Nano oil displacement agent for fracturing, preparation method and application thereof

Abstract

The present invention relates to the technical field of oil and gas reservoir transformation and production increase, and provides a nano oil-displacing agent for fracturing and its preparation method and application, wherein the method comprises: adding thiourea, molybdenum trioxide, and thioacetamide to deionized water in proportion and mixing, stirring until fully mixed to form a mixed solution; adding the mixed solution to a reactor with a polytetrafluoroethylene liner for reaction, and taking out the synthesized crude MoS2 mixed solution after the reaction; washing the crude MoS2 with an ethanol solution and deionized water with ultrasonic vibration respectively to obtain a pure MoS2 mixed solution; obtaining MoS2 nanosheets from the pure MoS2 mixed solution, weighing the MoS2 nanosheets and a surfactant, adding them to deionized water, and stirring fully; after the product is centrifuged and washed with deionized water, it is redispersed in deionized water to obtain a temperature-resistant and salt-resistant functional nano oil-displacing agent. The present invention can improve the imbibition oil displacement effect under high-salinity and high-temperature formation working conditions and enhance the reservoir transformation capacity.

Description

Technical Field

[0001] The present invention relates to the technical field of oil and gas reservoir transformation and production increase, and in particular to a nano oil displacement agent for fracturing, a preparation method thereof, and an application thereof. Background Art

[0002] As unconventional oil and gas exploration and development shifts from land to deep sea, offshore shale oil is becoming a major force in resource replacement and production stabilization and increase. Offshore fracturing operations are uniquely marine, and high-mineralization formation water and seawater place high demands on the stability of fracturing fluids. After traditional oil displacement agents are injected into the formation, they interact with the formation reservoir and reservoir fluids, reducing oil-water interfacial tension and improving recovery.

[0003] However, the above-mentioned traditional oil displacement agents have poor stability under high salinity and high temperature, and cannot be used in integrated imbibition and oil displacement fracturing fluids under complex formation working conditions. Summary of the Invention

[0004] The purpose of the present invention is to solve at least one technical problem in the background technology and provide a nano oil displacement agent for fracturing and a preparation method and application thereof.

[0005] To achieve the above object, the present invention provides a nano oil-displacing agent for fracturing, wherein the nano oil-displacing agent for fracturing is prepared by adding MoS2 nanosheets and a surfactant to deionized water and washing with deionized water. The molecular structure of the MoS2 nanosheets is:

[0006]

[0007] In the formula, R1 is a hydrophilic group selected from one or more of the following structures:

[0008]

[0009]

[0010] R2 is a lipophilic group with the structure:

[0011]

[0012] Among them, n=6-16.

[0013] According to one aspect of the present invention, the raw materials for preparing the MoS2 nanosheets include at least two of ammonium molybdate tetrahydrate, molybdenum trioxide, thiourea, urea, and thioacetamide.

[0014] According to one aspect of the present invention, the surfactant includes anionic surfactants, cationic surfactants, zwitterionic surfactants and nonionic surfactants;

[0015] The anionic surfactant is at least one of sodium dodecylbenzenesulfonate and sodium lauryl sulfate;

[0016] The cationic surfactant is at least one of dodecyldimethylbenzylammonium chloride and hexadecyltrimethylammonium bromide;

[0017] The zwitterionic surfactant is at least one of lauramidopropyl betaine and nonylphenol betaine;

[0018] The nonionic surfactant is at least one of lauryl alcohol polyoxyethylene ether and nonylphenol polyoxyethylene ether ammonium sulfate.

[0019] To achieve the above object, the present invention also provides a method for preparing a nano oil-displacing agent for fracturing, comprising:

[0020] Thiourea, molybdenum trioxide, and thioacetamide were added to 100 ml of deionized water in a ratio of 1:1:10, and stirred with a magnetic stirrer at 200 rpm for 2 h until the mixture was fully mixed to form a mixed solution.

[0021] The mixed solution is added into a reactor lined with polytetrafluoroethylene for reaction. After the reaction is completed and cooled, the reactor is cooled with water, and the synthesized crude MoS2 mixed solution is taken out;

[0022] The crude MoS2 mixture was poured into a centrifuge tube and ultrasonically vibrated with ethanol solution and deionized water respectively to mix the liquids thoroughly. The mixture was then centrifuged and the upper layer of liquid was skimmed off to obtain a pure MoS2 mixture.

[0023] The pure MoS2 mixed liquid is freeze-dried to form MoS2 nanosheets, and the MoS2 nanosheets and surfactant are weighed and added to deionized water, and ultrasonic treatment is performed to mix them evenly to form a MoS2 mixed liquid, and then the obtained MoS2 mixed liquid is stirred thoroughly; the product is centrifuged and washed with deionized water for multiple times, and then redispersed in the dispersion to obtain a temperature-resistant and salt-resistant functional nano oil-displacing agent.

[0024] According to one aspect of the present invention, the rotation speed of the reactor is 800 r / min, the reaction temperature is 220° C., and the reaction time is 12 h.

[0025] According to one aspect of the present invention, the rotation speed of the centrifuge is 8000-10000 r / min.

[0026] According to one aspect of the present invention, the crude MoS2 mixed solution is poured into a centrifuge tube and ultrasonically shaken three times with an ethanol solution and deionized water respectively.

[0027] According to one aspect of the present invention, the dispersion liquid is isopropyl alcohol or deionized water.

[0028] According to one aspect of the present invention, the concentration of the dispersion is 0.01 wt%.

[0029] According to one aspect of the present invention, the concentration of the surfactant is 0.1-0.3 wt%.

[0030] According to one aspect of the present invention, the surfactant is at least one of dodecyl mercaptan, sodium dodecylbenzene sulfonate, nonylphenol polyoxyethylene ether ammonium sulfate, and nonylphenol betaine.

[0031] To achieve the above object, the present invention also provides a use of the above nano oil-displacing agent for fracturing in oil and gas reservoir reconstruction and production increase.

[0032] According to the solution of the present invention, the heat-resistant and salt-resistant functionalized nano oil-displacing agent of the present invention is a nano oil-displacing agent obtained through a new synthesis method. The oil-displacing agent has good salt resistance and temperature resistance, can improve the imbibition oil displacement effect under high-mineralization and high-temperature formation working conditions, and enhance the reservoir transformation capacity.

[0033] The particle size of the MoS2 nanosheets synthesized by the present invention is 10-20nm, which is significantly smaller than the particle size of conventional MoS2 nanoflowers and has more stable dispersion performance.

[0034] The preparation method of the nano oil-displacing agent of the present invention is simple, easy to operate, and easy to control. The product type (powder or liquid) can be customized according to on-site requirements.

[0035] The nano oil-displacing agent of the present invention can be used for fracturing construction, reservoir transformation, and imbibition oil displacement under high salinity and seawater working conditions. It can solve the problem of integrated fracturing and recovery of unconventional oil and gas and prevent the problem of weakening of the effect of the oil-displacing agent under complex working conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 Schematic representation of a scanning electron micrograph of molybdenum disulfide nanosheets synthesized using thiourea, molybdenum trioxide, and thioacetamide in Example 1;

[0037] Figure 2 Schematic representation of a scanning electron microscope image of molybdenum disulfide nanosheets synthesized using thiourea and ammonium molybdate tetrahydrate in Example 3. Specific embodiments

[0038] The present invention will now be discussed with reference to exemplary embodiments. It should be understood that the embodiments discussed are only intended to enable those skilled in the art to better understand and implement the present invention, rather than to imply any limitation on the scope of the present invention.

[0039] As used herein, the term "including" and variations thereof are to be interpreted as open-ended terms meaning "including, but not limited to." The term "based on" is to be interpreted as "based, at least in part, on." The terms "one embodiment" and "an embodiment" are to be interpreted as "at least one embodiment."

[0040] Example 1

[0041] 1) Thiourea, molybdenum trioxide, and thioacetamide were added to 100 ml of deionized water in a ratio of 1:1:10, and stirred with a magnetic stirrer at 200 rpm for 2 h until fully mixed to form a mixed solution;

[0042] 2) adding the above mixed solution into a high-temperature and high-pressure reactor with a polytetrafluoroethylene liner, reacting at a speed of 800 r / min and a temperature of 220° C. for 12 h, cooling the reactor with water, and taking out the synthesized MoS2 mixed solution (crude MoS2 mixed solution);

[0043] 3) The prepared MoS2 mixed solution was poured into a centrifuge tube and ultrasonically washed with ethanol solution and deionized water respectively to mix the liquids thoroughly. The mixture was centrifuged at a certain speed and the upper layer of liquid was skimmed off. The mixture was washed repeatedly for 6 times until the upper layer of liquid was clear to obtain a clean MoS2 mixed solution (pure MoS2 mixed solution).

[0044] 4) The washed MoS2 mixed solution is freeze-dried to form MoS2 nanosheets, such as Figure 1 As shown, MoS2 nanosheets and a surfactant of a 1,3-dialkyl glycerol ether derivative are weighed and added to deionized water, ultrasonically treated and mixed evenly to form a MoS2 mixed solution, and then the obtained MoS2 mixed solution is fully stirred; the product is centrifuged and washed with deionized water for multiple times, and then redispersed in deionized water to finally obtain a temperature-resistant and salt-resistant functionalized nano oil-displacing agent.

[0045] Example 2

[0046] 1) Thiourea, molybdenum trioxide, and thioacetamide were added to 100 ml of deionized water in a ratio of 1:1:15, and stirred with a magnetic stirrer at 200 rpm for 2 h until fully mixed to form a mixed solution;

[0047] 2) adding the above mixed solution into a high-temperature and high-pressure reactor with a polytetrafluoroethylene liner, reacting at a speed of 800 r / min and a temperature of 220° C. for 12 h. After cooling, the reactor was water-cooled and the synthesized MoS2 mixed solution was taken out;

[0048] 3) Pour the prepared MoS2 mixed solution into a centrifuge tube and wash it with ethanol solution and deionized water respectively by ultrasonic vibration to mix the liquids thoroughly, and centrifuge it at a certain speed to skim off the upper liquid, and repeat the washing 6 times until the upper liquid is clear to obtain a clean MoS2 mixed solution;

[0049] 4) The washed MoS2 mixed solution is freeze-dried to form MoS2 nanosheets, and the MoS2 nanosheets and nonylphenol polyoxyethylene ether ammonium sulfate are weighed and added to deionized water, and ultrasonically mixed to form a MoS2 mixed solution, and then the obtained MoS2 mixed solution is fully stirred; the product is centrifuged and washed with deionized water for multiple times, and then redispersed in deionized water to finally obtain a temperature-resistant and salt-resistant functionalized nano oil-displacing agent.

[0050] Example 3

[0051] 1) Thiourea and ammonium molybdate tetrahydrate were added to 100 ml of deionized water in a ratio of 2:1, and stirred with a magnetic stirrer at 200 rpm for 2 h until fully mixed to form a mixed solution;

[0052] 2) adding the above mixed solution into a high-temperature and high-pressure reactor with a polytetrafluoroethylene liner, reacting at a speed of 800 r / min and a temperature of 220° C. for 12 h. After cooling, the reactor was water-cooled and the synthesized MoS2 mixed solution was taken out;

[0053] 3) Pour the prepared MoS2 mixed solution into a centrifuge tube and wash it with ethanol solution and deionized water respectively by ultrasonic vibration to mix the liquids thoroughly, and centrifuge it at a certain speed to skim off the upper liquid, and repeat the washing 6 times until the upper liquid is clear to obtain a clean MoS2 mixed solution;

[0054] 4) The washed MoS2 mixed solution is freeze-dried to form MoS2 nanosheets, such as Figure 2 As shown, MoS2 nanosheets and a surfactant of a 1,3-dialkyl glycerol ether derivative are weighed into deionized water, ultrasonically treated and mixed evenly to form a MoS2 mixed solution, and then the obtained MoS2 mixed solution is fully stirred; the product is centrifuged and washed with deionized water for multiple times, and then redispersed in deionized water to finally obtain a temperature-resistant and salt-resistant functionalized nano oil-displacing agent.

[0055] Example 4

[0056] 1) Thiourea, molybdenum trioxide, and thioacetamide were added to 100 ml of deionized water in a ratio of 1:1:10, and stirred with a magnetic stirrer at 200 rpm for 2 h until fully mixed to form a mixed solution;

[0057] 2) adding the above mixed solution into a high-temperature and high-pressure reactor with a polytetrafluoroethylene liner, reacting at a speed of 800 r / min and a temperature of 220° C. for 12 h. After cooling, the reactor was water-cooled and the synthesized MoS2 mixed solution was taken out;

[0058] 3) Pour the prepared MoS2 mixed solution into a centrifuge tube and wash it with ethanol solution and deionized water respectively by ultrasonic vibration to mix the liquids thoroughly, and centrifuge it at a certain speed to skim off the upper liquid, and repeat the washing 6 times until the upper liquid is clear to obtain a clean MoS2 mixed solution;

[0059] 4) The cleaned MoS2 mixed solution is freeze-dried to form MoS2 nanosheets, and MoS2 nanosheets (0.01 wt%) and a surfactant of a 1,3-dialkyl glycerol ether derivative (0.1 wt%) are weighed and added to deionized water, and ultrasonically treated and mixed to form a MoS2 mixed solution, and then the obtained MoS2 mixed solution is fully stirred; the product is centrifuged and washed with deionized water for multiple times, and then redispersed in deionized water to finally obtain a temperature-resistant and salt-resistant functionalized nano oil-displacing agent.

[0060] Example 5

[0061] 1) Thiourea, molybdenum trioxide, and thioacetamide were added to 100 ml of deionized water in a ratio of 1:1:10, and stirred with a magnetic stirrer at 200 rpm for 2 h until fully mixed to form a mixed solution;

[0062] 2) adding the above mixed solution into a high-temperature and high-pressure reactor with a polytetrafluoroethylene liner, reacting at a speed of 800 r / min and a temperature of 220° C. for 12 h. After cooling, the reactor was water-cooled and the synthesized MoS2 mixed solution was taken out;

[0063] 3) Pour the prepared MoS2 mixed solution into a centrifuge tube and wash it with ethanol solution and deionized water respectively by ultrasonic vibration to mix the liquids thoroughly, and centrifuge it at a certain speed to skim off the upper liquid, and repeat the washing 6 times until the upper liquid is clear to obtain a clean MoS2 mixed solution;

[0064] 4) The washed MoS2 mixed solution is freeze-dried to form MoS2 nanosheets, and MoS2 nanosheets (0.01 wt%) and a surfactant of a 1,3-dialkyl glycerol ether derivative (0.2 wt%) are weighed and added to deionized water, and ultrasonically treated and mixed to form a MoS2 mixed solution, and then the obtained MoS2 mixed solution is fully stirred; the product is centrifuged and washed with deionized water for multiple times, and then redispersed in deionized water to finally obtain a temperature-resistant and salt-resistant functionalized nano oil-displacing agent.

[0065] Example 6

[0066] 1) Thiourea, molybdenum trioxide, and thioacetamide were added to 100 ml of deionized water in a ratio of 1:1:10, and stirred with a magnetic stirrer at 200 rpm for 2 h until fully mixed to form a mixed solution;

[0067] 2) adding the above mixed solution into a high-temperature and high-pressure reactor with a polytetrafluoroethylene liner, reacting at a speed of 800 r / min and a temperature of 220° C. for 12 h. After cooling, the reactor was water-cooled and the synthesized MoS2 mixed solution was taken out;

[0068] 3) Pour the prepared MoS2 mixed solution into a centrifuge tube and wash it with ethanol solution and deionized water respectively by ultrasonic vibration to mix the liquids thoroughly, and centrifuge it at a certain speed to skim off the upper liquid, and repeat the washing 6 times until the upper liquid is clear to obtain a clean MoS2 mixed solution;

[0069] 4) The washed MoS2 mixed solution is freeze-dried to form MoS2 nanosheets, and MoS2 nanosheets (0.01 wt%) and a surfactant of a 1,3-dialkyl glycerol ether derivative (0.3 wt%) are weighed and added to deionized water, and ultrasonically treated and mixed to form a MoS2 mixed solution, and then the obtained MoS2 mixed solution is fully stirred; the product is centrifuged and washed with deionized water for multiple times, and then redispersed in deionized water to finally obtain a temperature-resistant and salt-resistant functionalized nano oil-displacing agent.

[0070] Test Example 1

[0071] 1) The temperature-resistant and salt-resistant functionalized nanosheets obtained in Examples 1 to 6 were subjected to particle size testing;

[0072] 2) The test method is as follows: deionized water is used to prepare a functionalized nanosheet dispersion at a concentration of 0.01 wt%, ultrasonic dispersion is performed using an ultrasonic multifunctional testing machine, and particle size is measured using a Delsa Nano particle size analyzer. The test results are shown in Table 1:

[0073] 3) Table 1

[0074]

[0075]

[0076] 4) Analysis of results: As shown in Table 1, the particle size of the synthesized functionalized nanosheets is all in the range of 15-70 nm. The particle size of the nanosheets obtained in Example 3 is relatively large, while the particle size of the nanosheets obtained in Examples 1, 2, 4, 5, and 6 is relatively small, smaller than the pore size of the core, and can enter the tiny pores of the core, interact with the crude oil, and drive out a large amount of residual oil in the reservoir, thereby improving the crude oil recovery rate.

[0077] Test Example 2

[0078] 1) performing an interfacial tension test on the heat-resistant and salt-resistant functionalized nano oil-displacing agents obtained in Examples 1 to 6;

[0079] 2) The test method is as follows: functionalized nano oil displacement agent is prepared using seawater at a concentration of 0.2 wt%, ultrasonic dispersion is performed using an ultrasonic multifunctional testing machine, and interfacial tension is tested using a TX500C rotating drop interfacial tension meter. The circulating water bath system is turned on, the test temperature in the experiment is set to the corresponding temperature in the formation, the rotation speed is adjusted to 6000 r / min, the oil sample is crude oil, and the instrument is started to perform interfacial tension testing. The test results are shown in Table 2:

[0080] 3) Table 2

[0081]

[0082]

[0083] 4) Result analysis: As shown in Table 2, the functionalized nano oil-displacing agent has good salt tolerance. When the salinity of seawater increases from 20,000 mg / L to 30,000 mg / L, the functionalized nanosheets do not precipitate, have good stability, and have excellent salt tolerance. The functionalized nanosheet oil-displacing agents have good interfacial activity. The interfacial tension of Examples 1, 2, and 3 can reach 10 -3 mN / m. In Examples 4, 5, and 6, the nano oil-displacing agents modified with surfactants of 1,3-dialkyl glycerol ether derivatives can reduce the interfacial tension to an ultra-low level as the proportion of the surfactant gradually increases, and have good universality.

[0084] Test Example 3

[0085] 1) The heat-resistant and salt-resistant functionalized nano oil-displacing agents obtained in Examples 1 to 6 were subjected to an imbibition oil displacement test;

[0086] 2) The test method is as follows: the physical properties of a sandstone core column from a certain place are measured, dried in an electric constant temperature drying oven at 80°C for 7 days, and then vacuum saturated with oil at a saturated oil temperature of 120°C and a saturated oil pressure of 20Mpa. After saturation, the core is weighed and the saturated oil mass is calculated. The saturated oil core is placed in a filtration bottle filled with a heat-resistant and salt-resistant functionalized nano-oil-displacing agent prepared with seawater. The water bath temperature is 80°C. In order to facilitate reading and reduce errors, the oil-displacing agent is filled to the 0.2ml scale line of the filtration bottle. The filtration displacement is continued for 7 days until no oil is produced. The oil displacement efficiency is calculated. The test results are shown in Table 3:

[0087] 3) Table 3

[0088]

[0089]

[0090] 4) Analysis of results: As can be seen from Table 3, the oil displacement efficiency of the functionalized nano-displacement agent with the synthetic configuration is significantly improved compared with the imbibition displacement efficiency under formation water conditions. The particle size of the nanosheets synthesized in Examples 1-6 is 10-70 nm, and the interfacial tension of Examples 4-6 can reach ultra-low. The nano-displacement agent can penetrate into the tiny pores of the sandstone core, greatly improving the crude oil recovery rate. The oil displacement efficiency can reach 40%-60%, and as the surface tension drops to ultra-low, the oil displacement efficiency is further improved. It can be seen that the interfacial activity is good and the crude oil is easily deformed, which proves that it has good stability under high salinity and high temperature.

[0091] The above experimental results show that the functionalized nano oil displacement agent synthesized by introducing heat-resistant and salt-resistant functional groups has good heat and salt resistance, can meet the requirements of imbibition oil displacement performance under high mineralization, seawater and high temperature, and has broad application prospects.

[0092] According to the above scheme of the present invention, the heat-resistant and salt-resistant functionalized nano oil-displacing agent of the present invention is a nano oil-displacing agent obtained by a new synthesis method. The oil-displacing agent has good salt resistance and temperature resistance, can improve the imbibition oil displacement effect under high mineralization and high temperature formation working conditions, and enhance the reservoir transformation capacity.

[0093] The particle size of the MoS2 nanosheets synthesized by the present invention is 10-20nm, which is significantly smaller than the particle size of conventional MoS2 nanoflowers and has more stable dispersion performance.

[0094] The preparation method of the nano oil-displacing agent of the present invention is simple, easy to operate, and easy to control. The product type (powder or liquid) can be customized according to on-site requirements.

[0095] The nano oil-displacing agent of the present invention can be used for fracturing construction, reservoir transformation, and imbibition oil displacement under high salinity and seawater working conditions. It can solve the problem of integrated fracturing and recovery of unconventional oil and gas and prevent the problem of weakening of the effect of the oil-displacing agent under complex working conditions.

[0096] Finally, it should be noted that the above embodiments are only preferred embodiments, which are only used to illustrate the technical solutions of the present invention and are not limiting. Although the present invention has been described in detail through the above preferred embodiments, those skilled in the art should understand that various changes can be made in form and details without departing from the scope defined by the claims of the present invention.

Claims

1. A nano oil displacement agent for fracturing, characterized in that: The nano oil displacement agent for fracturing is prepared by adding MoS2 nanosheets and a surfactant to deionized water and washing with deionized water; The raw materials for preparing the MoS2 nanosheets include molybdenum trioxide, thiourea and thioacetamide; The surfactant is a nonionic surfactant; The nonionic surfactant is nonylphenol polyoxyethylene ether ammonium sulfate.

2. A method for preparing a nano oil displacement agent for fracturing, characterized in that: include: Thiourea, molybdenum trioxide, and thioacetamide were added to 100 ml of deionized water in a ratio of 1:1:10, and stirred with a magnetic stirrer at 200 r / min for 2 h until the mixture was fully mixed to form a mixed solution. The mixed solution is added into a reactor lined with polytetrafluoroethylene for reaction. After the reaction is completed and cooled, the reactor is cooled with water, and the synthesized crude MoS2 mixed solution is taken out; The crude MoS2 mixture was poured into a centrifuge tube and ultrasonically vibrated with ethanol solution and deionized water respectively to mix the liquids thoroughly. The mixture was then centrifuged and the upper layer of liquid was skimmed off to obtain a pure MoS2 mixture. The pure MoS2 mixed liquid is freeze-dried to form MoS2 nanosheets, and the MoS2 nanosheets and a surfactant are weighed and added to deionized water, and ultrasonically mixed to form a MoS2 mixed liquid, and then the obtained MoS2 mixed liquid is fully stirred; the product is centrifuged and washed multiple times with deionized water, and then redispersed in the dispersion to obtain a temperature-resistant and salt-resistant functional nano oil-displacing agent; The surfactant is nonylphenol polyoxyethylene ether ammonium sulfate.

3. The method for preparing a nano oil-displacing agent for fracturing according to claim 2, wherein: The rotation speed of the reactor is 800 r / min, the reaction temperature is 220° C., and the reaction time is 12 h.

4. The method for preparing a nano oil-displacing agent for fracturing according to claim 2, wherein: The rotation speed of the centrifuge is 8000-10000 r / min.

5. The method for preparing a nano oil-displacing agent for fracturing according to claim 2, wherein: The crude MoS2 mixture was poured into a centrifuge tube and ultrasonically shaken three times with ethanol solution and deionized water respectively.

6. The method for preparing a nano oil-displacing agent for fracturing according to claim 2, wherein: The dispersion liquid is isopropyl alcohol or deionized water.

7. The method for preparing a nano oil-displacing agent for fracturing according to claim 2, wherein: The concentration of the MoS2 dispersion is 0.01-0.3 wt%.

8. The method for preparing a nano oil-displacing agent for fracturing according to claim 2, wherein: The surfactant concentration is 0.1-0.3 wt %.

9. Use of the nano oil-displacing agent for fracturing according to claim 1 in oil and gas reservoir reconstruction and production increase.

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