CO2 self-thickening gel foam system as well as preparation method and application thereof

Abstract

The invention discloses a CO2 self-thickening gel foam system, which is composed of the following components: 3-10 wt% of a nonionic responsive surfactant, 1-10 wt% of an anionic nonionic foaming agent, 1-5 wt% of a rheological modifier, 3-10 wt% of a salt auxiliary agent, and the balance of water. The invention discloses a preparation method of a CO2 self-thickening gel foam system, which comprises the following steps: (1) adding a formula amount of nonionic responsive surfactant and a formula amount of rheology modifier into a formula amount of water, and stirring at a first stirring speed for a first stirring time to obtain a uniformly dispersed mixed solution; and (2) respectively adding the anionic and nonionic foaming agent with the formula amount and the salt auxiliary agent with the formula amount into the mixed solution, and stirring at a second stirring speed for a second stirring time to obtain the CO2 self-thickening gel foam system. The invention also discloses an application of the CO2 self-thickening gel foam system as a CO2 channeling sealing agent.

Description

Technical Field

[0001] The present invention belongs to the field of petroleum engineering, and particularly relates to a CO 2 self-thickening gel foam system and its preparation method and application. Background Art

[0002] Wang Zhe from Northeast Petroleum University pointed out in his dissertation "Research and Application of Carbon Dioxide Flooding Technology": "Carbon dioxide flooding technology refers to injecting carbon dioxide gas into the oil reservoir to improve the oil reservoir recovery factor by extracting the residual oil and gas in the formation. Among many enhanced oil recovery technologies, carbon dioxide flooding technology has a broader application prospect and more obvious technical advantages. It can not only effectively reduce greenhouse gas emissions but also maximize energy extraction." That is to say, carbon dioxide flooding technology is an effective method to achieve a win-win situation of increasing oil production and carbon sequestration, realizing the resource utilization of greenhouse gases and improving the oil and gas recovery factor. 2 The density and viscosity of carbon dioxide are low, and it is prone to gravitational override, viscous fingering, and reservoir heterogeneity, which are the key factors affecting the sweep volume and gas channeling of carbon dioxide flooding. During the carbon dioxide flooding process, gas channeling has become the main factor restricting the carbon dioxide flooding effect. For example, Zhao Xisen et al. pointed out in the article "Study on the Gas Channeling Law of Carbon Dioxide Flooding in Heterogeneous Ultra-Low Permeability Reservoirs" published in the Journal of Southwest Petroleum University (Natural Science Edition) in 2017: "The sweep volume of carbon dioxide gas is severely affected by gas channeling. The stronger the core heterogeneity, the more serious the gas channeling phenomenon, and the worse the gas flooding effect; in the case of a smaller permeability contrast, the recovery factor decreases with the increase of the permeability contrast. When the contrast is greater than 100, the recovery factor drops sharply, gas channeling is serious, and it is difficult to reach the low-permeability reservoir, resulting in a low overall recovery factor." After fracturing in low-permeability reservoirs, there are fractures and high-permeability zones, which exacerbate reservoir heterogeneity and gas channeling, resulting in a reduction in the sweep volume of carbon dioxide, greatly affecting the development effect. 2 Among many enhanced oil recovery technologies, carbon dioxide flooding technology has a broader application prospect and more obvious technical advantages. It can not only effectively reduce greenhouse gas emissions but also maximize energy extraction. 2 That is to say, carbon dioxide flooding technology is an effective method to achieve a win-win situation of increasing oil production and carbon sequestration, realizing the resource utilization of greenhouse gases and improving the oil and gas recovery factor. 2 That is to say, carbon dioxide flooding technology is an effective way to achieve a win-win situation of increasing oil production and carbon sequestration, realizing the resource utilization of greenhouse gases and improving the oil and gas recovery factor.

[0003] CO 2 has low density and viscosity, is prone to gravitational override, viscous fingering, and reservoir heterogeneity, which are the key factors affecting the sweep volume and gas channeling of CO 2 flooding. During the CO 2 flooding process, gas channeling has become the main factor restricting the CO 2 flooding effect. For example, Zhao Xisen et al. pointed out in the article "Study on the Gas Channeling Law of CO 2 Flooding in Heterogeneous Ultra-Low Permeability Reservoirs" published in the Journal of Southwest Petroleum University (Natural Science Edition) in 2017: "The sweep volume of carbon dioxide gas is severely affected by gas channeling. The stronger the core heterogeneity, the more serious the gas channeling phenomenon, and the worse the gas flooding effect; in the case of a smaller permeability contrast, the recovery factor decreases with the increase of the permeability contrast. When the contrast is greater than 100, the recovery factor drops sharply, gas channeling is serious, and it is difficult to reach the low-permeability reservoir, resulting in a low overall recovery factor." After fracturing in low-permeability reservoirs, there are fractures and high-permeability zones, which exacerbate reservoir heterogeneity and gas channeling, resulting in a reduction in the sweep volume of CO 2 and greatly affecting the development effect.

[0004] Regarding CO 2 sealing channeling, currently, technical means such as injection-production control, gas-water alternation, stratified gas injection, well pattern adjustment, and chemical plugging have been developed to delay gas channeling and improve the CO 2 sweep efficiency.

[0005] Chinese Patent Application CN 107435532A discloses a method for controlling CO 2 by using a CO 2Method for driving gas channeling, the steps are as follows: First, mix CO 2 responsive surfactant with water evenly at normal temperature and pressure to obtain a CO 2 responsive surfactant solution, wherein the mass concentration of the CO 2 responsive surfactant is 0.1-10%; then, inject the CO 2 responsive surfactant solution into the reservoir; then resume injecting CO 2 fluid; the CO 2 responsive surfactant is selected from amidine compounds, guanidine compounds, and amidine / guanidine mixtures.

[0006] Chinese Patent Application CN 104975829A discloses a CO 2 flooding reservoir exploitation method. For a reservoir composed of homogeneous cores and heterogeneous cores with a permeability contrast not exceeding 30, the water alternating gas injection method is used for exploitation; for a reservoir composed of heterogeneous cores with a permeability contrast in the range of 30-100, the CO 2 flooding method is used for exploitation. During the CO 2 flooding process, when gas channeling occurs in the production well, a small molecule fatty amine is used as the main agent and injected into the formation for plugging; for a reservoir composed of heterogeneous cores with a permeability contrast above 100, the CO 2 flooding method is used for exploitation. During the CO 2 flooding process, when gas channeling first occurs in the production well, an elastic strong gel is injected into the formation for plugging. When gas channeling occurs again in the production well, a small molecule fatty amine is used as the main agent and injected into the formation for plugging.

[0007] Although the above technical solutions can achieve CO 2 channeling plugging to a certain extent, there is still no effective regulation technology for the fractures and high-permeability channels existing in low-permeability reservoirs. Especially for low-permeability reservoirs with a deep burial depth and a temperature as high as over 120°C, the stability of ordinary foam systems is poor under high-temperature conditions and they cannot effectively regulate high-permeability channels and fractures. Polymer gels are prone to polluting the reservoir and causing reservoir damage. Summary of the Invention

[0008] Object of the Invention: In order to overcome the technical problems that the existing plugging materials have limited ability to regulate high-permeability channels and fractures in low-permeability reservoirs, and polymer gels are prone to damage the reservoir matrix, the present invention provides a CO 2 self-thickening gel foam system and its preparation method and application, which have excellent injection performance, foaming performance, thickening performance, and channeling plugging performance, and break gel when encountering oil, causing less damage to the low-permeability reservoir matrix.

[0009] Technical Solution: CO 2Self-thickening gel foam system, by mass percentage, consists of the following components:

[0010] The content of the nonionic responsive surfactant is 3-10 wt%, the content of the anionic-nonionic foaming agent is 1-10 wt%, the content of the rheology regulator is 1-5 wt%, the content of the salt additive is 3-10 wt%, and the balance is water.

[0011] Furthermore, the nonionic responsive surfactant is a nonionic tertiary amine responsive surfactant with C16-C22.

[0012] Even further, the nonionic responsive surfactant is one or more of lauric acid diethanolamide, coconut oil diethanolamide, butyric acid diethanolamide, and palm oil diethanolamide.

[0013] Furthermore, the anionic-nonionic foaming agent is an anionic-nonionic surfactant containing a polyoxyethylene alkyl ether functional group.

[0014] Even further, the anionic-nonionic foaming agent is one or more of sodium C10-C18 alkyl polyoxyethylene ether carboxylate, sodium C10-C18 alkyl polyoxyethylene ether sulfonate, and sodium C10-C18 alkyl polyoxyethylene ether sulfate.

[0015] Furthermore, the rheology regulator is a nano-sized particulate rheology regulator.

[0016] Even further, the rheology regulator is one or more of nano-sized sodium bentonite, nano-sized calcium bentonite, and nano-sized fly ash.

[0017] Furthermore, the salt additive is CaCl 2 、NaCl、MgCl 2 One or more of them.

[0018] The above-mentioned CO 2 Preparation method of the self-thickening gel foam system, including the following steps:

[0019] (1), Add the formulated amount of nonionic responsive surfactant and the formulated amount of rheology regulator to the formulated amount of water, and stir at the first stirring speed for the first stirring time to obtain a uniformly dispersed mixture;

[0020] (2), Add the formulated amount of anionic-nonionic foaming agent and the formulated amount of salt additive to the mixture respectively, and stir at the second stirring speed for the second stirring time to obtain the CO 2 Self-thickening gel foam system.

[0021] Further, the first stirring speed in step (1) is at least 10,000 revolutions per minute, preferably 10,000 - 20,000 revolutions per minute;

[0022] The first stirring time is at least 30 minutes, preferably 30 - 60 minutes.

[0023] Further, the second stirring speed in step (2) is at least 200 revolutions per minute, preferably 200 - 1000 revolutions per minute;

[0024] The second stirring time is at least 10 minutes, preferably 10 - 30 minutes.

[0025] CO 2 The self - thickening gel foam system is prepared from any one of the above - mentioned CO 2 by the preparation method of the self - thickening gel foam system.

[0026] Any one of the above - mentioned CO 2 Application of the self - thickening gel foam system in oil exploitation.

[0027] Further, any one of the above - mentioned CO 2 The self - thickening gel foam system is used as a 2 channel - plugging agent.

[0028] Furthermore, the specific steps of the above application are as follows:

[0029] Continuously introduce CO 2 into the self - thickening gel foam system, then stir at a speed of 2000 - 5000 revolutions per minute for 2 - 5 minutes, and then inject it into the target formation. 2

[0030] Beneficial effects: A CO 2 self - thickening gel foam system and its preparation method and application provided by the present invention have the following beneficial effects:

[0031] (1) The CO 2 self - thickening gel foam system provided by the present invention includes a non - ionic responsive surfactant and an anionic - non - ionic foaming agent, and has a very low viscosity before encountering CO 2 and is easily injected into low - permeability reservoirs, so it has good injection characteristics;

[0032] (2) After the CO 2 self - thickening gel foam system is injected into the reservoir, it preferentially enters the large pores or fractures of the reservoir. After injection, then inject CO 2 . On the one hand, under the action of pore - throat shear, the anionic - non - ionic foaming agent in the system reacts with CO 2 to form CO 2On the other hand, as the foam is formed and CO 2 dissolves in the system, the nonionic responsive surfactant reacts with CO 2 to form a gel with a relatively high viscosity and improve the stability of the formed foam. Due to the foaming, viscosity increase and their synergistic effect in the system, a gel foam with a strong plugging function is formed to plug the cracks, forcing CO 2 to enter the matrix with low permeability, thereby expanding the CO 2 swept area of the system and improving the oil recovery rate. Therefore, the CO 2 responsive gel foam system has a better channel plugging effect;

[0033] (3) The CO 2 responsive gel foam system has the responsive characteristics of increasing viscosity and foaming when encountering CO 2 and reducing viscosity and defoaming when encountering oil. After the system increases viscosity and foams and then encounters crude oil, the gel-breaking viscosity decreases (when the CO 2 responsive gel foam system encounters crude oil, the network structure of the gel is damaged, resulting in a decrease in gel viscosity), and the large pores or cracks provide oil flow channels for the crude oil. Therefore, the CO 2 responsive gel foam channel plugging system has low damage characteristics to the reservoir.

[0034] (4) Compared with other ordinary CO 2 foams, the self-thickening gel foam system provided by the present invention can enhance the foam stability after gel formation and improve the CO 2 foam's temperature resistance characteristics. 2

[0035] (5) Compared with ordinary gel foams, the nonionic responsive surfactant enters the formation and protonates to increase viscosity when encountering CO 2 , having an intelligent thickening effect. Compared with traditional macromolecular polymer cross-linked gels, the CO 2 responsive gel is more intelligent, more shear-resistant and more heat-resistant.

[0036] (6) The preparation method of the CO 2 self-thickening gel foam system provided by the present invention is simple and easy to operate and can be prepared and injected online. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 Schematic diagram showing the change of the apparent viscosity of the CO 2 self-thickening gel foam system without anionic and nonionic foaming agents in Test Example 1 with the shear rate.

[0038] Figure 2 Schematic diagram showing the change of the foaming volume and the half-life of liquid drainage of the CO 2 self-thickening gel foam system A1 prepared in Example 1 with the stirring rate.

[0039] ​Figure 3 CO prepared for Example 2 2 Schematic diagram of the variation of the foaming volume and the half-life of liquid drainage of the self-thickening gel foam system A2 with the stirring rate.

[0040] Figure 4 CO prepared for Test Example 4 2 Schematic diagram of the variation of the foaming volume and the half-life of liquid drainage of the foam system D1 with the stirring rate.

[0041] Figure 5 CO prepared for Test Example 5 2 Schematic diagram of the variation of the foaming volume and the half-life of liquid drainage of the gel foam system D2 with the stirring rate.

[0042] Figure 6 CO 2 Self-thickening gel foam system A1 and CO 2 Schematic diagram of the variation of the injection pressure of the gel foam system D2. Specific implementation manners:

[0043] The following details the specific implementation manners of the present invention.

[0044] The endpoints and any values within the ranges disclosed herein are not limited to the exact ranges or values. These ranges or values should be understood to include values close to these ranges or values. For numerical ranges, between the endpoint values of each range, between the endpoint values of each range and individual point values, and between individual point values, they can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be regarded as specifically disclosed herein.

[0045] Detection parameters and detection means:

[0046] 1. CO 2 Apparent viscosity of the self-thickening gel foam system: The apparent viscosity of the CO self-thickening gel foam system was measured under different shear rate conditions using an Anton Paar rotational rheometer. 2 Among them:

[0047] The greater the apparent viscosity, the better the crack plugging effect of the CO 2 self-thickening gel foam system.

[0048] The test shear rate of the Anton Paar rotational rheometer is 0.01S -1 ~100S -1 .

[0049] 2. CO 2 Foam system (the CO 2 self-thickening gel foam system of the present application also belongs to CO 2Foaming performance of a foam system): The foaming performance of CO under different stirring speeds was tested using a high-temperature and high-pressure foam reactor. 2 The foaming performance of the foam system. Among them:

[0050] The larger the half-life, the better the stability of the CO 2 self-thickening gel foam system.

[0051] Specifically, the stirring speeds of the high-temperature and high-pressure reactor are 4000 r / min, 6000 r / min, 8000 r / min, and 10000 r / min.

[0052] Specific test method: Inject 100 - 500 mL of the foam system to be tested into the reactor, inject CO 2 gas to the required pressure and then close the valve. First, stir at a low speed to mix the foam system with CO 2 to form an acidic solution, and then stir at a high speed.

[0053] 3. Evaluation of injection ability: The plugging effect was tested using a high-temperature and high-pressure core flooding device. The core used has a length of 10 - 20 cm and a core permeability of 100 - 500 mD.

[0054] Specific test method: First, use an ISCO pump to inject clear water into the core to test the initial pressure; then pour the prepared CO 2 self-thickening gel foam system and polymer cross-linked gel foam system into an intermediate container, inject them into the core through an ISCO pump, and test the pressure to compare the injection pressures of the two systems.

[0055] The present invention will be described in detail below through examples.

[0056] Example 1

[0057] CO 2 Self-thickening gel foam system A1, in terms of mass percentage, consists of the following components:

[0058] The content of the non-ionic responsive surfactant is 5 wt%, the content of the anionic-nonionic foaming agent is 2 wt%, the content of the rheology regulator is 2 wt%, the content of the salt additive is 5 wt%, and the balance is water.

[0059] Further, the non-ionic responsive surfactant is a non-ionic tertiary amine responsive surfactant with C16 - C22.

[0060] Even further, the non-ionic responsive surfactant is lauric acid diethanolamide.

[0061] Further, the anionic-nonionic foaming agent is an anionic-nonionic surfactant containing a polyoxyethylene alkyl ether functional group.

[0062] Furthermore, the anionic-nonionic foaming agent is sodium C12 alkyl polyoxyethylene ether carboxylate.

[0063] Further, the rheology modifier is a nanoscale particulate rheology modifier.

[0064] Furthermore, the rheology modifier is nanoscale sodium bentonite.

[0065] Further, the salt additive is CaCl 2 .

[0066] The above-mentioned CO 2 self-thickening gel foam system preparation method includes the following steps:

[0067] (1) Add the formulated amount of nonionic responsive surfactant and the formulated amount of rheology modifier to the formulated amount of water, and stir at the first stirring speed for the first stirring time to obtain a uniformly dispersed mixture;

[0068] (2) Respectively add the formulated amount of anionic-nonionic foaming agent and the formulated amount of salt additive to the mixture, and stir at the second stirring speed for the second stirring time to obtain the CO 2 self-thickening gel foam system A1.

[0069] Further, in step (1), the first stirring speed is 15000 revolutions per minute;

[0070] The first stirring time is 45 minutes.

[0071] Further, in step (2), the second stirring speed is up to 500 revolutions per minute;

[0072] The second stirring time is 20 minutes.

[0073] CO 2 The self-thickening gel foam system is prepared by the preparation method of any one of the above-mentioned CO 2 self-thickening gel foam systems.

[0074] Any one of the above-mentioned CO 2 Application of the self-thickening gel foam system in oil exploitation.

[0075] Further, any one of the above-mentioned CO 2 The self-thickening gel foam system as a CO 2 Application as a channel plugging agent.

[0076] Further, the specific steps of the above application are as follows:

[0077] Introduce CO 2 Continuously introduce CO into the self-thickening gel foam system A1 2 , then stir it at a speed of 3500 revolutions per minute for 3 minutes, and then inject it into the target formation.

[0078] Example 2

[0079] CO 2 The self-thickening gel foam system A2, by mass percentage, consists of the following components:

[0080] The content of the non-ionic responsive surfactant is 8 wt%, the content of the anionic-nonionic foaming agent is 5 wt%, the content of the rheology regulator is 5 wt%, the content of the salt additive is 8 wt%, and the balance is water.

[0081] Further, the non-ionic responsive surfactant is a non-ionic tertiary amine responsive surfactant of C16-C22.

[0082] Furthermore, the non-ionic responsive surfactant is coconut oil diethanolamide.

[0083] Further, the anionic-nonionic foaming agent is an anionic-nonionic surfactant containing a polyoxyethylene alkyl ether functional group.

[0084] Furthermore, the anionic-nonionic foaming agent is sodium C10 alkyl polyoxyethylene ether sulfonate.

[0085] Further, the rheology regulator is a nano-sized particulate rheology regulator.

[0086] Furthermore, the rheology regulator is nano-sized calcium-based bentonite.

[0087] Further, the salt additive is NaCl.

[0088] The above-mentioned CO 2 The preparation method of the self-thickening gel foam system includes the following steps:

[0089] (1), Add the formulated amount of non-ionic responsive surfactant and the formulated amount of rheology regulator to the formulated amount of water, and stir at the first stirring speed for the first stirring time to obtain a uniformly dispersed mixture;

[0090] (2), Add the formulated amount of anionic-nonionic foaming agent and the formulated amount of salt additive to the mixture respectively, and stir at the second stirring speed for the second stirring time to obtain the CO 2 self-thickening gel foam system A2.

[0091] Furthermore, in step (1), the first stirring speed is 18000 rpm;

[0092] The first stirring time is 40 minutes.

[0093] Furthermore, in step (2), the second stirring speed is at least 500 rpm;

[0094] The second stirring time is 20 minutes.

[0095] CO 2 Self-thickening gel foam system, composed of any of the above CO 2 Prepared by the preparation method of the self-thickening gel foam system.

[0096] Any of the above CO 2 Application of self-thickening gel foam system in oil production.

[0097] Furthermore, any of the above CO 2 Self-thickening gel foam system as CO 2 Application of sealing agent.

[0098] Furthermore, the specific steps of the above application are as follows:

[0099] To CO 2 Self-thickening gel foam system A2 continuously introduces CO 2 Then, after stirring at 3000 rpm for 4 minutes, it is injected into the target formation.

[0100] Example 3

[0101] CO 2 The self-thickening gel foam system A3, calculated by mass percentage, consists of the following components:

[0102] The content of non-ionic responsive surfactant is 3wt%, the content of anionic non-ionic foaming agent is 10wt%, the content of rheology regulator is 1wt%, the content of salt auxiliary agent is 10wt%, and the balance is water.

[0103] Furthermore, the nonionic responsive surfactant is a C16-C22 nonionic tertiary amine responsive surfactant.

[0104] Furthermore, the nonionic responsive surfactant is tallow diethanolamide.

[0105] Furthermore, the anionic nonionic foaming agent is an anionic nonionic surfactant containing a polyoxyethylene alkyl ether functional group.

[0106] ​Furthermore, the anionic-nonionic foaming agent is sodium C18 alkyl polyoxyethylene ether sulfate.

[0107] Further, the rheology modifier is a nano-sized particulate rheology modifier.

[0108] Furthermore, the rheology modifier is nano-sized fly ash.

[0109] Further, the salt additive is MgCl 2 .

[0110] The above-mentioned CO 2 self-thickening gel foam system preparation method includes the following steps:

[0111] (1) Add the formulated amount of nonionic responsive surfactant and the formulated amount of rheology modifier to the formulated amount of water, and stir at the first stirring speed for the first stirring time to obtain a uniformly dispersed mixture;

[0112] (2) Respectively add the formulated amount of anionic-nonionic foaming agent and the formulated amount of salt additive to the mixture, and stir at the second stirring speed for the second stirring time to obtain the CO 2 self-thickening gel foam system A3.

[0113] Further, the first stirring speed in step (1) is 10,000 revolutions per minute;

[0114] The first stirring time is 60 minutes.

[0115] Further, the second stirring speed in step (2) is 200 revolutions per minute;

[0116] The second stirring time is 30 minutes.

[0117] CO 2 The self-thickening gel foam system is prepared by the preparation method of any one of the above-mentioned CO 2 self-thickening gel foam systems.

[0118] Any one of the above-mentioned CO 2 The application of the self-thickening gel foam system in oil exploitation.

[0119] Further, any one of the above-mentioned CO 2 The self-thickening gel foam system as a CO 2 plugging agent application.

[0120] Furthermore, the specific steps of the above application are as follows:

[0121] Continuously introduce CO into the CO 2 self-thickening gel foam system.2 , and then stir it at a speed of 2000 revolutions per minute for 5 minutes, and then inject it into the target formation.

[0122] Example 4

[0123] CO 2 Self-thickening gel foam system A4, by mass percentage, consists of the following components:

[0124] The content of the non-ionic responsive surfactant is 10 wt%, the content of the anionic-nonionic foaming agent is 1 wt%, the content of the rheology regulator is 4 wt%, the content of the salt auxiliary is 3 wt%, and the balance is water.

[0125] Furthermore, the non-ionic responsive surfactant is a non-ionic tertiary amine responsive surfactant of C16-C22.

[0126] Even further, the non-ionic responsive surfactant is palm oil diethanolamide. In another embodiment, the non-ionic responsive surfactant is a mixture of lauric acid diethanolamide, coconut oil diethanolamide, tallow acid diethanolamide, and palm oil diethanolamide in an equal mass ratio.

[0127] Furthermore, the anionic-nonionic foaming agent is an anionic-nonionic surfactant containing a polyoxyethylene alkyl ether functional group.

[0128] Even further, the anionic-nonionic foaming agent is a mixture of sodium C12 alkyl polyoxyethylene ether carboxylate, sodium C10 alkyl polyoxyethylene ether sulfonate, and sodium C18 alkyl polyoxyethylene ether sulfate in an equal mass ratio. In another embodiment, the anionic-nonionic foaming agent is sodium C10 alkyl polyoxyethylene ether carboxylate. In another embodiment, the anionic-nonionic foaming agent is sodium C15 alkyl polyoxyethylene ether carboxylate. In another embodiment, the anionic-nonionic foaming agent is sodium C18 alkyl polyoxyethylene ether carboxylate. In another embodiment, the anionic-nonionic foaming agent is sodium C10 alkyl polyoxyethylene ether sulfonate. In another embodiment, the anionic-nonionic foaming agent is sodium C18 alkyl polyoxyethylene ether sulfonate. In another embodiment, the anionic-nonionic foaming agent is sodium C12 alkyl polyoxyethylene ether sulfonate. In another embodiment, the anionic-nonionic foaming agent is sodium C10 alkyl polyoxyethylene ether sulfate. In another embodiment, the anionic-nonionic foaming agent is sodium C18 alkyl polyoxyethylene ether sulfate. In another embodiment, the anionic-nonionic foaming agent is sodium C12 alkyl polyoxyethylene ether sulfate.

[0129] Furthermore, the rheology regulator is a nano-scale particulate rheology regulator.

[0130] Further, the rheology modifier is a mixture of nano sodium bentonite, nano calcium bentonite, and nano fly ash with equal mass ratio.

[0131] Further, the salt additive is a mixture of CaCl 2 , NaCl, and MgCl 2 with equal mass ratio.

[0132] The preparation method of the above-mentioned CO 2 self-thickening gel foam system includes the following steps:

[0133] (1) Add the formulated amount of non-ionic responsive surfactant and the formulated amount of rheology modifier to the formulated amount of water, and stir at the first stirring speed for the first stirring time to obtain a uniformly dispersed mixture;

[0134] (2) Add the formulated amount of anionic-non-ionic foaming agent and the formulated amount of salt additive to the mixture respectively, and stir at the second stirring speed for the second stirring time to obtain the CO 2 self-thickening gel foam system.

[0135] Further, in step (1), the first stirring speed is 20,000 revolutions per minute;

[0136] The first stirring time is 30 minutes.

[0137] Further, in step (2), the second stirring speed is 1,000 revolutions per minute;

[0138] The second stirring time is 10 minutes.

[0139] The CO 2 self-thickening gel foam system is prepared by the preparation method of any one of the above-mentioned CO 2 self-thickening gel foam systems.

[0140] The application of any one of the above-mentioned CO 2 self-thickening gel foam systems in oil exploitation.

[0141] Further, the application of any one of the above-mentioned CO 2 self-thickening gel foam systems as a CO 2 channel plugging agent.

[0142] Furthermore, the specific steps of the above application are as follows:

[0143] Continuously introduce CO 2 into the CO 2 self-thickening gel foam system, then stir at a speed of 2,000 - 5,000 revolutions per minute for 2 - 5 minutes, and then inject it into the target formation.

[0144] Performance characterization:

[0145] Test Example 1

[0146] Configuration comparison CO 2 Self-thickening gel foam system A1, which is roughly the same as the CO prepared in Example 1 2 Responsive gel foam system A1, with the only difference being that it does not contain an anionic-nonionic foaming agent.

[0147] First, the CO without an anionic-nonionic foaming agent 2 Self-thickening gel foam system A1 was passed through CO 2 The influence of the shear rate on the apparent viscosity before passing through CO 2 Then, after passing through CO, the change of the apparent viscosity of the system with the shear rate was tested. The experimental results are shown in Figure 1 the following.

[0148] It can be seen from Figure 1 that when the CO without an anionic-nonionic foaming agent 2 Self-thickening gel foam system A1 was passed through CO 2 the apparent viscosity of the system before passing through was very low, only a few mPa·s, and with the increase of the shear rate, the viscosity of the system remained basically unchanged;

[0149] When the CO without an anionic-nonionic foaming agent 2 Self-thickening gel foam system A1 was passed through CO 2 after passing through, when the shear rate was zero (static state), the viscosity of the system after response reached more than 800 mPa·s; with the increase of the shear rate, the apparent viscosity first remained unchanged and then gradually decreased, indicating that the system has the property of shear thinning. This property can achieve the purpose of deep profile control of the CO 2 responsive gel system. The shear rate in the near-wellbore area is relatively large, reducing the viscosity of the system and increasing the fluidity of the system, enabling the system to migrate deep into the formation. The shear rate in the far-wellbore area is relatively small, and the viscosity of the system increases, which can meet the requirements of CO 2 fracture control in the deep formation.

[0150] Test Example 2

[0151] The CO prepared in Example 1 2 Self-thickening gel foam system A1 was tested for foam stability through the method of 2 obtaining the half-life at different stirring speeds. The experimental results are shown in Figure 2 the following. It can be seen from the results that with the increase of the shear rate, the CO 2The drainage half-life of the foam system also gradually increases. When the shear rate increases from 4000 r / min to 10000 r / min, the drainage half-life increases from 103 min to 192 min, further indicating that CO 2 The foam stability of the self-thickening gel foam system A1 is effectively improved.

[0152] Test Example 3

[0153] The CO prepared in Example 2 2 The self-thickening gel foam system A2 passes through CO 2 The test method of foam stability is used to obtain the half-life at different stirring speeds. The experimental results are as Figure 3 shown. It can be seen from the results that as the shear rate increases, CO 2 The drainage half-life of the foam system also gradually increases. When the shear rate increases from 4000 r / min to 10000 r / min, the drainage half-life increases from 133 min to 317 min. Compared with the CO prepared in Example 1 2 self-thickening gel foam system A1, CO 2 With the increase of the concentration of the responsive surfactant, the anionic-nonionic foaming agent, and the rheology regulator in the self-thickening gel foam system A2, the drainage half-life (stability) of the system also increases accordingly.

[0154] Experimental Example 4

[0155] The CO foam system D1 is prepared by using the same formula and method as in Example 1, except that D1 does not contain the nonionic responsive surfactant. 2

[0156] The half-life of the CO foam is tested under different shear rate conditions. The experimental results are as Figure 4 shown. It can be seen from the results that as the shear rate increases, CO 2 Figure 4 shown. It can be seen from the results that as the shear rate increases, CO 2 The drainage half-life of the foam system also gradually increases. When the shear rate increases from 4000 r / min to 10000 r / min, the drainage half-life increases from 36 min to 89 min. Compared with the CO prepared in Example 1 2 self-thickening gel foam system A1, when the shear rate increases from 4000 r / min to 10000 r / min, the drainage half-life increases from 108 min to 192 min. CO 2 The drainage half-life (stability) of the foam system D1 is 1 / 4 of that of the system A1 under different shear rate conditions. This is mainly because the ordinary nonionic surfactant does not have the CO 2 responsive characteristics, so it cannot self-thicken to form a gel to increase the viscosity of the foam liquid film, and thus cannot improve the foam stability.

[0157] Experimental Example 5

[0158] CO was prepared by the same method as in Example 1 2 Gel foam system D2, except that: 5 wt% of ordinary polymer cross-linked gel was used to replace 5 wt% of non-ionic responsive surfactant, and 5 wt% of polymer cross-linked gel was composed of polyacrylamide and 5 wt% of cross-linking agent methylenebisacrylamide, and CO was prepared 2 Gel foam system D2.

[0159] The half-life of CO foam was tested under different shear rate conditions 2 The experimental results are as follows Figure 5 As shown, it can be seen from the results that as the shear rate increases, the drainage half-life of the CO 2 foam system also gradually increases. When the shear rate increases from 4000 r / min to 10000 r / min, the drainage half-life increases from 62 min to 112 min. Compared with the CO 2 self-thickening gel foam system A1 prepared in Example 1, when the shear rate increases from 4000 r / min to 10000 r / min, the drainage half-life increases from 108 min to 192 min. The drainage half-life (stability) of the CO 2 gel foam system D2 is 1 / 4 of that of system A1 under different shear rate conditions. This is because in the CO 2 gel foam system D2, the polymer cross-linked gel is cross-linked by macromolecules. Under high-speed shear conditions, the macromolecular polymer chains break, the viscosity decreases, and the foam stability performance deteriorates.

[0160] Test Example 6

[0161] CO 2 The injection ability results of the self-thickening gel foam system A1 and CO 2 gel foam system D2 in the core are as follows Figure 6 As shown, the results show that the injection ability of the CO 2 gel foam system D2 is significantly lower than that of the CO 2 self-thickening gel foam system A1, further indicating that the injection performance of the CO 2 self-thickening gel foam system A1 has been greatly improved. This is mainly because the polymer is a macromolecule and has a relatively high viscosity itself between cross-linkings. The CO 2 self-thickening gel foam system is composed of small molecule responsive non-ionic surfactants and has a viscosity equivalent to that of water. Therefore, the CO 2 self-thickening gel foam system A1 has better injection ability.

[0162] The above has made a detailed description of the embodiments of the present invention. However, the present invention is not limited to the above embodiments, and various changes can be made without departing from the gist of the present invention within the scope of knowledge possessed by those of ordinary skill in the art.

Claims

1. CO2 self-thickening gel foam system, characterized in that: In terms of mass percentage, it is composed of the following components: The content of the nonionic responsive surfactant is 3-10wt%, the content of the anionic nonionic foaming agent is 1-10wt%, the content of the rheology regulator is 1-5wt%, the content of the salt auxiliary agent is 3-10wt%, and the balance is water.

2. The CO2 self-thickening gel foam system according to claim 1, characterized in that: The nonionic responsive surfactant is a C16-C22 nonionic tertiary amine responsive surfactant.

3. The CO2 self-thickening gel foam system according to claim 2, characterized in that: The nonionic responsive surfactant is one or more of lauric acid diethanolamide, coconut oil diethanolamide, tallow acid diethanolamide, and palm oil diethanolamide.

4. The CO2 self-thickening gel foam system according to claim 1, characterized in that: The anionic nonionic foaming agent is an anionic nonionic surfactant containing a polyoxyethylene alkyl ether functional group.

5. The CO2 self-thickening gel foam system according to claim 4, characterized in that: The anionic nonionic foaming agent is one or more of C10-C18 alkyl polyoxyethylene ether sodium carboxylate, C10-C18 alkyl polyoxyethylene ether sodium sulfonate, and C10-C18 alkyl polyoxyethylene ether sodium sulfate.

6. The CO2 self-thickening gel foam system according to claim 1, characterized in that: The rheology modifier is a nano-sized particle type rheology modifier.

7. The CO2 self-thickening gel foam system according to claim 6, characterized in that: The rheology regulator is one or more of nanometer sodium-based bentonite, nanometer calcium-based bentonite and nanometer fly ash.

8. The CO2 self-thickening gel foam system according to claim 1, characterized in that: The salt auxiliary agent is one or more of CaCl2, NaCl, and MgCl2.

9. The method for preparing the CO2 self-thickening gel foam system according to any one of claims 1 to 8, characterized in that: The following steps are involved: (1) adding a formulated amount of a nonionic responsive surfactant and a formulated amount of a rheology modifier to a formulated amount of water, stirring at a first stirring speed for a first stirring time to obtain a uniformly dispersed mixed solution; (2) Adding the formulated amount of anionic nonionic foaming agent and the formulated amount of salt auxiliary agent to the mixed solution respectively, stirring at a second stirring speed for a second stirring time, thereby obtaining a CO2 self-thickening gel foam system.

10. The method for preparing the CO2 self-thickening gel foam system according to claim 9, characterized in that: In step (1), the first stirring speed is at least 10,000 rpm, preferably 10,000 to 20,000 rpm; The first stirring time is at least 30 minutes, preferably 30 to 60 minutes.

11. The method for preparing the CO2 self-thickening gel foam system according to claim 9, characterized in that: In step (2), the second stirring speed is at least 200 rpm, preferably 200 to 1000 rpm; The second stirring time is at least 10 minutes, preferably 10 to 30 minutes.

12. A CO2 self-thickening gel foam system prepared by the method for preparing a CO2 self-thickening gel foam system according to any one of claims 9 to 11.

13. Use of the CO2 self-thickening gel foam system according to any one of claims 1 to 8 and 12 in oil production.

14. Use of the CO2 self-thickening gel foam system according to any one of claims 1 to 8 and 12 as a CO2 blocking agent.

15. The use according to claim 14, characterized in that The specific steps of the above application are as follows: CO2 is continuously introduced into the CO2 self-thickening gel foam system, and then stirred at a speed of 2000-5000 rpm for 2-5 minutes, and then injected into the target formation.

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