Low-density early-strength anti-channeling cement slurry for offshore cementing and preparation method thereof

Abstract

This invention discloses a low-density, early-strength, anti-channeling cement slurry for marine cementing and its preparation method, comprising low-temperature early-strength cement, a weight-reducing agent, an early-strength stabilizer, a mineral reinforcing agent, an anti-channeling agent, a fluid loss reducing agent, a dispersant, an antifoaming agent, and water; wherein, the low-temperature early-strength cement is formed by mixing tricalcium silicate, tricalcium aluminate, dicalcium silicate, gypsum dihydrate, and tetracalcium aluminoferrite in cement; the early-strength stabilizer is composed of modified nanoporous molecular sieve powder, nano-mesoporous clay, and ultrafine silica; the modified nanoporous... The sieve is prepared by exchanging metal cations in a mixed solution of aluminum chloride and zirconium nitrate with cations in MCM-48 mesoporous molecular sieve using a template agent exchange method, followed by adsorption modification with triethanolamine. The cement slurry has advantages such as good rheological properties, low water loss, and short thickening time. Its cement stone has a compressive strength higher than 10 MPa after curing at 10℃ for 12 h, a strength ≥16 MPa after 24 h, and a cement stone permeability <0.02 mD. Moreover, the preparation method is simple and the conditions are easy to control.

Description

Technical Field

[0001] This invention relates to the field of oil well cement slurry technology, and in particular to a low-density, early-strength, anti-channeling cement slurry for marine cementing and its preparation method. Background Technology

[0002] With the deepening of exploration and development, cementing operations in low-pressure lost circulation zones and low-pressure oil and gas formations are becoming increasingly common. Furthermore, offshore oil exploration and development is gradually becoming a key direction for future energy development. Currently, the surface and bottom-hole temperatures of offshore platforms are low, and offshore operations are generally conducted on a day-fee basis. Under normal circumstances, the seabed temperature is only around 4°C, which slows down cement hydration and affects the construction progress. For conventional oil well cement, this severely impacts the strength development of the cement slurry, potentially leading to insufficient strength and excessively slow setting. Moreover, shallow formations have poor cementing properties and are soft in texture, making them prone to well leakage and well collapse during cementing. Therefore, low-density cement slurry is required, placing higher demands on the strength development of the cement slurry. Simultaneously, some blocks contain shallow gas, requiring consideration of how to stabilize the formation and prevent gas intrusion during cementing. Summary of the Invention

[0003] The purpose of this invention is to provide a low-density, early-strength, anti-channeling cement slurry for marine cementing, suitable for low-temperature, easily lost formations in the ocean.

[0004] Another objective of this invention is to provide a method for preparing the aforementioned low-density, early-strength, anti-channeling cement slurry for marine cementing.

[0005] Therefore, the technical solution of the present invention is as follows:

[0006] A low-density, early-strength, anti-channeling cement slurry for marine cementing comprises, by weight, 100 parts of low-temperature early-strength cement, 6-35 parts of weight-reducing agent, 5-25 parts of early-strength stabilizer, 15-40 parts of mineral reinforcing agent, 3-8 parts of anti-channeling agent, 4-8 parts of fluid loss reducing agent, 0.2-0.8 parts of dispersant, 0.1-0.15 parts of defoamer, and 62-110 parts of water.

[0007] Low-temperature early-strength cement is formed by mixing 54-62 wt.% tricalcium silicate, 9-15 wt.% tricalcium aluminate, 20-28 wt.% dicalcium silicate, 2-3 wt.% gypsum dihydrate, and the balance tetracalcium aluminoferrite in 100 parts by weight of cement, and the total mass fraction of tricalcium silicate, tricalcium aluminate, dicalcium silicate, gypsum dihydrate, and tetracalcium aluminoferrite is 100%.

[0008] The weight-reducing agent has a density of 0.38-0.42 g / cm³. 3 Hollow glass microspheres with an average particle size of 50μm and a pressure resistance of ≥40MPa; specifically, a weight-reducing agent produced by China Steel Group Maanshan Mining Research Institute New Materials Technology Co., Ltd. can be used.

[0009] The early strength stabilizer is composed of 30-60 parts by weight of modified nano-mesoporous molecular sieve powder, 10-20 parts by weight of nano-metakaolin, and 20-30 parts by weight of ultrafine silica. The modified nano-mesoporous molecular sieve is prepared by exchanging the metal cations in the mixed solution of aluminum chloride and zirconium nitrate with the cationic surfactant in the MCM-48 mesoporous molecular sieve using a template agent exchange method, followed by adsorption modification with triethanolamine. The nano-metakaolin and ultrafine silica are purchased from commercially available products.

[0010] Preferably, the modified nanoporous molecular sieve powder has a particle size of 0.05–0.3 μm, the nano-kaolin has a particle size of 80–150 nm, and the ultrafine silica powder has a particle size of 0.1–2 μm. The three powder particles can achieve a better particle size distribution, and the resulting cement stone has strong compressive strength and low permeability. It can also improve the settling stability of the cement slurry itself and reduce cement slurry water separation and cement stone shrinkage.

[0011] This early strength stabilizer effectively increases the viscosity of the system and the active components of the cement paste in the suspension early strength agent. It not only has the advantages of good suspension performance and rapid early strength development at low temperature, but also improves the non-permeability of the cement paste by adding nano- to micron-sized particles.

[0012] Preferably, the specific preparation method of the modified nanoporous molecular sieve in the above-mentioned early strength stabilizer is as follows:

[0013] Exchange modification: Aluminum chloride and zirconium nitrate in a weight ratio of 1:1 were dissolved in water to prepare a 0.5 wt.% mixed salt solution; a mixing system was prepared by adding 10 parts by weight of MCM-48 mesoporous molecular sieve powder to every 100 parts by weight of the mixed salt solution. After stirring for 2-4 hours, the mixture was filtered, and the molecular sieve powder was calcined at 550℃ for 8 hours to obtain exchange-modified molecular sieve powder.

[0014] Adsorption modification: 50 parts by weight of exchange-modified molecular sieve powder were added to 1000 parts by weight of ethanol, and 0.5 parts by weight of triethanolamine were added under stirring conditions, and stirring was continued for at least 2 hours; after filtration and drying, modified nanoporous molecular sieve powder was obtained.

[0015] Preferably, the mineral reinforcing agent is a mixture of ultrafine cement and ultrafine slag, with a weight ratio of 1:1 to 1.5; wherein the ultrafine cement has a density of 3.1 g / cm³. 3 Ultrafine cement with a particle size range of 0.2–10 μm and an average particle size of 5 μm; ultrafine slag with a density of 2.75 g / cm³ is selected. 3Ultrafine slag with a particle size range of 0.1 to 5 μm and an average particle size of 2 μm.

[0016] Preferably, the fluid loss reducing agent is an AMPS-type fluid loss reducing agent, specifically the fluid loss reducing agent BH-F202S produced by Bohai Drilling Company of China National Petroleum Corporation.

[0017] Preferably, the anti-channeling agent is a powder-based anti-channeling agent, specifically the anti-channeling agent BH-G502S produced by Bohai Drilling Company of China National Petroleum Corporation.

[0018] Preferably, the dispersant is a formaldehyde-acetone condensate dispersant, specifically the dispersant BZGF-1 produced by China National Petroleum Corporation Bohai Drilling Company.

[0019] Preferably, the defoamer is a phosphate ester defoamer, specifically the defoamer BZXP-1 produced by Bohai Drilling Company of China National Petroleum Corporation.

[0020] The preparation method of this low-density early-strength anti-channeling cement slurry for marine cementing is as follows: low-temperature early-strength cement, weight-reducing agent, early-strength stabilizer, mineral reinforcing agent, anti-channeling agent, fluid loss reducing agent, dispersant, defoamer and water are mixed evenly in a predetermined ratio and stirred at a speed of 4000 rpm for 60 seconds to prepare the low-density early-strength anti-channeling cement slurry for marine cementing.

[0021] Compared with existing technologies, this low-density early-strength anti-channeling cement slurry for marine cementing is formulated by compounding low-temperature early-strength cement that can develop strength quickly at low temperatures with an early-strength stabilizer that has good suspension properties, rapid early strength development at low temperatures, and enhanced non-permeability. It is also formulated with auxiliary agents to obtain a cement slurry with a density range of [specific range missing]. This cement slurry has advantages such as good rheological properties, low water loss, and short thickening time. The cement stone formed by it has a compressive strength of over 10 MPa after curing at 10℃ for 12 hours, a strength of ≥16 MPa after 24 hours, and a cement stone permeability of <0.02 mD. Moreover, the preparation method is simple, the conditions are easy to control, and it is beneficial for on-site construction. Detailed Implementation

[0022] The present invention will be further described below with reference to specific embodiments, but the following embodiments are by no means intended to limit the present invention.

[0023] Example 1

[0024] A substance with a density of 1.60 g / cm³ 3 The low-density, early-strength, anti-channeling cement slurry for marine cementing is composed of 100 parts by weight of low-temperature early-strength cement, 6 parts of weight-reducing agent, 5 parts of early-strength stabilizer, 15 parts of mineral reinforcing agent, 3 parts of anti-channeling agent, 4 parts of fluid loss reducing agent, 0.2 parts of dispersant, 0.1 parts of defoamer, and 62 parts of water; among which,

[0025] Low-temperature early-strength cement is made by mixing 54 parts of tricalcium silicate, 12 parts of tricalcium aluminate, 22 parts of dicalcium silicate, 2.5 parts of gypsum dihydrate and 9.5 parts of tetracalcium aluminoferrite with 100 parts by weight of cement.

[0026] The weight-reducing agent used is hollow glass microspheres produced by Sinosteel Maanshan Mining Research Institute New Materials Technology Co., Ltd., with a density of 0.38–0.42 g / cm³. 3 The average particle size is 50μm, and the pressure resistance reaches 40MPa.

[0027] The early strength stabilizer is composed of 30 parts by weight of modified nano-mesoporous molecular sieve powder, 30 parts by weight of nano-meta-kaolin, and 40 parts by weight of ultrafine silica powder; the particle size of the modified nano-mesoporous molecular sieve powder is 0.05-0.3 μm, the particle size of the nano-meta-kaolin is 80-150 nm, and the particle size of the ultrafine silica powder is 0.1-2 μm.

[0028] The mineral reinforcing agent is a mixture of ultrafine cement and ultrafine slag in a 1:1 weight ratio; the ultrafine cement has a density of 3.1 g / cm³. 3 Ultrafine cement with a particle size range of 0.2–10 μm and an average particle size of 5 μm; ultrafine slag with a density of 2.75 g / cm³ is selected. 3 Ultrafine slag with a particle size range of 0.1–5 μm and an average particle size of 2 μm;

[0029] The anti-channeling agent used is BH-G502S produced by Bohai Drilling Company of China National Petroleum Corporation; the water loss reducing agent used is AMPS-type water loss reducing agent BH-F202S produced by Bohai Drilling Company of China National Petroleum Corporation; the dispersant used is formaldehyde-acetone condensate dispersant BZGF-1 produced by Bohai Drilling Company of China National Petroleum Corporation; and the defoamer used is phosphate ester defoamer BZXP-1 produced by Bohai Drilling Company of China National Petroleum Corporation.

[0030] Example 2

[0031] A substance with a density of 1.50 g / cm³ 3The low-density, early-strength, anti-channeling cement slurry for marine cementing is composed of 100 parts by weight of low-temperature early-strength cement, 10 parts of weight-reducing agent, 10 parts of early-strength stabilizer, 20 parts of mineral reinforcing agent, 5 parts of anti-channeling agent, 5 parts of fluid loss reducing agent, 0.4 parts of dispersant, 0.1 parts of defoamer, and 68 parts of water. The low-temperature early-strength cement is composed of 56 parts by weight of tricalcium silicate, 14 parts by weight of tricalcium aluminate, 25 parts by weight of dicalcium silicate, 2.5 parts by weight of gypsum dihydrate, and 2.5 parts by weight of tetracalcium aluminoferrite. The early-strength stabilizer is composed of 40 parts by weight of modified nano-mesoporous MCM-48, 30 parts by weight of nano-mesoporous metakaolin, and 30 parts by weight of ultrafine silica powder. The mineral reinforcing agent is a mixture of ultrafine cement and ultrafine slag in a weight ratio of 1:1.2. The weight-reducing agent, anti-channeling agent, fluid loss reducing agent, dispersant, and defoamer are the same as in Example 1.

[0032] Example 3

[0033] A substance with a density of 1.40 g / cm³ 3 The low-density, early-strength, anti-channeling cement slurry for marine cementing is composed of 100 parts by weight of low-temperature early-strength cement, 15 parts of weight-reducing agent, 15 parts of early-strength stabilizer, 25 parts of mineral reinforcing agent, 6 parts of anti-channeling agent, 6 parts of fluid loss reducing agent, 0.8 parts of dispersant, 0.15 parts of defoamer, and 80 parts of water. The low-temperature early-strength cement is composed of 58 parts by weight of tricalcium silicate, 13 parts by weight of tricalcium aluminate, 22 parts by weight of dicalcium silicate, 2.5 parts by weight of gypsum dihydrate, and 4.5 parts by weight of tetracalcium aluminoferrite. The early-strength stabilizer is composed of 50 parts by weight of modified nano-mesoporous MCM-48, 20 parts by weight of nano-mesoporous metakaolin, and 30 parts by weight of ultrafine silica powder. The mineral reinforcing agent is a mixture of ultrafine cement and ultrafine slag in a weight ratio of 1:1.2. The weight-reducing agent, anti-channeling agent, fluid loss reducing agent, dispersant, and defoamer are the same as in Example 1.

[0034] Example 4

[0035] A substance with a density of 1.30 g / cm³ 3The low-density, early-strength, anti-channeling cement slurry for marine cementing is composed of 100 parts by weight of low-temperature early-strength cement, 24 parts of weight-reducing agent, 20 parts of early-strength stabilizer, 30 parts of mineral reinforcing agent, 7 parts of anti-channeling agent, 7 parts of fluid loss reducing agent, 0.8 parts of dispersant, 0.15 parts of defoamer, and 88 parts of water. The low-temperature early-strength cement is composed of 56 parts by weight of tricalcium silicate, 14 parts by weight of tricalcium aluminate, 24 parts by weight of dicalcium silicate, 3 parts by weight of gypsum dihydrate, and 3 parts by weight of tetracalcium aluminoferrite. The early-strength stabilizer is composed of 50 parts by weight of modified nano-mesoporous MCM-48, 40 parts by weight of nano-mesoporous metakaolin, and 10 parts by weight of ultrafine silica powder. The mineral reinforcing agent is a mixture of ultrafine cement and ultrafine slag in a weight ratio of 1:1.4. The weight-reducing agent, anti-channeling agent, fluid loss reducing agent, dispersant, and defoamer are the same as in Example 1.

[0036] Example 5

[0037] A substance with a density of 1.20 g / cm³ 3 The low-density, early-strength, anti-channeling cement slurry for marine cementing is composed of 100 parts by weight of low-temperature early-strength cement, 35 parts of weight-reducing agent, 25 parts of early-strength stabilizer, 40 parts of mineral reinforcing agent, 8 parts of anti-channeling agent, 8 parts of fluid loss reducing agent, 0.8 parts of dispersant, 0.15 parts of defoamer, and 110 parts of water. The low-temperature early-strength cement is composed of 56 parts by weight of tricalcium silicate, 14 parts by weight of tricalcium aluminate, 24 parts by weight of dicalcium silicate, 3 parts by weight of gypsum dihydrate, and 3 parts by weight of tetracalcium aluminoferrite. The early-strength stabilizer is composed of 50 parts by weight of modified nano-mesoporous MCM-48, 40 parts by weight of nano-mesoporous metakaolin, and 10 parts by weight of ultrafine silica powder. The mineral reinforcing agent is a mixture of ultrafine cement and ultrafine slag in a weight ratio of 1:1.5. The weight-reducing agent, anti-channeling agent, fluid loss reducing agent, dispersant, and defoamer are the same as in Example 1.

[0038] Comparative Example 1

[0039] A substance with a density of 1.50 g / cm³ 3 The cement slurry is composed of 100 parts by weight of Grade G high-sulfur-resistant oil well cement, 10 parts of weight-reducing agent, 10 parts of early-strength stabilizer, 20 parts of mineral reinforcing agent, 5 parts of anti-channeling agent, 5 parts of fluid loss reducing agent, 0.4 parts of dispersant, 0.1 parts of defoamer, and 68 parts of water. The early-strength stabilizer is composed of 40 parts by weight of modified nano-mesoporous MCM-48, 30 parts by weight of nano-mesoporous metakaolin, and 30 parts by weight of ultrafine silica powder. The mineral reinforcing agent is a mixture of ultrafine cement and ultrafine slag in a weight ratio of 1:1.2. The weight-reducing agent, anti-channeling agent, fluid loss reducing agent, dispersant, and defoamer are the same as in Example 1. The difference between Comparative Example 1 and Example 2 is that Grade G high-sulfur-resistant oil well cement is used instead of low-temperature early-strength cement.

[0040] Comparative Example 2

[0041] A substance with a density of 1.50 g / cm³ 3 The cement slurry is composed of 100 parts by weight of low-temperature early-strength cement, 35 parts of weight-reducing agent, 25 parts of silica fume, 40 parts of mineral reinforcing agent, 8 parts of anti-channeling agent, 8 parts of water loss reducing agent, 0.8 parts of dispersant, 0.15 parts of defoamer, and 110 parts of water. The low-temperature early-strength cement is composed of 56 parts of tricalcium silicate, 14 parts of tricalcium aluminate, 24 parts of dicalcium silicate, 3 parts of gypsum dihydrate, and 3 parts of tetracalcium aluminoferrite added to 100 parts by weight of cement. The mineral reinforcing agent is a mixture of ultrafine cement and ultrafine slag in a weight ratio of 1:1.5. The weight-reducing agent, anti-channeling agent, water loss reducing agent, dispersant, and defoamer are the same as in Example 5.

[0042] In Examples 1 to 5 and Comparative Example 1 above, the modified nanoporous molecular sieve powder in the early strength stabilizer was prepared in the laboratory. The modified raw material MCM-48 mesoporous molecular sieve powder can be purchased directly from commercial products or prepared in the laboratory. In the examples and comparative examples above, the MCM-48 mesoporous molecular sieve powder was also prepared in the laboratory.

[0043] Specifically, the preparation method of modified nanoporous molecular sieve powder is as follows:

[0044] Step 1: At 25–30°C, mix 10 parts by weight of 28 wt.% ammonia, 35 parts by weight of ethanol, and 100 parts by weight of deionized water until homogeneous, then add 0.5 parts by weight of cetyl ammonium bromide (CTA). + Add 3.5 parts by weight of surfactant F127, and after it is fully dissolved, add 2 parts by weight of tetraethyl orthosilicate, stir at 1000 r / min for at least 20 min, let stand for 24 h, and then filter, wash and dry to obtain MCM-48 mesoporous molecular sieve.

[0045] Step 2: Dissolve aluminum chloride and zirconium nitrate in water at a weight ratio of 1:1 to prepare a 0.5 wt.% mixed salt solution; add 10 parts by weight of MCM-48 mesoporous molecular sieve powder to 100 parts by weight of the mixed salt solution, stir for at least 2 hours, and use the template exchange method to react the metal cations in the mixed salt solution with CTA. + Exchange occurs, and the ions are adsorbed into the molecular sieve channels. After filtration, the molecular sieve powder is calcined at 550℃ for 8 hours to obtain exchange-modified molecular sieve powder M-MCM-48 (M represents metal ions).

[0046] Step 3: Add 50 parts by weight of M-MCM-48 to 1000 parts by weight of ethanol solution, then add 0.5 parts by weight of triethanolamine and stir for 2 hours; after filtration and drying, modified nanoporous molecular sieve powder is obtained.

[0047] Performance testing:

[0048] The components of the low-density early-strength anti-channeling cement slurry for marine cementing prepared in Examples 1 to 5, and the cement slurries prepared in Comparative Examples 1 and 2 were weighed and placed sequentially on a constant-speed mixer and mixed at 4000 rpm for 60 s to prepare cement slurries. The properties of each group of newly prepared cement slurries were tested according to API specifications, including cement slurry density, API water loss (30°C), free liquid percentage, density difference, fluidity, compressive strength, thickening time, and permeability.

[0049] The specific test results are shown in Table 1 below.

[0050] Table 1:

[0051]

[0052] As can be seen from the test results in Table 1 above, the low-density cement slurry prepared in Examples 1-5 has the following advantages:

[0053] 1) The density range of cement grout is 1.2 g / cm³. 3 ~1.6g / cm 3 Between these conditions, the requirements for offshore cementing operations are met;

[0054] 2) The fluidity of the cement slurry is all >20cm, indicating good fluidity;

[0055] 3) Settling stability of cement slurry: The cement slurry has a low density and almost zero free liquid, which gives it better suspension performance than the cement slurries prepared in Comparative Example 1 and Comparative Example 2.

[0056] 4) The API water loss of cement slurry at 30℃ is ≤30mL, which can be controlled to be below 50mL;

[0057] 5) The compressive strength of the cement stone formed by the cement slurry was higher than 10 MPa after curing at 10℃ for 12 h, and the strength was ≥16 MPa after 24 h. Compared with the compressive strength of the cement stone formed by the cement slurry prepared in Comparative Example 1 and Comparative Example 2, the compressive strength was greatly improved, and the compressive performance was excellent.

[0058] 6) Compared with the cement slurry prepared in Comparative Example 1 and Comparative Example 2, the thickening time of the cement slurry is further shortened.

[0059] 7) The permeability of the cement stone formed by the cement slurry is all <0.02mD, which is much smaller than that of the cement stone formed by the cement slurry prepared in Comparative Example 1 and Comparative Example 2. In summary, the cement slurry prepared in this application has good rheological properties, stable slurry and low water loss, and the cement stone formed by it has good compressive strength and low permeability.

Claims

1. A low-density, early-strength, anti-channeling cement slurry for marine cementing, characterized in that, It includes, by weight, 100 parts low-temperature early-strength cement, 6-35 parts lightweight agent, 5-25 parts early-strength stabilizer, 15-40 parts mineral reinforcing agent, 3-8 parts anti-channeling agent, 4-8 parts water loss reducing agent, 0.2-0.8 parts dispersant, 0.1-0.15 parts defoamer, and 62-110 parts water; wherein, Low-temperature early-strength cement is prepared by mixing 54 parts of tricalcium silicate, 12 parts of tricalcium aluminate, 22 parts of dicalcium silicate, 2.5 parts of gypsum dihydrate, and 9.5 parts of tetracalcium aluminoferrite into 100 parts by weight of cement; or, low-temperature early-strength cement is prepared by mixing 58 parts of tricalcium silicate, 13 parts of tricalcium aluminate, 22 parts of dicalcium silicate, 2.5 parts of gypsum dihydrate, and 4.5 parts of tetracalcium aluminoferrite into 100 parts by weight of cement; or, low-temperature early-strength cement is prepared by mixing 56 parts of tricalcium silicate, 14 parts of tricalcium aluminate, 25 parts of dicalcium silicate, 2.5 parts of gypsum dihydrate, and 2.5 parts of tetracalcium aluminoferrite into 100 parts by weight of cement; or, low-temperature early-strength cement is prepared by mixing 56 parts of tricalcium silicate, 14 parts of tricalcium aluminate, 24 parts of dicalcium silicate, 3 parts of gypsum dihydrate, and 3 parts of tetracalcium aluminoferrite into 100 parts by weight of cement. The early strength stabilizer is composed of 30-60 parts by weight of modified nano-mesoporous molecular sieve powder, 10-20 parts by weight of nano-metakaolin and 20-30 parts by weight of ultrafine silica. The modified nano-mesoporous molecular sieve is prepared by exchanging the metal cations in the mixed solution of aluminum chloride and zirconium nitrate with the cationic surfactant in the MCM-48 mesoporous molecular sieve through template agent exchange, and then by adsorption modification with triethanolamine.

2. The low density early strength anti-channeling cement slurry for offshore cementing according to claim 1, characterized in that, The weight-reducing agent is made of hollow glass microspheres with an average particle size of 50μm and a pressure resistance of ≥40MPa.

3. The low density early strength anti-channeling cement slurry for offshore cementing according to claim 1, characterized in that, Nano-meta-kaolin uses meta-kaolin with a particle size of 80~150nm.

4. The low density early strength anti-channeling cement slurry for offshore cementing according to claim 1, characterized in that, The ultrafine silica powder uses silica powder with a particle size of 0.1~2μm.

5. The low density early strength anti-channeling cement slurry for offshore cementing according to claim 1, characterized in that, The particle size of the modified nanoporous molecular sieve powder is 0.05~0.3μm.

6. The low density early strength anti-channeling cement slurry for offshore cementing according to claim 1, characterized in that, In the early strength stabilizer, the modified nanoporous molecular sieve is prepared by the following method: Exchange modification: Aluminum chloride and zirconium nitrate in a weight ratio of 1:1 were dissolved in water to prepare a 0.5 wt.% mixed salt solution; a mixing system was prepared by adding 10 parts by weight of MCM-48 mesoporous molecular sieve powder to every 100 parts by weight of the mixed salt solution. After stirring for 2-4 hours, the mixture was filtered, and the molecular sieve powder was calcined at 550℃ for 8 hours to obtain exchange-modified molecular sieve powder. Adsorption modification: 50 parts by weight of exchange-modified molecular sieve powder were added to 1000 parts by weight of ethanol. Under stirring conditions, 0.5 parts by weight of triethanolamine were added and stirring was continued for at least 2 hours. After filtration and drying, modified nanoporous molecular sieve powder was obtained.

7. The low density early strength anti-channeling cement slurry for offshore cementing according to claim 1, characterized in that, The mineral reinforcing agent is a mixture of ultrafine cement and ultrafine slag with a weight ratio of 1:1 to 1.

5.

8. The low density early strength anti-channeling cement slurry for offshore cementing according to claim 7, characterized in that, The ultrafine cement used has a density of 3.1 g / cm³. 3 Ultrafine cement with a particle size range of 0.2~10μm and an average particle size of 5μm; ultrafine slag with a density of 2.75g / cm³ is selected. 3 Ultrafine slag with a particle size range of 0.1~5μm and an average particle size of 2μm.

9. The low-density, early-strength, anti-channeling cement slurry for marine cementing according to claim 1, characterized in that, The water loss reducing agent is an AMPS-type water loss reducing agent; the dispersant is a formaldehyde-acetone condensate dispersant; the anti-channeling agent is a powder-based anti-channeling agent; and the defoamer is a phosphate ester-based defoamer.

10. A method for preparing a low-density, early-strength, anti-channeling cement slurry for marine cementing according to any one of claims 1 to 9, characterized in that, The steps are: mixing low temperature early strength cement, lightening agent, early strength stabilizer, mineral reinforcing agent, anti-channeling agent, fluid loss additive, dispersing agent, defoaming agent and water uniformly in proportion, and stirring at a speed of 4000 revolutions per minute for 60 seconds to obtain the low density early strength anti-channeling cement slurry for ocean well cementation.