Anti-pollution agent, cement paste system containing anti-pollution agent and preparation method of anti-pollution agent

Abstract

The invention belongs to the technical field of well cementation, and particularly relates to an anti-pollution agent, a cement paste system containing the anti-pollution agent and a preparation method of the anti-pollution agent. The preparation method of the anti-pollution agent for the cement paste system, provided by the invention, comprises the following steps: dissolving biological gum xanthan gum and organic components in deionized water, and stirring until the biological gum xanthan gum and the organic components are completely dissolved to obtain a solution A; sodium aluminate is added into the solution A, the pH is adjusted to be alkaline, and a solution B is obtained; slowly adding hydroxyethyl carboxymethyl cellulose ether into the solution B, and stirring until the hydroxyethyl carboxymethyl cellulose ether is completely dissolved to obtain a solution C; and adding an inorganic component into the solution C, stirring and aging to obtain the anti-pollution agent. The anti-pollution cement paste system disclosed by the invention has the advantages that the cohesiveness is high, the self-separation effect can be realized when the anti-pollution cement paste system meets flushing fluid, spacer fluid and drilling fluid, other shaft working fluid is prevented from being mixed with the cement paste, the self-aggregation of the cement paste is kept to the greatest extent, and the effects of quickly solidifying and improving the strength of set cement are realized.

Description

Technical Field

[0001] The present invention belongs to the technical field of well cementing, and in particular relates to an anti-pollution agent, a cement slurry system containing the anti-pollution agent, and a preparation method thereof. Background Art

[0002] During cementing operations, cement slurry displaces drilling fluid, filling the annulus between the casing and the wellbore, and sealing the formation. When the drilling fluid comes into contact with the cement slurry and becomes contaminated, the slurry's flow properties can deteriorate rapidly, even leading to false setting or flash setting accidents.

[0003] To address the contamination issue caused by contact between drilling fluid and cement slurry, a spacer fluid or flushing fluid is typically pumped between the two to effectively isolate them. While these fluids can prevent drilling fluid from contaminating the cement slurry, their dilution and scouring effects can still lead to slow strength development of the cement paste and low strength in the mixed section. Summary of the Invention

[0004] The purpose of the present invention is to address the defects of the prior art and provide an anti-pollution agent, a cement slurry system containing the same and a preparation method.

[0005] Specifically, the preparation method of the anti-pollution agent for cement slurry system provided by the present invention comprises the following steps:

[0006] (1) slowly dissolving the biogel xanthan gum and the organic component in deionized water and stirring until completely dissolved to obtain solution A;

[0007] Wherein, the organic component is a mixture of one or more of anionic polyacrylamide, cationic polyacrylamide, nonionic polyacrylamide, cellulose ether, and biological glue;

[0008] (2) adding sodium aluminate to solution A and adjusting the pH to alkaline to obtain solution B;

[0009] (3) Slowly adding hydroxyethyl carboxymethyl cellulose ether to solution B and stirring until completely dissolved to obtain solution C;

[0010] (4) adding an inorganic component to solution C, stirring, and aging to obtain an anti-pollution agent;

[0011] The inorganic component is a mixture of one or more of nano calcium silicate, nano silicon dioxide emulsion, hydrophobic nano silicon dioxide, nano bentonite, nano calcium carbonate, sodium aluminate and aluminum sulfate.

[0012] The preparation method of the above-mentioned anti-pollution agent for cement slurry system comprises the following steps:

[0013] (1) Weigh 100 parts of deionized water, slowly add 0.5-1 parts of xanthan gum and 0.02-0.06 parts of anionic polyacrylamide, and stir until completely dissolved to obtain solution A;

[0014] (2) dissolving 1 to 2 parts of sodium aluminate in solution A, and adjusting the pH to 11 to 12 using sodium hydroxide solution to obtain solution B;

[0015] (3) Slowly add 2 to 4 parts of hydroxyethyl carboxymethyl cellulose ether to solution B and stir until completely dissolved to obtain solution C;

[0016] (4) Weigh 8 to 12 parts of nano-calcium silicate, 8 to 12 parts of nano-silica emulsion, and 0.5 to 1 part of hydrophobic silica, add them to solution C in sequence, stir, and age for 1 to 2 hours to obtain an anti-pollution agent.

[0017] In the preparation method of the above-mentioned anti-pollution agent for cement slurry system, the molecular weight of the anionic polyacrylamide is 16 million to 18 million; the molecular weight of the cationic polyacrylamide is 8 million to 12 million, and the ionicity is 40% to 60%; the molecular weight of the nonionic polyacrylamide needs to be ≥15 million; and the molecular weight of the cellulose ether is 100,000 to 1 million.

[0018] In the above-mentioned preparation method of the anti-pollution agent for cement slurry system, the molecular weight of the hydroxyethyl carboxymethyl cellulose ether is 80,000 to 100,000.

[0019] The preparation method of the above-mentioned anti-pollution agent for cement slurry system, the particle size of the nano calcium silicate is 10nm-50nm; the solid content of the nano silicon dioxide emulsion is 40%-50%, and the particle size is 50nm-100nm; the particle size of the hydrophobic silicon dioxide is 10-30nm; the particle size of the nano bentonite is 150-300nm; the particle size of the nano calcium carbonate is 20-80nm; the sodium aluminate content is ≥99% and is in powder form; the aluminum sulfate content is ≥99% and is in powder form or flake form.

[0020] On the other hand, the present invention provides an anti-pollution agent obtained by the above-mentioned preparation method.

[0021] In another aspect, the present invention provides an anti-pollution cement slurry system, which uses the above-mentioned anti-pollution agent.

[0022] The above-mentioned anti-pollution cement slurry system includes: 100 parts of oil well cement, 30-90 parts of slurry preparation water, 5-12 parts of fluid loss reducer, 0.5-1 part of defoamer, 3-10 parts of anti-pollution agent, 1-10 parts of enhancer, 0-4 parts of retarder, 0-1 part of dispersant, 0-50 parts of lightening agent and 0-100 parts of weighting agent.

[0023] In the above-mentioned anti-pollution cement slurry system, the oil well cement is G-grade silicate cement; the slurry preparation water is any one of seawater and fresh water; and the fluid loss additive includes a mixture of one or more of polyvinyl alcohol and AMPS-type multi-polymers.

[0024] In the above-mentioned anti-pollution cement slurry system, the defoaming agent includes a mixture of one or more of tributyl phosphate, polyether-modified polysiloxane, and mineral oil; the reinforcing agent includes a mixture of one or more of slag, fly ash, microsilica, metakaolin, slag, rice husk ash, and kiln ash.

[0025] In the above-mentioned anti-pollution cement slurry system, the retarder includes a mixture of one or more of lignin sulfonate, organic phosphate, and 2-acrylamido-2-methylpropanesulfonic acid / acrylic acid copolymer; and the dispersant is a mixture of one or more of sulfonated aldehyde ketone polymers or polycarboxylic acid polymers.

[0026] In the above-mentioned anti-pollution cement slurry system, the lightening agent is a mixture of one or more of calcined clay, expanded perlite, glass beads, and ceramic beads; the weighting agent is a mixture of one or more of hematite powder, ilmenite powder, pure iron ore powder, and manganese ore powder.

[0027] In another aspect, the present invention further provides a method for preparing the above-mentioned anti-pollution cement slurry system, comprising:

[0028] (1) Weigh the slurry water, add the defoamer, fluid loss reducer, anti-pollution agent, retarder, and dispersant in order according to the proportion, and stir to obtain mixed water;

[0029] (2) Weigh the oil well cement, add the lightening agent, weighting agent, and reinforcing agent according to the proportion, and mix them evenly to obtain a mixed ash sample;

[0030] (3) Add the mixed ash sample to the mixed water while stirring, and continue stirring to obtain an anti-pollution cementing slurry system.

[0031] Compared with the prior art, the anti-pollution cement slurry system of the present invention has the following beneficial effects:

[0032] (1) The anti-pollution cement slurry system of the present invention has strong cohesiveness and can achieve self-separation effect when encountering flushing fluid, isolation fluid, and drilling fluid, thereby preventing other wellbore working fluids from mixing with the cement slurry, maintaining the cement slurry's self-aggregation to the greatest extent, achieving the effect of rapid solidification and improving the strength of cement stone.

[0033] (2) The anti-pollution cement slurry system of the present invention has the following advantages: ① It has strong self-cohesiveness and is not easily mixed with other fluids, which solves the problem that traditional cement slurry is easily mixed with other wellbore working fluids, resulting in performance deterioration; ② The effect remains unchanged after heat curing, which solves the problem that traditional cement slurry systems become thinner and less cohesive when heated; ③ The strength of cement stone is high after mixing with other fluids, which solves the problem that conventional cement slurry has low strength after being contaminated; ④ No thickening occurs when the system is shut down, which facilitates safe construction;

[0034] (4) The anti-pollution cement slurry system of the present invention has a simple formula, excellent comprehensive performance, and a wide range of applications. It can be used for cementing in conventional formations on land and at sea, or in special formations such as high-pressure salt water formations, salt-gypsum formations, and leaky formations. The type of slurry water is not limited, and fresh water, sea water, and salt water can be used for preparation. The slurry density range is 1.2 to 2.5 g / cm 3 , applicable temperature 4℃~110℃, meeting the operation requirements of most well sections. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Various other advantages and benefits will become apparent to those skilled in the art by reading the following detailed description of the preferred embodiment.The accompanying drawings are only for the purpose of illustrating the preferred embodiment and are not to be considered as limiting the present invention.

[0036] Figure 1 Cement slurry of blank group;

[0037] Figure 2 For anti-pollution cement slurry. DETAILED DESCRIPTION

[0038] In order to fully understand the purpose, features and effects of the present invention, the present invention is described in detail through the following specific embodiments. Except for the following contents, the process of the present invention adopts conventional methods or devices in the art. Unless otherwise specified, the following terms have the meanings commonly understood by those skilled in the art.

[0039] The terms "first", "second", etc. used herein do not indicate any order or importance, but are used to distinguish one element from another. The terms "the", "said", "a", and "an" do not indicate a limitation on quantity, but rather indicate the presence of at least one of the objects mentioned. The terms "preferred", "more preferred", etc. refer to embodiments of the present invention that may provide certain beneficial effects in certain circumstances. However, other embodiments may also be preferred under the same circumstances or other circumstances. In addition, the description of one or more embodiments does not imply that other embodiments are not applicable, nor is it intended to exclude other embodiments from the scope of the present invention.

[0040] When a numerical range is disclosed herein, the range is considered continuous and includes the minimum and maximum values ​​of the range, as well as every value between such minimum and maximum values. Further, when a range refers to an integer, every integer between the minimum and maximum values ​​of the range is included. In addition, when multiple ranges are provided to describe a feature or characteristic, the ranges can be combined. In other words, unless otherwise indicated, all ranges disclosed herein are understood to include any and all subranges subsumed therein.

[0041] Specifically, the preparation method of the anti-pollution agent provided by the present invention comprises the following steps: (1) slowly dissolving bio-glue xanthan gum and an organic component in deionized water, stirring until completely dissolved, to obtain solution A; wherein the organic component is a mixture of one or more of anionic polyacrylamide, cationic polyacrylamide, nonionic polyacrylamide, cellulose ether, and bio-glue; (2) adding sodium aluminate to solution A, adjusting the pH to alkaline, to obtain solution B; (3) slowly adding hydroxyethyl carboxymethyl cellulose ether to solution B, stirring until completely dissolved, to obtain solution C; (4) adding inorganic components to solution C, stirring, and aging to obtain the anti-pollution agent; wherein the inorganic components are a mixture of one or more of nano-calcium silicate, nano-silica emulsion, hydrophobic nano-silica, nano-bentonite, nano-calcium carbonate, sodium aluminate, and aluminum sulfate.

[0042] In the present invention, xanthan gum, a biogel, is adsorbed onto the molecular chains of the organic components through hydrogen bonding, resulting in a positive synergistic effect that increases solution viscosity. After the addition of sodium aluminate and pH adjustment, the organic components are affected by ions, reducing solution viscosity. Under alkaline conditions, the electrostatic repulsion between the molecular chains of hydroxyethyl carboxymethyl cellulose ether increases, making it easier to dissolve. After the inorganic components are added to the solution, thoroughly stirred, and aged, a white, viscous solution is obtained.

[0043] The anti-pollution agent of the present invention is prepared by composite organic-inorganic materials, and the anti-pollution effect and the reinforcing effect are improved through the complementary performance of the organic-inorganic materials, thereby solving the problem that traditional cement slurry is easily mixed with other wellbore working materials and the strength of the cement stone after mixing is low.

[0044] In some preferred embodiments, the polyacrylamide is anionic with a molecular weight of 16 million to 18 million. The long molecular chains of the polyacrylamide are entangled with each other to form a network structure, which wraps the cement and admixture particles and reduces contact with external fluids.

[0045] In some preferred embodiments, the molecular weight of hydroxyethyl carboxymethyl cellulose ether is 80,000 to 100,000. The molecular chain of hydroxyethyl carboxymethyl cellulose ether contains hydroxyl groups, which can form hydrogen bonds with mixed water and adsorb on the surface of cement particles, binding free water and cement particles, thereby improving the anti-pollution effect of cement slurry.

[0046] In some preferred embodiments, the particle size of nano-calcium silicate is 10nm-50nm. Nano-calcium silicate has a nucleation effect, which can provide additional nucleation sites for cement hydration, improve the early strength and compressive strength of cement paste, and solve the problem of polyacrylamide and hydroxyethyl cellulose affecting the strength of cement paste.

[0047] In some preferred embodiments, the nano-silica emulsion has a solids content of 40% to 50% and a particle size of 50 nm to 100 nm. The nano-silica emulsion reacts rapidly with calcium hydroxide produced by cement hydration, forming small-particle calcium silicate hydrate gel on its surface. This serves as nucleation activation points for the cement hydration reaction, promoting rapid cement hydration and shortening both thickening and static gelation transition times.

[0048] In some preferred embodiments, the hydrophobic silica has a particle size of 10-30 nm. Utilizing its strong adsorption and hydrophobicity, it is adsorbed on the surface of cement particles, increasing the hydrophobicity of the cement particles and reducing the impact of other materials in the wellbore working fluid on it.

[0049] The sodium aluminate used in the present invention can improve the early strength of cement paste on the one hand, and on the other hand exert a thixotropic effect to reduce the erosion of the fluid on the cement slurry.

[0050] The cationic polyacrylamide used in the present invention has a molecular weight of 8 million to 12 million and an ionicity of 40% to 60%, and can absorb more cement particles through a bridging effect.

[0051] The nonionic polyacrylamide used in the present invention needs to have a molecular weight of ≥15 million, and the higher the molecular weight, the stronger the bridging effect on cement particles.

[0052] The cellulose ether used in the present invention has a molecular weight of 100,000 to 1,000,000. This type of material has good salt resistance and can further enhance the adsorption and bridging effects on cement particles.

[0053] The nano bentonite used in the present invention has a particle size of 150-300nm. The bentonite swells when it comes into contact with water and can absorb a large amount of free water, thereby improving the cohesiveness of the cement slurry.

[0054] The nano calcium carbonate used in the present invention has a particle size of 20-80 nm. The high specific surface area of ​​the nano material can be used to absorb a large amount of free water and improve the cohesiveness of the cement slurry.

[0055] The sodium aluminate used in the present invention has a content of ≥99% and is in powder form.

[0056] The aluminum sulfate used in the present invention has a content of ≥99% and can be in the form of powder or flakes.

[0057] In some preferred embodiments, the method for preparing the anti-pollution agent comprises the following steps:

[0058] (1) Weigh 100 parts of deionized water, slowly add 0.5-1 parts of xanthan gum and 0.02-0.06 parts of anionic polyacrylamide, and stir until completely dissolved to obtain solution A;

[0059] (2) dissolving 1 to 2 parts of sodium aluminate in solution A, and adjusting the pH to 11 to 12 using sodium hydroxide solution to obtain solution B;

[0060] (3) Slowly add 2 to 4 parts of hydroxyethyl carboxymethyl cellulose ether to solution B and stir until completely dissolved to obtain solution C;

[0061] (4) Weigh 8 to 12 parts of nano-calcium silicate, 8 to 12 parts of nano-silica emulsion, and 0.5 to 1 part of hydrophobic silica, add them to solution C in sequence, stir, and age for 1 to 2 hours to obtain an anti-pollution agent.

[0062] On the other hand, the present invention also provides an anti-pollution agent, which is obtained by the above-mentioned preparation method.

[0063] In another aspect, the present invention further provides an anti-pollution cement slurry system, which uses the above-mentioned anti-pollution agent.

[0064] In some preferred embodiments, the anti-pollution cement slurry system of the present invention comprises: 100 parts of oil well cement, 30-90 parts of slurry preparation water, 5-12 parts of fluid loss reducer, 0.5-1 part of defoamer, 3-10 parts of anti-pollution agent, 1-10 parts of enhancer, 0-4 parts of retarder, 0-1 part of dispersant, 0-50 parts of lightening agent and 0-100 parts of weighting agent.

[0065] Among them, components such as oil well cement, slurry water, fluid loss additive, defoamer, enhancer, retarder, dispersant, lightener and weighting agent can all be selected according to actual production needs.

[0066] As an example, in the anti-pollution cement slurry system of the present invention, the oil well cement is G-grade silicate cement; the slurry preparation water is any one of seawater and fresh water; the fluid loss reducer includes a mixture of one or more of polyvinyl alcohol and AMPS-type multi-polymers; the defoamer includes a mixture of one or more of tributyl phosphate, polyether-modified polysiloxane, and mineral oil; the enhancer includes a mixture of one or more of slag, fly ash, microsilica powder, metakaolin, slag, rice husk ash, and kiln ash; the retarder includes a mixture of one or more of lignin sulfonate, organic phosphate, and 2-acrylamido-2-methylpropanesulfonic acid / acrylic acid copolymer; the dispersant is a mixture of one or more of sulfonated aldehyde ketone polymers or polycarboxylic acid polymers; the lightener is a mixture of one or more of calcined clay, expanded perlite, glass microspheres, and ceramic microspheres; the weighting agent is a mixture of one or more of hematite powder, ilmenite powder, pure iron ore powder, and manganese ore powder.

[0067] On the other hand, the present invention also provides a method for preparing an anti-pollution cement slurry system, comprising: (1) weighing slurry water, adding a defoamer, a fluid loss reducer, an anti-pollution agent, a retarder, and a dispersant in order according to a proportion, and stirring to obtain mixed water; (2) weighing oil well cement, adding a lightening agent, a weighting agent, and a reinforcing agent in a proportion, and mixing them evenly to obtain a mixed ash sample; (3) adding the mixed ash sample to the mixed water while stirring, and continuing to stir to obtain an anti-pollution cement slurry system.

[0068] In some preferred embodiments, the preparation method of the anti-pollution cement slurry system of the present invention comprises: (1) weighing slurry water, then adding defoaming agent, fluid loss reducer, anti-pollution agent, retarder, and dispersant in order according to the proportion, and stirring at a speed of 4000r / min±200r / min for 10s±1s to prepare mixed water; (2) weighing cement, adding lightening agent, weighting agent, and reinforcing agent according to the proportion, mixing evenly, and obtaining a mixed ash sample; (3) stirring the mixed water at a speed of 4000r / min±200r / min, adding the mixed ash sample within 15s±1s, and then stirring at a high speed of 4000r / min±200r / min for 35s±1s to prepare the anti-pollution cementing cement slurry system.

[0069] Compared with the traditional cement slurry system, the anti-pollution cement slurry prepared according to the method of the present invention has a lower degree of compatibility with other fluids, strong self-cohesion, and the effect remains unchanged after heat curing. The strength of the cement stone after mixing with other fluids is higher, which solves the problem that conventional cement slurry is easily contaminated by external fluids and has low strength after contamination. It does not thicken when shut down, and is convenient for safe construction.

[0070] Example

[0071] The present invention is further illustrated by way of examples below, but the present invention is not limited to the scope of the examples. In the following examples, the experimental methods without specific conditions are based on conventional methods and conditions.

[0072] The sources of the raw materials used in the Examples and Comparative Examples are as follows:

[0073] Bio-glue xanthan gum: Shandong Fufeng Fermentation Co., Ltd.;

[0074] Anionic polyacrylamide: Shanghai Hengli Water Treatment Materials Co., Ltd.

[0075] Sodium aluminate: Aladdin Reagent (Shanghai) Co., Ltd., purity ≥98%;

[0076] Hydroxyethyl carboxymethyl cellulose ether: Shandong Heda Group Co., Ltd.

[0077] Nano calcium silicate: Tuoyi New Materials (Guangzhou) Co., Ltd., 11000 mesh;

[0078] Nano-silica emulsion: Blue Ocean Boda Technology Co., Ltd., C-GS13L;

[0079] Hydrophobic silica: Evonik Specialty Chemicals (Shanghai) Co., Ltd., Sipernat D10;

[0080] Defoamer: Blue Ocean Boda Technology Co., Ltd., C-DF60L;

[0081] Fluid loss additive: Blue Ocean Boda Technology Co., Ltd., C-FL86L;

[0082] Enhancer: Blue Ocean Boda Technology Co., Ltd., C-SE3;

[0083] Lightening agent: Blue Ocean Boda Technology Co., Ltd., C-P62;

[0084] The antifouling agent was prepared by the following method:

[0085] (1) Weigh 100 parts of deionized water, slowly add 0.75 parts of xanthan gum and 0.04 parts of anionic polyacrylamide, and stir for 10 minutes until the materials are completely dissolved to obtain solution A;

[0086] (2) dissolving 1.5 parts of sodium aluminate in solution A and adjusting the pH to 11-12 using 30% sodium hydroxide solution to obtain solution B;

[0087] (3) Slowly add 3 parts of hydroxyethyl carboxymethyl cellulose ether to solution B and stir for 10 minutes until it is completely dissolved to obtain solution C;

[0088] (4) Weigh 10 parts of nano-calcium silicate, 10 parts of nano-silica emulsion, and 0.5 parts of hydrophobic silica, add them to solution C in sequence, and stir for 30 minutes;

[0089] (5) Aging the mixed solution prepared in the previous step for 1 to 2 hours to obtain an anti-pollution agent.

[0090] Example 1

[0091] Anti-pollution cement slurry: 100% cement + fresh water + 0.5% defoamer + 8% fluid loss additive + 8% anti-pollution agent + 5% reinforcing agent + 9% lightening agent, 1.50g / cm 3 .

[0092] Weigh 46.6 parts by weight of fresh water, then add 0.5 parts by weight of defoamer, 8 parts by weight of fluid loss reducer, and 8 parts by weight of anti-pollution agent in sequence, and stir at a speed of 4000 r / min±200 r / min for 10s±1s to prepare mixed water; (2) Weigh 100 parts by weight of cement, add 5 parts by weight of reinforcing agent and 9 parts by weight of lightening agent according to the proportion, mix evenly, and obtain a mixed ash sample; (3) Stir the mixed water at a speed of 4000 r / min±200 r / min, add the mixed ash sample within 15s±1s, and then stir at a high speed of 4000 r / min±200 r / min for 35s±1s to prepare an anti-pollution cementing slurry system.

[0093] Comparative Example 1

[0094] Blank cement slurry: 100% cement + fresh water + 0.5% defoamer + 8% fluid loss additive + 5% reinforcing agent + 9% lightening agent, 1.50g / cm 3

[0095] Weigh 54.6 parts by weight of fresh water, then add 0.5 parts by weight of defoamer, 8 parts by weight of fluid loss reducer, and 8 parts by weight of anti-pollution agent in sequence, and stir at a speed of 4000 r / min±200 r / min for 10s±1s to prepare mixed water; (2) weigh cement, add reinforcing agent and lightening agent according to the proportion, mix evenly, and obtain a mixed ash sample; (3) stir the mixed water at a speed of 4000 r / min±200 r / min, add the mixed ash sample within 15s±1s, and then stir at a high speed of 4000 r / min±200 r / min for 35s±1s to prepare an anti-pollution cementing slurry system.

[0096] Performance Testing

[0097] According to GB / T19139-2012 Test Methods for Oil Well Cement, the ash setting time, rheological properties, thickening time, compressive strength, water loss, and slurry strength of the blank group cement slurry and the anti-pollution cement slurry were tested.

[0098] Use a syringe to draw 10mL of blank group cement slurry and anti-pollution cement slurry respectively, and slowly inject them into the measuring cup filled with fresh water, and observe the turbidity of the fresh water and the state of the cement slurry at the bottom. Figure 1 and Figure 2 It can be seen from the observation that the fresh water in the measuring cup injected with the blank group cement slurry became turbid and the cement slurry at the bottom showed a mixed compatibility phenomenon, while the fresh water in the measuring cup injected with the anti-pollution cement slurry became clear and transparent and the cement slurry at the bottom showed agglomeration phenomenon.

[0099]

[0100] From the data in the table, it can be seen that compared with the blank group cement slurry, the anti-pollution cement slurry system has smaller changes in ash laying time, rheological properties, thickening time and water loss after adding the anti-pollution agent. It can be seen that the anti-pollution agent has little effect on the conventional properties of cement slurry; after adding the anti-pollution agent, the compatibility with other fluids is poor, and the strength of cement stone and contaminated slurry are significantly improved.

[0101] The present invention has been disclosed above with reference to preferred embodiments. However, those skilled in the art will appreciate that these embodiments are intended only to illustrate the present invention and are not to be construed as limiting the scope of the present invention. It should be noted that any equivalent variations and substitutions to these embodiments are to be considered encompassed within the scope of the claims of the present invention. Therefore, the scope of protection of the present invention shall be subject to the scope defined in the claims.

Claims

1. A method for preparing an anti-pollution agent for a cement slurry system, characterized in that: The following steps are involved: (1) slowly dissolving the biogel xanthan gum and the organic component in deionized water and stirring until completely dissolved to obtain solution A; Wherein, the organic component is a mixture of one or more of anionic polyacrylamide, cationic polyacrylamide, nonionic polyacrylamide, cellulose ether, and biological glue; (2) adding sodium aluminate to solution A and adjusting the pH to alkaline to obtain solution B; (3) Slowly adding hydroxyethyl carboxymethyl cellulose ether to solution B and stirring until completely dissolved to obtain solution C; (4) adding an inorganic component to solution C, stirring, and aging to obtain an anti-pollution agent; The inorganic component is a mixture of one or more of nano calcium silicate, nano silicon dioxide emulsion, hydrophobic nano silicon dioxide, nano bentonite, nano calcium carbonate, sodium aluminate and aluminum sulfate.

2. The preparation method according to claim 1, characterized in that The following steps are involved: (1) Weigh 100 parts of deionized water, slowly add 0.5-1 parts of xanthan gum and 0.02-0.06 parts of anionic polyacrylamide, and stir until completely dissolved to obtain solution A; (2) dissolving 1 to 2 parts of sodium aluminate in solution A, and adjusting the pH to 11 to 12 using sodium hydroxide solution to obtain solution B; (3) Slowly add 2 to 4 parts of hydroxyethyl carboxymethyl cellulose ether to solution B and stir until completely dissolved to obtain solution C; (4) Weigh 8 to 12 parts of nano-calcium silicate, 8 to 12 parts of nano-silica emulsion, and 0.5 to 1 part of hydrophobic silica, add them to solution C in sequence, stir, and age for 1 to 2 hours to obtain an anti-pollution agent.

3. The preparation method according to claim 1, characterized in that The molecular weight of the anionic polyacrylamide is 16 million to 18 million; the molecular weight of the cationic polyacrylamide is 8 million to 12 million, and the ionicity is 40% to 60%; the molecular weight of the nonionic polyacrylamide must be ≥15 million; and the molecular weight of the cellulose ether is 100,000 to 1 million.

4. The preparation method according to claim 1, characterized in that The molecular weight of the hydroxyethyl carboxymethyl cellulose ether is 80,000 to 100,000.

5. The preparation method according to claim 1, characterized in that The particle size of the nano-calcium silicate is 10nm-50nm; the solid content of the nano-silicon dioxide emulsion is 40%-50%, and the particle size is 50nm-100nm; the particle size of the hydrophobic silicon dioxide is 10-30nm; the particle size of the nano-bentonite is 150-300nm; the particle size of the nano-calcium carbonate is 20-80nm; the sodium aluminate content is ≥99% and is in powder form; the aluminum sulfate content is ≥99% and is in powder form or flake form.

6. An anti-pollution agent, characterized in that The method is obtained by the preparation method according to any one of claims 1 to 5.

7. A pollution-resistant cement slurry system, characterized in that: The anti-pollution agent according to claim 6 is used.

8. The anti-pollution cement slurry system according to claim 7, characterized in that: include: 100 parts of oil well cement, 30-90 parts of slurry preparation water, 5-12 parts of fluid loss reducer, 0.5-1 part of defoamer, 3-10 parts of anti-pollution agent, 1-10 parts of reinforcing agent, 0-4 parts of retarder, 0-1 part of dispersant, 0-50 parts of lightening agent and 0-100 parts of weighting agent.

9. The anti-pollution cement slurry system according to claim 8, characterized in that: The oil well cement is Grade G Portland cement; the slurry preparation water is any one of seawater and fresh water; and the fluid loss additive comprises a mixture of one or more of polyvinyl alcohol and AMPS-type multi-polymers.

10. The anti-pollution cement slurry system according to claim 8, characterized in that: The defoaming agent includes a mixture of one or more of tributyl phosphate, polyether-modified polysiloxane, and mineral oil; the reinforcing agent includes a mixture of one or more of slag, fly ash, microsilica, metakaolin, slag, rice husk ash, and kiln ash.

11. The anti-pollution cement slurry system according to claim 8, characterized in that: The retarder comprises a mixture of one or more of lignin sulfonate, organic phosphate, and 2-acrylamido-2-methylpropanesulfonic acid / acrylic acid copolymer; and the dispersant is a mixture of one or more of sulfonated aldehyde ketone polymers or polycarboxylic acid polymers.

12. The anti-pollution cement slurry system according to claim 8, characterized in that: The lightening agent is a mixture of one or more of calcined clay, expanded perlite, glass microspheres, and ceramic microspheres; the weighting agent is a mixture of one or more of hematite powder, ilmenite powder, pure iron ore powder, and manganese ore powder.

13. The method for preparing the anti-pollution cement slurry system according to any one of claims 7 to 12, characterized in that: include: (1) Weigh the slurry water, add the defoamer, fluid loss reducer, anti-pollution agent, retarder, and dispersant in order according to the proportion, and stir to obtain mixed water; (2) Weigh the oil well cement, add the lightening agent, weighting agent, and reinforcing agent according to the proportion, and mix them evenly to obtain a mixed ash sample; (3) Add the mixed ash sample to the mixed water while stirring, and continue stirring to obtain an anti-pollution cementing slurry system.

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