Salt-water-resistant well cementation drag reducer and preparation method thereof

Abstract

The invention discloses a drag reducer for brine-resistant well cementation. The drag reducer comprises 45-60 parts by weight of a polycarboxylic acid polymer, 35-45 parts by weight of an aliphatic polymer and 5-10 parts by weight of a naphthalene sulfonic acid dispersant. The brine-resistant well cementation drag reducer provided by the invention is formed by mixing a plurality of polycarboxylic acid drag reducers, aliphatic drag reducers and naphthalene drag reducers which have dispersion effects, has the advantage of good dispersion at both high temperature and low temperature, and has a good salt-resistant effect; compared with the conventional drag reducer, the drag reducer provided by the invention has the advantages that the addition amount is greatly reduced, the efficiency is high, and the dispersing performance of a system is excellent; meanwhile, the rheological property is good, and the characteristic of sodium chloride brine resistance is also achieved; the drag reducer provided by the invention has broad spectrum performance and can be applied to conventional cement slurry, salt-containing cement slurry and high-density cement slurry systems.

Description

Technical Field

[0001] This invention relates to a drag-reducing agent for saltwater cementing and its preparation method. Background Technology

[0002] As exploration and development deepen, more and more wells encounter salt layers and thick salt deposits during drilling. Furthermore, in offshore operations, seawater is often used directly to prepare cement slurry. To prevent the salt layers from dissolving, semi-saturated or even saturated brine needs to be added to the cement slurry, which often leads to increased thixotropy and decreased rheological properties, affecting cement slurry application and well cementing displacement efficiency. This is especially true for high-density cement slurry systems or systems containing large amounts of toughening agents and anti-channeling agents, where the rheological properties of the cement slurry further decrease, directly impacting the successful completion of the operation. Currently used cement slurry drag-reducing agents are mainly aliphatic drag-reducing agents based on sulfonated aldehydes and ketones, and polycarboxylate drag-reducing agents. However, aliphatic drag-reducing agents have weak dispersing effects on salt-containing materials and exhibit particularly strong thixotropy; polycarboxylate drag-reducing agents have poor temperature resistance. While they have good dispersibility and high water-reducing properties at low temperatures, their drag-reducing ability decreases sharply at high temperatures, resulting in poor rheological properties of the cement slurry. Summary of the Invention

[0003] The purpose of this invention is to provide a high-performance drag-reducing agent for cementing that overcomes the problems of poor rheological properties of currently used cement slurries under high salt conditions or poor rheological properties at high temperatures.

[0004] As one aspect of the present invention, a drag-reducing agent for saltwater cementing is disclosed, comprising 45-60 parts of a polycarboxylic acid polymer, 35-45 parts of an aliphatic polymer, and 5-10 parts of a naphthalenesulfonic acid dispersant, wherein the polycarboxylic acid polymer is polymerized from 10-15 parts of 2-acrylamido-2-methylpropanesulfonic acid, 2.5-5 parts of maleic anhydride, 5-10 parts of acrylic acid, 20-30 parts of methyl allyl polyoxyethylene ether, and 40-50 parts of allyl polyoxyethylene ether, using ammonium persulfate and sodium bisulfite as initiators and mercaptopropionic acid as a chain transfer agent.

[0005] In a feasible specific embodiment, the above-mentioned salt water resistant cementing drag reducer preferably comprises 51-60 parts of polycarboxylic acid polymer, 35-41 parts of aliphatic polymer and 5-8 parts of naphthalenesulfonic acid dispersant, wherein the polycarboxylic acid polymer is preferably polymerized from 12-15 parts of 2-acrylamido-2-methylpropanesulfonic acid, 3-5 parts of maleic anhydride, 5-8 parts of acrylic acid, 24-30 parts of methyl allyl polyoxyethylene ether and 40-46 parts of allyl polyoxyethylene ether, using ammonium persulfate and sodium bisulfite as initiators and mercaptopropionic acid as a chain transfer agent.

[0006] In a feasible specific embodiment, the above-mentioned salt water resistant cementing drag reducer is further preferably composed of 51-54 parts of polycarboxylic acid polymer, 39-41 parts of aliphatic polymer and 5-8 parts of naphthalenesulfonic acid dispersant, wherein the polycarboxylic acid polymer is preferably polymerized from 12-13 parts of 2-acrylamide-2-methylpropanesulfonic acid, 3-4 parts of maleic anhydride, 7-8 parts of acrylic acid, 24-28 parts of methyl allyl polyoxyethylene ether and 44-46 parts of allyl polyoxyethylene ether, using ammonium persulfate and sodium bisulfite as initiators and mercaptopropionic acid as a chain transfer agent.

[0007] In a feasible specific embodiment, the naphthalene sulfonic acid dispersant is one or any combination of sodium methylene dinaphthalene sulfonate and sodium methylene dimethylnaphthalene sulfonate.

[0008] As another aspect of the present invention, a method for preparing the above-mentioned salt-resistant cementing drag-reducing agent for wellbore sealing is provided, the method comprising the following steps:

[0009] (1) Add 10-15 parts of 2-acrylamide-2-methylpropanesulfonic acid, 2.5-5 parts of maleic anhydride, 5-10 parts of acrylic acid, 20-30 parts of methyl allyl polyoxyethylene ether and 40-50 parts of allyl polyoxyethylene ether to 100 parts of water, dissolve and stir, and add sodium hydroxide to adjust the pH value to 5-6.

[0010] (2) Heat to 50-55℃, add initiator and chain transfer agent, heat to 70-80℃, and keep at 70-80℃ for 2-3 hours. Finally, dry the obtained polymer and grind it into powder to obtain polycarboxylic acid polymer.

[0011] (3) Mix 45 to 60 parts of the polycarboxylic acid polymer obtained in step (2), 35 to 45 parts of the aliphatic polymer and 5 to 10 parts of naphthalenesulfonic acid dispersant.

[0012] In a feasible specific implementation, steps (1) and (3) are preferably:

[0013] (1) Add 12-15 parts of 2-acrylamide-2-methylpropanesulfonic acid, 3-5 parts of maleic anhydride, 5-8 parts of acrylic acid, 24-30 parts of methyl allyl polyoxyethylene ether and 40-46 parts of allyl polyoxyethylene ether to 100 parts of water, dissolve and stir, and add sodium hydroxide to adjust the pH value to 5-6.

[0014] (3) Mix 51 to 60 parts of the polycarboxylic acid polymer obtained in step (2), 35 to 41 parts of the aliphatic polymer and 5 to 8 parts of naphthalenesulfonic acid dispersant.

[0015] In a feasible specific implementation, steps (1) and (3) are further preferably:

[0016] (1) Add 12-13 parts of 2-acrylamide-2-methylpropanesulfonic acid, 3-4 parts of maleic anhydride, 7-8 parts of acrylic acid, 24-28 parts of methyl allyl polyoxyethylene ether and 44-46 parts of allyl polyoxyethylene ether to 100 parts of water, dissolve and stir, and add sodium hydroxide to adjust the pH value to 5-6.

[0017] (3) Mix 51 to 54 parts of the polycarboxylic acid polymer obtained in step (2), 39 to 41 parts of the aliphatic polymer and 5 to 8 parts of naphthalenesulfonic acid dispersant.

[0018] In a feasible specific implementation, in step (2), the initiator is 1 part ammonium persulfate and 0.5 parts sodium bisulfite, and the chain transfer agent is 0.02-0.04 parts mercaptopropionic acid.

[0019] In a feasible specific implementation, in step (3), the naphthalene sulfonic acid dispersant is one or any combination of sodium methylene dinaphthalene sulfonate and sodium methylene dimethylnaphthalene sulfonate, and the naphthalene sulfonic acid dispersant is preferably a mixture of sodium methylene dinaphthalene sulfonate and sodium methylene dimethylnaphthalene sulfonate in a mass ratio of 1:1.

[0020] Compared with existing technologies, the beneficial effects of this saltwater resistant cementing drag reducer include:

[0021] (1) The salt water resistant cementing drag reducer is made of a mixture of various polycarboxylic acid drag reducers, aliphatic drag reducers and naphthalene drag reducers with dispersing effect. It has the advantages of good dispersion at high and low temperatures, and the polycarboxylic acid polymer has good salt resistance.

[0022] (2) Compared with conventional drag-reducing agents, this drag-reducing agent requires a much smaller dosage, is more efficient, and has excellent dispersion performance; at the same time, it has good rheological properties and also has the ability to resist saturated sodium chloride brine.

[0023] (3) This drag-reducing agent has broad-spectrum properties and can be applied to conventional cement slurry, salt-containing cement slurry and high-density cement slurry systems. Detailed Implementation

[0024] Unless otherwise stated, parts referred to in this application are parts by mass, and percentages are percentages by mass.

[0025] The present invention will be further described below with reference to specific embodiments, but the following embodiments are by no means intended to limit the present invention.

[0026] Example 1

[0027] (1) Add 10 parts of 2-acrylamide-2-methylpropanesulfonic acid, 2.5 parts of maleic anhydride, 10 parts of acrylic acid, 20 parts of allyl polyoxyethylene ether (HPEG2400) and 50 parts of allyl polyoxyethylene ether (APEG400) to 100 parts of water, dissolve and stir, and add sodium hydroxide to adjust the pH value to 5.5.

[0028] (2) Heat to 50℃, add 1 part ammonium persulfate and 0.5 parts sodium bisulfite as initiators, and add 0.02 parts mercaptopropionic acid as a chain transfer agent. Heat to 75℃ and maintain at 75℃ for 2.5 hours. Finally, dry the obtained polymer, grind it into powder, and obtain the polycarboxylic acid polymer. Using an Ubbelohde viscometer, the molecular weight is measured to be 5.5 × 10⁻⁶. 5 .

[0029] (3) Mix 45 parts of the polycarboxylic acid polymer obtained in step (2), 45 parts of the aliphatic polymer and 10 parts of naphthalenesulfonic acid dispersant to obtain a drag reducer.

[0030] The aliphatic polymer is formed by the polymerization and sulfonation of formaldehyde and acetone, specifically a USZ type drag reducer produced by Weihui Chemical Co., Ltd.; the naphthalene sulfonic acid dispersant is sodium methylene dinaphthalene sulfonate and sodium methylene dimethylnaphthalene sulfonate in a mass ratio of 1:1.

[0031] Example 2

[0032] 1) Add 11 parts of 2-acrylamide-2-methylpropanesulfonic acid, 3 parts of maleic anhydride, 9 parts of acrylic acid, 22 parts of allyl polyoxyethylene ether (HPEG2400) and 48 parts of allyl polyoxyethylene ether (APEG400) to 100 parts of water, dissolve and stir, and add sodium hydroxide to adjust the pH to 5.5.

[0033] (2) Heat to 50℃, add 1 part ammonium persulfate and 0.5 parts sodium bisulfite as initiators, and add 0.02 parts mercaptopropionic acid as a chain transfer agent. Heat to 75℃ and maintain at 75℃ for 2.5 hours. Finally, dry the obtained polymer, grind it into powder, and obtain the polycarboxylic acid polymer. Using an Ubbelohde viscometer, the molecular weight is measured to be 6.5 × 10⁻⁶. 5 .

[0034] (3) Mix 48 parts of the polycarboxylic acid polymer obtained in step (2), 43 parts of the aliphatic polymer and 9 parts of naphthalenesulfonic acid dispersant to obtain a drag reducer.

[0035] The aliphatic polymer is formed by the polymerization and sulfonation of formaldehyde and acetone, specifically a USZ type drag reducer produced by Weihui Chemical Co., Ltd.; the naphthalene sulfonic acid dispersant is sodium methylene dinaphthalene sulfonate and sodium methylene dimethylnaphthalene sulfonate in a mass ratio of 1:1.

[0036] Example 3

[0037] 1) Add 12 parts of 2-acrylamide-2-methylpropanesulfonic acid, 3.5 parts of maleic anhydride, 8 parts of acrylic acid, 24 parts of allyl polyoxyethylene ether (HPEG2400) and 46 parts of allyl polyoxyethylene ether (APEG400) to 100 parts of water, dissolve and stir, and add sodium hydroxide to adjust the pH to 5.0.

[0038] (2) Heat to 50℃, add 1 part ammonium persulfate and 0.5 parts sodium bisulfite as initiators, and add 0.02 parts mercaptopropionic acid as a chain transfer agent. Heat to 70℃ and maintain at 70℃ for 2 hours. Finally, dry the obtained polymer, grind it into powder, and obtain the polycarboxylic acid polymer. Using an Ubbelohde viscometer, the molecular weight was measured to be 6.8 × 10⁻⁶. 5 .

[0039] (3) Mix 51 parts of the polycarboxylic acid polymer obtained in step (2), 41 parts of the aliphatic polymer and 8 parts of naphthalenesulfonic acid dispersant to obtain a drag reducer.

[0040] The aliphatic polymer is formed by the polymerization and sulfonation of formaldehyde and acetone, specifically a USZ type drag reducer produced by Weihui Chemical Co., Ltd.; the naphthalene sulfonic acid dispersant is sodium methylene dinaphthalene sulfonate and sodium methylene dimethylnaphthalene sulfonate in a mass ratio of 1:1.

[0041] Example 4

[0042] 1) Add 13 parts of 2-acrylamide-2-methylpropanesulfonic acid, 4 parts of maleic anhydride, 7 parts of acrylic acid, 26 parts of allyl polyoxyethylene ether (HPEG2400) and 44 parts of allyl polyoxyethylene ether (APEG400) to 100 parts of water, dissolve and stir, and add sodium hydroxide to adjust the pH value to 5.5.

[0043] (2) Heat to 50℃, add 1 part ammonium persulfate and 0.5 parts sodium bisulfite as initiators, and add 0.04 parts mercaptopropionic acid as a chain transfer agent. Heat to 75℃ and maintain at 75℃ for 2.5 hours. Finally, dry the obtained polymer, grind it into powder, and obtain the polycarboxylic acid polymer. Using an Ubbelohde viscometer, the molecular weight was measured to be 7.6 × 10⁻⁶. 5 .

[0044] (3) Mix 54 parts of the polycarboxylic acid polymer obtained in step (2), 39 parts of the aliphatic polymer and 7 parts of naphthalenesulfonic acid dispersant to obtain a drag reducer.

[0045] The aliphatic polymer is formed by the polymerization and sulfonation of formaldehyde and acetone, specifically a USZ type drag reducer produced by Weihui Chemical Co., Ltd.; the naphthalene sulfonic acid dispersant is sodium methylene dinaphthalene sulfonate and sodium methylene dimethylnaphthalene sulfonate in a mass ratio of 1:1.

[0046] Example 5

[0047] 1) Add 14 parts of 2-acrylamide-2-methylpropanesulfonic acid, 4.5 parts of maleic anhydride, 6 parts of acrylic acid, 28 parts of allyl polyoxyethylene ether (HPEG2400) and 42 parts of allyl polyoxyethylene ether (APEG400) to 100 parts of water, dissolve and stir, and add sodium hydroxide to adjust the pH to 5.5.

[0048] (2) Heat to 50℃, add 1 part ammonium persulfate and 0.5 parts sodium bisulfite as initiators, and add 0.02 parts mercaptopropionic acid as a chain transfer agent. Heat to 75℃ and maintain at 75℃ for 2.5 hours. Finally, dry the obtained polymer, grind it into powder, and obtain the polycarboxylic acid polymer. Using an Ubbelohde viscometer, the molecular weight was measured to be 7.8 × 10⁻⁶. 5 ...

[0049] (3) Mix 57 parts of the polycarboxylic acid polymer obtained in step (2), 37 parts of the aliphatic polymer and 6 parts of naphthalenesulfonic acid dispersant to obtain a drag reducer.

[0050] The aliphatic polymer is formed by the polymerization and sulfonation of formaldehyde and acetone, specifically a USZ type drag reducer produced by Weihui Chemical Co., Ltd.; the naphthalene sulfonic acid dispersant is sodium methylene dinaphthalene sulfonate and sodium methylene dimethylnaphthalene sulfonate in a mass ratio of 1:1.

[0051] Example 6

[0052] 1) Add 15 parts of 2-acrylamide-2-methylpropanesulfonic acid, 5 parts of maleic anhydride, 5 parts of acrylic acid, 30 parts of allyl polyoxyethylene ether (HPEG2400) and 40 parts of allyl polyoxyethylene ether (APEG400) to 100 parts of water, dissolve and stir, and add sodium hydroxide to adjust the pH value to 5.5.

[0053] (2) Heat to 50℃, add 1 part ammonium persulfate and 0.5 parts sodium bisulfite as initiators, and add 0.02 parts mercaptopropionic acid as a chain transfer agent. Heat to 75℃ and maintain at 75℃ for 2.5 hours. Finally, dry the obtained polymer, grind it into powder, and obtain the polycarboxylic acid polymer. The molecular weight was measured to be 8.2 × 10⁻⁶ using an Ubbelohde viscometer. 5 ...

[0054] (3) Mix 60 parts of the polycarboxylic acid polymer obtained in step (2), 35 parts of the aliphatic polymer and 5 parts of naphthalenesulfonic acid dispersant to obtain a drag reducer.

[0055] The aliphatic polymer is formed by the polymerization and sulfonation of formaldehyde and acetone, specifically a USZ type drag reducer produced by Weihui Chemical Co., Ltd.; the naphthalene sulfonic acid dispersant is sodium methylene dinaphthalene sulfonate and sodium methylene dimethylnaphthalene sulfonate in a mass ratio of 1:1.

[0056] Example 7

[0057] 1) Add 12 parts of 2-acrylamide-2-methylpropanesulfonic acid, 3 parts of maleic anhydride, 8 parts of acrylic acid, 26 parts of allyl polyoxyethylene ether (HPEG2400) and 46 parts of allyl polyoxyethylene ether (APEG400) to 100 parts of water, dissolve and stir, and add sodium hydroxide to adjust the pH to 5.5.

[0058] (2) Heat to 50℃, add 1 part ammonium persulfate and 0.5 parts sodium bisulfite as initiators, and add 0.02 parts mercaptopropionic acid as a chain transfer agent. Heat to 75℃ and maintain at 75℃ for 2.5 hours. Finally, dry the obtained polymer, grind it into powder, and obtain the polycarboxylic acid polymer. Using an Ubbelohde viscometer, the molecular weight was measured to be 7.2 × 10⁻⁶. 5 ...

[0059] (3) Mix 52 parts of the polycarboxylic acid polymer obtained in step (2), 41 parts of the aliphatic polymer and 7 parts of naphthalenesulfonic acid dispersant to obtain a drag reducer.

[0060] The aliphatic polymer is formed by the polymerization and sulfonation of formaldehyde and acetone, specifically a USZ type drag reducer produced by Weihui Chemical Co., Ltd.; the naphthalene sulfonic acid dispersant is sodium methylene dinaphthalene sulfonate and sodium methylene dimethylnaphthalene sulfonate in a mass ratio of 1:1.

[0061] Example 8

[0062] 1) Add 13 parts of 2-acrylamide-2-methylpropanesulfonic acid, 3.5 parts of maleic anhydride, 7 parts of acrylic acid, 28 parts of allyl polyoxyethylene ether (HPEG2400) and 44 parts of allyl polyoxyethylene ether (APEG400) to 100 parts of water, dissolve and stir, and add sodium hydroxide to adjust the pH to 6.0.

[0063] (2) The temperature was raised to 55℃, and 1 part of ammonium persulfate and 0.5 parts of sodium bisulfite were added as initiators, and 0.02 parts of mercaptopropionic acid were added as chain transfer agents. The temperature was raised to 80℃ and maintained at 80℃ for 3 hours. Finally, the obtained polymer was dried and ground into powder to obtain the polycarboxylic acid polymer. The molecular weight was measured to be 7.3 × 10⁻⁶ using an Ubbelohde viscometer. 5 ...

[0064] (3) Mix 54 parts of the polycarboxylic acid polymer obtained in step (2), 41 parts of the aliphatic polymer and 5 parts of naphthalenesulfonic acid dispersant to obtain a drag reducer.

[0065] The aliphatic polymer is formed by the polymerization and sulfonation of formaldehyde and acetone, specifically a USZ type drag reducer produced by Weihui Chemical Co., Ltd.; the naphthalene sulfonic acid dispersant is sodium methylene dinaphthalene sulfonate and sodium methylene dimethylnaphthalene sulfonate in a mass ratio of 1:1.

[0066] Comparative Example 1

[0067] (1) Add 12 parts of 2-acrylamide-2-methylpropanesulfonic acid, 3.5 parts of maleic anhydride, 8 parts of acrylic acid, 24 parts of allyl polyoxyethylene ether (HPEG2400) and 46 parts of allyl polyoxyethylene ether (APEG400) to 100 parts of water, dissolve and stir, and add sodium hydroxide to adjust the pH value to 5.5.

[0068] (2) Heat to 50℃, add 1 part ammonium persulfate and 0.5 parts sodium bisulfite as initiators, and add 0.02 parts mercaptopropionic acid as a chain transfer agent. Heat to 75℃ and maintain at 75℃ for 2.5 hours. Finally, dry the obtained polymer, grind it into powder, and obtain the polycarboxylic acid polymer. Using an Ubbelohde viscometer, the molecular weight is measured to be 6.8 × 10⁻⁶. 5 .

[0069] (3) Simple polycarboxylic acid polymers as drag reducers.

[0070] Comparative Example 2

[0071] (1) Add 12 parts of 2-acrylamide-2-methylpropanesulfonic acid, 3.5 parts of maleic anhydride, 8 parts of acrylic acid, 24 parts of allyl polyoxyethylene ether (HPEG2400) and 46 parts of allyl polyoxyethylene ether (APEG400) to 100 parts of water, dissolve and stir, and add sodium hydroxide to adjust the pH value to 5.5.

[0072] (2) Heat to 50℃, add 1 part ammonium persulfate and 0.5 parts sodium bisulfite as initiators, and add 0.02 parts mercaptopropionic acid as a chain transfer agent. Heat to 75℃ and maintain at 75℃ for 2.5 hours. Finally, dry the obtained polymer, grind it into powder, and obtain the polycarboxylic acid polymer. Using an Ubbelohde viscometer, the molecular weight is measured to be 6.8 × 10⁻⁶. 5 .

[0073] (3) Mix 50 parts of the polycarboxylic acid polymer obtained in step (2) and 50 parts of the aliphatic polymer to obtain a drag reducer.

[0074] The aliphatic polymer is formed by the polymerization and sulfonation of formaldehyde and acetone, specifically a USZ type drag reducer produced by Weihui Chemical Co., Ltd.

[0075] Comparative Example 3

[0076] (1) Add 12 parts of 2-acrylamide-2-methylpropanesulfonic acid, 3.5 parts of maleic anhydride, 8 parts of acrylic acid, 24 parts of allyl polyoxyethylene ether (HPEG2400) and 46 parts of allyl polyoxyethylene ether (APEG400) to 100 parts of water, dissolve and stir, and add sodium hydroxide to adjust the pH value to 5.5.

[0077] (2) Heat to 50℃, add 1 part ammonium persulfate and 0.5 parts sodium bisulfite as initiators, and add 0.02 parts mercaptopropionic acid as a chain transfer agent. Heat to 75℃ and maintain at 75℃ for 2.5 hours. Finally, dry the obtained polymer, grind it into powder, and obtain the polycarboxylic acid polymer. Using an Ubbelohde viscometer, the molecular weight is measured to be 6.8 × 10⁻⁶. 5 .

[0078] (3) Mix 50 parts of the polycarboxylic acid polymer obtained in step (2) with 50 parts of naphthalenesulfonic acid dispersant to obtain drag-reducing agent.

[0079] The naphthalene sulfonic acid dispersant is sodium methylene dinaphthalene sulfonate and sodium methylene dimethylnaphthalene sulfonate in a mass ratio of 1:1.

[0080] Performance testing:

[0081] The drag-reducing agents prepared in Examples 1-8 and Comparative Examples 1-3 were subjected to performance tests, and the test results are shown in Table 1.

[0082] The method for testing the consistency of slurry is as follows:

[0083] After preparing the cement slurry according to GB / T 19139-2012 Oil Well Cement Test Method, the initial temperature was 27℃, the target temperature was 85℃, and the thickening test conditions were 85℃-42MPa-50min. Rheological and thickening experiments were conducted using a six-speed viscometer and a standard thickener. The flow index n and consistency coefficient K of the cement slurry were calculated using a power-law fluid model. The initial consistency of the slurry was recorded by taking the maximum consistency value within 15min to 30min. The results are shown in Table 1.

[0084] The cement slurry formulation is as follows: 100% high sulfate-resistant Grade G cement + 4% water loss reducing agent BH-F201L + 5% toughening agent BH-M1S + 4% anti-gas channeling agent BH-G502S + 1% drag-reducing agent + 46% semi-saturated brine (distilled water containing 18% sodium chloride). The amounts of water loss reducing agent, toughening agent, anti-gas channeling agent, drag-reducing agent, and semi-saturated brine are calculated based on 100% of the mass of the high sulfate-resistant Grade G cement. The drag-reducing agent is the one prepared in Examples 1-8 and Comparative Examples 1-3. The cement slurry density is 1.92 g / cm³. 3 .

[0085] Cement slurry without drag-reducing agent was used as a blank sample.

[0086] As shown in Table 1, the cement slurry system exhibits a significant thickening effect, and even in the case of semi-saturated salt water, the slurry thickens, resulting in strong thixotropy. The initial consistency of the cement slurry without drag-reducing agent was >40 Bc, and no data was available for the 300 r / min reading. Adding 1% of the drag-reducing agent prepared in Examples 1-8 significantly improved the rheological properties of the cement slurry, with minimal impact on thickening time and virtually no decrease in compressive strength. However, adding 1% of the drag-reducing agent prepared in Comparative Examples 1-3 resulted in an initial consistency >30 Bc, slightly lower than the slurry without drag-reducing agent, but the thixotropy remained strong, and the initial consistency was significantly higher than the example samples.

[0087] Table 1

[0088]

[0089] Comparing the above examples and comparative examples, it can be seen that in Examples 1-8, the consistency of the cement slurry was significantly improved by mixing the synthesized polycarboxylate polymer, polycarboxylate polymer, aliphatic polymer, and naphthalenesulfonic acid dispersant. Specifically, the initial consistency of the cement slurry was ≤30 Bc, the flow index n>0.55, and the consistency coefficient K<0.75 Pa·s. n Furthermore, the thickening time of the cement slurry has a relatively small impact, and the 24-hour compressive strength is ≥26MPa. The formulation and preparation method of the drag-reducing agent are as follows:

[0090] (1) Add 10-15 parts of 2-acrylamide-2-methylpropanesulfonic acid, 2.5-5 parts of maleic anhydride, 5-10 parts of acrylic acid, 20-30 parts of methyl allyl polyoxyethylene ether (HPEG2400) and 40-50 parts of allyl polyoxyethylene ether (APEG400) to 100 parts of water, dissolve and stir, and add sodium hydroxide to adjust the pH value to 5-6;

[0091] (2) Heat to 50-55℃, add initiator and chain transfer agent, heat to 70-80℃, and keep at 70-80℃ for 2-3 hours. Finally, dry the obtained polymer and grind it into powder to obtain polycarboxylic acid polymer.

[0092] (3) Mix 45 to 60 parts of the polycarboxylic acid polymer obtained in step (2), 35 to 45 parts of the aliphatic polymer and 5 to 10 parts of naphthalenesulfonic acid dispersant.

[0093] In a feasible specific implementation, in step (2), the initiator is 1 part ammonium persulfate and 0.5 parts sodium bisulfite, and the chain transfer agent is 0.02-0.04 parts by weight of mercaptopropionic acid.

[0094] The aliphatic polymer is formed by the polymerization and sulfonation of formaldehyde and acetone, specifically the USZ type drag reducer produced by Weihui Chemical Co., Ltd.

[0095] The naphthalene sulfonic acid dispersant is one or any combination of sodium methylene dinaphthalene sulfonate and sodium methylene dimethylnaphthalene sulfonate, preferably a mixture of sodium methylene dinaphthalene sulfonate and sodium methylene dimethylnaphthalene sulfonate in a mass ratio of 1:1.

[0096] Furthermore, as can be seen from Examples 3-8, the consistency of the cement slurry was significantly improved by mixing the synthesized polycarboxylate polymer, the polycarboxylate polymer, the aliphatic polymer, and the naphthalene sulfonic acid dispersant. Specifically, the initial consistency of the cement slurry was ≤20 Bc, the flow index n>0.70, and the consistency coefficient K<0.75 Pa. n Furthermore, the thickening time of the cement slurry has a relatively small impact, and the compressive strength after 24 hours is ≥30MPa. The formulation and preparation method of the drag-reducing agent are as follows:

[0097] (1) Add 12-15 parts of 2-acrylamide-2-methylpropanesulfonic acid, 3-5 parts of maleic anhydride, 5-8 parts of acrylic acid, 24-30 parts of methyl allyl polyoxyethylene ether (HPEG2400) and 40-46 parts of allyl polyoxyethylene ether (APEG400) to 100 parts of water, dissolve and stir, and add sodium hydroxide to adjust the pH value to 5-6;

[0098] (2) Heat to 50-55℃, add initiator and chain transfer agent, heat to 70-80℃, and keep at 70-80℃ for 2-3 hours. Finally, dry the obtained polymer and grind it into powder to obtain polycarboxylic acid polymer.

[0099] (3) Mix 51 to 60 parts of the polycarboxylic acid polymer obtained in step (2), 35 to 41 parts of the aliphatic polymer and 5 to 8 parts of naphthalenesulfonic acid dispersant.

[0100] In a feasible specific implementation, in step (2), the initiator is 1 part ammonium persulfate and 0.5 parts sodium bisulfite, and the chain transfer agent is 0.02-0.04 parts by weight of mercaptopropionic acid.

[0101] The aliphatic polymer is formed by the polymerization and sulfonation of formaldehyde and acetone, specifically the USZ type drag reducer produced by Weihui Chemical Co., Ltd.

[0102] The naphthalene sulfonic acid dispersant is one or any combination of sodium methylene dinaphthalene sulfonate and sodium methylene dimethylnaphthalene sulfonate, preferably a mixture of sodium methylene dinaphthalene sulfonate and sodium methylene dimethylnaphthalene sulfonate in a mass ratio of 1:1.

[0103] Furthermore, as can be seen from Examples 3-4 and 7-8, the consistency of the cement slurry was significantly improved by mixing the synthesized polycarboxylate polymer, the polycarboxylate polymer, the aliphatic polymer, and the naphthalenesulfonic acid dispersant. Specifically, the initial consistency of the cement slurry was ≤15 Bc, the flow index n>0.75, and the consistency coefficient K<0.55 Pa·s. n Furthermore, the thickening time of the cement slurry has a relatively small impact, and the 24-hour compressive strength is ≥33MPa. The formulation and preparation method of the drag-reducing agent are as follows:

[0104] (1) Add 12-13 parts of 2-acrylamide-2-methylpropanesulfonic acid, 3-4 parts of maleic anhydride, 7-8 parts of acrylic acid, 24-28 parts of methyl allyl polyoxyethylene ether (HPEG2400) and 44-46 parts of allyl polyoxyethylene ether (APEG400) to 100 parts of water, dissolve and stir, and add sodium hydroxide to adjust the pH value to 5-6;

[0105] (2) Heat to 50-55℃, add initiator and chain transfer agent, heat to 70-80℃, and keep at 70-80℃ for 2-3 hours. Finally, dry the obtained polymer and grind it into powder to obtain polycarboxylic acid polymer.

[0106] (3) Mix 51 to 54 parts of the polycarboxylic acid polymer obtained in step (2), 39 to 41 parts of the aliphatic polymer and 5 to 8 parts of naphthalenesulfonic acid dispersant.

[0107] In a feasible specific implementation, in step (2), the initiator is 1 part ammonium persulfate and 0.5 parts sodium bisulfite, and the chain transfer agent is 0.02-0.04 parts by weight of mercaptopropionic acid.

[0108] The aliphatic polymer is formed by the polymerization and sulfonation of formaldehyde and acetone, specifically the USZ type drag reducer produced by Weihui Chemical Co., Ltd.

[0109] The naphthalene sulfonic acid dispersant is one or any combination of sodium methylene dinaphthalene sulfonate and sodium methylene dimethylnaphthalene sulfonate, preferably a mixture of sodium methylene dinaphthalene sulfonate and sodium methylene dimethylnaphthalene sulfonate in a mass ratio of 1:1.

[0110] Although preferred embodiments of the invention have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including both the preferred embodiments and all changes and modifications falling within the scope of the invention.

[0111] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. A drag-reducing agent for saltwater cementing, characterized in that, The product comprises 45-60 parts of a polycarboxylic acid polymer, 35-45 parts of an aliphatic polymer, and 5-10 parts of naphthalenesulfonic acid dispersant. The polycarboxylic acid polymer is composed of 10-15 parts of 2-acrylamido-2-methylpropanesulfonic acid, 2.5-5 parts of maleic anhydride, 5-10 parts of acrylic acid, 20-30 parts of methyl allyl polyoxyethylene ether, and 40-50 parts of allyl polyoxyethylene ether, polymerized with ammonium persulfate and sodium bisulfite as initiators and mercaptopropionic acid as a chain transfer agent.

2. The drag-reducing agent for saltwater cementing as described in claim 1, characterized in that, The mixture comprises 51-60 parts of a polycarboxylic acid polymer, 35-41 parts of an aliphatic polymer, and 5-8 parts of naphthalenesulfonic acid dispersant. Preferably, the polycarboxylic acid polymer is polymerized from 12-15 parts of 2-acrylamide-2-methylpropanesulfonic acid, 3-5 parts of maleic anhydride, 5-8 parts of acrylic acid, 24-30 parts of methyl allyl polyoxyethylene ether, and 40-46 parts of allyl polyoxyethylene ether, using ammonium persulfate and sodium bisulfite as initiators and mercaptopropionic acid as a chain transfer agent.

3. The drag-reducing agent for saltwater cementing as described in claim 1, characterized in that, The mixture comprises 51-54 parts of a polycarboxylic acid polymer, 39-41 parts of an aliphatic polymer, and 5-8 parts of naphthalenesulfonic acid dispersant. Preferably, the polycarboxylic acid polymer is polymerized from 12-13 parts of 2-acrylamide-2-methylpropanesulfonic acid, 3-4 parts of maleic anhydride, 7-8 parts of acrylic acid, 24-28 parts of methyl allyl polyoxyethylene ether, and 44-46 parts of allyl polyoxyethylene ether, using ammonium persulfate and sodium bisulfite as initiators and mercaptopropionic acid as a chain transfer agent.

4. The drag-reducing agent for saltwater cementing according to any one of claims 1-3, characterized in that, The naphthalenesulfonic acid dispersant is one or any combination of sodium methylene dinaphthalenesulfonate and sodium methylene dimethylnaphthalenesulfonate.

5. A method for preparing a drag-reducing agent for saltwater cementing, characterized in that, The method includes the following steps: (1) Add 10-15 parts of 2-acrylamide-2-methylpropanesulfonic acid, 2.5-5 parts of maleic anhydride, 5-10 parts of acrylic acid, 20-30 parts of methyl allyl polyoxyethylene ether and 40-50 parts of allyl polyoxyethylene ether to 100 parts of water, dissolve and stir, and add sodium hydroxide to adjust the pH value to 5-6. (2) Heat to 50-55℃, add initiator and chain transfer agent, heat to 70-80℃, and keep at 70-80℃ for 2-3 hours. Finally, dry the obtained polymer and grind it into powder to obtain polycarboxylic acid polymer. (3) Mix 45 to 60 parts of the polycarboxylic acid polymer obtained in step (2), 35 to 45 parts of the aliphatic polymer and 5 to 10 parts of naphthalenesulfonic acid dispersant.

6. The method according to claim 5, characterized in that, Steps (1) and (3) are as follows: (1) Add 12-15 parts of 2-acrylamide-2-methylpropanesulfonic acid, 3-5 parts of maleic anhydride, 5-8 parts of acrylic acid, 24-30 parts of methyl allyl polyoxyethylene ether and 40-46 parts of allyl polyoxyethylene ether to 100 parts of water, dissolve and stir, and add sodium hydroxide to adjust the pH value to 5-6. (3) Mix 51 to 60 parts of the polycarboxylic acid polymer obtained in step (2), 35 to 41 parts of the aliphatic polymer and 5 to 8 parts of naphthalenesulfonic acid dispersant.

7. The method according to claim 5, characterized in that, Steps (1) and (3) are as follows: (1) Add 12-13 parts of 2-acrylamide-2-methylpropanesulfonic acid, 3-4 parts of maleic anhydride, 7-8 parts of acrylic acid, 24-28 parts of methyl allyl polyoxyethylene ether and 44-46 parts of allyl polyoxyethylene ether to 100 parts of water, dissolve and stir, and add sodium hydroxide to adjust the pH value to 5-6. (3) Mix 51 to 54 parts of the polycarboxylic acid polymer obtained in step (2), 39 to 41 parts of the aliphatic polymer and 5 to 8 parts of naphthalenesulfonic acid dispersant.

8. The method according to any one of claims 5-7, characterized in that, In step (2), the initiator is 1 part ammonium persulfate and 0.5 parts sodium bisulfite, and the chain transfer agent is 0.02-0.04 parts mercaptopropionic acid.

9. The method according to any one of claims 5-7, characterized in that, In step (3), the naphthalene sulfonic acid dispersant is one or any combination of sodium methylene dinaphthalene sulfonate and sodium methylene dimethylnaphthalene sulfonate.

10. The method according to any one of claims 5-7, characterized in that, In step (3), the naphthalene sulfonic acid dispersant is a mixture of sodium methylene dinaphthalene sulfonate and sodium methylene dimethylnaphthalene sulfonate in a mass ratio of 1:1.

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