U.S. patent application number 10/557106 was filed with the patent office on 2007-09-06 for self-adaptive cement systems.
Invention is credited to Keith Dismuke, Sylvaine Le Roy-Delage, Muriel Martin-Beurel, Erik Nelson.
Application Number | 20070204765 10/557106 |
Document ID | / |
Family ID | 33452388 |
Filed Date | 2007-09-06 |
United States Patent
Application |
20070204765 |
Kind Code |
A1 |
Le Roy-Delage; Sylvaine ; et
al. |
September 6, 2007 |
Self-Adaptive Cement Systems
Abstract
A self-healing cement system includes cement, water and at least
one additive that swells in contact with water from reservoir or
from formation in the case of a structural failure in the set
cement to provide a physical barrier in the zone of failure.
Examples of such material include particles of super-absorbent
polymer. These additives have the effect of making the cement
self-healing in the event of physical failure or damage such as
micro-annuli. The self healing property is produced by the contact
of the water itself, the potential repair mechanism is thus
activated if and when needed in case of start of loss of zonal
isolation. Several super-absorbent polymers have been identified
such as polyacrylamide, modified crosslinked poly(meth)acrylate and
non-solute acrylic polymers.
Inventors: |
Le Roy-Delage; Sylvaine;
(Paris, FR) ; Martin-Beurel; Muriel; (Lescar,
FR) ; Dismuke; Keith; (Katy, TX) ; Nelson;
Erik; (Houston, TX) |
Correspondence
Address: |
SCHLUMBERGER TECHNOLOGY CORPORATION;David Cate
IP DEPT., WELL STIMULATION
110 SCHLUMBERGER DRIVE, MD1
SUGAR LAND
TX
77478
US
|
Family ID: |
33452388 |
Appl. No.: |
10/557106 |
Filed: |
May 12, 2004 |
PCT Filed: |
May 12, 2004 |
PCT NO: |
PCT/EP04/05479 |
371 Date: |
December 11, 2006 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
60470341 |
May 14, 2003 |
|
|
|
Current U.S.
Class: |
106/802 ;
106/724; 106/727; 106/808; 106/823 |
Current CPC
Class: |
C04B 28/02 20130101;
C04B 28/02 20130101; C04B 40/0675 20130101; C04B 28/02 20130101;
C04B 28/02 20130101; C04B 28/02 20130101; C04B 28/02 20130101; C09K
8/467 20130101; C04B 28/02 20130101; C04B 28/02 20130101; C04B
2111/00146 20130101; C04B 2103/0062 20130101; C04B 28/02 20130101;
C04B 28/02 20130101; C04B 28/02 20130101; C04B 2103/0051 20130101;
C04B 2103/0062 20130101; C04B 20/0076 20130101; C04B 2103/408
20130101; C04B 24/2641 20130101; C04B 40/0259 20130101; C04B
40/0641 20130101; C04B 24/2652 20130101; C04B 40/0641 20130101;
C04B 40/0028 20130101; C04B 2103/22 20130101; C04B 40/0641
20130101; C04B 2103/22 20130101; C04B 2103/12 20130101; C04B 20/008
20130101; C04B 20/0076 20130101; C04B 24/2676 20130101; C04B
2103/12 20130101; C04B 40/0675 20130101; C04B 22/124 20130101; C04B
2103/46 20130101; C04B 24/2652 20130101; C04B 24/2652 20130101;
C04B 14/08 20130101; C04B 40/0028 20130101; C04B 2103/50 20130101;
C04B 24/2652 20130101; C04B 24/2641 20130101; C04B 40/0675
20130101; C04B 24/2676 20130101; C04B 40/0675 20130101; C04B
2103/46 20130101; C04B 40/0071 20130101; C04B 24/2652 20130101;
C04B 2103/22 20130101; C04B 2103/46 20130101; C04B 2103/50
20130101; C04B 2103/0051 20130101; C04B 2103/12 20130101; C04B
2103/12 20130101; C04B 22/124 20130101; C04B 14/08 20130101; C04B
22/124 20130101; C04B 20/008 20130101; C04B 40/0641 20130101; C04B
2103/0051 20130101; C04B 2103/408 20130101; C04B 2103/408 20130101;
C04B 2103/46 20130101; C04B 2103/408 20130101; C04B 24/2641
20130101; C04B 22/124 20130101; C04B 40/0641 20130101; C04B 40/0675
20130101; C04B 2103/50 20130101; C04B 20/0076 20130101; C04B
2103/12 20130101; C04B 2103/50 20130101; C04B 2103/22 20130101;
C04B 24/2641 20130101; C04B 2103/22 20130101; C04B 2103/46
20130101; C04B 40/0259 20130101; C04B 22/124 20130101; C04B 40/0641
20130101; C04B 2103/50 20130101; C04B 2103/408 20130101; C04B
40/0028 20130101; C04B 40/0675 20130101; C04B 40/0675 20130101;
C04B 2103/0049 20130101; C04B 24/2652 20130101; C04B 2111/00155
20130101; C04B 28/02 20130101 |
Class at
Publication: |
106/802 ;
106/823; 106/724; 106/727; 106/808 |
International
Class: |
C04B 24/00 20060101
C04B024/00; C04B 7/00 20060101 C04B007/00; C04B 40/00 20060101
C04B040/00 |
Claims
1. A composition for well cementing comprising: i. a pumpable
slurry of cement, ii. water and iii. a material having residual
water-absorption properties after the setting of the cement, so
that said material is susceptible to swell in contact with
underground water in case of failure of the cement matrix.
2. The composition of claim 1, wherein said material is a
super-absorbent polymer.
3. The cement system of claim 1, wherein the super-absorbent
polymer is selected from the list consisting of polymethacrylate
and polyacrylamide or a non-soluble acrylic polymers.
4. The cement system of claim 2, wherein the super-absorbent
polymer is added to the slurry dry-blended with the cement.
5. The cement system of claim 2, wherein the super-absorbent
polymer is added at a concentration between 0.05% and 3.2% by
weight of cement.
6. The cement system of claim 2 further comprising a salt.
7. The cement system of claim 6, wherein said salt is sodium
chloride or calcium chloride.
8. The cement slurry of claim 2, wherein the super-absorbent
polymer is added under the form of particles ranging from 10 .mu.m
to 1500 .mu.m.
9. The cement system of claim 1, whereby the material is provided
in a capsule that releases the material in response to exposure of
the cement to at least one downhole parameter.
10. The cement system of claim 1, whereby the material is provided
in a capsule that releases the material when the cement matrix
cracks.
11. The cement system of claim 1 further comprising at least one
additive selected from the list consisting of dispersing agent,
fluid loss control agent, set retarder, set accelerator and
anti-foaming agent.
12. The cement system of claim 2 whereby the material is provided
in a capsule that releases the material in response to exposure of
the cement to at least one downhole parameter.
13. The cement system of claim 2 whereby the material is provided
in a capsule that releases the material when the cement matrix
cracks.
14. The cement system of claim 2 further comprising at least one
additive selected from the list consisting of dispersing agent,
fluid loss control agent, set retarder, set accelerator and
anti-foaming agent.
Description
TECHNICAL FIELD OF THE INVENTION
[0001] The present invention relates to adaptive cement systems. In
particular, the invention relates to cement systems which are
"self-healing", i.e. system which can adapt to compensate for
changes or faults in the physical structure of the cement, or which
adapt their structure after the setting phase of the cement in the
cementing of oil, gas, water or geothermal wells, or the like.
BACKGROUND OF THE INVENTION
[0002] During the construction of underground wells, it is common,
during and after drilling, to place a liner or casing, secured by
cement pumped into the annulus around the outside of the liner. The
cement serves to support the liner and to provide isolation of the
various fluid-producing zones through which the well passes. This
later function is important since it prevents fluids from different
layers contaminating each other. For example, the cement prevents
formation fluids from entering the water table and polluting
drinking water, or prevents water from passing into the well
instead of oil or gas. In order to fulfill this function, it is
necessary that the cement be present as an impermeable continuous
sheath. However, for various reasons, over time this sheath can
deteriorate and become permeable. The deterioration can be due to
physical stresses caused by tectonic movements of temperature
effects, chemical degradation of the cement, or various other
reasons.
[0003] There have been a number of proposals to deal with the
problems of deterioration of the cement sheath over time. One
approach is to design the cement sheath to take into account
physical stresses that might be encountered during its lifetime.
Such an approach is described in U.S. Pat. No. 6,296,057. Another
approach is to include in the cement composition materials that
improve the physical properties of the set cement. U.S. Pat. No.
6,458,198 describes the addition of amorphous metal fibers to the
cement slurry to improve its strength and resistance to impact
damage. EP 1129047 and WO 00/37387 describe the addition of
flexible materials (rubber or polymers) to the cement to confer a
degree of flexibility on the cement sheath. WO 01/70646 and
PCT/EP03/01578 describe cement compositions that are formulated so
as to be less sensitive to the effects of temperature on the cement
when setting.
[0004] A number of proposals have been made for designs of
self-healing concretes for use in the construction industry. These
are described in U.S. Pat. No. 5,575,841, U.S. Pat. No. 5,660,624,
U.S. Pat. No. 5,989,334, U.S. Pat. No. 6,261,360 and U.S. Pat. No.
6,527,849, and in "Three designs for the internal release of
sealants, adhesives, and waterproofing chemicals into concrete to
reduce permeability", Dry, C. M., Cement and Concrete Research 30
(2000) 1969-1977. None of these are immediately applicable to well
cementing operations because of the need for the cement to be
pumpable during placement and because of the pressure and
temperature range.
[0005] It is an objective of the present invention to provide well
cementing systems that can be placed by pumping in the normal
manner, and which contain materials that allow the cement sheath to
adapt its structure in response to environmental conditions.
SUMMARY OF THE INVENTION
[0006] More precisely, the present invention aims at providing well
cementing systems that include at least one additive that reacts
and/or swells when the set cement is in contact with an aqueous
fluid, such as formation waters. This behavior has the effect of
making the cement self-healing in the event of physical failure or
damage.
[0007] The additive is a material which reacts/expands in contact
with water--for instance from the underground formation which
enters a fault in the cement matrix. Examples of such materials
include super-absorbent polymers. Super-absorbent polymers are
crosslinked networks of flexible polymer chains. The most efficient
water absorbers are polymer networks that carry dissociated, ionic
functional groups. When super-absorbent polymers absorb liquids, an
elastic gel forms. The gel is a soft, deformable solid composed of
water and the expanded polymer chains.
[0008] The polymer particles can be of almost any shape and size:
spherical, fiber-like, ovoid, mesh systems, ribbons, etc., which
allows their easy incorporation in cement slurries of comprising
solid materials in discrete particle size bands. In practice,
polymer particles ranging from about 10 to about 1500 .mu. can be
used.
[0009] The absorbent materials are preferably dry blended with the
cement and any other solid components before transport to the
well-site, mixing with water and placement in the well. The sizes
and quantities will be selected to allow even dispersion through
the cement matrix.
[0010] It has been found that though the super-absorbent polymers
such as polyacrylamide and modified crosslinked polymethacrylate
swell when incorporated in a cement slurry, they seem to release at
least part of the absorbed water during the cement hydration and
hence, have a reserve of absorbability that allow them to swell
again if they are later exposed to water due to a crack of the
matrix for instance. Since they are highly reactive with water, the
concentration of super-absorbent added to the blend must remain
relatively small, compositions with more than 3.2% of
super-absorbent (by weight, of cement) may typically have a
viscosity too high for pumping the slurry in favorable conditions.
In fact the maximum SAP concentration depends on the slurry density
and also on the nature of the Super Absorbent Polymer.
[0011] It has been found that the addition of salts such as sodium
chloride or calcium chloride for instance favors the rheology of
the systems thereby enabling increasing the concentration of
super-absorbent polymers. Cement slurries of lower density have
also a greater acceptability of higher concentrations of
super-absorbent polymers, even without salt.
[0012] In another aspect of the present invention, at least part of
the super-absorbent polymers are encapsulated so that they are--for
instance in the form of a resin or other material that releases the
polymer in response to exposure to a downhole parameter (for
instance such as temperature, a specific mineral system, pressure,
shear etc). In yet another aspect, the rupture of the encapsulating
means is actually induced by the failure of the cement matrix, in a
way similar to the mechanism described by Dry for instance in U.S.
Pat. No. 5,575,841, U.S. Pat. No. 5,660,624, U.S. Pat. No.
5,989,334, U.S. Pat. No. 6,261,360 and U.S. Pat. No. 6,527,849.
DETAILED DESCRIPTION
[0013] A screening has been carried out for identifying
super-absorbent polymers suitable for self-healing cementing
applications. The main issues were to check the ability to dry
blend the polymers with cement and to optimize the rheology and
thickening time.
Testing Procedure
[0014] Tests have been carrying out by incorporating powders of
various types of polymers as solid additives in cement slurries.
Properties of the slurry as well as properties of the set cement
have been studied.
[0015] The slurries were optimized with the mere objective of
obtaining stability. Focus was to get acceptable plastic viscosity
(PV) and yield stress (TY) at mixing time and after 20 minutes of
conditioning. Free water and sedimentation tests were also carried
out. Mixing and test procedure was according to API Spec 10.
[0016] The same equipment and bob was used for all rheology
measurements, whatever the tested design. Many tests were performed
at one slurry density (15.8 lbm/gal) and one temperature (BHCT
equal to 60.degree. C.). Some examples were studied at 12 lbm/gal
and at 14 lbm/gal. For lowest density, the temperature is equal
25.degree. C. and 85.degree. C. The design is based on tap water
and black Dyckerhoff North cement. Unless otherwise mentioned, all
designs include an antifoam agent based on polypropylene glycol at
0.03 gallon per US gallons per sack of 94 lbs of cement (in other
words, 1 gps=88.78 cc/kg), polynapthalene sulfonate as dispersing
agent at 0.04 gps and the superabsorbent polymer at concentration
ranging form 0.1% BWOC (by weight of cement) to 0.9% BWOC for 15.8
lbm/gal. Decreasing the density allows to increase the
concentration in Super Absorbent Polymer. For instance for a given
SAP the maximum concentration at 15.8 lbm/gal is 1% bwoc without
salt in the mixing water and can reach 3% bwoc at 12 lbm/gal.
[0017] Three types of superabsorbent polymers were tested:. S1, a
polyacrylamide available form Lamberti, Italy. Three grades were
tested, namely S1G-Lamseal.RTM. G, with particles ranging form 500
.mu. to 1500 .mu. (density 1.25 g/cm.sup.3), S1GS-Lamseal.RTM. GS,
with particles of about 200 .mu. (density 1.48 g/cm.sup.3), and
S1GM, Lamseal.RTM. GM, with particles of about 700.mu.(density 1.47
g/cm.sup.3). S2, a modified polyacrylate available from Itochu,
Japan, under the name Aqualic.RTM. CS-6HM, selected for its salt
resistance, in particular its capacity to keep super absorbent
capacity in high valent metal ions solutions. The average particle
size is 100 .mu. and the density 1.46 g/cm.sup.3. S3, a non soluble
acrylic polymers , Norsocryl C200 from Atofina with particles of
about 250 .mu. in average (density 1.6 g/cm.sup.3).
[0018] In the examples, bwoc or BWOC stands for by weight of cement
and bwow or BWOW for by weight of water.
EXPERIMENTAL RESULTS
Example 1
Addition Procedure
[0019] The first step was to define the best addition process. As
shown in table 1 below, dry blending induces lower effects on
rheology and free water and leads to an easy mixing TABLE-US-00001
TABLE 1 Design Reference A1 A2 A3 S1G (% bwoc) 0.1 0.1 0.1 Note
prehydrated prehydrated (static) dry blended under agitation at
2000 RPM during 15 minutes. Mixing rheology Ty (lbf/100 ft.sup.2)
2.3 2.8 1.4 3.2 PV (cP) 25.5 18.9 27.2 32.4 BHCT rheology at
60.degree. C. Ty (lbf/100 ft.sup.2) 24.6 21.2 27.3 52.8 PV (cP)
20.9 18.4 26.6 33.3 10'/1'gel 25/16 14/9 19/11 15/13 Free Water mL
1 7 trace 2.5 Sedimentation 1.14 1 0.4 0.7 ppg
Example 2
Influence of the Particle Sizes
[0020] For the S1 particles, the finer the particles, the higher
the rheology and free water. TABLE-US-00002 TABLE 2 Design
Reference S1 G S1 GM S1GS S1 (% bwoc) 0.1 0.1 0.1 Mixing rheology
Ty (lbf/100 ft.sup.2) 2.3 1.4 2.7 6.7 PV (cP) 25.5 27.2 29 41 BHCT
rheology at 60.degree. C. Ty (lbf/100 ft.sup.2) 24.6 27.3 24.4 38.7
PV (cP) 20.9 26.6 35.6 40.9 10'/1'gel 25/16 19/11 15/12 12/9 Free
Water mL 1 trace 2 4 Sedimentation ppg 1.14 0.4 1 0.9
Example 3
[0021] This test shows that cement slurry with super-absorbent
polymers S1 are compatible with conventional fluid loss control
additive (flac). This shows that the composition of the present
invention can still be optimized by the addition of conventional
additives such as dispersing agent, fluid loss control agent, set
retarder, set accelerator and anti-foaming agent. TABLE-US-00003
TABLE 3 Design X3.1 X3.2 S1G (% bwoc) 0.1 0.1 Flac 0.4 Mixing
rheology Ty (lbf/100 ft.sup.2) 1.4 7.9 PV (cP) 27.2 104.7 BHCT
rheology at 60.degree. C. Ty (lbf/100 ft.sup.2) 27.3 13.7 PV (cP)
26.6 125 10'/1'gel 19/11 13/7 Free Water mL trace trace
Example 4
[0022] Results with the polymethacrylate based superabsorbent
polymer S2 show less sensitivity to the addition mode.
TABLE-US-00004 TABLE 4.1 Design Reference X4.1 X4.2 X4.3 X4.4 S2 (%
bwoc) 0.05 0.1 0.1 0.15 -- dry blended dry blended prehydrated dry
blended Mixing rheology Ty (lbf/100 ft.sup.2) 2.3 4.8 5.6 6.4 5.3
PV (cP) 25.5 31.9 35.9 37.9 64.8 BHCT rheology at 60.degree. C. Ty
(lbf/100 ft.sup.2) 24.6 20.2 23.3 20.7 19.9 PV (cP) 20.9 24.3 22.4
30.3 57 10'/1'gel 25/16 17/9 15/9 12/7 12/10 Free Water mL 1 2.8
4.5 5.5 Sedimentation ppg 1.14 0.6 0.6 0.9 1
[0023] Polymer S2 can also be added in higher quantity, at least up
to 0.45% BWOC as shown in the following table 4.2: TABLE-US-00005
TABLE 4.2 Design Reference 1 2 3 4 antifoam (gps) 0.03 0.03 0.03
0.03 0.03 Dispersing agent (gps) 0.04 0.04 0.04 0.04 0.04 S2 (%
bwoc) 0 0.9 (exces) 0.2 0.45 0.45 S2 (% bwow) 0 2 0.44 1 1 Remarque
dry blended dry blended dry blended prehydrated Mixing rheology Ty
(lbf/100 ft.sup.2) 2.3 Too 8.3 19.7 24.9 PV (cP) 25.5 viscous 52.2
142.8 228.7 Comment Difficult mixing BHCT rheology at 60.degree. C.
Ty (lbf/100 ft.sup.2) 24.6 Too viscous 14.3 25.8 11.6 PV (cP) 20.9
40.3 172.5 178.4 10'/1'gel 25/16 14/9 25/7 18/9 Free water mL 1 0 7
6 4.5 Sedim ppg 1.14 0.1 1.2 0.2 0.2
Example 5
[0024] This example shows that the setting properties and the
rheological properties can be optimized, a key requirement for well
cementing applications. In all cases, the super-absorbent polymer
was dry blended with the cement. TABLE-US-00006 TABLE 5.1 Design 8
9 10 S2 (% bwoc) 0.1 0.1 0.1 Antifoam (gps) 0.03 0.03 0.03
Lignosulfonate (gps) 0.05 -- 0.025 Fluid loss control agent (gps)
0.4 0.4 0.4 Polynaphtalene (gps) 0.045 0.045 0.045 Mixing Ty
(lbf/100 ft.sup.2) 10.4 11 10.6 rheology PV (cP) 121.9 134 125.8
BHCT Ty (lbf/100 ft.sup.2) 15.5 16.7 16 rheology PV (cP) 132 132.4
129 at 60.degree. C. 10'/1'gel 24/10 9/5 12/7 Free water mL 0 0 0
Sedimentation ppg 0.2 0.2 0.4 Thickening test 100 Bc 13 h 30 min 3
h 03 min 8 h 49 min (hh:min)
[0025] TABLE-US-00007 TABLE 5.2 Design 29 30 31 32 Antifoam (gps)
0.03 0.03 0.03 0.03 Lignosulfonate (gps) 0.025 0.025 0.025 0.025
Fluid loss control agent (gps) 0.4 0.4 -- 0.2 Polynaphtalene (gps)
0.045 0.6 0.045 0.045 Mixing rheology Ty (lbf/100 ft.sup.2) 46.8
41.9 23 32 PV(cP) 303 293 92 154 BHCT rheology at 60.degree. C. Ty
(lbf/100 ft.sup.2) 32 35 6.6 19 PV(cP) 226 248 66 145 10'/1'gel
12/7 11/6 11/7 9/4 Free water mL Trace Trace 10 2.5
[0026] In the table 5.2, the designed slurries have a density of
15.8 lbm/gal, and the concentration of super-absorbent S2 is 0.3%
bwoc (corresponding to 0.7% bwow). TABLE-US-00008 TABLE 5.3 Design
33 34 35 Antifoam (gps) 0.03 0.03 0.03 Lignosulfonate (gps) 0.025
0.025 -- NaCl (by weight of water) 37 Fluid loss control agent
(gps) 0.2 0.15 -- Polynaphtalene (gps) 0.045 0.045 0.9 Mixing
rheology Ty (lbf/100 ft.sup.2) 46.8 45 4.4 PV (cP) 223 208 61 BHCT
rheology at 60.degree. C. Ty (lbf/100 ft.sup.2) 27 50 14 PV (cP)
217 240 51 10'/1'gel 10/5 10/7 20/9 Free water mL 1.5 1 -- API
Fluid loss (ml) 170
[0027] In the table 5.3, the designed slurries have a density of
15.8 lbm/gal, and the concentration of super-absorbent S2 is 0.4%
bwoc (corresponding to 0.9% bwow).
Example 6
[0028] This example shows that the addition of a salt allows an
increase of the concentration of superabsorbent polymer while
keeping acceptable rheology properties. In table 6.1, tests have
been carried out with sodium chloride as added salt. In table 6.2,
the added salt is calcium chloride. In both tables, the cements
have a density of 15.8 ppg. TABLE-US-00009 TABLE 6.1 Design 1 36 37
38 S2 (% bwoc) 0.9 0.9 0.9 0.9 Antifoam (gps) 0.03 0.03 0.05 0.05
NaCl (by weight of water) 0 37 18.5 37 Polynaphtalene (gps) 0.04
0.9 0.9 1.5 Mixing rheology Ty (lbf/100 ft.sup.2) Too viscous 13.4
27.1 61.8 PV (cP) 119 207 352 BHCT rheology at 60.degree. C. Ty
(lbf/100 ft.sup.2) 30.7 31.5 59 PV (cP) 107 1059 433 10'/1'gel
28/19 -- 433 Free water mL Trace
[0029] TABLE-US-00010 TABLE 6.2 Design 70 81 Antifoam (gps) 0.05
0.05 Flac (gps) 0.5 -- Lignosulfonate (gps) 0.05 -- Polynaphtalene
(gps) -- 0.9 Sulfonated melamine-formaldehyde (gps) 0.12 -- Sodium
chloride (% BWOW) -- 37 Calcium chloride (% BWOC) 2 -- S2 (% BWOC)
0.45 0.9 Mixing rheology Ty (lbf/100ft.sup.2) 29 30 PV (cP) 244 173
BHCT tests at 60.degree. C. Rheology Ty (lbf/100 ft.sup.2) 34 22
PV(cP) 211 110 10'gel/1'stiring 17/9 23/10 Free water (mL) 0 0
Fluid loss (mL API) 78 18 Thickening time 5 h 17 min --
Example 7
[0030] This example shows that if the slurry density is lower,
higher concentration of super-absorbent polymers can be used, even
without the addition of a salt. TABLE-US-00011 Design X7.1 X7.2
X7.3 Density (lbm/gal) 14 12 12 BHCT (deg C.) 60 25 85 Antifoam
(gps) 0.03 0.02 0.02 Flac (gps) 0.4 -- -- Lignosulfonate (gps)
0.025 -- -- Polynaphtalene (gps) 0.045 0.03 0.03 S2 (% bwoc) 0.9 3
3 S2 (% bwow) 1.4 2.4 2.4 Mixing rheology Ty (lbf/100 ft.sup.2)
21.18 19.2 19.63 PV (cP) 156.9 90.3 86.39 Rheology at BHCT Ty
(lbf/100 ft.sup.2) 49.31 27.5 4.92 PV (cP) 180.5 169.7 82.78
10'gel/1'stiring 32/22 28/12 11/6 Fluid loss (mL API) -- 149
240
Example 8
[0031] Cement samples comprising super-absorbent polymers were
taken form the sedimentation column and additional water was added
at the surface of broken pieces to simulate contact with formation
water after a crack. Tests were performed at room temperature and
at 60.degree. C. In all cases, swelling was observed showing that
the super-absorbent polymer particles remain effectively available
to absorb additional water (even though the cement matrix always
comprises residual water).
Example 9
[0032] This test was performed with super-absorbent S3. Good
rheology is obtained. TABLE-US-00012 TABLE 9 Design 5 13 19 Density
(lbm/gal) 15.8 15.8 15.8 BHCT (deg C.) 60 60 60 Antifoam (gps) 0.05
0.03 0.05 Flac (gps) 0.5 0.4 -- Lignosulfonate (gps) 0.05 0.025 --
Polynaphtalene (gps) -- 0.05 0.9 Sulfonated melamine formaldehyde
(gps) 0.12 -- -- Sodium chloride (% BWOW) -- -- 37 Calcium chloride
(% BWOC) 2 -- -- S3 (% bwoc) 3 0.9 2 S3 (% bwow) 7.7 2.2 4.5 Mixing
rheology Ty(lbf/100 ft.sup.2) 26 19 4 PV (cP) 262 195 54 BHCT
Rheology Ty (lbf/100 ft.sup.2) 13 19 4 PV (cP) 154 145 30
10'gel/1'stiring 7/5 14/4 15/6 Free water (mL) 0 0 -- Fluid loss
(mL API) 48 -- --
* * * * *