Novel lightening material taking saw dust as raw material, preparation method and low-density well cementation cement slurry system

Abstract

The invention discloses a novel lightening material taking saw dust as a raw material, a preparation method and a low-density well cementation cement slurry system, and belongs to the technical field of oil and gas development. The preparation method of the novel lightweight material comprises the following steps: grinding saw dust into powder, soaking the powder in alkaline water, and stirring until wood powder is completely soaked; raising the temperature, adding quick lime, and continuously stirring for reaction; fishing out the wood powder, washing, and removing excessive moisture; drying and carrying out surface carbonization treatment; the novel lightweight material is obtained. The low-density well cementation cement slurry system comprises 10 to 40 parts of the novel lightening material, 50 to 90 parts of cement, 0.5 to 4 parts of a retarder, 0.5 to 4 parts of an early strength agent, 0.3 to 0.6 part of a dispersant, 1 to 4 parts of a fluid loss agent, 1 to 5 parts of a stabilizer and 0.03 to 0.08 part of an antifoaming agent. The problems that the density of fly ash system well cementation cement slurry is limited, and the cost of floating bead system well cementation cement slurry is too high are solved; the fluidity of the cement paste system meets the engineering application standard, the early compressive strength is rapidly increased, and the subsequent construction requirements can be met.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of oil and gas development, and particularly relates to a new lightening material taking sawdust as a raw material, a preparation method and a low-density cementing slurry system. BACKGROUND

[0002] With the deepening of global oil and gas resource exploration and development, the situation of drilling into low-pressure and easy-leakage formations is increasing. Such formations have low pressure-bearing capacity, and cement slurry leakage and poor cementing quality are prone to occur in conventional cementing operations, which seriously affects the wellbore integrity and subsequent production safety. In order to meet the cementing needs of low-pressure and easy-leakage formations, reducing the density of cement slurry has become one of the key technical means. At present, the lightening materials commonly used in cementing engineering mainly include fly ash, microsilica and hollow glass microbeads.

[0003] Fly ash, as an industrial by-product, has certain lightening effect and cost advantage, but its density reduction capacity is limited (usually only the density of cement slurry can be reduced to 1.60 g / cm 3 The above), and the activity is low, which may lead to slow development of cement stone strength, and it is difficult to meet the design requirements of ultra-low density cement slurry.

[0004] Microsilica can improve the structure of cement stone through micro-filling effect and reduce the density to a certain extent, but its lightening effect is limited, and a large amount of water is needed, which may lead to the decrease of the stability of cement slurry system, and the high alkalinity requirement may also aggravate the material aggregation and affect the construction performance.

[0005] Hollow glass microbeads have significant lightening effect, and can realize the density of cement slurry below 1.30 g / cm 3 , but its compressive strength is low, and it is easy to break under the conditions of high-speed stirring, pumping and high pressure in the well, which leads to the dynamic increase of the density of cement slurry and further causes the leakage risk. In addition, the price of hollow glass microbeads is high, which greatly increases the cementing cost.

[0006] In summary, the existing lightening materials have certain limitations, or the density reduction amplitude is insufficient, or the mechanical properties, stability and economy are difficult to be considered, which restricts their wide application in cementing of low-pressure and easy-leakage formations. Therefore, it is urgent to develop a new lightening material, which can significantly reduce the density of cement slurry while having good strength characteristics, stability and cost feasibility, so as to meet the technical needs of current low-density cementing. SUMMARY

[0007] In order to solve the problems of density limitation of fly ash-based cementing slurry and high cost of the floating bead system cementing slurry in the prior art, the sawdust is used as raw material, the sawdust is ground into powder, and the saccharides and hemicelluloses and other substances in the sawdust are effectively removed through alkali water hydrothermal treatment combined with hot air drying carbonization. This can not only prevent the wood powder (sawdust powder) from adversely affecting the cement hydration process, but also regulate the water absorption performance of the wood powder, thereby relieving the problem of significant performance degradation of the cementing slurry caused by the strong water absorption of the wood powder.

[0008] In order to achieve the above-mentioned object, the technical scheme adopted by the present application is as follows:

[0009] The present application discloses a preparation method of a new lightweight material using sawdust as raw material, which comprises the following steps:

[0010] S1: grinding the sawdust into powder to obtain wood powder;

[0011] S2: soaking the wood powder in alkali water and stirring until the wood powder is fully soaked;

[0012] S3: heating and adding quicklime and continuing to stir and react;

[0013] S4: after the reaction, the wood powder is taken out, washed with clean water until the filtrate is neutral, and the excess water is removed;

[0014] S5: drying and surface carbonization treatment of the wood powder from which the excess water is removed to obtain the new lightweight material.

[0015] In some embodiments of the present application, in step S1, the sawdust is ground into wood powder of different particle size specifications, and then the wood powder of different particle size specifications is subjected to steps S2-S5 respectively.

[0016] Preferably, the sawdust is ground into wood powder of two specifications of 210-250 mesh and 150-190 mesh; more preferably, the wood powder is of two specifications of 230 mesh and 170 mesh.

[0017] In some embodiments of the present application, in step S2, the mass ratio of the wood powder to the alkali water is 1:5-20, preferably 1:10.

[0018] Preferably, the alkali water is a saturated aqueous solution of calcium hydroxide.

[0019] In some embodiments of the present application, in step S3, the alkali water is heated to boiling, and then quicklime is added.

[0020] Preferably, the mass ratio of the quicklime to the wood powder is 1:7-30; more preferably, the mass ratio is 1:15.

[0021] Preferably, after the addition of the quicklime, the stirring and reaction are continued for 3-12 h, preferably 6 h.

[0022] In some embodiments of the present application, in step S5, hot air is used to dry and surface carbonize the wood powder;

[0023] Preferably, the drying and surface carbonization treatment is performed at an inlet air temperature of 200-220°C, more preferably 210°C, for a duration of 1-3 minutes.

[0024] The second aspect of the present application discloses a new lightweight material prepared from sawdust as raw material, which is prepared by the above preparation method.

[0025] The third aspect of the present application discloses the application of the above new lightweight material in the preparation of a low-density cementing slurry system.

[0026] The fourth aspect of the present application discloses a low-density cementing slurry system, which comprises 10-40 parts by weight of the above new lightweight material and the following components: cement 50-90 parts, retarder 0.5-4 parts, early strength agent 0.5-4 parts, dispersant 0.3-0.6 parts, fluid loss additive 1-4 parts, stabilizer 1-5 parts, and defoaming agent 0.03-0.08 parts.

[0027] In some embodiments of the present application, in the low-density cementing slurry system, the new lightweight material made of wood powder with a mesh size of 210-250 is in a proportion of 0-40wt%, and the new lightweight material made of wood powder with a mesh size of 150-190 is in a proportion of 60-100wt%.

[0028] In some embodiments of the present application, the cement is at least one of high-sulfate-resistant cement and ultra-fine cement, preferably the ultra-fine cement is made by grinding G-grade cement,

[0029] and / or the retarder is at least one of gluconate, sulfonate, and tartrate;

[0030] and / or the early strength agent is at least one of sodium sulfate, calcium nitrate, and nano calcium carbonate;

[0031] and / or the fluid loss additive is an AMPS-amide-carboxylic acid polymer;

[0032] and / or the dispersant is a formaldehyde-acetone condensate;

[0033] and / or the stabilizer is at least one of microsilica, bentonite, and diatomite;

[0034] and / or the defoaming agent is tributyl phosphate.

[0035] In some embodiments of the present application, the ultra-fine cement is made by grinding G-grade cement,

[0036] In some embodiments of the present application, the G-grade cement accounts for 65-100 wt%, and the ultra-fine cement accounts for 0-35 wt%.

[0037] Compared with the prior art, the present application has the following beneficial effects:

[0038] The present application uses sawdust as a modified raw material to successfully prepare a new type of lightweight material with excellent performance. Compared with traditional lightweight materials fly ash and microsilica, the material significantly expands the lower limit of the density adjustment range of low-density cement slurry, enabling stable performance in a lower density range and broadening its application prospects in sensitive working conditions such as low-pressure leak-prone formations. At the same time, compared with vacuum glass microbeads, the present application not only significantly reduces raw material costs, but also simplifies the supporting cementing process, without the need for complex external control or additional protective measures. In actual operation, there is no risk of slurry density out of control due to material damage, thereby significantly improving construction reliability and efficiency and reducing the overall application cost of low-density cementing slurry.

[0039] In addition, in the entire modification and preparation process, the raw materials and process technologies used do not require any toxic or harmful chemical additives, meeting the requirements of green chemistry and clean production. This technical route is environmentally friendly, has no pollution emissions, and has both technical innovation and ecological sustainability, which helps to promote the continuous development of cementing materials towards high performance, low cost, and green. DETAILED DESCRIPTION

[0040] In order to make the purpose, technical solutions and advantages of the embodiments of the present application more clear, the technical solutions in the embodiments of the present application will be described clearly and completely below. If the specific conditions are not specified in the embodiments, they are carried out according to the conventional conditions or the conditions recommended by the manufacturer. If the reagents or instruments used are not specified by the manufacturer, they are all conventional products that can be purchased on the market.

[0041] Unless otherwise specified, the parts mentioned in the present application are all weight parts.

[0042] The G-grade cement and the ultra-fine cement mentioned in the present application are all provided by Jiuhua Special Cement Co., Ltd.

[0043] The sawdust mentioned in the present application is all pine sawdust.

[0044] The alkali water mentioned in the present application is a saturated aqueous solution of calcium hydroxide.

[0045] Example 1

[0046] As a preferred embodiment of the present application, this embodiment discloses a new type of lightweight material and a low-density cementing slurry system made of the same.

[0047] 1. New lightweight material

[0048] The preparation method of the new lightening material of the present embodiment is as follows:

[0049] S1: Sawdust is ground into two specifications of 230 mesh and 170 mesh, and the wood powder of the two different specifications is subjected to steps S2-S5 respectively;

[0050] S2: The wood powder is soaked in lye, and stirred constantly until the wood powder is soaked, and the mass ratio of wood powder to water is 1:10;

[0051] S3: The water temperature is raised to boiling, and quicklime is added, and stirring is continued for 6h, and the mass ratio of quicklime to wood powder is 1:15;

[0052] S4: The wood powder is fished out, washed with clean water until the filtrate is neutral, and left to stand for 24h, and the excess water is removed;

[0053] S5: The wood powder is dried and surface carbonized by using hot air drying, and the inlet air temperature is 210℃; wherein the carbonization drying time of the wood powder with a particle size of 230 mesh is 1.5min, and the carbonization drying time of the wood powder with a particle size of 170 mesh is 2min, and the new lightening material with a particle size of 230 mesh and the new lightening material with a particle size of 170 mesh are obtained respectively.

[0054] 2. Low-density cementing slurry system

[0055] The mass composition of the low-density cementing slurry system of the present embodiment is shown in Table 1.

[0056] Table 1 Composition of the low-density cementing slurry system of Example 1

[0057] Component Mass fraction / portion Cement New lightweight material 75 Retarder 25 Early strength agent 1.5 Fluid loss additive 4 Dispersant 4 Suspension stabilizer 0.2 Defoamer 1.5 Mixing water 0.03 Component Mass fraction / portion 85

[0058] The cement used in the present embodiment is a mixture of G-grade cement and superfine cement, wherein the G-grade cement is 65wt%, and the superfine cement is made by grinding the G-grade cement and accounts for 35%.

[0059] In the new lightening material of the present embodiment, the new lightening material with a particle size of 230 mesh accounts for 10wt%, and the new lightening material with a particle size of 170 mesh accounts for 90wt%.

[0060] The retarder used in the present embodiment is a gluconate salt;

[0061] The early strength agent used in the present embodiment is sodium sulfate;

[0062] The fluid loss additive used in the present embodiment is an AMPS-amide-carboxylic acid polymer;

[0063] The dispersant used in the present embodiment is a formaldehyde-acetone condensate;

[0064] The suspension stabilizer used in the embodiment is microsilica;

[0065] The defoaming agent used in the embodiment is tributyl phosphate.

[0066] Embodiment 2

[0067] As a preferred embodiment of the present application, the embodiment discloses a new lightening material and a low-density cementing slurry system made by using the same.

[0068] 1. New lightening material

[0069] The preparation method of the new lightening material of the embodiment is as follows:

[0070] S1: sawdust is ground into two specifications of 230 mesh and 170 mesh, and the wood powder of the two different specifications is subjected to steps S2-S5 respectively;

[0071] S2: the wood powder is soaked in lye, and stirring is continuously performed until the wood powder is soaked, and the mass ratio of the wood powder to water is 1:20;

[0072] S3: the water temperature is raised to boiling, and quicklime is added, and stirring is continuously performed for 8 hours, and the mass ratio of the quicklime to the wood powder is 1:20;

[0073] S4: the wood powder is fished out, and washed with clean water until the filtrate is neutral, and is left to stand for 24 hours, and the excess water is removed;

[0074] S5: hot air drying is used to dry and surface carbonize the wood powder, and the inlet air temperature is 210°C; wherein the carbonization drying time of the wood powder with a particle size of 230 mesh is 1.3 minutes, and the carbonization drying time of the wood powder with a particle size of 170 mesh is 1.5 minutes, and the new lightening material with a particle size of 230 mesh and the new lightening material with a particle size of 170 mesh are obtained respectively.

[0075] 2. Low-density cementing slurry system

[0076] The mass composition of the low-density cementing slurry system of the embodiment is shown in Table 1.

[0077] Table 2 Composition of the low-density cementing slurry system of Embodiment 2

[0078] Cement New lightweight material Retarder 87 Early strength agent 13 Fluid loss additive 1.2 Dispersant 2 Suspension stabilizer 2 Defoamer 0.3 Mixing water 2 Component Mass fraction / portion 0.03 Cement 58

[0079] The cement used in the embodiment is G-grade cement.

[0080] In the new lightening material of the embodiment, the new lightening material with a particle size of 230 mesh is 40wt%, and the new lightening material with a particle size of 170 mesh is 60wt%.

[0081] The retarder used in the embodiment is tartrate;

[0082] The early strength agent used in this embodiment is a mixture of sodium sulfate and calcium nitrate, with a mass ratio of sodium sulfate to calcium nitrate of 3:1;

[0083] The water loss reducing agent used in this embodiment is an AMPS-amide-carboxylic acid polymer;

[0084] The dispersant used in this embodiment is a formaldehyde-acetone condensate;

[0085] The suspension stabilizer used in this embodiment is a mixture of microsilica and bentonite, with a mass ratio of microsilica to bentonite of 7:3.

[0086] The defoamer used in this embodiment is tributyl phosphate.

[0087] Example 3

[0088] As a preferred embodiment of the present invention, this embodiment discloses a novel lightweight material and a low-density cementing slurry system made therefrom.

[0089] 1. New lightweight materials

[0090] The preparation method of the novel weight-reducing material in this embodiment is as follows:

[0091] S1: Grind the sawdust into 170-mesh wood powder;

[0092] S2: Soak the wood powder in alkaline water, stirring constantly until the wood powder is fully soaked. The mass ratio of wood powder to water is 1:5.

[0093] S3: When the water temperature reaches boiling, add quicklime and continue stirring for 3 hours. The mass ratio of quicklime to wood powder is 1:30.

[0094] S4: Remove the wood powder, rinse with clean water until the filtrate is neutral, let stand for 24 hours to remove excess water;

[0095] S5: The wood flour was dried and surface carbonized using hot air drying. The inlet air temperature was 210℃ and the carbonization drying time was 1.2 min, resulting in a new lightweight material with a wood flour particle size of 170 mesh.

[0096] 2. Low-density cement slurry system

[0097] The mass composition of the low-density cement slurry system in this embodiment is shown in Table 3.

[0098] Table 3. Composition of the low-density cement slurry system in Example 3

[0099] New lightweight material Retarder Early strength agent 92 Fluid loss additive 8 Dispersant 0.8 Suspension stabilizer 2.4 Defoamer 2 Mixing water 0.3 Component Mass fraction / portion 1.5 Cement 0.03 New lightweight material 65

[0100] The cement used in this embodiment is a mixture of grade G cement and ultrafine cement, wherein grade G cement accounts for 85 wt% and ultrafine cement is made by grinding grade G cement, accounting for 15%.

[0101] In this embodiment of the novel lightweight material, the novel lightweight material with a wood flour particle size of 170 mesh is 100 wt%.

[0102] The retarder used in this embodiment is a mixture of gluconate and sulfonate in a mass ratio of 1:1;

[0103] The early strength agent used in this embodiment is a mixture of sodium sulfate, calcium nitrate and nano calcium carbonate, with a mass ratio of 1:1:0.05;

[0104] The water loss reducing agent used in this embodiment is an AMPS-amide-carboxylic acid polymer;

[0105] The dispersant used in this embodiment is a formaldehyde-acetone condensate;

[0106] The suspension stabilizer used in this embodiment is a mixture of bentonite and diatomaceous earth in a mass ratio of 4:1.

[0107] The defoamer used in this embodiment is tributyl phosphate.

[0108] Example 4

[0109] As a preferred embodiment of the present invention, this embodiment discloses a novel lightweight material and a low-density cementing slurry system made therefrom.

[0110] 1. New lightweight materials

[0111] The preparation method of the novel weight-reducing material in this embodiment is as follows:

[0112] S1: Grind the sawdust into wood powder of two specifications: 230 mesh and 170 mesh. Then process the two different specifications of wood powder into steps S2 to S5 respectively.

[0113] S2: Soak the wood powder in alkaline water, stirring constantly until the wood powder is thoroughly soaked. The mass ratio of wood powder to water is 1:15.

[0114] S3: When the water temperature reaches boiling, add quicklime and continue stirring for 12 hours. The mass ratio of quicklime to wood powder is 1:7.

[0115] S4: Remove the wood powder, rinse with clean water until the filtrate is neutral, let stand for 24 hours to remove excess water;

[0116] S5: The wood flour is dried and surface carbonized using hot air drying at an inlet temperature of 210℃; the carbonization drying time for 230 mesh wood flour is 1.6 min and the carbonization drying time for 170 mesh wood flour is 2 min, resulting in novel lightweight materials with wood flour particle size of 230 mesh and 170 mesh, respectively.

[0117] 2. Low-density cement slurry system

[0118] The mass composition of the low-density cement slurry system in this embodiment is shown in Table 4.

[0119] Table 4. Composition of the low-density cement slurry system in Example 4

[0120]

[0121]

[0122] The cement used in this embodiment is a mixture of grade G cement and ultrafine cement, wherein grade G cement accounts for 78 wt% and ultrafine cement is made by grinding grade G cement, accounting for 22 wt%.

[0123] In this embodiment of the novel lightweight material, the novel lightweight material with a wood flour particle size of 230 mesh accounts for 40 wt%, and the novel lightweight material with a wood flour particle size of 170 mesh accounts for 60 wt%.

[0124] The retarder used in this embodiment is tartrate;

[0125] The early strength agent used in this embodiment is sodium sulfate and calcium nitrate, with a mass ratio of 1:1;

[0126] The water loss reducing agent used in this embodiment is an AMPS-amide-carboxylic acid polymer;

[0127] The dispersant used in this embodiment is a formaldehyde-acetone condensate;

[0128] The suspension stabilizer used in this embodiment is microsilicone;

[0129] The defoamer used in this embodiment is tributyl phosphate.

[0130] Example 5

[0131] As a preferred embodiment of the present invention, this embodiment discloses a novel lightweight material and a low-density cementing slurry system made therefrom.

[0132] 1. New lightweight materials

[0133] The preparation method of the novel weight-reducing material in this embodiment is as follows:

[0134] S1: Grind the sawdust into wood powder of two specifications: 230 mesh and 170 mesh. Then process the two different specifications of wood powder into steps S2 to S5 respectively.

[0135] S2: Soak the wood powder in alkaline water, stirring constantly until the wood powder is thoroughly soaked. The mass ratio of wood powder to water is 1:10.

[0136] S3: When the water temperature reaches boiling, add quicklime and continue stirring for 6 hours. The mass ratio of quicklime to wood powder is 1:15.

[0137] S4: Remove the wood powder, rinse with clean water until the filtrate is neutral, let stand for 24 hours to remove excess water;

[0138] S5: The wood powder is dried and surface carbonized using hot air drying at an inlet temperature of 210℃; the carbonization drying time for 230 mesh wood powder is 1.5 min and the carbonization drying time for 170 mesh wood powder is 2 min, respectively, to obtain novel lightweight materials with a wood powder particle size of 230 mesh and novel lightweight materials with a wood powder particle size of 170 mesh.

[0139] 2. Low-density cement slurry system

[0140] The mass composition of the low-density cement slurry system in this embodiment is shown in Table 5.

[0141] Table 5. Composition of the low-density cement slurry system in Example 5

[0142] Retarder Early strength agent Fluid loss additive 84 Dispersant 16 Suspension stabilizer 1.8 Defoamer 4 Mixing water 3 Component Mass fraction / portion 0.5 Cement 3 New lightweight material 0.05 Retarder Early strength agent Fluid loss additive Dispersant Suspension stabilizer Defoamer Mixing water 63

[0143] The cement used in this embodiment is a mixture of grade G cement and ultrafine cement, wherein grade G cement accounts for 88 wt% and ultrafine cement is made by grinding grade G cement, accounting for 12 wt%.

[0144] In this embodiment of the novel lightweight material, the novel lightweight material with a wood flour particle size of 230 mesh accounts for 18 wt%, and the novel lightweight material with a wood flour particle size of 170 mesh accounts for 82 wt%.

[0145] The retarder used in this embodiment is a mixture of sulfonate and tartrate in a mass ratio of 1:4;

[0146] The early strength agent used in this embodiment is a mixture of sodium sulfate and calcium nitrate in a mass ratio of 1:1;

[0147] The water loss reducing agent used in this embodiment is an AMPS-amide-carboxylic acid polymer;

[0148] The dispersant used in this embodiment is a formaldehyde-acetone condensate;

[0149] The suspension stabilizer used in this embodiment is a mixture of microsilica and bentonite in a mass ratio of 3:1;

[0150] The defoamer used in this embodiment is tributyl phosphate.

[0151] Comparative Example

[0152] Compared to Example 5, the low-density cement slurry system in this comparative example replaces the novel weight-reducing material in Example 5 with glass microspheres, which have a density of 0.46 g / cm³. 3 All other conditions remain unchanged.

[0153] Test case

[0154] The cement slurry systems of Examples 1-5 and the comparative example were prepared according to the requirements of GB / T 10238, and density, fluidity, compressive strength, thickening time and water loss tests were conducted. The curing conditions for compressive strength were 90℃×48h, and the conditions for thickening test were 90℃×45min×50MPa. The experimental results are shown in Table 6.

[0155] Table 6 Experimental Results

[0156]

[0157] The results above show that the fluidity of the cement slurry system with added modified wood flour meets the requirements of engineering applications, and the early compressive strength develops rapidly, all exceeding 7MPa, which meets the requirements of subsequent construction.

[0158] Compared to the comparative cement slurry, under similar density conditions, the cement stone in Example 5 exhibited higher compressive strength, lower water loss, and a more reasonable thickening time. This indicates that the novel lightweight material of the present invention significantly enhances the mechanical properties and filtration resistance of the cement stone while maintaining good construction adaptability.

[0159] The above description is merely a preferred embodiment of the invention and does not constitute any limitation on the invention. Any simple modifications, equivalent substitutions, and improvements made to the above embodiments based on the technical essence of the invention and within the spirit and principles of the invention shall still fall within the protection scope of the invention's technical solution.

Claims

1. A method for preparing a novel lightweight material using sawdust as raw material, characterized in that, Includes the following steps: S1: Grind the sawdust into powder to obtain wood flour; S2: Soak the wood powder in alkaline water, stirring until the wood powder is thoroughly soaked; S3: Increase the temperature, add quicklime, and continue stirring to react; S4: After the reaction, remove the wood powder and rinse it with water until the filtrate is neutral to remove excess water; S5: The wood flour, after excess moisture has been removed, is dried and surface carbonized to obtain the novel lightweight material.

2. The method for preparing a novel lightweight material using sawdust as raw material according to claim 1, characterized in that, In step S1, sawdust is ground into wood powder of different particle sizes, and then the wood powder of different particle sizes is processed into steps S2 to S5 respectively. Preferably, the sawdust is ground into wood flour of two specifications: 210-250 mesh and 150-190 mesh; more preferably, it is wood flour of two specifications: 230 mesh and 170 mesh.

3. The method for preparing a novel lightweight material using sawdust as raw material according to claim 1, characterized in that, In step S2, the mass ratio of wood flour to alkaline water is 1:5 to 20, preferably 1:

10. Preferably, the alkaline water is a saturated aqueous solution of calcium hydroxide.

4. The method for preparing a novel lightweight material using sawdust as raw material according to claim 1, characterized in that, In step S3, the alkaline water is heated to boiling and then quicklime is added; Preferably, the mass ratio of quicklime to wood flour is 1:7 to 30; more preferably, it is 1:

15. Preferably, after adding quicklime, the reaction is continued with stirring for 3 to 12 hours, more preferably 6 hours.

5. The method for preparing a novel lightweight material using sawdust as raw material according to claim 1, characterized in that, In step S5, hot air is used to dry the wood flour and perform surface carbonization treatment. Preferably, during the drying and surface carbonization treatment, the inlet air temperature is 200–220°C, more preferably 210°C, and the duration is 1–3 minutes.

6. A novel lightweight material using sawdust as raw material, characterized in that, It is prepared by the preparation method according to any one of claims 1-5.

7. The application of a novel lightweight material using sawdust as raw material as described in claim 6 in the preparation of a low-density cementitious slurry system.

8. A low-density cementing slurry system, characterized in that, The material comprises 10 to 40 parts by weight of the novel lightweight material as described in claim 6, and the following components in parts by weight: 50 to 90 parts of cement, 0.5 to 4 parts of retarder, 0.5 to 4 parts of early strength agent, 0.3 to 0.6 parts of dispersant, 1 to 4 parts of water loss reducing agent, 1 to 5 parts of stabilizer, and 0.03 to 0.08 parts of defoamer.

9. The low-density cement slurry system according to claim 8, characterized in that, The wood flour particle size specification in the novel lightweight material can be one or more; Preferably, the proportion of the novel lightweight material made from 210-250 mesh wood flour is 0-40 wt%, and the proportion of the novel lightweight material made from 150-190 mesh wood flour is 60-100 wt%.

10. The low-density cement slurry system according to claim 8, characterized in that, The cement is at least one of high sulfate-resistant cement and ultrafine cement; And / or the retarder is at least one of gluconate, sulfonate and tartrate; And / or the early strength agent is at least one of sodium sulfate, calcium nitrate and nano calcium carbonate; And / or the water loss reducing agent is an AMPS-amide-carboxylic acid polymer; And / or the dispersant is a formaldehyde-acetone condensate; And / or the stabilizer is at least one of microsilica, bentonite and diatomaceous earth; And / or the defoamer is tributyl phosphate.

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