FR2749843A1 - New cementation compositions useful for the support of drilling tubes in the drilling of petroleum wells - Google Patents

Abstract

New cementation composition for petroleum or analogous wells consists of: a mixture of solids comprising a matrix of an aluminous hydraulic cement, fine particles and hollow microspheres; water, to give a porosity of 0.25 - 0.5 (preferably 0.3 - 0.4); a dispersant, a setting accelerator and other conventional additives. Also claimed is its application to the cementation of conductor tubes in a petroleum well, or other type of well in arctic or deep water conditions.

Description

Cementation compositions and application
of these compositions for cementing
oil wells or the like
The present invention relates to drilling techniques for oil wells, gas, water, geothermal and the like. More specifically, the invention relates to cementing compositions more particularly adapted to low temperatures.

After drilling an oil well or the like, a casing or a coiled tubing is lowered into the borehole and cemented over all or part of its height.

The cementing allows in particular to suppress the exchange of fluids between the various formation layers traversed by the borehole, to prevent upwelling of the annulus surrounding the casing or to limit the inflow of water into the production well. It also has the main purpose of ensuring the maintenance of the casing.

In the case of drilling at sea, particular care must be taken in the first part of the so-called conductive tube (conductor pipe) which is lowered to the top of the well, in this case at the bottom of the water, because this initial column serves guide for further drilling so that the tolerance for its inclination does not exceed a few degrees.

Shallow, the conductive tube is very sensitive to the temperature at the wellhead. For deep-water drilling, this temperature is that of the ocean floor, 4 ° C. In the Arctic zones, it may be below 0 C. However, the petroleum cements are normally designed for a temperature of more than 50 ° C. , with a setting time longer as the temperature is low. At the limit, in the Arctic zones, Portland cement grouts commonly used can freeze.

Various additives intended in particular to accelerate the setting times are known but under these extreme conditions, they reach their limits with unacceptable negative effects on the quality of the grout of cement as well as that of the hardened cement. As a result, formulations based on specific cements have been developed essentially in two types: plaster based formulations and aluminous cement based formulations. The formulations based on plaster, or more precisely plaster / Portland cement mixture, are preferred by many authors to formulations based on aluminous cements because the aluminous cements have a very exothermic hydration reaction that can lead to thawing of the formation. surrounding the borehole. (see FR 2,673,620, US 3,581,825;
US 3,891,454; US 4,176,720; US 4482,379; US 5,346,550; US 5,447,198).

Nevertheless, the setting times remain long. In particular waiting after cementation (Waiting
Cement = WOC) that is to say the period that elapses between the pumping and the moment when the cement develops a sufficient resistance to support the conductive tube, is about twenty hours or even more. Throughout this period, the drilling operations are interrupted and the drilling team immobilized, which represents very large ancillary costs.

By tailors, ocean floors are often sandy, poorly consolidated. As a result, low density cement slurries, generally in the range of 11 to 13 ppg (pounds per gallon, ie 1.32 g / cm3 to 1.56 g / cm3), should be used. In a basic way, the lightening of a cement slurry is obtained by increasing the quantity of water and - to avoid the phenomena of separation of the liquid and solid phases - the viscosity of the liquid phase by the addition in particular of bentonite or of sodium silicate. If for ordinary cement the mass ratio water / solids is normally between 38 and 46%, for slurry of such low density, this ratio is commonly more than 50% or even more than 60%. Such quantities of water result in a delay in the development of the compressive strength and therefore an increase in the waiting time after cementation.

 It is also known to lighten the grout by the addition of an inert gas (cement foam, see US 5,484,019) or light materials such as silica dust (FR 2 463 104), ceramic hollow balls. or glass (US 3,804,058, US 3,902,911 or US 4,252,193). These materials reduce but not suppress the amount of additional water added to the cement slurry to lighten it so that the development of compressive strength is less delayed. Nevertheless, the amount of water required remains high and after 24 hours, the compressive strength remains very low, generally not exceeding 600 psi (4136 kPa).

An aluminous cement / water / microsphere formulation is known from the US Pat.
United States 4,234,344 relating to cementing compositions subjected to high temperatures, in particular for a steam injection well. For an experimental well, this patent indicates the use of a formulation consisting of 100 parts (by weight) of Ciment Fondu (a mark of an aluminous cement containing 40% of alumina marketed by Lafarge, France), 55, 5 parts of hollow glass beads, 65 parts of silica flour, 0.5 parts of dispersant and 110 parts of water. No data is provided on setting time and compressive strength.

The present invention aims new low temperature cementation formulations, low density, capable of rapid development of compressive strength.

This object is achieved according to the invention by a formulation based on a aluminous hydraulic cement, which is characterized on the one hand by a very low porosity (the porosity is equal to the ratio of the volume of water to the total volume of the grout ) typically between 0.25 and 0.50 and preferably between 0.30 and 0.40 and secondly by the addition of hollow microspheres and fine particles.

In general, a dispersing agent is added to the composition and a cement setting accelerating agent, the dispersing agents known in the art generally having a retarding effect on the setting of the cement which must be compensated. Paradoxically, this retarding effect is also desired at the time of the preparation of the grout because the mixture is made on the surface, therefore at a temperature often close to 20 ° C so that the grout is more likely to take on the platform. Only other conventional additives may be added, such as antifoam agents or filtrate control or gas migration control agents.

Preferably, the solid particles of the mixture are in respective proportions such that the compactness of the mixture is maximum. The addition of fine particles thus makes it possible to obtain PVF (Packing volume fraction) values preferably greater than 0.75 and more preferably greater than 0.8. In this way, the mixing of the formulation does not pose any particular difficulties even with porosities as low as in the case of the invention.

On the other hand, very satisfactory rheologies are obtained which are favorable to good pumping conditions with, in particular, a virtual absence of sedimentation.

The fraction of the mixture consisting of fine particles may consist in particular of quartz or crushed glass, finely ground calcium carbonate, micron-sized silica (micro-silica), carbon black, iron oxide dust , red mud or screened fly ash. In general, the products compatible with aluminous cement and whose average diameter is of the order of 2 to 100 times smaller than the average diameter of the cement particles are suitable (that is to say between 0.075 and 7.5 He). Quartz, a crystalline material that is not very reactive, is more particularly preferred.

The aluminous cements considered in the context of the present invention are cements whose monocalcium aluminate (CA) content is greater than or equal to 60%, and more generally of the order of 80%, with, in comparison with ordinary cements, in particular Portland type, a particularly low silica content. Among the commercial products that may be used in the case of the present invention include the Fused Cement, Secar 51 (Lafarge), CA14M aluminous cement from Alcoa or Lumnite.

By hydration, CA forms a hexagonal compound CAH10 which corresponds to a very rapid development of compressive strength. At 20 ° C, 80% of the final strength is reached in 24 hours while it may take several days with a Portland type cement, so aluminous cements are outstanding candidates for the applications envisaged here. Aluminous cements are considered very sensitive to contaminants and are therefore little used.

As mentioned above, the formulations according to the invention have very low porosities, and even more remarkable that lower densities are desired. The low density required is obtained not by adding larger amounts of water as in the art but by adding a very light material consisting of hollow microspheres, preferably with a density of less than 0.8. Preferably, the microspheres used have an average diameter of between 2 and 20 times the average diameter of the aluminous cement particles. Particularly suitable are silico-aluminates or cenospheres, residue obtained during the combustion of coal, whose average diameter is of the order of 150 IC (about 10 times the average diameter of the molten cement). Also suitable are hollow glass beads.

Preferably, the solid phase of the composition consists of 35 to 65% (by volume) of cenospheres, for 20 to 45% of aluminous cement and for 5 to 25% of fine particles. In a more especially preferred embodiment, a part of the aluminous cement is replaced by silica flour (added in an amount generally of between 5 and 30% by volume of the solid phase) Fly ash or slag residues of furnaces (slag) can also be used as a partial substitute material for aluminous cement.With the addition of such an agent 'diluent' - silica flour, fly ash or slag -, aluminous cement represents only about a third of the solid fraction of the formulation so that the heat given off by the hydration reaction of the cement is minimized.Otherwise, as taught in US Patent 3,581,825, the hydration reaction can be modulated by addition of a small amount of amount of clay (especially attapulgite or preferably bentonite).

Other details and advantageous features of the invention will emerge from the following description of tests established for different examples of additive compositions, with reference to the figures which represent:
Figure 1: a characteristic curve of the setting of an aluminous cement, in
static conditions, for temperatures between 20 "C and 50" C.

Figure 2: a characteristic curve of the development of the compressive strength
an aluminous cement placed at 10 C.

. Figure 3: a characteristic curve of the setting of an aluminous cement, in
dynamic conditions, for temperatures between 10 C and 300C.

FIG. 4: a curve illustrating the retarding effect of a dispersing agent on the setting of a
aluminous cement.

FIG. 5: a curve illustrating the accelerating effect of setting obtained with carbonate of
lithium.

. Figure 6: a particle distribution curve of the aluminous cement used for the
tests reported in this document.

 Figure 7: a distribution curve of different fine particles suitable for the invention.

The aluminous cements considered in the context of the present invention are cements whose monocalcium aluminate content is greater than or equal to 60%, with secondary mineralogical phases essentially C12A7, C2S, ferrites, C4AF. Particularly suitable is the aluminous cement marketed by Lafarge under the name Ciment Fondu which consists of (weight percentages: A1203 (37.541.5%), CaO (36.5-39.5), SiO2 (2.5-5 , 0) and Fe 2 O 3 + FeO (14.0-18.0).

For the Fused Cement, analysis under static conditions of setting shows a steady increase in setting times when the temperature decreases to about 30 ° C and, very typically, a decrease in setting times This results, for example, from the tests reported in FIG. 1 obtained with a slurry consisting simply of molten cement, of water (water ratio 0.46) and of a
cement antifoaming agent at 0.05 gal / sk (concentrations in gallons per bag of cement of 94 pounds a concentration of 0.1 gal / sk or 0.1 gps thus corresponds to 0.90 liters of dispersant for
100 kg of cement). The thermal flux released by the hydration reaction is recorded on the ordinate.

For low porosity, aluminous cements also exhibit a particularly rapid development of compressive strength. Thus with a grout identical to that used for the previous test - but with a weight ratio water / cement of 40% can be seen in Figure 2 after only 10 hours of setting at 10 C (under a pressure of 400 psi ( 2758 kPa), about 80% of the final resistance is already reached.

Note however that under dynamic conditions, ie under the measurement conditions recommended by the API (American Petroleum Institute) Spec. For the measurement of setting time or "Thickening time", the behavior of the grout is very different.

Figure 3 shows the evolution over time of the consistency of a slurry prepared under the conditions of the test of Figure 1. The consistency is measured in standardized BC units. In general, a grout with a consistency greater than 100 BC is not pumped. It is found that the grout passes in a few minutes of a consistency less than 10 BC to the limit consistency of 100 BC. On the other hand, and contrary to the prediction of tests under static conditions, setting time increases substantially between 30 "C and 100C.

The formulations used in the previous tests do not include a dispersing agent. However, if under the conditions of a laboratory it is possible to prepare such formulations by stirring very strongly at the time of mixing, a dispersing agent is in practice necessary as soon as the quantities prepared become important. Conventional dispersing agents are generally compatible with aluminous cements. Citric acid, sodium salts, in particular sodium gluconate, sulphonate derivatives such as polymelamine sulphonates or polynaphthalene sulphonates, especially sodium polynaphthalene sulphonate / formaldehyde, are particularly suitable. These dispersants, however, have a significant retarding effect on the setting of the cement. Thus, as shown in FIG. 4, at 20 ° C., with a slurry consisting of Melt Cement and water (46% by mass ratio), the setting time is almost doubled by the addition of 0.01% of sodium gluconate.

This setting retarding effect can be compensated according to the invention by the addition of sodium silicate, calcium hydroxide, lithium hydroxide or else a lithium salt, especially lithium carbonate. This accelerating effect on the setting of the aluminous cement is shown in FIG. 5 where, as a function of time, the flow of heat released by the hydration reaction of a formulation consisting simply of molten cement and water (46% of water by weight of cement), at 20 ° C., by varying the concentration of lithium carbonate Remarkably, the effect is relatively gradual so that the setting time can be modulated practically at will as needed.

With cement / microsphere / water type formulations, as in the case of the patent
No. 4,234,344, large quantities of water are required to be able to pump the mixture, which has a very unfavorable effect on the development of compressive strength. In the case of the invention, the desired rheological properties are obtained in particular by the addition of fine particles which make it possible in particular to increase the compactness of the solids mixture. The formulations are preferably such that the PVF of the mixture is greater than 0.8 and more preferably 0.85 - that is, extremely high compactness rates. This can be obtained in particular by placing itself under the conditions recommended in the French patent FR-2 704 218: at least 3 solid species with disjoint granulomers, at least one of which is constituted by fine particles, in relative proportions maximizing compaction (with a PVF, or volume fraction of the compaction solid particles, maximum or near maximum for the selected combination of solid species), and a solids concentration in the slurry above the concentration threshold where the so-called collective sedimentation.

The particle size distribution of a 40% Cement Fused Cemented Alumina cement (Lafarge - France) is very close to that of Class G Portland cement as can be seen from Figure 6. The average diameter of particles are close to 1 5. The cenospheres have an average diameter of about 150CL.

From these two materials, to obtain a compactness of the high solids mixture, the fine fraction of the mixture must consist of particles whose average diameter is between 0.1 and 5 microns. This is particularly the case with particles such as those whose particle size distribution curve is shown in Figure 7: red sludge, carbon black, iron oxide dust, screened fly ash, fine calcium carbonate or quartz crushed thin.

Fly ash is a residual product of coal combustion, especially in thermal power plants. In modern installations, the burners are fed with a previously pulverized coal. The unburned fraction is vaporized in the fumes and condenses after cooling in the form of finely divided particles approximately spherical. The electrostatic filters of the chimneys capture all the particles of less than 200 p so that the particle size distribution is about the same as that of an ordinary cement. After screening, in particular a 50 micron screen, a majority of particles having a diameter of between 1 and 10 microns are obtained and which may in particular be suitable as fine particles for formulations in accordance with the invention.

Example 1
According to API standards, various Cement Fused cement grouts (Lafarge) were prepared. For all formulations, the porosity was set at 40%, the grout density was 1.56 g / cm 3 (13 ppg). The solid fraction of the mixture is constituted in addition to the molten cement (density 3.23), hollow microspheres of Cenosphere type (density 0.75, reference D124 from Schlumberger Dowell) and finely ground quartz (density 2.65;
E600 from Sifraco, France) identical to that used for FIG. 6. The proportions indicated for the solid constituents correspond to volume fractions of the solid fraction (BWOB = "by weight of blend").

For additives, dispersant and accelerator, the amount indicated is the quantity added in grams for a standard volume of 600 ml of cement slurry. Lithium carbonate was used as cement accelerator and as a dispersant, citric acid (reference D45 from Schlumberger Dowell)

<tb>#<SEP><SEP> Cement <SEP> Spheres <SEP> Hollow <SEP> Fine <SEP> Dispersant <SEP> Accelerator
<tb><SEP> Fade <SEP> (% <SEP> volume) <SEP> (% <SEP> (g / 600ml) <SEP> (g / 600ml)
<tb><SEP> (% <SEP> vol.) <SEP> volume
<tb> 1 <SEP> 0.40 <SEP> 0.50 <SEP> 0.10 <SEP> 0 <SEP> 0
<tb> 2 <SEP> 0.40 <SEP> 0.50 <SEP> 0.10 <SEP> 1 <SEP> 0
<tb> 3 <SEP> 0.40 <SEP> 0.50 <SEP> 0.10 <SEP> 1 <SEP> 0.01
<tb> 4 <SEP> 0.40 <SEP> 0.50 <SEP> 0.10 <SEP> 1 <SEP> 0.02
<Tb>
The following table gathers the results obtained with regard to the rheology of the grout (PV 1: Plastic viscosity, Ty ": Shear threshold), the volume of free water FW iii (Free
Water) and TT iv (Thickening Time). Measurements were made at 40C under API conditions.

<Tb>

<SEP> PV 'SEP> Ty <SEP> FW <SEP> iii <SEP><SEP> TT <SEP><SEP> iY <SEP> v
<tb>#<SEP> cP <SEP> Pa.s <SEP> Ibf / 100ft2 <SEP> Pa <SEP> ml <SEP> hr: min
<tb> 1 <SEP> 280 <SEP> 0.28 <SEP> 23 <SEP> 11.01 <SEP> 0 <SEP> 08:12
<tb> 2 <SEP> 249 <SEP> 0.249 <SEP> 28 <SEP> 13.41 <SEP> 0 <SEP> not <SEP> from <SEP> taken
<tb> 3 <SEP> 245 <SEP> = 0.245 <SEP> 26 <SEP> = 12.45 <SEP> 0 <SEP> 05:30
<tb> 4 <SEP> 240 <SEP> 0.24 <SEP> 25 <SEP> 11.97 <SEP> 0 <SEP> 03:08 <SEP>
<Tb>
The formulations tested are perfectly stable and there is no tendency to sedimentation as shown by the void volumes of free water. Rheological measurements were not performed for test # 3; the values shown are values extrapolated from the tests &num; 2 and &num; 4. In the absence of dispersant (test # 1) the viscosity of the mixture is a little high. On the other hand, the setting time remains long. Such a formulation has therefore been discarded.

The addition of a dispersant (test # 2) makes it possible to improve the viscosity but the grout no longer takes. This retarding effect is largely offset by the addition of a small amount of lithium carbonate (test # 3). The setting time is of the order of 3 hours with a lithium salt concentration of 0.033 g / l (test 4).

Example 2
The formulations of Example 1 - with a porosity always set at 40% - were repeated, but by replacing part of the aluminous cement with silica flour (reference D66 from Schlumberger Dowell), a variety of silica whose particle size is very close to that of the Fused Cement and a density of 2.65. Grouts # 5, # 6, # 7 and # 8 have a density of 1.52 g / cm 3 (12.7 ppg), the slurry of 1.50 g / cm 3 (12.5 g / cm 3). ppg).

<Tb>

<SEP>&num;<SEP> Cement <SEP> Flour <SEP> of <SEP> silica <SEP> Spheres <SEP> hollow <SEP> Fine <SEP> Dispersant <SEP> Accelerator
<tb><SEP> Fade <SEP> (% <SEP> vol.) <SEP> (% <SEP> volume) <SEP> (% <SEP> (g / 600ml) <SEP> (g / 600ml)
<tb><SEP> (% <SEP> vol.) <SEP> volume
<tb><SEP> 5 <SEP> 0.30 <SEP> 0.10 <SEP> 0.50 <SEP> 0.10 <SEP> 1.5 <SEP> 0
<tb><SEP> 6 <SEP> 0.30 <SEP> 0.10 <SEP> 0.50 <SEP> 0.10 <SEP> 1 <SEP> 0.02
<tb><SEP> 7 <SEP> 0.30 <SEP> 0.10 <SEP> 0.50 <SEP> 0.10 <SEP> 1.5 <SEP> 0.03
<tb><SEP> 8 <SEP> 0.30 <SEP> 0.10 <SEP> 0.50 <SEP> 0.10 <SEP> 1.5 <SEP> 0.3
<tb> 9 <SEP> 0.25 <SEP> 0.15 <SEP> 0.50 <SEP> 0.10 <SEP> 1.5 <SEP> 0.03
<Tb>
The formulations tested here correspond to high volume fractions of compaction (PVF). Thus for tests &num; 5 to &num; 8, the PVF is 0.836. For the last case, it is 0.834.

The results obtained at 4 ° C are reported in the following table where the values of the compressive strength were further indicated after 6 hours (V) and 24 hours (seen).

<Tb>

<SEP> Pv <SEP> Ty <SEP> FW <SEP>'<SEP> TT <SEP> CS <SEP> 6 <SEP> h <SEP> v <SEP> CS <SEP> 24 <SEP> h
<tb>&num;<SEP> cP <SEP> Not <SEP> lbf / 100ft2 <SEP> Pa <SEP> nil <SEP> h: min <SEP> psi <SEP> | <SEP> N / cm2 <SEP> psi <SEP> N / cm2
<tb> 5 <SEP> 252 <SEP> 0.252 <SEP> 25 <SEP> 11.97 <SEP> O <SEP><SEP> 06:25 <SEP> Nil <SEP> 2300 <SEP> 1586
<tb> 6 <SEP> 232 <SEP> 0.232 <SEP> 22 <SEP> 10.53 <SEP> 0 <SEP> 03:25 <SEP> 2833 <SEP> 1953 <SEP> 3628 <SEP> 2502
<tb> 7 <SEP> 230 <SEP> 0.230 <SEP> 15 <SEP> 7.18 <SEP> 1 <SEP> 02:50 <SEP> 1230 <SE> 848 <SE> 3800 <SEP> 2620
<tb> 8 <SEP> 210 <SEP> 0.210 <SEP> 12 <SEP> 5.75 <SEP> 1.5 <SEP> 0:45 <SEP> 1700 <SEQ> 1172 <SEW> 4620 <SEP> 3185
<tb> 9 <SEP> 240 <SEQ> 0.240 <SEP> 18 <SEP> 8.62 <SEP> 1 <SEP> 03:20 <SEW> 1540 <SEW> 1062 <SEQ> 4000 <SEQ> 2758
<Tb>
Again, formulations with a lithium salt give very short setting times and very high compressive stresses at such temperatures. By modulating the amount of accelerator, the setting time can be very easily elongated or, on the contrary, delayed as needed.

On the other hand, the values of the compressive strength are particularly high.

Recall in this regard that values greater than 500 psi are hardly obtained with the compositions according to the art for similar temperatures.

Example 3
For this example, for the fine fraction of the mixture, the fine quartz was replaced by fly ash screened at 50p (density 2.3 g / cm3).

<tb>&num;<SEP>'<SEP> Cement <SEP> Flour <SEP> of <SEP> Silica <SEP><SEP> Hollow Spheres <SEP> Fine <SEP> Dispersant <SEP>SEP> Density <SEP>
<tb><SEP> Fade <SEP> (% <SEP> vol.) <SEP> (% <SEP> volume) <SEP> (% <SEP> (g / 600ml) <SEP> grout
<tb><SEP> (% <SEP> vol.) <SEP> volume) <SEP> (ç / cm3) <SEP>
<tb> 11 <SEP> 0.40 <SEP> 0.00 <SEP> 0.50 <SEP> 0.10 <SEP> 1 <SEP> 1.56
<tb> 12 <SEP> 0.30 <SEP> 0.10 <SEP> 0.50 <SEP> 0.10 <SEP> 1 <SEP> 1.52
<tb> 13 <SEP> 0.25 <SEP> ~ <SEP><SEP> 0.15 <SEP> ~ <SEP><SEP> 0.50 <SEP> 0.10 <SEP> 1 <SEP> 1 50
<Tb>
The formulations were tested at 40C. Since they do not include a cement setting accelerator, the measurements of setting time and compressive strength after 6 hours have not been performed. For this example, the value of the compressive strength at 24 hours is significant of the values that can be obtained in the short term with a setting accelerator of the cement.

<Tb>

<SEP> PV <SEP> Ty <SEP> FW <SEP> 24 <SEP> h <SEP>
<tb>#<SEP> cP <SEP> Pa.s <SEP> lbf / 100ft2 <SEP> Pa <SEP> ml <SEP> psi <SEP> Nlcm2 <SEP>
<tb> 11 <SEP> 266 <SEP> 0.266 <SEP> 9 <SEP> 4.31 <SEP> 0 <SEP> 3850 <SEP> 2655
<tb> 12 <SEP> 279 <SEP> 0.279 <SEP> 7 <SEP> 3.35 <SEP> 0 <SEP> 962 <SEP> 663
<tb> 13 <SEP> 273 <SEP> 0.273 <SEP> 6 <SEP> 2.87 <SEP> 0 <SEP> 752 <SEP> 519
<Tb>
Again, the rheologies are very satisfactory (the plastic viscosity may seem a little high but it should be noted that as previously, the porosity of the grout was fixed at only 40% and that at such a level, it is remarkable in itself that the grout is perfectly mixable and pumpable.

The compressive strength decreases as the amount of aluminous cement decreases in the grout. On the other hand, the rheological performances are slightly lower, which is notably due to a less compactness of the mixtures. Formulations with a low proportion of aluminous cement nevertheless remain interesting in the case where the exothermicity of the hydration reaction of the cement can pose a problem. On the other hand, aluminous cements are much more expensive than silica flour.

Example 4
It has been verified that other common dispersants can be used by testing a formulation with a PNS dispersant (Polynaphthalene Sulfonate;
Schlumberger Dowell) and a dispersant of the PMS type (Polymélanine Sulfoante;
D145A from Schlumberger Dowell). The slurries have a density of 1.52 g / cm3.

The setting accelerator of the cement is lithium carbonate.

<Tb>

&Num;<SEP> Cement <SEP> Flour <SEP> of <SEP> Silica <SEP><SEP> Spheres <SEP> Thin <S
The results of the measurements at 4 ° C. are summarized in the following table: The pumpability time corresponds to a consistency of 100 ° C.

<Tb>

<SEP> Properties of <SEP> Grout <SEP> Test <SEP> Test
<tb><SEP>&num; 16 <SEP>&num; 17
<tb> Viscosity <SEP> Plastic <SEP> cP <SEP> nd <SEP> 95.4
<tb><SEP> [Pa.s] <SEP> [0,954]
<tb> Threshold <SEP> of <SEP> shear <SEP> lbf / 100ft2) <SEP> nd <SEP> 0.2
<tb><SEP> [Pa] <SEP> [O, 10] <SEP>
<tb><SEP> time of <SEP> corresponding <SEP><SEP><SEP><SEP><SEP><SEP><SEP>
<tb> compression <SEP> of <SEP> ... 50 <SEP> psi <SEP> [34 <SEP> N / cm2] <SEP> 3:16 <SEP> 13:58
<tb><SEP> ... 500 <SEP> psi <SEP> [848 <SEQ> N / cm2] <SEP> 4:12 <SEP> 15: <SEP> 15
<tb> Resistance <SEP> to <SEP><SEP> Compression <SEP> After ... <SEP> 24 <SEP> Hours <SEP> (psi) <SEP> 3760 <SEP> 3349
<tb><SEP> [N / cm] <SEP> [2593] <SEP> [2309]
<tb><SEP> .48 <SEP> hours <SEP> (psi) <SEP> 4203 <SEP> n / a
<tb><SEP> [N / cm] <SEP> [2898]
<tb> Time <SEP> of <SEP> Pumpability <SEP> 3:45
<tb> Water <SEP> free <SEP> (ml) <SEP> O
<tb> Losses <SEP> of <SEP> fluids <SEP> (ml / 30 <SEP> min) <SEP> 40
<Tb>
The examples given above should not be considered as limiting. In particular, the principle of the invention can be applied to cementation compositions of 'normal' or even relatively high density. To do this, the hollow microspheres will be replaced by spherical particles of the same size but of greater density.

Claims (15)

claims 1. Cement composition for oil wells or the like essentially constituted  a mixture of solids comprising a medium component comprising at least one  aluminous hydraulic cement, fine particles, and hollow microspheres,  water, with a porosity of between 0.25 and 0.5 (preferably between 0.3 and 0.4).  conventional additives.  a dispersant, a setting accelerator of the aluminous cement and any other 2. Cementation composition according to claim 1, characterized in that the  relative proportions between the different solid constituents of the mixture are such that its  compactness is maximum. 3. Cementation composition according to claim 1 or 2, characterized in that said  aluminous hydraulic cement is made up of at least 60% aluminate  monocalcium. 4. Cementation composition according to one of the preceding claims, characterized in that  that the mixture of solids has, in volume,  - 20 to 45 parts of medium component,  5 to 25 parts of fine particles,  35 to 65 parts of hollow microspheres. 5. Cementation composition according to one of the preceding claims, characterized in that  that said medium component is a mixture of aluminous cement and a diluent agent  of particle size similar to silica flour type, fly ash or slag from high  furnaces. 6. Cementation composition according to one of the preceding claims, characterized in that  said diluent agent is in a volume proportion of between 5 and 30% of  mixture of solids. 7. Cementation composition according to one of the preceding claims, characterized in that  that said fine particles have an average diameter of between 0.01 and 0.5 times the  average diameter of aluminous cement particles. 8. Cementation composition according to claim 7, characterized in that said  Fine particles are quartz or ground glass, finely ground calcium carbonate,  microsilica, carbon black, iron oxide dust, red mud or fly ash  dim. 9. cementing composition according to one of the preceding claims, characterized in  that said microspheres have a mean diameter of between 2 and 20 times the  average diameter of aluminous cement particles. 10. Cementation composition according to claim 9, characterized in that said  microspheres are cenospheres. 11. cementing composition according to one of the preceding claims, characterized in  that the dispersant is of the citric acid type, sulfonate derivative such as polymelamine  sulphonates or polynaphthalene sulphonates, especially polynaphthalene sulphonate  sodium / formaldehyde. 12. Cementation composition according to one of the preceding claims, characterized in  what the cement setting accelerator is a lithium salt 13. Cementation composition according to claim 12, characterized in that the accelerator  Cement intake is lithium carbonate. 14. Cementation composition according to one of the preceding claims, characterized in  it further comprises an anti-foam agent. 15. Application of a cementing composition according to one of the claims  preceding the cementation of the conductive tube of a petroleum well or the like located  in an arctic zone or deep water drilling.