Gel channeling sealing agent capable of delaying gelling and preparation method of gel channeling sealing agent

Abstract

The invention relates to the technical field of oilfield development, in particular to a gel channeling sealing agent capable of delaying gelling and a preparation method thereof.The preparation method comprises the following steps that acrylamide and sodium alginate are added into deionized water and stirred to be uniform, and a hydrogel precursor solution is obtained; adding the hydrogel precursor solution and Tween 80 into the initiator microcapsule, performing ultrasonic treatment, and adding a cross-linking agent and a calcium carbonate suspension to obtain the gel channeling sealing agent. According to the preparation method of the gel channeling sealing agent capable of delaying gelling, the initiator is released into the hydrogel precursor solution through the holes in the initiator microcapsules to obtain polyacrylamide gel, calcium ions generated after calcium carbonate is decomposed are chelated with sodium alginate to generate calcium alginate, and then the polyacrylamide gel is prepared into the gel channeling sealing agent capable of delaying gelling. And interpenetrating with a polyacrylamide gel system to form a double-network gel system.

Description

Technical Field

[0001] The invention relates to the technical field of oilfield development, in particular to a gel sealing agent for delaying gelation and a preparation method thereof. Background Art

[0002] At present, CO2 flooding has become an effective development method for low permeability / ultra-low permeability oil fields, but gas channeling restricts the full play of CO2 flooding effect. The serious heterogeneity and natural / artificial fractures of low permeability / ultra-low permeability reservoirs further aggravate gas channeling and seriously reduce the displacement effect. Controlling and inhibiting or preventing gas channeling and expanding the swept volume of gas drive are of great significance to improving the development effect of CO2 flooding in low permeability / ultra-low permeability oil fields. In response to such gas channeling phenomenon, there are currently a series of methods such as water-gas alternating injection (WAG), gel channeling, chemical precipitation, carbon dioxide foam and carbon dioxide thickening to adjust the reservoir, selectively plug the high permeability layer or improve the mobility ratio of the displacement phase and the displaced phase to achieve the purpose of preventing and plugging gas channeling.

[0003] In the gel blocking method, the gel system can control gas channeling at all stages of gas flooding, but many gels are not acid-resistant and are not suitable for the low pH environment of the reservoir caused by CO2 flooding. There are also problems such as the gelation time of the gel system used is too short, resulting in poor injection capacity, inability to effectively block the deep reservoir, and non-degradable high-strength gels that harm the environment. Summary of the invention

[0004] The purpose of the present invention is to provide a gel blocking agent for delaying gelation and a preparation method thereof, so as to solve the problems that the gel blocking agent has a short gelation time and is not suitable for weak acid environment.

[0005] To achieve the above object, the present invention provides a method for preparing a gel blocking agent for delayed gelation, comprising the following steps: S1. Add acrylamide and sodium alginate into deionized water and stir evenly to obtain a hydrogel precursor solution; S2. Add the hydrogel precursor solution obtained in S1 and Tween 80 to the initiator microcapsule, perform ultrasound, add a cross-linking agent and a calcium carbonate suspension, and obtain a gel sealing agent.

[0006] Preferably, in S1, the mass ratio of acrylamide to sodium alginate is 1:0.05-0.15.

[0007] Preferably, in S2, the solid-liquid ratio of the initiator microcapsule and the hydrogel precursor solution is 3-4:1 mg / ml.

[0008] Preferably, the solid-to-liquid ratio of the crosslinking agent, calcium carbonate and hydrogel precursor solution is 5:1:10 mg / mg / ml.

[0009] Preferably, in S2, the crosslinking agent includes one or more of N,N-bisacrylamide, ethylene glycol dimethacrylate, trimethylolpropane trimethacrylate, polyethylene glycol dimethacrylate, divinylbenzene and triacrylate.

[0010] Preferably, in S2, the preparation of the initiator microcapsules comprises the following steps: S21, dissolving pyrrole and C5 petroleum resin in an organic solvent to obtain a first component; S22, mixing the initiator and the anionic surfactant in a mass ratio of 1:0.005-0.015 and grinding the mixture to obtain a mixed powder; S23, slowly dropwise adding the first component obtained in S21 to the mixed powder in S22, while stirring to obtain the second component; S24, placing the second component obtained in S23 into an oven, reacting at 50-80° C. for 3-8 h to obtain a product; S25. Wash the product obtained in S24, and dry it at 50-80° C. for 3-7 h to obtain initiator microcapsules.

[0011] Preferably, in S21, the solid-to-liquid ratio of C5 petroleum resin to pyrrole is 1:0.25-4 mg / μl; The organic solvent includes one or more of dichloromethane, toluene, ethyl acetate, acetone and carbon tetrachloride.

[0012] Preferably, in S22, the initiator includes one or more of di-tert-butyl peroxide, azobisisobutyronitrile, ammonium persulfate, potassium persulfate, boron trifluoride and sodium bisulfite; The anionic surfactant includes one or more of sodium dodecyl sulfate, sodium linear alkylbenzene sulfonate, sodium hexadecyl sulfonate, sodium dioctyl sulfosuccinate, and sodium lauryl sulfate.

[0013] Preferably, in S25, the washing is firstly to wash away the unreacted initiator with deionized water, and then to rinse with anhydrous ethanol.

[0014] The gel blocking agent is prepared by the preparation method of the gel blocking agent for delaying gelation.

[0015] Therefore, the present invention adopts the above-mentioned gel blocking agent for delaying gelation and its preparation method, and its beneficial effects are: 1. In the weak acid environment of CO2, the calcium ions after the decomposition of calcium carbonate in the gel sealing agent provided by the present invention chelate with sodium alginate to form calcium alginate, and interpenetrate with the polyacrylamide gel system to form a double network gel system; 2. The present invention realizes the slow release of the initiator by preparing the initiator microcapsules, effectively prolonging the gelation time. The initiator is released into the hydrogel precursor solution through the holes on the initiator microcapsules to obtain the polyacrylamide gel system; 3. The gel sealing agent provided by the present invention effectively prolongs the gelling time of the gel system, and the obtained gel system has good mechanical properties, salt resistance and swelling rate.

[0016] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 is an infrared spectrum of the initiator microcapsule and pyrrole in Example 1 of the present invention; Figure 2 It is a composite SEM image of the initiator microcapsules in Example 1 and Comparative Example 1 at different magnifications; Figure 3 This is a gelation delay test chart of the gel sealant; Figure 4 This is a compression test diagram of the gel sealant; Figure 5 This is the salt resistance test chart of gel sealant; Figure 6 This is the swelling test diagram of the gel sealant; Figure 7 This is a comparison diagram of the gel sealing agent in Example 10 before and after swelling. DETAILED DESCRIPTION

[0018] The present invention is further described below in conjunction with the accompanying drawings and embodiments. Unless otherwise defined, the technical terms or scientific terms used in the present invention should be the common meanings understood by people with ordinary skills in the field to which the present invention belongs. The above-mentioned features or features mentioned in the specific examples mentioned in the present invention can be combined arbitrarily, and these specific embodiments are only used to illustrate the present invention and are not used to limit the scope of the present invention.

[0019] Example 1 S1. Add acrylamide and sodium alginate into deionized water and stir evenly to obtain a hydrogel precursor solution.

[0020] In S1, the mass ratio of acrylamide to sodium alginate was 1:0.1, and 5 mg of sodium alginate was added per ml of deionized water.

[0021] S2. Add the hydrogel precursor solution and Tween80 obtained in S1 to the initiator microcapsules, then sonicate, add the crosslinker and calcium carbonate suspension, the solid-liquid ratio of the crosslinker N,N-bisacrylamide, calcium carbonate and the hydrogel precursor solution is 0.5 mg:0.1 mg:1 ml, the amount of Tween80 added is 8 mg / ml, and a gel sealing agent is obtained.

[0022] The parameters of the ultrasonic cleaning instrument KQ-50B during ultrasound are: power supply 220 V 50 Hz, operating frequency 40 KHz, and ultrasonic power 50W.

[0023] When gelling at 60°C, 4 mg of initiator microcapsules were added to each milliliter of hydrogel precursor solution, and when gelling at 70°C, 3 mg of initiator microcapsules were added to each milliliter of hydrogel precursor solution.

[0024] In S2, the preparation of the initiator microcapsules comprises the following steps: S21. Dissolve 80 μl of pyrrole and 20 mg of C5 petroleum resin in 200 μl of dichloromethane to obtain a first component.

[0025] S22. Mix 1 g of initiator ammonium persulfate and 0.01 g of anionic surfactant sodium dodecyl sulfate and grind them to obtain a mixed powder.

[0026] S23, slowly dropwise adding the first component obtained in S21 to the mixed powder in S22, stirring while adding to obtain the second component.

[0027] S24, placing the second component obtained in S23 into an oven, reacting at 60° C. for 5 h to obtain a product; S25. Wash the product obtained in S24, first wash away the unreacted ammonium persulfate with deionized water, then rinse with anhydrous ethanol, and dry at 60° C. for 6 h to obtain initiator microcapsules.

[0028] Example 2 The difference between this embodiment and embodiment 1 is that the amount of C5 petroleum resin added in preparing the initiator microcapsules is 40 mg, and the other steps are the same as those in embodiment 1 to obtain a gel blocking agent.

[0029] Example 3 The difference between this embodiment and embodiment 1 is that the amount of C5 petroleum resin added in preparing the initiator microcapsules is 60 mg, and the rest of the steps are the same as those in embodiment 1 to obtain a gel blocking agent.

[0030] Example 4 The difference between this embodiment and embodiment 1 is that the amount of C5 petroleum resin added in preparing the initiator microcapsules is 80 mg, and the other steps are the same as those in embodiment 1 to obtain a gel blocking agent.

[0031] Example 5 The difference between this example and example 4 is that the amount of pyrrole added in preparing the initiator microcapsules is 60 μl, and the rest of the steps are the same as those in example 1 to obtain a gel blocking agent.

[0032] Example 6 The difference between this example and Example 5 is that the amount of pyrrole added in preparing the initiator microcapsules is 40 μl, and the other steps are the same as those in Example 1 to obtain a gel blocking agent.

[0033] Example 7 The difference between this example and Example 6 is that the amount of pyrrole added in preparing the initiator microcapsules is 20 μl, and the rest of the steps are the same as those in Example 1 to obtain a gel blocking agent.

[0034] Example 8 The difference between this embodiment and embodiment 1 is that when the gel is formed at 70° C., the amount of sodium alginate used is 20 mg per milliliter of deionized water to obtain a gel blocking agent.

[0035] Example 9 The difference between this embodiment and embodiment 8 is that, when the gel is formed at 70° C., the amount of acrylamide used is 100 mg per milliliter of deionized water to obtain a gel blocking agent.

[0036] Example 10 The difference between this embodiment and embodiment 1 is that when gelling at 70° C., the amount of acrylamide used is 100 mg per milliliter of deionized water, and the amount of sodium alginate used is 10 mg per milliliter of deionized water to obtain a gel sealing agent.

[0037] Comparative Example 1 The difference between this comparative example and Example 1 is that no C5 petroleum resin is added when preparing the initiator microcapsules, and the rest of the steps are the same as those in Example 1 to obtain a gel blocking agent.

[0038] Comparative Example 2 The difference between this comparative example and Example 1 is that when the gel is formed at 70° C., the amount of sodium alginate used is 10 mg per milliliter of deionized water, and no calcium carbonate suspension is added. The rest of the steps are the same as those in Example 1 to obtain a gel sealing agent.

[0039] Comparative Example 3 The difference between this comparative example and comparative example 2 is that when gelling at 70° C., the amount of sodium alginate used is 20 mg per milliliter of deionized water, and no calcium carbonate suspension is added. The rest of the steps are the same as those in comparative example 2 to obtain a gel sealing agent.

[0040] Comparative Example 4 The difference between this comparative example and Example 1 is that when gelling at 70°C, the amount of initiator microcapsules used is 2 mg per milliliter of deionized water, and no calcium carbonate suspension is added. The rest of the steps are the same as in Example 1 to obtain a gel sealing agent.

[0041] Comparative Example 5 The difference between this comparative example and Example 1 is that no calcium carbonate suspension is added during gelation at 70° C., and the remaining steps are the same as those in Example 1 to obtain a gel sealing agent.

[0042] Comparative Example 6 The difference between this comparative example and Example 1 is that when gelling at 70°C, the amount of initiator microcapsules used is 4 mg per milliliter of deionized water, and no calcium carbonate suspension is added. The rest of the steps are the same as in Example 1 to obtain a gel sealing agent.

[0043] Comparative Example 7 The difference between this comparative example and Example 1 is that no calcium carbonate suspension and sodium alginate are added during gelation at 70° C., and the remaining steps are the same as those in Example 1 to obtain a gel sealing agent.

[0044] Comparative Example 8 The difference between this comparative example and comparative example 2 is that, when gelling at 70° C., the amount of acrylamide used is 100 mg per milliliter of deionized water, and no calcium carbonate suspension is added. The rest of the steps are the same as those in comparative example 2 to obtain a gel sealing agent.

[0045] Test Example 1 a. Fourier transform infrared spectroscopy test The initiator microcapsules prepared in Example 1 were tested by Fourier transform infrared spectroscopy. The results are as follows: Figure 1 As shown in the figure, it can be clearly seen that the symmetric and asymmetric stretching vibration peaks of the pyrrole ring are located at 1552 cm -1 and 1449 cm -1 , and the CN stretching vibration peak is located at 1176 cm -1 , at 1060 cm -1 and 1400 cm −1 The characteristic absorption peak of ammonium persulfate observed at is attributed to the sulfate group, indicating that ammonium persulfate is encapsulated in polypyrrole and the initiator microcapsules are successfully prepared.

[0046] b. SEM test The initiator microcapsules in Example 1 and Comparative Example 1 were tested by SEM. The results are as follows: Figure 2 As shown, Figure 2 a and Figure 2 b is the SEM image of the initiator microcapsule in Example 1 at different magnifications. Figure 2 c and Figure 2 d in the figure is the SEM image of the initiator microcapsule in comparative example 1 at different magnifications. It can be seen that the initiator microcapsule in example 1 has small holes, which facilitates the release of the initiator.

[0047] c. Delayed testing At 70°C, the gelling time of the gel blocking agent in Example 1, Comparative Example 4, Comparative Example 5 and Comparative Example 6 was tested. The results are as follows: Figure 3 As shown, after adding the initiator microcapsules, Example 1, Comparative Example 4, Comparative Example 5 and Comparative Example 6 can effectively prolong the gelation time from about 3 h to about 40 h. At 40 h, Comparative Example 4, Comparative Example 5 and Comparative Example 6 have a stable gelation rate of about 90%, while after adding calcium carbonate, the gelation rate of Example 1 is about 70%.

[0048] d. Gel sealant compression test Compression tests were performed on Example 8, Example 9, Comparative Example 2, Comparative Example 3 and Comparative Example 7. The results are as follows: Figure 4 As shown, it can be seen that the gel sealing agent in Example 9 has good mechanical properties and can withstand a maximum pressure of 0.18 MPa.

[0049] e. Gel sealant salt resistance test The gel sealing agent in Example 1 was tested for salt resistance at different concentrations. The results are as follows: Figure 5 As shown, it can be seen that after being placed at 85℃ for 144 h, the stable compression performance can still be maintained.

[0050] f. Gel sealing agent swelling test The gel sealing agents of Example 10, Comparative Example 2, Comparative Example 5 and Comparative Example 8 were subjected to swelling tests. The results are as follows: Figure 6 and Figure 7 As shown. Since the calcium ions decomposed from calcium carbonate and sodium alginate chelate to form calcium alginate in the weak acid environment of carbon dioxide in the gel sealing agent of Example 10, calcium alginate and polyacrylamide form an interpenetrating double network gel system. Therefore, the swelling rate of the double network gel system in Example 10 is higher than that of the semi-interpenetrating gel systems in Comparative Examples 2, 5 and 8.

[0051] g. Gel sealing agent gelation test The gel sealing agents in Examples 1-7 were subjected to gelling tests at different temperatures (60° C., 70° C., and 80° C.). The results are shown in Table 1.

[0052] Table 1. The gelation results of the gel blocking agents in Examples 1-7 at different temperatures

[0053] Therefore, the present invention adopts the above-mentioned gel blocking agent for delaying gelation and its preparation method, the initiator is released into the hydrogel precursor solution through the holes on the initiator microcapsule to obtain polyacrylamide gel, the calcium ions after the decomposition of calcium carbonate chelate with sodium alginate to generate calcium alginate, and interpenetrate with the polyacrylamide gel system to form a double network gel system.

[0054] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that they can still modify or replace the technical solution of the present invention with equivalents, and these modifications or equivalent replacements cannot cause the modified technical solution to deviate from the spirit and scope of the technical solution of the present invention.

Claims

1. A method for preparing a gel blocking agent for delayed gelation, characterized in that: The following steps are included: S1. Add acrylamide and sodium alginate into deionized water and stir evenly to obtain a hydrogel precursor solution; S2. Add the hydrogel precursor solution obtained in S1 and Tween 80 to the initiator microcapsule, perform ultrasound, add a cross-linking agent and a calcium carbonate suspension, and obtain a gel sealing agent.

2. The method for preparing a gel blocking agent for delayed gelation according to claim 1, characterized in that: In S1, the mass ratio of acrylamide to sodium alginate is 1:0.05-0.

15.

3. The method for preparing a gel blocking agent for delayed gelation according to claim 1, characterized in that: In S2, the solid-liquid ratio of the initiator microcapsule and the hydrogel precursor solution is 3-4:1 mg / ml.

4. The method for preparing a gel blocking agent for delayed gelation according to claim 1, characterized in that: The solid-liquid ratio of the crosslinker, calcium carbonate, and hydrogel precursor solution was 5:1:10 mg / mg / ml.

5. The method for preparing a gel blocking agent for delayed gelation according to claim 1, characterized in that: In S2, the cross-linking agent includes one or more of N,N-bisacrylamide, ethylene glycol dimethacrylate, trimethylolpropane trimethacrylate, polyethylene glycol dimethacrylate, divinylbenzene and triacrylate.

6. The method for preparing a gel blocking agent for delayed gelation according to claim 1, characterized in that: In S2, the preparation of the initiator microcapsules comprises the following steps: S21, dissolving pyrrole and C5 petroleum resin in an organic solvent to obtain a first component; S22, mixing the initiator and the anionic surfactant in a mass ratio of 1:0.005-0.015 and grinding the mixture to obtain a mixed powder; S23, slowly dropwise adding the first component obtained in S21 to the mixed powder in S22, while stirring to obtain the second component; S24, placing the second component obtained in S23 into an oven, reacting at 50-80° C. for 3-8 h to obtain a product; S25. Wash the product obtained in S24, and dry it at 50-80° C. for 3-7 h to obtain initiator microcapsules.

7. The method for preparing a gel blocking agent for delayed gelation according to claim 6, characterized in that: In S21, the solid-liquid ratio of C5 petroleum resin and pyrrole is 1:0.25-4 mg / μl; The organic solvent includes one or more of dichloromethane, toluene, ethyl acetate, acetone and carbon tetrachloride.

8. The method for preparing a gel blocking agent for delayed gelation according to claim 6, characterized in that: In S22, the initiator includes one or more of di-tert-butyl peroxide, azobisisobutyronitrile, ammonium persulfate, potassium persulfate, boron trifluoride and sodium bisulfite; The anionic surfactant includes one or more of sodium dodecyl sulfate, sodium linear alkylbenzene sulfonate, sodium hexadecyl sulfonate, sodium dioctyl sulfosuccinate, and sodium lauryl sulfate.

9. The method for preparing a gel blocking agent for delayed gelation according to claim 6, characterized in that: In S25, the washing is firstly to wash away the unreacted initiator with deionized water, and then to rinse with anhydrous ethanol.

10. The gel blocking agent prepared according to the method for preparing a gel blocking agent for delayed gelation according to any one of claims 1 to 9.

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