Evaluation method for rapid demulsification performance of crude oil demulsifier

Abstract

The invention discloses a method for evaluating the rapid demulsification performance of a crude oil demulsifier, which comprises the following steps: (1) adding high-purity water into a sample pool, adding simulated oil into the sample pool, and forming a layer of oil film on the water surface so as to simulate an oil-water interfacial film; (2) dropwise adding a solution containing a to-be-detected demulsifying agent on the oil-water interface film, recording the whole process that liquid drops of the solution containing the to-be-detected demulsifying agent break through the oil-water interface film, and recording the time t1 when the liquid drops of the solution containing the to-be-detected demulsifying agent start to contact the oil-water interface film and the time t2 when the liquid drops of the solution containing the to-be-detected demulsifying agent break through the oil-water interface film, the difference value is the rupture time of the oil-water interfacial film; (3) testing the interface expansion viscoelasticity of the simulated oil and the solution containing the demulsifier to be tested by using a hanging drop method, and determining main factors for controlling the stability of an oil-water interface film; and (4) defining an oil-water interfacial film strength coefficient k value. According to the invention, the rapid demulsification capability of the demulsifier can be quantified more accurately.

Description

Technical Field

[0001] The present invention relates to the technical field of oilfield surface production gathering and transportation, and particularly to an evaluation method for the rapid demulsification performance of crude oil demulsifiers. Background Art

[0002] At present, the up-to-standard dehydration of oilfield crude oil is a crucial link in surface production gathering and transportation. As one of the commonly used oilfield chemicals for crude oil dehydration, chemical demulsifiers have the advantages of low energy consumption, low cost, and simple operation, and play an important role in production. For example, Chinese Patent Application CN 1223896A relates to a crude oil demulsifier for oilfield crude oil gathering and transportation dehydration treatment and its preparation method. This crude oil demulsifier uses ethylene glycol or propylene glycol as the initiator, and a mixture of alkaline earth metal compounds and alkali metal hydroxides as the catalyst to initiate the copolymerization of ethylene oxide and propylene oxide to obtain a linear polyether, which reacts with polyisocyanate in an aromatic solvent. Currently, the commonly used evaluation method for demulsifiers is the bottle test method, and its principle is static sedimentation. The bottle test method has the advantages of portable instruments, simple operation, and wide adaptability of the operation site (it can be operated not only in the laboratory but also on-site). Although this method has the above advantages, inevitably, the influence of human factors is too large in the experimental operation process of the bottle test method. For example, in the operation process of shaking a stoppered graduated cylinder hundreds of times, different human strengths and shaking amplitudes cannot be controlled, which will result in inconsistent experimental results and experimental errors.

[0003] Chinese Patent Application CN 111474093A discloses a technical evaluation method for crude oil demulsifiers. Among them, the method includes the following steps: (1) obtaining the dehydration rate of the sample and calculating the dehydration rate score according to the weight value; (2) obtaining the oil content in the sewage of the sample and calculating the oil content in the sewage score according to the weight value; (3) obtaining the dehydration rate of the sample and calculating the dehydration rate score according to the weight value; (4) obtaining the score of the oil-water interface condition of the sample; (5) obtaining the consumption of the agent per unit liquid volume of the sample and calculating the consumption of the agent per unit liquid volume score according to the weight value; (6) calculating the total score according to the results obtained in steps (1)-(5) on a percentage basis.

[0004] Chinese Patent Application CN 104807981 A discloses an evaluation device and method for the dynamic demulsification and dehydration characteristics of crude oil emulsion, including an emulsion feed tank, an electric heating device, a high-speed shear disperser, an emulsion metering pump, a thermometer, a demulsification box, an emulsion recovery tank, a demulsifier feed tank, a dosing pump, a high-voltage power supply, and an oscilloscope; the emulsion feed tank and the emulsion recovery tank are connected to the inlet of the emulsion metering pump through a three-way valve, the outlet of the emulsion metering pump is connected to the inlet of the demulsification box, and the outlet of the demulsification box is connected to the emulsion feed tank and the emulsion recovery tank through a three-way valve; a front sampling port and a rear sampling port are respectively provided on the inlet pipeline and the outlet pipeline of the demulsification box, the high-voltage power supply and the oscilloscope are connected in sequence to apply a high-voltage electric field to the demulsification box, and a demulsifier feed tank and a dosing pump are provided on the inlet pipeline of the demulsification box before the front sampling port. It has a compact structure, uses less crude oil emulsion and has continuous flow, and the shell material of the demulsification box is transparent for easy observation, and can quickly evaluate the dynamic demulsification and dehydration characteristics of crude oil emulsion in the laboratory or on the engineering site.

[0005] However, both of the above two patent applications use the amount of water separated as the standard for evaluating the performance of the demulsifier, lacking the embodiment of the action mode of the demulsifier and the intuitive demulsification process and other mechanisms, and the detection time is relatively long.

[0006] In summary, there is currently a lack of research on the change state of the interfacial film of crude oil emulsion and the change process of crude oil emulsion after the addition of the demulsifier, as well as an evaluation method for the demulsification ability of the demulsifier in a short time. Summary of the Invention

[0007] Object of the Invention: Aiming at the deficiencies of the above-mentioned prior art, the present invention provides an evaluation method for the rapid demulsification performance of crude oil demulsifiers.

[0008] Technical Solution: An evaluation method for the rapid demulsification performance of crude oil demulsifiers, the steps are as follows:

[0009] (1) Add an appropriate amount of high-purity water to the sample cell, add an appropriate amount of simulated oil to the sample cell to form an oil film on the water surface to simulate the oil-water interfacial film;

[0010] (2) Through a syringe vertically hovering above the oil-water interfacial film, drop a certain volume of a solution containing the demulsifier to be tested on the oil-water interfacial film, and record the whole process of the droplet of the solution containing the demulsifier to be tested breaking through the oil-water interfacial film through a high-speed camera, where:

[0011] Record the time t1 when the droplet of the solution containing the demulsifier to be tested starts to contact the oil-water interfacial film and the time t2 when the droplet of the solution containing the demulsifier to be tested breaks through the oil-water interfacial film, and the difference between them is the oil-water interfacial film rupture time;

[0012] (3) Use the pendant drop method to test the interfacial dilatational viscoelasticity of the simulated oil and the solution containing the demulsifier to be tested, and determine the main factors controlling the stability of the oil-water interfacial film;

[0013] (4) Define the oil-water interfacial film strength coefficient k value, which is the relationship between the oil-water interfacial film rupture time obtained in step (2) and the main factors controlling the stability of the oil-water interfacial film determined in step (3).

[0014] Further, in step (1), the simulated oil is a mixture of crude oil and kerosene.

[0015] Further still, the volume ratio of the crude oil to the kerosene is 9:1.

[0016] Further, in step (1), the amount of the simulated oil used is 300 - 2000 μL.

[0017] Further still, in step (1), the amount of the simulated oil used is 800 μL.

[0018] Further, in step (2), the volume of the droplet of the solution containing the demulsifier to be tested is 5 - 15 μL.

[0019] Further still, in step (2), the volume of the droplet of the solution containing the demulsifier to be tested is 10 μL.

[0020] Further, in step (2), the concentration of the solution of the demulsifier to be tested is 100 - 200 mg / L.

[0021] Further, in step (2), the high-speed camera is located on one side of the sample cell, and the absolute height of the lens of the high-speed camera is adapted to the horizontal height of the oil-water interfacial film.

[0022] Further, in step (3), the instrument used for the pendant drop method is an interfacial rheometer, preferably a high-temperature and high-pressure interfacial rheometer.

[0023] Further, in step (4), the oil-water interfacial film strength coefficient k value is the ratio of the oil-water interfacial film rupture time obtained in step (2) to the main factors controlling the stability of the oil-water interfacial film determined in step (3).

[0024] Beneficial effects: The evaluation method for the rapid demulsification performance of a crude oil demulsifier disclosed in the present invention has the following

[0025] Beneficial effects:

[0026] 1. The evaluation method of the present invention can continuously observe and record the rupture process of the oil-water interfacial film of the crude oil emulsion, can more clearly understand the action mode of the demulsifier, and obtain a more intuitive demulsification process;

[0027] 2. The evaluation method of the present invention uses precision instruments and can more accurately quantify the rapid demulsification ability of demulsifiers.

[0028] 3. The evaluation method of the present invention takes less time than the bottle test method, can reduce the errors caused by manual operation, and provides reference and basis for the rapid demulsification ability of demulsifiers used in oilfield production. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 It is a schematic diagram of the experimental device for the evaluation method of the rapid demulsification performance of the crude oil demulsifier of the present invention.

[0030] Figure 2a It is a column chart of the screening results of the oil-water interface film volume.

[0031] Figure 2b It is a column chart of the screening results of the droplet volume.

[0032] Figure 2c It is a column chart of the screening results of the oil-water interface equilibrium time.

[0033] Figure 2d It is a column chart of the screening results of the simulated oil component ratio.

[0034] Figure 3 It is a flow chart of an evaluation method for the rapid demulsification performance of a crude oil demulsifier disclosed in the present invention.

[0035] Wherein:

[0036] a - high-speed camera, b - sample cell, c - syringe, d - light source, e - control system, f - support frame and drive system DETAILED DESCRIPTION OF THE INVENTION

[0037] The following is a detailed description of the specific embodiments of the present invention.

[0038] The following further elaborates on the technical solutions of the present invention in combination with specific embodiments, but the protection scope of the present invention is not limited thereto. At the same time, the experimental methods described in the following embodiments are all conventional methods unless otherwise specified; the reagents and materials described are all commercially available unless otherwise specified.

[0039] In this application: for the process parameters related to time, the measurement unit is seconds, such as the oil-water interface film rupture time.

[0040] The unit of the interfacial dilatational elastic modulus is all mN / m 2 .

[0041] The crude oil emulsion samples and demulsifiers in the following embodiments are from the Petroleum Engineering Technology Research Institute of Shengli Oilfield. Specific Embodiment 1

[0043] A method for evaluating the rapid demulsification performance of crude oil demulsifiers, the steps are as follows:

[0044] (1) Add an appropriate amount of high-purity water to the sample cell, add an appropriate amount of simulated oil to the sample cell, and form an oil film on the water surface to simulate the oil-water interface film;

[0045] (2) Through a syringe vertically hovering above the oil-water interface film, drop a certain volume of a solution containing the demulsifier to be tested on the oil-water interface film, and record the whole process of the solution droplet containing the demulsifier to be tested breaking through the oil-water interface film by a high-speed camera, where:

[0046] Record the time t1 when the solution droplet containing the demulsifier to be tested starts to contact the oil-water interface film and the time t2 when the solution droplet containing the demulsifier to be tested breaks through the oil-water interface film, and the difference is the oil-water interface film rupture time;

[0047] (3) Use the pendant drop method to test the interfacial dilational viscoelasticity of the simulated oil and the solution containing the demulsifier to be tested, and determine the main factors controlling the stability of the oil-water interface film;

[0048] (4) Define the k value of the oil-water interface film strength coefficient.

[0049] Furthermore, in step (1), the simulated oil is a mixed liquid of crude oil and kerosene.

[0050] Furthermore, the volume ratio of the crude oil to the kerosene is 9:1.

[0051] Furthermore, in step (1), the amount of the simulated oil used is 300 μL.

[0052] Furthermore, in step (2), the volume of the solution droplet containing the demulsifier to be tested is 5 μL.

[0053] Furthermore, in step (2), the concentration of the solution of the demulsifier to be tested is 200 mg / L.

[0054] Furthermore, in step (2), the high-speed camera is located on one side of the sample cell, and the absolute height of the lens of the high-speed camera is adapted to the horizontal height of the oil-water interface film.

[0055] Furthermore, in step (3), the instrument used for the pendant drop method is an interfacial rheometer.

[0056] Furthermore, in step (4), the k value of the oil-water interface film strength coefficient is the ratio of the oil-water interface film rupture time obtained in step (2) to the factors controlling the stability of the oil-water interface film determined in step (3). Specific Example 2

[0058] A method for evaluating the rapid demulsification performance of a crude oil demulsifier is as follows:

[0059] (1) Add an appropriate amount of high-purity water to a sample cell, add an appropriate amount of simulated oil to the sample cell, and form an oil film on the water surface to simulate the oil-water interface film;

[0060] (2) Through a syringe vertically hovering above the oil-water interface film, drop a certain volume of a solution containing the demulsifier to be tested on the oil-water interface film, and record the whole process of the solution droplet containing the demulsifier to be tested breaking through the oil-water interface film with a high-speed camera, where:

[0061] Record the time t1 when the solution droplet containing the demulsifier to be tested starts to contact the oil-water interface film and the time t2 when the solution droplet containing the demulsifier to be tested breaks through the oil-water interface film, and the difference therebetween is the oil-water interface film rupture time;

[0062] (3) Use the pendant drop method to test the interfacial dilatational viscoelasticity of the simulated oil and the solution containing the demulsifier to be tested, and determine the main factors controlling the stability of the oil-water interface film;

[0063] (4) Define the k value of the oil-water interface film strength coefficient.

[0064] Further, in step (1), the simulated oil is a mixed liquid of crude oil and kerosene.

[0065] Furthermore, the volume ratio of the crude oil to the kerosene is 9:1.

[0066] Further, in step (1), the amount of the simulated oil used is 2000 μL.

[0067] Further, in step (2), the volume of the solution droplet containing the demulsifier to be tested is 15 μL.

[0068] Further, in step (2), the concentration of the solution of the demulsifier to be tested is 150 mg / L.

[0069] Further, in step (2), the high-speed camera is located on one side of the sample cell, and the absolute height of the lens of the high-speed camera is adapted to the horizontal height of the oil-water interface film.

[0070] Further, in step (3), the instrument used for the pendant drop method is a high-temperature and high-pressure interfacial rheometer.

[0071] Further, in step (4), the k value of the oil-water interface film strength coefficient is the ratio of the oil-water interface film rupture time obtained in step (2) to the factors controlling the stability of the oil-water interface film determined in step (3). Specific Example 3

[0073] An evaluation method for the rapid demulsification performance of crude oil demulsifiers is as follows:

[0074] (1) Add 25 mL of high-purity water to the sample cell, and add 800 μL of simulated oil to the sample cell to form an oil film on the water surface to simulate the oil-water interface film.

[0075] (2) Through a syringe vertically hovering above the oil-water interface film, drop 10 μL of micro-droplets of the solution containing the demulsifier to be tested on the oil-water interface film, and record the whole process of the solution droplets containing the demulsifier to be tested breaking through the oil-water interface film by a high-speed camera, where:

[0076] Record the time t1 when the solution droplets containing the demulsifier to be tested start to contact the oil-water interface film and the time t2 when the solution droplets containing the demulsifier to be tested break through the oil-water interface film. The difference is the oil-water interface film rupture time, where:

[0077] The demulsifier concentration is 100 mg / L;

[0078] (3) Use the pendant drop method to test the interfacial dilational viscoelasticity of the simulated oil and the aqueous solution of the demulsifier to be tested, and select the main factor controlling the stability of the oil-water interface film as the interfacial dilational elastic modulus;

[0079] (4) Define the oil-water interface film strength coefficient k value.

[0080] The experimental results are shown in Table 1.

[0081] Table 1 Evaluation results of demulsifiers

[0082]

[0083] It can be seen from Table 1 that the magnitude of the oil-water interface film strength coefficient k value shows obvious differences due to different demulsifiers, where:

[0084] The reason why the oil-water interface film rupture time (s) is in the form of "302.8 ± 8.19" is the result of multiple repeated experiments. When calculating the oil-water interface film strength coefficient k value, the middle value is taken for all.

[0085] The corresponding relationship between the oil-water interface film strength coefficient k value of the demulsifier is: CR-C07 > CR-201 > PR-106 > SL > PR-205.

[0086] Performance test

[0087] Experimental Example 1: Use high-purity water droplets to screen the appropriate conditions for steps (1)-(2) above

[0088] When the experimental conditions are different, an oil film formed on the high-purity water surface is used as the oil-water interface film, and its rupture process is significantly different. For the convenience of comparison, experimental conditions with smaller experimental errors and longer rupture times of the oil-water interface film should be selected to achieve the purpose of making a significant difference in the rupture time of the oil-water interface film after adding the demulsifier.

[0089] The possible influencing factors affecting the rupture time of the oil-water interface film include the volume of the oil-water interface film, the volume of the droplets, the oil-water interface equilibrium time, and the proportion of the simulated oil components, etc.

[0090] The schematic diagram of the experimental device used in the experiment is as Figure 1 shown. It includes a high-speed camera a, a sample cell b, a syringe c, a light source d, a control system e, a support frame, and a drive system f.

[0091] The control variable method is used to optimize the conditions of the above four factors respectively, among which:

[0092] The selected volumes of the oil-water interface film are 300 μL, 400 μL, 500 μL, 600 μL, 700 μL, 800 μL, 900 μL, 1 mL, 1.5 mL, and 2 mL respectively;

[0093] The droplet volumes are 2 μL, 5 μL, 10 μL, and 15 μL respectively;

[0094] The oil-water interface equilibrium times are 0 min, 10 min, 20 min, 30 min, 40 min, 50 min, and 60 min respectively;

[0095] The ratios of crude oil to kerosene in the simulated oil are 1:1, 7:3, 9:1, and pure crude oil respectively for the simulation experiment of the rupture process of the oil-water interface film. The experimental results are shown in Figures 2a - 2d .

[0096] From Figure 2a it can be seen that the rupture time of the oil-water interface film is not a strictly proportional or inverse proportional relationship with the volume of the oil-water interface film. For example, when the volume of the oil-water interface film is 600 μL and 700 μL, the rupture times of the oil-water interface film are both less than 10 s. Therefore, the volume of the oil-water interface film with a longer rupture time, 800 μL, is selected;

[0097] From Figure 2b it can be seen that the larger the droplet volume, the longer the rupture time of the oil-water interface film. Although the rupture time of the oil-water interface film is the longest when the droplet volume is 15 μL, due to the large volume, it is easy to be divided into two droplets and drip. Therefore, in the next experiment, the droplet volume with a relatively long rupture time of the oil-water interface film (10 μL) is selected for the experiment;

[0098] From Figure 2cIt can be seen that the oil-water interface equilibrium time has little relation with the oil-water interface film rupture time. When the oil-water interface equilibrium time is 10, 30, or 60 minutes, the oil-water interface film rupture time exceeds 5 seconds, and for the rest of the time, it is below 5 seconds. In order to complete the experiment relatively quickly and achieve the expected results, the selected oil-water interface equilibrium time is 10 minutes;

[0099] It can be seen from Figure 2d that the oil-water interface film rupture time is directly proportional to the ratio of crude oil to kerosene in the simulated oil. Although the oil-water interface film rupture time is the longest when the oil phase is pure crude oil, its error is also the largest. Therefore, the ratio of crude oil to kerosene (9:1) with a relatively long oil-water interface film rupture time and relatively small error is selected for the experiment.

[0100] Test Example 2: The corresponding relationship between the oil-water interface film strength coefficient k value of the demulsifier determined in Specific Example 3 and the evaluation result of the dehydration rate by the bottle test method

[0101] The evaluation steps of the demulsifier by the bottle test method are as follows: First, prepare a crude oil emulsion with a water content of about 50%. Then, take 20 mL and put it into a stoppered graduated cylinder, add 200 μL of the prepared 10 g / L demulsifier solution, shake it up and down by hand more than 100 times, record the volume of the separated water, and calculate the dehydration rate. The corresponding relationship between the experimental results and the oil-water interface film strength coefficient k value of the demulsifier determined in Specific Example 3 is shown in Table 2.

[0102] Table 2 Comparison relationship between the evaluation method of the present invention and the bottle test method

[0103] Demulsifier Dehydration rate in 30 min by bottle test (%) Coefficient k value of oil - water interfacial film strength PR - 205 15 23.15 PR - 106 22 41.46 CR - 201 24 48.26 CR - C07 27 57.24 SL 19 30.53

[0104] It can be seen from Table 2 that the dehydration performance relationship of each demulsifier obtained by the bottle test method is: CR-C07 > CR-201 > PR-106 > SL > PR-205.

[0105] This relationship is consistent with the corresponding relationship between the oil-water interface film strength coefficient k values of each demulsifier determined in Specific Example 3, indicating that the larger the oil-water interface film strength coefficient k value, the better the dehydration effect, and there is a positive correlation trend between the oil-water interface film strength coefficient k value and the macroscopic dehydration rate. The above results show that the demulsifier can be evaluated by the oil-water interface film strength coefficient k value instead of the bottle test method.

[0106] In Specific Example 3, the experimental time is for the test of the oil-water interface film rupture time and the test of the interfacial dilational viscoelasticity. The time consumed for the test of the oil-water interface film rupture time is about 15 minutes, and the time consumed for the test of the interfacial dilational viscoelasticity is about 40 minutes. Therefore, the total experimental time is about 1 hour, which shortens the time compared with the bottle test method. The whole experiment is basically operated by instruments, reducing the error caused by manual operation. The oil-water interface film strength coefficient k value is a quantitative parameter, which is convenient for comparison.

[0107] The above has made a detailed description of the embodiments of the present invention. However, the present invention is not limited to the above embodiments, and various changes can be made without departing from the gist of the present invention within the scope of knowledge possessed by those of ordinary skill in the art.

Claims

1. A method for evaluating the rapid demulsification performance of a crude oil demulsifier, characterized in that: Here are the steps: (1) adding an appropriate amount of high-purity water into a sample pool, adding an appropriate amount of simulated oil into the sample pool, and forming an oil film on the water surface to simulate an oil-water interface film; (2) adding a certain volume of a solution containing a demulsifier to be tested onto the oil-water interface membrane by means of a syringe suspended vertically above the oil-water interface membrane, and recording the entire process of the droplets of the solution containing the demulsifier to be tested breaking through the oil-water interface membrane by means of a high-speed camera, wherein: Record the time t1 when the droplet of the solution containing the demulsifier to be tested begins to contact the oil-water interface film and the time t2 when the droplet of the solution containing the demulsifier to be tested breaks through the oil-water interface film, and the difference between them is the oil-water interface film rupture time; (3) using a hanging drop method to test the interfacial dilation viscoelasticity of the simulated oil and the solution containing the demulsifier to be tested, and determining the main factors controlling the stability of the oil-water interface film; (4) Define the oil-water interface film strength coefficient k.

2. The method for evaluating the rapid demulsification performance of a crude oil demulsifier according to claim 1, characterized in that: The simulated oil in step (1) is a mixture of crude oil and kerosene.

3. The method for evaluating the rapid demulsification performance of a crude oil demulsifier according to claim 2, characterized in that: The volume ratio of the crude oil to the kerosene is 9:

1.

4. The method for evaluating the rapid demulsification performance of a crude oil demulsifier according to claim 1, characterized in that: In step (1), the amount of the simulated oil used is 300-2000 μL.

5. The method for evaluating the rapid demulsification performance of a crude oil demulsifier according to claim 4, characterized in that: In step (1), the amount of the simulated oil used is 800 μL.

6. The method for evaluating the rapid demulsification performance of a crude oil demulsifier according to claim 1, characterized in that: In step (2), the volume of the solution droplets containing the demulsifier to be tested is 5-15 μL, preferably 10 μL.

7. The method for evaluating the rapid demulsification performance of a crude oil demulsifier according to claim 1, characterized in that: The concentration of the solution of the demulsifier to be tested in step (2) is 100-200 mg / L.

8. The method for evaluating the rapid demulsification performance of a crude oil demulsifier according to claim 1, characterized in that: In step (2), the high-speed camera is located on one side of the sample pool, and the absolute height of the lens of the high-speed camera is adapted to the horizontal height of the oil-water interface film.

9. The method for evaluating the rapid demulsification performance of a crude oil demulsifier according to claim 1, characterized in that: In step (3), the instrument used in the hanging drop method is an interfacial rheometer, preferably a high temperature and high pressure interfacial rheometer.

10. The method for evaluating the rapid demulsification performance of a crude oil demulsifier according to claim 1, characterized in that: The oil-water interface film strength coefficient k value in step (4) is the ratio of the oil-water interface film rupture time obtained in step (2) to the oil-water interface film stability control determined in step (3).

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