Viscosity reduction system for microwave extraction of heavy oil and preparation method thereof

Abstract

Disclosed belongs to the technical field of heavy oil extraction, and specifically relates to a viscosity reduction system for microwave extraction of heavy oil and a preparation method thereof. The viscosity reduction system is a magnetic graphene oxide. The viscosity reduction system added to heavy oil has a significant viscosity reduction effect after microwave treatment. The viscosity reduction system exhibits lipophilicity and can be adsorbed on oil droplets, so that the thermal effect of microwaves assisted by the viscosity reduction system mainly acts on a reservoir, which reduces heat loss during heat transfer. At the same time, the viscosity reduction system is magnetic, which helps directional regulation and separation under the action of a magnetic field.

Claims

1. A viscosity reduction system for microwave extraction of heavy oil, wherein the viscosity reduction system is a magnetic graphene oxide; wherein the magnetic graphene oxide is compounded by Fe.sub.3O.sub.4 nanospheres and a graphene oxide; wherein the mass ratio of the Fe.sub.3O.sub.4 nanospheres to the graphene oxide is 2:1; the viscosity reduction system is produced by the following steps: (1) preparing a catalyst suspension: adding the Fe.sub.3O.sub.4 nanospheres into deionized water to obtain a suspension, and adjusting the suspension to be acidic by an acid to obtain a catalyst suspension; (2) preparing a carrier solution: adding graphene oxide into deionized water, and stirring to obtain a graphene oxide carrier solution; (3) placing the catalyst suspension obtained in step (1) in a flask, introducing nitrogen into the flask, and heating in a constant temperature water bath of 60 C.; (4) adding the graphene oxide carrier solution into the flask heated in the constant temperature water bath of step (3) dropwise while stirring to obtain a mixed solution; wherein the weight ratio of the graphene oxide carrier solution to the catalyst suspension is 1:2; (5) placing the mixed solution obtained in step (4) in an infiltration bag to obtain a magnetic graphene oxide precipitate; and (6) placing the magnetic graphene oxide precipitate obtained in step (5) in a vacuum oven for drying to obtain the viscosity reduction system.

2. The viscosity reduction system for microwave extraction of heavy oil according to claim 1, wherein the diameter of the Fe.sub.3O.sub.4 nanospheres is 10 to 20 nm.

3. The viscosity reduction system for microwave extraction of heavy oil according to claim 1, wherein the graphene oxide has 1 to 2 layers and a diameter of 1 to 5 m.

4. The viscosity reduction system for microwave extraction of heavy oil according to claim 1, wherein in step (1), the Fe.sub.3O.sub.4 nanospheres are 0.4 to 1 g, and the deionized water is 200 mL; in step (2), the graphene oxide is 0.2 to 0.5 g, and the deionized water is 100 mL; and in step (4), the graphene oxide carrier solution is 100 parts by weight, and the catalyst suspension is 200 parts by weight.

5. The viscosity reduction system for microwave extraction of heavy oil according to claim 1, wherein in step (1), the Fe.sub.3O.sub.4 nanospheres are 0.5 g; and in step (2), the graphene oxide is 0.25 g.

6. The viscosity reduction system for microwave extraction of heavy oil according to claim 1, wherein in step (1), the pH value of the suspension is adjusted to 3 to 5 by 1 mol/L hydrochloric acid.

7. The viscosity reduction system for microwave extraction of heavy oil according to claim 1, wherein the stirring in step (2) is magnetic stirring, the revolving speed is 400 to 600 rpm, the stirring time is 0.5 to 1 h, and the stirring temperature is 20 to 30 C.; the flask in step (3) is a three-necked flask, and the inflow rate of nitrogen is 0.3 to 0.5 L/min; the stirring in step (4) is intense stirring, and the revolving speed is 800 to 1200 rpm; and vacuum drying is performed at 50 C. in step (6).

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a scanning electron microscope (SEM) image of magnetic graphene oxide (MGO) according to Embodiment 1. It can be seen from FIG. 1 that the black part is graphene oxide (GO) with few electrons reflected, and the white particles are Fe.sub.3O.sub.4 with many electrons reflected. The prepared magnetic graphene oxide (MGO) has a layered folding structure peculiar to graphene oxide, which is advantageous for obtaining a larger BET adsorption area and more adsorption sites, and facilitates adsorption of spherical Fe.sub.3O.sub.4 on its surface. In the figure, the average diameter of the black GO sheet layers is 5 m, and the average particle diameter of the white Fe.sub.3O.sub.4 is 20 nm. It shows that Fe.sub.3O.sub.4 has been successfully loaded on GO to form a magnetic material MGO.

(2) FIG. 2 is an X-ray diffraction (XRD) comparison diagram of the magnetic graphene oxide (MGO), graphene oxide (GO), and Fe.sub.3O.sub.4 nanospheres (Fe.sub.3O.sub.4) described in Embodiment 1. It can be seen from FIG. 2 that the 10.8 diffraction peak is a typical characteristic peak of GO. Among the 2angles of MGO diffraction peaks, 30.3, 35.5, 43.5, 53.5, 57.2, and 62.8 are typical characteristic peaks of iron oxides, and are identical to the crystal plane of Fe.sub.3O.sub.4, indicating that Fe.sub.3O.sub.4 nanoparticles have been successfully loaded on GO, and this result is consistent with the analysis of SEM results. A weak characteristic peak similar to GO occurs at 12.1, indicating that the interlayer spacing of MGO after loading Fe.sub.3O.sub.4 is reduced, due to the magnetic agglomeration of Fe.sub.3O.sub.4.

(3) FIG. 3 is a scanning electron microscope (SEM) image of magnetic graphene oxide (MGO) formed when the added amount of Fe.sub.3O.sub.4 nanospheres is higher than the proportion relationship described in Embodiment 1. It can be seen from FIG. 3 that the Fe.sub.3O.sub.4 nanospheres have severe agglomeration, and the loading effect is not good.

(4) FIG. 4 is a scanning electron microscope (SEM) image of graphene oxide in Embodiment 1.

(5) FIG. 5 is a comparison diagram of temperature rise changes of heavy oil with the use of magnetic graphene oxide nano-catalyst of Embodiment 1 in microwave treatment of heavy oil.

(6) FIG. 6 is a comparison diagram of viscosity changes with the use of magnetic graphene oxide nano-catalyst of Embodiment 1 in microwave treatment of heavy oil.

(7) FIG. 7 is a schematic principle diagram showing that the graphene oxide is reduced to graphene with enhanced wave absorption and lipophilicity and functions of auxiliary heat transfer and automatic oil search.

DETAILED DESCRIPTION OF THE EMBODIMENTS

(8) The present invention will be described in detail below through embodiments. Fe.sub.3O.sub.4 nanospheres were purchased from aladdin, and TEM tests showed that the Fe.sub.3O.sub.4 nanospheres had a purity of 99.0%, a diameter of 20 nm, and a spherical shape. Graphene oxide was purchased from Chinese Academy of Sciences in Chengdu, and had a purity of more than 98% by weight, 1-2 layers, an ash content of less than 1.5% by weight, and a diameter of 1-5 m.

Embodiment 1

(9) The viscosity reduction system for microwave extraction of heavy oil was a magnetic graphene oxide. The magnetic graphene oxide was compounded by Fe.sub.3O.sub.4 nanospheres and a graphene oxide. The Fe.sub.3O.sub.4 nanospheres were 0.5 g; and the graphene oxide was 0.25 g.

(10) The diameter of the Fe.sub.3O.sub.4 nanospheres was 20 nm. The graphene oxide had 2 layers and a diameter of 5 m.

(11) A preparation method of the viscosity reduction system for microwave extraction of heavy oil included the following steps that:

(12) (1) a catalyst suspension was prepared: 0.5 g of Fe.sub.3O.sub.4 nanospheres were added into 200 mL of deionized water to obtain a suspension, and the pH value of the suspension was adjusted to 3 by 1 mol/L hydrochloric acid to obtain a catalyst suspension;

(13) (2) a carrier solution was prepared: 0.25 g of graphene oxide was added into 100 mL of deionized water, and the mixed solution was subjected to magnetic stirring at a temperature of 25 C. and a revolving speed of 500 rpm for 1 h to obtain a graphene oxide carrier solution;

(14) (3) the catalyst suspension obtained in step (1) was placed in a three-necked flask, nitrogen was introduced into the flask at a flow rate of 0.5 L/min, and the flask was heated in a constant temperature water bath of 60 C.;

(15) (4) the graphene oxide carrier solution was added into the flask heated in the constant temperature water bath of step (3) dropwise while intense stirring was kept at a revolving speed of 1000 rpm to obtain a mixed solution; wherein the graphene oxide carrier solution was 100 parts, and the catalyst suspension was 200 parts;

(16) (5) the mixed solution obtained in step (4) was placed in an infiltration bag, and because the infiltration bag only allowed water molecules to pass through, but magnetic graphene oxide could not pass through the infiltration bag, so a magnetic graphene oxide precipitate was obtained; and

(17) (6) the magnetic graphene oxide precipitate obtained in step (5) was placed in a vacuum oven for vacuum drying at 50 C. to obtain the viscosity reduction system.

(18) The following tested the application performance of the viscosity reduction system described in Embodiment 1 in heavy oil.

(19) 1. Test on the heating effect of heavy oil added with the magnetic graphene oxide (0.5 wt %) of the viscosity reduction system for microwave treatment was as follows:

(20) Control groups were set: two groups of oil samples with the same initial condition were selected, one group did not contain additives, and the other group was added with 0.5 wt % of MGO. After 20 minutes of microwave treatment at a frequency of 2450 MHz and a power of 700 W, the temperature rise changes of the two groups of heavy oil were shown in FIG. 5.

(21) The initial temperature of the heavy oil was 20 C. at room temperature, and the temperature gradually rose after microwave heating. Compared with the heavy oil added with MGO, it can be found that the temperatures of the heavy oil without MGO and the heavy oil added with 0.5 wt % of MGO tended to approach at about 10 min; the heating rate of the heavy oil added with 0.5 wt % of MGO was faster after 0 to 10 min of microwave heating, and the temperatures of the heavy oil without MGO and the heavy oil added with 0.5 wt % of MGO were close after 10 to 20 min of microwave heating. The reasons analyzed are that: MGO-supported catalyst Fe.sub.3O.sub.4 nanospheres were rapidly heated under microwave radiation, the heat was transferred to GO and surrounding contacted heavy oil, GO was converted into RGO with strong wave absorption, and the RGO assisted the catalyst Fe.sub.3O.sub.4 nanospheres to transfer heat to the heavy oil; the temperature of the heavy oil added with 0.5 wt % of MGO increased, and the light components were volatilized more quickly than those of the heavy oil not added with MGO, because the catalyst Fe.sub.3O.sub.4 nanospheres modified the nature of the original heavy oil containing a few light components under the action of microwaves to increase the content of light components, while the volatilization of light components was a heat absorption process.

(22) 2. Test on the viscosity reduction effect of heavy oil added with the magnetic graphene oxide (0.5 wt %) of the viscosity reduction system for microwave treatment was as follows:

(23) Control groups were set: three groups of oil samples with the same initial condition were selected, one group did not contain additives, the other group was added with 0.5 wt % of MGO, and another group was added with 0.5 wt % of MGO and 1% wt of hydrogen donortetrahydronaphthalene (C.sub.10H.sub.12). After 10 minutes of microwave treatment at a frequency of 2450 MHz and a power of 700 W, the heavy oil was stood for 12 hours and cooled to room temperature, and the viscosity changes of the three groups of heavy oil were measured as shown in FIG. 6.

(24) At a standard temperature of 25 C., the initial viscosity of the untreated heavy oil was 1550000 mPa.Math.s, the viscosity of the heavy oil without MGO was 1478000 mPa.Math.s after 10 minutes of microwave treatment, the viscosity reduction rate was 4.65%, and the viscosity did not decrease significantly; the viscosity of the heavy oil added with 0.5 wt % of MGO was 1215000 mPa.Math.s after 10 minutes of microwave treatment, the viscosity reduction rate was 21.61%, and the viscosity decreased a little; and the viscosity of the heavy oil added with 0.5 wt % of MGO and 1% wt of hydrogen donor C.sub.10H.sub.12 was 874000 mPa.Math.s after 10 minutes of microwave treatment, the viscosity reduction rate was 43.61%, and the viscosity decreased significantly. The heavy oil added with MGO had a significant viscosity reduction effect after microwave treatment, because of the combined effect of microwave thermal effect and non-thermal effect. In the process of heating heavy oil with microwaves, the non-thermal effect of microwaves first acted to reduce the activation energy for breakage of long chains and branched chains of some alkanes and cracking of unstable cements in the heavy oil, so that reaction and cracking occurred at a relatively low temperature to generate light components; when the temperature of the heavy oil system reached the cracking temperature of heavy components, the thermal effect of microwaves on the heavy oil was produced, and some heavy components such as colloid and as phaltene generated light components such as saturated and aromatic components through hydrogenation chain breaking reaction under superheated conditions, thereby reducing the viscosity of heavy oil.

(25) 3. Composition changes of heavy oil added with the magnetic graphene oxide (0.5 wt %) of the viscosity reduction system after 10 minutes of microwave treatment were shown in Table 2:

(26) TABLE-US-00002 TABLE 2 Composition changes of heavy oil Four components, wt % Saturated Aromatic Sample component component Colloid Asphaltene Heavy oil 21.92 44.18 23.57 10.33 Microwave 21.38 44.15 23.96 10.51 treatment for heavy oil Heavy oil + MGO 23.62 43.29 23.33 9.76 microwave treatment Heavy oil + MGO + 24.18 45.16 22.27 8.39 hydrogen donor microwave treatment

(27) The light components were saturated and aromatic components, and the heavy components were colloid and asphaltene. It could be found from Table 2 that, after microwave treatment for heavy oil, the four components were not changed significantly, and the proportion of heavy components increased slightly due to the volatilization of light components; after heavy oil+MGO microwave treatment, because local hotspots were generated around MGO, the generation of light components was slightly faster than the volatilization, and the heavy components were reduced slightly; and after heavy oil+MGO+hydrogen donor microwave treatment, some heavy components were hydrocracked to light components at a high temperature, and the amount of light components generated was relatively large, which also provided a basis for the phenomenon of modification and viscosity reduction.