CN110306976A - Inert gas injection control annular pressure test device and its test method - Google Patents

Abstract

The invention provides an experimental device for injecting inert gas to control annular space with pressure. The main part of the test device includes oil pipe flow space, A ring space, and stratum simulation space from inside to outside in sequence; the oil pipe fluid constant temperature circulation and pressure control system is the oil pipe flow space. Simulate the service environment of the on-site tubing; the fluid injection and discharge system simulates the formation environment in the formation simulation space, and simulates the on-site A ring space environment in the A ring space; the data display and acquisition system is used to detect temperature, pressure and gas column height. By measuring the annular pressure value of annular space A at different inert gas lengths, the relationship curve between the amount of inert gas injected in the actual environment and the annular pressure value under the influence of temperature effect and inflation effect is obtained. The magnitude of the pressure drop determines the optimum inert gas column length for the site. The present invention can simulate the annular pressure situation in the field environment according to the actual situation, and the experimental results conform to the field reality.

Description

Inert gas injection control annular pressure test device and its test method

technical field

The invention relates to the technical field of safety control of oil and gas wells, in particular to an experimental device and an experimental method for injecting inert gas to control annulus with pressure.

technical background

In the process of oil and gas field development and gas storage construction in my country, the annular space between tubing and casing, and between casing and casing is usually filled with annular protection fluid to balance formation pressure and prevent tubing and casing corrosion. However, during the production process, the temperature and pressure in the wellbore change drastically, resulting in the volume change of the fluid in the annulus and the wellbore affected by the temperature effect and the bulging effect, forming a high annular pressure in the closed annulus. At present, the annulus of oil and gas wells in my country The problem of underpressure is very common, especially the problem of underpressure in the A ring space is the most prominent. Annulus pressure refers to the phenomenon that the annular pressure of the gas well returns to the pressure level before the pressure relief in a short period of time after the pressure relief. If the annular pressure is too high during the production process, it will cause oil casings, packers, and wellhead devices to be damaged. The collapse and failure will lead to the destruction of the integrity of the wellbore, which poses a huge threat to the safe production of gas wells. However, effective technical measures have not yet been formed to completely eradicate the problem of annular pressure. The most important response to the problem of annular pressure is to control it within a safe range, thereby effectively prolonging the safe development cycle of oil and gas wells. Injecting a certain amount of inert gas (such as nitrogen) into the annular space has been used as a new type of annular pressure control method in some oilfields in my country, but too much inert gas injection will greatly reduce the anti-corrosion effect. If the amount is too small, the best annular space pressure control effect cannot be achieved. However, the assumptions and calculation parameters of the current iterative calculation model of gas-bearing column annulus are different from the real wellbore environment. For oil and gas wells with large gas production, high temperature and pressure, the existing theoretical calculation model will There is a problem of non-convergence in the calculation, which makes it impossible to calculate and cannot be used to determine the optimal injection amount of inert gas. Therefore, relevant experimental research is urgently needed to determine the optimal injection amount of inert gas for the pressure control problem of the annulus injected with inert gas.

Contents of the invention

In order to overcome the deficiencies of existing theoretical calculations and the inadaptability of theoretical calculation models to the oil field environment, the present invention provides an experimental device and an experimental method for injecting inert gas to control annular space pressure, which can effectively solve the above technical problems and guide the oil field On-site annular pressure control problems.

In order to achieve the above research purposes, an experimental device for injecting inert gas to control the pressure of the annular space is firstly proposed.

Inert gas injection control annular pressure test device, including the main part of the test device, oil pipe fluid constant temperature circulation and pressure control system, data display and acquisition system, fluid filling and blowing system;

The main part of the test device includes a tubing flow space, an annular space A, and a formation simulation space from the inside to the outside; the formation simulation space is used to simulate formation temperature and pressure, and test the influence of the formation environment on the A annular space;

The oil pipe fluid constant temperature circulation and pressure control system simulates the on-site oil pipe service environment for the oil pipe flow space;

The fluid injection and discharge system simulates the formation environment in the formation simulation space, and simulates the on-site A annular space environment in the A annular space;

The data display and acquisition system is used to detect the temperature, pressure and gas column height in the tubing flow space, the A annular space, and the stratum simulation space.

Further, the fluid filling and spraying system includes an inert gas tank and an annulus protection liquid tank;

The main part of the test device includes a sleeve assembly, and the sleeve assembly includes coaxial test oil pipes, production casings, auxiliary pipe strings, test oil pipes, production casings, auxiliary pipe strings, sleeves from the inside to the outside. The ratio of the length to the radius of each part of the barrel combination is greater than 15. The upper and lower ends of the sleeve combination are respectively connected to the upper mechanical seal cover and the lower mechanical seal cover. A ring space is formed between the production casing and the auxiliary pipe string to form a formation simulation space; the auxiliary pipe string is wrapped with a detachable heat insulation pad;

The oil pipe flow space is connected to the oil pipe fluid injection pipe on the top, and the oil pipe fluid discharge pipe to the bottom. The oil pipe fluid injection pipe and the oil pipe fluid discharge pipe are respectively connected with the oil pipe fluid constant temperature circulation and pressure control system to form a circuit; The tubing fluid is controlled by the tubing fluid constant temperature circulation and pressure control system to simulate the temperature and pressure of the wellbore;

The lower part of the annular space A is connected to the annular space protection liquid injection pipe and the annular space protection liquid discharge pipe. Empty protection liquid injection and discharge circuit, thus forming an annular space protection liquid injection and blowing system; the upper part is connected with the inert gas injection pipe and the A ring space pressure balance pipe, and the inert gas injection pipe is connected with the inert gas tank, and through pneumatic pressurization The pump and valve three control the inert gas injection amount, the A annular space pressure balance pipe is connected with the soft rubber ball and the valve four, the volume of the soft rubber ball is larger than that of the A annular space, and it is used to balance the internal and external pressure of the A annular space to achieve Injection and discharge of annular space protection fluid and inert gas in a closed environment; A annular space pressure sensor, A annular space temperature sensor and high-precision laser liquid level are installed on the upper part of the annular space A, which are connected to the data display and acquisition system through the communication interface monitor;

In the stratum simulation space, the lower part is connected to the pressure relief pipe, and the upper part is connected to the pressurization pipe. The pressurization pipe is connected to the inert gas tank, and the pneumatic booster pump, valve 5, and valve 6 are used to control the pressure in the annular space. The upper part of the formation simulation space is equipped with a formation simulation space pressure sensor and a formation simulation space temperature sensor connected to the data display and acquisition system through a communication interface; oil receiving pipe fluid is installed on the outer wall of the production casing and the inner wall of the auxiliary string 32 symmetrical heating couples controlled by the constant temperature cycle and pressure control system are used to heat the formation simulation space.

Further, the oil pipe fluid constant temperature circulation and pressure control system includes a temperature control system, a pressure control system, a liquid storage tank, a high temperature and high pressure pipeline, a liquid pump 2, an insulated mixing tank, a pipeline booster pump, a pressure relief valve, and a pressure gauge 1. Pressure gauge 2. Pressure gauge 3. Safety valve;

A magnetic stirrer, a refrigeration circuit and a heating circuit controlled by a temperature control system, and a temperature detector are installed in the insulated mixing tank;

The pipeline booster pump and pressure gauge 1 are installed on the pipeline connected to the fluid injection pipe of the oil pipeline. The high-temperature and high-pressure resistant pipeline is connected with the fluid discharge pipe of the oil pipeline. Pressure gauge 3, pressure relief valve, pressure gauge 2, pipeline booster pump and pressure relief valve are respectively controlled by the pressure control system to control the fluid pressure in the oil pipe. If the pressure gauge 3 shows that the pressure is too high during the test, it will pass through the safety valve to relieve pressure;

The data display and acquisition system is also equipped with a temperature and pressure alarm, which can be shut down in time when the temperature and pressure are too high.

The present invention also provides an annulus with pressure test method, which uses the inert gas injection control annulus with pressure test device to carry out the experiment, including the following steps:

The first step, experimental preparation

Prepare the inert gas, annular protection fluid, oil pipe and production casing for on-site use, assemble the experimental instruments, measure the length of the pipe string to L meters, and detect the distribution and working status of the heating couples to ensure their uniform distribution and normal operation. And carry out a pressure test on the experimental device to ensure the sealing of the experimental device, inject the on-site tubing fluid (crude oil, natural gas, water, supercritical _CO2 , etc.) into the liquid storage tank, and collect on-site monitoring data, including formation temperature, formation pressure, oil Production parameters such as temperature in the pipe, pressure in the oil pipe, flow rate, reserved pressure in the annular space, etc.;

The second step is to set the temperature and pressure of the formation simulation space:

Use the stratum simulation space to simulate the actual stratum environment, first close the valve six, control the heating couple through the temperature control system to heat the stratum simulation space to the actual temperature of the stratum on site, open the valve five, inject inert gas into the pneumatic booster pump to raise the pressure to the scene The actual pressure of the formation is measured, and real-time monitoring is carried out through the data display and acquisition system. When the pressure rises to the actual measurement pressure of the formation on site, the valve is closed. 5. Pneumatic booster pump;

In the third step, the annular space of A is filled with protective fluid:

Open valve 2, valve 3, and the pneumatic booster cycle for 3 minutes to remove the air in the annular space of A, then close valve 2, valve 3, and the pneumatic booster, open valve 4 on the pressure balance pipe of the annular space of A, and open the valve 1. Liquid pump 1, inject the annular space protection liquid into the annular space of A, monitor the length and pressure of the gas column through the data display and acquisition system, when the length of the gas column is 0, close the valve 4 on the pressure balance pipe of the annular space of A, when A When the annular pressure rises to NMPa, the reserved annular pressure on site, close valve 1 and liquid pump 1;

The fourth step is to start the oil pipe fluid constant temperature circulation and pressure control system:

First, the temperature of the fluid in the thermal insulation mixing tank is raised to the temperature of the oil pipe fluid on site, the magnetic stirrer and the liquid pump are turned on to circulate the fluid and reach the fluid flow speed of the oil pipe on site, and the pipeline booster pump and pressure relief valve are controlled to maintain the pressure in the fluid space of the oil pipe For the on-site measured pressure;

The fifth step is to record the pressure of the annular space of A through the data display and acquisition system. When the pressure remains unchanged, record the pressure P ₀ . At this time, P ₀ is due to the temperature effect and swelling effect in the field environment when the length of the gas column is 0 meters. Leading to the pressure value of A annular space;

The sixth step is to turn off the heating system, and turn off the magnetic stirrer and the secondary circulation system of the liquid pump to reduce the temperature of the fluid space of the tubing to room temperature;

The seventh step, different volumes of inert gas injection:

When the pressure in the annular space of A is reduced to N MPa, open the valve four on the pressure balance pipe of the annular space in A to balance the internal and external pressure, open the valve two to discharge the annular space protection liquid, and monitor the height of the gas column through the data display and acquisition system. When the height rises to the preset height, close valve 2 and valve 4, open valve 3, inject inert gas into the pneumatic booster, monitor the pressure of A annular space through the data display and acquisition system, and close the valve when the pressure rises to N MPa Three, pneumatic supercharger;

For each experiment, the height of the air column rises to a preset height, and the preset heights are H ₁ meters, 2*H ₁ , 3*H ₁ , ... 30*H ₁ , H ₁ =L/100 meters;

The eighth step, repeat the fourth and fifth steps, and record the pressure of the annular space of A through the data display and acquisition system. When the pressure remains constant, record the pressure P ₁ , and the pressure at this time is H ₁ m of the inert gas injected. The pressure value of the annular space caused by the temperature effect and pressure effect;

In the ninth step, repeat the sixth, seventh and eighth steps, and record the pressure P ₂ of the annular space of A;

A annular pressure P ₂ corresponds to the air column 2*H ₁ meter in the seventh step, P3 corresponds to the air column 3*H ₁ meter in the seventh step...P ₃₀ corresponds to the air column 30*H ₂ meters in the seventh step.

The tenth step, after the experiment is over, pump the fluid out of the device and clean the experimental equipment;

The eleventh step is to draw the relationship curve between the annular space pressure and the length of the inert gas column, and determine the reasonable inert gas column length on site according to the drop rate of the annular space pressure under different inert gas column lengths. The optimal inert gas column length is n* H ₁ , the length of the inert gas column to be applied on site is H _X ＝(n*H ₁ *H _m )/L;

In the formula: H _X is the length of the inert gas column that should be reserved on site, m; n*H ₁ is the length of the best inert gas column measured in the experiment, m; L is the length of the experimental test string, m; H _m is the field packing Drilling depth of the device, m.

The present invention has the following technical effects:

(1) The present invention can simulate the pressure situation of the annulus caused by the temperature effect and the bulging effect in the field environment according to the needs of the actual situation, and the experimental results are in line with the field reality;

(2) The annular pressure optimization method based on the experimental device can effectively alleviate the wellbore integrity risk caused by the annular pressure on site, and effectively reduce the workload and management costs caused by frequent blowout on site;

(3) The present invention can simulate different types of annular protection fluids, different types of injection-production wells (natural gas injection in gas storage, _CO2 injection-production wells, oil wells, gas wells), different types of inert gases, different casing materials, and different sizes. The pressure optimization experiment of the annular space can realize the simulation of various working conditions;

(4) The present invention solves the limitation of the theoretical mathematical model, and can simulate the pressure control problem of the annulus under the extreme working conditions of high-temperature, high-pressure and high-yield wells, and has good field application value.

Description of drawings

Fig. 1 is a structural representation of the present invention;

Fig. 2 is a structural schematic diagram of the main part of the test device and the fluid filling and spraying system of the present invention;

Fig. 3 is a schematic diagram of the oil pipe fluid constant temperature circulation and pressure control system of the present invention;

Fig. 4 is the relationship curve of annular space pressure value under different nitrogen column lengths obtained in the experiment of the embodiment.

Detailed ways

The present invention will be further explained below in conjunction with the accompanying drawings and embodiments.

As shown in Figure 1, the experimental device for injecting inert gas to control the annular space under pressure includes the main part of the test device 1, the oil pipe fluid constant temperature circulation and pressure control system 2, the data display and acquisition system 3, and the fluid injection and discharge system 4;

The main part 1 of the test device includes a tubing flow space 11, an annular space 12 of A, and a formation simulation space 13 from the inside to the outside; the formation simulation space 13 is used to simulate formation temperature and pressure, and test the formation environment to A The impact of the annular space 12;

The oil pipe fluid constant temperature circulation and pressure control system 2 simulates the on-site oil pipe service environment for the oil pipe flow space 11;

The fluid filling and spraying system 4 simulates the formation environment in the formation simulation space 13, and simulates the on-site A annular space environment in the A annular space 12;

The data display and acquisition system 3 is used to detect the temperature, pressure and gas column height in the tubing flow space 11, the A annular space 12, and the formation simulation space 13.

The fluid filling and spraying system 4 includes an inert gas tank 27 and an annulus protection liquid tank 28;

As shown in Figure 2, the main part 1 of the test device includes a sleeve assembly, and the sleeve assembly sequentially includes a coaxial test oil pipe 5, a production casing 6, an auxiliary pipe string 7, and a test oil pipe from the inside to the outside. 5. Production casing 6, auxiliary pipe string 7, the ratio of the length of each part of the sleeve assembly to its radius is greater than 15, the upper and lower ends of the sleeve assembly are respectively sealed and connected with the upper mechanical seal cover 9 and the lower mechanical seal cover 10, The tubing flow space 11 is formed inside the test tubing 5, the A annular space 12 is formed between the test tubing 5 and the production casing 6, and the formation simulation space 13 is formed between the production casing 6 and the auxiliary string 7; the auxiliary string 7 is wrapped with The detachable heat insulation pad 8 prevents the experimental device from exchanging heat with the outside world;

The oil pipe flow space 11 is connected to the oil pipe fluid injection pipe 14 on the top, and the oil pipe fluid discharge pipe 15 to the bottom. The oil pipe fluid injection pipe 14 and the oil pipe fluid discharge pipe 15 are respectively connected with the oil pipe fluid constant temperature circulation and pressure control system 2 to form a circuit; In the tubing flow space 11 flows the tubing fluid controlled by the tubing fluid constant temperature circulation and pressure control system 2 to simulate the temperature and pressure of the wellbore;

The annular space 12 of A is connected to the annular space protection liquid injection pipe 16 and the annular space protection liquid discharge pipe 17 at the bottom. One 30 and valve two 31 form an annular space protection liquid injection and discharge circuit, thereby forming an annular space protection liquid filling and spraying system; the upper part is connected with an inert gas injection pipe 18, an annular space pressure balance pipe 32, and an inert gas injection pipe 18 It is connected with the inert gas tank 27, and the inert gas injection volume is controlled by the pneumatic booster pump 33 and the valve three 34. The A annular space pressure balance pipe 32 is connected with the soft rubber ball 35 and the valve four 36. The volume of the soft rubber ball 35 is larger than The volume of A annular space 12 is used to balance the internal and external pressure of A annular space, so as to realize the injection and discharge of annular space protection fluid and inert gas in a closed environment; The A annular space pressure sensor 19, the A annular space temperature sensor 20 and the high-precision laser liquid level monitor 21 connected to the system 3;

The stratum simulation space 13 is connected to the pressure relief pipe 22 at the bottom, and the pressurization pipe 23 at the top. The pressurization pipe 23 is connected to the inert gas tank 27, and is controlled by a pneumatic booster pump 33, valve five 37, and valve six. 38 controls pressurization and pressure release in the annular space; the upper part of the formation simulation space 13 is equipped with a formation simulation space pressure sensor 24 and a formation simulation space temperature sensor 25 connected with the data display and acquisition system 3 through a communication interface; 6 The outer wall and the inner wall of the auxiliary pipe string 7 are installed with 32 symmetrical heating couples 26 controlled by the oil pipe fluid constant temperature circulation and pressure control system 2, which are used to heat the formation simulation space 13.

As shown in Figure 3, the oil pipe fluid constant temperature circulation and pressure control system 2 includes a temperature control system 43, a pressure control system 44, a liquid storage tank 39, a high temperature and high pressure pipeline 40, a liquid pump 2 41, an insulated mixing tank 42, a pipeline Booster pump 45, pressure relief valve 46, pressure gauge one 47, pressure gauge two 48, pressure gauge three 49, safety valve 50;

A magnetic stirrer 51 is housed in the insulated stirring tank 42, and a refrigeration circuit 52 and a heating circuit 53 controlled by the temperature control system 43, and a temperature detector 54 is also installed;

A pipeline booster pump 45 and a pressure gauge 1 47 are installed on the pipeline connected to the fluid injection pipe 14 of the oil pipe. The high temperature and high pressure pipeline 40 communicates with the fluid discharge pipe 15 of the oil pipeline. The liquid storage tank 39, the safety valve 50, the pressure gauge three 49, the pressure relief valve 46, the pressure gauge two 48, the pipeline booster pump 45 and the pressure relief valve 46 are respectively controlled by the pressure control system 44 to control the fluid pressure in the oil pipe, During the test, if the pressure gauge 3 49 shows that the pressure is too high, the pressure is relieved through the safety valve 50;

The data display and acquisition system 3 is also equipped with a temperature and pressure alarm 55, which can be shut down in time when the temperature and pressure are too high.

Data display and acquisition system 3. Tubing fluid constant temperature circulation and pressure control system 2 simulates the on-site tubing service environment, fluid injection and spraying system 4 simulates the formation environment in the formation simulation space 13, and simulates the on-site A annular space environment in the A ring space 12 , by measuring the annular pressure value of annular space 12 at different inert gas lengths, the relationship curve between the amount of inert gas injected in the actual environment and the annular pressure value under the influence of temperature effect and inflation effect is obtained. According to the different inert gas column lengths The magnitude of the drop in annular pressure determines the optimum inert gas column length for the site.

The specific annular space pressure test method is carried out by using the described inert gas injection control annular space pressure test device, which includes the following steps:

The first step, experimental preparation

The inert gas used on site is nitrogen, and the inorganic salt annulus protection fluid is used. The size of the tubing is Casing size The length of the tubing string is 2 meters, the depth of the field packer is 4,000 meters, the tubing fluid is natural gas, the formation temperature is 80°C, the pressure is 45MPa, the maximum wellbore temperature is 180°C, the pressure is 37MPa during gas production, and the reserved annular pressure is 2MPa. Assemble the experimental equipment, detect the distribution and working status of the heating couples, ensure that they are evenly distributed and work normally, and conduct a pressure test on the experimental device to ensure the sealing of the experimental device.

In the second step, the formation simulation space 13 temperature and pressure setting:

Use the formation simulation space 13 to simulate the actual formation environment. First close valve 6 38, control the heating couple 26 to heat the formation simulation space 13 to 80°C through the temperature control system, open valve 5 37, inject inert gas into the pneumatic booster pump 33 to raise the pressure to 45MPa, and display and collect the data The system carries out real-time monitoring, and when the pressure rises to 45MPa, the valve five 37 and the pneumatic booster pump 33 are closed.

In the third step, the annular space of A is filled with protective fluid:

Open valve 2 31, valve 3 34, and pneumatic booster 33 to circulate for 3 minutes to remove the air in the A annular space, then close valve 2 31, valve 3 34, pneumatic booster 33, and open the A annular space pressure balance pipe 32 Valve 4 36 on the top, open valve 1 30, liquid pump 1 29, inject annular space protection fluid into A annular space 12, monitor the length and pressure of the gas column through the data display and acquisition system 3, when the length of the gas column is 0 meters, close The valve four 36 on the pressure balance pipe of the annular space of A, when the pressure of the annular space of A rises to 2MPa reserved on site, the valve one 30 and the liquid pump one 29 are closed.

The fourth step is to start the oil pipe fluid constant temperature circulation and pressure control system 2:

First, the temperature of the fluid in the heat preservation mixing tank 42 is raised to 180°C, the magnetic stirrer 51 and the liquid pump 2 41 are turned on to circulate the fluid and reach the flow rate of the oil pipe fluid on site, and the pipeline booster pump 45 and pressure relief valve 46 are controlled to make the oil pipe fluid space 11 The internal pressure is maintained at 37MPa.

The fifth step is to record the pressure of the annular space 12 of A through the data display and acquisition system 3. When the pressure remains unchanged, record the pressure P ₀ . At this time, P ₀ is due to the temperature effect and The inflation effect leads to the pressure value of the A ring space.

The sixth step is to turn off the heating system, and turn off the circulation system of the magnetic stirrer 51 and the liquid pump 2 41 to lower the temperature of the fluid space 11 of the tubing to room temperature.

The seventh step, different volumes of inert gas injection:

When the pressure in the annular space of A is reduced to 2 MPa, open the valve four 36 on the pressure balance pipe 32 of the annular space A to balance the internal and external pressure, open the valve two 31 to discharge the annular space protection liquid, and monitor the height of the gas column through the data display and acquisition system 3, When the height of the gas column rises to 0.02 meters (0.04, 0.06, ... 0.6), close valve 2 31, valve 4 36, open valve 3 34, and inject inert gas into the pneumatic booster 33, monitor A through the data display and acquisition system 3 Annular space 12 pressure, after pressure rises to 2MPa, close valve three 34, pneumatic supercharger 33.

In the eighth step, repeat the fourth and fifth steps, and record the pressure of the annular space 12 of A through the data display and acquisition system 3. When the pressure remains constant, record the pressure P ₁ , and the pressure at this time is 0.02 When is the pressure value of the annular space caused by the temperature effect and pressure effect.

In the ninth step, repeat the sixth, seventh and eighth steps, and record the pressure of the annular space P ₂ (the length of the inert gas in the annular space is 0.04 meters), P3 (the length of the inert gas in the annular space is 0.06 meters) ... P30 (the length of the inert gas in the annular space is 0.06 meters)... Inert gas length 0.6 meters).

In the tenth step, the experiment is over, the fluid is pumped out of the device, and the experimental instrument is cleaned.

The eleventh step is to draw the relationship curve between annular pressure and nitrogen column length, as shown in Figure 4. It can be seen that when the nitrogen column length is greater than 0.2 meters, the decrease in annular pressure is not obvious. Considering the corrosion protection effect and the annular zone If the field packer is lowered to a depth of 4000m, the nitrogen column should be injected with a length of 400m.

Claims (6)

1. Inert gas injection control annular pressure experimental device, characterized in that it includes the main part of the test device (1), oil pipe fluid constant temperature circulation and pressure control system (2), data display and acquisition system (3), fluid injection and spraying system (4); The main body part (1) of the test device includes the oil pipe flow space (11), the A annular space (12), and the formation simulation space (13) from the inside to the outside; the formation simulation space (13) is used for simulating Formation temperature, pressure, test the influence of formation environment on A annular space (12); The oil pipe fluid constant temperature circulation and pressure control system (2) is the oil pipe flow space (11) simulating the on-site oil pipe service environment; The fluid filling and spraying system (4) simulates the formation environment in the stratum simulation space (13), and simulates the on-site A annular space environment in the A annular space (12); The data display and acquisition system (3) is used to detect the temperature, pressure and gas column height in the tubing flow space (11), the A annular space (12), and the stratum simulation space (13). 2. The experimental device for injecting inert gas to control annular space under pressure according to claim 1, characterized in that: The fluid filling and spraying system (4) includes an inert gas filling (27) and an annular protection liquid filling (28); The main body part (1) of the test device includes a sleeve assembly, and the sleeve assembly sequentially includes a coaxial test tubing (5), a production casing (6), and an auxiliary string (7) from the inside to the outside, Test oil pipe (5), production casing (6), auxiliary pipe string (7), the ratio of the length of the pipe string of each part of the sleeve assembly to its radius is greater than 15, and the upper and lower ends of the sleeve assembly are respectively connected to the upper mechanical seal cover (9 ), the lower mechanical seal cover (10) is sealed and connected, the oil pipe flow space (11) is formed in the test oil pipe (5), the A annular space (12) is formed between the test oil pipe (5) and the production casing (6), and the production casing A formation simulation space (13) is formed between the pipe (6) and the auxiliary pipe string (7); the auxiliary pipe string (7) is wrapped with a detachable heat insulation pad (8); The oil pipe flow space (11) is connected to the oil pipe fluid injection pipe (14) on the top, and the oil pipe fluid discharge pipe (15) is connected to the bottom. The circulation and pressure control system (2) is connected to form a circuit; the tubing fluid flowing in the tubing flow space (11) is controlled by the tubing fluid constant temperature circulation and pressure control system (2) to simulate wellbore temperature and pressure; The A annular space (12), the lower part is connected to the annular space protection liquid injection pipe (16), the annular space protection liquid discharge pipe (17), the annular space protection liquid injection pipe (16) and the annular space protection liquid filling (28) connected, and form an annulus protection fluid injection and discharge circuit through liquid pump one (29), valve one (30) and valve two (31), thereby forming an annulus protection fluid filling and blowing system; the upper part is connected to inert gas injection Pipe (18), A annular space pressure balance pipe (32), inert gas injection pipe (18) is connected with inert gas tank (27), and inert gas injection is controlled by pneumatic booster pump (33) and valve three (34) A volume, A annular space pressure balance pipe (32) is connected with the soft rubber ball (35) and valve four (36), the volume of the soft rubber ball (35) is larger than that of the A annular space (12), and is used to balance the A annular space Internal and external pressure to realize the injection and discharge of annular space protection fluid and inert gas in a closed environment; the upper part of the A annular space (12) is equipped with an A annular space pressure sensor connected to the data display and acquisition system (3) through a communication interface. Sensor (19), A annular space temperature sensor (20) and high-precision laser liquid level monitor (21); The formation simulation space (13) is connected with a pressure relief pipe (22) at the bottom and a pressurization pipe (23) at the top, and the pressurization pipe (23) is connected with an inert gas tank (27), and is powered by a pneumatic booster. The pressure pump (33), valve five (37), and valve six (38) control pressurization and pressure release into the annular space; the upper part of the formation simulation space (13) is equipped with a communication interface and a data display and acquisition system (3) Connected formation simulation space pressure sensor (24), formation simulation space temperature sensor (25); on the outer wall of the production casing (6) and the inner wall of the auxiliary pipe string (7), a fluid constant temperature circulation and pressure control system (2 ) controlled 32 symmetrical heating couples (26) for heating the formation simulation space (13). 3. The experimental device for injecting inert gas to control annular space under pressure according to claim 2, characterized in that: the oil pipe fluid constant temperature circulation and pressure control system (2) includes a temperature control system (43), a pressure control system (44 ), liquid storage tank (39), high temperature and high pressure pipeline (40), liquid pump two (41), heat preservation mixing tank (42), pipeline booster pump (45), pressure relief valve (46), pressure gauge one ( 47), pressure gauge two (48), pressure gauge three (49), safety valve (50); A magnetic stirrer (51) is housed in the insulated stirring tank (42), and a refrigeration circuit (52) and a heating circuit (53) controlled by a temperature control system (43), and a temperature detector (54) are also installed; The pipeline booster pump (45) and the pressure gauge one (47) are installed on the pipeline connected to the oil pipe fluid injection pipe (14), the high temperature and high pressure pipeline (40) communicates with the oil pipeline fluid discharge pipe (15), and the high temperature and high pressure pipeline (40) are installed with liquid pump two (41), liquid storage tank (39), safety valve (50), pressure gauge three (49), pressure relief valve (46), pressure gauge two (48) successively, pipeline increasing The pressure pump (45) and the pressure relief valve (46) are respectively controlled by the pressure control system (44), and are used to control the fluid pressure in the oil pipe. If the pressure gauge three (49) shows that the pressure is too high during the test, the safety valve (50 ) to release the pressure. 4. The experimental device for injecting inert gas to control annular space under pressure according to claim 2, characterized in that: the data display and acquisition system (3) is also equipped with a temperature and pressure alarm (55), and when the temperature and pressure are too high Turn off the device in time. 5. The annular space pressure test method is characterized in that, the experiment is carried out using the described inert gas injection control annular space pressure test device, comprising the following steps: The first step, experimental preparation Inject the on-site tubing fluid into the liquid storage tank (39), and collect on-site monitoring data; In the second step, the formation simulation space (13) temperature and pressure setting: Use the formation simulation space (13) to simulate the actual formation environment, first close the valve six (38), control the heating couple (26) through the temperature control system (43) to heat the formation simulation space (13) to the actual measured temperature of the formation on site, and open Valve five (37) and pneumatic booster pump (33) inject inert gas to raise the pressure to the measured pressure of the formation on site, and conduct real-time monitoring through the data display and acquisition system (3), and close the valve when the pressure rises to the measured pressure of the formation on site Five (37), pneumatic booster pump (33); In the third step, the annular space of A is filled with protective fluid: Open valve two (31), valve three (34), and pneumatic booster (33) to circulate for 3 minutes to remove the air in the annular space of A, then close valve two (31), valve three (34), and pneumatic booster (33), open valve four (36) on the A annular space pressure balance pipe (32), open valve one (30), liquid pump one (29), inject annular space protection liquid into A annular space (12), pass The data display and acquisition system (3) monitors the length and pressure of the gas column. When the length of the gas column is 0, close the valve 4 (36) on the pressure balance pipe of the A annular space. When the air pressure is NMPa, close valve one (30) and liquid pump one (29); The fourth step is to start the oil pipe fluid constant temperature circulation and pressure control system (2): First, the temperature of the fluid in the thermal insulation mixing tank (42) is warmed up to the fluid temperature of the on-site oil pipe, the magnetic stirrer (51) and the second liquid pump (41) are turned on to circulate the fluid and reach the fluid flow speed of the on-site oil pipe, and the pipeline booster pump (45 ) and the relief valve (46) make the pressure in the fluid space (11) of the oil pipe remain the on-site measured pressure; The fifth step is to record the pressure of the annular space (12) of A through the data display and acquisition system (3). When the pressure remains constant, record the pressure P ₀ . At this time, P ₀ is the on-site environment when the length of the gas column is 0 meters. Due to the temperature effect and the inflation effect, the pressure value of the A ring is caused; The sixth step is to turn off the heating system, and turn off the magnetic stirrer (51), liquid pump two (41) circulation system, so that the temperature of the oil pipe fluid space (11) drops to room temperature; The seventh step, different volumes of inert gas injection: When the pressure in the annular space of A is reduced to N MPa, open the valve four (36) on the pressure balance pipe (32) of the annular space in A to balance the internal and external pressure, open the valve two (31) to discharge the annular space protection fluid, and display and collect the The system (3) monitors the height of the gas column, and when the height of the gas column rises to a preset height, valve two (31) and valve four (36) are closed, valve three (34) is opened, and the pneumatic booster (33) injects inert gas , monitor the A annular space (12) pressure through the data display and acquisition system (3), when the pressure rises to NMPa, close the valve three (34), and the pneumatic booster (33); In the eighth step, repeat the fourth and fifth steps, and record the pressure of the annular space (12) of A through the data display and acquisition system (3). When the pressure remains constant, record the pressure P ₁ , and the pressure at this time is The pressure value of the annular space caused by the temperature effect and pressure effect when injecting ₁ m of inert gas H; In the ninth step, repeat the sixth, seventh and eighth steps, and record the pressure P ₂ of the annular space of A; The tenth step, when the experiment is over, pump the fluid out of the device and clean the experimental instruments; The eleventh step is to draw the relationship curve between the annular space pressure and the length of the inert gas column, and determine the reasonable inert gas column length on site according to the drop rate of the annular space pressure under different inert gas column lengths. The optimal inert gas column length is n* H ₁ , the length of the inert gas column to be applied on site is H _X ＝(n*H ₁ *H _m )/L; In the formula: H _X is the length of the inert gas column that should be reserved on site, m; n*H ₁ is the length of the best inert gas column measured in the experiment, m; L is the length of the experimental test string, m; H _m is the field packing Drilling depth of the device, m. 6. the annular space pressure test method according to claim 1, is characterized in that, In the seventh step, the height of the air column rises to the preset height. For each experiment, the preset height is H ₁ meter, 2*H ₁ , 3*H ₁ , ... 30*H ₁ , H ₁ =L/100 meters ; In the ninth step, record A annular pressure P ₂ ... P ₃₀ ; A annular pressure P ₂ corresponds to the air column 2*H ₁ meter in the seventh step, and P ₃ corresponds to the air column 3*H ₁ meter in the seventh step... P ₃₀ corresponds to the air column 30*H ₂ meters in the seventh step.