Dual water shutoff profile control plugging agent and preparation method thereof

Abstract

The application provides a double water plugging profile control plugging agent and a preparation method thereof, and the method comprises the following steps: (1) stirring and uniformly mixing a sodium alginate aqueous solution and glycerol glycidyl ether to obtain a white emulsion; (2) spraying the white emulsion into a calcium ion aqueous solution to perform a reaction, and then performing freeze-drying to obtain calcium alginate microcapsules; and (3) mixing and reacting the calcium alginate microcapsules with a crosslinking agent solution to obtain the double water plugging profile control plugging agent. In the use process, firstly, the calcium alginate microcapsules are injected into a formation, and the microcapsules can firstly perform primary plugging on a dominant pore channel through a physical plugging mode; then, a crosslinking agent solution is further injected into the formation, and the calcium alginate microcapsules can be crosslinked with the crosslinking agent to form an elastic gel with good strength, so that the elastic gel can perform secondary plugging on the plugging position in the form of a gel, and thus the profile control plugging agent in the application has excellent plugging effect in a deep formation.

Description

Technical Field

[0001] This invention relates to the field of oil extraction technology, and in particular to a dual water-blocking and profile control agent and its preparation method. Background Technology

[0002] In the development of oilfields in my country, due to reservoir heterogeneity and development process factors, the sweep efficiency of injected fluids is typically low, a phenomenon prevalent in the industry. Taking Daqing and Shengli oilfields as examples, these oilfields have entered the high water-cut stage after water injection development. During this period, a large amount of injected water is absorbed by high-permeability layers, while low-permeability layers are rarely affected, resulting in extremely heterogeneous injection profiles and severely impacting the utilization rate of injected water. To improve the recovery efficiency of remaining oil in the later stages of high water cut, China has actively promoted profile control and water shut-off technologies, leading to their rapid development.

[0003] In related technologies, common profile control and water shut-off agents include granular profile control agents and polymer gel profile control and water shut-off agents. Among them, gel profile control agents are widely used due to their advantages of low cost, long gelation time, adjustable strength, and applicability to different reservoir conditions. Polymer gels can be divided into various systems. Currently, the most commonly used subsurface cross-linked polymer gel profile control agent in oilfields is the polyacrylamide gel system. However, traditional profile control and water shut-off agents still have problems such as short action period, poor time-effectiveness, and easy gelation near the wellbore.

[0004] Therefore, based on the above problems, there is an urgent need to provide a dual-stage water-blocking profile control agent and its preparation method. Summary of the Invention

[0005] This invention provides a dual-action water-blocking and profile control agent and its preparation method, which can solve the problems of poor action time, poor timeliness, and difficulty in controlling gelation time of traditional profile control and water-blocking agents.

[0006] In a first aspect, the present invention provides a method for preparing a dual-action water-blocking and profile control agent, the method comprising the following steps:

[0007] (1) Sodium alginate aqueous solution and glycerol glycidyl ether were stirred and mixed to obtain a white emulsion:

[0008] (2) The white emulsion was sprayed into a calcium ion aqueous solution for reaction, and then freeze-dried to obtain calcium alginate microcapsules;

[0009] (3) The calcium alginate microcapsules are mixed and reacted with a crosslinking agent solution to obtain the dual water-blocking profile control and sealing agent.

[0010] Preferably, in step (1), the mass concentration of the sodium alginate aqueous solution is 0.7-1.5%.

[0011] Preferably, the mass ratio of the sodium alginate aqueous solution to glycerol glycidyl ether is 1:(5-9).

[0012] Preferably, in step (2), the calcium ion aqueous solution is a calcium chloride aqueous solution or a calcium nitrate aqueous solution; the mass concentration of the calcium ion aqueous solution is 3-6%.

[0013] Preferably, the mass ratio of sodium alginate aqueous solution to calcium ion aqueous solution is 1:(2-3).

[0014] Preferably, in step (2), after the white emulsion and the calcium ion aqueous solution are mixed and reacted, the step of collecting the reaction product by filtration is also included.

[0015] Preferably, in step (2), the freeze-drying temperature is -40 to 50°C and the time is 3 to 5 hours.

[0016] Preferably, in step (2), the particle size of the calcium alginate microcapsules is 600-1600 nm.

[0017] Preferably, in step (3), the crosslinking agent solution is a polyethyleneimine solution, and the mass concentration of the polyethyleneimine solution is 5-25%.

[0018] Preferably, in step (3), the reaction temperature is 30-60℃ and the time is 10-20min.

[0019] In step (3), the mass ratio of calcium alginate microcapsules to crosslinking agent solution is 1:(1-2).

[0020] Secondly, the present invention provides a dual water-blocking and profile control agent, which is prepared by any of the preparation methods described in the first aspect above.

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

[0022] (1) In this invention, sodium alginate aqueous solution is first mixed with glycerol glycidyl ether to obtain a white mixed emulsion. Then, the white mixed solution is uniformly sprayed into calcium chloride aqueous solution. During the spraying process, sodium alginate in tiny droplets reacts rapidly with calcium ions in calcium ion aqueous solution to form a network structure and rapidly encapsulates glycerol glycidyl ether to form calcium alginate microcapsules with a core-shell structure. In the process of use, after the calcium alginate microcapsules are injected into the formation, the microcapsules can first block the dominant channels through physical blocking. Then, a crosslinking agent solution is injected into the formation. The calcium alginate microcapsules can crosslink with the crosslinking agent to form an elastic gel with good strength, so that it can block the blocking position in a gel state for a second time. Thus, the profile blocking agent of this invention has excellent blocking effect in deep formations.

[0023] (2) The profile control and plugging agent in this invention has good environmental friendliness, will not damage the stability of the formation during the plugging process, and has the advantages of simple preparation method and low cost. Attached Figure Description

[0024] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0025] Figure 1 This is a scanning electron microscope image of a dual water-blocking profile-modifying and sealing agent provided by the present invention;

[0026] Figure 2 This is a dynamic strain scanning curve of a dual water-blocking profile-adjusting sealing agent provided by the present invention; in the figure, the horizontal axis represents oscillation strain;

[0027] Figure 3 This is a frequency scan curve of a dual water-blocking profile-adjusting sealing agent provided by the present invention; in the figure, the horizontal axis represents the angular frequency. Detailed Implementation

[0028] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are some embodiments of the present invention, but not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0029] This invention provides a method for preparing a dual-action water-blocking and profile control agent, which includes the following steps:

[0030] (1) Sodium alginate aqueous solution and glycerol glycidyl ether were stirred and mixed to obtain a white emulsion:

[0031] (2) The white emulsion was sprayed into a calcium ion aqueous solution for reaction, and then freeze-dried to obtain calcium alginate microcapsules;

[0032] (3) The calcium alginate microcapsules are mixed and reacted with a crosslinking agent solution to obtain the dual water-blocking profile control and sealing agent.

[0033] In this embodiment of the invention, sodium alginate aqueous solution is first mixed with glycerol glycidyl ether to obtain a white mixed emulsion. Then, the white mixed solution is uniformly sprayed into calcium chloride aqueous solution. During the spraying process, the sodium alginate in the tiny droplets reacts rapidly with the calcium ions in the calcium ion aqueous solution to form a network structure and quickly encapsulates the glycerol glycidyl ether, thereby forming calcium alginate microcapsules with a core-shell structure. In the application process, after the calcium alginate microcapsules are injected into the formation, the microcapsules can first block the dominant channels through physical plugging. Then, a crosslinking agent solution is injected into the formation. The calcium alginate microcapsules can crosslink with the crosslinking agent to form an elastic gel with good strength, thereby enabling secondary blocking of the blocking position in a gel state. In this way, the profile control and blocking agent of the present invention has excellent blocking effect in deep formations.

[0034] According to some preferred embodiments, in step (1), the mass concentration of the sodium alginate aqueous solution is 0.7-1.5% (for example, it can be 0.7%, 0.8%, 1.0%, 1.2% or 1.5%).

[0035] In this embodiment of the invention, by controlling the mass concentration of the sodium alginate aqueous solution within a reasonable range, it is beneficial to prepare spherical microcapsules with good mechanical strength and a high content of glycerol glycidyl ether. Meanwhile, experiments of this invention have confirmed that if the concentration of the sodium alginate aqueous solution is too low, it is not conducive to ensuring good mechanical strength of the microcapsule shell, making it easy for the glycerol glycidyl ether inside the microcapsule to leak, and making it difficult to prepare microcapsules with good morphology and dispersibility. If the concentration of the sodium alginate aqueous solution is too high, it will cause uneven dispersion of the core and shell solutions during mixing, resulting in a decrease in the drug loading and encapsulation efficiency of the microcapsules.

[0036] According to some preferred embodiments, the mass ratio of the sodium alginate aqueous solution to glycerol glycidyl ether is 1:(5-9) (for example, it can be 1:5, 1:6, 1:7, 1:8 or 1:9).

[0037] Experimental results confirmed that the drug loading of microcapsules increases with the increase of the proportion of glycerol glycidyl ether. However, when the content of glycerol glycidyl ether is too high, the proportion of shell solution in the microcapsules decreases, resulting in some core material not being effectively encapsulated in the microcapsules, thus reducing the encapsulation rate and wasting the amount of core material used. In summary, controlling the quality of sodium alginate aqueous solution and glycerol glycidyl ether within the above-mentioned range is beneficial for preparing calcium alginate microcapsules with good drug loading and encapsulation properties.

[0038] According to some preferred embodiments, in step (2), the calcium ion aqueous solution is a calcium chloride aqueous solution or a calcium nitrate aqueous solution; the mass concentration of the calcium ion aqueous solution is 3-6% (for example, it can be 3%, 4%, 5% or 6%).

[0039] When the concentration of the calcium ion aqueous solution is within the above range, it is beneficial to prepare spherical microcapsules with good dispersibility and mechanical strength. If the concentration of the calcium ion aqueous solution is too low, it is not conducive to the complete reaction of the carboxyl groups in the sodium alginate molecule, resulting in a lower degree of cross-linking between sodium alginate and the calcium ion aqueous solution, lower mechanical strength of the microspheres, and adhesion of the calcium alginate microspheres obtained by the reaction, which is not conducive to the preparation of microcapsules with good sphericity. If the concentration of the calcium ion aqueous solution is too high, it will reduce the particle size of the microcapsules and significantly reduce the internal space, which will affect the encapsulation of the core and reduce the drug loading and encapsulation efficiency of the microcapsules.

[0040] According to some preferred embodiments, the mass ratio of sodium alginate aqueous solution to calcium ion aqueous solution is 1:(2-3) (for example, it can be 1:2, 1:2.5 or 1:3).

[0041] It should be noted that the mass concentration of the calcium ion aqueous solution is the main influencing factor on the reaction between sodium alginate aqueous solution and calcium ion aqueous solution. During the reaction, it is sufficient to ensure that the amount of calcium ion aqueous solution added is slightly more than that of sodium alginate aqueous solution.

[0042] According to some preferred embodiments, after the white emulsion is mixed and reacted with the calcium ion aqueous solution, the reaction product is further collected by filtration.

[0043] According to some preferred embodiments, in step (2), the freeze-drying temperature is -40 to -50°C (for example, it can be -40°C, -45°C or -50°C), and the time is 3 to 5 hours (for example, it can be 3 hours, 4 hours or 5 hours).

[0044] In this embodiment of the invention, a white emulsion containing sodium alginate aqueous solution and glycerol glycidyl ether can be uniformly sprayed into a calcium ion aqueous solution using an atomizer. When the white emulsion droplets come into contact with the calcium ion aqueous solution, the calcium ions will rapidly react with the sodium alginate on the surface of the white emulsion droplets and quickly encapsulate the glycerol glycidyl ether, thereby forming a spherical microcapsule solution with calcium alginate microshells and glycerol glycidyl ether as the core. The solution is then filtered to collect the spherical microcapsules, and the collected spherical microcapsules are placed in a vacuum freeze dryer for drying to obtain calcium alginate microcapsules.

[0045] In a preferred embodiment, in step (2), the particle size of the calcium alginate microcapsules is 600-1600 nm (for example, it can be 600 nm, 800 nm, 1000 nm, 1200 nm, 1400 nm or 1600 nm).

[0046] In this embodiment of the invention, by rationally controlling the various reaction raw materials in the preparation process of calcium alginate microcapsules, it is beneficial to prepare calcium alginate microcapsules with suitable particle size. Thus, when used for plugging applications, because calcium alginate microcapsules have a certain strength and suitable particle size, they can be used to initially plug the pores in the formation, thereby achieving the initial profile control of the formation.

[0047] After the initial sealing of the formation by injecting calcium alginate microcapsules, the sealing effect of the calcium alginate microcapsules decreases with the extension of the sealing time. Therefore, in this embodiment of the invention, by injecting a crosslinking agent aqueous solution into the formation again, the glycerol glycidyl ether in the calcium alginate microcapsules can crosslink with the crosslinking agent solution, thereby forming a gel-like sealing agent with good strength and viscoelasticity, thus achieving secondary sealing of the formation. In summary, the profile control and water plugging agent in this embodiment of the invention can first achieve the initial physical sealing of the formation in the form of calcium alginate spherical microcapsules. After the crosslinking agent solution is injected, the calcium alginate spherical microcapsules can further crosslink with the crosslinking agent solution, thereby achieving secondary sealing of the formation in a gel-like state with good strength. This makes the profile control and water plugging agent have the advantages of long action time, good timeliness, and easy control of gelation time.

[0048] In a preferred embodiment, in step (3), the crosslinking agent solution is a polyethyleneimine solution with a mass concentration of 5-25% (e.g., 5%, 10%, 15% or 25%).

[0049] According to the chemical reaction collision theory, as the concentration of the polyethyleneimine solution increases, the probability of effective collisions with the glycerol glycidyl ether molecules in the microcapsule core increases, and the gelation time gradually shortens. However, excessively high concentrations of polyethyleneimine solution not only fail to significantly shorten the gelation time but also waste raw materials. Therefore, in this embodiment of the invention, by controlling the mass concentration of the crosslinking agent solution, the gelation time can be further controlled, thereby improving the controllability of the sealing effect. In this embodiment of the invention, the crosslinking agent solution of the above concentration can control the gelation time within 2-20 minutes.

[0050] In a preferred embodiment, in step (3), the reaction temperature is 30-60°C (e.g., 30°C, 40°C, 50°C or 60°C) and the time is 2-20 min (e.g., 2 min, 8 min, 10 min, 15 min or 20 min).

[0051] In this embodiment of the invention, the microcapsules can react with the crosslinking agent solution at different temperatures to form a gel-like sealing agent. Higher temperatures increase the kinetic energy of the reactant molecules, thereby improving the crosslinking reaction rate and shortening the gelation time. In this embodiment, when the reaction temperature exceeds 50°C, the microspheres can rapidly form a gel with the polyethyleneimine solution within 10 minutes. Therefore, after the microspheres are injected into formations above 50°C to seal the dominant pores, the injected crosslinking agent solution can quickly form a gel at the sealing site (see reference). Figure 1 This creates a secondary blockage.

[0052] In a preferred embodiment, in step (3), the mass ratio of calcium alginate microcapsules to crosslinking agent solution is 1:(1-2) (for example, it can be 1:1, 1:1.5 or 1:2).

[0053] The present invention also provides a dual water-blocking and profile control agent, which is prepared by the preparation method provided in the present invention.

[0054] The plugging agent in this embodiment is suitable for use in low-temperature reservoirs. The gel formation temperature can be controlled within the range of 30–70°C, and it has a certain degree of salt resistance, making it suitable for applications with a salinity ≤10×10⁻⁶. 4 The formation has a mineralization concentration of mg / L, and the gelation time can be shortened by reducing the mineralization concentration. The gel plugging and profile control agent formed in the embodiments of the present invention has good viscoelastic properties, with a linear viscoelastic range of 0.1% to 100%, and also has good mechanical properties and excellent shear stability, and can be used for plugging dominant pores in formations.

[0055] To more clearly illustrate the technical solution and advantages of the present invention, the following examples provide a detailed description of a dual water-blocking profile control agent and its preparation method.

[0056] Example 1:

[0057] (1) Add glycerol glycidyl ether to an aqueous solution of sodium alginate (1% by mass), stir magnetically for 10 min to mix, and a white emulsion is obtained: the mass ratio of sodium alginate aqueous solution to glycerol glycidyl ether is 1:8.

[0058] (2) The white emulsion was uniformly sprayed into the calcium ion aqueous solution (calcium chloride aqueous solution with a mass concentration of 6%) using an atomizer to carry out the reaction. The reaction product was filtered and then placed in a vacuum freezer at -40℃ for 4 hours to dry, thereby obtaining calcium alginate microcapsules. The mass ratio of sodium alginate aqueous solution to calcium ion aqueous solution was 1:2.

[0059] (3) Mix calcium alginate microcapsules with a mass ratio of 1:2 and crosslinking agent aqueous solution (polyethyleneimine aqueous solution with a mass concentration of 10%) at 50°C for 10 min to obtain a dual water-blocking profile control and sealing agent.

[0060] Example 2:

[0061] (1) Add glycerol glycidyl ether to an aqueous solution of sodium alginate (mass concentration of 1.25%), stir magnetically for 10 min to mix, and a white emulsion is obtained: the mass ratio of sodium alginate aqueous solution to glycerol glycidyl ether is 1:8.

[0062] (2) The white emulsion was uniformly sprayed into the calcium ion aqueous solution (calcium nitrate aqueous solution with a mass concentration of 6%) using an atomizer to carry out the reaction. The reaction product was filtered and then placed in a vacuum freezer at -50℃ for 3 hours to dry, thereby obtaining calcium alginate microcapsules. The mass ratio of sodium alginate aqueous solution to calcium ion aqueous solution was 1:2.

[0063] (3) Mix calcium alginate microcapsules with a mass ratio of 1:2 and crosslinking agent aqueous solution (polyethyleneimine aqueous solution with a mass concentration of 10%) at 50°C for 10 min to obtain a dual water-blocking profile control and sealing agent.

[0064] Example 3:

[0065] (1) Add glycerol glycidyl ether to an aqueous solution of sodium alginate (mass concentration of 1%), stir magnetically for 10 min to mix, and a white emulsion is obtained: wherein the mass ratio of sodium alginate aqueous solution to glycerol glycidyl ether is 1:4.

[0066] (2) The white emulsion was uniformly sprayed into the calcium ion aqueous solution (calcium chloride aqueous solution with a mass concentration of 6%) using an atomizer to carry out the reaction. The reaction product was filtered and then placed in a vacuum freezer at -40℃ for 4 hours to dry, thereby obtaining calcium alginate microcapsules. The mass ratio of sodium alginate aqueous solution to calcium ion aqueous solution was 1:2.

[0067] (3) Mix calcium alginate microcapsules with a mass ratio of 1:2 and crosslinking agent aqueous solution (polyethyleneimine aqueous solution with a mass concentration of 10%) at 50°C for 10 min to obtain a dual water-blocking profile control and sealing agent.

[0068] Example 4:

[0069] (1) Add glycerol glycidyl ether to an aqueous solution of sodium alginate (1% by mass), stir magnetically for 10 min to mix, and a white emulsion is obtained: the mass ratio of sodium alginate aqueous solution to glycerol glycidyl ether is 1:6.

[0070] (2) The white emulsion was uniformly sprayed into the calcium ion aqueous solution (calcium chloride aqueous solution with a mass concentration of 6%) using an atomizer to carry out the reaction. The reaction product was filtered and then placed in a vacuum freezer at -40℃ for 4 hours to dry, thereby obtaining calcium alginate microcapsules. The mass ratio of sodium alginate aqueous solution to calcium ion aqueous solution was 1:2.

[0071] (3) Mix calcium alginate microcapsules with a mass ratio of 1:2 and crosslinking agent aqueous solution (polyethyleneimine aqueous solution with a mass concentration of 10%) at 50°C for 10 min to obtain a dual water-blocking profile control and sealing agent.

[0072] Example 5:

[0073] Example 5 is basically the same as Example 1, except that in step (1), the mass concentration of sodium alginate aqueous solution is 0.5%.

[0074] Example 6:

[0075] Example 6 is basically the same as Example 1, except that in step (1), the mass ratio of sodium alginate aqueous solution to glycerol glycidyl ether is 1:2.

[0076] Example 7:

[0077] Example 7 is basically the same as Example 1, except that in step (1), the mass ratio of sodium alginate aqueous solution to glycerol glycidyl ether is 1:10.

[0078] Example 8:

[0079] Example 8 is basically the same as Example 1, except that in step (2), the mass concentration of the calcium ion aqueous solution is 8%.

[0080] Example 9:

[0081] Example 9 is basically the same as Example 1, except that in step (2), the mass concentration of the calcium ion aqueous solution is 2%.

[0082] Comparative Example 1:

[0083] (1) Add 19.35g of octylamine to a three-necked flask, then add 40g of anhydrous methanol. After stirring thoroughly and dissolving completely, add 77.4g of methyl acrylate dropwise to the reaction system at 25°C. After reacting at 35°C for 24h, a hyperbranched polymer is obtained. Add 30.1g of the hyperbranched polymer to 60g of anhydrous methanol and stir thoroughly to dissolve completely. Then add 48g of ethylenediamine dropwise to the reaction system at 25°C and stir thoroughly at 35°C for 24h. Then remove unreacted ethylenediamine and solvent by vacuum distillation to obtain a transparent pale yellow viscous liquid, which is a hyperbranched macromolecule with amino terminal functional groups.

[0084] (2) Polyethylene glycol was stirred at 50°C until it was fully dissolved. Then, 0.65 g of tetrabutylammonium bromide and 15 mL of epichlorohydrin were added to the reaction solution while stirring. After stirring for 10 min, the temperature was raised to 55°C. 4 g of sodium hydroxide was added. After reacting for 4 h, a light yellow product was obtained, which is polyethylene glycol diglycidyl ether, denoted as PEGDGE-1000. Polyethylene glycol was stirred at 50°C until it was fully dissolved. Then, 0.78 g of tetrabutylammonium bromide and 25 mL of epichlorohydrin were added to the reaction solution while stirring. After stirring for 10 min, the temperature was raised to 55°C. 6.5 g of sodium hydroxide was added. After reacting for 4 h, the product was filtered while hot to obtain a light yellow product, which is polyethylene glycol diglycidyl ether, denoted as PEGDGE-600. Polyethylene glycol was stirred at 50°C until it was fully dissolved. Then, 0.25 g of tetrabutylammonium bromide and 11 mL of epichlorohydrin were added to the reaction solution while stirring. After stirring for 10 min, the temperature was raised to 55°C. 2 g of sodium hydroxide was added, and the reaction was carried out for 4 h. The mixture was then filtered while hot, and the filtrate was collected. This filtrate is polyethylene glycol diglycidyl ether, denoted as PEGDGE-2000.

[0085] (3) Hyperbranched macromolecules and PEGDGE-1000 were added to deionized water at a molar ratio of 1:3, wherein the mass ratio of the sum of the mass of hyperbranched macromolecules and PEGDGE-1000 to the mass of deionized water was 30:70. The mixture was sonicated for 10 min to obtain a well-mixed aqueous solution, which was then transferred to a glass test tube and sealed. The reaction was carried out at 45°C for 72 h. After the reaction was completed, the hydrogel water-blocking agent was obtained.

[0086] The water-blocking and profile control agents prepared in Examples 1 to 9 and Comparative Example 1 were subjected to performance tests, and the test results are shown in Table 1.

[0087] The microcapsules prepared in the examples and comparative examples were vacuum dried, then soaked in ethanol solution for 24 h, and rotary evaporated at 50 °C for 0.5 h. The mass of the microcapsules was weighed (the mass of glycerol glycidyl ether obtained in the rotary flask after rotary evaporation "M", the total mass of glycerol glycidyl ether to be weighed before preparing microspheres "M2", and the total mass of the microcapsules to be weighed after freeze-drying "M1"). The drug loading and encapsulation efficiency of the microcapsules were calculated using the following formula:

[0088]

[0089] In the formula, A is the drug loading of the microcapsule, B is the encapsulation efficiency of the microcapsule, M1 is the total mass of the microcapsule, M2 is the mass of glycerol glycidyl ether, and M is the mass of glycerol glycidyl ether in the microcapsule.

[0090] Rheological performance testing of the water-blocking and profile control agent: The dynamic rheological properties of the microcapsule gel samples in the examples and comparative examples were analyzed and tested using a hybrid rheometer. Two rheological parameters of the gel, namely the storage modulus (G′) and the loss modulus (G″), were obtained by scanning frequency and amplitude in oscillation mode. During the measurement process, parallel plates with a diameter of 40 mm and a plate spacing of 500 nm were used. Specifically, firstly, the frequency was fixed at 1 rad / s, and the strain range was 0.1% to 100%. Under these conditions, strain-frequency sweep tests were performed on the microcapsule gel. Then, with the strain range fixed at 0.5%, frequency sweep tests were performed on the microcapsule gel within a frequency range of 0.1 rad / s to 100 rad / s. All tests were conducted at 25°C.

[0091] Table 1

[0092]

[0093]

[0094] Note: "-" in the table indicates that the performance could not be tested;

[0095] Combining Table 1 and Figures 2 to 3 As can be seen from the embodiments of the present invention, the plugging agent is suitable for use in low-temperature reservoirs. The formed gel plugging and profile control agent has good viscoelastic properties. Within the stress range, the storage modulus (G') of the microcapsule gel remains relatively stable under deformation of 0.1%-100% and is always greater than the loss modulus (G”). This indicates that the three-dimensional network structure of the microcapsule gel is stably maintained within this range, exhibiting obvious strain-dependent viscoelastic response behavior and typical elastic (solid-like) properties. Figure 3As can be seen, within the test range of 0.1 rad / s to 100 rad / s, with increasing frequency, the G' of the microcapsule gel increases slowly, while the G” of the microcapsule gel decreases slowly, but there is no abrupt change. It remains stable under relatively small external forces, and the microcapsule gels all exhibit that G' is always greater than G”. The elastic response of the gel to deformation is generally dominant, indicating that the microcapsule gel can maintain its cross-linked structure at 25℃, possessing good mechanical properties and excellent shear stability, and exhibiting strong mechanical strength. In summary, the dual water-blocking and profile control agent prepared in the embodiments of this invention has good mechanical properties and excellent shear stability, and can be used for sealing dominant pores in formations.

[0096] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a dual-stage water-blocking and profile-modifying sealing agent, characterized in that, The method includes the following steps: (1) The sodium alginate aqueous solution and glycerol glycidyl ether are stirred and mixed to obtain a white emulsion: the mass concentration of the sodium alginate aqueous solution is 0.7-1.5%; the mass ratio of the sodium alginate aqueous solution to glycerol glycidyl ether is 1:(5-9). (2) The white emulsion is sprayed into a calcium ion aqueous solution for reaction, and then freeze-dried to obtain calcium alginate microcapsules; the mass concentration of the calcium ion aqueous solution is 3-6%; the mass ratio of sodium alginate aqueous solution to calcium ion aqueous solution is 1:(2-3). (3) The calcium alginate microcapsules are mixed and reacted with a crosslinking agent solution to obtain the dual water-blocking and profile-modifying sealing agent; the crosslinking agent solution is a polyethyleneimine solution with a mass concentration of 5-25%.

2. According to the preparation method of claim 1, in step (2), the calcium ion aqueous solution is a calcium chloride aqueous solution or a calcium nitrate aqueous solution.

3. According to the preparation method of claim 1, in step (2), after the white emulsion and the calcium ion aqueous solution are mixed and reacted, the step of collecting the reaction product by filtration is further included.

4. According to the preparation method of claim 1, in step (2), the freeze-drying temperature is -40 to 50°C and the time is 3 to 5 hours.

5. According to the preparation method of claim 1, in step (2), the particle size of the calcium alginate microcapsules is 600-1600 nm.

6. According to the preparation method of claim 1, in step (3), the reaction temperature is 30-60℃ and the time is 2-20min.

7. According to the preparation method of claim 1, in step (3), the mass ratio of calcium alginate microcapsules to crosslinking agent solution is 1:(1-2).

8. A dual-action water-blocking and profile-adjusting sealing agent, characterized in that, It is prepared by any of the preparation methods described in claims 1 to 7.

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