Foaming agent for oil and gas wells and preparation method thereof

Abstract

The present invention belongs to the field of oil production technology, and in particular to a kind of oil and gas well foaming agent and preparation method thereof. The preparation method is as follows: p-nonylphenol, 1-aza-18-crown ether-6, ethanol are added to a four-necked flask, stirred evenly, 40wt% formaldehyde solution is added dropwise, the reaction is stirred, the temperature is raised and refluxed, and a viscous liquid is obtained by vacuum distillation; the above-mentioned viscous liquid is transferred to an autoclave, a catalyst is added, the temperature is raised, ethylene oxide is passed through, the temperature is further raised, and the isothermal reaction is carried out. When the pressure drops to 0, the reaction is stopped to obtain a foaming agent; a foam stabilizer is added to the foaming agent, the system is cooled to less than 40 DEG C, the pH value is adjusted, and a product oil and gas well foaming agent is obtained. The oil and gas well foaming agent of the present invention has the advantages of strong foaming power, long half-life, and large liquid carrying capacity.

Description

Technical Field

[0001] The invention belongs to the technical field of petroleum extraction, and particularly relates to a foaming agent for oil and gas wells and a preparation method thereof. Background Art

[0002] Currently, most oil reservoirs have entered the late stages of development, and the proportion of difficult-to-extract oil reservoirs within the remaining reserves is increasing year by year. As reservoir pressure and temperature decrease, crude oil viscosity increases, fluidity deteriorates, and reservoir capillaries become clogged, resulting in large amounts of crude oil being trapped within the reservoir and difficult to extract. Further improving oil recovery has become an increasingly prominent issue.

[0003] Foam flooding utilizes a foam system formed by a mixture of a foaming agent and gas. Foam fluids are widely used in oilfield production due to their low density, high viscosity, and unique rheological properties. The ability of foam to displace oil lies in its flow characteristics within porous media. The foam first enters large, high-permeability pores with minimal flow resistance. This flow resistance increases with the amount of foam injected. Once it exceeds the flow resistance in smaller pores, the foam increasingly flows into smaller, low-permeability pores. The low viscosity of the foam as it flows within these pores ultimately leads to uniform foam propagation within both high- and low-permeability reservoirs, increasing its sweep efficiency. Foam also possesses a certain oil-washing capacity, resulting in a significant increase in oil recovery.

[0004] The foaming agent used to generate oil displacement foam is generally a surfactant. Its main function is to reduce interfacial tension at the air-water interface, encourage air to form small bubbles in the slurry, expand the separation interface, and ensure that the bubbles rise to form a foam layer. It can significantly reduce the oil-water interfacial tension, change the wettability of the rock surface, and make the originally bound oil become mobile oil through emulsification and liquid film replacement.

[0005] CN108485642A discloses the use of a star-shaped carboxylic acid-based zwitterionic surfactant as a foaming agent. The surfactant is prepared by the following steps: a predetermined amount of trimethylolpropane-tris(3-aziridinylpropionate) reaction solution is dropwise added to a reaction flask containing a long-chain fatty primary amine ethanol solution and an acidic catalyst to carry out a first step of an aziridine ring-opening reaction; a predetermined amount of chloromethane (or benzyl chloride) reaction solution is then added to the reaction solution to carry out a second step of a quaternization reaction. The resulting product is a multiply charged star-shaped zwitterionic surfactant. This zwitterionic surfactant can be used as a foaming agent in foam fracturing processes and in oil and gas well production processes. The foaming agent has advantages such as strong foaming ability, good foam stability, salt resistance, and a wide range of operating temperatures. However, due to the large number of ester groups in the invented molecule, the foaming agent has a temperature resistance of only 120°C. The reservoir temperatures in many oil fields exceed 150°C or even 200°C, thus limiting its scope of use.

[0006] CN111961451A discloses a slow-release foaming agent for oil and gas wells and its preparation method. The agent comprises the following raw materials: a novel fluorocarbon surfactant, a nonionic surfactant, a foam stabilizer, an alcohol, and water; the foam stabilizer is a polymer foam stabilizer or nano-dust; and the alcohol is selected from one or more of methanol, ethanol, propanol, isopropanol, ethylene glycol, glycerol, 1,3-propylene glycol, and 1,2-propylene glycol. The slow-release foaming agent produced by this invention exhibits excellent resistance to high temperatures, high salinity, high pressure, and oil, and exhibits excellent stability under high temperatures, high pressures, and high salinity. Therefore, it is suitable for the effective development of difficult-to-use reservoirs such as high-temperature, high-salinity, and heavy oil reservoirs in China, and has broad application prospects. However, this invention contains a large amount of fluorine, making it difficult to biodegrade and potentially causing environmental pollution. Summary of the Invention

[0007] The present invention addresses the deficiencies of the prior art and provides a foaming agent for oil and gas wells and a preparation method thereof. The foaming agent for oil and gas wells of the present invention has the advantages of strong foaming power, long half-life, and large liquid carrying capacity.

[0008] One of the purposes of the present invention is to disclose a foaming agent for oil and gas wells, wherein the composition and components of the foaming agent are as follows:

[0009] 1 part by mass of foaming agent;

[0010] Foam stabilizer 0.02-0.1 parts by mass;

[0011] The molecular structural formula of the foaming agent is as follows:

[0012]

[0013] Wherein, m=10-100.

[0014] The foam stabilizer is one of gelatin, carboxymethyl cellulose, hydroxyethyl cellulose and hydroxypropyl cellulose.

[0015] Preferably, the foam stabilizer is gelatin or carboxymethyl cellulose.

[0016] Another object of the present invention is to disclose a method for preparing a foaming agent for oil and gas wells, wherein the specific steps of the preparation method are as follows:

[0017] (1) Add p-nonylphenol, 1-aza-18-crown-6, and ethanol to a four-necked flask, stir evenly, add 40 wt% formaldehyde solution dropwise, stir and react for 30-60 min, heat and reflux for 30-60 min, and distill under reduced pressure to obtain a viscous liquid;

[0018] (2) The viscous liquid is transferred to an autoclave, a catalyst is added, nitrogen is introduced, and vacuum is applied; the mixture is then stirred and heated to 80-90°C, vacuum is applied again, and ethylene oxide is introduced. After completion, the mixture is heated to 150-160°C and reacted at a constant temperature. As the reaction proceeds, the pressure gradually decreases. When the pressure drops to 0, the reaction is stopped to obtain a foaming agent.

[0019] (3) Add a foam stabilizer to the foaming agent, cool the system to below 40°C, and adjust the pH to 7-8 with hydrochloric acid to obtain a foaming agent for oil and gas wells.

[0020] Preferably, based on 1 mol part of nonylphenol, the amounts of 1-aza-18-crown-6, 40 wt% formaldehyde and ethylene oxide are 1.9-2.3 mol parts, 2.0-2.5 mol parts and 10-100 mol parts respectively.

[0021] More preferably, based on 1 mol part of nonylphenol, the amounts of 1-aza-18-crown-6, 40 wt% formaldehyde and ethylene oxide are 2.0-2.2 mol parts, 2.2-2.5 mol parts and 40-100 mol parts respectively.

[0022] Preferably, in step (1), the weight ratio of ethanol to nonylphenol is 20-30:1.

[0023] Preferably, in step (2), the catalyst is one of sodium hydroxide and potassium hydroxide, and the weight ratio of the catalyst to nonylphenol is 0.01-0.02:1.

[0024] Preferably, in step (3), the weight ratio of the foaming agent to the foam stabilizer is 1:0.02-0.1.

[0025] The reaction equation of the foaming agent of the present invention is as follows:

[0026]

[0027]

[0028] The foaming agent for oil and gas wells of the present invention comprises a foaming agent and a foam stabilizer. The foaming agent is a multifunctional surfactant comprising a Gemini crown ether and an alkylphenol polyoxyethylene ether, and is a product obtained by a Mannich reaction of an azacrown ether, phenol, and formaldehyde. The foaming agent can significantly reduce the surface tension of water. After foam is formed, the nonylbenzene is located outside the liquid film, reducing water loss in the foam and enhancing the stability of the foam. The azacrown ether and the polyoxyethylene ether are located inside the liquid film, forming a thick hydration film around the liquid film, converting the highly mobile free water in the liquid film into less mobile bound water. When the foam liquid film becomes thinner, it can quickly laterally attract other parts of the liquid film to replenish the foam, thereby enhancing the stability of the foam. The foam stabilizer molecules have both hydrophilic and hydrophobic parts, so the molecules have both hydrophilic and lipophilic characteristics, forming a molecular film on the liquid surface to reduce surface tension. At the same time, the foam stabilizer can enhance the surface viscosity and film strength of the liquid film, thereby achieving the effect of stabilizing the foam.

[0029] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0030] (1) The foaming agent for oil and gas wells of the present invention has a strong foaming power. At a concentration of 0.1 wt%, the foaming height reaches 220 mm or more;

[0031] (2) The foaming agent for oil and gas wells of the present invention has a long half-life. At a concentration of 0.1 wt%, the half-life reaches more than 8 minutes.

[0032] (3) The foaming agent for oil and gas wells of the present invention has the characteristic of large liquid carrying capacity. At a concentration of 0.1 wt%, the liquid carrying capacity reaches 185 ml or more. DETAILED DESCRIPTION

[0033] The endpoints of the ranges and any values ​​disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoints of each range, the endpoints of each range and individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered to be specifically disclosed herein.

[0034] Example 1

[0035] (1) Add 0.05 mol of p-nonylphenol, 0.095 mol of 1-aza-18-crown-6, and 220 g of ethanol to a four-necked flask, stir evenly, add 0.1 mol of 40 wt% formaldehyde solution dropwise, stir and react for 60 min, heat and reflux for 30 min, and distill under reduced pressure to obtain a viscous liquid;

[0036] (2) The viscous liquid was transferred to an autoclave, 0.11 g of sodium hydroxide was added, nitrogen was introduced, and vacuum was applied. The mixture was then stirred and heated to 80°C, vacuumed again, and 0.5 mol of ethylene oxide was introduced. After completion, the mixture was heated to 150°C and reacted at a constant temperature. As the reaction proceeded, the pressure gradually decreased. When the pressure dropped to 0, the reaction was stopped to obtain a foaming agent.

[0037] (3) Add 0.2 g of gelatin to 10 g of foaming agent, cool the system to below 40°C, and adjust the pH to 7-8 with hydrochloric acid to obtain the product foaming agent A1 for oil and gas wells.

[0038] Example 2

[0039] (1) In a four-necked flask, 0.05 mol of p-nonylphenol, 0.115 mol of 1-aza-18-crown-6, and 280 g of ethanol were added and stirred evenly. 0.105 mol of 40 wt% formaldehyde solution was added dropwise. The mixture was stirred for 30 min, heated and refluxed for 60 min, and distilled under reduced pressure to obtain a viscous liquid.

[0040] (2) The viscous liquid was transferred to an autoclave, 0.13 g of sodium hydroxide was added, nitrogen was introduced, and vacuum was applied. Subsequently, the autoclave was stirred and heated to 80°C, vacuum was applied again, and 1 mol of ethylene oxide was introduced. After completion, the autoclave was heated to 155°C and the reaction was carried out at a constant temperature. As the reaction proceeded, the pressure gradually decreased. When the pressure dropped to 0, the reaction was stopped to obtain a foaming agent.

[0041] (3) Add 0.5 g of carboxymethyl cellulose to 10 g of foaming agent, cool the system to below 40° C., and adjust the pH to 7-8 with hydrochloric acid to obtain foaming agent A2 for oil and gas wells.

[0042] Example 3

[0043] (1) Add 0.05 mol of p-nonylphenol, 0.1 mol of 1-aza-18-crown-6, and 330 g of ethanol to a four-necked flask, stir evenly, add 0.125 mol of 40 wt% formaldehyde solution dropwise, stir and react for 30 min, heat and reflux for 40 min, and distill under reduced pressure to obtain a viscous liquid;

[0044] (2) The viscous liquid was transferred to an autoclave, 0.15 g of sodium hydroxide was added, nitrogen was introduced, and vacuum was applied. Subsequently, the autoclave was stirred and heated to 85°C, vacuum was applied again, and 1.5 mol of ethylene oxide was introduced. After completion, the autoclave was heated to 150°C and the reaction was carried out at a constant temperature. As the reaction proceeded, the pressure gradually decreased. When the pressure dropped to 0, the reaction was stopped to obtain a foaming agent.

[0045] (3) Add 0.6 g of hydroxyethyl cellulose to 10 g of foaming agent, cool the system to below 40°C, and adjust the pH to 7-8 with hydrochloric acid to obtain foaming agent A3 for oil and gas wells.

[0046] Example 4

[0047] (1) In a four-necked flask, 0.05 mol of p-nonylphenol, 0.112 mol of 1-aza-18-crown-6, and 278 g of ethanol were added and stirred evenly. 0.108 mol of 40 wt% formaldehyde solution was added dropwise. The mixture was stirred for 45 min, heated and refluxed for 50 min, and distilled under reduced pressure to obtain a viscous liquid.

[0048] (2) The viscous liquid was transferred to an autoclave, 0.18 g of sodium hydroxide was added, nitrogen was introduced, and vacuum was applied. The autoclave was then stirred and heated to 85°C, vacuumed again, and 2 mol of ethylene oxide was introduced. After completion, the autoclave was heated to 153°C and reacted at a constant temperature. As the reaction proceeded, the pressure gradually decreased. When the pressure dropped to 0, the reaction was stopped to obtain a foaming agent.

[0049] (3) Add 0.3 g of carboxymethyl cellulose to 10 g of foaming agent, cool the system to below 40° C., and adjust the pH to 7-8 with hydrochloric acid to obtain foaming agent A4 for oil and gas wells.

[0050] Example 5

[0051] (1) Add 0.05 mol of p-nonylphenol, 0.102 mol of 1-aza-18-crown-6, and 304 g of ethanol to a four-necked flask, stir evenly, add dropwise 0.122 mol of 40 wt% formaldehyde solution, stir and react for 60 min, heat and reflux for 60 min, and distill under reduced pressure to obtain a viscous liquid;

[0052] (2) The viscous liquid was transferred to an autoclave, 0.14 g of potassium hydroxide was added, nitrogen was introduced, and vacuum was applied. Subsequently, the autoclave was stirred and heated to 90°C, vacuum was applied again, and 3 mol of ethylene oxide was introduced. After completion, the autoclave was heated to 158°C and reacted at a constant temperature. As the reaction proceeded, the pressure gradually decreased. When the pressure dropped to 0, the reaction was stopped to obtain a foaming agent.

[0053] (3) Add 0.6 g of hydroxyethyl cellulose to 10 g of foaming agent, cool the system to below 40°C, and adjust the pH to 7-8 with hydrochloric acid to obtain the product foaming agent A5 for oil and gas wells.

[0054] Example 6

[0055] (1) In a four-necked flask, 0.05 mol of p-nonylphenol, 0.11 mol of 1-aza-18-crown-6, and 275 g of ethanol were added and stirred uniformly. 0.11 mol of 40 wt% formaldehyde solution was added dropwise. The mixture was stirred for 40 min, heated and refluxed for 52 min, and distilled under reduced pressure to obtain a viscous liquid.

[0056] (2) The viscous liquid was transferred to an autoclave, 0.2 g of potassium hydroxide was added, nitrogen was introduced, and vacuum was applied. Subsequently, the autoclave was stirred and heated to 90°C, vacuum was applied again, and 4 mol of ethylene oxide was introduced. After completion, the autoclave was heated to 158°C and the reaction was carried out at a constant temperature. As the reaction proceeded, the pressure gradually decreased. When the pressure dropped to 0, the reaction was stopped to obtain a foaming agent.

[0057] (3) Add 0.7 g of hydroxypropyl cellulose to 10 g of foaming agent, cool the system to below 40°C, and adjust the pH to 7-8 with hydrochloric acid to obtain the product foaming agent A6 for oil and gas wells.

[0058] Example 7

[0059] (1) In a four-necked flask, 0.05 mol of p-nonylphenol, 0.104 mol of 1-aza-18-crown-6, and 293 g of ethanol were added and stirred uniformly. 0.12 mol of 40 wt% formaldehyde solution was added dropwise. The mixture was stirred for 60 min, heated and refluxed for 30 min, and distilled under reduced pressure to obtain a viscous liquid.

[0060] (2) The viscous liquid was transferred to an autoclave, 0.22 g of potassium hydroxide was added, nitrogen was introduced, and vacuum was applied. Subsequently, the autoclave was stirred and heated to 90°C, vacuum was applied again, and 4.5 mol of ethylene oxide was introduced. After completion, the autoclave was heated to 160°C and the reaction was carried out at a constant temperature. As the reaction proceeded, the pressure gradually decreased. When the pressure dropped to 0, the reaction was stopped to obtain a foaming agent.

[0061] (3) Add 1 g of hydroxypropyl cellulose to 10 g of foaming agent, cool the system to below 40°C, and adjust the pH to 7-8 with hydrochloric acid to obtain the product foaming agent A7 for oil and gas wells.

[0062] Example 8

[0063] (1) Add 0.05 mol of p-nonylphenol, 0.107 mol of 1-aza-18-crown-6, and 313 g of ethanol to a four-necked flask, stir evenly, add 0.117 mol of 40 wt% formaldehyde solution dropwise, stir and react for 50 min, heat and reflux for 30 min, and distill under reduced pressure to obtain a viscous liquid;

[0064] (2) The viscous liquid was transferred to an autoclave, 0.19 g of potassium hydroxide was added, nitrogen was introduced, and vacuum was applied. Subsequently, the autoclave was stirred and heated to 90°C, vacuum was applied again, and 5 mol of ethylene oxide was introduced. After completion, the autoclave was heated to 160°C and the reaction was carried out at a constant temperature. As the reaction proceeded, the pressure gradually decreased. When the pressure dropped to 0, the reaction was stopped to obtain a foaming agent.

[0065] (3) Add 0.5 g of gelatin to 10 g of foaming agent, cool the system to below 40°C, and adjust the pH to 7-8 with hydrochloric acid to obtain the product foaming agent A8 for oil and gas wells.

[0066] Test Example 1

[0067] Refer to Part 11 of GB / T 13173-2021 "Test Methods for Surfactant Detergents" and test the foaming power according to the Ross-Miles method at a test concentration of 0.1 wt%.

[0068] A comparative experiment was conducted using a foaming agent drilled by Tianjin Xiongguan Technology Development Co., Ltd. The experimental results are shown in Table 1.

[0069] As can be seen from Table 1, the foaming heights of the foaming agents A1-A8 for oil and gas wells of the present invention all reach 220 mm or above when used at a concentration of 0.1 wt%, with the highest reaching 275 mm (A8). In a comparative experiment, the foaming height of the foaming agent used in the drilling of Tianjin Xiongguan Technology Development Co., Ltd. is 124 mm, which is significantly lower than that of the present invention.

[0070] Test Example 2

[0071] The foam liquid half-life was determined with reference to the method in SY / T 7494-2020 “Experimental Evaluation Method of Foaming Agents for Oil and Gas Fields”, and the test concentration was 0.1 wt%.

[0072] A comparative experiment was conducted using a foaming agent drilled by Tianjin Xiongguan Technology Development Co., Ltd. The experimental results are shown in Table 1.

[0073] As can be seen from Table 1, the half-life of the foaming agents A1-A8 for oil and gas wells of the present invention is more than 8 minutes when used at a concentration of 0.1 wt%, with the highest reaching 10.6 minutes (A8). In the comparative experiment, the half-life of the foaming agent used in the drilling of Tianjin Xiongguan Technology Development Co., Ltd. is 5.3 minutes, which is significantly lower than that of the present invention.

[0074] Test Example 3

[0075] The liquid carrying capacity was determined with reference to 4.8 of SY / T 5761-1995 "Frother CT5-2 for Drainage and Gas Recovery", and the test concentration was 0.1 wt%.

[0076] A comparative experiment was conducted using a foaming agent drilled by Tianjin Xiongguan Technology Development Co., Ltd. The experimental results are shown in Table 1.

[0077] Table 1 Foaming power, half-life, and liquid carrying capacity test results

[0078] foaming agent Foaming power, mm Half-life, min Liquid carrying capacity, ml <![CDATA[A1]]> 220 8.3 185 <![CDATA[A2]]> 235 8.9 188 <![CDATA[A3]]> 255 9.2 185 <![CDATA[A4]]> 240 9.5 190 <![CDATA[A5]]> 265 9.3 185 <![CDATA[A6]]> 260 10 188 <![CDATA[A7]]> 270 10.5 193 <![CDATA[A8]]> 275 10.6 195 Comparative Example 124 5.3 170

[0079] As can be seen from Table 1, the liquid carrying capacity of the foaming agents A1-A8 for oil and gas wells of the present invention reaches 185 ml or more when used at a concentration of 0.1 wt%, with the highest reaching 195 ml (A8). In the comparative experiment, the liquid carrying capacity of the foaming agent used in the drilling of Tianjin Xiongguan Technology Development Co., Ltd. is 170 ml, which is significantly lower than that of the present invention.

[0080] The preferred embodiments of the present invention have been described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, various simple variations of the technical solution of the present invention may be made, including combining the various technical features in any other appropriate manner. These simple variations and combinations should also be regarded as disclosed in the present invention and fall within the scope of protection of the present invention.

Claims

1. A foaming agent for oil and gas wells, characterized in that: The composition and components of the foaming agent are as follows: 1 part by mass of foaming agent; Foam stabilizer 0.02-0.1 parts by mass; The molecular structural formula of the foaming agent is as follows: ， Where m = 10-100; The foam stabilizer is one of gelatin, carboxymethyl cellulose, hydroxyethyl cellulose and hydroxypropyl cellulose.

2. A foaming agent for oil and gas wells according to claim 1, characterized in that: The foam stabilizer is gelatin or carboxymethyl cellulose.

3. A method for preparing a foaming agent for oil and gas wells, characterized in that: The specific steps of the preparation method are as follows: (1) Add p-nonylphenol, 1-aza-18-crown-6, and ethanol into a four-necked flask, stir evenly, add 40 wt% formaldehyde solution dropwise, stir and react for 30-60 min, heat and reflux for 30-60 min, and distill under reduced pressure to obtain a viscous liquid; (2) The viscous liquid is transferred to an autoclave, a catalyst is added, nitrogen is introduced, and vacuum is applied; the mixture is then stirred and heated to 80-90°C, vacuum is applied again, and ethylene oxide is introduced. After completion, the mixture is heated to 150-160°C and reacted at a constant temperature. As the reaction proceeds, the pressure gradually decreases. When the pressure drops to 0, the reaction is stopped to obtain a foaming agent. (3) Add a foam stabilizer to the foaming agent, cool the system to below 40°C, and adjust the pH to 7-8 with hydrochloric acid to obtain a foaming agent for oil and gas wells; Based on 1 mol part of nonylphenol, the amounts of 1-aza-18-crown-6, 40 wt% formaldehyde and ethylene oxide are 1.9-2.3 mol parts, 2.0-2.5 mol parts and 10-100 mol parts respectively.

4. The method for preparing a foaming agent for oil and gas wells according to claim 3, characterized in that: Based on 1 mol part of nonylphenol, the amounts of 1-aza-18-crown-6, 40 wt% formaldehyde and ethylene oxide are 2.0-2.2 mol parts, 2.2-2.5 mol parts and 40-100 mol parts respectively.

5. The method for preparing a foaming agent for oil and gas wells according to claim 3, characterized in that: In step (1), the weight ratio of ethanol to nonylphenol is 20-30:

1.

6. The method for preparing a foaming agent for oil and gas wells according to claim 3, characterized in that: In step (2), the catalyst is one of sodium hydroxide and potassium hydroxide.

7. The method for preparing a foaming agent for oil and gas wells according to claim 3 or 6, characterized in that: The weight ratio of the catalyst to nonylphenol is 0.01-0.02:

1.

8. The method for preparing a foaming agent for oil and gas wells according to claim 3, characterized in that: In step (3), the weight ratio of the foaming agent to the foam stabilizer is 1:0.02-0.1.

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