U.S. patent application number 11/285686 was filed with the patent office on 2007-05-24 for methods of consolidating unconsolidated particulates in subterranean formations.
Invention is credited to Matthew E. Blauch, Loyd E. JR. East, Kevin W. Halliburton, Philip D. Nguyen, Neil A. Stegent.
Application Number | 20070114032 11/285686 |
Document ID | / |
Family ID | 37561293 |
Filed Date | 2007-05-24 |
United States Patent
Application |
20070114032 |
Kind Code |
A1 |
Stegent; Neil A. ; et
al. |
May 24, 2007 |
Methods of consolidating unconsolidated particulates in
subterranean formations
Abstract
Methods for stabilizing portions of a subterranean formation
that comprise unconsolidated particulates. In one embodiment, the
methods of the present invention comprise: providing a
consolidating agent; introducing the consolidating agent into an
unconsolidated portion of a subterranean formation through a
dynamic diversion tool; and allowing the consolidating agent to at
least partially consolidate the unconsolidated portion of the
subterranean formation.
Inventors: |
Stegent; Neil A.; (Cypress,
TX) ; Nguyen; Philip D.; (Duncan, OK) ;
Halliburton; Kevin W.; (Tomball, TX) ; Blauch;
Matthew E.; (Duncan, OK) ; East; Loyd E. JR.;
(Tomball, TX) |
Correspondence
Address: |
Halliburton Energy Services, Inc.
2600 S. 2nd Street
Duncan
OK
73536-0440
US
|
Family ID: |
37561293 |
Appl. No.: |
11/285686 |
Filed: |
November 22, 2005 |
Current U.S.
Class: |
166/287 ;
166/290; 166/292; 166/295 |
Current CPC
Class: |
C09K 8/56 20130101 |
Class at
Publication: |
166/287 ;
166/290; 166/292; 166/295 |
International
Class: |
E21B 33/13 20060101
E21B033/13 |
Claims
1. A method comprising: providing a consolidating agent;
introducing the consolidating agent into an unconsolidated portion
of a subterranean formation through a dynamic diversion tool; and
allowing the consolidating agent to at least partially consolidate
the unconsolidated portion of the subterranean formation.
2. The method of claim 1 wherein the unconsolidated portion of the
subterranean formation comprises one or more fractures within the
subterranean formation.
3. The method of claim 1 wherein the consolidating agent is
selected from the group consisting of resins, tackifying agents,
gelable liquid compositions, derivatives thereof and combinations
thereof.
4. The method of claim 1 wherein the dynamic diversion tool is
selected from the group consisting of ported-sub assemblies,
hydroblast tools, hydrajetting tools, pulsonic tools and
combinations thereof.
5. The method of claim 1 wherein providing a consolidating agent
comprises providing a treatment fluid that comprises the
consolidating agent; and introducing the consolidating agent into
an unconsolidated portion of the subterranean formation comprises
introducing the treatment fluid that comprises the consolidating
agent into the unconsolidated portion of a subterranean
formation.
6. The method of claim 1 wherein the unconsolidated portion of the
subterranean formation comprises one or more fractures within the
subterranean formation wherein a plurality of particulates reside
within the open space of the one or more fractures.
7. The method of claim 1 wherein the unconsolidated portion of the
subterranean formation comprises a plurality of unconsolidated
proppant particulates.
8. The method of claim 1 further comprising introducing a preflush
fluid into a portion of the subterranean formation.
9. The method of claim 1 further comprising introducing an
afterflush fluid into a portion of the subterranean formation.
10. The method of claim 1 wherein the subterranean formation
comprises one or more casing strings, screens, gravel-packs, or a
combination thereof.
11. The method of claim 1 further comprising placing a static
diverting agent within a portion of the subterranean formation.
12. The method of claim 1 further comprising propelling a fluid
through the dynamic diversion tool at a pressure sufficient to
erode and/or fracture a portion of the subterranean formation.
13. A method comprising: providing a consolidating agent;
introducing the consolidating agent into an unconsolidated portion
of a subterranean formation through a dynamic diversion tool,
wherein a plurality of unconsolidated proppant particulates reside
within the subterranean formation; and allowing the consolidating
agent to at least partially consolidate the unconsolidated proppant
particulates within the unconsolidated portion of the subterranean
formation.
14. The method of claim 13 wherein the consolidating agent is
selected from the group consisting of resins, tackifying agents,
gelable liquid compositions, derivatives thereof and combinations
thereof.
15. The method of claim 13 further comprising placing a static
diverting agent within a portion of the subterranean formation.
16. The method of claim 13 wherein the unconsolidated portion of
the subterranean formation comprises one or more fractures within
the subterranean formation wherein the plurality of unconsolidated
proppant particulates reside within the open space of the one or
more fractures.
17. A method comprising: providing a consolidating agent;
introducing the consolidating agent into an unconsolidated portion
of a subterranean formation through a dynamic diversion tool,
wherein a plurality of unconsolidated formation particulates reside
within the subterranean formation; and allowing the consolidating
agent to at least partially consolidate the unconsolidated
formation particulates within the subterranean formation.
18. The method of claim 17 wherein the consolidating agent is
selected from the group consisting of resins, tackifying agents,
gelable liquid compositions, derivatives thereof and combinations
thereof.
19. The method of claim 17 further comprising placing a static
diverting agent within a portion of the subterranean formation.
20. The method of claim 17 wherein the unconsolidated portion of
the subterranean formation comprises one or more fractures within
the subterranean formation wherein the plurality of unconsolidated
formation particulates reside within the open space of the one or
more fractures.
Description
BACKGROUND
[0001] The present invention relates to the treatment of
subterranean formations. More particularly, the present invention
relates to methods for stabilizing portions of a subterranean
formation that comprise unconsolidated particulates.
[0002] Hydrocarbon wells are often located in subterranean
formations that contain unconsolidated particulates (e.g., sand,
gravel, proppant, fines, etc.) that may migrate out of the
subterranean formation into a well bore and/or may be produced with
the oil, gas, water, and/or other fluids produced by the well. The
presence of such particulates, in produced fluids is undesirable in
that the particulates may abrade pumping and other producing
equipment and/or reduce the production of desired fluids from the
well. Moreover, particulates that have migrated into a well bore
(e.g., inside the casing and/or perforations in a cased hole),
among other things, may clog portions of the well bore, hindering
the production of desired fluids from the well. The term
"unconsolidated particulates," and derivatives thereof, is defined
herein to include loose particulates and particulates bonded with
insufficient bond strength to withstand the forces created by the
production of fluids through the formation. Unconsolidated
particulates may comprise, among other things, sand, gravel, fines
and/or proppant particulates in the subterranean formation, for
example, proppant particulates placed in the subterranean formation
in the course of a fracturing or gravel-packing operation. The
terms "unconsolidated subterranean formations," "unconsolidated
portions of a subterranean formation," and derivatives thereof are
defined herein to include any formations that contain
unconsolidated particulates, as that term is defined herein.
"Unconsolidated subterranean formations," and "unconsolidated
portions of a subterranean formation," as those terms are used
herein, include subterranean fractures wherein unconsolidated
particulates reside within the open space of the fracture (e.g.,
forming a proppant pack within the fracture).
[0003] One method of controlling unconsolidated particulates in
subterranean formations involves placing a filtration bed
containing gravel (e.g., a "gravel pack") near the well bore to
present a physical barrier to the transport of unconsolidated
particulates with the production of desired fluids. Typically, such
"gravel-packing operations" involve the pumping and placement of a
quantity of certain particulate, into the unconsolidated
subterranean formation in an area adjacent to a well bore. One
common type of gravel-packing operation involves placing a screen
in the well bore and packing the surrounding annulus between the
screen and the well bore with gravel of a specific size designed to
prevent the passage of formation sand. The screen is generally a
filter assembly used to retain the gravel placed during the
gravel-pack operation. A wide range of sizes and screen
configurations are available to suit the characteristics of the
gravel-pack sand used. Similarly, a wide range of sizes of gravel
is available to suit the characteristics of the unconsolidated
particulates in the subterranean formation. To install the gravel
pack, the gravel is carried to the formation in the form of a
slurry by mixing the gravel with a fluid, which is usually
viscosified. Once the gravel is placed in the well bore, the
viscosity of the treatment fluid may be reduced, and it is returned
to the surface. The resulting structure presents a barrier to
migrating sand from the formation while still permitting fluid
flow.
[0004] However, the use of such gravel-packing methods may be
problematic. For example, gravel packs may be time consuming and
expensive to install. Due to the time and expense needed, it is
sometimes desirable to place a screen without the gravel. Even in
circumstances in which it is practical to place a screen without
gravel, it is often difficult to determine an appropriate screen
size to use as formation sands tend to have a wide distribution of
grain sizes. When small quantities of sand are allowed to flow
through a screen, formation erosion becomes a significant concern.
As a result, the placement of gravel as well as the screen is often
necessary to assure that the formation sands are controlled.
Expandable sand screens have been developed and implemented in
recent years. As part of the installation, an expandable sand
screen may be expanded against the well bore, cased hole, or open
hole for sand control purposes without the need for gravel packing.
However, expandable screens may still exhibit such problems as
screen erosion and screen plugging.
[0005] Another method used to control unconsolidated particulates
in subterranean formations involves consolidating unconsolidated
particulates into stable, permeable masses by applying a
consolidating agent (e.g., a resin or tackifying agent) to the
subterranean formation. However, it may be desirable in some cases
to preferentially place a consolidating agent in a particular
region of a subterranean formation (e.g., an unconsolidated
portion) penetrated by a well bore. To place the consolidating
agent in a specific region of a subterranean formation, certain
types of isolation tools, such as "pack off" devices, packers, gel
plugs, mechanical plugs, bridge plugs, ball sealers, and the like,
have been used in the art to isolate certain intervals of a
subterranean formation and place a consolidating agent in a region
of the subterranean formation in that interval. However, the use of
these isolation tools may be problematic. First, in applications
where it is desirable to treat multiple regions of a subterranean
formation in multiple different intervals, the isolation tools used
must be removed and repositioned to isolate subsequently treated
intervals, a process which may, among other things, risk damage to
the subterranean formation and/or the well bore, and increase the
cost, complexity, and duration of the operation. Moreover, in
methods employing these isolation tools, some amount of the
consolidating agent and/or associated treatment fluid(s) introduced
into the subterranean formation usually "leak" into regions of the
subterranean formation outside of the isolated interval, and thus
those methods generally require larger amounts of consolidating
agent (and/or the treatment fluid carrying the consolidating agent)
to ensure that the isolated interval of the subterranean formation
is completely treated.
SUMMARY
[0006] The present invention relates to the treatment of
subterranean formations. More particularly, the present invention
relates to methods for stabilizing portions of a subterranean
formation that comprise unconsolidated particulates.
[0007] In one embodiment, the present invention provides a method
comprising: providing a consolidating agent; introducing the
consolidating agent into an unconsolidated portion of a
subterranean formation through a dynamic diversion tool; and
allowing the consolidating agent to at least partially consolidate
the unconsolidated portion of the subterranean formation.
[0008] In another embodiment, the present invention provides a
method comprising: providing a consolidating agent; introducing the
consolidating agent into an unconsolidated portion of a
subterranean formation through a dynamic diversion tool, wherein a
plurality of unconsolidated proppant particulates reside within the
subterranean formation; and allowing the consolidating agent to at
least partially consolidate the unconsolidated proppant
particulates within the unconsolidated portion of the subterranean
formation.
[0009] In another embodiment, the present invention provides a
method comprising: providing a consolidating agent; introducing the
consolidating agent into an unconsolidated portion of a
subterranean formation through a dynamic diversion tool, wherein a
plurality of unconsolidated formation particulates reside within
the subterranean formation; and allowing the consolidating agent to
at least partially consolidate the unconsolidated formation
particulates within the subterranean formation.
[0010] The features and advantages of the present invention will be
apparent to those skilled in the art. While numerous changes may be
made by those skilled in the art, such changes are within the
spirit of the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] These drawings illustrate certain aspects of some of the
embodiments of the present invention, and should not be used to
limit or define the invention.
[0012] FIG. 1 illustrates a side view of a subterranean formation
that may be treated in certain embodiments of the present
invention.
[0013] FIG. 2 illustrates a side view of a subterranean formation
being treated during the course of one embodiment of the present
invention.
[0014] FIG. 3 illustrates a side view of a subterranean formation
being treated during the course of one embodiment of the present
invention.
[0015] FIG. 4 illustrates a side view of a subterranean formation
being treated during the course of one embodiment of the present
invention.
[0016] FIG. 5 illustrates a side view of a subterranean formation
being treated during the course of one embodiment of the present
invention.
[0017] FIG. 6 illustrates a side view of a subterranean formation
being treated during the course of one embodiment of the present
invention.
[0018] FIG. 7 illustrates a side view of a subterranean formation
that has been treated in the course of one embodiment of the
present invention.
DESCRIPTION OF PREFERRED EMBODIMENTS
[0019] The present invention relates to the treatment of
subterranean formations. More particularly, the present invention
relates to methods for stabilizing portions of a subterranean
formation that comprise unconsolidated particulates.
I. METHODS OF THE PRESENT INVENTION
[0020] The methods of the present invention generally comprise:
providing a consolidating agent; introducing the consolidating
agent into an unconsolidated portion of a subterranean formation
through a dynamic diversion tool; and allowing the consolidating
agent to at least partially consolidate the unconsolidated portion
of the subterranean formation. The consolidating agent may be
provided and/or introduced into the subterranean formation as a
component of one or more treatment fluids introduced into the
subterranean formation. The term "consolidating agent," is defined
herein to include any substance that may stabilize a portion of the
subterranean formation, which may, at least in part, stabilize
unconsolidated particulates such that they are prevented from
shifting or migrating. The term "dynamic diversion tool" is defined
herein to include any device that is capable of modifying (e.g.,
increasing) the velocity of a fluid into a subterranean formation
from the velocity of that fluid in a well bore. The methods of the
present invention may be used to at least partially consolidate a
selected interval in an unconsolidated portion of a subterranean
formation without the need for isolation tools used heretofore in
the art.
[0021] The subterranean formations treated in the methods of the
present invention may be any subterranean formation wherein at
least a plurality of unconsolidated particulates resides in the
formation. An example of such a subterranean formation is
illustrated in FIG. 1. A well bore 110 penetrates several different
intervals of the subterranean formation depicted therein; several
of the intervals comprise consolidated portions 121, 122, 123, 124,
and 125, while several intervals comprise unconsolidated portions
131, 132, 133, and 134, which comprise at least a plurality of
unconsolidated particulates. These unconsolidated particulates may
comprise, among other things, sand, gravel, fines and/or proppant
particulates within the open space of one or more fractures in the
subterranean formation (e.g., unconsolidated proppant particulates
that form a proppant pack within the fracture). Proppant
particulates may be comprised of any material suitable for use in
subterranean operations. Examples include, but are not limited to,
sand, bauxite, ceramic materials, glass materials (e.g., glass
beads), polymer materials, Teflon.RTM. materials, nut shell pieces,
seed shell pieces, cured resinous particulates comprising nut shell
pieces, cured resinous particulates comprising seed shell pieces,
fruit pit pieces, cured resinous particulates comprising fruit pit
pieces, wood, composite particulates, and combinations thereof.
Composite particulates also may be used, wherein suitable composite
materials may comprise a binder and a filler material wherein
suitable filler materials include silica, alumina, fumed carbon,
carbon black, graphite, mica, titanium dioxide, meta-silicate,
calcium silicate, kaolin, talc, zirconia, boron, fly ash, hollow
glass microspheres, solid glass, ground nut/seed shells or husks,
saw dust, ground cellulose fiber, and combinations thereof.
Typically, the particulates have a size in the range of from about
2 to about 400 mesh, U.S. Sieve Series. In particular embodiments,
particulates size distribution ranges are one or more of 6/12 mesh,
8/16, 12/20, 16/30, 20/40, 30/50, 40/60, 40/70, or 50/70 mesh. It
should be understood that the term "particulate," as used in this
disclosure, includes all known shapes of materials including
substantially spherical materials, fibrous materials, polygonal
materials (such as cubic materials) and mixtures thereof. Moreover,
fibrous materials that may be used, inter alia, to bear the
pressure of a closed fracture, are often included. In some
embodiments, the proppant particulates may be coated with any
suitable resin or tackifying agent known to those of ordinary skill
in the art.
[0022] The subterranean formations treated in the methods of the
present invention may be penetrated by a well bore through which
the consolidating agent and/or other treatment fluids may be
introduced, for example, as shown by well bore 110 in FIG. 1. A
well bore penetrating the subterranean formation being treated may
contain one or more pipes or casing strings (e.g., a "cased" or
"partially cased" well bore), as shown by casing 140 in well bore
110 in FIG. 1. In certain embodiments, the well bore may be
uncased. In certain embodiments, a well bore penetrating the
subterranean formation may contain one or more screens and/or
gravel-packs, among other purposes, to decrease the migration of
formation sands into the well bore. In other embodiments, the well
bore may contain no such screens or gravel-packs (e.g., an
"unscreened" well bore).
[0023] In those embodiments where the portion of the well bore
penetrating the portion of the subterranean formation being treated
is cased or partially cased, the dynamic diversion tool may
introduce fluids and/or the consolidating agent into the
subterranean formation by directing the through perforations or
holes in the casing that allow fluid communication between the
interior of the casing and the annulus (i.e., the space between the
walls of the well bore and the outer surface of the casing).
Referring now to FIG. 1, one or more perforations 150 may be
created in the casing 140 that is set in the well bore 110 to allow
fluid communication between the interior of the casing and an
unconsolidated portion 134 of the subterranean formation. In
certain embodiments, the dynamic diversion tool may be used to
create those perforations or holes in the casing, for example, by
propelling a fluid comprising abrasive materials (e.g., particulate
materials such as sand, gravel, degradable particulates, and the
like) at the interior surface of the casing and/or propelling a
fluid at a sufficiently high pressure at the interior surface of
the casing to create the perforations or holes in the casing. In
other embodiments, the perforations or holes may be created using
some other method or apparatus prior to or during the course of
conducting a method of the present invention. In certain
embodiments, particulates residing in the perforations or holes in
the casing may be displaced by the consolidating agent (or the
fluid comprising the consolidating agent), which may, inter alia,
enhance or restore the flow of fluid through those perforations or
holes in the casing.
[0024] Referring now to FIG. 2, the dynamic diversion tool 210 may
be placed in the well bore with a pipe string comprising 220 coiled
tubing or jointed pipe. The dynamic diversion tool 210 is placed in
a portion of the well bore adjacent to an unconsolidated portion
134 of the subterranean formation. Referring now to FIG. 3, the
consolidating agent may be introduced through the coiled tubing or
jointed pipe 220 to the dynamic diversion tool 210, where the tool
may direct the consolidating agent 320 into the unconsolidated
portion 134 of the subterranean formation.
[0025] In certain embodiments, it may not be desirable to use
certain types of dynamic diversion tools that are capable of
propelling fluid at a pressure sufficient to erode and/or fracture
a portion of the subterranean formation. However, in certain
embodiments, it may be desirable to use certain types of dynamic
diversion tools that are capable of propelling fluid at a pressure
to sufficient to penetrate through a gravel-pack and/or screen
residing in the well bore. One of ordinary skill in the art, with
the benefit of this disclosure, will recognize when certain types
of dynamic diversion tools are suitable or unsuitable for a
particular application of the methods of the present invention,
depending upon a variety of factors, including the rate and/or
pressure of fluid flow desired, the structure and/or composition of
the subterranean formation, the length of the interval in the
subterranean formation being treated, and the like. Examples of
dynamic diversion tools that may be suitable for the methods of the
present invention are described in Section II. below.
[0026] The methods of the present invention may optionally include
providing and introducing one or more preflush fluids into the
subterranean formation at any point prior to, during, or subsequent
to performing the methods of the present invention. Typically,
injection of a preflush fluid may occur at any time before the
consolidating agent is introduced into the subterranean formation.
In certain embodiments, a preflush fluid may be applied to the
subterranean formation, among other purposes, to clean out
undesirable substances (e.g., oil, residue, or debris) from the
pore spaces in the matrix of the subterranean formation, to clean
out such undesirable substances residing in perforations or holes
in a casing string, and/or to prepare the subterranean formation
for later placement of the consolidating agent. For example, an
acidic preflush fluid may be introduced into at least a portion of
the subterranean formation that may, inter alia, dissolve
undesirable substances in the subterranean formation. The preflush
fluid may be introduced into the subterranean formation through the
dynamic diversion tool, pumped directly into the annular space
between the walls of a well bore and a casing string penetrating
the subterranean formation, or introduced into the subterranean
formation by any other suitable means. Generally, the volume of the
preflush fluid introduced into the formation is between 0.1 times
to 50 times the volume of the consolidating agent. Examples of
preflush fluids suitable for use with the present invention are
described in more detail in Section III.A. below.
[0027] The methods of the present invention optionally may comprise
placing a static diverting agent within a portion of the
subterranean formation. As used herein, the term "static diverting
agent" is defined to include any static diverting agent or tool
(e.g., chemicals, fluids, particulates or equipment) that is
capable of diverting the flow of fluid away from a particular
portion of a subterranean formation to another portion of the
subterranean formation. Among other things, the static diverting
agent may aid in controlling the placement of the consolidating
agent in the desired area. Examples of suitable static diverting
agents include, but are not limited to fluids (e.g., aqueous-base
and/or non-aqueous-base fluids), emulsions, gels, foams, degradable
materials (e.g., polyesters, orthoesters, poly(orthoesters),
polyanhydrides, dehydrated organic and/or inorganic compounds),
particulates, packers (e.g., pinpoint packers and selective
injection packers), ball sealers, pack-off devices, particulates,
sand plugs, bridge plugs and the like. A person skilled in the art,
with the benefit of this disclosure will recognize when a static
diverting agent should be used in a method of the present
invention, as well as the appropriate type of placement of the
static diverting agent.
[0028] The methods of the present invention may be used to
consolidate a single interval in an unconsolidated portion of a
subterranean formation, or may be repeated to consolidate several
different intervals in a subterranean formation. Referring now to
FIG. 3, for example, the dynamic diversion tool 210 initially may
be positioned within a well bore so as to introduce the
consolidating agent 320 into a particular interval 134 in a portion
of a subterranean formation. As shown in FIG. 4, after introducing
the consolidating agent 320 into that particular interval 134, the
dynamic diversion tool 210 may be repositioned so as to introduce
the consolidating agent 420 into another interval 133 in the
subterranean formation (e.g., an interval closer to the surface
than the first interval treated). As shown in FIG. 5, this process
may be repeated for any number of other intervals comprising
unconsolidated portions 132 and 131 of a subterranean formation,
introducing the consolidating agent 520 into those portions of the
subterranean formation. In embodiments where several different
intervals are treated, the several intervals may be penetrated by a
single well bore, different contiguous well bores, or different
well bores that are not contiguous. After the treatment of one or
more intervals, the dynamic diversion tool 210 then may be
relocated to the bottom of the well bore 110, as shown in FIG.
5.
[0029] The methods of the present invention may optionally include
providing and applying one or more afterflush fluids into the
subterranean formation at any stage of the treatment process.
Typically, injection of an afterflush fluid may occur at any time
after the consolidating agent is introduced into the subterranean
formation. When used, the afterflush fluid is preferably placed
into the subterranean formation while the consolidating agent is
still in a flowing state. For example, an afterflush fluid may be
placed into the formation prior to a shut-in period. In certain
embodiments, an afterflush fluid may be applied to the subterranean
formation, among other purposes, to activate the consolidating
agent, and/or to restore the permeability of a portion of the
subterranean formation by displacing at least a portion of the
consolidating agent from the pore channels therein or forcing the
displaced portion of the consolidating agent further into the
subterranean formation where it may have negligible impact on
subsequent hydrocarbon production. The afterflush fluid may be
introduced into the subterranean formation through the dynamic
diversion tool, pumped directly into the annular space between the
walls of a well bore and a casing string penetrating the
subterranean formation, or introduced into the subterranean
formation by any other suitable means. As shown in FIG. 6, the
dynamic diversion tool 210 may be repositioned in the well bore 110
and used to circulate an afterflush fluid 660 in the well bore to
restore fluid circulation in the portion of the well bore 611 and
612 adjacent to a region 133 and 134 of the subterranean formation
that was consolidated in the methods of the present invention. As
shown in FIG. 7, this process may be repeated for each interval
until fluid circulation is restored to the entire length of the
well bore 711, and the dynamic diversion tool then may be removed
from the well bore. Generally, the volume of afterflush fluid
introduced into the subterranean formation ranges from about 0.1
times to about 50 times the volume of the consolidating agent. In
some embodiments of the present invention, the volume of afterflush
fluid introduced into the subterranean formation ranges from about
0.1 times to about 5 times the volume of the consolidating agent.
Examples of afterflush fluids suitable for use with the present
invention are described in more detail in Section III.A. below.
[0030] The methods of the present invention may be used prior to,
in combination with, or after any type of subterranean operation
being performed in the subterranean formation, including but not
limited to fracturing operations, gravel-packing operations,
frac-packing operations (i.e., combination of fracturing and
gravel-packing operations), and the like. For example, the methods
of the present invention may be used at some time after a
fracturing operation, wherein the methods of the present invention
are used to at least partially consolidate proppant particulates
placed within one or more fractures created or enhanced during the
fracturing operation. In certain embodiments, the methods of the
present invention optionally may comprise introducing other
additives and treatment fluids, such as relative permeability
modifiers, proppant, surfactants, gases, biocides, acids, or any
other suitable additives or treatment fluids, into the subterranean
formation through the dynamic diversion tool and/or by any other
means suitable for introducing those additives or treatment fluids
into the subterranean formation.
II. DYNAMIC DIVERSION TOOLS
[0031] The methods of the present invention utilize a dynamic
diversion tool to introduce the treatment fluids into the
subterranean formation. Suitable dynamic diversion tools for use in
the present invention may comprise any assembly that is capable of
modifying (e.g., increasing) the velocity of a fluid into a
subterranean formation from the velocity of that fluid in a well
bore. In certain embodiments, the dynamic diversion tool may
comprise a pipe string (e.g., coiled tubing, drill pipe, etc.) with
at least one port (e.g., nozzle or jet) thereon that is capable of
directing the flow of fluid from within the pipe string into a
subterranean formation in a desired direction. Examples of suitable
dynamic diversion tools include, but are not limited to, ported
subassemblies, hydroblast tools and hydrajetting tools, including
those described in the following U.S. patents and patent
applications, the relevant disclosures of which are incorporated
herein by reference: U.S. Pat. No. 5,765,642; U.S. Pat. No.
5,249,628; U.S. Pat. No. 5,325,923; U.S. Pat. No. 5,499,678; U.S.
Pat. No. 5,396,957; U.S. patent application Ser. No. 11/004,441 by
East, Jr. et al. In certain embodiments, the dynamic diversion tool
may comprise an acoustical tool or a pulsonic tool (e.g., a tool
capable of applying a pressure pulse having a given amplitude and
frequency to a fluid). Examples of suitable acoustical and pulsonic
tools include, but are not limited to, fluidic oscillators, and
those devices described in U.S. patent application Ser. No.
10/863,706 by Nguyen, et al., the relevant disclosure of which is
incorporated herein by reference. In embodiments where the dynamic
diversion tool comprises a pulsonic tool, the acoustical energy
generated by the pulsonic tool may, inter alia, further stabilize
the unconsolidated particulates in the subterranean formation, in
conjunction with the consolidating agent used. In certain
embodiments, the dynamic diversion tool may comprise an uncemented
liner having jets on the outer surface of the liner.
[0032] The selection of a suitable dynamic diversion tool for a
particular application of the present invention may depend upon a
variety of factors, including the rate and/or pressure of fluid
flow desired, the structure and/or composition of the subterranean
formation, the length of the interval in the subterranean formation
being treated, the particular composition of the fluid being
introduced into the subterranean formation, and the like. For
example, in certain embodiments, it may or may not be desirable to
use certain types of dynamic diversion tools that are capable of
propelling fluid at a pressure sufficient to erode and/or fracture
a portion of the subterranean formation. One of ordinary skill in
the art, with the benefit of this disclosure, will be able to
recognize which types of dynamic diversion tools are suitable for a
particular application of the methods of the present invention.
III. FLUIDS
[0033] In certain embodiments, the consolidating agent may be
provided and/or introduced into the subterranean formation as a
component of one or more treatment fluids introduced into the
subterranean formation. These treatment fluids may include any
fluid that does not adversely interact with the other components
used in accordance with this invention or with the subterranean
formation. Such treatment fluids may be aqueous-based or
non-aqueous-based. Aqueous-based treatment fluids may comprise
fresh water, salt water, brine, seawater, or a combination thereof.
Non-aqueous-based treatment fluids may comprise one or more organic
liquids, such as hydrocarbons (e.g., kerosene, xylene, toluene, or
diesel), oils (e.g., mineral oils or synthetic oils), esters, and
the like.
[0034] The preflush and afterflush fluids utilized in certain
embodiments of the present invention may include any fluid that
does not adversely interact with the other components used in
accordance with this invention or with the subterranean formation.
For example, the preflush or afterflush fluid may be an
aqueous-based fluid, a hydrocarbon-based fluid (e.g., kerosene,
xylene, toluene, diesel, oils, etc.), or a gas (e.g., nitrogen or
carbon dioxide). Aqueous-based fluids may comprise fresh water,
salt water, brine, or seawater, or any other aqueous fluid that
does not adversely react with the other components used in
accordance with this invention or with the subterranean formation.
In certain embodiments, an aqueous-based preflush or afterflush
fluid may comprise a surfactant. Any surfactant compatible with
later-used treatments (e.g., the consolidating agent) may be used
in the present invention, for example, to aid a consolidating agent
in flowing to the contact points between adjacent particulates in
the formation. Such surfactants include, but are not limited to,
ethoxylated nonyl phenol phosphate esters, mixtures of one or more
cationic surfactants, one or more non-ionic surfactants, and an
alkyl phosphonate surfactant. Suitable mixtures of one or more
cationic and nonionic surfactants are described in U.S. Pat. No.
6,311,773, the relevant disclosure of which is incorporated herein
by reference. A C.sub.12-C.sub.22 alkyl phosphonate surfactant is
preferred. The surfactant or surfactants used may be included in
the preflush or afterflush fluid in an amount sufficient to prepare
the subterranean formation to receive a treatment of a
consolidating agent. In some embodiments of the present invention,
the surfactant is present in the preflush or afterflush fluid in an
amount in the range of from about 0.1% to about 3% by weight of the
aqueous fluid.
[0035] The treatment fluids, preflush fluids, and/or afterflush
fluids utilized in methods of the present invention may comprise
any number of additional additives, including, but not limited to,
salts, surfactants, acids, fluid loss control additives, gas,
foamers, corrosion inhibitors, scale inhibitors, catalysts, clay
control agents, biocides, friction reducers, antifoam agents,
bridging agents, dispersants, flocculants, H.sub.2S scavengers,
CO.sub.2 scavengers, oxygen scavengers, lubricants, viscosifiers,
breakers, weighting agents, relative permeability modifiers,
particulate materials (e.g., proppant particulates) and the like.
In certain embodiments the treatment fluids, preflush fluids,
and/or afterflush fluids may comprise an activator or catalyst
which may be used inter alia, to activate the polymerization of the
consolidating agent. A person skilled in the art, with the benefit
of this disclosure, will recognize the types of additives that may
be included in the treatment fluids, preflush fluids, and/or
afterflush fluids for a particular application.
IV. CONSOLIDATING AGENTS
[0036] Suitable consolidating agents for the methods at the present
invention include any composition that may stabilize a portion of
the subterranean formation, which may, at least in part, stabilize
unconsolidated particulates such that they are prevented from
shifting or migrating. Examples of suitable consolidating agents
include resins, tackifying agents, and gelable liquid
compositions.
[0037] A. Resins
[0038] Resins suitable for use as the consolidating agents in the
methods of the present invention include any suitable resin that is
capable of forming a hardened, consolidated mass. The term "resin"
as used herein includes any of numerous physically similar
polymerized synthetics or chemically modified natural resins,
including but not limited to thermoplastic materials and
thermosetting materials. Many such resins are commonly used in
subterranean consolidation operations, and some suitable resins
include two component epoxy based resins, novolak resins,
polyepoxide resins, phenol-aldehyde resins, urea-aldehyde resins,
urethane resins, phenolic resins, furan resins, furan/furfuryl
alcohol resins, phenolic/latex resins, phenol formaldehyde resins,
polyester resins and hybrids and copolymers thereof, polyurethane
resins and hybrids and copolymers thereof, acrylate resins, and
mixtures thereof. Some suitable resins, such as epoxy resins, may
be cured with an internal catalyst or activator so that when pumped
downhole, they may be cured using only time and temperature. Other
suitable resins, such as furan resins, may be formulated to cure at
a delayed rate, or 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. Such external catalysts may be introduced into the
subterranean formation through the dynamic diversion tool (e.g., as
a component of a treatment fluid) and/or by some other means (e.g.,
pumped into the annulus from the surface). 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.
[0039] Selection of a suitable resin 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 may also be suitable.
[0040] Any solvent that is compatible with the chosen resin and
achieves the desired viscosity effect is suitable for use in the
present invention. Some preferred solvents are those having high
flash points (e.g., about 125.degree. F.) because of, among other
things, environmental and safety concerns; such solvents include
butyl lactate, butylglycidyl ether, dipropylene glycol methyl
ether, dipropylene glycol dimethyl ether, dimethyl form amide,
diethyleneglycol methyl ether, ethyleneglycol butyl ether,
diethyleneglycol butyl ether, propylene carbonate, methanol, butyl
alcohol, d-limonene, fatty acid methyl esters, and combinations
thereof. Other preferred solvents include aqueous dissolvable
solvents such as, methanol, isopropanol, butanol, glycol ether
solvents, and combinations thereof. Suitable glycol ether solvents
include, but are not limited to, diethylene glycol methyl ether,
dipropylene glycol methyl ether, 2-butoxy ethanol, ethers of a
C.sub.2 to C.sub.6 dihydric alkanol containing at least one C.sub.1
to C.sub.6 alkyl group, mono ethers of dihydric alkanols,
methoxypropanol, butoxyethanol, hexoxyethanol, and isomers thereof.
Selection of an appropriate solvent is dependent on the resin
chosen and is within the ability of one skilled in the art with the
benefit of this disclosure.
[0041] B. Tackifying Agents
[0042] Tackifying agents suitable for use in the methods of the
present invention exhibit a sticky character and, thus, impart a
degree of consolidation to unconsolidated particulates in the
subterranean formation. The term "tackifying agent" is defined
herein to include any composition having a nature such that it is
(or may be activated to become) somewhat sticky to the touch. In
certain embodiments, the tackifying agent may be formulated such
that it is "activated" at a delayed rate, by contact with a
catalyst or activator, or at certain conditions (e.g.,
temperature). Examples of suitable tackifying agents suitable for
use in the present invention include non-aqueous tackifying agents,
aqueous tackifying agents, and silyl-modified polyamides.
[0043] One type of tackifying agent suitable for use in the present
invention is a non-aqueous tackifying agent. An example of a
suitable tackifying agent may 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. One example of such a tackifying
agent comprises a condensation reaction product comprised of
commercially available polyacids and a polyamine. Suitable
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 non-aqueous tackifying agents include liquids
and solutions of, for example, polyesters, polycarbonates and
polycarbamates, natural resins such as shellac and the like. Other
suitable non-aqueous tackifying agents are described in U.S. Pat.
Nos. 5,853,048 and 5,833,000, the relevant disclosures of which are
herein incorporated by reference.
[0044] Non-aqueous 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 non-aqueous
tackifying agent to form a hardened coating. A "hardened coating,"
as used herein, means that the reaction of the tackifying agent
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 agent
alone with the particulates. In this instance, the non-aqueous
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 agent in an amount of from about 0.01 to about 50
percent by weight of the tackifying agent to effect formation of
the reaction product. In some preferable embodiments, the
multifunctional material 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,
the relevant disclosure of which is herein incorporated by
reference.
[0045] Solvents suitable for use with non-aqueous tackifying agents
include any solvent that is compatible with the non-aqueous
tackifying agent and achieves the desired viscosity effect. The
solvents that can be used in the present invention preferably
include those having high flash points (most preferably above about
125.degree. F.). Examples of solvents suitable for use in the
present invention include, but are not limited to, butylglycidyl
ether, dipropylene glycol methyl ether, butyl bottom alcohol,
dipropylene glycol dimethyl ether, diethyleneglycol methyl ether,
ethyleneglycol butyl ether, methanol, butyl alcohol, isopropyl
alcohol, diethyleneglycol butyl ether, propylene carbonate,
d-limonene, 2-butoxy ethanol, butyl acetate, furfuryl acetate,
butyl lactate, dimethyl sulfoxide, dimethyl formamide, fatty acid
methyl esters, and combinations thereof. It is within the ability
of one skilled in the art, with the benefit of this disclosure, to
determine whether a solvent is needed to achieve a viscosity
suitable to the subterranean conditions and, if so, how much.
[0046] Aqueous tackifying agents suitable for use in the present
invention are not significantly tacky when placed onto a
particulate, but are capable of being "activated" (that is,
destabilized, coalesced, and/or reacted) to transform the compound
into a sticky, tackifying compound at a desirable time. Such
activation may occur before, during, or after the aqueous tackifier
agent is placed in the subterranean formation. In some embodiments,
a pretreatment may be first contacted with the surface of a
particulate to prepare it to be coated with an aqueous tackifying
agent. Suitable aqueous tackifying agents are generally charged
polymers that comprise compounds that, when in an aqueous solvent
or solution, will form a non-hardening coating (by itself or with
an activator and/or catalyst) and, when placed on a particulate,
will increase the continuous critical resuspension velocity of the
particulate when contacted by a stream of water. The aqueous
tackifying agent may enhance the grain-to-grain contact between the
individual particulates within the formation (be they proppant
particulates, formation fines, or other particulates), helping
bring about the consolidation of the particulates into a cohesive,
flexible, and permeable mass. When used, the activator and/or
catalyst may be a component of a treatment fluid comprising the
aqueous tackifying agent, or may be introduced into the
subterranean formation separately through the dynamic diversion
tool (e.g., as a component of a treatment fluid) or by some other
means (e.g., pumped into the annulus from the surface).
[0047] Examples of aqueous tackifying agents suitable for use in
the present invention include, but are not limited to, acrylic acid
polymers, acrylic acid ester polymers, acrylic acid derivative
polymers, acrylic acid homopolymers, acrylic acid ester
homopolymers (such as poly(methyl acrylate), poly(butyl acrylate),
and poly(2-ethylhexyl acrylate)), acrylic acid ester co-polymers,
methacrylic acid derivative polymers, methacrylic acid
homopolymers, methacrylic acid ester homopolymers (such as
poly(methyl methacrylate), poly(butyl methacrylate), and
poly(2-ethylhexyl methacryate)), acrylamido-methyl-propane
sulfonate polymers, acrylamido-methyl-propane sulfonate derivative
polymers, acrylamido-methyl-propane sulfonate co-polymers, and
acrylic acid/acrylamido-methyl-propane sulfonate co-polymers, and
combinations thereof. The term "derivative" is defined herein to
include any compound that is made from one of the listed compounds,
for example, by replacing one atom in one of the listed compounds
with another atom or group of atoms, ionizing one of the listed
compounds, or creating a salt of one of the listed compounds.
Methods of determining suitable aqueous tackifying agents and
additional disclosure on aqueous tackifying agents can be found in
U.S. patent application Ser. No. 10/864,061, filed Jun. 9, 2004,
and U.S. patent application Ser. No. 10/864,618, filed Jun. 9,
2004, the relevant disclosures of which are hereby incorporated by
reference.
[0048] Silyl-modified polyamide compounds suitable for use in the
tackifying agents in the methods of the present invention may be
described as substantially self-hardening compositions that are
capable of at least partially adhering to particulates in the
unhardened state, and that are further capable of self-hardening
themselves to a substantially non-tacky state to which individual
particulates such as formation fines will not adhere to, for
example, in formation or proppant pack pore throats. Such
silyl-modified polyamides may be based, for example, on the
reaction product of a silating compound with a polyamide or a
mixture of polyamides. The polyamide or mixture of polyamides may
be one or more polyamide intermediate compounds obtained, for
example, from the reaction of a polyacid (e.g., diacid or higher)
with a polyamine (e.g., diamine or higher) to form a polyamide
polymer with the elimination of water. Other suitable
silyl-modified polyamides and methods of making such compounds are
described in U.S. Pat. No. 6,439,309, the relevant disclosure of
which is herein incorporated by reference.
[0049] Some suitable tackifying agents are described in U.S. Pat.
No. 5,249,627 by Harms, et al., the relevant disclosure of which is
incorporated by reference. Harms discloses aqueous tackifying
agents that comprise at least one member selected from the group
consisting of benzyl coco di-(hydroxyethyl) quaternary amine,
p-T-amyl-phenol condensed with formaldehyde, and a copolymer
comprising from about 80% to about 100% C.sub.1-30
alkylmethacrylate monomers and from about 0% to about 20%
hydrophilic monomers. In some embodiments, the aqueous tackifying
agent may comprise a copolymer that comprises from about 90% to
about 99.5% 2-ethylhexylacrylate and from about 0.5% to about 10%
acrylic acid. Suitable hydrophilic monomers may be any monomer that
will provide polar oxygen-containing or nitrogen-containing groups.
Suitable hydrophilic monomers include dialkyl amino alkyl (meth)
acrylates and their quaternary addition and acid salts, acrylamide,
N-(dialkyl amino alkyl) acrylamide, methacrylamides and their
quaternary addition and acid salts, hydroxy alkyl (meth)acrylates,
unsaturated carboxylic acids such as methacrylic acid or preferably
acrylic acid, hydroxyethyl acrylate, acrylamide, and the like.
These copolymers can be made by any suitable emulsion
polymerization technique. Methods of producing these copolymers are
disclosed, for example, in U.S. Pat. No. 4,670,501, the relevant
disclosure of which is incorporated herein by reference.
[0050] C. Gelable Liquid Compositions
[0051] Gelable liquid compositions suitable for use in the methods
of the present invention may comprise 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. That is, the gelled
substance should negatively impact the ability of the formation to
produce desirable fluids such as hydrocarbons. As discussed above,
the permeability of the formation may be restored through use of an
afterflush fluid or by fracturing through the consolidated portion.
As referred to herein, the term "flexible" refers to a state
wherein the treated formation or material is relatively malleable
and elastic and able to withstand substantial pressure cycling
without substantial breakdown. Thus, the resultant gelled substance
should be a semi-solid, immovable, gel-like substance, which, among
other things, 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 formation sands. Examples of suitable
gelable liquid compositions include, but are not limited to, resin
compositions that cure to form flexible gels, gelable aqueous
silicate compositions, crosslinkable aqueous polymer compositions,
and polymerizable organic monomer compositions.
[0052] Certain embodiments of the gelable liquid compositions
comprise curable resin compositions. Curable resin compositions are
well known to those skilled in the art and have been used to
consolidate portions of unconsolidated formations and to
consolidate proppant materials into hard, permeable masses. While
the curable resin compositions used in accordance with the present
invention may be similar to those previously used to consolidate
sand and proppant into hard, permeable masses, they are distinct in
that resins suitable for use with the present invention do not cure
into hard, permeable masses; rather they cure into flexible, gelled
substances. That is, suitable curable resin compositions form
resilient gelled substances between the particulates of the treated
portion of the unconsolidated formation and thus allow that portion
of the formation to remain flexible and to resist breakdown. It is
not necessary or desirable for the cured resin composition to
solidify and harden to provide high consolidation strength to the
treated portion of the formation. On the contrary, upon being
cured, the curable resin compositions useful in accordance with
this invention form semi-solid, immovable, gelled substances.
[0053] Generally, the curable resin compositions useful in
accordance with the present invention may 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, immovable,
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.
[0054] Examples of curable resins that can be used in the curable
resin compositions of 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.
[0055] Any diluent that is compatible with the curable resin and
achieves the desired viscosity effect is suitable for use in the
present invention. Examples of diluents that may be used in the
curable 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
curable resin composition to 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 curable resin composition in an amount
sufficient to provide the desired viscosity effect. Generally, the
diluent used is included in the curable resin composition in amount
in the range of from about 5% to about 75% by weight of the curable
resin.
[0056] 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 curable resin composition to convert into a
semi-solid, immovable, 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 curable 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 curable resin composition in an amount in the
range of from about 20% to about 75% by weight of the curable
resin.
[0057] As noted above, flexibilizer additives may be used, inter
alia, to provide flexibility to the gelled substances formed from
the curable resin compositions. The term "flexibilizer additive" is
defined herein to include any substance that is capable of
imparting properties of flexibility (e.g., malleability,
elasticity) to the gelled substances formed from the curable resin
compositions. Flexibilizer additives should be used where the resin
curing agent chosen would cause the organic resin composition to
cure into a hard and brittle material instead of desired gelled
substances described herein. 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 curable resin
composition in an amount in the range of from about 5% to about 80%
by weight of the curable 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.
[0058] In other embodiments, the gelable liquid compositions 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.
[0059] The aqueous alkali metal silicate solution component of the
gelable aqueous silicate compositions generally comprises 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.
[0060] 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,
immovable, gelled 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 which 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
range of from about 0.1% to about 5% by weight of the gelable
aqueous silicate composition. When used, the temperature activated
catalyst may be a component of a treatment fluid comprising the
gelable aqueous silicate composition, or may be introduced into the
subterranean formation separately through the dynamic diversion
tool (e.g., as a component of a treatment fluid) or by some other
means (e.g., pumped into the annulus from the surface).
[0061] In other embodiments, the gelable liquid compositions may
comprise crosslinkable aqueous polymer compositions. Generally,
suitable crosslinkable aqueous polymer compositions may comprise an
aqueous solvent, a crosslinkable polymer, and a crosslinking
agent.
[0062] 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.
[0063] 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.
[0064] The crosslinkable aqueous polymer compositions of the
present invention may further comprise a crosslinking agent for
crosslinking the crosslinkable polymers to form the desired gelled
substance. In some embodiments, the crosslinking agent may be 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.
[0065] 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 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.
[0066] Optionally, the crosslinkable aqueous polymer compositions
may further comprise a crosslinking delaying agent, such as a
polysaccharide crosslinking delaying agents 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.
[0067] In other embodiments, the gelled liquid compositions may
comprise polymerizable organic monomer compositions. Generally,
suitable polymerizable organic monomer compositions may comprise an
aqueous-base fluid, a water-soluble polymerizable organic monomer,
an oxygen scavenger, and a primary initiator.
[0068] The aqueous-base 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.
[0069] 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-methacrylamino-2-methylpropane 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
polyrnerizable 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 glycol acrylate, polypropylene glycol methacrylate,
and mixtures thereof. Of these, hydroxyethylacrylate is preferred.
An example of a particularly preferable monomer is
hydroxyethylcellulose-vinyl phosphoric acid.
[0070] 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(s) are 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(s) are 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.
[0071] 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.
[0072] 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
which 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(s) 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-aminopropane), 4,4'-azobis(4-cyanovaleric acid), and
2,2'-azobis(2-methyl-N-(2-hydroxyethyl) 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).
[0073] 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).
[0074] 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.
[0075] Therefore, the present invention is well adapted to attain
the ends and advantages mentioned as well as those that are
inherent therein. The particular embodiments disclosed above are
illustrative only, as the present invention may be modified and
practiced in different but equivalent manners apparent to those
skilled in the art having the benefit of the teachings herein.
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. Furthermore, no limitations are
intended to the details of construction or design herein shown,
other than as described in the claims below. It is therefore
evident that the particular illustrative embodiments disclosed
above may be altered or modified and all such variations are
considered within the scope and spirit of the present invention. In
particular, every range of values (e.g., "from about a to about b,"
or, equivalently, "from approximately a to b," or, equivalently,
"from approximately a-b") disclosed herein is to be understood as
referring to the power set (the set of all subsets) of the
respective range of values. The terms in the claims have their
plain, ordinary meaning unless otherwise explicitly and clearly
defined by the patentee.
* * * * *