EP0458852A1

EP0458852A1 - Thinned cement slurry for use in the cementation of wells for producing hydrocarbons

Info

Publication number: EP0458852A1
Application number: EP90903377A
Authority: EP
Inventors: Daniel Baffreau; Jean-Claude Laugerotte; Nicolas Musikas
Original assignee: Total Compagnie Francaise des Petroles SA; Ciments d'Origny
Current assignee: Total Compagnie Francaise des Petroles SA; Ciments d'Origny
Priority date: 1989-02-14
Filing date: 1990-02-12
Publication date: 1991-12-04
Also published as: BR9007048A; FR2643068A1; OA09900A; US5207832A; WO1990009357A1; FR2643068B1

Abstract

L'invention concerne un coulis allégé de ciment comprenant un ciment hydraulique, de l'eau et des additifs usuels des ciments. Ce coulis comprend entre 5 et 65 % et, de préférence, entre 25 et 40 %, rapporté au poids de ciment, de fumées de silice et de 1 à 25 % et, de préférence, de 5 à 15 %, rapporté au poids d'eau, d'au moins une polyéthylène imine ou d'au moins un dérivé d'une polyéthylène imine.The invention relates to a light cement grout comprising a hydraulic cement, water and usual cement additives. This grout comprises between 5 and 65% and preferably between 25 and 40%, based on the weight of cement, silica fumes and 1 to 25% and, preferably, 5 to 15%, based on the weight of water, at least one polyethylene imine or at least one derivative of a polyethylene imine.

Description

LIGHT CEMENT GROUT FOR USE IN CEMENTING HYDROCARBON WELLS.

The present invention relates to compositions called "cement slag" by petroleum companies and "cement slurry" by cement manufacturers. It more particularly relates to a lightened cement grout, suitable for being used for the cementing of wells for the production of natural hydrocarbons (oil or gas).

It is known that this cementing takes place between the external part of the casing and the wall of the well, with a view, on the one hand, to supporting all of the tubes, on the other hand, preventing the passage of liquid or gas under pressure from the underground layers in which drilling is carried out. It is particularly important that the cements used for this purpose exhibit, after hardening, a rapid and excellent resistance to compression, in order to have satisfactory mechanical characteristics.

Furthermore, it is often necessary for them to be gas-tight, in order to effectively oppose the passage of gas, under high pressure, present in the drilled layers, which risk migrating through the cement, even during the taken of it.

However, it is common for the drilled layers to have too low a mechanical strength for cements having a high specific mass, of the order of 1.6 to 1.9 g / cm ³ , to be used, and must in this case use so-called "light" cements, the density of which can be between 1 and 1.6, in which inert or active lightening charges are incorporated.

Many types of fillers have been proposed in the art.

It has thus been suggested to use hollow glass microspheres containing air or an inert gas. However, such charges pose serious risks to pumps and injection systems, as they can burst or implode. In addition, the density cement grout is difficult to adjust. Finally, such lightening products are expensive.

It has also been proposed to use silicates as lightening fillers, but these compounds have a low resistance to compression.

Finally, it has been envisaged to incorporate into the cement slurry compounds capable of producing a gas in situ, which forms bubbles there. This solution is possible for shallow areas and this process is more expensive, but it is difficult to implement, because the diameter of the gas bubbles cannot be effectively controlled and the bubbles facilitate cracking of the cement.

In all cases, the gas tightness of cements lightened by these means poses serious problems which have been sought for a long time to be resolved.

FR-A-2 587 988 thus proposes to use, in a slag of hydraulic cement containing as lightening charge light aggregates such as hollow microspheres, a sealing agent constituted by dust particles of silica, representing from 5 to 100% by weight of the hydraulic cement. These silica particles can be secondary products from electric furnaces used for the production of silicon or ferrosilicon. The present invention also relates to lightened cement grouts containing fine silica particles and it aims to improve the compressive strength of the cements obtained from these grouts and to eliminate or limit the shrinkage of these cements. An object of the invention is, therefore, to propose a formulation of light cement grout, with a density between 1.20 and 1.70, having high mechanical performance and whose compressive strength, in particular, variable , with the density, can reach and exceed 15 MPa for a density of 1.40 and 30 MPa for a density of 1.60, after 24 hours and at a temperature of 60 ° C.

Another object of the invention is to provide a grout lightened of this type which is gas tight, even under high pressure, during its installation in an oil drilling.

The invention also aims to provide a lightened grout of this type which is compatible with the usual additives and adjuvants of the art.

The object of the invention is also to propose a lightened grout of this type which can be used at high temperature (above 110 ° C.) without the addition of siliceous adjuvant, a product usually used to avoid the phenomenon of reduction in mechanical resistance, phenomenon observed with Portland type cements.

The invention finally aims to provide a lightened grout of this type whose rheological properties are close to those of conventional cement grouts and thus allow its injection and its establishment in hydrocarbon wells by the means usually used in the technique.

To this end, contrary to the teachings of the prior art mentioned above, the present invention no longer uses silica microparticles as a cement sealing agent, but as a load for lightening the grout, the sealing function being provided by a polyethylene imine, as taught in french patent application FR-a-2569759, in the name of the Applicant, this compound acting outr _e as a plasticizer within the grout.

The invention therefore relates to a lightened cement grout comprising a hydraulic cement, water and usual cement additives, characterized in that it comprises between 5 and 65% and, preferably, between 25 and 40 %, based on the weight of cement, silica fumes and 1 to 25% and preferably 5 to 15%, based on the weight of water, of at least one liquid polyethylene imine, having a molecular weight of between 600,000 and 1,000,000, or at least one derivative of such polyethylene.

The invention also relates to a method of cementing of a hydrocarbon production well, characterized in that a cement slag as defined above is prepared and that it is injected into the well, at the periphery of the tubes and on minus part of their length, between them and the adjoining terrain.

For the purposes of the present application, the expression “silica fumes” is understood to mean microparticles recovered from the fumes emitted by electric furnaces for manufacturing silicon and its alloys, in particular ferrosilicon, and the silica content of which is around 85 98%. These particles have a maximum size of between 0.01 micron and 1 micron, with an average size of a few tenths of a micron and a specific surface

1} between 15 and 25 m / g, some of these particles can be welded together to form small clusters.

The cement used can be of any type usually used in oil drilling. It will most usually be an artificial P0RTLAND cement.

It is possible to use either fresh water or sea water to prepare the lightened grout in accordance with the present invention, the exact proportions of the various constituents being simply adjusted according to the type of water used.

The polyethylene imine will preferably be incorporated in the form of an aqueous solution.

The silica fumes being very difficult to handle in the raw state, because of their very low density and their volatility, they will advantageously be used either in the form of a stable suspension, for example at 50% by weight of silica, or in a compacted form by vibration or pressure, reducing for example their apparent volume by a factor of 2.5. To avoid flocculation of the silica fumes when adding the polyethylene imine, the light slag will preferably be prepared by a process comprising the following successive phases: - incorporation of poly thylene imine in water intended for the mixing of cement, preferably in the presence of an anti-foaming product;

- incorporation of the silica fumes in the mixture of water and polyethylene imine to form a suspension;

- Redispersion of the silica fumes within the resulting mixture using ultrasonic and mechanical processes; - possible incorporation in the mixture of usual additives such as dispersants and / or retardants; mixing the cement with the mixture thus,, -, carried out.

It will be noted that such a method can be implemented very easily on construction sites, at a low cost and generally lower than those of the methods usually used in the art.

The tests carried out by the Applicant show that the grout compositions according to the invention which have the best compressive strength relative to the density sought are those comprising between 30 and 65% of silica fumes, relative to the weight of cement, and 5 to 15% polyethylene imine, based on the weight of water. Thus a cement slurry comprising PORTLAND cement, 30% of silica fumes relative to the weight of the cement, water and 10% of polyethylene imine relative to the weight of water has resistance to compression of 16 MPa (i.e. 2300 psi) which is quite remarkable. Likewise, a composition comprising PORTLAND cement, 35% of silica fumes relative to the weight of the cement, water and 15% of polyethylene imine relative to the weight of water has a compressive strength of 17 MPa, i.e. 2400 psi The examples of tests which will follow are not limiting. They illustrate, on the one hand, the advantages of the lightened grout of the cement of the invention, compared to those of the prior art, and, on the other hand part, a valuation of his own physical qualities.

In these examples, reference will be made to the appended drawings, in which:

FIG. 1 represents a curve relating to compression tests on cements in accordance with the invention;

FIG. 2 is a diagram of an apparatus used for testing gas flow through the cement;

Figures 3 to 8 are curves relating to other tests.

In all the examples which are given below, the polyethylene imine has a molecular weight of 800,000 and is used in the form of an aqueous solution at 33% by weight of polyethylene imine. I- COMPARATIVE EXAMPLES

Example 1 Two light cement grouts are prepared, the first, Ai, according to the prior art, the second I_, according to the invention. Both have a density of 1.4. Composition of Ai

- Cement G: 411 g,

- Bentonite

(incorporated in dry cement): 4 g,

- Glass microspheres: 102 g, - Dispersant: 0.7 ml,

- Water container: 2 g,

- Self-timer: 0.9 ml,

- Fresh water: 322 ml. Composition of Bi - Cement G: 267 g,

- Suspension of silica fumes: 232 g,

- Polyethylene imine: 46 ml,

- Dispersant: 5 g,

- Self-timer: 4 g, - Fresh water: 291 ml.

The two cement grouts of this composition were tested according to the conditions of cementing a casing of 9 "5/8 at 2650m. The results of the tests were as follows:

- Pump-down time or simulation of grout placement:

* Coulis Ai: 408 minutes; * Bi coulis: 247 minutes;

- Filtration test according to API standard:

* Coulis A: 282 ml / 30 minutes;

* Bi coulis: 16 ml / 30 minutes;

- Resistance to compression, after 24 and 48 hours, at 63 ° C, under a simulated pressure of 2500 p.s.i (17.50 MPa):

- Grout Ai: 3 MPa (525 p.s.i.) and 8.9 MPa (1300 p.s.i.);

- Bi grout: 19.8 MPa (2870 p.s.i.) and 28.2 MPa (4080 p.s.i.). Note: In this last test, we observe, for the grout Ai, a decrease in volume of the test pieces manufactured and an increase in the measured density of the grout (1.50 against 1.40).

Example 2 Two light cement grouts were prepared, one, A ₂ , of a type known per se, the other, B2, according to the invention, both with a density of 1.4. Composition of A2

- Cement G - 409 g, - Bentonite: 4 'g,

- Hollow glass microspheres: 102 g,

- Water container: 2 g,

- Dispersant: 0.7 ml,

- Self-timer: 0.9 rai, - Fresh water: - 322 ml.

Composition of B2

- Cement: 285 g,

- Silica fumes: 85 g,

- Polyethylene imine: 47 ml, - Fresh water: 423 ml.

The cements obtained from these compositions were tested at 52 ° C, under 9.6 MPa (1400 psi) after 24 hours, 48 hours and 72 hours. The results obtained are collated in the following Table I:

TABLE I

Composition Compressive strength

After 24h After 48h After 72h

Composition 4.2 MPa 8.9 MPa 9.5 MPa (608 p.s.i.) (1300 p.s.i.) (1380 p.s.i.)

Composition 7.7 MPa 12.3 MPa 13.3 MPa B ₂ (1120 psi) (1780 psi) (1930 psi)

These results show that the compressive strength of the lightened cement B2 according to the invention is much higher than that of the lightened cement A2 of the prior art.

The filtrate obtained was also determined with these two cement slurries at 52 ° C, under a pressure of 6.9 MPa (1000 p.s.i.) for 30 min (test according to the standard).

With the A2 grout, a 282 ml filtrate was obtained, which is much higher than the upper limit of 100 ml considered as bad. With the slurry B2 according to the invention, a 78 ml filtrate was collected.

Example 3

Three other low-fat slags of a known type C, C2 and C3 were also produced, containing bentonite, pre-hydrated bentonite and sodium silicate, respectively, and a slurry according to the invention. These four cement grouts had a density of 1.4.

Composition of Ci

- Cement G: 285 g,

- Bentonite: 71 g,

- Fresh water: 483 ml. Composition of C2

- Cement G:

- Bentonite:

- Fresh water: Composition of C3

- Cement G:

- Sodium silicate:

- Sea water: Composition of C

- Cement G:

- Silica fumes:

- Polyethylene imine

- Pure water :

The compressive strength of the four cements obtained from these grouts was tested after 24 hours at a temperature of 60 ° C and at atmospheric pressure. ,

The results obtained appear in Table II below:

TABLE II

The filtrate obtained was also determined with these various cement grouts at 52 ° C, under a pressure of 6.9 MPa (1000 psi) at 52 ° C.

The results obtained are collated in Table III below:

TABLE III

These results again show the clear superiority of the cement grout according to the invention.

EXAMPLE 4

Grouts with a density of 1.58 were produced based on prehydrated bentonite (composition Di) of sodium silicate (composition D2) and a grout according to the invention (composition D).

COMPOSITION D-,

- Cement G: 504 g,

- Pre-hydrated bentonite: 10.1 g,

- Fresh water: 435 ml. COMPOSITION D ₂

- Cement G: 485 g,

- Sodium silicate (0.36 g / s) 15.5 ml,

- Sea water: 430 ml. 11 COMPOSITION D

- Cement G: 413 g,

- Silica fumes: 145 g,

- Polyethylene imine: 40 ml, - Fresh water: 362 ml.

The compressive strength of the three cements obtained from these grouts was tested after 24 hours at a temperature of 60 ° C and at atmospheric pressure. The following results were obtained:

- Composition Di: 7.98 MPa (1160 p.s.i.)

- Composition D ₂ : 7.49 MPa (1090 psi)

- Composition D: 31.4 MPa (4550 p.s.i.)

These results show that the compressive strength of light cement D, according to the invention, is much higher than that of light cements D and D2. II- EXAMPLES OF RECOVERY

Production of grout and density 1.20 in accordance with the invention, comprising fresh water or sea water, ^er * varying the content of silica fumes.

EXAMPLE the

- Cement G: 131 g,

- Suspension of silica fumes *: 92 g ,,

- Polyethylene imine: 75 ml, - Fresh water: 416 * ml,

- Dispersant: 2 g.

* 50% silica fumes

EXAMPLE 2a

- Cement G: 120 g, - Suspension of silica fumes *: 120 g,

- Polyethylene imine: 74 ml,

- Fresh water: 400 ml,

- Dispersant: 1.8 g.

* at 50% of silica fumes EXAMPLE 3a

- Cement G: 116 g,

- Suspension of silica fumes: 82 g,

- Polyethylene imine: 82 ml, - Sea water 422 ml,

- Dispersing 1.7 g.

EXAMPLE 4a

- Cement G: 107 g,

- Suspension of silica fumes: 107 g,

- Polyethylene imine: 81 ml,

- Sea water: 406 ml,

- Dispersant: 1.5 g.

The compressive strengths of these different compositions, after 24 hours and 72 hours, at a temperature of 60 ° C., are given in the following table:

TABLE IV

III- Production of grout density 1.30 in accordance with the invention comprising fresh water or sea water.

EXAMPLE 1b

- Cement G:

- Silica fumes:

- Polyethylene imine:

- Pure water :

- Dispersant:

EXAMPLE 2b

- Cement G:

- Silica fumes:

- Polyethylene imine:

- Sea water :

- Dispersant: The compressive strength of the two cements obtained from these grouts was tested after 24 hours at a temperature of 60 ° C. and at ^" atmospheric pressure. RESULTS

- Composition 1: 5.2 MPa (755 p.s.i.)

- Composition 2: 6.9 MPa (1000 p.s.i.)

IV- Production of grouts with a density of 1.20 to 1.60 in accordance with the invention, comprising fresh water. Composition Ci of density 1.20

- Cement G: 133.g,

- Silica fumes: 46.8 g,

- Polyethylene imine: 57 ml,

- Dispersant: 2 g,

- Fresh water: 482 ml. Composition C of density 1.30

- Cement G: 184 g,

- Silica fumes: 73.5 g,

- Polyethylene imine: 50 ml,

- Dispersant: 3.7 g,

- Fresh water: 457 ml. Composition C3 of density 1.40

- Cement G: 264 g,

- Silica fumes: 106 g, * ^'" - Polyethylene imine: 47 ml,

- Dispersant: 5.2 g,

- Fresh water: 4 ^'20 ml * Composition C ₍ density 1.50

- Cement G: 345 g,

- Silica fumes: 121 g,

- Polyethylene imine: 43 ml,

- Dispersant: 6.9 g,

- Fresh water: ^' 392 ml. Composition C of density 1.60

- Cement G: 413 g,

- Silica fumes: 145 g,

- Polyethylene imine: 40 ml,

- Dispersant: 6.2 g, - Fresh water: 362 ml.

These compositions were subjected to compressive strength tests at 60 ° C after 24 hours and 72 hours. The results of these tests as a function of density appear in Figure 1 of the accompanying drawings.

V- Gas tightness tests

The cement slags were tested in a device simulating the gas path. This device is shown schematically in Figure 2 of the accompanying drawings.

It comprises a metal jacket 1, closed at the bottom by a permeable rock 2 allowing the flow of the filtrate and the application of a gas (helium) pressure through the conduit 3. The jacket 1 is filled with grout 4 and closed by a piston 5 responsible for transmitting the hydrostatic pressure 6. At 7 is a gas detection system, connected to a formation permeable at low pressure. The hydrostatic pressure, the upper formation pressure and the gas pressure are applied successively, then the gas pressure inlet is closed, as well as that simulating the upper formation pressure. The existence of a gas path is verified by the possible drop in helium pressure in 3, simulating the gas zone pressure, and the increase in upper formation pressure or aquifer pressure in 8.

Gas tracking tests were carried out with this apparatus on different grout compositions in accordance with the invention, under various conditions of pressure and temperature, after variable times.

The results of these tests are shown in Figures 3 to 8, which relate to the following tests: Figure 3

Composition tested: cement grout density 1.40, comprising class G cement, water, 35% silica fumes, based on the weight of cement, and 10% polyethylene imine (based on the weight of water), added with a retarder and a dispersant. Test conditions:

- Hydrostatic pressure: 1.8 MPa - Pressure of the upper formation or pressure of the aquifer zone: 0.6 MPa

- Pressure of the lower formation or pressure of the gas zone: 1.6 MPa

- Formation temperature or cement temperature: 49 ° C.

Figure 4

- Composition tested: identical to FIG. 3, except the concentration of polyethylene imine which is 15% by weight of water. - Test conditions: identical to Figure 3.

Figure 5

Composition tested: identical to FIG. 4.

Test conditions: identical to figure 4, except the temperature of the cement which is 80 ° C Figure 6

Composition tested: identical to FIGS. 4 and 5, except the content of polyethylene imine, which is 10% by weight of the water.

Test conditions: identical to Figure 5. Figure 7

Composition tested: identical to Figure 6, except the density of the grout which is 1.60

Test conditions: identical to the figure, 6.

Figure 8

Composition tested: identical to Figure 7.

Test conditions: identiq-ues in figure 7, except the cement temperature which is 49 ° C.

In all of these tests (Figures 3 to 8), there is no variation, over time, in the pressure of the gas zone or in the pressure of the upper or lower zone: no path of the gas therefore produced. VI- Production of grout of density 1.40 in accordance with the invention for permeability measurements.

Composition:

- Cement G: 272 g, - Suspension 50/50 microsilica in

Water: 190 g,

- Polyethylene imine: 47 ml,

- Dispersant: 4 g,

- Fresh water: 327 ml. A 72 hour test is carried out with this composition at a temperature of 60 ° C., followed by coring of a 39 mm diameter test tube and the permeability to filtered distilled water injected under a pressure of 80 bars. A permeability of less than 0.001 millidarcy is detected, while a conventional cement has a permeability of 0.004 millidarcy.

VII- Realization of grout of density 1.40 in accordance with the invention, for evaluation of the temperature resistance test of compression resistance. Composition tested:

- Cement G: 272.6 g,

- Silica fumes: 109.1 g,

- Polyethylene imine: 44.5 ml, - Dispersant: 5.4 g _;

- Fresh water: 440 ml. . RESULTS

. This composition subjected to a temperature of 130 ° C. * for 24 hours and 72 hours gives very high resistance to compressive strength results, compared to those obtained at 60 ° C and without dimensional modification of the test pieces tested.

NOTE

* Above 110 ° C, it is necessary to add fine sand or silica flour to avoid a drop in compressive strengths.

VIII- Production of cement grout in accordance with the invention for evaluation of their reactivity to retarders. It is important, in the petroleum field, to use setting retarders in order to be able to set up the cement slurry under the conditions of depth, temperature and pressure of the various wells. Two common retarders, one liquid and the other solid, of medium temperature type, and a last liquid, of high temperature type, were tested. Their adaptability to the conditions of use is illustrated by Figures 9 to 11, which relate to the following tests: Figure 9

Composition tested:

- Class G cement,

- Pure water,

- Silica fumes: 35% (based on the weight of - cement),

- Polyethylene imine: 10% (based on the weight of water),

- Powder dispersant: 1.5%,

- Liquid retarder Test conditions: - Temperature: 54 ° C,

- Pressure: 43.5 MPa.

The curve shown shows the variation in pumpability time, expressed in minutes, as a function of the retarder content, expressed in liters per tonne of cement. Figure 10

Composition tested:

- Class G cement,

- Pure water, - Silica fumes: 40% (based on the weight of cement),

- Dispersant powder: 2%,

- Powder retardant. Test conditions:

- Temperature: 54 ° C

- Pressure: 43.5 Mpa.

The curve shown shows the variation in pumpability time, expressed in minutes, as a function of the retarder content, expressed in% by weight of cement. Figure 11 Composition tested:

- Class G cement,

- Fresh water, - Silica fumes: 35% (based on the weight of cement),

- Polyethylene imine: 10% (based on the weight of water),

- Dispersant powder: 2%,

- Liquid retarder. Test conditions:

- Temperature 90 ° C,

- Pressure: 69 MPa.

The curve shown in the figure shows the variation in pumpability time, expressed in minutes, as a function of the content of liquid retardant, expressed in liters per tonne of cement.

Claims

1- Light cement grout comprising hydraulic cement, water and usual cement additives, characterized in that it comprises between 5 and 65% and, preferably, between 25 and 40%, based on the weight of cement , of silica fumes and from 1 to 25% and preferably from 5 to 15%, based on the weight of water, of at least one liquid polyethylene imine, having a molecular mass of between 600,000 and 1,000,000 , or at least one derivative of such a poly thylene imine.

2- Cement grout according to claim 1, characterized in that it comprises fresh water.

3- Cement grout according to claim 1, characterized in that it comprises sea water. 4- Cement grout according to one of claims 1 to 3, characterized in that it comprises at least one adjuvant of a usual type.

5- A method of preparing a cement slurry according to one of claims 1 to 4, characterized by the following successive phases:

- Incorporation of polyethylene imine in water intended for the mixing of cement, preferably in the presence of an anti-foaming product;

- Redispersion of the silica fumes within the resulting mixture using;

- possible incorporation in the mixture of usual additives such as dispersants and / or retardants; mixing the cement with the mixture thus produced.

6- A method according to claim 5, characterized in that the polyethylene imine is incorporated into water in the form of an aqueous solution.

7- Method according to one of claims 5 and 6, characterized in that the silica fumes are incorporated in the form of a stable aqueous suspension. 8- Method according to one of claims 5 and 6, characterized in that the silica fumes are incorporated in compacted form.

9- A method of cementing a well for producing hydrocarbons, characterized in that a cement slag is prepared according to one of claims 1 to 4, and in that it is injected into the well, at the periphery of the tubes and over at least part of the length thereof, between them and the adjoining terrain.