High-strength large-deformation double-network structure gel profile control agent as well as preparation method and application thereof

Abstract

The invention provides a high-strength large-deformation double-network structure gel profile control agent as well as a preparation method and application thereof. The preparation method of the gel profile control agent comprises the following steps: adding bentonite into water, then adding acrylamide, carrying out ultrasonic treatment until the mixture is uniformly dispersed, then adding a sodium alginate aqueous solution, then adding an initiator, uniformly stirring, and carrying out a reaction to obtain hydrogel with a single network structure; soaking the obtained hydrogel with the single-network structure in an aqueous solution of ferric trichloride to obtain hydrogel with a high-strength large-deformation double-network structure; and then cutting, drying, crushing and screening to obtain the product. The gel particle profile control agent disclosed by the invention can be used for effectively plugging a high-permeability layer to achieve the purposes of improving the water absorption profile and increasing the swept volume, so that the water absorption profile control requirements under different oil reservoir temperature conditions are met.

Description

Technical Field

[0001] The invention relates to a high-strength large-deformation double-network structure gel profile control agent and a preparation method and application thereof, belonging to the technical field of oil and gas field development. Background Art

[0002] In recent years, with the continuous development of water injection oil fields, the formation heterogeneity has become more and more serious. The injected water is prone to crossflow along the large pores and high permeability layers between the oil and water wells, which greatly reduces the volume of injected water swept, and ultimately leads to a significant decrease in water drive efficiency and higher and higher water content in the oil wells. Profile control technology is a technology specifically designed for the ineffective circulation of injected water. After the profile control agent enters the injection well, the high permeability formation will be blocked first, and then the seepage direction of the injected water in the original formation will change, resulting in an expansion of the swept volume, and finally achieving the effect of improving the water drive oil recovery rate.

[0003] At present, the main profile control and water plugging systems are polymer gel and pre-crosslinked particles. Among them, although polymer gel profile control agents have a wide range of sources and simple preparation, they have problems such as high injection viscosity, low underground gelation rate, serious chromatographic separation phenomenon, poor temperature resistance and salt resistance, which affect the field application effect. Pre-crosslinked particles are prepared on the ground, which effectively avoids the problems of no gelation underground, poor temperature resistance and salt resistance, and have good mechanical properties. The particle size selection range is wide and can be applied to reservoir conditions with different permeabilities. For example: Chinese patent document CN110903816A discloses a heat-resistant, salt-resistant, high-expansion plugging agent for plugging large cracks and a preparation method thereof. The agent system is composed of the following components in mass percentage: 6-10% main agent, 0.6-1% cross-linking agent, 0.006-0.01% initiator, 6-14% additives, and the rest is water; the preparation method provided by the present invention comprises the following steps: adding montmorillonite to water to prepare a montmorillonite dispersion system; adding the main agent, the cross-linking agent, and the initiator to the montmorillonite dispersion system to prepare a main agent solution; placing the main agent solution in a 90-120°C oven to gelate it for 9-48 hours.

[0004] At present, in the oil fields in the late stage of water flooding development, the interlayer water drive advantage channel is obvious, the interlayer contradiction is prominent, the water content remains high, and the oil production is reduced. For such oil reservoirs, it is of great significance to develop a gel profile control agent with high strength and excellent plugging ability to improve oil recovery. Summary of the invention

[0005] In view of the shortcomings of the prior art, the present invention provides a high-strength large-deformation double-network structure gel profile control agent and a preparation method and application thereof. The present invention forms a first network by hydrogen bonding cross-linking between sodium bentonite and polyacrylamide, and forms a second network by trivalent iron ions (Fe 3+ ) and sodium alginate to form a second network, and the sodium-based clay-polyacrylamide / Fe3+ -Sodium alginate double network structure physical hydrogel, the colloid is cut, dried, crushed and sieved to prepare a gel particle profile control agent. The gel particle profile control agent of the present invention can effectively block the high permeability layer, achieve the purpose of improving the water absorption profile and increasing the swept volume, thereby meeting the water absorption profile control needs under different reservoir temperature conditions.

[0006] The technical solution of the present invention is as follows:

[0007] A method for preparing a high-strength, large-deformation double-network structure gel profile control agent comprises the following steps:

[0008] (1) adding bentonite to water, then adding acrylamide, and after ultrasonication until uniform dispersion, adding sodium alginate aqueous solution, and then adding an initiator, stirring evenly, reacting to obtain a single network structure hydrogel;

[0009] (2) soaking the single network structure hydrogel obtained in step (1) in an aqueous solution of ferric chloride to obtain a high-strength and large-deformation double network structure hydrogel; and then cutting, drying, crushing, and screening to obtain a high-strength and large-deformation double network structure gel profile control agent.

[0010] Preferably according to the present invention, the bentonite in step (1) is sodium bentonite, and the ratio of the mass of the bentonite to the volume of water is 1g:15-35mL.

[0011] Preferably according to the present invention, the mass ratio of bentonite to acrylamide in step (1) is 0.08-0.25:1, more preferably 0.1-0.2:1.

[0012] Preferably, according to the present invention, the mass concentration of the sodium alginate aqueous solution in step (1) is 3-7wt%; and the mass ratio of the sodium alginate to acrylamide is 0.05-0.15:1.

[0013] Preferably, according to the present invention, the initiator in step (1) is potassium persulfate or sodium persulfate; the mass of the initiator is 0.1-1% of the mass of acrylamide; the initiator is added to the system in the form of an initiator aqueous solution, and the concentration of the initiator aqueous solution is 0.01-0.03 g / mL.

[0014] Preferably, according to the present invention, the reaction temperature in step (1) is 50-70° C., the reaction time is 4-8 h; and the reaction is carried out under static conditions.

[0015] Preferably, according to the present invention, the concentration of the ferric chloride aqueous solution in step (2) is 0.1-0.6 mol / L; the mass ratio of the ferric chloride aqueous solution to the single network structure hydrogel is not less than 5:1, and more preferably 8-15:1.

[0016] Preferably, according to the present invention, the soaking time in step (2) is 3-5 hours; the soaking is carried out at room temperature; the room temperature in the present invention has a well-known meaning, referring to 25±5°C.

[0017] Preferably, according to the present invention, the drying in step (2) is performed at 70-80° C. for 10-15 hours.

[0018] The present invention also provides a high-strength large-deformation double-network structure gel profile control agent, which is prepared by the above-mentioned preparation method.

[0019] According to the present invention, the application of the above-mentioned high-strength and large-deformation double-network structure gel profile control agent is used for deep profile control of low-permeability fractured oil reservoirs; preferably, the specific application method is as follows: the obtained high-strength and large-deformation double-network structure gel profile control agent is configured with oilfield injection water into a solution with a concentration of 0.05-0.3g / L, and then injected into the formation.

[0020] The technical features and effects of the present invention are as follows:

[0021] 1. The present invention combines sodium bentonite-polyacrylamide composite hydrogel with ion-crosslinked hydrogel of sodium alginate crosslinked by trivalent iron ions to prepare a high-strength and large-deformation double network structure gel, namely sodium clay-polyacrylamide / Fe 3 + -Sodium alginate double network structure hydrogel; wherein polyacrylamide and sodium bentonite are cross-linked through hydrogen bond interaction to form a first network, and sodium alginate and trivalent iron ions are cross-linked through coordination interaction to form a second network. These two interactions can play a synergistic role in enhancing the mechanical properties of the hydrogel. When subjected to external forces, the coordination interaction and hydrogen bond interaction within the system can also play an efficient energy dissipation role, thereby improving the strength, which is beneficial to the plugging of the high permeability strips of the oil well; at the same time, the amount of bentonite and sodium alginate added in the present invention needs to be controlled within the scope of the present invention. If the amount of bentonite and sodium alginate added is too high or too low, the performance of the profile control agent will be reduced.

[0022] 2. The preparation method of the high-strength large-deformation double-network structure gel particles used for oil field profile control of the present invention is simple to operate, has strong operability, mild conditions, and is easy to carry out large-scale industrial production. The obtained gel particles have high tensile strength, excellent elongation at break, good fatigue resistance and recovery performance.

[0023] 3. In the present invention, the product is prepared in stages. In the first stage, a gel having a first network structure is prepared. In the second stage, the colloid prepared in the first stage is soaked in a ferric chloride solution to construct a second three-dimensional network structure of the gel, which greatly improves the mechanical properties of the colloid. The profile control agent of the present invention has good thermal stability and is suitable for deep profile control of low-permeability fractured oil reservoirs with different salinities and temperatures. DETAILED DESCRIPTION

[0024] The present invention is further described below in conjunction with specific embodiments, but the present invention is not limited thereto.

[0025] Example 1

[0026] A method for preparing a high-strength, large-deformation double-network structure gel profile control agent comprises the following steps:

[0027] (1) 18 g of sodium bentonite was weighed and dissolved in 500 mL of deionized water, and then 150 g of acrylamide was added to the obtained bentonite dispersion, and ultrasonicated until uniformly dispersed; then 300 g of a 5 wt % sodium alginate aqueous solution was added; and 30 mL of a 0.02 g / mL potassium persulfate aqueous solution was added with a syringe, and the obtained hydrogel pre-solution was injected into a mold after stirring for 10 minutes, and reacted in an oven at 60° C. for 6 hours to obtain a single network structure hydrogel.

[0028] (2) At room temperature, the single network structure hydrogel obtained in step (1) is immersed in a 0.3 mol / L ferric chloride aqueous solution for 4 hours, wherein the mass ratio of the ferric chloride aqueous solution to the single network structure hydrogel is 10:1, and the ferric chloride aqueous solution completely immerses the single network structure hydrogel; then the hydrogel is taken out to obtain a high-strength and large-deformation double network structure hydrogel; the high-strength and large-deformation double network structure hydrogel is cut, dried at 80°C for 10 hours, and the solid-liquid obtained by drying is crushed and sieved to obtain a high-strength and large-deformation double network structure gel profile control agent.

[0029] Example 2

[0030] A method for preparing a high-strength, large-deformation double-network structure gel profile control agent is as described in Example 1, except that the amount of sodium bentonite added is 23 g, and the other raw material compositions and experimental steps are the same as in Example 1.

[0031] Example 3

[0032] A method for preparing a high-strength, large-deformation double-network structure gel profile control agent is as described in Example 1, except that the amount of sodium alginate aqueous solution added is 400 g, and the other raw material compositions and experimental steps are the same as in Example 1.

[0033] Comparative Example 1

[0034] A method for preparing a gel profile control agent is as described in Example 1, except that: instead of soaking in an aqueous solution of ferric chloride, the single network structure hydrogel obtained in step (1) is cut and dried at 80° C. for 10 h, and the solid-liquid obtained by drying is crushed and sieved to obtain the gel profile control agent.

[0035] Comparative Example 2

[0036] A method for preparing a gel profile control agent is as described in Example 1, except that the amount of sodium bentonite added in step (1) is 7.5 g, and the other raw material compositions and experimental steps are the same as in Example 1.

[0037] Comparative Example 3

[0038] A method for preparing a gel profile control agent is as described in Example 1, except that the amount of sodium alginate aqueous solution added in step (1) is 90 g, and the other raw material compositions and experimental steps are the same as in Example 1.

[0039] Test Example 1

[0040] The gel profile control agents prepared in Examples 1-2 and Comparative Example 1 were subjected to the following performance evaluations:

[0041] 1. Determination of expansion performance

[0042] 0.5g of gel profile control agent was placed in 3 portions of Daqing oilfield injection water (mineralization 5000-8500mg / L, divalent cation Ca 2+ Mg 2+ Less than 200 mg / L) in a sample bottle, sealed, and placed in an electric constant temperature drying oven at 45°C, 60°C, and 70°C, respectively, taken out regularly, and the mass M1 of the gel profile control agent after water absorption and expansion was measured, and the water absorption expansion multiple of the gel profile control agent was calculated according to the following formula;

[0043] S=(M1-0.5) / 0.5

[0044] In the formula, S is the water absorption expansion multiple, dimensionless; M1 is the mass of the gel profile control agent after water absorption expansion, g.

[0045] The experimental results of Examples 1-2 and Comparative Example 1 are shown in Tables 1-3 below:

[0046] Table 1 Water absorption expansion times of the gel profile control agent prepared in Example 1 at different times

[0047]

[0048]

[0049] Table 2 Water absorption expansion times of the gel profile control agent prepared in Example 2 at different times

[0050]

[0051] Table 3 Water absorption expansion times of the gel profile control agent prepared in Comparative Example 1 at different times

[0052]

[0053] In Table 1 and Table 3, Comparative Example 1 is a gel profile control agent which is not immersed in a ferric chloride solution and has the same other components as Example 1. From the comparison of the test results, it can be seen that Example 1 shows a slow expansion trend under different temperatures and different salinities within the 90-day test time, while Comparative Example 1 expands rapidly under the same conditions and dissolves after a period of time. The comparison between the two can prove that, therefore, immersion in a ferric chloride solution can increase the stability of the gel network structure, which is beneficial for the profile control system to effectively adjust the water absorption profile of the reservoir.

[0054] In Table 1 and Table 2, Example 2 is a gel profile control agent in which the addition amount of sodium bentonite is 23g and the other components are the same as those in Example 1. From the comparison of the test results, it can be seen that Example 1 shows a slow expansion trend within the 90-day test time at different temperatures and different mineralizations, and Example 2 also shows a similar trend under the same conditions, but the water absorption expansion multiple is slightly lower; the comparison between the two can prove that, within a certain range, the increase in the addition amount of sodium bentonite can increase the crosslinking density of the gel network, thereby causing a slight decrease in the swelling multiple.

[0055] 2. Strength measurement

[0056] The gel profile control agents prepared in Examples 1-3 and Comparative Examples 1-3 were subjected to the following performance tests:

[0057] 0.5g of gel profile control agent was placed in 3 portions of Daqing oilfield injection water (mineralization 5000-8500mg / L, divalent cation Ca 2+ Mg 2+ The gel particles were placed in sample bottles with a concentration of less than 200 mg / L), sealed, and placed in electric constant temperature drying ovens at 45°C, 60°C, and 70°C respectively. After swelling after absorbing water for 30 days, they were filtered and the compressive strength of the gel particles after swelling after absorbing water was measured using a particle parameter measuring instrument. The results are shown in Table 4 below.

[0058] Table 4 Compressive strength of gel profile control agents prepared in Examples and Comparative Examples

[0059]

[0060] From the comparison of the test results in Table 4, it can be seen that the compressive strength of Example 1 is higher than 1MPa at different temperatures and different salinities, while the compressive strength of Comparative Example 1 is only measured when the water salinity is 5607mg / L under the same conditions, but it is only 0.1MPa. Other salinities cannot be tested because the colloid is too soft; it can be proved by comparing the two that, therefore, soaking in ferric chloride solution can increase the strength of the gel, which is beneficial to the plugging of the water absorption profile of the reservoir by the profile control system. The amount of sodium bentonite added in Example 2 is slightly increased, and the compressive strength of the obtained gel profile control agent is higher than that of Example 1, so within a certain range, the increase in the amount of sodium bentonite added can increase the strength of the profile control agent, and the amount of sodium bentonite added in Comparative Example 2 is too low, and the strength of the profile control agent is low. In Example 3, the mass of sodium alginate was increased, and the strength of the profile control agent was slightly increased; in Comparative Example 3, the mass of sodium alginate was reduced, and the strength of the second network formed by cross-linking sodium alginate and trivalent iron ions through coordination interaction was reduced, so the strength of the profile control agent was relatively low. Therefore, it is necessary to strictly control the raw material ratio within the scope of the present invention.

Claims

1. A method for preparing a high-strength large-deformation double-network structure gel profile control agent, comprising the following steps: (1) adding bentonite to water, then adding acrylamide, and after ultrasonication until uniform dispersion, adding sodium alginate aqueous solution, and then adding an initiator, stirring evenly, reacting to obtain a single network structure hydrogel; (2) soaking the single network structure hydrogel obtained in step (1) in an aqueous solution of ferric chloride to obtain a high-strength and large-deformation double network structure hydrogel; and then cutting, drying, crushing, and screening to obtain a high-strength and large-deformation double network structure gel profile control agent.

2. The method for preparing the high-strength large-deformation double-network structure gel profile control agent according to claim 1, characterized in that: The bentonite in step (1) is sodium bentonite, and the ratio of the mass of the bentonite to the volume of water is 1g:15-35mL.

3. The method for preparing the high-strength large-deformation double-network structure gel profile control agent according to claim 1, characterized in that: The mass ratio of bentonite to acrylamide in step (1) is 0.08-0.25:1, preferably 0.1-0.2:

1.

4. The method for preparing the high-strength large-deformation double-network structure gel profile control agent according to claim 1, characterized in that: The mass concentration of the sodium alginate aqueous solution in step (1) is 3-7wt%; the mass ratio of the sodium alginate to acrylamide is 0.05-0.15:

1.

5. The method for preparing the high-strength large-deformation double-network structure gel profile control agent according to claim 1, characterized in that: The initiator in step (1) is potassium persulfate or sodium persulfate; the mass of the initiator is 0.1-1% of the mass of acrylamide; the initiator is added to the system in the form of an initiator aqueous solution, and the concentration of the initiator aqueous solution is 0.01-0.03 g / mL.

6. The method for preparing the high-strength large-deformation double-network structure gel profile control agent according to claim 1, characterized in that: The reaction temperature in step (1) is 50-70° C., and the reaction time is 4-8 hours; the reaction is carried out under static conditions.

7. The method for preparing the high-strength large-deformation double-network structure gel profile control agent according to claim 1, characterized in that: The concentration of the ferric chloride aqueous solution in step (2) is 0.1-0.6 mol / L; the mass ratio of the ferric chloride aqueous solution to the single network structure hydrogel is not less than 5:1, preferably 8-15:

1.

8. The method for preparing the high-strength and large-deformation double-network structure gel profile control agent according to claim 1, characterized in that: The soaking time in step (2) is 3-5 hours; the soaking is carried out at room temperature; and the drying is carried out at 70-80° C. for 10-15 hours.

9. A high-strength large-deformation double-network structure gel profile control agent, characterized in that: The preparation method according to claim 1 is used for preparation.

10. The application of the high-strength and large-deformation double-network structure gel profile control agent according to claim 1 is used for deep profile control of low-permeability fractured oil reservoirs; preferably, the specific application method is as follows: the obtained high-strength and large-deformation double-network structure gel profile control agent is prepared into a solution with a concentration of 0.05-0.3g / L using oilfield injection water, and then injected into the formation.

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