阅读说明：本技术 环保监测用油溶性示踪剂及其制备方法 (Oil-soluble tracer for environmental monitoring and preparation method thereof ) 是由 武双 于 2020-12-29 设计创作，主要内容包括：本发明提供一种环保监测用油溶性示踪剂及其制备方法。该环保监测用油溶性示踪剂,通过将油溶性量子点外包覆油溶性二氧化硅以形成壳核结构的纳米微球。本发明采用的壳核结构既保护了量子点,避免量子点受到外界干扰导致荧光量子点下降的问题,而且通过对二氧化硅改性,使示踪剂有较好的油溶性,不会轻易聚沉,可用于油田示踪。并且在酸碱盐各种情况下对本发明提供的环保监测用油溶性示踪剂进行检测,荧光发射峰均很明显,说明本发明提供的环保监测用油溶性示踪剂稳定性高。(The invention provides an oil-soluble tracer for environmental monitoring and a preparation method thereof. The oil-soluble tracer for environmental monitoring is prepared by coating oil-soluble silicon dioxide outside oil-soluble quantum dots to form nano microspheres with a shell-core structure. The shell-core structure adopted by the invention not only protects the quantum dots and avoids the problem that the quantum dots are interfered by the outside to cause the fluorescence quantum dots to be reduced, but also enables the tracer to have better oil solubility and not to easily aggregate and sink through modifying the silicon dioxide, and can be used for oil field tracing. And the environment-friendly monitoring oil-soluble tracer provided by the invention is detected under various conditions of acid, alkali and salt, and the fluorescence emission peak is obvious, which shows that the environment-friendly monitoring oil-soluble tracer provided by the invention has high stability.)

1. A preparation method of an oil-soluble tracer for environmental monitoring is characterized by comprising the following steps: the method comprises the following steps:

s1 preparation of oil-soluble quantum dots

Dissolving water-soluble metal salt and sodium oleate in a solvent consisting of ethanol, n-hexane and deionized water, mixing, adding into a three-neck flask, and refluxing at 80 ℃ for 2 h; naturally cooling the solution to room temperature, storing in a refrigerator, performing suction filtration by using a funnel after an upper organic layer turns white to obtain a solid metal oleate crude product, repeatedly washing with excessive distilled water, and then performing vacuum freeze drying for 4-5h to obtain metal oleate powder;

weighing oleic acid metal salt powder and tetrahydrofuran, adding into a three-neck flask, magnetically stirring and heating until the oleic acid metal salt powder is completely dissolved, adding 0.5mL of tetrabutylammonium hydroxide, adding into the three-neck flask, reacting at 50 ℃ for 3-6h, standing for 6-12h, and washing with acetone after rotary evaporation to obtain an oil-soluble quantum dot suspension;

s2 preparation of oil-soluble tracer

Under the condition of magnetic stirring, sequentially adding cyclohexane, oil-soluble quantum dot suspension, tetraethyl orthosilicate and surfactant into a container according to preset values, and uniformly mixing; finally, dropwise adding a catalyst, sealing the container, and reacting under the conditions of light shielding and magnetic stirring; after reacting for 24 hours, adding 2-4mL of acetone to lead the product to be aggregated, destroying the microemulsion system and stopping the reaction; and cleaning and purifying the product by centrifugation and ultrasound to obtain the oil-soluble tracer.

2. The method for preparing an oil-soluble tracer for environmental monitoring according to claim 1, wherein the method comprises the following steps: in step S1, the water-soluble metal salt includes, but is not limited to, zinc chloride, zinc sulfate, or zinc nitrate.

3. The method for preparing an oil-soluble tracer for environmental monitoring according to claim 1, wherein the method comprises the following steps: in step S2, the surfactant includes but is not limited to NP-5, NP-9, or Triton X-100.

4. The method for preparing an oil-soluble tracer for environmental monitoring according to claim 1, wherein the method comprises the following steps: in step S2, the catalyst includes, but is not limited to, ammonia, methyl acrylate or dimethylacetamide.

5. The method for preparing an oil-soluble tracer for environmental monitoring according to claim 1, wherein the method comprises the following steps: in step S2, the adding amount of tetraethyl orthosilicate is 0.5 ml; the amount of the surface modifier added was 1 ml.

6. The method for preparing an oil-soluble tracer for environmental monitoring according to claim 1, wherein the method comprises the following steps: in the step S2, the adding amount of the cyclohexane is 8 ml; the addition amount of the oil-soluble quantum dot suspension is 0.5 ml; the amount of the catalyst added was 1 ml.

7. The method for preparing an oil-soluble tracer for environmental monitoring according to claim 1, wherein the method comprises the following steps: in step S1, the adding amount of the water-soluble metal salt is 1 mmol; the amount of sodium oleate added is 5.0 mmol.

8. The method for preparing an oil-soluble tracer for environmental monitoring according to claim 1, wherein the method comprises the following steps: in step S1, the adding amount of tetrahydrofuran is 20.0 mL; the magnetic stirring temperature is 60 ℃; the addition amount of tetrabutylammonium hydroxide is 0.5 mL.

9. The method for preparing an oil-soluble tracer for environmental monitoring according to claim 1, wherein the method comprises the following steps: in step S1, the solvent consisted of 5ml of ethanol, 17.5ml of n-hexane, and 7.5ml of deionized water.

10. An oil-soluble tracer for environmental monitoring, which is characterized in that: the oil-soluble tracer for environmental monitoring is prepared according to the preparation method of any one of claims 1 to 9; the oil-soluble tracer for environmental monitoring is a core-shell structured nano microsphere and is formed by coating oil-soluble quantum dots with oil-soluble silicon dioxide.

Technical Field

The invention relates to the technical field of oil field chemical additives, in particular to an oil-soluble tracer for environmental monitoring and a preparation method thereof.

Background

In recent years, the application field of tracer technology is widened to single-well tests such as horizontal well production fluid profile tracer tests, staged fracturing effect tracer evaluation and the like, the tests need to use two types of water-soluble and oil-soluble tracers at the same time, and the types of the oil-soluble tracers are fewer compared with the mature water-soluble tracers. The patent with the publication number of CN111648765A provides an environment-friendly oil-soluble tracer and application thereof, wherein the oil-soluble tracer is prepared by mixing organic acid rare earth salt, a solvent, a surfactant and a preservative according to a certain proportion. The patent with the publication number of CN111764881A provides 'an oil-soluble trace element tracer for multistage fracturing and application thereof', which is prepared by mixing organic salt of trace metal elements, a dispersing agent, a defoaming agent and a diluent according to a certain proportion. The oil-soluble tracer and the common water-soluble trace element tracer can be used in the fracturing fluid at the same time, do not interfere with each other, and can be used for continuously monitoring the crude oil yield and the output speed of each layer section after multi-section fracturing.

Both of the above methods change the water-soluble trace element tracer to an oil-soluble tracer, and the research on other oil-soluble tracers is less. Particularly, the oil-soluble indicator required in the fluorescence detection technology has the advantages of high detection sensitivity, simple operation, low cost, adjustable detection range and the like, can quickly, simply and highly sensitively detect a fluorescence signal through a fluorescence spectrophotometer, and can be used in the field of oilfield tracing. However, in the implementation process of the technology, a suitable fluorescent tracer must be found, and the technology needs to have good optical stability and strong fluorescence, and needs to meet the characteristics of low background concentration in the stratum, low adsorption quantity on the surface of the stratum, no reaction with stratum minerals, easy detection, high sensitivity and the like. In view of the above, there is a need to design an oil-soluble tracer to solve the above problems.

Disclosure of Invention

The invention aims to provide an oil-soluble tracer for environmental monitoring and a preparation method thereof, so as to solve the problems.

In order to achieve the aim, the invention provides a preparation method of an oil-soluble tracer for environmental monitoring, which comprises the following steps:

s1 preparation of oil-soluble quantum dots

Dissolving water-soluble metal salt and sodium oleate in a solvent consisting of ethanol, n-hexane and deionized water, mixing, adding into a three-neck flask, and refluxing at 80 ℃ for 2 h; naturally cooling the solution to room temperature, storing in a refrigerator, performing suction filtration by using a funnel after an upper organic layer turns white to obtain a solid metal oleate crude product, repeatedly washing with excessive distilled water, and then performing vacuum freeze drying for 4-5h to obtain metal oleate powder;

weighing oleic acid metal salt powder and tetrahydrofuran, adding into a three-neck flask, magnetically stirring and heating until the oleic acid metal salt powder is completely dissolved, adding 0.5mL of tetrabutylammonium hydroxide, adding into the three-neck flask, reacting at 50 ℃ for 3-6h, standing for 6-12h, and washing with acetone after rotary evaporation to obtain an oil-soluble quantum dot suspension;

s2 preparation of oil-soluble tracer

Under the condition of magnetic stirring, sequentially adding cyclohexane, oil-soluble quantum dot suspension, tetraethyl orthosilicate and surfactant into a container according to preset values, and uniformly mixing; finally, dropwise adding a catalyst, sealing the container, and reacting under the conditions of light shielding and magnetic stirring; after reacting for 24 hours, adding 2-4mL of acetone to lead the product to be aggregated, destroying the microemulsion system and stopping the reaction; and cleaning and purifying the product by centrifugation and ultrasound to obtain the oil-soluble tracer.

As a further improvement of the present invention, in step S1, the water-soluble metal salt includes, but is not limited to, zinc chloride, zinc sulfate or zinc nitrate.

As a further improvement of the present invention, in step S2, the surfactant includes but is not limited to NP-5, NP-9 or Triton X-100.

As a further improvement of the present invention, in step S2, the catalyst includes, but is not limited to, ammonia, methyl acrylate or dimethylacetamide.

As a further improvement of the present invention, in step S2, the amount of tetraethyl orthosilicate added is 0.5 ml; the amount of the surface modifier added was 1 ml.

As a further improvement of the invention, in the step S2, the adding amount of the cyclohexane is 8 ml; the addition amount of the oil-soluble quantum dot suspension is 0.5 ml; the amount of the catalyst added was 1 ml.

As a further improvement of the invention, in step S1, the addition amount of the water-soluble metal salt is 1 mmol; the amount of sodium oleate added is 5.0 mmol.

As a further improvement of the invention, in step S1, the added amount of tetrahydrofuran is 20.0 mL; the magnetic stirring temperature is 60 ℃; the addition amount of tetrabutylammonium hydroxide is 0.5 mL.

As a further improvement of the invention, in step S1, the solvent consists of 5ml of ethanol, 17.5ml of n-hexane and 7.5ml of deionized water.

In order to achieve the above object, the present invention further provides an oil-soluble tracer for environmental monitoring, which is prepared according to the preparation method of any one of claims 1 to 9; the oil-soluble tracer for environmental monitoring is a core-shell structured nano microsphere and is formed by coating oil-soluble quantum dots with oil-soluble silicon dioxide.

The invention has the beneficial effects that:

according to the oil-soluble tracer for environmental monitoring, the quantum dots are protected by coating the oil-soluble silicon dioxide outside the quantum dots to form the nano microspheres with the shell-core structure, so that the problem that the fluorescence quantum dots are reduced due to external interference of the quantum dots is solved, and the tracer has good oil solubility and cannot easily aggregate and sink due to oil field tracing by modifying the silicon dioxide. And the environment-friendly monitoring oil-soluble tracer provided by the invention is detected under various conditions of acid, alkali and salt, and the fluorescence emission peak is obvious, which shows that the environment-friendly monitoring oil-soluble tracer provided by the invention has high stability.

Drawings

FIG. 1 is a standard graph of the tracer prepared in example 1.

FIG. 2 is a graph showing the fluorescence spectrum of the tracer prepared in example 1 in a petroleum sample.

FIG. 3 is a graph showing the fluorescence spectrum of the tracer prepared in example 1 in an acidic petroleum sample.

FIG. 4 is a graph showing the fluorescence spectrum of the tracer prepared in example 1 in an alkaline petroleum sample.

FIG. 5 is a graph showing the fluorescence spectrum of the tracer prepared in example 1 in a petroleum sample containing salt.

FIG. 6 is a graph showing a particle size distribution of the oil-soluble tracer obtained in example 2.

FIG. 7 is a fluorescence spectrum of the oil-soluble tracer obtained in example 3.

FIG. 8 is a graph showing the particle size distribution of the oil-soluble tracer obtained in example 4.

FIG. 9 is a graph showing the particle size distribution of the oil-soluble tracer obtained in example 5.

FIG. 10 is a fluorescence intensity fit chart of comparative example 1.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention will be described in detail with reference to the accompanying drawings and specific embodiments.

It should be noted that, in order to avoid obscuring the present invention with unnecessary details, only the structures and/or processing steps closely related to the aspects of the present invention are shown in the drawings, and other details not closely related to the present invention are omitted.

In addition, it is also to be noted that the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus.

An oil-soluble tracer for environmental monitoring and a preparation method thereof, which comprises the following steps:

s1 preparation of oil-soluble quantum dots

1.0mmol of a water-soluble metal salt solution and 5.0mmol of sodium oleate were dissolved in a solvent consisting of 5.0mL of ethanol, 17.5mL of n-hexane and 7.5mL of deionized water, mixed and added to a three-necked flask, and refluxed at 80 ℃ for 2 hours. Naturally cooling the solution to room temperature, storing in a refrigerator, performing suction filtration by using a funnel after an upper organic layer turns white to obtain a solid metal oleate crude product, repeatedly washing with excessive distilled water, and then performing vacuum freeze drying for 4-5h to obtain metal oleate powder;

weighing 1mmol of oleic acid metal salt powder and 20.0mL of tetrahydrofuran, adding into a 50mL three-neck flask, magnetically stirring and heating to 60 ℃ to completely dissolve the oleic acid metal salt powder, adding 0.5mL of tetrabutylammonium hydroxide into the three-neck flask, reacting for 3-6h at 50 ℃, standing for 6-12h, carrying out rotary evaporation, and washing with acetone to obtain the oil-soluble quantum dot particles.

S2 preparation of oil-soluble tracer

Firstly, adding 8mL of cyclohexane into a container, then adding 0.5mL of oil-soluble quantum dot particles, and magnetically stirring for about 1-3 min; then adding 0.5mL of tetraethyl orthosilicate (TEOS), after uniformly stirring by magnetic force, adding 1mL of surfactant, and stirring for 0.5-1h by magnetic force to uniformly mix; finally, 0.1mL of catalyst is dropped into the reaction kettle, and the reaction kettle is sealed in a container and is protected from light and is stirred by magnetic force for reaction. After 24h of reaction, 2-4mL of acetone is added to lead the product to be aggregated, destroy the microemulsion system and terminate the reaction. The product is purified by centrifugation and ultrasound. And obtaining the oil-soluble tracer.

Example 1

Embodiment 1 provides an oil-soluble tracer for environmental monitoring and a preparation method thereof, and the preparation method comprises the following specific steps:

s1 preparation of oil-soluble zinc oxide

1.0mmol of zinc chloride and 5.0mmol of sodium oleate were dissolved in a solvent consisting of 5.0mL of ethanol, 17.5mL of n-hexane and 7.5mL of deionized water, mixed and added to a three-necked flask, and refluxed at 80 ℃ for 2 hours. After the reaction, the upper organic layer became light yellow, the solution was naturally cooled to room temperature and stored in a refrigerator at 0 ℃ for 4 hours, at which time the upper organic layer became white, and suction filtration was performed with a funnel to obtain a crude product of solid zinc oleate, which was repeatedly washed with an excess of distilled water to remove unreacted metal salts, followed by drying in a vacuum freeze-dryer for 5 hours to obtain zinc oleate powder.

Weighing 1mmol of zinc oleate and 20.0mL of tetrahydrofuran, adding the zinc oleate and the tetrahydrofuran into a 50mL three-neck flask, magnetically stirring and heating the mixture to 60 ℃ to completely dissolve the zinc oleate, adding 0.5mL of tetrabutylammonium hydroxide into the three-neck flask, reacting for 12h at 50 ℃, standing for 6h, carrying out rotary evaporation to obtain yellow viscous liquid, washing with acetone, and drying to obtain oil-soluble zinc oxide particles.

S2 preparation of oil-soluble tracer

Firstly, adding 8mL of cyclohexane into a container, then adding 0.5mL of oil-soluble zinc oxide particles, and magnetically stirring for about 1 min; then 0.5mL of tetraethyl orthosilicate (TEOS) is added, and the mixture is stirred magnetically for about 10 min; then adding 1mL NP-5 as a surfactant, and magnetically stirring for about 30min to uniformly mix; finally, 0.1mL of ammonia water is dropped as a catalyst, the container is sealed, and the reaction is carried out under the conditions of light shielding and magnetic stirring. After 24h of reaction, 2-4mL of acetone was added to aggregate the product. Separating the product from the microemulsion by centrifugation, removing the supernatant, collecting the precipitate, adding ethanol, ultrasonically cleaning for about 10min, and centrifuging. And then respectively washing the mixture once by using butanol, ethanol and deionized water, and drying the mixture to obtain the oil-soluble tracer of the silicon dioxide coated zinc oxide, wherein the particle size of the silicon dioxide coated zinc oxide nano microspheres is 265 nm.

Oil solubility test: adding a certain amount of the oil-soluble tracer prepared in example 1 into base oil, heating to about 60 ℃, stirring to completely dissolve the oil-soluble tracer, sealing the solution in a test tube, standing for 1-2 days at room temperature or in an environment of 20-minus 10 ℃, and separating the test tube in a centrifuge, wherein no solid precipitate appears at the bottom of the test tube, which indicates that the oil-soluble tracer prepared in example 1 has oil solubility under the condition.

The oil-soluble tracer in example 1 was used to prepare a standard solution, and the solvent environment of the standard solution was NaOH (1mol/L) in ethanol. Wherein ethanol solutions of NaOH with the oil-soluble tracer contents of 50 mug/ml, 10 mug/ml, 0.5 mug/ml and 0.025mg/ml are respectively prepared. Then, the fluorescence intensity was measured (excitation wavelength is 550 nm), and the results of the measurement data are shown in the following table:

concentration of	50	10	0.5	0.025
					Intensity of fluorescence	0.9851	0.2094	0.02143	0.01135

From the table above, a standard curve is plotted for fluorescence intensity versus concentration for standard solutions of oil-soluble tracers at different concentrations, as shown in fig. 1, and it is found by fitting that the sensitivity of this method is S ═ 0.019. Then, the fluorescence intensity of the blank sample (an ethanol solution of NaOH without an oil-soluble tracer) was measured. The standard deviation of the blank sample was calculated to be 0.00014 and the detection limit was about 0.01. mu.g/ml based on the above-described multiple measurements of fluorescence intensity of the blank sample.

The temperature, acid, alkali, salt environment and the like in the underground oil reservoir all impose strict requirements on the stability of the petroleum tracer. To test the stability of the tracer, the oil-soluble tracer prepared in example 1 was placed in petroleum samples of different acids, bases, salts to test the stability of the tracer of the invention in petroleum tracing. The method comprises the following specific steps: a blank petroleum sample (a mixture of oil and water containing water and oil) was taken, and after the oil-soluble tracer in example 1 was added thereto, an appropriate amount of the above petroleum sample containing the oil-soluble tracer was taken, and then 10 ml of an ethanol solution was added thereto. After 5 minutes of reaction, the mixture was centrifuged to separate layers, and the supernatant, which was an ethanol solution containing sodium hydroxide and an oil-soluble tracer, was taken, and then the fluorescence emission peak of the supernatant was measured, and the result was shown in FIG. 2, where the fluorescence emission peak of the supernatant containing fluorescent quantum dots was about 455 nm.

Fig. 3, 4 and 5 are fluorescence spectra of the tracer prepared in this example under different conditions of acid base and salt, which are measured by adding excessive strong acid, strong base and salt solution during the stability detection process. As can be seen from FIGS. 2, 3, 4 and 5, the prepared tracer prepared in this example has a distinct fluorescence emission peak in different solvent environments such as acid or alkali, and no other interference peak is seen in the figure. It is fully demonstrated that the oil-soluble tracers in the present application have the advantages of easy identification and strong fluorescence signal.

Examples 2 to 5

Examples 2 to 5 respectively provide an oil-soluble tracer for environmental monitoring and a method for preparing the same, which are different from example 1 in that: the adding amount of TEOS and modifier in step S2 is changed, and other operations are not changed. Examples 2-5 the specific amounts of TEOS and modifier used in step S2 are shown in the following table:

table 2 examples 2-5 amounts of TEOS and modifier added in step S2

	TEOS addition	Amount of modifier added
			Example 2	0.1	1
Example 3	1	1
			Example 4	0.5	2
Example 5	0.5	0.5

The results of particle size detection and fluorescence intensity detection of the oil-soluble tracers obtained in examples 2 to 4 are shown in fig. 6, 7 and 8. FIG. 6 is a particle size distribution diagram of the oil-soluble tracer obtained in example 2; FIG. 7 is a fluorescence spectrum of the oil-soluble tracer obtained in example 3; FIG. 8 is a particle size distribution diagram of the oil-soluble tracer obtained in example 4; FIG. 9 is a particle size distribution diagram of the oil-soluble tracer obtained in example 5.

As can be seen from fig. 6 and 7: the particle size distribution of the microsphere is 2 peaks, which indicates that the prepared microsphere of the zinc oxide coated by the silicon dioxide is not uniform, probably because the nano microsphere is agglomerated, and indicates that the adding amount of TEOS is not suitable to be overlarge. When the amount of TEOS is less, it is not enough to completely coat the zinc oxide, and the zinc oxide particles alone are susceptible to external interference, which results in the decrease of the fluorescence quantum dots, as shown in fig. 7. The preferred amount of TEOS addition is therefore 0.5 ml.

As can be seen from fig. 8 and 9: the larger the amount of the modifier is, the smaller the particle size of the microsphere is, because a large amount of the modifier is bonded on the surface of the spherical silica nanoparticles, further growth of silica is prevented to a certain extent, the viscosity of a reaction system is increased due to the large amount of the modifier, post-treatment of a sample is difficult, and the modifier which is free in the reaction system is difficult to completely remove. If the modifier is too small, the particle size of the oil-soluble tracer is approximately the same as that of the tracer prepared in example 1, but further research shows that the oil-soluble tracer prepared in the case of the modifier is too small, the oil-soluble tracer is not good in solubility in base oil, and the tracer is easy to aggregate and precipitate. Therefore, the preferred amount of modifier added is 1 ml.

It should be noted that the water-soluble metal salt includes, but is not limited to, zinc chloride, zinc sulfate, zinc nitrate, etc.; the surface modifier can also be NP-9 or Triton X-100; the catalyst may also be methyl acrylate or dimethylacetamide.

Comparative example 1

Comparative example 1 is an improved oil-soluble tracer for environmental monitoring and a preparation method thereof, and compared with example 1, the difference is that: step S1 is not carried out, the oil-soluble zinc oxide particles are changed into common nano zinc oxide in step S2, and other operations are not changed.

The oil-soluble tracer in comparative example 1 was used to prepare a standard solution, the solvent environment of which was an ethanol solution of NaOH (1 mol/L). Wherein ethanol solutions of NaOH with the oil-soluble tracer contents of 50 mug/ml, 10 mug/ml, 0.5 mug/ml and 0.025mg/ml are respectively prepared. And then, the fluorescence intensity is respectively tested, a standard curve graph is drawn according to the fluorescence intensity-concentration of standard solutions of oil-soluble tracers with different concentrations, and as shown in fig. 10, the sensitivity of the method is shown as S being 0.025 by fitting. The standard deviation of the blank sample was calculated to be 0.00021 with a detection limit of about 0.01 μ g/ml, based on the above-described multiple measurements of fluorescence intensity of the blank sample. The sensitivity was lower and the bias value was larger than in example 1.

In summary, the invention provides an oil-soluble tracer for environmental monitoring and a preparation method thereof, the oil-soluble tracer for environmental monitoring protects quantum dots by coating oil-soluble silicon dioxide outside the quantum dots to form nanoparticles with a shell-core structure, so that the problem of fluorescence quantum dot reduction caused by external interference of the quantum dots is avoided, and the tracer has better oil solubility and cannot easily aggregate and sink due to oil field tracing by modifying the silicon dioxide. And the environment-friendly monitoring oil-soluble tracer provided by the invention is detected under various conditions of acid, alkali and salt, and the fluorescence emission peak is obvious, which shows that the environment-friendly monitoring oil-soluble tracer provided by the invention has high stability.

Although the present invention has been described in detail with reference to the preferred embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the spirit and scope of the present invention.