Title: Cementing compositions and application of such compositions for cementing oil wells or the like
Abstract: The present invention provides cementing compositions for oil wells or the like comprising an hydraulic binder and reinforcing particles constituted by a flexible material of low compressibility, and with an average grain size of less than 500 microns. The compositions of the invention are of particular advantage when cementing zones which are subjected to extreme dynamic stresses, such as perforation zones and the junctions of a multi-branch lateral well. They are also highly suitable for producing plugs.
Patent Number: 6,902,001 Issued on 06/07/2005 to Dargaud, et al.
| Inventors:
|
Dargaud; Bernard (Elancourt, FR);
Le Roy-Delage; Sylvaine (Paris, FR);
Thiercelin; Marc (Ville d'Avray, FR)
|
| Assignee:
|
Schlumberger Technology Corporation (Sugar Land, TX)
|
| Appl. No.:
|
457964 |
| Filed:
|
June 10, 2003 |
| Current U.S. Class: |
166/293; 166/295 |
| Intern'l Class: |
E21B 033/13 |
| Field of Search: |
166/293,295
|
References Cited [Referenced By]
U.S. Patent Documents
Primary Examiner: Marcantoni; Paul
Attorney, Agent or Firm: Nava; Robin, Echols; Brigitte L., Ryberg; John J.
Claims
1. A method of cementing a well, comprising pumping into the well a slurry comprising
water, a cement; and reinforcing particles having an average grain size not exceeding
500 μm, and being formed from a flexible material having a Poisson ratio
of more than 0.3, the flexible material being selected from the group consisting
of polyamide, polypropylene, polyethylene, styrene butadiene and styrene divinylbenzene.
2. A method as claimed in claim 1, comprising pumping the slurry into a zone
of a well that is subjected to dynamic stresses.
3. A method as claimed in claim 2, comprising pumping the slurry into a perforation
zone of the well.
4. A method as claimed in claim 2, comprising pumping the slurry into a junction
of a multi-branch lateral well.
5. A method as claimed in claim 1, comprising pumping the slurry into the well
as a plug.
6. A method as claimed in claim 1, wherein the reinforcing particles have an
average grain size in the range 80 μm to 500 μm.
7. A method as claimed in claim 6, wherein the reinforcing particles have an
average grain size in the range 100 μm to 400 μm.
8. A method as claimed in claim 1, wherein the reinforcing particles are formed
from a material having a Young's modulus of less than 5000 MPa.
9. A method as claimed in claim 8, wherein the particles are formed from a material
having a Young's modulus of less than 3000 MPa.
10. A method as claimed in claim 9, wherein the particles are formed from a material
having a Young's modulus of less than 2000 MPa.
11. A method as claimed in claim 1, wherein the density of the reinforcing particles
is less than 1.5 g/cm
3.
12. A method as claimed in claim 11, wherein the density of the reinforcing particles
is less than 1.2 g/cm
3.
13. A method as claimed in claim 1, wherein the slurry further comprises at least
one additive selected from the group consisting of suspension agents, dispersing
agents, anti-foaming agents, retarders, setting accelerators, fluid loss control
agents, gas migration control agents, and expansion agents.
14. A method as claimed in claim 13, wherein the reinforcing particles comprise
5% to 40% of the total volume of the slurry.
Description
The present invention relates to techniques for drilling oil, gas, water, or
geothermal wells or the like. More precisely, the invention relates to cementing
compositions which are particularly suitable for cementing zones which are subjected
to extreme dynamic stresses.
In general, a well which is over a few hundred meters deep is cased and the annular
space between the subterranean formation and the casing is cemented over all or
part of its depth. Cementing essentially prevents the exchange of fluid between
the different layers of formation traversed by the hole and controls the ingress
of fluid into the well, and in particular limits the ingress of water. In production
zones, the casing—and the cement and the formation—is perforated
over a height of several centimeters.
The cement placed in the annular space of an oil well is subjected to a number
of stresses throughout the lifetime of the well. The pressure inside a casing can
increase or decrease because the fluid which fills it can change or because a supplemental
pressure is applied to the well, for example when the drilling fluid is replaced
by a completion fluid, or during a stimulation operation. A change in temperature
also creates stress in the cement, at least during the transition period preceding
temperature equilibration between the steel and the cement. In the majority of
the above cases, the stress event is sufficiently slow for it to be treated as
a static event.
However, the cement is subject to other stresses which are dynamic in nature,
either because they are produced over a very short period or because they are either
periodic or repetitive in nature. Perforations create an over-pressure of several
hundred bars inside a well which is dissipated in the form of a shock wave. Further,
perforations create a shock when the projectile penetrates the cement and that
shock subjects the zone surrounding the hole to large forces over a depth of several meters.
A further event, which is now routine in oil well operations and which creates
dynamic stresses in the cement, is the opening of a window in a casing which is
already cemented to create a multi-branch lateral well. Milling the steel over
a depth of several meters followed by drilling a lateral well subjects the cement
to shocks and vibrations which frequently damage it irreparably.
The present invention aims to provide novel formulations, in particular for cementing
regions of oil wells or the like which are subjected to extreme dynamic stresses.
In an article presented at the SPE (Society of Petroleum Engineers) annual technical
conference and exhibition of 1997, Marc Thiercelin et al. (SPE 38598, 5-8 Oct.
1997)—and French patent application FR-A-97 11821 of 23
rd Sep.
1997, demonstrated that the risk of rupture of a cement sleeve depends on the thermoelastic
properties of the casing, the cement and the formation surrounding the well. A
detailed analysis of the mechanisms leading to rupture of the cement sleeve has
shown that the risk of rupture of a cement sleeve following an increase in pressure
and/or temperature in the well is directly linked to the tensile strength of the
cement and is attenuated when the ratio between the tensile strength R
T
of the cement and its Young's modulus E is increased.
Young's modulus is known to characterize the flexibility of a material. To
increase the R
T/E ratio, it is advantageous to select materials with
a low Young's modulus, in other words to select very flexible materials.
One known means for increasing the flexibility of a hardened cement is to reduce
the density of the slurry by extending it with water. However, that leads to a
degradation in the stability of the slurry, in particular with separation of the
solid and liquid phases. Such phenomena can, of course, be controlled in part by
adding materials such as sodium silicate, but the permeability of the hardened
cement is nevertheless very high, which means that it cannot fulfill its primary
function of isolating zones to prevent fluid migration, or at least it cannot guarantee
its long-term isolation. Further, lightened cements have lower strength, in particular
lower shock resistance, which constitutes a clear handicap for cements intended
for use in zones which are subjected to extreme mechanical stresses such as perforation zones.
In the building field, incorporating particles of rubber into a concrete is known
to result in better resilience, durability and elasticity (see, for example, A.
B. Sinouci, Rubber-Tire Particles as Concrete Aggregate, Journal of Materials in
Civil Engineering, 5, 4, 478-497 (1993)]. Concretes which include rubber particles
in their formulation can be used, for example, in highway construction to absorb
shocks, in anti-noise walls as a sound insulator and also in constructing buildings
to absorb seismic waves during earthquakes. In such applications, the mechanical
properties in particular are improved.
In the field of oil well cementing, it is also known [Well Cementing 1990, E.
B. Nelson, Schlumberger Educational Services] that adding ground rubber particles
(grain size in the range 4-20 mesh) can improve the impact strength and bending
strength. Such an improvement in mechanical properties has also been indicated
in Russian patents SU-1384724 and SU-1323699. More recently, U.S. Pat. No. 5,779,787
has proposed the use of particles derived from recycled automobile tires with grain
size in the range 10/20 or 20/30 mesh, to improve the mechanical properties of
hardened cements, in particular to improve their elasticity and ductility.
The present invention aims to provide oil well cements reinforced with flexible
particles, of low compressibility, with low density and with an average size not
exceeding 500 μm.
The term "flexible particles" means particles made of a material having a Young's
modulus of less than 5000 MPa, preferably less than 3000 MPa, more preferably less
than 2000 MPa. The elasticity of the materials selected for these flexible particles
is thus at least tour times greater than that of cement and more than thirteen
times that of the silica usually used as an additive in oil well cements.
The flexible particles added to the cementing compositions of the invention are
also remarkable because of their low compressibility and are characterized by a
Poisson ratio of over 0.3.
In order to lighten the slurry, it is also important for the density the flexible
particles to be less than 1.5 g/cm
3, preferably less than 1.2 g/cm
3,
more preferably less than 1 g/cm
3. Preferably, this low density is intrinsic
in the choice of the constituent materials and not by dint of high porosity or
hollow particles. Preferably again, materials of low porosity are used.
Further, the particles must be insoluble in an aqueous medium which may
be saline, and must be capable of resisting a hot basic medium, since the pH of
a cementing slurry is generally close to 13 and the temperature in a well is routinely
over 100° C.
Regarding particle size, essentially isotropic particles are preferred.
Spherical or near spherical particles may be synthesized directly, but usually
the particles are obtained by grinding, in particular cryo-grinding. The average
particle size is generally in the range 80 μm to 500 μm, preferably
in the range 100 μm to 400 μm. Particles which are too fine, or on
the other hand too coarse, are difficult to incorporate into the mixture or result
in pasty slurries which are unsuitable for use in an oil well.
Particular examples of materials which satisfy the various criteria cited
above are thermoplastics (polyamide, polypropylene, polyethylene, . . . ) or other
polymers such as styrene divinylbenzene or styrene butadiene (SBR). Recycled products
are generally not preferred because of the variability in supply sources and in
physico-chemical properties.
In addition to the flexible particles of the invention, the cementing compositions
of the invention comprise a hydraulic binder, in general based on Portland cement
and water. Depending on the specifications regarding the conditions for use, the
cementing compositions can also be optimized by adding additives common to the
majority of cementing compositions, such as suspension agents, dispersing agents,
anti-foaming agents, expansion agents (for example magnesium oxide), fine particles,
fluid loss control agents, gas migration control agents, retarders or setting accelerators.
Thus the systems are either bimodal in type, the solid fraction of the slurry being
constituted by a mixture of cement and flexible particles, or they can comprise
three (trimodal) or more types of solid constituents, the solid mixture comprising
fine micronic particles and possibly submicronic particles in addition to the cement
and flexible particles.
The volume of flexible particles represents between 5% and 40% of the total volume
of the cementing slurry, preferably between 10% and 35%, and preferably again,
between 15% and 30% of the total slurry volume.
The formulations of the invention are preferably based on Portland cements in
classes A, B, C, G and H as defined in Section 10 of the American Petroleum Institute's
(API) standards. Classes G and H Portland cements are particularly preferred but
other cements which are known in this art can also be used to advantage. For low-temperature
applications, aluminous cements and Portland/plaster mixtures (deepwater wells,
for example) or cement/silica mixtures (for wells where the temperature exceeds
120° C., for example) can be used.
The water used to constitute the slurry is preferably water with a low mineral
content such as tap water. Other types of water, such as seawater, can possibly
be used but this is generally not preferable.
These particles with low density with respect to the cement can reduce the
density of the slurry and result in lower permeability and better impact resistance.
It also affects the flexibility of the system, since adding flexible particles
produces cements with a lower Young's modulus.
The compositions comprising flexible particles of the invention have remarkable
mechanical properties which render them particularly suitable for cementing in
areas of an oil well which are subjected to extreme stresses, such as perforation
zones, junctions for branches of a lateral well or plug formation.
BRIEF DESCRIPTION OF THE DRAWINGS
The present invention is illustrated below in the following examples, along with
the enclosed drawings that show:
FIG. 1 plots the rupture modulus vs. the concentration of flexible particles
(in % vol.) for different types of particles;
FIG. 2 plots the Young/s modulus vs. the concentration of flexible particles
(in % vol.) for different types of particles;
FIG. 3 plots the bending Young's modulus vs. the concentration of flexible particles
(in % vol.) for different types of particles;
FIG. 4 plots compressive strength vs. the concentration of flexible particles
(in % vol.) for different types of particles;
FIG. 5 plots the compression Young's modulus vs. the concentration of flexible
particles (in % vol.) for different types of particles;
FIG. 6 plots the tensile strength of the cement vs. the bending Young's modulus
of the cement, showing the requirements for three rock types (hard, medium and
weak rock);
FIG. 7 plots the rupture modulus in bending (in MPa) vs. the effective porosity
(in %), defined as the sum of the porosity of the hardened cement and the volume
percentage of the flexible particles;
FIG. 8 plots the Young's modulus in bending (in MPa) vs. the effective porosity
(in %).
EXAMPLE 1
Formulations for Cement Slurries with Styrene Divinylbenzene Particles
In this example, particles of styrene divinylbenzene (STDVB) with grain size
in
the range 45-100 mesh (355 μm-150 μm) were tested.
The cement slurries were composed of Portland Dyckerhoff North class G cement,
styrene divinylbenzene particles, water, a dispersing agent and a retarder. The
formulations and properties of the cement slurry are given in Tables 1 to 3; they
were all optimized to the same temperature (76.7° C.—170° F.);
two cement slurry densities ρ were selected (1.677 g/cm
3—14
ppg and 1.431 g/cm
3—12 ppg). The dispersing agent was a polynaphthalene
sulfonate; the retarder was a lignosulfonate.
| TABLE 1 |
| Formulations for cement slurries with STDVB particles |
| Slurry |
STDVB |
Dispersing |
Retarder |
ρ |
Porosity of |
| n° |
% bwoc |
% vol |
agent gps |
gps |
g/cm3 |
slurry φ |
| A1 |
27.8 |
24.8 |
0.012 |
0.06 |
1.666 |
45% |
| A2 |
50.9 |
30.0 |
0.014 |
/ |
1.450 |
50% |
- bwoc is the abbreviation for "by weight of cement";
- % vol corresponds to the volume of flexible particles in the slurry
(aqueous and solid phases);
- gps is the abbreviation for "gallons per sack", namely 3.78541 liters
per sack of 42.637 kilograms (kg) of cement, in other words, 1 gps=0.0888 liters
(l) of additive per kg of Portland cement.
The rheology of the cement slurry and the free water were measured using the
procedure recommended in API 10 (American Petroleum Institute). At laboratory temperature,
the rheology was measured immediately after mixing and after 20 minutes of conditioning
to temperature. The results are shown in Table 2. The rheology of a slurry is characterized
by its plastic viscosity PV (in cP or mPa.s), the conversion factor being equal
to 1) and the yield point or Ty (in lbf/100 ft
2, conversion to Pascals
being obtained by multiplying by 0.478803), assuming the slurry to be a Bingham fluid.
| TABLE 2 |
| Rheology and free water for systems with STDVB particles |
| |
Rheology after |
|
|
| |
mixing at labora- |
| |
tory temperature |
Rheology after conditioning |
Free water |
| Formula- |
PV |
Ty (lbf/ |
at 76.6° C. |
after 2 |
| tion |
(mPa.s) |
100 ft2) |
PV (mPa.s) |
Ty (lbf/100 ft2) |
hours (ml) |
| A1 |
35.4 |
30 |
66.4 |
7.2 |
2 |
| A2 |
24.5 |
4.1 |
40.7 |
20.3 |
0 |
The development of the compressive strength during setting of the cement was
evaluated by UCA (Ultrasonic Cement Analyzer) measurements. These measurements
enabled the setting time required to produce a given strength (0.34 MPa—50
psi and 3.4 MPa=500 psi) and the compressive strength Rt obtained after a given
time (72 hours) at a pressure of 3000 psi (20.7 MPa) to be determined.
| TABLE 3 |
| UCA and setting time at T = 76.6° C. for systems |
| with STDVB particles |
| |
Time to 0.34 |
Time to 3.4 |
|
Setting |
| |
MPa at |
MPa at |
Compressive strength |
time |
| N° |
T (min) |
T (min) |
after 72 hours (psi) |
(min) |
| A1 |
970 |
1088 |
3000 |
270 |
| A2 |
171 |
383 |
1167 |
210 |
EXAMPLE 2
Formulations for Cement Slurries with Polyamide Particles
The cement slurries were principally composed of Portland Dyckerhoff North class
G cement, polyamide particles, water, a dispersing agent, a retarder and an anti-foaming agent.
A number of polyamides were tested: Nylon 6, Nylon 12 and a polyamide 11, the
principal
characteristics of which are shown in Table 4.
| TABLE 4 |
| Characteristics of test polyamides |
| |
|
|
|
Average |
|
| |
|
Product |
|
grain |
ρ |
| Source |
Supplier |
name |
Polyamide |
size (μm) |
(g/cm3) |
| 1 |
Goodfellow |
AM306015 |
Nylon 6 |
350 |
1.13 |
| 2 |
Goodfellow |
AM306010 |
Nylon 6 |
15-20 |
1.13 |
| 3 |
Elf Atochem |
Rilsan |
11 |
100 |
1.0 |
| 4 |
Huls |
Vestosint 1111 |
Nylon 12 |
100 |
1.06 |
The formulations and properties of the cement slurry are shown in Tables 5 to
9. They were all formulated at the same temperature (76.7° C.—170°
F.), the same slurry density (14 ppg), and different grain sizes were studied.
The dispersing agent used was a polynaphthalene sulfonate; the retarder was a lignosulfonate.
The fine particles used for test B2 was filtered fly ash, a detailed description
of which is given in French patent FR-A-96 1176. The magnesium oxide added for
test B5 acted as an expansion agent.
| TABLE 5 |
| Cement slurry with polyamide particles - list of formulations |
| |
|
Polyamide |
| N |
Description of solid fraction |
source |
| B1 |
Bimodal mixture: cement + polyamide |
1 |
| B2 |
Trimodal mixture: cement + polyamide + fine particles |
1 |
| B3 |
Trimodal mixture: cement + nylon 350 μm + |
1 and 2 |
| |
nylon 15-20 μm |
| B4 |
Bimodal mixture: cement + polyamide |
3 |
| B5 |
Bimodal mixture: cement + polyamide + |
1 |
| |
magnesium oxide |
| B6 |
Bimodal mixture: cement + polyamide |
4 |
It should be noted that it was not possible to prepare a slurry with source 2
alone as the slurry was too viscous even with a low concentration of reinforcing particles.
| TABLE 6 |
| Formulations for cement slurries with polyamide particles |
| |
Polyamides |
Fine |
Dispersing |
Retarder |
Anti-foaming |
ρ |
|
| |
% bwoc |
% vol |
% bvob |
agent gps |
gps |
agent gps |
g/cm3 |
φ |
| |
| B1 |
29.4 |
24.8 |
/ |
/ |
0.097 |
/ |
1.67 |
45% |
| B2 |
22.8 |
19.3 |
10 |
0.026 |
0.051 |
0.037 |
1.75 |
45% |
| B3 |
22.8 |
24.8 |
10 |
0.018 |
0.073 |
/ |
1.67 |
45% |
| B4 |
17.8 |
16.8 |
/ |
/ |
0.066 |
0.033 |
1.67 |
52% |
| B6 |
18.1 |
16.7 |
/ |
/ |
0.067 |
0.033 |
1.67 |
52% |
| TABLE 7 |
| Formulation for cement slurry with polyamide particles and an expansion agent |
| |
Polyamides |
Expansion agent |
Dispersing |
Retarder |
Anti-foaming |
Extension |
ρ |
|
| |
% bwoc |
% bwoc |
agent gps |
gps |
agent gps |
agent gps |
g/cm3 |
φ |
| |
| B5 |
24.9 |
5 |
0.059 |
0.176 |
0.035 |
0.106 |
1.77 |
45% |
| |
(22.6% vol) |
| TABLE 8 |
| Rheology and free water for systems with |
| polyamide particles |
| |
Rheology after |
|
|
| |
mixing at labora- |
| |
tory temperature |
Rheology after conditioning |
Free water |
| Formula- |
PV |
Ty (lbf/ |
at 76.6° C. |
after 2 |
| tion |
(mPa.s) |
100 ft2) |
PV (mPa.s) |
Ty (lbf/100 ft2) |
hours (ml) |
| B1 |
156.2 |
1.0 |
118.9 |
17.0 |
1.5 |
| B2 |
203.9 |
26.6 |
215.4 |
35.4 |
2.0 |
| B3 |
475.8 |
13.6 |
294.6 |
26.5 |
0 |
| B4 |
47.7 |
4.4 |
34.4 |
30.2 |
3.0 |
| B5 |
230.5 |
1.0 |
48.9 |
26.4 |
0.5 |
| B6 |
48.6 |
4.6 |
44.1 |
24.3 |
3 |
| TABLE 9 |
| UCA and setting time at 76.7° C. (170° F.) for |
| systems with polyamide particles |
| |
Time to 0.34 |
Time to 3.4 |
|
Setting |
| Formula- |
MPa at |
MPa at |
Compressive strength |
time |
| tion |
T (min) |
T (min) |
after 72 hours (psi) |
(min) |
| B1 |
1695 |
1916 |
1500 |
348 |
| B2 |
525 |
585 |
2377 |
221 |
| B3 |
580 |
699 |
1703 |
170 |
| B4 |
708 |
827 |
1829 |
205 |
| B5 |
661 |
738 |
2167 |
263 |
EXAMPLE 3
Formulations for Cement Slurries with Polypropylene Particles
The cement slurries were composed of Portland Dyckerhoff North Class G cement,
polypropylene particles, water, a dispersing agent, a retarder and an anti-foaming
agent. The polypropylene used in this Example was produced by ICO Polymer under
the trade name ICORENE 9013P. Its density was 0.905 g/cm
3. Its initial
grain size specification was such that at most 5% of particles had a size of more
than 800 μm, 30% had a size of more than 500 μm and less than 5% of
the particles had a size of less than 200 μm. For these tests, the particles
were also sieved at 300 μm. The polypropylene from Solvay, trade name ELTEX
P HV001PF, was also tested but it was found to be difficult to mix and optimize,
in particular for our bimodal systems. This can be explained by its very broad
grain size specifications since they wore in the range 30 μm-1500 μm;
this effect was reinforced by the low density of the polypropylene.
The formulations and properties of the cement slurry are shown in Tables 10 to
12; they were all optimized at the same temperature (76.7° C.—170°
F.), and a single cement slurry density was selected (14 ppg). The dispersing agent
used was a polynaphthalene sulfonate; the retarder was a lignosulfonate. Formulation
1 was constituted by a bimodal mixture (cement+polypropylene particles); formulation
2 was a trimodal mixture (cement+polypropylene particles+fine particles).
| TABLE 10 |
| Formulations for cement slurries with polypropylene particles |
| |
Polypropylene |
Fine |
Dispersing |
Retarder |
Anti-foaming |
ρ |
|
| N° |
% bwoc |
% vol |
% bvob |
agent gps |
gps |
agent gps |
g/cm3 |
φ |
| C1 |
19.4 |
19.4 |
0 |
0.022 |
0.045 |
0.030 |
1.67 |
45% |
| C2 |
23.9 |
23.9 |
10 |
0.059 |
0.046 |
0.039 |
1.65 |
42% |
- % bvob is the abbreviation for "by weight of blend", and is the proportion
of fine particles in the mixture of solid cement particles, flexible particles, fines.
| TABLE 11 |
| Rheology and free water for systems with polypropylene particles |
| |
Rheology after |
|
|
| |
mixing at labora- |
| |
tory temperature |
Rheology after conditioning |
Free water |
| Formula- |
PV |
Ty (lbf/ |
at 76.6° C. |
after 2 |
| tion |
(mPa.s) |
100 ft2) |
PV (mPa.s) |
Ty (lbf/100 ft2) |
hrs (ml) |
| C1 |
175 |
6.1 |
228 |
13.1 |
1.5 |
| C2 |
387 |
1.9 |
332 |
18.8 |
0.1 |
| TABLE 12 |
| UCA and setting time at 76.7° C. (170° F.) for |
| systems with polypropylene particles |
| |
Time to 0.34 |
Time to 3.4 |
|
Setting |
| Formula- |
MPa at |
MPa at |
Compressive strength |
time |
| tion |
T (min) |
T (min) |
after 72 hours (psi) |
(min) |
| C1 |
580 |
665 |
1911 |
173 |
| C2 |
863 |
973 |
2089 |
369 |
EXAMPLE 4
Formulations for Cement Slurries with SBR Particles
The cement slurries were composed of Portland Dyckerhoff North Class G cement,
SBR particles, water, a dispersing agent and a retarder. The formulations for and
properties of the cement slurries are shown in Tables 13 to 15; they were all optimized
at the same temperature (76.7° C.—170° F.), and a single cement
slurry density (14 ppg) was selected. The dispersing agent used was a polynaphthalene
sulfonate; the retarder was a lignosulfonate. Two different grain sizes were tested:
500 μm for formulation N1 and 200 μm for formulation N2.
| TABLE 13 |
| Formulations for cement slurries with SBR particles |
| |
SBR |
Dispersing agent |
Retarder |
ρ |
Porosity of |
| |
% bwoc |
% vol |
gps |
gps |
g/cm3 |
slurry φ |
| D1 |
30.6 |
24.8 |
0.037 |
0.025 |
1.69 |
45 |
| D2 |
20.5 |
16.8 |
0.017 |
0.023 |
1.70 |
52 |
| TABLE 14 |
| Rheology and free water for systems with SBR particles |
| |
Rheology after |
|
|
| |
mixing at labora- |
| |
tory temperature |
Rheology after conditioning |
Free water |
| Formula- |
PV |
Ty (lbf/ |
at 76.6° C. |
after 2 |
| tion |
(mPa.s) |
100 ft2) |
PV (mPa.s) |
Ty (lbf/100 ft2) |
hrs (ml) |
| 1 |
156.7 |
5.0 |
185.5 |
17.1 |
0 |
| 2 |
69.4 |
1.8 |
84.3 |
29.5 |
1.5 |
| TABLE 15 |
| UCA and setting time at 76.7° C. (170° F.) for |
| systems with SBR particles |
| |
Time to 0.34 |
Time to 3.4 |
|
Setting |
| Formula- |
MPa at |
MPa at |
Compressive strength |
time |
| tion |
T (min) |
T (min) |
after 72 hours (psi) |
(min) |
| 1 |
373 |
478 |
1535 |
130 |
| 2 |
291 |
492 |
1209 |
200 |
EXAMPLE 5
Optimized Formulations with Polyethylene Particles
The cement slurries were composed of Portland Dyckerhoff North Class G cement,
polyethylene particles, water, a dispersing agent, a retarder and an anti-foaming
agent. The formulations for and properties of the cement slurries are shown in
Tables 16 to 18; they were all optimized at the same temperature (76.7° C.—170°
F.), and a single density for the cement slurry (14 ppg) was selected. The dispersing
agent used was a polynaphthalene sulfonate.
Formulation 1 contained ground high density polyethylene powder sold
by BP Chemicals under the trade name RIGIDEX HD 3840-2WA. Its density was 0.94
g/cm
3 and its grain size was less than 500 μm. Formulation 2 also
contained polyethylene powder with a density of 0.96 g/cm
3 and a grain
size of less than 500 μm, but this was a recycled product.
| TABLE 16 |
| Formulations for cement slurries with polyethylene particles |
| |
|
Anti- |
Dispersing |
|
|
Porosity |
| |
Polyethylene |
foaming |
agent |
|
ρ |
of |
| |
% bwoc |
% vol |
agent |
(gps) |
Retarder |
g/cm3 |
slurry |
| |
| E1 |
24.4 |
24.7 |
0.035 |
/ |
0.094 |
1.63 |
45% |
| E2 |
25.0 |
24.7 |
0.038 |
0.035 |
0.047 |
1.64 |
45% |
| TABLE 17 |
| Rheology and free water for systems with polyethylene particles |
| |
Rheology after |
|
|
| |
mixing at labora- |
| |
tory temperature |
Rheology after conditioning |
Free water |
| Formula- |
PV |
Ty (lbf/ |
at 76.6° C. |
after 2 |
| tion |
(mPa.s) |
100 ft2) |
PV (mPa.s) |
Ty (lbf/100 ft2) |
hours (ml) |
| E1 |
84.4 |
3.7 |
147.8 |
46.6 |
3 |
| E2 |
82.9 |
5.1 |
54.7 |
7.5 |
| TABLE 18 |
| UCA and setting time at 76.7° C. (170° F.) for |
| systems with polyethylene particles |
| |
Time to 0.34 |
Time to 3.4 |
|
Setting |
| Formula- |
MPa at |
MPa at |
Compressive strength |
time |
| tion |
T (min) |
T (min) |
after 72 hours (psi) |
(min) |
| E1 |
784 |
871 |
2315 |
187 |
| E2 |
291 |
492 |
1209 |
200 |
EXAMPLE 6
Mechanical Properties—Bending and Compression
Bending and compression mechanical properties were measured for cement slurries
which contained flexible particles. The exact formulations are given in Examples
1 to 6.
The influence of flexible particles on the mechanical properties of a set cement
was studied using systems placed under high pressure and temperature in high pressure
and high temperature chambers for several days to simulate the conditions encountered
in an oil well.
The bending tests were carried out on 3 cm×3 cm×12 cm prisms obtained
from cement slurries placed at 76.7° C. (170° F.) and 20.7 MPa (3000
psi) for several days. The compression tests were carried out on cubes with 5 cm
(2 inch) sides obtained after several days at 76.7° C. (170° F.) and
at 20.7 MPa (3000 psi).
For comparison purposes, systems with no flexible particles with the formulations
given in Tables 19 and 20 were included:
- a NET "system" with a density of 1.89 g/cm (15.8 ppg) with 0.03 gps
of anti-foaming agent (S1) as the sole additive;
- a 1.67 g/cm3 (14 ppg) system extended with bentonite (S2);
- a 1.44 g/cm3 system (12 ppg) extended with sodium silicate (S3).
| TABLE 19 |
| Formulations for cement slurries without |
| flexible particles |
| |
Extender |
Retarder |
Anti-foaming |
ρ |
Porosity of |
| N° |
% bwoc |
gps |
agent gps |
(g/cm3) |
slurry % |
| S1 |
0 |
/ |
0.03 |
1.89 |
58 |
| S2 |
4 |
0.08 |
0.03 |
1.68 |
68 |
| S3 |
1.7 |
/ |
0.03 |
1.44 |
79 |
| TABLE 20 |
| Rheology and free water for systems without |
| flexible particles |
| |
Rheology after |
|
|
| |
mixing at |
Rheology after condi- |
| |
laboratory temperature |
tioning at 76.6° C. |
Free water |
| |
PV |
Ty (lbf/ |
PV |
Ty (lbf/ |
after 2 |
| Formulation |
(mPa.s) |
100 ft2) |
(mPa.s) |
100 ft2) |
hours (ml) |
| S1 |
30.8 |
23.3 |
/ |
/ |
3.5 |
| S2 |
12.7 |
3.5 |
11.2 |
26.7 |
3 |
| S3 |
9.2 |
9.9 |
8.5 |
8.5 |
0 |
The results are shown in Tables 21 and 22. Table 21 concerns the bending strength
(rupture modulus Mr and bending Young's modulus Ef). It also shows the number of
days of cure under pressure and temperature. Table 22 shows the compressive strengths
(compressive strength Cs and compression Young's modulus Ec).
The bending strength was easier to measure than the tensile strength. It was
empirically estimated that the bending strength was twice as high as the tensile strength.
The bending and compression tests were used to calculate the quantity of energy
released at rupture (obtained by integrating the stress-strain curve for a displacement
in the range 0 to the maximum displacement of the load (corresponding to rupture).
Each property is represented as a function of the concentration of flexible
particles expressed as the % by volume (FIGS. 1-6).
The results obtained for the flexible particles show that, for equal densities,
adding particles simultaneously resulted in:
- a reduction in the rupture modulus (FIG. 1);
