U.S. patent application number 10/229587 was filed with the patent office on 2004-03-04 for methods and compositons for forming subterranean fractures containing resilient proppant packs.
Invention is credited to Barton, Johnny A., Nguyen, Philip D..
Application Number | 20040040713 10/229587 |
Document ID | / |
Family ID | 28041409 |
Filed Date | 2004-03-04 |
United States Patent
Application |
20040040713 |
Kind Code |
A1 |
Nguyen, Philip D. ; et
al. |
March 4, 2004 |
METHODS AND COMPOSITONS FOR FORMING SUBTERRANEAN FRACTURES
CONTAINING RESILIENT PROPPANT PACKS
Abstract
Improved methods of forming fractures containing resilient
proppant particle packs which prevent the production of sand and
fines with produced fluids and prevent proppant flow-back in a
subterranean zone penetrated by a well bore are provided. As the
fractures are formed, a liquid hardenable resin component is mixed
with a liquid hardening agent component and a liquid rubber
component to form a hardenable resin composition. The hardenable
resin composition is coated onto dry proppant particles which are
suspended in the fracturing fluid and placed in the fractures. The
hardenable resin composition on the resin composition coated
proppant particles is allowed to harden and consolidate the
proppant particles into high strength resilient permeable
packs.
Inventors: |
Nguyen, Philip D.; (Duncan,
OK) ; Barton, Johnny A.; (Marlow, OK) |
Correspondence
Address: |
Robert A. Kent
Halliburton Energy Services
2600 South 2nd Street
Duncan
OK
73536
US
|
Family ID: |
28041409 |
Appl. No.: |
10/229587 |
Filed: |
August 28, 2002 |
Current U.S.
Class: |
166/295 ;
166/281 |
Current CPC
Class: |
Y10S 507/924 20130101;
Y10S 507/922 20130101; C09K 8/805 20130101; C09K 8/685
20130101 |
Class at
Publication: |
166/295 ;
166/281 |
International
Class: |
E21B 033/138; E21B
043/267 |
Claims
What is claimed is:
1. A method of forming fractures in a subterranean zone containing
resilient proppant particle packs which prevent the production of
formation sand and fines with produced fluids and proppant
flow-back comprising the steps of: (a) providing a liquid
hardenable resin component comprised of a hardenable resin; (b)
providing a liquid hardening agent component comprised of a
hardening agent; (c) providing a liquid rubber component comprised
of a rubber latex and a rubber latex stabilizing surfactant; (d)
providing a source of dry proppant particles; (e) providing a
gelled liquid fracturing fluid; (f) pumping said gelled liquid
fracturing fluid into said subterranean zone to form said fractures
therein and to place hardenable resin composition coated proppant
particles therein; (g) as said fractures are formed in step (f),
mixing said liquid hardenable resin component with said liquid
hardening agent component and said liquid rubber component to form
a liquid hardenable resin composition; (h) coating said liquid
hardenable resin composition produced in step (g) onto dry proppant
particles conveyed from said source thereof to form hardenable
resin composition coated proppant particles; (i) mixing said
hardenable resin composition coated proppant particles produced in
step (h) with said fracturing fluid pumped in accordance with step
(f) whereby said hardenable resin composition coated proppant
particles are suspended therein; (j) terminating steps (f), (g),
(h) and (i) when said resin composition coated proppant particles
have been placed in said fractures; and (k) allowing said
hardenable resin composition on said hardenable resin composition
coated proppant particles to harden and consolidate said proppant
particles into resilient permeable packs which prevent the
production of formation sand and fines with produced fluids and
proppant flow-back.
2. The method of claim 1 wherein said hardenable resin in said
liquid hardenable resin component is an organic resin comprising
one or more members selected from the group consisting of bisphenol
A-epichlorohydrin resin, polyepoxide resin, novolak resin,
polyester resin, phenol-aldehyde resin, urea-aldehyde resin, furan
resin, urethane resin and glycidyl ether.
3. The method of claim 1 wherein said hardenable resin in said
liquid hardenable resin component is comprised of a bisphenol
A-epichlorohydrin resin.
4. The method of claim 1 which further comprises a solvent for said
resin in said liquid hardenable resin component.
5. The method of claim 4 wherein said solvent for said resin in
said liquid hardenable resin component comprises one or more
members selected from the group consisting of dipropylene glycol
methyl ether, dipropylene glycol dimethyl ether, dimethyl
formamide, diethyleneglycol methyl ether, ethyleneglycol butyl
ether, diethyleneglycol butyl ether, propylene carbonate,
d'limonene and fatty acid methyl esters.
6. The method of claim 4 wherein said solvent for said resin in
said liquid hardenable resin component is comprised of dipropylene
glycol methyl ether.
7. The method of claim 1 wherein said hardening agent in said
liquid hardening agent component comprises one or more members
selected from the group consisting of amines, aromatic amines,
polyamines, aliphatic amines, amides, polyamides,
4,4'-diaminodiphenyl sulfone, 2-ethyl-4-methyl imidazole and
1,1,3-trichlorotrifluoroacetone.
8. The method of claim 1 wherein said liquid hardening agent
component includes a silane coupling agent, a hydrolyzable ester
for breaking gelled fracturing fluid films on said proppant
particles and a surfactant for facilitating the coating of said
resin on said proppant particles and for causing said hardenable
resin to flow to the contact points between adjacent resin coated
proppant particles and a liquid carrier fluid.
9. The method of claim 8 wherein said silane coupling agent in said
liquid hardening agent component comprises one or more members
selected from the group consisting of
N-2(aminoethyl)-3-aminopropyltrimethoxysilane,
3-glycidoxypropyltrimethoxysilane and
n-beta-(aminoethyl)-gamma-aminoprop- yl trimethoxysilane.
10. The method of claim 8 wherein said silane coupling agent in
said liquid hardening agent component is comprised of
n-beta-(aminoethyl)-gamm- a-aminopropyl trimethoxysilane.
11. The method of claim 8 wherein said hydrolyzable ester for
breaking gelled fracturing fluid films on said proppant particles
in said liquid hardening agent component comprises one or more
members selected from the group consisting of a mixture of
dimethylglutarate, dimethyladipate and dimethylsuccinate, sorbitol,
catechol, dimethylthiolate, methyl salicylate, dimethyl salicylate,
dimethyl succinate and ter-butylhydroperoxide.
12. The method of claim 8 wherein said hydrolyzable ester for
breaking gelled fracturing fluid films on said proppant particles
in said liquid hardening agent component is a mixture of
dimethylglutarate, dimethyladipate and dimethylsuccinate.
13. The method of claim 8 wherein said surfactant for facilitating
the coating of said resin on said proppant particles and for
causing said hardenable resin to flow to the contact points between
adjacent resin coated proppant particles in said liquid hardening
agent component is selected from the group consisting of an
ethoxylated nonyl phenol phosphate ester, mixtures of one or more
cationic surfactants and one or more non-ionic surfactants and a
C.sub.12-C.sub.22 alkyl phosphonate surfactant.
14. The method of claim 8 wherein said surfactant for facilitating
the coating of said resin on said proppant particles and for
causing said hardenable resin to flow to the contact points between
adjacent resin coated proppant particles in said liquid hardening
agent component is a C.sub.12-C.sub.22 alkyl phosphonate
surfactant.
15. The method of claim 8 wherein said liquid carrier fluid in said
liquid hardening agent component comprises one or more members
selected from the group consisting of dipropylene glycol methyl
ether, dipropylene glycol dimethyl ether, dimethyl formamide,
diethyleneglycol methyl ether, ethyleneglycol butyl ether,
diethyleneglycol butyl ether, propylene carbonate, d'limonene and
fatty acid methyl esters.
16. The method of claim 8 wherein said liquid carrier fluid in said
liquid hardening agent component is comprised of dipropylene glycol
methyl ether.
17. The method of claim 8 which further comprises a viscosifying
agent in said liquid hardening gent component for viscosifying said
carrier fluid and dispersing said hardening agent when said
hardening agent is a particulate solid.
18. The method of claim 17 wherein said viscosifying agent in said
liquid hardening agent component is comprised of a member selected
from the group consisting of hydroxypropylcellulose and
organophilic clays.
19. The method of claim 17 wherein said viscosifying agent in said
liquid hardening agent component is the reaction product of a
smectite clay and a quaternary ammonium salt.
20. The method of claim 1 wherein said rubber latex in said liquid
rubber component comprises one or more members selected from the
group consisting of natural rubber (cis-1,4polyisoprene) latex,
styrene/butadiene copolymer latex, cis-1,4-polybutadiene rubber
latex, butyl rubber latex, ethylene/propylene rubber latex,
neoprene rubber latex, nitrile rubber latex, silicone rubber latex,
chlorosulfonated rubber latex, polyethylene rubber latex,
epichlorohydrin rubber latex, fluorocarbon rubber latex,
fluorosilicone rubber latex, polyurethane rubber latex, polyacrylic
rubber latex and polysulfide rubber latex.
21. The method of claim 1 wherein said rubber latex in said liquid
rubber component is comprised of a styrene/butadiene copolymer
latex containing water in an amount in the range of from about 50%
by weight of said latex.
22. The method of claim 1 wherein said rubber latex stabilizing
surfactant in said liquid rubber component comprises one or more
members selected from the group consisting of surfactants having
the formula R--Ph--O(OCH.sub.2CH.sub.2).sub.mOH wherein R is an
alkyl group having from about 5 to about 30 carbon atoms, Ph is
phenyl and m is an integer of from about 5 to about 50 and
surfactants having the formula R.sub.1(R.sub.2O).sub.nSO.sub.3X
wherein R.sub.1 is an alkyl group having from about 5 to about 20
carbon atoms, R.sub.2 is the group --CH.sub.2--CH.sub.2--, n is an
integer from about 10 to about 40 and X is a cation.
23. The method of claim 1 wherein said rubber latex stabilizing
surfactant in said liquid rubber component is comprised of a
sulfonated and ethoxylated sodium salt having the formula
H(CH.sub.2).sub.12-15(CH.sub.2- CH.sub.2O).sub.15SO.sub.3Na.
24. A method of forming fractures in a subterranean zone containing
resilient proppant particle packs which prevent the production of
formation sand and fines with produced fluids and proppant
flow-back comprising the steps of: (a) providing a liquid
hardenable resin component comprised of bisphenol A-epichlorohydrin
resin present in an amount in the range of from about 70% to about
100% by weight of said liquid hardenable resin component and a
solvent for said resin comprised of dipropylene glycol methyl ether
present in an amount in the range of from 0% to about 30% by weight
of said liquid hardenable resin component; (b) providing a liquid
hardening agent component comprised of a 4,4-diaminodiphenyl
sulfone hardening agent present in an amount in the range of from
about 30% to about 60% by weight of said liquid hardening agent
component, a silane coupling agent comprised of
n-beta-(aminoethyl)-gamma-aminopropyltrimethoxysilane present in an
amount in the range of from about 0.1% to about 3% by weight of
said liquid hardening agent component, a hydrolyzable ester mixture
comprised of dimethylglutarate, dimethyladipate and
dimethylsuccinate present in an amount in the range of from about
0.1% to about 3% by weight of said liquid hardening agent
component, a surfactant comprised of a C.sub.12-C.sub.22 alkyl
phosphonate present in an amount in the range of from about 2% to
about 15% by weight of said liquid hardening agent component, a
liquid carrier fluid comprised of dipropylene glycol methyl ether
present in an amount in the range of from about 30% to about 60% by
weight of said hardening agent component and a viscosifying agent
comprised of the reaction product of a smectite clay and a
quaternary ammonium salt present in an amount in the range of from
0% to about 3% by weight of said liquid hardening agent component;
(c) providing a liquid rubber component comprised of a
styrene/butadiene copolymer latex containing water in an amount of
about 50% by weight of said latex present in an amount in the range
of from about 99.9% to about 97% by weight of said liquid rubber
component and a rubber latex stabilizing surfactant comprised of a
sulfonated and ethoxylated sodium salt having the formula
H(CH.sub.2).sub.12-15(CH.sub.2CH.sub.2O).sub.15SO.sub.3Na present
in an amount in the range of from about 0.1% to about 3% by weight
of said liquid hardening agent component; (d) providing a source of
dry proppant particles; (e) providing a gelled liquid fracturing
fluid; (f) pumping said gelled liquid fracturing fluid into said
subterranean zone to form said fractures therein and to place
hardenable resin composition coated proppant particles therein; (g)
as said fractures are formed in step (f), mixing said liquid
hardenable resin component with said liquid hardening agent
component and said liquid rubber component to form a liquid
hardenable resin composition; (h) coating said liquid hardenable
resin composition produced in step (g) onto dry proppant particles
conveyed from said source thereof to form hardenable resin
composition coated proppant particles; (i) mixing said hardenable
resin coated proppant particles produced in step (h) with said
fracturing fluid pumped in accordance with step (e) whereby said
hardenable resin composition coated proppant particles are
suspended therein; (j) terminating steps (f), (g), (h) and (i) when
said resin composition coated proppant particles have been placed
in said one or more fractures; and (k) allowing said hardenable
resin composition on said resin composition coated proppant
particles to harden and consolidate said proppant particles into
one or more high strength resilient permeable packs which prevent
the production of formation sand and fines with produced fluids and
proppant flow-back.
25. The method of claim 24 wherein said bisphenol A-epichlorohydrin
resin is present in an amount of about 85% by weight of said liquid
hardenable resin component.
26. The method of claim 24 wherein said dipropylene glycol methyl
ether solvent is present in an amount of about 15% by weight of
said liquid hardenable resin component.
27. The method of claim 24 wherein said 4,4-diaminodiphenyl sulfone
hardening agent is present in an amount of about 40% by weight of
said liquid hardening agent component.
28. The method of claim 24 wherein said
n-beta-(aminoethyl)-gamma-aminopro- pyltrimethoxysilane is present
in an amount of about 1.5% by weight of said liquid hardenable
resin component.
29. The method of claim 24 wherein said hydrolyzable ester mixture
comprised of dimethylglutarate, dimethyladipate and
dimethylsuccinate is present in an amount of about 2% by weight of
said liquid hardenable resin component.
30. The method of claim 24 wherein said surfactant comprised of a
C.sub.12-C.sub.22 alkyl phosphonate is present in an amount of
about 12% by weight of said liquid hardenable resin component.
31. The method of claim 24 wherein said dipropylene glycol methyl
ether carrier fluid is present in an amount of about 40% by weight
of said hardening agent component.
32. The method of claim 24 wherein said reaction product of a
smectite clay and a quaternary ammonium salt viscosifying agent is
present in an amount of about 3% by weight of said hardening agent
component.
33. The method of claim 24 wherein said styrene/butadiene copolymer
latex containing water in an amount of about 50% by weight of said
latex is present in an amount of about 99% by weight of said liquid
rubber component.
34. The method of claim 24 wherein said rubber latex stabilizing
surfactant comprised of a sulfonated and ethoxylated sodium salt
having the formula
H(CH.sub.2).sub.12-15(CH.sub.2CH.sub.2O).sub.15SO.sub.3Na is
present in an amount of about 1% by weight of said liquid rubber
component.
35. A liquid hardenable resin composition for consolidating
proppant particles in subterranean fractures whereby consolidated
proppant particle packs are formed which are resilient and prevent
the production of formation sand and fines with produced fluids and
proppant particle flow-back comprising: a hardenable resin; a
solvent for said resin; a hardening agent for hardening said resin;
a rubber latex; and a rubber latex stabilizing surfactant.
36. The composition of claim 35 wherein said hardenable resin is an
organic resin comprised of one or more members selected from the
group consisting of bisphenol A-epichlorohydrin resin, polyepoxide
resin, novolak resin, polyester resin, phenol-aldehyde resin,
urea-aldehyde resin, furan resin, urethane resin, glycidyl ether
and mixtures thereof.
37. The composition of claim 35 wherein said hardenable resin is
comprised of a bisphenol A-epichlorohydrin resin.
38. The composition of claim 35 wherein said hardenable resin is
present in an amount in the range of from about 70% to about 100%
by weight of said liquid hardenable resin composition.
39. The composition of claim 35 wherein said solvent for said resin
comprises one or more members selected from the group consisting of
dipropylene glycol methyl ether, dipropylene glycol dimethyl ether,
dimethyl formamide, diethyleneglycol methyl ether, ethyleneglycol
butyl ether, diethyleneglycol butyl ether, propylene carbonate,
d'limonene and fatty acid methyl esters.
40. The composition of claim 35 wherein said solvent for said resin
is comprised of dipropylene glycol methyl ether.
41. The composition of claim 35 wherein said solvent for said resin
is present in an amount in the range of from 0% to about 30% by
weight of said liquid hardenable resin composition.
42. The composition of claim 35 wherein said hardening agent
comprises one or more members selected from the group consisting of
amines, aromatic amines, polyamines, aliphatic amines, amides,
polyamides, 4,4'-diaminodiphenyl sulfone, 2-ethyl-4-methyl
imidazole and 1,1,3-trichlorotrifluoroacetone.
43. The composition of claim 35 wherein said hardening agent is
comprised of 4,4'-diaminodiphenyl sulfone.
44. The composition of claim 35 wherein said hardening agent is
present in an amount in the range of from about 40% to about 60% by
weight of said liquid hardenable resin composition.
45. The composition of claim 35 defined further to include a silane
coupling agent comprising one or more members selected from the
group consisting of N-2-(aminoethyl)-3-aminopropyltrimethoxysilane,
3-glycidoxypropyltrimethoxysilane and
n-beta-(aminoethyl)gamma-aminopropy- l trimethoxysilane.
46. The composition of claim 45 wherein said silane coupling agent
is comprised of n-beta-(aminoethyl)-gamma-aminopropyl
trimethoxysilane.
47. The composition of claim 45 wherein said silane coupling agent
is present in an amount in the range of from about 0.1% to about 3%
by weight of said liquid hardenable resin composition.
48. The composition of claim 35 defined further to include a
hydrolyzable ester for breaking gelled fracturing fluid films on
said proppant particles comprising one or more members selected
from the group consisting of a mixture of dimethylglutarate,
dimethyladipate and dimethylsuccinate, sorbitol, catechol,
dimethylthiolate, methyl salicylate, dimethyl salicylate, dimethyl
succinate and ter-butylhydroperoxide.
49. The composition of claim 48 wherein said hydrolyzable ester for
breaking gelled fracturing fluid films on said proppant particles
is comprised of a mixture of dimethylglutarate, dimethyladipate and
dimethylsuccinate.
50. The composition of claim 48 wherein said hydrolyzable ester is
present in an amount in the range of from about 0.1% to about 3% by
weight of said liquid hardenable resin composition.
51. The composition of claim 35 defined further to include a
surfactant for facilitating the coating of said resin on said
proppant particles and for causing said hardenable resin to flow to
the contact points between adjacent resin coated proppant particles
comprising one or more members selected from the group consisting
of an ethoxylated nonyl phenol phosphate ester, mixtures of one or
more cationic surfactants and one or more non-ionic surfactants and
a C.sub.12-C.sub.22 alkyl phosphonate surfactant.
52. The composition of claim 51 wherein said surfactant for
facilitating the coating of said resin on said proppant particles
and for causing said hardenable resin to flow to the contact points
between adjacent resin coated proppant particles is comprised of a
C.sub.12-C.sub.22 alkyl phosphonate surfactant.
53. The composition of claim 51 wherein said surfactant is present
in an amount in the range of from about 2% to about 15% by weight
of said liquid hardenable resin composition.
54. The composition of claim 35 defined further to include a liquid
carrier fluid comprising one or more members selected from the
group consisting of dipropylene glycol methyl ether, dipropylene
glycol dimethyl ether, dimethyl formamide, diethyleneglycol methyl
ether, ethyleneglycol butyl ether, diethyleneglycol butyl ether,
propylene carbonate, d'limonene and fatty acid methyl esters.
55. The composition of claim 54 wherein said liquid carrier fluid
is comprised of dipropylene glycol methyl ether.
56. The composition of claim 54 wherein said liquid carrier fluid
is present in an amount in the range of from 30% to about 60% by
weight of said liquid hardenable resin composition.
57. The composition of claim 35 defined further to include a
viscosifying agent.
58. The composition of claim 57 wherein said viscosifying agent is
present in an amount in the range of from about 0% to about 3% by
weight of said liquid hardenable composition.
59. The composition of claim 35 wherein said rubber latex comprises
one or more members selected from the group consisting of natural
rubber (cis-1,4-polyisoprene) latex, styrene/butadiene copolymer
latex, cis-1,4-polybutadiene rubber latex, butyl rubber latex,
ethylene/propylene rubber latex, neoprene rubber latex, nitrile
rubber latex, silicone rubber latex, chlorosulfonated rubber latex,
polyethylene rubber latex, epichlorohydrin rubber latex,
fluorocarbon rubber latex, fluorosilicone rubber latex,
polyurethane rubber latex, polyacrylic rubber latex and polysulfide
rubber latex.
60. The composition of claim 35 wherein said rubber latex is
comprised of a styrene/butadiene copolymer latex containing water
in an amount in the range of from about 50% by weight of said
latex.
61. The composition of claim 35 wherein said rubber latex is
present in an amount in the range of from about 0.1% to about 40%
by weight of said liquid hardenable resin composition.
62. The composition of claim 35 wherein said rubber latex
stabilizing surfactant comprises one or more members selected from
the group consisting of surfactants having the formula
R--Ph--O(OCH.sub.2CH.sub.2).- sub.mOH wherein R is an alkyl group
having from about 5 to about 30 carbon atoms, Ph is phenyl and m is
an integer of from about 5 to about 50 and surfactants having the
formula R.sub.1(R.sub.2O).sub.nSO.sub.3X wherein R.sub.1 is an
alkyl group having from about 5 to about 20 carbon atoms, R.sub.2
is the group --CH.sub.2--CH.sub.2--, n is an integer from about 10
to about 40 and X is a cation.
63. The composition of claim 35 wherein said rubber latex
stabilizing surfactant is comprised of a sulfonated and ethoxylated
sodium salt having the formula
H(CH.sub.2).sub.12-15(CH.sub.2CH.sub.2O).sub.15SO.sub.- 3Na.
64. The composition of claim 35 wherein said rubber latex
stabilizing surfactant is present in an amount in the range of from
about 0.1% to about 10% by weight of said liquid hardenable resin
composition.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to improved methods of forming
fractures containing resilient proppant particle packs which
prevent proppant flow-back in subterranean zones penetrated by well
bores.
[0003] 2. Description of the Prior Art
[0004] Hydrocarbon producing wells are often stimulated by
hydraulic fracturing treatments. In hydraulic fracturing
treatments, a viscous fracturing fluid which also functions as a
carrier fluid is pumped into a producing zone to be fractured at a
rate and pressure such that one or more fractures are formed in the
zone. Particulate proppant particles, e.g., graded sand for
propping the fractures are suspended in a portion of the fracturing
fluid so that the proppant particles are deposited in the fractures
when the fracturing fluid is broken. That is, a breaker is included
in the fracturing fluid whereby the fracturing fluid reverts to a
thin fluid which is returned to the surface. The proppant particle
packs formed in the fractures function to prevent the fractures
from closing so that conductive channels are formed through which
produced hydrocarbons can readily flow.
[0005] In order to prevent the subsequent flow-back of the proppant
particles as well as loose or incompetent sand in the fractured
zone with fluids produced therefrom, the proppant introduced into
the fractures has heretofore been coated with a hardenable resin
composition which is caused to harden and consolidate the proppant
particles in the zone. The flow-back of the proppant particles with
formation fluids is very detrimental in that it erodes metal goods,
plugs piping and vessels and causes damage to valves, instruments
and other production equipment.
[0006] While the consolidated proppant particle packs heretofore
formed in subterranean fractures have functioned satisfactorily in
wells which are produced continuously, when such consolidated
proppant particle packs are formed in wells which are frequently
placed on production and then shut-in, flow-back of the proppant
particles and formation fines with produced fluids often still
takes place. That is, in wells which are subjected to stress
cycling due to frequent opening and shutting in of the wells, the
consolidated proppant particle packs in fractures are also
subjected to the stress cycling which causes the consolidated
proppant particle packs to disintegrate and the flow-back of loose
proppant particles to occur. Thus, there are needs for improved
methods of forming proppant particle packs in subterranean
fractures which are resilient and do not disintegrate when
subjected to stress cycling.
SUMMARY OF THE INVENTION
[0007] The present invention provides improved methods and
compositions for forming subterranean fractures containing
resilient proppant particle packs which meet the needs described
above and overcome the deficiencies of the prior art. The resin
compositions of this invention harden and consolidate resin coated
proppant particles into resilient permeable packs which do not
allow proppant flow-back.
[0008] The methods of this invention are basically comprised of the
following steps. A liquid hardenable resin component is provided
comprised of a hardenable resin and optionally, a solvent for the
resin. A liquid hardening agent component is provided comprised of
a hardening agent, a silane coupling agent, a hydrolyzable ester
for breaking gelled fracturing fluid films on the proppant
particles, a surfactant for facilitating the coating of the resin
on the proppant particles and for causing the hardenable resin to
flow to the contact points between adjacent resin coated proppant
particles, a liquid carrier fluid having a high flash point and
optionally, a viscosifying agent for viscosifying the carrier fluid
and dispersing the hardening agent when the hardening agent is a
particulate solid. A liquid rubber component comprised of a rubber
latex and a rubber latex stabilizing surfactant is also provided.
In addition, a source of dry proppant particles and a gelled liquid
fracturing fluid are provided. The gelled liquid fracturing fluid
is pumped into a subterranean zone to form the fractures therein
and to place hardenable resin composition coated proppant particles
therein. As the fractures are formed by the fracturing fluid, the
liquid hardenable resin component is mixed with the liquid
hardening agent component and the liquid rubber component
(preferably on-the-fly) to form a liquid hardenable resin
composition. The liquid hardenable resin composition is
continuously coated on dry proppant particles conveyed from the
source thereof to form hardenable resin composition coated proppant
particles. The hardenable resin coated proppant particles are
continuously mixed with the fracturing fluid whereby the hardenable
resin composition coated proppant particles are suspended in the
fracturing fluid. When the hardenable resin composition coated
proppant particles have been placed in the one or more fractures,
the pumping of the fracturing fluid, the mixing of the liquid
hardenable resin component with the liquid hardening agent
component and the liquid rubber component, the coating of the dry
proppant particles with the hardenable resin composition and the
mixing and suspending the resin composition coated proppant
particles with the fracturing fluid are terminated. Thereafter, the
hardenable resin composition on the coated proppant particles is
allowed to harden and to consolidate the proppant into one or more
strong and resilient permeable packs which prevent the production
of formation sand and fines with formation fluids and proppant
flow-back.
[0009] The liquid hardenable resin composition of this invention
for consolidating proppant particles in subterranean fractures
whereby consolidated proppant particle packs are formed which are
resilient and prevent proppant particle flow-back due to stress
cycling is comprised of the following components: a hardenable
resin, optionally a solvent for the resin, a hardening agent for
hardening the resin, a silane coupling agent, a hydrolyzable ester
for breaking gelled fracturing films on the proppant particles, a
surfactant for facilitating the coating of the resin on the
proppant particles and for causing the hardenable resin to flow to
the contact points between adjacent resin coated proppant
particles, a liquid carrier fluid having a high flash point and
optionally, a viscosifying agent for viscosifying the carrier fluid
and dispersing the hardening agent when the hardening agent is a
particulate solid, a rubber latex and a rubber latex stabilizing
surfactant.
[0010] The objects, features and advantages of the present
invention will be readily apparent to those skilled in the art upon
a reading of the description of preferred embodiments which
follows.
DESCRIPTION OF PREFERRED EMBODIMENTS
[0011] As mentioned above, the consolidated proppant particle packs
formed in fractures heretofore have not been resilient enough to
remain consolidated in wells which are frequently placed on
production and shut-in. That is, the stress cycling caused by
frequently producing and shutting in wells causes the consolidated
proppant particle packs to disintegrate over time which causes
undesirable proppant particle flow-back.
[0012] In accordance with the methods and compositions of the
present invention, the resin consolidated proppant particle packs
formed in subterranean fractures are highly resilient whereby they
can withstand stress cycling without disintegration occurring.
[0013] The methods of the present invention for forming fractures
containing resilient proppant particle packs which prevent the
production of formation sand and fines with formation fluids and
proppant flow-back in subterranean zones penetrated by well bores
are comprised of the following steps. A liquid hardenable resin
component is provided comprised of a hardenable resin, and
optionally, a solvent for the resin having a high flash point. A
liquid hardening agent component is also provided comprised of a
hardening agent, a silane coupling agent, a hydrolyzable ester for
breaking gelled fracturing fluid films on the proppant particles, a
surfactant for facilitating the coating of the resin on the
proppant particles and for causing the hardenable resin to flow to
the contact points between adjacent coated proppant particles, a
liquid carrier fluid having a high flash point and optionally, a
viscosifying agent for viscosifying the carrier fluid and
dispersing the hardening agent when the hardening agent is a
particulate solid. A liquid rubber component comprised of a rubber
latex and a rubber latex stabilizing surfactant is also provided.
In addition, a source of dry proppant particles and a gelled liquid
fracturing fluid are provided. The gelled liquid fracturing fluid
is pumped into the subterranean zone to form fractures therein and
to place hardenable resin composition coated proppant particles
therein. As the fractures are formed, the liquid hardenable resin
component is mixed with the liquid hardening agent component and
the liquid rubber component (preferably on-the-fly) to form a
liquid hardenable resin composition. The liquid hardenable resin
composition is continuously coated onto dry proppant particles
(preferably on-the-fly) conveyed from the source thereof to form
hardenable resin composition coated proppant particles. The
hardenable resin composition coated proppant particles are
continuously mixed with the fracturing fluid being pumped
(preferably on-the-fly) whereby the hardenable resin composition
coated proppant particles are suspended therein. When the resin
composition coated proppant particles have been placed in the
fractures, the pumping of the gelled liquid fracturing fluid, the
mixing of the liquid hardenable resin component with the liquid
hardening agent component and the liquid rubber component to form
the liquid hardenable resin composition, the coating of the liquid
hardenable resin composition onto dry proppant particles and the
mixing of the hardenable resin composition coated proppant
particles with the fracturing fluid are terminated. Thereafter, the
hardenable resin composition on the resin composition coated
proppant particles is allowed to harden and consolidate the
proppant particles into resilient permeable packs which prevent the
production of formation sand and fines with produced fluids and
proppant flow-back.
[0014] The term "on-the-fly" is used herein to mean that a flowing
stream is continuously introduced into another flowing stream so
that the streams are combined and mixed while continuing to flow as
a single stream. While the mixing of the liquid hardenable resin
component with the liquid hardening agent component and the rubber
component to form the hardenable resin composition, the coating of
the dry proppant particles with the hardenable resin composition
and the mixing of the hardenable resin coated proppant particles
with the fracturing fluid are all preferably accomplished
on-the-fly, as is well understood by those skilled in the art such
mixing can also be accomplished by batch mixing or partial batch
mixing.
[0015] As is also well understood, when the fracturing fluid is
broken and the hardenable resin composition coated proppant
particles are deposited in the fractures formed, the fractures
close on the proppant particles. The partially closed fractures
apply pressure on the hardenable resin composition coated proppant
whereby the proppant particles are forced into contact with each
other while the resin composition hardens. The hardening of the
resin composition under pressure helps bring about the
consolidation of the resin coated particles into a hard permeable
pack having sufficient compressive strength to prevent
unconsolidated proppant and formation sand from flowing out of the
fractures with produced fluids. In fracture treatments carried out
in unconsolidated formations, good consolidation of proppant is
required in the perforations which extend from the inside of the
well bore through casing and cement into the unconsolidated
formation as well as in the fractured portions of the
unconsolidated formation surrounding the well bore. The last
portion of the proppant which is deposited in the perforations and
in the fractures is coated with the hardenable resin composition
and is caused to harden. The resulting consolidated proppant in the
perforations and fractures contributes to the prevention of
proppant flow-back. However, there is often little closure pressure
applied to the hardenable resin coated proppant in the fractures
close to the well bore and there is no closure pressure applied to
the hardenable resin coated proppant particles in the perforations.
In addition, the hardenable resin coated proppant particles can be
separated from each other by films of the gelled fracturing fluid
and because of the presence of the fracturing fluid films, the
proppant particles do not sufficiently consolidate. As a result,
the consolidated permeable packs formed in the perforations and
fractures often have less than sufficient compressive strength to
prevent unconsolidated proppant and formation sand from flowing out
of the perforations and fractures. These problems are solved by
including in the hardenable resin composition one or more
hydrolyzable esters which function to break gelled fracturing fluid
films on the particles, and a surfactant for facilitating the
coating of the resin composition on the proppant particles and for
causing the hardenable resin composition to flow to the contact
points between adjacent resin coated proppant particles so that the
particles are consolidated into a high strength permeable mass.
[0016] Examples of hardenable resins which can be utilized in the
liquid hardenable resin component include, but are not limited to,
organic resins such as bisphenol A-epichlorohydrin resin,
polyepoxide resin, novolac resin, polyester resin, phenol-aldehyde
resin, urea-aldehyde resin, furan resin, urethane resin, glycidyl
ethers and mixtures thereof. Of these, bisphenol A-epichlorohydrin
resin is preferred. The organic resin utilized is included in the
liquid hardenable resin component in an amount in the range of from
about 70% to about 100% by weight of the liquid hardenable resin
component, preferably an amount of about 85%.
[0017] Examples of solvents having high flash points (above about
125.degree. F.) which can optionally be used for the hardenable
resin in the liquid hardenable resin component include, but are not
limited to, dipropylene glycol methyl ether, dipropylene glycol
dimethyl ether, dimethyl formamide, diethylene glycol methyl ether,
ethylene glycol butyl ether, diethylene glycol butyl ether,
propylene carbonate, d'limonene and fatty acid methyl esters. Of
these, dipropylene glycol methyl ether is preferred. The amount of
the solvent utilized in the liquid hardenable resin component is in
the range of from about 0% to about 30% by weight of the liquid
hardenable resin component, preferably an amount of about 15%.
[0018] Examples of the hardening agents which can be used in the
liquid hardening agent component include, but are not limited to,
amines, aromatic amines, polyamines, aliphatic amines, amides,
polyamides, 4,4'-diaminodiphenyl sulfone, 2-ethyl-4-methyl
imidazole and 1,1,3-trichlorotrifluoroacetone. Of these,
4,4-diaminodiphenyl sulfone is preferred. The hardening agent is
included in the liquid hardening agent component in an amount in
the range of from about 30% to about 60% by weight of the liquid
hardening agent component, preferably in an amount of about
40%.
[0019] Examples of silane coupling agents which can be used in the
liquid hardenable resin component include, but are not limited to,
N-2-(aminoethyl)-3-aminopropyltrimethoxysilane,
3-glycidoxypropyltrimetho- xysilane and
n-beta-(aminoethyl)-gamma-aminopropyltrimethoxysilane. Of these,
n-beta-(aminoethyl)-gamma-aminopropyltrimethoxysilane is preferred.
The silane coupling agent is included in the liquid hardenable
resin component in an amount in the range of from about 0.1% to
about 3% by weight of the liquid hardenable resin component,
preferably in an amount of about 1.5%.
[0020] Examples of hydrolyzable esters which can be used in the
liquid hardenable resin component for facilitating the coating of
the resin composition on the proppant particles and for breaking
gelled fracturing fluid films thereon include, but are not limited
to, a mixture of dimethylglutarate, dimethyladipate and
dimethylsuccinate, sorbitol, catechol, dimethylthiolate, methyl
salicylate, dimethyl salicylate, dimethyl succinate and
ter-butylhydroperoxide. Of these, a mixture of dimethylglutarate,
dimethyladipate and dimethylsuccinate is preferred. The ester or
esters are present in the liquid hardenable resin component in an
amount in the range of from about 0.1% to about 3% by weight of the
liquid hardenable resin component, preferably in an amount of about
2%.
[0021] Examples of surfactants which can be utilized in the liquid
hardenable resin component for facilitating the coating of the
resin on the proppant particles and for causing the hardenable
resin to flow to the contact points between adjacent resin coated
proppant particles include, but are not limited to, an ethoxylated
nonylphenol phosphate ester, mixtures of one or more cationic
surfactants and one or more non-ionic surfactants and an alkyl
phosphonate surfactant. The mixtures of one or more cationic and
non-ionic surfactants which can be utilized are described in U.S.
Pat. No. 6,311,773 issued to Todd et al. on Nov. 6, 2001 which is
incorporated herein by reference. Of the surfactants that can be
used, a C.sub.12-C.sub.22 alkyl phosphonate surfactant is
preferred. The surfactant or surfactants utilized are included in
the liquid hardenable resin component in an amount in the range of
from about 2% to about 15% by weight of the liquid hardenable resin
component, preferably in an amount of about 12%.
[0022] The liquid carrier fluid having a high flash point (above
about 125.degree. F.) in the liquid hardening agent component is
selected from the group consisting of dipropylene glycol methyl
ether, dipropylene glycol dimethyl ether, dimethyl formamide,
diethyleneglycol methyl ether, ethyleneglycol butyl ether,
diethyleneglycol butyl ether, propylene carbonate, d'limonene and
fatty acid methyl esters. Of these, dipropylene glycol methyl ether
is preferred. The liquid carrier fluid is present in the liquid
hardening agent component in an amount in the range of from about
30% to about 60% by weight of the liquid hardening agent component,
preferably in an amount of about 40%.
[0023] Examples of viscosifying agents that can optionally be
utilized in the liquid hardening agent component, include, but are
not limited to hydroxypropyl cellulose and organophilic clays. Of
these, organophilic clay is preferred. Organophilic clays are the
reaction product of purified smectite clay (either hectorite or
bentonite) and a quaternary ammonium salt. The viscosifying agent
is present in the liquid hardening agent component in an amount in
the range of from about 0% to about 3% by weight of the liquid
hardening agent component, preferably in an amount of about 1%.
[0024] Examples of aqueous rubber latexes, i.e., aqueous
dispersions or emulsions, which can be used in the liquid rubber
component include, but are not limited to, natural rubber
(cis-1,4-polyisoprene) latex, styrene/butadiene rubber latex,
cis-1,4-polybutadiene rubber latex, butyl rubber latex,
ethylene/propylene rubber latex, neoprene rubber latex, nitrile
rubber latex, silicone rubber latex, chlorosulfonated rubber latex,
polyethylene rubber latex, epichlorohydrin rubber latex,
fluorocarbon rubber latex, fluorosilicone rubber latex,
polyurethane rubber latex, polyacrylic rubber latex and polysulfide
rubber latex.
[0025] Of the various latexes which can be utilized, those prepared
by emulsion polymerization processes are preferred. A particularly
preferred latex for use in accordance with this invention is a
styrene/butadiene copolymer latex emulsion prepared by emulsion
polymerization. The aqueous phase of the emulsion is an aqueous
colloidal dispersion of the styrene/butadiene copolymer. The latex
dispersion usually includes water in an amount in the range of from
about 40% to about 70% by weight of the latex, and in addition to
the dispersed styrene/butadiene particles, the latex often includes
small quantities of an emulsifier, polymerization catalysts, chain
modifying agents and the like. The weight ratio of styrene to
butadiene in the latex can range from about 10%:90% to about
90%:10%.
[0026] A particularly suitable styrene/butadiene aqueous latex has
a styrene/butadiene weight ratio of about 25%:75%, and the
styrene/butadiene copolymer is suspended in a 50% by weight aqueous
emulsion A latex of this type is available from Halliburton Energy
Services of Duncan, Okla. under the trade designation "LATEX
2000.TM.." The amount of the rubber latex utilized in the liquid
rubber component is in the range of from about 99.9% to about 97%
by weight of the liquid rubber component, preferably in an amount
of about 99%.
[0027] In order to prevent the aqueous rubber latex from
prematurely coagulating and increasing the viscosity of the liquid
rubber component, an effective amount of a latex stabilizer is
included in the liquid rubber component. Latex stabilizers are
comprised of one or more surfactants which function to prevent
latex coagulation. Examples of rubber latex stabilizing surfactants
which can be utilized in the liquid rubber component include, but
are not limited to, surfactants having the formula
R--Ph--O(OCH.sub.2CH.sub.2).sub.mOH wherein R is an alkyl group
having from about 5 to about 30 carbon atoms, Ph is phenyl and m is
an integer of from about 5 to about 50 and surfactants having the
formula R.sub.1(R.sub.2O).sub.nSO.sub.3X wherein R.sub.1 is an
alkyl group having from about 5 to about 20 carbon atoms, R.sub.2
is the group --CH.sub.2--CH.sub.2--, n is an integer from about 10
to about 40 and X is a cation. Of the various latex stabilizing
surfactants which can be utilized, a sulfonated and ethoxylated
sodium salt having the formula
H(CH.sub.2).sub.12-15(CH.sub.2CH.sub.2O).sub.15SO.sub.3Na is
preferred. The rubber latex stabilizing surfactant utilized is
included in the liquid rubber component in an amount in the range
of from about 0.1% to about 3% by weight of the liquid rubber
component, more preferably in an amount of about 1%.
[0028] The liquid hardenable resin component is included in the
liquid hardenable resin composition in an amount in the range of
from about 40% to about 55% by weight of the liquid hardenable
resin composition, preferably about 48%. The liquid hardening agent
component is included in the liquid hardenable resin composition in
an amount in the range of from about 25% to about 35% by weight of
the liquid hardenable resin composition, preferably about 32%. The
liquid rubber component is included in the liquid hardenable resin
composition in an amount in the range of from about 10% to about
35% by weight of the liquid hardenable resin composition,
preferably about 20%.
[0029] A variety of fracturing fluids can be utilized in accordance
with the present invention including aqueous gels, emulsions and
other fluids used for forming fractures in subterranean zones and
carrying resin composition coated proppant particles into the
fractures. The aqueous gels are generally comprised of water and
one or more gelling agents. The emulsions can be comprised of two
immiscible liquids such as an aqueous gelled liquid and a
liquefied, normally gaseous fluid such as nitrogen.
[0030] The preferred fracturing fluids for use in accordance with
this invention are aqueous gels comprised of water, a gelling agent
for gelling the water and increasing its viscosity, and optionally,
a cross-linking agent for cross-linking the gel and further
increasing the viscosity of the fluid. The increased viscosity of
the gelled or gelled and cross-linked fracturing fluid reduces
fluid loss and allows the fracturing fluid to transport significant
quantities of suspended proppant particles. The water utilized to
form the fracturing fluid can be fresh water, salt water, brine,
seawater or any other aqueous liquid which does not adversely react
with the other components utilized in accordance with this
invention.
[0031] A variety of gelling agents can be utilized including
hydratable polymers which contain one or more functional groups
such as hydroxyl, cis-hydroxyl, carboxyl, sulfate, sulfonate, amino
or amide. Particularly useful polymers are polysaccharides and
derivatives thereof which contain one or more monosaccharide units
galactose, mannose, glucoside, glucose, xylose, arabinose,
fructose, glucuronic acid or pyranosyl sulfate. Examples of natural
hydratable polymers containing the foregoing functional groups and
units which are particularly useful in accordance with the present
invention include guar gum and derivatives thereof such as
hydroxypropyl guar and cellulose derivatives such as
hydroxyethylcellulose. Hydratable synthetic polymers and copolymers
which contain the above mentioned functional groups can also be
utilized. Examples of such synthetic polymers include, but are not
limited to, polyacrylate, polymethacrylate, polyacrylamide,
polyvinyl alcohol and polyvinyl pyrrolidone. The gelling agent used
is generally combined with the water in the fracturing fluid in an
amount in the range of from about 0.1% to about 1% by weight of the
water.
[0032] Examples of cross-linking agents which can be utilized to
further increase the viscosity of a gelled fracturing fluid are:
alkali metal borates, borax, boric acid and compounds which are
capable of releasing multi-valent metal ions in aqueous solutions.
Examples of the multi-valent metal ions are chromium, zirconium,
antimony, titanium, iron, zinc or aluminum. When used, the
cross-linking agent is generally added to gelled water in an amount
in the range of from above 0.01% to about 1% by weight of the
water.
[0033] The above described gelled or gelled and cross-linked
fracturing fluids typically also include internal delayed gel
breakers such as those of the enzyme type, the oxidizing type, the
acid buffer type and the temperature activated type, all of which
are well known to those skilled in the art. Particularly suitable
delayed gel breakers include, but are not limited to, alkali metal
and ammonium persulfates which are delayed by being encapsulated in
a material that slowly releases the breaker and alkali metal
chlorites, alkali metal hypochlorites and calcium hypochlorite. The
gel breakers cause the viscous fracturing fluids to revert to thin
fluids that can be produced back to the surface after they have
been used to place proppant particles in subterranean fractures.
The gel breaker used is generally present in the fracturing fluid
in an amount in the range of from about 1% to about 5% by weight of
the gelling agent therein. The fracturing fluids can also include
one or more of a variety of well known additives such as gel
stabilizers, fluid loss control additives, clay stabilizers,
bacteriacides and the like.
[0034] The proppant particles utilized in accordance with the
present invention are generally of a size such that formation
particulate solids, e.g., sand and other solid fines, which migrate
with produced fluids are prevented from being produced from the
subterranean zone. Various kinds of proppant particles can be
utilized including graded sand, bauxite, ceramic materials, glass
materials, walnut hulls, polymer beads and the like. Generally, the
proppant particles have a size in the range of from about 2 to
about 400 mesh, U.S. Sieve Series. The preferred proppant is graded
sand having a particle size in the range of from about 10 to about
70 mesh, U.S. Sieve Series. Preferred sand particle size
distribution ranges are one or more of 10-20 mesh, 20-40 mesh,
40-60 mesh or 50-70 mesh, depending on the particular size and
distribution of formation solids to be screened out by the
consolidated proppant particles.
[0035] The liquid hardenable resin compositions of this invention
are utilized for consolidating proppant particles in subterranean
fractures whereby consolidated proppant particle packs are formed
which are resilient and prevent the production of formation sand
and fines as well as proppant particle flow-back due to stress
cycling or the like. The compositions are basically comprised of a
hardenable resin, optionally a solvent for the resin having a high
flash point, a hardening agent for hardening the resin, a silane
coupling agent, a hydrolyzable ester for breaking gelled fracturing
films on the proppant particles, a surfactant for facilitating the
coating of the resin on the proppant particles and for causing the
hardenable resin to flow to the contact points between adjacent
resin coated proppant particles, a liquid carrier fluid having a
high flash point, optionally a viscosifying agent for viscosifying
the carrier fluid and dispersing the hardening agent when the
hardening agent is a particulate solid, a rubber latex and a rubber
latex stabilizing surfactant.
[0036] The various components of the liquid hardenable resin
composition are the same as those described above in connection
with the methods of this invention and are utilized in the amounts
set forth above.
[0037] A preferred method of the present invention for forming
fractures in a subterranean zone containing resilient proppant
particle packs which prevent the production of formation sand and
fines with produced fluids and proppant flow-back is comprised of
the steps of: (a) providing a liquid hardenable resin component
comprised of bisphenol A-epichlorohydrin resin present in an amount
in the range of from about 70% to about 100% by weight of the
liquid hardenable resin component and a solvent for the resin
comprised of dipropylene glycol methyl ether present in an amount
in the range of from about 0% to about30% by weight of the liquid
hardenable resin component; (b) providing a liquid hardening agent
component comprised of a 4,4-diaminodiphenylsulfone hardening agent
present in an amount in the range of from about 40% to about 60% by
weight of the liquid hardening agent component, a silane coupling
agent comprised of n-beta-(aminoethyl)-gamma-aminopropyltrimetho-
xysilane present in an amount in the range of from about 0.1% to
about 3% by weight of the liquid hardenable resin component, a
hydrolyzable ester mixture comprised of dimethylglutarate,
dimethyladipate and dimethylsuccinate present in an amount in the
range of from about 0.1% to about 3% by weight of the liquid
hardenable resin component and a surfactant comprised of a
C.sub.12-C.sub.22 alkylphosphonate present in an amount in the
range of from about 2% to about 15% by weight of the liquid
hardenable resin component, a liquid carrier fluid comprised of
dipropylene glycol methyl ether present in an amount in the range
of from about 20% to about 40% by weight of the liquid hardenable
resin component and a viscosifying agent comprised of an
organophilic clay present in an amount in the range of from about
0% to about 3% by weight of the liquid hardenable resin component;
(c) providing a liquid rubber component comprised of a
styrene/butadiene copolymer latex containing water in an amount of
about 50% by weight of the latex present in an amount in the range
of from about 99.9% to about 97% by weight of the liquid rubber
component and a rubber latex stabilizing surfactant comprised of a
sulfonated and ethoxylated sodium salt having the formula
H(CH.sub.2).sub.12-15(CH.sub.2CH.sub.2O).sub.15SO.sub.3Na present
in an amount in the range of from about 0.1% to about 3% by weight
of the liquid rubber component; (d) providing a source of dry
proppant particles; (e) providing a gelled liquid fracturing fluid;
(f) pumping the gelled liquid fracturing fluid into the
subterranean zone to form the fractures therein and to place
hardenable resin composition coated proppant particles therein; (g)
as the fractures are formed in step (f), mixing the liquid
hardenable resin component with the liquid hardening agent
component and the liquid rubber component to form a liquid
hardenable resin composition; (h) coating the liquid hardenable
resin composition provided in step (g) onto dry proppant particles
conveyed from the source thereof to form hardenable resin
composition coated proppant particles; (i) mixing the hardenable
resin coated proppant particles produced in step (h) with the
fracturing fluid pumped in accordance with step (f) whereby the
hardenable resin composition coated proppant particles are
suspended therein; (j) terminating steps (f), (g), (h) and (i) when
the resin composition coated proppant particles have been placed in
the fractures; and (k) allowing the hardenable resin composition on
the resin composition coated proppant particles to harden and
consolidate said proppant particles into resilient permeable packs
which prevent proppant flow-back.
[0038] A preferred liquid hardenable resin composition of this
invention for consolidating proppant particles in subterranean
fractures whereby consolidated proppant particle packs are formed
which are resilient and prevent the production of formation sand
and fines with produced fluids and proppant particle flow-back
comprises: a hardenable resin present in an amount in the range of
from about 70% to about 100% by weight of the liquid hardenable
resin composition; a solvent for the resin present in an amount in
the range of from about 0% to about 30% by weight of the liquid
hardenable resin composition; a hardening agent present in an
amount in the range of from about 40% to about 60% by weight of the
liquid hardenable resin composition; a silane coupling agent
present in an amount in the range of from about 0.1% to about 3% by
weight of the liquid hardenable resin composition; a hydrolyzable
ester present in an amount in the range of from about 0.1% to about
3% by weight of the liquid hardenable resin composition; a
surfactant present in an amount in the range of from about 2% to
about 15% by weight of the liquid hardenable resin composition; a
liquid carrier fluid comprised of dipropylene glycol methyl ether
present in an amount in the range of from about 20% to about 40% by
weight of the liquid hardenable resin component; a viscosifying
agent comprised of an organophilic clay present in an amount in the
range of from about 0% to about 3% by weight of the liquid
hardenable resin composition; a rubber latex present in an amount
in the range of from about 0.1% to about 40% by weight of the
liquid hardenable resin composition; and a rubber latex stabilizing
surfactant present in an amount in the range of from about 0.1% to
about 10% by weight of the liquid hardenable resin composition.
[0039] In order to further illustrate the methods and compositions
of this invention, the following examples are given.
EXAMPLE
[0040] A resin composition was prepared by mixing 8.2 milliliters
of liquid hardenable resin component, 5.3 milliliters of liquid
hardening agent component, and 3.4 milliliters of liquid latex
agent. These components were mixed well to form a homogeneous
mixture. A volume of 9.0 milliliters of this mixture was dry coated
onto 250 grams of 20/40-mesh bauxite proppant. The treated proppant
was then added to 300 milliliters of 35 lb per 1,000-gal
carboxymethylhydroxypropyl guar fracturing fluid while the fluid
was stirring with a stirrer. The slurry was placed in a heat bath
at 180.degree. F. and continued to be stirred for 15 minutes to
simulate the proppant slurry when it is being pumped downhole.
After stirring, the treated proppant was packed in the flow
chambers and placed in oven for 3-hour cure at 325.degree. F.
without applying closure stress.
[0041] After curing, consolidated cores were obtained for
unconfined compressive strength measurements and stress cycling
testing. An average value of 470 psi compressive strength was
obtained for the consolidated cores. For stress cycling testing,
the consolidated proppant cores were installed in a confining cell.
Axial stress and confining pressure were increased to 1,000 psi.
Confining pressure was held at 1,000 psi, while the axial stress
was increased to 2,700 psi, held constant for 10 minutes, decreased
to 1,100 psi and held constant for another 10 minutes. The axial
stress cycle was repeated 19 times for a total of 20 cycles. The
core samples appeared to stabilize after about 10 cycles. The core
samples were intact when removed at the end of the test. This
result indicates that the addition of latex as a flexibilizing
agent greatly improves the capability of a consolidated proppant
pack to undergo stress cycling due to frequent shut-ins and returns
to production.
[0042] Thus, the present invention is well adapted to carry out the
objects 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.
* * * * *