Method and equipment for testing asphaltene agglomerated and deposited particles and deposition thickness

Abstract

The invention discloses a method and equipment for testing agglomerated and deposited asphaltene particles and deposition thickness, which are characterized in that crude oil and a settling agent are mixed under a set temperature condition, the mixed mixture gradually enters a sample tube, when a test tube is filled with the mixture, the crude oil is injected into the sample tube at different flow rates respectively, and the settling agent is added into the sample tube; recording the inlet pressure and the outlet pressure of the sample tube in real time; calculating the pressure difference of the sample tube, and calculating the deposition thickness of asphaltene in the crude oil at different flow velocities in real time based on the pressure difference of the sample tube; when the experiment is finished, collecting the sediments in the mixed liquid, obtaining the initial particle size of the sediments in the mixed liquid, replacing the residual liquid in the sample tube, drying and collecting the sediments precipitated in the sample tube, and obtaining the particle size of the sediments collected at the moment; according to the method, the deposition thickness of asphaltene in deposited crude oil at different flow rates and the particle size of deposited particles can be obtained, and prediction of the size and the deposition thickness of asphalt agglomerated deposited particles in application is facilitated.

Description

Technical Field

[0001] The invention belongs to the technical field of asphaltene precipitation testing in crude oil, and relates to a method and equipment for testing asphaltene agglomerated sedimentation particles and sedimentation thickness. Background Art

[0002] In the oil industry, as the physical or chemical conditions inside the reservoir and wellbore change, the originally stable asphaltene in the crude oil will be deposited during transportation. Asphaltene is often deposited in reservoirs, pipelines, separators and other systems along the production line. The restricted flow of oil due to asphaltene precipitation will damage the equipment and instruments along the pipeline, resulting in significant production losses. The asphaltene deposition process is that asphaltene molecules adsorb and agglomerate to form micro-nano particles, and the asphaltene micro-nano particles are then deposited in the transportation pipeline to form a blockage. Therefore, the agglomeration and deposition process of asphaltene molecules in the wellbore environment is a key issue affecting the development of oil and gas resources.

[0003] At present, the research on the asphaltene molecular agglomeration and deposition process in the wellbore environment is concentrated in three aspects: on the one hand, in the prediction of oil and gas flow safety, the asphaltene deposition characteristics of the wellbore are predicted by measuring the asphaltene deposition thickness and the particle size of the deposited particles; on the other hand, in the research and development of chemical agents, by measuring the component characteristics of the asphaltene deposition particles, a reference for the research and development of asphaltene interpretation agents is provided; on the third hand, in the wellbore process design, by measuring the changes in asphaltene deposition thickness, a data reference is provided for the oilfield wellbore design.

[0004] In addition, the particle size of asphaltene molecular agglomeration particles under wellbore environment also plays an important role in the selection of drag reducer and crystallizer molecules, and the study of the influence of dissolved gas molecules on asphaltene agglomeration. Therefore, the study of asphaltene molecular agglomeration deposition characteristics under wellbore environment plays an important role in oil and gas resource development, wellbore injection research, wellbore dissolved gas characteristics, etc.

[0005] At present, there are three main research methods for the agglomeration and deposition characteristics of asphaltene in wellbore environment: one is the method of computer simulation, which obtains the agglomeration characteristics of asphaltene molecules by inputting the initial molecular structure of asphaltene molecules and the force field between molecules through molecular dynamics simulation; the second is the method of microscopic observation, which injects crude oil into the microscope into the microfluidic chip or the visualization microchannel, and directly observes the agglomeration and deposition of asphaltene by cooling the temperature or injecting the sedimentation agent; the third method is to add crude oil to a large-volume reactor, and then add the sedimentation agent under high temperature and high pressure conditions, separate the deposited asphaltene after the asphaltene is deposited and agglomerated, and observe the agglomeration characteristics of asphaltene under a microscope. The existing methods for detecting the initial sedimentation agent concentration of wellbore asphaltene deposition and the corresponding initial deposition particle size, such as microscopy and computer simulation, cannot obtain accurate sedimentation agent concentration and initial particle size of asphaltene deposition. Because the previous research methods are all non-in-situ and separate detection, there are few studies on the asphaltene agglomeration deposition system under the temperature and pressure conditions of the wellbore environment, and it is impossible to achieve the simultaneous measurement of the asphaltene deposition particle size and deposition thickness. Summary of the invention

[0006] The purpose of the present invention is to solve the problem in the prior art that it is impossible to simultaneously measure the size and thickness of asphaltene deposited particles in the study of asphaltene, and to provide a method and equipment for testing asphaltene agglomerated deposited particles and deposited thickness.

[0007] In order to achieve the above object, the present invention adopts the following technical solutions:

[0008] A method for testing asphaltene agglomerated deposition particles and deposition thickness, comprising the following steps:

[0009] The mixing temperature is set, the crude oil and the sedimentation agent are mixed under the set temperature condition, the mixed mixture gradually enters the sample tube, and the pressure in the sample tube is set;

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

[0011] The pressure difference of the sample tube is calculated based on the inlet pressure and outlet pressure 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] When the experiment is finished, the sediment in the mixed liquid is collected, and the initial particle size of the sediment in the mixed liquid is obtained;

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

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

[0015] When setting the pressure in 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] The crude oil was injected into the sample tube at different flow rates, including injection into the sample tube at flow rates of 1 mL / h, 2 mL / h and 4 mL / h.

[0017] Each flow rate of 1 mL / h, 2 mL / h and 4 mL / h lasts for 10-50 h, and the inlet pressure and outlet pressure of the sample tube are recorded every 1-60 s.

[0018] Calculating the deposition thickness of asphaltene in crude oil under different flows includes the following steps:

[0019] The pressure drop ΔP0 at both ends of the sample tube can be expressed as:

[0020]

[0021] Wherein, μ represents viscosity, Q represents volume 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 with a deposition thickness of Δr(t), then the relationship between the pressure drop ΔP(t) at both ends of the sample tube 2 and time is expressed as:

[0022] When asphaltene is gradually and evenly deposited along the inner surface of the capillary sample tube 2 with a thickness of Δr(t), the pressure drop ΔP(t) changes with time (t) as follows:

[0023]

[0024] Collecting sediment in the mixed liquid and obtaining the initial particle size of the sediment 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 recoverer, and the initial particle size of the sediment is observed by a scanning electron microscope or a microscope.

[0026] The method of replacing the residual liquid in the sample tube, drying and collecting the sediment precipitated in the sample tube, and obtaining the particle size of the sediment collected at this time comprises the following steps:

[0027] Nitrogen is introduced into the sample tube, and the nitrogen replaces the mixed liquid remaining in the sample tube. The nitrogen continues to flow to dry the sample tube;

[0028] Toluene and tetrahydrofuran were injected into the sample tube until the effluent was completely colorless, and the particle size of the sediment at this time was observed by liquid phase microscope.

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

[0030] An asphaltene precipitation test device used in the method of the present invention comprises a water bath, a sample tube is arranged 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 sedimentation agent pump and the nitrogen pump, and the outlet of the sample tube is connected to the recovery device;

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

[0033] The further improvement of this equipment is:

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

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

[0036] The invention discloses a method for testing asphaltene agglomerated deposition particles and deposition thickness. The method first simulates the environment of actual application by setting temperature and pressure values, thereby providing basic conditions for the accuracy of prediction results. In the experiment, crude oil is continuously injected into a sample tube at different flow rates. During the process, the inlet and outlet pressure differences of the sample tube are collected and calculated in real time, and the deposition thickness is calculated in real time based on the real-time pressure difference. The change of deposition thickness under different flow rates and pressure differences is recorded, and after the experiment, the particle sizes of the deposition particles in the mixed liquid and the deposition particles precipitated in the tube are respectively observed. The method can obtain the deposition thickness of asphaltene in the deposited crude oil at different flow rates and the particle size of the deposition particles. The acquired data is helpful to improve the accuracy of the existing asphaltene deposition model, facilitates the prediction of the size and deposition thickness of asphalt agglomerated deposition particles in the later application, and also provides basic reference data for the later research and development of wellbore asphaltene chemical injection agents.

[0037] The invention discloses an asphaltene precipitation test device. The device can simulate the actual application environment of a wellbore, ensure that the crude oil asphaltene agglomeration deposition particle size and deposition thickness are measured in situ under the wellbore ambient temperature and pressure. In the experiment, the experiment can be carried out at different crude oil flow rates according to experimental requirements to obtain the deposition thickness of asphaltene in the deposited crude oil and the particle size of the deposition particles at different flow rates. The acquired data is helpful to improve the accuracy of the existing asphaltene deposition model, facilitate the prediction of the asphalt agglomeration deposition particle size and deposition thickness in the later application, and also provide basic reference data for the later research and development of wellbore asphaltene chemical injection agents. The device has a simple structure and simple experimental operation. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments are briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without creative work.

[0039] Figure 1 is a flow chart of the present invention;

[0040] Figure 2 The figure is a schematic diagram of the device disclosed in the present invention.

[0041] Among them: 1-water bath; 2-sample tube; 3-crude oil pump; 4-sedimentation agent pump; 5-nitrogen pump; 6-recovery device; 7-back pressure valve; 8-pressure sensor; 9-heating device; 10-tee; 11-data acquisition device; 12-computer; 13-ultrasonic zone. DETAILED DESCRIPTION

[0042] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings here can be arranged and designed in various different configurations.

[0043] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the invention claimed for protection, but merely represents selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0044] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, further definition and explanation thereof is not required in subsequent drawings.

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

[0046] In addition, if the term "horizontal" appears, it does not mean that the component must be absolutely horizontal, but can be slightly tilted. For example, "horizontal" only means that its direction is more horizontal than "vertical", which 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 is also necessary to explain that, unless otherwise clearly specified and limited, the terms "set", "install", "connect", and "connect" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal connection of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0048] The present invention is further described in detail below in conjunction with the accompanying drawings:

[0049] See also Figure 1 The embodiment of the present invention discloses a method for testing asphaltene agglomeration deposition particles and deposition thickness, which is proposed for the deposition problem of crude oil asphaltene. The embodiment of the present invention is actually applied to the determination of asphaltene agglomeration deposition particle size and deposition thickness in the wellbore environment. The obtained asphaltene deposition particle size and deposition thickness help to improve the accuracy of the existing asphaltene deposition model and provide basic data for the research and development of wellbore asphaltene chemical injection. This experimental method actually measures the particle size and deposition thickness of crude oil asphaltene agglomeration deposition in situ under the wellbore ambient temperature and pressure, and the determination of the asphaltene deposition agglomeration deposition behavior characteristics is more accurate.

[0050] The following steps are involved:

[0051] Step 1:

[0052] Inject crude oil and sedimentation agent into crude oil pump 3 and sedimentation agent pump 4 respectively, open water bath 1; mix the original sample with the n-alkane precipitate upstream of the sedimentation test gross sample tube 2 to destabilize the asphaltene and make the mixture entering the gross 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°C, and the water bath temperature error is less than 0.5°C.

[0054] Step 2:

[0055] Inject crude oil into the sample tube 2 at a flow rate of 1 mL / h, and adjust the back pressure valve 7 to make the pressure at the outlet of the sample tube 2 about 5 atmospheres;

[0056] Step 3:

[0057] According to the wellbore ambient temperature and pressure, crude oil is injected into the 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 lasts for 10-50 h, and the pressure of the sample tube 2 at the inlet and outlet is recorded every 1-60 s;

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

[0060] Step 4:

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

[0062] Calculating the deposition thickness of asphaltene in crude oil under different flows includes the following steps:

[0063] The pressure drop ΔP0 at both ends of the sample tube can be expressed as:

[0064]

[0065] Wherein, μ represents viscosity, Q represents volume 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 with a deposition thickness of Δr(t), then the relationship between the pressure drop ΔP(t) at both ends of the sample tube 2 and time is expressed as:

[0066] When asphaltene is gradually and evenly deposited along the inner surface of the capillary sample tube 2 with a thickness of Δr(t), the pressure drop ΔP(t) changes with time (t) as follows:

[0067]

[0068] Step 5:

[0069] After the crude oil sedimentation test is completed, the crude oil pump 3 and the sedimentation agent pump 4 are turned off. During the experiment, the mixed liquid of crude oil and sedimentation agent continues to enter the recovery device 6;

[0070] At the end of the deposition test, the sediment in the mixed liquid in the recovery device 6 is collected, and the initial particle size of the deposited asphaltene is observed based on a scanning electron microscope or a microscope;

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

[0072] Inject nitrogen into the sample tube 2, and the mixed liquid remaining in the sample tube 2 is slowly replaced by nitrogen, and dry for several hours with a high-flow nitrogen flow;

[0073] Step 6:

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

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

[0076] Step 7:

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

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

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

[0080] Step 8:

[0081] According to the ASTM D2007-93 procedure, the asphaltene was separated by dilution with n-pentane, and 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 was evaporated to remove n-pentane and the non-asphaltenic residue in the sediment was recovered and heated to 120°C to ensure complete removal of toluene.

[0084] See also Figure 2 The embodiment of the present invention also discloses an asphaltene precipitation testing device, comprising:

[0085] Water bath 1; sample tube 2; crude oil pump 3; sedimentation agent pump 4; nitrogen pump 5; recovery device 6; back pressure valve 7; pressure sensor 8; heating device 9; pressure sensor 8; data acquisition device 11; computer 12; ultrasonic zone 13 and three-way 10.

[0086] Specifically includes the following structures:

[0087] Example 1

[0088] The present embodiment discloses an asphaltene precipitation test device, comprising a water bath 1, a sample tube 2 is arranged inside the water bath 1, and the water bath 1 is connected to a heating device 9; the inlet of the sample tube 2 is connected to a crude oil pump 3, a sedimentation agent pump 4 and a nitrogen pump 5, and the outlet of the sample tube 2 is connected to a recoverer 6; a back pressure valve 7 is arranged 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 of the sample tube 2 , and the pressure sensors 8 are electrically connected to the data acquisition device 11 and the computer 12 .

[0091] Furthermore, in this embodiment, the outlets of the crude oil pump 3 and the sedimentation agent pump 4 converge at the ultrasonic zone 13 for ultrasonic mixing, and a tee 10 is provided between the ultrasonic zone 13 and the sample tube 2, and the tee 10 connects 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 the sample tube 2 are:

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

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

[0097] The capacity of the crude oil pump 3 and the sedimentation agent pump 4 are both 500 mL, and the flow rate is 0-200 mL / h.

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

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

[0100] Four pressure sensors with maximum spans of 27, 100, 300 and 1000 psi;

[0101] The accuracy of each sensor is +0.1% of its calibrated 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 recorder was calibrated using an AMETEK modular tester to 0.1, 0.6, 0.5 and 2.3 psi for the 27, 100, 300 and 1000 psi sensors, respectively.

[0103] Where possible, use short span sensors to achieve greater accuracy.

[0104] The temperature of the capillary is controlled at +0.58°C and immersed in a water bath 1.

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

[0106] Further, a test experiment was conducted based on the device disclosed in the present invention:

[0107] Step 1:

[0108] Inject 200 mL of crude oil and sedimentation agent into crude oil pump 3 and sedimentation agent pump 4 respectively;

[0109] The heating device 9 is turned on to heat the water bath 1, and the water bath temperature is set to 60°C. When the water bath temperature error is less than 0.5°C, the crude oil and the sedimentation agent are ultrasonically mixed. Ultrasonic mixing can make the asphaltene unstable and make the mixture entering the sample tube 2 supersaturated. When the mixture flows through the sample tube 2, it can proceed in 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 pressure at the outlet about 5 atmospheres;

[0112] Step 3:

[0113] When the mixture fills the sample tube 2, the 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 wellbore ambient temperature and pressure (air pressure is 0-80 MPa, temperature is 20-170°C), 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] Collect and deposit the capillary pressure difference in real time, and calculate the deposited thickness in real time;

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

[0117]

[0118] μ is the viscosity, Q is the volume flow rate, the radius of the sample tube is ro, and the length of the sample tube is L. 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) at both ends of the capillary can be expressed as follows:

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

[0120]

[0121] Step 5:

[0122] After the crude oil sedimentation test is completed, the crude oil pump 3 and the sedimentation agent pump 4 are turned off;

[0123] Collecting the sediment in the recovered mixed liquor, and observing the initial particle size of the sediment asphaltene collected at this time based on a scanning electron microscope or a microscope;

[0124] Furthermore, the mixed liquid remaining in the sample tube 2 is slowly replaced by the nitrogen pump 5, and dried for several hours by a high-flow nitrogen flow.

[0125] Step 6:

[0126] The sediment precipitated in the sample tube 2 is recovered by alternately pumping toluene and tetrahydrofuran into the sample tube 2 until the outflow is completely colorless, and the particle size of the sediment is observed by a liquid microscope.

[0127] Step 7:

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

[0129] Finally, the sediment from which toluene and tetrahydrofuran were removed was heated to 120 °C to ensure that no solvent remained before the final weighing;

[0130] Furthermore, the heated sediment is stirred and dissolved by toluene.

[0131] Step 8:

[0132] The mixture was diluted with 40 volumes of n-pentane to separate asphaltene according to ASTM D2007-93 procedure The separated asphaltene was filtered through a 0.22 mm filter, dried and weighed;

[0133] Step 9: The filtrate is evaporated to remove n-pentane and the non-asphaltenic residue in the sediment is recovered and heated to 120°C to ensure complete removal of toluene.

[0134] This embodiment follows the following when testing:

[0135] When starting a deposition experiment, the equipment was first prefilled with oil only, and all lines were bled to eliminate air pockets.

[0136] During the pre-filling step, a small pocket of air was trapped between the crude oil and the settler to prevent mixing of the two liquids before the experiment, and the oil was allowed to flow into the heptane tube. Once the equipment was filled with oil and back pressure was established, the flow of the settler was started.

[0137] During the initial phase of the experiment, the settler flow pushes the gas capsule and crude oil into the sedimentation device. Strict adherence to the start-up procedure allows accurate measurement of when heptane is introduced into the system, which can be identified by the sharp drop in pressure drop caused by the decrease in fluid viscosity in sample tube 2 after the addition of heptane.

[0138] The time t at which heptane enters the system is defined as t = 0. This procedure minimizes error and improves repeatability by allowing heptane to enter the system only after the appropriate flow rate and back pressure have been determined. All generated pressure drop curves are offset based on the initial steady-state pressure drop ΔPo, which is the pressure drop of the oil-heptane mixture flowing through the device before any deposition is detected.

[0139] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for testing asphaltene agglomerated deposition particles and deposition thickness, characterized in that: The following steps are involved: The mixing temperature is set, the crude oil and the sedimentation agent are mixed under the set temperature condition, the mixed mixture gradually enters the sample tube, and the pressure in the sample tube is set; When the mixture fills the test tube, the crude oil is injected into the sample tube at different flow rates, and the inlet and outlet pressures of the sample tube are recorded in real time; The pressure difference of the sample tube is calculated based on the inlet pressure and outlet pressure 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; When the experiment is finished, the sediment in the mixed liquid is collected, and the initial particle size of the sediment in the mixed liquid is obtained; The residual liquid in the sample tube is replaced, and the sediment precipitated in the sample tube is dried and collected to obtain the particle size of the sediment collected at this time.

2. A method for testing asphaltene agglomerated deposition particles and deposition thickness according to claim 1, characterized in that: The method comprises the following steps: when setting the pressure in the sample tube, a back pressure valve is arranged at the outlet of the sample tube, and the pressure at the back pressure valve is five times of the atmospheric pressure.

3. A method for testing asphaltene agglomerated deposition particles and deposition thickness according to claim 1, characterized in that: The crude oil was injected into the sample tube at different flow rates, including injection into the sample tube at flow rates of 1 mL / h, 2 mL / h and 4 mL / h.

4. A method for testing asphaltene agglomerated deposition particles and deposition thickness according to claim 3, characterized in that: Each flow rate of 1 mL / h, 2 mL / h and 4 mL / h lasts for 10-50 h, and the inlet pressure and outlet pressure of the sample tube are recorded every 1-60 s.

5. The asphaltene agglomerated deposition particle and deposition thickness testing method according to claim 1, characterized in that: Calculation of asphaltene deposition thickness in crude oil under different flow conditions The following steps are involved: The pressure drop ΔP0 at both ends of the sample tube can be expressed as: Wherein, μ represents viscosity, Q represents volume 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 with a deposition thickness of Δr(t), then the relationship between the pressure drop ΔP(t) at both ends of the sample tube 2 and time is expressed as: When asphaltene is gradually and evenly deposited along the inner surface of the capillary sample tube 2 with a thickness of Δr(t), the pressure drop ΔP(t) changes with time (t) as follows:

6. A method for testing asphaltene agglomerated deposition particles and deposition thickness according to claim 1, characterized in that: Collecting sediment in the mixed liquid and obtaining the initial particle size of the sediment in the mixed liquid includes the following steps: The mixed liquid flowing out of the sample tube is collected in real time by a recoverer, and the initial particle size of the sediment is observed by a scanning electron microscope or a microscope.

7. A method for testing asphaltene agglomerated deposition particles and deposition thickness according to claim 1, characterized in that: The method of replacing the residual liquid in the sample tube, drying and collecting the sediment precipitated in the sample tube, and obtaining the particle size of the sediment collected at this time comprises the following steps: Nitrogen is introduced into the sample tube, and the nitrogen replaces the mixed liquid remaining in the sample tube. The nitrogen continues to flow to dry the sample tube; Toluene and tetrahydrofuran were injected into the sample tube until the effluent was completely colorless, and the particle size of the sediment at this time was observed by liquid phase microscope.

8. The asphaltene agglomerated deposition particle and deposition thickness testing method according to claim 1, characterized in that: When the mixing temperature is set, a water bath is included, the water bath is filled with water, the water bath is connected to a heater, and the sample tube is placed inside the water bath.

9. An asphaltene precipitation test device for use in the method according to any one of claims 1 to 8, characterized in that: It comprises a water bath (1), a sample tube (2) is arranged 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 a crude oil pump (3), a sedimentation 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).

10. An asphaltene precipitation testing device according to claim 9, characterized in that: A pressure sensor (8) is provided on the sample tube (2).

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