Low-temperature low-density early-strength cement paste system and preparation method thereof

Abstract

The invention relates to the technical field of low-temperature well cementation, and particularly discloses a low-temperature low-density early-strength cement paste system and a preparation method thereof. The cement paste system comprises the following components: oil well cement, a density reducing material, an early strength supplement material, a fluid loss agent, a dispersing agent, a retarder and water. The preparation method of the cement paste system comprises the following steps: uniformly dry-mixing the oil well cement, the density reducing material, the early strength supplementing material, the fluid loss agent and the dispersing agent to obtain a solid-phase dry powder mixture of the cement paste system; and dissolving the retarder in water, then adding the solid-phase dry powder mixture of the cement slurry system, and uniformly stirring to obtain the low-temperature low-density early-strength cement slurry system. According to the invention, the oil well cement is mixed with the density reducing material, the early strength supplement material and the like, and additives such as the fluid loss agent, the dispersing agent, the retarder and the like are added, so that the density, the fluidity, the sedimentation stability and the early strength at low temperature of a cement slurry system are improved.

Description

Technical Field

[0001] This invention relates to the field of low-temperature cementing technology, specifically to a low-temperature, low-density, early-strength cement slurry system for cementing oil and gas wells in low-temperature areas and its preparation method. Background Technology

[0002] Marine and permafrost regions are rich in oil and gas resources and are key areas for future oil and gas exploration and development. However, these regions typically face challenges such as low ambient temperatures, weak formation pressure, and extremely low fracturing pressure. Therefore, the sensitive formation pressure and low fracturing pressure necessitate the use of low-density cement slurry systems to ensure safe sealing of the target formation. Furthermore, low temperatures significantly affect the hydration process of commonly used G-grade oil well cement, even causing it to stop hydrating, leading to insufficient early strength development of the cement stone, prolonged cement slurry setting time, increased oil and gas well production costs, and exacerbated gas channeling risks. To address these issues, there is an urgent need to develop low-density cement slurry systems suitable for low-temperature, low-pressure, and easily leaking formations.

[0003] Currently, there are two main methods for preparing low-density cement slurry systems: one is to introduce hollow glass microspheres into the oil well cement slurry system, relying on the low density of the materials themselves to reduce the density of the cement slurry; the other is to introduce highly absorbent lightweight inorganic admixtures, such as diatomaceous earth and bentonite, into the cement slurry system. However, the above-mentioned low-density cement slurry systems generally suffer from poor settling stability, easy segregation, and poor rheological properties. Furthermore, the incorporation of lightweight materials leads to lower early compressive strength of the cement stone, which is further exacerbated at low temperatures.

[0004] Therefore, the development of oil and gas resources in offshore and permafrost areas has placed increasingly higher demands on the performance of cementing slurry systems. In order to meet the cementing requirements of low-pressure and easily lost formations in offshore and permafrost areas, it has become an urgent problem to solve the issue of ensuring that the cement slurry has low density and excellent slurry properties while also having high early strength. Summary of the Invention

[0005] The purpose of this invention is to provide a low-temperature, low-density, early-strength cement slurry system for cementing oil and gas wells in low-temperature areas, which has both low density and high early strength.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: According to a first aspect of the present invention, a low-temperature, low-density, early-strength cement slurry system is provided, comprising the following components: oil well cement, density-reducing material, early-strength supplementary material, water loss reducing agent, dispersant, retarder, and water.

[0007] According to one embodiment of the present invention, the components of the cement slurry system are proportioned as follows by weight: oil well cement: 100 parts; density reducing material: 35-60 parts; early strength supplement material: 30-45 parts; water loss reducing agent: 2-5 parts; dispersant: 0.5-1 part; retarder: 0.25-0.35 parts; water: 100-130 parts.

[0008] According to one embodiment of the present invention, the oil well cement is Grade G oil well cement. Preferably, the oil well cement is Grade G high sulfate-resistant oil well cement.

[0009] According to one embodiment of the present invention, the density-reducing material is a resin. Preferably, the density-reducing material is a phenolic resin.

[0010] According to one embodiment of the present invention, the early strength supplementing material is rapid-hardening high-iron sulfoaluminate cement. Preferably, the early strength supplementing material is R·FAC42.5 type rapid-hardening high-iron sulfoaluminate cement.

[0011] According to one embodiment of the present invention, the density-reducing material is a resin powder of 100-300 mesh.

[0012] According to one embodiment of the present invention, the dehydration reducing agent is one or more of locust bean gum, tamarind gum, flaxseed gum, and gum arabic.

[0013] According to one embodiment of the present invention, the retarder is one or more of tetrasodium glutamate diacetate and tetrasodium iminodisuccinate.

[0014] According to one embodiment of the present invention, the dispersant is one or more of tetrasodium aspartate diacetate and sodium polyaspartate.

[0015] According to one embodiment of the present invention, the solid density of the density-reducing material is 0.30 g / cm³. 3 ~0.50 g / cm 3 .

[0016] According to a second aspect of the present invention, a method for preparing the above-mentioned low-temperature, low-density, early-strength cement slurry system is provided, comprising the following steps: Step 1: Dry mix the oil well cement, density-reducing material, early strength supplement, water loss reducing agent, and dispersant evenly to obtain a solid dry powder mixture of cement slurry system; Step 2: Dissolve the retarder in water, then add the cement slurry system solid dry powder mixture obtained in Step 1, stir evenly, and obtain the low temperature low density early strength cement slurry system.

[0017] By adopting the above technical solutions, the present invention has the following advantages compared with the prior art: The low-temperature, low-density, early-strength cement slurry system provided by this invention improves the density, fluidity, settling stability, and early-strength at low temperatures of the cement slurry system by mixing oil well cement with density-reducing materials, early-strength supplementary materials, and adding admixtures such as fluid loss reducers, dispersants, and retarders. This low-temperature, low-density cement slurry system features low and widely adjustable density, rapid setting at low temperatures, and rapid early-strength development, making it particularly suitable for cementing engineering of oil and gas wells in low-temperature, low-pressure, and easily leaky areas. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 A flowchart illustrating the preparation method of the low-temperature, low-density, early-strength cement slurry system provided by this invention; Figure 2 Thickening curve of the low-temperature, low-density, early-strength cement slurry system provided in Example 1; Figure 3 Thickening curve of the low-temperature, low-density, early-strength cement slurry system provided in Example 2; Figure 4 Thickening curve of the low-temperature, low-density, early-strength cement slurry system provided in Example 3; Figure 5 Thickening curve of the low-temperature, low-density, early-strength cement slurry system provided in Example 4; Figure 6 Thickening curve of the low-temperature, low-density, early-strength cement slurry system provided in Example 5; Figure 7 The thickening curve of the low-temperature, low-density, early-strength cement slurry system provided in Example 6. Detailed Implementation

[0020] 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. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0021] Specific embodiments of the invention are disclosed herein as needed; however, it should be understood that the embodiments disclosed herein are merely examples of the invention that may be implemented in various alternative forms. In the following description, various operating parameters and components are described in several contemplated embodiments. These specific parameters and components are provided as examples only and are not intended to be limiting.

[0022] The first aspect of the present invention provides a low-temperature, low-density, early-strength cement slurry system, which includes the following components: oil well cement, density-reducing material, early-strength supplementary material, water loss reducing agent, dispersant, retarder, and water.

[0023] In some embodiments, the components of the cement slurry system are proportioned as follows by weight: oil well cement: 100 parts; density reducing material: 35-60 parts; early strength supplement material: 30-45 parts; water loss reducing agent: 2-5 parts; dispersant: 0.5-1 part; retarder: 0.25-0.35 parts; water: 100-130 parts.

[0024] Preferably, the oil well cement is Grade G oil well cement, Grade D oil well cement, or slag BFS cement. More preferably, the oil well cement is Grade G high sulfate-resistant oil well cement.

[0025] Preferably, the density-reducing material is resin. More preferably, the density-reducing material is phenolic resin. Even more preferably, the density-reducing material is 2123 phenolic resin. Compared with using hollow glass microspheres or diatomaceous earth, bentonite, etc., as density-reducing materials, using phenolic resin as the density-reducing material has the following advantages: phenolic resin is relatively inexpensive, widely available, and different functional groups can be introduced into it according to different needs. Compared with other density-reducing materials, phenolic resin has a lower density, higher mechanical strength, better chemical corrosion resistance, and less tendency to deform. After being added to cement slurry, it will not deform due to external influences, thus preventing the formation of micropores in the cement stone matrix and affecting the mechanical properties of the cement stone.

[0026] In some embodiments, the density-reducing material is a resin in powder form, i.e., resin powder. Preferably, the density-reducing material is a 100-300 mesh resin powder. More preferably, the density-reducing material is a 200 mesh resin powder.

[0027] In a preferred embodiment, the density-reducing material has a particle size of 200 mesh and a density of 0.43 g / cm³. 3 2123 phenolic resin powder.

[0028] In some embodiments, the early-strength additive is rapid-hardening ferrous sulfate cement. Compared to other types of early-strength additives, using rapid-hardening ferrous sulfate cement offers several advantages: Ferrous sulfate cement, as a type of sulfoaluminate cement, possesses higher early-strength, stronger hydration and hardening capabilities, shorter hardening time, and can still rapidly undergo hydration reactions at low temperatures. As an early-strength additive, it not only exhibits better compatibility with oil well cement, promoting the hydration reaction of oil well cement at low temperatures, but also possesses higher later-stage strength, ensuring the long-term integrity of the cement sheath. Furthermore, compared to other early-strength additives, ferrous sulfate cement offers advantages such as low price, wide availability, strong environmental and energy-saving properties, and contribution to reducing carbon emissions.

[0029] In a preferred embodiment, the early strength supplement material is R·FAC42.5 type rapid-hardening high-iron sulfoaluminate cement, whose oxide composition is 20.04% alumina, 7.99% silicon dioxide, 15.93% sulfur trioxide, 45.76% calcium oxide, 7.65% ferric oxide, 1.20% magnesium oxide, and 1.07% titanium dioxide, with a density of 2.96 g / cm³. 3 .

[0030] In some embodiments, the solid density of the oil well cement is approximately 3.15 g / cm³. 3 .

[0031] In some embodiments, the solid density of the density-reducing material is 0.30 g / cm³. 3 ~0.50 g / cm 3 Preferably, the solid density of the density-reducing material is approximately 0.43 g / cm³. 3 .

[0032] In some embodiments, the solid density of the early strength supplement material is approximately 2.96 g / cm³. 3 .

[0033] In some embodiments, the water loss reducing agent is a plant-derived water loss reducing agent, preferably one or more of locust bean gum, tamarind gum, flaxseed gum, and gum arabic.

[0034] In some embodiments, the retarder is one or more of tetrasodium glutamate diacetate and tetrasodium iminodisuccinate.

[0035] In some embodiments, the dispersant is one or more of tetrasodium aspartate diacetate and sodium polyaspartate.

[0036] The low-temperature, low-density, early-strength cement slurry system provided by this invention mainly consists of oil well cement, density-reducing materials, early-strength supplementary materials, water loss control agents, dispersants, and retarder. The density-reducing materials have a lower solid density than both the oil well cement and the early-strength supplementary materials, leading to stratification during the preparation of the low-density cement slurry, where the density-reducing materials float and the oil well cement particles sink. This low-temperature, low-density, early-strength cement slurry system utilizes the close-packing theory and particle size distribution principle, while preferentially using plant-derived water loss control agents to improve the stability of the cement slurry system and reduce the floating of density-reducing materials and the sedimentation of oil well cement. Specifically, the plant-derived water loss control agents are dispersed in water, with some dissolving to form a sol, increasing the viscosity of the cement slurry. Furthermore, the viscosity increases with increasing concentration of the plant-derived water loss control agents. After stirring, the density-reducing materials and oil well cement particles are uniformly dispersed in the cement slurry. Due to the presence of the plant-derived water loss control agents, the cement slurry has a higher viscosity, which, under the influence of electrostatic forces, ensures the stable dispersion of the density-reducing materials within the cement slurry system. At this time, the liquid phase in the cement slurry is in a sol-like state, which can ensure that the cement particles in the oil well are suspended in the liquid phase and reduce the sedimentation of cement particles.

[0037] The addition of early-strength supplementary materials makes cement hydration more rapid, which can improve the early strength of cement paste and shorten the thickening time of cement paste. The addition of water loss reducer can reduce the water loss of cement paste and improve the suspension stability of cement paste. Dispersant can improve the fluidity of cement paste, while retarder can adjust the initial setting time of cement paste.

[0038] In this invention, by mixing oil well cement with density-reducing materials, early strength-enhancing materials, etc. in a certain proportion, and adding a certain amount of admixtures such as fluid loss reducers, dispersants, and retarders, the density, fluidity, settling stability, and early strength at low temperatures of the cement slurry system are improved. This low-temperature, low-density cement slurry system has the characteristics of low and widely adjustable density, rapid setting at low temperatures, and rapid early strength development, and is particularly suitable for cementing engineering of oil and gas wells in low-temperature, low-pressure, and easily leaky areas.

[0039] A second aspect of the present invention provides a method for preparing the above-mentioned low-temperature, low-density, early-strength cement slurry system, such as... Figure 1 As shown, the preparation method includes the following steps: S1: Dry mix oil well cement, density-reducing material, early strength supplement material, water loss reducing agent and dispersant evenly to obtain a cement slurry system solid dry powder mixture; S2: Dissolve the retarder in water, then add the cement slurry system solid dry powder mixture obtained in step 1, stir evenly, and obtain the low temperature low density early strength cement slurry system.

[0040] In this invention, in response to the requirements of cement slurry for the comprehensive performance of cement in low-temperature, low-pressure, easily leaking oil and gas wells, oil well cement, density-reducing materials, early-strength supplementary materials, fluid loss control agents, dispersants, and retarders are mixed in a certain proportion to obtain a cement slurry system with excellent comprehensive performance that can meet the requirements of low temperature, high early strength, and low density in cementing construction and subsequent mining.

[0041] The present invention will be described in detail below through specific embodiments.

[0042] In Examples 1-6 below, the oil well cement is Grade G high-sulfuric acid resistant oil well cement produced by Jiahua Special Cement Co., Ltd. Grade G oil well cement is currently the most commonly used type in oil and gas cementing construction. It can be formulated with different admixtures and additives to meet the performance requirements of cement slurry under different well conditions. Moreover, Grade G oil well cement is a commercially available product, making it easy to purchase. The density-reducing material is type 2123 phenolic resin powder produced by Leixiang Chemical Industry and Commerce Store in Erqi District, Zhengzhou City. Its particle size is 200 mesh, and its density is 0.43 g / cm³. 3 The early-strength supplementary material is R·FAC42.5 type rapid-hardening high-iron sulfoaluminate cement produced by Guangxi Yunyan Special Cement Building Materials Co., Ltd. Its oxide composition is: alumina 20.04%, silicon dioxide 7.99%, sulfur trioxide 15.93%, calcium oxide 45.76%, ferric oxide 7.65%, magnesium oxide 1.20%, and titanium dioxide 1.07%. The density of the early-strength supplementary material is 2.96 g / cm³. 3 The dehydration reducer is one or more of the following: locust bean gum, tamarind gum, flaxseed gum, and gum arabic; the dispersant is one or more of the following: tetrasodium aspartate diacetate and sodium polyaspartate; and the retarder is one or more of the following: tetrasodium glutamate diacetate and tetrasodium iminodisuccinate. All of these are commercially available products.

[0043] Example 1 A low-temperature, low-density, early-strength cement paste system is prepared as follows: S1. Preparation of dehydration reducing agent: Weigh 10 g of locust bean gum, 10 g of tamarind gum and 10 g of flaxseed gum, dry mix and stir evenly, and set aside; S2. Preparation of a low-temperature, low-density, early-strength cement slurry system: Weigh 400 g of Grade G high sulfate-resistant oil well cement, 140 g of 2123 phenolic resin powder, 180 g of R·FAC42.5 type rapid-hardening high-iron sulfoaluminate cement, 8 g of water loss reducer, and 2 g of tetrasodium aspartate diacetate. Dry mix the above materials evenly to obtain a solid-phase dry powder mixture of the low-temperature, low-density, early-strength cement slurry system, and set aside for later use. Weigh 1 g of tetrasodium glutamate diacetate and 400 g of water. Dissolve the retarder in the water first, then add it to the solid-phase dry powder mixture of the low-temperature, low-density, early-strength cement slurry system and stir evenly to obtain the low-temperature, low-density, early-strength cement slurry system.

[0044] Example 2 S1. Preparation of dehydration reducing agent: Weigh 20 g of locust bean gum, 15 g of tamarind gum and 10 g of gum arabic, dry mix and stir evenly, and set aside for use; S2. Preparation of a low-temperature, low-density, early-strength cement slurry system: Weigh 400 g of Grade G high sulfate-resistant oil well cement, 150 g of 2123 phenolic resin powder, 140 g of R·FAC42.5 type rapid-hardening high-iron sulfoaluminate cement, 12 g of water loss reducer, and 4 g of sodium polyaspartate. Dry mix the above materials evenly to obtain a solid-phase dry powder mixture of the low-temperature, low-density, early-strength cement slurry system, and set aside for later use. Weigh 1 g of tetrasodium iminodisuccinate and 480 g of water. Dissolve the retarder in the water first, then add it to the solid-phase dry powder mixture of the low-temperature, low-density, early-strength cement slurry system and stir evenly to obtain the low-temperature, low-density, early-strength cement slurry system.

[0045] Example 3 S1. Preparation of dehydration reducing agent: Weigh 30 g of locust bean gum, 10 g of flaxseed gum and 10 g of gum arabic, dry mix and stir evenly, and set aside for use; S2. Preparation of a low-temperature, low-density, early-strength cement slurry system: Weigh 400 g of Grade G high sulfate-resistant oil well cement, 240 g of 2123 phenolic resin powder, 120 g of R·FAC42.5 type rapid-hardening high-iron sulfoaluminate cement, 20 g of water loss reducer, 2 g of tetrasodium aspartate diacetate, and 2 g of sodium polyaspartate. Dry mix the above materials evenly to obtain a solid-phase dry powder mixture of the low-temperature, low-density, early-strength cement slurry system, and set aside for later use. Weigh 1 g of tetrasodium glutamate diacetate and 520 g of water. Dissolve the retarder in the water first, then add it to the solid-phase dry powder mixture of the low-temperature, low-density, early-strength cement slurry system and stir evenly to obtain the low-temperature, low-density, early-strength cement slurry system.

[0046] Example 4 S1. Preparation of dehydration reducing agent: Weigh 10 g of locust bean gum, 10 g of flaxseed gum, 10 g of tamarind gum and 10 g of gum arabic, dry mix and stir evenly, and set aside for use; S2. Preparation of a low-temperature, low-density, early-strength cement slurry system: Weigh 400 g of Grade G high sulfate-resistant oil well cement, 160 g of 2123 phenolic resin powder, 130 g of R·FAC42.5 type rapid-hardening high-iron sulfoaluminate cement, 15 g of water loss reducer, and 3 g of sodium polyaspartate. Dry mix the above materials evenly to obtain a solid-phase dry powder mixture of the low-temperature, low-density, early-strength cement slurry system, and set aside for later use. Weigh 0.5 g of tetrasodium diacetate of glutamic acid and 0.5 g of tetrasodium iminodisuccinate, and weigh 500 g of water. Dissolve the retarder in the water first, then add it to the solid-phase dry powder mixture of the low-temperature, low-density, early-strength cement slurry system and stir evenly to obtain the low-temperature, low-density, early-strength cement slurry system.

[0047] Example 5 S1. Preparation of dehydration reducing agent: Weigh 10 g of flaxseed gum, 15 g of tamarind gum and 10 g of gum arabic, dry mix and stir evenly, and set aside; S2. Preparation of a low-temperature, low-density, early-strength cement slurry system: Weigh 400 g of Grade G high sulfate-resistant oil well cement, 200 g of 2123 phenolic resin powder, 150 g of R·FAC42.5 type rapid-hardening high-iron sulfoaluminate cement, 18 g of water loss reducer, and 2.5 g of tetrasodium aspartate diacetate. Dry mix the above materials evenly to obtain a solid-phase dry powder mixture of the low-temperature, low-density, early-strength cement slurry system, and set aside for later use. Weigh 1.2 g of tetrasodium iminodisuccinate and 510 g of water. Dissolve the retarder in the water first, then add it to the solid-phase dry powder mixture of the low-temperature, low-density, early-strength cement slurry system and stir evenly to obtain the low-temperature, low-density, early-strength cement slurry system.

[0048] Example 6 S1. Preparation of dehydration reducing agent: Weigh 20 g of locust bean gum and 20 g of flaxseed gum, dry mix and stir evenly, and set aside for use; S2. Preparation of a low-temperature, low-density, early-strength cement slurry system: Weigh 400 g of Grade G high sulfate-resistant oil well cement, 160 g of 2123 phenolic resin powder, 160 g of R·FAC42.5 type rapid-hardening high-iron sulfoaluminate cement, 10 g of water loss reducer, and 2 g of tetrasodium aspartate diacetate. Dry mix the above materials evenly to obtain a solid-phase dry powder mixture of the low-temperature, low-density, early-strength cement slurry system, and set aside for later use. Weigh 1 g of tetrasodium glutamate diacetate and 0.4 g of tetrasodium iminodisuccinate, and weigh 490 g of water. Dissolve the retarder in the water first, then add it to the solid-phase dry powder mixture of the low-temperature, low-density, early-strength cement slurry system and stir evenly to obtain the low-temperature, low-density, early-strength cement slurry system.

[0049] The density, fluidity, filtration performance, settling stability, and compressive strength of the low-temperature, low-density, early-strength cement slurry systems obtained in Examples 1-6 were tested according to the national standard GB / T 19139-2012, "Test Methods for Cement in Oil Wells". The test results are shown in Table 1.

[0050] Table 1. Basic properties of the low-temperature, low-density, early-strength cement paste systems in Examples 1-6

[0051] Figures 2-7 The figures are the thickening curves of the low-temperature, low-density, early-strength cement slurry systems in Examples 1-6, respectively. The experimental temperature was 34 ℃ and the experimental pressure was 20 MPa.

[0052] As shown in Table 1 above, the density of the low-temperature, low-density, early-strength cement paste system is less than 1.30 g / cm³. 3The lowest concentration can reach 1.03 g / cm³. 3 Its density is between 1.03 and 1.23 g / cm³. 3 It is adjustable within a certain range, has good fluidity (around 20 cm), is easy to pump with cement slurry, has an extremely low separation rate of 0%, an API water loss of 29-41 mL, and exhibits good settling stability with a density difference of 0-0.01 g / cm³ between the upper and lower parts. 3 The compressive strength can reach over 7.0 MPa after curing at 4 ℃ for 48 h, which can meet the cementing requirements.

[0053] Depend on Figures 2-7 It can be seen that the initial consistency of the cement slurry system is low, the consistency value is relatively stable, it basically thickens at right angles, and the thickening time is adjustable, ranging from 214 min to 276 min, which can meet the requirements of well cementing construction.

[0054] In summary, the cement slurry system provided by this invention has the characteristics of stable slurry performance, rapid setting at low temperature, and high early strength, making it particularly suitable for cementing engineering of oil and gas wells in low-temperature, low-pressure, and easily leaky formations.

[0055] The above descriptions are merely several preferred embodiments of the present invention, but the present invention is not limited to the specific embodiments described above. The specific embodiments described above are illustrative and not restrictive. Researchers in the art, under the guidance of the present invention and in accordance with the spirit and principles of the present invention, can make improvements and modifications, all of which fall within the protection scope of the present invention.

[0056] Matters not covered in this invention are common knowledge.

Claims

1. A low-temperature, low-density, early-strength cement slurry system, characterized in that, It includes the following components: oil well cement, density-reducing materials, early-strength supplement materials, fluid loss control agents, dispersants, retarder, and water.

2. The low-temperature, low-density, early-strength cement slurry system according to claim 1, characterized in that, The components of the cement slurry system are proportioned by weight as follows: oil well cement: 100 parts; density reducing material: 35-60 parts; early strength supplement material: 30-45 parts; water loss reducing agent: 2-5 parts; Dispersant: 0.5~1 part; Retarder: 0.25~0.35 parts; Water: 100-130 parts.

3. The low-temperature, low-density, early-strength cement slurry system according to claim 1, characterized in that, The oil well cement is Grade G oil well cement; and / or The density-reducing material is a resin; and / or The early strength supplementary material is rapid-hardening high-iron sulfoaluminate cement.

4. The low-temperature, low-density, early-strength cement slurry system according to claim 3, characterized in that, The oil well cement is Grade G high sulfate-resistant oil well cement; and / or The density-reducing material is phenolic resin; and / or The early strength supplement material is R·FAC42.5 type rapid hardening high-iron sulfoaluminate cement.

5. The low-temperature, low-density, early-strength cement slurry system according to claim 3, characterized in that, The density-reducing material is a 100-300 mesh resin powder.

6. The low-temperature, low-density, early-strength cement slurry system according to claim 1, characterized in that, The dehydration reducing agent is one or more of the following: locust bean gum, tamarind gum, flaxseed gum, and gum arabic.

7. The low-temperature, low-density, early-strength cement slurry system according to claim 1, characterized in that, The retarder is one or more of tetrasodium glutamate diacetate and tetrasodium iminodisuccinate.

8. The low-temperature, low-density, early-strength cement slurry system according to claim 1, characterized in that, The dispersant is one or more of tetrasodium aspartate diacetate and sodium polyaspartate.

9. The low-temperature, low-density, early-strength cement slurry system according to claim 1, characterized in that, The solid density of the density-reducing material is 0.30 g / cm³. 3 ~0.50 g / cm 3 .

10. The method for preparing the low-temperature, low-density, early-strength cement slurry system according to any one of claims 1-9, characterized in that, Includes the following steps: Step 1: Dry mix the oil well cement, density-reducing material, early strength supplement, water loss reducing agent, and dispersant evenly to obtain a solid-phase dry powder mixture of cement slurry system; Step 2: Dissolve the retarder in water, then add it to the solid dry powder mixture of the cement slurry system obtained in Step 1, and stir evenly to obtain the low-temperature low-density early-strength cement slurry system.

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