CO2 gas-driven channeling sealing agent as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of oilfield exploitation, and particularly relates to a CO2 gas drive channeling sealing agent and a preparation method and application thereof. The CO2 gas flooding channeling sealing agent comprises the following raw materials: a surfactant, gemini tertiary amine and water, and the gemini tertiary amine is obtained by reacting N, N-methylene bisacrylamide with secondary amine. The response type gel anti-channeling agent disclosed by the invention has good injection performance; the preparation is simple, the performance can be flexibly regulated and controlled, and the damage to the reservoir is small; the plugging agent has good thickening performance under the condition of CO2 and can effectively plug a matrix, and the plugging rate reaches 95% or above.

Description

Technical Field

[0001] The invention belongs to the technical field of oilfield exploitation, and in particular relates to a CO2 gas drive sealing agent and a preparation method and application thereof. Background Art

[0002] The recovery rate of ultra-low permeability reservoirs relying on natural energy is generally less than 10%. To improve the recovery rate of reservoirs, it is necessary to supplement reservoir energy through water injection or gas injection. Since hydration film is easily formed during water injection, clay minerals in the formation swell when exposed to water, and the pores tend to close, the water injection pressure rises rapidly, the injection volume is greatly reduced, and even no water can be injected, resulting in low matrix utilization. Compared with water injection, gas injection is easy to enter micro-nano pores, which can effectively displace crude oil in the matrix and significantly improve oil recovery efficiency. In particular, CO2 gas is more soluble in water than general hydrocarbon gases, and its solubility in crude oil is greater than that in water. CO2 can be transferred from aqueous solution to crude oil, and has the advantages of easy flow, viscosity reduction, volume expansion, reduced interfacial tension, acidification and plugging, extraction of light hydrocarbons, and easy miscibility. Therefore, CO2 flooding has received widespread attention at home and abroad as an effective means of improving the recovery rate of low-permeability oil reservoirs.

[0003] Most of my country's oil reservoirs are continental deposits with serious heterogeneity. In the process of CO2 gas flooding, gas channeling is very likely to occur due to the gas slippage effect, viscous fingering and reservoir heterogeneity. The gas channeling varies greatly, and there are generally problems such as large pore channeling and high permeability layer breakthrough. Early breakthrough of CO2 injection will result in most of the reservoir being unaffected, making it difficult for the CO2 injection development of the reservoir to achieve the expected development effect. Therefore, before the CO2 gas drive work, it is very important to effectively block the high permeability layer to prevent gas channeling along the high permeability zone during CO2 gas drive.

[0004] Chinese invention patent application CN202010262672.5 discloses a foam sealing agent for CO2 flooding in heavy oil reservoirs, its preparation method and application, which belongs to the technical field of CO2 flooding in heavy oil reservoirs and can solve the technical problems of the existing foam sealing agent such as complex process, poor foaming ability and low stability. The mass concentration of α-olefin sulfonate in the foam sealing agent for CO2 flooding in heavy oil reservoirs is 40-60%, the mass concentration of quaternary ammonium salt type imidazoline is 10-20%, the mass concentration of hydroxyethyl cellulose is 3-5%, and the mass concentration of Na5P3O 10 The mass concentration is 10-15%, and the balance is water. The invention can effectively control gas channeling and fluidity, thereby increasing the swept volume of CO2 flooding, so as to achieve the purpose of adjusting the flooding and isofluidity control, and then achieve the goal of improving the recovery rate. However, the construction of foam sealing on site is difficult. Foam is formed on the ground and cannot be injected; foam is formed underground, and the quality and quantity are difficult to guarantee.

[0005] Chinese invention patent application CN201410662306.3 discloses an organic particle plugging agent for CO2-driven high-temperature, low-permeability, water-sensitive oil reservoirs and its preparation method. The plugging agent is composed of organic phenol, formaldehyde, furfural, p-toluenesulfonic acid, organic alcohol, and dispersant; the isolation plug used is gas: N2 or CO2; the plugging agent is mainly formed by carbonyl addition and condensation reaction of the above raw materials under the action of catalyst to form a polymer with furan methylene as bridge and furan hydroxymethyl as end group, and organic gel particles are synthesized by solution-sol-gel method in acidic or supercritical CO2 atmosphere; as the polymer molecules of the polymerization reaction increase to a certain extent and exceed their solubility, the polymer molecules condense to form organic particles. However, the synthesis process of this product involves many toxic substances and the preparation process is relatively complicated.

[0006] In view of the problems existing in the CO2 gas flooding process of high-temperature and low-permeability oil reservoirs, it is urgent to develop a temperature-resistant, salt-resistant, and easy-to-inject sealing agent with excellent performance to improve the CO2 displacement effect. In view of this, it is necessary to develop a new temperature-resistant, salt-resistant, and easy-to-inject sealing agent. Summary of the invention

[0007] Based on the above shortcomings, the present invention provides a CO2 gas drive anti-channeling agent and its preparation method and application. The present invention prepares a gemini tertiary amine, which has CO2 responsiveness. When CO2 is introduced, the gemini tertiary amine is protonated so that both ends of the molecule have positive charges, and then self-assembles with a surfactant in a solution under the action of electrostatic attraction to form a CO2 responsive gel, which can be used as a CO2 drive responsive gel anti-channeling agent. It is particularly suitable for use as a CO2 responsive gel anti-channeling agent for increasing production in tight oil reservoirs.

[0008] To achieve the above purpose, the technical solution adopted by the present invention is as follows:

[0009] A CO2 gas drive sealing agent, the raw materials of which include surfactant, gemini tertiary amine and water, wherein the gemini tertiary amine is obtained by the reaction of N,N-methylenebisacrylamide and secondary amine.

[0010] Preferably, the chemical structure of the gemini tertiary amine is as follows:

[0011]

[0012] Among them, R1 and R2 are C n H 2n+1 .

[0013] Preferably, the raw materials of the CO2 gas flooding sealing agent include, by weight percentage, 1%-5% of a surfactant, 1%-5% of a gemini tertiary amine and the balance of water.

[0014] Preferably, the surfactant is selected from one or more of sodium dodecyl sulfate, sodium α-olefin sulfonate and sodium fatty acid methyl ester sulfonate.

[0015] The synthetic route of the gemini tertiary amine is as follows:

[0016] Preferably, the molar ratio of the N,N-methylenebisacrylamide to the secondary amine is 1:1-3.

[0017] Preferably, the secondary amine is selected from any one of dimethylamine, dipropylamine and diisopropylamine.

[0018]

[0019] The gemini tertiary amine is CO2 responsive. When CO2 is introduced, the gemini tertiary amine is protonated so that both ends of the molecule have positive charges. Then, it self-assembles with a surfactant in a solution under the action of electrostatic attraction to form a CO2 responsive gel, which can be used as a CO2-driven responsive gel anti-channeling agent.

[0020] The present invention also relates to a method for preparing the above-mentioned CO2 gas flooding sealing agent, comprising the following steps:

[0021] (1) N,N-methylenebisacrylamide, secondary amine and water are mixed and reacted to obtain gemini tertiary amine;

[0022] (2) Gemini tertiary amine, surfactant and water are mixed to obtain the CO2 gas drive sealing agent.

[0023] Preferably, the reaction temperature in step (1) is 20-80°C, and the reaction time is 20-28h.

[0024] Preferably, after the reaction in step (1), the step of removing the secondary amine by rotary evaporation is also included.

[0025] The present invention also relates to the application of the CO2 gas drive channeling blocking agent as a channeling blocking agent in oil field and oil reservoir exploitation.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] (1) The responsive gel anti-channeling agent of the present invention has good injection performance;

[0028] (2) The responsive gel anti-channeling agent of the present invention is easy to prepare, its performance can be flexibly adjusted, and it is less harmful to the reservoir;

[0029] (3) The responsive gel anti-channeling agent of the present invention has good thickening performance under CO2 conditions and can effectively block the matrix with a blocking rate of more than 95%. DETAILED DESCRIPTION

[0030] The technical solutions in the embodiments of the present invention are further clearly described. The described embodiments are only a part of the present invention and are used to explain the present invention but not to limit the present invention. Therefore, other embodiments obtained by other technicians in the field without creative work all belong to the protection scope of the present invention.

[0031] Sodium dodecyl sulfate, sodium α-olefin sulfonate, sodium fatty acid methyl ester sulfonate and lauramide propyl betaine were purchased from Chengdu Kelong Chemical Co., Ltd.

[0032] Example 1

[0033] The raw materials of the CO2 gas drive sealing agent are, by weight percentage, 3% sodium dodecyl sulfate, 1% gemini tertiary amine A and 96% water.

[0034] Preparation method:

[0035] (1) reacting N,N-methylenebisacrylamide with a dimethylamine aqueous solution at 20° C. for 24 hours, wherein the molar ratio of N,N-methylenebisacrylamide to dimethylamine is 1:2;

[0036] (2) After the reaction, remove excess dimethylamine by rotary evaporation to obtain gemini tertiary amine A;

[0037] (3) 3 wt % of sodium dodecyl sulfate, 1 wt % of gemini tertiary amine A and 96 wt % of water are mixed uniformly to obtain a CO2 gas drive sealing agent.

[0038] Example 2

[0039] The raw materials of the CO2 gas drive sealing agent are, by weight percentage, 4% sodium α-olefin sulfonate, 2% gemini tertiary amine B and 94% water.

[0040] Preparation method:

[0041] (1) reacting N,N-methylenebisacrylamide with a dimethylamine aqueous solution at 30° C. for 24 hours, wherein the molar ratio of N,N-methylenebisacrylamide to dimethylamine is 1:3;

[0042] (2) After the reaction, remove excess dimethylamine by rotary evaporation to obtain gemini tertiary amine B;

[0043] (3) 4 wt% of sodium α-olefin sulfonate, 2 wt% of gemini tertiary amine B and 94 wt% of water are mixed uniformly to obtain a CO2 gas drive sealing agent.

[0044] Example 3

[0045] The raw materials of the CO2 gas drive sealing agent are: 5% sodium fatty acid methyl ester sulfonate, 1.5% gemini tertiary amine C and 93.5% water, calculated by weight percentage.

[0046] Preparation method:

[0047] (1) reacting N,N-methylenebisacrylamide with an aqueous solution of diisopropylamine at 50° C. for 24 hours, wherein the molar ratio of N,N-methylenebisacrylamide to dimethylamine is 1:2;

[0048] (2) After the reaction, remove the excess diisopropylamine by rotary evaporation to obtain the gemini tertiary amine C;

[0049] (3) 5 wt% of sodium fatty acid methyl ester sulfonate, 1.5 wt% of gemini tertiary amine C and 96 wt% of water are mixed uniformly to obtain a CO2 gas drive sealing agent.

[0050] Example 4

[0051] The raw materials of the CO2 gas drive sealing agent are: 4% sodium fatty acid methyl ester sulfonate, 1% gemini tertiary amine D and 95% water, calculated by weight percentage.

[0052] Preparation method:

[0053] (1) reacting N,N-methylenebisacrylamide with an aqueous solution of diisopropylamine at 60° C. for 24 hours, wherein the molar ratio of N,N-methylenebisacrylamide to dimethylamine is 1:3;

[0054] (2) After the reaction, remove the excess diisopropylamine by rotary evaporation to obtain the gemini tertiary amine D;

[0055] (3) 4 wt% of sodium fatty acid methyl ester sulfonate, 1 wt% of gemini tertiary amine D and 95 wt% of water are mixed uniformly to obtain a CO2 gas drive sealing agent.

[0056] Example 5

[0057] The raw materials of the CO2 gas drive sealing agent are, by weight percentage, 2% sodium dodecyl sulfate, 3% sodium fatty acid methyl ester sulfonate, 2% gemini tertiary amine E and 93% water.

[0058] Preparation method:

[0059] (1) reacting N,N-methylenebisacrylamide with an aqueous solution of dipropylamine at 70° C. for 24 hours, wherein the molar ratio of N,N-methylenebisacrylamide to dipropylamine is 1:1.5;

[0060] (2) After the reaction, remove the excess dipropylamine by rotary evaporation to obtain the gemini tertiary amine E;

[0061] (3) 2 wt% of sodium dodecyl sulfate, 3 wt% of sodium fatty acid methyl ester sulfonate, 2 wt% of gemini tertiary amine E and 93 wt% of water are mixed uniformly to obtain a CO2 gas drive sealing agent.

[0062] Example 6

[0063] The raw materials of the CO2 gas drive sealing agent are: 5% sodium dodecyl sulfate, 5% gemini tertiary amine F and 90% water, calculated by weight percentage.

[0064] Preparation method:

[0065] (1) reacting N,N-methylenebisacrylamide with an aqueous solution of dipropylamine at 80° C. for 24 hours, wherein the molar ratio of N,N-methylenebisacrylamide to dipropylamine is 1:3;

[0066] (2) After the reaction, remove the excess dipropylamine by rotary evaporation to obtain the gemini tertiary amine F;

[0067] (3) 5% sodium dodecyl sulfate, 5% gemini tertiary amine F and 90% water are mixed evenly to obtain a CO2 gas drive sealing agent.

[0068] Comparative Example 1

[0069] The raw materials of the CO2 gas drive sealing agent are, by weight percentage, 5% sodium dodecyl sulfate, 5% N,N-methylenebisacrylamide, 2.5% dipropylamine and 87.5% water.

[0070] Preparation method:

[0071] Mix sodium dodecyl sulfate, N,N-methylenebisacrylamide, dipropylamine and water evenly to obtain the product.

[0072] Comparative Example 2

[0073] The raw materials of the CO2 gas drive sealing agent are: 5% sodium dodecylbenzene sulfonate, 5% gemini tertiary amine F and 90% water, calculated by weight percentage.

[0074] Preparation method:

[0075] (1) reacting N,N-methylenebisacrylamide with an aqueous solution of dipropylamine at 80° C. for 24 hours, wherein the molar ratio of N,N-methylenebisacrylamide to dipropylamine is 1:3;

[0076] (2) After the reaction, remove the excess dipropylamine by rotary evaporation to obtain the gemini tertiary amine F;

[0077] (3) 5% sodium dodecylbenzene sulfonate, 5% gemini tertiary amine F and 90% water are mixed evenly to obtain a CO2 gas drive sealing agent.

[0078] Comparative Example 3

[0079] The raw materials of the CO2 gas drive sealing agent are: 5% sodium dodecyl sulfate, 5% gemini tertiary amine H and 90% water, calculated by weight percentage.

[0080] Preparation method:

[0081] (1) reacting N,N-methylenebisacrylamide and a diacetone acrylamide aqueous solution at 80° C. for 24 hours, wherein the molar ratio of N,N-methylenebisacrylamide to diacetone acrylamide is 1:3;

[0082] (2) After the reaction, remove the excess diacetone acrylamide by rotary evaporation to obtain the gemini tertiary amine H;

[0083] (3) 5 wt% of sodium dodecyl sulfate, 5 wt% of gemini tertiary amine H and 90 wt% of water are mixed uniformly to obtain a CO2 gas drive sealing agent.

[0084] Comparative Example 4

[0085] The raw materials of the CO2 gas drive sealing agent are: 5% sodium dodecyl sulfate, 5% gemini tertiary amine F mixture and 90% water, calculated by weight percentage.

[0086] Preparation method:

[0087] (1) reacting N,N-methylenebisacrylamide with an aqueous solution of dipropylamine at 80° C. for 24 hours, wherein the molar ratio of N,N-methylenebisacrylamide to dipropylamine is 1:3, to obtain a mixture of gemini tertiary amines F;

[0088] (2) 5% sodium dodecyl sulfate, 5% gemini tertiary amine F mixture and 90% water are mixed evenly to obtain a CO2 gas drive sealing agent.

[0089] Effect test

[0090] The performance tests of the CO2 gas flooding sealing agents in Examples 1-6 and Comparative Examples 1-4 were performed respectively, and the specific methods are as follows:

[0091] 1. Tackifying performance test

[0092] The test method is as follows: 1) weigh the CO2 gas-driven sealing agent and add it to distilled water in a beaker, stir evenly, and test its initial viscosity using an NDJ rotational viscometer; 2) introduce CO2 into the beaker while stirring until the viscosity no longer changes, thereby obtaining a CO2-responsive gel, which is then tested for viscosity using an NDJ rotational viscometer.

[0093] 2. Plugging performance test

[0094] The test method is as follows: 1) Wash the core with a mixture of ethanol and toluene for 3-4 days, dry it, and determine the basic data of the core; 2) Saturate the core with crude oil; 3) Place the core in a holder, add a confining pressure of 10MPa, inject CO2 at a certain flow rate until the core gasifies, and record the gas outlet pressure P1 at this time; 4) Inject 0.8PV CO2 gas drive sealing agent solution, act in a CO2 atmosphere for 30 minutes, and make the CO2 gas drive sealing agent gel; 5) Pass CO2 at a certain flow rate, wait for it to break through, and record its breakthrough pressure P2; 6) Calculate its plugging rate through the pressure changes before and after.

[0095] Table 1 CO2 gas drive sealing agent performance test results

[0096]

[0097]

[0098] The above detailed description is a specific description of one feasible embodiment of the present invention. The embodiment is not intended to limit the patent scope of the present invention. Any equivalent implementation or modification that does not deviate from the present invention should be included in the scope of the technical solution of the present invention.

Claims

1. A CO2 gas flooding sealing agent, characterized in that: The raw materials of the CO2 gas flooding sealing agent include surfactant, gemini tertiary amine and water, wherein the gemini tertiary amine is obtained by the reaction of N,N-methylenebisacrylamide and secondary amine.

2. The CO2 gas flooding sealing agent according to claim 1, characterized in that: The chemical structure of the gemini tertiary amine is as follows: Among them, R1 and R2 are C n H 2n+1 .

3. The CO2 gas flooding sealing agent according to claim 1, characterized in that: Calculated by weight percentage, the raw materials of the CO2 gas drive sealing agent include: 1%-5% surfactant, 1%-5% gemini tertiary amine and the balance water.

4. The CO2 gas flooding sealing agent according to any one of claims 1 to 3, characterized in that: The surfactant is selected from one or more of sodium lauryl sulfate, sodium α-olefin sulfonate and sodium fatty acid methyl ester sulfonate.

5. The CO2 gas flooding sealing agent according to claim 1, characterized in that: The molar ratio of the N,N-methylenebisacrylamide to the secondary amine is 1:1-3.

6. The CO2 gas flooding sealing agent according to claim 5, characterized in that: The secondary amine is selected from any one of dimethylamine, dipropylamine and diisopropylamine.

7. A method for preparing a CO2 gas flooding sealing agent according to any one of claims 1 to 6, characterized in that: The following steps are involved: (1) N,N-methylenebisacrylamide, secondary amine and water are mixed and reacted to obtain gemini tertiary amine; (2) Gemini tertiary amine, surfactant and water are mixed to obtain the CO2 gas drive sealing agent.

8. The preparation method according to claim 7, characterized in that: The reaction temperature in step (1) is 20-80°C, and the reaction time is 20-28h.

9. The preparation method according to claim 7, characterized in that: After the reaction in step (1), the process further comprises the step of removing the secondary amine by rotary evaporation.

10. Use of the CO2 gas flooding sealing agent according to any one of claims 1 to 6 as a sealing agent in oil field and oil reservoir exploitation.

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