A borehole wall face wax deposit thickness measuring device and method

Abstract

The embodiment of the application provides a kind of pore wall wax deposition thickness measuring device and method, including first thermostat, hex valve, first high-precision displacement pump, second thermostat, first gas flow meter, third thermostat, second high-precision displacement pump, third high-precision displacement pump, fourth high-precision displacement pump, third pressure sensor, fourth pressure sensor, fourth electric valve, differential pressure sensor, fifth electric valve and control terminal, first thermostat is provided with first high-temperature autoclave and second high-temperature autoclave, second thermostat is provided with core holder, back pressure valve and oil-gas separation mechanism, third thermostat is provided with third high-temperature autoclave.Based on first thermostat, second thermostat and third thermostat etc., the influence of fluid heat transfer and porous medium heat transfer on wall wax deposition can be simulated, and the influence of different temperature and cooling rate on wall wax deposition can be analyzed by adjusting temperature.

Description

Technical Field

[0001] This application relates to the field of oil and gas reservoir physics technology, specifically to a device and method for measuring the thickness of wax deposition on the pore wall surface. Background Technology

[0002] In high-wax oil reservoirs, wax deposition within the reservoir is a prominent problem affecting development efficiency. During water injection development, due to the difference in thermal properties between crude oil and the porous media of the reservoir, the rock skeleton cools down faster than the crude oil, creating a temperature gradient between the pores (cold) and the crude oil (hot). Paraffin molecules, mainly composed of C17-C35 n-alkanes in the crude oil, adsorb onto the surface of the porous media, forming a wax deposit that is difficult to break down. This deposit layer leads to a decrease in reservoir permeability and may even block pore throats, thus severely affecting reservoir development. Therefore, in the production of high-wax crude oil, accurately obtaining the thickness of pores at different temperatures to avoid wax deposition is particularly important for the efficient development of such reservoirs.

[0003] The existing technologies for testing wax deposition mainly include the following methods: (1) An experimental method for testing wax deposition and its effects in porous media of reservoirs under normal temperature and pressure conditions has been established. In the literature "Paraffin precipitation during fracture stimulation[J]. Journal of Petroleum Technology", Sutton et al. conducted the first quantitative analysis of the effects of wax deposition in pores through core experiments. They found that the permeability of a core with a permeability of 0.0042 μm2 decreased to 0.12 of the original permeability after injecting about 0.5 PV (Pore Volume). (2) A method for evaluating the degree of damage to reservoir permeability and porosity by wax deposition based on a one-dimensional capillary bundle model has been established. In the literature "Damage to Reservoirs by Paraffin Deposition", Yang Fan and Li Zhiping derived the relationship between the amount of paraffin deposition and formation parameters based on a one-dimensional capillary model and conducted numerical simulation. They found that porosity and permeability increased with the increase of paraffin deposition thickness. The relationship is exponential and linear. In the literature "Experimental study on wax deposition law in porous media", Jiang Bin et al. quantitatively calculated the amount and rate of wax deposition based on a one-dimensional capillary model and found that the reservoir permeability decreased linearly with the increase of wax deposition in the porous media. (3) Experimental and calculation methods for wax deposition in porous media of oil reservoir under high temperature and high pressure conditions were established. In the literature "Water injection development of loose sandstone high pour point oil reservoir", Nie Xiangrong simulated the wax deposition of formation crude oil in porous media under oil reservoir conditions through experiments. By comparing the ratio of core permeability at different temperatures to the initial oil permeability (85℃), the equivalent wax deposition thickness in porous media at different temperatures was calculated.

[0004] Based on the patents and literature retrieved so far, the following problems exist: (1) The fluid used is high-wax crude oil under normal pressure, and its physical properties and wax deposition characteristics are quite different from those of crude oil under high temperature and high pressure conditions in the reservoir; (2) The viscosity value used in the permeability calculation method is under normal pressure and high shear rate, which results in low accuracy of the wall wax deposition thickness; (3) The viscous resistance and the additional resistance formed by the wall wax deposition layer are not distinguished. In the calculation process, the influence of viscous resistance is also included in the influence of the wall wax deposition layer, which results in the calculated wall wax deposition thickness being too large and inconsistent with the actual thickness. Summary of the Invention

[0005] In view of this, this application provides a method for measuring the thickness of wax deposition on the pore wall surface, in order to solve the problem of low testing accuracy in the prior art.

[0006] This application provides a device for measuring the thickness of wax deposition on the pore wall surface, including:

[0007] The first constant temperature chamber is equipped with a first high temperature and high pressure vessel and a second high temperature and high pressure vessel. The first high temperature and high pressure vessel is used to hold kerosene, and the second high temperature and high pressure vessel is used to hold gaseous crude oil.

[0008] A hexagonal valve and a first high-precision displacement pump are provided. One end of the first high-temperature and high-pressure vessel and one end of the second high-temperature and high-pressure vessel are respectively connected to one end of the hexagonal valve. The other end of the hexagonal valve is connected to the first high-precision displacement pump. A first pressure sensor is provided between the first high-precision displacement pump and the hexagonal valve.

[0009] The second constant temperature chamber is equipped with a core holder, a back pressure valve, and an oil-gas separation mechanism. The core holder contains a core, and one end of the core holder is connected to the other end of the first high-temperature and high-pressure reactor and the other end of the second high-temperature and high-pressure reactor. A first electric valve is provided between the core holder and the first high-temperature and high-pressure reactor, and a second electric valve is provided between the core holder and the second high-temperature and high-pressure reactor. The other end of the core holder is connected to the oil-gas separation mechanism, and the back pressure valve is provided between the two. The core holder includes an inner channel and an outer channel that are separated from each other. An inlet and an outlet are provided on the outer channel.

[0010] A first gas flow meter is connected to the oil-gas separation mechanism;

[0011] The third constant temperature chamber is equipped with a third high temperature and high pressure vessel. The third high temperature and high pressure vessel is connected to the water inlet and a second pressure sensor is installed between them. The third high temperature and high pressure vessel is used to hold gaseous crude oil.

[0012] A second high-precision displacement pump is connected to the third high-temperature and high-pressure reactor.

[0013] A third high-precision displacement pump is connected to the outlet, and a third electric valve is provided between the two.

[0014] The fourth high-precision displacement pump is connected to the back pressure valve;

[0015] A third pressure sensor and a fourth pressure sensor are disposed at both ends of the core holder;

[0016] The fourth electric valve, the differential pressure sensor, and the fifth electric valve are connected in sequence, with one end of the connection located between the third pressure sensor and the core holder, and the other end located between the fourth pressure sensor and the core holder.

[0017] The control terminal is equipped with the first pressure sensor, the second pressure sensor, the third pressure sensor, the fourth pressure sensor, the differential pressure sensor, the first electric valve, the second electric valve, the third electric valve, the fourth electric valve, and the fifth electric valve, which are all electrically connected to the control terminal.

[0018] In one embodiment, the accuracy of the first pressure sensor, the second pressure sensor, the third pressure sensor, and the fourth pressure sensor is at least 0.01 grade, and the accuracy of the differential pressure sensor is at least 1 kPa.

[0019] In one embodiment, the temperature control accuracy of the first constant temperature chamber, the second constant temperature chamber, and the third constant temperature chamber is 0.5℃, and a heat insulation component is provided between the three chambers.

[0020] In one embodiment, a constant temperature heating element is wound around the back pressure valve and the pipeline between the back pressure valve and the oil-gas separation mechanism.

[0021] In one embodiment, the inner channel and the outer channel are separated by a rubber sleeve.

[0022] This application provides a method for measuring the thickness of wax deposition on the pore wall surface, implemented using the pore wall wax deposition thickness measuring device described above, including:

[0023] Step S1: Prepare a device for measuring the thickness of wax deposition on the borehole wall and prepare formation crude oil;

[0024] Step S2: Measure the viscosity of crude oil at different temperatures, pressures, and displacement rates using a high-pressure capillary rheometer.

[0025]

[0026]

[0027] The crude oil viscosity and shear rate are corrected to obtain the corrected shear rate. Where Q is the volumetric flow rate, in cubic meters per second (m³). 3 / s, r is the capillary radius in meters, n is the non-Newtonian exponent; τ app γ is the shear stress of the fluid, measured in MPa; app The apparent shear rate experienced by the fluid, measured in seconds (s). -1 γ′ represents the actual shear rate experienced by the fluid, measured in seconds. -1 ;

[0028] Step S3: Using the system-first-core-later model, measure the pressure ΔP1 at both ends of the core when the pressure is stable during the displacement process without wall wax deposition.

[0029] Step S4: Using the core-first-system approach, measure the pressure ΔP2 at both ends of the core when the pressure is stable during the displacement process when there is wall wax deposition.

[0030] Step S5, according to

[0031] ΔP 沉 =ΔP2-ΔP1 Formula (3)

[0032] Calculate the additional resistance ΔP formed by the formation of the wall wax deposit layer. 沉 , where ΔP 沉 ΔP1 is the additional resistance to the formation of the wall wax deposition layer, in bar; ΔP2 is the pressure difference between the two ends of the core when the pressure is stable in the first system then core model, in bar;

[0033] Step S6, according to

[0034]

[0035] Calculate the flow rate Q 孔 The shear rate γ of the crude oil at the inner wall of the lower capillary bundle model is used to obtain the crude oil viscosity at different temperatures when the crude oil is subjected to shear rate γ in the porous medium of the reservoir, according to step S2. Wherein, Q 孔 The volumetric flow rate within the capillary bundle model is expressed in cubic meters per second (m³). 3 / s,r 孔 γ is the pore radius of the capillary bundle model, in meters (m), and γ is the shear rate of the crude oil at the inner wall of the capillary bundle model, in seconds (s). -1 ;

[0036] Step S7, according to

[0037]

[0038] Calculate the core permeability considering the wall wax deposition layer at different temperatures during the cooling process, where K T The permeability of the core sample from the wax-deposited layer is considered at the experimental temperature, in μm. 2 K Ti The core permeability at the experimental temperature, without considering the wax deposit layer, is expressed in μm. 2 μ T ΔP represents the crude oil viscosity corresponding to the shear rate γ at the experimental temperature, in mPa·s. 沉 The additional resistance to the formation of the wall wax deposition layer is expressed in bar, and A is the core cross-sectional area in cm². 2 Q 驱替 Pump displacement flow rate, unit: cm 3 / s, ΔL is the core length in cm;

[0039] Step S8, according to

[0040] h = r 孔 (1-(K T / K i ) 0.5 ) Formula (6)

[0041] Calculate the average thickness h of the wax deposit layer on the pore wall, where K T Core permeability at the experimental temperature, in μm. 2 K i Core permeability at the original reservoir temperature, in μm. 2 h represents the wall wax deposition thickness in μm, r 孔 The capillary radius is calculated based on the capillary bundle model, and the unit is μm;

[0042] According to the formula

[0043]

[0044] Calculate the additional resistance ΔP caused by the increase in viscous resistance. 粘滞 ,according to

[0045]

[0046] Calculate the additional resistance ΔP caused by wax crystal blockage. 固 , where K i Core permeability at the original formation temperature, in μm. 2 μ Tμ represents the crude oil viscosity corresponding to the shear rate γ at the experimental temperature, in mPa·s. i γ represents the crude oil viscosity at the original reservoir temperature corresponding to the shear rate γ, in mPa·s; A represents the core cross-sectional area, in cm². 2 Q 驱替 Pump displacement flow rate, unit: cm 3 / s; ΔL is the core length in cm; ΔP1 is the pressure difference between the two ends of the core when the pressure is stable in the system-first-core-later model, in bar;

[0047] Step S9: Change the experimental temperature and repeat steps S2-S8 to obtain the wax deposition thickness on the pore wall at different temperatures.

[0048] In one embodiment, step S3 includes:

[0049] Step S31: Transfer the formation crude oil from the PVT analyzer to the second high-temperature and high-pressure reactor, and keep it from degassing;

[0050] Step S32: Evacuate the pore wall wax deposition thickness measuring device for 24 hours;

[0051] Step S33: The back pressure valve is maintained at the experimental pressure by the fourth high-precision displacement pump, kerosene is displaced into the core in the core holder by the first high-precision displacement pump, the pressure in the first constant temperature chamber is increased to the experimental pressure by the first high-precision displacement pump, and the confining pressure of the core holder is kept higher than the pressure in the first constant temperature chamber and kept constant by the second high-precision displacement pump and the third high-precision displacement pump.

[0052] Step S34: Reduce the temperature of the second and third constant temperature chambers from the reservoir temperature to the experimental temperature. During the cooling process, the pressure is set to the experimental pressure and kept constant. After the cooling is completed, maintain constant temperature and pressure for 24 hours to ensure complete equilibrium.

[0053] Step S35: Close the first electric valve, open the second electric valve, and use the formation crude oil to displace the kerosene in the core holder at a constant flow rate. During the displacement process, record the pressure difference ΔP1 at both ends of the core holder and the number of injected PV.

[0054] Step S36: After the displacement is completed, close the second electric valve, reduce the pressure in the first constant temperature chamber to atmospheric pressure using the first high-precision displacement pump, reduce the confining pressure of the core holder to 2MPa using the second and third high-precision displacement pumps, raise the temperature to the reservoir temperature using the second and third constant temperature chambers, and clean the wax deposit and formation crude oil in the borehole wall wax deposition thickness measuring device with petroleum ether using the displacement method.

[0055] In one embodiment, in step S4, the core-first-system mode includes:

[0056] Step S41: Transfer the formation crude oil from the PVT analyzer to the second high-temperature and high-pressure reactor, ensuring that it is not degassed;

[0057] Step S42: Evacuate the pore wall wax deposition thickness measuring device for 24 hours;

[0058] Step S43: The back pressure valve is maintained at the experimental pressure by the fourth high-precision displacement pump. Kerosene is displaced into the core in the core holder by the first high-precision displacement pump. The pressure in the first constant temperature chamber is then increased to the experimental pressure by the first high-precision displacement pump. The confining pressure of the core holder is kept higher than the pressure in the first constant temperature chamber and kept constant by the second and third high-precision displacement pumps.

[0059] Step S44: Maintain the temperature of the second and third constant temperature chambers at the reservoir temperature, close the first electric valve, open the second electric valve, and use the first high-precision displacement pump to displace the kerosene in the core with 1.2PV of gas-containing high-pour-point oil.

[0060] Step S45: After the displacement is completed, the pressure in the first constant temperature chamber is kept stable by the first high-precision displacement pump, and the temperature is reduced to the experimental temperature by the second constant temperature chamber and the third constant temperature chamber. After the temperature is reduced, it is maintained at the experimental pressure for 24 hours.

[0061] Step S46: Displace the kerosene in the core with the formation crude oil at a constant flow rate. During the displacement process, record the pressure difference ΔP2 at both ends of the core and the number of injected PV.

[0062] Step S47: After the displacement is completed, close the second electric valve, reduce the pressure in the first constant temperature chamber to atmospheric pressure using the first high-precision displacement pump, reduce the confining pressure of the core holder to 2MPa using the second and third high-precision displacement pumps, raise the temperature to the reservoir temperature using the second and third constant temperature chambers, and clean the wax deposit and formation crude oil in the borehole wall wax deposition thickness measuring device using petroleum ether via displacement method.

[0063] In one embodiment, in step S33, the back pressure valve is maintained at the experimental pressure by the fourth high-precision displacement pump, kerosene is displaced into the core in the core holder by the first high-precision displacement pump, the pressure in the first constant temperature chamber is raised to the experimental pressure by the first high-precision displacement pump, and the confining pressure of the core holder is kept constant by 2-3 MPa higher than the pressure in the first constant temperature chamber by the second and third high-precision displacement pumps.

[0064] In step S43, the back pressure valve is maintained at the experimental pressure by the fourth high-precision displacement pump, kerosene is displaced into the core in the core holder by the first high-precision displacement pump, and the pressure in the first constant temperature chamber is raised to the experimental pressure by the first high-precision displacement pump. The confining pressure of the core holder is kept 2-3 MPa higher than the pressure in the first constant temperature chamber by the second and third high-precision displacement pumps and is kept constant.

[0065] In one embodiment, in step S1, the formation crude oil is prepared according to standard SH / T 5542-2009 under reservoir conditions. Attached Figure Description

[0066] To more clearly illustrate the technical solutions of the embodiments of this application, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0067] Figure 1 This is a schematic diagram of the device for measuring the wax deposition thickness on the hole wall surface according to an embodiment of this application;

[0068] Figure 2 This is a flowchart of the method for measuring the wax deposition thickness on the pore wall surface according to an embodiment of this application;

[0069] Figure 3 This is a schematic diagram of a crude oil rheology testing mechanism according to an embodiment of this application;

[0070] Figure 4 The mechanism by which wall wax deposition has no influence in the "system first, core later" model of this application embodiment;

[0071] Figure 5 The mechanism of wall wax deposition in the "core first, system later" mode of this application embodiment;

[0072] Figure 6 The wall wax deposition thickness at different temperatures in the embodiments of this application;

[0073] Figure 7 The degree to which each wax precipitation mechanism contributes to the seepage resistance in the porous medium at different temperatures in the embodiments of this application;

[0074] Figure 8 This is a diagram showing the physical property data of the artificial rock core in an embodiment of this application;

[0075] Figure 9 The shear rate in this embodiment is 52.14 s. -1 Crude oil viscosity at different temperatures.

[0076] Figure label:

[0077] 1. First constant temperature chamber; 101. First high temperature and high pressure autoclave; 102. Second high temperature and high pressure autoclave;

[0078] 2. Hexagonal valve;

[0079] 3. First high-precision displacement pump; 301. First pressure sensor;

[0080] 4. Second constant temperature chamber; 401. Core holder; 402. Back pressure valve; 403. Oil-gas separation mechanism; 404. First electric valve; 405. Second electric valve; 4011. Inner channel; 4012. Outer channel; 4013. Water inlet; 4014. Water outlet;

[0081] 5. PVT constant temperature chamber; 501. PC reactor; 502. FPC reactor; 503. First gas flow meter; 504. Oil-gas separation assembly; 505. High-pressure capillary tube; 506. First high-pressure valve; 507. Second high-pressure valve; 508. Third high-pressure valve; 509. Fourth high-pressure valve; 510. Fifth high-pressure valve;

[0082] 6. Second gas flow meter;

[0083] 7. Third constant temperature chamber; 701. Third high temperature and high pressure autoclave; 702. Second pressure sensor;

[0084] 8. Second high-precision displacement pump;

[0085] 9. Third high-precision displacement pump; 901. Third electric valve;

[0086] 10. The fourth high-precision displacement pump;

[0087] 11. Third pressure sensor;

[0088] 12. Fourth pressure sensor;

[0089] 13. Fourth electric valve;

[0090] 14. Differential pressure sensor;

[0091] 15. Fifth electric valve;

[0092] 16. Constant temperature heating element;

[0093] 17. Control terminal. Detailed Implementation

[0094] To better understand the technical solution of this application, the embodiments of this application will be described in detail below with reference to the accompanying drawings.

[0095] It should be understood that the described embodiments are merely some, not all, of the embodiments in this application. All other embodiments obtained by those skilled in the art based on the embodiments in this application without inventive effort are within the scope of protection of this application.

[0096] The terminology used in the embodiments of this application is for the purpose of describing particular embodiments only and is not intended to be limiting of this application. The singular forms “a,” “the,” and “the” used in the embodiments of this application and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise.

[0097] It should be understood that the term "and / or" used in this article is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone. Additionally, the character " / " in this article generally indicates that the preceding and following related objects have an "or" relationship.

[0098] like Figure 1 As shown, this application provides a device for measuring the thickness of wax deposition on the pore wall surface, comprising:

[0099] The first constant temperature chamber 1 is equipped with a first high temperature and high pressure vessel 101 and a second high temperature and high pressure vessel 102. The first high temperature and high pressure vessel 101 is used to hold kerosene, and the second high temperature and high pressure vessel 102 is used to hold gaseous crude oil.

[0100] A hexagonal valve 2 and a first high-precision displacement pump 3 are provided. One end of the first high-temperature and high-pressure vessel 101 and one end of the second high-temperature and high-pressure vessel 102 are respectively connected to one end of the hexagonal valve 2. The other end of the hexagonal valve 2 is connected to the first high-precision displacement pump 3. A first pressure sensor 301 is provided between the first high-precision displacement pump 3 and the hexagonal valve 2.

[0101] The second constant temperature chamber 4 is equipped with a core holder 401, a back pressure valve 402, and an oil-gas separation mechanism 403. The core holder 401 contains a core. One end of the core holder 401 is connected to the other end of the first high-temperature and high-pressure reactor 101 and the other end of the second high-temperature and high-pressure reactor 102. A first electric valve 404 is provided between the core holder 401 and the first high-temperature and high-pressure reactor 101, and a second electric valve 405 is provided between the core holder 401 and the second high-temperature and high-pressure reactor 102. The other end of the core holder 401 is connected to the oil-gas separation mechanism 403, and the back pressure valve 402 is provided between the two. The core holder 401 includes an inner channel 4011 and an outer channel 4012 that are separated from each other. An inlet 4013 and an outlet 4014 are provided on the outer channel 4012.

[0102] The first gas flow meter 6 is connected to the oil-gas separation mechanism 403;

[0103] The third constant temperature chamber 7 is equipped with a third high temperature and high pressure vessel 701. The third high temperature and high pressure vessel 701 is connected to the water inlet 4013 and a second pressure sensor 702 is provided between the two. The third high temperature and high pressure vessel 701 is used to hold gaseous crude oil.

[0104] The second high-precision displacement pump 8 is connected to the third high-temperature and high-pressure reactor 701.

[0105] The third high-precision displacement pump 9 is connected to the outlet 4014, and a third electric valve 901 is provided between the two.

[0106] A fourth high-precision displacement pump 10 is connected to the back pressure valve 402.

[0107] The third pressure sensor 11 and the fourth pressure sensor 12 are disposed at both ends of the core holder 401;

[0108] The fourth electric valve 13, the differential pressure sensor 14, and the fifth electric valve 15 are connected in sequence, with one end of the connection located between the third pressure sensor 11 and the core holder 401, and the other end located between the fourth pressure sensor 12 and the core holder 401.

[0109] The control terminal 17 is electrically connected to the first pressure sensor 301, the second pressure sensor 702, the third pressure sensor 11, the fourth pressure sensor 12, the differential pressure sensor 14, the first electric valve 404, the second electric valve 405, the third electric valve 901, the fourth electric valve 13, and the fifth electric valve 15.

[0110] In this embodiment, based on the calculation of crude oil viscosity at different temperatures and pressures and different displacement rates in permeable core samples, the increase in viscous resistance after wax precipitation can be accurately obtained, laying the foundation for subsequent calculation of wall wax deposition thickness. Using a first constant temperature chamber 1, a second constant temperature chamber 4, and a third constant temperature chamber 7, the effects of fluid heat transfer and porous media heat transfer on wall wax deposition can be simulated. By adjusting the temperature, the effects of different temperatures and cooling rates on wall wax deposition can be analyzed. This device enables precise measurement of wall wax deposition thickness and the resulting additional resistance, providing reliable experimental data for the numerical simulation of wax deposition mechanisms in reservoirs, and facilitating the efficient development of high-wax reservoirs.

[0111] In one embodiment, the first pressure sensor 301, the second pressure sensor 702, the third pressure sensor 11, and the fourth pressure sensor 12 have an accuracy of at least 0.01, and the differential pressure sensor 14 has an accuracy of at least 1 kPa.

[0112] In one embodiment, the temperature control accuracy of the first constant temperature chamber 1, the second constant temperature chamber 4, and the third constant temperature chamber 7 is 0.5℃, and a heat insulation component is provided between the three.

[0113] In one embodiment, a constant temperature heating element 16 is wound around the back pressure valve 402 and the pipeline between the back pressure valve 402 and the oil-gas separation mechanism 403.

[0114] In one embodiment, the inner channel 4011 and the outer channel 4012 are separated by a rubber sleeve.

[0115] like Figure 2 As shown, another embodiment of this application provides a method for measuring the wax deposition thickness on the pore wall surface, including:

[0116] Step S1: Prepare a device for measuring the thickness of wax deposition on the borehole wall and prepare formation crude oil;

[0117] Step S2: Measure the viscosity of crude oil at different temperatures, pressures, and displacement rates using a high-pressure capillary rheometer (505). Based on...

[0118]

[0119]

[0120] The crude oil viscosity and shear rate are corrected to obtain the corrected shear rate. Where Q is the volumetric flow rate, in cubic meters per second (m³). 3 / s, r is the capillary radius in meters, n is the non-Newtonian exponent; τ app γ is the shear stress of the fluid, measured in MPa; app The apparent shear rate experienced by the fluid, measured in seconds (s). -1 γ′ represents the actual shear rate experienced by the fluid, measured in seconds. -1 ;

[0121] Step S3: Using the system-first-core-later model, measure the pressure ΔP1 at both ends of the core when the pressure is stable during the displacement process without wall wax deposition.

[0122] Step S4: Using the core-first-system approach, measure the pressure ΔP2 at both ends of the core when the pressure is stable during the displacement process when there is wall wax deposition.

[0123] Step S5, according to

[0124] ΔP 沉 =ΔP2-ΔP1 Formula (3)

[0125] Calculate the additional resistance ΔP formed by the formation of the wall wax deposit layer. 沉 , where ΔP 沉 ΔP1 is the additional resistance to the formation of the wall wax deposition layer, in bar; ΔP2 is the pressure difference between the two ends of the core when the pressure is stable in the first system then core model, in bar;

[0126] Step S6, according to

[0127]

[0128] Calculate the flow rate Q 孔 The shear rate γ of the crude oil at the inner wall of the lower capillary bundle model is used to obtain the crude oil viscosity at different temperatures when the crude oil is subjected to shear rate γ in the porous medium of the reservoir, according to step S2. Wherein, Q 孔 The volumetric flow rate within the capillary bundle model is expressed in cubic meters per second (m³). 3 / s,r 孔 γ is the pore radius of the capillary bundle model, in meters (m), and γ is the shear rate of the crude oil at the inner wall of the capillary bundle model, in seconds (s). -1 ;

[0129] Step S7, according to

[0130]

[0131] Calculate the core permeability considering the wall wax deposition layer at different temperatures during the cooling process, where K T The permeability of the core sample from the wax-deposited layer is considered at the experimental temperature, in μm. 2 K Ti The core permeability at the experimental temperature, without considering the wax deposit layer, is expressed in μm. 2 μ T ΔP represents the crude oil viscosity corresponding to the shear rate γ at the experimental temperature, in mPa·s. 沉 The additional resistance to the formation of the wall wax deposition layer is expressed in bar, and A is the core cross-sectional area in cm². 2 Q 驱替 Pump displacement flow rate, unit: cm 3 / s, ΔL is the core length in cm;

[0132] Step S8, according to

[0133] h = r 孔 (1-(K T / K i ) 0.5 ) Formula (6)

[0134] Calculate the average thickness h of the wax deposit layer on the pore wall, where K T Core permeability at the experimental temperature, in μm. 2 K i Core permeability at the original reservoir temperature, in μm. 2 h represents the wall wax deposition thickness in μm, r 孔 The capillary radius is calculated based on the capillary bundle model, and the unit is μm;

[0135] According to the formula

[0136]

[0137] Calculate the additional resistance ΔP caused by the increase in viscous resistance. 粘滞 ,according to

[0138]

[0139] Calculate the additional resistance ΔP caused by wax crystal blockage. 固 , where K i Core permeability at the original formation temperature, in μm. 2 μ T μ represents the crude oil viscosity corresponding to the shear rate γ at the experimental temperature, in mPa·s. iγ represents the crude oil viscosity at the original reservoir temperature corresponding to the shear rate γ, in mPa·s; A represents the core cross-sectional area, in cm². 2 ;P 驱替 Pump displacement flow rate, unit: cm 3 / s; ΔL is the core length in cm; ΔP1 is the pressure difference between the two ends of the core when the pressure is stable in the system-first-core-later model, in bar;

[0140] Step S9: Change the experimental temperature and repeat steps S2-S8 to obtain the wax deposition thickness on the pore wall at different temperatures.

[0141] In this application embodiment, to address the problem of low testing efficiency, a method for measuring the thickness of wax deposition on the pore wall is disclosed. Based on the measurement of the rheological properties of formation crude oil under different temperatures and pressures, the method adopts two modes: "system first, then core" and "core first, then system," to accurately measure the thickness of wax deposition on the pore wall and the additional resistance formed. This provides reliable experimental data for the realization of wax deposition mechanism in reservoir numerical simulation, promotes a correct understanding of the impact of wax deposition on the pore wall, and ultimately achieves efficient development of high-wax reservoirs.

[0142] In one embodiment, step S3 includes:

[0143] Step S31: Transfer the formation crude oil from the PVT analyzer to the second high-temperature and high-pressure reactor 102, and keep it from degassing;

[0144] Step S32: Evacuate the pore wall wax deposition thickness measuring device for 24 hours;

[0145] Step S33: The back pressure valve 402 is maintained at the experimental pressure by the fourth high-precision displacement pump 10, kerosene is displaced into the core in the core holder 401 by the first high-precision displacement pump 3, the pressure in the first constant temperature chamber 1 is raised to the experimental pressure by the first high-precision displacement pump 3, and the confining pressure of the core holder 401 is kept higher than the pressure in the first constant temperature chamber 1 and kept constant by the second high-precision displacement pump 8 and the third high-precision displacement pump 9.

[0146] Step S34: The temperature of the second constant temperature chamber 4 and the third constant temperature chamber 7 is reduced from the reservoir temperature to the experimental temperature. During the cooling process, the pressure is set to the experimental pressure and kept constant. After the cooling is completed, the temperature and pressure are kept constant for 24 hours to ensure complete equilibrium.

[0147] Step S35: Close the first electric valve 404, open the second electric valve 405, and use the formation crude oil to displace the kerosene in the core holder 401 in a constant flow rate. During the displacement process, record the pressure difference ΔP1 at both ends of the core holder 401 and the number of injected PV.

[0148] Step S36: After the displacement is completed, close the second electric valve 405, reduce the pressure in the first constant temperature chamber 1 to atmospheric pressure through the first high-precision displacement pump 3, reduce the confining pressure of the core holder 401 to 2MPa through the second high-precision displacement pump 8 and the third high-precision displacement pump 9, raise the temperature to the reservoir temperature through the second constant temperature chamber 4 and the third constant temperature chamber 7, and clean the wax deposit and formation crude oil in the borehole wall wax deposition thickness measuring device with petroleum ether using the displacement method.

[0149] In one embodiment, in step S4, the core-first-system mode includes:

[0150] Step S41: Transfer the formation crude oil from the PVT analyzer to the second high-temperature and high-pressure reactor 102, ensuring that it does not degas;

[0151] Step S42: Evacuate the pore wall wax deposition thickness measuring device for 24 hours;

[0152] Step S43: The back pressure valve 402 is maintained at the experimental pressure by the fourth high-precision displacement pump 10, kerosene is displaced into the core in the core holder 401 by the first high-precision displacement pump 3, and the pressure in the first constant temperature chamber 1 is raised to the experimental pressure by the first high-precision displacement pump 3. The confining pressure of the core holder 401 is higher than the pressure in the first constant temperature chamber 1 and kept constant by the second high-precision displacement pump 8 and the third high-precision displacement pump 9.

[0153] Step S44: Maintain the temperature of the second constant temperature chamber 4 and the third constant temperature chamber 7 at the reservoir temperature, close the first electric valve 404, open the second electric valve 405, and use the first high-precision displacement pump 3 to displace the kerosene in the core with 1.2PV gas-containing high-pour-point oil.

[0154] Step S45: After the displacement is completed, the pressure inside the first constant temperature chamber 1 is kept stable by the first high-precision displacement pump 3, and the temperature is reduced to the experimental temperature by the second constant temperature chamber 4 and the third constant temperature chamber 7. After the temperature is reduced, it is maintained at the experimental pressure for 24 hours.

[0155] Step S46: Displace the kerosene in the core with the formation crude oil at a constant flow rate. During the displacement process, record the pressure difference ΔP2 at both ends of the core and the number of injected PV.

[0156] Step S47: After the displacement is completed, close the second electric valve 405, reduce the pressure in the first constant temperature chamber 1 to atmospheric pressure through the first high-precision displacement pump 3, reduce the confining pressure of the core holder 401 to 2MPa through the second high-precision displacement pump 8 and the third high-precision displacement pump 9, raise the temperature to the reservoir temperature through the second constant temperature chamber 4 and the third constant temperature chamber 7, and clean the wax deposit and formation crude oil in the borehole wall wax deposition thickness measuring device with petroleum ether using the displacement method.

[0157] In one embodiment, in step S33, the back pressure valve 402 is maintained at the experimental pressure by the fourth high-precision displacement pump 10, kerosene is displaced into the core in the core holder 401 by the first high-precision displacement pump 3, the pressure in the first constant temperature chamber 1 is raised to the experimental pressure by the first high-precision displacement pump 3, and the confining pressure of the core holder 401 is kept constant by the second high-precision displacement pump 8 and the third high-precision displacement pump 9, which are 2-3 MPa higher than the pressure in the first constant temperature chamber 1.

[0158] In step S43, the back pressure valve 402 is maintained at the experimental pressure by the fourth high-precision displacement pump 10, kerosene is displaced into the core in the core holder 401 by the first high-precision displacement pump 3, and the pressure in the first constant temperature chamber 1 is raised to the experimental pressure by the first high-precision displacement pump 3. The confining pressure of the core holder 401 is 2-3 MPa higher than the pressure in the first constant temperature chamber 1 and is kept constant by the second high-precision displacement pump 8 and the third high-precision displacement pump 9.

[0159] In one embodiment, in step S1, the formation crude oil is prepared according to standard SH / T 5542-2009 under reservoir conditions.

[0160] In this embodiment, crude oil sample A was used for the experiment. The density of crude oil in sample A at 0.101 MPa and 70℃ was 0.812 g / cm³. 3 The viscosity of crude oil at 100℃ is 5.84 mPa·s. The dissolved gas-oil ratio under high temperature and high pressure conditions is 37 m... 3 / m 3 The dissolved gas consisted of 94% methane, 3.62% ethane, 1.16% propane, 0.35% carbon dioxide, and 0.84% ​​nitrogen. To avoid the influence of differences in core porosity, permeability, and pore structure on the flow of high-pour-point oil, artificial cores were used in the experiment. The core properties are shown in the attached figure. Figure 8 As shown.

[0161] according to Figure 1 The device shown is connected to the hole wall surface wax deposition thickness measuring device, which includes:

[0162] The first constant temperature chamber 1 is equipped with a first high temperature and high pressure vessel 101 and a second high temperature and high pressure vessel 102. The first high temperature and high pressure vessel 101 is used to hold kerosene, and the second high temperature and high pressure vessel 102 is used to hold gaseous crude oil.

[0163] A hexagonal valve 2 and a first high-precision displacement pump 3 are provided. One end of the first high-temperature and high-pressure vessel 101 and one end of the second high-temperature and high-pressure vessel 102 are respectively connected to one end of the hexagonal valve 2. The other end of the hexagonal valve 2 is connected to the first high-precision displacement pump 3. A first pressure sensor 301 is provided between the first high-precision displacement pump 3 and the hexagonal valve 2.

[0164] The second constant temperature chamber 4 is equipped with a core holder 401, a back pressure valve 402, and an oil-gas separation mechanism 403. The core holder 401 contains a core. One end of the core holder 401 is connected to the other end of the first high-temperature and high-pressure reactor 101 and the other end of the second high-temperature and high-pressure reactor 102. A first electric valve 404 is provided between the core holder 401 and the first high-temperature and high-pressure reactor 101, and a second electric valve 405 is provided between the core holder 401 and the second high-temperature and high-pressure reactor 102. The other end of the core holder 401 is connected to the oil-gas separation mechanism 403, and the back pressure valve 402 is provided between the two. The core holder 401 includes an inner channel 4011 and an outer channel 4012 that are separated from each other. An inlet 4013 and an outlet 4014 are provided on the outer channel 4012.

[0165] The first gas flow meter 6 is connected to the oil-gas separation mechanism 403;

[0166] The third constant temperature chamber 7 is equipped with a third high temperature and high pressure vessel 701. The third high temperature and high pressure vessel 701 is connected to the water inlet 4013 and a second pressure sensor 702 is provided between the two. The third high temperature and high pressure vessel 701 is used to hold gaseous crude oil.

[0167] The second high-precision displacement pump 8 is connected to the third high-temperature and high-pressure reactor 701.

[0168] The third high-precision displacement pump 9 is connected to the outlet 4014, and a third electric valve 901 is provided between the two.

[0169] A fourth high-precision displacement pump 10 is connected to the back pressure valve 402.

[0170] The third pressure sensor 11 and the fourth pressure sensor 12 are disposed at both ends of the core holder 401;

[0171] The fourth electric valve 13, the differential pressure sensor 14, and the fifth electric valve 15 are connected in sequence, with one end of the connection located between the third pressure sensor 11 and the core holder 401, and the other end located between the fourth pressure sensor 12 and the core holder 401.

[0172] The control terminal 17 is electrically connected to the first pressure sensor 301, the second pressure sensor 702, the third pressure sensor 11, the fourth pressure sensor 12, the differential pressure sensor 14, the first electric valve 404, the second electric valve 405, the third electric valve 901, the fourth electric valve 13, and the fifth electric valve 15. The first pressure sensor 301, the second pressure sensor 702, the third pressure sensor 11, and the fourth pressure sensor 12 have an accuracy of at least 0.01, and the differential pressure sensor 14 has an accuracy of at least 1 kPa. The first constant temperature chamber 1, the second constant temperature chamber 4, and the third constant temperature chamber 7 have a temperature control accuracy of 0.5℃, and a heat insulation component is provided between them. A constant temperature heating element 16 is wound around the back pressure valve 402 and the pipeline between the back pressure valve 402 and the oil-gas separation mechanism 403. The inner channel 4011 and the outer channel 4012 are separated by a rubber sleeve. The first electric valve 404, the second electric valve 405, the third electric valve 901, the fourth electric valve 13, and the fifth electric valve 15 are all high-temperature and high-pressure resistant electric valves, and have a fine-tuning function.

[0173] like Figure 2 As shown, follow these steps to perform the test:

[0174] Step S1: Prepare a device for measuring the thickness of wax deposition on the borehole wall. Under reservoir conditions, prepare formation crude oil according to standard SH / T 5542-2009. During preparation, maintain the temperature at 70℃ and the pressure at 19.5 MPa.

[0175] Step S2: Measure the viscosity of crude oil at different temperatures, pressures, and displacement rates using a high-pressure capillary rheometer (505). Based on...

[0176]

[0177]

[0178] The crude oil viscosity and shear rate are corrected to obtain the corrected shear rate. Where Q is the volumetric flow rate, in cubic meters per second (m³). 3 / s, r is the capillary radius in meters, n is the non-Newtonian exponent; τ app γ is the shear stress of the fluid, measured in MPa; app The apparent shear rate experienced by the fluid, measured in seconds (s). -1 γ′ represents the actual shear rate experienced by the fluid, measured in seconds. -1 ;

[0179] In step S2, the viscosity of the crude oil is specifically determined using a crude oil rheology testing apparatus, such as... Figure 3 As shown, the crude oil flow deformation testing mechanism includes a PVT constant temperature chamber 5, a PC reactor 501, an FPC reactor 502, a second gas flow meter 503, an oil-gas separation assembly 504, and a high-pressure capillary tube 505. The PC reactor 501, FPC reactor 502, second gas flow meter 503, oil-gas separation assembly 504, and high-pressure capillary tube 505 are housed within the PVT constant temperature chamber 5. The two ends of the high-pressure capillary tube 505 are connected to the PC reactor 501 and the FPC reactor 502, respectively. A first high-pressure valve 506 and a second high-pressure valve 507 are sequentially arranged between the PC reactor 501 and the first high-pressure reactor. A third high-pressure reactor is arranged between the PC reactor 501 and the first high-pressure reactor. A fourth high-pressure valve 509 and a fifth high-pressure valve 510 are sequentially arranged between the FPC reactor 502 and the high-pressure capillary tube 505. The PC reactor 501 and the FPC reactor 502 contain gaseous crude oil. The gaseous crude oil is converted into degassed crude oil by the oil-gas separation component 504 and stored in the oil-gas separation component 504. The high-pressure capillary tube 505 has a length of 152.4 cm, a diameter of 0.076 cm, and a length-to-diameter ratio greater than 40 / 1. The specific steps are as follows:

[0180] Step S21: Heat history elimination, heating to 75°C under constant pressure and holding for 24 hours to eliminate the thermal history of crude oil;

[0181] Step S22: PVT constant temperature chamber 5, PC reactor 501 and FPC reactor 502 work together in constant pressure mode. Under a constant pressure of 19.5MPa, the temperature is reduced at a rate of 2℃ / h. The temperature difference above the wax precipitation point is 2-4℃, and the temperature below the wax precipitation point is reduced at intervals of 2℃. When the temperature of the first constant temperature chamber 1 reaches the set temperature, it is kept at the set temperature for another 4 hours.

[0182] Step S23: To reduce the damage to the wax crystal network structure caused by excessive shear rates, experiments were conducted with pump speeds increasing from low to high. The screw pump in PC reactor 501 was fed at rates of 0.03, 0.05, 0.13, 0.26, 0.52, 0.78, 1, 2, and 3 mL / min, while the pump in FPC reactor 502 was withdrawn at the same rate. Based on the formula, the apparent shear rates corresponding to the gas-containing high-pour-point oil at the above flow rates were calculated to be 11.5, 19.2, 49.9, 99.8, 199.5, 299.3, 383.7, 767.4, and 1151.1 s, respectively. -1 At the same time, the crude oil viscosity at the corresponding shear rate can also be calculated.

[0183] Step S24: Effect of pressure on high pour point oil. After completing the rheological test of high pour point oil, reduce the experimental pressure to 18, 15, 12 and 9 MPa respectively, and repeat the above steps.

[0184] Step S25: Correct the measured value.

[0185] Step S3: Using the system-first, core-later model, determine the pressure ΔP1 at both ends of the core when the pressure stabilizes during the displacement process without wall wax deposition. The specific steps are as follows:

[0186] Step S31: Transfer the formation crude oil from the PVT analyzer to the second high-temperature and high-pressure reactor 102, and keep it from degassing;

[0187] Step S32: Evacuate the pore wall wax deposition thickness measuring device for 24 hours;

[0188] Step S33: The back pressure valve 402 is maintained at the experimental pressure of 18 MPa by the fourth high-precision displacement pump 10. Kerosene is displaced into the core in the core holder 401 by the first high-precision displacement pump 3. The pressure in the first constant temperature chamber 1 is increased to the experimental pressure of 18 MPa by the first high-precision displacement pump 3. The confining pressure of the core holder 401 is higher than the pressure in the first constant temperature chamber 1 and is kept constant at 21 MPa by the second high-precision displacement pump 8 and the third high-precision displacement pump 9.

[0189] Step S34: The temperature of the second constant temperature chamber 4 and the third constant temperature chamber 7 is reduced from the reservoir temperature of 70°C to the experimental temperature of 55°C. During the cooling process, the pressure is set to the experimental pressure of 18 MPa and kept constant. After the cooling is completed, the temperature and pressure are kept constant for 24 hours to ensure complete equilibrium.

[0190] Step S35: As Figure 4As shown, the first electric valve 404 is closed, and the second electric valve 405 is opened. The kerosene in the core holder 401 is displaced by the formation crude oil at a constant flow rate of 0.4 mL / min. During the displacement process, the pressure difference ΔP1 = 89 kPa and the injected PV number are recorded across the core holder 401. The core permeability K, without considering the influence of the wall wax deposition thickness, is calculated according to Darcy's formula. Ti It is 705mD;

[0191] Step S36: After the displacement is completed, close the second electric valve 405, reduce the pressure in the first constant temperature chamber 1 to atmospheric pressure through the first high-precision displacement pump 3, reduce the confining pressure of the core holder 401 to 2MPa through the second high-precision displacement pump 8 and the third high-precision displacement pump 9, raise the temperature to the reservoir temperature of 70°C through the second constant temperature chamber 4 and the third constant temperature chamber 7, and clean the wax deposit and formation crude oil in the borehole wall wax deposition thickness measuring device with petroleum ether using the displacement method.

[0192] Step S4: Using the core-first, system-later approach, determine the pressure ΔP2 at both ends of the core when the pressure is stable during the displacement process when wall wax deposition is present. The specific steps are as follows:

[0193] Step S41: Transfer the formation crude oil from the PVT analyzer to the second high-temperature and high-pressure reactor 102, ensuring that it does not degas;

[0194] Step S42: Evacuate the pore wall wax deposition thickness measuring device for 24 hours;

[0195] Step S43: The back pressure valve 402 is maintained at the experimental pressure of 18 MPa by the fourth high-precision displacement pump 10. Kerosene is displaced into the core in the core holder 401 by the first high-precision displacement pump 3. The pressure in the first constant temperature chamber 1 is then raised to the experimental pressure of 18 MPa by the first high-precision displacement pump 3. The confining pressure of the core holder 401 is higher than the pressure in the first constant temperature chamber 1 and is kept constant at 21 MPa by the second high-precision displacement pump 8 and the third high-precision displacement pump 9.

[0196] Step S44: Maintain the temperature of the second constant temperature chamber 4 and the third constant temperature chamber 7 at the reservoir temperature of 70°C, close the first electric valve 404, open the second electric valve 405, and use the first high-precision displacement pump 3 to displace the kerosene in the core with 1.2PV gas-containing high-pour-point oil.

[0197] Step S45: After the displacement is completed, the pressure inside the first constant temperature chamber 1 is kept stable by the first high-precision displacement pump 3, and the temperature is reduced to the experimental temperature of 55°C by the second constant temperature chamber 4 and the third constant temperature chamber 7. After the temperature is reduced, it is maintained at the experimental pressure of 18 MPa for 24 hours.

[0198] Step S46, as follows Figure 5 As shown, the kerosene in the core was displaced by the formation crude oil at a constant flow rate of 0.4 mL / min. During the displacement process, the pressure difference ΔP2 = 91 kPa and the number of injected PVs at both ends of the core were recorded.

[0199] Step S47: After the displacement is completed, close the second electric valve 405, reduce the pressure in the first constant temperature chamber 1 to atmospheric pressure through the first high-precision displacement pump 3, reduce the confining pressure of the core holder 401 to 2MPa through the second high-precision displacement pump 8 and the third high-precision displacement pump 9, and raise the temperature to the reservoir temperature of 70°C through the second constant temperature chamber 4 and the third constant temperature chamber 7. Use petroleum ether to clean the wax deposit and formation crude oil in the borehole wall wax deposition thickness measuring device using the displacement method.

[0200] Step S5, based on ΔP 沉 =ΔP2-ΔP1=0.02bar Calculate the additional resistance ΔP formed by the wax deposition layer on the wall. 沉 .

[0201]

[0202] The calculated flow rate in a single capillary tube is 5.92 × 10⁻⁹ cm⁻¹. 3 The shear rate γ of crude oil in the artificial core at / s was obtained from step S2, which showed that the crude oil experienced a shear rate of 52.14s within the porous reservoir medium. -1 Crude oil viscosity at different temperatures, such as Figure 9 As shown.

[0203] Step S7, as follows Figure 6 As shown, the core permeability considering the wall wax deposition layer at different temperatures during the cooling process is calculated to be 0.68976 μm according to the formula. 2

[0204]

[0205] Step S8: The average thickness of the wax deposited layer on the pore wall is calculated to be h = 0.06 μm.

[0206] h = r 孔 (1-(K T / K i ) 0.5= 5.24 × (1 - (0.68976 / 0.706)) 2 ) = 0.06μm

[0207] like Figure 7 As shown, the crude oil viscosity resistance caused by wax precipitation is calculated to be 0.78 bar according to the formula.

[0208]

[0209] The additional resistance ΔPsolid caused by wax crystal blockage is calculated using the formula.

[0210]

[0211] Step S9: Change the experimental temperature and repeat steps S2-S8 to obtain the wax deposition thickness on the pore wall at different temperatures.

[0212] In this application embodiment, "at least one" refers to one or more, and "more than one" refers to two or more. "And / or" describes the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent the existence of A alone, the simultaneous existence of A and B, or the existence of B alone. A and B can be singular or plural. The character " / " generally indicates that the preceding and following related objects are in an "or" relationship. "At least one of the following" and similar expressions refer to any combination of these items, including any combination of single or plural items. For example, at least one of a, b, and c can represent: a, b, c, ab, ac, bc, or abc, where a, b, and c can be single or multiple.

[0213] The above description is merely a specific embodiment of this application. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the protection scope of this application. The protection scope of this application should be determined by the protection scope of the claims.

Claims

1. A method for measuring the thickness of wax deposition on the pore wall surface, characterized in that, The device used to measure the thickness of wax deposition on the pore wall includes: The first constant temperature chamber is equipped with a first high temperature and high pressure vessel and a second high temperature and high pressure vessel. The first high temperature and high pressure vessel is used to hold kerosene, and the second high temperature and high pressure vessel is used to hold gaseous crude oil. A hexagonal valve and a first high-precision displacement pump are provided. One end of the first high-temperature and high-pressure vessel and one end of the second high-temperature and high-pressure vessel are respectively connected to one end of the hexagonal valve. The other end of the hexagonal valve is connected to the first high-precision displacement pump. A first pressure sensor is provided between the first high-precision displacement pump and the hexagonal valve. The second constant temperature chamber is equipped with a core holder, a back pressure valve, and an oil-gas separation mechanism. The core holder contains a core, and one end of the core holder is connected to the other end of the first high-temperature and high-pressure reactor and the other end of the second high-temperature and high-pressure reactor. A first electric valve is provided between the core holder and the first high-temperature and high-pressure reactor, and a second electric valve is provided between the core holder and the second high-temperature and high-pressure reactor. The other end of the core holder is connected to the oil-gas separation mechanism, and the back pressure valve is provided between the two. The core holder includes an inner channel and an outer channel that are separated from each other. An inlet and an outlet are provided on the outer channel. A first gas flow meter is connected to the oil-gas separation mechanism; The third constant temperature chamber is equipped with a third high temperature and high pressure vessel. The third high temperature and high pressure vessel is connected to the water inlet and a second pressure sensor is installed between them. The third high temperature and high pressure vessel is used to hold gaseous crude oil. A second high-precision displacement pump is connected to the third high-temperature and high-pressure reactor. A third high-precision displacement pump is connected to the outlet, and a third electric valve is provided between the two. The fourth high-precision displacement pump is connected to the back pressure valve; A third pressure sensor and a fourth pressure sensor are disposed at both ends of the core holder; The fourth electric valve, the differential pressure sensor, and the fifth electric valve are connected in sequence, with one end of the connection located between the third pressure sensor and the core holder, and the other end located between the fourth pressure sensor and the core holder. The control terminal is equipped with the first pressure sensor, the second pressure sensor, the third pressure sensor, the fourth pressure sensor, the differential pressure sensor, the first electric valve, the second electric valve, the third electric valve, the fourth electric valve, and the fifth electric valve, which are all electrically connected to the control terminal. The method for measuring the wax deposition thickness on the pore wall surface, based on the aforementioned device, includes: Step S1: Prepare a device for measuring the thickness of wax deposition on the borehole wall and prepare formation crude oil; Step S2: Measure the viscosity of crude oil at different temperatures, pressures, and displacement rates using a high-pressure capillary rheometer. Official (1) Official (2) The crude oil viscosity and shear rate are corrected to obtain the corrected shear rate. Where Q is the volumetric flow rate, in cubic meters per second (m³). 3 / s, r is the capillary radius in meters, and n is the non-Newtonian exponent; This represents the shear stress of the fluid, expressed in MPa. The apparent shear rate experienced by the fluid, measured in seconds (s). -1 ; Step S3: Using a system-first, core-later model, measure the pressure at both ends of the core when the pressure stabilizes during the displacement process without wall wax deposition. ; Step S4: Using the core-first, system-later approach, measure the pressure at both ends of the core when the pressure stabilizes during the displacement process when wall wax deposition is present. ; Step S5, according to Official (3) Calculate the additional resistance to the formation of the wall wax deposit layer. ,in, Additional resistance to the formation of the wall wax deposit layer, measured in bars. This represents the pressure difference between the two ends of the core when the pressure is stable in the system-first-core-later model, expressed in bar. The pressure difference between the two ends of the core when the pressure is stable in the core-first-systems-later model, expressed in bar. Step S6, according to Official (4) Calculate the flow rate Shear rate of crude oil at the inner wall of the lower capillary bundle model The shear rate of crude oil within the porous medium of the reservoir is obtained according to step S2. The viscosity of the crude oil at different temperatures, wherein, The volumetric flow rate within the capillary bundle model is expressed in cubic meters per second (m³). 3 / s, The pore radius of the capillary bundle model is in meters. The shear rate of crude oil at the inner wall of the capillary bundle model is expressed in seconds. -1 ; Step S7, according to Official (5) Calculate the core permeability considering the wall wax deposition layer at different temperatures during the cooling process, where, Core permeability at the experimental temperature, in units of , The core permeability at the experimental temperature does not consider the wax deposit layer, and the unit is... , Shear rate at the experimental temperature The corresponding crude oil viscosity, in mPa∙s. The additional resistance to the formation of the wall wax deposition layer is expressed in bar, and A is the core cross-sectional area in cm². 2 , Pump displacement flow rate, unit: cm 3 / s, This refers to the core length, in cm. Step S8, according to h= Formula (6) Calculate the average thickness h of the wax deposit layer on the pore wall surface, where, Core permeability at the experimental temperature, in units of , Core permeability at the original reservoir temperature, in units of h represents the wall wax deposition thickness, in µm. The capillary radius is calculated based on the capillary bundle model, and the unit is µm; According to the formula Formula (7) Calculate the additional resistance caused by the increase in viscous resistance. ,according to Official (8) Calculate the additional resistance caused by wax crystal blockage. ,in, Core permeability at the original formation temperature, in units of ; Shear rate at the experimental temperature The corresponding crude oil viscosity, in mPa∙s; γ represents the crude oil viscosity at the original reservoir temperature corresponding to the shear rate γ, in mPa·s; A represents the core cross-sectional area, in cm². 2 ; Pump displacement flow rate, unit: cm 3 / s; This refers to the core length, in cm. The pressure difference between the two ends of the core when the pressure is stable in the system-first-core-later model, expressed in bar. Step S9: Change the experimental temperature and repeat steps S2-S8 to obtain the wax deposition thickness on the pore wall at different temperatures. In step S3, the system-first-core-later mode includes: Step S31: Transfer the formation crude oil from the PVT analyzer to the second high-temperature and high-pressure reactor, and keep it from degassing; Step S32: Evacuate the pore wall wax deposition thickness measuring device for 24 hours; Step S33: The back pressure valve is maintained at the experimental pressure by the fourth high-precision displacement pump, kerosene is displaced into the core in the core holder by the first high-precision displacement pump, the pressure in the first constant temperature chamber is increased to the experimental pressure by the first high-precision displacement pump, and the confining pressure of the core holder is kept higher than the pressure in the first constant temperature chamber and kept constant by the second high-precision displacement pump and the third high-precision displacement pump. Step S34: Reduce the temperature of the second and third constant temperature chambers from the reservoir temperature to the experimental temperature. During the cooling process, the pressure is set to the experimental pressure and kept constant. After the cooling is completed, maintain constant temperature and pressure for 24 hours to ensure complete equilibrium. Step S35: Close the first electric valve, open the second electric valve, and use the formation crude oil to displace the kerosene in the core holder at a constant flow rate. During the displacement process, record the pressure difference across the core holder. and the number of PVs injected; Step S36: After the displacement is completed, close the second electric valve, reduce the pressure in the first constant temperature chamber to atmospheric pressure using the first high-precision displacement pump, reduce the confining pressure of the core holder to 2MPa using the second and third high-precision displacement pumps, raise the temperature to the reservoir temperature using the second and third constant temperature chambers, and clean the wax deposit and formation crude oil in the borehole wall wax deposition thickness measuring device with petroleum ether using the displacement method; In step S4, the core-first-then-system mode includes: Step S41: Transfer the formation crude oil from the PVT analyzer to the second high-temperature and high-pressure reactor, ensuring that it is not degassed; Step S42: Evacuate the pore wall wax deposition thickness measuring device for 24 hours; Step S43: The back pressure valve is maintained at the experimental pressure by the fourth high-precision displacement pump. Kerosene is displaced into the core in the core holder by the first high-precision displacement pump. The pressure in the first constant temperature chamber is then increased to the experimental pressure by the first high-precision displacement pump. The confining pressure of the core holder is kept higher than the pressure in the first constant temperature chamber and kept constant by the second and third high-precision displacement pumps. Step S44: Maintain the temperature of the second and third constant temperature chambers at the reservoir temperature, close the first electric valve, open the second electric valve, and use the first high-precision displacement pump to displace the kerosene in the core with 1.2 PV of gas-containing high-pour-point oil. Step S45: After the displacement is completed, the pressure in the first constant temperature chamber is kept stable by the first high-precision displacement pump, and the temperature is reduced to the experimental temperature by the second constant temperature chamber and the third constant temperature chamber. After the temperature is reduced, it is maintained at the experimental pressure for 24 hours. Step S46: Displace the kerosene in the core with the formation crude oil at a constant flow rate. During the displacement process, record the pressure difference between the two ends of the core. and the number of PVs injected; Step S47: After the displacement is completed, close the second electric valve, reduce the pressure in the first constant temperature chamber to atmospheric pressure using the first high-precision displacement pump, reduce the confining pressure of the core holder to 2MPa using the second and third high-precision displacement pumps, raise the temperature to the reservoir temperature using the second and third constant temperature chambers, and clean the wax deposit and formation crude oil in the borehole wall wax deposition thickness measuring device using petroleum ether via displacement method.

2. The method for determining the wax deposition thickness on the pore wall surface according to claim 1, characterized in that, In step S33, the back pressure valve is maintained at the experimental pressure by the fourth high-precision displacement pump, kerosene is displaced into the core in the core holder by the first high-precision displacement pump, the pressure in the first constant temperature chamber is increased to the experimental pressure by the first high-precision displacement pump, and the confining pressure of the core holder is kept constant by 2-3 MPa higher than the pressure in the first constant temperature chamber by the second and third high-precision displacement pumps. In step S43, the back pressure valve is maintained at the experimental pressure by the fourth high-precision displacement pump, kerosene is displaced into the core in the core holder by the first high-precision displacement pump, and the pressure in the first constant temperature chamber is raised to the experimental pressure by the first high-precision displacement pump. The confining pressure of the core holder is made 2-3 MPa higher than the pressure in the first constant temperature chamber by the second and third high-precision displacement pumps and is kept constant.

3. The method for determining the wax deposition thickness on the pore wall surface according to claim 1, characterized in that, In step S1, the formation crude oil is prepared according to standard SH / T 5542-2009 under reservoir conditions.

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