Gelled material prepared from industrial waste residue for plugging oilfield water layer and preparation method and water plugging cement slurry

Abstract

The application discloses a gelatinous material prepared by using industrial waste residues and used for oilfield water layer plugging, a preparation method and a water plugging cement slurry, and relates to the technical field of oilfield water plugging materials. The gelatinous material is composed of 25-40 parts of superfine siliceous material, 50-65 parts of superfine calcareous material, 4-8 parts of superfine silico-aluminous material, 1-2 parts of nano calcium silicate, 2-4 parts of superfine expanding agent and 1-3 parts of starch density stabilizer in terms of weight percentage. The application solves the technical problems of low plugging strength, poor plugging effect, poor durability and high cost of the existing water plugging materials, and meets the oilfield water layer plugging requirements of different working conditions.

Description

Technical Field

[0001] This invention relates to the field of oilfield water plugging materials technology, and more specifically to a cementitious material prepared from industrial waste residue for sealing water layers in oilfields, its preparation method, and water plugging cement slurry. Background Technology

[0002] The oil extraction process mainly goes through three stages: Primary recovery flooding (CLF) technology relies primarily on natural energy extraction, which can recover about 10% of the reservoir's oil reserves. Secondary recovery flooding (LLF) technology mainly uses physical methods such as artificial water or gas injection to increase the amount of oil extracted from the reservoir, but at most, it can only improve the oil recovery rate to about 30%, with a large amount of oil resources still scattered in the formation. Tertiary recovery flooding (TLF) technology uses high-pressure steam injection, microbial injection, chemical agent injection, and ultrasonic injection to extract oil and gas resources and provide corresponding pressure replenishment to the underground reservoir, improving the oil recovery efficiency to about 70%. This technology is an effective method for increasing oil production and reducing water content, and is also known as the enhanced oil recovery technology stage. However, as the average depth, structure, heterogeneity, and physical properties of the reservoir continuously change, the reservoir permeability and porosity also continuously change, gradually forming ineffective channeling in large pores, making it impossible to further improve the recovery rate.

[0003] For a long time, the need for continuous water injection to maintain reservoir pressure during oil extraction in my country's major oilfields has exacerbated the heterogeneity of the formations, resulting in water cuts exceeding 80%. This has not only led to a continuous decline in oil recovery but also caused serious environmental pollution. Therefore, it is necessary to inject profile control agents into the formation to adjust the water absorption profile of injection wells or to seal high-permeability layers in production wells, thereby blocking high-permeability water channels in the formation and significantly improving oil recovery while reducing reservoir water cut.

[0004] Currently, there are many types of profile control agents commonly used, each with different plugging principles. However, most utilize one or more of their properties to seal the target layer. Based on their form, they can be divided into granular, resin-based, gel-based, foam-based, inorganic salt precipitate-based, and microbial-based agents. Granular profile control agents were the earliest plugging materials used in oilfield profile control operations. They mainly involve dispersing solid particles such as cement, limestone, and fly ash in a solution, pumping it to the near-wellbore area, and permanently blocking the pores after solidification in high-permeability layers. Granular materials offer high plugging strength and low processing costs, but due to the large particle size, they cannot penetrate deep into the reservoir, thus limiting their application to near-wellbore areas.

[0005] To facilitate the penetration of particulate materials into the formation, small-particle powder materials are typically used. For example, the invention patent CN1323220C, entitled "High-Strength Easily Soluble Nanoscale Water-Blocking Agent," is composed of 5%-8% nano-silica, 3%-5% nano-iron oxide, 13%-20% nano-calcium carbonate, 5%-10% nano-alumina, 20%-30% ultrafine cement, 1%-3% sodium hydroxide, 1%-2% iron chromium salt, and 30%-50% water. This water-blocking agent, after hydration and solidification, is as hard as cement stone and does not shrink in volume, does not produce microcracks, and reacts completely in a yellow, transparent aqueous solution without residue after chemical dissolution. However, the high cost of this water-blocking agent due to the extensive use of nanoparticle materials results in substantial material costs.

[0006] To control material costs, as illustrated in the invention patent application CN111635744A, entitled "A Composition for Profile Control and Water Blocking, a Profile Control and Water Blocking Agent and its Preparation Method, and a Method for Resource Utilization of White Clay Slag," a profile control and water blocking material is prepared using white clay slag and oil well cement. Its components are: 20-25 parts white clay slag and 20-30 parts oil well cement. The composition for profile control and water blocking is mixed with water to form a profile control and water blocking agent.

[0007] For example, the invention patent with authorization announcement number CN101898860B and titled "Inorganic Composite Profile Modifier for Oily Sludge and Its Application Method" includes oily sludge, cement, fly ash, retarder, curing agent, and surfactant mixed and formulated. The surfactant is sodium dodecylbenzene sulfonate. The raw materials are in the following weight parts: 10-15 parts oily sludge, 5-25 parts cement, 0-5 parts fly ash, 0-10 parts curing agent, 0-10 parts retarder, and 0-0.2 parts surfactant.

[0008] The aforementioned water-blocking materials reduce the cost of water-blocking materials to some extent, but they still cannot effectively avoid the defects of cement-based granular materials in sealing water layers.

[0009] To further improve the ability of particles to penetrate the water layer, ultrafine cement is usually selected as an inorganic water-blocking material. This material has the advantages of wide availability, good durability, high mechanical properties, and high sealing strength, and is widely used in oilfield water layer sealing operations.

[0010] However, existing ultrafine cement still has many shortcomings in water-blocking operations: First, the admixtures of ultrafine cement have poor adaptability, making it difficult to adjust their workability. The cement slurry has poor fluidity and large water loss, which can easily cause problems such as pumping difficulties and channeling, affecting the sealing effect. Second, silicate cement undergoes volume shrinkage after hydration, which reduces the sealing efficiency and makes it impossible to completely seal the water layer. Third, the large-scale use of ultrafine cement as a water-blocking material leads to high construction costs.

[0011] Therefore, developing a sealing material suitable for sealing water layers in deep oil wells using industrial waste residue is of great practical significance for improving the sealing effect of oil fields, reducing extraction costs, and realizing the resource utilization of waste. Summary of the Invention

[0012] To overcome the defects and shortcomings of the existing technology, this invention provides a cementitious material for sealing water layers in oilfields, prepared from industrial waste residue, along with its preparation method and water-blocking cement slurry. Addressing the aforementioned technical problems in the existing technology, the purpose of this invention is to provide a cementitious material for sealing water layers in oilfields and its preparation process, solving the technical problems of low sealing strength, poor sealing effect, poor durability, and high cost of existing water-blocking materials, and adapting to the sealing needs of oilfield water layers under different operating conditions.

[0013] To address the problems existing in the prior art, the present invention is achieved through the following technical solution.

[0014] The first aspect of this invention provides a cementitious material for sealing water-bearing formations in oilfields, prepared from industrial waste residue, comprising the following raw materials in parts by weight: 25 to 40 parts of ultrafine silicon material, wherein the ultrafine silicon material is microsilica or polycrystalline silicon abrasive with a particle size D90 < 1 μm; 50 to 65 parts of ultrafine calcareous material, wherein the ultrafine calcareous material is carbide slag or ultrafine calcium hydroxide, and the particle size D90 < 20 μm; Four to eight parts of ultrafine aluminosilicate material, wherein the ultrafine aluminosilicate material is metakaolin or lithium slag, and the particle size D90 < 20 μm; 1-2 parts of nano-calcium silicate, particle size D90 < 100 nm, specific surface area < 100 m² 2 / kg; 2 to 4 parts of ultrafine expanding agent, with a particle size D90 < 15 μm; Starch-based density stabilizer: 1 to 3 parts.

[0015] More preferably, the silica content of the ultrafine silicon or ultrafine polycrystalline silicon abrasive is >85%.

[0016] More preferably, the calcium oxide content of the ultrafine calcium carbide slag or ultrafine calcium hydroxide is >60%.

[0017] More preferably, the ultrafine metakaolin or ultrafine lithium slag has a silica content >50% and an alumina content >20%.

[0018] More preferably, the ultrafine expanding agent is light magnesium oxide with an MgO content > 90%.

[0019] More preferably, the starch-based density stabilizer is mung bean starch, pea starch, or potato starch.

[0020] The second aspect of this invention provides a method for preparing a cementitious material for sealing water layers in oil fields using industrial waste residue, specifically including the following steps: S1. Weigh the ultrafine calcareous material, ultrafine siliceous material and ultrafine aluminosilicate material according to the weight ratio of the components, put them into a ball mill for ball milling, and then use an airflow separation device to separate them to control the particle size D90 of the mixed powder to be less than 20μm. S2. The sorted mixed powder is mixed evenly with ultrafine expanding agent, nano calcium silicate and starch density stabilizer according to the weight ratio to obtain the gelling material.

[0021] A third aspect of this invention provides a water-blocking cement slurry for sealing water-bearing formations in oilfields. This slurry is prepared by adding the cementitious material to a water and admixture system. The admixture system comprises 3.8%–4% of the mass of the cementitious material; the mass ratio of water to cementitious material is 0.6–0.8:1; the admixture system consists of a drag-reducing agent, a water-loss-reducing agent, and a retarder, wherein the drag-reducing agent is used at 0.3%–0.5% of the mass of the cementitious material; the water-loss-reducing agent is used at 2.5% of the mass of the cementitious material; and the retarder is used at 1% of the mass of the cementitious material.

[0022] More preferably, the drag-reducing agent is an aliphatic drag-reducing agent or a polycarboxylic acid drag-reducing agent; the water loss reducing agent is an AMPS polymer-based water loss reducing agent; the retarder is an organophosphonic acid retarder; and the thickening time can be adjusted within 200 min to 500 min.

[0023] Compared with the prior art, the beneficial technical effects of the present invention are as follows: 1. The cementitious material of this invention has strong sealing capabilities. This invention primarily uses ultrafine siliceous and ultrafine calcareous materials, which can effectively penetrate into the water-bearing fissures and channels of the formation. Under high-temperature hydrothermal conditions in the formation, through an in-situ reaction mechanism of dissolution-nucleation growth, it gradually generates and forms robust hydration products, ultimately sealing the water-bearing channels. Furthermore, because ultrafine expanding agent lightweight magnesium oxide is added to the cementitious material, magnesium oxide reacts to form magnesium hydroxide during hydration. Through the volume expansion effect during the reaction, the problem of sealing failure caused by the volume shrinkage of hydrated calcium silicate is effectively avoided.

[0024] 2. The cementitious material of the present invention exhibits good workability. The present invention incorporates a starch-based density stabilizer into the cementitious material. This starch-based density stabilizer is approximately spherical at room temperature, which improves fluidity; at high temperatures, it gelatinizes to form a large number of high-molecular-weight chain polymers, increasing the viscosity of the cement slurry at high temperatures and effectively avoiding the problems of difficult mixing at room temperature and high-temperature settling present in ultrafine cement slurries.

[0025] 3. The cementitious material of the present invention has good durability. The cementitious material of the present invention incorporates ultrafine aluminosilicate materials, which have good pozzolanic activity and can participate in the in-situ reaction between ultrafine silica and ultrafine calcareous materials. Aluminum ions enter the hydration products, effectively improving the stability of the hydration product structure, thereby enhancing the durability of the water-blocking cementitious material.

[0026] 4. The cementitious material of this invention has good temperature resistance. By optimizing the ratio of ultrafine silicate material to ultrafine calcareous material and controlling the calcium-silica molar ratio of the hydration products produced by the in-situ reaction, it is ensured that the water-blocking material forms a snow-silica-calcium stone-like product with temperature resistance under high temperature conditions, and that the hydration products have good mechanical properties under high temperature conditions.

[0027] 5. The materials used in this invention are green and environmentally friendly. This invention utilizes industrial waste such as carbide slag, microsilicon, polycrystalline silicon abrasives, and lithium slag, realizing the resource utilization of waste and reducing environmental pollution caused by the stockpiling of industrial waste. This aligns with the concept of green and environmentally friendly development and also reduces the cost of cementing materials for sealing water layers in oil fields, laying a solid foundation for large-scale promotion and application. Attached Figure Description

[0028] Figure 1 SEM image of mung bean starch; Figure 2 This is a thickening curve of the oilfield water-sealing cementitious material in Example 1 at 150℃; Figure 3 This is a laser particle size distribution diagram of the cementitious material used for sealing oilfield water layers in Example 2. Detailed Implementation

[0029] The present invention will be further described in detail below with reference to specific embodiments, but the scope of protection of the present invention is not limited to the following embodiments.

[0030] Example 1 As a preferred embodiment of the present invention, this embodiment provides a cementitious material for sealing water layers in oilfields, prepared using industrial waste residue. It is composed of the following basic raw materials in parts by weight, pretreated: 40 parts ultrafine silica material, 50 parts ultrafine calcareous material, 6 parts ultrafine aluminosilicate material, 1 part nanocrystalline seed, 2 parts ultrafine expanding agent, and 1 part starch-based density stabilizer. The ultrafine silica material is microsilica with a silica content >85% and a particle size D90 <1μm; the ultrafine calcareous material is calcium hydroxide with a calcium oxide content >60% and a particle size D90 <20μm; the ultrafine aluminosilicate material is lithium slag with a silica content >50% and an alumina content >20% and a particle size D90 <20μm; the nanocrystalline seed is nano-calcium silicate with a particle size D90 <100nm and a specific surface area <100m². 2 / kg; the ultrafine expanding agent is light magnesium oxide, with MgO content >90% and particle size D90 <15μm; the starch density stabilizer is mung bean starch.

[0031] Microsilica, calcium hydroxide, and lithium slag were weighed according to the weight ratio of the components and put into a ball mill for ball milling. After ball milling, they were separated by an airflow separation device. The D90 of the mixed powder was 17.5μm. The ultrafine material obtained by grinding and separation was mixed evenly with nano-calcium silicate, light magnesium oxide, and mung bean starch according to the weight ratio.

[0032] Prepare the water-blocking cement slurry according to the following proportions: 100% cementitious material + 70% water (by weight of cementitious material) + 0.5% drag-reducing agent (by weight of cementitious material) + 1% retarder (by weight of cementitious material) + 2.5% water-loss-reducing agent (by weight of cementitious material). Conduct thickening time and compressive strength tests at 150℃. The results are attached. Figure 2 As shown in the figure. The drag-reducing agent is an aliphatic drag-reducing agent, the water loss reducing agent is an AMPS polymer-based water loss reducing agent, and the retarder is an organophosphonic acid retarder.

[0033] Example 2 As another preferred embodiment of the present invention, this embodiment provides a cementitious material for sealing water layers in oilfields, prepared using industrial waste residue. It is composed of the following basic raw materials in parts by weight, pretreated: 25 parts ultrafine siliceous material, 65 parts ultrafine calcareous material, 4 parts ultrafine aluminosilicate material, 1 part nanocrystalline seed, 3 parts ultrafine expanding agent, and 2 parts starch-based density stabilizer. The ultrafine siliceous material is polycrystalline silicon abrasive with a silica content >85% and a particle size D90 <1μm; the ultrafine calcareous material is carbide slag with a calcium oxide content >60% and a particle size D90 <20μm; the ultrafine aluminosilicate material is metakaolin with a silica content >50% and an alumina content >20% and a particle size D90 <20μm; the nanocrystalline seed is nano-calcium silicate with a particle size D90 <100nm and a specific surface area <100m². 2 / kg; the ultrafine expanding agent is light magnesium oxide, with MgO content >90% and particle size D90 <15μm; the starch density stabilizer is pea starch.

[0034] Polycrystalline silicon abrasive, carbide slag, and metakaolin were weighed according to their weight ratios and fed into a ball mill for ball milling. After ball milling, the mixture was separated using an air classifier, resulting in a mixed powder with a D90 of 16.2 μm. The ultrafine material obtained from the grinding and separation process was then mixed evenly with nano-calcium silicate, light magnesium oxide, and pea starch according to their weight ratios.

[0035] Prepare the water-blocking cement slurry according to the following proportions: 100% cementitious material + 70% water (by weight of cementitious material) + 0.3% drag-reducing agent (by weight of cementitious material) + 1% retarder (by weight of cementitious material) + 2.5% water-loss reducing agent (by weight of cementitious material). Conduct thickening time and compressive strength tests at 150℃. The drag-reducing agent is a polycarboxylate drag-reducing agent, the water-loss reducing agent is an AMPS polymer-based water-loss reducing agent, and the retarder is an organophosphonic acid retarder.

[0036] Example 3 As another preferred embodiment of the present invention, this embodiment provides a cementitious material for sealing water layers in oilfields, prepared using industrial waste residue. It is made from the following basic raw materials in parts by weight through pretreatment: 30 parts ultrafine silica material, 58 parts ultrafine calcareous material, 5 parts ultrafine aluminosilicate material, 2 parts nanocrystalline seeds, 3 parts ultrafine expanding agent, and 2 parts starch-based density stabilizer. The ultrafine silica material is microsilica with a silica content >85% and a particle size D90 <1μm; the ultrafine calcareous material is calcium hydroxide with a calcium oxide content >60% and a particle size D90 <20μm; the ultrafine aluminosilicate material is lithium slag with a silica content >50% and an alumina content >20% and a particle size D90 <20μm; the nanocrystalline seeds are nano-calcium silicate with a particle size D90 <100nm and a specific surface area <100m². 2 / kg; the ultrafine expanding agent is light magnesium oxide, with MgO content >90% and particle size D90 <15μm; the starch density stabilizer is potato starch.

[0037] Microsilica, calcium hydroxide, and lithium slag were weighed according to the weight ratio of the components and fed into a ball mill for ball milling. After ball milling, the mixture was separated using an air classifier, and the D90 of the mixed powder was 15.5 μm. The ultrafine material obtained from the grinding and separation was then mixed evenly with nano-calcium silicate, light magnesium oxide, and potato starch according to the weight ratio.

[0038] Prepare the water-blocking cement slurry according to the following proportions: 100% cementitious material + 80% water (by weight of cementitious material) + 0.4% drag-reducing agent (by weight of cementitious material) + 1% retarder (by weight of cementitious material) + 2.5% water-loss reducing agent (by weight of cementitious material). Conduct thickening time and compressive strength tests at 150℃. The drag-reducing agent is a polycarboxylate drag-reducing agent, the water-loss reducing agent is an AMPS polymer-based water-loss reducing agent, and the retarder is an organophosphonic acid retarder.

[0039] Example 4 As another preferred embodiment of the present invention, this embodiment provides a cementitious material for sealing water layers in oilfields, prepared using industrial waste residue. It is made from the following basic raw materials in parts by weight through pretreatment: 28 parts ultrafine silica material, 55 parts ultrafine calcareous material, 8 parts ultrafine aluminosilicate material, 2 parts nanocrystalline seeds, 4 parts ultrafine expanding agent, and 3 parts starch-based density stabilizer. The ultrafine silica material is microsilica with a silica content >85% and a particle size D90 <1μm; the ultrafine calcareous material is calcium hydroxide with a calcium oxide content >60% and a particle size D90 <20μm; the ultrafine aluminosilicate material is lithium slag with a silica content >50% and an alumina content >20% and a particle size D90 <20μm; the nanocrystalline seeds are nano-calcium silicate with a particle size D90 <100nm and a specific surface area <100m². 2 / kg; the ultrafine expanding agent is light magnesium oxide, with MgO content >90% and particle size D90 <15μm; the starch density stabilizer is potato starch.

[0040] Microsilica, calcium hydroxide, and lithium slag were weighed according to the component weight ratio and fed into a ball mill for ball milling. After ball milling, the mixture was separated using an air classifier, and the D90 of the mixed powder was 17.8 μm. The ultrafine material obtained from the grinding and separation was then mixed evenly with nano-calcium silicate, light magnesium oxide, and potato starch according to the weight ratio.

[0041] Prepare the water-blocking cement slurry according to the following proportions: 100% cementitious material + 60% water (by weight of cementitious material) + 0.3% drag-reducing agent (by weight of cementitious material) + 1% retarder (by weight of cementitious material) + 2.5% water-loss reducing agent (by weight of cementitious material). Conduct thickening time and compressive strength tests at 150℃. The drag-reducing agent is a polycarboxylate drag-reducing agent, the water-loss reducing agent is an AMPS polymer-based water-loss reducing agent, and the retarder is an organophosphonic acid retarder.

[0042] Comparative experiment Water-blocking cement slurry was prepared using Type II ultrafine cement as the base material. The experimental formula was: 100% ultrafine cement + 0.3% drag-reducing agent (by weight of ultrafine cement) + 1.0% retarder (by weight of ultrafine cement) + 2.5% water-loss-reducing agent (by weight of ultrafine cement) + 60% water (by weight of ultrafine cement). Thickening time and compressive strength were tested at 150℃.

[0043]

[0044] The test results of Examples 1-4 and the comparative test show that the density of Examples 1-4 is between 1.53 and 1.55 g / cm³. 3The material exhibits good fluidity and excellent workability at 150℃, indicating good compatibility with admixtures. The thickening time can be extended to over 300 minutes, meeting safe construction requirements. Furthermore, the settling stability (density difference between the top and bottom layers of the cement slurry) at 150℃ is less than 0.03 g / cm³. 3 This indicates that the cement slurry exhibits good stability under high-temperature conditions, without significant settling. The compressive strength, after curing at 150℃ for 2 days, reaches a maximum of 22.3 MPa, fully meeting the mechanical performance requirements for sealing water layers. Under the same conditions, while water-blocking materials prepared with ultrafine cement exhibit fluidity at room temperature, they suffer from severe core-forming at 150℃, failing to demonstrate good workability. The settling stability (density difference between the top and bottom layers of the cement slurry) at 150℃ is as high as 0.03 g / cm³. 3 This indicates the presence of severe settlement and stratification. The compressive strength after curing at 150℃ for 2 days is 5.4 MPa, and its workability and mechanical properties are far inferior to the waterproofing cementitious material of this application.

Claims

1. A cementitious material prepared from industrial waste residue for sealing water layers in oil fields, characterized in that, The cementitious material is composed of the following raw materials in parts by weight: 25 to 40 parts of ultrafine silicon material, wherein the ultrafine silicon material is microsilica or polycrystalline silicon abrasive with a particle size D90 < 1 μm; 50 to 65 parts of ultrafine calcareous material, wherein the ultrafine calcareous material is carbide slag or calcium hydroxide, and the particle size D90 < 20 μm; Four to eight parts of ultrafine aluminosilicate material, wherein the ultrafine aluminosilicate material is metakaolin or lithium slag, and the particle size D90 < 20 μm; 1-2 parts of nano-calcium silicate, particle size D90 < 100 nm, specific surface area < 100 m² 2 / kg; 2 to 4 parts of ultrafine expanding agent, with a particle size D90 < 15 μm; Starch-based density stabilizer: 1 to 3 parts.

2. The cementitious material for sealing water layers in oilfields, prepared from industrial waste residue as described in claim 1, is characterized in that: The silica content of the ultrafine silicon or ultrafine polycrystalline silicon abrasive is >85%.

3. The cementitious material for sealing oilfield water layers prepared from industrial waste residue as described in claim 1, characterized in that: The calcium oxide content of the ultrafine calcium carbide slag or ultrafine calcium hydroxide is >60%.

4. The cementitious material for sealing oilfield water layers prepared from industrial waste residue as described in claim 1, characterized in that: The ultrafine metakaolin or ultrafine lithium slag has a silica content >50% and an alumina content >20%.

5. The cementitious material for sealing oilfield water layers prepared from industrial waste residue as described in claim 1, characterized in that: The ultrafine expanding agent is light magnesium oxide with an MgO content > 90%.

6. The cementitious material for sealing water layers in oilfields, prepared from industrial waste as described in claim 1, is characterized in that: The starch-based density stabilizer is mung bean starch, pea starch, or potato starch.

7. The method for preparing a cementitious material for sealing water layers in oilfields using industrial waste residue as described in any one of claims 1-6, characterized in that: Includes the following steps, S1. Weigh the ultrafine calcareous material, ultrafine siliceous material and ultrafine aluminosilicate material according to the weight ratio of the components, put them into a ball mill for ball milling, and then use an airflow separation device to separate them to control the particle size D90 of the mixed powder to be less than 20μm. S2. The sorted mixed powder is mixed evenly with ultrafine expanding agent, nano calcium silicate and starch density stabilizer according to the weight ratio to obtain the gelling material.

8. A water-plugging cement slurry for sealing water layers in oil fields, characterized in that: The water-blocking cement grout is prepared by adding the cementitious material as described in any one of claims 1-6 to a water and admixture system, wherein the admixture system accounts for 3.8% to 4% of the mass of the cementitious material; the mass ratio of water to cementitious material is 0.6 to 0.8:1; the admixture system consists of a drag-reducing agent, a water-loss reducing agent, and a retarder, wherein the amount of drag-reducing agent is 0.3% to 0.5% of the mass of the cementitious material; the amount of water-loss reducing agent is 2.5% of the mass of the cementitious material; and the amount of retarder is 1% of the mass of the cementitious material.

9. The water-blocking cement slurry for sealing water layers in oilfields as described in claim 8, characterized in that: The drag-reducing agent is an aliphatic drag-reducing agent or a polycarboxylic acid drag-reducing agent; the water loss reducing agent is an AMPS polymer water loss reducing agent; the retarder is an organophosphonic acid retarder; and the thickening time can be adjusted within 200 min to 500 min.

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