U.S. patent application number 11/236743 was filed with the patent office on 2006-04-13 for well cementing material.
Invention is credited to Eric Lecolier, Alain Rivereau.
Application Number | 20060075932 11/236743 |
Document ID | / |
Family ID | 34950110 |
Filed Date | 2006-04-13 |
United States Patent
Application |
20060075932 |
Kind Code |
A1 |
Lecolier; Eric ; et
al. |
April 13, 2006 |
Well cementing material
Abstract
The present invention relates to a formulation of a
high-performance foamed cement material, comprising: at least one
hydraulic binder, microparticles whose grain size ranges between
0.1 and 30 .mu.m, whose proportion ranges between 15% and 50% by
mass in relation to the mass of hydraulic binder, mineral particles
whose grain size ranges between 1 and 500 .mu.m, whose proportion
ranges between 10% and 35% by mass in relation to the mass of
hydraulic binder, the proportion of particles being lower than the
proportion of microparticles, a hydrosoluble polymer thinning agent
whose proportion ranges between 0.1% and 8% by mass in relation to
the mass of hydraulic binder, water whose proportion is at most 40%
by mass in relation to the mass of hydraulic binder, a foaming
agent whose proportion ranges between 0.1% and 10% by mass in
relation to the mass of hydraulic binder.
Inventors: |
Lecolier; Eric; (Chaville,
FR) ; Rivereau; Alain; (Rueil Malmaison, FR) |
Correspondence
Address: |
ANTONELLI, TERRY, STOUT & KRAUS, LLP
1300 NORTH SEVENTEENTH STREET
SUITE 1800
ARLINGTON
VA
22209-3873
US
|
Family ID: |
34950110 |
Appl. No.: |
11/236743 |
Filed: |
September 28, 2005 |
Current U.S.
Class: |
106/677 |
Current CPC
Class: |
Y02W 30/94 20150501;
C04B 28/02 20130101; Y10S 106/01 20130101; C09K 8/473 20130101;
C04B 38/10 20130101; Y02W 30/91 20150501; C04B 28/02 20130101; C04B
14/04 20130101; C04B 18/146 20130101; C04B 20/008 20130101; C04B
24/26 20130101; C04B 38/10 20130101; C04B 2103/40 20130101; C04B
28/02 20130101; C04B 14/04 20130101; C04B 18/146 20130101; C04B
20/008 20130101; C04B 38/10 20130101; C04B 2103/0053 20130101; C04B
2103/40 20130101; C04B 38/10 20130101; C04B 28/02 20130101; C04B
28/06 20130101; C04B 28/065 20130101; C04B 2103/0035 20130101; C04B
2103/0036 20130101 |
Class at
Publication: |
106/677 |
International
Class: |
C04B 16/08 20060101
C04B016/08; C04B 20/00 20060101 C04B020/00 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 29, 2004 |
FR |
04/10.330 |
Claims
1) A cementing material comprising: at least one hydraulic binder
from the group consisting of class G Portland cements, class H
Portland cements, aluminous cements whose alumina content is at
least above 30% by mass, and sulfoaluminous cements, microparticles
from the group consisting of microsilica particles and
silico-aluminate particles, whose grain size ranges between 0.1 and
30 .mu.m, whose proportion ranges between 15% and 50% by mass in
relation to the mass of hydraulic binder, mineral particles whose
grain size ranges between 1 and 500 .mu.m, whose proportion ranges
between 10% and 35% by mass in relation to the mass of hydraulic
binder, the proportion of particles being lower than the proportion
of microparticles, a hydrosoluble polymer thinning agent whose
proportion ranges between 0.1% and 8% by mass in relation to the
mass of hydraulic binder, water whose proportion is at most 40% by
mass in relation to the mass of hydraulic binder, a foaming agent
whose proportion ranges between 0.1% and 10% by mass in relation to
the mass of hydraulic binder.
2) A material as claimed in claim 1, further comprising a foam
stabilizing additive whose proportion ranges between 0.1% and 2% by
mass in relation to the mass of hydraulic binder, the additive
being a hydrosoluble associative polymer comprising hydrophobic
units.
3) A material as claimed in claim 1, wherein the foaming agent is a
surfactant compound in a proportion ranging between 0.1% and 3% by
mass in relation to the mass of hydraulic binder.
4) A material as claimed in claim 3, wherein the surfactant
compound is selected from among the following products: abietic
acid salts, sodium alkyl-aryl sulfonates, phenol-ethoxylates and
perfluoroalkyl betaine.
5) A material as claimed in claim 1, wherein the foaming agent is a
hydrosoluble associative polymer comprising hydrophobic chains, the
polymer being in a proportion ranging between 0.1% and 10% by mass
in relation to the mass of hydraulic binder.
6) A material as claimed in claim 1, wherein the associative
polymer is a polymer with hydrophilic units Hy and hydrophobic
units Hb containing C1 to C30 alkyl, aryl, alkyl-aryl groups.
7) A material as claimed in claim 6, wherein the associative
polymer has a molecular mass of between 10.sup.4 and
5.times.10.sup.6 daltons and a proportion of hydrophobic units Hb
ranging between 0.5% and 60%.
8) A material as claimed in claim 1, wherein the mass of
microparticles ranges between 15% and 30% in relation to the mass
of hydraulic binder.
9) A material as claimed in claim 1, wherein the proportion of
water ranges between 20% and 35% by mass in relation to the mass of
hydraulic binder.
10) A material as claimed in claim 1, wherein the hydrosoluble
polymer thinning agent is selected from among the group consisting
of: a polynaphthalene sulfonate, a polycarboxylate and a
polyoxyethylene poly-carboxylate.
11) A material as claimed in claim 1, further comprising a
retarding agent for controlling the setting time of the slurry.
12) A material as claimed in claim 1, further comprising an
accelerating agent for controlling the setting time of the
slurry.
13) A material as claimed in claim 1, used for cementing an oil
well.
14) A method of producing a foamed cement slurry, wherein the
following stages are carried out: mixing a powder with water
comprising a hydrosoluble polymer thinning agent so as to obtain a
cement slurry, the powder comprising a hydraulic binder,
microparticles and mineral particles, the hydraulic binder being
selected from the group consisting of class G Portland cements,
class H Portland cements, aluminous cements whose alumina content
is at least above 30% by mass, and sulfoaluminous cements, the
microparticles being selected from the group consisting of
microsilica particles and silico-aluminate particles, of grain size
ranging between 0.1 and 30 .mu.m, whose proportion ranges between
15% and 50% by mass in relation to the mass of hydraulic binder,
the mineral particles having a grain size ranging between 1 and 500
.mu.m, with a proportion ranging between 10% and 35% by mass in
relation to the mass of hydraulic binder, the proportion of
particles being lower than the proportion of microparticles, the
hydrosoluble polymer thinning agent having a proportion ranging
between 0.1% and 8% by mass in relation to the mass of hydraulic
binder, introducing a foaming agent in the cement slurry, the
proportion of foaming agent ranging between 0.1% and 10% by mass in
relation to the mass of hydraulic binder, pumping the cement slurry
comprising the foaming agent, and injecting a gas into the cement
slurry comprising the foaming agent and stirring the mixture of
slurry and of gas so as to foam the slurry and to obtain a foamed
cement slurry.
15) A method as claimed in claim 14, wherein the foaming agent is a
surfactant compound in a proportion ranging between 0.1% and 3% by
mass in relation to the mass of hydraulic binder.
16) A method as claimed in claim 15, wherein the surfactant is
introduced in powder form into the cement slurry.
17) A method as claimed in claim 16, wherein the foaming agent is a
hydrosoluble associative polymer comprising hydrophobic chains, the
polymer being in a proportion ranging between 0.1% and 10% by mass
in relation to the mass of hydraulic binder.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to a slurry for cementing a
well, notably a well intended for exploration or development of
underground reservoirs, such as hydrocarbon or geothermal
reservoirs. The invention provides new cementing material
formulations having simultaneously low densities, high mechanical
properties and a low permeability.
BACKGROUND OF THE INVENTION
[0002] Hydrocarbon development well cementing is a complex
operation with multiple goals: mechanically secure the casing
strings in the geologic formation, isolate a producing layer from
adjacent layers, protect the strings against the corrosion due to
the fluids contained in the layers crossed through. The cement
sheaths therefore have to provide good mechanical strengths and low
permeability to the fluids and to the gas contained in the
formations drilled.
[0003] Under certain geothermal or hydrocarbon reservoir
development conditions, it is essential to have cementing materials
with both low densities and excellent physical properties
(mechanical strength and permeability). These two conditions are
difficult to combine with conventional cementing materials. It is
well-known since Feret's research work that the mechanical strength
varies conversely to the porosity. Feret notably showed that the
compressive strength Rc was expressed as follows: R c .function. (
t ) = K .function. ( t ) .times. ( c c + e + v ) 2 ##EQU1## where
c, e and v are the volumes of cement, water and air respectively,
and K(t) a kinetic function.
[0004] In order to lighten cementing slurries, it is common
practice to increase either the amount of water or the amount of
air (using hollow balls or by entraining intentionally a large
amount of air so as to form a cement foam). According to the above
formula, these two means lead to a mechanical strength degradation
and, simultaneously, to a great increase in the permeability of the
hardened material.
[0005] When the formations drilled are fragile and unconsolidated,
it is impossible to carry out operations with a dense cement slurry
for fear of exceeding the fracture pressure of the formations. This
problem is notably encountered when cementing the casings of
offshore wells or wells drilled in mature fields.
[0006] To cement wells crossing fragile formations, i.e. with a low
fracture gradient, it is well-known to significantly lighten the
slurry by adding gas. This gas can be introduced by means of hollow
ceramic or glass microspheres. This technique is notably described
in documents U.S. Pat. No. 3,804,058 and U.S. Pat. No. 4,252,193.
The gas can also be introduced into the slurry by creating a foam
by means of foaming agents added to this slurry. This technique is
notably described in documents U.S. Pat. No. 5,806,594 and U.S.
Pat. No. 5,484,019.
[0007] Cements lightened by means of hollow balls have certain
drawbacks. One drawback is the destruction of the balls under the
effect of the hydrostatic pressure. This destruction translates
into a density increase while pumping the slurry: the fracture
pressure can thus be reached. Another drawback of hollow glass
balls comes from the destruction, in the hardened cement, of the
walls of the balls as a result of pozzolanic reactions. This
destruction translates into an increase in the permeability of the
cement matrix.
[0008] Common formulations of a foamed cement slurry for cementing
wells comprise a proportion of water ranging between 40% and 60% by
weight of cement. This high water amount, necessary to lower the
cement slurry densities and to optimize the rheology, generates a
high porosity which translates into poor properties of the cement
sheath in terms of permeability, mechanical strength, cracking and
durability.
[0009] The problem now consists in formulating a pumpable hydraulic
binder foam (i.e. having a viscosity range compatible with the
viscosities required for setting the slurry in the annulus) for
cementing oil wells or other wells, with higher mechanical
strengths and a lower permeability. The present invention therefore
describes the way to formulate a low-density cementing material by
introducing gas in form of bubbles that will be separated by a very
compact cement matrix. In this case, although the material obtained
is very porous, the permeability of this material remains very low
because the invention described allows to obtain a foamed cement
wherein the bubbles are not interconnected.
[0010] There are cement formulations with much better mechanical
properties, as described for example in document EP-950,034. These
formulations are based on maximization of the packing volume
fraction by optimization of the grain size of the mineral
particles. In fact, it has been known for a long time in the
profession (see Feret's formula above) that the properties of
cement materials are improved by increasing the compactness of the
mixture (or, which comes to the same thing, by reducing the
porosity). These materials can have compressive strengths above 100
MPa and gas permeabilities of the order of one nanoDarcy. It is
well-known that the viscosity of suspensions increases
exponentially with the volume fraction in solid particles: the
significant increase in the cement slurry viscosity is very serious
from an operational point of view because, in this case, the
material can no longer be set in place by pumping. Now, in the
invention described in document EP-950,034, optimization of the
grain packing of the mixture of mineral powders achieved by
properly selecting both the size of the mineral particles and their
concentration allows to obtain slurries that are much more fluid
than conventional cement slurries. Unlike conventional cements, the
high-performance cementing materials described in document
EP-950,034 can have a zero yield point. However, the densities of
these high-performance cements as described in document EP-950,034
are above 1.9 gcm.sup.-3 and they are therefore not suitable for
cementing fragile and unconsolidated zones such as those
encountered in deep-sea drilling or for cementing wells in depleted
reservoirs. Recently, low-density formulations, typically ranging
between 1.2 and 1.6 gcm.sup.-3, were developed for cementing wells
drilled in unconsolidated geologic layers. These cementing
materials are high-performance materials to which hollow
microspheres have been added. These materials thus have the same
drawbacks as conventional cements containing hollow microspheres:
microsphere crushing during pumping in the well, pozzolanic
reaction between the portlandite and the silica contained in the
microsphere walls. Furthermore, it is impossible to vary the
density of the cement during cementing.
[0011] The present invention thus provides a cementing material
formulation having simultaneously low densities and excellent
physical properties, notably compressive strength and permeability.
This combination of low densities and of improved physical
properties in relation to the state of the art is achieved by
foaming cements whose packing volume fraction is maximized by
adjusting the proportions of the various grain size classes that
make up the material.
SUMMARY OF THE INVENTION
[0012] In general terms, the present invention relates to a
cementing material comprising: [0013] at least one hydraulic binder
from the group consisting of class G Portland cements, class H
Portland cements, aluminous cements whose alumina content is at
least above 30% by mass, and sulfoaluminous cements, [0014]
microparticles from the group consisting of microsilica particles
and silico-aluminate particles, whose grain size ranges between 0.1
and 30 .mu.m, whose proportion ranges between 15% and 50% by mass
in relation to the mass of hydraulic binder, [0015] mineral
particles whose grain size ranges between 1 and 500 .mu.m, whose
proportion ranges between 10% and 35% by mass in relation to the
mass of hydraulic binder, the proportion of particles being lower
than the proportion of microparticles, [0016] a hydrosoluble
polymer thinning agent whose proportion ranges between 0.1% and 8%
by mass in relation to the mass of hydraulic binder, [0017] water
whose proportion is at most 40% by mass in relation to the mass of
hydraulic binder, [0018] a foaming agent whose proportion ranges
between 0.1% and 10% by mass in relation to the mass of hydraulic
binder.
[0019] According to the invention, the material can also comprise a
foam stabilizing additive whose proportion ranges between 0.1% and
2% by mass in relation to the mass of hydraulic binder, the
additive being a hydrosoluble associative polymer comprising
hydrophobic units.
[0020] The foaming agent can consist of a surfactant compound in a
proportion ranging between 0.1% and 3% by mass in relation to the
mass of hydraulic binder. The surfactant compound can be selected
from among the following products: abietic acid salts, sodium
alkyl-aryl sulfonates, phenol-ethoxylates and perfluoroalkyl
betaine.
[0021] The foaming agent can also be a hydrosoluble polymer
referred to as "associative polymer", comprising hydrophobic
chains, the polymer being in a proportion ranging between 0.1% and
10% by mass in relation to the mass of hydraulic binder. The
associative polymer can be a polymer with hydrophilic units Hy and
hydrophobic units Hb containing C1 to C30 alkyl, aryl, alkyl-aryl
groups. The associative polymer can have a molecular mass of
between 10.sup.4 and 5.times.10.sup.6 daltons and a proportion of
hydrophobic units Hb ranging between 0.5% and 60%.
[0022] According to the invention, the mass of microparticles can
range between 15% and 30% in relation to the mass of hydraulic
binder.
[0023] The proportion of water can range between 20% and 35% by
mass in relation to the mass of hydraulic binder.
[0024] According to the invention, the hydrosoluble polymer
thinning agent can be selected from among the group consisting of:
a polynaphthalene sulfonate, a polycarboxylate and a
polyoxyethylene polycarboxylate.
[0025] The cementing material according to the invention can also
comprise a retarding agent for controlling the setting time of the
slurry.
[0026] The cementing material according to the invention can
further comprise an accelerating agent for controlling the setting
time of the slurry.
[0027] The cementing material according to the invention can be
used for cementing an oil well.
[0028] The invention also relates to a method of producing a foamed
cement slurry wherein the following stages are carried out: [0029]
mixing a powder with water comprising a hydrosoluble polymer
thinning agent so as to obtain a cement slurry, the powder
comprising a hydraulic binder, microparticles and mineral
particles, the hydraulic binder being selected from the group
consisting of class G Portland cements, class H Portland cements,
aluminous cements whose alumina content is at least above 30% by
mass, and sulfoaluminous cements, the microparticles being selected
from the group consisting of microsilica particles and
silico-aluminate particles, of grain size ranging between 0.1 and
30 .mu.m, whose proportion ranges between 15% and 50% by mass in
relation to the mass of hydraulic binder, the mineral particles
having a grain size ranging between 1 and 500 .mu.m, with a
proportion ranging between 10% and 35% by mass in relation to the
mass of hydraulic binder, the proportion of particles being lower
than the proportion of microparticles, the hydrosoluble polymer
thinning agent having a proportion ranging between 0.1% and 8% by
mass in relation to the mass of hydraulic binder, [0030]
introducing a foaming agent in the cement slurry, the proportion of
foaming agent ranging between 0.1% and 10% by mass in relation to
the mass of hydraulic binder, [0031] pumping the cement slurry
comprising the foaming agent, and [0032] injecting a gas into the
cement slurry comprising the foaming agent and stirring the mixture
of slurry and of gas so as to foam the slurry and to obtain a
foamed cement slurry.
[0033] In the method according to the invention, the foaming agent
can be a surfactant compound in a proportion ranging between 0.1%
and 3% by mass in relation to the mass of hydraulic binder. The
surfactant can be introduced in powder form in the cement slurry.
The foaming agent can also be a hydrosoluble associative polymer
comprising hydrophobic chains, the polymer being in a proportion
ranging between 0.1% and 10% by mass in relation to the mass of
hydraulic binder.
[0034] In the present invention, the cement material of the walls
separating the foam bubbles thus has a higher compactness than the
materials commonly used in the profession. The porosity of the
cement pastes of these new materials was measured by means of a
mercury-pump porosimeter and it is below 12%, whereas the porosity
of the cement pastes of conventional foamed cements is above
25%.
[0035] The walls between the bubbles of the cement foam described
in the invention being less porous (or more compact, which is
equivalent), the permeability and the mechanical strengths are
therefore higher than those of the foamed cements obtained from a
conventional cement slurry, whose water content is above 40% by
weight of cement.
[0036] High-performance cements being very fluid, it is difficult
to obtain, from these slurries, a stable foam, i.e. whose bubbles
do not coalesce. If the bubbles coalesce before the cement hardens,
the hardened material will be very permeable and have little
mechanical strength. Adjustment of the proportions of the various
aggregates that make up the cement slurry according to the
invention allows to obtain a stable cement foam, despite the high
fluidity of the cementing material. The invention described in this
patent allows to obtain stable high-performance cement foams and
therefore, in fine, a hardened material of very low permeability
and thus of improved durability.
[0037] Furthermore, the setting time of the formulations developed
in the present invention is shorter than the setting time of a
conventional foamed cement. In fact, it is known to the man skilled
in the art that the setting time decreases when the water/cement
ratio decreases. Thus, the formulations developed within the scope
of the present invention can be preferred to conventional foamed
cements when the temperatures of the wells are low.
[0038] Thus, the foamed cement formulations according to the
present invention allow to carry out all the cementing operations
required in the case of wells drilled in low-cohesion formations.
The formulations of the present invention can also be used for
cementing cavernous, fault zones and more generally zones where
fluid losses occur during drilling.
BRIEF DESCRIPTION OF THE FIGURES
[0039] Other features and advantages of the invention will be clear
from reading the description hereafter, with reference to the
accompanying figures wherein:
[0040] FIGS. 1 and 2 are photographs of a foamed cement with a foam
stability problem,
[0041] FIG. 3 is a photograph of a stable foamed cement obtained
according to the invention,
[0042] FIG. 4 diagrammatically shows a method of producing a foamed
cement slurry according to the invention.
DETAILED DESCRIPTION
[0043] According to the invention, the low density and the
excellent physical properties (compressive strength and
permeability) of the cementing material formulations are optimized
by combining the following constituents: [0044] a hydraulic binder
from the group consisting of the Portland cements and other
hydraulic binders, for example of aluminous cement type, whose
alumina content is above 30%, or sulfoaluminous cement, or plaster,
[0045] a microsilica (also referred to as silica fume) of grain
size ranging between 0.1 .mu.m and 30 .mu.m (the BET surface area
can range between 10 and 30 m.sup.2/g, preferably 18 m.sup.2/g),
whose proportion in the composition according to the invention
ranges between 15% and 50% by mass in relation to the mass of
hydraulic binder. In the invention, the microsilica can be replaced
by fly ash (silico-aluminous, sulfocalcic or silico-calcic
particles), [0046] a mineral addition of grain size ranging between
1 .mu.m and 500 .mu.m (which corresponds to a D50 ranging between
35 .mu.m and 210 .mu.m, or to a specific surface ranging between
0.03 m.sup.2/g and 0.65 m.sup.2/g). The amount of mineral added
ranges between 10% and 35% by mass in relation to the mass of
hydraulic binder. The proportion of mineral added remains lower
than the proportion of microsilica so as to respect optimization of
the compactness of the packing of the various aggregates, [0047] a
superplasticizing agent, also referred to as hydrosoluble thinning
agent, in a proportion ranging between 0.1% and 8% by mass in
relation to the mass of hydraulic binder. The thinning agent can be
either a polynaphthalene sulfonate or a polycarboxylate, or a
polyoxyethylene polycarboxylate, [0048] water in a proportion of at
most 40% by mass in relation to the mass of hydraulic binder. It
more particularly ranges between 15% and 40%, preferably between
20% and 35%, [0049] a foaming agent whose concentration ranges
between 0.1% and 10% by mass in relation to the mass of hydraulic
binder. This foaming agent can be an anionic surfactant (such as
sodium dodecyl sulfate) or a non-ionic surfactant, or a
hydrosoluble polymer comprising hydrophobic links (referred to as
associative polymers), or an air-entraining product, or a mixture
of these molecules, and [0050] possibly a foam stabilizing
additive. This additive can be a hydrophobic modified hydrosoluble
polymer.
[0051] The Portland cements can be Black Label, HTS or CEMOIL
cement manufactured by the Dyckerhoff, Lafarge and CCB Companies
respectively. The aluminous cements can be the Secar 51 or Temal
cements manufactured by the Lafarge Aluminates Company.
[0052] When the foaming agent is a surfactant compound, it can be
in a proportion ranging between 0.1% and 3% by mass in relation to
the mass of hydraulic binder. The surfactants used in the cement
slurry formulation according to the invention can be fatty alcohol
sulfates also referred to as alkylsulfates of general formula
R--O--SO.sub.3X where X can be a sodium, ammonium or alkylolamine
salt and R a hydrocarbon chain comprising a number of carbon atoms
ranging between 8 and 20. Another surfactant class can be the one
corresponding to the alkylethersulfates, which comprise between 1
and 10 groups of ethylene oxide. The general formula of these
products is R--O--(CH.sub.2CH.sub.2O).sub.n--SO.sub.3X where n
ranges between 1 and 10 and R is a hydrocarbon chain comprising a
number of carbon atoms ranging between 8 and 20. The surfactants of
general formula
R--(C.sub.6H.sub.6)--O--(CH.sub.2--CH.sub.2O).sub.n--SO.sub.3X
where n ranges between 3 and 15 and R is a hydrocarbon chain
comprising a number of carbon atoms ranging between 8 and 20 can
also be used to obtain a cement foam. Phenol-ethoxylates of general
formula R--(C.sub.6H.sub.6)--O--(CH.sub.2O).sub.n--HNa where n
ranges between 3 and 15 and R is a hydrocarbon chain comprising
between 8 and 18 carbon atoms can be used as foaming agent.
Similarly, a cement foam can be obtained using sodium sulfonate
alkyl-aryl surfactants of general formula
R--(C.sub.6H.sub.6)--SO.sub.3Na where R is a hydrocarbon chain
comprising between 8 and 18 carbon atoms. Non-ionic surfactants of
general formula
R--(COO)--(CH.sub.2CH.sub.2)--(CH.sub.2--CH.sub.2--O).sub.n--H
where n ranges between 1 and 24, as well as non-ionic surfactants
whose hydrophobic part is a hydrocarbon chain of formula
CH.sub.3(CH.sub.2).sub.m and whose hydrophilic part is an
oxyethylene chain of formula (CH.sub.2CH.sub.2O).sub.n where m
ranges between 8 and 20 and n ranges between 2 and 24 can also be
used in the invention. The hydrophilic groups can also be sugars or
glycerol derivatives. These types of surfactant, notably
alkylpolyglucosides, have a higher efficiency in the formation of
foams and their use is advantageous in highly salted media such as
cement slurries. Furthermore, these surfactants have a very good
biodegradability. Cationic surfactants can be used, notably
alkylamine salts of general formula: ##STR1## where R is a
hydrocarbon chain consisting of 8 to 20 carbon atoms, R', R'' and
R''' correspond to hydrogen atoms or methyl, ethyl, benzyl or
oxyethylene groups, and X an anion.
[0053] The foaming agent can also be abietic acid salt of general
formula C.sub.20H.sub.30O.sub.2--X, where X is a sodium, potassium
salt.
[0054] Advantageously, zwiterrionic surfactants can be used, for
example alkyl amidobetaine of general formula
C.sub.nH.sub.2n+1CONH(CH.sub.2).sub.3N.sup.+(CH.sub.3).sub.2CH.sub.2COO.s-
up.- where n ranges between 10 and 18. It is also possible to use
the fluorinated form of this surfactant. Perfluoroalkyl betaine
gives good quality and stable foams. Perfluorobetaine also affords
the advantage of being chemically stable at high temperatures.
[0055] A mixture of these surfactants can be advantageously used.
This mixture can also comprise cosurfactants. These cosurfactants
can be fatty alcohols.
[0056] When the foaming agent is an associative polymer, it can be
in a proportion ranging between 0.1% and 10% by mass in relation to
the mass of hydraulic binder.
[0057] The associative polymers used in the composition of the
cement slurry according to the invention can be a polymer with
hydrophilic (Hy) and hydrophobic (Hb) units in aqueous solution,
the hydrophobic units (Hb) containing C1 to C30 alkyl, aryl,
alkyl-aryl groups, the polymer having the following structure
-(Hb)-(Hy)- with a statistical distribution with: [0058] Hy of the
form: ##STR2## where R5 is H or CH.sub.3, Z1 is COOH or CONH.sub.2
or CONHR1SO.sup.3- or CONHR''1, R''1 is CH.sub.3, [0059] or of the
form: ##STR3## where R5 is H or CH.sub.3, Z1 is CONH.sub.2 or
CONHR''1, R''1 is CH.sub.3 and R''5 is H or CH.sub.3, Z3 is COOH or
CONHR1SO.sup.3-, and where R1 is C.sub.3H.sub.8 or C.sub.6H.sub.5,
[0060] Hb is of the form: ##STR4## where R'5 is H or CH.sub.3 and
Z2 is COOR7, COOR'1, CONR1R'1 or CONR1R7, R7 being a non-ionic
surfactant consisting of an alkyl polyoxyethylene chain, R1 is H or
a C1-C30 alkyl, aryl or alkyl-aryl radical, and R'1 is a
C.sub.1-C.sub.30 alkyl, aryl or alkyl-aryl radical.
[0061] In particular, the polymer can have a molecular mass of
between 10.sup.4 and 5.times.10.sup.6 daltons, more precisely
between 10.sup.4 and 1.5.times.10.sup.6, and a proportion of
hydrophobic units Hb ranging between 0.5 and 60%.
[0062] According to the present invention, the associative polymer
can also be a derivative of the hydrophilically and hydrophobically
modified galactomanane described in patent U.S. Pat. No. 4,960,876.
This associative polymer is produced by the Lamberti Company and
marketed under references HPG19, HPG21, HM21, HM22. The molecular
mass of the modified galactomanane can be below 5.times.10.sup.6
daltons, preferably below 2.times.10.sup.6 daltons. The hydrophobic
group can be a linear or branched alkyl radical, saturated or with
an ethylene unsaturation, comprising between 10 and 32 carbon
atoms, preferably between 12 and 30. Adding to the cement slurry a
proportion of hydrophilically and hydrophobically modified
galactomanane derivative or a proportion of a mixture of
hydrophobically modified hydrosoluble polymers as described above
and of hydrophilically and hydrophobically modified galactomanane
derivatives allows to obtain cement foams of different densities,
lower than the initial density of the cement slurry.
[0063] The associative polymer can be selected from the group
consisting of: [0064] HMPAM1: where R5 is H and Z1 is CONH.sub.2,
R'5=CH.sub.3, Z2 is COOR'1 with R'1=C.sub.9H.sub.19, [0065] HMPAM2:
where R5 is H and Z1 is CONH.sub.2, R'5=H, Z2 is CONR'1R'1 with
R'1=C.sub.6H.sub.13, [0066] HMPAM3: where R5 is H and Z1 is CONH2,
R''5=H, Z3 is COOH or CONHR1SO.sub.3, where R1 is C.sub.3H.sub.8
(AMPS), R'5=H, Z2 is CONR'1R'1 with R'1=C.sub.6H.sub.13, [0067] S1:
where R5 is H and Z1 is CONH.sub.2, R'5=H and Z2 is C.sub.6H.sub.4
SO.sub.3H, [0068] HB1: where R5 is H, Z1 is COOH, R'5 is H and Z2
is COOR'1 with R'1=C.sub.4H.sub.9.
[0069] In particular, the polymer called HMPAM1 or HMPAM2 or HMPAM3
can have a molecular mass of between 5.times.10.sup.5 daltons and
2.times.10.sup.6 daltons, and a proportion of hydrophobic units
(Hb) ranging between 0.5 and 3%.
[0070] Polymer S1, an acrylamide (Hy)/styrene sulfonate (Hb)
copolymer, branched or not, according to the description above can
have a molar ratio of about 50/50 and a molar mass ranging between
5.times.10.sup.5 daltons 5.times.10.sup.6 daltons. If it is
branched, it is referred to as S2. The branching agent used in this
case can be N,N' methylene bis acrylamide MBA.
[0071] Polymer HB1, an acrylate (Hy)/butyl acrylate (Hb) copolymer,
with R5 being H, Z1 COOH, R'5H and Z2 COOR'1 with R'1 C4, can
comprise between 50% and 80% acrylate units, and have a molecular
mass of between 10.sup.4 and 5.times.10.sup.6 daltons, preferably
between 10.sup.4 and 5.times.10.sup.4 daltons.
[0072] In order to obtain a cement slurry as stable as possible,
proportions of the various constituents of the cement slurry can be
selected from the following range: [0073] 20 g to 50 g microsilica
or fly ash to 100 g hydraulic binder, the microsilica preferably
having a specific surface ranging between 10 and 30 m.sup.2/g,
[0074] 10 g to 35 g mineral addition to 100 g hydraulic binder, the
mineral addition preferably having a D50 ranging between 35 and 210
.mu.m, for example between 35 and 90 .mu.m or between 140 and 210
.mu.m.
[0075] When a surfactant is added to a slurry conventionally used
in the profession (which behaves like a Bingham fluid) and stirred
so as to entrain air within, the presence of the yield point
prevents migration of the air bubbles created. Migration of the air
bubbles can lead either to a non-foamed slurry when the air bubbles
migrate to the surface, or to a very weakly foamed slurry (with a
higher density than that expected), or to a foamed or very little
foamed slurry but with a greatly connected foam structure (due to
the coalescence of the air bubbles). The presence of a yield point
in the slurry to be foamed is an advantage when it is desired to
obtain high-quality foamed cements. In the case of cement slurries
comprising various grain sizes, there is not necessarily a yield
point: the slurry has a Newtonian type behaviour. It is then
difficult to maintain the air bubbles evenly distributed in the
volume. To obtain a stable and homogeneous foam with these very
fluid slurries, there are several solutions. Viscosifiers such as
those known and used in the profession can for example be added. It
is also possible to add to the very fluid cement slurry formulation
associative polymers in proportions ranging between 0.1% and 2.0%,
and preferably between 0.1% and 1.0%. Another way to obtain stable
foams from very fluid slurries (i.e. having a very low yield point
or with a Newtonian behaviour) consists in preparing the cement
slurry, then in adding the surfactant in powder form just before
stirring. It has been observed in the laboratory that with this
method the foams obtained were more stable than when the surfactant
was added in liquid form. To obtain homogeneous foamed cements with
different densities, the stirring time has to be optimized. The
stirring time depends on the type of slurry, on the type of
surfactant used and possibly on the presence of a viscosifier: each
case requires optimization of the stirring time (stirring is
understood to be entrainment of air in the slurry). For example,
above a certain stirring time, it has been observed in the
laboratory that the density no longer decreases. It has also been
noticed that too long a stirring time could eventually break the
cement foam. Producing a foamed cement from a cement slurry more
fluid (fluid means that the yield point is low or non-existent,
like the cement slurries involving different grain sizes, such as
the cement slurry according to the invention) than those generally
used in the profession is not a trivial operation.
[0076] The cement slurry comprising different grain sizes is very
fluid and, according to circumstances, there may be an absence of
yield point, i.e. the cement flows only under the effect of the
gravity force. This fluidity can be the cause for a lack of
stability of the cement foam. An associative polymer can be added
to improve the foam stability, in a proportion ranging between 0.1%
and 2%, preferably between 0.1% and 1%. This associative polymer
allows to increase the viscosity of the slurry, which has the
effect of limiting coalescence of the gas bubbles.
[0077] When the foaming agent is an associative polymer, the cement
formulation does not necessarily require a foam stabilizing
additive. In fact, certain associative polymers, for example HB1,
simultaneously allow to foam the cement slurry and to stabilize the
foam.
[0078] Furthermore, the formulation of the cementing material
according to the invention can comprise a retarding agent allowing
to retard the setting time of the cement slurry.
[0079] The retarding agents can be organic products or
water-soluble mineral materials.
[0080] Among the organic products, the following molecules can be
distinguished: [0081] (calcium, sodium) lignosulfonates whose sugar
proportions are below 20%, [0082] acids and salts (sodium,
potassium, calcium) of hydroxycarboxylic acids, [0083] oxalic and
gluconic acids, efficient with very low dosages, [0084] sodium
gluconate of formula CH.sub.2OH(CHOH).sub.4COONa is very active for
retarding materials containing hydraulic binders, [0085] calcium
gluconate, [0086] carbon hydrates of general formula
C.sub.n(H.sub.2O).sub.n; among these molecules, the saccharose of
formula C.sub.12H.sub.22O.sub.11 is very efficient; it is also
possible to use glucoses (C.sub.6H.sub.12O.sub.6), starch
(C.sub.6H.sub.12O.sub.6).sub.n, and cellulose, [0087] corn
syrup.
[0088] These organic products can be used in dosages ranging
between 0.1% and 5% by mass of dry extract in relation to the mass
of hydraulic binder.
[0089] Among the retarding agents based on mineral salts, the
following products can be used: [0090] boron compounds used with
very low dosages can be used to retard the cementing materials;
boric acid (BO.sub.3H.sub.3), borax
(Na.sub.2B.sub.4O.sub.710H.sub.2O), sodium metaborate
Na.sub.2B.sub.2O.sub.4 and sodium tetraborate
(Na.sub.2B.sub.4O.sub.7) can be preferably used, [0091] tin sulfate
(S.sub.2SO.sub.4), [0092] lead acetate
(Pb(C.sub.2H.sub.3O.sub.2).sub.2), [0093] calcium monophosphate
(Ca(H.sub.2PO.sub.4).sub.2).
[0094] These retarding agents based on mineral salts can be used
with dosages ranging between 0.1% and 2% by mass in relation to the
mass of hydraulic binder.
[0095] Furthermore, the formulation of the cementing material
according to the invention can comprise an accelerating agent
allowing to accelerate the setting time of the cement slurry. This
accelerating agent can be used for cementing zones with low
temperatures between -4.degree. C. and 10.degree. C. For example,
the zones close to the sea bottom in deep-sea drilling can be at
temperatures of about 4.degree. C.
[0096] The accelerating agents can be selected from among the
following products: [0097] calcium chloride (CaCl.sub.2), [0098]
calcium nitrite (Ca(NO.sub.2).sub.2), [0099] calcium formiate
(Ca(HCO.sub.2).sub.2).
[0100] These products can be used at concentrations ranging between
0.5% and 5% by mass in relation to the mass of hydraulic binder.
For temperatures below 15.degree. C., calcium chloride should not
be used at concentrations above 2.5% in relation to the mass of
cement. Above this concentration, it behaves like a setting
retarding agent under low-temperature conditions.
[0101] Non-chlorinated accelerating agents available on the market
can also be used.
[0102] Depending on the proportion of the various constituents
mentioned above, the foamed cement obtained may not be stable as
shown in FIGS. 1 and 2. In fact, depending on the proportion of the
various constituents, the slurry may have a segregation.
[0103] In this type of formulation, a considerable drainage occurs
before the cement hardens. In FIG. 1, a two-phase system has formed
with a cement slurry in lower part 1 and a very aerated and
connected foam in upper part 2. FIG. 2 shows an enlargement of part
2 of FIG. 1. Such a foamed cement formulation is not satisfactory
for well cementing. According to the invention, the proportion of
the different constituents has been optimized to obtain a stable
and homogeneous foamed cement with improved properties. Obtaining
stable foamed cements with improved properties notably requires
optimizing the grain packing and the amount of foaming agents.
[0104] FIG. 3 shows the foamed cement structure obtained according
to the present invention: it can be clearly seen that the bubbles
have not coalesced. The bubbles are separate and independent.
[0105] The following cement slurry formulations allow to illustrate
the invention.
[0106] The influence of the foaming agent concentration was
evaluated for a slurry comprising: a water/cement ratio E/C=0.27;
microsilica=24%; mineral addition=20%. TABLE-US-00001 Anionic
surfactant concentration (g/100 g cement) 0.25 0.40 0.75 Density
(g/cm.sup.3) 1.70 1.32 1.24 Rc (MPa) 32 17 12.5
[0107] The influence of the foaming agent concentration was
evaluated for a slurry comprising: a water/cement ratio E/C=0.27;
microsilica=50%; mineral addition=20%. TABLE-US-00002 Anionic
surfactant concentration (g/100 g cement) 0 0.25 0.5 0.75 Density
(g/cm.sup.3) 2.25 2.03 1.74 1.63 Rc (MPa) 123 74 40 39
[0108] The influence of the foaming microsilica content was
evaluated for a slurry comprising: a water/cement ratio E/C=0.27;
mineral addition=20%, foaming agent (surfactant)
concentration=0.75%. TABLE-US-00003 Microsilica content (g/100 g
cement) 24 30 50 Density (g/cm.sup.3) 1.24 1.42 1.63 Rc (MPa) 12.5
19 39
[0109] By varying the amount of foaming agent between 0 and 0.75%,
it is observed that it is possible to lower the density of the
material from 2.25 to 1.24 g/cm.sup.3.
[0110] When an identical amount of foaming agent (0.75% for
example) is added, it is observed that lower densities are obtained
when the amount of microsilica is small. Foamed cements of lower
densities are obtained by selecting formulations comprising
microsilica amounts ranging between 15% and 30% by mass in relation
to the mass of hydraulic binder.
[0111] Finally, it can be noted that the formulations with 50%
microsilica afford a very high compressive strength Rc. Thus, for a
formulation of density 1.63 g/cm.sup.3 containing 50% microsilica
and prepared according to the invention, the compressive strength
is 39 MPa, which is above the value measured for a non-foamed
cement paste of density 1.9 g/cm.sup.3. The cementing materials
obtained according to the invention thus allow to reach low
densities without losing their mechanical strength however.
[0112] Two cement slurries of equivalent density are compared: a
conventional foamed cement and a high-performance foamed cement
according to the invention.
[0113] Conventional Foamed Cement Formulation: [0114] Class G
Portland cement: 100 [0115] Water/Cement: 44% [0116] Sodium Dodecyl
Sulfate/Cement: 4.4.times.10.sup.-2%.
[0117] High-Performance Foamed Cement Formulation According to the
Invention: [0118] Class G Portland cement: 100 [0119] Water/Cement:
27% [0120] Microsilica: 24% [0121] Mineral addition: 20% [0122]
Sodium Dodecyl Sulfate/Cement: 0.625%.
[0123] The following table allows to compare the properties of the
two materials: TABLE-US-00004 Conventional High-performance
Measured quantities foamed cement foamed cement Density (g
cm.sup.-3) 1.32 1.30 Compressive strength (MPa) 6.8 18.4 Bending
strength (MPa) 2.7 3.9 Young's modulus (GPa) 4.302 7.394 Gas
permeability (m.sup.2) 3.9 .times. 10.sup.-16 7.8 .times.
10.sup.-17
[0124] From the values obtained for the two materials, it is clear
that the high-performance foamed cement according to the invention
has better properties than a conventional foamed cement as regards
its mechanical strength and permeability.
[0125] It is very interesting to note that the permeability
obtained for the high-performance foamed cement is equivalent to
that of a non-lightened cement (of water/cement ratio 0.44)
conventionally used for cementing casings in oil wells. In fact,
the permeability of such a cement is 8.times.10.sup.-17 m.sup.2.
Thus, although the material which is the object of the present
invention has a markedly higher porosity (of the order of 50%) than
a conventional cement, its permeability is equivalent, which is an
advantage notably in terms of durability.
[0126] FIG. 4 diagrammatically shows a method of producing a foamed
cement slurry according to the invention.
[0127] Mixer 7 allows to mix a powder comprising a hydraulic binder
with microparticles and mineral particles added, as described
above, coming from tank 1 through line 5, with water coming from
tank 2 through line 6. The water contains thinning agents. Valves 3
and 4 allow to control and to adjust the amounts of water and of
the powder mixture containing the hydraulic binder introduced in
mixer 7. A homogeneous cement slurry is obtained at the outlet of
mixer 7 and flows through line 8.
[0128] Tank 9 contains foaming agents: surfactants or hydrosoluble
polymers comprising hydrophobic links. Foaming agents are injected
by means of pump 10, valve 11 and line 12 into the cement slurry
circulating in line 8. The surfactants can be introduced in the
slurry in powder form just at the mixer outlet.
[0129] The cement slurry comprising foaming agents is pumped by
slurry pump 13 until a high pressure ranging for example between 10
and 100 bars is reached.
[0130] A gas is then injected into the slurry at high pressure
through line 14. The gas can be air or nitrogen. Injection of air
into the cement slurry is achieved in foam generator 15 whose
function is to stir the slurry and the gas so as to foam the cement
slurry. Foam generator 15 can create turbulences in the slurry in
different ways known to the man skilled in the art. A foamed cement
slurry is obtained at the outlet of foam generator 15 and
discharged through line 16.
[0131] The foamed cement slurry is either sent into a tank through
line 17 or introduced into a well to be cemented through line
18.
[0132] Densimeters 19, 20 and pressure detectors 21, 22 allow to
control the density and the pressure of the slurry prior to and
after foaming.
* * * * *