Pore throat asphaltene deposition test system and rock core asphaltene rapid evaluation method

Abstract

The invention discloses a pore throat asphaltene deposition test system and a rock core asphaltene rapid evaluation method, and the test system mainly comprises a micro-nano simulation tube used for simulating a pore throat, an injection module used for injecting crude oil and CO2 into the micro-nano simulation tube, a purging module used for purging and returning the crude oil under the action of CO2 in the micro-nano simulation tube, and a sample loading module used for loading the crude oil into the micro-nano simulation tube, and the collecting module is used for collecting the backflow crude oil. By adopting the scheme, the asphaltene deposition condition of crude oil in the simulated size pore throat under the action of CO2 can be more accurately measured, the test result is more accurate, the operation is relatively more convenient, the consumption of asphaltene in an intermediate link is reduced, the calculation precision is favorably improved, the asphaltene deposition rule of an oil reservoir corresponding to a rock core is favorably and quickly determined, and the calculation efficiency is improved. And a more accurate theoretical basis is provided for CO2 injection development.

Description

Technical Field

[0001] The invention belongs to the technical field of oil reservoir development, and in particular relates to a pore throat asphaltene deposition testing system and a core asphaltene rapid evaluation method. Background Art

[0002] CO2 injection is one of the important means of oil reservoir exploitation and is widely used in the development of tight reservoirs. CO2 gas has better injectability than water. Relying on the special physical and chemical properties of CO2 gas, it can significantly reduce viscosity and swell during its contact with crude oil, improving the development effect of tight oil reservoirs. However, the asphaltene deposition produced by crude oil under the action of CO2 will damage the oil-bearing reservoir, which seriously restricts the development effect of CO2 injection in tight oil reservoirs. Asphaltene is the polar component with the largest relative molecular weight in crude oil. During the CO2 injection development process, CO2 dissolves in crude oil or extracts light components of crude oil, which will cause changes in the thermodynamic parameters and composition of the crude oil system, causing the asphaltene in the crude oil to precipitate and aggregate into asphaltene solid particles, changing the pore throat structure and reducing the connectivity between pore throats. Crude oil asphaltene in the micro-nano pore throats of tight reservoirs is more likely to precipitate under the influence of the nano-confinement effect, and the precipitation amount is much higher than that of conventional reservoirs.

[0003] Therefore, before the CO2 injection mining construction, it is particularly important to accurately study and evaluate the impact of asphaltene produced during the CO2 injection mining process on the development effect. In the prior art, some related methods and technologies have also appeared, such as the patent number "CN113916926B", named "Pore throat blockage characteristics evaluation method under CO2 drive asphaltene deposition in tight reservoirs", in which the asphaltene content in crude oil before and after CO2 displacement in the core and the core nuclear magnetic resonance T2 spectrum scanning results are compared to obtain the CO2 drive asphaltene deposition amount and pore throat blockage degree. However, this method can only analyze and test the CO2 drive asphaltene deposition amount at the core scale, and the dense core is composed of many pore throats of different sizes, resulting in different asphaltene deposition amounts in pore throats of different sizes during CO2 displacement. The nuclear magnetic resonance analysis results cannot quantitatively describe the corresponding influence of the core pore throat size, so this method is not suitable for the ability of crude oil asphaltene rules in micro-nano pore throats. In addition, due to the limitation of experimental core length, the contact time between CO2 and crude oil is short during the displacement process, which results in this method being unable to simulate the long-term contact between CO2 and crude oil during the production process and unable to meet the needs of on-site production.

[0004] In the patent with the patent number "CN117192068A" and the name "An experimental device for the deposition characteristics of crude oil containing asphaltene during CO2 injection and a quantitative evaluation method", a segmented modular heating method is used to simulate the temperature environment in the wellbore. A core clamp is set upstream to simulate the flow of crude oil in the formation, and the occurrence of asphaltene deposition is observed through a reserved observation window. However, this method can only test the deposition phenomenon of asphaltene in the wellbore, and cannot intuitively analyze the asphaltene law of crude oil in micro-nano pore throats. Summary of the invention

[0005] In view of this, the present invention provides a pore throat asphaltene deposition test system and a core asphaltene rapid evaluation method to solve the problem that the prior art cannot accurately and quantitatively analyze the effect of asphaltene on pore throats.

[0006] The technical solution is as follows:

[0007] A pore throat asphaltene deposition test system, the key of which is that it includes the following steps:

[0008] The micro-nano simulated tube has an inlet micro-tube holder and an outlet micro-tube holder 120 connected at both ends, the upstream micro-tube holder has an inlet end inflow channel and an inlet end outflow channel connected to the micro-nano simulated tube, and the outlet micro-tube holder has an outlet end inflow channel and an outlet end outflow channel connected to the micro-nano simulated tube;

[0009] The injection module is connected to the inlet end inflow channel through a filling pipeline and is used to fill crude oil and CO2 into the micro-nano simulation tube;

[0010] The purge module is connected to the outlet inflow channel through a purge pipeline, and is used to purge the crude oil in the micro-nano simulation tube that has been acted upon by CO2 back to the inlet outflow channel;

[0011] The collection module is connected to the inlet outflow channel through a collection pipeline, and is used to collect the crude oil flowing back from the inlet outflow channel 112 .

[0012] A method for rapid evaluation of core asphaltene, the key of which is to include the following steps:

[0013] S1. Select typical core samples and test the core samples by porosity and high-pressure mercury injection to obtain the core porosity, permeability, maximum pore throat radius and median radius, as well as the capillary pressure curve and pore throat distribution histogram of mercury injection test;

[0014] S2, using the above-mentioned pore throat asphaltene deposition test system to measure the asphaltene deposition amount of a single simulated pore throat, in this process, according to the pore throat distribution histogram obtained in step S1, multiple micro-nano simulated tubes with different radii are selected for testing with reference to the pore throat distribution frequency, and the asphaltene deposition amounts corresponding to the micro-nano simulated tubes 100 with different radii are obtained;

[0015] S3, fitting the measured data in step S2 to obtain a relationship equation and a relationship diagram between the micro-nano simulated tube and the asphaltene deposition amount;

[0016] S4. Based on the fitting results in step S3, the asphaltene deposition amount under different pore throat diameters in step S1 is calculated, and then according to the formula Calculate the amount of asphaltene deposited in the core sample;

[0017] Among them, W c is the asphaltene deposition amount of the core sample, wt%; F ri is the distribution frequency of a certain pore throat radius, %; W ri is the asphaltene deposition amount at a certain pore throat radius, wt%.

[0018] Compared with the prior art, the pore throat asphaltene deposition test system and core asphaltene rapid evaluation method provided by the present invention have the following beneficial effects:

[0019] 1. The test system using micro-nano simulation tubes and reflux purge can effectively reduce residual oil and more accurately measure the asphaltene deposition of crude oil in pore throats of simulated size under the action of CO2, making the test results more accurate.

[0020] 2. The concentration of asphaltene is obtained by photometric analysis of a toluene mixed solution containing asphaltene, and then the mass of asphaltene is calculated. The operation is relatively more convenient and reduces the consumption of asphaltene in the intermediate links, which is conducive to improving the calculation accuracy.

[0021] 3. Mercury injection experiments are used to make more accurate analysis and calculation of the pore throat distribution of core samples. Combined with the precise asphaltene deposition of single pore throats, accurate asphaltene conditions of core samples can be obtained, which is conducive to quickly clarifying the asphaltene deposition law of the core corresponding to the reservoir and providing a more accurate theoretical basis for CO2 gas injection development. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a schematic diagram of the test system of the present invention;

[0023] Figure 2 Schematic diagram of the inlet microtube holder structure;

[0024] Figure 3 Schematic diagram of the structure of the outlet microtube holder;

[0025] Figure 4 It is a schematic diagram of the structure of the PES filter;

[0026] Figure 5 It is a schematic diagram of the pressure buffer structure;

[0027] Figure 6Schematic diagram of light absorption curves of toluene mixed solutions with different asphaltene concentrations;

[0028] Figure 7 is the standard working curve of toluene mixed solution with different asphaltene concentrations;

[0029] Figure 8 The graph and equation showing the relationship between the amount of asphaltene deposited and the inner diameter of the micro-nano simulated tube in this embodiment;

[0030] Fig. 9 Mercury injection curve of core samples. DETAILED DESCRIPTION

[0031] The present invention will be further described in detail below in conjunction with the accompanying drawings.

[0032] refer to Figures 1 to 9 The pore-throat asphaltene deposition test system and the core asphaltene rapid evaluation method shown in the figure, wherein the test system mainly includes a micro-nano simulation tube 100, an injection module 200, a purge module 300, and a collection module 400.

[0033] Among them, the micro-nano simulation tube 100 is mainly used to simulate the pore throat. Different inner diameters and different lengths can be selected as needed. Generally, a micron-level thick-walled elastic fused silica capillary is preferably used. The two ends of the micro-nano simulation tube 100 are clamped and fixed by an inlet micro-tube clamp 110 and an outlet micro-tube clamp 120 respectively. The structures of the inlet micro-tube clamp 110 and the outlet micro-tube clamp 120 are basically the same. The upstream micro-tube clamp 110 has an inlet end inflow channel 111 and an inlet end outflow channel connected to the micro-nano simulation tube 100. 112, the outlet microtube clamp 120 has an outlet inflow channel 121 and an outlet outflow channel 122 connected to the micro-nano simulated tube 100. In order to facilitate the clamping and fixing of the two ends of the micro-nano simulated tube 100, an inlet end fixer 113 is provided on the inlet microtube clamp 110, and an outlet end fixer 123 is provided on the outlet microtube clamp 120. The structure of the two clamps in this embodiment is similar to the structure of patent CN108562514A, and the difference lies in the design of the inlet and outlet.

[0034] The injection module 200 is connected to the inlet end inflow channel 111 through the filling pipeline 210, and is used to fill crude oil and CO2 into the micro-nano simulated tube 100.

[0035] The purge module 300 is connected to the outlet inflow channel 121 through the purge pipeline 310 , and is used to purge the crude oil in the micro-nano simulated tube 100 that has been acted upon by CO2 back to the inlet outflow channel 112 .

[0036] The collection module 400 is connected to the inlet outflow channel 112 through a collection pipeline 410 and is used to collect crude oil flowing back from the inlet outflow channel 112 .

[0037] Specifically, the injection module 200 includes a micro-injection pump A220, a crude oil container 230 and a CO2 container 240. The crude oil container 230 and the CO2 container 240 are arranged in parallel on the filling pipeline 210 and have corresponding valves. As shown in the figure, the filling pipeline 210 is provided with a pressure master control valve A211, a gas injection control valve 212, an oil injection control valve 213, a downstream master control valve 214 and a near-inlet valve 215 in sequence, wherein the inlet valve 215 is relatively close to the inlet end inflow channel 111.

[0038] The collection module 400 includes a recovery valve 411 , a PES filter 420 , a pressure master control valve B412 and a micro back pressure control pump 430 which are sequentially connected to the collection pipeline 410 in a direction away from the inlet outflow channel 112 .

[0039] A pressure buffer 440 is provided between the PES filter 420 and the micro back pressure control pump 430. The PES filter 420 mainly includes a sealing base 421 which is generally in a concave shape. A PES filter membrane 422 is laid on the bottom of the inner cavity of the sealing base 421. In this embodiment, a polyethersulfone filter membrane with a pore size of 0.05 μm is preferably used as the PES filter membrane 422. In addition, the sealing base 421 is provided with a sealing cover 423, and the sealing cover 423 is connected to the sealing base 421 by bolts. In the specific implementation process, there is a mutually coordinated sealing structure between the two. The sealing cover 423 has a fluid inlet, and the sealing base 421 has a fluid outlet, wherein the fluid inlet is connected to the inlet outflow channel 112, and the fluid inlet is connected to the pressure buffer 440.

[0040] The pressure buffer 440 is a hollow structure, which mainly plays the role of pressure buffering and back pressure, and has better pressure control accuracy. It has a liquid collecting chamber 442 and a pressure chamber 443 separated by a rubber piston 441. The pressure chamber 443 is filled with pressure transmission liquid. The inlet of the liquid collecting chamber 442 is connected to the fluid outlet of the PES filter 420 through a pipeline. Usually, the liquid collecting chamber 442 is a transparent structure and has scale lines to quickly read the internal fluid capacity. The outlet of the pressure chamber 443 is connected to the micro back pressure control pump 430.

[0041] It should be noted that in order to improve the accuracy of the results, in this embodiment, the collection pipeline 410 uses a micron-level pipeline, which can minimize the error caused by loss during the experiment.

[0042] The purge module 300 includes a nitrogen container 320 and a micro injection pump B330 disposed on a purge line 310. Figure 1As shown, a purge main control valve 311, a nitrogen outlet valve 312 and a purge pressure control valve 313 are provided in sequence on the purge pipeline 310 in the direction away from the inlet end and flowing into the channel 111. In the present application, the micro-injection pump B330 is similar to the micro-injection pump A220, and has an accuracy of 0.000001 mL / min and a maximum pressure of 70 MPa.

[0043] In addition, in order to further improve the reliability of the experimental simulation results, a pressure acquisition module 500 and a constant temperature device 600 are usually also provided. The pressure acquisition module 500 includes an inlet pressure sensor 510 installed on the filling pipeline 210, an outlet pressure sensor 520 on the purge pipeline 310, and a pressure acquisition terminal 530 for receiving and reading the pressure signals of the inlet pressure sensor 510 and the outlet pressure sensor 520. The inlet pressure sensor 510 and the outlet pressure sensor 520 are both close to the ends of the corresponding micro-nano simulation tube 100. It should be noted that the outlet pressure sensor 520 is closer to the inlet inflow channel 111 than the purge main control valve 311, thereby achieving the purpose of accurate pressure monitoring.

[0044] The constant temperature device 600 is mainly used to control the temperature of the simulated environment. During the test, except for the micro-injection pump B330, the micro-injection pump A220, the micro-back pressure control pump 430 and the pressure acquisition terminal 530 which are outside the constant temperature device 600, all others are inside the constant temperature device 600, which can more realistically simulate the reservoir temperature environment.

[0045] In specific implementation, in order to avoid excessive injection during crude oil injection, which causes crude oil to flow out of the outlet outflow channel 122 and pollute the environment, the outlet outflow channel 122 is connected to a conventional collection control valve 140 and a conventional liquid collector 130 .

[0046] Based on the above-mentioned pore throat asphaltene deposition test system, this application simultaneously proposes a core asphaltene rapid evaluation method, which is mainly used to understand the deposition conditions and laws of asphaltene in reservoir cores under the action of CO2, and mainly includes the following steps:

[0047] Step S1, select a typical core sample, and test the core sample through porosity and high-pressure mercury injection to obtain the core porosity, permeability, maximum pore throat radius and median radius, as well as the capillary pressure curve and pore throat distribution histogram of the mercury injection test.

[0048] Step S2, using the above-mentioned pore throat asphaltene deposition test system to measure the asphaltene deposition amount of a single simulated pore throat. In this process, according to the pore throat distribution histogram obtained in step S1, multiple micro-nano simulated tubes 100 with different radii are selected for testing with reference to the pore throat distribution frequency to obtain the asphaltene deposition amounts corresponding to the micro-nano simulated tubes 100 with different radii.

[0049] Step S3, fitting the measured data in step S2 to obtain a relationship equation and a relationship diagram between the micro-nano simulated tube 100 and the asphaltene deposition amount.

[0050] Step S4: Based on the fitting result in step S3, the asphaltene deposition amount at different pore throat diameters in step S1 is calculated, and then the asphaltene deposition amount of the core sample is calculated according to formula (1).

[0051]

[0052] In the above formula (1), W c is the asphaltene deposition amount of the core sample, wt%; F ri is the distribution frequency of a certain pore throat radius, %; W ri is the asphaltene deposition amount at a certain pore throat radius, wt%.

[0053] It should be noted that the measurement process of step S2 using the pore throat asphaltene deposition test system includes the following subdivision steps:

[0054] Step S2.1: Select crude oil from the same reservoir as the core sample and measure the initial crude oil asphaltene content W i ,

[0055] Step S2.2, add the selected crude oil into the crude oil container 230, and inject the crude oil in the crude oil container 230 into the micro-nano simulated tube 100 through the micro injection pump A220 until crude oil flows out of the outlet outlet channel 122, and close all valves downstream of the outlet microtube clamp 120.

[0056] Step S2.3, use the micro-injection pump A220 to inject the CO2 in the CO2 container 240 into the micro-nano simulated tube 100, monitor the pressure value inside the micro-nano simulated tube 100 through the pressure acquisition module 500, adjust the micro-injection pump A220 to the constant pressure injection mode after reaching the designed value, and close all valves upstream of the inlet microtube clamp 110 after the pressure stabilizes.

[0057] Step S2.4, after stabilizing and standing for a set time, adjust the micro-back pressure control pump 430 to a constant pressure injection mode, and set the pressure value to 0.1-0.6 MPa lower than the current micro-nano simulated tube 100. Open the corresponding valve of the inlet outflow channel 112, and the crude oil in the micro-nano simulated tube 100 that has been acted upon by CO2 passes through the PES filter 420 and enters the pressure buffer 440.

[0058] Step S2.5, adjust the micro-injection pump B330 to a constant pressure injection pressure of 0.1-0.6 MPa higher than that of the micro-nano simulated tube 100. When the pressure stabilizes, open the valve on the purge line 310, and use nitrogen to push the remaining crude oil in the micro-nano simulated tube 100 through the PES filter 420 and into the pressure buffer 440.

[0059] Step S2.6: When all the crude oil in the micro-nano simulated tube 100 passes through the PES filter 420, close the valve between the PES filter 420 and the inlet outflow channel 112, lower the pressure setting value of the micro back pressure control pump 430, and reduce the pressure in the pressure buffer 440 to near atmospheric pressure.

[0060] Step S2.7, taking out the PES filter membrane of the PES filter 420, immersing the PES filter membrane in a toluene solvent, stirring to form a toluene mixed solution containing asphaltene, and obtaining the asphaltene concentration in the toluene mixed solution by photometric analysis.

[0061] Step S2.8: Calculate the crude oil mass M in the micro-nano simulated tube 100 according to the parameters of the micro-nano simulated tube 100 and the crude oil parameters. o , calculate the asphaltene mass M according to the asphaltene concentration in the toluene mixed solution a , according to the crude oil quality M o and asphaltene mass M a The asphaltene content W of the crude oil in the micro-nano simulation tube 100 after being acted upon by CO2 is calculated. o , combined with the initial crude oil asphaltene content W i The asphaltene deposition amount W in the micro-nano simulation tube 100 after the action of CO2 is calculated. a ;

[0062] The above crude oil quality

[0063] Among them, M o is the mass of crude oil in the micro-nano simulation tube, mg; D is the inner diameter of the micro-nano simulation tube, μm; L is the length of the micro-nano simulation tube, cm; ρ ο is the density of crude oil under specific simulated formation pressure, g / cm 3 .

[0064] The above asphaltene mass M a =V m ×λ a (3)

[0065] Among them, M a is the mass of asphaltene, mg; V m is the volume of the solution, L; λ a is the asphaltene concentration in the solution, mg / L.

[0066] Asphaltene content

[0067] The above W a =W i -W o (5)

[0068] Among them, W a is the asphaltene deposition amount, wt%; W i is the initial crude oil asphaltene content, wt%; W o is the crude oil asphaltene content in the micro-nano simulated tube, wt%.

[0069] Step S2.9, repeating steps S2.2 to S2.8 to calculate the asphaltene deposition amounts corresponding to the micro-nano simulated tubes 100 with different radii.

[0070] refer to Figures 1 to 9 The core of a reservoir is evaluated using the pore throat asphaltene deposition test system and the core asphaltene rapid evaluation method provided in this application. The specific process is as follows:

[0071] The first step is to select typical core samples of the reservoir and use porosity and high-pressure mercury injection tests to obtain the mercury injection curve as shown in the figure. Fig. 9 As shown, the core porosity was measured to be 6.7%, the permeability was 0.15 mD, the maximum pore throat radius was 4.594 μm, and the median radius was 0.453 μm.

[0072] The crude oil from the same reservoir was selected for chromatographic analysis, and the density of the crude oil was measured to be 0.91 g / cm 3 , and the four-component analysis results were obtained, among which the asphaltene content was 2.54wt%. On the other hand, the crude oil was directly passed through the PES filter 420, and then the PES filter membrane 422 was taken out and the asphaltene mass was obtained by weighing. In addition, the PES filter membrane 422 with asphaltene attached was immersed in a toluene solvent and stirred thoroughly to obtain a toluene mixed solution containing asphaltene. The band was selected from 200nm to 500nm under the ultraviolet spectrophotometer and the band was scanned to obtain the absorption curves of the toluene solution under different asphaltene concentrations, as shown in FIG. Figure 6 As shown. Each curve of toluene solution at different asphaltene concentrations has an obvious absorption peak near 280nm. The absorbance corresponding to the maximum absorption wavelength in the absorbance and scanning wavelength relationship curve is selected to make the concentration and absorbance relationship curve, that is, the standard working curve, as shown in Figure 7 According to the standard working curve, the relationship between concentration and absorbance can be expressed, so the concentration of asphaltene can be calibrated according to the absorbance of toluene solution.

[0073] At the same time, the selected crude oil is loaded into the CO2 container 240 for subsequent testing.

[0074] The second step is to control the temperature in the constant temperature device 600 to be close to the reservoir temperature, which is about 70°C. The inner diameter of the micro-nano simulated tube 100 is 5μm and the length is 20cm. The pressure master control valve A211, the oil injection control valve 213, the downstream master control valve 214 and the near-inlet valve 215, as well as the conventional collection control valve 140 are opened. The remaining valves are all in the closed state. Then, the micro-injection pump A220 is used to allow crude oil to enter the micro-nano simulated tube 100. When the conventional liquid collector 130 can continuously collect crude oil, the injection is stopped and the conventional collection control valve 140 is closed.

[0075] The third step is to use the micro-injection pump A220 to inject CO2 into the micro-nano simulated tube 100. When the pressure monitored by the inlet pressure sensor 510 reaches about 10 MPa, the micro-injection pump A220 is adjusted to the constant pressure injection mode. After the pressure stabilizes at 10 MPa, the near-inlet valve 215 and all upstream valves are closed to allow CO2 to fully react with the crude oil in the micro-nano simulated tube 100. The mass of the crude oil inside the micro-nano simulated tube 100 is calculated to be 0.00357 mg by formula (2).

[0076] Step 4: After stabilization for 2 hours (this time can be adjusted as needed or determined in combination with the production site), set the micro-back pressure control pump 430 to the constant pressure injection mode, set the pressure value to 9.5MPa, and then open the recovery valve 411 and the pressure master control valve B412 to allow the crude oil in the micro-nano simulated tube 100 to enter the pressure buffer device after passing through the PES filter 420. When all the crude oil in the micro-nano simulated tube 100 enters the pressure buffer 440, close the recovery valve 411, and gradually lower the pressure setting value of the micro-back pressure control pump 430 to reduce the pressure in the pressure buffer device to near atmospheric pressure.

[0077] The fifth step is to open the recovery valve 411, adjust the micro-injection pump B330 to the constant pressure injection mode, set the pressure value to 10.5MPa, open the valve on the purge pipeline 310, and allow the nitrogen to push the micro-nano simulation tube 100 and the remaining crude oil in the two clamps through the PES filter and enter the pressure buffer device.

[0078] When no crude oil is observed to enter the pressure buffer device, the recovery valve 411 is closed, and the pressure setting value of the micro-back pressure control pump 430 is gradually lowered to reduce the pressure in the pressure buffer device to near atmospheric pressure. The PES filter membrane 422 inside the PES filter is removed, and the PES filter membrane and the attached asphaltene are immersed in a toluene solvent and stirred thoroughly to obtain a toluene solution containing asphaltene. The absorbance of the toluene solution is tested by an ultraviolet spectrophotometer, and the asphaltene concentration is determined from the standard comparison curve. The asphaltene mass is calculated by formula (3) as 1.25×10 -4 The crude oil asphaltene content in the micro-nanotubes was calculated to be 3.51 wt% by formula (4), and the asphaltene deposition amount was calculated to be 0.97 wt% by formula (5).

[0079] By selecting micro-nano simulated tubes 100 with different inner diameters and repeating the above steps, the asphaltene deposition amounts under different sizes can be obtained. In this embodiment, according to the distribution frequency of pore throat radius in the mercury injection curve of the core sample, the inner diameters of 0.1 μm, 0.5 μm and 1 μm are mainly selected for testing. The results are shown in Table 1 below:

[0080] Table 1

[0081]

[0082] Step 6: Draw the results obtained in step 5 as shown below: Figure 8 The graph shown shows the relationship between the amount of asphaltene deposition and the inner diameter of the micro-nano simulated tube, and the corresponding relationship is obtained by data fitting. In this way, the asphaltene deposition amounts of more micro-nano simulated tubes of different sizes can be obtained based on the fitting relationship.

[0083] Step 7: The micro-nano simulated tube in this application is a simulated pore throat, combined with Fig. 9 The distribution of pore throats can be calculated by using the relationship between the asphaltene deposition amount and the inner diameter of the micro-nano simulation tube and the relationship. The asphaltene deposition amount of more pore throats with different sizes can be calculated. The calculation results are shown in Table 2 below.

[0084] Table 2

[0085]

[0086]

[0087] Finally, the asphaltene deposition amount of the core can be calculated using formula (1). In this embodiment, the asphaltene deposition amount of the core is calculated to be 1.1583 wt%.

[0088] Finally, it should be noted that the above description is only a preferred embodiment of the present invention. Under the guidance of the present invention, ordinary technicians in this field can make various similar expressions without violating the purpose and claims of the present invention, and such changes all fall within the scope of protection of the present invention.

Claims

1. A pore throat asphaltene deposition test system, characterized in that: include: A micro-nano simulated tube (100) having an inlet micro-tube holder (110) and an outlet micro-tube holder (120) connected at both ends, the upstream micro-tube holder (110) having an inlet end inflow channel (111) and an inlet end outflow channel (112) connected to the micro-nano simulated tube (100), and the outlet micro-tube holder (120) having an outlet end inflow channel (121) and an outlet end outflow channel (122) connected to the micro-nano simulated tube (100); The injection module (200) is connected to the inlet end inflow channel (111) through a filling pipeline (210) and is used to fill crude oil and CO2 into the micro-nano simulation tube (100); The purge module (300) is connected to the outlet inflow channel (121) through a purge pipeline (310) and is used to purge the crude oil in the micro-nano simulation tube (100) that has been acted upon by CO2 back to the inlet outflow channel (112); The collection module (400) is connected to the inlet outflow channel (112) through a collection pipeline (410) and is used to collect crude oil flowing back from the inlet outflow channel (112).

2. The pore throat asphaltene deposition testing system according to claim 1, characterized in that: The invention comprises a pressure acquisition module (500), wherein the pressure acquisition module (500) comprises an inlet pressure sensor (510) installed on a filling pipeline (210), an outlet pressure sensor (520) on a purge pipeline (310), and a pressure acquisition terminal (530) for receiving and reading pressure signals of the inlet pressure sensor (510) and the outlet pressure sensor (520), wherein the inlet pressure sensor (510) and the outlet pressure sensor (520) are both close to the ends of corresponding micro-nano simulation tubes (100).

3. The pore throat asphaltene deposition testing system according to claim 1 or 2, characterized in that: The collection module (400) comprises a PES filter (420) and a micro back pressure control pump (430) which are sequentially connected to the collection pipeline (410) in a direction away from the inlet outflow channel (112).

4. The pore throat asphaltene deposition testing system according to claim 3, characterized in that: A pressure buffer (440) is provided between the PES filter (420) and the micro-back pressure control pump (430). The pressure buffer (440) is a hollow structure having a liquid collecting chamber (442) and a pressure bearing chamber (443) separated by a rubber piston (441). The pressure bearing chamber (443) is filled with a pressure transmission liquid. The inlet of the liquid collecting chamber (442) is connected to the outlet of the PES filter (420) through a pipeline, and the outlet of the pressure bearing chamber (443) is connected to the micro-back pressure control pump (430).

5. The method according to claim 1 or 2, characterized in that: The injection module (200) comprises a micro injection pump A (220), a crude oil container (230) and a CO2 container (240). The crude oil container (230) and the CO2 container (240) are arranged in parallel on the filling pipeline (210) and have corresponding valves.

6. The pore throat asphaltene deposition testing system according to claim 1, characterized in that: The outlet outflow channel (122) is connected to a conventional liquid collector (130).

7. The pore throat asphaltene deposition testing system according to claim 1 or 2, characterized in that: The purge module (300) includes a nitrogen container (320) and a micro-injection pump B (330) disposed on a purge pipeline (310).

8. The pore throat asphaltene deposition testing system according to claim 1 or 2, characterized in that: It comprises a constant temperature device (600), wherein at least the micro-nano simulated tube (100) is located inside the constant temperature device (600).

9. A rapid evaluation method for core asphaltene, characterized in that: The steps include: S1. Select typical core samples and test the core samples by porosity and high-pressure mercury injection to obtain the core porosity, permeability, maximum pore throat radius and median radius, as well as the capillary pressure curve and pore throat distribution histogram of mercury injection test; S2. Using the pore throat asphaltene deposition test system as described in any one of claims 1 to 8, measuring the asphaltene deposition amount of a single simulated pore throat, in which a plurality of micro-nano simulated tubes (100) with different radii are selected for testing based on the pore throat distribution histogram obtained in step S1 and with reference to the pore throat distribution frequency, to obtain the asphaltene deposition amounts corresponding to the micro-nano simulated tubes (100) with different radii; S3, fitting the measured data in step S2 to obtain a relationship equation and a relationship diagram between the micro-nano simulated tube (100) and the asphaltene deposition amount; S4. Based on the fitting results in step S3, the asphaltene deposition amount under different pore throat diameters in step S1 is calculated, and then according to the formula Calculate the amount of asphaltene deposited in the core sample; Among them, W c is the asphaltene deposition amount of the core sample, wt%; F ri is the distribution frequency of a certain pore throat radius, %; W ri is the asphaltene deposition amount at a certain pore throat radius, wt%.

10. The method for rapid evaluation of core asphaltene according to claim 9, characterized in that: The measurement process of step S2 includes the following steps: S2.

1. Select crude oil from the same reservoir as the core sample and measure the initial crude oil asphaltene content W i ; S2.2, adding the selected crude oil into the crude oil container (230), and injecting the crude oil in the crude oil container (230) into the micro-nano simulation tube (100) through the micro injection pump A (220), until crude oil flows out of the outlet outlet channel (122), and closing all valves downstream of the outlet micro-tube holder (120); S2.3, using a micro-injection pump A (220) to inject CO2 in the CO2 container (240) into the micro-nano simulation tube (100), monitoring the pressure value in the micro-nano simulation tube (100) through the pressure acquisition module (500), adjusting the micro-injection pump A (220) to a constant pressure injection mode after reaching the designed value, and closing all valves upstream of the inlet micro-tube holder (110) after the pressure stabilizes; S2.4, after being allowed to stand for a set period of time, the micro-back pressure control pump (430) is adjusted to a constant pressure injection mode, and its pressure value is set to be 0.1-0.6 MPa lower than the current micro-nano simulated tube (100), and the corresponding valve of the inlet outflow channel (112) is opened, and the crude oil in the micro-nano simulated tube (100) that has been acted upon by CO2 passes through the PES filter (420) and then enters the pressure buffer (440); S2.5, adjusting the micro injection pump B (330) to a constant pressure injection pressure of 0.1-0.6 MPa higher than that of the micro-nano simulated tube (100); when the pressure is stable, opening the valve on the purge pipeline (310), using nitrogen to push the remaining crude oil in the micro-nano simulated tube (100) through the PES filter (420) and into the pressure buffer (440); S2.6, when all the crude oil in the micro-nano simulation tube (100) passes through the PES filter (420), the valve between the PES filter (420) and the inlet outflow channel (112) is closed, and the pressure setting value of the micro back pressure control pump (430) is lowered to reduce the pressure in the pressure buffer (440) to near atmospheric pressure; S2.7, taking out the PES filter membrane of the PES filter (420), immersing the PES filter membrane in a toluene solvent, stirring to form a toluene mixed solution containing asphaltene, and obtaining the asphaltene concentration in the toluene mixed solution by photometric analysis; S2.

8. Calculate the crude oil mass M in the micro-nano simulated tube (100) based on the parameters of the micro-nano simulated tube (100) and the crude oil parameters. o , calculate the asphaltene mass M according to the asphaltene concentration in the toluene mixed solution a , according to the crude oil quality M o and asphaltene mass M a The asphaltene content W of the crude oil in the micro-nano simulation tube (100) after being acted upon by CO2 is calculated. o , combined with the initial crude oil asphaltene content W i The asphaltene deposition amount W in the micro-nano simulation tube (100) after the action of CO2 was calculated. a ; IN a =In i -IN o Among them, W a is the asphaltene deposition amount, wt%; W i is the initial crude oil asphaltene content, wt%; W o is the crude oil asphaltene content in the micro-nano simulated tube, wt%; S2.9, repeating steps S2.2 to S2.8 to calculate the asphaltene deposition amounts corresponding to the micro-nano simulated tubes (100) with different radii.

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