Device and method for measuring the start-up temperature of thick oil in a porous medium

Abstract

The present application belongs to the field of oil and gas field development technology, and particularly relates to a device and method for measuring heavy oil starting temperature in porous medium, wherein the method for measuring heavy oil starting temperature in porous medium comprises the following steps: first, preparing crude oil sample and core sample; then, injecting the crude oil sample into the core sample to stabilize the injection end pressure; second, changing the experimental flow rate to obtain the relationship curve between flow rate and pressure gradient and calculating the core pseudo-starting pressure gradient value; then, changing the experimental temperature to obtain the core pseudo-starting pressure gradient value at different temperatures, so as to obtain the heavy oil starting temperature; finally, changing the permeability to obtain the heavy oil starting temperature at different permeabilities, and performing linear fitting to obtain the calculation formula of the heavy oil starting temperature. By considering the influence of the permeability of the porous medium during the experiment, the calculation formula of the heavy oil starting temperature can be applied in oil reservoirs with different permeabilities, thereby improving the application range of the method for measuring heavy oil starting temperature in porous medium.

Description

Technical Field

[0001] This invention belongs to the field of oil and gas field development technology, and in particular relates to a device and method for measuring the start-up temperature of heavy oil in porous media. Background Technology

[0002] Heavy oil resources are extremely abundant globally, accounting for approximately 70% of the world's total oil resources. Generally, under reservoir conditions, crude oil with a viscosity higher than 100 mPa·s after degassing can be classified as heavy oil. Under typical reservoir conditions, heavy oil with a viscosity of several thousand to tens of thousands of millipascals·s cannot flow. It only begins to flow when the displacement pressure gradient exceeds the heavy oil initiation pressure gradient. The magnitude of the heavy oil initiation pressure gradient is related to the permeability of the porous medium and the viscosity of the fluid.

[0003] In existing oilfield techniques, most rely on static methods to test anomalous temperature points of heavy oil to determine its flowability in porous media. This typically involves identifying temperature points where the relevant physical properties of heavy oil undergo abrupt changes, such as a sudden drop in viscosity or a reduction in yield stress to zero, based on viscosity-temperature curves or rheological curves. This allows for the assessment of whether the heavy oil reservoir has reached the conditions for steam drive. However, these techniques neglect the influence of porous media properties, making them unsuitable for reservoirs with varying permeability. Consequently, they are not universally applicable and are only suitable for specific ranges. Summary of the Invention

[0004] The main objective of this invention is to provide an apparatus and method for measuring the start-up temperature of heavy oil in porous media, in order to solve the technical problem that existing technologies cannot be applied to reservoirs with different permeabilities, resulting in a limited application range.

[0005] To achieve the above objectives, the present invention provides a method for measuring the start-up temperature of heavy oil in a porous medium, comprising:

[0006] S1: Prepare crude oil samples and core samples;

[0007] S2: The core sample is kept at the experimental temperature and crude oil sample is continuously injected into the core sample at the initial flow rate until the pressure at the injection end of the core sample stabilizes.

[0008] S3: The crude oil sample is continuously injected into the core sample with stable injection end pressure at the experimental flow rate, and the pressure value after the injection end pressure stabilizes for the second time is obtained.

[0009] S4: Repeat step S3 by changing the experimental flow rate multiple times, and calculate the core initiation pressure gradient value.

[0010] S5: Change the experimental temperature multiple times and repeat steps S2 to S4 to obtain the heavy oil start-up temperature based on the core simulated start-up pressure gradient value at different experimental temperatures.

[0011] S6: Repeat steps S2 to S5 by changing the permeability of the core sample multiple times. Based on the heavy oil start-up temperature under different permeabilities, obtain the calculation formula for the heavy oil start-up temperature.

[0012] In an embodiment of the present invention, step S1 includes:

[0013] S11: Use a crude oil dehydration device to dehydrate crude oil;

[0014] S12: Crude oil samples are obtained by filtering the dehydrated crude oil using a sieve.

[0015] S13: Select a core model with known permeability and measure its length. Inject crude oil samples into the core model at a constant rate until saturation.

[0016] S14: After the core model has been saturated, allow it to stand for a first preset time to obtain a core sample.

[0017] In an embodiment of the present invention, the temperature range of the filtration process is 75°C to 80°C, and the first preset duration is not less than 24 hours.

[0018] In an embodiment of the present invention, step S2 includes:

[0019] S21: Place the core sample in the experimental temperature environment;

[0020] S22: The second preset duration of isothermal treatment after the core sample reaches the experimental temperature;

[0021] S23: Inject crude oil sample into the isothermal-treated core sample at the initial flow rate;

[0022] S24: After the injection pressure of the core sample stabilizes, perform a static treatment for the third preset time.

[0023] In an embodiment of the present invention, step S4 includes:

[0024] The experimental flow rate was changed multiple times to obtain different pressure values ​​corresponding to different experimental flow rates;

[0025] Multiple pressure gradient values ​​at different experimental flow rates were calculated based on multiple pressure values ​​and the length of the core model.

[0026] The first relationship curve was plotted based on the experimental flow rate and pressure gradient value, and a linear regression equation was fitted.

[0027] The intercept of the calculated linear regression equation is the core initiation pressure gradient value.

[0028] In an embodiment of the present invention, step S5 includes:

[0029] The experimental temperature was continuously changed until the core sample pressure gradient value was 0, at which point the experiment was stopped. This experimental temperature is the heavy oil start-up temperature.

[0030] In an embodiment of the present invention, step S6 includes:

[0031] Calculate the 50℃ mobility corresponding to multiple permeabilities, where the 50℃ mobility is the ratio between the permeability and the viscosity of the crude oil sample at 50℃.

[0032] Plot the second relationship curve between the reciprocal of the start-up temperature of heavy oil with different permeability and the logarithm of the mobility at 50℃;

[0033] The formula for calculating the start-up temperature of heavy oil is derived by fitting the second relationship curve.

[0034] In an embodiment of the present invention, the formula for calculating the heavy oil start-up temperature is as follows:

[0035]

[0036] Among them, T s is the heavy oil start-up temperature, °C; k is the permeability, mD; μ 50 denoted as ν, where ν is the viscosity of the crude oil sample at 50℃, in mPa·s; a and b are constants.

[0037] In the embodiments of the present invention, the initial flow rate range is 0.001 mL / min to 0.01 mL / min, the experimental flow rate range is 0.05 mL / min to 0.5 mL / min, and the experimental temperature is not less than 30°C.

[0038] In an embodiment of the present invention, an apparatus for measuring the start-up temperature of heavy oil in a porous medium is also provided, applied to the method for measuring the start-up temperature of heavy oil in a porous medium as described above. The apparatus for measuring the start-up temperature of heavy oil in a porous medium includes:

[0039] Piston, used to load crude oil samples;

[0040] The core holder is connected to the outlet end of the piston and is used to hold the core sample.

[0041] Displacement pump, connected to the inlet end of the piston, is used to pump crude oil samples into the core holder.

[0042] A constant temperature chamber is used to regulate the experimental temperature.

[0043] Data acquisition equipment is used to measure and collect pressure values.

[0044] Through the above technical solution, the method for measuring the start-up temperature of heavy oil in porous media provided by the embodiments of the present invention has the following beneficial effects:

[0045] In the measurement process, crude oil samples and core samples meeting the experimental conditions were first prepared. Then, crude oil samples were continuously injected into the core samples at a low rate to stabilize the pressure at the injection end. Next, the experimental flow rate was varied to obtain the relationship curve between flow rate and pressure gradient, and the core's simulated start-up pressure gradient was calculated. Then, the experimental temperature was varied to obtain the simulated start-up pressure gradient at different experimental temperatures, thus obtaining the heavy oil start-up temperature. Finally, the permeability of the core samples was varied to obtain the heavy oil start-up temperature at different permeabilities, thus deriving the calculation formula for the heavy oil start-up temperature. The calculation formula for the heavy oil start-up temperature was obtained through experiments, taking into account the influence of porous media. This allows the formula to be applied to reservoirs with different permeabilities, thereby expanding the application range of the method for measuring the heavy oil start-up temperature in porous media. Attached Figure Description

[0046] The accompanying drawings are provided to illustrate the invention and form part of the specification. They are used together with the following detailed description to explain the invention, but do not constitute a limitation thereof. In the drawings:

[0047] Figure 1 This is a schematic flowchart of a method for measuring the start-up temperature of heavy oil in a porous medium according to an embodiment of the present invention;

[0048] Figure 2 This is a schematic diagram of a device for measuring the start-up temperature of heavy oil in a porous medium according to an embodiment of the present invention;

[0049] Figure 3 This is a schematic diagram of the first relationship curve of core model No. 1 according to an embodiment of the present invention;

[0050] Figure 4 This is a schematic diagram of the first relationship curve of core model No. 2 according to an embodiment of the present invention;

[0051] Figure 5 This is a schematic diagram of the first relationship curve of core model No. 3 according to an embodiment of the present invention;

[0052] Figure 6 This is a schematic diagram of the relationship between the core initiation pressure gradient value and temperature according to an embodiment of the present invention;

[0053] Figure 7 This is a schematic diagram of the second relationship curve according to an embodiment of the present invention.

[0054] Explanation of reference numerals in the attached figures

[0055] label name label name 1 piston 3 Core holder 2 Displacement pump 4 Data acquisition equipment Detailed Implementation

[0056] The specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are for illustration and explanation only and are not intended to limit the present invention.

[0057] The method for measuring the start-up temperature of heavy oil in a porous medium according to the present invention is described below with reference to the accompanying drawings.

[0058] like Figure 1 As shown, in an embodiment of the present invention, a method for measuring the start-up temperature of heavy oil in a porous medium is provided, comprising:

[0059] S1: Prepare crude oil samples and core samples;

[0060] S2: The core sample is kept at the experimental temperature and crude oil sample is continuously injected into the core sample at the initial flow rate until the pressure at the injection end of the core sample stabilizes.

[0061] S3: The crude oil sample is continuously injected into the core sample with stable injection end pressure at the experimental flow rate, and the pressure value after the injection end pressure stabilizes for the second time is obtained.

[0062] S4: Repeat step S3 by changing the experimental flow rate multiple times, and calculate the core initiation pressure gradient value.

[0063] S5: Change the experimental temperature multiple times and repeat steps S2 to S4 to obtain the heavy oil start-up temperature based on the core simulated start-up pressure gradient value at different experimental temperatures.

[0064] S6: Repeat steps S2 to S5 by changing the permeability of the core sample multiple times, and obtain the calculation formula for the heavy oil start-up temperature based on the heavy oil start-up temperature under different permeabilities.

[0065] In the derivation of the calculation formula, crude oil samples and core samples meeting experimental conditions were first prepared. Then, crude oil samples were continuously injected into the core samples at a low rate to stabilize the injection end pressure. Next, the experimental flow rate was varied to obtain the relationship curve between flow rate and pressure gradient, and the core sample's simulated start-up pressure gradient was calculated. Then, the experimental temperature was varied to obtain the simulated start-up pressure gradient at different experimental temperatures, thus obtaining the heavy oil start-up temperature. Finally, the permeability of the core samples was varied to obtain the heavy oil start-up temperature at different permeabilities, thus deriving the calculation formula for the heavy oil start-up temperature. The calculation formula for the heavy oil start-up temperature was obtained experimentally, taking into account the influence of porous media. This allows the formula to be applied to reservoirs with different permeabilities, thereby expanding the application range of the method for measuring the heavy oil start-up temperature in porous media. By fully considering the influence of multiple factors such as temperature and pressure during the derivation of the calculation formula, the reliability of the calculation method is improved.

[0066] In an embodiment of the present invention, step S1 includes:

[0067] S11: Use a crude oil dehydration device to dehydrate crude oil;

[0068] S12: Crude oil samples are obtained by filtering the dehydrated crude oil using a sieve.

[0069] S13: Select a core model with known permeability and measure its length. Inject crude oil samples into the core model at a constant rate until saturation.

[0070] S14: After the core model has been saturated, allow it to stand for a first preset time to obtain a core sample.

[0071] Specifically, the crude oil was first dehydrated in a constant-temperature environment until its water content fell below 0.3%. After dehydration, a stainless steel sieve with a pore size of 0.045 mm was used for filtration. This filtration removed some large particulate impurities from the crude oil, thus reducing their impact on subsequent experiments. The filtration process was conducted within a temperature range of 75℃ to 80℃, with 80℃ being the optimal temperature for thorough impurity removal. The resulting crude oil sample was then used in the experiment.

[0072] Furthermore, the saturated core model needs to undergo a settling period of at least 24 hours until the core model is fully aged to obtain the core sample used in the experiment. This settling process allows the crude oil sample to fully integrate with the core model, enabling the core sample to better simulate the shear force experienced by the crude oil sample in the real formation, thereby more accurately obtaining the start-up temperature of heavy oil in porous media.

[0073] In an embodiment of the present invention, step S2 includes:

[0074] S21: Place the core sample in the experimental temperature environment;

[0075] S22: The second preset duration of isothermal treatment after the core sample reaches the experimental temperature;

[0076] S23: Inject crude oil sample into the isothermal-treated core sample at the initial flow rate;

[0077] S24: After the injection pressure of the core sample stabilizes, perform a static treatment for the third preset time.

[0078] Specifically, after placing the core sample in the experimental temperature environment, the temperature of the core sample needs to be monitored continuously. Once the experimental temperature is reached, the temperature should not be changed immediately, but should be maintained for at least 2 hours before placing the core sample into the experimental apparatus for testing. The third preset time is no less than 8 hours, so as to allow the core sample to age fully.

[0079] Furthermore, the initial flow rate range is 0.001 mL / min to 0.01 mL / min. Generally, an initial flow rate of 0.001 mL / min is selected to slowly displace the liquid to the inlet end of the core sample. By injecting the crude oil sample slowly at a slower initial flow rate, the impact of excessively fast flow rate on the pressure stabilization process is reduced, thereby accelerating the pressure stabilization speed at the injection end of the core sample.

[0080] In an embodiment of the present invention, step S4 includes:

[0081] The experimental flow rate was changed multiple times to obtain different pressure values ​​corresponding to different experimental flow rates;

[0082] Multiple pressure gradient values ​​at different experimental flow rates were calculated based on multiple pressure values ​​and the length of the core model.

[0083] The first relationship curve was plotted based on the experimental flow rate and pressure gradient value, and a linear regression equation was fitted.

[0084] The intercept of the calculated linear regression equation is the core initiation pressure gradient value.

[0085] Specifically, the experimental flow rate ranged from 0.05 mL / min to 0.5 mL / min. Each change in the experimental flow rate caused fluctuations in the injection end pressure of the core sample. When the injection end pressure of the core sample stabilized again, the pressure value corresponding to the experimental flow rate at that time was obtained. The pressure value was then divided by the length of the core model to obtain the pressure gradient value. Finally, the experimental flow rate and pressure gradient value for each group were plotted on a coordinate system with the pressure gradient value on the x-axis and the experimental flow rate on the y-axis to form the first relationship curve. The first relationship curve was then fitted to obtain the linear regression equation between the experimental flow rate and the pressure gradient value. Finally, the intercept of the linear regression equation was calculated to obtain the core initiation pressure gradient value at the experimental temperature at that time.

[0086] Among them, the core start-up pressure gradient value refers to the pressure gradient value that the crude oil sample can flow in the core sample, that is, the crude oil sample can be successfully extracted.

[0087] In an embodiment of the present invention, step S5 includes:

[0088] The experimental temperature was continuously changed until the core sample pressure gradient value was 0, at which point the experiment was stopped. This experimental temperature is the heavy oil start-up temperature.

[0089] Specifically, each change in experimental temperature yields the corresponding core simulated start-up pressure gradient value. The experimental temperature increases from low to high, with a minimum increase of 30°C. The increase stops when the simulated start-up pressure gradient reaches zero at a certain experimental temperature; this temperature represents the heavy oil start-up temperature corresponding to the core model at this permeability. By incorporating experimental temperature into the calculation formula for heavy oil start-up temperature, the application range of the method for measuring heavy oil start-up temperature in porous media is expanded.

[0090] In an embodiment of the present invention, step S6 includes:

[0091] Calculate the 50°C mobility corresponding to multiple permeabilities, where the 50°C mobility is the ratio between the permeability and the crude oil viscosity at 50°C.

[0092] Plot the second relationship curve between the reciprocal of the start-up temperature of heavy oil with different permeability and the logarithm of the mobility at 50℃;

[0093] The formula for calculating the start-up temperature of heavy oil is derived by fitting the second relationship curve.

[0094] In an embodiment of the present invention, the formula for calculating the heavy oil start-up temperature is as follows:

[0095]

[0096] Among them, T s is the heavy oil start-up temperature, °C; k is the permeability, mD; μ 50 denoted as ν, where ν is the viscosity of the crude oil sample at 50℃, in mPa·s; a and b are constants.

[0097] Specifically, by incorporating permeability into the calculation formula for heavy oil start-up temperature using a 50°C mobility factor, the resulting formula can be applied to reservoirs with varying permeabilities, thereby expanding the applicability of the method for measuring heavy oil start-up temperature in porous media. The 50°C mobility factor is the ratio between permeability and the viscosity of crude oil at 50°C, which is measured using a viscometer.

[0098] Furthermore, this invention calculates the temperature point at which heavy oil of different viscosities flows smoothly in the core under different permeabilities by establishing the relationship between mobility parameters and heavy oil initiation temperature. It comprehensively considers the flowability limit of heavy oil under the influence of multiple factors such as temperature and pressure, thereby expanding the application range of the method for measuring the initiation temperature of heavy oil in porous media. By applying the calculation formula for heavy oil initiation temperature to the reservoir development of this type of crude oil, the flowability of this crude oil in reservoirs with different permeabilities can be accurately predicted. This provides theoretical support and assistance for determining the drainage radius and transfer temperature of heavy oil in the reservoir field, as well as optimizing operating parameters and correcting the numerical simulation model of heavy oil.

[0099] In an embodiment of the present invention, an apparatus for measuring the start-up temperature of heavy oil in a porous medium is also provided, applied to the method for measuring the start-up temperature of heavy oil in a porous medium as described above. The apparatus for measuring the start-up temperature of heavy oil in a porous medium includes:

[0100] Piston 1 is used to load crude oil samples;

[0101] The core holder 3 is connected to the outlet end of the piston 1 and is used to hold the core sample.

[0102] Displacement pump 2 is connected to the inlet end of piston 1. Displacement pump 2 is used to pump crude oil samples into core holder 3.

[0103] A constant temperature chamber is used to regulate the experimental temperature.

[0104] Data acquisition device 4 is used to measure and acquire pressure values.

[0105] The following describes the process of preparing crude oil samples using ordinary heavy oil from Xinjiang Oilfield and core samples using three different core models with varying permeabilities. The core model parameters are shown in Table 1. The apparatus and method for measuring the start-up temperature of heavy oil in porous media are also explained.

[0106]

[0107] Table 1 Parameters of the core model used in the experiment

[0108] First, select core model No. 1 and load it into core holder 3, prepare crude oil sample and load it into piston 1, and use displacement pump 2 to pump crude oil sample into core model No. 1 for saturation.

[0109] Second, place the core holder 3 and piston 1 into the constant temperature chamber and set the experimental temperature to 30℃ to start the constant temperature. Then, use the displacement pump 2 to slowly pump the crude oil sample into the core sample at an initial flow rate of 0.001mL / min. At this time, the data acquisition device 4 continuously monitors the injection end pressure until it stabilizes.

[0110] like Figures 3 to 5A linear fit was performed between the pressure gradient and the experimental flow rate. As temperature and permeability increased, the slope of the fitted line gradually increased, while the intercept on the horizontal axis gradually decreased, indicating that the simulated start-up pressure gradient gradually decreased. At a certain temperature, i.e., above the heavy oil start-up temperature T... s Afterwards, the fitted straight line begins to pass through the origin, meaning the core initiation pressure gradient is approximately zero, as detailed below:

[0111] Third, the experimental flow rate was changed to 0.05 mL / min, 0.1 mL / min, 0.3 mL / min and 0.5 mL / min using displacement pump 2, and four data points were obtained with pressure value as the abscissa and experimental flow rate as the ordinate. The first relationship curve corresponding to 30℃ was fitted and the corresponding linear regression equation was fitted, and then the core simulated starting pressure gradient value corresponding to 30℃ was obtained.

[0112] Fourth, such as Figure 3 As shown, by changing the experimental temperature to 40℃, 50℃, 70℃, 75℃ and 80℃ using a constant temperature chamber, the first relationship curve and the core simulated start-up pressure gradient value corresponding to each temperature were obtained. Until the core simulated start-up pressure gradient value was 0 at 80℃, the heavy oil start-up temperature corresponding to Model 1 was found to be 80℃.

[0113] Sixth, such as Figure 4 As shown, the corresponding heavy oil start-up temperature measured using the No. 2 core model is 70℃;

[0114] Seventh, such as Figure 5 As shown, the corresponding heavy oil start-up temperature measured using the No. 3 core model is 65℃;

[0115] Eighth, plot the obtained data on a coordinate system with temperature on the x-axis and the core simulated initiation pressure gradient on the y-axis to obtain the relationship curve between the core simulated initiation pressure gradient and temperature, as shown below. Figure 6 As shown, the initiation temperatures of this ordinary heavy oil in cores with low, medium, and high permeability are 80℃, 65℃, and 60℃, respectively.

[0116] Ninth, such as Figure 7 As shown, a 50℃ mobility parameter was introduced. By fitting experimental results, the effective starting pressure gradient at different permeabilities and temperatures was obtained. Only when the driving pressure gradient was greater than the effective flow pressure gradient did the crude oil sample flow in the core. A second relationship curve was plotted between the reciprocal of the heavy oil starting temperature and the logarithm of the 50℃ mobility, showing that the heavy oil starting temperature decreases with increasing permeability. A linear fit was then performed between the reciprocal of the starting temperature and the logarithm of the 50℃ mobility to obtain a formula for calculating the heavy oil starting temperature with a correlation coefficient of 0.9978.

[0117]

[0118] The above experimental procedure is an embodiment of the present invention. The result is only a calculation formula for the heavy oil start-up temperature corresponding to the crude oil used in the present invention, and does not represent the actual protection scope of the present invention. The embodiment is only used to further illustrate the specific operation steps of the measurement experiment so that those skilled in the art can better understand the technical solution.

[0119] In the description of this invention, it should be understood that the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0120] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection, an electrical connection, or a connection that allows communication between them; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components, unless otherwise explicitly limited. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0121] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0122] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A method for measuring the start-up temperature of heavy oil in a porous medium, characterized in that, include: S1: Prepare crude oil samples and core samples; S2: The core sample is kept at the experimental temperature and the crude oil sample is continuously injected into the core sample at the initial flow rate until the pressure at the injection end of the core sample stabilizes. S3: The crude oil sample is continuously injected into the core sample whose injection end pressure has stabilized at the experimental flow rate, and the pressure value after the injection end pressure has stabilized for the second time is obtained. S4: Repeat step S3 by changing the experimental flow rate multiple times, and calculate the core initiation pressure gradient value. S5: Change the experimental temperature multiple times and repeat steps S2 to S4 to obtain the heavy oil start-up temperature based on the core simulated start-up pressure gradient value under different experimental temperatures. S6: Change the permeability of the core sample multiple times, repeat steps S2 to S5, and obtain the calculation formula for the heavy oil start-up temperature based on the heavy oil start-up temperature under different permeabilities. Step S6 includes: Calculate the 50°C mobility corresponding to multiple permeabilities, where the 50°C mobility is the ratio between the permeability and the crude oil viscosity at 50°C. Plot the second relationship curve between the reciprocal of the start-up temperature of heavy oil with different permeability and the logarithm of the mobility at 50℃; The calculation formula for the heavy oil start-up temperature is derived by fitting the second relationship curve.

2. The method for measuring the start-up temperature of heavy oil in a porous medium according to claim 1, characterized in that, Step S1 includes: S11: Use a crude oil dehydration device to dehydrate crude oil; S12: The dehydrated crude oil is filtered using a sieve to obtain the crude oil sample; S13: Select a core model with known permeability and measure its length, then inject the crude oil sample into the core model at a constant rate until saturation; S14: After the core model is saturated, it is left to stand for a first preset time to obtain the core sample.

3. The method for measuring the start-up temperature of heavy oil in a porous medium according to claim 2, characterized in that, The temperature range for filtration is 75℃~80℃, and the first preset time is not less than 24 hours.

4. The method for measuring the start-up temperature of heavy oil in a porous medium according to claim 1, characterized in that, Step S2 includes: S21: Place the core sample in the experimental temperature environment; S22: After the core sample reaches the experimental temperature, it undergoes a second preset time of isothermal treatment; S23: Inject the crude oil sample into the core sample after isothermal treatment at the initial flow rate; S24: After the injection end pressure of the core sample stabilizes, a static treatment is performed for a third preset time.

5. The method for measuring the start-up temperature of heavy oil in a porous medium according to claim 1, characterized in that, Step S4 includes: The experimental flow rate was changed multiple times to obtain different pressure values ​​corresponding to different experimental flow rates; Multiple pressure gradient values ​​at different experimental flow rates were calculated based on the multiple pressure values ​​and the length of the core model. A first relationship curve was plotted based on the experimental flow rate and the pressure gradient value, and a linear regression equation was fitted. The intercept of the linear regression equation is calculated as the core initiation pressure gradient value.

6. The method for measuring the start-up temperature of heavy oil in a porous medium according to claim 1, characterized in that, Step S5 includes: The experimental temperature is continuously changed until the core sample pressure gradient value is 0, at which point the experimental temperature is the heavy oil start-up temperature.

7. The method for measuring the start-up temperature of heavy oil in a porous medium according to claim 1, characterized in that, The formula for calculating the heavy oil start-up temperature is as follows: in, T s The starting temperature for heavy oil is ℃; k Permeability, mD; μ 50 ρ is the viscosity of the crude oil sample at 50℃, in mPa·s; a and b are constants.

8. The method for measuring the start-up temperature of heavy oil in a porous medium according to any one of claims 1 to 7, characterized in that, The initial flow rate range is 0.001 mL / min to 0.01 mL / min, the experimental flow rate range is 0.05 mL / min to 0.5 mL / min, and the experimental temperature is not less than 30℃.

9. An apparatus for measuring the start-up temperature of heavy oil in a porous medium, characterized in that, The method for measuring the start-up temperature of heavy oil in a porous medium according to any one of claims 1 to 8, wherein the apparatus for measuring the start-up temperature of heavy oil in a porous medium comprises: Piston, used to load the crude oil sample; A core holder is connected to the outlet end of the piston, and the core holder is used to hold the core sample; A displacement pump is connected to the inlet end of the piston, and the displacement pump is used to pump the crude oil sample into the core holder; A constant temperature chamber, used to regulate the experimental temperature; and Data acquisition equipment is used to measure and acquire the pressure value of the core sample.

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