A high temperature resistant drilling fluid performance testing device and testing method

Abstract

The present invention discloses a high-temperature resistant drilling fluid performance testing device and testing method, which belongs to the technical field of material performance analysis. The testing device includes a mud cup, a piston assembly and an air source device, wherein the piston assembly includes a piston body, two groups of sealing rings located on the side wall of the piston body and spaced apart along its axial direction, and a drainage channel. One end opening of the drainage channel is located between the two groups of sealing rings, and the other end opening is connected to the drainage discharge pipe at the bottom of the mud cup through a hose. The air source device is used to replenish gas to the bottom of the mud cup to push the piston assembly to move upward. The present invention uses gas to drive the movement of the piston in the mud cup. When the displacement is completed, the residual displacement medium in the mud cup is gas. There is no need to recover it. It can be directly discharged to start the next round of experiments, which saves experimental time. The present invention sets a drainage channel between the sealing rings of the piston to guide the leaking fluid to the outside of the mud cup to prevent gas from entering the drilling fluid, which is conducive to improving the accuracy of the test data.

Description

Technical Field

[0001] The present invention relates to the technical field of material performance analysis, in particular to a high-temperature resistant drilling fluid performance testing device and a testing method, which are used for analyzing the filtration loss performance of the drilling fluid. Background Art

[0002] Fluid loss performance is an important parameter in the evaluation of drilling fluid performance. Currently, the main equipment for testing this performance is the static fluid loss meter, which evaluates the fluid loss performance of drilling fluid by measuring the time or rate at which drilling fluid passes through a filter medium (such as filter paper) under a specific pressure differential.

[0003] Existing static fluid loss meters primarily consist of a graduated cylinder, a vertically arranged mud cup, and a thermostatic jacket that heats the mud cup. The mud cup is a pressure vessel with openings at both ends that holds drilling fluid, while the graduated cylinder measures the amount of drilling fluid that passes through a filter medium. Early static fluid loss meters placed the filter medium at the bottom of the mud cup. During use, gas was injected into the cup through the top opening to increase the drilling fluid pressure and force it through the filter medium. However, drilling fluid often contains solid particulate impurities, which easily settle and accumulate on the filter medium when left static, affecting the formation of a filter cake on the filter medium's surface and leading to significant deviations in fluid loss measurements. For this reason, some devices later adopted a filter medium positioned at the top outlet of the mud cup and a piston installed in the mud cup. A hydraulic pump was used to inject silicone oil into the mud cup to drive the piston upward, thereby forcing the drilling fluid upward through the filter medium. This avoided the problem of solid particle deposition affecting filter cake formation. However, in the early days of gas-boosted filtration, the mud cup was essentially filled with gas after displacement. After one experiment, the gas was simply discharged and a new experiment could begin. After silicone oil displacement, the silicone oil, serving as the power fluid, needed to be recovered. However, during high-temperature testing, the silicone oil temperature was high and required cooling, which significantly increased the experiment time. Furthermore, during the experiment, the drilling fluid and silicone oil were primarily separated by the piston. Due to the gap between the piston and the mud cup, this separation was not absolutely reliable. Especially during repeated temperature increases and decreases during the experiment, the piston aged rapidly, and some leakage often occurred, allowing silicone oil to mix with the drilling fluid. Since the density of silicone oil is generally lower than that of drilling fluid, it rises after entering the drilling fluid and preferentially passes through the filter medium, ultimately resulting in large deviations in the fluid loss rate. Summary of the Invention

[0004] In order to solve at least one of the above problems, the present invention provides a high-temperature resistant drilling fluid performance testing device, which arranges the filter medium on the upper end surface of the mud cup to prevent solid particle deposition from affecting filter cake formation, uses gas to drive the piston in the mud cup to move, and sets a drainage channel between the sealing rings of the piston to lead the leaking fluid to the outside of the mud cup, thereby preventing gas from entering the drilling fluid and affecting the drilling fluid loss. When the displacement is completed, there is still residual gas in the mud cup, which can be directly discharged to start the next round of experiments, saving experimental time.

[0005] In order to achieve the above object, the specific scheme of the present invention is as follows:

[0006] A high temperature resistant drilling fluid performance testing device, comprising:

[0007] a mud cup arranged vertically and having a filter medium provided on the top inner wall thereof;

[0008] The piston assembly is connected to the inner wall of the mud cup in a sliding and sealing manner and can slide axially along the mud cup. The piston assembly divides the interior of the mud cup into a sample chamber and a power chamber, and the sample chamber is located above the power chamber. The piston assembly includes:

[0009] Piston body;

[0010] Two sets of sealing rings are arranged at intervals along the axial direction of the piston body, and each set of sealing rings is fixed to the side wall of the piston body and abuts against the inner wall of the mud cup;

[0011] A drainage channel is arranged in the piston body, one end of the drainage channel is opened on the side wall of the piston body and between the two sets of sealing rings, and the other end is connected to the drainage discharge pipe at the bottom of the mud cup through a hose, and a valve is provided on the drainage discharge pipe;

[0012] Two pressure gauges, used to measure the pressure of the sample chamber and drainage channel respectively;

[0013] Gas source equipment, used to supply gas to the power chamber and drainage channel;

[0014] a graduated cylinder for receiving the drilling fluid that passes through the filter medium;

[0015] Constant temperature jacket for heating the mud cup.

[0016] As a specific embodiment of the present invention, it also includes a separator sealing ring located between the two sets of sealing rings and spaced apart therefrom, the separator sealing ring being fixed to the side wall of the piston body and abutting against the inner wall of the mud cup; the two sets of sealing rings are an upper sealing ring and a lower sealing ring located below the upper sealing ring, and a water-swellable rubber ring is provided between the lower sealing ring and the separator sealing ring;

[0017] Drainage channels include:

[0018] a first branch pipe, one end of which is opened on the side wall of the piston body and is located between the upper sealing ring and the separating sealing ring;

[0019] A second branch pipe, one end of which is opened on the side wall of the piston body and is located between the water-swellable rubber ring and the separation sealing ring;

[0020] A main pipe is arranged vertically, and the other end of the first branch pipe and the other end of the second branch pipe are respectively connected to the main pipe;

[0021] The gas in the power chamber is a gas containing water vapor.

[0022] It also includes a separating sealing ring fixed to the side wall of the piston body and abutting the inner wall of the mud cup. The separating sealing ring is spaced apart from the two sets of sealing rings. The two sets of sealing rings are an upper sealing ring and a lower sealing ring located below the upper sealing ring. A water-expandable rubber ring is provided between the lower sealing ring and the separating sealing ring. The drainage channel includes:

[0023] a first branch pipe, one end of which is opened on the side wall of the piston body and is located between the upper sealing ring and the separating sealing ring;

[0024] A second branch pipe, one end of which is opened on the side wall of the piston body and is located between the water-swellable rubber ring and the separation sealing ring;

[0025] A main pipe is arranged vertically, and the other end of the first branch pipe and the other end of the second branch pipe are respectively connected to the main pipe;

[0026] The gas in the power chamber is a gas containing water vapor.

[0027] Furthermore, the main pipe is a stepped hole, and the connection port between the second branch pipe and the main pipe is located on the step surface of the stepped hole; an annular floating body is provided in the stepped hole, which can float on the surface of the drilling fluid and the hollow part of the annular floating body is larger than or equal to the size of the small hole in the stepped hole, so that when the upper end surface of the annular floating body abuts the step surface of the stepped hole, it can block the connection port between the second branch pipe and the main pipe.

[0028] Furthermore, a mixing chamber is provided between the gas source device and the power chamber, and is also equipped with an atomized water mechanism for spraying atomized water into the mixing chamber, thereby increasing the water content of the gas entering the power chamber.

[0029] As a specific embodiment of the present invention, the power chamber is also provided with a pressure gauge for measuring the gas pressure in the power chamber.

[0030] The present invention also discloses a method for testing the performance of high-temperature resistant drilling fluid, which uses the high-temperature resistant drilling fluid performance testing device to measure the filtration performance of the drilling fluid, comprising the following steps:

[0031] S1. Drilling fluid is loaded into the sample chamber, and gas is injected into the power chamber to drive the piston assembly to move until the drilling fluid overflows into the graduated cylinder; the outlet of the sample chamber is closed, and gas is injected into the power chamber and the drainage channel to increase the pressure to prevent the drilling fluid from vaporizing during the subsequent heating process. When the gas is injected, the pressure in the sample chamber is greater than the pressure in the drainage channel;

[0032] S2. Start the thermostatic jacket to heat the drilling fluid to the test temperature, and add gas to the sample chamber to adjust the pressure of the sample chamber to the test pressure;

[0033] S3. Open the outlet of the sample chamber, add gas to the sample chamber to push the piston assembly to move, and maintain a constant pressure in the sample chamber during the movement;

[0034] In steps S2 and S3, the pressure of the sample chamber is greater than the pressure of the drainage channel.

[0035] As a specific embodiment of the present invention, in steps S1 to S3, the pressure difference between the sample chamber and the drainage channel is constant.

[0036] As a specific embodiment of the present invention, it also includes: discharging the gas in the power chamber and the drainage channel after the drilling fluid is filtered, and maintaining the pressure difference between the power chamber and the drainage channel stable during the discharge process.

[0037] The beneficial effects of the present invention are as follows:

[0038] The high-temperature resistant drilling fluid performance testing device of the present invention arranges the filter medium on the upper end surface of the mud cup to prevent solid particle deposition from affecting filter cake formation; uses gas to drive the movement of the piston in the mud cup, and when the displacement is completed, the residual displacement medium in the mud cup is gas, which does not need to be recovered and can be directly discharged to start the next round of experiments, saving experimental time; a drainage channel is set between the sealing rings of the piston to guide the leaking fluid out of the mud cup, thereby preventing gas from entering the drilling fluid and affecting the drilling fluid loss. Combined with the above characteristics, it can quickly and accurately measure the filtration loss performance of the drilling fluid. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 2 is a schematic structural diagram of a device for testing the performance of high-temperature resistant drilling fluid according to an embodiment of the present invention;

[0040] Figure 2 yes Figure 1 Schematic diagram of the structure of the piston assembly;

[0041] Figure 3 is a schematic structural diagram of a piston assembly in another embodiment of the present invention;

[0042] Figure 4 is a structural schematic diagram of a piston assembly in yet another embodiment of the present invention;

[0043] In the figure, there are a mud cup 100, a piston assembly 200, a pressure gauge 300, a measuring cylinder 400, a thermostatic sleeve 500, a filter medium 600, an air source device 700, a cooler 900, a sample chamber 110, a power chamber 120, a piston body 210, a sealing ring 220, a drainage channel 230, a separating sealing ring 240, a water-expandable rubber ring 250, a mixing chamber 810, a water atomizing mechanism 820, an upper sealing ring 221, a lower sealing ring 222, a first branch pipe 231, a second branch pipe 232, a main pipe 233, an annular floating body 234, and a step surface 2331. DETAILED DESCRIPTION

[0044] The present invention will be further described below in conjunction with the accompanying drawings and specific implementation methods. It should be noted that, under the premise of no conflict, the various embodiments or technical features described below can be arbitrarily combined to form new embodiments.

[0045] Please refer to Figure 1 and Figure 2 , which shows the overall structure of a specific embodiment of the high-temperature resistant drilling fluid performance testing device of the present invention. The high-temperature resistant drilling fluid performance testing device of the present invention includes a mud cup 100, a piston assembly 200, a pressure gauge 300, a measuring cylinder 400, a thermostatic sleeve 500 and an air source device 700. Among them, the mud cup 100 is a vertically arranged pressure vessel with openings at both ends and a filter medium 600 on the top inner wall. The filter medium 600 is used to filter the drilling fluid, and filter paper or filter mesh can be selected. The measuring cylinder 400 is used to receive the drilling fluid that passes through the filter medium 600, and the thermostatic sleeve 500 is used to heat the mud cup 100. These components are all conventional equipment in the industry, and the installation of the filter medium 600 is also a conventional operation in the industry, which will not be described in detail here.

[0046] In the present invention, the piston assembly 200 is slidingly and sealingly connected to the inner wall of the mud cup 100 and can slide axially along the mud cup 100. At the same time, the piston assembly 200 divides the interior of the mud cup 100 into two independent cavities, namely the sample chamber 110 and the power chamber 120. The sample chamber 110 is located above the power chamber 120 and is used to store drilling fluid; the air source equipment 700 is connected to the power chamber 120 and is used to replenish gas into the power chamber 120, driving the piston assembly 200 to move upward, thereby displacing the drilling fluid through the filter medium 600. The piston assembly 200 includes a piston body 210, two sets of sealing rings 220, and a drainage channel 230. The two sets of sealing rings 220 are arranged axially along the piston body 210 at intervals. Each set of sealing rings 220 is fixed to the side wall of the piston body 210 and abuts the inner wall of the mud cup 100, thereby sealing the gap between the piston body 210 and the mud cup 100. The two sets of sealing rings 220, the inner wall of the mud cup 100, and the side wall of the piston body 210 form an annular cavity for accommodating leaked fluid. The drainage channel 230 is arranged in the piston body 210 to drain the fluid leaking into the annular cavity to the outside of the mud cup 100, as shown in FIG. Figure 1 and Figure 2 As shown, one end opening of the drainage channel 230 is located on the side wall of the piston body 210 and between the two sets of sealing rings 220, and the other end opening is connected to the drainage discharge pipe at the bottom of the mud cup 100 through a hose, so that the fluid leaking from the power chamber 120 and the sample chamber 110 to between the two sealing rings 220 can be discharged, preventing gas from entering the sample chamber 110 and contaminating the drilling fluid, thereby improving the measurement accuracy. There are two pressure gauges 300, which are used to measure the pressure of the sample chamber 110 and the drainage channel 230 respectively, so as to monitor the pressure difference between the sample chamber 110 and the drainage channel 230. In the present invention, the gas source device 700 is also connected to the drainage channel 230, and is used to replenish gas into the drainage channel 230 at the initial stage of the experiment. A valve is provided on the drainage discharge pipe to facilitate the discharge of leaked fluid during the experiment. By filling and discharging fluid into the drainage channel 230, the pressure of the sample chamber 110 can be maintained slightly higher than the pressure of the drainage channel 230. In this way, the pressure difference on both sides of each set of sealing rings 220 can be reduced, the leakage amount can be reduced, and the leakage fluid can be ensured not to enter the sample chamber 110. The smaller the specific value of this pressure difference, the better, and the more stable the better. This is not only conducive to reducing the leakage amount, but also conducive to extending the service life of the sealing ring 220.

[0047] The present invention uses gas as the power medium to drive the piston assembly 200 to move. At the end of displacement, the main residual medium in the mud cup 100 is gas, which can be directly discharged without cooling and recovery, thereby greatly saving experimental time. At the same time, the special piston assembly 200 can guide the leaked fluid to the outside of the mud cup 100 to prevent gas from leaking into the sample chamber 110, thereby improving the accuracy of the test results.

[0048] When the device of the present invention is in use, it needs to frequently increase and decrease the temperature, and the sealing ring 220 is prone to leakage. At the same time, the viscosity of gas is much lower than that of liquid. Under the same conditions, gas is more likely to leak than liquid. Therefore, the sealing ring 220 near the power chamber 120 is more likely to leak. In order to reduce the leakage at this location, in some embodiments, such as Figure 3 As shown, the two groups of sealing rings 220 are respectively called the upper sealing ring 221 and the lower sealing ring 222. The upper sealing ring 221 is located above the lower sealing ring 222. A separating sealing ring 240 is arranged between the two groups of sealing rings 220. The separating sealing ring 240 is arranged at intervals from the two groups of sealing rings 220. At the same time, the separating sealing ring 240 is fixed to the side wall of the piston body 210 and abuts the inner wall of the mud cup 100, thereby further dividing the annular cavity containing the leaking fluid into two parts. A water-swellable rubber ring 250 is provided between the lower sealing ring 222 and the separating sealing ring 240. The water-swellable rubber ring 250 is made of water-swellable material. The gas in the power chamber 120 contains water vapor. Therefore, when the lower sealing ring 222 leaks, the water-swellable rubber ring 250 will come into contact with the water vapor and expand to self-seal, thereby reducing the leakage amount. Of course, in order to prevent the fluid leaking from the upper sealing ring 221 from flowing by itself and contacting the water-swellable rubber ring 250, causing it to expand at an inappropriate time, it is necessary to lead out the fluid leaking from the two sealing rings 220 separately, such as Figure 3 As shown, the drainage channel 230 includes a first branch pipe 231, a second branch pipe 232 and a main pipe 233, wherein the main pipe 233 is arranged vertically, one end opening of the first branch pipe 231 is located on the side wall of the piston body 210 and between the upper sealing ring 221 and the separating sealing ring 240, and the other end opening is connected to the main pipe 233, one end opening of the second branch pipe 232 is located on the side wall of the piston body 210 and between the water-swellable rubber ring 250 and the separating sealing ring 240, and the other end opening is also connected to the main pipe 233.

[0049] In the above embodiment, branch pipes are provided to guide the leakage fluid outward. However, when the amount of leakage liquid is significantly greater than the amount of leakage gas, there is still a risk that the drilling fluid will flow back along the second branch pipe 232 and contact the water-swellable rubber ring 250. Therefore, in some embodiments, the main pipe 233 is configured as a stepped hole with a smaller upper diameter and a larger lower diameter. The connection between the second branch pipe 232 and the main pipe 233 is located on the stepped surface 2331 of the stepped hole. An annular float 234 is provided in the stepped hole. The annular float 234 is capable of floating on the drilling fluid level, and its hollow portion is larger than or equal to the size of the small hole in the stepped hole. Therefore, when drilling fluid accumulates in the stepped hole, the annular float 234 will rise with the drilling fluid level. When the upper end surface of the annular float 234 abuts the stepped surface 2331 of the stepped hole, it will block the connection between the second branch pipe 232 and the main pipe 233. In this way, the fluid discharged from the first branch pipe 231 can be discharged outside through the hollow part of the annular float 234. At the same time, when the drilling fluid level in the main pipe 233 has not yet reached the connection port between the second branch pipe 232 and the main pipe 233, the annular float 234 can be used to automatically close the connection port between the second branch pipe 232 and the main pipe 233 to prevent the drilling fluid from flowing back to the water-expandable rubber ring 250.

[0050] In the present invention, when a water-expandable rubber ring 250 is used, water vapor needs to be carried by gas. The commonly used gas can be nitrogen, etc., and its saturated water vapor content is not high. Therefore, measures can be taken to increase the water vapor content of the gas in the power chamber 120. In some embodiments, a mixing chamber 810 is provided between the gas source device 700 and the power chamber 120, and an atomizing water mechanism 820 is also provided for spraying atomized water into the mixing chamber 810, thereby increasing the water content of the gas entering the power chamber 120.

[0051] In addition, after the experiment is completed, the gas in the power chamber 120 needs to be discharged. During the exhaust process, the pressure of the sample chamber 110 will be higher than the pressure of the power chamber 120. In order to avoid excessive pressure difference on both sides of the lower sealing ring 222, in some embodiments, the power chamber 120 is also provided with a pressure gauge 300 for measuring the pressure of the power chamber 120. When the gas is discharged after the displacement is completed, the pressure difference between the power chamber 120 and the drainage channel 230 is maintained stable, which is beneficial to extending the life of the sealing ring 220.

[0052] For the drilling fluid passing through the filter medium 600, in some embodiments, a back pressure receiver can be provided to process it, and in other embodiments, a cooler 900 can also be provided to cool it. These are conventional components in existing filter loss instruments and will not be described in detail here.

[0053] A method for testing the performance of a high-temperature resistant drilling fluid, using the high-temperature resistant drilling fluid performance testing device to measure the filtration performance of the drilling fluid, comprises the following steps:

[0054] S1. Drilling fluid is loaded into the sample chamber 110, and gas is injected into the power chamber 120 to drive the piston assembly 200 to move until the drilling fluid overflows into the measuring cylinder 400, thereby ensuring that the pipeline is full of liquid; the outlet of the sample chamber 110 is closed, and gas is injected into the power chamber 120 and the drainage channel 230 to increase the pressure to prevent the drilling fluid from vaporizing during the subsequent heating process. When the gas is injected, the pressure in the sample chamber 110 is greater than the pressure in the drainage channel 230, thereby preventing the fluid leaking between the two sets of sealing rings 220 from entering the sample chamber 110;

[0055] S2. Start the constant temperature jacket 500 to heat the drilling fluid to the test temperature, then add gas to the sample chamber 110 and adjust the pressure of the sample chamber 110 to the test pressure;

[0056] S3, opening the outlet of the sample chamber 110, replenishing gas into the sample chamber 110 to push the piston assembly 200 to move, and maintaining a constant pressure in the sample chamber 110 during the movement;

[0057] In steps S2 and S3 , the pressure of the sample chamber 110 is greater than the pressure of the drainage channel 230 .

[0058] In some embodiments, when filling and draining the drainage channel 230 in steps S1 to S3, the pressure difference between the sample chamber 110 and the drainage channel 230 is controlled to be constant, and the pressure difference is lower than the pressure difference that the sealing ring 220 can withstand, which is beneficial to reducing leakage and extending the life of the sealing ring 220.

[0059] In some embodiments, after the drilling fluid is filtered, the gas in the power chamber 120 and the drainage channel 230 is directly discharged. In other embodiments, the exhaust operation is performed after the drilling fluid is filtered. During the exhaust operation, the pressure difference between the power chamber 120 and the drainage channel 230 is controlled to be constant, and the pressure difference is lower than the pressure difference that the sealing ring 220 can withstand. This is beneficial to reducing leakage and extending the life of the sealing ring 220.

[0060] Those skilled in the art can make various other corresponding changes and deformations based on the technical solutions and concepts described above, and all of these changes and deformations should fall within the scope of protection of the claims of the present invention.

Claims

1. A high temperature resistant drilling fluid performance testing device, characterized in that: include: a mud cup arranged vertically and having a filter medium provided on the top inner wall thereof; A piston assembly is slidably and sealingly connected to the inner wall of the mud cup and can slide axially along the mud cup. The piston assembly divides the interior of the mud cup into a sample chamber and a power chamber, and the sample chamber is located above the power chamber. The piston assembly includes: Piston body; Two sets of sealing rings are arranged at intervals along the axial direction of the piston body, and each set of sealing rings is fixed to the side wall of the piston body and abuts against the inner wall of the mud cup; A drainage channel is arranged in the piston body, one end of the drainage channel is opened on the side wall of the piston body and between the two sets of sealing rings, and the other end is opened and connected to the drainage discharge pipe at the bottom of the mud cup through a hose, and a valve is provided on the drainage discharge pipe; Two pressure gauges, used to measure the pressure of the sample chamber and the drainage channel respectively; A gas source device, used for replenishing gas to the power chamber and the drainage channel, wherein the gas in the power chamber is a gas containing water vapor; a graduated cylinder for receiving drilling fluid that passes through the filter medium; a constant temperature jacket, used for heating the mud cup; a separating sealing ring located between and spaced apart from the two sets of sealing rings, the separating sealing ring being fixed to the side wall of the piston body and abutting against the inner wall of the mud cup; the two sets of sealing rings are an upper sealing ring and a lower sealing ring located below the upper sealing ring, a water-swellable rubber ring being provided between the lower sealing ring and the separating sealing ring; The drainage channel comprises: a first branch pipe, one end of which is opened on the side wall of the piston body and between the upper sealing ring and the separating sealing ring; a second branch pipe, one end of which is opened on the side wall of the piston body and is located between the water-swellable rubber ring and the separation sealing ring; The other end of the first branch pipe and the other end of the second branch pipe are respectively connected to the main pipe.

2. A high temperature resistant drilling fluid performance testing device according to claim 1, characterized in that: The main pipe is a stepped hole, and the connection port of the second branch pipe and the main pipe is located on the step surface of the stepped hole; an annular floating body is provided in the stepped hole, and the annular floating body can float on the surface of the drilling fluid and the hollow part is larger than or equal to the size of the small hole in the stepped hole, so that the connection port of the second branch pipe and the main pipe can be blocked when the upper end surface of the annular floating body abuts the step surface of the stepped hole.

3. A high temperature resistant drilling fluid performance testing device according to claim 1, characterized in that: A mixing chamber is provided between the air source device and the power chamber, and is also equipped with an atomized water mechanism for spraying atomized water into the mixing chamber.

4. A high temperature resistant drilling fluid performance testing device according to claim 1, characterized in that: The power chamber is also provided with a pressure gauge for measuring the gas pressure in the power chamber.

5. A method for testing the performance of high-temperature resistant drilling fluid, comprising testing the fluid loss performance of the drilling fluid using a high-temperature resistant drilling fluid performance testing device according to any one of claims 1 to 4, characterized in that: The steps include: S1. Drilling fluid is loaded into the sample chamber, and gas is injected into the power chamber to drive the piston assembly to move until the drilling fluid overflows into the graduated cylinder; the outlet of the sample chamber is closed, and gas is injected into the power chamber and the drainage channel to increase the pressure to prevent the drilling fluid from vaporizing during the subsequent heating process. When the gas is injected to increase the pressure, the pressure in the sample chamber is greater than the pressure in the drainage channel; S2, starting the constant temperature jacket to heat the drilling fluid to the test temperature, and adding gas to the sample chamber to adjust the pressure of the sample chamber to the test pressure; S3, opening the outlet of the sample chamber, replenishing gas into the sample chamber to push the piston assembly to move, and maintaining a constant pressure in the sample chamber during the movement; Wherein, in steps S2 and S3, the pressure of the sample chamber is greater than the pressure of the drainage channel.

6. A method for testing the performance of high temperature resistant drilling fluid according to claim 5, characterized in that: In steps S1 to S3, the pressure difference between the sample chamber and the drainage channel is constant.

7. A method for testing the performance of high temperature resistant drilling fluid according to claim 6, characterized in that: After the drilling fluid is filtered, the gas in the power chamber and the drainage channel is discharged, and during the discharge process, the pressure difference between the power chamber and the drainage channel is maintained constant.

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