Preparation method, product and application of polymer gel particles

Abstract

The invention relates to the technical field of oilfield chemistry and high-temperature and high-salt oil reservoir profile control and water shutoff, in particular to a preparation method, a product and application of polymer gel particles with enhanced mechanical properties through a double-crosslinking domain structure. The preparation method comprises the following steps: dissolving a monomer, a cross-linking agent and an initiator in water, and carrying out free radical polymerization reaction to obtain polymer hydrogel; and drying the polymer hydrogel to obtain the polymer gel particles, the monomers comprise acrylamide, acrylic acid, N-(hydroxymethyl) acrylamide and 2-acrylamide-2-methylpropanesulfonic acid; the cross-linking agent comprises methacrylic acid esterified lignosulfonate and / or N, N '-methylene bisacrylamide. The preparation method disclosed by the invention is simple, and the polymer gel particles prepared by utilizing the method have a unique double-crosslinking domain structure, have excellent mechanical properties and excellent temperature resistance and salt tolerance, and are suitable for profile control and water shutoff of high-temperature and high-salt oil reservoirs.

Description

Technical Field

[0001] The present invention relates to the technical fields of oilfield chemistry and high-temperature and high-salinity oil reservoir profile control and water plugging, and in particular to a preparation method, product and application of polymer gel particles with enhanced mechanical properties through a double cross-linked domain structure. Background Art

[0002] As oilfield development deepens, long-term water injection operations lead to the formation of high-permeability channels in the reservoir, and the water-oil ratio gradually increases, increasing the cost of post-processing and separation. At the same time, water flooding will lead to uneven distribution of fluids in the reservoir, resulting in low water injection efficiency or even ineffective circulation, thereby reducing oil recovery efficiency. To solve this problem, pre-cross-linked gel particles, as an effective profile control and water plugging material, can absorb water and swell in the reservoir, plug high permeability areas, and promote water flow to low permeability areas, thereby increasing crude oil recovery.

[0003] Pre-crosslinked gel particles are a three-dimensional cross-linked polymer network system synthesized indoors. They can be injected into oil reservoirs to plug high-permeability channels, thereby improving water drive sweep efficiency and recovery. However, with the gradual deepening of exploration and development, reservoir conditions are becoming increasingly complex, especially in high-temperature and high-salinity reservoirs. Traditional pre-crosslinked gel particles often have insufficient temperature and salt resistance and low mechanical properties, resulting in reduced plugging effects, making it difficult to meet the needs of profile control and water plugging in harsh environments. These particles have poor stability under high-temperature and high-salinity conditions, insufficient mechanical properties, and are prone to failure, resulting in the profile control and water plugging effects failing to meet expectations.

[0004] Therefore, providing a polymer gel particle with good mechanical properties and high temperature and high salt resistance to improve the shortcomings of traditional pre-cross-linked gel particles under complex reservoir conditions is of great significance to the fields of oilfield chemistry and high temperature and high salt reservoir profile control and water plugging technology. Summary of the invention

[0005] Based on the above content, the present invention provides a preparation method, product and application of polymer gel particles with enhanced mechanical properties through a double cross-linked domain structure, so as to overcome the problems of insufficient mechanical properties, poor stability in high temperature and high salt environment and easy failure of plugging in existing pre-cross-linked gel particles.

[0006] To achieve the above object, the present invention provides the following solutions:

[0007] One of the technical solutions of the present invention is a method for preparing polymer gel particles, comprising the following steps:

[0008] Dissolving the monomer, the crosslinking agent and the initiator in water to carry out a free radical polymerization reaction to obtain a polymer hydrogel; drying the polymer hydrogel to obtain the polymer gel particles;

[0009] The monomers include acrylamide (AM), acrylic acid (AA), N-(hydroxymethyl)acrylamide (NMA) and 2-acrylamide-2-methylpropanesulfonic acid (AMPS);

[0010] The crosslinking agents include methacrylated lignin sulfonate (MLS) and N,N'-methylenebisacrylamide (MBAA).

[0011] The second technical solution of the present invention is a polymer gel particle prepared according to the above-mentioned preparation method.

[0012] A third technical solution of the present invention is the application of the above-mentioned polymer gel particles in profile control and water plugging in high-temperature and high-salinity oil reservoirs.

[0013] A fourth technical solution of the present invention is a profile control and water plugging agent suitable for high-temperature and high-salinity oil reservoirs, the raw materials of which include the above-mentioned polymer gel particles.

[0014] The present invention discloses the following technical effects:

[0015] The polymer gel particles of the present invention have a unique double cross-linked domain structure and excellent mechanical properties, including excellent elastic modulus (G'=48478Pa), high strength (0.14MPa) and excellent toughness (2.96MJ·m -3 ).

[0016] The preparation process of the polymer gel particles with double cross-linked domain structure of the present invention is simpler, and the particles have excellent temperature resistance and salt resistance. 4 The gel swelling ratio can reach 3.45 under the conditions of (100 mg / L) solution and temperature of 140 °C.

[0017] After the polymer gel particles with a double cross-linked domain structure of the present invention are injected into the formation as a profile control and water plugging agent, the gel particles can block water in the high permeability area, improve the heterogeneity of the formation, increase the water drive swept area, and thus achieve the effect of improving the recovery rate. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0019] Figure 1 The figure is a schematic diagram of the process flow for preparing polymer gel particles having a double cross-linked domain structure according to the present invention.

[0020] Figure 2This is the SEM image of the PAANA-L1B1 hydrogel in Example 2.

[0021] Figure 3 FT-IR graphs of the PAANA-L1B1 hydrogel in Example 2, the PAANA-L1B0 hydrogel in Comparative Example 1, and the PAANA-L0B1 hydrogel in Comparative Example 2.

[0022] Figure 4 This is a diagram of the plugging performance of PAANA-L1B1 gel particles in Example 2. DETAILED DESCRIPTION

[0023] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as limiting the present invention, but should be understood as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0024] It should be understood that the terms described in the present invention are only for describing a particular embodiment and are not intended to limit the present invention. In addition, for the numerical range in the present invention, it should be understood that each intermediate value between the upper and lower limits of the scope is also specifically disclosed. The intermediate value in any stated value or stated range, and each smaller range between any other stated value or intermediate value in the described range is also included in the present invention. The upper and lower limits of these smaller ranges can be independently included or excluded in the scope.

[0025] Unless otherwise indicated, all technical and scientific terms used herein have the same meanings as those generally understood by those skilled in the art. Although the present invention describes only preferred methods and materials, any methods and materials similar or equivalent to those described herein may also be used in the implementation or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials associated with the documents. In the event of a conflict with any incorporated document, the content of this specification shall prevail.

[0026] It will be apparent to those skilled in the art that various modifications and variations may be made to the specific embodiments of the present invention description without departing from the scope or spirit of the present invention. Other embodiments derived from the present invention description will be apparent to the skilled artisan. The present invention description and examples are exemplary only.

[0027] The words “include,” “including,” “have,” “contain,” etc. used in this document are open-ended terms, meaning including but not limited to.

[0028] The "room temperature" described in the present invention, unless otherwise specified, refers to 20-30°C.

[0029] To overcome this shortcoming, the present invention proposes polymer gel particles based on a double cross-linked domain network structure. By introducing two cross-linking agents (MLS and MBAA), a double cross-linked structure is formed, which not only ensures the flexibility and water absorption of the hydrogel, but also significantly improves its mechanical strength and high temperature and high salt resistance. The double cross-linked domain network structure effectively enhances the stability of the hydrogel in the high temperature and high salt reservoir environment, so that it can maintain an excellent plugging effect in complex reservoirs, thereby greatly improving the recovery rate of the reservoir. Therefore, the polymer gel particles with a double cross-linked domain structure, by virtue of their excellent mechanical properties and high temperature and high salt resistance, significantly improve the deficiencies of traditional pre-cross-linked gel particles under complex reservoir conditions, and become an ideal material for profile control and water plugging in high temperature and high salt composite reservoirs, and have broad application prospects.

[0030] The first aspect of the present invention provides a method for preparing polymer gel particles, comprising the following steps:

[0031] Dissolving the monomer, the crosslinking agent and the initiator in water to carry out a free radical polymerization reaction to obtain a polymer hydrogel; drying the polymer hydrogel to obtain the polymer gel particles;

[0032] The monomers include acrylamide (AM), acrylic acid (AA), N-(hydroxymethyl)acrylamide (NMA) and 2-acrylamide-2-methylpropanesulfonic acid (AMPS);

[0033] The crosslinking agent includes methacrylated lignin sulfonate (MLS) and / or N,N'-methylenebisacrylamide (MBAA).

[0034] In a specific embodiment, the monomer may be first dissolved in water, and nitrogen may be passed through to remove air from the solution. Then, an initiator may be added to the solution, and nitrogen may be passed through the solution while stirring, and then a free radical polymerization reaction may be carried out.

[0035] In a preferred embodiment of the present invention, the concentration of the monomers in the mixed solution for free radical polymerization is 15 wt% to 30 wt%.

[0036] In a preferred embodiment of the present invention, the initiator is at least one of potassium persulfate, ammonium persulfate and azobisisobutylimidazoline hydrochloride.

[0037] In a preferred embodiment of the present invention, the mass ratio of acrylamide, acrylic acid, N-(hydroxymethyl)acrylamide and 2-acrylamide-2-methylpropanesulfonic acid is 5:3:1:1.

[0038] In a preferred embodiment of the present invention, the added amount of the cross-linking agent is 1%-4% of the mass of the monomer; when the cross-linking agent is a mixture of methacrylated lignin sulfonate and N,N'-methylenebisacrylamide, the mass ratio of methacrylated lignin sulfonate to N,N'-methylenebisacrylamide is (1-3):1.

[0039] When the cross-linking agent is a mixture of MLS and MBAA, the mass ratio of the two, MLS:MBAA, is (1-3):1, which can be 1:1, 2:1 or 3:1, and the amount of MBAA added in the cross-linking agent is 1wt% of the monomer mass; when the cross-linking agent is a single MLS or a single MBAA, the amount of the cross-linking agent MLS or MBAA added is 1wt% of the monomer mass respectively.

[0040] In a preferred embodiment of the present invention, the cross-linking agent is a mixture of MLS:MBAA in a mass ratio of 1:1, and the added amount of the cross-linking agent is 2% of the mass of the monomer.

[0041] In a preferred embodiment of the present invention, the added amount of the initiator is 1% of the mass of the monomer.

[0042] In a preferred embodiment of the present invention, the temperature of the free radical polymerization reaction is 55-75° C., and the time is 3-6 hours; the temperature of the drying is 60° C., and the time is 12 hours.

[0043] After the drying, the method further comprises the step of crushing and grinding to pass through a 100-mesh sieve.

[0044] The second aspect of the present invention provides polymer gel particles prepared according to the above preparation method.

[0045] The third aspect of the present invention provides the use of the above-mentioned polymer gel particles in profile control and water plugging in high-temperature and high-salinity oil reservoirs.

[0046] A fourth aspect of the present invention provides a profile control and water plugging agent suitable for high-temperature and high-salinity oil reservoirs, the raw material of which includes the above-mentioned polymer gel particles.

[0047] The present invention proposes a novel polymer gel particle with enhanced mechanical properties through a double cross-linked domain structure, which has significant advantages in profile control, water plugging and improving oil field recovery. The gel particle is prepared by a one-pot method, wherein methacrylated lignin sulfonate (MLS) is mixed with N,N'-methylenebisacrylamide (MBAA) cross-linking agent and monomers, and a polymer hydrogel (PAANA-L x B y), and then dried, crushed, ground and screened to obtain uniform gel particles. MLS, as a macromolecular crosslinking agent, can form low-density crosslinking points in the hydrogel network, and then construct a three-dimensional network structure with loose and flexible characteristics, thereby giving the hydrogel good toughness, water absorption and swelling, and effectively improving its fracture resistance and ductility. The small molecule crosslinking agent MBAA, through its structure with multiple crosslinking sites, prompts the hydrogel to form a high-density crosslinked network, significantly enhancing the mechanical strength, heat resistance and stability of the hydrogel in a complex reservoir environment. The double crosslinking domain structure enables the polymer gel particles to maintain high mechanical strength and stability in a high-temperature and high-salt environment, effectively solving the problems of poor stability and insufficient mechanical properties of traditional pre-crosslinked gel particles. The preparation method is simple in process, can maintain good plugging effect and water drive control performance under complex reservoir conditions, significantly improves the recovery rate of complex reservoirs, and has important application value.

[0048] The technical solutions described in the present invention, unless otherwise specified, are all conventional solutions in the art, and the reagents or raw materials used, unless otherwise specified, are purchased from commercial channels or have been disclosed.

[0049] The preparation steps of methacrylated lignin sulfonate (MLS) used in the embodiment of the present invention are as follows:

[0050] First, sodium lignin sulfonate (SLS, 3.5 g), methacrylic anhydride (MAA, 8.5 g) and N,N-diisopropylethylamine (DIPEA, 1 g) were dissolved in 60 mL of deionized water. The solution was heated to 70 ° C and stirred for 24 h. After cooling to room temperature, the reaction mixture was poured into ethanol and washed three times with excess ethanol to obtain a brown precipitate. The precipitate was then freeze-dried in a vacuum freeze dryer to obtain methacrylated lignin sulfonate, which was then stored in a refrigerator for later use.

[0051] The test methods involved in the present invention: the swelling rate test refers to the GB / T 1033.1-2008 standard, the rheological property test refers to the ISO 11443:2006 standard, and the uniaxial compression property test refers to the GB / T 1041-2008 standard.

[0052] The technical solutions provided by the present invention are described in detail below in conjunction with the embodiments, but they should not be construed as limiting the protection scope of the present invention.

[0053] Example 1

[0054] A method for preparing polymer gel particles having a double cross-linked domain structure, comprising the following steps:

[0055] Step 1: Dissolve 5 g of acrylamide, 3 g of acrylic acid, 1 g of N-(hydroxymethyl)acrylamide and 1 g of 2-acrylamide-2-methylpropanesulfonic acid in 40 mL of deionized water and stir with a magnetic stirrer to completely dissolve. Then add 0.1 g of methacrylate lignin sulfonate and 0.1 g of N,N'-methylenebisacrylamide to the mixed solution, and continuously inject nitrogen for 15 minutes during stirring to remove oxygen from the mixed solution.

[0056] Step 2: Then add 0.1 g of potassium persulfate to the above mixed solution and continue stirring until the initiator is completely dissolved, while continuously passing nitrogen into the mixed solution for 15 minutes.

[0057] Step 3: Pour the completely dissolved mixed solution into a glass bottle, transfer it to a 55°C forced air drying oven to react for 4 hours to obtain a polymer hydrogel, then dry it in a 60°C oven for 12 hours, and then crush and grind it through a 100-mesh sieve to obtain polymer gel particles with a double cross-linked domain structure.

[0058] The process flow diagram of preparing polymer gel particles with a double cross-linked domain structure in this embodiment is as follows: Figure 1 shown.

[0059] Example 2

[0060] The only difference from Example 1 is that the reaction temperature in step 3 is 65° C.; the remaining steps and parameters are the same as those in Example 1. The polymer hydrogel prepared in this example is labeled PAANA-L1B1.

[0061] Figure 2 The SEM images of the PAANA-L1B1 hydrogel prepared in Example 2 at different magnifications; Figure 2 It can be seen that the interior of the gel presents an ordered porous structure, which helps to regulate fluid flow, thereby increasing the oil-water ratio and improving the recovery factor. Figure 2 (b) is a high-magnification magnified image of the PAANA-L1B1 hydrogel, from which it can be observed that the internal network of the gel is arranged in an orderly manner and evenly distributed.

[0062] Figure 3 FT-IR image of PAANA-L1B1 hydrogel prepared in Example 2; Figure 3 It can be seen that 2934cm -1 The peak at 1620cm corresponds to the symmetric stretching vibration of the -CH2 group. -1 、1181cm -1 and 1038cm -1The peaks at 1660 cm-1 are attributed to the vinyl C=C stretching vibration, the symmetric stretching vibration of S=O, and the CO stretching vibration. The peak of -C=O stretching vibration appears at 1660 cm-1. -1 With PAANA-L x B y As the MLS content in the hydrogel increases, the peak areas of S=O, -C=O and CO groups also increase. The FTIR spectrum of PAAN-L0B1 is similar to that of other PAAN-L x B y Comparison of the FTIR spectra of the hydrogels (PAAN-L1B0, PAAN-L1B1) showed significant differences between the two spectra. In addition, the changes in the characteristic absorption peaks (such as vinyl and carbonyl) indicated that PAAN-L x B y MLS and MBA cross-linking mechanisms exist in the hydrogel.

[0063] Note: To simplify understanding, the prepared hydrogel is denoted as PAANA-L x B y , where L and B represent the cross-linking agents MLS and MBAA, respectively. x and y represent the mass ratio of MLS and MBAA.

[0064] Example 3

[0065] The only difference from Example 1 is that the reaction temperature in step 3 is 75° C.; the remaining steps and parameters are the same as in Example 1.

[0066] Example 4

[0067] The only difference from Example 2 is that the amount of methacrylated lignin sulfonate added in step 1 is 0.2 g; the remaining steps and parameters are the same as those in Example 1.

[0068] Example 5

[0069] The only difference from Example 2 is that the amount of methacrylated lignin sulfonate added in step 1 is 0.3 g; the remaining steps and parameters are the same as those in Example 1.

[0070] Comparative Example 1

[0071] The only difference from Example 2 is that the addition of N,N'-methylenebisacrylamide in step 1 is omitted; the remaining steps and parameters are the same as those in Example 2. The prepared polymer hydrogel is labeled as PAAN-L1B0.

[0072] Comparative Example 2

[0073] The only difference from Example 2 is that the addition of methacrylated lignin sulfonate in step 1 is omitted; the remaining steps and parameters are the same as those in Example 2. The obtained polymer hydrogel is labeled as PAAN-LOB1.

[0074] The test results are shown in Table 1:

[0075] Table 1

[0076]

[0077]

[0078] Plugging performance test:

[0079] The experiment used a natural core with a diameter of 2.51 cm and a length of 5.02 cm for fracture design, and created a rough fracture surface through the Brazilian splitting test. In order to produce a 0.5 mm crack in the core and avoid closure, stainless steel plates were clamped on both sides of the core, and holes were drilled at the entrance to improve injection capacity. The experimental steps are as follows:

[0080] (1) Place the broken core in a holder and load the surrounding pressure to keep it 3 MPa higher than the injection pressure. Inject 2% NaCl solution at a rate of 0.5 mL / min until the injection pressure and flow rate are stable. Calculate the permeability before plugging (K) using Darcy's law. b ).

[0081] (2) Inject 2% PAANA-L1B1 gel particle solution (carried by guar gum) at the same injection rate until the injection pressure stabilizes and particles are observed to flow out from the outlet, then stop injecting. Raise the core temperature to 80°C and age for 24 hours.

[0082] (3) Re-inject 2% NaCl solution at an injection rate of 0.5 mL / min until the pressure and flow rate are stable and gel particles are observed to flow out of the outlet, then stop the process;

[0083] (4) Then the core temperature was raised to 120°C and aged for 24 h. A 2% NaCl solution was injected for the third time at a rate of 0.5 mL / min, and the permeability after plugging (K a ). The maximum pressure reached in each process was recorded as the breakthrough pressure, and the plugging effect of the gel particles was evaluated by the breakthrough pressure gradient and the plugging efficiency (E).

[0084] E=(K b -K a ) / K b ×100 (1)

[0085] The blocking performance of the PAANA-L1B1 gel particles in Example 2 was tested, and the results were as follows: Figure 4To evaluate the sealing effect of reservoir fractures, 0.5 mm steel plates were added to the natural cores to simulate fractures and filled with 100 mesh PAANA-L1B1 gel particles. Figure 4 It shows that when 2wt% NaCl solution is injected for the first time, the cracks cause high permeability and stable pressure changes. After the injection of PAANA-L1B1 gel particles, the injection pressure rises rapidly to a maximum value (194psi / ft), and then as the particles flow out, the pressure drops and stabilizes at 168psi / ft. The core temperature is raised to 80°C, and the gel particles expand further. After the second injection of NaCl solution, the breakthrough pressure gradient is 260psi / ft, and the stable pressure gradient is 195psi / ft. The core temperature is raised to 120°C again, and after the third injection of NaCl solution, the breakthrough pressure gradient is 235psi / ft, and the stable pressure gradient is 179psi / ft. After the injection of PAANA-L1B1 gel particles, the plugging efficiency is 96.8%, the plugging rate is increased to 98.1% after the second injection of NaCl solution, and the plugging rate is increased to 97.2% after the third injection of NaCl solution. The results show that the PAANA-L1B1 gel particles prepared in Example 2 can effectively plug the high permeability layer and expand at high temperature to form a stable plug.

[0086] The embodiments described above are only descriptions of the preferred modes of the present invention, and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should all fall within the protection scope determined by the claims of the present invention.

Claims

1. A method for preparing polymer gel particles, characterized in that: The following steps are involved: Dissolving the monomer, the crosslinking agent and the initiator in water to carry out a free radical polymerization reaction to obtain a polymer hydrogel; drying the polymer hydrogel to obtain the polymer gel particles; The monomers include acrylamide, acrylic acid, N-(hydroxymethyl)acrylamide and 2-acrylamide-2-methylpropanesulfonic acid; The crosslinking agent includes methacrylated lignin sulfonate and N,N'-methylenebisacrylamide.

2. The preparation method according to claim 1, characterized in that: The initiator is at least one of potassium persulfate, ammonium persulfate and azobisisobutylimidazoline hydrochloride.

3. The preparation method according to claim 1, characterized in that: The mass ratio of acrylamide, acrylic acid, N-(hydroxymethyl)acrylamide and 2-acrylamide-2-methylpropanesulfonic acid is 5:3:1:

1.

4. The preparation method according to claim 1, characterized in that: The added amount of the crosslinking agent is 1%-4% of the mass of the monomer; when the crosslinking agent is a mixture of methacrylate lignin sulfonate and N,N'-methylenebisacrylamide, the mass ratio of methacrylate lignin sulfonate to N,N'-methylenebisacrylamide is (1-3):

1.

5. The preparation method according to claim 1, characterized in that: The added amount of the initiator is 1% of the mass of the monomer.

6. The preparation method according to claim 1, characterized in that: The temperature of the free radical polymerization reaction is 55-75° C., and the time is 3-6 hours; the temperature of the drying is 60° C., and the time is 12 hours.

7. The polymer gel particles prepared according to the preparation method according to any one of claims 1 to 6.

8. Use of the polymer gel particles according to claim 7 in profile control and water plugging in high-temperature and high-salinity oil reservoirs.

9. A profile control and water plugging agent suitable for high-temperature and high-salinity oil reservoirs, characterized in that: The raw material comprises the polymer gel particles described in claim 7.

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