U.S. patent application number 13/477810 was filed with the patent office on 2012-09-13 for permeability-modifying drilling fluids and methods of use.
Invention is credited to Eldon D. Dalrymple, Larry S. Eoff, B. Raghava Reddy.
Application Number | 20120231978 13/477810 |
Document ID | / |
Family ID | 34750001 |
Filed Date | 2012-09-13 |
United States Patent
Application |
20120231978 |
Kind Code |
A1 |
Eoff; Larry S. ; et
al. |
September 13, 2012 |
Permeability-Modifying Drilling Fluids and Methods of Use
Abstract
Drilling fluids comprising a base fluid and a hydrophobically
modified polymer. The hydrophobically modified polymer consisting
of alkyl chains having a carbon chain length between about 4 and
about 22 carbons bound to a hydrophilic polymer. The hydrophilic
polymer (1) consists of a polymer backbone that contains polar
heteroatoms, at least one of which is not a nitrogen atom, and at
least a portion of the polar heteroatoms are functionalized with
the alkyl chains; and, (2) comprises at least one hydrophilic
polymer selected from the group consisting of a cellulose, a
chitosan, a polyetheramine, a polyhydroxyetheramine, a polylysine,
and a polysulfone.
Inventors: |
Eoff; Larry S.; (Duncan,
OK) ; Dalrymple; Eldon D.; (Duncan, OK) ;
Reddy; B. Raghava; (Duncan, OK) |
Family ID: |
34750001 |
Appl. No.: |
13/477810 |
Filed: |
May 22, 2012 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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13206848 |
Aug 10, 2011 |
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13477810 |
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10806894 |
Mar 23, 2004 |
8008235 |
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13206848 |
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10760443 |
Jan 20, 2004 |
7759292 |
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10806894 |
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Current U.S.
Class: |
507/112 ;
507/110; 507/117 |
Current CPC
Class: |
C09K 8/72 20130101; C09K
8/035 20130101; C09K 8/5086 20130101; C09K 8/68 20130101; C09K
8/5083 20130101; C09K 8/514 20130101; C09K 8/508 20130101 |
Class at
Publication: |
507/112 ;
507/117; 507/110 |
International
Class: |
C09K 8/20 20060101
C09K008/20; C09K 8/24 20060101 C09K008/24 |
Claims
1.-68. (canceled)
69. A drilling fluid for use in a well bore in a subterranean
formation comprising: a base fluid and a hydrophobically modified
polymer, the hydrophobically modified polymer consisting of alkyl
chains having a carbon chain length between about 4 and about 22
carbons bound to a hydrophilic polymer, wherein the hydrophilic
polymer: consists of a polymer backbone that contains polar
heteroatoms, at least one of which is not a nitrogen atom, and at
least a portion of the polar heteroatoms are functionalized with
the alkyl chains; and, comprises at least one hydrophilic polymer
selected from the group consisting of a cellulose, a chitosan, a
polyetheramine, a polyhydroxyetheramine, a polylysine, and a
polysulfone.
70. The drilling fluid of claim 69 wherein the hydrophobically
modified polymer has a molecular weight in the range of from about
100,000 to about 10,000,000.
71. The drilling fluid of claim 69 wherein the polar heteroatoms
comprise at least one polar heteroatom selected from the group
consisting of oxygen, nitrogen, sulfur, and phosphorous.
72. The drilling fluid of claim 69 wherein the hydrophobic compound
is selected from the group consisting of an alkyl halide, a
sulfonate, an organic acid derivative, and a combination
thereof.
73. The drilling fluid of claim 69 wherein the hydrophobic compound
is an organic acid derivative selected from the group consisting of
an octenyl succinic acid; a dodecenyl succinic acid; an anhydride;
an ester; an amide of octenyl succinic acid; an amide of dodecenyl
succinic acid; and combinations thereof.
74. The drilling fluid of claim 69 wherein the water-soluble
relative permeability modifier is present in the drilling fluid in
an amount in the range of from about 0.02% to about 10% by weight
of the drilling fluid.
75. The drilling fluid of claim 69 wherein the water-soluble
relative permeability modifier is present in the drilling fluid in
an amount in the range of from about 0.05% to about 1% by weight of
the drilling fluid.
76. A drilling fluid for use in a well bore in a subterranean
formation comprising: a base fluid and a hydrophobically modified
polymer, the hydrophobic compound consisting of an alkyl halide
having a carbon chain length between about 4 and about 22 carbons,
and the hydrophilic polymer: consists of a polymer backbone that
contains polar heteroatoms, at least one of which is not a nitrogen
atom, and at least a portion of the polar heteroatoms are
functionalized with the alkyl chains; and, comprises at least one
hydrophilic polymer selected from the group consisting of a
cellulose, a chitosan, a polyetheramine, a polyhydroxyetheramine, a
polylysine, and a polysulfone.
77. The drilling fluid of claim 76 wherein the hydrophobically
modified polymer has a molecular weight in the range of from about
100,000 to about 10,000,000.
78. The drilling fluid of claim 76 wherein the polar heteroatoms
comprise at least one polar heteroatom selected from the group
consisting of oxygen, nitrogen, sulfur, and phosphorous.
79. The drilling fluid of claim 76 wherein the water-soluble
relative permeability modifier is present in the drilling fluid in
an amount in the range of from about 0.02% to about 10% by weight
of the drilling fluid.
80. The drilling fluid of claim 76 wherein the water-soluble
relative permeability modifier is present in the drilling fluid in
an amount in the range of from about 0.05% to about 1% by weight of
the drilling fluid.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation-in-part of U.S.
application Ser. No. 10/760,443 entitled Methods and Compositions
for Reducing the Production of Water and Stimulating Hydrocarbon
Production from a Subterranean Formation, filed on Jan. 20,
2004.
BACKGROUND OF THE INVENTION
[0002] The present invention relates to subterranean drilling
operations, and more particularly, the present invention relates to
methods and compositions for reducing the permeability of a
subterranean formation to aqueous-based fluids during the drilling
phase.
[0003] The process of drilling a well bore in a subterranean
formation typically requires the use of a drilling fluid. During
the drilling process, the drilling fluid is passed down through the
inside of the drill string, exits through the drill bit, and
returns to the surface through the annulus between the drill string
and the well bore. Among other things, the circulating drilling
fluid lubricates the drill bit, carries drill cuttings to the
surface, and balances the formation pressure exerted on the well
bore. This process in the life of a well is known as the "drilling
phase." It is understood that there is also a "production phase" in
the life of a well, during which hydrocarbons or other desired
substances may be produced.
[0004] While well bores usually are drilled in
hydrocarbon-producing formations, the formations may contain layers
of water or may be located adjacent to water-producing zones. The
high mobility of water may allow it to flow into the well bore by
way of natural fractures and/or high permeability streaks present
in the formation. Over the life of such wells, the ratio of water
to hydrocarbons recovered often becomes so high that the cost of
producing the water, separating it from the hydrocarbons, and
disposing of this water may represent a significant economic loss.
Besides being highly undesirable during the production phase,
water-producing zones may cause problems in the well bore with
certain completions activities. However, these problems with the
production of undesired water generally are not addressed during
the drilling phase.
[0005] To reduce the production of undesired water from
hydrocarbon-producing formations, aqueous polymer solutions that
may contain cross-linking agents have been used. Such polymer
solutions are injected into the formation and cross-linked to form
stiff gels that may stop or reduce the flow of the undesired water.
Even when a polymer solution is properly placed in a
water-producing section, however, the cross-linked gels formed may
not remain stable in the zone due to thermal degradation and/or
differences in the adsorption characteristics of the polymer,
associated cross-linker, and the like. Further, the selected
placement of a polymer solution in a producing formation may
require expensive, time-consuming mechanical zonal isolation. Zonal
isolation also may be inaccurate, which may lead to plugging and/or
damaging the hydrocarbon-bearing sections. Damage to
hydrocarbonproducing pathways is undesirable.
[0006] Recently, wells in the production phase have been treated
with compounds to reduce the production of water with hydrocarbons.
These compounds are commonly referred to as "relative permeability
modifiers." Relative permeability modifiers, such as
polyacrylamide, may be dissolved in water and pumped into a
subterranean formation that produces water and hydrocarbons,
reducing the permeability of the formation to water without
substantially affecting the permeability therein to hydrocarbons.
The use of these relative permeability modifiers, however, has
resulted in only small temporary reductions in water production
and/or unacceptable levels of reduction in hydrocarbon production.
Further, conventional relative permeability modifiers heretofore
have not been used in the drilling phase.
SUMMARY OF THE INVENTION
[0007] The present invention relates to subterranean drilling
operations, and more particularly, the present invention relates to
methods and compositions for reducing the permeability of a
subterranean formation to aqueous-based fluids during the drilling
phase.
[0008] Some embodiments of the present invention provide a method
of reducing the permeability of a subterranean formation to
aqueous-based fluids during the drilling phase that comprises the
steps of providing a water-soluble relative permeability modifier
that comprises a hydrophobically modified polymer; and placing the
water-soluble relative permeability modifier into the subterranean
formation during the drilling phase.
[0009] Another embodiment of the present invention provides a
method of reducing the permeability of a subterranean formation to
aqueous-based fluids during the drilling phase that comprise the
steps of providing a water-soluble relative permeability modifier
that comprises a hydrophilically modified polymer; and placing the
water-soluble relative permeability modifier into the subterranean
formation during the drilling phase.
[0010] Another embodiment of the present invention provides a
method of reducing the permeability of a subterranean formation to
aqueous-based fluids during the drilling phase that comprises the
steps of providing a water-soluble relative permeability modifier
that comprises a water-soluble polymer without hydrophobic or
hydrophilic modification; and placing the water-soluble relative
permeability modifier into the subterranean formation during the
drilling phase.
[0011] Some embodiments of the present invention provide a method
of drilling a well bore in a subterranean formation that comprises
the steps of providing a drilling fluid that comprises a base
fluid, and a water-soluble relative permeability modifier that
comprises a hydrophobically modified polymer; and placing the
drilling fluid in the well bore in the subterranean formation.
[0012] Another embodiment of the present invention provides a
method of drilling a well bore in a subterranean formation that
comprises the steps of providing a drilling fluid that comprises a
base fluid, and a water-soluble relative permeability modifier that
comprises a hydrophilically modified polymer; and placing the
drilling fluid in the well bore in the subterranean formation.
[0013] Another embodiment of the present invention provides a
method of drilling a well bore in a subterranean formation that
comprises the steps of providing a drilling fluid that comprises a
base fluid, and a water-soluble polymer without hydrophobic or
hydrophilic modification; and placing the drilling fluid in the
well bore in the subterranean formation.
[0014] Another embodiment of the present invention provides a
drilling fluid that comprises a base fluid, and a water-soluble
relative permeability modifier that comprises a hydrophobically
modified polymer.
[0015] Yet another embodiment of the present invention provides a
drilling fluid that comprises a base fluid, and a water-soluble
relative permeability modifier that comprises a hydrophilically
modified polymer.
[0016] The features and advantages of the present invention will be
readily apparent to those skilled in the art upon a reading of the
description of the exemplary embodiments which follows.
DESCRIPTION OF EXEMPLARY EMBODIMENTS
[0017] The present invention relates to subterranean drilling
operations, and more particularly, the present invention relates to
methods and compositions for reducing the permeability of a
subterranean formation to aqueous-based fluids during the drilling
phase.
[0018] In certain embodiments of the present invention, the
water-soluble relative permeability modifiers comprise
hydrophobically modified polymers. As used herein, "water-soluble"
refers to at least 0.01 weight percent soluble in distilled water.
As used herein, "hydrophobically modified" refers to the
incorporation into the hydrophilic polymer structure of hydrophobic
groups, wherein the alkyl chain length is from about 4 to about 22
carbons. In another embodiment of the present invention, the
water-soluble relative permeability modifiers comprise
hydrophilically modified polymers. As used herein, "hydrophilically
modified" refers to the incorporation into the hydrophilic polymer
structure of hydrophilic groups. In yet another embodiment of the
present invention, the water-soluble relative permeability
modifiers comprise water-soluble polymers without hydrophobic or
hydrophilic modification.
[0019] The hydrophobically modified polymers that may be used in
the present invention typically have a molecular weight in the
range of from about 100,000 to about 10,000,000. In an exemplary
embodiment, the hydrophobically modified polymers may comprise a
polymer backbone that comprises polar heteroatoms. Generally, the
polar heteroatoms present within the polymer backbone of the
hydrophobically modified polymers include, but are not limited to,
oxygen, nitrogen, sulfur, or phosphorous.
[0020] In certain embodiments of the present invention, the
hydrophobically modified polymers may be a reaction product of a
hydrophilic polymer and a hydrophobic compound. The hydrophilic
polymers suitable for forming the hydrophobically modified polymers
used in the present invention should be capable of reacting with
hydrophobic compounds. Suitable hydrophilic polymers include,
homo-, co-, or terpolymers such as, but not limited to,
polyvinylamines, poly(vinylamines/vinyl alcohols), and alkyl
acrylate polymers in general. Additional examples of alkyl acrylate
polymers include, but are not limited to, polydimethylaminoethyl
methacrylate, polydimethylaminopropyl methacrylamide,
poly(acrylamide/dimethylaminoethyl methacrylate), poly(methacrylic
acid/dimethylaminoethyl methacrylate), poly(2-acrylamido-2-methyl
propane sulfonic acid/dimethylaminoethyl methacrylate),
poly(acrylamide/dimethylaminopropyl methacrylamide), poly (acrylic
acid/dimethylaminopropyl methacrylamide), and poly(methacrylic
acid/dimethylaminopropyl methacrylamide). In certain embodiments,
the hydrophilic polymers contain reactive amino groups in the
polymer backbone or as pendant groups, which are capable of
reacting with hydrophobic compounds. In an exemplary embodiment,
the hydrophilic polymers comprise dialkyl amino pendant groups. In
an exemplary embodiment, the hydrophilic polymers comprise a
dimethyl amino pendant group and at least one monomer comprising
dimethylaminoethyl methacrylate or dimethylaminopropyl
methacrylamide. In certain exemplary embodiments of the present
invention, the hydrophilic polymers comprise a polymer backbone
that comprises polar heteroatoms, wherein the polar heteroatoms
present within the polymer backbone of the hydrophilic polymers
include, but are not limited to, oxygen, nitrogen, sulfur, or
phosphorous. Suitable hydrophilic polymers comprising polar
heteroatoms within the polymer backbone include homo-, co-, or
terpolymers, such as, but not limited to, celluloses, chitosans,
polyamides, polyetheramines, polyethyleneimines,
polyhydroxyetheramines, polylysines, polysulfones, and starches. In
an exemplary embodiment, the starch is a cationic starch. A
suitable cationic starch may be formed by reacting a starch, such
as corn, maize, waxy maize, potato, tapioca, and the like, with the
reaction product of epichlorohydrin and trialkylamine.
[0021] The hydrophobic compounds that are capable of reacting with
the hydrophilic polymers of the present invention include, but are
not limited to, alkyl halides, sulfonates, sulfates, and organic
acid derivatives. Examples of suitable organic acid derivatives
include, but are not limited to, octenyl succinic acid; dodecenyl
succinic acid; and anhydrides, esters, and amides of octenyl
succinic acid or dodecenyl succinic acid. In certain exemplary
embodiments, the hydrophobic compounds may have an alkyl chain
length of from about 4 to about 22 carbons. For example, where the
hydrophobic compound is an alkyl halide, the reaction between the
hydrophobic compound and hydrophilic polymer may result in the
quaternization of at least some of the hydrophilic polymer amino
groups with an alkyl halide, wherein the alkyl chain length is from
about 4 to about 22 carbons.
[0022] In another embodiment of the present invention, the
water-soluble relative permeability modifiers of the present
invention comprise a hydrophilically modified polymer. The
hydrophilically modified polymers used in the present invention
typically have a molecular weight in the range of from about
100,000 to about 10,000,000. In an exemplary embodiment, the
hydrophilically modified polymers comprise a polymer backbone that
comprises polar heteroatoms. Generally, the polar heteroatoms
present within the polymer backbone of the hydrophilically modified
polymers include, but are not limited to, oxygen, nitrogen, sulfur,
or phosphorous.
[0023] In certain embodiments of the present invention, the
hydrophilically modified polymer may be a reaction product of a
hydrophilic polymer and a hydrophilic compound. The hydrophilic
polymers suitable for forming the hydrophilically modified polymers
used in the present invention should be capable of reacting with
hydrophilic compounds. In certain exemplary embodiments, suitable
hydrophilic polymers include, homo-, co-, or terpolymers, such as,
but not limited to, polyvinylamines, poly(vinylamines/vinyl
alcohols), and alkyl acrylate polymers in general. Additional
examples of alkyl acrylate polymers include, but are not limited
to, polydimethylaminoethyl methacrylate, polydimethylaminopropyl
methacrylamide, poly(acrylamide/dimethylaminoethyl methacrylate),
poly(methacrylic acid/dimethylaminoethyl methacrylate),
poly(2-acrylamido-2-methyl propane sulfonic acid/dimethylaminoethyl
methacrylate), poly(acrylamide/dimethylaminopropyl methacrylamide),
poly (acrylic acid/dimethylaminopropyl methacrylamide), and
poly(methacrylic acid/dimethylaminopropyl methacrylamide). In
certain embodiments, the hydrophilic polymers contain reactive
amino groups in the polymer backbone or as pendant groups, which
are capable of reacting with hydrophilic compounds. In an exemplary
embodiment, the hydrophilic polymers comprise dialkyl amino pendant
groups. In an exemplary embodiment, the hydrophilic polymers
comprise a dimethyl amino pendant group and at least one monomer
comprising dimethylaminoethyl methacrylate or dimethylaminopropyl
methacrylamide. In another exemplary embodiment, the hydrophilic
polymers comprise a polymer backbone comprising polar heteroatoms,
wherein the polar heteroatoms present within the polymer backbone
of the hydrophilic polymers include, but are not limited to,
oxygen, nitrogen, sulfur, or phosphorous. Suitable hydrophilic
polymers comprising polar heteroatoms within the polymer backbone
include homo-, co-, or terpolymers, such as, but not limited to,
celluloses, chitosans, polyamides, polyetheramines,
polyethyleneimines, polyhydroxyetheramines, polylysines,
polysulfones, and starches. In an exemplary embodiment, the starch
is a cationic starch. A suitable cationic starch may be formed by
reacting a starch, such as corn, maize, waxy maize, potato,
tapioca, and the like, with the reaction product of epichlorohydrin
and trialkylamine.
[0024] The hydrophilic compounds suitable for reaction with the
hydrophilic polymers include polyethers comprising halogen;
sulfonates; sulfates; and organic acid derivatives. Examples of
suitable polyethers include, but are not limited to, polyethylene
oxides, polypropylene oxides, polybutylene oxides, and mixtures
thereof. In an exemplary embodiment, the polyether comprises an
epichlorohydrin terminated polyethylene oxide methyl ether.
[0025] The hydrophilically modified polymers formed from the
reaction of a hydrophilic polymer with a hydrophilic compound may
have estimated molecular weights in the range of from about 100,000
to about 10,000,000 and may have weight ratios of the hydrophilic
polymers to the polyethers in the range of from about 1:1 to about
10:1. Suitable hydrophilically modified polymers having molecular
weights and weight ratios in the ranges set forth above include,
but are not limited to, the reaction product of
polydimethylaminoethyl methacrylate with epichlorohydrin terminated
polyethyleneoxide methyl ether; the reaction product of
polydimethylaminopropyl methacrylamide with epichlorohydrin
terminated polyethyleneoxide methyl ether; and the reaction product
of poly(acrylamide/dimethylaminopropyl methacrylamide) with
epichlorohydrin terminated polyethyleneoxide methyl ether. In an
exemplary embodiment, the hydrophilically modified polymer
comprises the reaction product of a polydimethylaminoethyl
methacrylate with epichlorohydrin terminated polyethyleneoxide
methyl ether having a weight ratio of polydimethylaminoethyl
methacrylate to epichlorohydrin terminated polyethyleneoxide methyl
ether of 3:1.
[0026] In another embodiment of the present invention, the
water-soluble relative permeability modifiers comprise a
water-soluble polymer without hydrophobic or hydrophilic
modification. Examples of suitable water-soluble polymers include,
but are not limited to, homo-, co-, and terpolymers of acrylamide,
2-acrylamido-2-methyl propane sulfonic acid,
N,N-dimethylacrylamide, vinyl pyrrolidone, dimethylaminoethyl
methacrylate, acrylic acid, dimethylaminopropylmethacrylamide,
vinyl amine, vinyl acetate, trimethylammoniumethyl methacrylate
chloride, methacrylamide, hydroxyethyl acrylate, vinyl sulfonic
acid, vinyl phosphonic acid, methacrylic acid, vinyl caprolactam,
N-vinylformamide, N,N-diallylacetamide, dimethyldiallyl ammonium
halide, itaconic acid, styrene sulfonic acid,
methacrylamidoethyltrimethyl ammonium halide, quaternary salt
derivatives of acrylamide and quaternary salt derivatives of
acrylic acid.
[0027] In certain embodiments of the present invention, the
water-soluble relative permeability modifiers of the present
invention may be placed into a subterranean formation during the
drilling phase. As filtrate from the drilling fluids leaks off into
the subterranean formation, it is believed that the water-soluble
relative permeability modifier, among other things, may attach to
surfaces within the subterranean formation. The presence of the
water-soluble relative permeability modifiers in the subterranean
formation may reduce the permeability of the treated zones of the
subterranean formation to aqueous-based fluids (e.g., water)
without substantially changing the permeability to hydrocarbons.
This may reduce the subsequent problems associated with water
flowing into the well bore from the subterranean formation.
[0028] In one embodiment of the present invention, the
water-soluble relative permeability modifiers of the present
invention may be placed into the subterranean formation in a
drilling fluid that comprises the water-soluble relative
permeability modifiers. The drilling fluids of the present
invention generally comprise a base fluid and a water-soluble
relative permeability modifier of the present invention. Moreover,
other additives suitable for use in drilling fluids optionally may
be added to the drilling fluids of the present invention as
desired.
[0029] The base fluid utilized in the drilling fluids of the
present invention may comprise aqueous-based fluids, oil-based
fluids, or mixtures thereof. Where the base fluid is aqueous-based,
the water utilized can be fresh water, salt water (e.g., water
containing one or more salts dissolved therein), brine (e.g.,
saturated salt water), or seawater. Generally, the water may be
from any source provided that it does not contain an excess of
compounds that may adversely affect other components in the
drilling fluid. Where the base fluid is oil-based, examples of
suitable oils include, but are not limited to, mineral oils,
synthetic oils, esters and the like. Generally, any oil that can be
emulsified is suitable for use as a base fluid in the drilling
fluids of the present invention. It should be understood that where
oil-based drilling fluids are used in the present invention, such
oil-based drilling fluids may comprise an emulsified aqueous phase
that allows the modified water-soluble polymer to be incorporated
into the oil-based drilling fluids.
[0030] The water-soluble relative permeability modifier generally
should be present in the drilling fluids in an amount sufficient to
provide the desired degree of permeability modification. In an
exemplary embodiment, the water-soluble relative permeability
modifier is present in the drilling fluids of the present invention
in an amount in the range of from about 0.02% to about 10% by
weight of the drilling fluid. In an exemplary embodiment, the
water-soluble relative permeability modifier is present in the
drilling fluids of the present invention in an amount in the range
of from about 0.05% to about 1.0% by weight of the drilling
fluid.
[0031] Additional additives may be added to the drilling fluids of
the present invention as deemed appropriate by one skilled in the
art for improving the performance of the drilling fluids with
respect to one or more properties. Examples of such additives
include, but are not limited to, emulsifiers, viscosifiers, fluid
loss additives, salts, shale swelling inhibitors, weighting agents,
and numerous other additives suitable for use in drilling
operations.
[0032] While a number of exemplary embodiments described herein
relate to drilling fluids, it is to be understood that the relative
permeability modifiers of the present invention may be placed into
the subterranean formation as part of other well bore fluids, used
in the drilling phase, such as drill-in fluids and completion
fluids.
[0033] Some embodiments of the present invention provide a method
of reducing the permeability of a subterranean formation to
aqueous-based fluids during the drilling phase that comprises the
steps of providing a water-soluble relative permeability modifier
that comprises a hydrophobically modified polymer; and placing the
water-soluble relative permeability modifier into the subterranean
formation during the drilling phase.
[0034] Another embodiment of the present invention provides a
method of reducing the permeability of a subterranean formation to
aqueous-based fluids during the drilling phase that comprises the
steps of providing a water-soluble relative permeability modifier
that comprises a hydrophilically modified polymer; and placing the
water-soluble relative permeability modifier into the subterranean
formation during the drilling phase.
[0035] Another embodiment of the present invention provides a
method of reducing the permeability of a subterranean formation to
aqueous-based fluids during the drilling phase that comprises the
steps of providing a water-soluble relative permeability modifier
that comprises a water-soluble polymer without hydrophobic or
hydrophilic modification; and placing the water-soluble relative
permeability modifier into the subterranean formation during the
drilling phase.
[0036] Some embodiments of the present invention provide a method
of drilling a well bore in a subterranean formation that comprises
the steps of providing a drilling fluid that comprises a base
fluid, and a water-soluble relative permeability modifier that
comprises a hydrophobically modified polymer; and placing the
drilling fluid in the well bore in the subterranean formation.
[0037] Another embodiment of the present invention provides a
method of drilling a well bore in a subterranean formation that
comprises the steps of providing a drilling fluid that comprises a
base fluid, and a water-soluble relative permeability modifier that
comprises a hydrophilically modified polymer; and placing the
drilling fluid in the well bore in the subterranean formation.
[0038] Another embodiment of the present invention provides a
method of drilling a well bore in a subterranean formation that
comprises the steps of providing a drilling fluid that comprises a
base fluid, and a water-soluble polymer without hydrophobic or
hydrophilic modification; and placing the drilling fluid in the
well bore in the subterranean formation.
[0039] Another embodiment of the present invention provides a
drilling fluid that comprises a base fluid, and a water-soluble
relative permeability modifier that comprises a hydrophobically
modified polymer.
[0040] Yet another embodiment of the present invention provides a
drilling fluid that comprises a base fluid, and a water-soluble
relative permeability modifier that comprises a hydrophilically
modified polymer.
[0041] To facilitate a better understanding of the present
invention, the following examples of the preferred embodiments are
given. In no way should the following examples be read to limit, or
define, the scope of the invention.
EXAMPLES
[0042] Permeability reduction tests were performed using two
treatment solutions and a multipressure tap Hassler sleeve
containing a Berea sandstone core. These permeability reduction
tests were performed at 175.degree. F. Further, Test No. 1 was
conducted using a brine containing 2% by weight potassium chloride,
and Test No. 2 was conducted using a brine containing 7% potassium
chloride. Two treatment solutions were prepared for this series of
tests.
[0043] The treatment solution used in Test No. 1 comprised 5,000
ppm of a sample polymer and 500 ppm of "ARQUAD.RTM. DMCB 80"
dissolved in 2% potassium chloride brine. "ARQUAD.RTM. DMCB 80" is
a surfactant that is commercially available from Akzo Nobel Inc.,
Chicago, Ill. The sample polymer comprises a hydrophobically
modified polymer that comprises a polymer backbone comprising polar
heteroatoms formed from the reaction of a cationic starch and an
organic acid derivative, such as octenyl acid or dodecenyl succinic
acid.
[0044] The treatment solution used in Test No. 2 comprised 5,000
ppm of the sample polymer dissolved in 7% potassium chloride
brine.
[0045] The following procedure was used for this series of tests,
the results of which are provided in Table 1. For each test, the
above-described brines were flowed through the Berea core, followed
by oil (kerosene), followed by brine. This third brine flow was
maintained until the pressure stabilized, yielding an initial brine
permeability. Next, a treatment solution was flowed into the core.
Next, the brine flow was reestablished until the pressure
stabilized, yielding a final permeability from which the brine
permeability was calculated using the formula [1-(final
permeability/initial permeability)].times.100. The multipressure
tap Hassler sleeve allowed the core permeability to be divided into
four segments. In the tests, the initial brine flow was from
segment 1 to segment 4. The treatment solution flow was from
segment 4 to segment 1, and the final brine flow was from segment 1
to segment 4. The results of the tests are provided below in Table
1.
TABLE-US-00001 TABLE 1 Sample Polymer Initial Water Water
Concentration Surfactant Permeability Permeability Test (ppm) Brine
Surfactant Concentration (milli Darcy) Reduction Test 5000 2%
ARQUAD 500 ppm 90 85% No. 1 KCL DMCB-80 Test 5000 7% None None 120
69% No. 2 KCL
[0046] This example indicates, inter alia, that a water-soluble
relative permeability modifier of the present invention may reduce
the permeability of a subterranean formation to aqueous-based
fluids.
[0047] Therefore, the present invention is well adapted to carry
out the objects and attain the ends 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.
* * * * *