WO1999033763A1

WO1999033763A1 - Controlling setting in a high-alumina cement

Info

Publication number: WO1999033763A1
Application number: PCT/EP1998/008535
Authority: WO
Inventors: Michel Michaux
Original assignee: Sofitech NV; Schlumberger Canada Ltd; Compagnie des Services Dowell Schlumberger SA
Current assignee: Sofitech NV; Schlumberger Canada Ltd; Compagnie des Services Dowell Schlumberger SA
Priority date: 1997-12-24
Filing date: 1998-12-17
Publication date: 1999-07-08
Anticipated expiration: 2000-06-24
Also published as: FR2772743A1; FR2772743B1; AU2277199A

Abstract

The invention relates to the use of at least one additive selected from ethylene-diamine-tetraacetic acid, ethylene-diamine-tetramethylene phosphonic acid, polyoxyethylene phosphonic acid, citric acid, orthoboric acid, and their salts, mono- and di-saccharides, their acid derivatives, and their salts, as a retarder for setting a high-alumina cement at a high temperature. Setting of a cement slurry containing one of these additives can be induced at the desired moment by adding a lithium salt.

Description

CONTROLLING SETTING IN A HIGH-ALUMINA CEMENT

The present invention relates to controlling setting in cementation compositions.

When drilling wells or tunnels, the walls often have to be cemented as work proceeds to consolidate them and/or to hold the structures introduced therein. A cement slurry is normally prepared outside the well or tunnel and is injected into it to be projected against the wall of the zone to be consolidated.

In order to obtain the desired consolidation as quickly as possible and avoid slowing down the drilling operation, a quick-setting cement is usually used; however, the cement slurry must remain liquid until it is used, to avoid blocking the injection and application apparatus. It is possible to increase the setting rate of a cement slurry by adding accelerators; for Portland type cements based on tricalcium silicate, for example, strongly alkaline solutions of silicates or aluminates are routinely used. United States patent us-A-5 591 259 describes the use of alkaline salts of malic acid or citramalic acid; such accelerators are added to the cement slurry immediately prior to projection.

Portland type cements are most frequently used; however, for applications such as well consolidation, high-alumina cements have the advantage of rapidly developing high compressive strength.

The essential constituent of high-alumina cements is monocalcium aluminate (CA, using the standard cement nomenclature, where: C=Ca0, A=A1₂0₃, S=SiO₂, F=Fe₂0₃, H=H O). High-alumina cements in normal use contain at least about 40% of monocalcium aluminate; examples are Ciment Fondu and SECAR 51 sold by LAFARGE, CA14M cement sold by ALCOHA, and Lumnite sold by LEHY PORTLAND CEMENT Co. Such cements also contain a secondary mineral phase principally constituted by ferrites, Cι₂A₇, C₂S, C AF.

Setting and hardening of high-alumina cements principally results from hydration of monocalcium aluminate. After cement powder has been mixed with water, there is a latency period of several minutes to several hours, depending on the reaction conditions, during which a supersaturated solution of hydration products AH₃, CAH_]0, and C₂AH_g forms. At the end of that period, a transition period is observed during which massive precipitation of the hydration products occurs, along with acceleration of the hydration reaction, resulting in the cement setting. Cement cohesion and strength are essentially due to interlocking of hexagonal hydrated calcium aluminate crystals CAH₁₀ and C₇AH_g. Rapid formation of such products causes high initial strength.

Lithium salts are generally used to accelerate setting of high-alumina cements; setting can be almost immediate in this way.

Even in the absence of an accelerator, the setting time for high-alumina cements is substantially reduced when the temperature rises above 30°C. This is a major disadvantage when the cement has to be prepared in advance and used at high temperatures, for example in an injection apparatus.

In general, high-alumina cements are more difficult to use than Portland cements; they are particularly sensitive to contaminants and the use and/or conditions for use of certain additives can modify their properties in an unpredictable manner.

In the construction industry, certain additives used for their dispersing properties, such as citric acid or sodium salts, are known to retard setting; to compensate for that, lithium salts are added to the mixing water at the same time as the additives when preparing high-alumina cement slurries.

The inventor envisaged using such additives to retard setting in high-alumina cements, in particular to enable them to be transported to the point of use.

However, it was not known whether such agents would also have an effect at high temperatures where, as indicated above, setting is much faster. Further, the effect of adding accelerators such as lithium salts during the latency period of a slurry "retarded" by other additives was not known.

The inventor has researched high-alumina cement retarders which are active at high temperatures, i.e., over 30°C. This research has led to a selection of certain additives with this property, and among these, to retarders which remain very active up to temperatures of the order of 80°C to 100°C.

The inventor has also established that rapid setting, and even flash setting, of a slurry retarded by these additives can be caused by adding lithium salts during the latency period.

The present invention provides the use of an additive selected from the group formed by ethylene-diamine-tetraacetic acid, ethylene-diamine-tetramethylene phosphonic acid, polyoxyethylene phosphonic acid, citric acid, orthoboric acid, and their salts, mono- and di-saccharides, their acid derivatives, and their salts, as a retarder for a high-alumina cement at a temperature of over 30°C, in particular at a temperature of over 40°C. Preferred additives for use in accordance with the invention are selected from the group formed by the disodium salt of ethylene-diamine-tetraacetic acid, the sodium and calcium salt of ethylene-diamine-tetramethylene phosphonic acid, polyoxyethylene phosphonic acid, citric acid, trisodium citrate, orthoboric acid, glucose, saccharose, calcium glucoheptonate, and sodium gluconate.

In a preferred implementation of the present invention, the additive is used in a concentration which is in the range 0.01% to 2% (by weight of cement), preferably at a concentration which is in the range 0.05% to 0.5% BWOC.

Advantageously, depending on the maximum temperature at which the cement is intended to be used, the following is selected:

- for a temperature of the order of 40°C, orthoboric acid, calcium glucoheptonate, polyoxyethylene di-phosphonate, the disodium salt of EDTA, and sodium gluconate;

- for a temperature of the order of 50°C, the disodium salt of EDTA and sodium gluconate;

- for a temperature of over 60°C, the disodium salt of EDTA, sodium gluconate, glucose and saccharose; the latter two are particularly suitable for use at temperatures of the order of 70°C to 80°C or above. Particularly preferred additives are those which, while prolonging the latency period, do not significantly reduce the intensity of the heat flow peak. This indicates that these additives cause optimal development of the massive hydration reaction which is the source of the initial strength.

The present invention also provides a process for controlling setting in a high-alumina cement slurry, characterized in that it comprises:

during preparation of the slurry, adding at least one retarder selected from those cited above;

activating setting by adding lithium salts to the slurry during the latency period.

The process of the invention can suspend setting for the required period, for example during transport or pumping to the location that is to be cemented, and bring about setting at the desired time. Steps a) and b) are generally carried out at an interval of the order of several minutes to several hours.

As an example, the process of the invention can be implemented for cementing a well using an apparatus for pumping the retarded slurry obtained from step a) to the zone to be cemented, and mixing that slurry with the lithium salts immediately before application to the zone to be cemented, for example by projection through a nozzle.

For a given temperature, the nature and concentration of the retarder, the concentration of the lithium salt, the period during which setting of the slurry is to be suspended, and the moment for intervention are selected. Depending on the temperature at which the operation is to be carried out, the retarder used and the concentration at which the retarder is used, lithium salts can then be added in a concentration which is in the range 0.001% to 1% BWOC, generally less than 0.05%.

The present invention is illustrated in the following non limiting examples.

EXAMPLE 1 : SELECTION OF POTENTIAL RETARDERS :

The influence of various additives on the setting properties of Ciment Fondu was studied under static conditions by calorimetry, at temperatures of 40°C to 80°C. Cement slurries were prepared with a W/C (water/cement) ratio of 0.40, in the presence of anti-foaming agent DO47 (sold by SCHLUMBERGER DOWELL) in a concentration of 0.03 gps (gallons (gal) per 94 pound (lb) sack of cement; a concentration of 0.1 gps corresponds to 0.90 litres of anti-foaming agent per 100 kg of cement). The density of the slurry was 16.5 lb/gal, i.e., 1.98 kg/1. Each additive to be tested was dissolved in mixing water before adding the cement.

The various additives tested were:

calcium glucoheptonate, sodium gluconate, CHRYSOFLUIDE OPTIMA 100 (polyoxyethylene chain of 70 monomers, carrying a di-phosphonate end group, sold by CHRYSO), DEQUEST 2047 (sodium and calcium salt of ethylene-diamine- tetramethylene phosphonic acid, sold by MONSANTO), citric acid, orthoboric acid, trisodium citrate, sodium dihydrogen phosphate, the disodium salt of EDTA, lignosulphonate (LS), polynaphtalene sulphonate (pns), a mixture of lignin amine and Na glucoheptonate, glucose, and saccharose.

30 g of slurry was placed in a test tube which was introduced into an oven heated to the test temperature. The heat flow around the tube was measured using a series of thermocouples, and recorded over time. Cement setting appeared as a peak in the heat flow resulting from the heat released by hydration of the cement.

For each test, the following was determined from the thermograms obtained:

The time between the start of the test and the start of the heat flow peak: this time corresponded to the duration of the latency period;

The time between the start of the test and the maximum of the heat flow peak;

The transition time, defined as the time between the start of the heat flow peak and its maximum;

The intensity of the heat flow peak at its maximum. The results of these tests are shown in Tables I to IV below; for each additive, the concentration of the active ingredient or mixture of active ingredients is expressed in % BWOC.

Table I shows the results of tests carried out at 40°C.

TABLE I

These results show that at 40°C, a large number of the tested additives had a large retarding effect. The most effective were: orthoboric acid, calcium glucoheptonate, CHRYSOFLUIDE OPTIMA 100, the disodium salt of EDTA, and sodium gluconate. Other additives such as DEQUEST 2047, trisodium citrate and citric acid can also be used, but are less effective at the same concentration.

In contrast, other additives, in particular Na^PO^ and polynaphtalene sulphonate, slightly accelerated setting.

Table II below shows the results of tests carried out at 50°C.

TABLE π

These results confirm that at 50°C, the effectiveness of the majority of retarders which were active at 40°C reduced; the retarders which were the most effective at this temperature were the disodium salt of EDTA and sodium gluconate, and in particular glucose and saccharose, which exhibited a very large retarding effect even at the lower test concentration.

Tables III and IV below respectively show the results of tests carried out at 70°C and at 80°C.

TABLE m

TABLE IV

At temperatures of the order of 70°C to 80°C, only sodium gluconate, glucose and saccharose could be used as retarders. The most effective of these products was saccharose.

Further, for glucose and saccharose (in particular the latter), it can be seen that, while the latency period was considerably prolonged by the presence of the additive, the transition time remained short and the intensity of the peak of the heat flow was not significantly reduced. This indicates that the additive did not reduce the degree of hydration when the cement set, and thus compression strength development remained rapid.

Thickening tests were carried out at temperatures of 40°C, 50°C, 60°C and 70°C, with additives which appeared from the above results to be the most suitable for each of these temperatures. The thickening time, TT, measured at atmospheric pressure, was determined under dynamic conditions using the method recommended by the API (American Petroleum Institute), Spec.10.

The results of these tests are shown in Table V below:

TABLE V

EXEMPLE 2 : ACCELERATION OF SETTING USING LITHIUM SALTS.

In order to determine whether the action of selected retarders interfered with the activating effects of lithium salts or otherwise, the effect of adding these latter to a cement slurry after a certain hydration time in the presence of a retarder was tested.

The slurries were prepared as described in Example 1. The influence of the different retarders and various concentrations of lithium salts on setting of Ciment Fondu was studied by isothermal calorimetry under the conditions described in Example 1 above.

When the slurry reached the test temperature (indicated by a heat flow of 0), the tube was removed from the oven. A small volume (between 0.5 ml and 1 ml) of a dilute lithium salt solution was then introduced into the slurry, which was stirred for 20 seconds. The test tube was then immediately re-introduced into the oven to follow the hydration kinetics.

The results are shown in Figures 1 to 6.

Figure 1 represents thermograms obtained at 40°C in the presence of 0.1% BWOC citric acid, in the absence of lithium (■), or at concentrations of 0.02% (•), 0.05% (A), or 0.1% (♦) BWOC of lithium nitrate.

Figure 2 represents thermograms obtained at 40°C, in the presence of 0.1% BWOC of Na EDTA, in the absence of lithium (■), or at concentrations of 0.02% (•), 0.05% (A), or 0.1 % (♦) BWOC of lithium nitrate.

Figure 3 represents thermograms obtained at 50°C, in the presence of 0.2% BWOC of sodium gluconate, in the absence of lithium (■), or at concentrations of 0.01% (•), 0.02% (A), or 0.1% (♦) BWOC of lithium nitrate.

Figure 4 represents thermograms obtained at a 70°C, in the presence of 0.5% BWOC of glucose, in the absence of lithium (■), or at concentrations of 0.01% (•), 0.02% (A), 0.05% (♦), or 0.1% (D) BWOC of lithium nitrate.

Figure 5 represents thermograms obtained at 70°C, in the presence of 0.2% BWOC of saccharose, in the absence of lithium (■), or at concentrations of 0.05% (•), or 0.1% (A) BWOC of lithium nitrate.

Figure 6 represents thermograms obtained at 70°C, in the presence of 0.5% BWOC of saccharose, in the absence of lithium (■), or at concentrations of 0.02% (•), 0.05% (A), 0.075% (♦), 0.1% (D), 0.2% (O), 0.5% (Δ) BWOC of lithium nitrate. It can be seen that the latency period reduced as the concentration of lithium increased: immediate setting (flash setting) was observed for a lithium nitrate concentration of 0.1 % BWOC.

These results show that the addition of small quantities of lithium nitrate to a slurry which has been previously prepared in the presence of a retarder can inhibit the effect of that retarder, leading to flash setting if the concentration of the activator is sufficiently high.

The nature of the retarder is not critical, although it can be seen that a slurry retarded with saccharose appeared to be more difficult to activate than that retarded with glucose.

The same experiments were carried out with other lithium salts (hydroxide and chloride). The results were very similar for the same lithium concentration.

It has thus been demonstrated that it is possible to effectively activate (flash set) a Ciment Fondu slurry which has previously been retarded, at temperatures ranging from 40°C to 70°C, whatever the retarder employed.

Claims

1) Use of at least one additive selected from the group formed by ethylene-diamine- tetraacetic acid, ethylene-diamine-tetramethylene phosphonic acid, polyoxyethylene phosphonic acid, citric acid, orthoboric acid, and their salts, mono- and di-saccharides, their acid derivatives, and their salts, as a retarder for a high-alumina cement at a temperature of over 30°C.

2) Use according to claim 1, characterized in that said additive is used in a concentration which is in the range 0.01% to 2% by weight of cement.

3) Use according to claim 1 or claim 2, characterized in that the additive used is selected from the group formed by orthoboric acid, polyoxyethylene phosphonic acid, and salts of glucoheptonic acid, as a retarder for a high-alumina cement at a temperature of less than about 50°C.

4) Use according to claim 1 or claim 2, characterized in that the additive used is selected from the group formed by gluconic salts and salts of ethylene-diamine- tetraacetic acid, as a retarder for a high-alumina cement at a temperature of less than about 70°C.

5) Use according to claim 1 or claim 2, characterized in that the additive used is selected from the group formed by glucose and saccharose, as a retarder for a high- alumina cement at a temperature of less than 100°C.

6) A process for controlling setting of a high-alumina cement slurry, characterized in that it comprises:

a) adding to said slurry during preparat

b) ion, at least one retarder selected from the group formed by ethylene-diamine- tetraacetic acid, ethylene-diamine-tetramethylene phosphonic acid, polyoxyethylene phosphonic acid, citric acid, orthoboric acid, and their salts, mono- and di-saccharides, their acid derivatives, and their salts, c) activating setting by adding at least one lithium salt to said slurry during the latency period.

7) A process according to claim 6, characterized in that the lithium salt is added in a concentration which is in the range 0.001% to 1% by weight of cement.