U.S. patent application number 11/503634 was filed with the patent office on 2006-12-07 for methods of preparing settable fluids comprising particle-size distribution-adjusting agents, and associated methods.
This patent application is currently assigned to Halliburton Energy Services, Inc.. Invention is credited to Russell M. Fitzgerald, B. Raghava Reddy, Ahok K. Santra.
Application Number | 20060272819 11/503634 |
Document ID | / |
Family ID | 39082384 |
Filed Date | 2006-12-07 |
United States Patent
Application |
20060272819 |
Kind Code |
A1 |
Santra; Ahok K. ; et
al. |
December 7, 2006 |
Methods of preparing settable fluids comprising particle-size
distribution-adjusting agents, and associated methods
Abstract
Base cement compositions comprising particle-size
distribution-adjusting agents, and methods of using such base
cement compositions in subterranean operations and surface
applications are provided. An example of a method comprises:
providing a base cement composition comprising water, a hydraulic
cement, a set retarder, and a particle-size distribution-adjusting
agent, the base cement composition having a density; adjusting the
density of the base cement composition on-the-fly with a density
modifying agent to provide a density-adjusted cement; activating
the density-adjusted cement composition; placing the
density-adjusted cement composition in a subterranean formation;
and permitting the density-adjusted cement composition to set in
the subterranean formation. Another example of a method comprises:
providing a base cement composition comprising water, a hydraulic
cement, a set retarder, and a particle-size distribution-adjusting
agent, the base cement composition having a density; and adjusting
the density of the base cement composition at the job site by
variably injecting a density modifier into the base cement
composition.
Inventors: |
Santra; Ahok K.; (Duncan,
OK) ; Reddy; B. Raghava; (Duncan, OK) ;
Fitzgerald; Russell M.; (Waurika, OK) |
Correspondence
Address: |
CRAIG W. RODDY;HALLIBURTON ENERGY SERVICES
P.O. BOX 1431
DUNCAN
OK
73536-0440
US
|
Assignee: |
Halliburton Energy Services,
Inc.
|
Family ID: |
39082384 |
Appl. No.: |
11/503634 |
Filed: |
August 14, 2006 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10759678 |
Jan 16, 2004 |
|
|
|
11503634 |
Aug 14, 2006 |
|
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Current U.S.
Class: |
166/292 |
Current CPC
Class: |
C09K 8/48 20130101; C04B
28/02 20130101; C04B 28/02 20130101; C04B 28/02 20130101; C09K
8/467 20130101; C09K 8/473 20130101; C04B 14/306 20130101; C04B
14/308 20130101; C04B 2103/22 20130101; C04B 24/2652 20130101; C04B
14/30 20130101; C04B 2103/22 20130101; C04B 38/08 20130101; C04B
24/383 20130101; C04B 20/002 20130101; C04B 14/26 20130101 |
Class at
Publication: |
166/292 |
International
Class: |
E21B 33/13 20060101
E21B033/13 |
Claims
1. A method of cementing in a subterranean formation, comprising:
providing a base cement composition comprising water, a hydraulic
cement, a set retarder, and a particle-size distribution-adjusting
agent, the base cement composition having a density; adjusting the
density of the base cement composition on-the-fly with a density
modifying agent to provide a density-adjusted cement composition;
activating the density-adjusted cement composition; placing the
density-adjusted cement composition in a subterranean formation;
and permitting the density-adjusted cement composition to set in
the subterranean formation.
2. The method of claim 1 wherein the particle-size
distribution-adjusting agent is a cationic polymer.
3. The method of claim 2 wherein the cationic polymer is a cationic
polyacrylamide, a cationic hydroxyethyl cellulose, a
poly(dimethyldiallylammonium chloride), or a cationic starch.
4. The method of claim 1 wherein the step of adjusting the density
of the base cement composition comprises injecting a density
modifier into the base cement composition.
5. The method of claim 4 wherein the density modifier comprises a
densifier selected from the group consisting of iron oxides,
manganese oxides, zinc oxide, zirconium oxide, iron carbonate,
aqueous solutions of soluble salts, and mixtures thereof.
6. The method of claim 4 wherein the density modifier comprises a
densifier which has a specific gravity in the range of from about
3.5 to about 10.
7. The method of claim 4 wherein the density modifier comprises a
density reducer selected from the group consisting of water, gas,
low bulk density inorganic materials containing entrapped air, and
microspheres.
8. The method of claim 4 wherein the density modifier comprises a
density reducer which has a specific gravity in the range of from
about 0.1 to about 3.
9. The method of claim 1 wherein the step of activating the cement
composition comprises adding an activator composition to the cement
composition.
10. The method of claim 9 wherein the activator composition is a
mixture of a trialkanolamine and an alkali or a mixture of a
trialkanolamine and an alkaline earth metal hydroxide.
11. The method of claim 1 wherein the step of activating the cement
composition is performed before, during, or after adjusting the
density of the base cement composition.
12. The method of claim 1 wherein the step of adjusting the density
on-the-fly of the base cement composition comprises injecting a
density modifying additive into the base cement composition such
that the hydrostatic pressure of the composition does not exceed a
fracture gradient of the subterranean formation.
13. A method of customizing the density of a base cement
composition for use at a job site comprising: providing a base
cement composition comprising water, a hydraulic cement, a set
retarder, and a particle-size distribution-adjusting agent, the
base cement composition having a density; and adjusting the density
of the base cement composition at the job site by variably
injecting a density modifier into the base cement composition.
14. The method of claim 13 wherein the particle-size
distribution-adjusting agent is a cationic polymer.
15. The method of claim 14 wherein the cationic polymer is selected
from the group consisting of cationic polyacrylamides, cationic
hydroxyethyl cellulose, poly(dimethyldiallylammonium chloride), and
cationic starches.
16. The method of claim 13 wherein the step of adjusting the
density of the base cement composition at the job site comprises
injecting a density modifier into the base cement composition
before or during placement of the cement composition within a
subterranean formation.
17. The method of claim 13 wherein the density modifier comprises a
densifier selected from the group consisting of iron oxides,
manganese oxides, zinc oxide, zirconium oxide, iron carbonate,
aqueous solutions of soluble salts, and mixtures thereof.
18. The method of claim 13 wherein the density modifier comprises a
densifier which has a specific gravity in the range of from about
3.5 to about 10.
19. The method of claim 13 wherein the density modifier comprises a
density reducer selected from the group consisting of water, gas,
low bulk density inorganic materials containing entrapped air, and
microspheres.
20. The method of claim 13 wherein the density modifier comprises a
density reducer which has a specific gravity in the range of from
about 0.1 to about 3.
21. The method of claim 13 wherein the step of adjusting the
density of the base cement composition at the job site comprises
variably injecting a density modifying additive into the base
cement composition in response to hydrostatic pressure of the
composition in a subterranean formation.
22. The method of claim 13 wherein the step of adjusting the
density of the base cement composition at the job site comprises
variably injecting a density modifying additive into the base
cement composition to counter cement circulation loss into a
subterranean formation.
Description
CROSS REFERENCE TO RELATED APPLICATION
[0001] The present invention is a continuation-in-part application
of U.S. patent application Ser. No. 10/759,678, filed on Jan. 16,
2004, titled "Settable Fluids Comprising Particle-Size
Distribution-Adjusting Agents and Methods of Use," the disclosure
of which is incorporated herein by reference in its entirety.
BACKGROUND
[0002] The present invention relates to settable fluid
compositions, and more particularly, to settable fluid compositions
that comprise particle-size distribution-adjusting agents, and
associated methods.
[0003] Hydraulic cement compositions are commonly utilized in
subterranean operations, particularly in subterranean well
completion and remedial operations. For example, hydraulic cement
compositions are used in primary cementing operations whereby pipe
strings, such as casings and liners, are cemented in well bores. In
performing primary cementing, hydraulic cement compositions are
pumped into the annular space between the walls of a well bore and
the exterior surface of the pipe string disposed therein. The
cement composition is permitted to set in the annular space,
thereby forming an annular sheath of hardened substantially
impermeable cement therein that substantially supports and
positions the pipe string in the well bore and bonds the exterior
surface of the pipe string to the walls of the well bore. Hydraulic
cement compositions are also used in remedial cementing operations
such as plugging highly permeable zones or fractures in well bores,
plugging cracks and holes in pipe strings, and the like.
[0004] Set-delayed cement compositions are often utilized at a
number of job sites in circumstances where an operator finds it
desirable to prepare a volume of a cement composition that remains
in a pumpable state for a long period of time (e.g., for about two
weeks or more), and that can be selectively activated to set into a
hard mass at a desired time. For example, in circumstances where
large volumes of cement are utilized (such as in offshore platform
grouting), the equipment required for mixing and pumping the
requisite large volumes of cement composition may be very
expensive, and may be difficult to assemble at the desired
location. The storage of the requisite amount of dry cement prior
to use may be another problem. As another example, the use of a
set-delayed cement composition may also be desirable in
circumstances where a relatively small volume of cement composition
is used, such as a small construction job, for example, or a
plugging and squeezing operation performed in the petroleum
industry, for instance.
[0005] In such circumstances, the cost to transport the cement
composition to a job site, and to mix and pump it on location may
be undesirable relative to the revenue generated from performing
the cementing operation. A job site may include any location
above-ground or below-ground for which a cement composition may be
suitable as well as the area surrounding such locations.
Set-delayed cement compositions may be useful in such
circumstances, as they can be prepared at a convenient location,
then transported to and stored at a job site until use. At a
desired time, the set-delayed cement composition may be mixed with
a set activating agent; the resulting mixture may then be placed
into a desired location (e.g., into a subterranean formation) and
permitted to set therein.
[0006] In some conventional formulations, an excessive amount of
set-activating agents have been added to the set-delayed cement
compositions, thereby "over-activating" the cement composition,
after which a retarder is then added to the cement composition, in
an attempt to fine-tune the eventual set time of the cement
composition. This can be difficult to manage.
[0007] Additionally, operations involving conventional set-delayed
cement compositions may encounter a number of other difficulties.
For example, the cement composition may thicken or gel with time,
increasing the cement composition's viscosity, and thus impairing
its pumpability. Another difficulty is that the activation process
may be quite complicated, as exemplified by operations wherein the
cement composition's set-time is first delayed until shortly before
use, after which the cement composition is over-activated and again
retarded.
[0008] Another problem that may occur with some conventional
set-delayed cement compositions is that the addition of
set-activating agents may cause premature localized setting of the
cement, e.g., localized regions within the bulk cement slurry
wherein the set-activating agent becomes concentrated, thereby
causing premature setting of a portion of the bulk cement. Such
premature localized setting of the cement composition may be likely
to occur, for instance, when the cement composition is inadequately
mixed. Premature localized setting of the cement composition may
lead to pumping problems (e.g., hardened cement particles may
damage pump impellers), and may also cause problems such as setting
of the bulk cement while in storage tanks.
[0009] An additional difficulty posed by some conventional
set-delayed cement compositions is that the performance of the
set-activating agents commonly used to selectively activate the
cement compositions may be unpredictable. This may cause premature
setting of the cement before placement (e.g., where the activating
agent imparts an unexpectedly strong activating effect), or delayed
setting of the cement after placement (e.g., where the activating
agent imparts an unexpectedly weak activating effect). Both are
usually undesirable.
[0010] Moreover, conventional set-delayed cement compositions often
may be prepared in batch and stored at a central location, rather
than being prepared at a job site shortly before use. Typically, if
there is a need for density modifications to the slurry at a job
site prior to pumping, addition of dry density modifying additives
to achieve a desired density would be required, which may be
inconvenient and would require additional equipment for the
addition and the mixing stages. Furthermore, if multiple job sites
needing slurries with different densities are to be supplied cement
slurries from a single slurry stored in a central location, current
technology requires that density adjustment at each job site be
accomplished by addition of different levels and types of dry
density modifying additives, which would lower the benefits of
using a single storable slurry for multiple cementing jobs. Thus,
conventional set-delayed cement compositions may lack the ability
or flexibility to tune the density as needed from a single
set-delayed slurry used in different wells or in a single wellbore
at different depths or a single well with varying fracture
gradients. Thus, presently the use of conventional set-delayed
cement compositions is limited only to those subterranean
formations for which the design density of the set-delayed cement
composition matches the required slurry density at a job site.
There is a need to increase the flexibility of on-the-fly density
modification to enable use of a single cement slurry to service
multiple wells or multiple depths in a single well.
SUMMARY OF THE INVENTION
[0011] The present invention relates to settable fluid
compositions, and more particularly, to settable fluid compositions
that comprise particle-size distribution-adjusting agents, and
associated methods.
[0012] In one embodiment, the present invention provides a method
of cementing in a subterranean formation, comprising: providing a
base cement composition comprising water, a hydraulic cement, a set
retarder, and a particle-size distribution-adjusting agent, the
base cement composition having a density; adjusting the density of
the base cement composition on-the-fly with a density modifying
agent to provide a density-adjusted cement; activating the
density-adjusted cement composition; placing the density-adjusted
cement composition in a subterranean formation; and permitting the
density-adjusted cement composition to set in the subterranean
formation.
[0013] In one embodiment, the present invention provides a method
of customizing the density of a settable composition for use at a
job site comprising: providing a base cement composition comprising
water, a hydraulic cement, a set retarder, and a particle-size
distribution-adjusting agent, the base cement composition having a
density; and adjusting the density of the base cement composition
at the job site by variably injecting a density modifier into the
base cement composition.
[0014] 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 exemplary embodiments, which follows.
DETAILED DESCRIPTION
[0015] The present invention relates to settable fluid
compositions, and more particularly, to settable fluid compositions
that comprise particle-size distribution-adjusting agents, and
associated methods. The settable fluid compositions of the present
invention are density-adjusted cement compositions wherein a base
cement composition (that comprises a particle size distribution
agent) is or has been treated with a density modifying agent. These
settlable fluid compositions can be used in any application
requiring a settable fluid. One of the many advantages of the
present invention is that the base cement composition comprising
particle-size distribution-adjusting agents may be prepared in
batch with a standard density, and then customized to obtain a
cement composition with a density appropriate for a particular
application. Moreover, this can be done on-the-fly, which is
desirable in many instances.
[0016] In some embodiments, the present invention provides methods
of cementing in a subterranean formation. An example of such
embodiments is a method of cementing in a subterranean formation,
comprising: providing a base cement composition comprising water, a
hydraulic cement, a set retarder, and a particle-size
distribution-adjusting agent, the base cement composition having a
density; adjusting the density of the base cement composition
on-the-fly with a density modifying agent to provide a
density-adjusted cement composition; activating the
density-adjusted cement composition with an activator composition;
placing the density-adjusted cement composition in a subterranean
formation; and permitting the density-adjusted cement composition
to set in the subterranean formation. A "base cement composition",
as that term is used herein, refers to a cement composition of the
present invention prior to some density adjustment.
[0017] In some embodiments, the present invention provides methods
of customizing the density of a settable fluid for use at a job
site. An example of such a method comprises: providing a base
cement composition comprising water, a hydraulic cement, a set
retarder, and a particle-size distribution-adjusting agent, the
base cement composition having a density; and adjusting the density
of the base cement composition at the job site by variably
injecting a density modifier into the base cement composition.
[0018] The base cement compositions used in conjunction with the
present invention generally comprise water, a cement, a set
retarder, and a particle-size distribution-adjusting agent. Density
modifying agents with specific gravities in the range of from about
0.1 to about 10 may be added into the fluid stream while carrying
out a pumping operation (e.g. on-the-fly) to adjust the density of
the base cement composition, if desired. Optionally, other
additives suitable for use in a settable fluid may be added.
Density modifying additives may be included in aqueous suspensions
or other solutions for improved rheology (e.g., mixability and
pumpability).
[0019] Generally, the density-adjusted cement compositions of the
present invention may have a density in the range of from about 4
to about 25 pounds per gallon. Higher or lower densities may be
appropriate depending on the application. In certain exemplary
embodiments, the density-adjusted cement compositions of the
present invention may have a density in the range of from about 10
to about 25 pounds per gallon.
[0020] In certain exemplary embodiments of the present invention,
the base cement composition provided may be formulated as a
"densified" base cement composition (e.g., formulated with a
significantly higher density than that which is calculated to be
necessary for its intended use) before the addition of the density
modifying agent and activator composition. Such a densified base
cement composition may be provided in a variety of ways, such as
through the addition of high-density particles, or by formulating
the base cement composition with less water than necessary for its
intended use. Among other benefits, the employment of a densified
base cement composition will facilitate the addition of an
activator composition in the form of a dilute solution. For
example, if a cement composition having a 16.4 pounds per gallon
density is required, a densified base cement composition having a
density of, for example, 17 pounds per gallon or higher may be
provided and activated with an activator composition diluted with
sufficient water to ultimately provide the desired 16.4 pounds per
gallon slurry. Among other benefits, the addition of the activator
composition in a dilute solution to a densified base cement
composition may minimize the possibility of developing localized
zones having excessive activator concentration due to inadequate
mixing. Examples of suitable density modifying agents that may be
added for the purpose of reducing the density of the provided
densified base cement composition of the present invention include,
but are not limited to, density reducers such as water, gas, low
bulk density inorganic materials containing entrapped air such as
expanded mica and expanded vermiculite, and microspheres. In some
embodiments, the density reducer may have specific gravities in the
range of from about 0.1 to about 3.0.
[0021] In certain exemplary embodiments, where the density of the
provided base cement compositions is to be reduced, microspheres
may be directly added to the densified base cement composition.
Suitable microspheres that may be utilized in accordance with the
present invention include hollow, solid, and porous microspheres.
The microspheres may be present in the settable compositions of the
present invention in an amount in the range of from about 1% to
about 90% by weight of base cement composition. The size of the
microspheres present in the base cement composition is in the range
of from about 5 microns to about 1000 microns, and can be present
in a variety of sizes or in a uniform size. The microspheres may
utilize a variety of materials in accordance with the present
invention, including, but not limited to, glass, soda lime
borosilicate glass, silica, gold, silver, palladium, platinum,
polymethylmethacrylate, poly(L-lactic acid), polyacrylic acid,
latex, alumina, titania, melamine, dextran, fly ashes as mined or
expanded, ceramic, other polymeric materials for example,
thermoplastics such as polyethylene, polypropylene, polystyrene,
and elastomers such styrene-butadiene random or block polymers,
ethylene-propylene-dienemonomer (EPDM), and mixtures thereof. In
some embodiments of the settable compositions of the present
invention, the microspheres utilized are hollow microspheres. The
microspheres may be obtained from any suitable source. Examples of
suitable microspheres are fly ash hollow beads commercially
available from Halliburton under the tradename SPHERELITE, hollow
synthetic glass beads commercially available from 3M Corporation
under the tradename SCOTCHLITE, elastomeric hollow beads comprising
organic fluids under the tradename EXPANCEL, and expandable
polystyrene (EPS grade) beads available from Huntsman
Corporation.
[0022] Where the base cement compositions of the present invention
are to be foamed (e.g., to reduce the density of the base cement
composition, or to improve its mechanical properties), the base
cement composition may be foamed by direct addition of the gas into
the base cement composition. For instance, where the base cement
composition is foamed by the direct injection of gas into the
composition, the gas utilized can be air or any suitable inert gas,
such as nitrogen, or even a mixture of such gases. In certain
exemplary embodiments, nitrogen is used. Where foaming is achieved
by direct injection of gas, the gas may be present in the
composition in an amount sufficient to foam the composition,
generally in an amount in the range of from about 0.01% to about
60% by volume of the composition under downhole conditions. The
base cement composition may also be foamed by gas generated by a
reaction between the cement slurry and an expanding additive
present in the base cement composition in particulate form. For
example, the composition may be foamed by hydrogen gas generated in
situ as the product of a reaction between the slurry and fine
aluminum powder present in the base cement composition. To
stabilize the foam, surfactants optionally may be added to the base
cement composition. Surfactant compositions suitable for use in the
present invention are described in U.S. Pat. Nos. 6,063,738 and
6,367,550, the relevant disclosures of which are hereby
incorporated herein by reference.
[0023] In certain exemplary embodiments of the present invention,
the base cement composition provided may be formulated as a
"lightened" base cement composition (e.g., formulated with a
significantly lower density than that which is calculated to be
necessary for its intended use) before the addition of the density
modifying agent, for example a densifying agent, and activator
composition. Such a lightened base cement composition may be
provided in a variety of ways, such as by formulating the base
cement composition with more water than necessary for its intended
use. Suitable density modifying agents for the purpose of
increasing the density of the provided base cement composition of
the present invention are densifiers such as iron oxides, manganese
oxides, zinc oxide, zirconium oxide, iron carbonate or aqueous
solutions of soluble salts such as sodium chloride, calcium
chloride, cesium chloride, cesium formate and the like. In some
embodiments, the densifiers have specific gravities in the range of
from about 3.5 to about 10. Examples of suitable densifying agents
are HI-DENSE 3 commercially available from Halliburton, HI-DENSE 4
from Halliburton, and MicroMax.TM. FF from Halliburton. Densifying
agents may be included in the cement compositions of the present
invention in an amount up to 100% by weight of dry cement.
[0024] The water present in the base cement compositions of the
present invention may be from any source provided that it does not
contain an excess of compounds that adversely affect other
compounds in the base cement composition. For example, a base
cement compositions of the present invention can comprise fresh
water, salt water (e.g., water containing one or more salts
dissolved therein), brine (e.g., saturated salt water), or
seawater. The water may be present in an amount sufficient to
produce a pumpable slurry. Generally, the water may be present in
the base cement compositions of the present invention in an amount
in the range of from about 25% to about 150% by weight of cement
("bwoc") therein. In certain exemplary embodiments, the water may
be present in the base cement compositions of the present invention
in an amount in the range of from about 40% to about 55% bwoc
therein.
[0025] Any cements suitable for use in subterranean applications
are suitable for use in the present invention. Furthermore, any
cements suitable for use in surface applications, e.g.,
construction cements, are suitable for use in the present
invention. In certain exemplary embodiments, the improved cement
compositions of the present invention comprise a hydraulic cement.
A variety of hydraulic cements are suitable for use including those
comprised of calcium, aluminum, silicon, oxygen, and/or sulfur,
which set and harden by reaction with water. Such hydraulic cements
include, but are not limited to, Portland cements, pozzolana
cements, gypsum cements, high alumina content cements, silica
cements, and high alkalinity cements.
[0026] The base cement compositions of the present invention may
further comprise a set retarder. Generally, any set retarder may be
used with the base cement compositions of the present invention. In
certain exemplary embodiments, the set retarders used in the
present invention comprise phosphonic acid derivatives, such as
those that are described in U.S. Pat. No. 4,676,832, the relevant
disclosure of which is hereby incorporated herein. Commercially
available examples of a suitable set retarder include those
available from Solutia Corporation of St. Louis, Mo. under the
tradename "DEQUEST." In certain exemplary embodiments of the
present invention, a sodium salt of a phosphonic acid commercially
available from Solutia Corporation of St. Louis, Mo. under the
tradename "DEQUEST 2006" is used. A suitable phosphonic acid based
retarder is commercially available from Halliburton under the
tradename "MMCR", micromatrix cement retarder. Generally, the set
retarder is present in the base cement compositions of the present
invention in an amount in the range of from about 0.1% to about 5%
bwoc.
[0027] The particle-size distribution-adjusting agents suitable for
use in the base cement compositions of the present invention may be
any compound that desirably affects the particle-size distribution
of the base cement composition by agglomerating particles therein
such that the base cement composition's rheology remains desirably
stable for a chosen period of time. Even though dispersants affect
the particle size distribution by deagglomeration, it is believed
that particle size adjusting agents which effect the particle size
distribution by agglomeration of fine particles are more suitable
in the present invention. Among other benefits, the presence of the
particle-size distribution-adjusting agent in the base cement
compositions may forestall the onset of gelation for a desired
period of time. Accordingly, certain embodiments of the base cement
compositions of the present invention are capable of remaining
stable in a slurry state for several weeks or more before being
activated by the addition of an activator composition. Among other
benefits, the presence of the particle-size distribution-adjusting
agent in the base cement composition tends to cause smaller
particles in the base cement composition to agglomerate, thereby
tending to narrow the distribution range of the size of the
particles in the base cement composition.
[0028] One example of a suitable particle-size
distribution-adjusting agent is a cationic polymer. Examples of
cationic polymers suitable for use with the present invention
include, but are not limited to, cationic polyacrylamides, cationic
hydroxyethyl cellulose, poly(dimethyldiallylammonium chloride), and
cationic starches. In an exemplary embodiment, the cationic polymer
used in the base cement compositions of the present invention is a
cationic starch. A commercially available example of a cationic
starch is available under the tradename "REDIBOND 5330 A," from
National Starch Co. of Bridgewater, Conn.
[0029] Generally, the particle-size distribution-adjusting agent
may be present in the base cement compositions in an amount
sufficient to adjust the particle-size distribution of the base
cement composition to a desired range. More particularly, the
particle-size distribution-adjusting agent may be present in the
base cement composition in an amount in the range of from about
0.01% to about 4% bwoc. Other amounts may be suitable in some
applications.
[0030] Optionally, the base cement compositions of the present
invention may further comprise a yield stress reducing agent. The
use of such yield stress reducing agents may be particularly
beneficial in certain exemplary embodiments where a densified base
cement compositions is used. Among other benefits, the use of a
yield stress reducing agent may facilitate pumping of the densified
base cement compositions, inter alia, by reducing the force
required to move the densified base cement compositions from a
static position. While the present invention is not limited by any
particular theory, it is believed that the yield stress reducing
agent, inter alia, increases the repulsive force between cement
particles, thereby preventing them from approaching each other. An
example of a suitable yield stress reducing agent is a sulfonated
melamine formaldehyde condensate that is commercially available
under the tradename "MELADYNE" from Handy Chemicals, Ltd., of
Beachwood, Ohio. Another example of a suitable yield stress
reducing agent is a sulfite adduct of an acetone formaldehyde
condensate, commercially available from Halliburton Energy
Services, Inc., of Duncan, Okla., under the tradename "CFR-3."
Another example of a suitable yield stress reducing agent is a
sulfonated naphthalene condensate, commercially available from
Halliburton Energy Services, Inc., of Duncan, Okla., under the
tradename "CFR-6." One of ordinary skill in the art, with the
benefit of this disclosure, will be able to identify a suitable
yield stress reducing agent for a particular application.
[0031] Optionally, the base cement compositions of the present
invention may further comprise an expanding additive. Where an
expanding additive in particulate form is used, aluminum powder,
gypsum blends, and deadburned magnesium oxide are preferred.
Preferred expanding additives comprising aluminum powder are
commercially available under the tradenames "GAS-CHEK.RTM." and
"SUPER CBL" from Halliburton Energy Services, Inc., of Duncan,
Okla.; a preferred expanding additive comprising a blend containing
gypsum is commercially available under the tradename "MICROBOND"
from Halliburton Energy Services, Inc., of Duncan, Okla.; and
preferred expanding additives comprising deadburned magnesium oxide
are commercially available under the tradenames "MICROBOND M" and
"MICROBOND HT" from Halliburton Energy Services, Inc., of Duncan,
Okla. Such preferred expanding additives are described in
commonly-owned U.S. Pat. Nos. 4,304,298; 4,340,427; 4,367,093;
4,450,010; and 4,565,578, the relevant disclosures of which are
hereby incorporated herein by reference. One of ordinary skill in
the art, with the benefit of this disclosure, will be able to
determine the appropriate amount of expanding additive to include
in the base cement compositions of the present invention for a
particular application.
[0032] Additional additives may be added to the base cement
compositions of the present invention as deemed appropriate by one
skilled in the art with the benefit of this disclosure. Examples of
such additives include, inter alia, fluid loss control additives,
salts, vitrified shale, fly ash, fumed silica, bentonite,
fixed-density weighting agents, and the like. An example of a
suitable fluid loss control additive is commercially available from
Halliburton Energy Services, Inc., of Duncan, Okla., under the
tradename "HALAD.RTM. 9."
[0033] To prepare the base cement compositions of the present
invention for use, an activator composition of the present
invention may be added. The activator compositions of the present
invention generally comprise a mixture of at least one alkali or
alkaline earth metal hydroxide, and a trialkanolamine. A wide
variety of alkali or alkaline earth metal hydroxides are suitable
for use in the present invention. In certain exemplary embodiments,
the alkali or alkaline earth metal hydroxide is selected from the
group consisting of sodium hydroxide and potassium hydroxide. A
wide variety of trialkanolamines are suitable for use in the
present invention. In certain exemplary embodiments, the
trialkanolamine is selected from the group consisting of:
triethanolamine ("TEA"), tripropanolamine, and triisopropanolamine.
Such combinations have been found to provide a synergistic effect,
resulting in cement compositions that achieve desirably high
compressive strengths at a faster rate than would be achieved had
the TEA or alkali metal hydroxide been added individually. In
certain exemplary embodiments, the alkali metal hydroxide is sodium
hydroxide. Generally, the activator composition may be added to a
base cement composition of the present invention in an amount
sufficient to enable the cement composition to achieve a desired
compressive strength and a desired thickening time. More
particularly, the activator composition may be added to the base
cement composition in an amount in the range of from about 0.1% to
5% bwoc. Generally, the alkali or alkaline earth metal hydroxide
may be present in the activator composition in an amount in the
range of from about 50% to about 99.9% by weight. Generally, the
trialkanolamine may be present in the activator composition in an
amount in the range of from about 0.1% to about 50% by weight.
[0034] The activator composition may be added in a variety of ways.
For example, the activator composition may be added to the base
cement composition while the latter is still in storage. In certain
other exemplary embodiments, the activator composition may be
variably injected into the base cement composition at the same time
that the cement composition is injected into the subterranean
formation. Among other benefits, the injection of the activator
composition while the cement composition is injected into the
formation may assist in minimizing the development within the
cement composition of localized regions having a high activator
concentration.
[0035] One example of injecting density modifying agents or other
additives on-the-fly into flowing cement slurry includes connecting
fluid suspensions to the suction side of the cementing pumping
unit. Another example is to variably inject the suspension or
solution of a density modifying additive into the flowing cement
slurry stream under pressure using a separate pump. By variably
controlling the rate of injection, the amount of density modifying
material, and as a consequence the density of the slurry can be
precisely controlled. This is particularly useful in cases where
the formation penetrated by the well is heterogeneous and exhibits
different fracture gradients and hence slurry density has to be
closely monitored so that the hydrostatic pressure from the cement
slurry does not exceed the fracture gradient of the formation
resulting in loss circulation. In fact, the method of on-the-fly
density modification allows for a quick response in cases where
cement circulation loss is encountered during pumping, at which
time the density can be variably adjusted appropriately, for
example by lowering the density of the slurry being pumped by
increasing the amount of density reducing additive or decreasing
the amount of density increasing additive being injected, to stop
the loss circulation. The ability to control the cement slurry
density by on-the-fly adjustment of slurry density is also
important in cementing long strings of vertical casing where
significant density variation may be needed from the bottom of
casing (for example the shoe area) to the top of the cement column.
Examples of mixing systems suitable for on-the-fly adjustment of
slurry density include the RCM.RTM. II Mixing System and RCM.RTM.
IIe Mixing System commercially available from Halliburton. Using
conventional method of single density slurry could potentially may
be inadequate to prevent loss of fluids in the deepest part of the
cemented zone and sufficient to exceed the fracture gradient near
the top of the cement column.
[0036] To facilitate a better understanding of the present
invention, the following examples of some exemplary embodiments are
given. In no way should such examples be read to limit the scope of
the invention.
EXAMPLES
[0037] The base cement composition provided in the following
examples comprised Class G cement (100% bwoc), SSA-1 (35% bwoc),
HALAD-9 (0.27% bwoc), CFR-6 (0.196% bwoc), FDP-C754-04 (1% bwoc),
FDP-C662-02 (0.375% bwoc), and water (5.62 gausack); with density
(16.2 pound per gallon) and yield (1.45 Cuft/sack). The density and
compressive strength of the density-adjusted cement compositions
described in the following examples were measured according to API
Specification 10B, Twenty-Second Edition, December, 1997.
Example 1
[0038] Sample No. 1 comprised the provided base cement composition
described above, to which 14% bwoc hollow beads were added. Sample
No. 2 comprised the provided base cement composition, to which 60%
bwoc Micromax.TM. was added. Sample No. 3 comprised the provided
base cement composition, to which 32% by volume of slurry nitrogen
foamer were added. The resulting densities of the density-adjusted
cement compositions are set forth in the table below.
TABLE-US-00001 TABLE 1 Density Additive (pounds per gallon) Sample
No. 1 Hollow beads 10.74 Sample No. 2 Micromax .TM. 18.0 Sample No.
3 Foamer and nitrogen 11.0
[0039] Example 1 demonstrates, inter alia, that we can successfully
vary the density and obtain reasonable compressive strength out of
the set materials.
Example 2
[0040] Sample Nos. 1 and 2 described in the previous example were
cured at autoclave under 300.degree. F. and 3000 psi for 72 hours.
The base slurry sample comprised Class G cement (100% bwoc), SSA-1
(35% bwoc), HALAD-9 (0.27% bwoc), CFR-6 (0.196% bwoc), FDP-C754-04
(1% bwoc), FDP-C662-02 (0.375% bwoc), and water (5.62 gal/sack);
with density (16.2 pound per gallon) and yield (1.45 Cuft/sack).
The compressive strengths were measured using standard Tinius Olsen
equipment (model no. 398) and are set forth in the table below.
TABLE-US-00002 TABLE 2 Density Compressive (pound per Strength
gallon) (psi) Base Slurry 16.2 9340 Sample No. 1 10.74 1709 Sample
No. 2 18.0 7600
[0041] Example 2 demonstrates, inter alia, that the
density-adjusted cement compositions of the present invention could
be prepared from a base cement composition successfully.
[0042] 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.
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 (of
the form, "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, and set
forth every range encompassed within the broader range of values.
Also, the terms in the claims have their plain, ordinary meaning
unless otherwise explicitly and clearly defined by the
patentee.
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