Pre-crosslinked zwitterionic nano composite gel temporary plugging particle and preparation method thereof

Abstract

The invention relates to pre-crosslinked zwitterionic nano composite gel temporary plugging particles and a preparation method thereof, and belongs to the technical field of oilfield chemical temporary plugging. The temporary plugging particles comprise the following raw materials: sodium carboxymethyl cellulose, a nano material, a zwitterionic monomer, a cationic monomer, a temperature-resistant monomer and a composite cross-linking agent. The preparation method comprises the following steps: dissolving and stirring the sodium carboxymethyl cellulose, the nano material, the anionic monomer, the zwitterionic monomer, the temperature-resistant monomer, the acrylamide and the cross-linking agent, and heating to 70 DEG C; adding an initiator into the solution, stirring and reacting for 3 hours in a nitrogen atmosphere, and cleaning, cutting, drying and grinding the obtained polymer gel to obtain the pre-crosslinked zwitterionic nano composite gel temporary plugging particles. The temporary plugging particles prepared by the invention are relatively stable in quality after being aged for 30 days at the high temperature of 160 DEG C, and can absorb 33.21 g / g of potassium formate water with the concentration of 1.55 g / cm < 3 > within one day.

Description

Technical Field

[0001] The invention relates to the technical field of oilfield chemistry, and in particular to pre-crosslinked zwitterionic nanocomposite gel temporary plugging particles and a preparation method thereof. Background Art

[0002] Problems with chemical and mechanical temporary plugging technologies in high-temperature reservoirs: Deep, high-temperature reservoirs and complex wellbore environments result in insufficient reliability and poor effectiveness of temporary plugging technologies. With the continued advancement of exploration and development, deep, heterogeneous gas reservoirs face urgent demands for reservoir protection and productivity release. The complex geological conditions at depth and the impact of low reservoir permeability pose additional challenges to completion processes. For openhole completions in abnormally high-pressure reservoirs, to meet the dual requirements of well control safety and wellbore cleanliness, large amounts of high-density completion fluids are required during the scraping and flushing phase, resulting in fluid losses. Furthermore, high-volume circulation flushing can easily cause openhole leakage, necessitating the use of downhole mechanical plugging tools such as reservoir isolation valves and leakage prevention valves. However, complex factors such as high reservoir temperatures, oil-based drilling fluid environments, complex wellbore trajectories, and abnormal reservoir pressures place even higher demands on the safety and reliability of mechanical plugging tools. Failure to properly close or open these tools leads to further wellbore complexity, limited treatment options, and increased engineering complexity and operational costs. Secondly, when openhole completion is not possible, casing perforation completion is required. Conventional chemical temporary plugging fluids have a temperature limit of only 140°C, making it difficult to effectively seal the reservoir during the perforation and production string installation stages, and therefore unable to meet the temporary plugging needs of high-temperature wells in the East China Sea. Furthermore, they are prone to filtration and water lock in the reservoir, causing reservoir damage and hindering subsequent induced blowback and production release. To address the problem of the existing solidified water temperature limit of only 120°C, we constructed pre-crosslinked zwitterionic nanocomposite gel temporary plugging particles through optimization of key material components and research on basic physical properties. Summary of the Invention

[0003] In view of the problems existing in the prior art, the present invention provides a pre-crosslinked zwitterionic nanocomposite gel temporary plugging particle. By adopting a specific mass ratio of two-phase ionic monomers, nanomaterials, anionic monomers and high-temperature resistant crosslinking agents, a temperature resistance of 160°C and an absorption density of 1.55g / cm 3 The pre-crosslinked zwitterionic nanocomposite gel of potassium formate brine temporarily plugs the particles, thereby ensuring the problem of completion fluid loss during the perforation completion process of high-temperature and high-pressure wells and reducing reservoir damage.

[0004] To achieve this object, the present invention adopts the following technical solutions:

[0005] In a first aspect, the present invention provides pre-crosslinked zwitterionic nanocomposite gel temporary plugging particles. The pre-crosslinked zwitterionic nanocomposite gel temporary plugging particles are composed of 5% to 15% sodium carboxymethylcellulose (CMC) (relative to the mass of acrylic acid, the same below), 5% to 15% zwitterionic monomers, and one or more of 2-methacryloyloxyethylphosphorylcholine (PC), [2-(methacryloyloxy)ethyl]dimethyl-(3-sulfopropyl)ammonium hydroxide (SB), (3-(methacrylamido)propyl)dimethyl(3-thiopropyl)ammonium hydroxide inner salt (SPP), and trimethylamine N-oxide (TMAO). The particles also contain 0.1% to 1% nanomaterial, which is a combination of one or both of nanosilica and carboxymethylated nanofibers. The particles also contain 0.1% to 1% crosslinking agent, which is tetraallyl ammonium chloride (TAAC). The invention comprises a certain mass of acrylic acid (neutralization degree 60% to 90%), the anionic monomer being provided by neutralized acrylic acid salt, the neutralization raw material being sodium hydroxide solution or potassium hydroxide solution, 10wt% to 30wt% of a temperature-resistant monomer, 2-acrylamido-2-methylpropanesulfonic acid (AMPS), and 0.5wt% to 1wt% of an initiator, which is one or a combination of potassium persulfate (KPS) and ammonium persulfate (APS).

[0006] The preparation method of the pre-crosslinked zwitterionic nanocomposite gel temporary plugging particles of the present invention comprises: adding a certain amount of carboxymethylated nanofibers and an appropriate amount of distilled water into a flask, ultrasonicating for 10 minutes to completely disperse the nanomaterials, then adding a certain amount of sodium carboxymethyl cellulose (CMC), heating to 60°C and stirring to dissolve the sodium carboxymethyl cellulose; taking a certain amount of deionized water into a beaker, adding an initiator and stirring until dissolved, and then pouring the initiator into a sodium carboxymethyl cellulose solution to activate it; taking a certain amount of deionized water into a clean beaker, adding sodium hydroxide, and stirring in an ice-water bath to completely dissolve it to obtain a sodium hydroxide solution, weighing a certain amount of acrylic acid, and adding the acrylic acid dropwise to the sodium hydroxide solution to obtain an anionic monomer solution so that the acrylic acid reaches a designed neutralization degree; then weighing a certain amount of a temperature-resistant monomer, a zwitterionic monomer and a crosslinking agent in sequence into a beaker, adding a certain amount of deionized water and stirring until completely dissolved to obtain a composite solution; finally, adding the acrylic acid solution and the composite solution into the activation solution, heating to 70°C while stirring, and reacting for 3 hours. After the reaction, the gel in the flask was removed, chopped, and washed three or more times with deionized water to remove unreacted monomers. The washed gel was placed in an 85°C oven for 12 hours and finally ground into a 40-60 mesh size to obtain the desired pre-crosslinked zwitterionic nanocomposite gel temporary plugging particles.

[0007] Notes: ① To increase the reaction rate and yield, use a stirrer to stir the solution thoroughly to ensure uniform concentration throughout the reaction. ② To prevent oxidation of the reactants by oxygen in the air, maintain a constant flow of nitrogen through the system. ③ To allow the reaction system to communicate with the outside world, remove nitrogen, and retain low-boiling-point reactants, install a reflux condenser on the flask.

[0008] The final pre-crosslinked zwitterionic nanocomposite gel temporary plugging particles obtained in the present invention need to be mixed with high-density brine to swell and form solidified water nanocomposite gel particles with a certain shape and mechanical properties to play a role. The solidified water particles enter the wellbore blasthole with the high-density brine and then accumulate at the blasthole to reduce the loss of brine to the formation.

[0009] The composition of the pre-crosslinked zwitterionic nanocomposite gel temporary plugging particles of the present invention includes 5% to 15% sodium carboxymethyl cellulose (CMC), for example, 5%, 6%, 7%, 10%, 12% or 15%, etc., but is not limited to the listed values. Other values not listed within the numerical range are also applicable.

[0010] 5 wt% to 15 wt% of the cationic monomer, for example, 5%, 6%, 10%, 12%, 14% or 15%, etc., but is not limited to the values listed, and other values not listed within the numerical range are also applicable;

[0011] 0.1 wt% to 1 wt% of nanomaterials may be, for example, 0.1%, 0.6%, 0.7%, 0.8%, 0.9% or 1%, etc., but is not limited to the listed values, and other values not listed within the numerical range are also applicable.

[0012] 0.1 wt% to 1 wt% of the crosslinking agent may be, for example, 0.1%, 0.6%, 0.7%, 0.8%, 0.9%, 0.95% or 1%, etc., but is not limited to the listed values, and other values not listed within the numerical range are also applicable.

[0013] Acrylic acid with a neutralization degree of 60% to 90% can be, for example, 60%, 74%, 86%, 88% or 90%, etc., but is not limited to the listed values. Other values not listed within the numerical range are also applicable.

[0014] 10 wt% to 30 wt% of the temperature-resistant monomer may be, for example, 10%, 20%, 25% or 30%, etc., but is not limited to the listed values, and other values not listed within the numerical range are also applicable.

[0015] 0.5 wt% to 1 wt% initiator, for example, can be 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 0.95% or 1%, etc., but is not limited to the listed values, and other unlisted values within the numerical range are also applicable.

[0016] In the present invention, when the mass percentage of sodium carboxymethyl cellulose is preferably between 5% and 15%, the pre-crosslinked zwitterionic nanocomposite gel temporary plugging particles have good temperature resistance and salt water absorption performance. When the mass percentage is higher than this, the network structure complexity of the gel temporary plugging particles will increase, resulting in a decrease in salt water absorption performance. When the mass percentage is lower than this percentage range, the network pore size of the gel temporary plugging particles will increase, the particle strength will decrease, and the temperature resistance will decrease.

[0017] Preferably, the zwitterionic monomers include one or more of 2-methacryloyloxyethylphosphorylcholine (PC), [2-(methacryloyloxy)ethyl]dimethyl-(3-sulfopropyl)ammonium hydroxide (SB), (3-(methacrylamido)propyl)dimethyl(3-thiopropyl)ammonium hydroxide inner salt (SPP), and trimethylamine N-oxide (TMAO). Because the zwitterionic content within each monomer molecule is the same, different ratios of the monomers will not significantly affect the positive charge density of the gel temporary plugging particle network. However, due to different intramolecular functional groups (double bonds, lipid bonds, anionic groups), the molecular weight of the zwitterionic monomers is different, so different compounding ratios will affect the salt water absorption and mechanical properties of the gel temporary plugging particles.

[0018] Preferably, the anionic monomer is provided by neutralized acrylic acid, and the acrylic acid is neutralized by sodium hydroxide solution or potassium hydroxide solution. The mass fraction of the anion is determined by the neutralization degree of acrylic acid. The greater the neutralization degree, the greater the anion mass fraction.

[0019] Preferably, the initiator is one or more combinations of potassium persulfate (KPS) and ammonium persulfate (APS). Different ratios of the two initiator combinations will result in different amounts of substances under the same initiator mass, which will ultimately affect the polymerization effect. When the initiator mass fraction is too high, the polymerization rate will be accelerated, resulting in an incomplete gel network structure, and ultimately reducing the water absorption and temperature resistance.

[0020] The molecule described in the present invention has high temperature resistance and salt water absorption performance, and is applied to the completion and testing process of high-temperature wells to ensure safe, accurate and efficient operations. The water absorption performance of pre-crosslinked particles is mainly related to the fixed charge of the gel network charge structure, the hydrophilicity and the degree of gel crosslinking. The more fixed charge, the stronger the hydrophilicity and the smaller the degree of crosslinking, the stronger the salt water absorption performance; in addition, it is also related to the salt water density (i.e., ionic strength). The higher the salt water density of the same salt, the worse the salt water absorption performance. According to Flory's law of water absorption, the increase in the fixed charge and hydrophilicity inside the unexpanded gel network structure can enhance the water absorption performance. The present invention uses amphoteric monomers, anionic monomers, and cationic crosslinking agents to crosslink and polymerize, while improving the fixed charge inside the gel network and the hydrophilicity of the polymer, thereby improving the salt water absorption performance. In addition, the temperature-resistant crosslinking agent increases the complexity of the cross-linked polymer network and improves the temperature resistance.

[0021] Compared with the prior art, the present invention has at least the following beneficial effects:

[0022] The pre-crosslinked zwitterionic nanocomposite gel temporary plugging particles provided by the present invention have good high-temperature stability, can quickly absorb high-density saline and form high-density gel temporary plugging particles, and are suitable for large-scale promotion and application. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 Example 1: Performance of pre-crosslinked zwitterionic nanocomposite gel temporarily blocking particles in absorbing saline water

[0024] Figure 2 Example 1: Temperature resistance performance of pre-crosslinked zwitterionic nanocomposite gel temporary plugging particles

[0025] Figure 3 Example 2: Performance of pre-crosslinked zwitterionic nanocomposite gel temporarily blocking particles in absorbing saline water

[0026] Figure 4 Example 2: Temperature resistance performance of pre-crosslinked zwitterionic nanocomposite gel temporary plugging particles

[0027] Figure 5 Example 3: Performance of pre-crosslinked zwitterionic nanocomposite gel temporarily blocking particles in absorbing saline water

[0028] Figure 6 Example 3: Temperature resistance performance of pre-crosslinked zwitterionic nanocomposite gel temporary plugging particles

[0029] Figure 7 Example 4: Performance of pre-crosslinked zwitterionic nanocomposite gel temporarily blocking particles in absorbing saline water

[0030] Figure 8 Example 4: Temperature resistance performance of pre-crosslinked zwitterionic nanocomposite gel temporary plugging particles

[0031] Figure 9 Example 5: Performance of pre-crosslinked zwitterionic nanocomposite gel temporarily blocking particles in absorbing saline water DETAILED DESCRIPTION

[0032] The technical solution of the present invention will be further described below with reference to the accompanying drawings and through specific implementation methods.

[0033] The present invention is further described in detail below. However, the following examples are merely simplified examples of the present invention and do not represent or limit the scope of protection of the present invention. The scope of protection of the present invention shall be subject to the claims.

[0034] In the following examples and comparative examples, all raw materials used are commercially available products, and all methods used are conventional methods in the art.

[0035] The high temperature resistance and salt water absorption rate and performance testing methods of the pre-crosslinked zwitterionic nanocomposite gel temporary plugging particles in the following examples and comparative examples include:

[0036] Weigh a certain amount of product into a beaker, then add excess high-density saline into the beaker. After a period of time, the product will absorb the liquid completely.

[0037] Pour the mixture in the beaker into a 120-mesh sieve and let it sit for 30 minutes. Finally, weigh the filtered gel using an electronic balance and calculate the gel's liquid absorption performance using the following formula.

[0038] Q s =(M1-M0) / M0

[0039] Where:

[0040] Q s ———Brine solution absorption rate, g / g. The larger the rate, the better the salt solution absorption performance;

[0041] M1——The mass of solidified water temporarily blocked particles when they completely absorb the salt solution, g;

[0042] M0——dry weight of solidified water temporary blocking particles, g;

[0043] In the following examples, the temperature resistance was measured using the following method:

[0044] After saturation, solidified water particles are filtered and weighed, and the solid phase mass is recorded as m0. Then, the solidified water particles are mixed with high-density brine and poured into an aging tank. The aging tank is placed in a high-temperature constant temperature oven for aging. The aging tank is opened every other day, filtered and re-weighed, and recorded as m1, m2...m i , the curing water mass retention rate is calculated by the following formula to evaluate its temperature resistance:

[0045] F=mi / m0*100%

[0046] Among them, F represents the quality retention rate of the curing water after aging, with a maximum value of 100%. For the same aging time, the larger the F value, the better the temperature resistance of the curing water.

[0047] Example 1

[0048] This embodiment provides a raw material ratio and preparation method for pre-crosslinked zwitterionic nanocomposite gel temporary plugging particles. In terms of mass percentage, the raw materials of the pre-crosslinked zwitterionic nanocomposite gel temporary plugging particles include 10wt% sodium carboxymethylcellulose (CMC) (relative to the mass of acrylic acid, the same below). It also includes 10wt% of a zwitterionic monomer, which is a compound of 5wt% 2-methacryloyloxyethyl phosphorylcholine (PC) and 5wt% [2-(methacryloyloxy)ethyl]dimethyl-(3-sulfonic acid propyl) ammonium hydroxide (SB). 1wt% of nanomaterial, which is nanosilica. 0.5wt% of a crosslinking agent, which is tetraallyl ammonium chloride (TAAC). A certain mass of acrylic acid (neutralization degree 80%), the anionic monomer is provided by the neutralized acrylate, and the raw material used for neutralization is sodium hydroxide solution. 30 wt% of a temperature-resistant monomer, wherein the temperature-resistant monomer is 2-acrylamido-2-methylpropanesulfonic acid (AMPS); 0.5 wt% of an initiator, wherein the initiator is potassium persulfate (KPS).

[0049] This embodiment also provides a method for preparing the above-mentioned pre-crosslinked zwitterionic nanocomposite gel temporary plugging particles, the preparation method comprising:

[0050] Add an appropriate amount of distilled water and 0.1g of nano-silica to a flask, ultrasonicate for 10 minutes to uniformly disperse it, then add 1g of sodium carboxymethyl cellulose (CMC) to the nano-dispersion liquid, heat to 60°C and stir to dissolve the sodium carboxymethyl cellulose to obtain a sodium carboxymethyl cellulose solution; take a certain amount of deionized water to a beaker, add 0.05g of initiator and stir until dissolved, then pour it into the sodium carboxymethyl cellulose solution to activate it; take a certain amount of deionized water to a clean beaker, add 4.44g of sodium hydroxide and stir under an ice water bath to completely dissolve it to obtain a sodium hydroxide solution, weigh 10g of acrylic acid and use a dropper to add it dropwise to the sodium hydroxide solution to make the acrylic acid reach the designed neutralization degree to obtain an anionic monomer solution; then, weigh 3g of temperature-resistant monomer, 1g of acrylamide, and zwitterionic monomer (0.5g 2-Methacryloxyethyl phosphorylcholine (PC), 0.5g of [2-(methacryloyloxy)ethyl]dimethyl-(3-sulfonic acid propyl)ammonium hydroxide (SB), and 0.05g of a crosslinker are placed in a beaker. A certain amount of deionized water is added and stirred until completely dissolved to obtain a composite solution. Finally, the acrylic acid solution and the composite solution are added to the activation solution and heated to 70°C while stirring for 3 hours. After the reaction, the gel in the flask is removed, cut into pieces, and washed with deionized water at least three times to remove unreacted monomers. The washed gel is placed in an 85°C constant temperature oven for 12 hours and finally ground into 40-60 mesh to obtain the desired high-density, high-temperature-resistant zwitterionic gel temporary plugging particles.

[0051] In this embodiment, the mass of brine absorbed by the high-density high-temperature resistant zwitterionic gel temporary plugging particles in 24 hours is 33.21 g / g. Figure 1 As shown in Figure 2, after aging at 160 °C for 30 days, the mass retention rate is 98.51%. Figure 2 As shown, the particles are complete in shape and have a certain elasticity.

[0052] Example 2

[0053] This embodiment provides a raw material ratio and preparation method for pre-crosslinked zwitterionic nanocomposite gel temporary plugging particles. In terms of mass percentage, the raw materials of the pre-crosslinked zwitterionic nanocomposite gel temporary plugging particles include 10wt% sodium carboxymethylcellulose (CMC) (relative to the mass of acrylic acid, the same below). It also includes 10wt% of a zwitterionic monomer, which is a compound of 5wt% 2-methacryloyloxyethyl phosphorylcholine (PC) and 5wt% [2-(methacryloyloxy)ethyl]dimethyl-(3-sulfonic acid propyl) ammonium hydroxide (SB). 0.5wt% of nanomaterial, which is carboxymethylated nanofibers (CNFs). 0.5wt% of a crosslinking agent, which is tetraallyl ammonium chloride (TAAC). A certain mass of acrylic acid (neutralization degree 80%), the anionic monomer is provided by the neutralized acrylate, and the raw material used for neutralization is sodium hydroxide solution. 10 wt% of a temperature-resistant monomer, wherein the temperature-resistant monomer is 2-acrylamido-2-methylpropanesulfonic acid (AMPS); 0.5 wt% of an initiator, wherein the initiator is ammonium persulfate (APS).

[0054] The preparation method of the pre-crosslinked zwitterionic nanocomposite gel temporary plugging particles in this embodiment is the same as that in Example 1 and will not be further described.

[0055] In this embodiment, the mass of the pre-crosslinked zwitterionic nanocomposite gel temporary plugging particles absorbing saline for 24 hours is 29.74 g / g. Figure 3 As shown in Figure 2, after aging at 160 °C for 30 days, the mass retention rate is 95.36%. Figure 4 As shown, the particles are complete in shape and have a certain elasticity.

[0056] Example 3

[0057] This embodiment provides a raw material ratio and preparation method for pre-crosslinked zwitterionic nanocomposite gel temporary plugging particles. In terms of mass percentage, the raw materials of the pre-crosslinked zwitterionic nanocomposite gel temporary plugging particles include 10wt% sodium carboxymethylcellulose (CMC) (relative to the mass of acrylic acid, the same below). It also includes 10wt% of a zwitterionic monomer, which is a compound of 5wt% (3-(methacrylamido)propyl)dimethyl(3-thiopropyl)ammonium hydroxide inner salt (SPP) and 5wt% trimethylamine N-oxide (TMAO). 1wt% of nanomaterial, which is a compound of 5wt% nanosilica and 5wt% carboxymethylated nanofibers (CNFs). 0.5wt% of a crosslinking agent, which is tetraallyl ammonium chloride (TAAC). A certain mass of acrylic acid (neutralization degree 80%), the anionic monomer is provided by the neutralized acrylate, and the raw material used for neutralization is sodium hydroxide solution. 10 wt% of a temperature-resistant monomer, wherein the temperature-resistant monomer is 2-acrylamido-2-methylpropanesulfonic acid (AMPS); 0.5 wt% of an initiator, wherein the initiator is potassium persulfate (KPS).

[0058] The preparation method of the high-density, high-temperature-resistant zwitterionic gel temporary plugging particles in this embodiment is the same as that in Example 1 and will not be further described.

[0059] In this embodiment, the mass of brine absorbed by the high-density high-temperature resistant zwitterionic gel temporary plugging particles in 24 hours is 35.70 g / g. Figure 5 As shown in Figure 2, after aging at 160 °C for 30 days, the mass retention rate is 90.11%. Figure 6 As shown, the particles are complete in shape and have a certain elasticity.

[0060] Example 4

[0061] This embodiment provides a raw material ratio and preparation method for pre-crosslinked zwitterionic nanocomposite gel temporary plugging particles. In terms of mass percentage, the raw materials of the pre-crosslinked zwitterionic nanocomposite gel temporary plugging particles include 10wt% sodium carboxymethylcellulose (CMC) (relative to the mass of acrylic acid, the same below). It also includes 10wt% of a zwitterionic monomer, which is 15wt% [2-(methacryloyloxy)ethyl]dimethyl-(3-sulfonic acid propyl)ammonium hydroxide (SB). 0.5wt% of a nanomaterial, which is a carboxymethylated nanofiber. 0.5wt% of a crosslinking agent, which is tetraallyl ammonium chloride (TAAC). A certain mass of acrylic acid (neutralization degree 60%), the anionic monomer is provided by a neutralized acrylate, and the raw material used for neutralization is sodium hydroxide solution. 10wt% of a temperature-resistant monomer, which is 2-acrylamido-2-methylpropanesulfonic acid (AMPS), and 0.5wt% of an initiator, which is potassium persulfate (KPS).

[0062] The preparation method of the high-density, high-temperature-resistant zwitterionic gel temporary plugging particles in this embodiment is the same as that in Example 1 and will not be further described.

[0063] In this embodiment, the mass of the pre-crosslinked zwitterionic nanocomposite gel temporary plugging particles absorbing saline for 24 hours is 28.13 g / g. Figure 7 As shown in Figure 2, after aging at 160 °C for 30 days, the mass retention rate is 92.55%. Figure 8 As shown, the particles are complete in shape and not elastic.

[0064] Example 5

[0065] This embodiment provides a raw material ratio and preparation method for pre-crosslinked zwitterionic nanocomposite gel temporary plugging particles. In terms of mass percentage, the raw materials of the pre-crosslinked zwitterionic nanocomposite gel temporary plugging particles include 5wt% sodium carboxymethylcellulose (CMC) (relative to the mass of acrylic acid, the same below). It also includes 10wt% of a zwitterionic monomer, which is 10wt% 2-methacryloyloxyethyl phosphorylcholine (PC). 1wt% of a nanomaterial, which is nanosilica. 0.1wt% of a crosslinking agent, which is tetraallyl ammonium chloride (TAAC). A certain mass of acrylic acid (neutralization degree 60%), the anionic monomer is provided by a neutralized acrylate, and the raw material used for neutralization is potassium hydroxide solution. 10wt% of a temperature-resistant monomer, which is 2-acrylamido-2-methylpropanesulfonic acid (AMPS), and 0.7wt% of an initiator, which is ammonium persulfate (KPS).

[0066] The preparation method of the high-density, high-temperature-resistant zwitterionic gel temporary plugging particles in this embodiment is the same as that in Example 1 and will not be further described.

[0067] In this embodiment, the mass of brine absorbed by the high-density, high-temperature-resistant zwitterionic gel temporary plugging particles in 24 hours is 16.39 g / g. Figure 9 As shown in the figure, however, starting from the 6th hour of further swelling, the edge of the particles began to dissolve. The temperature resistance of this particle was not further evaluated. The reason for the dissolution may be that the cross-linking agent concentration is too low, the degree of cross-linking is low, and a complete gel network structure cannot be formed, allowing the long hydrophilic polymer chain to dissolve in the saline.

[0068] In summary, the high-density, high-temperature-resistant zwitterionic gel temporary plugging particles provided by the present invention have good salt water absorption performance and high-temperature stability, can work for a long time in high-temperature and high-pressure wells, ensure the safe completion of well completion operations, and have broad prospects for large-scale promotion and application.

[0069] The applicant declares that the above is only a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention fall within the scope of protection and disclosure of the present invention.

Claims

1. A pre-crosslinked zwitterionic nanocomposite gel temporary plugging particle and a preparation method thereof, characterized in that: In terms of mass percentage, the raw materials of the pre-crosslinked zwitterionic nanocomposite gel temporary plugging particles include 5wt% to 15wt% of sodium carboxymethylcellulose (CMC) (relative to the mass of acrylic acid, the same below); and also include 5wt% to 15wt% of zwitterionic monomers, wherein the zwitterionic monomers are 2-methacryloyloxyethyl phosphorylcholine (PC), [2-(methacryloyloxy)ethyl]dimethyl-(3-sulfonic acid propyl) ammonium hydroxide (SB), (3-(methacryloylamino)propyl)dimethyl (3- One or more of thiopropyl)ammonium hydroxide inner salt (SPP) and trimethylamine N-oxide (TMAO); 0.1% to 1% nanomaterial, wherein the nanomaterial is a combination of one or both of nano-silica and carboxymethylated nanofibers; 0.1wt% to 1wt% of a crosslinking agent, wherein the crosslinking agent is tetraallyl ammonium chloride (TAAC); a certain mass of acrylic acid (neutralization degree 60% to 90%), wherein the anionic monomer is provided by a neutralized acrylic acid salt, and the raw material used for neutralization is a sodium hydroxide solution or a potassium hydroxide solution; 10 wt% to 30 wt% of a temperature-resistant monomer, wherein the temperature-resistant monomer is 2-acrylamido-2-methylpropanesulfonic acid (AMPS); 0.5 wt% to 1 wt% of an initiator, wherein the initiator is one or more combinations of potassium persulfate (KPS) and ammonium persulfate (APS).

2. The pre-crosslinked zwitterionic nanocomposite gel temporary plugging particles according to claim 1, characterized in that: Measured in percentage by mass, the raw materials of the high-density, high-temperature-resistant zwitterionic gel temporary plugging particles include 5wt% to 15wt% of sodium carboxymethylcellulose (CMC), 5wt% to 15wt% of zwitterionic monomers, 0.1wt% to 1wt% of a cross-linking agent, 0.1% to 1% of a nanomaterial, a certain mass of acrylic acid (neutralization degree 60% to 90%), 10wt% to 30wt% of a temperature-resistant monomer, and 0.5wt% to 1wt% of an initiator.

3. The pre-crosslinked zwitterionic nanocomposite gel temporary plugging particles according to claim 1 or 2, characterized in that: The nano material is one or a combination of nano silicon dioxide (SiO2) and carboxyl nanofibers (CNFs).

4. The pre-crosslinked zwitterionic nanocomposite gel temporary plugging particles according to claims 1 to 3, characterized in that: The zwitterionic monomer is one or more of 2-methacryloyloxyethyl phosphorylcholine (PC), [2-(methacryloyloxy)ethyl]dimethyl-(3-sulfonatepropyl)ammonium hydroxide (SB), (3-(methacryloylamino)propyl)dimethyl(3-thiopropyl)ammonium hydroxide inner salt (SPP), and trimethylamine N-oxide (TMAO).

5. The pre-crosslinked zwitterionic nanocomposite gel temporary plugging particles according to any one of claims 1 to 4, characterized in that: The zwitterionic monomer contains a positively charged ammonium salt ion, a negatively charged sulfonic acid group, phosphoric acid group, carboxylic acid group or oxygen anion; and an olefin double bond group for polymerization onto the gel network.

6. The pre-crosslinked zwitterionic nanocomposite gel temporary plugging particles according to any one of claims 1 to 5, characterized in that: The anionic monomer is provided by the carboxyl group of the neutralized acrylate, and the mass fraction of the anion is determined by the neutralization degree of acrylic acid. The greater the neutralization degree, the greater the anion mass fraction.

7. The pre-crosslinked zwitterionic nanocomposite gel temporary plugging particles according to any one of claims 1 to 6, characterized in that: The cross-linking agent is tetraallyl ammonium chloride (TAAC), which is cross-linked with the monomer main chain through four double bonds, thereby increasing the temperature resistance and strength of the temporary plugging particles. At the same time, its molecule contains a positively charged ammonium salt ion, which can effectively increase the positive charge inside the gel network.

8. The pre-crosslinked zwitterionic nanocomposite gel temporary plugging particles according to any one of claims 1 to 7, characterized in that: The maximum operating temperature of the pre-crosslinked zwitterionic nanocomposite gel temporary plugging particles is 160°C.

9. The pre-crosslinked zwitterionic nanocomposite gel temporary plugging particles according to any one of claims 1 to 8, characterized in that: The pre-crosslinked zwitterionic nanocomposite gel temporary plugging particles can absorb saline and have a maximum density of 1.55 g / cm 3 Potassium formate saturated brine.

10. The pre-crosslinked zwitterionic nanocomposite gel temporary plugging particles according to any one of claims 1 to 9, characterized in that: The pre-crosslinked zwitterionic nanocomposite gel temporary plugging particles have a solid phase mass remaining of 98.51% after aging at 160° C. for 30 days, and have good strength and elasticity.

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