbore to isolate upper and lower sections of production zones. By creating a pressure seal in the wellbore, bridge plugs and frac-plugs allow pressurized fluids or solids to treat an isolated formation.
FIG. 1
is a cross sectional view of a conventional bridge plug
50
. The bridge plug
50
generally includes a metallic body
80
, a synthetic sealing member
52
to seal an annular area between the bridge plug
50
and an inner wall of casing there-around (not shown), and one or more metallic slips
56
,
61
. The sealing member
52
is disposed between an upper metallic retaining portion
55
and a lower metallic retaining portion
60
. In operation, axial forces are applied to the slip
56
while the body
80
and slip
61
are held in a fixed position. As the slip
56
moves down in relation to the body
80
and slip
61
, the sealing member is actuated and the slips
56
,
61
are driven up cones
55
,
60
. The movement of the cones and slips axially compress and radially expand the sealing member
52
thereby forcing the sealing portion radially outward from the plug to contact the inner surface of the well bore casing. In this manner, the compressed sealing member
52
provides a fluid seal to prevent movement of fluids across the bridge plug
50
.
Like the bridge plug described above, conventional packers typically comprise a synthetic sealing element located between upper and lower metallic retaining rings. Packers are typically used to seal an annular area formed between two co-axially disposed tubulars within a wellbore. For example, packers may seal an annulus formed between production tubing disposed within wellbore casing. Alternatively, packers may seal an annulus between the outside of a tubular and an unlined borehole. Routine uses of packers include the protection of casing from pressure, both well and stimulation pressures, as well as the protection of the wellbore casing from corrosive fluids. Other common uses include the isolation of formations or leaks within a wellbore casing or multiple producing zones, thereby preventing the migration of fluid between zones. Packers may also be used to hold kill fluids or treating fluids within the casing annulus.
One problem associated with conventional element systems of downhole tools arises in high temperature and/or high pressure applications. High temperatures are generally defined as downhole temperatures above 200° F. and up to 450° F. High pressures are generally defined as downhole pressures above 7,500 psi and up to 15,000 psi. Another problem with conventional element systems occurs in both high and low pH environments. High pH is generally defined as less than 6.0, and low pH is generally defined as more than 8.0. In these extreme downhole conditions, conventional sealing elements become ineffective. Most often, the physical properties of the sealing element suffer from degradation due to extreme downhole conditions. For example, the sealing element may melt, solidify, or otherwise loose elasticity.
Yet another problem associated with conventional element systems of downhole tools arises when the tool is no longer needed to seal an annulus and must be removed from the wellbore. For example, plugs and packers are sometimes intended to be temporary and must be removed to access the wellbore. Rather than de-actuate the tool and bring it to the surface of the well, the tool is typically destroyed with a rotating milling or drilling device. As the mill contacts the tool, the tool is “drilled up” or reduced to small pieces that are either washed out of the wellbore or simply left at the bottom of the wellbore. The more metal parts making up the tool, the longer the milling operation takes. Metallic components also typically require numerous trips in and out of the wellbore to replace worn out mills or drill bits.
There is a need, therefore, for a non-metallic element system that will effectively seal an annulus at high temperatures and withstand high pressure differentials without experiencing physical degradation. There is also a need for a downhole tool made substantially of a non-metallic material that is easier and faster to mill.
SUMMARY OF THE INVENTION
A non-metallic element system is provided which can effectively seal or pack-off an annulus under elevated temperatures. The element system can also resist high differential pressures as well as high and low pH environments without sacrificing performance or suffering mechanical degradation. Further, the non-metallic element system will drill up considerably faster than a conventional element system that contains metal.
The element system comprises a non-metallic, composite material that can withstand high temperatures and high pressure differentials. In one aspect, the composite material comprises an epoxy blend reinforced with glass fibers stacked layer upon layer at about 30 to about 70 degrees.
A downhole tool, such as a bridge plug, frac-plug, or packer, is also provided that consists essentially of a non-metallic, composite material which is easier and faster to mill than a conventional bridge plug containing metallic parts. In one aspect, the tool comprises a non-metallic element system, comprising a first and second support ring having one or more tapered wedges, a first and second expansion ring, and a sealing member disposed between the expansion rings and the support rings.
A method is further provided for sealing an annulus in a wellbore. In one aspect, the method comprises running a body into the wellbore, the body comprising a non-metallic sealing system having a first and second support ring, a first and second expansion ring, and a sealing member disposed between the expansion rings and the support rings, wherein the support ring comprises one or more tapered wedges. The method further comprises expanding the one or more tapered wedges to engage an inner surface of a surrounding tubular, and flowing the expansion ring to fill voids between the expanded wedges.
REFERENCES:
patent: 1342780 (1920-06-01), Vedder
patent: 1512621 (1924-10-01), Packer
patent: 1648377 (1927-11-01), Crowell
patent: 1684266 (1928-09-01), Fisher
patent: 2043225 (1936-06-01), Armentrout
patent: 2084611 (1937-06-01), Crickmer
patent: 2092042 (1937-09-01), Armentrout
patent: 2134749 (1938-11-01), Burt
patent: 2155129 (1939-04-01), Hall
patent: 2160804 (1939-05-01), Hall
patent: 2171049 (1939-08-01), Simmons
patent: 2204659 (1940-06-01), Burt
patent: 2205119 (1940-06-01), Hall
patent: 2299057 (1942-10-01), McClain
patent: 2319514 (1943-05-01), Penfield
patent: 2331185 (1943-10-01), Gordy
paten
Al Oudat Rami
Eldridge William J.
Fishbeck Craig
Freihet Roland
Hines, III William F.
Bagnell David
Collins G M
Moser, Patterson & Sheridan L.L.P.
Weatherford / Lamb, Inc.
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