Polymer crosslinking system with siloxane structure for deep profile control

Abstract

The application discloses a polymer crosslinking system with a siloxane structure for deep profile control. A preparation method of the polymer crosslinking system for deep profile control comprises the following steps: S1, in an inert atmosphere, under the condition that an initiator exists, performing a polymerization reaction on nonionic monomers, anionic monomers and an epoxy monomer in water to obtain an epoxy polymer; S2, in an inert atmosphere, performing a grafting reaction on polyethyleneimine, an epoxy compound-1 and an epoxy compound-2 in an organic solvent to obtain a silicon-containing polymer; and S3, performing a crosslinking reaction on the epoxy polymer and the silicon-containing polymer in water to obtain the polymer crosslinking system. The polymer crosslinking system has certain delayed crosslinking characteristics and excellent temperature resistance and salt resistance.

Description

Technical Field

[0001] This invention relates to a polymer crosslinking system for deep profile control with a siloxane structure, belonging to the field of oilfield chemical technology. Background Technology

[0002] With the continuous development of the global economy and human society, the demand for oil in all sectors of production and daily life is increasing daily. Therefore, maximizing the production of existing oil fields is of paramount importance. It is estimated that primary and secondary oil recovery can only extract one-third of the formation crude oil, leaving a large amount of residual oil in the formation. Although tertiary oil recovery technologies such as chemical flooding can further improve the recovery rate of oil fields, due to the heterogeneity of the formation, once a water flow advantage channel is formed in the middle and late stages of oil field production, the water production of oil wells increases. This produced water will not only corrode production pipelines and occupy a large amount of construction space, but also lead to persistently high water cut in oil wells, significantly affecting oil production.

[0003] Subsurface crosslinked polymer systems, as important profile control agents, offer advantages such as controllable gelation time, high gel strength, and simple construction processes, leading to their widespread application in oilfields both domestically and internationally. These systems primarily consist of polymers and crosslinking agents, which react to form gel materials with a certain mechanical strength. The most commonly used polymers are acrylamide-based polymers, including partially hydrolyzed polyacrylamide and acrylamide / 2-acrylamido-2-methylpropanesulfonic acid copolymers. The most commonly used crosslinking agents are high-valent heavy metal salts, phenolic resin prepolymers, and polyethyleneimine. High-valent heavy metal ions crosslink through coordination with carboxyl groups on the polymer, but suffer from drawbacks such as rapid crosslinking speed and poor long-term gel stability. Phenolic resin prepolymers crosslink through reaction with amide groups on the polymer, but exhibit drawbacks such as high toxicity and self-crosslinking at high temperatures. Polyethyleneimine offers controllable crosslinking time and good long-term stability, but is characterized by large dosage requirements and high cost. In addition, the above-mentioned crosslinking system utilizes the coordination or covalent interaction between the polymer and the crosslinking agent to form a three-dimensional network structure between molecules. It can generally only be applied to profile control operations in near-wellbore areas and is difficult to maintain good gelling properties after being transported to deeper formations.

[0004] Dynamic covalent bonds are chemical bonds that can reversibly break, form, and recombine under certain external stimuli, possessing the characteristics of "reversibility" and "dynamic nature." Common dynamic covalent bonds include imine bonds, borate ester bonds, siloxane bonds, and acylhydrazone bonds. Using dynamic covalent bonds to construct three-dimensional network structures, when local over-crosslinking occurs, the crosslinked structures can spontaneously diffuse from high-concentration areas to low-concentration areas, eventually forming a homogeneous gel. When the overall crosslinking density is high, dynamic covalent bonds can form a new equilibrium with the dissociated structures, gradually improving the system's flow properties and making the crosslinking more gentle. Therefore, polymer crosslinking systems based on dynamic covalent bonds have better injection and flowability, overcoming the shortcomings of conventional profile control systems such as difficulty in controlling the crosslinking process and dehydration caused by over-crosslinking. Summary of the Invention

[0005] The purpose of this invention is to provide a polymer crosslinking system for deep profile control with a siloxane structure, which has excellent gelation properties, certain delayed crosslinking characteristics, and excellent temperature and salt resistance.

[0006] This invention involves copolymerizing nonionic monomers, anionic monomers, and epoxy monomers in an aqueous solution. By controlling the content and structure of the epoxy monomers, epoxy polymer powder with reactive sites, high molecular weight, and excellent water solubility is prepared. Polyethyleneimine, an epoxy compound containing carboxylic esters, and an epoxy compound containing silicate esters are reacted in an organic solvent. By controlling the types and ratios of the two epoxy compounds, a silicon-containing polymer with controllable silicon content and excellent water solubility is prepared. After the epoxy polymer reacts with the silicon-containing polymer, a polymer crosslinking system is constructed using the condensation reaction between the silicon-containing units on the polymer.

[0007] Specifically, the method for preparing a polymer crosslinking system with a siloxane structure for deep profile control provided by the present invention includes the following steps:

[0008] S1. In an inert atmosphere and in the presence of an initiator, nonionic monomers, anionic monomers, and epoxy monomers undergo a polymerization reaction in water to obtain an epoxy polymer.

[0009] S2. In an inert atmosphere, polyethyleneimine, epoxy compound-1 and epoxy compound-2 are grafted in an organic solvent to obtain a silicon-containing polymer.

[0010] S3. The epoxy polymer and the silicon-containing polymer are cross-linked in water to obtain the product.

[0011] The epoxy monomer is one or a mixture of two or more of epoxy monomer-1, epoxy monomer-2, and epoxy monomer-3, and the structural formulas of epoxy monomer-1, epoxy monomer-2, and epoxy monomer-3 are shown in Formulas I-III, respectively:

[0012]

[0013] In the formula, a is 1 to 10, b is 1 to 6, c is 1 to 6, d is 1 to 6, X is Cl or Br, and R1 and R2 are alkyl chains with 1 to 4 carbon atoms;

[0014] Preferably, a is 1 to 6, b is 1 to 4, c is 1 to 4, and d is 1 to 4.

[0015] In the preparation method of this invention, the conditions for the polymerization reaction in step S1 are as follows:

[0016] pH value 6-11, temperature 0-20℃, time 1-24h;

[0017] Preferably, the pH value is 6-9, the temperature is 0-10℃, and the time is 1-12h.

[0018] In the preparation method of the present invention, in step S1, the mass ratio of the nonionic monomer to the anionic monomer is 1:0.01 to 1, preferably 1:0.05 to 0.8;

[0019] The ratio of the total mass of the nonionic monomer and the anionic monomer to the mass of the epoxy monomer is 1:0.001 to 0.1, preferably 1:0.005 to 0.06;

[0020] The ratio of the total mass of the nonionic monomer, the anionic monomer, and the epoxy monomer to the mass of the water is 1:1 to 20, preferably 1:1.5 to 10;

[0021] The ratio of the total mass of the nonionic monomer, the anionic monomer, the epoxy monomer, and the water to the mass of the azo initiator, the reducing initiator, and the oxidizing initiator is 1:0.00001-0.005:0.00001-0.002:0.00001-0.002, preferably 1:0.00006-0.002:0.00004-0.001:0.00004-0.001;

[0022] The water is preferably deionized water.

[0023] In the preparation method of the present invention, the azo initiator is one or a mixture of two or more of azobisisobutylamidine hydrochloride, azobisisopropylimidazoline hydrochloride and azobiscyanopentanoic acid;

[0024] The reducing initiator is one or a mixture of two or more of sodium sulfite, sodium bisulfite, sodium dithionite and sodium thiosulfate;

[0025] The oxidizing initiator is one or a mixture of two or more of potassium persulfate, ammonium persulfate, sodium persulfate, and hydrogen peroxide.

[0026] In the preparation method of the present invention, in step S2, the epoxy compound-1 is one or a mixture of two or more of methyl glycidyl propionate, ethyl glycidyl propionate, propyl glycidyl propionate, butyl glycidyl propionate, pentyl glycidyl propionate, hexyl glycidyl propionate, heptyl glycidyl propionate and octyl glycidyl propionate, preferably ethyl glycidyl propionate, propyl glycidyl propionate and butyl glycidyl propionate;

[0027] The epoxy compound-2 is one or a mixture of two or more of glycidyl etheroxypropyltriethoxysilane, glycidyl etheroxypropylmethyldiethoxysilane, glycidyl etheroxypropyldimethylethoxysilane, glycidyl etheroxypropyltrimethoxysilane, glycidyl etheroxypropylmethyldimethoxysilane, and glycidyl etheroxypropyldimethylmethoxysilane; preferably, it is glycidyl etheroxypropyltriethoxysilane, glycidyl etheroxypropylmethyldiethoxysilane, glycidyl etheroxypropyltrimethoxysilane, and glycidyl etheroxypropylmethyldimethoxysilane.

[0028] The organic solvent is one or a mixture of two or more of the following: formamide, N,N-dimethylformamide, dimethyl sulfoxide, methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol, and tert-butanol.

[0029] The molecular weight of the polyethyleneimine is 300–100,000 g / mol, preferably 600–50,000 g / mol.

[0030] In the preparation method of the present invention, in step S2, the mass ratio of the polyethyleneimine, the epoxy compound-1 and the epoxy compound-2 is 1:0.05 to 10:0.01 to 2, preferably 1:0.15 to 4:0.03 to 1.

[0031] In the preparation method of the present invention, in step S2, the temperature of the polymerization reaction is 10-70°C and the time is 1-48h, preferably, the temperature is 25-50°C and the time is 3-24h.

[0032] In the preparation method of the present invention, in step S3, the mass ratio of the epoxy polymer to the silicon-containing polymer is 1:0.01-5, preferably 1:0.05-2;

[0033] The ratio of the total mass of the epoxy polymer and the silicon-containing polymer to the mass of the water is 1:20 to 2500, preferably 1:20 to 1000, and more preferably 1:25 to 400.

[0034] The polymer crosslinking system prepared by the method of this invention is also within the scope of protection of this invention.

[0035] The present invention has the following beneficial technical effects:

[0036] 1. The raw materials of this invention are readily available, the reaction conditions are mild, the process is simple and safe, and it can be used for large-scale industrial production.

[0037] 2. This invention forms a dynamic covalent cross-linked structure through siloxane bonds. The reaction process is reversible and mild, and the system has better injectability, enabling deep profile control.

[0038] 3. In epoxy polymers, by controlling the structure and amount of epoxy monomers, it is possible to ensure that the polymer has further reaction sites while also ensuring that the polymer has good water solubility and high molecular weight. In silicon-containing polymers, by reacting in organic solvents and introducing carboxylic acid ester units, it is possible to ensure that the product has good water solubility while minimizing its adsorption capacity in the formation.

[0039] 4. The product of this invention has excellent temperature and salt resistance properties and is applicable to a wide range of oil reservoirs.

[0040] 5. The product of this invention has good compatibility with conventional oil displacement additives.

[0041] 6. The products prepared by this invention are easy to store and meet environmental protection requirements. Attached Figure Description

[0042] Figure 1 This is a diagram illustrating codes for different gel strengths. Detailed Implementation

[0043] Unless otherwise specified, the experimental methods used in the following examples are conventional methods.

[0044] Unless otherwise specified, all materials and reagents used in the following examples are commercially available.

[0045] Example 1:

[0046] (1) Preparation of epoxy polymers

[0047] 100g acrylamide, 25g acrylic acid, 2.5g epoxy monomer-2 (a is 4, b is 2, c is 2, R1 is methyl, X is Br), and 600g deionized water were added to a three-necked glass flask equipped with a stirrer, a nitrogen purging tube, and a thermometer. After stirring until all raw materials were dissolved, nitrogen gas was purged for 30 minutes, the pH was controlled at 7.5, and the temperature was controlled at 5℃. Then, 0.45g azobisisobutylamidine hydrochloride, 0.2g sodium bisulfite, and 0.15g ammonium persulfate were added, and the reaction was carried out for 10 hours. The product was dried and pulverized to obtain the epoxy polymer.

[0048] (2) Preparation of silicon-containing polymers

[0049] 50g of polyethyleneimine (molecular weight 1800g / mol), 20g of ethyl glycidyl propionate, 10g of glycidyl etheroxypropyltrimethoxysilane, and 500g of ethanol were added to a three-necked glass flask equipped with a stirrer, a nitrogen purging tube, and a thermometer. After stirring until all the raw materials were dissolved, nitrogen gas was purged for 10 minutes, the temperature was controlled at 30℃, and the reaction was carried out for 10 hours to obtain a silicon-containing polymer.

[0050] (3) Preparation of polymer crosslinking system

[0051] Add 1g of epoxy polymer to 200g of on-site polymer-mixing water, stir and dissolve, then add 0.75g of silicon-containing polymer, stir and mix evenly to obtain a polymer crosslinking system.

[0052] Example 2:

[0053] As described in Example 1, except that in step (1) the nonionic monomer-1 is 70g of acrylamide and 30g of vinylpyrrolidone.

[0054] Example 3:

[0055] As described in Example 1, except that in step (1), the anionic monomer is 10g of acrylic acid and 30g of 2-acrylamido-2-methylpropanesulfonic acid.

[0056] Example 4:

[0057] As described in Example 1, the difference is that in step (1), the epoxy monomer is 2.5g epoxy monomer-1 (a is 4, b is 2, R1 and R2 are methyl, X is Cl) and 2g epoxy monomer-2 (a is 4, b is 2, c is 2, R1 is methyl, X is Br).

[0058] Example 5:

[0059] As described in Example 1, the difference is that in step (1), the epoxy monomers are 0.5g epoxy monomer-1 (a is 2, b is 1, R1 and R2 are ethyl, X is Cl) and 1.5g epoxy monomer-3 (a is 4, b is 2, c is 2, d is 2, X is Br).

[0060] Example 6:

[0061] As described in Example 1, the difference is that in step (1), the azo initiator is 0.3g of azodicyanovalerate, the reducing initiator is 0.3g of sodium thiosulfate, and the oxidizing initiator is 0.3g of potassium persulfate.

[0062] Example 7:

[0063] As described in Example 1, except that in step (1), the reaction pH is 6.8, the temperature is 2°C, and the time is 8 hours.

[0064] Example 8:

[0065] As described in Example 1, except that the molecular weight of polyethyleneimine in step (2) is 10000 g / mol.

[0066] Example 9:

[0067] As described in Example 1, except that in step (2) the epoxy compound-1 is 12g of butyl epoxypropionate.

[0068] Example 10:

[0069] As described in Example 1, except that in step (2) the epoxy compound-2 is 15g glycidyl etheroxypropylmethyl diethoxysilane and 5g glycidyl etheroxypropyl dimethyl methoxysilane.

[0070] Example 11:

[0071] As described in Example 1, except that the organic solvent in step (2) is 500g methanol and 200g formamide.

[0072] Example 12:

[0073] As described in Example 1, except that the reaction temperature in step (2) is 45°C and the time is 6 hours.

[0074] Example 13:

[0075] As described in Example 1, except that the amount of silicon-containing polymer added in step (3) is 1.1g.

[0076] Example 14:

[0077] As described in Example 1, except that the amount of water added in step (3) is 300g.

[0078] Performance evaluation:

[0079] (1) Sample preparation

[0080] Prepare the polymer crosslinking system according to the composition in Table 1. After the polymer crosslinking system is prepared, add it to the ampoule, seal it, and set it aside for later use.

[0081] (2) Evaluation of gelling performance

[0082] The ampoules were placed in a 90°C constant temperature oven, and the crosslinking dynamics were determined by observing the changes in the flow state of the crosslinking system over time. Based on different flow states, suspension states, and tongue-out states, the system can be divided into 9 levels (A to I), such as... Figure 1As shown. The time when the system strength in the ampoule reaches grade D is recorded as the initial gelation time, and the time when the system strength no longer changes under high temperature conditions is recorded as the gelation time. The system strength at this point is recorded as the gelation strength of the system.

[0083] (3) Evaluation of temperature resistance

[0084] After gelation, the ampoules were placed in a 90°C constant temperature chamber, and the amount of water dehydrated was recorded at different aging times. The dehydration rate of the crosslinked system was calculated according to the following formula.

[0085]

[0086] In the formula, WR represents the dehydration rate, in percentages (%).

[0087] V0 - Volume of the crosslinked system during gelation, in mL;

[0088] V t - Volume of the crosslinked system after aging time t, in mL.

[0089] As can be seen from Table 2, the epoxy polymer and silicon-containing polymer prepared by this invention have good reaction gelation effect; during the gelation process, the crosslinking reaction between polymers has a certain delay property, which is suitable for profile control operations in deep formations; the crosslinking system has excellent anti-aging properties, with a dehydration rate of less than 10% after 120 days of aging, which meets the needs of oilfield sites.

[0090] Table 1 Composition of simulated mineralized water

[0091]

[0092] Table 2. Gel formation and anti-aging properties of different samples

[0093]

[0094]

Claims

1. A method for preparing a polymer crosslinking system for deep profile control with a siloxane structure, comprising the following steps: S1. In an inert atmosphere and in the presence of an initiator, nonionic monomers, anionic monomers, and epoxy monomers undergo a polymerization reaction in water to obtain an epoxy polymer. The nonionic monomer is acrylamide and / or vinylpyrrolidone; The anionic monomer is acrylic acid and / or 2-acrylamido-2-methylpropanesulfonic acid; The mass ratio of the nonionic monomer to the anionic monomer is 1:0.01 to 1; The ratio of the total mass of the nonionic monomer and the anionic monomer to the mass of the epoxy monomer is 1:0.001 to 0.1; The ratio of the total mass of the nonionic monomer, the anionic monomer, and the epoxy monomer to the mass of the water is 1:1 to 20; The ratio of the total mass of the nonionic monomer, the anionic monomer, the epoxy monomer, and the water to the mass of the azo initiator, the reducing initiator, and the oxidizing initiator is 1:0.00001~0.005:0.00001~0.002:0.00001~0.002; S2. In an inert atmosphere, polyethyleneimine, epoxy compound-1 and epoxy compound-2 are grafted in an organic solvent to obtain a silicon-containing polymer. The epoxy compound-1 is one or a mixture of two or more of the following: methyl glycidate, ethyl glycidate, propyl glycidate, butyl glycidate, pentyl glycidate, hexyl glycidate, heptyl glycidate, and octyl glycidate. The epoxy compound-2 is one or a mixture of two or more of the following: glycidyl etheroxypropyltriethoxysilane, glycidyl etheroxypropylmethyldiethoxysilane, glycidyl etheroxypropyldimethylethoxysilane, glycidyl etheroxypropyltrimethoxysilane, glycidyl etheroxypropylmethyldimethoxysilane, and glycidyl etheroxypropyldimethylmethoxysilane. The mass ratio of the polyethyleneimine, the epoxy compound-1, and the epoxy compound-2 is 1:0.05 to 10:0.01 to 2. S3. The epoxy polymer and the silicon-containing polymer are cross-linked in water to obtain the product. The epoxy monomer is one or a mixture of two or more of epoxy monomer-1, epoxy monomer-2, and epoxy monomer-3, and the structural formulas of epoxy monomer-1, epoxy monomer-2, and epoxy monomer-3 are shown in Formulas I-III, respectively: In the formula, a The range is 1 to 10. b The range is 1 to 6. c The range is 1 to 6. d The range is 1 to 6. X It is Cl or Br, and R1 and R2 are alkyl chains with 1 to 4 carbon atoms.

2. The preparation method according to claim 1, characterized in that: In step S1, the conditions for the polymerization reaction are as follows: pH value 6–11, temperature 0–20℃, time 1–24 h.

3. The preparation method according to claim 2, characterized in that: The azo initiator is one or a mixture of two or more of azobisisobutylamidine hydrochloride, azobisisopropylimidazoline hydrochloride, and azobiscyanopentanoic acid; The reducing initiator is one or a mixture of two or more of sodium sulfite, sodium bisulfite, sodium dithionite and sodium thiosulfate; The oxidizing initiator is one or a mixture of two or more of potassium persulfate, ammonium persulfate, sodium persulfate, and hydrogen peroxide.

4. The preparation method according to any one of claims 1-3, characterized in that: In step S2, the organic solvent is one or a mixture of two or more of the following: formamide, N,N-dimethylformamide, dimethyl sulfoxide, methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol, and tert-butanol. The molecular weight of the polyethyleneimine is 300–100,000 g / mol.

5. The preparation method according to any one of claims 1-3, characterized in that: In step S2, the polymerization reaction is carried out at a temperature of 10–70°C for a time of 1–48 h.

6. The preparation method according to any one of claims 1-3, characterized in that: In step S3, the mass ratio of the epoxy polymer to the silicon-containing polymer is 1:0.01 to 5; The ratio of the total mass of the epoxy polymer and the silicon-containing polymer to the mass of the water is 1:20 to 2500.

7. The polymer crosslinking system prepared by the method of any one of claims 1-6.

8. The application of the polymer crosslinking system of claim 7 as a deep profile control agent for high-temperature and high-salinity oil reservoirs or in the deep profile control of high-temperature and high-salinity oil reservoirs.

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