Device and method for measuring nonlinear seepage characteristics and starting pressure of high-temperature and high-pressure fluid

Abstract

The present invention discloses a device and method for measuring the nonlinear seepage characteristics and starting pressure of high-temperature, high-pressure fluids. The device comprises: a core holder containing a core to be measured; a coarse injection system connected to the inlet of the core holder, comprising an intermediate container and a first injection pump; a fine injection system comprising a first fine injection system connected to the inlet of the core holder and a second fine injection system connected to the outlet of the core holder; and a drainage system comprising a back-pressure valve and a desorption meter connected to the outlet of the core holder. This device enables measurement of nonlinear seepage characteristics and starting pressure. The present invention faithfully restores formation fluids. The displacement medium selected for this research is gas-bearing oil, perfectly restoring high-pressure physical properties such as viscosity and density of the formation fluid. The resulting starting pressure gradient and nonlinear seepage characteristics studies can better reflect the true state of the reservoir.

Description

Technical Field

[0001] The present invention relates to the technical field of oil and gas field development, and in particular to a device and method for measuring nonlinear seepage characteristics and starting pressure of high-temperature and high-pressure fluid. Background Art

[0002] Fluid flow in porous media is generally Darcy-linear. However, in special cases such as the flow of non-Newtonian fluids like heavy oil, "microscale" flow in ultra-low permeability porous media, and dynamic interaction between high-temperature, high-pressure fluids and pore walls, the flow characteristics deviate from the linear flow pattern, resulting in the measured flow curve exhibiting a starting pressure gradient and curved, nonlinear segments.

[0003] Traditionally, the testing method for nonlinear seepage is primarily a steady-state method. When studying nonlinear seepage patterns, the method of measuring pressure during unsteady-state seepage is often used to determine the starting pressure gradient. The main drawback of traditional experimental methods lies in the lack of representativeness of the displacement fluid selection. Simulated formation fluids such as formation water, kerosene, and degassed oil have been selected as displacement fluids, but high-temperature, high-pressure gas oil has rarely been selected. These simulated fluids often have properties equivalent to those of high-temperature, high-pressure formation fluids (e.g., kerosene with a viscosity equivalent to high-temperature, high-pressure formation crude oil). Consequently, the measured experimental results struggle to reflect the dynamic fluid-solid interaction between the actual formation fluid and the core pore wall, or to characterize the actual seepage characteristics of the formation fluid under high-temperature, high-pressure reservoir conditions. Consequently, the resulting starting pressure gradient is not the true starting pressure gradient of the reservoir.

[0004] To this end, existing technicians have attempted to simultaneously test nonlinear seepage characteristics and the starting pressure gradient. For example, the "capillary balance method" uses the principle of communicating vessels. When measuring the starting pressure gradient, capillaries are connected at the inlet and outlet ends of the core. The effect of gravity causes the fluid at the inlet end to flow through the core to the outlet end. After the liquid levels at both ends are fully balanced, a height difference will eventually be maintained. This height difference is the minimum starting pressure value of the sample. Because the test device usually uses a glass tube, which cannot withstand high temperature and pressure, the measurement conditions of this method are all low pressure or even normal pressure, and cannot truly portray the seepage characteristics of the fluid under high temperature and high pressure conditions in the formation.

[0005] Chinese patent CN107676083A discloses an experimental method for measuring the starting pressure gradient under low-permeability reservoir formation conditions. The method comprises the following steps: 1. preparing a low-permeability rock sample; 2. conducting a dynamic high-temperature, high-pressure water-rock simulation test under the low-permeability sample formation fluid temperature and pressure conditions, recording the fluid pressure and seepage velocity at different pressures; and 3. determining the starting pressure of the low-permeability rock sample based on multiple sets of fluid pressure and seepage velocity values, and obtaining the starting pressure of the low-permeability reservoir section based on the starting pressures of multiple cores. Analysis shows that although the experimental conditions for testing the starting pressure gradient are formation temperature and pressure conditions, the fluid used is formation water, and the test is not based on actual gas-bearing crude oil in the formation.

[0006] Chinese patent CN117607005B discloses an experimental method for measuring the starting pressure gradient of rock. The method mainly includes the following steps: Step 1: pressurizing the rock sample to be tested for a period of time after being filled with a first test fluid; Step 2: connecting an intermediate container filled with the first test fluid and under a certain pressure to a core holder, recording the pressure difference between the two ends of the rock sample to be tested, and calculating the starting pressure gradient of the first test fluid based on the pressure difference when the change in the pressure difference is less than a set threshold of 0.001 MPa; Step 3: when the volume of the first test fluid collected in the graduated cylinder no longer changes, connecting the intermediate container filled with a second test fluid and under a certain pressure to the core holder to obtain the starting pressure gradients of each phase fluid under different saturation conditions. Through analysis, it can be seen that compared with the method of CN107676083A which only selects single-phase formation water as the test medium, this method further considers the starting pressure gradient of oil-water two-phase fluid under different water saturation conditions. However, according to its description, the fluid selected is still ground degassed crude oil, and the test is not based on real formation gas-containing crude oil. The experimental temperature is also room temperature, and the description of judging whether the displacement state has reached stability by real-time acquisition of the pressure difference change at the core inlet and outlet is not detailed. Summary of the Invention

[0007] To solve at least one of the above problems, the present invention proposes a device and method for measuring the nonlinear seepage characteristics and starting pressure of high-temperature and high-pressure fluids.

[0008] The technical solution of the present invention is: a device for measuring the nonlinear seepage characteristics and starting pressure of high-temperature and high-pressure fluids, comprising:

[0009] A core holder, wherein the core to be tested is arranged in the core holder;

[0010] a coarse injection system connected to the inlet of the core holder, comprising an intermediate container and a first injection pump;

[0011] A fine injection system, comprising a first fine injection system connected to the inlet of the core holder and a second fine injection system connected to the outlet of the core holder; the first fine injection system comprises a first transparent pressure-resistant injection pipe and a second injection pump connected in sequence to the core holder, the first transparent pressure-resistant injection pipe being provided with a piston; the second fine injection system comprises a second transparent pressure-resistant injection pipe and a third injection pump connected in sequence to the core holder, the second transparent pressure-resistant injection pipe being provided with a piston; the inner diameter of each of the first and second transparent pressure-resistant injection pipes being no greater than 10 mm;

[0012] The drainage system includes a back pressure valve connected to the core holder outlet and a desorption meter;

[0013] An oven is used to heat the core holder, the intermediate container and the fine injection system.

[0014] One embodiment of the present invention is that a sample dispenser is further provided, the sample dispenser is used to prepare crude oil containing dissolved gas, and the first transparent pressure-resistant injection pipe and the second transparent pressure-resistant injection pipe are both connected to the sample dispenser.

[0015] One embodiment of the present invention is that the shapes of the first transparent pressure-resistant injection tube and the second transparent pressure-resistant injection tube are one of a plane spiral, a bow shape, and a three-dimensional spiral shape, and the first transparent pressure-resistant injection tube and the second transparent pressure-resistant injection tube are provided with scales.

[0016] One embodiment of the present invention is that it also includes a metering system, which includes a camera, which is used to take pictures of the first transparent pressure-resistant injection tube and the second transparent pressure-resistant injection tube. The camera is electrically connected to an image recognition system, and the image is used to identify the picture transmitted by the camera, thereby obtaining the position of the piston and further obtaining the injection volume.

[0017] Another object of the present invention is to disclose a method for measuring the nonlinear seepage characteristics and starting pressure of a high-temperature and high-pressure fluid. The method is based on any of the above-mentioned devices and comprises the following steps:

[0018] Connect the device, inject degassed oil into the intermediate container, and inject gasified oil into the first transparent pressure-resistant injection pipe and the second transparent pressure-resistant injection pipe;

[0019] The temperature is raised to the reservoir temperature, and then the degassed oil is injected into the core through the first injection pump to saturate the core;

[0020] Injecting fluid into the core through a second injection pump until the oil-gas ratio of the fluid at the core holder outlet is the same as the oil-gas ratio of the gas-containing oil, and recording the amount of gas-containing oil in the first transparent pressure-resistant injection tube;

[0021] Connect the first fine injection system, the core holder, and the second fine injection system. While maintaining the gas and oil content in the first transparent pressure-resistant injection pipe and the second transparent pressure-resistant injection pipe unchanged, the outlet pressure difference between the second displacement pump and the third displacement pump is the starting pressure. Calculate the starting pressure gradient based on the starting pressure and the core length. Simultaneously record the outlet pressure P1 of the second displacement pump and the outlet pressure P2 of the third displacement pump at this time.

[0022] Maintain the outlet pressure of the third displacement pump at P2, increase the outlet pressure of the second displacement pump to the first pressure, until the gas-oil content in the first transparent pressure-resistant injection pipe and the second transparent pressure-resistant injection pipe change at the same rate, and record the change in the gas-oil content in the first transparent pressure-resistant injection pipe per unit time at this time; then change the magnitude of the first pressure to obtain the change in the gas-oil content in the first transparent pressure-resistant injection pipe per unit time under multiple pressure differential conditions, and draw a forward nonlinear seepage curve based on the aforementioned change.

[0023] Furthermore, the method also includes the following steps: maintaining the outlet pressure of the second displacement pump at P1, increasing the outlet pressure of the third displacement pump to the second pressure, until the gas-oil content in the second transparent pressure-resistant injection pipe and the first transparent pressure-resistant injection pipe change at the same rate, and recording the change in the gas-oil content in the second transparent pressure-resistant injection pipe per unit time at this time; then changing the magnitude of the second pressure to obtain the change in the gas-oil content in the second transparent pressure-resistant injection pipe per unit time under multiple pressure difference conditions, and drawing a reverse nonlinear seepage curve based on the above changes.

[0024] Beneficial Effects: This invention faithfully reproduces formation fluids. Using gas-bearing oil as the displacement medium, it perfectly reproduces high-pressure physical properties of formation fluids, such as viscosity and density. The resulting studies of start-up pressure gradients and nonlinear seepage characteristics better reflect the true reservoir conditions. Furthermore, the test can be conducted under high-pressure conditions, reproducing the true formation environment and providing more reliable results. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 Schematic diagram of the overall structure of the device of Example 1;

[0026] Figure 2 This is a schematic structural diagram of the first transparent pressure-resistant injection tube and the second transparent pressure-resistant injection tube.

[0027] In the figure, 1 is a core holder, 2 is an intermediate container, 3 is a first injection pump, 4 is a back pressure valve, 5 is a desorption meter, 6 is a first transparent pressure-resistant injection pipe, 7 is a second injection pump, 8 is a third injection pump, 9 is a camera, 10 is a sample dispenser, 11 is a second transparent pressure-resistant injection pipe, 12 is a gas tank, 13 is a crude oil tank, 14 is a pressurizing device, and 15 is an oven. DETAILED DESCRIPTION

[0028] The specific implementation methods of the present invention will be clearly and completely described below with reference to examples and drawings. Obviously, the described examples are only some embodiments of the present invention, rather than all embodiments.

[0029] Example 1

[0030] like Figures 1-2 As shown, a device for measuring nonlinear seepage characteristics and starting pressure of high-temperature and high-pressure fluids comprises:

[0031] A core holder 1, wherein the core to be tested is arranged in the core holder 1;

[0032] As for the core holder 1, it is a conventional core holder 1 in the art, for example, it is provided with components such as a plug, a shell, a confining pressure chamber and a rubber cylinder.

[0033] a coarse injection system connected to the inlet of the core holder 1 , comprising an intermediate container 2 and a first injection pump 3 ;

[0034] A fine injection system includes a first fine injection system connected to the inlet of the core holder 1 and a second fine injection system connected to the outlet of the core holder 1; the first fine injection system includes a first transparent pressure-resistant injection pipe 6 and a second injection pump 7 connected in sequence to the core holder 1, and a piston is provided in the first transparent pressure-resistant injection pipe 6; the second fine injection system includes a second transparent pressure-resistant injection pipe 11 and a third injection pump 8 connected in sequence to the core holder 1, and a piston is provided in the second transparent pressure-resistant injection pipe 11; the inner diameter of the first transparent pressure-resistant injection pipe 7 and the second transparent pressure-resistant injection pipe 11 is not greater than 10 mm;

[0035] The crude injection system is primarily used to inject degassed oil into the core during the initial stages of the experiment. When crude oil is produced to the surface, the pressure drops, causing a large amount of dissolved gas in the crude oil to desorb, forming degassed oil. The properties of degassed oil differ significantly from those of the live oil before desorption. For example, the viscosity of live oil flooded with carbon dioxide is significantly lower than that of degassed oil. Natural gas in crude oil can also reduce its viscosity to a certain extent.

[0036] At the same time, for gas-containing oil, if it is directly injected into the core, due to the low initial pressure in the core, the gas-containing oil is easily desorbed in the core and other parts, resulting in a mixture of degassed oil and gas actually injected into the core. The final result is still not the true result in the reservoir.

[0037] To this end, in this embodiment, a coarse injection system and a fine injection system are used to inject degassed oil and live oil, respectively. The coarse injection system employs a conventional injection device, such as an intermediate container 2 and a first injection pump 3. The intermediate container 2 is filled with degassed oil. One end of the intermediate container 2 is connected to the first injection pump 3, and the other end is connected to the inlet of the core holder 1, facilitating the injection of degassed oil into the core holder 1.

[0038] As for the fine injection system, since the device of this embodiment needs to study nonlinear seepage characteristics and starting pressure, considering the research characteristics of starting pressure and the forward and reverse displacement of nonlinear seepage characteristics, a first fine injection system and a second fine injection system are provided. The structures of the two fine injection systems are exactly the same, except that one end of the first fine injection system is connected to the inlet end of the core holder 1, and one end of the second fine injection system is connected to the outlet end of the core holder 1. The combination of the first and second fine injection systems not only enables the device to study starting pressure, but also enables the study of both forward and reverse nonlinear seepage characteristics, greatly broadening the scope of application of the device.

[0039] The first fine injection system includes a first transparent pressure-resistant injection tube 6 and a second injection pump 7, which are sequentially connected to the core holder 1. A piston is installed within the first transparent pressure-resistant injection tube 6; the piston separates the first transparent pressure-resistant injection tube 6. When the second injection pump 7 is operating, the gas-containing oil below the piston is injected into the core of the core holder 1 through the piston. During subsequent nonlinear seepage characteristic testing and start-up pressure testing, flow rate changes during this process need to be recorded. During this process, flow rate changes are relatively low, typically a few milliliters or a fraction of a milliliter. If the first transparent pressure-resistant injection tube 6 is too large, the error will be large, and the reliability of the final results will be reduced. Therefore, in this embodiment, the inner diameter of the first transparent pressure-resistant injection tube 6 is limited to no more than 10 mm, and can typically be set to 3.5 to 8 mm. The first transparent pressure-resistant injection tube 6 can be made of existing high-strength, transparent, pressure-resistant materials, such as common pressure-resistant sapphire glass. Those skilled in the art can also choose other materials suitable for this embodiment.

[0040] For the second fine injection system, it includes a second transparent pressure-resistant injection pipe 11 and a third injection pump 8 connected in sequence to the core clamp 1. A piston is provided in the second transparent pressure-resistant injection pipe 11. Its specific component settings are the same as those of the first fine injection system and will not be repeated in this embodiment.

[0041] The first transparent pressure-resistant injection tube 6 and the second transparent pressure-resistant injection tube 11 can be set to a plurality of different shapes, such as a common straight tube, a curved tube, etc. However, since the first transparent pressure-resistant injection tube 6 and the second transparent pressure-resistant injection tube 11 have a small diameter, if they are prepared as common straight tubes and curved tubes, their length will be too long, which is not conducive to monitoring the changes in the amount of gas and oil in the tube, and it will also take up a large space. For this reason, the shape of the first transparent pressure-resistant injection tube 6 and the second transparent pressure-resistant injection tube 11 can be set to a flat spiral shape (such as Figure 2 a), bow shape (as shown in Figure 2 b) and a three-dimensional spiral shape (not shown in the figure). In this case, the normal operation of the first transparent pressure-resistant injection pipe 6 and the second transparent pressure-resistant injection pipe 11 will not be affected, while the space occupied by them is also reduced. At the same time, it is also beneficial to monitor the changes in the gas and oil content in the pipes.

[0042] The drainage system includes a back pressure valve 4 connected to the outlet of the core holder 1 and a desorption meter 5;

[0043] The drainage system is connected to the outlet of the core holder 1, and is mainly used to discharge excess liquid in the core holder 1. At the same time, as shown above, gas-containing oil is injected into this device, and it is difficult to verify whether the core is completely filled with gas-containing oil using conventional methods. For this reason, in this embodiment, the produced liquid discharged from the core holder 1 is separated and tested by the provided desorption meter 5 until the oil-gas ratio of the produced liquid is substantially the same as the oil-gas ratio of the gas-containing oil, indicating that the gas-containing oil has completely replaced the degassed oil in the core. The desorption meter used is a common device in the art for detecting the desorbed gas content, and its structure will not be described in detail here. As for the back pressure valve 4, it is a conventional device in the art, such as being provided with a back pressure pump, etc., so its specific structure will not be described in detail here.

[0044] The oven 15 is used to heat the core holder 1, the intermediate container 2 and the fine injection system. The oven 15 is mainly used to maintain a high temperature environment of the device.

[0045] In some cases, it is difficult to obtain gas-containing oil directly from the formation. In order to solve this problem, the inventor sets up a sample dispenser 10 to configure the corresponding gas-containing oil. The sample dispenser 10 is connected to the crude oil storage tank 13 and the gas tank 12. At the same time, a booster 14 is provided on the gas tank 12. The booster 14 can pressurize the crude oil and gas inside the sample dispenser 10. Under the action of a long time, the gas will dissolve into the crude oil to form gas-containing oil. Of course, those skilled in the art can also accelerate the preparation of gas-containing oil by setting an agitator inside the sample dispenser 10. These are conventional settings in this field, and their specific structures are not described here. The sample dispenser 10 is also connected to the first transparent pressure-resistant injection pipe 6 and the second transparent pressure-resistant injection pipe 11. After the oil and gas are configured, the oil and gas are injected into the first transparent pressure-resistant injection pipe 6 and the second transparent pressure-resistant injection pipe 11.

[0046] This embodiment also includes a metering system, which includes a camera 9. The camera 9 is used to take pictures of the first transparent pressure-resistant injection tube 6 and the second transparent pressure-resistant injection tube 11. The camera 9 is electrically connected to an image recognition system. The image is used to identify the picture transmitted by the camera 9, thereby obtaining the position of the piston and further obtaining the injection volume.

[0047] Conventionally, the changes in the oil content of the first transparent pressure-resistant injection tube 9 and the second transparent pressure-resistant injection tube 11 can be monitored by the human eye, but human eye monitoring not only wastes manpower, but also has relatively poor results. To this end, this embodiment provides an automatic metering system. The system takes pictures through a camera 9, and then uses an image recognition system to perform image recognition on the taken pictures to obtain the specific oil content in the first transparent pressure-resistant injection tube 6 and the second transparent pressure-resistant injection tube 11 at this time. By comparing multiple consecutive pictures, the change in oil content can be obtained. For the image recognition used in this process, conventional means in the field can be used. For example, for the taken pictures, the scale point at the edge of the piston is read through a deep learning image segmentation algorithm to realize automatic scale recognition, thereby calculating the injection amount.

[0048] Example 2

[0049] A method for measuring the nonlinear seepage characteristics and starting pressure of a high-temperature and high-pressure fluid, based on the apparatus of Example 1, comprises the following steps:

[0050] Connect the device, inject degassed oil into the intermediate container, and inject gasified oil into the first transparent pressure-resistant injection pipe and the second transparent pressure-resistant injection pipe;

[0051] In this step, in order to avoid differences between different oil products, the base oil used in the gas oil preparation process is the aforementioned degassed oil.

[0052] The gas in this step can be prepared gas oil or gas oil extracted from the formation, but from a cost perspective, it is better to use prepared gas oil. At the same time, the gas in the gas oil can be natural gas, carbon dioxide, etc. commonly used in the oil displacement process.

[0053] The temperature is raised to the reservoir temperature, and then the degassed oil is injected into the core through the first injection pump to saturate the core;

[0054] In this step, the purpose of first injecting degassed oil is to maintain the pressure in the core and avoid rapid desorption of the subsequent gas-containing oil injected into the core.

[0055] Injecting fluid into the core through a second injection pump until the oil-gas ratio of the fluid at the core holder outlet is the same as the oil-gas ratio of the gas-containing oil, and recording the amount of gas-containing oil in the first transparent pressure-resistant injection tube;

[0056] In this step, live oil is injected to simulate the actual conditions of underground crude oil, resulting in more accurate measurements. To verify whether the core is saturated with live oil, the gas-oil ratio of the core outlet oil after desorption is tested. If the gas-oil ratio of the outlet oil is lower than that of the live oil, the core still contains a certain amount of degassed oil and requires further injection of live oil. If the gas-oil ratio of the outlet oil is roughly the same as that of the live oil, the core is saturated with live oil.

[0057] Connect the first fine injection system, the core holder, and the second fine injection system. While maintaining the gas and oil content in the first transparent pressure-resistant injection pipe and the second transparent pressure-resistant injection pipe unchanged, the outlet pressure difference between the second displacement pump and the third displacement pump is the starting pressure. Calculate the starting pressure gradient based on the starting pressure and the core length. Simultaneously record the outlet pressure P1 of the second displacement pump and the outlet pressure P2 of the third displacement pump at this time.

[0058] As described in Example 1, in this embodiment, P1 and P2 can be observed by human eyes or calculated and analyzed by an automatic metering system. The starting pressure gradient is calculated using the following formula: Starting pressure gradient = Starting pressure / core length.

[0059] Maintain the outlet pressure of the third displacement pump at P2, increase the outlet pressure of the second displacement pump to the first pressure, until the gas-oil content in the first transparent pressure-resistant injection pipe and the second transparent pressure-resistant injection pipe change at the same rate, and record the change in the gas-oil content in the first transparent pressure-resistant injection pipe per unit time at this time; then change the magnitude of the first pressure to obtain the change in the gas-oil content in the first transparent pressure-resistant injection pipe per unit time under multiple pressure differential conditions, and draw a forward nonlinear seepage curve based on the aforementioned change.

[0060] After the forward nonlinear seepage curve is calculated by the above process, the reverse nonlinear seepage curve can also be calculated by the following steps: maintain the outlet pressure of the second displacement pump at P1, increase the outlet pressure of the third displacement pump to the second pressure, until the gas-oil content in the second transparent pressure-resistant injection pipe and the first transparent pressure-resistant injection pipe change at the same rate, and record the change in the gas-oil content in the second transparent pressure-resistant injection pipe per unit time at this time; then change the magnitude of the second pressure to obtain the change in the gas-oil content in the second transparent pressure-resistant injection pipe per unit time under multiple pressure difference conditions, and draw the reverse nonlinear seepage curve based on the above changes.

[0061] The above description is merely a preferred embodiment of the present invention and does not constitute any form of limitation to the present invention. Although the present invention has been disclosed as a preferred embodiment as above, it is not intended to limit the present invention. Any technician familiar with this profession can make some changes or modifications to equivalent embodiments of the technical contents disclosed above without departing from the scope of the technical solution of the present invention. However, any simple modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention are still within the scope of the technical solution of the present invention.

Claims

1. A device for measuring the nonlinear seepage characteristics and starting pressure of high-temperature and high-pressure fluids, characterized in that: include: A core holder, wherein the core to be tested is arranged in the core holder; a coarse injection system connected to the inlet of the core holder, comprising an intermediate container and a first injection pump; A fine injection system, comprising a first fine injection system connected to the inlet of the core holder and a second fine injection system connected to the outlet of the core holder; the first fine injection system comprises a first transparent pressure-resistant injection pipe and a second injection pump connected in sequence to the core holder, the first transparent pressure-resistant injection pipe being provided with a piston; the second fine injection system comprises a second transparent pressure-resistant injection pipe and a third injection pump connected in sequence to the core holder, the second transparent pressure-resistant injection pipe being provided with a piston; the inner diameter of each of the first and second transparent pressure-resistant injection pipes being no greater than 10 mm; The drainage system includes a back pressure valve connected to the core holder outlet and a desorption meter; An oven is used to heat the core holder, the intermediate container and the fine injection system.

2. The device according to claim 1, characterized in that A sample dispenser is also provided, which is used to prepare crude oil with dissolved gas. The first transparent pressure-resistant injection pipe and the second transparent pressure-resistant injection pipe are both connected to the sample dispenser.

3. The device according to claim 1, characterized in that The shapes of the first transparent pressure-resistant injection tube and the second transparent pressure-resistant injection tube are one of a plane spiral, a bow shape, and a three-dimensional spiral shape, and the first transparent pressure-resistant injection tube and the second transparent pressure-resistant injection tube are provided with scales.

4. The device according to claim 1, characterized in that It also includes a metering system, which includes a camera. The camera is used to take pictures of the first transparent pressure-resistant injection tube and the second transparent pressure-resistant injection tube. The camera is electrically connected to an image recognition system. The image is used to identify the picture transmitted by the camera, thereby obtaining the position of the piston and further obtaining the injection volume.

5. A method for measuring the nonlinear seepage characteristics and starting pressure of high-temperature and high-pressure fluids, characterized in that: The method is based on the device according to any one of claims 1 to 4, and comprises the following steps: Connect the device, inject degassed oil into the intermediate container, and inject gasified oil into the first transparent pressure-resistant injection pipe and the second transparent pressure-resistant injection pipe; The temperature is raised to the reservoir temperature, and then the degassed oil is injected into the core through the first injection pump to saturate the core; Injecting fluid into the core through a second injection pump until the oil-gas ratio of the fluid at the core holder outlet is the same as the oil-gas ratio of the gas-containing oil, and recording the amount of gas-containing oil in the first transparent pressure-resistant injection tube; Connect the first fine injection system, the core holder, and the second fine injection system. While maintaining the gas and oil content in the first transparent pressure-resistant injection pipe and the second transparent pressure-resistant injection pipe unchanged, the outlet pressure difference between the second displacement pump and the third displacement pump is the starting pressure. Calculate the starting pressure gradient based on the starting pressure and the core length. Simultaneously record the outlet pressure P1 of the second displacement pump and the outlet pressure P2 of the third displacement pump at this time. Maintain the outlet pressure of the third displacement pump at P2, increase the outlet pressure of the second displacement pump to the first pressure, until the gas-oil content in the first transparent pressure-resistant injection pipe and the second transparent pressure-resistant injection pipe change at the same rate, and record the change in the gas-oil content in the first transparent pressure-resistant injection pipe per unit time at this time; then change the magnitude of the first pressure to obtain the change in the gas-oil content in the first transparent pressure-resistant injection pipe per unit time under multiple pressure differential conditions, and draw a forward nonlinear seepage curve based on the aforementioned change.

6. The method according to claim 5, characterized in that The following steps are also included: Maintain the outlet pressure of the second displacement pump at P1, increase the outlet pressure of the third displacement pump to the second pressure, until the gas-oil content in the second transparent pressure-resistant injection pipe changes at the same rate as the first transparent pressure-resistant injection pipe, and record the change in the gas-oil content in the second transparent pressure-resistant injection pipe per unit time at this time; then change the magnitude of the second pressure to obtain the change in the gas-oil content in the second transparent pressure-resistant injection pipe per unit time under multiple pressure differential conditions, and draw a reverse nonlinear seepage curve based on the aforementioned changes.

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