U.S. patent application number 10/246943 was filed with the patent office on 2004-03-25 for elastomeric admixtures for improving cement elasticity.
Invention is credited to Ravi, Krishna M., Reddy, B. Raghava.
Application Number | 20040055748 10/246943 |
Document ID | / |
Family ID | 29250287 |
Filed Date | 2004-03-25 |
United States Patent
Application |
20040055748 |
Kind Code |
A1 |
Reddy, B. Raghava ; et
al. |
March 25, 2004 |
Elastomeric admixtures for improving cement elasticity
Abstract
A method and cementing composition is provided for sealing a
subterranean zone penetrated by a well bore, wherein the cementing
composition comprises a mixture of cementitious material,
acrylonitrile butadiene styrene (ABS), and sufficient water to form
a slurry.
Inventors: |
Reddy, B. Raghava; (Duncan,
OK) ; Ravi, Krishna M.; (Kingwood, TX) |
Correspondence
Address: |
CRAIG W. RODDY
HALLIBURTON ENERGY SERVICES
P.O. BOX 1431
DUNCAN
OK
73536-0440
US
|
Family ID: |
29250287 |
Appl. No.: |
10/246943 |
Filed: |
September 19, 2002 |
Current U.S.
Class: |
166/293 ;
106/808; 106/819; 106/823; 166/295; 524/2 |
Current CPC
Class: |
C04B 24/2652 20130101;
C09K 8/46 20130101; C04B 28/02 20130101; C04B 14/062 20130101; C04B
24/2652 20130101; C04B 28/02 20130101 |
Class at
Publication: |
166/293 ;
166/295; 106/808; 106/819; 106/823; 524/002 |
International
Class: |
E21B 033/138; C04B
024/12; C04B 024/24 |
Claims
1. A method of sealing a subterranean zone penetrated by a well
bore comprising: preparing a cementing composition comprising
cement, acrylonitrile butadiene styrene polymer, and water; placing
the cementing composition into the subterranean zone; and allowing
the cementing composition to set therein.
2. The method of claim 1 wherein the cementing composition further
comprises silica flour.
3. The method of claim 1 wherein the cement is Portland cement,
pozzolan cement, gypsum cement, aluminous cement, silica cement, or
alkaline cement.
4. The method of claim 1 wherein the acrylonitrile butadiene
styrene polymer is made with a 70% polybutadiene substrate.
5. The method of claim 1 wherein the acrylonitrile butadiene
styrene polymer is made with a 65% styrene-butadiene rubber
substrate.
6. The method of claim 1 wherein the acrylonitrile butadiene
styrene polymer is made with a 35% styrene-butadiene rubber
substrate.
7. The method of claim 1 wherein the acrylonitrile butadiene
styrene polymer is present in a range of 5% to 30% by weight of the
cement.
8. The method of claim 1 wherein the water is present in a range of
38% to 70% by weight of the cement.
9. A cementing composition for sealing a subterranean zone
penetrated by a well bore comprising: cement, acrylonitrile
butadiene styrene polymer, and water.
10. The composition of claim 9 further comprising silica flour.
11. The composition of claim 9 wherein the cement is Portland
cement, pozzolan cement, gypsum cement, aluminous cement, silica
cement, or alkaline cement.
12. The composition of claim 9 wherein the acrylonitrile butadiene
styrene polymer is made with a 70% polybutadiene substrate.
13. The composition of claim 9 wherein the acrylonitrile butadiene
styrene polymer is made with a 65% styrene-butadiene rubber
substrate.
14. The composition of claim 9 wherein the acrylonitrile butadiene
styrene polymer is made with a 35% styrene-butadiene rubber
substrate.
15. The composition of claim 9 wherein the acrylonitrile butadiene
styrene polymer is present in a range of 5% to 30% by weight of the
cement.
16. The composition of claim 9 wherein the water is present in a
range of 38% to 70% by weight of the cement.
17. A method of sealing a subterranean zone penetrated by a well
bore comprising: preparing a cementing composition comprising
cement, acrylonitrile butadiene styrene polymer, and water, wherein
the acrylonitrile butadiene styrene polymer is present in a range
of 5% to 30% by weight of the cement; placing the cementing
composition into the subterranean zone; and allowing the cementing
composition to set therein.
18. The method of claim 17 wherein the cement is Portland cement,
pozzolan cement, gypsum cement, aluminous cement, silica cement, or
alkaline cement.
19. The method of claim 17 wherein the acrylonitrile butadiene
styrene polymer is made with a 70% polybutadiene substrate.
20. The method of claim 17 wherein the acrylonitrile butadiene
styrene polymer is made with a 65% styrene-butadiene rubber
substrate.
21. The method of claim 17 wherein the acrylonitrile butadiene
styrene polymer is made with a 35% styrene-butadiene rubber
substrate.
22. The method of claim 17 wherein the water is present in a range
of 38% to 70% by weight of the cement.
23. The method of claim 17 wherein the cementing composition
further comprises silica flour.
Description
BACKGROUND
[0001] The present embodiment relates generally to a cementing
composition for sealing a subterranean zone penetrated by a well
bore.
[0002] In the drilling and completion of an oil or gas well, a
cementing composition is often introduced in the well bore for
cementing pipe string or casing. In this process, known as "primary
cementing," the cementing composition is pumped into the annular
space between the walls of the well bore and the casing. The
cementing composition sets in the annular space, supporting and
positioning the casing, and forming a substantially impermeable
barrier, or cement sheath, which isolates the well bore into
subterranean zones. Thus, the undesirable migration of fluids
between zones is prevented after primary cementing.
[0003] Changes in pressure or temperature in the well bore over the
life of the well can result in compromised zonal isolation. Also,
activities undertaken in the well bore, such as pressure testing,
well completion operations, hydraulic fracturing, and hydrocarbon
production can affect zonal isolation. Such compromised zonal
isolation is often evident as cracking or plastic deformation in
the cementing composition, or de-bonding between the cementing
composition and either the well bore or the casing.
[0004] As the name implies, cementing compositions are made chiefly
of cement. Due to its incompressible nature, neat cement is
undesirable for use where there is a chance of expansion or
contraction in the well bore. Cement has a high Young's modulus,
and fractures at slight strains when subjected to stresses
("brittle failure"). When the imposed stresses exceed the stress at
which the cement fails, the cement sheath can no longer provide
zonal isolation. While the Young's modulus of cementing
compositions can be lowered by adding silica compositions, such
silica treated cementing compositions ("water-extended slurries")
suffer from lower compressive and tensile strengths.
[0005] Therefore, a cementing composition that can provide greater
elasticity and compressibility, while retaining high compressive
and tensile strengths, is desirable for primary cementing.
DESCRIPTION
[0006] A cementing composition for sealing a subterranean zone
penetrated by a well bore according to the present embodiment
comprises a mixture of cementitious material ("cement"),
acrylonitrile butadiene styrene (ABS) polymer, and sufficient water
to form a slurry.
[0007] In another embodiment, ABS is added to water-extended
slurries to create a cementing composition with a lower Young's
modulus while achieving high compressive and tensile strengths.
[0008] A variety of cements can be used with the present
embodiments, including cements comprised of calcium, aluminum,
silicon, oxygen, and/or sulfur which set and harden by reaction
with water. Such hydraulic cements include Portland cements,
pozzolan cements, gypsum cements, aluminous cements, silica
cements, and alkaline cements. Portland cements of the type defined
and described in API Specification 10, 5.sup.th Edition, Jul. 1,
1990, of the American Petroleum Institute (the entire disclosure of
which is hereby incorporated as if reproduced in its entirety) are
preferred. API Portland cements include Classes A, B, C, G, and H,
of which API Classes A, G, and H are particularly preferred for the
present embodiment. The desired amount of cement is understandably
dependent on the cementing operation.
[0009] ABS used with the present embodiments is often produced as a
composite material. In the production of such a composite material,
a preformed elastomer such as polybutadiene or styrene butadiene
rubber is used as a substrate, and styrene and acrylonitrile
monomers are grafted onto the substrate by polymerization. In
addition, styrene and acrylonitrile that fail to graft to the
substrate copolymerize to form a matrix, with the grafted substrate
dispersed in the matrix. Higher levels of butadiene in the final
product increases the elastomeric properties of the composite
material. In contrast, higher levels of styrene and acrylonitrile
in the final product decrease the elastomeric properties of the
composite material. As can be appreciated, the character of the ABS
varies by the composition of the composite material, and thus
affects the mechanical properties of the cementing composition.
[0010] ABS is normally sold in a fine particulate or pellet form.
ABS with particle sizes ranging from 5-500 microns is preferable.
More preferably, the particle size is in the 50-300 micron range,
and most preferably in the 100-250 micron range. Such ABS is widely
available commercially. Some examples of commercially available ABS
includes BLENDEX 338.TM. ABS made with a 70% polybutadiene
substrate (the remaining 30% being a mixture of styrene and
acrylonitrile), 180 micron particle size ("Type I"), BLENDEX
336.TM. ABS made with a 65% styrene-butadiene rubber substrate, 180
micron particle size ("Type II"), BLENDEX 415.TM. ABS made with a
65% styrene-butadiene rubber substrate, 250 micron particle size
("Type III"), and BLENDEX 102S.TM. ABS with a 35% styrene-butadiene
rubber substrate, less than 1 mm particle size ("Type IV"), all
available from GE Specialty Chemicals, Parkersburg, W.Va., U.S.A.
ABS is present in an amount that is 5-30% by weight of the cement
in a particular cementing composition.
[0011] Water in the cementing composition is present in an amount
sufficient to make a slurry which is pumpable for introduction down
hole. The water used to form a slurry in the present embodiment can
be fresh water, unsaturated salt solution, including brines and
seawater, and saturated salt solution. Generally, any type of water
can be used, provided that it does not contain an excess of
compounds, well known to those skilled in the art, that adversely
affect properties of the cementing composition. The water is
present in an amount of about 38-70% by weight of the cement, and
more preferably in an amount of about 60% by weight of the
cement.
[0012] A variety of additives may be added to the cementing
composition to alter its physical properties. Such additives may
include slurry density modifying materials (e.g., silica flour,
silica fume, sodium silicate, microfine sand, iron oxides and
manganese oxides), dispersing agents, set retarding agents, set
accelerating agents, fluid loss control agents, strength
retrogression control agents, and viscosifying agents well known to
those skilled in the art.
[0013] The following example is illustrative of the methods and
compositions discussed above.
EXAMPLE 1
[0014] Class G cement, silica flour, and the components in the
amounts listed in TABLE 1 were added to form seven batches. The
batches were prepared according to API Specification RP 10B,
22.sup.nd Edition, 1997, of the American Petroleum Institute (the
entire disclosure of which is hereby incorporated as if reproduced
in its entirety). For example, Batch 6 was prepared by combining
500 grams of Class G cement, 175 grams of silica flour, 50 grams of
Type IV ABS (Particle size, <1 mm), and 317 grams of tap water
in a Waring blender to obtain a slurry with density of 14.8 pounds
per gallon. All batches had the same density.
[0015] ABS Types I-IV are described above. ABS Type V has a high
butadiene content and a density of 1.040 g/cc, with a particle size
less than 500 microns, and is available from Sigma-Aldrich Co., St.
Louis, Mo., U.S.A.
[0016] To test each batch for various strength parameters, a
portion of each batch was placed into a corresponding 2".times.2"
brass mold, and another portion of each batch was placed into a
corresponding cylindrical plastic container provided with a lid.
The seven molds and seven cylinders were cured in a 180.degree. F.
water bath for 24 hours to form samples of the batches.
[0017] Using the above-described samples, the strength parameters
were measured by a strength testing instrument manufactured by
Tinius Olsen, Willow Grove, Pa., U.S.A., according to the American
Society for Testing and Materials ASTM 109 procedure (the entire
disclosure of which is hereby incorporated as if reproduced in its
entirety). The tensile strengths were measured on the same
instrument according to the ASTM C190-97 procedure (the entire
disclosure of which is hereby incorporated as if reproduced in its
entirety). The burst strengths were measured on an MTS load frame
instrument manufactured by MTS Systems Corporation, Eden Prairie,
Minn., U.S.A. The Young's modulus, Poisson's ratio, Brazilian
tensile strength, and permeability were also determined for each
batch, and are listed in TABLE 1.
1TABLE 1 Components Batch 1 Batch 2 Batch 3 Batch 4 Batch 5 Batch 6
Batch 7 Water % bwoc 72 62.5 61.6 61.6 58 63.3 58 ABS Type -- Type
I Type II Type III Type III Type IV Type V ABS % bwoc -- 10 10 10
15 10 15 Compressive 1320 1950 1750 1800 2060 1990 2680 strength,
psi Tensile strength, psi -- 270 284 284 -- 300 -- Burst strength,
psi -- 264 255 270 -- -- -- Young's modulus 0.460 0.858 0.861 0.720
0.427 0.728 0.879 Poisson's ratio 0.114 0.139 0.142 0.128 0.118
0.130 0.138 Brazilian tensile 98 210 194 220 180 255 222 strength,
psi Permeability, mD -- 0.020 0.016 0.020 -- -- --
[0018] TABLE 1 shows that Batch 1, the water-extended slurry, had
poor compressive strength, even though the Young's modulus value
was low. This can result in failure of the cement sheath to provide
effective zonal isolation. In contrast, the ABS batches, Batches
2-7, had much higher compressive strengths, and favorable tensile
strengths (where measured).
[0019] TABLE 1 also shows that selection of the ABS type affects
the mechanical properties of the cementing composition, thus
allowing the cementing composition to be tailored to suit
conditions in a particular well bore.
[0020] It is speculated that the acrylonitrile in ABS hydrolyzes in
the cement slurries and generates carboxylates which facilitate
bonding of the normally incompatible elastomer to the cement. Such
bonding may allow dissipation of imposed stresses, thus preventing
brittle failure of the cement sheath.
[0021] Using the raw stress-strain data used in the determination
of the compressive strength, Young's modulus, and Poisson's ratios
listed in TABLE 1, the areas under the curves extending from no
stress to the maximum stress (reached at the ultimate yield point)
in the axial stress-strain and radial stress-strain graphs were
determined, and the values are listed in TABLE 2. The Young's
modulus and Poisson's ratio listed in TABLE 2 correspond to the
values observed at the maximum stress. Batch 7 was not tested.
2TABLE 2 Components Batch 1 Batch 2 Batch 3 Batch 4 Batch 5 Batch 6
Stress at ultimate yield 1130 2070 2080 1690 1300 2370 point, psi
Area under curve for 2270 6000 4730 4290 3662 7280 axial
displacement at ultimate yield point, Kpsi .times. microinch/inch
Area under curve for 640 1430 750 1135 1050 1000 radial
displacement at ultimate yield point, Kpsi .times. microinch/inch
Poisson's ratio at 0.210 0.207 0.143 0.220 0.219 0.128 ultimate
yield point Young's modulus at 0.336e+6 0.476e+6 0.580e+6 0.444e+6
0.298e+6 0.510e+6 ultimate yield point, psi
[0022] The maximum stress at the ultimate yield point indicates the
ability of the cementing composition to absorb the imposed stresses
without failing, and the ABS containing Batches 2-6 all showed
greater stress values than Batch 1. The resiliency of the
composition is indicated by higher ratios of the area under radial
stress-strain curve to the area under axial stress-strain curve.
While the ability of Batches 2-6 to plastically deform without
failing could not be directly quantified, it was apparent that they
plastically deformed past the load bearing stage.
[0023] Although only a few exemplary embodiments of this invention
have been described in detail above, those skilled in the art will
readily appreciate that many other modifications are possible in
the exemplary embodiments without materially departing from the
novel teachings and advantages of this invention. Accordingly, all
such modifications are intended to be included within the scope of
this invention as defined in the following claims.
* * * * *