U.S. patent application number 10/852811 was filed with the patent office on 2005-12-01 for methods for stabilizing and stimulating wells in unconsolidated subterranean formations.
Invention is credited to Nguyen, Philip D..
Application Number | 20050263283 10/852811 |
Document ID | / |
Family ID | 35423940 |
Filed Date | 2005-12-01 |
United States Patent
Application |
20050263283 |
Kind Code |
A1 |
Nguyen, Philip D. |
December 1, 2005 |
Methods for stabilizing and stimulating wells in unconsolidated
subterranean formations
Abstract
The present invention relates to methods of stabilizing an
unconsolidated portion in a subterranean formation and stimulating
fluid production from the stabilized portion. Some embodiments of
the present invention provide methods of substantially stabilizing
a portion of a subterranean formation penetrated by a well bore and
stimulating fluid production therefrom comprising placing a
stabilizing composition into a near well bore area of a portion in
a formation to create a stabilized portion; and, stimulating the
stabilized portion so as to place the well bore in fluid
communication with both the stabilized portion in the near-well
bore area and an unstabilized portion of the formation in the
far-well bore area.
Inventors: |
Nguyen, Philip D.; (Duncan,
OK) |
Correspondence
Address: |
Robert A. Kent
Halliburton Energy Services
2600 S. 2nd Street
Duncan
OK
73536-0440
US
|
Family ID: |
35423940 |
Appl. No.: |
10/852811 |
Filed: |
May 25, 2004 |
Current U.S.
Class: |
166/281 ;
166/280.1; 166/292; 166/295; 166/300; 507/219; 507/221; 507/260;
507/267 |
Current CPC
Class: |
C09K 8/5751 20130101;
C09K 8/80 20130101; E21B 43/26 20130101; E21B 43/114 20130101; C09K
8/5756 20130101; C09K 8/805 20130101 |
Class at
Publication: |
166/281 ;
507/219; 507/221; 507/260; 507/267; 166/280.1; 166/295; 166/300;
166/292 |
International
Class: |
E21B 043/267; E21B
033/138 |
Claims
What is claimed is:
1. A method of substantially stabilizing a portion of a
subterranean formation penetrated by a well bore and stimulating
fluid production therefrom comprising: placing a stabilizing
composition into a near well bore area of a portion in a formation
to create a stabilized portion; and, stimulating the stabilized
portion so as to place the well bore in fluid communication with
both the stabilized portion in the near-well bore area and an
unstabilized portion of the formation in the far-well bore
area.
2. The method of claim 1 wherein the stabilizing composition
comprises a curable resin composition.
3. The method of claim 2 wherein the curable resin composition
comprises a novolak resin, a polyepoxide resin, a phenol-aldehyde
resin, a urea-aldehyde resin, a urethane resin, a phenolic resin, a
furan/furfuryl alcohol resin, a phenolic/latex resin, a phenol
formaldeyhe resin, a polyester resin, including hybrids and
copolymers thereof, a polyurethane resin and hybrids and copolymers
thereof, an acrylate resin, or a mixture thereof.
4. The method of claim 2 further comprising an internal catalyst or
activator.
5. The method of claim 2 further comprising a time-delayed catalyst
or an external catalyst.
6. The method of claim 1 wherein the stabilizing composition
comprises a gelable composition.
7. The method of claim 6 wherein the gelable composition comprises
a gelable resin composition, a gelable aqueous silicate
composition, a polymerizable organic monomer composition, or a
crosslinkable aqueous polymer composition.
8. The method of claim 7 wherein the gelable resin composition
comprises a curable resin composition that comprises a curable
resin, a diluent, and a resin curing agent.
9. The method of claim 8 wherein the curable resin comprises an
organic resin that comprises a polyepoxide resin, a polyester
resin, a urea-aldehyde resin, a furan resin, a urethane resin, or a
mixture thereof.
10. The method of claim 8 wherein the diluent comprises a phenol, a
formaldehyde, a furfuryl alcohol, a furfural, an alcohol, an ether,
or a mixture thereof.
11. The method of claim 8 wherein the diluent is present in the
curable resin composition in an amount in the range of from about
5% to about 75% by weight of the curable resin.
12. The method of claim 8 wherein the resin curing agent comprises
an amine, a polyamine, an amide, a polyamide, or a methylene
dianiline.
13. The method of claim 8 wherein the resin curing agent is present
in the curable resin composition in an amount in the range of from
about 5% to about 75% by weight of the curable resin.
14. The method of claim 8 wherein the curable resin composition
further comprises a flexibilizer additive.
15. The method of claim 14 wherein the flexibilizer additive
comprises an organic ester, an oxygenated organic solvent, an
aromatic solvent, or combinations thereof.
16. The method of claim 14 wherein the flexibilizer additive is
present in the curable resin composition in an amount in the range
of from about 5% to about 80% by weight of the curable resin.
17. The method of claim 7 wherein the gelable aqueous silicate
composition comprises an aqueous alkali metal silicate solution and
a temperature activated catalyst.
18. The method of claim 17 wherein the aqueous alkali metal
silicate solution generally comprises an alkali metal silicate and
an aqueous liquid.
19. The method of claim 18 wherein the alkali metal silicate
comprises sodium silicate, potassium silicate, lithium silicate,
rubidium silicate, or cesium silicate.
20. The method of claim 18 wherein the aqueous liquid comprises
fresh water, salt water, brine, or seawater.
21. The method of claim 17 wherein the temperature activated
catalyst comprises an ammonium sulfate, a sodium acid
pyrophosphate, a citric acid, or an ethyl acetate.
22. The method of claim 7 wherein the polymerizable organic monomer
composition comprises an aqueous-base fluid, a water soluble
polymerizable organic monomer, an oxygen scavenger, and a primary
initiator.
23. The method of claim 22 wherein the aqueous solvent comprises
fresh water, salt water, brine, seawater, or any other aqueous
liquid that does not adversely react with the other components used
in accordance with this invention or with the subterranean
formation.
24. The method of claim 22 wherein the water soluble polymerizable
organic monomer comprises acrylic acid, methacrylic acid,
acrylamide, methacrylamide, 2-methacrylamido-2-methylpropane
sulfonic acid, 2-dimethylacrylamide, vinyl sulfonic acid,
N,N-dimethylaminoethylmethacry- late,
2-triethylammoniumethylmethacrylate chloride,
N,N-dimethyl-aminopropylmethacryl-amide,
methacrylamidepropyltriethylammo- nium chloride, N-vinyl
pyrrolidone, vinyl-phosphonic acid, methacryloyloxyethyl
trimethylammonium sulfate, or a mixture thereof.
25. The method of claim 22 wherein the water soluble polymerizable
organic monomer comprises hydroxyethylacrylate,
hydroxymethylacrylate, hydroxyethylmethacrylate,
N-hydroxymethylacrylamide, N-hydroxy-methylmethacrylamide,
polyethylene acrylate, polyethylene methacrylate, polyethylene
glycol acrylate, polyethylene glycol methacrylate,
hydroxyethylcellulose-vinyl phosphoric acid, or a mixture
thereof.
26. The method of claim 22 wherein the water soluble polymerizable
organic monomer is present in the polymerizable organic monomer
composition in an amount in the range of from about 1% to about 20%
by weight of the aqueous-base fluid.
27. The method of claim 22 wherein the oxygen scavenger comprises
stannous chloride.
28. The method of claim 22 wherein the oxygen scavenger is present
in the polymerizable organic monomer composition in an amount in
the range of from about 0.005% to about 0.1 % by weight of the
polymerizable organic monomer composition.
29. The method of claim 22 wherein the primary initiator comprises
an alkali metal persulfate, a peroxide, an oxidation-reduction
system employing reducing agents, or an azo polymerization
initiator.
30. The method of claim 22 wherein the primary initiator comprises
2,2'-azobis(2-imidazole-2-hydroxyethyl)propane,
2,2'-azobis(2-aminopropan- e), 4,4'-azobis(4-cyanovaleric acid), or
2,2'-azobis(2-methyl-N-(2-hydroxy- ethyl)propionamide.
31. The method of claim 22 wherein the polymerizable organic
monomer composition further comprises a secondary initiator.
32. The method of claim 22 wherein the polymerizable organic
monomer composition further comprises a crosslinking agent.
33. The method of claim 7 wherein the crosslinkable aqueous polymer
comprises an aqueous solvent, a crosslinkable polymer, and a
crosslinking agent.
34. The method of claim 33 wherein the aqueous solvent comprises
fresh water, salt water, brine, seawater, or any other aqueous
liquid that does not adversely react with the other components used
in accordance with this invention or with the subterranean
formation.
35. The method of claim 33 wherein the crosslinkable polymer
composition is present in the crosslinkable aqueous polymer
composition in an amount in the range of from about 1% to about 30%
by weight of the aqueous solvent.
36. The method of claim 33 wherein the crosslinkable polymer
comprises a carboxylate-containing polymer or an
acrylamide-containing polymer.
37. The method of claim 33 wherein the crosslinkable polymer is a
polyacrylamide, a partially hydrolyzed polyacrylamide, a copolymer
of acrylamide and acrylate, or a carboxylate-containing terpolymers
and tetrapolymers of acrylate.
38. The method of claim 33 wherein the crosslinking agent comprises
a molecule or complex containing a reactive transition metal
cation.
39. The method of claim 33 wherein the crosslinking agent comprises
trivalent chromium cations complexed or bonded to anions, atomic
oxygen, or water.
40. The method of claim 33 wherein the crosslinking agent is
present in the aqueous crosslinkable polymer composition in an
amount in the range of from about 0.001% to about 5% by weight of
the crosslinkable polymer composition.
41. The method of claim 32 wherein the crosslinkable aqueous
polymer further comprises a crosslinking delaying agent.
42. The method of claim 41 wherein the crosslinking delaying agent
comprises a polysaccharide crosslinking delaying agent.
43. The method of claim 1 wherein the stabilizing composition
penetrates into the near well bore area of a portion in a formation
to a depth of from about a few inches to about three well bore
diameters.
44. The method of claim 1 wherein the stimulating step comprises
hydrajetting, puncturing, fracturing, or a combinations
thereof.
45. The method of claim 1 further comprising the step of, after
stimulating the stabilized portion, placing proppant into the area
or fluid communication.
46. The method of claim 45 wherein the proppant comprises a
hardenable resin coating.
47. The method of claim 45 wherein the proppant comprises a
tackyfier coating.
48. The method of claim 1 wherein the well bore comprises an open
hole well bore.
49. The method of claim 1 wherein the well bore comprises a cased
well bore.
50. A method of controlling formation sands in a portion of a
formation penetrated by a well bore and stimulating fluid
production therefrom comprising: placing a stabilizing composition
into a near well bore area of a portion in a formation to create a
stabilized portion; and, stimulating the stabilized portion so as
to place the well bore in fluid communication with both the
stabilized portion in the near-well bore area and an unstabilized
portion of the formation in the far-well bore area.
51. The method of claim 50 wherein the stabilizing composition
comprises a curable resin composition.
52. The method of claim 51 wherein the curable resin composition
comprises a novolak resin, a polyepoxide resin, a phenol-aldehyde
resin, a urea-aldehyde resin, a urethane resin, a phenolic resin, a
furan/furfuryl alcohol resin, a phenolic/latex resin, a phenol
formaldeyhe resin, a polyester resin, including hybrids and
copolymers thereof, a polyurethane resin and hybrids and copolymers
thereof, an acrylate resin, or mixtures thereof.
53. The method of claim 51 further comprising an internal catalyst,
an activator, a time-delayed catalyst, or an external catalyst.
54. The method of claim 50 wherein the stabilizing composition
comprises a gelable composition.
55. The method of claim 54 wherein the gelable composition
comprises a gelable resin composition, a gelable aqueous silicate
composition, a polymerizable organic monomer composition, or a
crosslinkable aqueous polymer composition.
56. The method of claim 55 wherein the gelable resin composition
comprises a curable resin composition that comprises a curable
resin, a diluent, and a resin curing agent.
57. The method of claim 56 wherein the curable resin comprises an
organic resin that comprises a polyepoxide resin, a polyester
resin, a urea-aldehyde resin, a furan resin, a urethane resin, or a
mixture thereof.
58. The method of claim 56 wherein the diluent comprises a phenol,
a formaldehyde, a furfuryl alcohol, a furfural, an alcohol, an
ether, or a mixture thereof.
59. The method of claim 56 wherein the resin curing agent comprises
an amine, a polyamine, an amide, a polyamide, or a methylene
dianiline.
60. The method of claim 56 wherein the curable resin composition
further comprises a flexibilizer additive, wherein the flexibilizer
additive comprises an organic ester, an oxygenated organic solvent,
an aromatic solvent, or combinations thereof.
61. The method of claim 55 wherein the gelable aqueous silicate
composition comprises an aqueous alkali metal silicate solution and
a temperature activated catalyst.
62. The method of claim 61 wherein the aqueous alkali metal
silicate solution generally comprises an aqueous liquid and an
alkali metal silicate selected from the group consisting of sodium
silicate, potassium silicate, lithium silicate, rubidium silicate,
and cesium silicate.
63. The method of claim 61 wherein the temperature activated
catalyst comprises an ammonium sulfate, a sodium acid
pyrophosphate, a citric acid, or an ethyl acetate.
64. The method of claim 55 wherein the polymerizable organic
monomer composition comprises an aqueous-base fluid, a water
soluble polymerizable organic monomer, an oxygen scavenger, and a
primary initiator.
65. The method of claim 64 wherein the water soluble polymerizable
organic monomer comprises acrylic acid, methacrylic acid,
acrylamide, methacrylamide, 2-methacrylamido-2-methylpropane
sulfonic acid, 2-dimethylacrylamide, vinyl sulfonic acid,
N,N-dimethylaminoethylmethacry- late,
2-triethylammoniumethylmethacrylate chloride,
N,N-dimethyl-aminopropylmethacryl-amide,
methacrylamidepropyltriethylammo- nium chloride, N-vinyl
pyrrolidone, vinyl-phosphonic acid, methacryloyloxyethyl
trimethylammonium sulfate, or a mixture thereof.
66. The method of claim 64 wherein the water soluble polymerizable
organic monomer comprises hydroxyethylacrylate,
hydroxymethylacrylate, hydroxyethylmethacrylate,
N-hydroxymethylacrylamide, N-hydroxy-methylmethacrylamide,
polyethylene acrylate, polyethylene methacrylate, polyethylene
glycol acrylate, polyethylene glycol methacrylate,
hydroxyethylcellulose-vinyl phosphoric acid, or a mixture
thereof.
67. The method of claim 64 wherein the oxygen scavenger comprises
stannous chloride.
68. The method of claim 64 wherein the primary initiator comprises
an alkali metal persulfate, a peroxide, an oxidation-reduction
system employing reducing agents, or an azo polymerization
initiator.
69. The method of claim 64 wherein the primary initiator comprises
2,2'-azobis(2-imidazole-2-hydroxyethyl)propane,
2,2'-azobis(2-aminopropan- e), 4,4'-azobis(4-cyanovaleric acid), or
2,2'-azobis(2-methyl-N-(2-hydroxy- ethyl)propionamide.
70. The method of claim 55 wherein the crosslinkable aqueous
polymer composition comprises an aqueous solvent, a crosslinkable
polymer, and a crosslinking agent.
71. The method of claim 70 wherein the aqueous solvent comprises
fresh water, salt water, brine, or seawater.
72. The method of claim 70 wherein the crosslinkable polymer
comprises a carboxylate-containing polymer or an
acrylamide-containing polymer.
73. The method of claim 70 wherein the crosslinkable polymer is a
polyacrylamide, a partially hydrolyzed polyacrylamide, a copolymer
of acrylamide and acrylate, or a carboxylate-containing terpolymers
and tetrapolymers of acrylate.
74. The method of claim 70 wherein the crosslinkable aqueous
polymer further comprises a crosslinking delaying agent.
76. The method of claim 50 wherein the stabilizing composition
penetrates into the near well bore area of a portion in a formation
to a depth of from about a few inches to about three well bore
diameters.
77. The method of claim 50 wherein the stimulating step comprises
hydrajetting, puncturing, fracturing, or a combinations
thereof.
78. The method of claim 50 further comprising the step of, after
stimulating the stabilized portion, placing proppant into the area
or fluid communication.
79. The method of claim 78 wherein the proppant comprises a
hardenable resin coating.
80. The method of claim 78 wherein the proppant comprises a
tackyfier coating.
81. The method of claim 50 wherein the well bore comprises an open
hole well bore.
82. The method of claim 50 wherein the well bore comprises a cased
well bore.
83. A system for stabilizing and stimulating a portion of a
subterranean formation penetrated by a well bore comprising:
placing a stabilizing composition into a near well bore area of a
portion in a formation to create a stabilized portion; and,
stimulating the stabilized portion so as to place the well bore in
fluid communication with both the stabilized portion in the
near-well bore area and an unstabilized portion of the formation in
the far-well bore area.
84. The method of claim 83 wherein the stabilizing composition
comprises a curable resin composition.
85. The method of claim 84 wherein the curable resin composition
comprises a novolak resin, a polyepoxide resin, a phenol-aldehyde
resin, a urea-aldehyde resin, a urethane resin, a phenolic resin, a
furan/furfuryl alcohol resin, a phenolic/latex resin, a phenol
formaldeyhe resin, a polyester resin, including hybrids and
copolymers thereof, a polyurethane resin and hybrids and copolymers
thereof, an acrylate resin, or mixtures thereof.
86. The method of claim 84 further comprising an internal catalyst,
an activator, a time-delayed catalyst, or an external catalyst.
87. The method of claim 83 wherein the stabilizing composition
comprises a gelable composition.
88. The method of claim 87 wherein the gelable composition
comprises a gelable resin composition, a gelable aqueous silicate
composition, a polymerizable organic monomer composition, or a
crosslinkable aqueous polymer composition.
89. The method of claim 88 wherein the gelable resin composition
comprises a curable resin composition that comprises a curable
resin, a diluent, and a resin curing agent.
90. The method of claim 89 wherein the curable resin comprises an
organic resin that comprises a polyepoxide resin, a polyester
resin, a urea-aldehyde resin, a furan resin, a urethane resin, or a
mixture thereof.
91. The method of claim 89 wherein the diluent comprises a phenol,
a formaldehyde, a furfuryl alcohol, a furfural, an alcohol, an
ether, or a mixture thereof.
92. The method of claim 89 wherein the resin curing agent comprises
an amine, a polyamine, an amide, a polyamide, or a methylene
dianiline.
93. The method of claim 89 wherein the curable resin composition
further comprises a flexibilizer additive wherein the flexibilizer
additive comprises an organic ester, an oxygenated organic solvent,
an aromatic solvent, or combinations thereof.
94. The method of claim 88 wherein the gelable aqueous silicate
composition comprises an aqueous alkali metal silicate solution and
a temperature activated catalyst.
95. The method of claim 94 wherein the aqueous alkali metal
silicate solution comprises an aqueous liquid and an alkali metal
silicate selected from the group consisting of sodium silicate,
potassium silicate, lithium silicate, rubidium silicate, and cesium
silicate.
96. The method of claim 94 wherein the temperature activated
catalyst comprises an ammonium sulfate, a sodium acid
pyrophosphate, a citric acid, or an ethyl acetate.
97. The method of claim 88 wherein the polymerizable organic
monomer composition comprises an aqueous-base fluid, a water
soluble polymerizable organic monomer, an oxygen scavenger, and a
primary initiator.
98. The method of claim 97 wherein the water soluble polymerizable
organic monomer comprises acrylic acid, methacrylic acid,
acrylamide, methacrylamide, 2-methacrylamido-2-methylpropane
sulfonic acid, 2-dimethylacrylamide, vinyl sulfonic acid,
N,N-dimethylaminoethylmethacry- late,
2-triethylammoniumethylmethacrylate chloride,
N,N-dimethyl-aminopropylmethacryl-amide,
methacrylamidepropyltriethylammo- nium chloride, N-vinyl
pyrrolidone, vinyl-phosphonic acid, methacryloyloxyethyl
trimethylammonium sulfate, or a mixture thereof.
99. The method of claim 97 wherein the water soluble polymerizable
organic monomer comprises hydroxyethylacrylate,
hydroxymethylacrylate, hydroxyethylmethacrylate,
N-hydroxymethylacrylamide, N-hydroxy-methylmethacrylamide,
polyethylene acrylate, polyethylene methacrylate, polyethylene
glycol acrylate, polyethylene glycol methacrylate,
hydroxyethylcellulose-vinyl phosphoric acid, or a mixture
thereof.
100. The method of claim 97 wherein the oxygen scavenger comprises
stannous chloride.
101. The method of claim 97 wherein the primary initiator comprises
an alkali metal persulfate, a peroxide, an oxidation-reduction
system employing reducing agents, or an azo polymerization
initiator.
102. The method of claim 97 wherein the primary initiator comprises
2,2'-azobis(2-imidazole-2-hydroxyethyl)propane,
2,2'-azobis(2-aminopropan- e), 4,4'-azobis(4-cyanovaleric acid), or
2,2'-azobis(2-methyl-N-(2-hydroxy- ethyl)propionamide.
103. The method of claim 88 wherein the crosslinkable aqueous
polymer composition comprises an aqueous solvent, a crosslinkable
polymer, and a crosslinking agent.
104. The method of claim 103 wherein the aqueous solvent comprises
fresh water, salt water, brine, or seawater.
105. The method of claim 103 wherein the crosslinkable polymer
comprises a carboxylate-containing polymer or an
acrylamide-containing polymer.
106. The method of claim 103 wherein the crosslinkable polymer is a
polyacrylamide, a partially hydrolyzed polyacrylamide, a copolymer
of acrylamide and acrylate, or a carboxylate-containing terpolymers
and tetrapolymers of acrylate.
107. The method of claim 103 wherein the aqueous crosslinkable
polymer composition further comprises a crosslinking delaying
agent.
108. The method of claim 83 wherein the stabilizing composition
penetrates into the near well bore area of a portion in a formation
to a depth of from about a few inches to about three well bore
diameters.
109. The method of claim 83 wherein the stimulating step comprises
hydrajetting, puncturing, fracturing, or a combinations
thereof.
110. The method of claim 83 further comprising the step of, after
stimulating the stabilized portion, placing proppant into the area
or fluid communication.
111. The method of claim 110 wherein the proppant comprises a
hardenable resin coating.
112. The method of claim 110 wherein the proppant comprises a
tackyfier coating.
113. The method of claim 83 wherein the well bore comprises an open
hole well bore.
114. The method of claim 83 wherein the well bore comprises a cased
well bore.
Description
BACKGROUND OF THE INVENTION
[0001] The present invention relates to methods of stabilizing an
unconsolidated portion in a subterranean formation and stimulating
fluid production from the stabilized portion.
[0002] One method of stimulating fluid production from a portion of
a subterranean formation along a producing zone of a well bore,
known as hydrajetting, involves the use of hydraulic jets, inter
alia, that increases the permeability and production capabilities
of a formation. In an example of a common hydrajetting operation, a
hydrajetting tool having at least one fluid jet forming nozzle is
positioned adjacent to a formation to be fractured, and proppant
slurry is then jetted through the nozzle against the formation at a
pressure sufficient to form a cavity, or slot therein to fracture
the formation, e.g., by stagnation pressure in the cavity. U.S.
Pat. Nos. 5,765,642, 5,494,103, and 5,361,856, the relevant
portions of which are herein incorporated by reference, describe
suitable hydrajetting tools known in the art. Hydrajetting provides
the ability to selectively form a desired number of fractures at
desired intervals.
[0003] Another method of stimulating fluid production from a
subterranean formation is hydraulic fracturing, wherein a formation
is treated to increase its permeability by hydraulically fracturing
the formation to create or enhance one or more cracks or
"fractures." In most cases, a hydraulic fracturing treatment
involves pumping a proppant-free, viscous fluid (known as a pad
fluid) into a subterranean formation faster than the fluid can
escape into the formation so that the pressure in the formation
rises, creating artificial fractures or enlarging natural
fractures. Thereafter, proppant slurry oftentimes is pumped into
the formation to place proppant inside the created fractures to
keep them opened even after the hydraulic pressure has been
released.
[0004] Stimulation techniques, such as fracturing and hydrajetting,
are most successfully performed on portions of a subterranean
formation that are substantially consolidated. However, hydrocarbon
wells are often located in unconsolidated portions, that is,
portions having loose particulates or particulates bonded together
with insufficient strength to remain bonded when a fluid (such as
produced oil) flows through the portion. The presence of
particulates, such as formation sand, in produced fluids may be
disadvantageous and undesirable in that the particulates may abrade
pumping and other producing equipment and reduce the fluid
production capabilities of the producing zones. Thus, it is often
desirable to control, or "stabilize," particulates in relatively
unconsolidated areas in a subterranean formation before performing
a stimulation treatment.
[0005] One method of stabilizing particulates in unconsolidated
subterranean portions has been to produce fluids from such
formations at low flow rates, whereby the near well stability of
sand bridges and the like may be preserved. However, the collapse
of such sand bridges may occur due to unintentionally high
production rates and/or pressure cycling (as may occur from
frequent shut-ins and start ups of a well). The frequency of
pressure cycling is very critical to the longevity of the near well
formation, especially during the depletion stage of the well when
the pore pressure of the formation has been significantly
reduced.
[0006] Another method of controlling the migration of particulates
so that they are not produced along with the produced fluids is
gravel packing. Gravel packing involves placing a filtration bed
containing gravel near the well bore in order to present a physical
barrier to the transport of unconsolidated formation fines with the
production of hydrocarbons. Typically, gravel packing operations
involve the pumping and placement of a quantity of a desired
particulate into the unconsolidated formation in an area adjacent
to a well bore. Such packs are often time consuming and expensive
to install. In some situations, the processes of fracturing and
gravel packing are combined into a single treatment to provide a
stimulated production and an annular gravel pack to prevent
formation sand production. Such treatments are often referred to as
"frac pack" operations.
[0007] Another method used to stabilize particulates in
unconsolidated formations involves consolidating unconsolidated
subterranean producing zones by applying a resin followed by a
spacer fluid and then a catalyst. Such resin application may be
problematic when, for example, an insufficient amount of spacer
fluid is used between the application of the resin and the
application of the external catalyst. The resin may come into
contact with the external catalyst in the well bore itself rather
than in the unconsolidated subterranean producing zone. When resin
is contacted with an external catalyst an exothermic reaction
occurs that may result in rapid polymerization, potentially
damaging the formation by plugging the pore channels, halting
pumping when the well bore is plugged with solid material, or
resulting in a down hole explosion as a result of the heat of
polymerization.
SUMMARY OF THE INVENTION
[0008] The present invention relates to methods of stabilizing an
unconsolidated portion in a subterranean formation and stimulating
fluid production from the stabilized portion.
[0009] One embodiment of the present invention provides a method of
substantially stabilizing a portion of a subterranean formation
penetrated by a well bore and stimulating fluid production
therefrom comprising placing a stabilizing composition into a near
well bore area of a portion in a formation to create a stabilized
portion; and, stimulating the stabilized portion so as to place the
well bore in fluid communication with both the stabilized portion
in the near-well bore area and an unstabilized portion of the
formation in the far-well bore area.
[0010] Other embodiments of the present invention provide methods
of controlling formation sands in a portion of a formation
penetrated by a well bore and stimulating fluid production
therefrom comprising placing a stabilizing composition into a near
well bore area of a portion in a formation to create a stabilized
portion; and, stimulating the stabilized portion so as to place the
well bore in fluid communication with both the stabilized portion
in the near-well bore area and an unstabilized portion of the
formation in the far-well bore area.
[0011] Other embodiments of the present invention provide systems
for stabilizing and stimulating a portion of a subterranean
formation penetrated by a well bore comprising placing a
stabilizing composition into a near well bore area of a portion in
a formation to create a stabilized portion; and, stimulating the
stabilized portion so as to place the well bore in fluid
communication with both the stabilized portion in the near-well
bore area and an unstabilized portion of the formation in the
far-well bore area.
[0012] Other and further 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.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] FIG. 1 illustrates near-well bore and far-well bore areas
and how fluid communication may be established.
DETAILED DESCRIPTION
[0014] The present invention relates to methods of stabilizing an
unconsolidated portion in a subterranean formation and stimulating
fluid production from the stabilized portion.
[0015] Some embodiments of the present invention provide methods of
stabilizing subterranean formations and stimulating fluid
production comprising the steps of: injecting a stabilizing
composition into a near well bore area of a portion in a
subterranean formation; allowing the stabilizing composition to
substantially cure to form a stabilized portion; stimulating the
stabilized portion so as to place the well bore in fluid
communication with both the stabilized portion in the near-well
bore area and an unstabilized portion of the formation in the
far-well bore area. As used herein the term "near well bore area"
refers to a distance up to about three well bore diameters from the
surface of the well bore into the formation. The term "far well
bore area" refers to distances beyond the near well bore area. The
methods of the present invention may result in hydrocarbon
production at a higher rate with less risk of producing
particulates from the formation that may be problematic.
[0016] Stabilizing Compositions
[0017] Stabilizing compositions suitable for use in the present
invention include curable resin compositions that are capable of
curing to form hardened substances and gelable substances that cure
to form a semi-solid, gel-like substance. Regardless of whether a
curable resin composition that cures to form hardened substance is
chosen or a gelable substance that cures to form a semi-solid,
gel-like substance is chosen, generally, a desirable depth of
penetration of the stabilizing composition into the formation
surrounding the well bore is from about a few inches in some
embodiments to about three well bore diameters in other
embodiments.
[0018] Stabilizing Compositions: Curable Resin Compositions.
[0019] Suitable curable resin compositions include those resins
that are capable of forming a hardened, consolidated mass. Such
resins include, but are not limited to, novolak resins, polyepoxide
resins, phenol-aldehyde resins, urea-aldehyde resins, urethane
resins, phenolic resins, furan/furfuryl alcohol resins,
phenolic/latex resins, phenol formaldehyde resins, polyester
resins, polyurethane resins and hybrids and copolymers thereof,
acrylate resins, and hybrids and copolymers thereof, and mixtures
thereof. Some suitable resins, such as epoxy resins, may be cured
with an internal catalyst or activator so that when pumped down
hole, they may be cured using only time and temperature. Other
suitable resins, such as furan resins generally require a
time-delayed catalyst or an external catalyst to help activate the
polymerization of the resins if the cure temperature is low (i.e.,
less than 250.degree. F.), but will cure under the effect of time
and temperature if the formation temperature is above about
250.degree. F., preferably above about 300.degree. F. It is within
the ability of one skilled in the art, with the benefit of this
disclosure, to select a suitable resin for use in embodiments of
the present invention and to determine whether a catalyst is
required to trigger curing.
[0020] Stabilizing Compositions: Gelable Compositions.
[0021] Gelable compositions suitable for use in the present
invention include those compositions that cure to form a
semi-solid, gel-like substance. The gelable composition may be any
gelable liquid composition capable of converting into a gelled
substance capable of substantially plugging the permeability of the
formation while allowing the formation to remain flexible. As
referred to herein, the term "flexible" refers to a state wherein
the treated portion of the formation is relatively malleable and
elastic and able to withstand substantial pressure cycling without
substantial breakdown of the formation. Thus, the resultant gelled
substance stabilizes the treated portion of the formation while
allowing the formation to absorb the stresses created during
pressure cycling. As a result, the gelled substance may aid in
preventing breakdown of the formation both by stabilizing and by
adding flexibility to the treated portion. Examples of suitable
gelable liquid compositions include, but are not limited to, (1)
gelable resin compositions, (2) gelable aqueous silicate
compositions, (3) crosslinkable aqueous polymer compositions, and
(4) polymerizable organic monomer compositions.
[0022] Stabilizing Compositions: Gelable Compositions--Gelable
Resin Compositions.
[0023] Certain embodiments of the gelable liquid compositions of
the present invention comprise gelable resin compositions that cure
to form flexible gels. Unlike the curable resin compositions
described above, which cure into hardened masses, the gelable resin
compositions cure into flexible, gelled substances that form
resilient gelled substances between the particulates of the treated
zone of the unconsolidated formation. Gelable resin compositions
allow the treated portion of the formation to remain flexible and
resist breakdown.
[0024] Generally, the gelable resin compositions useful in
accordance with this invention comprise a curable resin, a diluent,
and a resin curing agent. When certain resin curing agents, such as
polyamides, are used in the curable resin compositions, the
compositions form the semi-solid, gelled substances described
above. Where the resin curing agent used may cause the organic
resin compositions to form hard, brittle material rather than a
desired gelled substance, the curable resin compositions may
further comprise one or more "flexibilizer additives" (described in
more detail below) to provide flexibility to the cured
compositions.
[0025] Examples of gelable resins that can be used in the present
invention include, but are not limited to, organic resins such as
polyepoxide resins (e.g., Bisphenol a-epichlorihydrin resins),
polyester resins, urea-aldehyde resins, furan resins, urethane
resins, and mixtures thereof. Of these, polyepoxide resins are
preferred.
[0026] Any diluent that is compatible with the gelable resin and
achieves the desired viscosity effect is suitable for use in the
present invention. Examples of diluents that may be used in the
gelable resin compositions of the present invention include, but
are not limited to, phenols; formaldehydes; furfuryl alcohols;
furfurals; alcohols; ethers such as butyl glycidyl ether and cresyl
glycidyl etherphenyl glycidyl ether; and mixtures thereof. In some
embodiments of the present invention, the diluent comprises butyl
lactate. The diluent may be used to reduce the viscosity of the
gelable resin composition from about 3 to about 3,000 centipoises
("cP") at 80.degree. F. Among other things, the diluent acts to
provide flexibility to the cured composition. The diluent may be
included in the gelable resin composition in an amount sufficient
to provide the desired viscosity effect. Generally, the diluent
used is included in the gelable resin composition in amount in the
range of from about 5% to about 75% by weight of the curable
resin.
[0027] Generally, any resin curing agent that may be used to cure
an organic resin is suitable for use in the present invention. When
the resin curing agent chosen is an amide or a polyamide, generally
no flexibilizer additive will be required because, inter alia, such
curing agents cause the gelable resin composition to convert into a
semi-solid, gelled substance. Other suitable resin curing agents
(such as an amine, a polyamine, methylene dianiline, and other
curing agents known in the art) will tend to cure into a hard,
brittle material and will thus benefit from the addition of a
flexibilizer additive. Generally, the resin curing agent used is
included in the gelable resin composition, whether a flexibilizer
additive is included or not, in an amount in the range of from
about 5% to about 75% by weight of the curable resin. In some
embodiments of the present invention, the resin curing agent used
is included in the gelable resin composition in an amount in the
range of from about 20% to about 75% by weight of the curable
resin.
[0028] As noted above, flexibilizer additives may be used, inter
alia, to provide flexibility to the gelled substances formed from
the curable resin compositions. Flexibilizer additives may be used
where the resin curing agent chosen would cause the gelable resin
composition to cure into a hard and brittle material--rather than a
desired gelled substance. For example, flexibilizer additives may
be used where the resin curing agent chosen is not an amide or
polyamide. Examples of suitable flexibilizer additives include, but
are not limited to, an organic ester, an oxygenated organic
solvent, an aromatic solvent, and combinations thereof. Of these,
ethers, such as dibutyl phthalate, are preferred. Where used, the
flexibilizer additive may be included in the gelable resin
composition in an amount in the range of from about 5% to about 80%
by weight of the gelable resin. In some embodiments of the present
invention, the flexibilizer additive may be included in the curable
resin composition in an amount in the range of from about 20% to
about 45% by weight of the curable resin.
[0029] Stabilizing Compositions: Gelable Compositions--Gelable
Aqueous Silicate Compositions.
[0030] In other embodiments, the gelable liquid compositions of the
present invention may comprise a gelable aqueous silicate
composition. Generally, the gelable aqueous silicate compositions
that are useful in accordance with the present invention generally
comprise an aqueous alkali metal silicate solution and a
temperature activated catalyst for gelling the aqueous alkali metal
silicate solution.
[0031] The aqueous alkali metal silicate solution component of the
gelable aqueous silicate compositions generally comprise an aqueous
liquid and an alkali metal silicate. The aqueous liquid component
of the aqueous alkali metal silicate solution generally may be
fresh water, salt water (e.g., water containing one or more salts
dissolved therein), brine (e.g., saturated salt water), seawater,
or any other aqueous liquid that does not adversely react with the
other components used in accordance with this invention or with the
subterranean formation. Examples of suitable alkali metal silicates
include, but are not limited to, one or more of sodium silicate,
potassium silicate, lithium silicate, rubidium silicate, or cesium
silicate. Of these, sodium silicate is preferred. While sodium
silicate exists in many forms, the sodium silicate used in the
aqueous alkali metal silicate solution preferably has a
Na.sub.2O-to-SiO.sub.2 weight ratio in the range of from about 1:2
to about 1:4. Most preferably, the sodium silicate used has a
Na.sub.2O-to-SiO.sub.2 weight ratio in the range of about 1:3.2.
Generally, the alkali metal silicate is present in the aqueous
alkali metal silicate solution component in an amount in the range
of from about 0.1% to about 10% by weight of the aqueous alkali
metal silicate solution component.
[0032] The temperature-activated catalyst component of the gelable
aqueous silicate compositions is used, inter alia, to convert the
gelable aqueous silicate compositions into the desired semi-solid,
gel-like substance described above. Selection of a
temperature-activated catalyst is related, at least in part, to the
temperature of the subterranean formation to which the gelable
aqueous silicate composition will be introduced. The
temperature-activated catalysts that can be used in the gelable
aqueous silicate compositions of the present invention include, but
are not limited to, ammonium sulfate (which is most suitable in the
range of from about 60.degree. F. to about 240.degree. F.); sodium
acid pyrophosphate (which is most suitable in the range of from
about 60.degree. F. to about 240.degree. F.); citric acid (which is
most suitable in the range of from about 60.degree. F. to about
120.degree. F.); and ethyl acetate (which is most suitable in the
range of from about 60.degree. F. to about 120.degree. F.).
Generally, the temperature-activated catalyst is present in the
gelable aqueous silicate composition in the range of from about
0.1% to about 5% by weight of the gelable aqueous silicate
composition.
[0033] Stabilizing Compositions: Gelable
Compositions--Crosslinkable Aqueous Polymer Compositions.
[0034] In other embodiments, the gelable liquid compositions of the
present invention comprise crosslinkable aqueous polymer
compositions. Generally, suitable crosslinkable aqueous polymer
compositions comprise an aqueous solvent, a crosslinkable polymer,
and a crosslinking agent. Such compositions are similar to those
used to form gelled treatment fluids, such as fracturing fluids,
but, according to the methods of the present invention, they are
not exposed to breakers or de-linkers and so they retain their
viscous nature over time.
[0035] The aqueous solvent may be any aqueous solvent in which the
crosslinkable composition and the crosslinking agent may be
dissolved, mixed, suspended, or dispersed therein to facilitate gel
formation. For example, the aqueous solvent used may be fresh
water, salt water, brine, seawater, or any other aqueous liquid
that does not adversely react with the other components used in
accordance with this invention or with the subterranean
formation.
[0036] Examples of crosslinkable polymers that can be used in the
crosslinkable aqueous polymer compositions include, but are not
limited to, carboxylate-containing polymers and
acrylamide-containing polymers. Preferred acrylamide-containing
polymers include polyacrylamide, partially hydrolyzed
polyacrylamide, copolymers of acrylamide and acrylate, and
carboxylate-containing terpolymers and tetrapolymers of acrylate.
Additional examples of suitable crosslinkable polymers include
hydratable polymers comprising polysaccharides and derivatives
thereof and that contain one or more of the monosaccharide units
galactose, mannose, glucoside, glucose, xylose, arabinose,
fructose, glucuronic acid, or pyranosyl sulfate. Suitable natural
hydratable polymers include, but are not limited to, guar gum,
locust bean gum, tara, konjak, tamarind, starch, cellulose, karaya,
xanthan, tragacanth, and carrageenan, and derivatives of all of the
above. Suitable hydratable synthetic polymers and copolymers that
may be used in the crosslinkable aqueous polymer compositions
include, but are not limited to, polyacrylates, polymethacrylates,
polyacrylamides, maleic anhydride, methylvinyl ether polymers,
polyvinyl alcohols, and polyvinylpyrrolidone. The crosslinkable
polymer used should be included in the crosslinkable aqueous
polymer composition in an amount sufficient to form the desired
gelled substance in the subterranean formation. In some embodiments
of the present invention, the crosslinkable polymer is included in
the crosslinkable aqueous polymer composition in an amount in the
range of from about 1% to about 30% by weight of the aqueous
solvent. In another embodiment of the present invention, the
crosslinkable polymer is included in the crosslinkable aqueous
polymer composition in an amount in the range of from about 1% to
about 20% by weight of the aqueous solvent.
[0037] The crosslinkable aqueous polymer compositions of the
present invention further comprise a crosslinking agent for
crosslinking the crosslinkable polymers to form the desired gelled
substance. In some embodiments, the crosslinking agent is a
molecule or complex containing a reactive transition metal cation.
A most preferred crosslinking agent comprises trivalent chromium
cations complexed or bonded to anions, atomic oxygen, or water.
Examples of suitable crosslinking agents include, but are not
limited to, compounds or complexes containing chromic acetate
and/or chromic chloride. Other suitable transition metal cations
include chromium VI within a redox system, aluminum III, iron II,
iron III, and zirconium IV.
[0038] The crosslinking agent should be present in the
crosslinkable aqueous polymer compositions of the present invention
in an amount sufficient to provide, inter alia, the desired degree
of crosslinking. In some embodiments of the present invention, the
crosslinking agent is present in the crosslinkable aqueous polymer
compositions of the present invention in an amount in the range of
from about 0.01% to about 5% by weight of the crosslinkable aqueous
polymer composition. The exact type and amount of crosslinking
agent or agents used depends upon the specific crosslinkable
polymer to be crosslinked, formation temperature conditions, and
other factors known to those individuals skilled in the art.
[0039] Optionally, the crosslinkable aqueous polymer compositions
may further comprise a crosslinking delaying agent, such as a
polysaccharide crosslinking delaying agent derived from guar, guar
derivatives, or cellulose derivatives. The crosslinking delaying
agent may be included in the crosslinkable aqueous polymer
compositions, inter alia, to delay crosslinking of the
crosslinkable aqueous polymer compositions until desired. One of
ordinary skill in the art, with the benefit of this disclosure,
will know the appropriate amount of the crosslinking delaying agent
to include in the crosslinkable aqueous polymer compositions for a
desired application.
[0040] Stabilizing Compositions: Gelable
Compositions--Polymerization Organic Monomer Compositions.
[0041] In other embodiments, the gelled liquid compositions of the
present invention comprise polymerizable organic monomer
compositions. Generally, suitable polymerizable organic monomer
compositions comprise an aqueous-base fluid, a water-soluble
polymerizable organic monomer, an oxygen scavenger, and a primary
initiator.
[0042] The aqueous-based fluid component of the polymerizable
organic monomer composition generally may be fresh water, salt
water, brine, seawater, or any other aqueous liquid that does not
adversely react with the other components used in accordance with
this invention or with the subterranean formation.
[0043] A variety of monomers are suitable for use as the
water-soluble polymerizable organic monomers in the present
invention. Examples of suitable monomers include, but are not
limited to, acrylic acid, methacrylic acid, acrylamide,
methacrylamide, 2-methacrylamido-2-methylpr- opane sulfonic acid,
2-dimethylacrylamide, vinyl sulfonic acid,
N,N-dimethylaminoethylmethacrylate,
2-triethylammoniumethylmethacrylate chloride,
N,N-dimethyl-aminopropylmethacryl-amide,
methacrylamidepropyltriethylammonium chloride, N-vinyl pyrrolidone,
vinyl-phosphonic acid, and methacryloyloxyethyl trimethylammonium
sulfate, and mixtures thereof. Preferably, the water-soluble
polymerizable organic monomer should be self-crosslinking. Examples
of suitable monomers which are self crosslinking include, but are
not limited to, hydroxyethylacrylate, hydroxymethylacrylate,
hydroxyethylmethacrylate, N-hydroxymethylacrylamide,
N-hydroxymethyl-methacrylamide, polyethylene glycol acrylate,
polyethylene glycol methacrylate, polypropylene gylcol acrylate,
polypropylene glycol methacrylate, and mixtures thereof. Of these,
hydroxyethylacrylate is preferred. An example of a particularly
preferable monomer is hydroxyethylcellulose-vinyl phosphoric
acid.
[0044] The water-soluble polymerizable organic monomer (or monomers
where a mixture thereof is used) should be included in the
polymerizable organic monomer composition in an amount sufficient
to form the desired gelled substance after placement of the
polymerizable organic monomer composition into the subterranean
formation. In some embodiments of the present invention, the
water-soluble polymerizable organic monomer is included in the
polymerizable organic monomer composition in an amount in the range
of from about 1% to about 30% by weight of the aqueous-base fluid.
In another embodiment of the present invention, the water-soluble
polymerizable organic monomer is included in the polymerizable
organic monomer composition in an amount in the range of from about
1% to about 20% by weight of the aqueous-base fluid.
[0045] The presence of oxygen in the polymerizable organic monomer
composition may inhibit the polymerization process of the
water-soluble polymerizable organic monomer or monomers. Therefore,
an oxygen scavenger, such as stannous chloride, may be included in
the polymerizable monomer composition. In order to improve the
solubility of stannous chloride so that it may be readily combined
with the polymerizable organic monomer composition on the fly, the
stannous chloride may be pre-dissolved in a hydrochloric acid
solution. For example, the stannous chloride may be dissolved in a
0.1% by weight aqueous hydrochloric acid solution in an amount of
about 10% by weight of the resulting solution. The resulting
stannous chloride-hydrochloric acid solution may be included in the
polymerizable organic monomer composition in an amount in the range
of from about 0.1% to about 10% by weight of the polymerizable
organic monomer composition. Generally, the stannous chloride may
be included in the polymerizable organic monomer composition of the
present invention in an amount in the range of from about 0.005% to
about 0.1% by weight of the polymerizable organic monomer
composition.
[0046] The primary initiator is used, inter alia, to initiate
polymerization of the water-soluble polymerizable organic
monomer(s) used in the present invention. Any compound or compounds
that form free radicals in aqueous solution may be used as the
primary initiator. The free radicals act, inter alia, to initiate
polymerization of the water-soluble polymerizable organic monomer
present in the polymerizable organic monomer composition. Compounds
suitable for use as the primary initiator include, but are not
limited to, alkali metal persulfates; peroxides;
oxidation-reduction systems employing reducing agents, such as
sulfites in combination with oxidizers; and azo polymerization
initiators. Preferred azo polymerization initiators include
2,2'-azobis(2-imidazole-2-hydroxyethyl)propane,
2,2'-azobis(2-aminopropan- e), 4,4'-azobis(4-cyanovaleric acid),
and 2,2'-azobis(2-methyl-N-(2-hydrox- yethyl)propionamide.
Generally, the primary initiator should be present in the
polymerizable organic monomer composition in an amount sufficient
to initiate polymerization of the water-soluble polymerizable
organic monomer(s). In certain embodiments of the present
invention, the primary initiator is present in the polymerizable
organic monomer composition in an amount in the range of from about
0.1% to about 5% by weight of the water-soluble polymerizable
organic monomer(s). One skilled in the art will recognize that as
the polymerization temperature increases, the required level of
activator decreases.
[0047] Optionally, the polymerizable organic monomer compositions
further may comprise a secondary initiator. A secondary initiator
may be used, for example, where the immature aqueous gel is placed
into a subterranean formation that is relatively cool as compared
to the surface mixing, such as when placed below the mud line in
offshore operations. The secondary initiator may be any suitable
water-soluble compound or compounds that may react with the primary
initiator to provide free radicals at a lower temperature. An
example of a suitable secondary initiator is triethanolamine. In
some embodiments of the present invention, the secondary initiator
is present in the polymerizable organic monomer composition in an
amount in the range of from about 0.1% to about 5% by weight of the
water-soluble polymerizable organic monomer(s).
[0048] Also optionally, the polymerizable organic monomer
compositions of the present invention further may comprise a
crosslinking agent for crosslinking the polymerizable organic
monomer compositions in the desired gelled substance. In some
embodiments, the crosslinking agent is a molecule or complex
containing a reactive transition metal cation. A most preferred
crosslinking agent comprises trivalent chromium cations complexed
or bonded to anions, atomic oxygen, or water. Examples of suitable
crosslinking agents include, but are not limited to, compounds or
complexes containing chromic acetate and/or chromic chloride. Other
suitable transition metal cations include chromium VI within a
redox system, aluminum III, iron II, iron III, and zirconium IV.
Generally, the crosslinking agent may be present in polymerizable
organic monomer compositions in an amount in the range of from
0.01% to about 5% by weight of the polymerizable organic monomer
composition.
[0049] Stimulation Treatments.
[0050] Once the stabilizing composition is placed into the
formation, it is allowed to substantially cure and stabilize the
treated portion of the formation. Once the treated portion of the
formation is so stabilized, a stimulation treatment is
performed.
[0051] In certain embodiments, the stimulating step of the methods
of the present invention may involve perforating, hydrajetting,
fracturing, or some other stimulating method known in the art. One
object of the stimulation treatment is to place the well bore in
fluid communication with the treated portion of the formation
surrounding the well bore and with an untreated portion. This
concept is illustrated in FIG. 1 to show how fluid communication
may be established where the chosen stimulation treatment is
fracturing. FIG. 1 shows a top view of well bore 10 with a stylized
fracture 20. Well bore 10 has been stabilized in the near well bore
region (30) to a distance of approximately one-half of a well bore
diameter, as shown by stabilizing treatment penetration 30.
[0052] Stimulation Treatments: Hydrajetting.
[0053] One stimulation treatment suitable for use in the methods of
the present invention is hydrajetting. Hydrajetting, as described
above, refers to a treatment in which a hydrajetting tool having at
least one fluid jet forming nozzle is positioned adjacent to a
formation to be fractured, and fluid is then jetted through the
nozzle against the formation at a pressure sufficient to form a
cavity, or slot therein to fracture the formation by stagnation
pressure in the cavity. In some embodiments of the present
invention, the hydrajetting tool is used to create slots
substantially uniformly around the well bore circumference. Because
the jetted fluids would have to flow out of the slot in a direction
generally opposite to the direction of the incoming jetted fluid,
they are trapped in the slot and create a relatively high
stagnation pressure at the tip of a cavity. This high stagnation
pressure often causes a microfracture to be formed that extends a
short distance into the formation. That microfracture may be
further extended by pumping a fluid into the well bore to raise the
ambient fluid pressure exerted on the formation while the formation
is being hydrajetted. Such a fluid in the well bore will flow into
the slot and fracture produced by the fluid jet and, if introduced
into the well bore at a sufficient rate and pressure, may be used
to extend the fracture an additional distance from the well bore
into the formation. Then a proppant is generally added to the fluid
to form a slurry that is pumped into the fracture to prevent the
fracture from closing when the pumping pressure is released. A
portion of the proppant may be coated with a tackifying agent,
inter alia, to control fines from migrating into the proppant pack.
A portion of the proppant may also be coated with curable resin so
that, once cured, the placed proppant forms a consolidated mass and
prevents the proppant from flowing back during production of the
well.
[0054] Stimulation Treatments: Hydraulic Fracturing.
[0055] Another stimulation treatment suitable for use in some
embodiments of the methods of the present invention is hydraulic
fracturing, wherein a formation is treated to increase its
permeability by hydraulically fracturing the formation to create or
enhance one or more cracks or "fractures." In most cases, a
hydraulic fracturing treatment involves pumping a proppant-free,
viscous fluid (known as a pad fluid) into a subterranean formation
faster than the fluid can escape into the formation so that the
pressure in the formation rises and the formation breaks, creating
an artificial fracture or enlarging a natural fracture. Similar to
hydrajetting, a proppant is then generally added to the fluid to
form a slurry that is pumped into the fracture to prevent the
fracture from closing when the pumping pressure is released. A
portion of the proppant may be coated with a tackifying agent,
inter alia, to control fines from migrating into the proppant pack.
A portion of the proppant may also be coated with curable resin so
that, once cured, the placed proppant forms a consolidated mass and
prevents the proppant from flowing back during production of the
well.
[0056] Suitable Proppants.
[0057] Proppants that may be used in the embodiments of the
stimulation treatments of the present invention include a wide
variety of particulate materials suitable for use in subterranean
applications. Examples include, but are not limited to, man-made
proppant; sand; bauxite; ceramic materials; glass materials;
polymer materials; plastic materials; "TEFLON.TM." materials;
lightweight particulates; ground or crushed nut shells; ground or
crushed seed shells; ground or crushed fruit pits; processed wood;
composite particulates prepared from a binder with filler
particulate including silica, alumina, fumed carbon, carbon black,
graphite, mica, titanium dioxide, meta-silicate, calcium silicate,
kaolin, talc, zirconia, boron, fly ash, hollow glass microspheres,
and solid glass; or mixtures thereof. The proppant used may have a
particle size in the range of from about 2 to about 400 mesh, U.S.
Sieve Series. Preferably, the proppant is graded sand having a
particle size in the range of from about 10 to about 70 mesh, U.S.
Sieve Series.
[0058] In certain preferred embodiments, the proppant used is
coated with either a resin that is capable of consolidating the
proppant particles into a hardened, permeable mass; a tackifying
agent capable of controlling particulate production from the
unstabilized portion of the formation; or a combination thereof. It
is well within the ability of one skilled in the art, with the
benefit of this disclosure, to select a suitable resin or
tackifying agent to coat the proppant used in the present
invention.
[0059] Resins suitable for use in coating proppant used in the
present invention include, but are not limited to, two-component
epoxy-based resins, furan-based resins, phenolic-based resins,
high-temperature (HT) epoxy-based resins, and phenol/phenol
formaldehyde/furfuryl alcohol resins. Selection of a suitable resin
coating material may be affected by the temperature of the
subterranean formation to which the fluid will be introduced. By
way of example, for subterranean formations having a bottom hole
static temperature ("BHST") ranging from about 60.degree. F. to
about 250.degree. F., two-component epoxy-based resins comprising a
hardenable resin component and a hardening agent component
containing specific hardening agents may be preferred. For
subterranean formations having a BHST ranging from about
300.degree. F. to about 600.degree. F., a furan-based resin may be
preferred. For subterranean formations having a BHST ranging from
about 200.degree. F. to about 400.degree. F., either a
phenolic-based resin or a one-component HT epoxy-based resin may be
suitable. For subterranean formations having a BHST of at least
about 175.degree. F., a phenol/phenol formaldehyde/furfuryl alcohol
resin also may be suitable.
[0060] Tackifying agents suitable for use in coating proppant used
in the present invention comprise any compound that, when in liquid
form or in a solvent solution, will form a non-hardening coating
upon a particulate. A particularly preferred group of tackifying
agents comprise polyamides that are liquids or in solution at the
temperature of the subterranean formation such that they are, by
themselves, non-hardening when introduced into the subterranean
formation. A particularly preferred product is a condensation
reaction product comprised of commercially available polyacids and
a polyamine. Such commercial products include compounds such as
mixtures of C.sub.36 dibasic acids containing some trimer and
higher oligomers and also small amounts of monomer acids that are
reacted with polyamines. Other polyacids include trimer acids,
synthetic acids produced from fatty acids, maleic anhydride,
acrylic acid, and the like. Such acid compounds are commercially
available from companies such as Witco Corporation, Union Camp,
Chemtall, and Emery Industries. The reaction products are available
from, for example, Champion Technologies, Inc. and Witco
Corporation. Additional compounds which may be used as tackifying
compounds include liquids and solutions of, for example,
polyesters, polycarbonates and polycarbamates, natural resins such
as shellac and the like. Other suitable tackifying agents are
described in U.S. Pat. No. 5,853,048 issued to Weaver, et al. and
U.S. Pat. No. 5,833,000 issued to Weaver, et al., the relevant
disclosures of which are herein incorporated by reference.
[0061] Tackifying agents suitable for use in the present invention
may be either used such that they form non-hardening coating or
they may be combined with a multifunctional material capable of
reacting with the tackifying compound to form a hardened coating. A
"hardened coating" as used herein means that the reaction of the
tackifying compound with the multifunctional material will result
in a substantially non-flowable reaction product that exhibits a
higher compressive strength in a consolidated agglomerate than the
tackifying compound alone with the particulates. In this instance,
the tackifying agent may function similarly to a hardenable resin.
Multifunctional materials suitable for use in the present invention
include, but are not limited to, aldehydes such as formaldehyde,
dialdehydes such as glutaraldehyde, hemiacetals or aldehyde
releasing compounds, diacid halides, dihalides such as dichlorides
and dibromides, polyacid anhydrides such as citric acid, epoxides,
furfuraldehyde, glutaraldehyde or aldehyde condensates and the
like, and combinations thereof. In some embodiments of the present
invention, the multifunctional material may be mixed with the
tackifying compound in an amount of from about 0.01 to about 50
percent by weight of the tackifying compound to effect formation of
the reaction product. In some preferable embodiments, the compound
is present in an amount of from about 0.5 to about 1 percent by
weight of the tackifying compound. Suitable multifunctional
materials are described in U.S. Pat. No. 5,839,510 issued to
Weaver, et al., the relevant disclosure of which is herein
incorporated by reference.
[0062] Therefore, the present invention is well adapted to carry
out the objects and attain the ends and advantages mentioned as
well as those that are inherent therein. While numerous changes may
be made by those skilled in the art, such changes are encompassed
within the spirit and scope of this invention as defined by the
appended claims.
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