A method and apparatus for testing asphaltene agglomerate deposition particles and deposition thickness

Abstract

The application discloses a kind of asphaltene agglomerated deposition particles and deposition thickness test method and equipment, under the condition of setting temperature, crude oil and settling agent are mixed, the mixture after mixing gradually enters sample tube, when mixture fills test tube, crude oil is injected into sample tube at different flow rates respectively, the inlet pressure and outlet pressure of sample tube are recorded in real time;The pressure difference of sample tube is calculated, and the deposition thickness of asphaltene in crude oil under different flow rates is calculated in real time based on the pressure difference of sample tube;When experiment ends, the deposit in mixed liquid is collected, the initial particle size of deposit in mixed liquid is obtained, the residual liquid in sample tube is replaced, the deposit precipitated in sample tube is dried and collected, and the particle size of the deposit collected at this time is obtained, the method can obtain the deposition thickness and the particle size of deposition particles of asphaltene in deposited crude oil under different flow rates, which is convenient for predicting the size of asphaltene agglomerated deposition particles and deposition thickness in application.

Description

Technical Field

[0001] This invention belongs to the technical field of asphaltene sedimentation testing in crude oil, and relates to a method and equipment for testing asphaltene agglomeration sediment particles and sedimentation thickness. Background Technology

[0002] In the petroleum industry, as the physical or chemical conditions within oil reservoirs and wellbores change, the originally stable asphaltenes in crude oil will deposit during transportation. Asphaltenes often deposit in reservoirs, pipelines, separators, and other systems along the production line. The restricted oil flow caused by asphaltenes settling can damage equipment and instruments along pipelines, resulting in significant production losses. The asphaltenes deposition process involves the adsorption and aggregation of asphaltenes molecules to form micro- and nano-particles, which then redeposit into transportation pipelines, causing blockages. Therefore, the asphaltenes molecular aggregation and deposition process in the wellbore environment is a key issue affecting oil and gas resource development and other fields.

[0003] Current research on the deposition process of asphaltene molecular aggregation in wellbore environments focuses on three aspects: First, in predicting the safety of oil and gas flow, the characteristics of asphaltene deposition in wellbore are predicted by measuring the thickness and particle size of asphaltene deposits; second, in the development of chemical reagents, the characteristics of asphaltene deposition particle composition are measured to provide a reference for the development system of asphaltene reagents; and third, in wellbore process design, the changes in asphaltene deposition thickness are measured to provide data reference for oilfield wellbore design.

[0004] In addition, the particle size of asphaltene molecular aggregates deposited in wellbore environments plays an important role in the selection of drag-reducing agents and crystallizing agents, as well as the influence of dissolved gas molecules on asphaltene agglomeration. Therefore, research on the deposition characteristics of asphaltene molecular aggregates in wellbore environments is of great significance for oil and gas resource development, wellbore injection research, and wellbore dissolved gas characteristics.

[0005] Currently, there are three main research methods for the characteristics of asphaltene agglomeration and deposition in wellbore environments: The first is computer simulation, which uses molecular dynamics simulation to obtain the agglomeration characteristics of asphaltene molecules by inputting the initial molecular structure and intermolecular force fields of the asphaltene molecules. The second is microscopic observation, where crude oil is injected into a microfluidic chip or visualization microchannel, and asphaltene agglomeration and deposition are induced by temperature reduction or the injection of a flocculant, allowing direct observation of the agglomeration and deposition. The third method involves adding crude oil to a large-volume reactor, followed by the addition of a flocculant under high temperature and pressure conditions. After asphaltene agglomeration, the deposited asphaltene is separated, and the agglomeration characteristics are observed under a microscope. Existing methods for detecting the initial flocculant concentration and corresponding initial particle size in wellbore asphaltene deposition, such as microscopy and computer simulation, cannot accurately obtain the flocculant concentration and initial particle size of the asphaltene deposits. This is because previous research methods were non-in-situ and involved separate detections, resulting in limited research on asphaltene agglomeration and deposition systems under the temperature and pressure conditions of the wellbore environment, making it impossible to simultaneously measure the particle size and deposition thickness of the asphaltene deposits. Summary of the Invention

[0006] The purpose of this invention is to solve the problem in the prior art that it is impossible to simultaneously measure the size and thickness of asphalt deposit particles in the study of asphalt, and to provide a method and equipment for testing asphalt aggregate deposit particles and deposition thickness.

[0007] To achieve the above objectives, the present invention employs the following technical solution:

[0008] A method for testing asphaltene agglomerates and deposition thickness includes the following steps:

[0009] Set the mixing temperature, mix the crude oil and the settling agent under the set temperature conditions, and gradually introduce the mixture into the sample tube, and set the pressure inside the sample tube.

[0010] When the mixture fills the test tube, crude oil is injected into the sample tube at different flow rates, and the inlet pressure and outlet pressure of the sample tube are recorded in real time.

[0011] The pressure difference of the sample tube is calculated based on the inlet and outlet pressures of the sample tube, and the deposition thickness of asphaltene in crude oil at different flow rates is calculated in real time based on the pressure difference of the sample tube.

[0012] At the end of the experiment, the sediment in the mixed liquid was collected, and the initial particle size of the sediment in the mixed liquid was obtained;

[0013] The residual liquid in the sample tube was replaced, and the sediment precipitated in the sample tube was dried and collected to obtain the particle size of the collected sediment.

[0014] A further improvement of the present invention is that:

[0015] When setting the pressure inside the sample tube, a back pressure valve is installed at the outlet of the sample tube, and the pressure at the back pressure valve is five times the atmospheric pressure.

[0016] When crude oil is injected into the sample tube at different flow rates, including 1 mL / h, 2 mL / h and 4 mL / h respectively.

[0017] For the 1 mL / h, 2 mL / h and 4 mL / h flow rates, each flow rate was maintained for 10-50 h, and the inlet and outlet pressures of the sample tube were recorded every 1-60 s.

[0018] Calculating the deposition thickness of asphaltenes in crude oil under different flow conditions includes the following steps:

[0019] The pressure drop ΔP0 across the sample tube can be expressed as:

[0020]

[0021] Where μ represents viscosity, Q represents volumetric flow rate, ro represents sample tube radius, and L represents sample tube length. If the precipitant injected into the sample tube can be uniformly deposited along the sample tube, and the deposition thickness is Δr(t), then the pressure drop ΔP(t) across sample tube 2 over time is expressed as follows:

[0022] As asphalt gradually and uniformly deposits along the inner surface of the capillary sample tube 2 with a thickness Δr(t), the pressure drop ΔP(t) changes with time (t) as follows:

[0023]

[0024] Collecting sediments from a mixed liquid and determining the initial particle size of the sediments in the mixed liquid includes the following steps:

[0025] The mixed liquid flowing out of the sample tube is collected in real time by a recovery device, and the initial particle size of the sediment is observed by scanning electron microscopy or microscopy.

[0026] The process of replacing the residual liquid in the sample tube and drying and collecting the precipitated sediment to obtain the particle size of the collected sediment includes the following steps:

[0027] Nitrogen gas is introduced into the sample tube, which replaces the mixed liquid remaining in the sample tube. The nitrogen gas continues to flow and dries the inside of the sample tube.

[0028] Toluene and tetrahydrofuran were injected into the sample tube until the effluent was completely colorless. The particle size of the effluent at this point was then observed using a liquid phase microscope.

[0029] When setting the mixing temperature, a water bath is included, which is filled with water and connected to a heater. The sample tube is placed inside the water bath.

[0030] A bituminous sedimentation testing device for the method described in this invention includes a water bath, a sample tube is provided inside the water bath, and the water bath is connected to a heating device.

[0031] The inlet of the sample tube is connected to the crude oil pump, the settling agent pump and the nitrogen pump, and the outlet of the sample tube is connected to the recovery unit.

[0032] A back pressure valve is installed at the outlet of the sample tube.

[0033] Further improvements to this equipment are as follows:

[0034] A pressure sensor is installed on the sample tube.

[0035] Compared with the prior art, the present invention has the following beneficial effects:

[0036] This invention discloses a method for testing asphaltene agglomeration deposition particles and deposition thickness. The method first simulates the actual application environment by setting temperature and pressure values, providing a foundation for accurate prediction results. In the experiment, crude oil is continuously injected into the sample tube at different flow rates. During this process, the inlet and outlet pressure differences of the sample tube are collected and calculated in real time, and the deposition thickness is calculated based on the real-time pressure difference. The changes in deposition thickness under different flow rates and pressure differences are recorded. After the experiment, the particle size of the deposits in the mixed liquid and the particle size of the deposits precipitated in the tube are observed. This method can obtain the deposition thickness and particle size of asphaltene in deposited crude oil at different flow rates. The obtained data helps improve the accuracy of existing asphaltene deposition models, facilitates the prediction of asphaltene agglomeration deposition particle size and deposition thickness in later applications, and also provides basic reference data for the later development of wellbore asphaltene chemical injection agents.

[0037] This invention discloses an asphaltene sedimentation testing device. This device can simulate the actual application environment of the wellbore, ensuring in-situ measurement of the particle size and thickness of crude oil asphaltene agglomeration deposition under the ambient temperature and pressure of the wellbore environment. During the experiment, experiments can be conducted at different crude oil flow rates according to experimental needs to obtain the deposition thickness and particle size of asphaltene in the deposited crude oil at different flow rates. The obtained data helps to improve the accuracy of existing asphaltene deposition models, facilitates the prediction of asphalt agglomeration deposition particle size and deposition thickness in later applications, and also provides basic reference data for the later development of wellbore asphaltene chemical injection agents. Moreover, this device has a simple structure and is easy to operate. Attached Figure Description

[0038] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0039] Figure 1 This is a flowchart of the present invention;

[0040] Figure 2 This is a schematic diagram of the device disclosed in this invention.

[0041] Wherein: 1-Water bath; 2-Sample tube; 3-Crude oil pump; 4-Flocculant pump; 5-Nitrogen pump; 6-Recovery unit; 7-Back pressure valve; 8-Pressure sensor; 9-Heating device; 10-T-way; 11-Data acquisition unit; 12-Computer; 13-Ultrasonic zone. Detailed Implementation

[0042] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0043] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0044] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0045] In the description of the embodiments of the present invention, it should be noted that if terms such as "upper," "lower," "horizontal," or "inner" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship commonly used when the product of the invention is in use, they are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the present invention. Furthermore, terms such as "first" and "second" are only used to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0046] Furthermore, the use of the term "horizontal" does not imply that the component must be absolutely horizontal, but rather that it can be slightly tilted. For example, "horizontal" simply means that its direction is more horizontal than "vertical," and does not mean that the structure must be completely horizontal, but can be slightly tilted.

[0047] In the description of the embodiments of the present invention, it should also be noted that, unless otherwise explicitly specified and limited, the terms "set," "install," "connect," and "link" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in the present invention according to the specific circumstances.

[0048] The present invention will now be described in further detail with reference to the accompanying drawings:

[0049] See Figure 1 This invention discloses a method for testing the particle size and thickness of asphaltene agglomerates, addressing the deposition problem of crude oil asphaltene. This invention is practically applied to the determination of particle size and thickness of asphaltene agglomerates in wellbore environments. The obtained particle size and thickness data help improve the accuracy of existing asphaltene deposition models and provide fundamental data for the development of wellbore asphaltene chemical injection agents. This experimental method performs in-situ determination of the particle size and thickness of crude oil asphaltene agglomerates under wellbore environmental temperature and pressure, resulting in more accurate determination of the deposition behavior characteristics of asphaltene agglomerates.

[0050] Includes the following steps:

[0051] Step 1:

[0052] Crude oil and flocculant are injected into crude oil pump 3 and flocculant pump 4 respectively. Water bath 1 is turned on. The original sample is mixed with the n-alkane precipitate upstream of the sedimentation test sample tube 2 to make the asphalt unstable and the mixture entering the sample tube 2 supersaturated. When the mixture flows through the tube, a slow flocculation process takes place.

[0053] In this step, the water bath temperature is 60℃, and the water bath temperature error is less than 0.5℃.

[0054] Step 2:

[0055] Crude oil was injected into sample tube 2 at a flow rate of 1 mL / h. The back pressure valve 7 was adjusted to make the pressure at the outlet of sample tube 2 about 5 atmospheres.

[0056] Step 3:

[0057] Based on the ambient temperature and pressure of the wellbore, crude oil was injected into sample tube 2 at flow rates of 1 mL / h, 2 mL / h, and 4 mL / h, respectively.

[0058] In this step, each flow rate is maintained for 10-50 hours, and the pressure at the inlet and outlet of sample tube 2 is recorded every 1-60 seconds.

[0059] In this step, the temperature is 20-170℃ and the pressure is 0-80MPa.

[0060] Step 4:

[0061] Calculate the inlet and outlet pressure difference of sample tube 2, and calculate the deposition thickness in real time;

[0062] Calculating the deposition thickness of asphaltenes in crude oil under different flow conditions includes the following steps:

[0063] The pressure drop ΔP0 across the sample tube can be expressed as:

[0064]

[0065] Where μ represents viscosity, Q represents volumetric flow rate, ro represents the radius of the sample tube, and L represents the length of the sample tube, if the precipitant injected into the sample tube can be uniformly deposited along the sample tube, and the deposition thickness is Δr(t), then the pressure drop ΔP(t) across the two ends of sample tube 2 changes with time as follows:

[0066] As asphalt gradually and uniformly deposits along the inner surface of the capillary sample tube 2 with a thickness Δr(t), the pressure drop ΔP(t) changes with time (t) as follows:

[0067]

[0068] Step 5:

[0069] After the crude oil settling test is completed, the crude oil pump 3 and the settling agent pump 4 are turned off. During the experiment, the mixture of crude oil and settling agent will continue to enter the recovery unit 6.

[0070] At the end of the deposition test, the sediment in the mixture in the recovery unit 6 was collected, and the initial particle size of the deposited bitumen was observed based on scanning electron microscopy or microscopy.

[0071] Collect the sediment precipitated in sample tube 2:

[0072] Nitrogen gas is injected into sample tube 2. The mixed liquid remaining in sample tube 2 is slowly replaced by nitrogen gas, and the high-flow-rate nitrogen gas is used to dry it for several hours.

[0073] Step 6:

[0074] Toluene and tetrahydrofuran were alternately pumped into sample tube 2 to recover the sediment until the effluent was completely colorless. The particle size of the sediment obtained at this time was observed by liquid chromatography microscopy.

[0075] This embodiment also discloses the subsequent processing procedure after obtaining the deposited asphaltene particles:

[0076] Step 7:

[0077] Toluene and tetrahydrofuran are removed from sediments containing toluene and tetrahydrofuran by evaporation.

[0078] Furthermore, the precipitate after removing toluene and tetrahydrofuran was heated to 120°C to ensure that no solvent residue remained before final weighing;

[0079] Furthermore, the sediment obtained in the previous step is dissolved by ultrasonic stirring in toluene;

[0080] Step 8:

[0081] According to the ASTM D2007-93 procedure, the asphaltene was diluted with n-pentane to separate it. The separated asphaltene was filtered through a 0.22 mm filter, dried and weighed. In this step, the ratio of n-pentane to sediment was 40:1.

[0082] Step 9:

[0083] The filtrate is evaporated to remove n-pentane, non-asphaltite residues in the sediment are recovered, and the sediment is heated to 120°C to ensure complete removal of toluene.

[0084] See Figure 2 The present invention also discloses an asphalt sedimentation testing device, comprising:

[0085] 1. Water bath; 2. Sample tube; 3. Crude oil pump; 4. Settling agent pump; 5. Nitrogen pump; 6. Recovery device; 7. Back pressure valve; 8. Pressure sensor; 9. Heating device; 11. Data acquisition device; 12. Computer; 13. Ultrasonic zone; 10. Tee.

[0086] Specifically, it includes the following structure:

[0087] Example 1

[0088] This embodiment discloses an asphalt sedimentation testing device, including a water bath 1, a sample tube 2 inside the water bath 1, and a heating device 9 connected to the water bath 1; the inlet of the sample tube 2 is connected to a crude oil pump 3, a settling agent pump 4 and a nitrogen pump 5, and the outlet of the sample tube 2 is connected to a recovery device 6; a back pressure valve 7 is provided at the outlet of the sample tube 2.

[0089] Furthermore, in this embodiment, the water bath 1 is filled with water, the sample tube 2 is placed in the water, and the heating device 9 can heat the water in the water bath 1 according to experimental requirements.

[0090] Furthermore, in this embodiment, pressure sensors 8 are installed at the inlet and outlet inside the sample tube 2, and the pressure sensors 8 are electrically connected to the data acquisition unit 11 and the computer 12.

[0091] Furthermore, in this embodiment, the outlets of the crude oil pump 3 and the settling agent pump 4 converge at the ultrasonic zone 13 for ultrasonic mixing. A tee 10 is provided between the ultrasonic zone 13 and the sample tube 2, and the tee 10 connects to the outlet of the ultrasonic zone 13 and the outlet of the nitrogen pump 5, respectively.

[0092] Furthermore, this embodiment also discloses a specific application:

[0093] In the device disclosed in this embodiment, the sample tube 2 is a long capillary tube;

[0094] Specifically, the specifications of sample tube 2 are as follows:

[0095] Length 16-32 meters, inner diameter 0.5mm (seamless, annealed and soft-tempered 316 stainless steel pipe).

[0096] Furthermore, both crude oil pump 3 and flocculant pump 4 are two high-pressure injector pumps (ISCO 500X), and the crude oil pump 3 and flocculant pump 4 inject liquid at a constant flow rate.

[0097] Both crude oil pump 3 and flocculant pump 4 have a capacity of 500 mL and a flow rate of 0-200 mL / h.

[0098] Furthermore, a pneumatic back pressure regulator, namely back pressure valve 7, is connected to the outlet of sample tube 2 to control the downstream pressure.

[0099] Furthermore, four pressure sensors were installed to continuously measure the pressure drop of the capillary.

[0100] The maximum spans of the four pressure sensors are 27, 100, 300 and 1000 psi;

[0101] The accuracy of each sensor is +0.1% of its calibration span. The analog output of the sensors (1-5V) is recorded by a computer using an ADAC data acquisition board (model 5500MF, resolution 2.4mV).

[0102] The overall accuracy of the pressure records was calibrated using an AMETEK modular tester, with pressure readings of 0.1, 0.6, 0.5, and 2.3 psi for the 27, 100, 300, and 1000 psi sensors, respectively.

[0103] Where possible, use sensors with smaller spans to achieve higher accuracy.

[0104] The capillary tube is immersed in water bath 1 with the temperature controlled within +0.58℃.

[0105] In the co-injection test, the oil flow from crude oil pump 3 and the precipitant (n-alkane) from precipitant pump 4 are mixed through a mixing node in an ultrasonic tank to ensure complete mixing. At a total flow rate of 4.8 mL / h or lower, laminar flow (Reynolds number from 0.8 to 4) is expected.

[0106] Furthermore, tests were conducted based on the device disclosed in this invention:

[0107] Step 1:

[0108] 200 mL of crude oil and 200 mL of flocculant were injected into crude oil pump 3 and flocculant pump 4, respectively.

[0109] Turn on the heating device 9 to heat the water bath 1. Set the water bath temperature to 60℃. When the water bath temperature error is less than 0.5℃, ultrasonically mix the crude oil and the settling agent. Ultrasonic mixing can make the asphalt unstable and make the mixture entering the sample tube 2 supersaturated. When the mixture flows through the sample tube 2, it can carry out a slow flocculation process.

[0110] Step 2:

[0111] Inject crude oil into the capillary tube at a flow rate of 1 mL / h, and adjust the back pressure valve 7 to make the outlet pressure about 5 atmospheres.

[0112] Step 3:

[0113] When the mixture fills the sample tube 2, crude oil is injected into the sample tube 2 at flow rates of 1 mL / h, 2 mL / h and 4 mL / h respectively, according to the ambient temperature and pressure of the wellbore (gas pressure is 0-80 MPa and temperature is 20-170℃). Each flow rate lasts for 20 hours, and the pressure at the inlet and outlet of the sample tube 2 is recorded every 10 seconds.

[0114] Step 4:

[0115] Real-time acquisition and deposition of capillary pressure differential, and real-time calculation of deposition thickness;

[0116] According to the Hagen–Poiseuille equation, the pressure drop ΔP0 across the capillary tube can be expressed as:

[0117]

[0118] μ is the viscosity, Q is the volumetric flow rate, ro is the radius of the sample tube, and L is the length of the sample tube. If the precipitant injected into the capillary can be uniformly deposited along the capillary, and the deposition thickness is Δr(t), then the pressure drop ΔP(t) across the capillary can be expressed as follows over time:

[0119] When asphalt is gradually and uniformly deposited along the inner surface of the capillary with a thickness Δr(t), the pressure drop ΔP(t) changes with time (t) as follows:

[0120]

[0121] Step 5:

[0122] After the crude oil settling test is completed, turn off crude oil pump 3 and settling agent pump 4;

[0123] Collect the sediments from the recovered mixture and observe the initial particle size of the collected asphalt at this time based on scanning electron microscopy or microscopy;

[0124] Furthermore, the mixed liquid remaining in the sample tube 2 is slowly replaced by nitrogen pump 5, and the high-flow-rate nitrogen gas is used to dry it for several hours.

[0125] Step 6:

[0126] The sediment precipitated in sample tube 2 was recovered by alternately pumping toluene and tetrahydrofuran into sample tube 2 until the effluent was completely colorless, and the particle size of the sediment was observed by liquid phase microscopy.

[0127] Step 7:

[0128] Toluene and tetrahydrofuran were removed from the sediment obtained in step 6 by evaporation.

[0129] Finally, the sediment, from which toluene and tetrahydrofuran have been removed, is heated to 120°C to ensure that no solvent remains before final weighing.

[0130] Furthermore, the heated sediment was dissolved by stirring with toluene.

[0131] Step 8:

[0132] Following the ASTM D2007-93 procedure, the mixture was diluted with 40 volumes of n-pentane to separate the asphaltenes. The separated asphaltenes were filtered through a 0.22 mm filter, dried, and weighed.

[0133] Step 9: Evaporate the filtrate to remove n-pentane, recover non-asphaltite residues from the sediment, and heat to 120°C to ensure complete removal of toluene.

[0134] This embodiment follows the following during testing:

[0135] When the deposition experiment begins, the equipment is first prefilled with oil and all pipelines are bled to eliminate cavitation.

[0136] In the pre-filling step, to prevent the two liquids from mixing before the experiment, a small bag of air is left between the crude oil and the settling agent, and oil is allowed to flow into the heptane tube. Once the equipment is filled with oil and back pressure is established, the flow of the settling agent is initiated.

[0137] In the initial stage of the experiment, the settling agent flow pushes the gasbag and crude oil into the deposition device. By strictly adhering to the startup procedure, it is possible to accurately measure when heptane is introduced into the system, which is identified by the sharp drop in pressure caused by the decrease in fluid viscosity within sample tube 2 after the addition of heptane.

[0138] The time t for heptane to enter the system is defined as t=0. This procedure only allows heptane to enter the system after the appropriate flow rate and back pressure have been determined, thereby minimizing errors and improving repeatability. All generated pressure drop profiles are offset from the initial steady-state pressure drop ΔPo, which is the pressure drop of the oil-heptane mixture flowing through the unit before any deposits are detected.

[0139] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for testing asphaltene agglomerates and deposition thickness, characterized in that, Includes the following steps: Set the mixing temperature, mix the crude oil and the settling agent under the set temperature conditions, and gradually introduce the mixture into the sample tube, and set the pressure inside the sample tube. When the mixture fills the test tube, crude oil is injected into the sample tube at different flow rates, and the inlet pressure and outlet pressure of the sample tube are recorded in real time. The pressure difference of the sample tube is calculated based on the inlet and outlet pressures of the sample tube, and the deposition thickness of asphaltene in crude oil at different flow rates is calculated in real time based on the pressure difference of the sample tube. At the end of the experiment, the sediment in the mixed liquid was collected, and the initial particle size of the sediment in the mixed liquid was obtained; The residual liquid in the sample tube was replaced, and the sediment precipitated in the sample tube was dried and collected to obtain the particle size of the collected sediment. The process of replacing the residual liquid in the sample tube and drying and collecting the precipitated sediment to obtain the particle size of the collected sediment includes the following steps: Nitrogen gas is introduced into the sample tube, which replaces the mixed liquid remaining in the sample tube. The nitrogen gas continues to flow and dries the inside of the sample tube. Toluene and tetrahydrofuran were injected into the sample tube until the effluent was completely colorless. The particle size of the effluent at this point was then observed using a liquid phase microscope.

2. The method for testing asphaltene agglomerates and deposition thickness according to claim 1, characterized in that, The process includes the following steps: when setting the pressure inside the sample tube, a back pressure valve is installed at the outlet of the sample tube, and the pressure at the back pressure valve is five times the atmospheric pressure.

3. The method for testing asphaltene agglomerates and deposition thickness according to claim 1, characterized in that, When crude oil is injected into the sample tube at different flow rates, including 1 mL / h, 2 mL / h and 4 mL / h respectively.

4. The method for testing asphaltene agglomerates and deposition thickness according to claim 3, characterized in that, For the 1 mL / h, 2 mL / h and 4 mL / h flow rates, each flow rate was maintained for 10-50 h, and the inlet and outlet pressures of the sample tube were recorded every 1-60 s.

5. The method for testing asphaltene agglomerates and deposition thickness according to claim 1, characterized in that, Calculate the deposition thickness of asphaltenes in crude oil under different flow conditions. Includes the following steps: The pressure drop ΔP0 across the sample tube can be expressed as: in, Let represent viscosity, Q represent volumetric flow rate, ro represent sample tube radius, and L represent sample tube length. If the precipitant injected into the sample tube can be uniformly deposited along the sample tube, with a deposition thickness of Δr(t), then the pressure drop ΔP(t) across sample tube 2 over time is expressed as: As asphalt gradually and uniformly deposits along the inner surface of the capillary sample tube 2 with a thickness Δr(t), the pressure drop ΔP(t) changes with time (t) as follows:

6. The method for testing asphaltene agglomerates and deposition thickness according to claim 1, characterized in that, Collecting sediments from a mixed liquid and determining the initial particle size of the sediments in the mixed liquid includes the following steps: The mixed liquid flowing out of the sample tube is collected in real time by a recovery device, and the initial particle size of the sediment is observed by scanning electron microscopy or microscopy.

7. The method for testing asphaltene agglomerates and deposition thickness according to claim 1, characterized in that, When setting the mixing temperature, a water bath is included, which is filled with water and connected to a heater. The sample tube is placed inside the water bath.

8. The method for testing asphaltene agglomerates and deposition thickness according to claim 1, characterized in that, It also includes an asphalt sedimentation testing device, which includes a water bath (1), a sample tube (2) is provided inside the water bath (1), and the water bath (1) is connected to a heating device. The inlet of the sample tube (2) is connected to the crude oil pump (3), the settling agent pump (4) and the nitrogen pump (5), and the outlet of the sample tube (2) is connected to the recovery unit (6). A back pressure valve (7) is installed at the outlet of the sample tube (2).

9. The method for testing asphaltene agglomerates and deposition thickness according to claim 8, characterized in that, A pressure sensor (8) is installed on the sample tube (2).

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