A low-density foaming agent for increasing drainage and production in low-pressure and low-yield wells and its preparation method

Abstract

The present invention discloses a low-density foaming agent for drainage and production increase in low-pressure and low-yield wells, comprising the following components in weight percentage: 15% to 20% hexadecyl or octadecyl dimethylamine oxide, 7% to 12% oleamidopropylamine oxide, 7% to 12% hexadecyl or octadecyl dihydroxyethylamine oxide, 2% to 5% sodium α-olefin sulfonate, and 47% to 74% water. Preparation method: First, sodium α-olefin sulfonate is added to water, the temperature is raised to 70-90°C, and the temperature is kept constant and stirred for 2 to 3 hours until the sodium α-olefin sulfonate is completely dissolved to obtain a transparent solution; then, alkyl dihydroxyethylamine oxide is slowly added to the transparent solution until the paste is completely dissolved and the stirring is continued for 30 minutes; then, oleamidopropylamine oxide is slowly added and the stirring is continued for 1 hour, and finally, alkyl dimethylamine oxide is added and the stirring is continued for 1 to 2 hours to obtain the foaming agent. The foaming agent of the present invention only requires extremely low energy to lift the fluid in low-yield and low-pressure wells, thereby achieving drainage, production increase, and production restoration effects.

Description

Technical Field

[0001] The invention relates to the technical field of natural gas drainage and gas production, in particular to a low-density foaming agent for drainage and production increase of low-pressure and low-yield wells and a preparation method thereof. Background Art

[0002] With the deep development of a large number of gas fields, many gas wells have been experiencing a continuous decrease in pressure, an increase in water production, and serious liquid accumulation in the near-well area and wellbore, resulting in a continuous decrease in gas production or even flooding. Currently, there are many technologies to solve this problem, but there are also some shortcomings in the use process. For example, (1) the use of gas lift drainage or open well depressurization with liquid can basically achieve increased production and continuous stable production for most gas wells, but the cost of gas lift is too high and requires a large amount of equipment, while open well depressurization with liquid is more harmful to gas wells and is not conducive to long-term exploitation. (2) The use of foam drainage agents has the advantages of convenient construction, simple equipment, low cost, wide applicable well depth range, fast results, and no impact on the normal production of gas wells. However, for gas wells with extremely low energy, especially those with bottom hole pressure below 5MPa and daily water production below 1m 3 , daily gas production is less than 1m 3 , conventional foaming agents cannot achieve effective stable production with liquid, and may even easily remain at the bottom of the well and introduce excessive water, causing additional burden. (3) Patent CN115433558A discloses a gas well self-generated gas drainage energy-enhancing return agent and its application, which uses a large amount of fluorocarbon and AEO surfactants, which are difficult to degrade and not environmentally friendly, and are harmful to the formation. Patent CN111218267A discloses a foaming agent with low foam water content and its preparation method, which forms a foam with an extremely small liquid film thickness, thereby forming an extremely low foam water content to produce a low-density foam, which is easier to lift. However, this technology also uses perfluorinated surfactants, which are extremely difficult to degrade, cause damage to the formation, and are not environmentally friendly. This technology is not suitable for wells with a bottom flow pressure below 10MPa and a gas well flow rate less than 5000m 3 / d low-pressure and low-yield wells, but there are no actual application results or simulation examples that actually match such wells; there is no relevant technical solution for gas wells with relatively high gas production but high water production and low bottom hole pressure, such as gas wells with a gas production of 1×10 4 m 3 , water production 1-3m 3 However, the bottom hole pressure is only about 2MPa, and the accumulated fluid cannot be discharged with the help of airflow. Summary of the Invention

[0003] The present invention provides a low-density foaming agent specifically for draining and increasing production in low-pressure, low-yield wells, addressing the problems that existing foaming agents used for draining and increasing production in natural gas wells are not suitable for extremely low-energy gas wells, cannot effectively achieve stable production with liquid, and contain a large amount of difficult-to-degrade components that are harmful to the bottom layer.

[0004] The low-density foaming agent specially used for drainage and production increase of low-pressure and low-yield wells provided by the present invention comprises the following components in percentage by weight:

[0005] Alkyl dimethyl amine oxide 15% to 20%, oleic acid amide propyl amine oxide 7% to 12%, alkyl dihydroxyethyl amine oxide 7% to 12%, α-olefin sodium sulfonate 2% to 5%, water 47% to 74%.

[0006] Wherein, the alkyl dimethyl amine oxide is one or a mixture of hexadecyl dimethyl amine oxide and octadecyl dimethyl amine oxide;

[0007] The alkyl dihydroxyethyl amine oxide is one of hexadecyl dihydroxyethyl amine oxide and octadecyl dihydroxyethyl amine oxide, or a mixture of both.

[0008] Preferably, the weight percentages of the components are as follows:

[0009] Alkyl dimethyl amine oxide 20%, oleamidopropyl amine oxide 9%, alkyl dihydroxyethyl amine oxide 9%, sodium α-olefin sulfonate 2%, water 60%.

[0010] Wherein, the alkyl dimethyl amine oxide is a mixture of hexadecyl dimethyl amine oxide and octadecyl dimethyl amine oxide in a molar ratio of 2:1; the alkyl dihydroxyethyl amine oxide is a mixture of hexadecyl dihydroxyethyl amine oxide and octadecyl dihydroxyethyl amine oxide in a molar ratio of 2:1.

[0011] The preparation method of a low-density foaming agent for drainage and production increase of low-pressure and low-yield wells comprises the following steps:

[0012] (1) Add sodium α-olefin sulfonate to water, heat to 70-90°C, and stir at constant temperature for 2-3 hours until the sodium α-olefin sulfonate is completely dissolved to obtain a transparent solution;

[0013] (2) Slowly add alkyl dihydroxyethyl amine oxide to the transparent solution, continue stirring for 30 minutes after the paste is completely dissolved; then slowly add oleic acid amide propyl amine oxide, continue stirring for 1 hour, and finally add alkyl dimethyl amine oxide, continue stirring for 1 to 2 hours to obtain a foaming agent.

[0014] Preferably, the preparation process is carried out in a reaction vessel equipped with a condensation reflux device.

[0015] Preferably, in step (1), the temperature is raised to 80° C. and stirred at the constant temperature for 3 h.

[0016] Compared with the prior art, the present invention is beneficial in that:

[0017] (1) The foaming agent of the present invention can make the molecules distribute in an orderly manner at the liquid film interface, the space occupied by the molecules is small, the effective adsorption rate is high, and the foam liquid film formed is thicker, has stronger compressive resistance and lower foam density (foam density is less than 0.02g / cm 3 , which is less than half the density of conventional foaming agents, reduces the energy required for gas-liquid agitation, so that it can lift and carry liquid with extremely low energy in low-yield and low-pressure wells. It has a stronger liquid-carrying capacity than conventional products under low airflow and low energy, thereby achieving the effect of drainage, production increase and resumption of production.

[0018] (2) The foaming agent molecules can be efficiently and directionally arranged at the liquid film interface, forming spherical foams with neat and clear boundaries, so that the number of foaming molecules required to form stable foam is very low, the effective amount of agent required to carry the same volume of accumulated liquid is low, and the effective utilization rate of the agent is high, thereby avoiding the additional burden on the gas well caused by the introduction of too much liquid into the wellbore and the difficulty in carrying liquid; moreover, the liquid carrying can last for a long time, and continuous and stable production can be achieved.

[0019] (3) The foaming agent of the present invention can effectively help the bottom hole pressure to be between 2 and 5 MPa and the gas well flow rate to be less than 3000m 3 / d ultra-low-yield and low-pressure wells can remove fluid accumulation, resume production, increase production, and stabilize production; it can solve the problem that conventional foaming agents are difficult to effectively drain and stabilize production in fluid-accumulated wells.

[0020] (4) The foaming agent of the present invention is prepared using environmentally friendly and easily degradable ingredients, is harmless to the formation, and has good compatibility with formation water, so there is no need to worry about incompatibility issues.

[0021] Other advantages, objectives and features of the present invention will be reflected in part from the following description and will be understood by those skilled in the art through study and practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 Comparative Example 9: Microscopic images of foam film thickness at 1 L / min airflow. The upper image shows the instantaneous film morphology, and the lower image shows the 5-minute film morphology.

[0023] Figure 2 Comparative Example 9: Microscopic images of foam film thickness at 3 L / min airflow. The upper image shows the instantaneous film morphology, and the lower image shows the 5-minute film morphology.

[0024] Figure 3 Comparative Example 6: Microscopic images of foam film thickness at 1 L / min airflow. The upper image shows the instantaneous film morphology, and the lower image shows the 5-minute film morphology.

[0025] Figure 4Comparative Example 6: Microscopic images of foam film thickness at 3 L / min airflow. The upper image shows the instantaneous film morphology, and the lower image shows the 5-minute film morphology.

[0026] Figure 5 , Example 7: Microscopic images of foam film thickness at an airflow rate of 1 L / min. The upper image shows the instantaneous film morphology, and the lower image shows the 5-minute film morphology.

[0027] Figure 6 , Example 7: Microscopic images of foam film thickness at 3 L / min airflow. The upper image shows the instantaneous film morphology, and the lower image shows the 5-minute film morphology.

[0028] Figure 7 , production curve of Wei 204H34-7 well in Sichuan block in application example 1.

[0029] Figure 8 , the production curve of Wei 204H34-2 well in Sichuan block in application example 2.

[0030] Figure 9 , Production curve of Longsui 27D-1 well in application example three. DETAILED DESCRIPTION

[0031] The preferred embodiments of the present invention are described below with reference to the accompanying drawings. It should be understood that the preferred embodiments described herein are only used to illustrate and explain the present invention, and are not used to limit the present invention.

[0032] The following 11 examples and 9 comparative examples illustrate the key roles of each material. The dosages of the components in Examples 1-11 and Comparative Examples 1-4 are shown in Table 1. In the table, OA is a mixture of hexadecyldimethylamine oxide and octadecyldimethylamine oxide in a molar ratio of 2:1; OAE is a mixture of hexadecyldihydroxyethylamine oxide and octadecyldihydroxyethylamine oxide in a molar ratio of 2:1.

[0033] The preparation methods of Examples 1-11 are as follows:

[0034] (1) Prepare a three-necked flask, weigh the corresponding amount of clean water in the flask, start magnetic stirring at 600-800 rpm, add the weighed sodium α-olefin sulfonate, install a condensation device and start the condensation water circulation, set the temperature to 80°C and start heating. After the temperature is constant at 80°C, continue stirring for 3 hours until the sodium α-olefin sulfonate is completely dissolved and the solution is a uniform transparent liquid;

[0035] (2) Slowly add hexadecyl / octadecyl dihydroxyethylamine oxide until the paste is completely dissolved and continue stirring for 30 minutes;

[0036] (3) Slowly add oleamidopropylamine oxide and continue stirring for 1 hour;

[0037] (4) Finally, add hexadecyl / octadecyl dimethylamine oxide and continue stirring for 2 hours to obtain a foaming agent.

[0038] Comparative Examples 1-4 are foaming agents prepared by removing one component based on the formulation and preparation method of Example 7.

[0039] Table 1 Formulations of Examples 1-11 and Comparative Examples 1-4

[0040]

[0041]

[0042] Comparative Examples 5-9 use similar products currently available on the market. The details are as follows:

[0043] Comparative Example 5: XHY-6 gas well liquid foam drainage agent from Huayang Xinghua Chemical Co., Ltd.

[0044] Comparative Example 6: XHY-4 gas well liquid foam drainage agent from Huayang Xinghua Chemical Co., Ltd.

[0045] Comparative Example 7: XHY-2 gas well liquid foam drainage agent from Huayang Xinghua Chemical Co., Ltd.

[0046] Comparative Example 8: Chengdu Lawnpus Technology Co., Ltd.'s foaming agent product LP-PP-04, which is mainly composed of a compound of betaine and sodium sulfonate, is heat-resistant, salt-resistant, and oil-resistant. It is suitable for mineralization below 300g / L and has an oil resistance of less than 30%;

[0047] Comparative Example 9: Chengdu Lawnpus Technology Co., Ltd.'s foaming agent product LP-PP-02, which is mainly composed of a compound of betaine and amine oxide. It is resistant to high temperatures, has a certain oil resistance (oil content below 10%), is suitable for medium and low mineralization, and has excellent foaming and foam stabilizing capabilities.

[0048] The performance test experiments of the above-mentioned various foaming agents are as follows:

[0049] Test Example 1: Foam Density Test

[0050] Foam density tests were performed on 11 groups of examples and 9 groups of comparative examples;

[0051] (1) Test method:

[0052] Weigh 2.5 g of the sample to be tested in a beaker and add 100 mL of mineral water (prepared according to the 40 g / L mineral water preparation requirements in Q / SY 17815-2015) for pre-dissolution. Then pour the dissolved sample into a 500 mL volumetric flask and rinse the beaker three times with mineral water. All the rinse liquid is introduced into the volumetric flask and diluted to 500 mL with mineral water to obtain a foaming agent solution with a concentration of 0.2%.

[0053] Place the prepared test solution in a super constant temperature water bath at 80℃±2℃ and let it stand for 10 minutes. Preheat the liquid carrier to 80℃±2℃ with a super constant temperature water bath, take 50mL of the test solution after standing and pour it evenly into the liquid carrier for rinsing, open the lower cock and drain the rinsing liquid until there is no visible liquid surface. Close the drainage cock, use a 250mL graduated cylinder to take 250mL of the test solution after standing and add it to the liquid carrier, connect the airflow pipeline and the drainage collection device, pass the airflow at a speed of 5L / min, place the foam collection tube, weigh the mass of the foam collection tube and record it as m0, the foam collection tube collects 1000mL of foam (calculate the average value of the foam collected 5 times in a row), and then weigh the weight of the foam collection tube after collecting the foam again m1, and calculate the foam density according to the following formula:

[0054]

[0055] Where: ρ is the foam density, g / cm 3 ; m0 and m1 are the mass of the foam collection tube and the weight of the foam collection tube after collecting foam, respectively, in g.

[0056] (2) Test results

[0057] The foam density test results of Examples 1-11 and Comparative Examples 1-9 are shown in Table 2. Based on the foam density test results of Examples 1-11 and Comparative Examples 1-9, the foam density of Examples 3, 7, and 11 is relatively low, followed by Examples 8 and 9. However, the foam density of all Examples is significantly lower than that of Comparative Examples 1-9. The test results of Comparative Examples 1-4 indicate that the lack of a component in the foaming agent of the present invention will have a significant impact on the foam density, significantly increasing it. The foam density of the conventional foaming agents of Comparative Examples 5-9 is relatively high, essentially more than double that of Examples 3, 7, and 11. This demonstrates that the foaming agent of the present invention has a relatively low foam density.

[0058] Table 2 Foam density of Examples 1 to 11 and Comparative Examples 1 to 9

[0059]

[0060]

[0061] Test Example 2: Foaming, Foam Stability and Liquid Carrying Performance Test

[0062] (1) Test method

[0063] The foaming, foam stabilization and liquid carrying properties of Examples 1-11 and Comparative Examples 1-9 were tested using a Roche foam meter and a liquid carrying device.

[0064] Test parameters: test concentration 0.2%, test temperature 80°C, test mineralization 40g / L.

[0065] The test results are shown in Table 3. From the perspective of foaming, stabilizing foam and liquid carrying performance, the foam and liquid carrying performance of Examples 1-11 are slightly lower than those of the comparative example, but the overall performance is still good.

[0066] Table 3 Foaming, foam stabilization and liquid carrying performance tests of Examples and Comparative Examples

[0067] name <![CDATA[Foam density g / cm 3 > Bubble height (mm) Stable bubble height (mm) Liquid volume ml Example 1 0.01705 170 153 145 Example 2 0.01802 175 165 143 Example 3 0.01568 145 130 125 Example 4 0.01720 175 145 142 Example 5 0.01771 170 155 140 Example 6 0.01738 165 150 145 Example 7 0.01450 154 140 120 Example 8 0.01666 160 155 140 Example 9 0.01628 152 145 135 Example 10 0.01710 170 165 150 Example 11 0.01550 160 150 130 Comparative Example 1 0.02543 175 140 110 Comparative Example 2 0.02422 180 155 120 Comparative Example 3 0.02365 178 145 115 Comparative Example 4 0.02565 175 80 110 Comparative Example 5 0.02925 180 150 165 Comparative Example 6 0.02005 162 145 148 Comparative Example 7 0.02327 170 150 152 Comparative Example 8 0.02077 175 165 138 Comparative Example 9 0.03680 190 185 160

[0068] Test Example 3: Surface Tension

[0069] Surface and interfacial tensions were measured for Examples 1-11 and Comparative Examples 1-9, and the test results are shown in Table 4. The results for Comparative Examples 1-4 show that the absence of a key component significantly affects the surface and interfacial tension values, indicating that the increase in surface and interfacial tension caused by the absence of the key component is one of the factors affecting foam density. However, when comparing the results for Examples 1-11 with the results for Comparative Examples 5-9, there is essentially no difference in the surface tension values, indicating that surface tension has no effect on changes in foam density. Furthermore, the interfacial tension values show no regular pattern, indicating that interfacial tension is not a key factor in determining foam density.

[0070] Table 4 Interfacial tension of Examples and Comparative Examples

[0071] name Foam density Surface tension / mN·m Interfacial tension / mN·m Example 1 0.01705 27.484 0.739 Example 2 0.01802 27.522 0.824 Example 3 0.01568 27.229 0.669 Example 4 0.01720 27.626 0.467 Example 5 0.01771 26.031 0.458 Example 6 0.01738 27.744 0.855 Example 7 0.01450 27.127 0.659 Example 8 0.01666 27.972 0.680 Example 9 0.01628 28.625 0.684 Example 10 0.01710 27.86 0.547 Example 11 0.01550 26.468 0.648 Comparative Example 1 0.02543 28.542 1.250 Comparative Example 2 0.02422 30.781 1.336 Comparative Example 3 0.02365 28.259 1.214 Comparative Example 4 0.02565 28.833 1.289 Comparative Example 5 0.02925 26.939 0.437 Comparative Example 6 0.02005 26.803 0.924 Comparative Example 7 0.02327 26.780 0.598 Comparative Example 8 0.02077 26.711 1.047 Comparative Example 9 0.03680 26.478 0.359

[0072] Test Example 4:

[0073] Preferred examples 3, 7, 8, 9, and 11, which have low foam density and excellent foaming, stabilizing, and liquid-carrying properties, were subjected to foam density review tests at different concentrations. The results are shown in Table 5. As the concentration of the examples increases, the foam density decreases, and Example 7 exhibits excellent low foam density.

[0074] Table 5 Foam density test at different concentrations

[0075]

[0076]

[0077] Test Example 5:

[0078] Preferred Example 7 measured the surface interfacial tension at different concentrations. The results are shown in Table 6. It can be concluded that the surface interfacial tension values at different concentrations are not much different.

[0079] Table 6 Interfacial tension measurement at different concentrations in Example 7

[0080] name Test concentration% Surface tension mN / m Interfacial tension mN / m Example 7 0.1 27.064 0.670 Example 7 0.2 26.590 0.630 Example 7 0.3 26.813 0.577

[0081] Test Example 6

[0082] Preferred Example 7 was tested for foaming, foam stabilization, and liquid-carrying performance at various concentrations. Test conditions: 80°C constant temperature for 30 minutes, Roche foam analyzer, salinity of 4w, and air flow rate of 3 L / min. Test results are shown in Table 7. As can be seen, foaming, foam stabilization, and liquid-carrying capabilities increased with increasing concentration, and the foam performance met the requirements for foam removal.

[0083] Table 7 Foaming, foam stabilization and liquid carrying performance of different concentrations of Example 7

[0084] name concentration% Bubble height (mm) 5min soaking height mm Foam stability rate% Liquid volume ml Example 7 0.1 130 120 92.31％ 90 Example 7 0.2 140 128 91.43％ 114 Example 7 0.3 145 130 89.66％ 150

[0085] Test Example 7

[0086] Comparative testing of liquid carrying capacity and sustained liquid carrying time was conducted on Example 7 and Comparative Example 9 at different gas flow rates. The test dosage was 0.2%, the test temperature was 80°C, and the test salinity was 40 g / L. The test results (Table 8) show that while Example 7 did not carry as much liquid as Comparative Example 9 (a conventional foaming agent) at high gas flow rates, it exhibited a stronger liquid carrying effect and a longer sustained liquid carrying time than conventional foaming agents at low gas flow rates, making it more suitable for liquid-carrying lift applications in low-yield, low-pressure wells.

[0087] Table 8 Liquid carrying performance of Example 7 and Comparative Example 9 at different gas flow rates

[0088]

[0089] Test Example 8

[0090] 1. Foam liquid film thickness test

[0091] Test parameters: mineralization 40g / L, temperature 80℃, 0.2% foaming agent concentration, flow rate 1L / min and 3L / min

[0092] Test method: The foam density test method was used to test the liquid film thickness of Example 7, Comparative Example 6, and Comparative Example 9. 1000 ml of foam was collected and observed under an electron microscope to measure its instantaneous liquid film thickness and the liquid film thickness after 5 minutes. The average value of the film thickness at three observable locations was calculated.

[0093] From the test results (Table 9), it can be seen that under the same addition amount and different airflow, the liquid film thickness of Example 7 is thicker than that of Comparative Examples 6 and 9. In addition, the foam liquid film thickness of Example 7 does not decrease after 5 minutes, while the liquid film thickness of Comparative Examples 6 and 9 decreases slightly, indicating that Example 7 has a better foam stabilizing effect.

[0094] Table 9 Foam liquid film thickness under different gas volumes in Example 7 and Comparative Examples 6 and 9

[0095]

[0096] 2. Foam liquid film micro thickness test

[0097] Polarized electron microscopy was used to test the microscopic morphology of the foam liquid film of Example 7, Comparative Example 6 and Comparative Example 9 at two air flow rates. The results are shown in Figure 2. Figure 1-6 It can be seen that the thickness of the foam liquid film of Example 7 is significantly higher than that of Comparative Examples 6 and 9. The thickness of the liquid film is basically not reduced after 5 minutes, indicating that the foam stability is excellent. In addition, Example 7 obviously forms neat and clearly defined spherical foams under different airflows, indicating that the molecules can be efficiently and directionally arranged at the liquid film interface, the effective adsorption rate of the molecules at the liquid film interface is high, and the effective amount of the agent required to carry the same volume of effusion is lower, thereby forming a low-density foam.

[0098] Application Example 1

[0099] Well Wei 204H34-7 in the Sichuan block was selected as the research object. The well started foaming on November 12, 22, using conventional foaming agents. Initially, it was injected at 20L / d. Before the foaming, the well could not produce normally and the production was 0. Through gas lift + conventional foaming agents, the drainage effect was not obvious and the production could only be maintained at 2,000 cubic meters / day. On March 10, a low-density foaming agent specially used for drainage and production increase of low-pressure and low-yield wells was replaced. Through casing injection + open well drainage, the well was successfully resumed on March 18, and the initial daily production was stable at 23,000 cubic meters / day. On March 22, the injection system was adjusted to 24h continuous injection with an injection volume of 40L / d, and the production was stabilized to 17,000 cubic meters. Compared with conventional foaming, the average daily gas production increased by 15,000 cubic meters, and the production increase effect was obvious. The production curve is detailed. Figure 7 .

[0100] Application Example 2

[0101] Well Wei 204H34-2 in the Sichuan block was selected as the research object. The well began to use conventional foaming agents on January 30, 2023. Initially, it was injected at 20L / d. The production recovered to a certain extent and returned to 15,000 cubic meters / day. After March 3, the production dropped rapidly to 9,000 cubic meters / day. The injection system was adjusted twice in the middle and adjusted to 30L / day. The effect was still not obvious. On March 10, a low-density foam foaming agent was replaced. Initially, it was injected at 20L / d, twice a day, just to maintain the current production. There was no significant change in production. On March 18, the injection system was adjusted to 30L / d, 3 times a day. The production of the well increased significantly on the 20th, from 7,000 cubic meters / day to 15,000 cubic meters / day. Compared with conventional foaming, the daily average gas production increased significantly by 8,000 cubic meters and remained stable. The production curve is shown in detail. Figure 8 .

[0102] Application Example 3

[0103] The Luodai Gas Field in Sichuan was put into development and production in June 1997. The main producing layer is the shallow Penglaizhen Formation gas reservoir. The Penglaizhen Formation gas reservoir in the Luodai Gas Field is a normal pressure gas reservoir with low gas well pressure and low production. The average daily gas production of a single well is less than 0.2×10 4 m 3 The bottom hole pressure of old wells is 2-5MPa. Gas wells generally produce water, but the water production is low, with a daily water production of less than 0.5m 3 The block has been developed for more than 20 years so far, and its gas wells have been in a low-pressure and low-yield state for a long time. The production of more than 80% of the gas wells in the block is generally lower than the critical liquid carrying flow rate of the existing foam drainage technology. The conventional foam drainage agent has poor drainage effect, so a low-density foaming agent specially designed for drainage and production increase of low-pressure and low-yield wells is used.

[0104] For example, the conventional foaming agent used in Longsui 27D-1 well was not effective. The injection cycle was once a week, and 5L was added at a time. On October 25, 2022, a low-density foaming agent specially designed for drainage and production increase of low-pressure and low-yield wells was used. 5L was added at a time. After implementation, the gas well production increased from 0.56 to 0.73 thousand cubic meters / day, with a daily increase of 1.5 thousand cubic meters. The production was stable and the production increase effect was obvious. The production curve is detailed in the following table. Figure 9 .

[0105] Subsequently, the technology was applied to 13 wells in Longsui, with 12 wells achieving drainage effects and 9 wells experiencing increased gas production, of which 6 wells achieved increased production of 500m 3 / d or more, 7 wells maintained stable production for more than 7 days, and the overall implementation effect was good.

[0106] The above description is merely a preferred embodiment of the present invention and does not constitute any form of limitation to the present invention. Although the present invention has been disclosed as a preferred embodiment as above, it is not intended to limit the present invention. Any technician familiar with this profession can make some changes or modifications to equivalent embodiments of the technical contents disclosed above without departing from the scope of the technical solution of the present invention. However, any simple modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention are still within the scope of the technical solution of the present invention.

Claims

1. A low-density foaming agent for increasing the production of low-pressure and low-yield wells, characterized in that: The following components are included in weight percentage: Alkyl dimethyl amine oxide 15% to 20%, oleamidopropyl amine oxide 7% to 12%, alkyl dihydroxyethyl amine oxide 7% to 12%, sodium α-olefin sulfonate 2% to 5%, water 47% to 74%; The alkyl dimethyl amine oxide is one of hexadecyl dimethyl amine oxide and octadecyl dimethyl amine oxide, or a mixture of both; The alkyl dihydroxyethyl amine oxide is one or a mixture of hexadecyl dihydroxyethyl amine oxide and octadecyl dihydroxyethyl amine oxide; The preparation method of the foaming agent comprises the following steps: (1) Add sodium α-olefin sulfonate to water, raise the temperature to 70-90°C, and stir at constant temperature for 2-3 hours until the sodium α-olefin sulfonate is completely dissolved to obtain a transparent solution; (2) Slowly add alkyl dihydroxyethyl amine oxide to the transparent solution, continue stirring for 30 minutes after the paste is completely dissolved; then slowly add oleic acid amide propyl amine oxide, continue stirring for 1 hour, and finally add alkyl dimethyl amine oxide, continue stirring for 1 to 2 hours to obtain a foaming agent.

2. The low-density foaming agent for increasing drainage and production of low-pressure and low-yield wells according to claim 1, characterized in that: The weight percentages of each component are as follows: Alkyl dimethyl amine oxide 20%, oleamidopropyl amine oxide 9%, alkyl dihydroxyethyl amine oxide 9%, sodium α-olefin sulfonate 2%, water 60%.

3. The low-density foaming agent for increasing drainage and production of low-pressure and low-yield wells according to claim 2, characterized in that: The alkyl dimethyl amine oxide is a mixture of hexadecyl dimethyl amine oxide and octadecyl dimethyl amine oxide in a molar ratio of 2:1; the alkyl dihydroxyethyl amine oxide is a mixture of hexadecyl dihydroxyethyl amine oxide and octadecyl dihydroxyethyl amine oxide in a molar ratio of 2:

1.

4. The low-density foaming agent for increasing drainage and production of low-pressure and low-yield wells according to claim 1, characterized in that: The preparation process is carried out in a reaction vessel equipped with a condensation reflux device.

5. The low-density foaming agent for increasing drainage and production of low-pressure and low-yield wells according to claim 1, characterized in that: In step (1), the temperature was raised to 80° C. and stirred at the constant temperature for 3 h.

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