Methods of sealing plugs in well bores

The present invention provides improved methods of sealing a bridge plug or the like in a pipe disposed in a well bore. The methods basically include the steps of preparing a hardenable epoxy sealing composition which hardens into a resilient solid mass having a high pipe surface bond strength, placing the epoxy composition into the pipe adjacent to the bridge plug therein and allowing the epoxy composition to harden.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates generally to improved methods of sealing 
bridge plugs in pipes disposed in well bores, and more particularly, to 
such methods wherein the sealant is highly resilient and has high bond 
strength. 
2. Description of the Prior Art 
Mechanical bridge plugs are commonly utilized to provide isolation of a 
subterranean zone penetrated by a well bore having a pipe string such as 
casing or a liner disposed therein. For example, in perforating casing in 
the zone and/or in stimulation treatments performed therein after 
perforations have been formed, a bridge plug is set in the casing above 
the zone. Because bridge plugs are mechanical and rigid after being set, 
when a pressure differential is exerted across the plug and the casing 
expands as a result of the pressure, the seal between the plug and the 
pipe is often lost which allows the plug to be moved within the pipe by 
the pressure differential. 
Heretofore, in attempts to prevent the loss of seal and movement of a 
bridge plug, a quantity of a conventional Portland cement slurry has been 
placed in the pipe adjacent to the bridge plug and allowed to harden. 
However, when the pressure differential exerted on the bridge plug and the 
set cement column adjacent thereto reaches a sufficient level, the ability 
of the cement to maintain a bond to the pipe is overcome and the entire 
column comprised of bridge plug and set cement is moved in the pipe. This 
allows fluid to flow around the plug and cement which makes the drill-out 
of the plug and cement extremely difficult. 
Thus, there is a need for improved methods of sealing a bridge plug in a 
pipe whereby the sealant used hardens into a highly resilient 
non-permeable mass which has a high pipe surface bond strength and can 
withstand pipe movements and high pressure differentials without failure. 
SUMMARY OF THE INVENTION 
The present invention provides improved methods of sealing a bridge plug or 
the like in a pipe disposed in a well bore using epoxy sealing 
compositions. The methods basically comprise the steps of preparing a 
hardenable epoxy sealing composition which hardens into a solid mass 
having high resiliency and a high pipe surface bond strength, placing the 
epoxy composition into the pipe adjacent to the bridge plug therein and 
allowing the epoxy composition to harden. 
The epoxy compositions which are useful in accordance with this invention 
having high resiliencies and high bond strengths after hardening are 
comprised of an epoxy resin or an epoxide containing liquid, or both, an 
organosilane compound and at least one hardening agent. The epoxy 
compositions can also include a filler such as crystalline silica or the 
like. 
It is, therefore, a general object of the present invention to provide 
improved methods of sealing bridge plugs and the like in pipes disposed in 
well bores. 
Other and further objects, features and advantages of the present invention 
will be apparent to those skilled in the art upon a reading of the 
description of preferred embodiments which follows. 
DESCRIPTION OF PREFERRED EMBODIMENTS 
The present invention provides improved methods of sealing a bridge plug or 
the like in a pipe disposed in a well bore using a sealing composition 
which hardens after being placed in the pipe. In accordance with the 
methods, a sealing composition which hardens into a resilient solid mass 
having high pipe bond strength is prepared, placed in a pipe disposed in a 
well bore adjacent to a plug therein and allowed to harden. The sealing 
compositions which are useful in accordance with the present invention are 
epoxy compositions basically comprised of an epoxy resin or an epoxide 
containing liquid, or both, an organosilane compound and at least one 
hardening agent. 
While various epoxy resins can be utilized, preferred such resins are those 
selected from the condensation products of epichlorohydrin and bisphenol 
A. A particularly suitable such resin is commercially available from the 
Shell Chemical Company under the trade designation "EPON.RTM.RESIN 828". 
This epoxy resin has a molecular weight of about 340 and a one gram 
equivalent of epoxide per about 180 to about 195 grams of resin. Another 
preferred epoxy resin is a condensation product of epichlorohydrin and 
bisphenol A which is predispersed in a non-ionic aqueous fluid and is 
commercially available from the Shell Chemical Company under the trade 
designation "EPI-REZ.RTM.-3510-W-60". This epoxy resin has a molecular 
weight of about 340 and a one gram equivalent of epoxide per 195 grams of 
resin. Another preferred epoxy resin is an epoxidized bisphenol A novalac 
resin which is predispersed in a non-ionic aqueous fluid and is 
commercially available from the Shell Chemical Company under the trade 
designation "EPI-REZ.RTM.-5003-W-55". This epoxy resin has a one gram 
equivalent of epoxide per about 205 grams of resin. 
When used, the epoxy resin is generally included in an epoxy composition of 
this invention in an amount in the range of from about 10% to about 90% by 
weight of the epoxy composition, preferably in an amount of about 50%. 
A solvent comprised of one or more aromatic hydrocarbons or a low viscosity 
epoxide containing liquid or a mixture of such epoxide containing liquids 
can be utilized to modify the viscosity of the epoxy resin used and to add 
flexibility and resiliency to the epoxy composition after hardening. An 
epichlorohydrin/bisphenol A condensation epoxy resin which has been 
modified with an aromatic solvent is commercially available from the Shell 
Chemical Company under the trade designation "EPSEAL RE.RTM.". A 
particularly suitable solvent which is presently preferred is comprised of 
a mixture of hydrocarbons containing from about 50% to about 99% of one or 
more aromatic hydrocarbons by weight of the solvent. Such a preferred 
solvent is commercially available under the tradename "CYCLO SOL 63.TM." 
from Shell Chemical Co. of Houston Tex. 
When an aromatic solvent or an epoxide containing liquid or mixture of such 
liquids is included in an epoxy composition of this invention to modify 
the viscosity of an epoxy resin therein, the solvent or epoxide containing 
liquid or mixture is generally present in an amount in the range of from 
about 20% to about 40% by weight of the epoxy composition, preferably in 
an amount of about 27%. An epoxide containing liquid or a mixture of such 
liquids can also be utilized as the only epoxide source in an epoxy 
composition of this invention. 
While various epoxide containing liquids can be used, preferred such 
liquids are the diglycidyl ether of 1,4-butanediol, the diglycidyl ether 
of neopentyl glycol and the diglycidol ether of cyclohexanedimethanol. A 
suitable epoxide containing liquid comprised of the diglycidyl ether of 
1,4-butanediol is commercially available from the Shell Chemical Company 
under the trade name "HELOXY.RTM.67". This epoxide containing liquid has a 
viscosity at 25.degree. C. in the range of from about 13 to about 18 
centipoises, a molecular weight of 202 and a one gram equivalent of 
epoxide per about 120 to about 130 grams of the liquid. A suitable 
diglycidyl ether of neopentylglycol is commercially available from Shell 
Chemical Company under the trade name "HELOXY.RTM.68". This epoxide 
containing liquid has a viscosity at 25.degree. C. in the range of from 
about 13 to about 18 centipoises, a molecular weight of 216 and a one gram 
equivalent of epoxide per about 130 to about 140 grams of the liquid. A 
suitable diglycidyl ether of cyclohexanedimethanol is commercially 
available from Shell Chemical Company under the trade name 
"HELOXY.RTM.107". This epoxide containing liquid has a viscosity at 
25.degree. C. in the range of from about 55 to about 75 centipoises, a 
molecular weight of 256 and a one gram equivalent of epoxide per about 155 
to about 165 grams of the liquid. 
When an epoxide containing liquid or mixture is utilized as the only 
epoxide source in an epoxy composition of this invention, the epoxide 
containing liquid or mixture is generally present in an amount in the 
range of from about 20% to about 80% by weight of the epoxy composition, 
preferably in an amount of about 50%. 
The organosilane compound functions in the epoxy compositions of this 
invention to impart high metal pipe surface bond strengths to the 
compositions. The organosilane compound undergoes hydrolysis in the 
presence of trace quantities of water whereby trialkoxysilanols are formed 
which dehydrate and form strong bonds to pipe surfaces. That is, the 
dehydration results in the formation of bonds with iron oxide on the pipe. 
Suitable organosilane compounds include 3-aminopropyltrimethyoxysilane, 
3-aminopropyltriethoxysilane, N-2-(aminoethyl)-3-ammopropyltriethoxysilane 
and 3-glycidoxy-propyltrimethoxysilane. Of these, 
3-glycidoxypropyltrimethoxysilane is preferred. The organosilane compound 
is included in an epoxy composition of this invention in an amount in the 
range of from about 0.1% to about 5% by weight of the epoxy composition, 
preferably in an amount of about 0.5%. 
A variety of hardening agents including, but not limited to, aliphatic 
amines, amide amines, amido amines, imidazoles, aliphatic tertiary amines, 
aromatic amines, cycloaliphatic amines, heterocyclic amines, polyamides, 
polyethylamines and carboxylic acid anhydrides can be utilized in the 
compositions of this invention containing the above described epoxy resins 
and/or epoxide containing liquids. Of these, aliphatic amines, aromatic 
amines and carboxylic acid anhydrides are the most suitable. 
Examples of aliphatic and aromatic amine hardening agents are 
triethylenetetraamine, ethylenediamine, N-cocoalkyltrimethylenediamine, 
isophoronediamine, diethyltoluenediamine, and 
tris(dimethylaminomethylphenol). Examples of suitable carboxylic acid 
anhydrides are methyltetrahydrophthalic anhydride, hexahydrophthalic 
anhydride, maleic anhydride, polyazelaic polyanhydride and phthalic 
anhydride. Of these, triethylenetetraamine, ethylenediamine, 
N-cocoalkyltrimethylenediamine, isophoronediamine, diethyltoluenediamine 
and tris(dimethylaminomethylphenol) are preferred, with isophoronediamine, 
diethyletoluenediamine and tris(dimethylaminomethylphenol) being the most 
preferred. The hardening agent or agents utilized are included in the 
epoxy compositions of the present invention in an amount in the range of 
from about 20% to about 50% by weight of the compositions. 
As mentioned above, the epoxy compositions can also include a particulate 
filler such as crystalline silicas, amorphous silicas, clays, calcium 
carbonate or barite. When such a filler is utilized, it is added to an 
epoxy composition of this invention in an amount in the range of from 
about 100% to about 300% by weight of the composition. 
A preferred method of this invention for sealing a plug in a pipe disposed 
in a well bore comprises the following steps. A hardenable epoxy sealing 
composition of this invention is prepared which hardens into a resilient 
solid mass having high bond strength. The epoxy composition is basically 
comprised of an epoxy resin or an epoxide containing liquid, or both, of 
the types described above, an organosilane compound of the type described 
above and at least one hardening agent of the type described above. After 
the epoxy composition has been prepared, it is placed in a pipe disposed 
in a well bore adjacent to a plug therein and the epoxy composition is 
allowed to harden. 
In order to further illustrate the methods and epoxy compositions of this 
invention, the following examples are given.

EXAMPLE 1 
An epoxide containing liquid comprised of diglycidyl ether of cyclohexane 
dimethanol and an epoxide resin comprised of the condensation product of 
epichlorohydrin and bisphenol A mixed with an aromatic solvent were tested 
individually and in 50% mixtures with each other. The epoxides were mixed 
with an organosilane, i.e., N-2-(aminoethyl)-3-aminopropyltrimethoxysilane 
and a hardening agent comprised of 2-ethyl-4-methylimidazole or a mixture 
of diethyltoluenediamine and tris(dimethylaminoethylphenol). Microsand 
(powdered crystalline silica) was added to the mixtures, and the mixtures 
were tested for shear bond strength. Additional identical mixtures were 
prepared without the organosilane compound, and they were also tested for 
shear bond strength. 
The apparatus used to determine the shear bond strength included a standard 
ASTM 2".times.2".times.2" cube mold with a plastic liner and a metal plate 
to which the epoxide mixtures tested bonded to. A plastic liner was used 
to prevent the epoxide mixtures from bonding to the sides and bottom of 
the mold. The metal plate was 2" wide.times.3" high.times.0.5" thick with 
smooth surfaced ends at the top and bottom of the 3" height. The surfaced 
bottom served as a means to obtain a vertical positioning of the metal 
plate in the mold during pouring and curing of the epoxy mixture and the 
surfaced top was used for applying even loading to the plate. The other 
surfaces of the plate were sand blasted. The plate was placed in the 
center of the plastic mold and the epoxide mixtures tested were poured on 
both sides of the plate. 
Each epoxide mixture tested was cured in the mold for 72 hours at 
140.degree. F. Thereafter, the bonding plate with the cured epoxy mixture 
bonded thereto was placed in a support apparatus whereby the bottom and 
sides of the cured epoxy mixture were supported but the area immediately 
below the bonding plate was not. The support system was then placed 
between the loading platens of a load press, and a load was applied to the 
bottom of the support system and the top of the bonding plate. The load 
(in psi.) at which the bond between the plate surfaces and the epoxide 
mixture failed, i.e., the shear bond strength was noted. 
The quantities of the various components of each epoxide mixture tested and 
the shear bond strengths determined are set forth in Table I below. 
TABLE I 
__________________________________________________________________________ 
SHEAR BOND STRENGTH TESTS 
Quantities of Components, % by weight of Epoxide Liquid, Epoxy Resin or 
mixtures thereof. 
Epoxy.sup.2 Resin 
First.sup.3 
Second.sup.4 
Third.sup.5 
Organo.sup.7 - 
Sample 
Epoxide.sup.1 
Diluted with 
Hardening 
Hardening 
Hardening 
Micro.sup.6 
Silane 
Shear Bond 
No. Liquid 
Aromatic Solvent 
Agent 
Agent 
Agent 
Sand 
Compound 
Strength, psi 
__________________________________________________________________________ 
1 None 100 3 None None 150 0.05 185 
2 50 50 3 None None 150 0.05 460 
3 100 None None 28 0.3 150 0.475 
3020 
4 None 100 3 None None 150 None 81 
5 50 50 3 None None 150 None 171 
6 100 None None 28 0.3 150 None 258 
__________________________________________________________________________ 
.sup.1 Diglycidyl ether of cyclohexane dimethanol "HELOXY .RTM.107" from 
Shell Chemical Co. 
.sup.2 Epichlorohydrin and bisphenol A resin ("EPON .RTM.RESIN 828") 
diluted with aromalic solvent "EPSEAL .RTM.RE" from Shell Chemical Co. 
.sup.3 2ethyl-4-methyl imidazole 
.sup.4 Diethyltoluenediamine 
.sup.5 Tris(dimethylaminoethylphenol) 
.sup.6 Powdered crystalline silica 
.sup.7 N2-(aminoethyl)-3-aminopropyltrimethoxysilane 
From Table I it can be seen that the presence of the organosilane compound 
in the epoxide mixtures substantially increased the shear bond strengths 
of the mixtures. 
EXAMPLE 2 
Additional epoxide mixtures of the type described above were prepared 
except that the hardening agent utilized was a mixture of 
diethyltoluenediamine and tris(dimethylaminoethylphenol). Also, two 
different organosilane compounds were utilized which were compared to each 
other and to identical epoxy mixtures without a silane compound. The 
results of these tests are set forth in Table II below. 
TABLE II 
__________________________________________________________________________ 
COMPRESSIVE STRENGTH AND SHEAR BOND STRENGTH TESTS 
Quantities of Components, % by Weight of Epoxide Liquid, Epoxy Resin or 
Mixture Thereof. 
First.sup.6 
Second.sup.7 
Epoxy.sup.2 Resin 
First.sup.3 
Second.sup.4 
Organo- 
Organo- 
Sample 
Epoxide.sup.1 
Diluted With 
Hardening 
Hardening 
Micro.sup.5 
Silane 
Silane 
Compressive 
Shear Bond 
No. Liquid 
Aromatic Solvent 
Agent 
Agent 
Sand 
Compound 
Compound 
Strength, psi 
Strength, 
__________________________________________________________________________ 
psi 
1 100 None 28 2.5 150 0.5 None 20,900 
1294 
2 80 20 28 2.5 150 0.5 None 18,780 
628 
3 60 40 28 2.5 150 0.5 None 14,410 
288 
4 100 None 28 2.5 150 1 None 22,900 
1315 
5 80 20 28 2.5 150 1 None 21,900 
583 
6 60 40 28 2.5 150 1 None 17,280 
476 
7 100 None 2S 2.5 150 None 0.5 22,400 
963 
8 80 20 28 2.5 150 None 0.5 20,100 
538 
9 60 40 28 2.5 150 None 0.5 15,770 
362 
10 100 None 28 2.5 150 None None 17,620 
759 
11 80 20 28 2.5 150 None None 16,940 
566 
12 60 40 28 2.5 150 None None 14,450 
408 
__________________________________________________________________________ 
.sup.1 Diglycidyl ether of cyclohexane dimethanol "HELOXY .RTM.107" from 
Shell Chemical Co. 
.sup.2 Epichlorohydrin and bisphenol A resin ("EPON .RTM.RESIN 828") 
diluted with aromatic solvent "EPSEAL .RTM.RE" from Shell Chemical Co. 
.sup.3 Diethyltoluenediamine. 
.sup.4 Tris(dimethylaminoethylphenol). 
.sup.5 Powdered crystalline silica. 
.sup.6 3glycidoxypropyltrimethoxysilane. 
.sup.7 3aminopropyltrimethoxysilane. 
From Table II it can be seen that the presence of an organosilane compound 
in the epoxide mixtures substantially increased both the compressive 
strengths and shear bond strengths of the hardened mixtures. 
Thus, the present invention is well adapted to carry out the objects and 
attain the features and advantages mentioned as well as those which are 
inherent therein. While numerous changes may be made by those skilled in 
the art, such changes are encompassed within the spirit of this invention 
as defined by the appended claims.