U.S. patent application number 10/789846 was filed with the patent office on 2005-08-04 for hydrogel for use in downhole seal applications.
Invention is credited to Li, Yanmei, Zhou, Jian.
Application Number | 20050171248 10/789846 |
Document ID | / |
Family ID | 34811426 |
Filed Date | 2005-08-04 |
United States Patent
Application |
20050171248 |
Kind Code |
A1 |
Li, Yanmei ; et al. |
August 4, 2005 |
Hydrogel for use in downhole seal applications
Abstract
The present invention is a composition for forming seals. The
composition includes a base material and a hydrogel. The base
materials is preferably an elastomer or a thermoplastic. Seals
formed with the composition are particularly suited for use in a
wellbore environment. The inclusion of hydrogel in the seals allows
the seals to be manipulated or altered through certain
environmental factors. For instance, temperature, oil/water ratio,
pH and the electronic field may all be used to alter the
characteristics of the hydrogel. In this way, the seal may be
caused to swell in response to a specific stimulus, thereby
preventing or sealing a leak without requiring additional work or
input from the operator.
Inventors: |
Li, Yanmei; (Houston,
TX) ; Zhou, Jian; (Sugar Land, TX) |
Correspondence
Address: |
SCHLUMBERGER TECHNOLOGY CORPORATION
IP DEPT., WELL STIMULATION
110 SCHLUMBERGER DRIVE, MD1
SUGAR LAND
TX
77478
US
|
Family ID: |
34811426 |
Appl. No.: |
10/789846 |
Filed: |
February 27, 2004 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60541035 |
Feb 2, 2004 |
|
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Current U.S.
Class: |
524/35 |
Current CPC
Class: |
C08L 1/28 20130101; C08L
1/28 20130101; C09K 2200/06 20130101; C08L 1/28 20130101; C09K
2200/0657 20130101; C08L 5/14 20130101; C08L 101/14 20130101; C09K
2200/0627 20130101; C08L 1/28 20130101; C08L 101/14 20130101; C08L
5/14 20130101; C08L 101/14 20130101; C09K 3/10 20130101; C08L
2666/06 20130101; C08L 2666/26 20130101; C08L 2666/08 20130101;
C08L 2666/02 20130101; C08L 2666/08 20130101; C08L 2666/06
20130101; C08L 2666/02 20130101; C08L 2666/06 20130101; C08L 5/14
20130101; C08L 101/00 20130101; C09K 2200/0685 20130101; C09K
2200/0632 20130101; C09K 2200/0617 20130101; E21B 33/12 20130101;
C08L 101/00 20130101; C08L 5/14 20130101; C08L 2666/08
20130101 |
Class at
Publication: |
524/035 |
International
Class: |
C08L 001/00 |
Claims
We claim:
1. A composition for forming a seal comprising: (a) a hydrogel and
(b) a base material.
2. The composition of claim 1, wherein said base material is a
polymer.
3. The composition of claim 2, wherein said polymer is an
elastomer.
4. The composition of claim 3, wherein said elastomer is selected
from the group consisting of nitrile rubber, hydrogenated nitrile
rubber, carboxyl nitrile rubber, silicon rubber,
ethylene-propylene-diene copolymers, fluoroelastomers and
perfluoroelastomers.
5. The composition of claim 2 wherein said polymer is a
thermoplastic.
6. The composition of claim 5, wherein said thermoplastic is
selected from the group consisting of Teflon.RTM.,
polyetheretherketone, polypropylene, polystyrene and polyphenylene
sulfide.
7. The composition of claim 1 wherein said hydrogel is selected
from the group consisting of: methylcellulose, cellulose acetate
pthalate and hydroxypropyl methylcellulose polymers, poly (ethylene
oxide) polymers, guar, derivatized guar, polyacrylamide,
silicon-based polymers and fluorosilicone-based polymers.
8. The composition of claim 1 wherein said hydrogel is a metal
complex of a polymer selected from the group consisting of:
methylcellulose, cellulose acetate pthalate and hydroxypropyl
methylcellulose polymers, poly (ethylene oxide) polymers, guar,
derivatized guar, polyacrylamide, silicon-based polymers and
fluorosilicone-based polymers.
9. A seal for use in a wellbore comprising the composition of claim
1.
10. The composition of claim 1, wherein said composition forms a
seal.
11. The composition of claim 10, wherein said seal is an
o-ring.
12. The composition of claim 10, wherein said seal is a t-seal.
13. The composition of claim 10, wherein said seal is a chevron
seal.
14. The composition of claim 10, wherein said seal is a spring
seal.
15. The composition of claim 10, wherein said seal is a packer
element.
16. The composition of claim 10, wherein said seal is a bridge
plug.
Description
REFERENCE TO RELATED PROVISIONAL APPLICATION
[0001] This application claims the benefit of U.S. Provisional
Application Ser. No. 60/541,035.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates generally to seals for
oilfield applications. More specifically the present invention
describes the use of hydrogel in seals for downhole use.
[0004] 2. Description of the Prior Art
[0005] Seals, including o-rings, packer elements, Chevron seals,
gaskets, etc., are widely used for numerous downhole oilfield
applications. One ongoing issue in this area is how to energize
seals and maintain sealing forces throughout seal service life.
Capital loss or remediation associated with seal failure can be
tremendous in certain operation areas.
[0006] One conventional method to energize seal is to utilize
mechanical force to deform seal between sealing surfaces. For seals
with large cross-section and/or large sealing gaps, satisfactory
sealing performance is hard to achieve due to limited mechanical
force. The other major problem encountered during operation is the
relaxation of contact force between the seal and the sealing
surfaces. This is caused primarily by the viscoelastic nature of
polymeric materials used in conventional seals.
[0007] Another technique for improving seals involves the use of a
pressure activated sealant that is specifically designed to seal
leaks in wells and severe-environment hydraulic systems. The
sealant functions by causing a pressure drop through a leak site,
which in turn causes the sealant fluid to polymerize into a
flexible solid seal. However, the major drawback of this technique
is it requires a service engineer and a special tool to deliver the
sealant to the leak site and complete the job. At that time, a
significant amount of damage may have already occurred. Another
disadvantage is that often tools which are installed 20,000 ft deep
in the well where it is difficult and inefficient to deliver the
sealant to the exact location where the leak occurs. Yet another
drawback of this technique is that the sealant only starts to
polymerize after a leak occurs. In certain cases, where the leakage
is catastrophic, operation can fail before the polymerization
process is completed.
[0008] Hydrogel technology has been rapidly developed in medical
industry due to its unique response to environmental changes such
as pH value, salinity, electrical current, temperature and
antigens. Hydrogel is a flexible, rubber-like and solvent-swollen
polymer. In an aqueous environment, hydrogel can undergo a
reversible phase transformation that results in dramatic volumetric
swelling and shrinking upon exposure and removal of a stimulus. A
property common to all gels is their unique ability to undergo
abrupt changes in volume. Gel can swell or shrink as much as 1000
times in response to small external condition changes. Through the
conversion of chemical or electrical energy into mechanical work, a
number of device have already been constructed which can produce
forces up to 100 N/cm.sup.2 and contraction rate on the order of a
second. Using microscale hydrogel, the volumetric transition can
occur within minutes or even seconds. The favorable scaling of
hydrogel dynamic has been the essential element in the development
of micro-fluidic devices that employ hydrogel valves for flow
control. One major benefit of these devices is that they are
completely autonomous and therefore require no external power
source.
SUMMARY OF THE INVENTION
[0009] The present invention provides an improved seal material for
use with both dynamic and static seal applications. In particular,
the invention provides a seal material that is useful for downhole
wellbore applications, including, but not limited to, o-rings,
packer elements, chevron seals and gaskets.
[0010] A seal which is prepared or formed in accordance with the
present invention includes a hydrogel polymer incorporated or
included as part of the seal body. In this way, the seal may be
activated when certain environmental parameters are manipulated or
changed. These environmental parameters may include water/oil
concentration, differential pressure, temperature, pH, and
electronic field. The hydrogel polymer may be embedded, coated,
attached or blended with other seal components to form the seal.
Commonly used seal components may include elastomers, plastics or
other materials known in the art.
[0011] Once incorporated into the seal body, the hydrogel provides
several advantages over typical seal body components. First, the
hydrogel allows the seal be to energized via swelling. Since
hydrogel can swell as much as 1,000 times in volume, high swelling
force can be utilized to energize the main seal body as well as
anti-extrusion device.
[0012] The hydrogel may also allow potential leak paths to be
sealed. Hydrogel swells in aqueous environment. That is, whenever
it contacts an aqueous medium, it starts to absorb water and swell.
For applications with hard-to-seal voids or surfaces, hydrogel can
stop leak via swelling. Swelling leads to greater squeeze of main
seal body. This, in turn, seals the leak path and prevents seal
failure.
[0013] Another feature of seals incorporating hydrogel is the
ability of the seals to be reset. That is, the seals may be
provided in a first configuration, then upon exposure to a certain
environmental parameter, the seal may change or take a second
configuration. Upon removal of the certain environmental parameter,
or upon exposure to yet another environmental parameter, the seal
may then return to it's original configuration. This characteristic
is particularly beneficial in downhole applications where a
resettable seal is required.
[0014] These and other features of may be used employed either
alone or in combination, depending on the specific nature of the
application in which they are used.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] FIG. 1 shows a three-rubber element array.
[0016] FIG. 2 shows a garter spring element array.
[0017] FIG. 3 shows a packer element array.
[0018] FIG. 4 shows an o-ring with backup rings.
[0019] FIG. 5 shows a t-seal.
[0020] FIG. 6 shows a chevron seal stack.
[0021] FIG. 7 shows a spring energized seal.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0022] Seals formed in accordance with the present invention
comprise two primary elements:
[0023] (1) a base material and (2) a hydrogel. The respective
ratios of these two materials in the seal is determined the
specific nature of the application in which the seals will be used.
As previously mentioned, hydrogels can change their swelling
behavior upon exposure to an external stimulus, such as pH,
temperature, light, and electric field. Therefore, factors which
may contribute to the selection of a proper ratio of base material
to hydrogel may include the temperature to which the seal will be
exposed, the pH at which the seal will be used, the nature of any
chemicals the seal may come into contact with (including, for
instance, the oil/water ratio), the differential pressure which the
seal must withstand and the electronic environment of the
application. Any number of these factors may effect the performance
of the seal.
[0024] The base material of the seal is generally selected from any
suitable material known in the industry for forming seals.
Preferably, the base material is a polymer. More preferably, the
base material is an elastomer or a thermoplastic. Elastomers that
are particularly useful in the present invention include nitrile
rubber (NBR), hydrogenated nitrile rubber (HNBR), carboxyl nitrile
rubber (XNBR), silicone rubber, ethylene-propylene-diene copolymer
(EPDM), fluoroelastomer (FKM, FEPM) and perfluoroelastomer (FFKM).
Thermoplastics which are particularly useful in the present
invention include Teflon.RTM., polyetheretherketone, polypropylene,
polystyrene and polyphenylene sulfide.
[0025] As used herein the term hydrogel is a broad phrase referring
in general to a polymer that swells when used in aqueous
environment. Hydrogel polymers useful in the present invention are
preferably formed of a crosslinked polymer network. When this
polymer network is exposed or immersed in a suitable solvent, the
polymer chains in the network become solvated. In certain cases,
crosslinkers may be provided to prevent the complete mixing of the
polymer chains and the solvent by providing an elastic restoring
force that counters the expansion of the network.
[0026] The polymer network of the hydrogel may be formed from any
suitable polymeric material. In a preferred embodiment, the polymer
network is formed from cross-linked polymers including
water-soluble methylcellulose, cellulose acetate phtalate, and
hydroxypropyl methylcellulose polymers, poly (ethylene oxide)
polymers, guar and its derivatives, polyacrylamide, silicon-based
materials, and flouro-silicone based materials.
[0027] Seals described in the present invention comprise a polymer
and a hydrogel. The polymer and hydrogel may be combined in any
suitable ratio using any suitable method. In a preferred
embodiment, polymer/hydrogel blends may be prepared using any of
the following methods: (1) a solution process; (2) a mesophase
mediated process; (3) physical mixing/compounding, (4) injection or
extrusion, (5) in-situ polymerization or (6) melt processing.
Curing methods may be any suitable method, but is preferably
thermal curing, microwave radiation or electronic beam radiation.
Chemical modification, such as branching or grafting, of the
hydrogel may be performed prior to manufacturing of
polymer/hydrogel blends to achieve optimum dispersion of the
hydrogel polymer.
[0028] Without limiting the scope of the invention, the following
examples show specific seal configurations which may particularly
benefit from the incorporation or inclusion of hydrogel in the seal
material.
EXAMPLE 1
Packer Elements
[0029] FIG. 1 shows three-piece rubber element array or packer
element 10, such as that commonly used in downhole packers. The
packer elements are external packer seals that seal the annulus
space between tubing and casing (not shown). Elements are energized
by axial deflection of the seals after the packer is run into the
hole. Commonly used packer elements typically consist of backup end
rings 16 and a center seal or element 18. The center seal 18
typically includes a ring 20 which establishes the inner diameter
of the seal. Hydrogel may be included or incorporated into any or
all of the seal elements. The hydrogel allows the seals to be
energized in response to external stimuli, as previously
described.
[0030] FIG. 2 shows a garter spring element array 50. The array 50
includes a main element or seal 52, a garter spring 54 and backup
end rings 56. The array also includes an ID ring 58. Hydrogel may
be included in any or all of the seals of the array. As with the
assembly of FIG. 1, the garter spring array also benefits from the
inclusion of hydrogel seal components by allowing them to respond
to external stimuli.
[0031] FIG. 3 shows yet another packer element array 100. This
array includes a main seal 70, backup seals 72 and an ID ring 74.
As with the seals shown in FIGS. 1 and 2, hydrogel may be included
in any or all of the seals.
EXAMPLE 2
O-Ring
[0032] O-rings are simple bi-directional static seals. For high
temperature and/or high pressure sealing applications, backup rings
are used to prevent O-ring extrusion. As shown in FIG. 4, the
o-ring 150 includes two backup rings 152 which are formed of
thermoplastic materials blended with hydrogel polymer. The O-ring
may also be formed of elastomers blended with hydrogel polymer. In
this application, the hydrogel is able to seal off potential leak
paths as well as keep the o-ring energized via swelling. These
characteristics are not achievable with existing conventional
rubber materials used for o-ring applications.
EXAMPLE 3
T-Seal
[0033] T-seals are typically used as reciprocating bi-directional
dynamic seals. As shown in FIG. 5, T-seal 200 including seal body
202 and retaining ring 204. The seal body is formed of a hydrogel
modified thermoplastic or elastomer. Hydrogel can seal off
potential leak paths as well as keep the T-seal energized via
swelling. These benefits are not achievable with existing
conventional rubber materials used for T-seal application.
EXAMPLE 4
Seal Stack/Packing
[0034] Vee packing or chevron seal stacks are multiple seal lip
multi-component seal sets that are energized by differential
pressure. Seal stacks are also suited to internal dynamic seal
applications. Most conventional packing stacks are combinations of
softer elastomer parts and harder plastic parts. The incorporation
of hydrogel in the seal elements allows any potential leak paths to
be sealed, as well as keeping seal stack energized via swelling.
This is not achievable with existing conventional rubber materials
used for seal stack applications.
[0035] FIG. 6 shows a seal stack 250 having first
hydrogel/elastomer elements 252 and second hydrogel/plastic
elements 254. These first and second elements are preferably
alternating, as shown. However, depending on the specific nature of
the application any configuration of first and second elements may
be used.
EXAMPLE 5
Spring-Energized Seal
[0036] Spring-energized seals are uni-directional seals and may be
either static or dynamic. These seals combine the benefits of
packing, as seen in vee or chevron seals and radial compression as
seen in o-rings. As shown in FIG. 7, a spring-energized seal 300
will be made of hydrogel modified thermoplastic or rubber
materials. Hydrogel can seal off potential leak path as well as
keep seal energized via swelling which is not achievable with
existing conventional rubber materials used for seal
application.
* * * * *