Silicon quantum dot crosslinking agent for jelly-type plugging agent and preparation method thereof

Abstract

The present invention relates to a silicon quantum dot crosslinking agent for a jelly-type plugging agent and a preparation method thereof, belonging to the technical field of oilfield chemistry. Silicon quantum dots are modified by a modifier containing epoxy and siloxane structures to prepare epoxy silicon quantum dots. On this basis, epoxy silicon quantum dots are modified by a modifier containing amino, polyoxyethylene and dicarboxymethylimino structures to prepare silicon quantum dots with multiple functional groups on the surface. Test results show that at low concentrations, the modified silicon quantum dots can well crosslink acrylamide polymers, and the prepared jelly has high strength and good anti-aging ability under high temperature and high salinity conditions. The jelly crosslinking agent prepared by the present invention has broad application prospects in high-temperature oil reservoir profile control and water plugging.

Description

Technical Field

[0001] The invention relates to a silicon quantum dot cross-linking agent for a jelly-type plugging agent and a preparation method thereof, belonging to the technical field of oilfield chemistry. Background Art

[0002] Oil has played a crucial role in the evolution of human civilization and remains a dominant player in the global energy system, with consumption continuing to expand. Therefore, to meet the growing demand for oil, oil production efforts will continue to increase. However, most oil fields in my country are currently in the mid-to-late stage of tertiary oil recovery (TER), characterized by high water content and severe water production. Recovering the remaining oil and improving oil recovery have become key objectives. Profile control and water plugging technology can increase the water flooding sweep volume by blocking high-permeability water flow channels in reservoirs, displacing crude oil from porous media and enhancing oil recovery. Therefore, it has attracted widespread attention as a key production-enhancing measure.

[0003] Profile control and water plugging are primarily categorized into mechanical and chemical plugging. Gel-type plugging agents, as a chemical plugging method, are widely used due to their advantages over mechanical methods, such as low cost, simple construction, and flexible plugging locations. Gel-type plugging agents primarily consist of a polymer and a crosslinker. Currently, three main types of crosslinkers are commonly used in oilfields: metal ion crosslinkers, organic phenolic crosslinkers, and polyethyleneimine crosslinkers. Metal ion crosslinkers react with carboxyl groups in the polymer through coordination, but suffer from rapid crosslinking and poor long-term stability of the crosslinked gel. Organic phenolic crosslinkers react with amide groups in the polymer via prepolymers, but are prone to failure and are susceptible to environmental influences. Polyethyleneimine crosslinkers react with amide groups in the polymer via aminolysis, offering controllable crosslinking time and high crosslinking strength. However, they also suffer from high cost, high dosage, and poor salt tolerance. Silicon quantum dots (SiQDs) are widely used as nanoparticles in oilfield chemistry due to their unique physical properties. Their large surface area and particle size provide more crosslinking sites and a rigid structure. Therefore, developing a SiQD crosslinker with a high amino group to replace polyethyleneimine crosslinkers is crucial for reducing costs and improving the overall performance of jelly. Summary of the Invention

[0004] In view of the deficiencies in the prior art, the present invention provides a silicon quantum dot cross-linking agent for a jelly-type plugging agent and a preparation method thereof. SUMMARY OF THE INVENTION

[0006] This invention modifies silicon quantum dots with modifiers containing epoxy and siloxane structures to prepare epoxy silicon quantum dots. Furthermore, epoxy silicon quantum dots are modified with modifiers containing amino, polyoxyethylene, and dicarboxymethylimino structures to prepare silicon quantum dots with multiple surface functional groups. Test results show that at low concentrations, the modified silicon quantum dots can effectively crosslink acrylamide polymers, resulting in a jelly with high strength and excellent aging resistance in high-temperature and high-salt environments. Detailed Description of the Invention

[0008] The technical solutions of the present invention are as follows.

[0009] A silicon quantum dot crosslinking agent for a jelly-type plugging agent and a preparation method thereof, comprising the following steps:

[0010] (1) Preparation of epoxy silicon quantum dots

[0011] Deionized water and an organic solvent are mixed, silicon quantum dots are added, ultrasonic dispersion is performed, modifier-1 is added, the pH is adjusted to 5-12, the reaction is carried out at 50-80°C for 3-8 hours, the product is filtered and dried to obtain the product; the particle size of the silicon quantum dots is 1-10 nm, and the mass ratio of silicon quantum dots, modifier-1, deionized water, and organic solvent is 1:(0.1-1):(1-3):(20-50);

[0012] (2) Preparation of silicon quantum dot crosslinker

[0013] Add epoxy silicon quantum dots to deionized water, ultrasonically disperse, add modifier-2, modifier-3, and modifier-4 under stirring, the temperature is 30-70°C, react for 6-24 hours, filter and dry the product to obtain; the mass ratio of epoxy silicon quantum dots, modifier-2, modifier-3, modifier-4, and deionized water is 1:(0.1-3):(0.05-0.2):(0.1-1):(10-30).

[0014] According to the present invention, preferably, the average particle size of the silicon quantum dots in step (1) is 1 to 5 nm;

[0015] Preferably, the organic solvent is one of methanol, ethanol, n-propanol, isopropanol, acetone, dioxane, formamide, and N,N-dimethylformamide;

[0016] Preferably, the modifier-1 is one or a mixture of two or more of 3-glycidyloxypropyltrimethoxysilane, 3-glycidyloxypropyltriethoxysilane, 3-glycidyloxypropyldimethoxymethylsilane, 3-glycidyloxypropyldiethoxymethylsilane, 3-glycidyloxypropylmethoxydimethylsilane, and 3-glycidyloxypropylethoxydimethylsilane;

[0017] Preferably, the mass ratio of silicon quantum dots, modifier-1, deionized water, and organic solvent is 1: (0.2-0.6): (1.5-2.5): (30-45);

[0018] Preferably, the pH is 6 to 8, the reaction temperature is 65 to 80° C., and the reaction time is 4 to 8 hours.

[0019] According to the present invention, preferably, the modifier modifier-2 described in step (2) is one or a mixture of two or more of ethylenediamine, propylenediamine, butylenediamine, pentamethylenediamine, hexamethylenediamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, pentaethylenehexamine, hexaethyleneheptamine, and heptaethyleneoctamine;

[0020] Preferably, modifier-3 is

[0021]

[0022] wherein n is 5 to 40, and R is one of -SO3Na, -CH2COONa, -H, -CH3, and -CH2-CH3;

[0023] Preferably, modifier-4 is

[0024]

[0025] Where m is 1 to 6;

[0026] Preferably, the mass ratio of epoxy silicon quantum dots, modifier-2, modifier-3, modifier-4, and deionized water is 1:(0.5-2):(0.1-0.2):(0.2-0.8):(15-30);

[0027] Preferably, the reaction temperature is 40-65° C., and the reaction time is 8-18 h.

[0028] The excellent effects of the present invention are as follows:

[0029] 1. The raw materials of the present invention are easily available, the reaction conditions are mild, and the process is simple and safe.

[0030] 2. Taking advantage of the large surface area and size characteristics of silicon quantum dots, by loading amino groups on the surface, sufficient cross-linking sites and suitable reaction structures are provided, which reduces the product dosage and improves the cross-linking strength.

[0031] 3. By introducing ionic groups and polyethylene oxide segments on the surface of silicon quantum dots, the hydrophilicity of silicon quantum dots is improved, ensuring that they still have good dispersion stability under high temperature and high salt conditions.

[0032] 4. Introduce dicarboxymethylimino structure on the surface of silicon quantum dots, through its interaction with Ca 2+ Mg 2+The interaction between ions reduces the impact of these ions on the polymer and improves the anti-aging properties of the gel.

[0033] 5. Utilize the molecular rigidity of silicon quantum dots and their ability to form a composite structure with the polymer main chain to improve the temperature resistance and anti-aging properties of the gel.

[0034] 6. The product prepared by the present invention is easy to store and meets the requirements of environmental protection. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 This is a schematic diagram of the jelly strength code. DETAILED DESCRIPTION

[0036] Unless otherwise specified, the experimental methods used in the following examples are conventional methods.

[0037] The silicon quantum dots used in the following examples were purchased from Jiangsu Xianfeng Nanomaterial Technology Co., Ltd., the acrylamide polymer was AN-105 produced by SNF, the polyethyleneimine crosslinker was CL-JY produced by Puyang Lutong Petrochemical Co., Ltd., and the other raw materials were conventional commercial products.

[0038] The present invention will be further described below with reference to specific embodiments, but the protection scope of the present invention is not limited thereto.

[0039] Example 1:

[0040] (1) Preparation of epoxy silicon quantum dots

[0041] Mix 10 g of deionized water with 200 g of dioxane, add 6 g of silicon quantum dots with an average particle size of 2 to 3 nm, and disperse them ultrasonically. Add 2.4 g of 3-glycidyloxypropyltrimethoxysilane, adjust the pH to 7, react at 80°C for 4 h, filter, and dry to obtain epoxy silicon quantum dot particles.

[0042] (2) Preparation of silicon quantum dot crosslinker

[0043] 5 g of epoxy silicon quantum dot particles were added to 100 g of deionized water and ultrasonically dispersed. 3 g of diethylenetriamine, 0.5 g of modifier-3, and 2.5 g of modifier-4 were added while stirring and continuously stirred. The mixture was reacted at 50° C. for 8 h. The product was filtered and dried to obtain a silicon quantum dot crosslinker.

[0044] Example 2:

[0045] As described in Example 1, except that the organic solvent in step (1) is ethanol.

[0046] Example 3:

[0047] As described in Example 1, except that the average particle size of the silicon quantum dots in step (1) is 4 to 5 nm.

[0048] Example 4:

[0049] As described in Example 1, the difference is that in step (1), the modifier-1 is 3-glycidyloxypropyldiethoxymethylsilane.

[0050] Example 5:

[0051] As described in Example 1, except that the amount of 3-glycidyloxypropyltrimethoxysilane added in step (1) is 3.6 g.

[0052] Example 6:

[0053] As described in Example 1, the difference is that the amount of silicon quantum dots added in step (1) is 10 g.

[0054] Example 7:

[0055] As described in Example 1, except that in step (1), the reaction temperature is 70° C. and the reaction time is 5 h.

[0056] Example 8:

[0057] As described in Example 1, except that in step (1), the organic solvent is 250 g of n-propanol and the modifier-1 is 3.6 g of 3-glycidyloxypropyldiethoxymethylsilane.

[0058] Example 9:

[0059] As described in Example 1, except that in step (2), the reaction temperature is 60° C. and the reaction time is 10 h.

[0060] Example 10:

[0061] As described in Example 1, the difference is that in step (2), the modifier-2 is ethylenediamine and triethylenetetramine.

[0062] Example 11:

[0063] As described in Example 1, except that the amount of diethylenetriamine added in step (2) is 5 g.

[0064] Example 12:

[0065] As described in Example 1, except that the amount of modifier-3 added in step (2) is 1 g.

[0066] Example 13:

[0067] As described in Example 1, except that the amount of modifier-4 added in step (2) is 3 g.

[0068] Example 14:

[0069] As described in Example 1, the difference is that in step (2), the amount of deionized water added is 75g, the amount of modifier-2 added is 2g of hexamethylenediamine and 2g of triethylenetetramine, and the amount of modifier-3 added is 1g.

[0070] Example 15:

[0071] As described in Example 1, the difference is that in step (2), the amount of epoxy silicon quantum dot particles added is 4 g, the reaction time is 12 h, and the amount of modifier-4 added is 3 g.

[0072] Example 16:

[0073] As described in Example 1, the difference is that in step (2), the amount of modifier-2 is 5g of pentaethylenehexamine, the amount of modifier-3 is 0.7g, and the amount of modifier-4 is 4g.

[0074] Performance evaluation

[0075] Simulated formation water was prepared according to the composition in Table 1. Examples 1 to 16 were added to mineralized water at a concentration of 5,000 mg / L and ultrasonically dispersed for 10 minutes. CL-JY was dissolved in mineralized water at a concentration of 12,000 mg / L, and AN-105 was dissolved in mineralized water at a concentration of 20,000 mg / L to serve as the mother liquor.

[0076] (1) Evaluation of gel strength

[0077] AN-105 and Example 1 or CL-JY were mixed at the target concentration, added to a glass pressure tube, and sealed. The glass pressure tube was placed in a constant-temperature oven at 130°C. The gel formation dynamics were determined by observing the gel flow state over time. The gel system can be divided into nine grades (A to I) based on the gel flow state, suspension state, and tongue-out state. Figure 1 The gel strength is defined as the strength level at which the gel strength in the glass pressure tube no longer changes. The results are shown in Table 2.

[0078] (2) Evaluation of salt resistance and long-term stability

[0079] AN-105 and Example 1 or CL-JY were mixed in a 1:1 volume ratio and placed in a sealed glass pressure tube. The tube was placed in a 130°C oven. The dehydration of the gel was recorded after aging for 30, 90, and 120 days. The dehydration rate of the gel was calculated according to the following formula. The results are shown in Table 3.

[0080]

[0081] Wherein, WR-dehydration rate, %;

[0082] V0-volume of the jelly when gelling, mL;

[0083] V t - Volume of the jelly after aging time t, mL.

[0084] Table 1 Composition of simulated formation water

[0085]

[0086] Table 2 Gel strength of samples with different concentrations

[0087] Sample number <![CDATA[Crosslinker concentration / mg·L -1 > <![CDATA[Polymer concentration / mg·L -1 > Gel strength CL-JY 5000 8000 E CL-JY 6000 8000 F CL-JY 6000 10000 G Example 1 1000 8000 H Example 1 2000 8000 I Example 1 2000 10000 I

[0088] Table 3 Gel strength, salt resistance and long-term stability of different samples

[0089] Sample number Gel strength 30-day dehydration rate (%) 90-day dehydration rate (%) 120-day dehydration rate (%) CL-JY G 8.9 25.7 38.9 Example 1 H 2.2 7.9 13.4 Example 2 H 2.0 7.3 12.5 Example 3 H 2.4 8.1 14.1 Example 4 H 1.9 7.5 11.3 Example 5 I 1.1 6.8 9.4 Example 6 I 1.3 7.2 9.5 Example 7 H 1.5 7.4 10.5 Example 8 I 1.4 7.7 10.1 Example 9 I 0.9 6.7 8.6 Example 10 H 1.6 7.5 11.1 Example 11 I 1.8 7.8 11.9 Example 12 I 1.7 7.3 11.3 Example 13 H 2.2 7.8 13.1 Example 14 I 1.5 7.3 10.9 Example 15 I 0.9 6.7 8.6 Example 16 I 1.1 6.9 9.0

[0090] As shown in Table 2, compared to conventional polyethyleneimine crosslinkers, the crosslinker prepared in the present invention requires less dosage and exhibits high gel strength after crosslinking with acrylamide polymers at low concentrations. As shown in Table 3, all gel systems prepared with the crosslinker prepared in the present invention achieve gel strengths above Grade H. After gelation, the gels exhibit excellent aging resistance, with dehydration rates remaining around 10% after 120 days of aging.

Claims

1. A silicon quantum dot crosslinker for a jelly-type plugging agent and a preparation method thereof, comprising the following steps: (1) Preparation of epoxy silicon quantum dots Deionized water and an organic solvent are mixed, silicon quantum dots are added, ultrasonic dispersion is performed, modifier-1 is added, the pH is adjusted to 5-12, the reaction is carried out at 50-80°C for 3-8 hours, the product is filtered and dried to obtain the product; the particle size of the silicon quantum dots is 1-10 nm, and the mass ratio of silicon quantum dots, modifier-1, deionized water, and organic solvent is 1:(0.1-1):(1-3):(20-50); The organic solvent is one of methanol, ethanol, n-propanol, isopropanol, acetone, dioxane, formamide, and N,N-dimethylformamide; Modifier-1 is one or a mixture of two or more of 3-glycidyloxypropyltrimethoxysilane, 3-glycidyloxypropyltriethoxysilane, 3-glycidyloxypropyldimethoxymethylsilane, 3-glycidyloxypropyldiethoxymethylsilane, 3-glycidyloxypropylmethoxydimethylsilane, and 3-glycidyloxypropylethoxydimethylsilane; (2) Preparation of crosslinking agent Add epoxy silicon quantum dots to deionized water, disperse by ultrasonication, add modifier-2, modifier-3, and modifier-4 under stirring, and react at a temperature of 30 to 70° C. for 6 to 24 hours. Filter and dry the product to obtain the product; the mass ratio of epoxy silicon quantum dots, modifier-2, modifier-3, modifier-4, and deionized water is 1:(0.1 to 3):(0.05 to 0.2):(0.1 to 1):(10 to 30); Modifier-2 is one or a mixture of two or more of ethylenediamine, propylenediamine, butylenediamine, pentamethylenediamine, hexamethylenediamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, pentaethylenehexamine, hexaethyleneheptamine, and heptaethyleneoctamine; Modifier-3 is wherein n is 5 to 40, and R is one of -SO3Na, -CH2COONa, -H, -CH3, and -CH2-CH3; Modifier-4 is Where m is 1 to 6.

2. The silicon quantum dot crosslinking agent for jelly-type plugging agent and the preparation method thereof according to claim 1, characterized in that: The particle size of the silicon quantum dots in step (1) is 1 to 5 nm.

3. The silicon quantum dot crosslinking agent for jelly-type plugging agent and the preparation method thereof according to claim 1, characterized in that: In step (1), the mass ratio of silicon quantum dots, modifier-1, deionized water, and organic solvent is 1: (0.2-0.6): (1.5-2.5): (30-45).

4. The silicon quantum dot crosslinking agent for jelly-type plugging agent and the preparation method thereof according to claim 1, characterized in that: In step (1), the reaction pH is 6-8, the reaction temperature is 65-80° C., and the reaction time is 4-8 h.

5. The silicon quantum dot crosslinking agent for jelly-type plugging agent and the preparation method thereof according to claim 1, characterized in that: In step (2), the mass ratio of epoxy silicon quantum dots, modifier-2, modifier-3, modifier-4, and deionized water is 1:(0.5-2):(0.1-0.2):(0.2-0.8):(15-30).

6. The silicon quantum dot crosslinking agent for jelly-type plugging agent and the preparation method thereof according to claim 1, characterized in that: In step (2), the reaction temperature is 40-65° C., and the reaction time is 8-18 h.

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