Zwitterionic petroleum drilling aid and method of making same

Abstract

This invention discloses an amphoteric petroleum drilling additive and its preparation method. First, furfuryl acrylate, alkenyl sulfonic acid, alkenyl acid, acrylamide, and methacryloyloxyethyltrimethylammonium chloride are polymerized to obtain an amphoteric copolymer. Then, a bismaleimide derivative is added to crosslink with the furan rings on the polymer side chains to obtain the amphoteric polymer. The amphoteric polymer obtained by this invention simultaneously exhibits unique temperature-responsive rheological properties and an anti-polyelectrolyte effect. At low temperatures, it is beneficial for cutter carryover and wellbore purification; at high temperatures, the crosslinked network dissociates, the molecular chains extend, enhancing inhibition and plugging capabilities, and possessing reversible plugging ability, reducing the difficulty of subsequent drilling and unblocking.

Description

Technical Field

[0001] This invention relates to the field of drilling fluid additives, and in particular to an amphoteric petroleum drilling additive and its preparation method. Background Technology

[0002] Amphoteric drilling additives are a class of polymer additives whose molecular chains contain both anionic, cationic, and nonionic groups. Through their unique amphoteric structure, they combine the dispersing and hydration capabilities of anionic polymers with the strong adsorption and inhibition capabilities of cationic polymers, making them a key technology for addressing the challenges of drilling in complex formations.

[0003] Patent No. 200610102016.9 discloses an amphoteric polymeric alcohol for drilling fluid and its preparation method. The method involves polymerizing alkenyl acid, alkenyl amide, alkenyl sulfonic acid, alkenyl quaternary ammonium salt with ethylene oxide, propylene oxide, and alkenyl monomers to form amphoteric ions. These ions not only possess the traditional adsorption and hydration-inhibiting effects of zwitterions but also exhibit excellent anti-collapse effects due to their cloud point effect, capable of sealing micro-fractures. However, this method primarily utilizes multi-point hydrogen bonds for physical adsorption, resulting in a relatively weak sealing effect. Furthermore, the zwitterionic polymeric alcohol itself has a weak ability to carry rock cuttings, making it unsuitable for high-salt environments. Moreover, the polymeric alcohol adsorbed in pores is difficult to completely remove, especially after high-temperature precipitation, which can damage the reservoir and make subsequent unblocking difficult. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of the prior art and provide an amphoteric oil drilling additive and its preparation method, so as to solve the problems of weak cuttings carrying capacity, poor sealing effect and irreversible unblocking of existing amphoteric drilling additives.

[0005] The objective of this invention is achieved through the following technical solution: an amphoteric petroleum drilling additive, prepared according to the following steps. S1. Furfuryl acrylate, alkenyl sulfonic acid, acrylamide, and methacryloyloxyethyltrimethylammonium chloride are polymerized to obtain a zwitterionic copolymer; S2. Crosslinking the bismaleimide derivative with the furan ring on the polymer side chain yields an amphoteric polymer.

[0006] Preferably, in step S1, the polymer monomer is added to a solvent to prepare a solution with a mass fraction of 15-25%, nitrogen gas is introduced for 30 minutes, an initiator is added, and under nitrogen protection, the reaction system is heated to 60-70°C and stirred for 6-8 hours. Precipitation is carried out using a poor solvent, and the mixture is filtered, washed, and dried to obtain the zwitterionic copolymer.

[0007] Preferably, in step S2, the zwitterionic copolymer is prepared into a solution with a mass fraction of 5-10%, and after the bismaleimide is prepared into a solution, it is slowly added to the zwitterionic copolymer solution. The mixed solution is stirred and reacted at 60-80°C for 4-8 hours.

[0008] Preferably, the molar amount of the added bismaleimide derivative is half the molar amount of the furfuryl acrylate.

[0009] Preferably, the alkenyl sulfonic acid is one or more of vinyl sulfonic acid, allyl sulfonic acid, styrene sulfonic acid, or 2-acrylamidododecyl sulfonic acid.

[0010] Preferably, the alkenyl acid is one of acrylic acid or methacrylic acid.

[0011] Preferably, the initiator is azobisisobutyronitrile.

[0012] Preferably, the bismaleimide derivative is one of bismaleimide, N,N'-m-phenylenebismaleimide, or 4,4'-methylenebis(N-phenylmaleimide).

[0013] The present invention has the following advantages: 1. By embedding furan groups into the main chain of a zwitterionic polymer, a furan-maleimide bridging group is generated through a Diels-Alder reaction with a bismaleimide derivative. The Diels-Alder reaction is carried out at low temperatures of 60-80℃ and graft polymerization is performed at 110-130℃. This gives the polymer unique temperature-responsive rheological properties. At low temperatures, it is beneficial for rock carrying and wellbore purification. At high temperatures, the reverse DA reaction occurs, the crosslinked network dissociates, the molecular chain extends, and the viscosity increases significantly. At the same time, the released zwitterionic groups can be effectively adsorbed on the shale surface, enhancing the inhibition and plugging capabilities, and enabling reversible plugging, which greatly reduces the difficulty of subsequent unplugging. 2. The petroleum drilling additive of the present invention is a polymer obtained by combining zwitterions with DA reversible groups. Zwitterions have a unique anti-polyelectrolyte effect, which enables them to stretch their molecular chains more and hydrate better in high salinity environments. DA reversible groups have thermosensitive properties, which enable them to stretch their molecular chains under high temperature conditions. The combination of the two makes the polymer simultaneously have excellent properties for harsh high-temperature and high-salt environments. 3. This invention provides a production process for zwitterionic polymers, which has fewer steps, is easier to control, and is easier to use in industrial production. Detailed Implementation

[0014] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. The components of the embodiments of the present invention described and shown herein can be arranged and designed in various different configurations.

[0015] An amphoteric petroleum drilling additive is prepared according to the following steps. S1. A zwitterionic copolymer is obtained by polymerizing furfuryl acrylate, alkenyl sulfonic acid, alkenyl acid, acrylamide, and methacryloyloxyethyltrimethylammonium chloride. The alkenyl sulfonic acid is one or more of vinyl sulfonic acid, allyl sulfonic acid, styrene sulfonic acid, or 2-acrylamidododecyl sulfonic acid, with allyl sulfonic acid being the preferred choice. The alkenyl acid is one of acrylic acid or methacrylic acid, with acrylic acid being the preferred choice. Furfuryl acrylate, allyl sulfonic acid, acrylic acid, acrylamide, and methacryloyloxyethyltrimethylammonium chloride can undergo free radical polymerization to form a polymer with a carbon-carbon chain as the main chain. Furfuryl acrylate is a nonionic monomer and does not affect the anion-cation balance. The anion-cation balance can be dynamically adjusted by adjusting the ratio of allyl sulfonic acid, acrylic acid, acrylamide, and methacryloyloxyethyltrimethylammonium chloride. S2. Crosslinking a bismaleimide derivative with the furan ring on the polymer side chain yields an amphoteric polymer. The bismaleimide derivative is one of bismaleimide, N,N'-m-phenylenebismaleimide, or 4,4'-methylenebis(N-phenylmaleimide), preferably bismaleimide, which acts as a bridge. The furan ring on the furoate acrylate can serve as a diene in the Diels-Alder reaction. The bismaleimide derivative can introduce maleimide groups, serving as a dienophile. The two maleimide end groups of the bismaleimide can react with the furan rings on different polymer chains to form a reversible crosslinked network.

[0016] Furfuryl acrylate is synthesized using the acyl chloride method, which involves synthesizing furfuryl alcohol, acyl chloride, and triethylamine.

[0017] An amphoteric petroleum drilling additive is prepared according to the following steps. 1. Weigh 0.4 mol of allyl sulfonic acid, 0.2 mol of acrylic acid, 0.2 mol of acrylamide, 0.6 mol of methacryloyloxyethyltrimethylammonium chloride, and 0.5 mol of furfuryl acrylate. Add each polymer monomer to an ethanol / water mixed solvent to prepare a 15% (w / w) solution. Purge with nitrogen for 30 min to remove oxygen. Add 0.5% (w / w) of azobisisobutyronitrile initiator (azobisisobutyronitrile) as the total monomer mass. Under continuous nitrogen purging, heat the reaction system to 60-70°C and stir for 6-8 h. Precipitate with diethyl ether, filter, wash, and dry at 40-50°C to obtain the zwitterionic copolymer. 2. Dissolve the zwitterionic copolymer in DMF to prepare a 10% (w / w) solution. Dissolve 0.25 mol of bismaleimide in a small amount of DMF to prepare a solution, and then slowly add it to the zwitterionic copolymer solution. Heat the mixture and stir at 60-80℃ for 4-8 hours to allow the DA reaction to proceed fully. After cooling, precipitate the product with diethyl ether to remove the solvent, and dry it at 40-50℃ to obtain the zwitterionic copolymer.

[0018] Example 2 An amphoteric petroleum drilling additive is prepared according to the following steps. 1. Weigh 0.4 mol of allyl sulfonic acid, 0.2 mol of acrylic acid, 0.2 mol of acrylamide, 0.6 mol of methacryloyloxyethyltrimethylammonium chloride, and 0.2 mol of furfuryl acrylate. Add each polymer monomer to an ethanol / water mixed solvent to prepare a 25% (w / w) solution. Purge with nitrogen for 30 min to remove oxygen. Add 0.5% (w / w) of azobisisobutyronitrile initiator (based on the total mass of monomers). Under continuous nitrogen purging, heat the reaction system to 60-70°C and stir for 6-8 h. Precipitate with diethyl ether, filter, wash, and dry at 40-50°C to obtain the zwitterionic copolymer. 2. Dissolve the zwitterionic copolymer in DMF to prepare a 10% (w / w) solution. Dissolve 0.1 mol of bismaleimide in a small amount of DMF to prepare a solution, and then slowly add it to the zwitterionic copolymer solution. Heat the mixture and stir at 60-80℃ for 4-8 hours to allow the DA reaction to proceed fully. After cooling, precipitate the product with diethyl ether to remove the solvent, and dry it at 40-50℃ to obtain the zwitterionic copolymer.

[0019] Comparative Example An amphoteric petroleum drilling additive is prepared according to the following steps. Weigh 0.4 mol of allyl sulfonic acid, 0.2 mol of acrylic acid, 0.2 mol of acrylamide, and 0.6 mol of methacryloyloxyethyltrimethylammonium chloride. Add each polymer monomer to an ethanol / water mixed solvent to prepare a 25% (w / w) solution. Purge with nitrogen for 30 min to remove oxygen. Add 0.5% (w / w) of azobisisobutyronitrile initiator (by mass of total monomers). Under continuous nitrogen purging, heat the reaction system to 60-70°C and stir for 6-8 h. Precipitate with diethyl ether, filter, wash, and dry at 40-50°C to obtain the zwitterionic copolymer.

[0020] Experiments on shale recovery rate The base slurry was a 4% sodium-based bentonite freshwater slurry, and the shale core was taken from a depth of 2100m. After crushing, the core was passed through an 8-10 mesh sieve. 1% of the sample and 50g of the core were added to the base slurry, and the mixture was rolled at 150℃ for 16 hours. After cooling, the core was passed through a 40-mesh sieve, washed clean with water, and dried at 105±3℃, representing the primary recovery rate. The recovered core was rolled in clean water at 150℃ for 4 hours and then passed through a 40-mesh sieve, representing the secondary recovery rate. The results are shown in the table below. Conduct drilling fluid rheological experiments 4% Freshwater-based slurry: Add 16g of bentonite to a high-speed stirring cup containing 400mL of distilled water, stir at high speed for 20min, interrupting at least twice to scrape off the clay adhering to the cup wall, place in a constant temperature incubator, and cure in a sealed environment at 24℃±2℃ for 24h to obtain freshwater-based slurry; Saltwater-based slurry: Take 400mL of the prepared freshwater-based slurry, add 18g of sodium chloride, 5.2g of magnesium chloride and 2g of calcium chloride, stir at high speed for 20min to obtain composite saltwater-based slurry.

[0021] As can be seen from the table, compared with existing zwitterionic polymers, adding furan-maleimide bridging groups to the main chain can significantly increase the apparent viscosity of the system while reducing the filtration loss. It can also be seen that the apparent viscosity does not decrease significantly after aging, which suggests that the furan-maleimide bridging groups will decompose at 150℃, allowing the long chain to expand and compensate for the reduction.

[0022] Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing an amphoteric petroleum drilling additive, characterized in that, Includes the following steps, S1. Furfuryl acrylate, alkenyl sulfonic acid, alkenyl acid, acrylamide, and methacryloyloxyethyltrimethylammonium chloride are polymerized to obtain a zwitterionic copolymer; S2. Crosslinking the bismaleimide derivative with the furan ring on the polymer side chain yields an amphoteric polymer.

2. The method for preparing an amphoteric petroleum drilling additive according to claim 1, characterized in that, In step S1, the polymer monomer is added to a solvent to prepare a solution with a mass fraction of 15-25%, nitrogen gas is introduced for 30 min, an initiator is added, and under nitrogen protection, the reaction system is heated to 60-70℃ and stirred for 6-8 h. Precipitation is carried out using a poor solvent, and the mixture is filtered, washed, and dried to obtain the zwitterionic copolymer.

3. The method for preparing an amphoteric petroleum drilling additive according to claim 1, characterized in that, In step S2, the zwitterionic copolymer is prepared into a solution with a mass fraction of 5-10%. After the bismaleimide is prepared into a solution, it is slowly added to the zwitterionic copolymer solution. The mixed solution is stirred and reacted at 60-80°C for 4-8 hours.

4. The method for preparing an amphoteric petroleum drilling additive according to claim 3, characterized in that, The molar amount of the added bismaleimide derivative is half the molar amount of the added furfuryl acrylate.

5. The method for preparing an amphoteric petroleum drilling additive according to claim 1, characterized in that, The alkenyl sulfonic acid is one or more of vinyl sulfonic acid, allyl sulfonic acid, styrene sulfonic acid, or 2-acrylamidododecyl sulfonic acid.

6. The method for preparing an amphoteric petroleum drilling additive according to claim 2, characterized in that, The alkenyl acid is one of acrylic acid or methacrylic acid.

7. The method for preparing an amphoteric petroleum drilling additive according to claim 2, characterized in that, The initiator is azobisisobutyronitrile.

8. The method for preparing an amphoteric petroleum drilling additive according to claim 1, characterized in that, The bismaleimide derivative is one of bismaleimide, N,N'-m-phenylenebismaleimide, or 4,4'-methylenebis(N-phenylmaleimide).

9. An amphoteric petroleum drilling additive, characterized in that, Obtained by any one of the methods of claims 1-8.

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