Large-temperature-difference low-density well cementation cement paste for ultra-deep well and preparation method thereof

Abstract

The invention discloses large-temperature-difference low-density well cementation cement slurry for an ultra-deep well and a preparation method of the large-temperature-difference low-density well cementation cement slurry. The preparation method comprises the following steps: preparing a phosphoric acid solution from a 60% HEDP solution, sodium hexametaphosphate and water according to the ratio of 6: 3: 41; preparing a 10% zinc nitrate aqueous solution; the preparation method comprises the following steps: uniformly dry-mixing 450 parts of oil well G-grade cement, 120 parts of silicon powder, 100-85 parts of low-density light material and 120-80 parts of active strength enhancer to obtain dry-mixed aggregate; the method comprises the following steps: dissolving 22-15 parts of a high-temperature fluid loss agent G33S in 435-340 parts of tap water to obtain an aqueous solution of the high-temperature fluid loss agent; uniformly mixing an aqueous solution of a fluid loss agent with the dry-mixed aggregate to obtain mixed cement paste; 4.8-14 parts of a zinc nitrate aqueous solution is taken and poured into the cement paste mixed slurry to be mixed, then 9-35 parts of the hydrolyzed phosphoric acid solution is poured into the cement paste mixed slurry to be mixed evenly, and the cement paste is obtained. The cement paste can play a role in retarding at the high temperature of the well bottom and can prevent gas channeling at the low temperature of the top.

Description

Technical Field

[0001] The invention relates to cement slurry for well cementing, in particular to a cement slurry with large temperature difference and low density for ultra-deep well cementing; the invention also relates to a method for preparing the cement slurry with large temperature difference and low density for ultra-deep well cementing, belonging to the technical field of petroleum cementing. Background Art

[0002] In recent years, there are more and more deep wells over 4,000 meters and ultra-deep wells over 5,000 meters in China. The high temperature and pressure at the bottom of the well bring more technical challenges to cementing construction. The ultra-slow setting at the top increases the static gelling transition time and brings the risk of gas and water channeling. Therefore, for ultra-deep wells, it is necessary to meet the high temperature performance requirements at the bottom of the long cementing section and the low temperature performance requirements at the top at the same time, that is, at the high temperature at the bottom of the well, the cement slurry is stable and the thickening time meets the construction requirements; at the low temperature at the top, there is no phenomenon of ultra-slow setting leading to slow strength development.

[0003] In China, for example, in the Tarim Basin, Sichuan Basin, and Northeast China, not only are oil and gas resources buried deep, but there are also low-pressure leakage layers. High-temperature resistant low-density cement slurry systems are often used in cementing. The strength of the top low-density cement slurry is more difficult to develop than that of the conventional density, and the strength is lower. High-temperature retarders are used to adjust the thickening time of cement slurry so that the cement slurry can meet the high-temperature flow state. Currently, the commonly used polymer retarders have strong high-temperature resistance, but the amount added is large. When the cement slurry returns to the top along the casing annulus, the super-retardation is obvious, and the strength of the top of the sealing section develops slowly. Strength is often not generated in 72 hours, and it is also not generated in 96 hours, 120 hours, and 128 hours.

[0004] The Chinese invention patent application with publication number CN 104263331A discloses a new type of high-temperature low-density cement slurry system, which mainly solves the problems of poor gas channeling prevention, slow low-temperature strength development and high-temperature sedimentation of high-temperature low-density cement slurry. It is suitable for high-temperature cementing in deep wells and ultra-deep wells with low pressure and easy leakage, long sealing section, and large temperature difference. The components and weight proportions of the low-density cement slurry system are: 100 parts of oil well cement, 50-80 parts of fly ash, 30-40 parts of silica sand, 24-76 parts of active enhancer I, 13-60 parts of active enhancer II, 8.0-17 parts of high-temperature fluid loss reducer, 0.2-0.8 parts of high-temperature retarder, 0.0-0.5 parts of dispersant, and 140-200 parts of water. The density is 1.40-1.60 parts / cm 3 It is adjustable and can be used for cementing operations in the range of 70-150℃. It has outstanding advantages such as good high-temperature stability, strong anti-gas channeling ability and high low-temperature strength, which can greatly reduce the cost of high-temperature cementing. Its disadvantage is that the minimum top strength maintenance temperature is 75℃. In actual field applications, the top temperature is often far below 75℃. This invention cannot completely solve the problem of slow development of top low-temperature strength.

[0005] The Chinese invention patent application with publication number CN 111662409B discloses a high-temperature oil well cement retarder capable of inhibiting abnormal gelation and a preparation method thereof. The preparation method comprises: (1) dissolving 2-acrylamide-2-methylpropanesulfonic acid and unsaturated carboxylic acid monomers in deionized water, stirring evenly, and adjusting the pH to 5-6; (2) adding steric hindrance functional monomers and cationic functional monomers to the solution obtained in step (1), stirring evenly, and heating to 55-65° C.; (3) dissolving an initiator in deionized water to prepare a solution, adding the solution to the solution obtained in step (2) under stirring, keeping the solution at 55-65° C. for 20-40 minutes, heating the solution to 70-85° C. and reacting the solution at a constant temperature for 2-4 hours, thereby obtaining a high-temperature oil well cement retarder capable of inhibiting abnormal gelation. The retarder of this invention can inhibit the "bulging" and "core" phenomena of cement slurry in the temperature range of 120-150°C without affecting the strength development of cement stone. It solves the high temperature resistance of cement slurry and maintains the stability of cement slurry in high temperature environment, but it does not solve the problem of super-retarded setting at the top caused by large temperature difference. Summary of the invention

[0006] The primary purpose of the present invention is to overcome the problems existing in the prior art and provide a low-density cementing slurry with a large temperature difference for ultra-deep wells. During the thickening process, there is no "bulging" and "core wrapping" phenomenon, the cement slurry is stable, can play a retarding effect at high temperature at the bottom of the well, and can prevent gas channeling at low temperature at the top.

[0007] In order to solve the above technical problems, the present invention provides a large temperature difference low-density cementing slurry for ultra-deep wells, wherein the raw material components and weight contents are as follows: 450 parts of oil well grade cement, 120 parts of silicon powder, 100-85 parts of low-density lightweight material, 120-80 parts of active strength enhancer, 22-15 parts of high-temperature fluid loss reducer, 435-340 parts of water, 12-35 parts of TL-2 phosphoric acid solution and 4.8-14 parts of 10%wt TY zinc nitrate aqueous solution.

[0008] Preferably, the TL-2 phosphoric acid solution comprises hydroxyethylene diphosphoric acid solution, sodium hexametaphosphate and tap water in a weight ratio of hydroxyethylene diphosphoric acid solution: sodium hexametaphosphate: tap water = 6:3:41, wherein the mass concentration of the hydroxyethylene diphosphoric acid solution is 60%.

[0009] Preferably, the low-density lightweight material is a silicon-aluminum hollow microsphere with a particle size distribution range of 25.58-408.7 μm and a density of 0.59*10 -3 kg / m 3 .

[0010] Preferably, the activity strength enhancer is DY02 activity strength enhancer.

[0011] Preferably, the high-temperature fluid loss additive is G33S high-temperature fluid loss additive.

[0012] Preferably, the raw material components and weight contents are as follows: 450 parts of oil well grade cement, 120 parts of silica fume, 100 parts of low-density lightweight material, 120 parts of active strength enhancer, 22 parts of high-temperature fluid loss reducer, 435 parts of water, 12 parts of TL-2 phosphoric acid solution and 4.8 parts of 10%wt TY zinc nitrate aqueous solution.

[0013] Preferably, the raw material components and weight contents are as follows: 450 parts of oil well grade cement, 120 parts of silica fume, 90 parts of low-density lightweight material, 100 parts of active strength enhancer, 20 parts of high-temperature fluid loss reducer, 400 parts of water, 16 parts of TL-2 phosphoric acid solution and 6.4 parts of 10%wt TY zinc nitrate aqueous solution.

[0014] Preferably, the raw material components and weight contents are as follows: 450 parts of oil well grade cement, 120 parts of silica fume, 90 parts of low-density lightweight material, 100 parts of active strength enhancer, 18 parts of high-temperature fluid loss reducer, 380 parts of water, 25 parts of TL-2 phosphoric acid solution and 6.4 parts of 10%wt TY zinc nitrate aqueous solution.

[0015] Preferably, the raw material components and weight contents are as follows: 450 parts of oil well grade cement, 120 parts of silica fume, 85 parts of low-density lightweight material, 80 parts of active strength enhancer, 15 parts of high-temperature fluid loss reducer, 340 parts of water, 35 parts of TL-2 phosphoric acid solution and 14 parts of 10%wt TY zinc nitrate aqueous solution.

[0016] Another object of the present invention is to overcome the problems existing in the prior art and provide a method for preparing a large temperature difference and low density cementing slurry for ultra-deep wells. The prepared cement slurry has no "bulging" and "core wrapping" phenomena during the thickening process. The cement slurry is stable and can play a retarding role at high temperature at the bottom of the well and prevent gas channeling at low temperature at the top.

[0017] In order to solve the above technical problems, the preparation method of ultra-deep well large temperature difference low density cementing slurry of the present invention comprises the following steps in sequence:

[0018] S1. Preparation of phosphoric acid solution: weigh the raw materials according to the following weight ratio: hydroxyethylene diphosphoric acid solution: sodium hexametaphosphate: tap water = 6:3:41, wherein the mass concentration of hydroxyethylene diphosphoric acid solution is 60%; first, gradually pour sodium hexametaphosphate into tap water while stirring, keep the stirring speed at 500rpm, and keep the water temperature at 40°C. After the sodium hexametaphosphate is completely dissolved, gradually add the hydroxyethylene diphosphoric acid solution, continue stirring for 5 minutes, and keep the stirring speed at 200rpm; set aside for use 30 minutes after the preparation is completed, and obtain a mixed aqueous solution composed of hydroxyethylene diphosphoric acid and sodium hexametaphosphate, which is called TL-2 phosphoric acid solution;

[0019] S2, dissolving zinc nitrate in tap water to prepare a 10%wt TY zinc nitrate aqueous solution;

[0020] S3, dry-mix 450 parts of oil well G grade cement, 120 parts of silica fume, 100-85 parts of low-density lightweight material, and 120-80 parts of active strength enhancer to obtain dry-mixed aggregate;

[0021] S4, take 22-15 parts of high temperature fluid loss reducer G33S, dissolve in 435-340 parts of tap water, to obtain an aqueous solution of the high temperature fluid loss reducer;

[0022] S5, mixing the aqueous solution of the high-temperature fluid loss reducer with the dry-mixed aggregate to obtain a cement slurry;

[0023] S6, take 4.8-14 parts of the TY zinc nitrate aqueous solution of step S2, pour it into the cement slurry of step S5 within 10 seconds, keep the rotation speed at 4500 rpm; after 1 minute, pour 9-35 parts of the TL-2 phosphoric acid solution after the hydrolysis of step S1 within 10 seconds, keep the rotation speed at 4500 rpm, mix evenly to obtain the large temperature difference low density cementing slurry for ultra-deep wells.

[0024] Compared with the prior art, the present invention has achieved the following beneficial effects: (1) The main component of the oil well G grade cement used is tricalcium silicate C3S, and it also contains 3.5-4.5% of tricalcium aluminate C3A and a certain proportion of tetracalcium aluminoferrate C4AF, C4AF+2C3A is not more than 24%, and tricalcium silicate is hydrated to form a gelling material hydrated calcium silicate CSH, and hydroxyethylidene diphosphoric acid is referred to as HEDP, which has a strong adsorption capacity on the surface of cement particles, and the adsorption rate of the same admixture is twice that of carboxylic acid polymer, and it is not easy to reach a saturated adsorption state, HEDP and Ca 2+ Chelation occurs, promoting the dissolution of gypsum in the early stage of hydration. The dissolved sulfate ions react with C3A to promote the formation of trisulfur hydrated calcium sulfoaluminate AFt, and the precipitation of the complex HEDP-Ca, which is adsorbed on the cement surface, inhibiting the growth of CSH and calcium hydroxide seeds. However, as the precipitation consumes time, the seeds continue to grow. The strength development of cement paste after the induction period is not affected, and the cement paste is more dense and has higher strength. If HEDP is excessive, it will delay the development of the early strength of cement paste, but the appropriate amount of addition matches the appropriate hydration conditions, which can not only show excellent retarding effect, but also be beneficial to the strength development of cement paste.

[0025] ⑵ Sodium hexametaphosphate has a strong complexing effect on metals and free Ca in cement slurry. 2+It forms a slightly soluble complex, wraps around the surface of cement particles, and inhibits the hydration of cement minerals. At the same time, the addition of sodium hexametaphosphate increases the alkalinity of cement paste, inhibits the dissolution of CaO to form calcium hydroxide, and delays cement hydration. Sodium hexametaphosphate forms a large amount of aluminophosphate gelling with aluminum-containing cement, which inhibits the formation of low-strength C3AH6 crystals. The appropriate dosage can increase the 3d, 7d and 28d strength of cement paste. Sodium hexametaphosphate has a high resistance to high temperatures, which makes up for the high-temperature instability of HEDP in cement paste. Sodium hexametaphosphate with a low dosage has a retarding effect, and an excessive dosage shows a accelerating effect.

[0026] ⑶ Zinc nitrate provides heavy metal ions Zn 2+ , Zn 2+ It forms a coordination polymer with hydroxyethylene diphosphate (HEDP) and sodium hexametaphosphate, combines organic phosphoric acid with inorganic phosphoric acid through coordination bonds to form an organic-inorganic composite coordination polymer, which is adsorbed on the surface of cement particles together, and the effects of organic polyphosphoric acid and inorganic sodium hexametaphosphate are stably exerted in the cement paste. Figure 1 The reaction process of the coordination polymer in alkaline cement paste is that the hydroxyethylidene diphosphate (HEDP) molecules, sodium metaphosphate molecules and zinc ions generate coordination polymers, part of which is adsorbed on the surface of cement particles, and part of which is complexed with free calcium ions.

[0027] ⑷Silica powder is quartz powder, which enhances the high temperature resistance of cement. Its main component is silicon dioxide. The particle size is mainly distributed between 20.50μm-50.25μm, and the density is 2.2*10 -3 k copies / m 3 .

[0028] ⑸ High-temperature fluid loss reducer G33S is an AMPS polymer, which is modified by polymerization of 2-acrylamide-2-methylpropanesulfonic acid (AMPS) with low molecular weight amides, maleic anhydride, and polyhydroxy carboxylic acids. Low molecular weight amides such as acrylamide (AM) and N, N-dimethylacrylamide (DMAA) and polyhydroxy carboxylic acids are organic acids with multiple hydroxyl groups in their molecular structure, and have excellent water loss reduction performance.

[0029] ⑹DY02 active strength enhancer is composed of SiO2, CaO, K2O, MgO, Al2O3, with SiO2 content of 80%-95%. After high-temperature vaporization and cooling at 1200℃, the particle size distribution range is 1.25-15.89μm, which is smaller than the particle size of lightweight materials. It can effectively fill the gaps in cement, has a large specific surface area, and a large contact surface with cement particles, which is conducive to the development of cement stone strength. High-temperature calcination enhances activity and has strong volcanic ash activity. CaO, K2O, and Al2O3 are calcined at 1100℃ in a muffle furnace, and the activity is enhanced, the particles are dispersed, the particle size becomes smaller, and it is grayish white with a density of 2.2*10 -3 kg / m3 .

[0030] ⑺ The particle size distribution of low-density lightweight materials is wide. The hollow microspheres of large particles significantly reduce the density. The hollow microspheres of medium and small particles reduce the density value. The larger the particles, the smaller the particles. The wide particle size distribution is conducive to the formation of particle grading, the smaller the pores between particles, and the enhanced mechanical properties of cement paste.

[0031] ⑻ After simulating the dynamic changes of temperature and pressure of the top cement slurry in the wellbore, simulating the high temperature and high pressure environment of 150℃ at the bottom of the well, simulating the low temperature environment of 30℃ at the top, a cooling top strength test experiment was carried out to evaluate the strength value of the top cement stone; the high temperature and high pressure conditions were changed to test the thickening performance of the cement slurry under high temperature conditions, that is, to evaluate the high temperature stability of the cement slurry under high temperature conditions at the bottom of the well. All performance data are excellent, as shown in the following table and figure.

[0032] ⑼ The composite organic-inorganic coordination polymer that produces a retarding effect in the cement slurry of the present invention uses an in-situ generation method to generate a coordination polymer in the cement slurry in situ, adsorb to the surface of cement particles, and produce a retarding effect. At the same time, it has the advantages of the stability of traditional inorganic materials and the controllable structure and high performance of organic materials. The low-density cement slurry is prepared in situ, the process is simple, and it is conducive to on-site promotion and utilization. Currently, most commonly used high-temperature retarders are macromolecular organic polymers, and organic high-temperature resistant functional monomers are introduced into the polymerization chain. The addition of multi-polymerization and functional monomers significantly increases the cost. The high-temperature retarder GH-9 of Weihui Chemical, which is currently more commonly used in the present invention, saves 32% of the cost per ton of retarder. At a circulating temperature of 120°C and calculated on the basis of 100 tons of cement in a single well, the cost is saved by 21,050, and the performance index is better than that of the high-temperature retarder GH-9.

[0033] ⑽ In the present invention, zinc ions are transition metal ions with large effective nuclear charge, strong polarization force and deformability, and can produce strong binding force with ligands, and are good center-forming bodies. Compared with calcium ions, it is easier to form stable coordination polymers with hydroxyethylene diphosphoric acid and sodium hexametaphosphate. A small amount of zinc ions form stable organic-inorganic composite coordination polymers with organic phosphoric acid and inorganic phosphoric acid, enhance the performance of high temperature resistance, increase the molecular structure chain, and combine the characteristics of sodium hexametaphosphate and HEDP. It can be better adsorbed on cement particles and is resistant to high temperatures. A small number of coordinated atoms on the ligand produce coordination bonds with zinc ions, and other coordinated atoms provide electron pairs for the organic-inorganic composite polymer to be adsorbed on the surface of cement particles. Under high temperature conditions, within the circulation temperature of 150℃, there is no bulging or stepping phenomenon in the thickening curve, and there is no core-encapsulation phenomenon in the thickening process. The initial consistency and the consistency during the thickening process can basically be maintained within 10BC. Even if the initial consistency is slightly higher than 20BC and less than 30BC, the shear thinning property is strong during the flow process and can be quickly reduced to within 20BC within 5 minutes, which is conducive to on-site pumping; the right-angle thickening of the cement slurry is obvious, which effectively reduces the risk of gas and water channeling in the wellbore.

[0034] ⑾ In addition to the retarding effect, the hydroxyethylidene diphosphate HEDP and sodium hexametaphosphate in the present invention will not have an adverse effect on the development of cement stone strength. Keeping the appropriate amount is beneficial to the development of cement stone strength in the later stage. The cement system can solve the problem of low top temperature (30°C or room temperature) and slow development of top cement stone strength. When the temperature difference between the top and the bottom exceeds 90°C, the top will produce strength in 48 hours, and the top strength is greater than 6.0MPa at 72 hours. It is much better than the requirements of SY / T 6544-2017 "Performance Requirements for Oil Well Cement Slurry" that the temperature difference between the top and the bottom is greater than 60°C or the length of the sealing section is greater than 2000m, and the top cement stone strength is greater than 3.15MPa at 72 hours. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] The present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments. The accompanying drawings are only provided for reference and explanation and are not intended to limit the present invention.

[0036] Figure 1 Schematic diagram of the reaction process of coordination polymer in alkaline cement slurry;

[0037] Figure 2 is a cement slurry thickening curve diagram of Example 1 of the present invention;

[0038] Figure 3 is a cement slurry thickening curve diagram of Example 2 of the present invention;

[0039] Figure 4 is a cement slurry thickening curve diagram of Example 3 of the present invention;

[0040] Figure 5 This is a cement slurry thickening curve diagram of Example 4 of the present invention. DETAILED DESCRIPTION

[0041] In the following description of the present invention, the term "part(s)" refers to parts by weight unless otherwise specified.

[0042] In order to make the technical means, creative features, objectives and effects achieved by the present invention easy to understand, the present invention is further explained below with reference to specific diagrams.

[0043] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art of the present invention. The terms used in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention.

[0044] Example 1

[0045] The method for preparing the ultra-deep well cementing slurry with large temperature difference and low density comprises the following steps in sequence:

[0046] S1. Preparation of phosphoric acid solution: weigh the raw materials according to the following weight ratio: hydroxyethylene diphosphoric acid solution: sodium hexametaphosphate: tap water = 6:3:41, wherein the mass concentration of hydroxyethylene diphosphoric acid solution is 60%; first, gradually pour sodium hexametaphosphate into tap water while stirring, keep the stirring speed at 500rpm, and keep the water temperature at 40°C. After the sodium hexametaphosphate is completely dissolved, gradually add the hydroxyethylene diphosphoric acid solution, continue stirring for 5 minutes, and keep the stirring speed at 200rpm; set aside for use 30 minutes after the preparation is completed, and obtain a mixed aqueous solution composed of hydroxyethylene diphosphoric acid and sodium hexametaphosphate, which is called TL-2 phosphoric acid solution;

[0047] S2, dissolving zinc nitrate in tap water to prepare a 10%wt TY zinc nitrate aqueous solution;

[0048] S3, dry-mix 450 parts of oil well G grade cement, 120 parts of silica fume, 100 parts of low-density lightweight material, and 120 parts of active strength enhancer to obtain dry-mixed aggregate;

[0049] S4, take 22 parts of high-temperature fluid loss reducer G33S, dissolve them in 435 parts of tap water to obtain an aqueous solution of the high-temperature fluid loss reducer;

[0050] S5, mixing the aqueous solution of the high-temperature fluid loss reducer with the dry-mixed aggregate to obtain a cement slurry;

[0051] S6. Take 4.8 parts of the TY zinc nitrate aqueous solution of step S2, pour it into the cement slurry of step S5 within 10 seconds, and mix it while maintaining a rotation speed of 4500 rpm; after 1 minute, pour 9 parts of the TL-2 phosphoric acid solution after hydrolysis in step S1 within 10 seconds, maintain a rotation speed of 4500 rpm, and mix evenly to obtain a large temperature difference and low density cementing slurry for ultra-deep wells.

[0052] The performance of the cement slurry of Example 1 was evaluated according to the standard GB / T 19139-2003 "Test Methods for Oil Well Cement". The temperature difference between the top and the bottom of the oil well was set to be greater than 90°C, the top temperature was 30°C, and the circulation temperature was 120°C, simulating the dynamic change of temperature and pressure of the top cement slurry at the bottom of the well. The cement slurry was cured using a high-temperature and high-pressure thickener, the temperature was raised to 120°C for 50 minutes, the pressure was increased to 60 MPa, and then this thickening condition was maintained for 60 minutes. After naturally cooling to 90°C, the cement slurry was taken out, poured into a mold, and placed in a normal-pressure water bath for curing for 48 hours and 72 hours. The temperature of the normal-pressure water bath was set to 30°C.

[0053] The cement slurry thickening curve of Example 1 is as follows: Figure 2 shown.

[0054] Comparative Example 1

[0055] The raw material components and weight contents of the comparative cement slurry are as follows: 450 parts of oil well G grade cement, 12 parts of high temperature retarder GH-9, 22 parts of G33S high temperature fluid loss reducer, 120 parts of SY silica fume, 100 parts of DY01 low density lightweight material, 120 parts of DY02 active strength enhancer, 435 parts of tap water, and the obtained density is 1.35g / cm 3 Low-density cement slurry. The performance test method and experimental conditions are consistent with those in Example 1.

[0056] Example 2

[0057] The method for preparing the ultra-deep well cementing slurry with large temperature difference and low density comprises the following steps in sequence:

[0058] S1. Preparation of phosphoric acid solution: weigh the raw materials according to the following weight ratio: hydroxyethylene diphosphoric acid solution: sodium hexametaphosphate: tap water = 6:3:41, wherein the mass concentration of hydroxyethylene diphosphoric acid solution is 60%; first, gradually pour sodium hexametaphosphate into tap water while stirring, keep the stirring speed at 500rpm, and keep the water temperature at 40°C. After the sodium hexametaphosphate is completely dissolved, gradually add the hydroxyethylene diphosphoric acid solution, continue stirring for 5 minutes, and keep the stirring speed at 200rpm; set aside for use 30 minutes after the preparation is completed, and obtain a mixed aqueous solution composed of hydroxyethylene diphosphoric acid and sodium hexametaphosphate, which is called TL-2 phosphoric acid solution;

[0059] S2, dissolving zinc nitrate in tap water to prepare a 10%wt TY zinc nitrate aqueous solution;

[0060] S3, dry-mix 450 parts of oil well G grade cement, 120 parts of silica fume, 90 parts of low-density lightweight material, and 100 parts of active strength enhancer to obtain dry-mixed aggregate;

[0061] S4, take 20 parts of high-temperature fluid loss reducer G33S, dissolve them in 400 parts of tap water to obtain an aqueous solution of the high-temperature fluid loss reducer;

[0062] S5, mixing the aqueous solution of the high-temperature fluid loss reducer with the dry-mixed aggregate to obtain a cement slurry;

[0063] S6, take 6.4 parts of the TY zinc nitrate aqueous solution of step S2, pour it into the cement slurry of step S5 within 10 seconds, keep the rotation speed at 4500 rpm; after 1 minute, pour 16 parts of the TL-2 phosphoric acid solution after the hydrolysis of step S1 within 10 seconds, keep the rotation speed at 4500 rpm, mix evenly to obtain the large temperature difference low density cementing slurry for ultra-deep wells.

[0064] The performance of the cement slurry prepared in Example 2 was evaluated according to the standard GB / T 19139-2003 "Test Method for Oil Well Cement". The temperature difference between the top and the bottom of the oil well was set to be greater than 100°C, the top temperature was 30°C, and the circulation temperature was 130°C. The dynamic changes in temperature and pressure of the top cement slurry at the bottom of the well were simulated. The cement slurry was cured using a high-temperature and high-pressure thickener, the temperature was raised to 130°C for 60in, the pressure was raised to 70MPa, and then the thickening conditions were maintained for 60min. After naturally cooling to 90°C, the cement slurry was taken out, poured into a mold, and placed in a normal-pressure water bath for curing for 48h and 72h. The temperature of the normal-pressure water bath was set to 30°C.

[0065] The cement slurry thickening curve of Example 2 is as follows: Figure 3 shown.

[0066] Comparative Example 2

[0067] The raw material components and weight contents of the comparative cement slurry are as follows: 450 parts of oil well G grade cement, 16 parts of high temperature retarder GH-9, 20 parts of G33S high temperature fluid loss reducer, 120 parts of SY silica fume, 90 parts of DY01 low density lightweight material, 100 parts of DY02 active strength enhancer, and 400 parts of tap water, resulting in a density of 1.48 g / cm 3 Low-density cement slurry. The performance test method and experimental conditions are consistent with those in Example 2.

[0068] Example 3

[0069] The method for preparing the ultra-deep well cementing slurry with large temperature difference and low density comprises the following steps in sequence:

[0070] S1. Preparation of phosphoric acid solution: weigh the raw materials according to the following weight ratio: hydroxyethylene diphosphoric acid solution: sodium hexametaphosphate: tap water = 6:3:41, wherein the mass concentration of hydroxyethylene diphosphoric acid solution is 60%; first, gradually pour sodium hexametaphosphate into tap water while stirring, keep the stirring speed at 500rpm, and keep the water temperature at 40°C. After the sodium hexametaphosphate is completely dissolved, gradually add the hydroxyethylene diphosphoric acid solution, continue stirring for 5 minutes, and keep the stirring speed at 200rpm; set aside for use 30 minutes after the preparation is completed, and obtain a mixed aqueous solution composed of hydroxyethylene diphosphoric acid and sodium hexametaphosphate, which is called TL-2 phosphoric acid solution;

[0071] S2, dissolving zinc nitrate in tap water to prepare a 10%wt TY zinc nitrate aqueous solution;

[0072] S3, dry-mix 450 parts of oil well G grade cement, 120 parts of silica fume, 90 parts of low-density lightweight material, and 100 parts of active strength enhancer to obtain dry-mixed aggregate;

[0073] S4, take 18 parts of high temperature fluid loss reducer G33S, dissolve them in 380 parts of tap water to obtain an aqueous solution of the high temperature fluid loss reducer;

[0074] S5, mixing the aqueous solution of the high-temperature fluid loss reducer with the dry-mixed aggregate to obtain a cement slurry;

[0075] S6. Take 6.4 parts of the TY zinc nitrate aqueous solution of step S2, pour it into the cement slurry of step S5 within 10 seconds, and mix it while maintaining a rotation speed of 4500 rpm; after 1 minute, pour 25 parts of the TL-2 phosphoric acid solution after the hydrolysis of step S1 within 10 seconds, maintain a rotation speed of 4500 rpm, and mix evenly to obtain a large temperature difference and low density cementing slurry for ultra-deep wells.

[0076] The performance of the cement slurry prepared in Example 3 was evaluated according to the standard GB / T 19139-2003 "Test method for oil well cement". The temperature difference between the top and the bottom of the oil well was set to be greater than 110°C, the top temperature was 30°C, and the circulation temperature was 140°C. The dynamic changes in temperature and pressure of the top cement slurry at the bottom of the well were simulated. The cement slurry was cured using a high-temperature and high-pressure thickener, the temperature was raised to 140°C for 70 minutes, the pressure was increased to 75 MPa, and then the thickening conditions were maintained for 60 minutes. After naturally cooling to 90°C, the cement slurry was taken out, poured into a mold, and placed in a normal-pressure water bath for curing for 48 hours and 72 hours. The temperature of the normal-pressure water bath was set to 30°C.

[0077] The cement slurry thickening curve of Example 3 is as follows: Figure 4 shown.

[0078] Comparative Example 3

[0079] The raw material components and weight contents of the comparative cement slurry are as follows: 450 parts of oil well G grade cement, 20 parts of high temperature retarder GH-9, 18 parts of G33S high temperature fluid loss reducer, 120 parts of SY silica fume, 90 parts of DY01 low density lightweight material, 100 parts of DY02 active strength enhancer, 350 parts of tap water, and the density is 1.55 g / cm 3 Low-density cement slurry. The performance test method and experimental conditions are consistent with those in Example 3.

[0080] Example 4

[0081] The method for preparing the ultra-deep well cementing slurry with large temperature difference and low density comprises the following steps in sequence:

[0082] S1. Preparation of phosphoric acid solution: weigh the raw materials according to the following weight ratio: hydroxyethylene diphosphoric acid solution: sodium hexametaphosphate: tap water = 6:3:41, wherein the mass concentration of hydroxyethylene diphosphoric acid solution is 60%; first, gradually pour sodium hexametaphosphate into tap water while stirring, keep the stirring speed at 500rpm, and keep the water temperature at 40°C. After the sodium hexametaphosphate is completely dissolved, gradually add the hydroxyethylene diphosphoric acid solution, continue stirring for 5 minutes, and keep the stirring speed at 200rpm; set aside for use 30 minutes after the preparation is completed, and obtain a mixed aqueous solution composed of hydroxyethylene diphosphoric acid and sodium hexametaphosphate, which is called TL-2 phosphoric acid solution;

[0083] S2, dissolving zinc nitrate in tap water to prepare a 10%wt TY zinc nitrate aqueous solution;

[0084] S3, dry-mix 450 parts of oil well G grade cement, 120 parts of silica fume, 85 parts of low-density lightweight material, and 80 parts of active strength enhancer to obtain a dry-mixed aggregate;

[0085] S4, take 15 parts of high-temperature fluid loss reducer G33S, dissolve them in 340 parts of tap water to obtain an aqueous solution of the high-temperature fluid loss reducer;

[0086] S5, mixing the aqueous solution of the high-temperature fluid loss reducer with the dry-mixed aggregate to obtain a cement slurry;

[0087] S6. Take 14 parts of the TY zinc nitrate aqueous solution of step S2, pour them into the cement slurry of step S5 within 10 seconds, and mix them while maintaining a rotation speed of 4500 rpm; after 1 minute, pour 35 parts of the TL-2 phosphoric acid solution after the hydrolysis of step S1 within 10 seconds, maintain a rotation speed of 4500 rpm, and mix them evenly to obtain a large temperature difference and low density cementing slurry for ultra-deep wells.

[0088] The performance of the cement slurry prepared in Example 3 was evaluated according to the standard GB / T 19139-2003 "Test method for oil well cement". The temperature difference between the top and the bottom of the oil well was set to be greater than 110°C, the top temperature was 30°C, and the circulation temperature was 140°C. The dynamic changes in temperature and pressure of the top cement slurry at the bottom of the well were simulated. The cement slurry was cured using a high-temperature and high-pressure thickener, the temperature was raised to 140°C for 70 minutes, the pressure was increased to 75 MPa, and then the thickening conditions were maintained for 60 minutes. After naturally cooling to 90°C, the cement slurry was taken out, poured into a mold, and placed in a normal-pressure water bath for curing for 48 hours and 72 hours. The temperature of the normal-pressure water bath was set to 30°C.

[0089] The cement slurry thickening curve of Example 4 is as follows: Figure 5 shown.

[0090] Comparative Example 4

[0091] The raw material components and weight contents of the comparative cement slurry are as follows: 450 parts of oil well G grade cement, 28 parts of high temperature retarder GH-9, 15 parts of G33S high temperature fluid loss reducer, 120 parts of SY silica fume, 85 parts of DY01 low density lightweight material, 80 parts of DY02 active strength enhancer, 340 parts of tap water, and the obtained density is 1.6g / cm 3 Low-density cement slurry. The performance test method and experimental conditions are consistent with those of Example 4.

[0092] The cement performance parameters obtained from the above examples and comparative examples are summarized in Table 1 below.

[0093] Table 1

[0094]

[0095] As can be seen from Table 1, in each group of comparative examples and embodiments, when the density is the same and the thickening time is basically the same, there is almost no difference in the fluidity, free liquid and water loss parameters of the cement slurry. The free liquid in the comparative example is slightly less than that in the embodiment. However, the top compressive strength at 48h and 72h in each embodiment is significantly higher than that in the comparative example. It can be determined that each embodiment solves the problem of low-temperature ultra-slow setting at the top of the oil well cement sealing section where the temperature difference between the top and the bottom is greater than 90-120°C compared with the comparative example.

[0096] from Figures 2 to 5 It can be seen from the thickening curve that when the top and bottom circulation temperature is 120-150℃, the cement slurry thickens smoothly, indicating that under high temperature conditions, the cement slurry has good stability, and the transition time of the cement slurry consistency from 30-70BC is very short, which is conducive to reducing the risk of gas and water channeling.

[0097] The index requirements and manufacturers of various raw materials in the present invention are shown in Table 2.

[0098] Table 2

[0099]

[0100] The above is only a preferred embodiment of the present invention, which shows and describes the basic principles, main features and advantages of the present invention, but does not limit the scope of patent protection of the present invention. Those skilled in the art should understand that the present invention is not limited by the above embodiments. In addition to the above embodiments, the present invention may have other implementation modes without departing from the spirit and scope of the present invention. The present invention may also have various changes and improvements, and all technical solutions formed by equivalent substitution or equivalent transformation fall within the scope of protection required by the present invention. The scope of protection required by the present invention is defined by the attached claims and their equivalents. The technical features not described in the present invention can be realized by or using existing technologies, which will not be repeated here.

Claims

1. A low-density cementing slurry with large temperature difference for ultra-deep wells, characterized in that: The raw material components and weight contents are as follows: 450 parts of oil well grade cement, 120 parts of silica fume, 100-85 parts of low-density lightweight material, 120-80 parts of active strength enhancer, 22-15 parts of high-temperature fluid loss reducer, 435-340 parts of water, 12-35 parts of TL-2 phosphoric acid solution and 4.8-14 parts of 10%wt TY zinc nitrate aqueous solution.

2. The ultra-deep well cementing slurry with large temperature difference and low density according to claim 1 is characterized by: The TL-2 phosphoric acid solution includes hydroxyethylene diphosphoric acid solution, sodium hexametaphosphate and tap water in a weight ratio of hydroxyethylene diphosphoric acid solution: sodium hexametaphosphate: tap water = 6:3:41, wherein the mass concentration of the hydroxyethylene diphosphoric acid solution is 60%.

3. The ultra-deep well cementing slurry with large temperature difference and low density according to claim 1 is characterized by: The low-density lightweight material is a silicon-aluminum hollow microsphere with a particle size distribution range of 25.58-408.7 μm and a density of 0.59*10 -3 kg / m 3 .

4. The ultra-deep well cementing slurry with large temperature difference and low density according to claim 1 is characterized in that: The activity strength enhancer is DY02 activity strength enhancer.

5. The ultra-deep well cementing slurry with large temperature difference and low density according to claim 1 is characterized in that: The high temperature fluid loss additive is G33S high temperature fluid loss additive.

6. The ultra-deep well cementing slurry with large temperature difference and low density according to claim 1 is characterized in that: The raw material components and weight contents are as follows: 450 parts of oil well grade cement, 120 parts of silica fume, 100 parts of low-density lightweight material, 120 parts of active strength enhancer, 22 parts of high-temperature fluid loss reducer, 435 parts of water, 12 parts of TL-2 phosphoric acid solution and 4.8 parts of 10%wt TY zinc nitrate aqueous solution.

7. The ultra-deep well cementing slurry with large temperature difference and low density according to claim 1 is characterized in that: The raw material components and weight contents are as follows: 450 parts of oil well grade cement, 120 parts of silica fume, 90 parts of low-density lightweight material, 100 parts of active strength enhancer, 20 parts of high-temperature fluid loss reducer, 400 parts of water, 16 parts of TL-2 phosphoric acid solution and 6.4 parts of 10%wt TY zinc nitrate aqueous solution.

8. The ultra-deep well cementing slurry with large temperature difference and low density according to claim 1 is characterized in that: The raw material components and weight contents are as follows: 450 parts of oil well grade cement, 120 parts of silica fume, 90 parts of low-density lightweight material, 100 parts of active strength enhancer, 18 parts of high-temperature fluid loss reducer, 380 parts of water, 25 parts of TL-2 phosphoric acid solution and 6.4 parts of 10%wt TY zinc nitrate aqueous solution.

9. The ultra-deep well cementing slurry with large temperature difference and low density according to claim 1, characterized in that: The raw material components and weight contents are as follows: 450 parts of oil well grade cement, 120 parts of silica fume, 85 parts of low-density lightweight material, 80 parts of active strength enhancer, 15 parts of high-temperature fluid loss reducer, 340 parts of water, 35 parts of TL-2 phosphoric acid solution and 14 parts of 10%wt TY zinc nitrate aqueous solution.

10. A method for preparing a low-density cement slurry with large temperature difference for ultra-deep wells, characterized in that: The steps are as follows: S1. Preparation of phosphoric acid solution: weigh the raw materials according to the following weight ratio: hydroxyethylene diphosphoric acid solution: sodium hexametaphosphate: tap water = 6:3:41, wherein the mass concentration of hydroxyethylene diphosphoric acid solution is 60%; first, gradually pour sodium hexametaphosphate into tap water while stirring, keep the stirring speed at 500rpm, and keep the water temperature at 40°C. After the sodium hexametaphosphate is completely dissolved, gradually add the hydroxyethylene diphosphoric acid solution, continue stirring for 5 minutes, and keep the stirring speed at 200rpm; set aside for use 30 minutes after the preparation is completed, and obtain a mixed aqueous solution composed of hydroxyethylene diphosphoric acid and sodium hexametaphosphate, which is called TL-2 phosphoric acid solution; S2, dissolving zinc nitrate in tap water to prepare a 10%wt TY zinc nitrate aqueous solution; S3, dry-mix 450 parts of oil well G grade cement, 120 parts of silica fume, 100-85 parts of low-density lightweight material, and 120-80 parts of active strength enhancer to obtain dry-mixed aggregate; S4, take 22-15 parts of high temperature fluid loss reducer G33S, dissolve in 435-340 parts of tap water, to obtain an aqueous solution of the high temperature fluid loss reducer; S5, mixing the aqueous solution of the high-temperature fluid loss reducer with the dry-mixed aggregate to obtain a cement slurry; S6, take 4.8-14 parts of the TY zinc nitrate aqueous solution of step S2, pour it into the cement slurry of step S5 within 10 seconds, keep the rotation speed at 4500 rpm; after 1 minute, pour 9-35 parts of the TL-2 phosphoric acid solution after the hydrolysis of step S1 within 10 seconds, keep the rotation speed at 4500 rpm, mix evenly to obtain the large temperature difference low density cementing slurry for ultra-deep wells.

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