U.S. patent application number 13/454959 was filed with the patent office on 2012-08-16 for water swelling rubber compound for use in reactive packers and other downhole tools.
This patent application is currently assigned to Baker Hughes Incorporated. Invention is credited to James Edward Goodson, James R. Korte, John J. Thurston.
Application Number | 20120208934 13/454959 |
Document ID | / |
Family ID | 40342491 |
Filed Date | 2012-08-16 |
United States Patent
Application |
20120208934 |
Kind Code |
A1 |
Korte; James R. ; et
al. |
August 16, 2012 |
Water Swelling Rubber Compound for Use in Reactive Packers and
Other Downhole Tools
Abstract
Through the combination of at least two polymer families, and
the optimization of other components, a rubber compound has been
developed for use in downhole applications that will swell in
water-based fluids. A cellulose component, such as carboxy methyl
cellulose (CMC), is used together with an acrylate copolymer (AC)
that can increase the swelling capacity of an acrylonitrile
butadiene rubber (NBR) in water. The amount of swelling achieved
depends on physical boundaries and limitations, the salinity of the
water, and the temperature.
Inventors: |
Korte; James R.; (Katy,
TX) ; Thurston; John J.; (Houston, TX) ;
Goodson; James Edward; (Porter, TX) |
Assignee: |
Baker Hughes Incorporated
Houston
TX
|
Family ID: |
40342491 |
Appl. No.: |
13/454959 |
Filed: |
April 24, 2012 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
12242338 |
Sep 30, 2008 |
8181708 |
|
|
13454959 |
|
|
|
|
60976575 |
Oct 1, 2007 |
|
|
|
Current U.S.
Class: |
524/43 ; 524/45;
524/46 |
Current CPC
Class: |
C08L 31/02 20130101;
C08L 9/02 20130101; C08L 33/20 20130101; C08L 1/28 20130101; C08L
1/28 20130101; C08L 1/284 20130101; C08L 1/284 20130101; C08L
2205/03 20130101; C08L 1/02 20130101; C08L 1/286 20130101; E21B
33/1208 20130101; C08L 1/286 20130101; C08L 33/00 20130101; C08L
33/00 20130101; C08L 31/02 20130101; C08L 33/08 20130101; C08L 1/02
20130101; C08L 33/08 20130101; C08L 33/20 20130101; C08L 31/02
20130101; C08L 9/02 20130101; C08L 2666/04 20130101; C08L 2666/26
20130101; C08L 2666/02 20130101; C08L 2666/04 20130101; C08L
2666/02 20130101; C08L 2666/04 20130101; C08L 2666/04 20130101;
C08L 2666/04 20130101; C08L 2666/04 20130101; C08L 2666/04
20130101; C08L 2666/26 20130101; C08L 33/00 20130101 |
Class at
Publication: |
524/43 ; 524/45;
524/46 |
International
Class: |
C08L 1/26 20060101
C08L001/26; C08L 9/02 20060101 C08L009/02; C08L 1/28 20060101
C08L001/28 |
Claims
1. A water swellable elastomer comprising: about 100 phr of at
least one base polymer, about 50 to about 150 phr of at least one
cellulose, about 80 to about 140 phr of at least one acrylic
copolymer (AC), and about 0.2 to about 6 phr of at least one
curative.
2. The water swellable elastomer of claim 1 where the water
swellable elastomer is responsive to contact with water.
3. The water swellable elastomer of claim 1 where the cellulose is
selected from the group consisting of carboxy methyl cellulose
(CMC), hydroxypropylmethyl cellulose (HPMC) or methylcellulose
(MC), and combinations thereof.
4. The water swellable elastomer of claim 1 where the base polymer
is selected from the group consisting of acrylonitrile butadiene
rubber (NBR), ethylene propylene diene monomer rubber (EPDM),
polychloroprene rubber, fluorinated polymer rubber, tetrafluoro
ethylene propylene rubber (FEPM), fluorosilicone rubber (FVMR),
butyl rubber (IIR) and combinations thereof.
5. The water swellable elastomer of claim 1 where the elastomer
comprises at least one additional component selected from the group
consisting of fillers, activators, antioxidants, process aids, and
combinations thereof.
6. The water swellable elastomer of claim 5 where the components of
the elastomer have the proportions: about 100 phr NBR, about 50 to
about 150 phr cellulose, about 80 to about 140 phr AC, about 0.2 to
about 6 phr curative, about 30 to about 100 phr carbon black
filler, about 30 to about 100 phr silica filler, about 1 to about
10 phr activator, about 0.5 to about 5 phr antioxidant, and about
0.5 to about 5 phr process aid.
7. The water swellable elastomer of claim 1 in the absence of a
water-soluble resin.
8. A water swellable elastomer for a flow channel, where the water
swellable elastomer is responsive to contact with water and
comprises: about 100 phr of at least one base polymer is selected
from the group consisting of acrylonitrile butadiene rubber (NBR),
ethylene propylene diene monomer rubber (EP DM), polychloroprene
rubber, fluorinated polymer rubber, tetrafluoro ethylene propylene
rubber (FEPM), fluorosilicone rubber (FVMR), butyl rubber (IIR) and
combinations thereof, about 50 to about 150 phr of at least one
cellulose is selected from the group consisting of carboxy methyl
cellulose (CMC), hydroxypropylmethyl cellulose (HPMC) or
methylcellulose (MC), and combinations thereof, about 80 to about
140 phr of at least one acrylic copolymer (AC), and about 0.2 to
about 6 phr of at least one curative.
9. The water swellable elastomer of claim 8 where the elastomer
comprises at least one additional component selected from the group
consisting of fillers, activators, antioxidants, process aids, and
combinations thereof.
10. The water swellable elastomer of claim 9 where the components
of the elastomer have the proportions: about 100 phr NBR, about 50
to about 150 phr cellulose, about 80 to about 140 phr AC, about 0.2
to about 6 phr curative, about 30 to about 100 phr carbon black
filler, about 30 to about 100 phr silica filler, about 1 to about
10 phr activator, about 0.5 to about 5 phr antioxidant, and about
0.5 to about 5 phr process aid.
11. The water swellable elastomer of claim 10 in the absence of a
water-soluble resin.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a divisional application of U.S. patent
application Ser. No. 12/242,338, filed Sep. 30, 2008, issued ______
as U.S. Pat. No. ______, which in turn claims the benefit of U.S.
Provisional Patent Application No. 60/976,575 filed Oct. 1, 2007,
all of which are incorporated herein by reference in their
entirety.
TECHNICAL FIELD
[0002] The present invention relates to water-swellable elastomers,
and more particularly relates, in one non-limiting embodiment, to
compositions useful for forming water-swellable seals on downhole
tools and methods of using them.
TECHNICAL BACKGROUND
[0003] Well pipe such as coiled or threaded production tubing, for
example, is surrounded by an annular space between the exterior
wall of the tubing and the interior wall of the well casing or
borehole wall. Frequently, it is necessary to seal this annular
space between upper and lower portions of the well depth.
Appliances for accomplishing the sealing function are known in the
well drilling arts as "packers". Traditionally, the sealing element
of a packer is a ring of rubber or other elastomer that is in some
manner secured and sealed to the interior well surface which may be
the interior casing wall or the raw borehole wall. By compression,
for example, the ring of rubber is expanded radially against the
casing or borehole wall.
[0004] "Bridge plugs" are well appliances for obstructing the flow
continuity of an entire bore; whether it is the entire
cross-section of the wellbore, the cross-section of a well casing
or the cross-section of a production tube.
[0005] One of the greater utilities for a well packer or bridge
plug is to isolate a designated section of well bore along the
wellbore length that penetrates a particular zone or earth strata.
In some cases, the isolated zone may be burdened with an
inordinately high internal pressure. For that reason, the packer or
bridge plug may be called upon to confine an unusually high
pressure differential.
[0006] In other cases, where the packer engages the raw borehole
wall to seal the annulus, for example, the packer must tightly and
continuously engage a rough and highly irregular wall surface.
[0007] Either of the two examples above necessitate unusually high
applications of setting force against the sealant to attain the
degree of rigidity and seal quality required with elastomers having
the essential stiffness and other properties necessary to confine
high differential pressure loads or expand into deep contours.
However, high force and stress loads on a well tube also introduce
the potential for other forms of tool and equipment failure.
[0008] Reactive Element Packers or REPackers available from Baker
Oil Tools are commercial isolation tools that use elastomer
swelling technology to provide a barrier in casing/open hole and
casing/casing annuli. Such packers may have a water reactive
section, an oil reactive section, or both. A water reactive section
may consist of water-absorbing particles incorporated in a
field-proven nitrile-based polymer. These particles swell via
absorbing water, which in turn expands the rubber without being
physically absorbed into the rubber matrix, which can adversely
affect properties. An oil reactive section may utilize oleophilic
polymers that absorb hydrocarbons into the matrix. This process may
be a physical uptake of the hydrocarbon which swells, lubricates
and decreases the mechanical strength of the polymer chain as it
expands.
[0009] It would be desirable if the elastomers used in reactive
element packers could be improved to swell to a greater volume than
previously known. Such greater volumes would give greater tightness
and continuity when the isolation tools engage the casing or the
borehole wall.
SUMMARY
[0010] There is provided, in one non-limiting form, a water
swellable elastomer that includes at least one base polymer, which
may be acrylonitrile butadiene rubber (NBR), at least one
cellulose, at least one acrylic copolymer (AC), and at least one
curative.
[0011] In another non-restrictive embodiment, there is further
provided a selectively deployed sealing element for a well flow
channel. The sealing element is responsive to contact with water
and involves an elastomer that again includes at least one base
polymer (e.g. NBR), at least one cellulose, at least one AC, and at
least one curative.
[0012] Also, in an alternative non-limiting embodiment, there is
provided a well packer having an expandable packing element for
sealing a well annulus and an elastomer for expanding the packing
element into operative engagement across said annulus. Once more,
the elastomer includes at least one base polymer (e.g. NBR), at
least one cellulose, at least one AC, and at least one
curative.
[0013] Further there is offered in a different non-restrictive
embodiment, a method for sealing a well flow channel that involves
introducing a sealing element into a well adjacent a flow channel
and contacting the sealing element with water to deploy, expand or
enlarge the sealing element to seal the flow channel. The sealing
element may again involve an elastomer including at least one base
polymer (e.g. NBR), at least one cellulose, at least one AC, and at
least one curative. All of these elastomers may also contain
fillers, activators, antioxidants, process aids, and combinations
thereof.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] FIG. 1 is a graph of % volume increase as a function of
temperature over time for an improved water swelling compound
described herein contacting 3.5% NaCl Brine at three different
temperatures: 180.degree. F. (82.degree. C.), 130.degree. F.
(54.degree. C.), and 70.degree. F. (21.degree. C.);
[0015] FIG. 2 is a graph of % volume increase as a function of NaCl
concentration over time for an improved water swelling compound
herein contacting water at 180.degree. F. (82.degree. C.), where
the water contains no NaCl, and then 3.5% and 6% NaCl;
[0016] FIG. 3 is a graph of % volume increase as a function of
different salts and ion types over time for an improved water
swelling compound herein contacting water at room temperature,
where the water contains 3.5% of three different salts: NaCl, ZnBr
and CaCl.sub.2;
[0017] FIG. 4 is a graph of % volume increase over time for an
improved water swelling compound herein contacting water at room
temperature contrasted with a prior water swelling compound;
[0018] FIG. 5 is a schematic, cross-section view of a downhole tool
having a central support substrate or base pipe which bears a
selectively deployable sealing element (a water swellable elastomer
as described herein) in its original, first stable state or initial
cross-sectional shape, shown in elevation; and
[0019] FIG. 6 is a schematic, cross-section view of the downhole
tool of FIG. 5 where the selectively deployable sealing element has
been deployed or permitted to expand or enlarge up against the
walls of a well borehole into which it has been inserted or run
in.
[0020] It will be appreciated that FIGS. 5 and 6 are simply
schematic illustrations which are not to scale and that the
relative sizes and proportions of different elements may be
exaggerated for clarity or emphasis.
DETAILED DESCRIPTION
[0021] A new water-swelling rubber compound has been discovered
that gives improved water swelling volumes under the same
conditions as compared with conventional compounds. Through the
combination of at least two polymer families, as well as the
optimization of other components, a rubber compound has been
developed for use in downhole applications that will swell in
water-based fluids such as water based muds or brines to an
improved extent. In one non-limiting embodiment, a cellulose
component, such as carboxy methyl cellulose (CMC), is used together
with an acrylate copolymer (AC) that can increase the swelling
capacity of an acrylonitrile butadiene rubber (NBR) in water to
over 1000%. The amount of swelling achieved and the rate of
swelling depends on physical boundaries and limitations, the
salinity of the water, and the temperature. The swell amount may
also be affected by the salinity of the water-based fluid. The
lower the salinity of mono-valent salts (e.g. NaCl, KCl), the
faster the rate of swelling and the more swelling that can be
achieved. Similarly, the lower the concentration of co-valent salts
ions present (e.g. CaCl.sub.2) the faster the rate of swelling and
the more swelling that can be achieved. A typical bonded section of
the new rubber may increase its original volume up to 150% in a
typical down-hole fluid containing 3.5 NaCl (typical salt water
concentration) at temperatures from as low as ambient (70.degree.
F. or 21.degree. C.) to as high as 260.degree. F. (127.degree. C.),
possibly as high as 300.degree. F. (149.degree. C.). In a nearly
salt free water environment, the compound could expand on a mandrel
with sufficient rubber in the range of 300-400 volume %. Increasing
the volume of the elastomer by swelling in water, improves the
ability of the elastomer to more completely and forcefully seal off
a flow channel such as a well annulus and the like.
[0022] The water-swelling elastomer compound described herein is a
nitrile-based formulation. A water swelling copolymer which is
emulsified in a nitrile soluble oil allows incorporation of this
polymer/oil mixture into the nitrile base polymer. In addition to
these two materials, several other materials such as fillers and
curatives are typically added to give the rubber strength and
suitable final properties. Another key material added is a
cellulose-based material.
[0023] The "base" polymer may be an acrylonitrile butadiene rubber
(NBR) and/or any polymer that is tolerated by or compatible with
the liquid dispersed polymers (LDP) described below or to be
developed. NBR is a family of unsaturated copolymers of
2-propenenitrile and various butadiene monomers (1,2-butadiene and
1,3-butadiene). Although its physical and chemical properties vary
depending on the polymer's composition of acrylonitrile (the more
acrylonitrile within the polymer, the higher the resistance to oils
but the lower the flexibility of the material), this form of
synthetic rubber is generally resistant to oil, fuel, and other
chemicals. Other grades of NBR may also be optionally used herein,
in non-limiting examples hydrogenated NBR (HNBR) and carboxylated
hydrogenated NBR (XHNBR). Suitable, but non-limiting examples of
NBR include, but are not limited to NIPOL.RTM. 1014 NBR available
from Zeon Chemicals, LP; Perbunan NT-1846 from LanXess or N22L from
JSR. Given a suitable LDP, Other suitable base polymers may
include, but are not necessarily limited to, EPDM, synthetic
rubbers based on polychloroprene (NEOPRENE.RTM. polymers from
DuPont), fluorinated polymer rubbers (e.g. FKM), tetrafluoro
ethylene propylene rubbers (FEPM, such as AFLAS.RTM.
fluoroelastomers available from Asahi Glass Co. Ltd.),
fluorosilicone rubber (FVMR), butyl rubbers (IIR) and the like.
[0024] NBR does not swell significantly in water, thus the addition
of the two important ingredients, an Acrylic Copolymer (AC), for
instance dispersed in a nitrile-compatible phthalate ester, and a
Carboxy Methyl Cellulose (CMC), help make this compound unique.
[0025] The AC is a mixture comprised of approximately 50% active
polymer and 50% phthalate ester oil carrier. Suitable examples of
this material include, but are not necessarily limited to, those
produced by CIBA Specialty Chemicals (UK) and is sold to others for
use in PVC, as well as any other material generally regarded as a
Super Absorbent Polymer (SAP) in solid or liquid form. This
oil/polymer blend is referred to herein as Liquid Dispersed Polymer
(LDP). However, it should be understood that other LDPs besides the
above-described one are expected to be useful in the water
swellable elastomers herein. In a non-limiting example, another
potentially suitable LDP available from CIBA Specialty Chemicals is
one that is based in either a paraffinic, naphthenic or aromatic
based oil or any combination thereof, which is compatible with EPDM
(ethylene propylene diene monomer). Thus, EPDM is another
possibility for the base polymer herein, and other oils besides
phthalate esters are also expected to be suitable. It will be
appreciated that this LDP material may have ratios other than 50%
polymer and 50% oil carrier and still be useful and effective for
the purposes and elastomers set out herein. Another alternative
material includes AQUALIC CS-6S, a water absorbent polymer
available from Nippon Shokubai Co., Ltd. in solid powder form.
[0026] It should also be understood that unless otherwise noted
herein, the term "polymer" comprises polymers of one monomer,
copolymers, terpolymers and polymeric forms of more than one type
of monomer.
[0027] An important feature of the compound described herein is the
combined swelling effect gained when the LDP is used together with
the CMC. The rubber may be made to swell with either, but there are
physical limitations of adding each. For instance, the LDP is a
liquid and the cellulose is a dry powder. Without wishing to be
limited to any particular explanation, it is believed that there is
no chemical interaction occurring between the two components.
However, there may be a physical interaction of water transference
between the two additives, although the inventors do not want to be
restricted by this theory. There appears to be a synergistic effect
between the two which ultimately yields a rubber compound which has
more swelling ability, more desirable processing and better
physical properties as compared to otherwise identical compounds
where one or the other is not included. The CMC being a solid
powder helps to absorb the oil portion of the LDP which helps to
give the rubber strength as well as making the rubber less soft
during processing and ultimately a higher hardness when cured.
[0028] The proportions of the three important ingredients, NBR,
LDP, CMC, are all in the 15-35 weight % range for each, based on
the total components. Normally, with rubber compounds, composition
is expressed in terms of parts per hundred parts rubber or phr. All
recipes start with 100 parts of raw polymer and then other
materials are expressed in parts compared to that. In one
non-limiting embodiment in this case, as will be shown, the base
polymer is 100 phr NBR with from about 18 to 52 vol % ACN
(acrylonitrile). In the compound herein, the range of LDP may be in
the range of about 80 to about 140 phr. That would be equivalent to
about 40-70 phr of the swelling AC. The high oil content may become
a limiting factor as to how much of the LDP may be physically added
to the NBR. If a higher concentration of the swelling polymer was
to become commercially available, then the phr range of 80-140
would still be applicable, however, the active level of polymer
would increase beyond the current 40-70 phr range which should
result in an elastomer capable of even higher swelling. The CMC
would be thus be in the range of about 50-150 phr.
[0029] Suitable acrylic copolymers include, but are not necessarily
limited to copolymers of acrylic acid and its esters with other
materials such as sodium hydroxide, polyacrylamide copolymer,
ethylene maleic anhydride copolymer, cross linked CMC, polyvinyl
alcohol copolymers, cross linked polyethylene oxide and starch
grafted copolymer of poly ACN. Cellulose is a general name and in
general a commodity. One non-limiting, suitable example is
chemically referred to as Carboxy Methyl Cellulose (CMC) and is
generally sold under some form of this name. Other suitable
specific examples of CMC include, but are not limited to,
AKUCELL.RTM. AF3281 CMC available from Akzo Nobel, CMC from
Aqualon, and CMC from Quingdae Rich Chemicals. Any other general
cellulose forms such as hydroxypropylmethyl cellulose (HPMC) or
methylcellulose (MC) and combinations thereof that function to
accomplish the properties and goals of the water swellable
elastomers herein and which are compatible with the other
components are acceptable for use herein.
[0030] Other important ingredients or components in addition to the
three discussed above include fillers, activators, antioxidants,
process aids, and curatives. There are various other grades of
fillers which may be used alone or in combination, and in lesser or
greater amounts that may yield comparable, desirable or improved
rubber properties. Suitable fillers include, but are not
necessarily limited to, carbon black, silica (silicon dioxide,
SiO.sub.2), clays, calcium carbonate, bentonite and the like and
combinations thereof. The proportion of filler may range between
about 30 and 100 phr. Suitable activators include, but are not
necessarily limited to, magnesium oxide (MgO), zinc oxide (ZnO),
zinc stearate, stearic acid and the like and combinations thereof.
The proportion of activator may be in the range from about 1-10
phr. Suitable antioxidants include, but are not necessarily limited
to, any of the diphenyl amines (e.g. NAUGARD.RTM. antioxidants
available from Chemtura Corporation), or any of the
mercaptobenzimidazoles (e.g. VANOX ZMTI from RT Vanderbilt) and the
like and combinations thereof. Suitable process aids include, but
are not necessarily limited to, waxes (e.g. VANFRE.RTM. waxes
available from R. T. Vanderbilt Company), or process aids such as
WB-16 process additive from Strucktol and the like and combinations
thereof. The antioxidants and the process aids may each be in the
range of from about 0.5 to about 5.0 phr.
[0031] A variety of various curatives or agents may be used in the
cure package (generally sulfur and at least one accelerator).
Suitable curatives or curing agents may include, but are not
necessarily limited to, sulfur, peroxide and their co-agents (such
as VULCUP 40KE available from Crompton and triallyl isocyanurate
(TAIC)) and the like and an accelerator. Suitable sulfur
accelerators include, but are not necessarily limited to, mercapto
compounds, sulfenamides, thiuram compounds, and the like and
combinations thereof. Non-limiting examples of more specific
mercapto compounds include 2-mercaptobenzothiazole (MBT),
mercaptobenzothiazyl disulfide (MBTS), sulfenamides such as
benzothiazyl-2-t-butyl sulfenamide (TBBS), and thiurams such as
tetramethyl thiuram disulfide (TMTD) and the like, and combinations
thereof. Suitable curatives and accelerators may be each present in
the range from about 0.2 to about 3.0 phr.
[0032] Non-limiting, suitable ranges for each of the components of
the water swellable elastomers herein are summarized in Table
I.
TABLE-US-00001 TABLE I Component Proportions for Water Swellable
Elastomers Component phr alternative phr Nitrile (NBR) with ACN %
(18-52%) 100 100 CMC 50-150 100-150 Carbon Black 30-100 60-100
Silica 30-100 20-50 Acrylic Copolymer (AC) 80-140 100-130 Magnesium
Oxide 1-10 3-8 Antioxidant 0.5-5.0 0.5-3.0 Wax 0.5-5.0 0.5-3.0
Sulfur 0.2-3.0 0.2-3.0 Accelerator 0.2-3.0 0.2-3.0
[0033] In one non-limiting embodiment, the composition of the water
swelling elastomer does not include a water soluble resin. Such
water soluble resins that may be avoided in some non-restrictive
versions include polyethylene oxides, polyvinylpyrrolidones,
hydroxyethylcelluloses or hydroxypropylcelluloses.
[0034] The addition, blending or compounding of these components
may be performed by any conventional technique or method to be
developed in the future. For instance, the rubber compound may be
mill mixed or mixed in a Banbury or other internal mixer.
Furthermore, there are no special curing conditions required. These
compounds may be cured in normal, ambient settings or as more
commonly done they can be cured in a heated oven or autoclave. As
is typical, the amount of cure needed may vary by the size and
thickness. Increases or decreases in the time and/or temperature of
cure may be readily made depending on a particular application.
[0035] The water swellable elastomers herein may find a wide
variety of uses and are not limited to downhole tools used in
hydrocarbon recovery operations, although this is certainly one
suitable application. In particular, the water swellable compounds
are expected to be useful as selectively deployed sealing elements
for flow channels, particularly well flow channels such as annuli
and the like. Suitable downhole tools for use in hydrocarbon
exploration and recovery operations include, but are not
necessarily limited to well packers, bridge plugs, expandable pipes
or any other well tool requiring a swelling or expanding area to
seal or block fluid flow. These tools once deployed, swollen,
enlarged and/or expanded are not desired to shrink and be
extracted. In some non-limiting instances, the elastomeric seals
may shrink should they no longer become in contact with an aqueous
fluid and be allowed to "dry out", but this is highly unlikely in a
downhole application.
[0036] An example of using the water swellable elastomers described
herein on a downhole tool, in a specific case a packer, is
schematically illustrated in FIGS. 5 and 6 where the overall
downhole tool or downhole zone isolator (packer) 10 has a central
support substrate or mandrel 12, shown in partial cross-section as
of generally tubular shape, around which has been formed a
selectively deployed sealing element 14 of the water swellable
elastomer. The expansion element 14. The selectively deployed
sealing element 14 has a first or initial size as seen in FIG.
5.
[0037] During run-in of the tool into the wellbore, the selectively
deployed sealing element 14 is in its first or initial state which
will allow it to be put in the correct place easily. After contact
with water or brine, the selectively deployed sealing element 14'
will expand, swell or be deployed to it's a second shape and
volume, and will then conform to the borehole walls 16 of the
subterranean formation 18. This will be some different or second
size of selectively deployed sealing element 14' as shown in FIG. 6
of greater than the volume of the initial or first size shown in
FIG. 5. In this manner, wellbore 20 is sealed at this point. The
water or brine to deploy the selectively deployed sealing element
14 outward may come from the water in the subterranean formation,
or may be pumped down hole from the surface.
[0038] In particular, the water swellable elastomers herein are
expected to be used in wellbore isolation products similar to the
Reactive Element Packer (REPackers) and FORMPAC.TM. packers, which
are considered expandable tools, all available from Baker Oil
Tools. Expandable tools are made from special pipe that is swaged
when in place, which thins and expands the pipe to make it larger
by about 20-25%. Adding or applying the water swelling rubber to
the outside of this pipe allows the tool to seal in a slightly
larger or irregular hole than the expandable pipe could do on its
own.
[0039] The invention will now be illustrated using certain specific
Examples which are not meant to limit it in any way, but simply to
further illuminate it.
Examples
[0040] Shown in FIGS. 1-4 are several plots which show the increase
in swell capability of the water swellable elastomer compound
compared to an identical compound without CMC, the effect of
temperature on the rate of swell, the effect of salt concentration,
and the effect that various salts have on the swelling of the
compound. As will be seen, the water swellable rubber works best in
water-based fluids with low salt content. The higher the salt
content, the less it will swell. This is believed to be due to the
ionic hindrance that the mono-valent salts; such as Na.sup.+ and
K.sup.+ impart around the water swelling elastomer. This ionic
affinity essentially blocks the polymer from absorbing the water
molecules. As the concentration of salt increases, the more
hindrance there is and thus less water swelling. As the temperature
increases from ambient to 200.degree. F. (93.degree. C.) the rate
of swell will increase. Above 200.degree. F. (93.degree. C.) the
rate increase is less significant. Initially, the bulk of
applications are expected to be in this range, but it is
anticipated that the water swelling elastomers may find uses and
applications up to temperatures as high as 300.degree. F.
(149.degree. C.) or higher.
[0041] The water swellable formulation used in the experiments that
gave the data presented in the Figures had the composition given in
Table II.
TABLE-US-00002 TABLE II Component Proportions for Water Swellable
Elastomer used in Figures Data Component phr Nitrile (NBR) with ACN
100 CMC 150 Carbon Black 80 Silica 40 Acrylic Copolymer (AC) 120
Magnesium Oxide 5 Antioxidant 2 Wax 1 Sulfur 0.8 Accelerator 0.5
TOTAL 499.3
[0042] FIG. 1 presents a graph of % volume increase as a function
of temperature over time for an improved water swelling compound
herein generated by contacting the rubber with 3.5% NaCl Brine at
three different temperatures: 180.degree. F. (82.degree. C.),
130.degree. F. (54.degree. C.), and 70.degree. F. (21.degree. C.).
It may be seen that the vol % increase of 130% was achieved in each
case, but that the swelling rate was faster with increasing
temperature.
[0043] FIG. 2 shows a graph of % volume increase as a function of
NaCl concentration over time for an improved water swelling
compound herein contacting water at 180.degree. F. (82.degree. C.),
where the water contains no NaCl, and then 3.5% and finally 6%
NaCl. It may be seen that maximum swelling decreased with
increasing sodium chloride content. Where no NaCl was present, the
vol % increase was about 413%, whereas when the water was 6% NaCl
brine, the vol % increase was only about 90%.
[0044] FIG. 3 presents a graph of % volume increase as a function
of different salts and ion type over time for an improved water
swelling compound herein contacting water at room temperature,
where the water contains 3.5% of three different salts: NaCl, ZnBr
and CaCl.sub.2. It may be seen that of the three aqueous brines,
the volume increase was greatest and fastest for the mono valiant
NaCl brine. The vol % increase was slowest and lowest for the
di-valiant CaCl.sub.2 brine, and intermediate for the ZnBr brine.
This is because it takes less of the larger di-valent salts such as
Ca.sup.++, to sufficiently block or interfere with the water from
reacting with the elastomer. Thus, concentrations of as low as 2%
of these di-valent salts can be sufficient to significantly reduce
the swelling of these compounds to levels that might not allow the
tool to swell to the required amount, even in requirements of less
than 15%.
[0045] Finally, FIG. 4 demonstrates a graph of % volume increase
over time for an improved water swelling compound herein contacting
water at room temperature contrasted with a prior water swelling
compound. It may be readily seen that the inventive compound herein
relatively rapidly gave an increase of over 1300 vol % after about
240 hours, whereas the comparative compound after about the same
period of time leveled off at about a 520 vol % increase.
[0046] It may thus be seen that the water swelling elastomer
compound herein has improved swelling as compared with an otherwise
identical compound absent the cellulose component. In addition, the
water swelling elastomers herein have improved processing and
better physical properties than the comparative compounds.
[0047] In addition it has been common knowledge that acids will
chemically react with and breakdown Acrylic Copolymers. Acids such
as HCl are commonly used in acidizing situations and lab tests have
verified that the HCl will chemically breakdown the AC and prevent
the elastomer from swelling. This is different from the salt
interference which is reversible; acid breakdown is not.
[0048] In the foregoing specification, the invention has been
described with reference to specific embodiments thereof, and has
been demonstrated as effective in providing methods and
compositions for an elastomer with improved swelling volumes.
However, it will be evident that various modifications and changes
may be made thereto without departing from the broader scope of the
invention as set forth in the appended claims. Accordingly, the
specification is to be regarded in an illustrative rather than a
restrictive sense. For example, specific combinations of base
polymers, NBRs, celluloses, acrylic copolymers, fillers, curatives,
activators, antioxidants, process aids, and other components
falling within the claimed parameters, but not specifically
identified or tried in a particular composition or method, are
anticipated to be within the scope of this invention.
[0049] The terms "comprises" and "comprising" in the claims should
be interpreted to mean including, but not limited to, the recited
elements.
[0050] The present invention may suitably comprise, consist or
consist essentially of the elements disclosed and may be practiced
in the absence of an element not disclosed.
* * * * *