A multi-condition high-temperature and high-pressure corrosion simulation experimental device and method

Abstract

The present invention relates to a multi-condition high-temperature and high-pressure corrosion simulation experimental device and method, belonging to the field of oil and gas cementing. The device is composed of a nitrogen bottle, a corrosive medium storage tank, a flow pump and a maintenance / corrosion kettle. The maintenance / corrosion kettle includes a kettle body, a maintenance gland, a corrosion gland and a back-pressure upper cover. The side wall of the kettle body has a liquid inlet pressure port, a liquid discharge pressure relief port and an exhaust port. The maintenance gland and the kettle body form a closed kettle cavity for curing cement stone; the cement ring upper cover passes through the corrosion gland to form a sealed kettle cavity corrosion cement ring assembly. The method comprises: injecting the corrosive medium into the kettle through a flow pump and pressurizing it, so that the corrosive medium forms a circulation between the reactor and the storage tank, adjusting the pressure of the upper cavity and the kettle cavity to reach the required pressure difference, and ensuring that the cement stone and the corrosive medium form contact under different working conditions. The present invention can simulate the corrosion of the corrosive medium to the cement stone under various working conditions at one time, accurately reflect the corrosion law of cement stone in the well, and thus evaluate the corrosion resistance of the cement stone.

Description

Technical Field

[0001] The invention belongs to the field of oil and gas cementing, and in particular relates to a multi-condition high-temperature and high-pressure corrosion simulation experimental device and method. Background Art

[0002] The main function of cementing stone is to protect the well wall, isolate the formation fluid, prevent interlayer cross-flow, and provide an alkaline environment to prevent casing corrosion. In the oil and gas layer, CO2 and H2S often exist as associated gases of oil and natural gas. Under moderate pressure and temperature environment, they will corrode the cementing stone, seriously affecting the safe production of oil and gas wells.

[0003] After a well is built, the casing and cement remain in the well. The cement of the open hole section is between the casing and the formation, and the cement is in direct contact with the corrosive medium in the formation fluid and corroded; the cement after the upper casing is cemented is between the two layers of casing, and the corrosive medium must pass through the cement of the open hole section to contact and corrode it; the cement at the perforation hole is in direct contact with the corrosive medium, and will not only be corroded by the corrosive medium, but also eroded by the corrosive medium. It can be seen that the corrosion process and corrosion results of the cement are different in different locations, and the differences are even huge.

[0004] Domestic researchers have conducted a lot of research on cement stone corrosion. "An experimental device for evaluating the acid gas corrosion resistance of cement stone" (CN217878823U) can improve the detection accuracy of cement stone under static end face corrosion by setting a reaction barrel in the box, using the reaction barrel to generate cement slurry in the box, curing cement stone and detecting its acid gas corrosion resistance; "A cement stone curing mold and dynamic gas corrosion experimental device" (CN11896339A) drives the cement stone curing mold inside the kettle to rotate through the rotating base of the corrosion kettle to realize the relative flow between the cement stone surface and the corrosive gas, and the external motor can adjust the speed of the mold in the kettle to rotate, which more accurately and truly reflects the dynamic corrosion of cement stone in the kettle; "An evaluation device for simulating CO2 dynamic corrosion resistance" (CN218629430U) simulates the corrosion of cement stone in a CO2 environment, and can place several different types of cement stone in it. The cement stone rotates in a CO2 aqueous solution environment through a rotating device to realize the flow and replacement of corrosive media on the surface of cement stone and the comparative analysis of different cement stones under the same corrosive medium. However, this type of device adopts a sealed structure, and the acidic corrosive medium in the reactor cannot be updated in time. As the reaction time increases, the concentration of the corrosive medium gradually decreases, and the corrosion rate also becomes lower and lower. Compared with the sufficient corrosive medium in the actual well, the experimentally measured corrosive medium has a much lower corrosion efficiency on cement stone.

[0005] "Experimental device and experimental method for simulating the corrosion process of cement ring in the formation" (CN108593533B) uses a constant flow and constant pressure pump to uniformly fill the corrosive medium into the kettle to ensure that the concentration of the corrosive medium in the formation water will not decline as the experiment proceeds, thus realizing the dynamic update of the corrosive medium. However, the device uses a spiral liquid separation hole to corrode the surface of the cement stone, which does not conform to the situation where underground fluids seep and corrode the cement stone along the formation, and the concentration of the corrosive medium flowing out along the flow direction remains unchanged, which does not conform to the situation where the concentration of the corrosive medium fluid in the well changes continuously during the flow process.

[0006] "Indoor simulation experimental device and method for dynamic erosion and corrosion of cement by carbon dioxide" (CN112179832A) simulates the dynamic renewal of downhole fluid by setting up upper and lower inlet and outlet ports and flow pumps. Movable cement stone fixing clamps are installed on both sides of the reaction container to simulate the cracks formed by cement stone, reflecting the process of coupling erosion and corrosion of acidic fluid along the cementing surface and cement body containing microcracks. However, the device uses a displacement sensor to adjust the distance between two rectangular cement stone samples to simulate microcracks, which is too idealized compared with the actual cracks formed in the well and cannot reflect the corrosion of cement stone containing tortuous microcracks in an acidic fluid environment.

[0007] Although some progress has been made in the research on cement stone corrosion, the current devices and methods are difficult to simulate the corrosion process of corrosive media seeping through the formation to the cement stone and rising from the lower cement stone to the upper cement stone. This does not conform to the actual situation of cement stone corrosion in the well and cannot accurately reflect the corrosion law of cementing cement stone in the well. Summary of the invention

[0008] The purpose of the present invention is to provide a multi-condition high-temperature and high-pressure corrosion simulation experimental device. The device has reliable principle and is easy to operate. It can not only realize the dynamic renewal of corrosive fluid, but also reflect the static end face corrosion, dynamic scouring corrosion and seepage corrosion of cement stone by corrosive medium under different pressure differences and temperatures, which is more in line with the actual situation of cement stone corrosion in the well and accurately reflects the corrosion law of cementing cement stone in the well.

[0009] Another object of the present invention is to provide a method for conducting multi-condition high-temperature and high-pressure corrosion simulation experiments using the above-mentioned device. Through the seepage corrosion of the corrosive medium from the formation surrounding rock to the cement stone under high temperature and high pressure, the upward corrosion of the cement stone by the seepage from the bottom of the well to the wellhead, and the direct corrosion of the cement stone at the blasthole, the corrosion process and corrosion results of the cement stone in different positions can be fully and truly reflected, thereby evaluating the corrosion resistance of the cement stone.

[0010] In order to achieve the above technical objectives, the present invention adopts the following technical solutions.

[0011] A multi-condition high-temperature and high-pressure corrosion simulation experimental device is mainly composed of a nitrogen bottle, a corrosion medium storage tank, a flow pump and a curing / corrosion kettle.

[0012] The curing / corrosion kettle comprises a kettle body, a curing gland, a corrosion gland and a back-pressure upper cover. The curing gland, the corrosion gland and the kettle body are connected by bolts, and the back-pressure upper cover and the corrosion gland are connected by bolts.

[0013] The kettle body is a hollow, bottomed, open-top thick-walled cylindrical steel cylinder, with a kettle cavity inside and a heating and heat-insulating jacket outside. The side wall is provided with a liquid inlet pressure port with a valve, a liquid discharge pressure relief port with a valve, a condensation tank, and a back pressure valve, and an exhaust port with a valve. The liquid inlet pressure port is connected to a flow pump and a corrosive medium storage tank to inject corrosive medium into the kettle cavity; the exhaust port is connected to a nitrogen bottle to fill and exhaust the kettle cavity before the experiment and to fill and discharge the kettle cavity after the experiment.

[0014] The maintenance gland is a thick-walled circular steel plate with circular through holes on the periphery, which is connected to the kettle body through threads to form a closed kettle cavity for maintaining the cement ring assembly.

[0015] The cement ring assembly has an intermediate casing with solid plugs at both ends as the center, the plugs are provided with internal threads and can be connected to the upper / lower supporting plates of the cement ring through threads; the outer layer is composed of the cement ring upper cover, upper casing, permeable core and buckled steel cylinder from top to bottom; there is an annular space between the intermediate casing and the outer layer.

[0016] The cement ring upper cover is composed of two steel cylinders with different inner diameters, and an annular space is formed between the upper steel cylinder with a smaller inner diameter and the middle casing; the lower steel cylinder with a larger inner diameter has an internal thread and is connected to the upper casing with an external thread, and an annular space of the same size is also formed between the upper casing and the middle casing.

[0017] The permeable core has the same inner and outer diameters as the upper casing, is located below the upper casing, and cooperates with the middle casing to simulate the open hole formation and form an annular space with the middle casing.

[0018] The buckled steel cylinder is composed of two symmetrical semicircular steel cylinders connected by bolts, and its inner and outer diameters are the same as those of the upper casing, and is located below the simulated rock core.

[0019] The upper / lower supporting plate of the cement ring is a circular thick-walled steel plate with a through hole in the center, which is connected to the middle casing by bolts, and presses the upper cover of the cement ring, the upper casing, the simulated rock core and the interlocking steel cylinder to prevent the simulated rock core and the interlocking steel cylinder from moving, forming an annular space for containing cement slurry and cement stone formed after the cement slurry solidifies.

[0020] The corrosion gland is a thick-walled annular steel plate with circular through holes around its periphery. Its inner diameter is consistent with the upper steel cylinder of the cement ring upper cover and is connected to the kettle body through threads. The upper steel cylinder of the cement ring upper cover passes through the corrosion gland to form a sealed kettle cavity for corroding the cement ring assembly.

[0021] The back-pressure upper cover is a hollow cylindrical steel pipe with a top and an opening at the lower end. The bottom of the steel pipe is sealed and connected to the corrosion pressure cover by threads. The upper steel cylinder of the cement ring upper cover passes through the corrosion pressure cover and enters the back-pressure upper cover. A pressure plate with holes is arranged inside the back-pressure upper cover to press the cement ring assembly and form an upper cavity into which the corrosive medium can be injected between the back-pressure upper cover and the cement ring assembly. A drain port with a valve is arranged on the top of the back-pressure upper cover to pressurize or drain the liquid into the upper cavity to simulate the pressure difference environment of the formation. At the same time, an overflow pipeline with a back-pressure valve and a condensation tank is also arranged to send excess corrosive fluid back to the corrosive medium storage tank to form a circulation.

[0022] When the kettle is used for cement stone curing, the lower support plate must be connected to the thick-walled cylindrical steel cylinder through threads, and the buckle steel cylinder, permeable core, upper casing and cement ring cover are placed on the lower support plate from bottom to top. The cement ring cover and the upper casing are connected by threads, and the buckle steel cylinder and the upper and lower ends of the simulated core are coated with high-viscosity butter to ensure the sealing of the cement ring. After the annular space is filled with cement slurry, the plug on the top of the middle casing is installed on the support plate through threads to compress the cement ring assembly, and the upper support plate is equipped with a lifting ring for easy removal.

[0023] When the kettle body is corroding cement stone, it is necessary to remove the upper and lower supporting plates and the buckled steel cylinders on the basis of maintaining the cement ring, install sealing rings on the upper parts of steel cylinders with different inner diameters on the cement ring, and drill several holes in the lower part of the cement ring to simulate blastholes.

[0024] When the kettle body is corroding cement stone, after the cement ring assembly is pressed into the kettle body, a corrosion pressure cover and a back pressure upper cover are installed on the top of the kettle body, wherein the bottom steel plate of the back pressure upper cover is connected to the corrosion pressure cover by bolts.

[0025] When the kettle body is conducting a corrosion simulation experiment, the process of direct contact and corrosion between the corrosive medium and the cement stone, the corrosion of the corrosive medium entering the cement stone through the blasthole, and the seepage corrosion of the corrosive medium through the core and the cement stone can be simulated in the early stage, and the situation of the corrosive medium passing through the cement stone under the pressure difference to penetrate upward and corrode in the later stage. After a certain corrosion time, the cement ring is removed to observe the position where the corrosive medium finally corrodes the cement stone, and the performance change of the corroded cement stone: according to the corrosion of the corrosive medium seepage through the core to the different positions of the cement stone, the seepage corrosion between the actual formation surrounding rock and the cement stone is simulated; the upper casing is removed to observe the situation of the corrosive medium passing through the cement stone under the pressure difference.

[0026] The present invention injects the corrosive medium into the reactor through a pump and pressurizes it to the pressure required for the experiment, adjusts the pressure of the upper chamber and the reactor chamber to achieve the pressure difference required for the experiment, sets the required temperature, and after the temperature reaches the requirement, debugs the top back pressure valve to make the corrosive medium circulate between the reactor and the storage tank, ensuring that the cement stone and the corrosive medium form contact under different working conditions.

[0027] The present invention can simulate the corrosion of cement stone by corrosive media under various conditions at one time, which is convenient for comparative analysis of the corrosion conditions of cement stone under different working conditions.

[0028] The method for conducting a multi-condition high temperature and high pressure corrosion simulation experiment using the above device comprises the following steps in sequence:

[0029] (1) Prepare cement slurry according to API standards and pour it into the annular space of the cement ring assembly. Install the upper and lower supporting plates of the cement ring assembly and place it inside the kettle body. Tighten the maintenance gland.

[0030] (2) Inject pressure into the kettle body, turn on the thermostat to heat the kettle body, and perform cement stone curing;

[0031] (3) After the curing is completed, open the curing gland and take out the cement ring assembly, disassemble the upper and lower support plates and the buckle steel cylinder, and drill several blastholes at the bottom of the permeable core;

[0032] (4) Place and fix the cement ring assembly in the kettle body, and install the corrosion gland and back pressure cover;

[0033] (5) Open the liquid inlet and pressure relief port and the exhaust port, inject the corrosive medium into the kettle body, close the exhaust port after the air in the kettle body is exhausted, and continue to inject the corrosive medium into the kettle body and pressurize it through the liquid inlet and pressure relief port;

[0034] (6) The corrosive medium is filled into the upper chamber through the liquid inlet of the back pressure cover and pressurized. The seepage pressure difference of the corrosive medium on the cement stone and the pressure difference of the corrosive medium circulation are adjusted through the back pressure valve of the back pressure cover. The temperature controller heats the kettle body to reach the temperature and pressure required for the experiment;

[0035] (7) Use a flow pump to continuously inject the corrosive medium into the kettle body to form a circulation flow of the corrosive medium, ensuring that the corrosive medium continuously seeps through the permeable core and cement stone in the cement sheath assembly;

[0036] (8) After the time required by the experimental design is reached, stop injecting the corrosive medium, turn off the temperature controller, release the pressure in the kettle chamber and the upper chamber, take out the cement ring assembly, and observe, test and analyze the corrosion of the cement stone in different parts and under different corrosion conditions.

[0037] By observing and detecting the corrosion conditions of cement stone in different parts and under different working conditions (including corrosion depth, compressive strength, etc.), the influence of corrosive media on cement stone under different corrosion modes is obtained; by simulating the erosion process of different cement stones, different corrosive media, different pressure differences, cement stones in different positions and different flow rates, the corrosion law of cement sheath is analyzed and obtained.

[0038] The present invention forms different corrosion modes of the same cement ring by constructing a cement ring assembly; and simulates the corrosion conditions of different cement stones under different pressure differences and different flow rate erosion in different corrosive media by adjusting the pressure difference between the two chambers, changing the cement stone formula and the corrosive medium, so as to more accurately analyze the corrosion results of the cement ring under various working conditions of the corrosive medium.

[0039] Compared with the prior art, the present invention has the following beneficial effects:

[0040] (1) The present invention can simulate the actual corrosion of cement sheath by simulating the corrosion of corrosive media under different working conditions, and can compare and analyze the corrosion of different positions of cement sheath by different corrosion modes;

[0041] (2) The present invention provides a more excellent and effective technical means for further studying the corrosion law of cement stone and improving the long-term sealing stability of cement sheath. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 It is a schematic diagram of the curing kettle structure of a multi-condition high-temperature and high-pressure corrosion simulation experimental device.

[0043] Figure 2 It is a schematic diagram of the corrosion kettle structure of a multi-condition high-temperature and high-pressure corrosion simulation experimental device.

[0044] Description of reference numerals:

[0045] 1-Maintenance gland; 2, 3, 4, 23, 26, 27-Bolts; 5-Heating and insulation sleeve; 6, 22-Supporting plate; 7-Cement ring cover; 8, 15, 20, 34-Valve; 9-Vent; 10-Cement ring; 11-Upper casing; 12-Kettle body; 13-Pressure gauge; 14-Liquid inlet and pressure injection port; 16-Permeability core; 17-Blast hole; 18, 36-Back pressure valve; 19-Pressure relief and drainage port; 21-Steel cylinder; 24-Middle casing; 25-Kettle chamber; 28, 29-Sealing rubber ring; 30-Corrosion gland; 31-Pressing plate with holes; 32-Upper chamber; 33-Back pressure cover; 35-Top liquid inlet; 37, 38-Condensation reflux pipe. DETAILED DESCRIPTION

[0046] In order to explain the present invention more clearly, the present invention is further described below in conjunction with embodiments. It should be understood by those skilled in the art that the content described below is illustrative rather than restrictive, and should not be used to limit the scope of protection of the present invention.

[0047] See also Figure 1 , Figure 2 .

[0048] A multi-condition high-temperature and high-pressure corrosion simulation experimental device comprises a curing / corrosion kettle, a cement ring assembly, a flow pump, a corrosive medium storage tank and a nitrogen cylinder. The curing / corrosion kettle comprises a kettle body 12, a curing gland 1, a corrosion gland 30 and a back-pressure upper cover 33.

[0049] The kettle body 12 is a thick-walled cylindrical steel cylinder, with a kettle cavity 25 inside and a heating and insulation sleeve 5 outside. The heating and insulation sleeve is connected to a temperature controller. The side wall is provided with a liquid inlet and pressure injection port 14 with a pressure gauge 13 and a valve 15, a pressure relief and liquid discharge port 19 with a back pressure valve 18, a valve 20, and a condensation reflux pipe 38, and an exhaust port 9 with a valve 8. The liquid inlet and pressure injection port and the pressure relief and liquid discharge port are externally connected to a flow pump and a corrosive medium storage tank, and the exhaust port is connected to a nitrogen bottle. A cement ring assembly is placed in the kettle cavity.

[0050] The cement ring assembly has an intermediate casing 24 at its center, and the outer layers are, from top to bottom, a cement ring cover 7, an upper casing 11, a permeable core 16 and a buckle steel cylinder 21, and an annular space is formed between the intermediate casing and the outer layer; the cement ring cover 7 is composed of two steel cylinders with different inner diameters, the inner diameter of the upper steel cylinder is consistent with the inner diameter of the upper casing 11, and the lower steel cylinder has an internal thread and is connected to the upper casing with an external thread; the inner and outer diameters of the permeable core 16 and the buckle steel cylinder 21 are the same as those of the upper casing, and the buckle steel cylinder is composed of two symmetrical semicircular steel cylinders connected by bolts.

[0051] The curing gland 1 is a thick-walled circular steel plate with through holes around the periphery, which is connected to the kettle body 12 by bolts to form a closed kettle cavity 25 with the kettle body for curing cement stone.

[0052] The corrosion pressure cover 30 is a thick-walled annular steel plate with through holes on the periphery. Its inner diameter is consistent with the upper steel cylinder of the cement ring cover. It is connected to the kettle body 12 by bolts. The back pressure cover 33 is connected to the corrosion pressure cover by bolts. The top of the back pressure cover is provided with a liquid inlet 35 with a valve 34 and an overflow pipeline with a back pressure valve 36 and a condensation reflux pipe 37. The liquid inlet is connected to the corrosive medium storage tank for corrosion experiments.

[0053] Furthermore, the curing cement stone refers to that the middle casing 24 is connected to the upper and lower supporting plates 6 and 22 by bolts 2 and 23 through the plugs at both ends, the annular space is filled with cement slurry, the lower supporting plate is fixed in the kettle body, the curing gland 1 is connected to the kettle body 12 by bolts 3 and 4, and forms a closed kettle cavity 25 with the kettle body, and the cement ring 10 is formed by curing under a certain temperature and pressure.

[0054] Furthermore, the corrosion experiment refers to removing the maintenance pressure cover 1 and the upper and lower supporting plates 6 and 22, the cement ring assembly is fixed in the kettle body, the corrosion pressure cover 30 is connected to the kettle body 12 by bolts 3 and 4, and the back pressure upper cover 33 is connected to the corrosion pressure cover by bolts 26 and 27; the upper steel cylinder of the cement ring upper cover 7 passes through the corrosion pressure cover and enters the back pressure upper cover, and a perforated pressure plate 31 is provided in the back pressure upper cover for pressing the cement ring assembly and forming an upper cavity 32 between the back pressure upper cover and the cement ring assembly, thereby forming the required pressure difference between the upper cavity 32 and the kettle cavity 25.

[0055] Furthermore, sealing rubber rings 28 and 29 are arranged on the outer walls of the steel cylinders with different inner diameters of the cement ring upper cover, so that a seal is formed between the cement ring upper cover and the corrosion pressure cover and the back pressure upper cover.

[0056] Further, when the cement sheath curing is completed, several holes are drilled in the permeable core to simulate blastholes 17 .

[0057] Furthermore, the buckled steel cylinder is composed of two symmetrical semicircular steel cylinders connected by bolts, and its inner and outer diameters are the same as those of the upper casing. After disassembly, part of the cement ring is exposed.

[0058] Furthermore, the liquid inlet pressure port 14 and the pressure relief liquid outlet 19 are connected to the corrosive medium storage tank, and a circulation flow of the corrosive medium in the kettle chamber 25 is formed by a flow pump.

[0059] Furthermore, the liquid inlet pressure injection port 14 and the condensation reflux pipe 37 on the top of the back pressure upper cover are connected to the external corrosive medium storage tank. Under the pressure difference between the kettle chamber 25 and the upper chamber 32, the corrosive medium flows upward in the cement sheath assembly.

[0060] Furthermore, the pressure of the upper chamber 32 is lower than the pressure of the kettle chamber 25, ensuring that the corrosive medium can flow from bottom to top through the cement ring.

[0061] The method for conducting a multi-condition high temperature and high pressure corrosion simulation experiment using the above device comprises the following steps in sequence:

[0062] (1) Assemble the cement ring assembly, pour cement slurry into the annular space, tighten the support plate and place it inside the kettle body, and install the maintenance gland 1;

[0063] (2) Inject pressure through the exhaust port 9 and open the heating and insulation sleeve 5 to cure the cement ring;

[0064] (3) After the cement ring is cured, take out the cement ring assembly, disassemble the supporting plates 6, 22 at both ends and the buckle steel cylinder 21, and install the rubber sealing rings 28, 29 on the cement ring upper cover 7;

[0065] (4) Slowly press the cement ring assembly into the kettle body 12, install and tighten the corrosion gland 30 on the top of the kettle body, install the perforated pressure plate 31 on the top of the cement ring, and then install the back pressure cover 33;

[0066] (5) Connect the kettle body liquid inlet pressure port 14 and the top liquid inlet 35 to the corrosive medium storage tank;

[0067] (6) Open the liquid inlet and pressure injection port 14 and the exhaust port 9, fill the required corrosive fluid into the kettle body, then close the inlet and exhaust port 9, and continue to pressurize the kettle cavity through the liquid inlet and pressure injection port 14;

[0068] (7) Open the top liquid inlet 35 to inject corrosive fluid into the upper chamber for pressurization, close it after a certain period of time, open the pressure relief drain port 19 to form a cycle, open the top back pressure valve 36 to adjust the pressure difference between the two chambers, start the heating and insulation jacket 5 to heat the kettle body, and start the simulation experiment after reaching the required temperature, pressure and pressure difference of the experiment;

[0069] (8) After the time required by the experimental design is reached, stop injecting the corrosive medium, turn off the temperature controller, and after the kettle temperature drops to room temperature, release the pressure of the corrosive fluid in the two chambers of the kettle. Open the kettle and take out the cement stone assembly for subsequent testing.

[0070] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not limitations on the implementation methods of the present invention. For ordinary technicians in the relevant field, other different forms of changes or modifications can be made on the basis of the above description. It is impossible to list all the implementation methods here. All obvious changes or modifications derived from the technical solution of the present invention are still within the protection scope of the present invention.

Claims

1. A multi-condition high-temperature and high-pressure corrosion simulation experimental device, comprising a curing / corrosion kettle, a cement sheath assembly, a flow pump, a corrosive medium storage tank and a nitrogen cylinder, wherein the curing / corrosion kettle comprises a kettle body (12), a curing gland (1), a corrosion gland (30) and a back-pressure upper cover (33), characterized in that: The kettle body (12) is a thick-walled cylindrical steel cylinder, the interior of which is a kettle cavity (25), and the exterior is covered with a heating and heat-insulating sleeve (5), which is connected to a temperature controller. The side wall is provided with a liquid inlet pressure injection port (14), a pressure relief and drainage port (19) and an exhaust port (9), the liquid inlet pressure injection port and the pressure relief and drainage port are externally connected to a flow pump and a corrosive medium storage tank, the exhaust port is connected to a nitrogen bottle, and the pressure relief and drainage port is provided with a back pressure valve and a condensation reflux pipe. A cement ring assembly is placed in the kettle cavity; the cement ring assembly has an intermediate sleeve (24) at the center, and the outer layers are, from top to bottom, A cement ring upper cover (7), an upper casing (11), a permeable core (16) and a buckled steel cylinder (21), wherein an annular space is formed between the middle casing and the outer layer; the cement ring upper cover (7) is composed of two steel cylinders with different inner diameters, the inner diameter of the upper steel cylinder is consistent with the inner diameter of the upper casing (11), and the lower steel cylinder has an internal thread and is connected to the upper casing with an external thread; the inner and outer diameters of the permeable core (16) and the buckled steel cylinder (21) are the same as those of the upper casing, and the buckled steel cylinder is composed of two symmetrical semicircular steel cylinders connected by bolts; The curing gland (1) is a thick-walled circular steel plate with through holes on the periphery, which is connected to the kettle body (12) by bolts to form a closed kettle cavity (25) with the kettle body for curing cement stone; The corrosion pressure cover (30) is a thick-walled annular steel plate with through holes on the periphery, and its inner diameter is consistent with the outer diameter of the upper steel cylinder of the cement ring cover, and is connected to the kettle body (12) by bolts. The back pressure cover (33) is connected to the corrosion pressure cover by bolts. The top of the back pressure cover is provided with a liquid inlet (35) and an overflow pipeline with a back pressure valve and a condensation reflux pipe. The liquid inlet is connected to the corrosive medium storage tank for corrosion experiments.

2. A multi-condition high temperature and high pressure corrosion simulation experimental device as claimed in claim 1, characterized in that: The curing cement stone refers to the middle casing (24) being connected to the upper and lower support plates through plugs at both ends, the annular space being filled with cement slurry, the lower support plate being fixed in the kettle body, the curing gland (1) being connected to the kettle body (12) through bolts, forming a closed kettle cavity (25) with the kettle body, and curing under a certain temperature and pressure to form a cement ring (10).

3. A multi-condition high temperature and high pressure corrosion simulation experimental device as claimed in claim 2, characterized in that: The corrosion experiment refers to removing the maintenance pressure cover and the upper and lower supporting plates, fixing the cement ring assembly in the kettle body, connecting the corrosion pressure cover (30) to the kettle body (12) by bolts, and connecting the back pressure upper cover (33) to the corrosion pressure cover by bolts; the upper steel cylinder of the cement ring upper cover (7) passes through the corrosion pressure cover and enters the back pressure upper cover, and a pressure plate (31) with holes is provided in the back pressure upper cover for pressing the cement ring assembly, and forming an upper cavity (32) between the back pressure upper cover and the cement ring assembly, so as to form a required pressure difference between the upper cavity (32) and the kettle cavity (25).

4. The multi-condition high temperature and high pressure corrosion simulation experimental device according to claim 1, characterized in that: Sealing rubber rings are respectively arranged on the outer walls of steel cylinders with different inner diameters of the cement ring upper cover to form a seal between the cement ring upper cover and the corrosion pressure cover and the back pressure upper cover.

5. The multi-condition high temperature and high pressure corrosion simulation experimental device according to claim 1, characterized in that: When the cement sheath is cured, several holes are drilled in the permeable core to simulate blastholes (17).

6. The multi-condition high temperature and high pressure corrosion simulation experimental device according to claim 1, characterized in that: The buckled steel cylinder is composed of two symmetrical semicircular steel cylinders connected by bolts, and its inner and outer diameters are the same as those of the upper casing. After disassembly, part of the cement ring is exposed.

7. The multi-condition high temperature and high pressure corrosion simulation experimental device according to claim 3, characterized in that: The liquid inlet pressure injection port and the condensation reflux pipe on the top of the back pressure upper cover are connected to the corrosive medium storage tank. Under the pressure difference between the kettle cavity and the upper cavity, the corrosive medium flows upward in the cement sheath assembly.

8. The multi-condition high temperature and high pressure corrosion simulation experimental device according to claim 7, characterized in that: The pressure of the upper chamber is lower than the pressure of the kettle chamber, which ensures that the corrosive medium can flow from bottom to top through the cement ring.

9. A method for conducting a multi-condition high temperature and high pressure corrosion simulation experiment using the device of claim 3, comprising the following steps in sequence: (1) Pour cement slurry into the annular space of the cement ring assembly, install the upper and lower supporting plates of the cement ring assembly, place it in the kettle, and tighten the maintenance gland; (2) Inject pressure into the kettle body, turn on the thermostat to heat the kettle body, and perform cement stone curing; (3) After the curing is completed, open the curing gland and take out the cement ring assembly, disassemble the upper and lower support plates and the buckle steel cylinder, and drill several blastholes at the bottom of the permeable core; (4) Place and fix the cement ring assembly in the kettle body, and install the corrosion gland and back pressure cover; (5) Open the liquid inlet and pressure relief port and the exhaust port, inject the corrosive medium into the kettle body, close the exhaust port after the air in the kettle body is exhausted, and continue to inject the corrosive medium into the kettle body and pressurize it through the liquid inlet and pressure relief port; (6) The corrosive medium is filled into the upper chamber through the liquid inlet of the back pressure cover and pressurized. The seepage pressure difference of the corrosive medium on the cement stone and the pressure difference of the corrosive medium circulation are adjusted through the back pressure valve of the back pressure cover. The temperature controller heats the kettle body to reach the temperature and pressure required for the experiment; (7) Use a flow pump to continuously inject the corrosive medium into the kettle body to form a circulation flow of the corrosive medium, ensuring that the corrosive medium continuously seeps through the permeable core and cement stone in the cement sheath assembly; (8) After the time required by the experimental design is reached, stop injecting the corrosive medium, turn off the temperature controller, release the pressure in the kettle chamber and the upper chamber, take out the cement ring assembly, and observe, test and analyze the corrosion of the cement stone in different parts and under different corrosion conditions.

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