CO2-responsive deep profile control agent, preparation method and application thereof

Abstract

The application belongs to the field of oil and gas development, and particularly relates to a CO2-responsive deep profile control agent, a preparation method and application thereof. The preparation method comprises the following steps: a) adding an aqueous phase solution into an oil phase solution, emulsifying to obtain a reverse emulsion; the aqueous phase solution contains a reaction monomer and a crosslinking agent, the reaction monomer comprises a first monomer and a second monomer, the first monomer is acrylamide and / or methacrylic acid, and the second monomer is one or more of dimethylaminoethyl methacrylate, dimethylaminopropyl methacrylamide and diethylaminoethyl methacrylate; the oil phase solution contains an emulsifier; b) the reverse emulsion is subjected to a polymerization reaction in the presence of an initiator to obtain the CO2-responsive deep profile control agent. The deep profile control agent prepared by the application can be injected into a deep formation at an injection pressure close to that of water, and after reacting with CO2 in the deep formation, the deep profile control agent is subjected to secondary swelling, so that the purpose of selectively plugging CO2 channeling layers is achieved.

Description

Technical Field

[0001] This invention belongs to the field of oil and gas development, and particularly relates to a CO2-responsive deep profile control agent, its preparation method, and its application. Background Technology

[0002] Carbon capture, utilization, and storage (CCUS) has become an important method for addressing global warming caused by CO2. Depleted and late-stage oil and gas reservoirs are considered ideal locations for storing excess carbon dioxide emitted by human activities. They can safely and stably store CO2 and fully utilize pipelines and surface facilities built during production. Simultaneously, the injected CO2 can act as a displacement agent, generating additional oil and gas production, thus offsetting some of the costs of CCUS. However, late-stage oil and gas reservoirs have complex seepage channels and strong formation heterogeneity. Injected CO2 easily penetrates along formation microfractures and high-permeability layers, hindering CO2 contact with crude oil and reducing oil and gas production. Furthermore, the presence of formation microfractures and high-permeability layers also increases the risk of CO2 leakage.

[0003] Currently, common methods for improving CO2 sweep efficiency include gas-water alternating flooding, foam, in-situ gel, and pre-formed particles. However, these methods all have certain drawbacks. For example, the main plugging force in gas-water alternating flooding is capillary force at the pore scale, resulting in weak plugging effectiveness. Foam systems have limited stability in high-temperature and high-salt environments. The gelation time, gel strength, and stability of in-situ gels are significantly affected by formation factors such as temperature, pH, and salt concentration. Furthermore, in-situ gels may cause permeability damage in the near-wellbore zone, increasing the difficulty of subsequent water injection. Pre-formed particles face challenges such as the inability to migrate to distant wellbore zones. Additionally, the acidity of CO2 can cause some carboxylic acid polymers to dehydrate and shrink, greatly affecting the plugging effect. Summary of the Invention

[0004] In view of this, the purpose of the present invention is to provide a CO2-responsive deep profile control agent, its preparation method and application. The polymer microgel in the deep profile control agent prepared by the present invention has a uniform and adjustable particle size distribution. The deep profile control agent can be injected into the deep formation at an injection pressure close to that of water. After reacting with CO2 in the deep formation, it undergoes secondary swelling, thereby achieving the purpose of selectively blocking CO2 from entering the formation.

[0005] This invention provides a method for preparing a CO2-responsive deep profile control agent, comprising the following steps:

[0006] a) Add the aqueous solution to the oil phase solution and emulsify to obtain a reverse emulsion;

[0007] The aqueous phase solution contains reactive monomers and crosslinking agents. The reactive monomers include a first monomer and a second monomer. The first monomer is acrylamide and / or methacrylic acid, and the second monomer is one or more of dimethylaminoethyl methacrylate, dimethylaminopropylmethacrylamide, and diethylaminoethyl methacrylate. The oil phase solution contains an emulsifier.

[0008] b) The reverse emulsion undergoes polymerization in the presence of an initiator to obtain a CO2-responsive deep profile control agent.

[0009] Preferably, in step a), the mass ratio of the first monomer to the second monomer is 1:(1 to 12).

[0010] Preferably, in step a), the crosslinking agent is N,N'-methylenebisacrylamide and / or ethylene glycol dimethacrylate; the crosslinking agent accounts for 0.1-2% of the mass of the reactant monomer.

[0011] Preferably, in step a), the aqueous solution further contains HCl in an amount equal to the molar amount of the reactant monomer.

[0012] Preferably, in step a), the emulsifier is Span-80 and Tween-80, and the mass ratio of Span-80 to Tween-80 is (1~5):1.

[0013] Preferably, in step a), the total content of the reactive monomer and crosslinking agent in the aqueous solution is 50-70 wt%; the content of the emulsifier in the oil solution is 5-20 wt%; and the mass ratio of the aqueous solution to the oil solution is 1:(1.5-3).

[0014] Preferably, in step b), the initiator is ammonium persulfate; the amount of the initiator is 0.1-2% of the mass of the reactant monomer.

[0015] Preferably, in step b), the polymerization reaction temperature is 50–90°C, and the polymerization reaction time is 2–6 hours.

[0016] The present invention also provides a CO2-responsive deep profile control agent, which is prepared according to the preparation method described in the above technical solution.

[0017] The present invention also provides an application of the CO2-responsive deep profile control agent described in the above technical solution in deep profile control in oil fields.

[0018] Compared with existing technologies, this invention provides a CO2-responsive deep profile control agent, its preparation method, and its application. The preparation method provided by this invention includes the following steps: a) adding an aqueous solution to an oil phase solution and emulsifying to obtain a reverse emulsion; the aqueous solution contains reactive monomers and a crosslinking agent, the reactive monomers including a first monomer and a second monomer, the first monomer being acrylamide and / or methacrylic acid, and the second monomer being one or more of dimethylaminoethyl methacrylate, dimethylaminopropylmethacrylamide, and diethylaminoethyl methacrylate; the oil phase solution contains an emulsifier; b) the reverse emulsion undergoes a polymerization reaction in the presence of an initiator to obtain a CO2-responsive deep profile control agent. The method provided by this invention can prepare a polymer microgel dispersion with uniform particle size distribution, and the particle size of the microgel can be further adjusted by adjusting reaction conditions such as reaction temperature, monomer ratio, initiator addition amount, and emulsifier addition amount. The polymer microgel dispersion prepared by this invention can be injected into deep formations at extremely low injection pressure. After reacting with CO2 deep in the formation, it undergoes secondary swelling, which has a good sealing effect on CO2 leaking out of the formation. Attached Figure Description

[0019] 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 only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0020] Figure 1 This is a microscopic observation result of the microgel dispersion provided in Example 4 of the present invention before contact with CO2;

[0021] Figure 2 This is a microscopic observation result of the microgel dispersion provided in Example 4 of the present invention after CO2 was introduced for 30 seconds;

[0022] Figure 3 This is a particle size distribution diagram of the microgel dispersion provided in Example 4 of the present invention before contact with CO2 and after CO2 is introduced for 30 s;

[0023] Figure 4 This is a graph showing the displacement pressure difference experiment results of alternating CO2-salt water flooding and alternating CO2-microgel dispersion flooding provided in Example 4 of the present invention;

[0024] Figure 5 This is a graph showing the displacement pressure difference of the microgel dispersion provided in Example 4 of the present invention before and after CO2 activation. Detailed Implementation

[0025] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0026] This invention provides a method for preparing a CO2-responsive deep profile control agent, comprising the following steps:

[0027] a) Add the aqueous solution to the oil phase solution and emulsify to obtain a reverse emulsion;

[0028] b) The reverse emulsion undergoes polymerization in the presence of an initiator to obtain a CO2-responsive deep profile control agent.

[0029] In the preparation method provided by the present invention, in step a), the aqueous solution contains a reactive monomer and a crosslinking agent; wherein, the reactive monomer includes a first monomer and a second monomer; the first monomer is acrylamide and / or methacrylic acid; the second monomer is one or more of dimethylaminoethyl methacrylate, dimethylaminopropylmethacrylamide, and diethylaminoethyl methacrylate; the mass ratio of the first monomer and the second monomer is preferably 1:(1-12), specifically 1:1, 1:1.5, 1:2, 1:2.5, 1:3, 1:3.5, 1:4, 1:4.5, 1:4.55, 1:5, 1:5.5, 1:6, 1:6.5, 1:7, 1:7.5, 1:8, 1:8.5, 1:9, 1:9.5, 1:10, 1:10.5, 1:11, 1:11.2, 1:11.5, or 1:12.

[0030] In the preparation method provided by the present invention, in step a), the crosslinking agent contained in the aqueous solution is preferably N,N'-methylenebisacrylamide and / or ethylene glycol dimethacrylate; the crosslinking agent preferably accounts for 0.1% to 2% of the mass of the reactant monomers, specifically 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, or 2%.

[0031] In the preparation method provided by the present invention, in step a), the total content of the reactive monomer and crosslinking agent in the aqueous solution is preferably 50-70 wt%, specifically 50 wt%, 51 wt%, 52 wt%, 53 wt%, 54 wt%, 55 wt%, 56 wt%, 57 wt%, 58 wt%, 59 wt%, 60 wt%, 61 wt%, 62 wt%, 63 wt%, 64 wt%, 65 wt%, 66 wt%, 67 wt%, 68 wt%, 69 wt%, or 70 wt%.

[0032] In the preparation method provided by the present invention, in step a), in order to promote the dissolution of the reaction monomer, the aqueous solution preferably also contains HCl in an amount equal to the molar amount of the reaction monomer.

[0033] In the preparation method provided by the present invention, in step a), the solvent in the aqueous solution is preferably deionized water.

[0034] In the preparation method provided by the present invention, in step a), the oil phase solution contains an emulsifier; the emulsifier is preferably Span-80 and / or Tween-80, and the mass ratio of Span-80 and Tween-80 is preferably (1-5):1, specifically 1:1, 1.2:1, 1.5:1, 1.7:1, 2:1, 2.3:1, 2.5:1, 2.7:1, 3:1, 3.2:1, 3.5:1, 3.7:1, 4:1, 4.2:1, 4.5:1, 4.7:1 or 5:1.

[0035] In the preparation method provided by the present invention, in step a), the content of emulsifier in the oil phase solution is preferably 5-20 wt%, specifically 5 wt%, 6 wt%, 7 wt%, 7.3 wt%, 8 wt%, 9 wt%, 9.5 wt%, 10 wt%, 11 wt%, 12 wt%, 13 wt%, 14 wt%, 15 wt%, 16 wt%, 17 wt%, 18 wt%, 19 wt%, or 20 wt%.

[0036] In the preparation method provided by the present invention, in step a), the solvent in the oil phase solution is preferably one or more of n-heptane, n-hexane, and white oil.

[0037] In the preparation method provided by the present invention, in step a), the mass ratio of the aqueous phase solution to the oil phase solution is preferably 1:(1.5-3), specifically 1:1.5, 1:1.6, 1:1.7, 1:1.8, 1:1.9, 1:2, 1:2.1, 1:2.2, 1:2.3, 1:2.4, 1:2.5, 1:2.6, 1:2.7, 1:2.8, 1:2.9 or 1:3.

[0038] In the preparation method provided by the present invention, in step a), the stirring rate of the emulsification is preferably 500 to 1000 rpm, specifically 500 rpm, 550 rpm, 600 rpm, 650 rpm, 700 rpm, 750 rpm, 800 rpm, 850 rpm, 900 rpm, 950 rpm or 1000 rpm.

[0039] In the preparation method provided by the present invention, in step a), the emulsification temperature is preferably 50-90°C, specifically 50°C, 52°C, 55°C, 57°C, 60°C, 62°C, 65°C, 67°C, 70°C, 72°C, 75°C, 77°C, 80°C, 82°C, 85°C, 87°C or 90°C.

[0040] In the preparation method provided by the present invention, in step a), the emulsification time is preferably 15 to 60 min, specifically 15 min, 20 min, 25 min, 30 min, 35 min, 40 min, 45 min, 50 min, 55 min or 60 min.

[0041] In the preparation method provided by this invention, in step b), the initiator is preferably ammonium persulfate (APS); the amount of the initiator is preferably 0.1% to 2% of the mass of the reactant monomer, specifically 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, or 2%. In this invention, the initiator is preferably added to the reverse emulsion in the form of an aqueous initiator solution, and the concentration of the aqueous initiator solution is preferably 5% to 10 wt%, specifically 5 wt%, 5.5 wt%, 6 wt%, 6.5 wt%, 7 wt%, 7.5 wt%, 8 wt%, 8.5 wt%, 8.6 wt%, 9 wt%, 9.5 wt%, or 10 wt%.

[0042] In the preparation method provided by the present invention, in step b), the temperature of the polymerization reaction is preferably 50-90°C, specifically 50°C, 52°C, 55°C, 57°C, 60°C, 62°C, 65°C, 67°C, 70°C, 72°C, 75°C, 77°C, 80°C, 82°C, 85°C, 87°C or 90°C.

[0043] In the preparation method provided by the present invention, in step b), the polymerization reaction time is preferably 2 to 6 hours, specifically 2 hours, 2.3 hours, 2.5 hours, 2.7 hours, 3 hours, 3.2 hours, 3.5 hours, 3.7 hours, 4 hours, 4.2 hours, 4.5 hours, 4.7 hours, 5 hours, 5.2 hours, 5.5 hours, 5.7 hours, or 6 hours.

[0044] The present invention also provides a CO2-responsive deep profile control agent, which is prepared according to the preparation method described in the above technical solution.

[0045] The present invention also provides an application of the CO2-responsive deep profile control agent described in the above technical solution in deep profile control in oil fields.

[0046] The technical solution provided by this invention can prepare a polymer microgel dispersion with uniform particle size distribution. Furthermore, the particle size of the microgel can be adjusted by regulating reaction conditions such as reaction temperature, monomer ratio, initiator dosage, and emulsifier dosage. The polymer microgel dispersion prepared by this invention can be injected deep into the formation at extremely low injection pressure. After reacting with CO2 deep within the formation, it undergoes secondary swelling, exhibiting excellent sealing effects against leaking CO2 from the formation.

[0047] For clarity, the following examples will be used to provide a detailed description.

[0048] Example 1

[0049] Using dimethylaminoethyl methacrylate and acrylamide as reactive monomers and N,N'-methylenebisacrylamide as a crosslinking agent, dimethylaminoethyl methacrylate, acrylamide and N,N'-methylenebisacrylamide were mixed in a mass percentage of 81.0%:17.8%:1.2%, and hydrochloric acid solution (5.73 mol / L) in an equimolar ratio with the functional monomers was added to aid dissolution, finally preparing an aqueous solution with a total content of 60% of reactive monomers and crosslinking agent.

[0050] Using Span 80 and Tween 80 as emulsifiers, Span 80 and Tween 80 were dissolved in white oil at a mass percentage of 70%:30% to finally prepare an oil phase solution with an emulsifier content of 17%.

[0051] The oil phase solution was gradually heated to 70°C, and then the aqueous phase solution was gradually added dropwise to the oil phase solution at a mass ratio of 2:1 between the oil phase solution and the aqueous phase solution at 700 rpm. The mixture was continuously stirred and emulsified for 30 min to obtain a reverse emulsion.

[0052] An aqueous solution of ammonium persulfate (concentration 8.6 wt%) was added dropwise to the above reverse emulsion to initiate a polymerization reaction; wherein the amount of ammonium persulfate added was 0.8% of the mass of the reactant monomer, the reaction temperature was 70℃, and the reaction time was 4 h; after the reaction was completed, a microgel dispersion with an initial particle size of about 5 μm and a swelling ratio of about 2.0 was obtained, and this microgel dispersion is the CO2-responsive deep profile control agent prepared in this embodiment.

[0053] Example 2

[0054] Using dimethylaminoethyl methacrylate and acrylamide as reactive monomers and N,N'-methylenebisacrylamide as a crosslinking agent, dimethylaminoethyl methacrylate, acrylamide, and N,N'-methylenebisacrylamide were mixed in a mass percentage of 90.7%:8.1%:1.2%, and hydrochloric acid solution (5.73 mol / L) in an equimolar ratio with the functional monomers was added to aid dissolution, finally preparing an aqueous solution with a total content of 60% of reactive monomers and crosslinking agent.

[0055] Using Span 80 and Tween 80 as emulsifiers, Span 80 and Tween 80 were dissolved in white oil at a mass percentage of 70%:30%, and finally formulated into an oil phase solution with an emulsifier content of 9.5%.

[0056] The oil phase solution was gradually heated to 70°C, and then the aqueous phase solution was gradually added dropwise to the oil phase solution at a mass ratio of 2:1 between the oil phase solution and the aqueous phase solution at 700 rpm. The mixture was continuously stirred and emulsified for 30 min to obtain a reverse emulsion.

[0057] An aqueous solution of ammonium persulfate (concentration 8.6 wt%) was added dropwise to the above reverse emulsion to initiate a polymerization reaction; wherein the amount of ammonium persulfate added was 0.8% of the mass of the reactant monomer, the reaction temperature was 70℃, and the reaction time was 4 h; after the reaction was completed, a microgel dispersion with an initial particle size of about 5 μm and a swelling ratio of about 2.5 was obtained, and this microgel dispersion is the CO2-responsive deep profile control agent prepared in this embodiment.

[0058] Example 3

[0059] Using dimethylaminoethyl methacrylate and acrylamide as reactive monomers and N,N'-methylenebisacrylamide as a crosslinking agent, dimethylaminoethyl methacrylate, acrylamide and N,N'-methylenebisacrylamide were mixed in a mass percentage of 81.0%:17.8%:1.2%, and hydrochloric acid solution (5.73 mol / L) in an equimolar ratio with the functional monomers was added to aid dissolution, finally preparing an aqueous solution with a total content of 60% of reactive monomers and crosslinking agent.

[0060] Using Span 80 and Tween 80 as emulsifiers, Span 80 and Tween 80 were dissolved in white oil at a mass percentage of 70%:30%, and finally formulated into an oil phase solution with an emulsifier content of 7.3%.

[0061] The oil phase solution was gradually heated to 70°C, and then the aqueous phase solution was gradually added dropwise to the oil phase solution at a mass ratio of 2:1 between the oil phase solution and the aqueous phase solution at 700 rpm. The mixture was continuously stirred and emulsified for 30 min to obtain a reverse emulsion.

[0062] An aqueous solution of ammonium persulfate (concentration 8.6 wt%) was added dropwise to the above-mentioned reverse emulsion to initiate a polymerization reaction; wherein, the amount of ammonium persulfate added was 0.8% of the mass of the reactant monomer, the reaction temperature was 70°C, and the reaction time was 4 h; after the reaction was completed, a microgel dispersion with an initial particle size of about 10 μm and a swelling ratio of about 2.0 was obtained, and this microgel dispersion is the CO2-responsive deep profile control agent prepared in this embodiment.

[0063] Example 4

[0064] (1) The morphology and particle size changes of the microgel dispersion in Example 2 before and after contact with CO2 were tested using a microscope and a laser particle size analyzer, thereby evaluating its CO2-responsive swelling performance:

[0065] The results are as follows Figures 1-3 As shown. Combined with Figures 1-2 It can be seen that after CO2 was introduced, the microspheres swelled significantly, increased in volume, and overlapped each other. Through... Figure 3 It can be seen that after CO2 is introduced, the microsphere size increases proportionally, confirming that the response monomers are evenly distributed and the microsphere size increases to about 2.5 times the original size.

[0066] (2) The CO2 blocking performance of the microgel dispersion in Example 2 was tested by core displacement experiments:

[0067] The results are as follows Figure 4As shown. The core permeability was 1.39D. The injection pressure was maintained above 5MPa using a back pressure regulator, and the experimental temperature was 70℃. To control variables, alternating CO2-brine flooding and alternating CO2-microgel dispersion flooding were tested in the same core. The brine composition is detailed in Table 1. The injection fluids and sequence for alternating CO2-brine (WAG) flooding were: 1PV brine—1PV CO2—0.5PV brine—0.5PV CO2—0.5PV brine—0.5PV CO2—0.5PV brine—2PV CO2, where PV is the pore volume, and 1PV represents one times the core pore volume. The injection fluids and sequence for alternating CO2-microgel dispersion (MAG) flooding were: 1PV brine—1PV CO2—0.5PV microgel dispersion—0.5PV CO2—0.5PV microgel dispersion—0.5PV CO2—0.5PV microgel dispersion—2PVCO2. As the number of slugs in the microgel dispersion-CO2 slug increases, the plugging pressure differential gradually increases. Eventually, the residual CO2 resistance of the CO2-microgel dispersion stabilizes at 0.35 MPa, which is approximately 33 times that of the CO2-saltwater alternating drive.

[0068] Table 1. Composition of saline solution

[0069]

[0070] (3) The deep transport and response plugging performance of the microgel dispersion in Example 2 were tested by multi-pressure core displacement experiments:

[0071] The results are as follows Figure 5 As shown. The injection rate was 1.5 mL / min, the core permeability was 1.23D, and the pore volume was 16.83 mL. The experimental procedure was as follows: 3 pore volumes of microgel dispersion were injected; the core outlet was closed and CO2 was injected to raise the core pressure to 1 MPa; 5 PV of microgel dispersion was then injected. During the initial 3 PV (0–30 min) injection of microgel dispersion, the average injection pressure difference was only 0.001–0.025 MPa. After CO2 activation, the injection pressure difference of microgel dispersion increased to 0.2–0.33 MPa, an increase of more than 100 times.

[0072] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a CO2-responsive deep profile control agent, characterized by, The method comprises the following steps: a) adding an aqueous phase solution into an oil phase solution, emulsifying to obtain a reverse emulsion; the aqueous phase solution contains reaction monomers and a crosslinking agent, the reaction monomers include a first monomer and a second monomer, the first monomer is acrylamide and / or methacrylic acid, and the second monomer is one or more of dimethylaminoethyl methacrylate, dimethylaminopropyl methacrylamide and diethylaminoethyl methacrylate; the oil phase solution contains an emulsifier; b) the reverse emulsion is subjected to a polymerization reaction in the presence of an initiator to obtain the CO2-responsive deep profile control agent.

2. The production method according to claim 1, characterized by, In step a), the mass ratio of the first monomer to the second monomer is 1:(1-12).

3. The production method according to claim 1, characterized by, In step a), the crosslinking agent is N,N'-methylenebisacrylamide and / or ethylene glycol dimethacrylate, and the content of the crosslinking agent is 0.1-2% of the mass of the reaction monomers.

4. The method of claim 1, wherein, In step a), the aqueous phase solution further contains HCl in an equimolar amount of the reaction monomers.

5. The preparation method according to claim 1, characterized in that, In step a), the emulsifier is Span-80 and Tween-80, and the mass ratio of Span-80 to Tween-80 is (1-5):

1.

6. The method of claim 1, wherein, In step a), the total content of the reaction monomers and the crosslinking agent in the aqueous phase solution is 50-70wt%, the content of the emulsifier in the oil phase solution is 5-20wt%, and the mass ratio of the aqueous phase solution to the oil phase solution is 1:(1.5-3).

7. The preparation method according to claim 1, characterized in that, In step b), the initiator is ammonium persulfate, and the content of the initiator is 0.1-2% of the mass of the reaction monomers.

8. The method of claim 1, wherein, In step b), the temperature of the polymerization reaction is 50-90℃, and the time of the polymerization reaction is 2-6h.

9. A CO2-responsive deep profile control agent, characterized by, The CO2-responsive deep profile control agent is prepared by the method according to any one of claims 1-8.

10. The use of the CO2-responsive deep profile control agent according to claim 9 in deep profile control of an oilfield.

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