MXPA01003481A - Cementing compositions and the use of such compositions for cementing oil wells or the like - Google Patents

Abstract

Cementing compositions for oil wells or the like comprise between 30%and 100%(by weight of cement) of rubber particles, with grain size in the 40-60 mesh range. Adding rubber particles in accordance with the invention produces a low density slurry while keeping the cement permeability low. Compositions of the invention are particularly advantageous for cementing zones subjected to extreme dynamic stresses such as perforation zones and the junctions of branches in a multi-sidetrack well.

Description

CEMENTING AND USE OF COMPOSITIONS FOR CEMENTING PETROLEUM OR SIMILAR WELLS The present invention relates to techniques for drilling oil, gas, water, geothermal or similar wells. More precisely, the present invention relates to cementing compositions which are suitable for cementing zones subjected to extreme dynamic stresses. In general, a well that is more than a few hundred meters deep is covered, and the annular space between the underground formation and the coating is cemented to prevent the exchange of fluids along all or a portion of their length. The essential function of the coating is to prevent the exchange of fluids between different layers of formations through which the perforation passes and to control the entry of fluids into the well, in particular to limit the ingress of water. In production areas, the coating, the cement and the formation are all drilled along a depth of a few centimeters. The cement placed in the annular space in an oil well undergoes a number of efforts throughout the life of the well. The pressure inside the coating can increase or decrease by changing the fluid that fills it or by applying additional pressure to the well, such as when the drilling fluid is replaced by a finishing fluid or by a fluid used in a simulation operation. . A temperature change also generates stresses on the cement, at least during the transition period before the steel and cement temperatures reach a point of equilibrium. In most of the cases above, the process of the efforts is slow enough to allow it to be treated as a static process. However, the cement is subjected to other efforts which are dynamic in nature either because they occur during a short period of time or because they are periodic or repetitive to a greater or lesser degree. The perforation not only causes an over-pressure of a few bars inside the well which dissipates in the form of a shock wave. In addition, the perforation creates a shock when the projectile penetrates the cement and the shock subjects the area surrounding the perforation to greater forces that extend several meters. Another process which generates dynamic efforts in cement and which is now very common in operations in oil wells is when a window is cut in a cemented overlay to create a bypass. The milling of the steel a depth of several meters followed by the perforation of derivations subject the cement to shocks and vibrations which often damage it irreversibly. The present invention aims to provide novel formulas, in particular for regions of cementing in oil wells or the like which are subjected to extreme dynamic stresses such as in drilling zones and in junctions for branch branches. In an article presented at the annual conference and exhibition of the SPE (Society of Petroleum Engineers) (SPE 38598, 5-8 October 1997) and in the French patent application FR 97 11821, September 23, 1997, Marc Thiercelin et al. They have shown that the risk of rupture of a cement sheath depends on the thermo-elastic properties of the roof, on the cement and the formation which surrounds the well. A detailed analysis of the mechanisms that lead to the rupture of the cement sheath has shown that the risk of rupture of the cement sheath after an increase in pressure and / or temperature in the well are directly related to the force to the stress of cement and decreases when the force ratio to the stress Rt of the cement on the Young E modulus increases. Young's modulus is known to characterize the flexibility of a material. Therefore, to increase the Rt / E ratio, materials must be selected to obtain a low Young moduleIn other words, materials that are highly flexible. A known way to increase the flexibility of hardened cement is to reduce the density of the cement paste by adding water. However, this leads to degradation in the stability of the paste and in particular to the separation of the liquid and solid phases. Said phenomenon can, of course, be controlled in part by adding materials such as sodium silicate, but the permeability of the hardened cement is still very high which means that it can not fulfill its main function of isolating zones to prevent the migration of fluids, or at least guarantee the permanence of said insulation. In addition, lighter cements have lower mechanical characteristics, in particular lower resistance to impact which clearly constitutes a disadvantage for cements intended for areas which are subject to extreme mechanical stresses, such as in drilling areas. The object of the present invention is to provide cement for oil wells reinforced with recycled rubber. The particles of ground rubber reduce the density of the paste and therefore, in the second term, they affect the flexibility of the system; Mainly, the rubber particles do not improve the mechanical characteristics of the cements.

In the construction industry, it is known that including rubber particles in concrete increases hardness, durability and resilience (see, for example, NN Eldin and AB Sinouci, Tire Rubber Particles as aggregate for Concrete, Materials Newspaper in Civil Engineering, 5, 4, 478-497 (1993)). Concretes that include rubber particles in their formulations have application in, for example, in the construction of roads to absorb impacts, in anti-noise walls as a noise-absorbing material, and also in the construction of buildings to absorb seismic waves during earthquakes . For such applications, the purpose of the rubber particles is essentially to improve the mechanical properties of the concrete. The addition of rubber particles (with a grain size in the range of 4-20 mesh) is known in the oil well industry (Well Cemented 1990, EB Nelson, Schlumberger Educational Services) to improve the impact resistance and the resistance to bending. Said improvement of the mechanical properties is also indicated in the Russian patents SU-1384724 and SU-1323699. More recently, US Pat. No. 5,779,787 has proposed the use of particles derived from the recycling of automotive tires, with particle size in the mesh 10/20 (850-2000 μm) or 20/30 mesh (600 - 850 μm), to improve the mechanical properties of hardened cements, in particular the resilience, ductility and expansion properties. It should be noted that the densities of the pulps disclosed in the American patent were within the range of 1.72 g / cm3 and 2.28 g / cm3. In contrast to the disclosures of the prior art, the present invention aims to provide a paste with a density not exceeding 1.70 g / cm 3 and which can, for example, be as low as 1.44 g / cm 3. In other words, the invention consists of preparing a low density paste by replacing a portion of the paste water with rubber particles of a density (1.2 ql cm3) which is close to that of the water. Therefore, a cement with low permeability and is produced. with improved impact resistance. Second, the rubber particles also impart flexibility to the system by reducing the Young's modulus. This results in the reduction of the permeability, in a reduction of the compressibility of the system and in an increase in the resistance to shock even when mainly, the rubber particles do not improve the mechanical properties of the cements. The cement pastes of the present invention consist essentially of cement, water and between 30% and 100% (by weight of cement) of rubber particles obtained, for example, by grinding recycled automotive tires, with grain sizes in the range of 40-60 mesh (250 - 425 μm). The rubber particles used originate from recycled tires from the automotive industry. They are obtained by grinding or by disintegrating at low tire temperature. Particles with a diameter in the range of 250 μm and 400 μm are preferred. These particle sizes produce pumping pastes with adequate rheology. The formulations of the present invention are preferably based on Portland Cements classes A, B, C, G and H defined in section 10 of the American Petroleum Institute (API) standards. Portland class G cements are particularly preferred, but other cements which are known in the art can also be used advantageously. For low temperature applications, aluminous cements are particularly suitable, also Portland / Gypsum pastes for low temperature wells (deep water wells, for example), or cement / silica pastes (for wells where temperatures exceed 120 ° C, for example). The water used to make the pasta is water with a low mineral content such as tap water. Another type of water, such as seawater, can be used optionally, but it is not usually indicated. The compositions of the present invention can also comprise additives which are routinely used in most cementing compositions, for example, dispersing agents, antifoaming agents, suspending agents, cementation retarders or accelerating agents and loss control agents. fluids In one variation, the cementing compositions are also reinforced by adding amorphous metal fibers. Amorphous molten metal fibers are known, for example, from US-A-4, 520, 859 and are obtained by melting a thin strip of molten metal in a cold drum. Rapid cooling prevents crystallization, and the metal solidifies as amorphous material. The length of the fibers used - or, more specifically, the strips - is typically within the order of ten millimeters, preferably in the range of 5 to 15 millimeters. The molten amorphous metal fibers are added to the cement paste of the present invention in an amount of between 1% and 25% by weight of fibers relative to the weight of cement, this being, with fiber concentrations in the order of 50 kg. / m3 and 200 kg / m3. Adding amorphous molten metal fibers can advantageously compensate for the reduction in compressive force which results from adding rubber particles, while increasing the modulus of rupture in bending and the ratio of that modulus to Young's modulus. The present invention is illustrated in the following examples.

EXAMPLE 1 Non-optimized formulations were used to show the basic principle of the present invention. With the exception of a dispersing agent, no cementing additives were included. In this example, the recycled rubber originated from the American Tire Ricyclers, Inc., Jacksonville, USA. The trademark is "Mesh Molled Rubber 40'A Its density is 1.2 g / cm3, and its granulometry was 40 mesh (425 μm) .The cement pastes were composed of Portland Cement Dyckerhoff North Class G, recycled rubber particles, water and a dispersing agent The formulations are given in Table 1, all were studied at the same temperature (170 ° F, this being 76.7 ° C) The dispersing agent was poly naphthalene sulfonate, in liquid form. : Formulations of cement pastes Formulation Density Water Rubber Cement Other additives (ppg -g / cm3) (vol (vol (vol (= agents%)%)%) dispersants vol%) A 12.0 - 1.44 50.0 32.5 17.5 0 B 13.1 - 1.56 55.0 20.2 24.8 0 C 13.6 - 1.63 49.9 22.5 27.5 0.1 D 14.1 - 1.69 44.7 24.7 30.3 0.3 E 15.2 - 1.82 49.6 12.5 37.5 0.4 F 16.4 - 1.97 53.5 0.0 44.8 1.7 * P g is an abbreviation for "pounds per gallon". The rheology of the cement paste and the free water were measured using the procedure recommended in API 10. The rheology was measured immediately after mixing at room temperature in the laboratory, and the rheology was Measure after 20 minutes at conditioning temperature. The results are shown in Table 2. PV means plastic viscosity and TY means yield point. Table 2: Rheology and free water tulitation Rheology after rheology after mealable free water to condition after 76. 7 ° C for 2 hours PV (mPa., S) TY (Pa) PV (mPa.s :) TY (Pa) (mi) A 58.8 1.9 87.1 9.3 0 B 25.2 2.4 97 32.4 0 C 48.5 5.3 98.3 11.6 0 D 120.2 7.7 179.9 12.6 0 E 57.8 1.9 87.0 25.3 0 F 50.8 1.7 24.0 1.9 1 The bending tests were carried out on prisms of 3 cm X 3 cm X 12 cm obtained from cement pastes maintained at 76.7 ° C and at 20.68 MPa (3000 psi) for 3 days. The compression tests were carried out on cubes with sides of 5 cm (2 inches) obtained after 3 days at 76.7 ° C and 20.68 MPa. The results are presented in Table 3 for the flexural strength (modulus of rupture Mr and modulus Young in bending Ec). The resistance to bending was easier to measure than the tensile strength. It was empirically estimated that the resistance to bending was twice that of the tensile strength. Table 3: Mechanical Properties Formulation Mr Ef Mr / Ef CS (Mpa) Ec (Mpa) CS / Ec (Mpa) (Mpa) (X1000) (X1000) A 1.29 516.70 2.52 2.88 496.65 5.80 BB 1 1..9988 963.58 2.07 5.73 1049.10 5.48 C 2.90 1320.12 2.21 7.93 1431.87 5.63 D 3.31 1678.04 2.02 12.46 2416.31 5.17 E 5.45 3223.38 1.71 20.21 3608.18 5.61 FF 9 9.005 6042.00 1.52 27.51 4800.88 5.82 The results above show that an increase in the concentrations of rubber particles in the cement paste result simultaneously in: • A reduction in the modulus of rupture; • A reduction in compressive strength; • A reduction in the Young modulus in bending and also in compression; "An increase in the ratio in the modulus of break in the flexion on the Young's modulus in the flexion In order to compare these different systems, a flexibility criterion was defined (indicated as MT below), a cement is considered It is better if the ratio of its modulus of flexion rupture exceeds the Young's modulus in bending This flexibility criterion can, for example, be observed in FIGURE 1 where the stress resistance RT of the cement is shown as a function of the Young module in the flexure MYF of the cement This FIGURE was obtained using the following points: the cover had an outer diameter of 8 1/2"" (21.6 cm) and an inner diameter of 7"(17.8 cm), the degree of steel was 35 lb / ft (52 (kg / m)) and the pressure increase in the well was assumed to be 5000 psi (34.5 Mpa). (In this FIGURE "= rubber and • = net.) This FIGURE shows that the minimum condition required for three types of rock (hard rock -, medium rock and little consolidated rock). Each curve obtained defines the minimum condition required for good cement strength for the geometry and pressure increments selected for this example. For a given rock, a cement was considered satisfactory if its characteristics (tensile strength and Young's modulus in flexion) place the cement on the curve.

Therefore, formulations A to E satisfy the criteria of flexibility regardless of the type of rock. However, these trends are directly related to a reduction in density resulting from an increase in the concentration of the rubber particles and therefore in the porosity of the system. Therefore, the porosity of the different cement samples obtained after 3 days at 76.7 ° C and 20.68 MPa (3000 psi) was measured for the different formulations. The principle of porosity measurement was as follows. Cylinders of 12.7 cm (1/2 inch) in diameter and 1 cm long were cut out of hardened cement and placed under temperature and pressure. They were dried for 2 weeks in a lyophilizer and during this period their weight loss was studied as a function of time. When the samples were dry (corresponding to a constant weight for a time), their actual volume Vs or skeletal volume was measured using a helium pycnometer; the average volume Vb was obtained by the external dimensions of the cylinder. The difference between the two volumes (Vb - Vs) gave the empty volume and therefore the porosity F of the material accessible to helium. The porosity F of the paste was% by volume of water and liquid additives in the formulation. For each formulation, a percentage volume for rubber was calculated and the porosity F was defined as the sum of the porosity of the material plus the percentage volume of the rubber. The results are shown in Table 4. Table 4: Porosity results Formulation Fpasta Fmaterial Vol. Of rubber Fefective (1) 8 (2)% (3)% (2) + (3)% A 50 40.7 32.5 73.2 B 55 42.5 20.2 62.7 50 37.6 22.5 60.1 45 32.1 24.8 56.9 50 30.9 12.5 43.4 55 25.3 0 25.3 FIGURES 2 and 3 show how the Young's modulus in flexion MYF and the modulus of rupture vary as a function of the effective porosity PE; it can be seen that the Young's modulus decreases almost linearly as a function of the effective porosity with a saturation threshold after 70% porosity (FIGURE 2). The same comment applies to the modulus of fracture in flexure (FIGURE 3) (In these FIGURES 2 and 3, "= AF formulations.) In conclusion, apparently the particles of ground rubber can reduce the density of the paste and therefore, Secondly, to affect the flexibility of the system, mainly rubber particles do not improve the mechanical properties of the cements EXAMPLE 2 Examples of complete formulations are given.The cement pastes were composed of Portland cement Dyckerhoff North class G, particles of recycled rubber, water and different additives (anti-foaming agent and retarder, the retarder was different depending on the temperature.) Table 5 indicates the formulations Formulations 1 and 7 do not contain rubber particles Formulations 2 to 5 contain rubber mesh 40 identical to that of the previous example Formulation 6 used 45 mesh rubber (350 μm) obtained from Vredenstein Rubber Resourses, Maastricht, Netherlands ECORR RNM 45, with a density of 1.2 g / cm3. The influence of parameters such as the density of the paste and the optimization of temperature were studied. For temperatures of 120 ° C or more, silica dust was used due to back-up reinforcement problems. It is important to mix the rubber particles with the cement. Otherwise, poor incorporation or migration of the rubber to the surface after mixing is observed. Table 5: List of Formulations Studied Tm Density Water Rubber Cement Other additives (° C) (g / cm3) (% vol) (% vol) (% vol) (% vol) 1 76.7 1.68 67.3 0 31.7 1.0 2 76.7 1.68 44.5 24.8 30.3 0.4 3 121.1 1.68 45.3 21.6 22.9 10.2 4 150 1.68 46.0 21.6 22.9 9.5 5 76.7 1.44 50.0 32.5 17.1 0.4 6 76.7 1.68 44.2 24.8 30.3 0.7 7 76.7 1.44 79.3 0 20.2 0.5 The detailed composition of the "other additives" is given in the following table. Retarding Powder Anti-foaming antifouling agent Anti-foaming sedimentation agent % bo c ((11 // mm33 dde (cement)%% bbwwoocc (1 / m3 cement) 1 0 10.7 / 4.0 2 0 8.02 0.26 / 3 35 14.71 0.34 / 4 35 0.60 * 0.34 / 5 0 / / 6 0 13.37 / / 7 0 / / 4.0 sizing% bwoc 1 4 2/3/4/5 1.7 6 / 7 1.7 bwoc is an abbreviation for "by weight of cement". • 0.60% bwoc, the retardant used at this temperature was a solid. For formulations 1 and 5, the extender was bentonite. For formulation 7, sodium silicate was used. It should be noted that all the formulations were optimized to obtain a thickening time within the range of 2 to 6 hours. The rheology of the cement paste and the free water were measured using the procedure recommended in API 10 (American Petroleum Institute). The results are shown in Table 6. Table 6: Rheology and Free Water ulation Rheology time thickening after mixing (minutes) PV (mPa.s) TY (Pa) 1 354 12.7 1.7 2 33 97.3 15.6 3 372 119.7 13.9 4 260 152.5 8.1 5 128 96.2 20.3 6 262 290.8 0.9 7 not measured 9.2 4.7 (continuation of table 6) Formulation Rheology after Free water after after conditioning for 2 hours at Tm * PV (mPa.s) TY (Pa) mi 1 11.2 12.8 3 2 215.6 17.0 2 3 61.6 7.1 1 4 101.6 8.5 0 5 75.4 8.5 0 6 175.8 23.7 2 7 8.5 4.1 0 * For formulations 3 and 4, for technical reasons the rheology was measured at 85 ° C and not at temperature Tm as indicated in Table 5. EXAMPLE 3 Ground 32 mesh (500 μm) rubber particles were tested.

In this example, two paste formulations were used as described in the preceding examples, formulation D of the Example 1, and formulation 2 of Example 2; both were formulated at 14 ppg (1.68 g / cm3) with a paste porosity of 45% and comprised 31% bwoc of rubber particles. The only change was in the rubber particles which differed in the manufacturer and in the grain size, the 32 mesh (500 μm) grains replacing the 40 mesh (425 μm) grains. Formulation D with the new rubber source was not mixable according to API, and a portion of the rubber remained on the surface. This phenomenon persisted even if, for example, the concentration of dispersing agent (a poly naphthalene sulfate) was multiplied by 2. Regarding formulation 2, it was observed that the paste was a poor API paste and that after conditioning, the cement paste was very thick and molded badly. To reduce the viscosity by omitting the anti-sedimentation agent and keeping the retardant, it was necessary during the mixing for 10 minutes at 12000 rpm (revolutions per minute) before no more particles were observed on the surface, and the fluid obtained after mixing and conditioning at temperature was very thick and molded badly. EXAMPLE 4 The bending and compression properties of a cement paste containing particles of ground recycled rubber were measured. The exact formulations are given in Example 1. In addition, as a comparison with the preceding formulations, a NET (formulation 8) with a density of 1.89 g / cm3 was added with 4.01 1 / m3 of anti-foaming agent as the only additive and not containing rubber particles. The influence of the rubber particles on the mechanical properties of the cured cement was studied in systems for several days under pressure and temperature in a chamber of high temperature and pressure to simulate the conditions found in an oil well. Compression and bending tests were carried out under the same conditions as in Example 1, at the conditioning temperatures indicated in Table 5; the same abbreviations were used in Table 7 below. For the flexion and compression tests, the amount of energy released at the break (obtained by integrating the load displacement curve on a displacement in the range of 0 to the maximum displacement of the load (corresponding to the rupture) Table 7: Properties Mechanical Mr Ef Mr / Ef Energy CS (Mpa) (Mpa) (X1000) rupture, (Mpa) bending (J) 1 6.69 3758.81 1.81 0.0437 22.88 2 3.44 2213.71 1.57 0.0223 9.97 3 3.61 1849.87 1.98 0.0292 9.51 4 4.68 2905.07 1.63 0.0318 13.81 5 1.11 443.05 2.52 0.0122 2.51 6 4.24 2383.70 1.78 0.0305 13.78 7 1.19 504.22 2.37 0.0101 3.21 8 8.47 5021.56 1.69 0.0706 36.61 Table 7: Mechanical Properties Ec CS / Ec Energy (Mpa) (X1000) of rupture, compression (J) 1 3341.82 6.88 12.97 2 1370.72 7.31 7.94 3 2062.34 4.58 5.37 4 2589.84 5.62 8.71 5 647.67 3.88 1.79 6 2897.45 4.77 6.97 7 519.64 6.24 1.88 8 6257.28 5.85 16.22 For formulations with a density of 1.68 g / cm3 (14 ppg), adding rubber particles reduced the modulus of rupture in bending and also reduced the Young modulus. However, the reasons for the modulus of rupture in bending to the Young modulus remained high and the flexibility criterion defined above was satisfied. It was possible to retard a system with rubber particles and for the full range of temperatures studied, the cement obtained satisfied the flexibility criterion. The compressive strength was reduced with the addition of rubber particles but the values remained acceptable. The porosity of the hardened material was measured for different cement paste formulations. The principle of measuring the porosity of the material was defined in Example 1. The porosity results are shown in Table 8. As expected, they show that the addition of rubber particles reduced the porosity F of the final material (comparing formulation 1 with formulation 2, for example). As in Example 1, it was observed that the Young's modulus in MYF bending decreased almost linearly as a function of effective PE porosity with a saturation threshold after 70% porosity (FIGURE 4) for all formulations optimized at 76.76 ° C. The same comment applies to the modulus of rupture in flexion (FIGURE 5). In this FIGURE 4, A = formulations A-F and B = formulations 1 to 8 and FIGURE 5, M = formulations A-F and A = formulations 1-8). The conclusions of Example 1 are confirmed for optimized formulations: the particles of ground rubber reduced the density of the paste and therefore the secondary effect of the flexibility of the system; Mainly, the rubber particles do not improve the mechanical properties of the cements. Tables 8: Porosity Results Fpasta Formulation Fmaterial Rubber Vol. F (1)% (2)% (3) Effective% (2) + (3) 68 45.7 0 45.7 45 29.7 24.8 54.5 46 37.3 21.6 58.9 4 46 36.6 21.6 58.2 5 50 43.9 32.5 76.4 6 45 30.5 24.8 55.3 7 79 65.5 0 65.5 8 60 36.9 0 36.9 EXAMPLE 5 A base paste with a density of 14 ppg was composed of Portland cement, rubber particles and water (formulation 2 in the preceding examples). To this base paste, fibers or amorphous metal casting strips were added, available with the Fibraflex 5 mm mark from SEVA, Chalon-sur-Saone, France. Different concentrations of fibers were studied. Bending tests were carried out at 170 ° C using the same conditions as in the preceding examples. The results are shown in Tables 9 and 10. Table 9 refers to the flexural strength (modulus of rupture Mr and modulus Young in bending Ef). Table 10 concerns the compressive strength (compression force Cs and Young modulus in compression Ec). Table 9: Mechanical properties: Flexural tests Concentration Mr Ef Mr / Ef Energy of fibers (X1000) (J) (Mpa) (Mpa) 0 3.44 2213.71 1.57 0.0223 30 4.07 2328.83 1.75 0.0287 60 4.48 2772.52 1.65 0.0402 100 5.05 2551.87 2.01 0.0602 Table 10: Mechanical Properties: Compression Tests Concentration Mr Ef Mr / Ef Energy of fibers (X1000) (J ((Mpa) (Mpa) 0 9.97 1370.72 7.31 7.94 30 14.00 2545.63 5.52 6.95 90 14.04 2521.05 5.5Í 7.35 It can be seen that The addition of fibers increases the modulus of rupture in the flexion and the proportion of that modulus of rupture on the Young's modulus, the same tendency was observed for the rupture energies obtained in the bending tests. Rubber particles and fibers were found to have good compressive strength.Further, FIGURE 6 is a plot of displacement d as a function of the load c in Newtons exerted during the bending test.An increase in the load between cement without particles was observed. of rubber and cement with rubber particles In this FIGURE - = ppg, - = rubber and - = rubber and fibers (100 gr / 1) However, the behavior after the break was very different to the cement without rubber particles. Tenacity was improved with ground rubber particles, and this post-breakage performance was further improved with a rubber and fiber paste. Tenacity is an important parameter in a well with several derivations. EXAMPLE 6 Cement samples were generated under pressure (3000 psi, 20.68 MPa) and temperature (170 ° F, 76.76 ° C) under the same conditions as those used for the flexion and compression tests and during the same period. The hardened material obtained was nucleated to the following dimensions: diameter of 51.4 mm and length of 25 mm. The wet sample was placed in a Hassler-type cell and a confining pressure between 10 and 100 bar was applied to the sample. A small constant flow of water (in the range between 0.010 ml / min and 0.80 ml / min) was passed through the sample using a chromatographic pump. The differential pressure on the sides of the sample was measured and recorded. The registered value corresponded to the equilibrium. The permeability K in milli-Darcy (mDa) was calculated using Darcy's law: QμL K = 14700 AP Where Q is the flow expressed in ml / s, μ is the viscosity of the water in MpA.s., L is the length of the sample in cm, A is the surface area of the sample in cm and P is the pressure difference in psi (1 psi = 6.89 kPa). The results for the different formulations are shown in Table 17 and demonstrate that the addition of rubber particles reduces the permeability of the cement. Table 10: Permeability Results Formulation Density Rubber Permeability (g / cm3% bwoc to water milli-Darcy 1 1 .67 0 0.0076 2 1 .67 31 0.0015 7 1. 44 0 0.1380 8 1 .89 0 0.0010 EXAMPLE 7 They were taken The tests were to allow a 1-meter-long projectile to fall on hardened cement discs, the discs were circumferential, 70 mm in diameter and 10 mm thick. measured and recorded in time cement without rubber particles (formulations 1 and 7) behaved as a fragile material and the energy absorbed by the sample was estimated at less than 10 Joules The energy absorbed by the cements formulated with rubber particles was much larger, as shown in Table 11.

Table 11: Flexible Particle Impact Results Energy Formulation (J) 1 7.4 2 25.3 7 4.0 This impact behavior is particularly important when wells with several derivations are cemented. EXAMPLE 8 The linear expansion of cement pastes during curing at temperatures simulating the conditions in the well was measured in an annular expansion mold. This mold consists of two flat discs placed on both sides of an expandable ring which has two bolts at its ends; the assembly consists of a cylinder of 100 mm diameter of little thickness (22 mm). The two discs were fixed with screws. The cement paste to be studied was emptied into the mold, and the mold was placed in a thermostatic water bath at 76.76 ° C. The paste remained in contact with the water during the test. During curing, the cement expanded, the outer diameter of the expandable ring also expanded and the distance between the two ring bolts was increased. The linear expansion L of the cement paste was obtained using the following ratio: L = (D2-D1) x 10.95 Where L is expressed as a percentage, DI is the icrometric measurement in inches before settling is established, D2 is the Micrometric measurement in inches after hardening and 10.95 is a constant which takes into account the geometry of the mold. The expansion results are shown in Table 12 and it is shown that a paste containing rubber particles has advantageous expansion properties. Table 12: Expansion Results Rubber% expansion%% expansion% expansion % bwoc line 1 after linear after linear after 1 day of 2 days of 7 days 0 0 0 0 31 0.25 0.28 0.28 71 0.15 0.25 0.29 EXAMPLE 9 A pumping and mixing test was carried out using a paste with formulation 2, with a density of 1.76 g / cm3 containing 31% bwoc of rubber particles. The rubber was mixed dry with the cement and then added to the tank containing the mixing water. The paste obtained was homogeneous, and was circulated with a Triples-type pump used routinely in oil fields without problems.

Mixing problems were observed in an additional test after the addition of the rubber. Therefore, the dry mixing method is preferable for the incorporation of rubber particles in the cement paste in the field.

Claims (1)

1. CLAIMS A cement paste composition for an oil well or similar, comprising cement, water, and between 30% and 100% (by weight of cement) of rubber particles; characterized in that the rubber particles have a grain size within the range of 40-60 mesh (250-425 μm), and the paste has a density less than 1.70 g / cm3. A cement paste composition according to Claim 1, characterized in that the diameter of said rubber particles is within the range of 250 mm and 400 mm. A cement paste composition according to any of the preceding claims, characterized in that said rubber particles are obtained by recycling tires of the automotive industry. A cement paste composition according to any of the preceding claims, characterized in that it additionally comprises amorphous molten metal fibers in a proportion between 1% and 25% by weight with respect to the weight of the cement. A cement paste composition according to any of the preceding claims, characterized in that it additionally comprises one or more additives of the following type: a suspending agent, a dispersing agent, an anti-foaming agent, a retardant, a curing accelerator, cement and a fluid loss control agent. The use of cement paste compositions according to any of Claims 1 to 5 for cementing areas subjected to extreme mechanical stresses such as in drilling zones and junctions of derivations in a well with multiple branches.