A low temperature low density cement slurry system

Abstract

The application discloses a low-temperature and low-density cementing slurry system, and aims at solving the problems of low hydration rate and slow early strength development of the low-density cementing slurry in a low-temperature environment. The application comprises the following components in mass fractions: cement: 80-90 parts; lightening material: 10-20 parts; composite early strength agent: 4-8 parts; retarder: 0-2 parts; fluid loss additive: 0.5-4 parts; dispersant: 0.2-1 part; suspension stabilizer: 2-4 parts; defoaming agent: 0.03-0.3 parts; and mixing water: 60-80 parts. The application can improve the compactness of the cement stone by in-situ precipitation of nano C-S-H seeds, and can improve the compressive strength of the cement stone in the early and later curing stages. The application adopts tobermorite hollow spheres to provide nucleation sites for the hydration of the cement and the in-situ precipitation of the nano C-S-H seeds, and makes up for the shortage of low compressive strength.

Description

Technical Field

[0001] This invention relates to the field of oil and gas cementing technology, specifically to a low-temperature, low-density cement slurry system. Background Technology

[0002] Deepwater cementing faces completely different well conditions compared to onshore cementing, primarily encountering two major challenges. First, the surface mudline temperature in deepwater is extremely low, sometimes as low as 0°C. At these low temperatures, the cement hydration rate is significantly slowed, resulting in sluggish early strength development and an inability to form effective interlayer seals to prevent the migration of shallow oil and gas. Second, the formation near the surface is loose and weakly cemented, with low formation fracturing pressure and a narrow safe density window. To maintain formation pressure balance, low-density cement slurry systems are often required. However, low-density cement slurry systems also suffer from slow early strength development, and the combined effect of low temperatures on cement hydration further increases the difficulty of low-temperature cementing.

[0003] To maximize the low-temperature compressive strength of cement paste, the use of early-strength agents is unavoidable; however, most early-strength agents have limited effectiveness under low-temperature conditions. Current research indicates that nano-CSH seeds are an excellent low-temperature early-strength agent, but their preparation is cumbersome and costly, and the large number of hydroxyl groups on their surface makes them prone to agglomeration in cement paste. To address this agglomeration, additional admixtures need to be introduced during the preparation process for surface modification, further increasing the cost of using nano-CSH seeds.

[0004] Currently, commonly used cementing slurry systems include low-density cement slurry systems with microspheres, fly ash, glass microspheres, microsilica, and bentonite. However, all of these cement slurry systems have certain problems in practical use. For example, the addition of bentonite requires increasing the water-to-solid ratio, which increases the fluidity of the slurry but can easily lead to the deposition of solid materials in the slurry; fly ash has limited ability to reduce the density of the slurry, generally around 1.5 g / cm³. 3 The density is around 1000 ppm, and may be even higher in actual use; the floating beads are fragile during the mixing process, causing the slurry density to deviate from the design density; hollow glass microspheres are expensive and have poor interfacial bonding with the cement matrix, making them difficult to apply on a large scale.

[0005] To avoid the above problems, there is an urgent need to develop a low-density cement slurry system suitable for low-temperature cementing. Summary of the Invention

[0006] The purpose of this invention is to provide a low-temperature cementing slurry system to solve the problems of low hydration rate and slow early strength development of low-density cement slurry in low-temperature environments, and to meet the requirements of cementing construction.

[0007] Another objective of this invention is to provide a low-density cement slurry system based on hard silica-calcium stone, avoiding the use of glass microspheres and reducing construction costs.

[0008] Another objective of this invention is to provide an in-situ generated nano-CSH seed crystal to improve the strength of cement stone in ultra-low temperature environments around 0°C and reduce the cost of using nano-CSH seed crystals.

[0009] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0010] A low-temperature, low-density cementing slurry system, comprising the following components by weight:

[0011] Cement: 80-90 parts;

[0012] Lightening materials: 10-20 portions;

[0013] Composite early strength agent: 4-8 parts;

[0014] Retarder: 0-2 parts;

[0015] Water loss reducer: 0.5–4 parts;

[0016] Dispersant: 0.2–1 part;

[0017] Suspension stabilizer: 2-4 parts;

[0018] Defoamer: 0.03–0.3 parts;

[0019] Mixing water: 60-80 parts.

[0020] Furthermore, the cement is at least one of Grade G high sulfate-resistant oil well cement and ultrafine cement.

[0021] Furthermore, the weight-reducing material is a mixture of hollow calcareous silica spheres composed of calcareous silica fibers and calcareous silica-soybean oil phase change microcapsules, with a density of 0.6 g / cm³. 3 The preparation method is as follows:

[0022] S1: Soybean oil with a freezing point of 2℃ was added to deionized water at 70℃, with a mass ratio of soybean oil to deionized water of 1:10. Sodium dodecylbenzene sulfonate was added at a mass of 0.7% of the soybean oil mass. The mixture was stirred to form a suspension. Then, silane coupling agent KH550 was added at a mass of 1% of the soybean oil mass. The mixture was stirred until homogeneous. Simultaneously, calcium chloride solution and sodium silicate solution, both with a concentration of 1 mol / L, were added dropwise at a core-to-wall ratio of 1:4. The mixture was stirred continuously for 12 hours at a stirring speed of 300 rpm. The mixture was then filtered and dried to obtain the phase change microcapsule precursor.

[0023] S2: Weigh quicklime and quartz sand according to Ca / Si = 1.05, and add phase change microcapsule precursor at the same time. The core-to-wall ratio is 1:3. Then place it in deionized water. The amount of deionized water added is 50 times the total mass of quicklime, quartz sand and phase change microcapsule precursor. After aging for 3 hours, add silane coupling agent KH550. The amount added is 0.5% of the mass of phase change microcapsule precursor. Then heat to 190℃ at a rate of 1.4℃ / min and stir continuously at a stirring rate of 300 rpm. Keep warm for 11 hours, filter and dry to obtain hard silica calcium stone-soybean oil phase change microcapsules.

[0024] S3: Weigh quicklime and quartz sand according to Ca / Si = 1.05, then put them into deionized water with a total mass of 50 times that of quicklime and quartz sand, age for 3 hours, then heat to 210℃ at a rate of 1.4℃ / min and stir continuously, keep warm for 11 hours, filter and dry to obtain hard calcium silicate hollow spheres.

[0025] S4: Mix the hard silica-calcium stone-soybean oil phase change microcapsules and hard silica-calcium stone hollow spheres prepared in S2 and S3 respectively at a weight ratio of 3:7 to obtain the weight-reducing material.

[0026] The mixed lightening material used in this invention can, on the one hand, reduce the density of cement stone and reduce the release of hydration heat as a lightening agent, and it has excellent interfacial bonding with the cement stone matrix. On the other hand, it can provide nucleation sites to promote cement hydration reaction and in-situ precipitation of nano CSH seeds, thereby improving the density of cement stone.

[0027] Furthermore, the composite early-strength agent comprises component A and component B, wherein component A is a water-soluble calcium salt and component B is a water-soluble silicate; before using the composite early-strength agent, component A needs to be added to the mixing water and dissolved to form Ca2+ 24 hours in advance. 2+ The solution, component B, is added as a solid powder to the cement and mixed evenly.

[0028] The early-strength agent used in this invention is based on classical crystal nucleation theory and precipitation and dissolution phenomena. Since CaSiO3 is insoluble in water, when a large amount of Ca is present in the solution... 2+ and SiO3 2- During this process, CaSiO3, or nano-CSH seed crystals, will precipitate directly in situ. The precipitated nano-CSH seed crystals provide nucleation sites for cement hydration in the early stage of hydration, participate in the construction of the CSH gel skeleton, and promote the improvement of early compressive strength of cement stone. On the other hand, they fill the pores in cement stone in the later stage of hydration, reduce the number of harmful pores, and increase the density of cement stone, thereby further improving the compressive strength of cement stone.

[0029] Furthermore, component A is at least one of anhydrous calcium chloride and calcium nitrate tetrahydrate.

[0030] Furthermore, component B is sodium silicate nonahydrate.

[0031] Furthermore, the retarder is calcium gluconate.

[0032] Furthermore, the water loss reducing agent is an AMPS-amide-carboxylic acid polymer.

[0033] Furthermore, the dispersant is an acetone-formaldehyde condensate.

[0034] Furthermore, the suspension stabilizer is bentonite.

[0035] The preparation method of the low-temperature, low-density cement slurry system of the present invention is as follows:

[0036] 1. Weigh component A of the composite early strength agent and add it to the mixing water. Let it stand for 24 hours to dissolve and obtain a mixed solution.

[0037] 2. Weigh out cement, light-reducing materials, component B of the composite early-strength agent, retarder, water loss reducer, dispersant, suspension stabilizer and defoamer, and mix them evenly to obtain a mixed dry powder;

[0038] 3. Mix the mixed solution and mixed dry powder evenly, and prepare the cement slurry in accordance with GB / T 19139-2012.

[0039] Compared with the prior art, the present invention has the following beneficial effects:

[0040] (1) This invention is based on the technical concept of in-situ precipitation of nano-CSH seeds, which is more advanced than directly doping CSH.

[0041] Seed crystals reduce usage costs;

[0042] (2) This invention improves the density of cement stone by in-situ precipitation of nano CSH seeds, which can improve the compressive strength of cement stone in both the early and late stages of curing.

[0043] (3) The present invention incorporates phase change microcapsules with soybean oil as the core material into the material to control the heat of hydration, while being environmentally friendly and green and pollution-free.

[0044] (4) Compared with glass microspheres, the hard silica calcium stone hollow spheres of the present invention have better thermal insulation performance, are simpler to manufacture, and have lower manufacturing costs.

[0045] (5) Compared with glass microspheres, the hard silica calcium stone hollow spheres of the present invention are made of fine fibers, which can provide nucleation sites for cement hydration and in-situ precipitation of nano CSH seeds, promote interfacial bonding with cement matrix, and effectively compensate for the problem of reduced compressive strength caused by the introduction of ultra-low density materials. Detailed Implementation

[0046] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. Obviously, the described embodiments are merely some embodiments of this invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0047] In this embodiment of the invention, the weight-reducing material is a mixture of hollow spheres composed of hard calcium silicate fibers and hard calcium silicate-soybean oil phase change microcapsules, with a density of 0.6 g / cm³. 3 The preparation method is as follows:

[0048] S1: Soybean oil with a freezing point of 2℃ was added to deionized water at 70℃, with a mass ratio of soybean oil to deionized water of 1:10. Sodium dodecylbenzene sulfonate was added at a mass of 0.7% of the soybean oil mass. The mixture was stirred to form a suspension. Then, silane coupling agent KH550 was added at a mass of 1% of the soybean oil mass. The mixture was stirred until homogeneous. Simultaneously, calcium chloride solution and sodium silicate solution, both with a concentration of 1 mol / L, were added dropwise at a core-to-wall ratio of 1:4. The mixture was stirred continuously for 12 hours at a stirring speed of 300 rpm. The mixture was then filtered and dried to obtain the phase change microcapsule precursor.

[0049] S2: Weigh quicklime and quartz sand according to Ca / Si = 1.05, and add phase change microcapsule precursor at the same time. The core-to-wall ratio is 1:3. Then place it in deionized water. The amount of deionized water added is 50 times the total mass of quicklime, quartz sand and phase change microcapsule precursor. After aging for 3 hours, add silane coupling agent KH550. The amount added is 0.5% of the mass of phase change microcapsule precursor. Then heat to 190℃ at a rate of 1.4℃ / min and stir continuously at a stirring rate of 300 rpm. Keep warm for 11 hours, filter and dry to obtain hard silica calcium stone-soybean oil phase change microcapsules.

[0050] S3: Weigh quicklime and quartz sand according to Ca / Si = 1.05, then put them into deionized water with a total mass of 50 times that of quicklime and quartz sand, age for 3 hours, then heat to 210℃ at a rate of 1.4℃ / min and stir continuously, keep warm for 11 hours, filter and dry to obtain hard calcium silicate hollow spheres.

[0051] S4: Mix the hard silica-calcium stone-soybean oil phase change microcapsules and hard silica-calcium stone hollow spheres prepared in S2 and S3 respectively at a weight ratio of 3:7 to obtain the weight-reducing material.

[0052] In this embodiment of the invention, the composite early-strength agent includes component A and component B, wherein component A is a water-soluble calcium salt and component B is a water-soluble silicate; before using the composite early-strength agent, component A needs to be dissolved in water to form Ca2+ 24 hours in advance. 2+ The solution, component B, is added as a solid powder to the dry cement powder and mixed evenly.

[0053] In this embodiment of the invention, component A is at least one of anhydrous calcium chloride and calcium nitrate tetrahydrate.

[0054] In this embodiment of the invention, component B is sodium silicate nonahydrate.

[0055] In this embodiment of the invention, the retarder is calcium gluconate.

[0056] In this embodiment of the invention, the water loss reducing agent is an AMPS-amide-carboxylic acid polymer.

[0057] In this embodiment of the invention, the dispersant is an acetone-formaldehyde condensate.

[0058] In this embodiment of the invention, the suspension stabilizer is bentonite.

[0059] In this embodiment of the invention, the preparation method of the low-temperature, low-density cement slurry system is as follows:

[0060] 1. Weigh component A of the composite early strength agent and add it to the mixing water. Let it stand for 24 hours to dissolve and obtain a mixed solution.

[0061] 2. Weigh out cement, light-reducing materials, component B of the composite early-strength agent, retarder, water loss reducer, dispersant, suspension stabilizer and defoamer, and mix them evenly to obtain a mixed dry powder;

[0062] 3. Mix the mixed solution and mixed dry powder evenly, and prepare the cement slurry in accordance with GB / T 19139-2012.

[0063] Example 1

[0064] As a preferred embodiment of the present invention, this embodiment provides a low-temperature, low-density cement slurry system, comprising the following components by mass parts, as shown in Table 1.

[0065] Table 1

[0066] Components Number of parts by weight / part cement 90 Lightweight materials 10 Composite early strength agent 5 Retarder 0.2 Water loss reducer 1 dispersant 1 Suspension stabilizer 1.5 Defoamer 0.05 Mixing water 60

[0067] In this embodiment, the cement includes 70 parts of Grade G oil well cement and 20 parts of ultrafine cement;

[0068] In this embodiment, the composite early strength agent includes 3 parts of component A and 5 parts of component B. Component A is a mixture of 0.5 parts of anhydrous calcium chloride and 2.5 parts of calcium nitrate tetrahydrate, and component B is sodium silicate nonahydrate.

[0069] Example 2

[0070] As a preferred embodiment of the present invention, this embodiment provides a low-temperature, low-density cement slurry system, which includes the following components by mass parts, as shown in Table 2.

[0071] Table 2

[0072]

[0073]

[0074] In this embodiment, the cement is Grade G oil well cement;

[0075] In this embodiment, the composite early strength agent includes 3 parts of component A and 3 parts of component B. Component A is a mixture of 1 part of anhydrous calcium chloride and 2 parts of calcium nitrate tetrahydrate, and component B is sodium silicate nonahydrate.

[0076] Example 3

[0077] As a preferred embodiment of the present invention, this embodiment provides a low-temperature, low-density cement slurry system, comprising the following components by mass parts, as shown in Table 3.

[0078] Table 3

[0079] Components Number of parts by weight / part cement 84 Lightweight materials 16 Composite early strength agent 7 Retarder 1.4 Water loss reducer 1 dispersant 0.5 Suspension stabilizer 2 Defoamer 0.05 Mixing water 75

[0080] In this embodiment, the cement includes 74 parts of Grade G oil well cement and 10 parts of ultrafine cement;

[0081] In this embodiment, the composite early strength agent includes 3 parts of component A and 4 parts of component B. Component A is anhydrous calcium chloride and component B is sodium silicate nonahydrate.

[0082] Example 4

[0083] As a preferred embodiment of the present invention, this embodiment provides a low-temperature, low-density cement slurry system, which includes the following components by mass parts, as shown in Table 4.

[0084] Table 4

[0085] Components Number of parts by weight / part cement 86 Lightweight materials 14 Composite early strength agent 6.4 Retarder 0.4 Water loss reducer 2 dispersant 0.5 Suspension stabilizer 1.6 Defoamer 0.05 Mixing water 74

[0086] In this embodiment, the cement includes 78 parts of Grade G oil well cement and 8 parts of ultrafine cement;

[0087] In this embodiment, the composite early strength agent includes 3.4 parts of component A and 3 parts of component B. Component A is a mixture of 0.8 parts of anhydrous calcium chloride and 2.6 parts of calcium nitrate tetrahydrate, and component B is sodium silicate nonahydrate.

[0088] Example 5

[0089] As a preferred embodiment of the present invention, this embodiment provides a low-temperature, low-density cement slurry system, comprising the following components by mass parts, as shown in Table 5.

[0090] Table 5

[0091]

[0092]

[0093] In this embodiment, the cement includes 68 parts of Grade G oil well cement and 12 parts of ultrafine cement;

[0094] In this embodiment, the composite early strength agent includes 4 parts of component A and 3 parts of component B. Component A is calcium nitrate tetrahydrate and component B is sodium silicate nonahydrate.

[0095] Comparative Example 1

[0096] In this comparative example, the weight-reducing material was replaced with commercially available glass microspheres (density 0.46 g / cm³). 3 Except for ), the rest is the same as in Example 1.

[0097] Comparative Example 2

[0098] In this comparative example, except that only anhydrous calcium chloride was used as an early strength agent, everything else was the same as in Example 1.

[0099] Comparative Example 3

[0100] In this comparative example, except that only calcium nitrate tetrahydrate was used as an early strength agent, everything else was the same as in Example 1.

[0101] Comparative Example 4

[0102] In this comparative example, except that sodium silicate nonahydrate was used as an early strength agent, everything else was the same as in Example 1.

[0103] The components of Examples 1 to 5 and Comparative Examples 1 to 4 were prepared according to the preparation method of the cementing slurry system described above, and the corresponding cementing slurries were tested for slurry properties and compressive strength under 0℃ curing. The test results are shown in Tables 6 and 7, respectively.

[0104] Table 6

[0105]

[0106]

[0107] As shown in Table 1, the water loss of all embodiments and comparative examples meets the requirements for cementing construction. The density difference of the embodiments and comparative examples using hard silica hollow spheres as weight-reducing materials is smaller than that of comparative example 1 (the weight-reducing material is commercially available hollow glass microspheres), and the density is between 1.3 and 1.6 g / cm³. 3 Adjustable; meanwhile, Comparative Example 1 exhibits the highest flowability, while the flowability of the other examples and comparative examples is less than 24 cm, meeting the requirements for cementing operations. The hydration heat results after 48 hours indicate that the hard silica-calcium stone-soybean oil phase change microcapsules can effectively control the release of cement hydration heat. The release of cement hydration heat in the examples is comparable to that of Grade G cement at 6°C. The low hydration heat in Comparative Example 1 is due to the incorporation of glass microspheres not participating in the hydration reaction.

[0108] Table 7

[0109]

[0110] Note: The curing conditions for cement stone are 0℃ and normal pressure.

[0111] As shown in Table 2, all examples and comparative examples with in-situ CSH seed generation showed some strength after 1 day of curing, indicating that the method of directly generating CSH inside the cement paste can significantly improve the early compressive strength of the cement paste. With the extension of curing time (2 days of curing), the compressive strength of all examples was greater than 3.5 MPa, which meets the conditions for cementing construction. The compressive strength of comparative example 1 was 3.4 MPa, while comparative examples 2 to 4 still had no strength after 2 days of curing. With the further extension of curing time, the strength difference between examples and comparative examples became more and more obvious. After 7 days of curing, the highest compressive strength of example 1 was 15.6 MPa, while the highest among the comparative examples, comparative example 1, was only 11.5 MPa. Example 1 improved by 35.65% compared with comparative example 1. The reasons are that firstly, the precipitation time of nano CSH seed inside the cement paste is longer, and secondly, the hard silicate can provide hydration nucleation sites and precipitation crystallization sites during the hydration process of cement, and the interfacial bonding with the cement matrix is ​​better than that of hollow glass microspheres.

[0112] The above experimental data show that the low-temperature, low-density cement slurry based on the hard silica-calcium stone system of the present invention has higher compressive strength in the early stage of hydration and higher compressive strength in the later stage of hydration compared with the glass microsphere cement slurry system.

[0113] Finally, it should be noted that the above embodiments are merely preferred embodiments of the present invention used to illustrate the technical solutions of the present invention, and are not intended to limit the invention, nor are they intended to limit the patent scope of the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. These modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention. That is to say, any changes or refinements made to the main design concept and spirit of the present invention that are not of substantial significance, but whose technical problems are still consistent with the present invention, should be included within the protection scope of the present invention. In addition, the direct or indirect application of the technical solutions of the present invention to other related technical fields are similarly included within the patent protection scope of the present invention.

Claims

1. A low temperature, low density cement slurry system characterized in that, The cement is at least one of G-grade high-sulfate-resistant oil well cement and superfine cement. The cement is at least one of G-grade high-sulfate-resistant oil well cement and superfine cement. The cement is at least one of G-grade high-sulfate-resistant oil well cement and superfine cement. The cement is at least one of G-grade high-sulfate-resistant oil well cement and superfine cement. The cement is at least one of G-grade high-sulfate-resistant oil well cement and superfine cement. The cement is at least one of G-grade high-sulfate-resistant oil well cement and superfine cement. The cement is at least one of G-grade high-sulfate-resistant oil well cement and superfine cement. The cement is at least one of G-grade high-sulfate-resistant oil well cement and superfine cement. The cement is at least one of G-grade high-sulfate-resistant oil well cement and superfine cement. S1: Soybean oil with a solidification point of 2 ℃ is added to 70 ℃ deionized water, the mass ratio of soybean oil to deionized water is 1:10, sodium dodecyl benzene sulfonate is added, the amount of sodium dodecyl benzene sulfonate added is 0.7% of the mass of soybean oil, and stirring is performed to prepare a suspension, then silane coupling agent KH550 is added, the amount of silane coupling agent KH550 added is 1% of the mass of soybean oil, stirring is performed until uniform, and 1 mol / L calcium chloride solution and sodium silicate solution are added dropwise, the core-to-wall ratio is 1:4, stirring is continuously performed at a stirring rate of 300 rpm for 12 h, and the phase change microcapsule precursor is prepared by filtering and drying; The lightening material is a mixed material composed of hard silicon calcium fiber hollow spheres and hard silicon calcium-soybean oil phase change microcapsules, and the density of the mixed material is 0.6 g / cm 3 , and the preparation method is as follows: S2: According to Ca / Si=1.05, lime and quartz sand are weighed, the phase change microcapsule precursor is added, the core-to-wall ratio is 1:3, the phase change microcapsule precursor is placed in deionized water, the amount of deionized water added is 50 times the total mass of lime, quartz sand and phase change microcapsule precursor, silane coupling agent KH550 is added after aging for 3 h, the amount of silane coupling agent KH550 added is 0.5% of the mass of phase change microcapsule precursor, the temperature is raised to 190 ℃ at a rate of 1.4 ℃ / min, stirring is continuously performed at a stirring rate of 300 rpm, and the hard silicon calcium stone-soybean oil phase change microcapsule is prepared by filtering and drying after heat preservation for 11 h; S3: According to Ca / Si=1.05, lime and quartz sand are weighed, and the lime and quartz sand are placed in deionized water, the amount of deionized water added is 50 times the total mass of lime and quartz sand, the temperature is raised to 210 ℃ at a rate of 1.4 ℃ / min after aging for 3 h, stirring is continuously performed, and the hard silicon calcium stone hollow sphere is prepared by filtering and drying after heat preservation for 11 h; S4: The hard silicon calcium stone-soybean oil phase change microcapsule and the hard silicon calcium stone hollow sphere prepared in S2 and S3 are mixed in a weight ratio of 3:7 to obtain the lightening material. The cement is at least one of G-grade high-sulfate-resistant oil well cement and superfine cement.

2. The low temperature, low density cement slurry system of claim 1, wherein, The component A is at least one of anhydrous calcium chloride and calcium nitrate tetrahydrate.

3. A low temperature, low density cement slurry system according to claim 1, characterized in that, The composite early strength agent comprises component A and component B, the component A is a calcium salt easily soluble in water, the component B is a silicate easily soluble in water; before use of the composite early strength agent, the component A needs to be added into mixing water to be dissolved into Ca 2+ solution, the component B is added into cement as a solid powder to be mixed uniformly.

4. A low temperature, low density cement slurry system according to claim 3, characterized in that, The component B is sodium silicate nonahydrate.

5. The low temperature, low density cement slurry system of claim 3, wherein, The retarder is calcium gluconate.

6. The low temperature, low density cement slurry system of claim 1, wherein, The fluid loss additive is an AMPS-amide-carboxylic acid polymer.

7. The low temperature, low density cement slurry system of claim 1, wherein, The dispersant is an acetone-formaldehyde condensate.

8. The low temperature, low density cement slurry system of claim 1, wherein, The suspension stabilizer is bentonite.

9. The low temperature, low density cement slurry system of claim 1, wherein, ​

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