Interface regulation and control wetting oil displacement agent for improving recovery ratio of low-permeability oil field

Abstract

The invention discloses an interface regulation and control wetting oil displacement agent for improving the recovery ratio of a low-permeability oil field, and the interface regulation and control wetting oil displacement agent comprises the following components in parts by weight: 6-10 parts of dimethylol lauryl sodium sulfate, 2-5 parts of polysorbate-80, 2-4 parts of nanoscale titanium dioxide, 1-2 parts of ethanol and 100-120 parts of deionized water. The interface regulation and control wetting oil-displacing agent can effectively enhance the adsorption effect of the oil-displacing agent on the rock surface, so that the wetting regulation and control capability is improved, and the recovery efficiency of a low-permeability oil field is remarkably enhanced by changing the wettability of the rock surface and an oil-water interface and optimizing distribution and flowing of fluid in pores.

Description

Technical Field

[0001] The invention relates to the technical field of oil production, in particular to an interface-controlled wetting oil-displacing agent for improving the recovery rate of low-permeability oil fields. Background Art

[0002] Low permeability oil fields, also known as low permeability oil fields, refer to oil fields with low reservoir permeability, low abundance and low single well productivity. According to the average permeability of the oil layer, low permeability oil reservoirs can be further divided into low permeability oil reservoirs, ultra-low permeability oil reservoirs and ultra-low permeability oil reservoirs.

[0003] The reservoirs of low-permeability oil fields usually have the characteristics of low porosity and low permeability, poor oil storage properties, relatively high rock cement content, small rock development scale, and crude oil with low viscosity, low density and uneven flow rate. After the oil layer encounters water, the oil recovery index will continue to decrease, which will have an adverse effect on the oil field recovery rate. Even if oil field production is carried out, it will cause a large loss of resources. Due to the low permeability, it is necessary to overcome a large flow resistance during the mining process. Therefore, development is difficult and requires the use of corresponding oil production engineering and technical measures.

[0004] Conventional waterflooding is an effective method for developing low-permeability reservoirs with relatively high permeability. Water is injected into the reservoir to increase reservoir pressure, thereby driving crude oil out. However, waterflooding recovery rates remain suboptimal. This is because the adhesion between crude oil and rock in the reservoir is one of the main factors hindering crude oil flow. Displacement agents, by injecting specific chemicals into the well, alter the interaction between crude oil and the rock surface, reducing adhesion and allowing crude oil to flow more easily from the reservoir. Summary of the Invention

[0005] In order to solve the above technical problems, the present invention provides an interface-controlled wetting oil-displacing agent for improving the recovery rate of low-permeability oil fields.

[0006] The technical solution of the present invention is: an interface-controlled wetting and oil-displacing agent for improving the recovery rate of low-permeability oil fields. The interface-controlled wetting and oil-displacing agent comprises, by weight, 6 to 10 parts of sodium dihydroxymethyl dodecyl sulfate, 2 to 5 parts of polysorbate 80, 2 to 4 parts of nano-sized titanium dioxide, 1 to 2 parts of ethanol, and 100 to 120 parts of deionized water.

[0007] Description: By adopting the interface-controlled wettability oil-displacing agent composed of the above components, its adsorption effect on the rock surface can be effectively enhanced, and the wettability control ability can be enhanced, thereby realizing the adjustment of wettability from oleophilic to strongly hydrophilic / strongly oleophobic. By changing the wettability of the rock surface and the oil-water interface, the distribution and flow of the fluid in the pores are optimized, thereby significantly enhancing the recovery rate of low-permeability oil fields.

[0008] Furthermore, the synthesis method of the dihydroxymethyl sodium lauryl sulfate is:

[0009] Sodium lauryl sulfate and a solvent are mixed in a ratio of 10-15 g:100 mL to obtain a mixed system. The mixed system is heated in a water bath to a reflux temperature of 68-75° C., and then formaldehyde is slowly added dropwise to the mixed system while stirring. After reacting for 3-5 hours, the solvent is removed by rotary evaporation to obtain a white solid, which is sodium dihydroxymethyl lauryl sulfate.

[0010] Description: Through the rational design of the sodium dodecyl sulfate molecule, two hydroxymethyl groups are added to the sodium dodecyl sulfate using formaldehyde and process conditions. The hydroxyl groups in the dihydroxymethyl sodium dodecyl sulfate are used to produce hydrogen bonds with the oxygen-containing groups on the rock surface, making it easier to adsorb on the rock surface. At the same time, the hydroxyl groups in the dihydroxymethyl sodium dodecyl sulfate help to form semi-micelle adsorption on the rock surface through hydrogen bonding and hydrophobic effects to produce interface aggregates, thereby enhancing the effect of the oil displacement agent on interface wetting control and improving the recovery rate of low-permeability oil fields.

[0011] Furthermore, the added amount of formaldehyde is n, and the added amount of sodium lauryl sulfate is n[4,5], wherein n∈[2,3].

[0012] Description: Based on the above-mentioned addition amounts of formaldehyde and sodium lauryl sulfate, the target product we need, dihydroxymethyl sodium lauryl sulfate, can be effectively synthesized, avoiding the problem of low synthesis efficiency of dihydroxymethyl sodium lauryl sulfate caused by inaccurate dosage of formaldehyde and sodium lauryl sulfate.

[0013] Furthermore, let m be the solvent volume rate coefficient and m∈ a positive integer, that is, the amount of solvent added is m

[100] mL, and the solvent is methanol;

[0014] The formaldehyde drop rate is m[1,5] drops / min, and the stirring speed is 100-180 rpm. It can be understood that 1 mL = 20 drops.

[0015] Note: Too fast a formaldehyde dropwise acceleration may lead to excessively high local concentration, resulting in local overheating or violent reaction, and uneven mixing, which will affect the synthesis efficiency of the target product - dihydroxymethyl sodium lauryl sulfate. The above-mentioned dropwise addition acceleration can effectively ensure that formaldehyde and sodium lauryl sulfate are fully mixed, and the reaction is more uniform and controllable, thereby improving the synthesis efficiency of dihydroxymethyl sodium lauryl sulfate.

[0016] Furthermore, the interface regulating wetting and oil displacement agent comprises, by weight, 8 to 9 parts of sodium dihydroxymethyl dodecyl sulfate, 3 to 4 parts of polysorbate 80, 3 to 4 parts of nano-sized titanium dioxide, 1 to 2 parts of ethanol, and 110 to 115 parts of deionized water.

[0017] Note: By further optimizing the ratio of each component of the interface-controlled wetting displacement agent, the use effect of the displacement agent can be improved and the recovery effect of low-permeability oil fields can be enhanced. The interface-controlled wetting displacement agent with the above ratio can further enhance the adsorption effect on the rock surface, strengthen the wettability control ability, and enhance the distribution and flow of fluids in the pores, thereby significantly improving the recovery rate of low-permeability oil fields.

[0018] The present invention also provides a method for preparing the above-mentioned interface-controlled wetting and oil-displacing agent, which comprises the following specific steps:

[0019] Step 1: Add 100-120 parts of deionized water to a container, heat it to 30-40° C., then add 2-5 parts of polysorbate 80, 6-10 parts of sodium dihydroxymethyldodecyl sulfate, and 1-2 parts of ethanol in sequence, and stir until completely dissolved to obtain a mixed solution;

[0020] Step 2: Add 2 to 4 parts of nano-sized titanium dioxide to the mixed solution, stir and disperse the mixed solution at a speed of 3000 to 4000 rpm for 20 to 40 minutes, and ultrasonically treat the stirred and dispersed mixed solution to obtain an interface-controlled wetting and oil-displacing agent.

[0021] Description: By using the above preparation method to prepare the interface-controlled wetting displacement agent, the target product - the interface-controlled wetting displacement agent can be effectively obtained, and by regulating its mixing temperature, the various components can be evenly dispersed in the oil displacement system, thereby enhancing the adsorption effect of the interface-controlled wetting displacement agent on the rock surface, enhancing its wettability regulation ability, and realizing the adjustment of wettability from oleophilic to strongly hydrophilic / strongly oleophobic, thereby optimizing the distribution and flow of oil reservoirs in the pores and improving the recovery rate.

[0022] Furthermore, the method of ultrasonically dispersing the stirred and dispersed mixed liquid is as follows: ultrasonically dispersing the stirred and dispersed mixed liquid for 10 to 15 minutes at an ultrasonic frequency of 30 to 50 KHz and a dispersion speed of 4000 to 6000 rpm.

[0023] Description: The high-frequency vibration of ultrasound can quickly disperse nano-scale titanium dioxide into a uniform state, avoiding the aggregation and sedimentation of nano-scale titanium dioxide. Under the above conditions, the particle size distribution range is small, the single particle size is highly consistent, and the dispersion quality is high, thereby improving the stability and use effect of the interface-controlled wetting and oil-displacing agent.

[0024] Furthermore, the nano-scale titanium dioxide is modified nano-scale titanium dioxide, and the modification method is:

[0025] 1) heating nano-sized titanium dioxide to 40-60° C. and adding it to the impregnation solution at room temperature, stirring and mixing to obtain a base solution, and then evaporating and drying the base solution to obtain a modified initial material;

[0026] The impregnation solution is prepared by mixing linear polysiloxane and n-hexane in a ratio of 15-25 g:100 mL, and the mass fraction of the linear polysiloxane is 15-25%.

[0027] 2) The modified raw material is heated to 550-600° C. at a rate of 8-12° C. / min and then kept at this temperature for 2-3 hours to obtain modified nano-scale titanium dioxide.

[0028] Description: By modifying nano-scale titanium dioxide with silicon deposition, its performance can be enhanced and its hydrophilicity can be improved, so that the nano-scale titanium dioxide can be dispersed more evenly and stably in the mixed system, thereby improving the use effect of nano-scale titanium dioxide;

[0029] At the same time, by mixing the nano-scale titanium dioxide with the impregnation liquid through temperature difference, the nano-scale titanium dioxide will cause the added impregnation liquid to locally produce an instantaneous temperature rise, thereby increasing the molecular movement speed in the local area, increasing the collision frequency, and increasing the deposition rate, thereby further improving the effect of linear polysiloxane deposition on titanium dioxide, and thus improving the use effect of the modified nano-scale titanium dioxide.

[0030] The beneficial effects of the present invention are:

[0031] (1) The interface-controlled wetting oil-displacing agent of the present invention can effectively enhance the adsorption effect of the oil-displacing agent on the rock surface, thereby improving the wettability control capability, and optimizing the distribution and flow of fluids in the pores by changing the wettability of the rock surface and the oil-water interface, thereby significantly enhancing the recovery efficiency of low-permeability oil fields.

[0032] (2) The interface-controlled wetting oil-displacing agent of the present invention can enhance the effect of the oil-displacing agent on interface-controlled wetting by using sodium dihydroxymethyldodecyl sulfate as a component of the oil-displacing agent, thereby improving the recovery rate of low-permeability oil fields.

[0033] (3) The method for preparing the interface-regulated wetting and oil-displacing agent provided by the present invention can effectively obtain the interface-regulated wetting and oil-displacing agent, and by regulating its mixing temperature, each component can be evenly dispersed in the oil-displacing system, thereby optimizing the use effect of the interface-regulated wetting and oil-displacing agent. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 This is a schematic diagram of the synthesis of sodium dihydroxymethyl dodecyl sulfate. DETAILED DESCRIPTION

[0035] The present invention will be further described in detail below in conjunction with specific implementation methods to better demonstrate the advantages of the present invention.

[0036] Example 1: An interface-controlled wetting and oil-displacing agent for improving the recovery rate of low-permeability oil fields. The interface-controlled wetting and oil-displacing agent comprises, by weight: 9 parts of sodium dihydroxymethyl dodecyl sulfate, 4 parts of polysorbate 80, 3 parts of nano-sized titanium dioxide, 2 parts of ethanol, and 112 parts of deionized water.

[0037] The synthesis method of the dihydroxymethyl sodium lauryl sulfate is:

[0038] Sodium lauryl sulfate and a solvent are mixed in a ratio of 12 g: 100 mL to obtain a mixed system. The mixed system is heated in a water bath to a reflux temperature of 71° C., and then formaldehyde is slowly added dropwise to the mixed system while stirring. After reacting for 4 hours, the solvent is removed by rotary evaporation to obtain a white solid, which is sodium dihydroxymethyl lauryl sulfate.

[0039] Specifically, the amount of sodium lauryl sulfate added is n[4.5], i.e. 12 g, and the amount of formaldehyde added is n, n is 2.7 g, wherein n∈[2,3], which is consistent with the range of n values;

[0040] Let m be the solvent volume rate coefficient and m∈ a positive integer, that is, the amount of solvent added is m

[100] mL, that is, m is 1, and the solvent is methanol; the dropwise addition speed of the formaldehyde is 3 drops / min, and the stirring speed is 140 rpm. It can be understood that 1mL=20 drops.

[0041] Example 2: This example provides a method for preparing the interface-controlled wetting and oil-displacing agent of Example 1, comprising the following steps:

[0042] Step 1: Add 112 parts of deionized water to a container, heat it to 36° C., then add 4 parts of polysorbate 80, 9 parts of sodium dihydroxymethyldodecyl sulfate, and 2 parts of ethanol in sequence, and stir until completely dissolved to obtain a mixed solution;

[0043] Step 2: Add 3 parts of nano-sized titanium dioxide to the mixed solution, stir and disperse the mixed solution at a speed of 3500 rpm for 30 minutes, and ultrasonically disperse the stirred and dispersed mixed solution at an ultrasonic frequency of 45 kHz and a dispersion speed of 5200 rpm for 12 minutes to obtain an interface-regulated wetting and oil-displacing agent.

[0044] Example 3: This example is different from Example 1 in that, in parts by weight, the interface regulating wetting and oil displacement agent comprises: 6 parts of sodium dihydroxymethyl dodecyl sulfate, 2 parts of polysorbate 80, 2 parts of nano-sized titanium dioxide, 1 part of ethanol, and 100 parts of deionized water.

[0045] Example 4: This example differs from Example 1 in that, by weight, the interface regulating wetting and oil displacement agent comprises: 10 parts of sodium dihydroxymethyl dodecyl sulfate, 5 parts of polysorbate 80, 4 parts of nano-sized titanium dioxide, 2 parts of ethanol, and 120 parts of deionized water.

[0046] Example 5: This example is different from Example 1 in that sodium lauryl sulfate and the solvent are mixed in a ratio of 10 g:100 mL to obtain a mixed system.

[0047] Example 6: This example is different from Example 1 in that sodium lauryl sulfate and the solvent are mixed in a ratio of 15 g:100 mL to obtain a mixed system.

[0048] Example 7: This example is different from Example 1 in that the mixed system is heated in a water bath to a reflux temperature of 68° C., and then formaldehyde is slowly added dropwise to the mixed system while stirring. After reacting for 3 hours, the solvent is removed by rotary evaporation.

[0049] Example 8: This example is different from Example 1 in that the mixed system is heated in a water bath to a reflux temperature of 75°C, and then formaldehyde is slowly added dropwise to the mixed system while stirring. After reacting for 5 hours, the solvent is removed by rotary evaporation.

[0050] Example 9: This example is different from Example 1 in that the amount of sodium lauryl sulfate added is n[4], i.e. 12 g, and the amount of formaldehyde added is n, where n is 3 g.

[0051] Example 10: This example is different from Example 1 in that the amount of sodium lauryl sulfate added is n[5], i.e. 12 g, and the amount of formaldehyde added is n, which is 2.4 g.

[0052] Example 11: The difference between this example and Example 1 is that m is the solvent volume rate coefficient and m∈ is a positive integer, that is, the amount of solvent added is m

[100] mL, that is, m is 1, and the solvent is methanol; the dropwise addition acceleration of the formaldehyde is 1 drop / min, and the stirring speed is 100rpm.

[0053] Example 12: This example is different from Example 1 in that m is the solvent volume rate coefficient and m∈ is a positive integer, that is, the amount of solvent added is m

[100] mL, that is, m is 1, and the solvent is methanol; the formaldehyde addition rate is 5 drops / min, and the stirring speed is 180rpm.

[0054] Example 13: This example is different from Example 2 in that, in step 1, the temperature is raised to 30°C.

[0055] Example 14: This example is different from Example 2 in that, in step 1, the temperature is raised to 40°C.

[0056] Example 15: This example differs from Example 2 in that, in step 2, the mixed solution is stirred and dispersed at a rotation speed of 3000 rpm for 20 minutes.

[0057] Example 16: This example differs from Example 2 in that, in step 2, the mixed solution is stirred and dispersed at a rotation speed of 4000 rpm for 40 minutes.

[0058] Example 17: This example differs from Example 2 in that the stirred and dispersed mixed solution is subjected to ultrasonic dispersion treatment at an ultrasonic frequency of 30 kHz and a dispersion speed of 4000 rpm for 10 minutes to obtain an interface-regulated wetting and oil-displacing agent.

[0059] Example 18: This example differs from Example 2 in that the stirred and dispersed mixed solution is subjected to ultrasonic dispersion treatment for 15 minutes at an ultrasonic frequency of 50 KHz and a dispersion speed of 6000 rpm to obtain an interface-regulated wetting and oil-displacing agent.

[0060] Example 19: This example differs from Example 2 in that the nano-sized titanium dioxide is modified nano-sized titanium dioxide, and the modification method is as follows:

[0061] 1) heating nano-sized titanium dioxide to 48° C. and adding it to an impregnation solution at room temperature, i.e., an impregnation solution at 25° C., stirring and mixing to obtain a base solution, and then evaporating and drying the base solution to obtain a modified initial material;

[0062] The impregnation liquid is prepared by mixing linear polysiloxane and n-hexane in a ratio of 20 g: 100 mL, wherein the mass fraction of the linear polysiloxane is 20%, specifically methyl silicone oil;

[0063] 2) The modified raw material was heated to 580° C. at a rate of 10° C. / min and then kept at this temperature for 2.5 h to obtain modified nano-scale titanium dioxide.

[0064] Example 20: This example differs from Example 19 in that the nano-sized titanium dioxide is heated to 40°C and then added to the impregnation liquid at room temperature, i.e., the impregnation liquid at 25°C, and stirred to obtain the base liquid.

[0065] Example 21: This example differs from Example 19 in that the nano-sized titanium dioxide is heated to 60°C and then added to the impregnation liquid at room temperature, i.e., the impregnation liquid at 25°C, and stirred to obtain the base liquid.

[0066] Example 22: This example differs from Example 19 in that the impregnation liquid is prepared by mixing linear polysiloxane and n-hexane in a ratio of 15 g:100 mL, and the mass fraction of the linear polysiloxane is 15%.

[0067] Example 23: This example differs from Example 19 in that the impregnation liquid is prepared by mixing linear polysiloxane and n-hexane in a ratio of 25 g:100 mL, and the mass fraction of the linear polysiloxane is 25%.

[0068] Example 24: This example differs from Example 19 in that the modified initial material is heated to 550°C at a rate of 8°C / min and then kept warm for 2 hours.

[0069] Example 25: This example differs from Example 19 in that the modified initial material is heated to 600°C at a rate of 12°C / min and then kept warm for 3 hours.

[0070] Application experiment (I):

[0071] The structures of the dihydroxymethyl sodium lauryl sulfate synthesized in Examples 1 and 5 to 12 were characterized by infrared spectroscopy and hydrogen nuclear magnetic resonance spectroscopy. After infrared spectroscopy analysis, it was found that the stretching vibration peak of -OH in the products synthesized in each example was the most obvious, and it can be inferred that the product is dihydroxymethyl sodium lauryl sulfate; at the same time, using D2O as the solvent, it can be seen from the hydrogen nuclear magnetic resonance spectrum that the presence of -OH in the product and the position of Figure 1 Where shown;

[0072] At the same time, in order to explore the synthetic effects of the above embodiments, the products synthesized in Examples 1, 5 to 12 are used as the actual addition amount of sodium dihydroxymethyl dodecyl sulfate and the preparation method of Example 2 is used to compound the interface control wetting oil displacement agent, wherein the indoor simulated low permeability oil field (permeability is (0.01 to 5) × 10 -2 μm 2 ) conditions, as shown in Table 1 below:

[0073] Table 1 Core parameters of low permeability oilfield

[0074] project Length / cm Diameter / cm <![CDATA[Permeability / (10 -3 μm 2 )]]> Porosity / % Low permeability oil fields 8.627 3.175 34.7 10.5

[0075] Then, the oil displacement effect was tested, simulating low permeability oilfield water flooding, oil displacement agent flooding, and subsequent simulated low permeability oilfield water flooding. In the initial low permeability oilfield water flooding, when the water content of the produced fluid was greater than 98%, the calculated recovery rate was 22.91%. After injecting 3.729 mL of the interface regulating wetting oil displacement agent and maintaining the constant temperature for 12 hours, the subsequent simulated low permeability oilfield water flooding was performed. When the water content of the produced fluid was greater than 98%, the recovery rates after the interface regulating wetting oil displacement agent of each embodiment were calculated.

[0076] A control was set up, which was based on Example 1, except that an equal amount of dihydroxymethyl sodium lauryl sulfate was replaced by sodium lauryl sulfate, and the other conditions remained unchanged;

[0077] The results are shown in Table 2 below:

[0078] Table 2 Recovery enhancement rate of interface-controlled wetting oil displacement agent in each embodiment

[0079] Group Recovery rate / % Improved oil recovery / % Group Recovery rate / % Improved oil recovery / % Example 1 36.12 13.21 Example 9 36.14 13.23 Example 5 36.01 13.10 Example 10 36.10 13.19 Example 6 35.58 12.67 Example 11 36.17 13.26 Example 7 35.66 12.75 Example 12 35.83 12.92 Example 8 36.21 13.30 comparison 33.54 10.63

[0080] From the results in Table 2, it can be seen that there is a significant difference between the control using sodium lauryl sulfate and the dihydroxymethyl sodium lauryl sulfate used in each embodiment. At the same time, there are some differences in the use effects of the products synthesized under different conditions. This may be due to the different synthesis purities of dihydroxymethyl sodium lauryl sulfate. The following analysis is made on this:

[0081] 1) Effect of different mixing ratios of sodium lauryl sulfate and solvent on the use effect of the product

[0082] By comparing Example 5 and Example 6 with Example 1, it can be seen that the use of different mixing ratios of sodium lauryl sulfate and solvent has a certain impact on the use effect of the synthesized product. On the basis of Example 1, reducing the addition amount of sodium lauryl sulfate reduces the lifting rate to a certain extent, while increasing the addition amount of sodium lauryl sulfate also reduces the lifting rate to a certain extent. This may be because the excessive addition amount of sodium lauryl sulfate does not fully participate in the synthesis, and the proportion of sodium lauryl sulfate contained in the same product amount increases. Therefore, the use effect of the product synthesized in Example 1 is relatively optimal.

[0083] 2) The influence of different synthesis conditions on the use effect of the product

[0084] By comparing Example 7 and Example 8 with Example 1, it can be seen that the use of different reflux temperatures and reaction times has a certain impact on the use effect of the synthesized product. On the basis of Example 1, lowering the reflux temperature and reaction time reduces the improvement rate to a certain extent, while increasing the reflux temperature and reaction time improves the improvement rate to a certain extent. However, considering the possibility of error (±0.1%), the improvement effect is not obvious. Example 8 uses a longer synthesis time, etc. Therefore, from the perspective of economy, the use effect of the product synthesized in Example 1 is relatively optimal.

[0085] 3) Effect of different ratios of sodium lauryl sulfate and formaldehyde on the use effect of the product

[0086] By comparing Example 9, Example 10 with Example 1, it can be seen that under the regulation based on the ratio relationship, taking into account the possibility of error (±0.1%), the effects of Example 9, Example 10 and Example 1 are basically the same. Therefore, under the regulation based on the above ratio relationship, adaptive adjustments can be made according to the actual addition situation; at the same time, the experiment was repeated 3 times for this purpose, and it was found that the improvement rate of Example 1 was relatively more stable, so it is more inclined to the current ratio relationship of Example 1, and its specific influencing reasons will continue to be studied later.

[0087] 4) Effect of different formaldehyde addition speeds on product performance

[0088] By comparing Example 11 and Example 12 with Example 1, it can be seen that the use effect of the synthesized product is affected to a certain extent when using different formaldehyde dropping speeds. On the basis of Example 1, reducing the dropping speed improves the lifting rate to a certain extent, but considering the possibility of error (±0.1%), the lifting effect is not obvious. Increasing the dropping speed reduces the lifting rate to a certain extent. This may be due to the relatively insufficient mixing of formaldehyde and sodium lauryl sulfate and the relatively uneven reaction. Therefore, the use effect of the product synthesized in Example 11 is relatively optimal. Considering that the effects of Example 11 and Example 1 are not much different, and the efficiency of Example 11 is lower, Example 1 is relatively optimal overall.

[0089] Application experiment (II):

[0090] Based on the above experimental method (I), the ratio and preparation method of the interface-controlled wetting and oil-displacing agent are now studied. The results are shown in Table 3 below:

[0091] Table 3 Recovery enhancement rate of interface-controlled wetting oil displacement agent in each embodiment

[0092]

[0093]

[0094] From the results in Table 3, it can be seen that there are certain differences in the use effects when using the ratio and preparation method of the interface-controlled wetting and oil-displacing agent. The following analysis is made:

[0095] 1) The effect of different interface-controlled wetting ratios on the performance of oil displacement agents

[0096] By comparing Example 2 and Example 3 with Example 1, it can be seen that the use of different interface-regulated wetting and oil-displacing agent ratios has a certain impact on the use effect of the oil-displacing agent. On the basis of Example 1, the ratio and content of each component are changed, and the improvement rate is reduced to a certain extent. Therefore, the use effect of the interface-regulated wetting and oil-displacing agent in Example 1 is relatively optimal.

[0097] 2) Effect of heating temperature of different preparation methods on the effect of oil displacement agent

[0098] By comparing Example 13 and Example 14 with Example 1, it can be seen that the use of elevated temperature for the preparation of the oil-displacing agent has a certain impact on its use effect. On the basis of Example 1, lowering or increasing the elevated temperature results in a certain degree of reduction in the improvement rate. Therefore, the preparation method of Example 2 is relatively optimal.

[0099] 3) Effect of stirring and dispersion time of different preparation methods on the effect of oil displacement agent

[0100] By comparing Example 15 and Example 16 with Example 1, it can be seen that the stirring and dispersing time of different preparation methods for preparing the oil-displacing agent has a certain impact on its use effect. On the basis of Example 1, reducing the stirring and dispersing time reduces the lifting rate to a certain extent, which may be due to the relatively insufficient mixing of the components, which affects the use effect of the oil-displacing agent. Increasing the stirring and dispersing time improves the lifting rate to a certain extent, but considering the possibility of error (±0.1%), the improvement effect is not obvious. Therefore, the preparation method of Example 2 is relatively optimal.

[0101] 4) Effects of ultrasonic dispersion treatments using different preparation methods on the effectiveness of oil displacement agents

[0102] By comparing Example 17 and Example 18 with Example 1, it can be seen that the preparation of oil-displacing agent by ultrasonic dispersion treatment using different preparation methods has a certain impact on its use effect. On the basis of Example 1, reducing the parameters of the ultrasonic dispersion treatment reduces the lifting rate to a certain extent, which may be due to the relatively insufficient mixing of the components, which affects the use effect of the oil-displacing agent. Increasing the parameters of the ultrasonic dispersion treatment improves the lifting rate to a certain extent, but considering the possibility of error (±0.1%), the improvement effect is not obvious. Therefore, the preparation method of Example 2 is relatively optimal.

[0103] Application experiment (III):

[0104] Based on the above experimental method (I), the effects of different nano-sized titanium dioxide are investigated, and the results are shown in Table 4 below:

[0105] Table 4 Recovery enhancement rate of interface-controlled wetting oil displacement agent in each embodiment

[0106] Group Recovery rate / % Improved oil recovery / % Group Recovery rate / % Improved oil recovery / % Example 1 36.12 13.21 Example 22 36.68 13.77 Example 19 36.87 13.96 Example 23 36.76 13.85 Example 20 36.58 13.67 Example 24 36.72 13.81 Example 21 36.74 13.83 Example 25 36.65 13.74

[0107] From the results in Table 4, it can be seen that the use effect of the oil displacement agent after using the modified nano-sized titanium dioxide is improved compared with the use effect of Example 1, and the following analysis is made:

[0108] 1) Effect of different nano-sized titanium dioxide mixed with the impregnation solution temperature difference on the effect of oil displacement agent

[0109] By comparing Example 20 and Example 21 with Example 1, it can be seen that the use of different nano-scale titanium dioxide and the temperature difference of the impregnation liquid has a certain impact on the use effect of the oil-displacing agent. On the basis of Example 19, increasing or decreasing this parameter, the improvement rate is reduced to a certain extent. Therefore, the use effect of the modified nano-scale titanium dioxide in Example 19 is relatively optimal.

[0110] At the same time, a control was set up. The control was based on Example 19, in which nano-scale titanium dioxide was added to the impregnation solution at room temperature without heating. The recovery rate of the oil displacement agent prepared therefrom was 36.45, that is, the improvement rate was 13.54%, which was significantly different from the improvement rate of Example 19. It can be seen that by temperature difference mixing of nano-scale titanium dioxide and the impregnation solution, nano-scale titanium dioxide will cause the added impregnation solution to produce a local instantaneous temperature rise, thereby increasing the molecular motion speed in the local area, increasing the collision frequency, and increasing the deposition rate, thereby further improving the effect of linear polysiloxane deposition on titanium dioxide, and thereby improving the use effect of the modified nano-scale titanium dioxide.

[0111] 2) Effect of different ratios of methyl silicone oil and n-hexane on the effect of oil displacement agent

[0112] By comparing Example 22 and Example 23 with Example 1, it can be seen that the use of different ratios of methyl silicone oil and n-hexane has a certain impact on the use effect of the oil-displacing agent. On the basis of Example 1, reducing or increasing the content of methyl silicone oil will reduce the improvement rate to a certain extent. Therefore, the use effect of the modified nano-titanium dioxide in Example 19 is relatively optimal.

[0113] 3) Effect of different high-temperature calcination parameters on the effect of oil displacement agent

[0114] By comparing Example 24 and Example 25 with Example 1, it can be seen that the preparation of modified nano-scale titanium dioxide using different high-temperature calcination parameters has a certain impact on its use effect. On the basis of Example 1, lowering or increasing the high-temperature calcination parameters will reduce the improvement rate to a certain extent. Therefore, the use effect of the modified nano-scale titanium dioxide in Example 19 is relatively optimal.

Claims

1. An interface-controlled wetting oil-displacing agent for improving the recovery rate of low-permeability oil fields, characterized in that: The interface regulating wetting and oil displacement agent comprises, by weight, 6 to 10 parts of sodium dihydroxymethyl dodecyl sulfate, 2 to 5 parts of polysorbate 80, 2 to 4 parts of nano-sized titanium dioxide, 1 to 2 parts of ethanol, and 100 to 120 parts of deionized water.

2. The interface-controlled wetting and oil-displacing agent for improving the recovery rate of low-permeability oil fields according to claim 1, characterized in that: The synthesis method of the dihydroxymethyl sodium lauryl sulfate is: Sodium lauryl sulfate and a solvent are mixed in a ratio of 10-15 g:100 mL to obtain a mixed system. The mixed system is heated in a water bath to a reflux temperature of 68-75° C., and then formaldehyde is slowly added dropwise to the mixed system while stirring. After reacting for 3-5 hours, the solvent is removed by rotary evaporation to obtain a white solid, which is sodium dihydroxymethyl lauryl sulfate.

3. The interface-controlled wetting and oil-displacing agent for improving the recovery rate of low-permeability oil fields according to claim 2, characterized in that: The added amount of the formaldehyde is n, and the added amount of the sodium lauryl sulfate is n[4,5], wherein n∈[2,3].

4. The interface-controlled wetting and oil-displacing agent for improving the recovery rate of low-permeability oil fields according to claim 2, wherein: Let m be the solvent volume rate coefficient and m∈ a positive integer, that is, the amount of solvent added is m[100]mL, and the solvent is methanol; the dropwise addition speed of the formaldehyde is m[1,5] drops / min, and the stirring speed is 100-180rpm.

5. The interface-controlled wetting oil-displacing agent for improving the recovery rate of low-permeability oil fields according to claim 1, characterized in that: The interface regulating wetting and oil displacement agent comprises, by weight, 8 to 9 parts of sodium dihydroxymethyl dodecyl sulfate, 3 to 4 parts of polysorbate 80, 3 to 4 parts of nano-sized titanium dioxide, 1 to 2 parts of ethanol, and 110 to 115 parts of deionized water.

6. The interface-controlled wetting oil-displacing agent for improving the recovery rate of low-permeability oil fields according to claim 1, characterized in that: The preparation method of the interface-controlled wetting and oil-displacing agent is as follows: Step 1: Add 100-120 parts of deionized water to a container, heat it to 30-40° C., then add 2-5 parts of polysorbate 80, 6-10 parts of sodium dihydroxymethyldodecyl sulfate, and 1-2 parts of ethanol in sequence, and stir until completely dissolved to obtain a mixed solution; Step 2: Add 2 to 4 parts of nano-sized titanium dioxide to the mixed solution, stir and disperse the mixed solution at a speed of 3000 to 4000 rpm for 20 to 40 minutes, and subject the stirred and dispersed mixed solution to ultrasonic dispersion treatment to obtain an interface-controlled wetting and oil-displacing agent.

7. The interface-controlled wetting oil-displacing agent for improving the recovery rate of low-permeability oil fields according to claim 6, characterized in that: 2 to 4 parts of nano-sized titanium dioxide are added to the mixed solution, and the mixed solution is stirred and dispersed at a rotation speed of 3000 to 4000 rpm for 20 to 40 minutes. The method of ultrasonically dispersing the stirred and dispersed mixed solution is as follows: ultrasonically dispersing the stirred and dispersed mixed solution at an ultrasonic frequency of 30 to 50 kHz and a dispersion speed of 4000 to 6000 rpm for 10 to 15 minutes.

8. The interface-controlled wetting oil-displacing agent for improving the recovery rate of low-permeability oil fields according to claim 6, characterized in that: The nano-scale titanium dioxide is modified nano-scale titanium dioxide, and the modification method is as follows: 1) heating nano-sized titanium dioxide to 40-60° C. and adding it to the impregnation solution at room temperature, stirring and mixing to obtain a base solution, and then evaporating and drying the base solution to obtain a modified initial material; The impregnation solution is prepared by mixing linear polysiloxane and n-hexane in a ratio of 15-25 g:100 mL, and the mass fraction of the linear polysiloxane is 15-25%. 2) The modified raw material is heated to 550-600° C. at a rate of 8-12° C. / min and then kept at this temperature for 2-3 hours to obtain modified nano-scale titanium dioxide.

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