Carbon nanoparticle-based heavy oil viscosity reducer as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of thick oil viscosity reduction in oil exploitation, and particularly relates to a carbon nanoparticle-based thick oil viscosity reducer as well as a preparation method and application thereof. The preparation method of the carbon nanoparticle-based heavy oil viscosity reducer comprises the following steps: (1) adding a H2O2 solution into carbon nanoparticles CNPs, carrying out ultrasonic treatment to uniformly disperse the nanoparticles, carrying out centrifugal separation after oxidation reaction, and washing and drying a solid to prepare nanoparticles CNPs-OH; and (2) adding the nanoparticles CNPs-OH into an aqueous solution of a cationic surfactant, uniformly mixing, carrying out ultrasonic treatment at 60-70 DEG C, and finally drying to obtain the carbon nanoparticle-based heavy oil viscosity reducer. The carbon nanoparticles are oxidized through hydrogen peroxide, the surface potential of the carbon nanoparticles is changed into a negative value, the cationic surface active agent with positive charges and the oxidized carbon nanoparticles are blended, the carbon nanoparticle-based thick oil viscosity reducer is prepared through electrostatic interaction and has an excellent viscosity reduction effect, and the highest viscosity reduction rate can reach 70% or above.

Description

Technical Field

[0001] This invention belongs to the field of heavy oil viscosity reduction technology in petroleum extraction, specifically relating to a carbon nanoparticle-based heavy oil viscosity reducer, its preparation method and application. Functionalized carbon nanoparticles are prepared as heavy oil viscosity reducers through electrostatic interactions between carbon nanoparticles and surfactants based on the positive and negative charges. Background Technology

[0002] Heavy oil, as an important component of petroleum resources, presents numerous challenges to its extraction, transportation, and processing due to its high viscosity. Currently, the main methods for reducing the viscosity of heavy oil fall into four categories: heating methods, physical methods, microbiological methods, and chemical reagent methods. However, the first three methods consume a lot of energy and are costly, limiting the extraction of heavy oil. Chemical reagent viscosity reduction injection is a promising technology due to its simplicity and high maturity. Common chemical viscosity reducers include oil-soluble, water-soluble, and nanoparticle viscosity reducers. Oil-soluble viscosity reducers, with their large molecular weight, cannot effectively penetrate reservoirs and asphaltene aggregates. Water-soluble viscosity reducers suffer from poor thermal stability, are prone to foaming, and are not salt-resistant, limiting their application.

[0003] Nanoparticles, due to their small size, high specific surface area, and ease of surface functional group modification, have become an ideal system for developing viscosity reducers. Nanoparticle-based viscosity reducers for heavy oil have been reported in the literature, including SiO2, Fe3O4, Fe2O3, Al2O3, NiO, CuO, ZnO, and carbon nanotubes. However, the preparation of these nanoparticles is difficult, generally requiring covalent modification, which involves complex processes and high costs, limiting their industrial application in the field of heavy oil viscosity reduction. Furthermore, non-carbon-based nanoparticles can introduce other atoms into the heavy oil system, causing contamination.

[0004] Therefore, there is an urgent need in this field to develop a cost-effective and easily industrialized nanoparticle as a matrix for heavy oil viscosity reducers. Summary of the Invention

[0005] Based on the aforementioned shortcomings and deficiencies in the prior art, one of the objectives of this invention is to at least solve one or more of the aforementioned problems in the prior art. In other words, one of the objectives of this invention is to provide a carbon nanoparticle-based heavy oil viscosity reducer that meets one or more of the aforementioned requirements, as well as its preparation method and application.

[0006] To achieve the above-mentioned objectives, the present invention adopts the following technical solution: A method for preparing a carbon nanoparticle-based thick oil viscosity reducer includes the following steps: (1) Add H2O2 solution to carbon nanoparticles CNPs, sonicate to disperse the nanoparticles evenly, centrifuge after oxidation reaction, wash and dry the solid to obtain nanoparticles CNPs-OH; (2) Add nanoparticles CNPs-OH to an aqueous solution of cationic surfactant, mix evenly, sonicate at 60-70℃, and finally dry to obtain carbon nanoparticle-based thick oil viscosity reducer.

[0007] As a preferred embodiment, in step (1), the mass fraction of the H2O2 solution is 20-40%.

[0008] As a preferred embodiment, in step (1), the duration of ultrasonic treatment is 20 to 40 minutes.

[0009] As a preferred embodiment, in step (1), the oxidation reaction temperature is 100-110°C and the duration is 4-6 hours.

[0010] As a preferred embodiment, in step (2), the cationic surfactant is at least one of hexadecyltrimethylammonium bromide (CTAB) and octadecyltrimethylammonium bromide (STAB).

[0011] As a preferred embodiment, in step (2), the solid-liquid ratio of the cationic surfactant to water in the aqueous solution of the cationic surfactant is (0.01~0.25) g: 25 mL; The cationic surfactant is 5 to 50 wt% of the weight of the CNPs-OH nanoparticles.

[0012] As a preferred option, in step (2), the duration of ultrasound is 30 to 90 minutes.

[0013] The present invention also provides a carbon nanoparticle-based heavy oil viscosity reducer prepared by the preparation method described in any of the preceding embodiments.

[0014] The present invention also provides the application of the carbon nanoparticle-based heavy oil viscosity reducer as described above. After the heavy oil is preheated, a toluene solution of the carbon nanoparticle-based heavy oil viscosity reducer is added to it and mixed evenly.

[0015] As a preferred embodiment, the preheating temperature of the heavy oil is 50-70°C, and the time is 1-3 hours; The ratio of carbon nanoparticle-based thick oil viscosity reducer to thick oil is (1-3) mg: 10 mL, and the amount of toluene added is 0.5-1.5 vol of thick oil.

[0016] Compared with the prior art, the beneficial effects of this invention are: (1) The carbon nanoparticles of the present invention are commercial products. They are oxidized by only a mild oxidant, hydrogen peroxide. The process is green and pollution-free, and the oxidation process is simple and suitable for industrial production. (2) The carbon nanoparticle-based thick oil viscosity reducer of the present invention is easy to prepare. It is prepared by oxidizing carbon nanoparticles to make their surface negatively charged, and then mixing them with the positively charged cationic surfactant through electrostatic interaction. It is prepared in one pot without complicated chemical reactions, which simplifies the process and reduces costs. (3) The carbon nanoparticle-based heavy oil viscosity reducer of the present invention can reduce the viscosity of heavy oil by more than 76%, which exceeds that of conventional surfactant systems; (4) Compared with other non-carbon nanoparticle systems, the carbon nanoparticle-based heavy oil viscosity reducer of the present invention does not introduce other metal elements, does not pollute the heavy oil system, and does not require subsequent treatment. Attached Figure Description

[0017] Figure 1 Comparison of Fourier transform infrared spectra of the modified CNPs; Figure 2 The change in zeta potential when oxidized carbon nanoparticles are blended with different amounts of surfactant; Figure 3 A comparison of the contact angle changes when oxidized carbon nanoparticles are blended with different amounts of surfactant; Figure 4 SEM images of carbon nanoparticles before modification, after oxidation, and after blending. Figure 5 Comparative photos of the dispersion effect of carbon nanoparticle-based thick oil viscosity reducers in different solvents; Figure 6 The graph shows the relationship between the addition of CNPs-CTAB / 5% and the viscosity-reducing effect on heavy oil. Figure 7 The graph shows the relationship between the addition of CNPs-CTAB / 20% and the viscosity-reducing effect on heavy oil. Figure 8 The graph shows the relationship between the addition of CNPs-CTAB / 50% and the viscosity-reducing effect on heavy oil. Figure 9 The graph shows the relationship between the addition of CNPs-STAB / 5% and the viscosity-reducing effect on heavy oil. Figure 10 The graph shows the relationship between the addition of CNPs-STAB / 20% and the viscosity-reducing effect on heavy oil. Figure 11 The graph shows the relationship between the addition of CNPs-STAB / 50% and the viscosity-reducing effect on heavy oil. Figure 12 A bar chart comparing the viscosity reduction rates of unmodified carbon nanoparticles (CNPs), oxidized carbon nanoparticles (CNPs-OH), octadecyltrimethylammonium bromide (STAB), and carbon nanoparticle-based heavy oil viscosity reducer CNPs-20% STAB. Detailed Implementation

[0018] The carbon nanoparticle-based heavy oil viscosity reducer of the present invention, its preparation method and application are described in detail below.

[0019] This invention provides a method for preparing functionalized nanoparticle viscosity reducers using commercially available and inexpensive carbon nanoparticles with a size of less than 100 nm as raw materials. First, the commercially available carbon nanoparticles are oxidized with hydrogen peroxide, an environmentally friendly oxidant, to give the nanoparticles a negative surface charge. Then, a cationic surfactant is added to allow the two to combine through electrostatic interactions, forming functionalized carbon nanoparticles with alkyl chains on their surface. When these nanoparticles are added to toluene in heavy oil, the viscosity of the system can be reduced by up to 70% or more.

[0020] Specifically, the preparation method of the carbon nanoparticle-based heavy oil viscosity reducer of the present invention includes the following steps: (1) Add H2O2 solution to carbon nanoparticles CNPs, sonicate to disperse the nanoparticles evenly, centrifuge after oxidation reaction, wash the solid with deionized water and dry to obtain nanoparticles CNPs-OH. (2) Add nanoparticles CNPs-OH to an aqueous solution of cationic surfactant, mix evenly, sonicate at a high temperature of 60-70℃, and finally dry in an oven to obtain carbon nanoparticle-based thick oil viscosity reducer.

[0021] In step (1) above, the mass fraction of the H2O2 solution is 20-40%, and the specific mass fraction can be selected according to the actual application requirements.

[0022] In step (1) above, the duration of ultrasonic treatment is 20 to 40 minutes to ensure that hydrogen peroxide and carbon nanoparticles are fully mixed. The specific duration can be determined according to the actual application requirements.

[0023] In step (1) above, the oxidation reaction temperature is 100-110℃ and the duration is 4-6 hours to ensure full oxidation; the specific oxidation reaction temperature and duration can be determined according to actual application requirements.

[0024] In step (2) above, the cationic surfactant is at least one of hexadecyltrimethylammonium bromide (CTAB) and octadecyltrimethylammonium bromide (STAB). The specific type of cationic surfactant can be determined according to the actual application requirements.

[0025] In step (2) above, the solid-liquid ratio of the cationic surfactant to water in the aqueous solution of the cationic surfactant is (0.01~0.25) g: 25 mL; The cationic surfactant is 5–50 wt% of the weight of the CNPs-OH nanoparticles. The specific ratio can be determined based on actual application needs.

[0026] In step (2) above, the duration of ultrasound is 30 to 90 minutes, and the specific duration can be determined according to the actual application requirements.

[0027] This invention provides a carbon nanoparticle-based thick oil viscosity reducer prepared by the above preparation method.

[0028] This invention also provides the application of the above-mentioned carbon nanoparticle-based heavy oil viscosity reducer, used to reduce heavy oil viscosity, reduce surface / interfacial tension, and improve heavy oil reservoir recovery. The specific operation process is as follows: after preheating the heavy oil, a toluene solution of the carbon nanoparticle-based heavy oil viscosity reducer is added and mixed thoroughly.

[0029] The preheating temperature of the above-mentioned heavy oil is 50-70℃, and the time is 1-3 hours; the specific preheating temperature and time can be determined according to the actual application requirements. The ratio of the carbon nanoparticle-based heavy oil viscosity reducer to the heavy oil is (1-3) mg: 10 mL, and the amount of toluene added is 0.5-1.5 vol of the heavy oil.

[0030] The carbon nanoparticle-based heavy oil viscosity reducer of the present invention, its preparation method, and its application are further explained and illustrated below through specific embodiments.

[0031] Example 1: The preparation method of the carbon nanoparticle-based heavy oil viscosity reducer in this embodiment includes the following steps: (1) Weigh 10 g of carbon nanoparticles with an average particle size of 30-50 nm, add 200 mL of H2O2 solution (30 wt%), sonicate for 30 minutes, stir and reflux for 5 hours in an oil bath at 105℃, cool naturally, transfer to a centrifuge tube, centrifuge at 8000 rpm for 10 min, collect the solid, wash with deionized water, repeat 5 times, place the obtained solid in a vacuum oven at 60℃ to dry, and obtain nanoparticles CNPs-OH; (2) Using 0.5 g CNPs-OH as a reference, weigh 0.025 g, 0.05 g, 0.075 g, 0.100 g, 0.150 g, and 0.250 g of cetyltrimethylammonium bromide (CTAB) powder respectively, add 25 mL of deionized water, and prepare a series of surfactant aqueous solutions with mass concentration gradients of 5%, 10%, 15%, 20%, 30%, and 50%; the operation of the STAB system is the same, and will not be repeated here. (3) After mixing 0.5 g of nanoparticles CNPs-OH with aqueous solutions of surfactants of different mass concentrations, the mixture was sonicated at 65℃ for 1 h and then dried in an oven at 60℃ to obtain different carbon nanoparticle-based heavy oil viscosity reducers CNPs-5%CTAB, CNPs-10%CTAB, CNPs-15%CTAB, CNPs-20%CTAB, CNPs-30%CTAB, CNPs-50%CTAB and carbon nanoparticle-based heavy oil viscosity reducers CNPs-5%STAB, CNPs-10%STAB, CNPs-15%STAB, CNPs-20%STAB, CNPs-30%STAB, CNPs-50%STAB.

[0032] Figure 1 The image shows a comparison of the Fourier transform infrared spectra of CNPs before and after modification. Figure 2 The change in Zeta potential is shown when oxidized carbon nanoparticles are blended with different amounts of surfactant. Figure 3 The change in contact angle when oxidized carbon nanoparticles are blended with different amounts of surfactant. Figure 4 The images show SEM images of carbon nanoparticles before modification, after oxidation, and after blending. The results indicate that the oxidized carbon nanoparticles in Example 1 interacted with the surfactant to form functionalized carbon nanoparticles with different surface energies, and their morphology did not change significantly.

[0033] Example 2: Application of carbon nanoparticle-based heavy oil viscosity reducer in heavy oil viscosity reduction; (a) The dispersibility of carbon nanoparticle-based heavy oil viscosity reducers in different solvents was tested using deionized water and toluene as solvents; Weigh an equal amount of sample powder into a sample tube, ultrasonically disperse for 30 min, and let stand at room temperature; (b) The heavy oil was preheated in an oven at 60°C for 2 hours; 0.01 g of carbon nanoparticle-based heavy oil viscosity reducer and 500 μL of toluene were ultrasonically dispersed to form a nanofluid, which was then injected into 50 mL of preheated, flowable heavy oil and mixed evenly; the viscosity of the heavy oil was tested at 80°C.

[0034] Figure 5 To compare the dispersion effects of the carbon nanoparticle-based heavy oil viscosity reducers of the present invention in different solvents, each carbon nanoparticle-based heavy oil viscosity reducer, CNPs-CTAB, rapidly separated into layers after standing in aqueous solution, while remaining stably dispersed in toluene. Therefore, toluene was used as the dispersion system for heavy oil viscosity reduction.

[0035] Figure 6 , Figure 7 and Figure 8The viscosity-reducing effects of carbon nanoparticle-based heavy oil viscosity reducers CNPs-5%CTAB, CNPs-20%CTAB, and CNPs-50%CTAB as a function of viscosity reducer content were compared. Figure 9 , Figure 10 and Figure 11 The viscosity-reducing effects of carbon nanoparticle-based heavy oil viscosity reducers CNPs-5% STAB, CNPs-20% STAB, and CNPs-50% STAB were compared with the viscosity reducer content. The results indicate that the ratio of cationic surfactant to carbon oxide nanoparticles and the addition amount of CNPs-CTAB / CNPs-STAB both significantly affect the viscosity-reducing effect. For the CNPs-CTAB system, when the CTAB content is 5 wt% of carbon oxide nanoparticles and the CNPs-CTAB content in heavy oil is 2%, the viscosity-reducing effect is better, approximately 62%. For the CNPs-STAB system, when the STAB content is 20% of carbon oxide nanoparticles and the CNPs-CTAB content in heavy oil is 2%, the viscosity-reducing effect is better, approximately 72%.

[0036] Using carbon nanoparticle-based heavy oil viscosity reducer CNPs-20% STAB as a benchmark, a comparison was made with unmodified carbon nanoparticle CNPs, oxidized carbon nanoparticle CNPs-OH, and octadecyltrimethylammonium bromide STAB (maintaining the same amount of STAB as in CNPs-20% STAB in Example 1). The results show that... Figure 12 As shown, unmodified carbon nanoparticles (CNPs), oxidized carbon nanoparticles (CNPs-OH), octadecyltrimethylammonium bromide (STAB), and carbon nanoparticle-based heavy oil viscosity reducer CNPs-20% are present. The viscosity reduction rates of STAB were 32%, 21%, 43%, and 72%, respectively. These data show that the viscosity reduction effect of nanoparticles functionalized based on electrostatic interactions is significantly improved. The surface of CNPs mainly consists of hydrophobic benzene rings, which have strong π-π interactions with asphaltenes, making the interaction strong and preventing asphaltenes clusters in heavy oil from disaggregating, resulting in a poor viscosity reduction effect. The CNPs-OH surface has too many polar groups, resulting in poor interaction with non-polar asphaltenes, making it difficult to disperse them and leading to a poor viscosity reduction effect. When STAB is added to heavy oil, its molecules agglomerate, making it difficult to reduce the viscosity of heavy oil. For the CNPs-STAB system, firstly, the alkyl chain of STAB interacts with the polar groups on the surface of CNPs-OH, reducing the polarity of CNPs-STAB and preventing STAB from agglomerating. Secondly, the alkyl chain of STAB and the remaining polar groups on the surface of CNPs-OH interact with asphaltenes, thereby driving the functionalized carbon nanoparticles into the asphaltenes clusters and dispersing them, achieving the purpose of viscosity reduction.

[0037] Given that there are numerous embodiments of the present invention, and the raw materials and quantities involved can be selected within a limited range according to actual needs, and that the experimental data for each embodiment are extensive and numerous, it is not suitable to list and describe them one by one here. However, the content to be verified and the final conclusions obtained in each embodiment are similar. Therefore, the verification content of each embodiment will not be described one by one here.

[0038] The above description is merely a detailed explanation of preferred embodiments and principles of the present invention. For those skilled in the art, there may be changes in specific implementation methods based on the ideas provided by the present invention, and these changes should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a carbon nanoparticle-based thick oil viscosity reducer, characterized in that, Includes the following steps: (1) Add H2O2 solution to carbon nanoparticles CNPs, sonicate to disperse the nanoparticles evenly, centrifuge after oxidation reaction, wash and dry the solid to obtain nanoparticles CNPs-OH; (2) Add nanoparticles CNPs-OH to an aqueous solution of cationic surfactant, mix evenly, sonicate at 60-70℃, and finally dry to obtain carbon nanoparticle-based thick oil viscosity reducer.

2. The preparation method according to claim 1, characterized in that, In step (1), the mass fraction of the H2O2 solution is 20-40%.

3. The preparation method according to claim 1, characterized in that, In step (1), the duration of ultrasonic treatment is 20 to 40 minutes.

4. The preparation method according to claim 1, characterized in that, In step (1), the oxidation reaction is carried out at a temperature of 100-110°C for 4-6 hours.

5. The preparation method according to claim 1, characterized in that, In step (2), the cationic surfactant is at least one of hexadecyltrimethylammonium bromide (CTAB) and octadecyltrimethylammonium bromide (STAB).

6. The preparation method according to claim 1, characterized in that, In step (2), the solid-liquid ratio of the cationic surfactant to water in the aqueous solution of the cationic surfactant is (0.01~0.25) g: 25 mL; The cationic surfactant is 5 to 50 wt% of the weight of the CNPs-OH nanoparticles.

7. The preparation method according to claim 1, characterized in that, In step (2), the duration of ultrasound is 30 to 90 minutes.

8. A carbon nanoparticle-based heavy oil viscosity reducer prepared by the preparation method according to any one of claims 1-7.

9. The application of the carbon nanoparticle-based heavy oil viscosity reducer as described in claim 8, characterized in that, After the heavy oil is preheated, a toluene solution of carbon nanoparticle-based heavy oil viscosity reducer is added and mixed evenly.

10. The application according to claim 9, characterized in that, The preheating temperature of the heavy oil is 50-70°C, and the time is 1-3 hours; The ratio of carbon nanoparticle-based thick oil viscosity reducer to thick oil is (1-3) mg: 10 mL, and the amount of toluene added is 0.5-1.5 vol of thick oil.

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