A multi-functional testing device and method for foam cement slurry

Abstract

This invention belongs to the field of physical simulation and monitoring technology for oil and gas field fracturing, and relates to a multifunctional testing device and method for foamed cement slurry. The device includes a testing mechanism connected to a slurry preparation mechanism via a high-pressure slurry pipeline. The testing mechanism includes a testing vessel, an inner cylinder, a piston, and a pressure measurement and control component. The inner cylinder is located inside the testing vessel, and the piston is slidably connected to the inner wall of the inner cylinder. The piston divides the inner cylinder into an upper pressurization chamber and a lower testing chamber. The upper pressurization chamber is used to contain pressurized fluid, and the lower testing chamber is used to contain foamed cement slurry. The pressure measurement and control component is connected to the top of the testing vessel. This invention achieves high-pressure closed-loop slurry preparation through a magnetic drive component, and achieves pressurized transfer and multifunctional testing through the cooperation of a floating piston, a back pressure valve, and a precision pressure pump. It effectively solves the problems of existing technologies, such as the disconnect between slurry preparation and testing conditions, the single function of the testing device and the limited temperature and pressure simulation range, and the insufficient testing accuracy caused by the testing method not being adapted to the characteristics of foamed cement slurry.

Description

Technical Field

[0001] This invention relates to the field of performance testing of cement slurry for oil and gas well cementing, and more specifically, to a multifunctional testing device and method for foamed cement slurry. Background Technology

[0002] Foamed cement slurry contains a large amount of gas, and its density is significantly affected by temperature and pressure. The density of the slurry fluctuates significantly at different locations downhole, and air bubbles tend to aggregate and rise, requiring much higher precision in slurry preparation and performance testing than conventional cement slurry. However, existing technologies have many limitations: First, the mixing process cannot be sealed and pressure controlled, making it difficult to precisely adjust the gas injection volume. This results in large-sized and unstable air bubbles in the indoor-prepared foamed cement slurry, which is severely out of sync with on-site high-pressure aeration construction. Second, existing testing devices generally have limited functionality and a limited temperature and pressure simulation range. For example, CN102539280A provides a heated and pressurized foamed cement slurry density testing device, consisting of a pressure vessel, piston, displacement sensor, and computer acquisition system, which measures the density of foamed cement slurry under different temperatures and pressures. However, it has limited functionality, high equipment cost, and cannot perform other performance tests such as water loss and suspension stability, requiring additional testing devices. While conventional methods can assist in measurement, the expansion and rupture of air bubbles during sample transfer can damage the slurry structure, making the test results unable to reflect the actual working conditions downhole. CN202141664U provides a rapid density measurement device for foamed cement slurry, consisting of a graduated transparent cup, a piston, and a pressure backup system. It is used to measure density under closed and pressurized conditions, but the pressure range is only 0-0.8 MPa, which is far lower than the actual downhole pressure, leading to distorted test results. Thirdly, conventional methods for testing the density, water loss, suspension stability, and compressive strength of cement slurry are not suitable for the high compressibility and temperature and pressure sensitivity of foamed cement slurry, resulting in distorted test results. Summary of the Invention

[0003] This invention provides a multifunctional testing device and method for foamed cement slurry, which aims to solve the problems of insufficient testing accuracy caused by the disconnect between slurry preparation and testing conditions, the limited testing function of the testing device and the limited temperature and pressure simulation range, and the testing method not being adapted to the characteristics of foamed cement slurry in the existing technology.

[0004] The technical solution of the present invention is as follows: According to one aspect of the present invention, a multifunctional testing device for foamed cement slurry is provided, comprising: The testing mechanism is connected to a slurry mixing mechanism via a high-pressure slurry pipeline. The testing mechanism includes a testing vessel, an inner cylinder, a piston, and a pressure measurement and control component. The inner cylinder is disposed inside the testing vessel, and the piston is slidably connected to the inner wall of the inner cylinder. The piston divides the inner cylinder into an upper pressurization chamber and a lower testing chamber. The upper pressurization chamber is used to contain pressurized fluid, and the lower testing chamber is used to contain foamed cement slurry. The pressure measurement and control component is connected to the top of the testing vessel. The slurry mixing mechanism includes a slurry mixing tank, a stirring assembly, and a magnetic drive assembly. The stirring assembly is rotatably connected inside the slurry mixing tank, and the magnetic drive assembly is connected to the bottom of the slurry mixing tank to drive the stirring assembly.

[0005] Furthermore, a test vessel top cover is connected to the top of the test vessel, and the pressure measurement and control component includes a precision pressure pump, a back pressure valve, a pressure regulating pipeline, and an exhaust and drainage pipeline; the pressure regulating pipeline and the exhaust and drainage pipeline both pass through the test vessel top cover and communicate with the upper pressurization chamber, the precision pressure pump is connected to the pressure regulating pipeline, the back pressure valve is connected to the exhaust and drainage pipeline, and the exhaust and drainage pipeline is also connected to a second pressure gauge.

[0006] Furthermore, the bottom of the test vessel is connected to a test vessel bottom cover, which includes a first sealing section and a second sealing section. The first sealing section is in sealing fit with the inner wall of the inner cylinder, and the second sealing section is in sealing fit with the inner wall of the test vessel.

[0007] Furthermore, the bottom cover of the test vessel is also provided with a slurry inlet pipeline and a filtration hole. The slurry inlet pipeline is connected to a tee connector, which includes a first interface, a second interface, and a third interface. The first interface is connected to the slurry inlet pipeline, the second interface is connected to the high-pressure slurry delivery pipeline, and the third interface is connected to an exhaust valve. A filtration rod is provided inside the filtration hole. A circular groove is formed on the upper surface of the bottom cover of the test vessel, and the filtration hole is formed at the center of the circular groove. A filter screen is embedded in the circular groove. An evacuation pipeline is provided at the bottom of the side wall of the test vessel.

[0008] Furthermore, the magnetic drive assembly includes a speed-regulating motor, an inner magnetic drive magnet, and an outer magnetic drive magnet. The speed-regulating motor is disposed at the bottom of the outer wall of the mixing tank, the outer magnetic drive magnet is connected to the output shaft of the speed-regulating motor, the inner magnetic drive magnet is disposed at the bottom of the inner cavity of the mixing tank, and the inner magnetic drive magnet is connected to the stirring assembly. The outer magnetic drive magnet and the inner magnetic drive magnet are magnetically coupled to drive the stirring assembly to rotate while the mixing tank is kept sealed.

[0009] Furthermore, the stirring assembly includes a blade, a blade support, and a blade shaft, wherein the blade is connected to the outer wall of the blade shaft, and the blade support is connected to the top of the inner cavity of the mixing tank; The bottom of the inner cavity of the mixing tank is provided with a positioning groove, a positioning block is provided in the positioning groove, and a positioning hole is provided on the upper end face of the positioning block. The top end of the blade shaft is rotatably connected to the blade support, and the bottom end passes through the magnet in the magnetic drive and is rotatably connected to the positioning hole. A compression spring is provided between the top end of the blade shaft and the blade support to provide axial preload.

[0010] Furthermore, the top of the slurry mixing tank is connected to a slurry mixing tank cover, and the slurry mixing tank cover is equipped with an air inlet pipeline. The air inlet pipeline passes through the slurry mixing tank cover and communicates with the inner cavity of the slurry mixing tank. The air inlet pipeline is connected to an air inlet valve, a first pressure gauge, and an air source. The bottom of the side wall of the slurry mixing tank is connected to a slurry discharge pipeline, and the slurry discharge pipeline is connected to the high-pressure slurry delivery pipeline.

[0011] Furthermore, the outer wall of the slurry mixing vessel is provided with a first heating and heat preservation sleeve, and the outer wall of the testing vessel is provided with a second heating and heat preservation sleeve.

[0012] Furthermore, the magnetic drive assembly also includes a torque sensor, which is disposed between the speed-regulating motor and the external magnet of the magnetic drive. The input end of the torque sensor is connected to the output shaft of the speed-regulating motor, and the output end is connected to the external magnet of the magnetic drive.

[0013] According to another aspect of the present invention, a multifunctional testing method for foamed cement slurry is provided, using the aforementioned apparatus, comprising the following steps: Slurry preparation: Inject cement-based slurry, foaming agent and foam stabilizer into the slurry preparation tank, introduce high-pressure gas to the preset pressure, start the magnetic drive component to stir, so that the cement-based slurry and gas are fully mixed to form foamed cement slurry; Pressurized transfer: The prepared foamed cement slurry is transferred under pressure to the inner cylinder of the test vessel through a high-pressure slurry pipeline. During the transfer, the pressurized fluid in the upper pressurized chamber of the inner cylinder is discharged by the back pressure valve set on the top cover of the test vessel. The volume of foamed cement slurry entering the lower test chamber of the inner cylinder is controlled by controlling the discharge volume of the back pressure valve. Performance testing: The foamed cement slurry transferred to the inner cylinder is subjected to performance testing, which includes at least one of the following: Density test: Pressurized fluid is injected or discharged into the upper pressurized chamber by a precision pressure pump, the pressure in the test vessel is adjusted, and the density of the foamed cement slurry at the current temperature and pressure is calculated based on the volume of pressurized fluid injected or discharged by the precision pressure pump. Water loss test: The pressure inside the test vessel is controlled to the preset water loss pressure by a precision pressure pump. The filter rod set on the bottom cover of the test vessel is loosened to allow the filtrate to be discharged from the filter hole. The amount of filtrate lost within the preset time is recorded. Suspension stability test: The foamed cement slurry in the test vessel is heated to the preset temperature through the second heating and insulation jacket, and the pressure is adjusted to the preset pressure through a precision pressure pump. It is then cured until the foamed cement slurry solidifies into cement stone. The cement stone is removed and the density of different parts is measured. The suspension stability of the foamed cement slurry is evaluated based on the density difference.

[0014] The beneficial effects of this invention are as follows: First, the magnetic drive assembly of this invention adopts a structure in which the inner magnet and the outer magnet of the magnetic drive are magnetically coupled, eliminating the need for a through hole for the rotating shaft on the slurry mixing vessel. This ensures that the inner cavity of the slurry mixing vessel remains completely sealed, achieving leak-free mixing under high pressure. It can precisely control the amount of gas injected, matching the indoor slurry mixing conditions with the high-pressure gas filling operation on site. At the same time, a floating piston is installed in the test vessel to divide the inner cylinder into an upper pressurization chamber and a lower test chamber. With the help of a back pressure valve, an equal volume of pressurized fluid is discharged during the transfer process, enabling precise pressurized injection of foamed cement slurry. This avoids the problem of bubble expansion and rupture during sample transfer, which can lead to damage to the slurry structure and ensure that the test results truly reflect the downhole conditions. Secondly, the test vessel of this invention isolates the slurry from the pressurized medium through a floating piston. A precision pressure pump injects or discharges pressurized fluid into the pressurized chamber and accurately measures volume changes, enabling density testing at different temperatures and pressures within the same device. Through the filter holes, filter rods, and filter screen on the bottom cover, API water loss testing can be performed directly after the initial test. Independent temperature control of the test vessel via a heating insulation jacket, combined with pressure regulation by the precision pressure pump, allows for suspension stability testing and cement stone curing to be completed within the same device. This achieves integrated, multi-functional testing of multiple properties such as density, API water loss, suspension stability, and thickening time, eliminating the need to change equipment or transfer samples, effectively avoiding testing errors caused by inconsistent testing conditions. Furthermore, the mixing assembly of this invention forms a double constraint between the blade support and the positioning block, and provides axial preload with the help of the compression spring, effectively limiting the radial sway and axial movement of the blade shaft during high-speed rotation, ensuring a stable and reliable mixing process; a three-way connector and an exhaust valve are installed on the slurry inlet pipeline to vent residual gas in the high-pressure slurry delivery pipeline before transfer, preventing gas from entering and affecting the accuracy of slurry volume measurement and subsequent test results; the filter screen on the bottom cover blocks cement particles during the water loss test, and the venting pipeline facilitates rapid pressure relief and cleaning after the experiment, effectively improving the convenience of experimental operation and the reliability of test data; In summary, this invention achieves high-pressure closed-loop slurry preparation through a magnetic drive assembly, and realizes pressurized transfer and multi-functional testing through the coordinated operation of a floating piston, back pressure valve, and precision pressure pump. Combined with the dual-constraint structure and three-way venting design of the stirring assembly, it effectively solves the problems of existing technologies such as the disconnect between slurry preparation and testing conditions, the limited testing function of the testing device and the limited temperature and pressure simulation range, and the insufficient testing accuracy caused by the testing method not being adapted to the characteristics of foamed cement slurry. It realizes the simulation of the entire process from slurry preparation to performance testing, and provides reliable data support for field foamed cement slurry cementing. Attached Figure Description

[0015] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained from these drawings without creative effort.

[0016] Figure 1 This is a schematic diagram of the pulp mixing mechanism provided by the present invention; Figure 2 This is a schematic diagram of the testing mechanism structure provided by the present invention.

[0017] Icon labels: 1-Pulping vessel cover; 2-Pulping vessel; 3-Paddle support; 4-Paddle shaft; 5-Magnetic drive inner magnet; 6-Pulping discharge pipeline; 7-Torque sensor; 8-Speed-regulating motor; 9-Vessel body support; 10-Magnetic drive outer magnet; 11-Positioning hole; 12-Paddle; 13-First sealing ring; 14-Bolt; 15-First pressure gauge; 16-Inlet valve; 17-Inlet pipeline; 18-First heating and insulation jacket; 19-Exhaust vent 20-Second pressure gauge; 21-Test vessel top cover; 22-Test vessel; 23-Second heating and insulation jacket; 24-Inner cylinder; 25-Foamed cement slurry; 26-Drainage pipeline; 27-Filter rod; 28-Slurry inlet pipeline; 29-Test vessel bottom cover; 30-Filter screen; 31-Second sealing ring; 32-Piston; 33-Pressed fluid; 34-Pressure regulating pipeline; 35-Precision pressure pump; 36-Back pressure valve. Detailed Implementation

[0018] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, not all of them. Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to represent selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0019] Example 1 refer to Figure 1-2 This embodiment provides a multifunctional testing device for foamed cement slurry, including: The testing mechanism is connected to a slurry mixing mechanism via a high-pressure slurry pipeline. The testing mechanism includes a testing vessel 22, an inner cylinder 24, a piston 32, and a pressure measurement and control component. The inner cylinder 24 is located inside the testing vessel 22. The piston 32 is slidably connected to the inner wall of the inner cylinder 24. The piston 32 divides the inner cylinder 24 into an upper pressurization chamber and a lower testing chamber. The upper pressurization chamber is used to contain pressurized fluid 33, and the lower testing chamber is used to contain foamed cement slurry. The pressure measurement and control component is connected to the top of the testing vessel 22. The mixing mechanism includes a mixing tank 2, a stirring assembly, and a magnetic drive assembly. The stirring assembly is rotatably connected inside the mixing tank 2, and the magnetic drive assembly is connected to the bottom of the mixing tank 2 to drive the stirring assembly.

[0020] In this embodiment, the mixing tank 2 adopts a thick-walled, high-strength metal cylindrical structure with one open end. A flange is provided at the upper opening for sealing connection with the mixing tank cover 1. A circular positioning groove is provided in the center of the bottom plate of the tank body, and a wear-resistant metal positioning block is placed in the groove for fixing the lower end of the stirring assembly.

[0021] The test vessel 22 adopts a thick-walled, high-strength metal cylindrical structure with openings at both ends. Flanges are provided on both the upper and lower end faces, which are sealed to the test vessel top cover 21 and the test vessel bottom cover 29 respectively by bolts 14. The inner cylinder 24 is located inside the test vessel 22, and its lower end is detachably connected to the test vessel bottom cover 29 by bolts 14. It is used to hold foamed cement slurry.

[0022] The piston 32 is a metal disc structure, and its outer diameter matches the inner diameter of the inner cylinder 24. A second sealing ring 31 is embedded in the circumference of the side of the piston 32, which slides and seals against the inner wall of the inner cylinder 24. The piston 32 divides the inner cylinder 24 into an upper pressurization chamber and a lower test chamber. The upper pressurization chamber is used to contain pressurized fluid 33, and the lower test chamber is used to contain foamed cement slurry. The piston 32 can slide up and down inside the inner cylinder 24 according to the pressure difference between the upper and lower chambers.

[0023] The high-pressure slurry delivery pipeline is made of high-pressure resistant metal pipeline, with both ends connected to the slurry discharge pipeline 6 at the bottom of the slurry mixing vessel 2 and the slurry inlet pipeline 28 on the bottom cover 29 of the test vessel, respectively. The pipeline is equipped with a control valve, which is used to transfer the foamed cement slurry under pressure to the inner cylinder 24 of the test vessel 22 after the slurry mixing is completed.

[0024] It is worth noting that the mixing vessel 2 and the testing vessel 22 are equipped with a vessel support 9, which is mounted on the vessel support 9. The vessel support 9 is made of high-strength metal profiles, welded or integrally cast, and has an overall frame structure, including an upper top plate, a lower bottom plate, and several vertical support columns connecting the upper top plate and the lower bottom plate. The upper top plate is a high-strength metal panel with a first positioning hole and a second positioning hole. The size of the first positioning hole matches the outer diameter of the mixing vessel 2, and the size of the second positioning hole matches the outer diameter of the testing vessel 22. Limiting blocks are symmetrically arranged on the upper outer side of the mixing vessel 2. After the mixing vessel 2 is inserted into the first positioning hole from top to bottom, it is rotated at a certain angle so that the limiting block engages with the groove on the edge of the first positioning hole, realizing the vertical positioning and anti-rotation fixation of the mixing vessel 2, ensuring the stability of the mixing vessel 2 when the stirring assembly rotates at high speed. The testing vessel 22 is also fixed by the limiting structure on its upper outer side engaging with the groove of the second positioning hole. The bottom plate of the vessel support 9 is equipped with casters at the four corners. The casters are equipped with a braking mechanism to facilitate the movement and positioning of the entire device.

[0025] Furthermore, the magnetic drive assembly includes a speed-regulating motor 8, an inner magnetic drive magnet 5, and an outer magnetic drive magnet 10. The speed-regulating motor 8 is located at the bottom of the outer wall of the mixing tank 2. The outer magnetic drive magnet 10 is connected to the output shaft of the speed-regulating motor 8. The inner magnetic drive magnet 5 is located at the bottom of the inner cavity of the mixing tank 2 and is connected to the stirring assembly. The outer magnetic drive magnet 10 and the inner magnetic drive magnet 5 are magnetically coupled to drive the stirring assembly to rotate while the mixing tank 2 remains sealed.

[0026] The variable-speed motor 8 is installed below the mixing tank 2 and is fixedly connected to the bottom of the mixing tank 2 or the crossbeam of the tank body support 9 via a motor mounting base. The external magnetic drive magnet 10 has a disc-shaped structure and is fixedly connected to the output shaft of the variable-speed motor 8 via a coupling, rotating synchronously with the motor output shaft. The internal magnetic drive magnet 5 also has a disc-shaped structure and is located at the bottom of the inner cavity of the mixing tank 2, fixedly connected to the lower end of the impeller shaft 4 of the stirring assembly. The external magnetic drive magnet 10 and the internal magnetic drive magnet 5 are separated by the bottom wall of the mixing tank 2, and the two achieve contactless power transmission through magnetic coupling. When the variable-speed motor 8 starts, the external magnetic drive magnet 10 rotates, driving the internal magnetic drive magnet 5 to rotate synchronously through magnetic force, thereby driving the stirring assembly to rotate and stir inside the mixing tank 2. Since there is no need to set a through hole for the rotating shaft on the mixing tank 2, the inner cavity of the mixing tank 2 always remains completely sealed, effectively avoiding the problem of high-pressure gas leakage along the stirring shaft and ensuring stable and controllable gas pressure during the mixing process.

[0027] Furthermore, the stirring assembly includes a blade 12, a blade support 3, and a blade shaft 4. The blade 12 is connected to the outer wall of the blade shaft 4, and the blade support 3 is connected to the top of the inner cavity of the mixing tank 2. The bottom of the inner cavity of the mixing tank 2 is provided with a positioning groove, and a positioning block is provided in the positioning groove. The upper end face of the positioning block is provided with a positioning hole 11. The top end of the blade shaft 4 is rotatably connected to the blade support 3, and the bottom end passes through the magnet 5 in the magnetic drive and is rotatably connected to the positioning hole 11. A compression spring is provided between the top of the blade shaft 4 and the blade support 3 to provide axial preload.

[0028] In this embodiment, the impeller shaft 4 is a slender metal rod, and the impeller blades 12 are made of wear-resistant metal and are symmetrically arranged on the outer wall of the impeller shaft 4 to form a multi-layer impeller structure to enhance the mixing effect. The impeller support 3 is fixedly installed at the center of the top of the inner cavity of the mixing vessel 2, and has a shaft hole in its center. The top of the impeller shaft 4 passes through the shaft hole and can rotate freely. A compression spring is sleeved on the top of the impeller shaft 4, with its upper end abutting against the lower end face of the impeller support 3 and its lower end abutting against the shoulder on the impeller shaft 4, providing a downward axial preload to the impeller shaft 4 to prevent axial movement of the impeller shaft 4 during high-speed rotation. The positioning block is a wear-resistant metal cylinder, the outer diameter of which matches the inner diameter of the positioning groove on the bottom plate of the mixing vessel 2, and is fixed in the positioning groove by interference fit or screws. A positioning hole 11 is provided at the center of the upper end face of the positioning block. The bottom end of the impeller shaft 4 passes through the magnet 5 inside the magnetic drive and is inserted into the positioning hole 11. A bushing or rolling bearing can be installed in the positioning hole 11 so that the bottom end of the impeller shaft 4 can rotate freely within the positioning hole 11. Through the double constraint of the impeller support 3 and the positioning block, the radial sway of the impeller shaft 4 during high-speed rotation is effectively limited, ensuring a stable and reliable stirring process.

[0029] Furthermore, the top of the mixing tank 2 is connected to the mixing tank cover 1, the mixing tank cover 1 is equipped with an air inlet pipe 17, the air inlet pipe 17 passes through the mixing tank cover 1 and communicates with the inner cavity of the mixing tank 2, and the air inlet pipe 17 is connected to an air inlet valve 16, a first pressure gauge 15 and an air source; the bottom of the side wall of the mixing tank 2 is connected to a slurry discharge pipe 6, and the slurry discharge pipe 6 is connected to a high-pressure slurry delivery pipe.

[0030] In this embodiment, the mixing vessel cover 1 is a two-section metal disc structure. The upper, larger portion has the same diameter as the flange on the upper end face of the mixing vessel 2 and is provided with corresponding bolt holes. The lower, smaller outer circle is fitted with a first sealing ring 13, which cooperates with the inner wall of the mixing vessel 2 to form a high-pressure seal. The mixing vessel cover 1 and the mixing vessel 2 are fastened together by bolts 14. The air inlet pipeline 17 is a high-pressure resistant metal pipeline. One end of it passes through the mixing vessel cover 1 and communicates with the inner cavity of the mixing vessel 2, and the other end is connected to a high-pressure gas cylinder or air compressor. The air inlet pipeline 17 is sequentially equipped with an air inlet valve 16, a first pressure gauge 15, and a gas source. The air inlet valve 16 is used to control the gas flow, and the first pressure gauge 15 is used to display the gas pressure in the mixing vessel 2 in real time. The discharge pipeline 6 is also a high-pressure resistant metal pipeline, connected to the bottom of the side wall of the mixing vessel 2 near the bottom of the vessel, and the valve is set close to the mixing vessel 2 to reduce the influence of the pipeline volume at the valve front end on the mixing accuracy. The outlet end of the slurry discharge pipeline 6 is connected to the slurry inlet pipeline 28 on the bottom cover 29 of the test vessel via a high-pressure slurry delivery pipeline, which is used to transfer the prepared foamed cement slurry under pressure to the inner cylinder 24 of the test vessel 22.

[0031] It is worth noting that a high-pressure gas pump is used as the gas source to provide the gas and pressure required for preparing foamed cement slurry to the mixing tank 2; a high-pressure air / nitrogen cylinder can also be used as the gas source, which is not limited here.

[0032] Furthermore, the outer wall of the mixing vessel 2 is provided with a first heating and insulation sleeve 18, and the outer wall of the testing vessel 22 is provided with a second heating and insulation sleeve 23.

[0033] In this embodiment, a first heating and insulation sleeve 18 is wrapped around the outer wall of the slurry mixing vessel 2, and a second heating and insulation sleeve 23 is wrapped around the outer wall of the testing vessel 22. Both the first heating and insulation sleeve 18 and the second heating and insulation sleeve 23 are equipped with temperature sensors and temperature controllers. When it is necessary to adjust the temperature parameters, the first heating and insulation sleeve 18 and the second heating and insulation sleeve 23 are activated to heat the vessel body. The temperature controller automatically adjusts the heating power according to the signal fed back by the temperature sensor installed on the vessel body, so that the temperature inside the vessel is maintained within a preset range. The arrangement of the first heating and insulation sleeve 18 and the second heating and insulation sleeve 23 allows the slurry mixing vessel 2 and the testing vessel 22 to be independently temperature controlled, respectively simulating the surface slurry mixing temperature and the downhole testing temperature, meeting the experimental requirements under different working conditions.

[0034] Furthermore, the magnetic drive assembly also includes a torque sensor 7, which is disposed between the speed control motor 8 and the external magnet 10 of the magnetic drive. The input end of the torque sensor 7 is connected to the output shaft of the speed control motor 8, and the output end is connected to the external magnet 10 of the magnetic drive.

[0035] Torque sensor 7 detects the torque value output by speed-regulating motor 8 in real time and transmits the torque signal to the control system or display instrument. During the preparation and subsequent mixing of the foamed cement slurry, the consistency changes over time, and its flow resistance also changes accordingly, resulting in a corresponding change in the torque required for mixing. By continuously monitoring the torque change curve through torque sensor 7, the time elapsed until the torque value reaches a preset threshold is the thickening time of the foamed cement slurry under that temperature and pressure condition. Specifically: First, a reference cement slurry with known standard consistency characteristics conforming to API standards was used as the calibration sample. The device and an API standard pressurized thickener, which had been calibrated, were started and tested simultaneously under the same temperature, pressure, stirring speed, and slurry filling volume conditions. The Bc consistency values ​​of the standard instrument and the torque values ​​of the device were continuously collected at the same time points during the full thickening cycle of the two devices. Data fitting methods (such as the least squares method) were used to fit the two sets of data to establish a continuous torque-Bc consistency conversion curve or lookup table for the device. The torque critical values ​​corresponding to the 70Bc and 100Bc standard thresholds were calibrated simultaneously.

[0036] In the actual measurement of the thickening time of foamed cement slurry, after completing the slurry preparation, pressurized transfer and temperature and pressure regime settings according to the established steps of this device, the speed-regulating motor 8 is started to drive the mixing component to shear the slurry at a constant speed. The torque sensor 7 records the torque change curve in real time, and converts the torque value into a Bc value in real time according to the pre-calibrated conversion relationship. When the converted consistency value reaches 70 Bc for the first time, it is recorded as the pumpable time; when it reaches 100 Bc for the first time, it is recorded as the thickening time. At the same time, the volume change of pressurized fluid recorded by the precision pressure pump 35 is combined to eliminate the interference of gas compression effect on the torque reading, so as to obtain the standard thickening time data.

[0037] Furthermore, the top of the test vessel 22 is connected to a test vessel top cover 21. The pressure measurement and control components include a precision pressure pump 35, a back pressure valve 36, a pressure regulating line 34, and an exhaust and drainage line 19. The pressure regulating line 34 and the exhaust and drainage line 19 both pass through the test vessel top cover 21 and are connected to the upper pressurization chamber. The precision pressure pump 35 is connected to the pressure regulating line 34, the back pressure valve 36 is connected to the exhaust and drainage line 19, and the exhaust and drainage line 19 is also connected to a second pressure gauge 20.

[0038] In this embodiment, the test vessel top cover 21 is a two-section metal disc structure, sealed to the upper flange of the test vessel 22 by bolts 14. The pressure regulating line 34 is a high-pressure resistant metal line, one end of which passes through the test vessel top cover 21 and communicates with the upper pressurization chamber, and the other end is connected to the precision pressure pump 35. The precision pressure pump 35 is a plunger or piston precision metering pump, which can inject pressurized fluid 33 into the upper pressurization chamber and also extract pressurized fluid 33 from the upper pressurization chamber, and accurately measure the volume of fluid injected or discharged. The exhaust and drainage line 19 also passes through the test vessel top cover 21 and communicates with the upper pressurization chamber, and a back pressure valve 36 and a second pressure gauge 20 are sequentially installed on the line. The back pressure valve 36 is used to set the back pressure value of the upper pressurization chamber. When the pressure in the upper pressurization chamber exceeds the set pressure of the back pressure valve 36, the back pressure valve 36 automatically opens to discharge the excess pressurized fluid 33, so that the pressure is maintained near the set value. The second pressure gauge 20 is used to display the pressure value in the upper pressurization chamber in real time. Through the coordinated operation of the precision pressure pump 35 and the back pressure valve 36, the pressure in the upper pressurization chamber can be precisely controlled and stably maintained.

[0039] Furthermore, the bottom of the test vessel 22 is connected to a test vessel bottom cover 29, which includes a first sealing section and a second sealing section. The first sealing section is sealed to the inner wall of the inner cylinder 24, and the second sealing section is sealed to the inner wall of the test vessel 22.

[0040] Furthermore, the bottom cover 29 of the test vessel is also provided with a slurry inlet pipeline 28 and a filtration hole. The slurry inlet pipeline 28 is connected to a tee connector, which includes a first interface, a second interface, and a third interface. The first interface is connected to the slurry inlet pipeline 28, the second interface is connected to the high-pressure slurry delivery pipeline, and the third interface is connected to an exhaust valve. A filtration rod 27 is provided in the filtration hole. A circular groove is opened on the upper end face of the bottom cover 29 of the test vessel, and the filtration hole is opened in the center of the circular groove. A filter screen 30 is embedded in the circular groove. An evacuation pipeline 26 is provided at the bottom of the side wall of the test vessel 22.

[0041] In this embodiment, the slurry inlet pipeline 28 is connected to the slurry outlet pipeline 6 of the slurry mixing vessel 2 via a tee connector and a high-pressure slurry delivery pipeline, and is used to inject the prepared foamed cement slurry in the mixing vessel 2 into the lower test chamber under pressure. The filter screen 30 embedded in the circular groove is made of woven stainless steel wire, and the mesh size is adapted to the particle size of solid particles in the foamed cement slurry. It can prevent cement particles from being discharged with the filtrate during the filtration test, allowing only liquid to pass through. A filtration rod 27 is provided in the filtration hole. When the filtration rod 27 is tightened, it cooperates with the sealing seat in the filtration hole to form a seal. When loosened, it opens the filtration channel for the filtrate to be discharged. The drain pipeline 26 is connected to the inner cavity of the test vessel 22 and is used to discharge the pressurized fluid 33 in the vessel after the experiment.

[0042] Example 2 refer to Figure 1-2Based on Example 1, this example provides a multifunctional testing method for foamed cement slurry, including the following steps: Slurry preparation: Inject cement-based slurry, foaming agent and foam stabilizer into slurry preparation tank 2, introduce high-pressure gas to the preset pressure, start the magnetic drive component to stir, so that the cement-based slurry and gas are fully mixed to form foamed cement slurry; Pressurized transfer: The prepared foamed cement slurry is transferred under pressure to the inner cylinder 24 of the test vessel 22 via a high-pressure slurry pipeline. During the transfer, the pressurized fluid 33 in the upper pressurized chamber of the inner cylinder 24 is discharged using the back pressure valve 36 installed on the top cover 21 of the test vessel. The volume of foamed cement slurry entering the lower test chamber of the inner cylinder 24 is controlled by controlling the discharge volume of the back pressure valve 36. The discharge volume of the back pressure valve 36 can be measured by a graduated cylinder installed on the exhaust and discharge pipeline 19. Performance testing: The foamed cement slurry transferred to the inner cylinder 24 is subjected to performance testing, which includes at least one of the following: Density test: Pressurized fluid 33 is injected or discharged into the upper pressurization chamber by precision pressure pump 35, the pressure in the test vessel 22 is adjusted, and the density of foamed cement slurry at the current temperature and pressure is calculated based on the volume of pressurized fluid 33 injected or discharged by precision pressure pump 35. The initial density of the foamed cement slurry can be calculated in the mixing tank 2. The mixing tank 2 is a closed container with a fixed volume. The initial density of the cement slurry can be calculated by the total mass of the injected cement-based slurry, foaming agent, and foam stabilizer. The current density can be calculated based on the discharge volume recorded by the precision pressure pump 35. Water loss test: The pressure inside the test vessel 22 is controlled to the preset water loss pressure by the precision pressure pump 35, the filter rod 27 set on the bottom cover 29 of the test vessel is loosened, and the filtrate is discharged from the filter hole. The amount of filtrate lost within the preset time is recorded. Suspension stability test: The foamed cement slurry in the test vessel 22 is heated to the preset temperature through the second heating and insulation jacket 23, and the pressure is adjusted to the preset pressure through the precision pressure pump 35. The foamed cement slurry is cured until it solidifies into cement stone. The cement stone is taken out and the density of different parts is measured. The suspension stability of the foamed cement slurry is evaluated based on the density difference.

[0043] In this embodiment, the pulp preparation step is as follows: First, close the valve on the slurry discharge pipeline 6 of the mixing tank 2. Based on the internal volume of the mixing tank 2, calculate the required amounts of cement-based slurry, foaming agent, and foam stabilizer for the foamed cement slurry, and inject the calculated components sequentially into the mixing tank 2. Place the mixing assembly, ensuring the lower end of the impeller shaft 4 is inserted into the positioning hole 11 of the positioning block, and the upper end of the impeller shaft 4 is supported by the impeller bracket 3. Install and tighten the mixing tank cover 1, achieving a high-pressure seal through the first sealing ring 13 on the mixing tank cover 1. Open the air inlet pipeline 17 valve to introduce nitrogen or compressed air into the mixing tank 2 to a preset pressure, which is determined based on the simulated well bottom pressure requirements. Start the speed-regulating motor 8, which drives the mixing assembly to rotate at high speed via the magnetic drive assembly, stirring for a preset time to ensure thorough mixing of the cement-based slurry and high-pressure gas, forming a uniform and fine foamed cement slurry.

[0044] To test the thickening time of foamed cement slurry, the first heating and insulation jacket 18 can be activated after the slurry is prepared to heat the foamed cement slurry to the target temperature. Then, the speed-regulating motor 8 can be started to drive the mixing component to rotate continuously at a constant speed. The torque sensor 7 can monitor the torque change during the mixing process in real time. As the cement slurry gradually thickens, its flow resistance increases, and the torque value detected by the torque sensor 7 gradually rises. When the torque value reaches the preset threshold, the elapsed time is recorded, which is the thickening time of the foamed cement slurry under the specified temperature and pressure conditions.

[0045] If the subsequent experiment is an API water loss test or a suspension stability test, the first heating and insulation jacket 18 of the mixing vessel 2 will be activated after the mixing is completed to heat and insulate the foamed cement slurry inside the mixing vessel 2. At the same time, the foamed cement slurry will be stirred at a low speed for a preset time to simulate the process of pumping the foamed cement slurry from the ground to the well, thus completing the pre-preparation of the foamed cement slurry. During this process, the test vessel 22 can be preheated to reach the required test temperature.

[0046] The specific steps for live transfer are as follows: Before transferring the foamed cement slurry, the test vessel 22 should be prepared first. Check the connection status of all components of the test vessel 22, open the valve of the slurry inlet line 28 on the bottom cover 29 of the test vessel, tighten the filter rod 27, and seal the filter hole to prevent slurry leakage during subsequent operations. Open the vent and drain line 19 valve on the top cover 21 of the test vessel, and adjust the back pressure of the back pressure valve 36 on the vent and drain line 19 to the maximum to prevent leakage from the back pressure valve 36.

[0047] Start the precision pressure pump 35 and inject pressurized fluid 33 into the inner cavity of the test vessel 22 through the pressure regulating line 34 until continuous liquid is discharged from the venting and draining line 19. This indicates that the inner cavity of the test vessel 22, except for the inner cylinder 24 below the piston 32, is filled with pressurized fluid 33. At this point, close the valve of the venting and draining line 19. Continue to inject liquid into the inner cavity of the test vessel 22 through the precision pressure pump 35, pushing the piston 32 downward until the pressure inside the test vessel 22 rises rapidly, indicating that the piston 32 has reached its bottom and is in position. Continue to inject liquid through the precision pressure pump 35 until the pressure inside the test vessel 22 reaches a value equivalent to the pressure of the foamed cement slurry in the mixing vessel 2. Then, gradually reduce the back pressure of the back pressure valve 36 until it begins to drip, indicating that the back pressure of the back pressure valve 36 has been set. At this point, the back pressure valve 36 is in the ready-to-open state.

[0048] Close the valve on the slurry inlet line 28 of the test vessel 22 and the vent valve. Connect the slurry discharge line 6 of the mixing vessel 2 to the slurry inlet line 28 of the test vessel bottom cover 29 via the high-pressure slurry delivery line. Open the valve on the slurry discharge line 6 of the mixing vessel 2, and slowly open the vent valve on the tee joint of the slurry inlet line 28 of the test vessel 22 to vent the slurry discharge line 6 until foamed cement slurry drips from the vent line, indicating that the gas in the line has been completely vented. Then close the vent valve.

[0049] The gas pump is started to pressurize the mixing vessel 2, ensuring its pressure is 0.5 MPa to 1 MPa higher than the initial pressure to overcome pipeline resistance and smoothly transfer the slurry. The valve 28 of the slurry inlet line of the test vessel 22 is opened, and the prepared or pre-made foamed cement slurry begins to enter the inner cylinder 24 of the test vessel 22 under pressure. As the foamed cement slurry enters the inner cylinder 24 and pushes the piston 32 upward, the back pressure valve 36 automatically discharges pressurized fluid 33 equal to the inlet volume. By controlling the discharge volume of the back pressure valve 36, the volume of foamed cement slurry entering the lower test chamber of the inner cylinder 24 can be precisely controlled. When the amount of foamed cement slurry entering the inner cylinder 24 reaches the required experimental volume, the valves of the mixing vessel 2 slurry discharge line 6, the test vessel 22 slurry inlet line 28, and the mixing vessel 2 air inlet line 17 are closed.

[0050] Record the volume of the slurry under the current temperature and pressure, and record the initial parameters (including temperature, pressure, volume, and density) as reference values ​​for subsequent comparison.

[0051] Disconnect the slurry discharge line 6 of the mixing vessel 2 from the slurry inlet line 28 of the test vessel 22. Disconnect the high-pressure air source from the mixing vessel 2. Slowly open the air inlet line 17 valve of the mixing vessel 2 to depressurize it. After depressurization, remove the mixing vessel cover 1, open the slurry discharge line 6 valve of the mixing vessel 2, and repeatedly rinse the inner cavity of the mixing vessel 2 and the stirring blade assembly with clean water. After cleaning, close the slurry discharge line 6 valve.

[0052] The specific performance testing steps are as follows: During density testing, pressurized fluid 33 is injected or discharged into the upper pressurization chamber via a precision pressure pump 35, changing the pressure inside the test vessel 22. Based on the volume of fluid injected or discharged by the precision pressure pump 35 and the cross-sectional area of ​​the inner cylinder 24, the volume change of the foamed cement slurry is calculated, thus obtaining its density under the current pressure. While maintaining a constant pressure, the second heating and insulation jacket 23 is activated to heat the test vessel 22. Based on the volume of fluid discharged by the precision pressure pump 35 during heating, the volume change of the foamed cement slurry at different temperatures is calculated, thus obtaining its density at different temperatures.

[0053] During the API water loss test, the pressure inside the test vessel 22 is controlled to 6.9 MPa by the precision pressure pump 35. Then, the filter rod 27 is loosened to open the filter hole. The filtrate is filtered through the filter screen 30 and discharged from the filter hole. The amount of filtrate lost within 30 minutes is recorded as the API water loss of the foamed cement slurry.

[0054] During the suspension stability test, the foamed cement slurry in the test vessel 22 is heated to a preset temperature by the second heating and insulation jacket 23. When the temperature reaches the set requirement, the pressure of the upper pressure chamber is adjusted to the preset pressure by the precision pressure pump 35, so that the foamed cement slurry in the lower test chamber is under the set temperature and pressure conditions. The foamed cement slurry is maintained under these temperature and pressure conditions until it is completely solidified to form cement stone.

[0055] When removing the foamed cement stone from the test vessel 22, first close the second heating and insulation jacket 23 of the test vessel 22. After its temperature drops to room temperature or the set temperature, slowly open the venting line 26 valve at the bottom of the side wall of the test vessel 22 to slowly release the high pressure inside the test vessel 22 using a step-by-step pressure reduction method. Connect the precision pressure pump 35 to the slurry inlet line 28 on the bottom cover, open the slurry inlet line 28 valve, and start the precision pressure pump 35 to slowly inject pressurized fluid into the bottom of the piston 32. Use the pressurized fluid 33 to push the piston 32 and the cement stone upward. The inner wall of the inner cylinder 24 needs to be coated with a release agent beforehand. Record the maximum hydraulic pressure required to push the cement stone and piston 32. By converting this peak pressure with the force-bearing area of ​​the piston 32, the interfacial shear bond strength between the foamed cement slurry and the inner wall of the inner cylinder 24 can be determined. Continue to push the cement stone and piston 32 until the upward pressure suddenly drops rapidly, indicating that the cement stone and piston 32 have been pushed out of the inner cylinder 24. Open the vent valve inside the test vessel 22 and the vent / drain valve on the top cover 19 to drain the pressurized fluid 33 inside the test vessel 22 by gravity. Remove the bottom cover 29 of the test vessel and take out the foamed cement stone.

[0056] The extracted foamed cement stone was cut and sampled at different heights. The density of each section of cement stone was measured using Archimedes' principle, and the density difference between the upper and lower sections was calculated to evaluate the suspension stability of the foamed cement slurry under the given temperature and pressure conditions. The extracted cement stone can also be further tested for mechanical properties using a compressive strength testing machine or a triaxial compression testing machine to obtain parameters such as compressive strength, elastic modulus, and Poisson's ratio, providing data support for formula optimization.

[0057] In summary, this invention achieves one-stop testing of foamed cement slurry preparation, density, water loss, suspension stability, and thickening time through multifunctional integrated testing. Existing testing devices, due to their limited functionality, can only perform single-performance tests. When conducting multi-performance evaluations, frequent equipment changes and multiple sample transfers are required. Furthermore, foamed cement slurry is sensitive to temperature and pressure, and its air content makes it prone to expansion and rupture. Sample transfers can damage its original bubble structure and slurry state. In addition, the testing conditions of different devices are difficult to standardize, ultimately resulting in large deviations in test data and a lack of cross-verification, leading to insufficient accuracy in the overall performance testing of foamed cement slurry. This invention simultaneously completes multiple performance tests under the same high-temperature, high-pressure, and sealed conditions, eliminating the need for frequent sample transfers and equipment switching. Combined with multi-parameter synchronous testing and data linkage verification, it effectively reduces testing errors caused by the aforementioned factors, solves the problem of insufficient performance testing accuracy due to limited device functionality, and improves the accuracy of overall performance testing of foamed cement slurry.

[0058] The above description is not intended to limit the present invention in any way. Although the present invention has been disclosed above through embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A multifunctional testing device for foamed cement slurry, characterized in that, include: The testing mechanism is connected to a slurry mixing mechanism via a high-pressure slurry pipeline. The testing mechanism includes a testing vessel (22), an inner cylinder (24), a piston (32), and a pressure measurement and control component. The inner cylinder (24) is located inside the testing vessel (22). The piston (32) is slidably connected to the inner wall of the inner cylinder (24). The piston (32) divides the inner cylinder (24) into an upper pressurization chamber and a lower testing chamber. The upper pressurization chamber is used to contain pressurized fluid (33), and the lower testing chamber is used to contain foamed cement slurry. The pressure measurement and control component is connected to the top of the testing vessel (22). The mixing mechanism includes a mixing tank (2), a stirring assembly, and a magnetic drive assembly. The stirring assembly is rotatably connected inside the mixing tank (2), and the magnetic drive assembly is connected to the bottom of the mixing tank (2) to drive the stirring assembly.

2. The apparatus according to claim 1, characterized in that, The test vessel (22) is connected to a test vessel top cover (21). The pressure measurement and control component includes a precision pressure pump (35), a back pressure valve (36), a pressure regulating line (34), and an exhaust and drainage line (19). The pressure regulating line (34) and the exhaust and drainage line (19) both pass through the test vessel top cover (21) and are connected to the upper pressurization chamber. The precision pressure pump (35) is connected to the pressure regulating line (34), the back pressure valve (36) is connected to the exhaust and drainage line (19), and the exhaust and drainage line (19) is also connected to a second pressure gauge (20).

3. The apparatus according to claim 2, characterized in that, The bottom of the test vessel (22) is connected to a test vessel bottom cover (29). The test vessel bottom cover (29) includes a first sealing section and a second sealing section. The first sealing section is sealed to the inner wall of the inner cylinder (24), and the second sealing section is sealed to the inner wall of the test vessel (22).

4. The apparatus according to claim 3, characterized in that, The test vessel bottom cover (29) is also provided with a slurry inlet pipeline (28) and a filter outlet. The slurry inlet pipeline (28) is connected to a three-way connector. The three-way connector includes a first interface, a second interface and a third interface. The first interface is connected to the slurry inlet pipeline (28), the second interface is connected to the high-pressure slurry delivery pipeline, and the third interface is connected to an exhaust valve. A filter outlet rod (27) is provided in the filter outlet. A circular groove is opened on the upper end face of the test vessel bottom cover (29). The filter outlet is opened at the center of the circular groove. A filter screen (30) is embedded in the circular groove. An evacuation pipeline (26) is provided at the bottom of the side wall of the test vessel (22).

5. The apparatus according to claim 1, characterized in that, The magnetic drive assembly includes a speed-regulating motor (8), an inner magnetic drive magnet (5), and an outer magnetic drive magnet (10). The speed-regulating motor (8) is located at the bottom of the outer wall of the mixing tank (2). The outer magnetic drive magnet (10) is connected to the output shaft of the speed-regulating motor (8). The inner magnetic drive magnet (5) is located at the bottom of the inner cavity of the mixing tank (2) and is connected to the stirring assembly. The outer magnetic drive magnet (10) and the inner magnetic drive magnet (5) are magnetically coupled to drive the stirring assembly to rotate while the mixing tank (2) is kept sealed.

6. The apparatus according to claim 5, characterized in that, The stirring assembly includes a blade (12), a blade support (3), and a blade shaft (4). The blade (12) is connected to the outer wall of the blade shaft (4), and the blade support (3) is connected to the top of the inner cavity of the mixing tank (2). The bottom of the inner cavity of the mixing tank (2) is provided with a positioning groove, a positioning block is provided in the positioning groove, and a positioning hole (11) is provided on the upper end face of the positioning block. The top end of the blade shaft (4) is rotatably connected to the blade support (3), and the bottom end passes through the magnet (5) in the magnetic drive and is rotatably connected to the positioning hole (11). A compression spring is provided between the top end of the blade shaft (4) and the blade support (3) to provide axial preload.

7. The apparatus according to claim 6, characterized in that, The top of the mixing tank (2) is connected to the mixing tank cover (1), and the mixing tank cover (1) is equipped with an air inlet pipeline (17). The air inlet pipeline (17) passes through the mixing tank cover (1) and communicates with the inner cavity of the mixing tank (2). The air inlet pipeline (17) is connected to an air inlet valve (16), a first pressure gauge (15) and an air source. The bottom of the side wall of the mixing tank (2) is connected to a slurry discharge pipeline (6), and the slurry discharge pipeline (6) is connected to the high-pressure slurry delivery pipeline.

8. The apparatus according to claim 1, characterized in that, The outer wall of the mixing vessel (2) is provided with a first heating and heat preservation sleeve (18), and the outer wall of the test vessel (22) is provided with a second heating and heat preservation sleeve (23).

9. The apparatus according to claim 5, characterized in that, The magnetic drive assembly also includes a torque sensor (7), which is disposed between the speed-regulating motor (8) and the magnetic drive external magnet (10). The input end of the torque sensor (7) is connected to the output shaft of the speed-regulating motor (8), and the output end is connected to the magnetic drive external magnet (10).

10. A multifunctional testing method for foamed cement slurry, using the apparatus described in any one of claims 1-9, characterized in that, Includes the following steps: Slurry preparation: Inject cement-based slurry, foaming agent and foam stabilizer into the slurry preparation tank (2), introduce high-pressure gas to the preset pressure, start the magnetic drive assembly to stir, so that the cement-based slurry and gas are fully mixed to form foam cement slurry; Pressurized transfer: The prepared foamed cement slurry is transferred under pressure to the inner cylinder (24) of the test vessel (22) through a high-pressure slurry pipeline. During the transfer, the pressurized fluid (33) in the upper pressurized chamber of the inner cylinder (24) is discharged by the back pressure valve (36) set on the top cover (21) of the test vessel. The volume of foamed cement slurry entering the lower test chamber of the inner cylinder (24) is controlled by controlling the discharge volume of the back pressure valve (36). Performance testing: The foamed cement slurry transferred to the inner cylinder (24) is subjected to performance testing, the performance testing including at least one of the following: Density test: Pressurized fluid (33) is injected or discharged into the upper pressurized chamber by a precision pressure pump (35), the pressure in the test vessel (22) is adjusted, and the density of the foamed cement slurry at the current temperature and pressure is calculated based on the volume of pressurized fluid (33) injected or discharged by the precision pressure pump (35). Water loss test: The pressure inside the test vessel (22) is controlled to the preset water loss pressure by the precision pressure pump (35), the filter rod (27) set on the bottom cover (29) of the test vessel is loosened, so that the filtrate is discharged from the filter hole, and the amount of filtrate lost within the preset time is recorded; Suspension stability test: The foamed cement slurry in the test vessel (22) is heated to the preset temperature through the second heating insulation jacket (23), and the pressure is adjusted to the preset pressure through the precision pressure pump (35). The foamed cement slurry is cured until it solidifies into cement stone. The cement stone is taken out and the density of different parts is measured. The suspension stability of the foamed cement slurry is evaluated based on the density difference.

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