Balance point method well killing simulation experiment device and simulation experiment method

Abstract

The balance point method well killing simulation experiment device comprises a containing chamber, a simulation wellbore, a vacuumizing mechanism, a liquid injection mechanism and a gas injection mechanism, the containing chamber is used for containing a rock sample in a sealed mode, and a gap is reserved between the rock sample and the inner wall of the containing chamber; the output end of the simulation shaft is hermetically communicated with the accommodating chamber; the vacuumizing mechanism is communicated with the input end of the simulation shaft and is used for enabling the simulation shaft and the accommodating chamber to be in a vacuum state; the liquid injection mechanism is communicated with the input end of the simulation wellbore and is used for injecting drilling fluid and well killing fluid into the simulation wellbore; and the gas injection mechanism is communicated with the accommodating chamber through a booster pump, and is used for injecting pressurized gas into the gap and simulating an in-well slurry blowout process and a well shut-in state after blowout. The problem that key parameters required by the balance point method cannot be scientifically and accurately obtained can be solved. The invention discloses a balance point method well killing simulation experiment method which can solve the problem that the balance point method well killing success rate cannot be ensured.

Description

Technical Field

[0001] The invention relates to the technical field of petroleum drilling engineering, and in particular to a well-killing simulation experimental device and a simulation experimental method using a balance point method. Background Art

[0002] With the rapid growth of domestic natural gas demand and the country's high attention to energy security, the exploration and development of oil and gas resources has been increasing, and the target layer has rapidly extended from the medium and shallow layers to the deep and ultra-deep layers. Compared with the medium and shallow layers, the deep and ultra-deep layers usually have the characteristics of ultra-high temperature, ultra-high pressure, and complex pressure systems. From top to bottom, geological engineering problems such as fractures, holes, and faults may be encountered, resulting in great difficulty in drilling and a high frequency of complex accidents in the well during the drilling process.

[0003] Drilling is an essential part of oil and gas production. When the bottom hole pressure cannot balance the formation pressure during drilling, the fluid in the formation will invade the wellbore and overflow will occur. The main cause of overflow is drilling into abnormally high-pressure formations, well sections with developed fractures and caves, or the same open hole section with multiple pressure systems interlayered. Especially when drilling into high-pressure gas layers, once overflow occurs, if it is not handled in time, it is easy to cause the drilling fluid in the drill string and annulus to be blown out, the wellbore will be in an empty well state, and a normal wellbore circulation channel cannot be established. Faced with this situation, conventional well killing methods such as engineer method well killing and driller method well killing can no longer be handled. In order to control the overflow and establish a new bottom hole pressure balance relationship, unconventional well killing methods such as balance point method well killing can only be adopted.

[0004] Balance point well killing is a well killing method that can safely and quickly deal with overflow after a gas well is blown out. This method is suitable for natural gas well killing after the drilling fluid in the well is blown out, but it requires the wellhead blowout preventer to be intact and closed, the drill string to be at the bottom of the well, and the gas to be released through the release relationship.

[0005] Although the balance point method of well killing has been actually applied in the field, many key parameters, such as the density of the killing fluid and the balance point well depth, can still only be determined based on experience, resulting in the possibility of ineffective well killing when the balance point method is actually implemented. Summary of the invention

[0006] The first purpose of the present invention is to provide a balance point method well killing simulation experimental device to solve the problem that the key parameters required by the balance point method cannot be obtained scientifically and accurately.

[0007] The second purpose of the present invention is to provide a balanced point method for well killing simulation experiment to solve the problem that the success rate of balanced point method well killing cannot be ensured.

[0008] The present invention is achieved through the following technical solutions:

[0009] A balance point method well-killing simulation experiment device comprises: a holding chamber, the holding chamber is used to contain rock samples in a sealed manner, a gap is reserved between the rock sample and the inner wall of the holding chamber; a simulated wellbore, the output end of the simulated wellbore is in sealed communication with the holding chamber; a vacuum pumping mechanism, the vacuum pumping mechanism is in communication with the input end of the simulated wellbore, and is used to put the simulated wellbore and the holding chamber in a vacuum state; a liquid injection mechanism, the liquid injection mechanism is in communication with the input end of the simulated wellbore, and is used to inject drilling fluid and well-killing fluid into the simulated wellbore; a gas injection mechanism, the gas injection mechanism is in communication with the holding chamber through a booster pump, and is used to inject pressurized gas into the gap, and is used to simulate the mud blowout process in the well and the well shut-in state after the blowout.

[0010] Optionally, the simulated wellbore includes a vertical well section, an inclined section and a horizontal section that are connected in sequence; the horizontal section is horizontally arranged, and one end of the horizontal section away from the inclined section is closed and connected to the containing chamber; the vertical well section is vertically arranged, and the vacuum extraction mechanism, the liquid injection mechanism and the gas-liquid separation mechanism are respectively connected to one end of the vertical well section away from the inclined section.

[0011] Optionally, an injection pipe is coaxially penetrated in the simulated wellbore, the injection pipe is used to guide the well-killing fluid, and one end of the injection pipe is penetrated in the rock sample.

[0012] Optionally, a gas-liquid separation mechanism is further included, and the gas-liquid separation mechanism is connected to the input end of the simulated wellbore and is used to separate the well killing fluid and the pressurized gas.

[0013] Optionally, a circulation mechanism is further included, and the gas-liquid separation mechanism is connected to the liquid injection mechanism through the circulation mechanism, so that the well-killing fluid separated by the gas-liquid separation mechanism flows back to the liquid injection mechanism.

[0014] Optionally, an emptying mechanism is further included, and the emptying mechanism is connected to the gas-liquid separation mechanism to empty the gas separated by the gas-liquid separation mechanism.

[0015] Optionally, the top of the vertical well section is connected to multiple ports, and the vacuum pumping mechanism, the liquid injection mechanism, the gas-liquid separation mechanism and the emptying mechanism are respectively connected to the multiple ports.

[0016] Optionally, the vacuum extraction mechanism and the liquid injection mechanism are connected to the same side of the multi-port through a blowout preventer.

[0017] A balance point method for well killing simulation experiment is carried out using any of the above balance point method for well killing simulation experiment devices, and comprises the following steps:

[0018] Using the vacuum pumping mechanism to vacuum the containing chamber and the simulated wellbore;

[0019] Using the injection mechanism to inject a preset amount of drilling fluid into the simulated wellbore;

[0020] The booster pump is started to pressurize the gas source of the gas injection mechanism to a preset pressure, and then the pressurized gas is continuously injected into the containing chamber at the preset pressure to simulate the mud blowout process in the well and the well shut-in state after the blowout;

[0021] Using the injection mechanism to inject well-killing fluid into the simulated wellbore until the well-killing fluid returns to the input end of the simulated wellbore;

[0022] The balance point well depth and the density of the required well-killing fluid are calculated.

[0023] Optionally, the calculation of the equilibrium point well depth and the required density of the well killing fluid comprises the following steps:

[0024] Calculation formula for component formation pressure;

[0025] Obtain the calculation formula for the gas density and gas velocity in the well;

[0026] Substituting the calculation formula of the gas density and the gas flow velocity into the calculation formula of the formation pressure to obtain a conversion formula;

[0027] The bottom hole pressure during the blowout process is calculated by the conversion formula using an iterative method;

[0028] The calculation formula of the blowdown volume is obtained according to the first horizontal well productivity formula;

[0029] Calculate the equilibrium formation pressure according to the bottom hole pressure, the calculation formula of the blowdown volume and the second horizontal well productivity formula;

[0030] Calculating the required density of the well killing fluid according to the equilibrium formation pressure;

[0031] The balance point well depth is calculated based on the required density of the well killing fluid.

[0032] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0033] The present invention provides a balanced point method well-killing simulation experimental device, which simulates the downhole situation by setting up a closed containing chamber and setting a rock sample in the containing chamber, and effectively simulates the actual wellbore by setting up a simulated wellbore to build a similar test scene; on this basis, a vacuum pumping mechanism is set up to evacuate the simulated wellbore and the containing chamber, and a gas injection mechanism and a booster pump are set up at the same time to continuously inject pressurized gas into the containing chamber to simulate the mud blowout process in the well and the well shut-in state after the blowout; on this basis, a liquid injection mechanism is set up to inject drilling fluid into the simulated wellbore to simulate the actual working conditions during drilling, and the gas injection mechanism is used to simulate the mud blowout process in the well, and then the well-killing fluid can be continuously injected into the simulated wellbore to effectively simulate the well-killing process of the balanced point method, and various dynamic data are recorded during the simulation process to calculate the well depth of the balanced point and the required density of the well-killing fluid, thereby effectively guiding the actual implementation of the well-killing method of the balanced point method. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] The drawings described herein are used to provide a further understanding of the embodiments of the present invention, constitute a part of this application, and do not constitute a limitation of the embodiments of the present invention. In the drawings:

[0035] Figure 1 A schematic diagram of a well-killing simulation experimental device using a balance point method provided in Example 1 of the present invention;

[0036] Figure 2 A schematic diagram of a well-killing simulation experimental device using a balance point method provided in Example 2 of the present invention;

[0037] Figure 3 A schematic diagram of a well-killing simulation experimental device using a balance point method provided in Example 3 of the present invention;

[0038] Figure 4 A schematic diagram of a well-killing simulation experimental device using a balance point method provided in Example 4 of the present invention;

[0039] Figure 5 A schematic diagram of a well-killing simulation experimental device using a balance point method provided in Example 5 of the present invention;

[0040] Figure 6 This is a flow chart of the equilibrium point method well killing simulation experimental method provided in Example 1 of the present invention.

[0041] Marks and corresponding parts names in the attached drawings:

[0042] 10-holding chamber; 11-rock sample; 12-gap; 20-simulated wellbore; 21-vertical well section; 22-inclined section; 23-horizontal section; 24-injection pipe; 25-multi-way; 26-blowout preventer; 30-boosting pump; 31-gas injection mechanism; 40-vacuum extraction mechanism; 50-liquid injection mechanism; 60-gas-liquid separation mechanism; 70-circulation mechanism; 80-emptying mechanism. DETAILED DESCRIPTION

[0043] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with embodiments and drawings. The exemplary embodiments of the present invention and their description are only used to explain the present invention and are not intended to limit the present invention.

[0044] Example 1

[0045] Please refer to Figure 1 The present embodiment provides a balanced point method well-killing simulation experimental device, comprising: a holding chamber 10, the holding chamber 10 is used to contain a rock sample 11 in a sealed manner, and a gap 12 is reserved between the rock sample 11 and the inner wall of the holding chamber 10; a second part comprises a simulated wellbore 20, and the output end of the simulated wellbore 20 is in sealed communication with the holding chamber 10; a third part comprises a vacuum pumping mechanism 40, the vacuum pumping mechanism 40 is in communication with the input end of the simulated wellbore 20, and is used to put the simulated wellbore 20 and the holding chamber 10 in a vacuum state; a fourth part comprises a liquid injection mechanism 50, the liquid injection mechanism 50 is in communication with the input end of the simulated wellbore 20, and is used to inject drilling fluid and well-killing fluid into the simulated wellbore 20; a fifth part comprises a gas injection mechanism 31, the gas injection mechanism 31 is in communication with the holding chamber 10 through a booster pump 30, and is used to inject pressurized gas into the gap 12, and is used to simulate the mud blowout process in the well and the well shut-in state after the blowout.

[0046] The balance point method well-killing simulation experimental device provided in the present embodiment simulates the downhole situation by setting up a closed containing chamber 10 and setting a rock sample 11 in the containing chamber 10, and effectively simulates the actual wellbore by setting up a simulated wellbore 20 to build a similar test scene; on this basis, by setting up a vacuum pumping mechanism 40, the simulated wellbore 20 and the containing chamber 10 are vacuumed, and at the same time, a gas injection mechanism 31 and a booster pump 30 are set to continuously inject pressurized gas into the containing chamber 10 to simulate the mud blowout process in the well and the well shut-in state after the blowout; on this basis, by setting up a liquid injection mechanism 50, drilling fluid can be injected into the simulated wellbore 20 to simulate the actual working conditions during drilling, and the gas injection mechanism 31 is used to simulate the mud blowout process in the well, and then the well-killing fluid can be continuously injected into the simulated wellbore 20 to effectively simulate the balance point method well-killing process. During the simulation process, various dynamic data are recorded, and the balance point well depth and the required density of the well-killing fluid can be calculated, thereby effectively guiding the actual implementation of the balance point method well-killing.

[0047] It should be further explained that, in order to further simulate the actual wellbore, the simulated wellbore 20 includes a straight well section 21, an inclined section 22 and a horizontal section 23 which are connected in sequence; the horizontal section 23 is horizontally arranged, and the end of the horizontal section 23 away from the inclined section 22 is tightly connected to the containing chamber 10; the straight well section 21 is vertically arranged, and the vacuum extraction mechanism 40, the liquid injection mechanism 50 and the gas-liquid separation mechanism 60 are respectively connected to the end of the straight well section 21 away from the inclined section 22.

[0048] It should be further explained that, in order to further simulate the actual wellbore, an injection pipe 24 is coaxially penetrated in the simulated wellbore 20 . The injection pipe 24 is used to guide the well-killing fluid. One end of the injection pipe 24 is penetrated in the rock sample 11 .

[0049] Example 2

[0050] Please Figure 1 Based on the reference Figure 2 This embodiment provides a balanced point method well killing simulation experimental device, which is a further improvement of the embodiment 1, and the difference is only in that:

[0051] In order to effectively separate the pressed-back well-killing fluid from the high-pressure gas, the equilibrium point method well-killing simulation experimental device also includes a gas-liquid separation mechanism 60, which is connected to the input end of the simulated wellbore 20 and is used to separate the well-killing fluid and the pressurized gas.

[0052] Example 3

[0053] Please Figure 2 Based on the reference Figure 3 This embodiment provides a balanced point method well killing simulation experimental device, which is a further improvement of embodiment 2, and the difference is only in that:

[0054] In order to further reuse the well-killing fluid, the equilibrium point method well-killing simulation experimental device also includes a circulation mechanism 70 , through which the gas-liquid separation mechanism 60 is connected to the injection mechanism 50 , so that the well-killing fluid separated by the gas-liquid separation mechanism 60 flows back to the injection mechanism 50 .

[0055] Example 4

[0056] Please Figure 3 Based on the reference Figure 4 This embodiment provides a balanced point method well killing simulation experimental device, which is a further improvement of embodiment 3, and the difference is only in that:

[0057] In order to effectively process the gas separated by the gas-liquid separation mechanism, the equilibrium point method well-killing simulation experimental device also includes an emptying mechanism 80, which is connected to the gas-liquid separation mechanism 60 to empty the gas separated by the gas-liquid separation mechanism 60.

[0058] Example 5

[0059] Please Figure 4 Based on the reference Figure 5 This embodiment provides a balanced point method well killing simulation experimental device, which is a further improvement of embodiment 3, and the difference is only in that:

[0060] In order to facilitate and effectively connect each mechanism with the entrance end of the simulated wellbore 20, a multi-port 25 is connected to the top of the vertical well section 21, and the vacuuming mechanism 40, the liquid injection mechanism 50, the gas-liquid separation mechanism 60 and the emptying mechanism 80 are respectively connected to the multi-port 25.

[0061] Preferably, in order to prevent the mud in the simulated wellbore 20 from spraying into the vacuum mechanism 40 and the injection mechanism 50 , causing blockage or damage to both, the vacuum mechanism 40 and the injection mechanism 50 are connected to the same side of the multi-port 25 through the blowout preventer 26 .

[0062] Example 6

[0063] This embodiment provides a balanced point method for well killing simulation experiment, which is carried out using the balanced point method for well killing simulation experiment device described in Example 1, and includes the following steps:

[0064] S1, using the vacuum pumping mechanism 40 to evacuate the containing chamber 10 and the simulated wellbore 20;

[0065] S2, injecting a preset amount of drilling fluid into the simulated wellbore 20 using the injection mechanism 50;

[0066] S3, starting the booster pump 30 to pressurize the gas source of the gas injection mechanism 31 to a preset pressure, and then continuously injecting the pressurized gas into the receiving chamber 10 at the preset pressure to simulate the mud blowout process in the well and the well shut-in state after the blowout;

[0067] S4, injecting well-killing fluid into the simulated wellbore 20 using the injection mechanism 50 until the well-killing fluid returns to the input end of the simulated wellbore 20;

[0068] S5. Calculate the well depth at the equilibrium point and the density of the required well-killing fluid.

[0069] Specifically, the calculation to obtain the equilibrium point well depth and the required density of the well killing fluid includes the following steps:

[0070] S5.1, Calculation formula of component formation pressure;

[0071] Because the annulus is full of gas after the air jet, the flow in the annulus is gas phase pipe flow, and the basic equation of gas phase pipe flow is:

[0072]

[0073] That is, the total pressure gradient can be expressed by formula (1) as the sum of three components, that is, the total pressure gradient

[0074] When the annular flow satisfies one-dimensional stable flow, equation (1) becomes:

[0075]

[0076] Usually, the acceleration pressure gradient is small and can be ignored, so equation (2) can be written as:

[0077]

[0078] It can be seen from formula (3) that the total pressure gradient includes the gravity pressure gradient, that is, the pressure gradient generated by the gravity of the gas column itself. However, the gravity of the gas column itself is difficult to determine and is greatly affected by the change of wellbore temperature. Therefore, it is necessary to accurately obtain the wellbore temperature distribution.

[0079] Moreover, it can be seen from formula (3) that the total pressure gradient includes the friction pressure gradient, that is, the pressure gradient caused by the friction resistance during the fluid flow process, and the fluid flow velocity u g Closely related.

[0080] S5.2, obtain the calculation formula of gas density and gas velocity in the well;

[0081] The gas density ρ is obtained according to the gas state equation g :

[0082]

[0083] Among them, M g is the kilomolar mass of natural gas, 16.043 kg / mol, and R is the gas constant, 0.008314 MPa·m 3 / (kmol·K), Z is the compression factor, and T is the temperature.

[0084] Gas flow rate u g The volume flow rate q g Sure:

[0085]

[0086] However, due to the different temperatures and pressures at different locations in the wellbore, the same amount of gas occupies different volumes. Therefore, it is necessary to convert the blowdown volume at the surface blowdown line to the blowdown volume at different locations underground, which can be determined by equations (6) and (7):

[0087]

[0088]

[0089] Among them B g is the natural gas compressibility factor, T sc is the temperature at ground level, usually 293.15K, P sc is the pressure under ground conditions, usually 0.101325MPa, Z sc is the gas compressibility factor under ground conditions and can be approximately taken as 1.

[0090] S5.3, substituting the calculation formula of the gas density and the gas flow velocity into the calculation formula of the formation pressure to obtain a conversion formula;

[0091] Substituting equations (4), (6) and (7) into equation (3), we can get:

[0092]

[0093]

[0094] S5.4, using an iterative method, the bottom hole pressure during the blowout process is calculated using the conversion formula;

[0095] Since the compression factor Z is a function of pressure P and temperature T, and pressure P and temperature T are functions of well depth, it is difficult to obtain an analytical solution for equation (9). Usually, an iterative method is used to solve it, and the bottom hole pressure P during the blowout process can be obtained. wf .

[0096] S5.5. The calculation formula of the blowdown rate is obtained according to the first horizontal well productivity formula;

[0097] The first horizontal well productivity formula adopts the productivity formula proposed by Joshi:

[0098]

[0099] in,

[0100]

[0101]

[0102] Among them, K h is the horizontal permeability, mD; K vis the vertical permeability, mD; L is the length of the horizontal section, m; β is the anisotropy ratio; P e is the formation pressure, MPa; P wf is the formation pressure, MPa; a * is the major axis of the ellipsoid, m; δ is the eccentricity, m; r eh is the horizontal well discharge radius, m; r w is the wellbore radius, m; h g is the thickness of the gas layer, m; is the average viscosity of the formation gas; Average compressibility factor of formation gas.

[0103] The calculation formula for the spray volume is:

[0104]

[0105] S5.6, according to the bottom hole pressure P wf , the calculation formula of the blowdown volume and the second horizontal well productivity formula, calculate the equilibrium formation pressure P e ;

[0106] It should be noted that the second horizontal well production formula may adopt any existing horizontal well production formula, as long as it is different from the first production formula.

[0107] S5.7, according to the balanced formation pressure P e , calculate the density of the required well killing fluid ρ kill ;

[0108]

[0109] Among them, H ver is the vertical depth, m.

[0110] S5.8. Calculate the balance point well depth based on the required density of the well killing fluid.

[0111] After the well-killing fluid reaches the equilibrium point, the casing pressure is controlled to keep the vertical pressure unchanged at the value after the first stage of well-killing.

[0112] After the well-killing fluid returns to the equilibrium point B, the flow resistance and gravity of the annular air column close to the wellhead are very small and can be approximately ignored. At the same time, due to the reduction of well-killing displacement, the flow resistance of the annular space liquid column is small and can also be approximately ignored.

[0113] When the air-liquid two-phase mixed flow in the lower annulus is not considered, the following relationship exists:

[0114] P amax +ρ kill g(HHB )sinθ=ρ kill gH sinθ; (12)

[0115] Where H is the well depth, m; θ is the well inclination angle, degrees. From formula (1), we can know:

[0116]

[0117] When considering the air-liquid two-phase mixed flow in the lower annulus, however, for the gas-liquid mixed phase flow area, the flow is usually unsteady flow, and there is:

[0118]

[0119] Equation (14) is difficult to obtain an analytical solution. It is usually solved by an iterative method to obtain the pressure P at any position in the gas-liquid miscible zone, that is, the pressure distribution along the well depth. The pressure corresponding to a certain depth is P e , then the corresponding depth is the equilibrium point depth H B .

[0120] When the above two parameters are used to guide the actual balance point method for well killing, it mainly includes two stages:

[0121] The first stage (before the bottom hole pressure can balance the formation pressure): the well-killing fluid has not returned to the equilibrium point H B Before the well depth reaches a certain level, the liquid column pressure is low, and the sum of the circulation friction and the annular back pressure cannot balance the formation pressure. In order to increase the pressure on the formation as much as possible, the casing pressure must be controlled to the maximum allowable casing pressure P amax , and remain unchanged.

[0122] At the same time, record the change of standing pressure P t ; When the drilling fluid returns to the well depth H B When the vertical pressure is recorded, the value is P cf .

[0123] The bottom hole pressure P wf Reaching equilibrium formation pressure P e Before, natural gas had to continue to enter the well, so in order to quickly build up the annular liquid column to balance the formation pressure P e , the well pressure displacement should be calculated based on the maximum pump pressure under the cylinder liner in use.

[0124] The second stage: the well killing fluid returns to the well depth H B From then on until the wellhead, in order to maintain the bottom hole pressure P wf Balanced formation pressure P e At this time, the vertical pressure P should be controlled t Keep unchanged as P cf As the annular liquid column pressure increases, the casing pressure P is gradually reduced. a, from P amax Gradually decreases to 0.

[0125] The specific implementation methods described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific implementation method of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A balance point method well killing simulation experimental device, characterized in that: include: A containing chamber (10), the containing chamber (10) being used to contain a rock sample (11) in a sealed manner, a gap (12) being reserved between the rock sample (11) and an inner wall of the containing chamber (10); A simulated wellbore (20), wherein an output end of the simulated wellbore (20) is in sealed communication with the receiving chamber (10); A vacuum pumping mechanism (40), the vacuum pumping mechanism (40) being in communication with an input end of the simulated wellbore (20) and being used to place the simulated wellbore (20) and the containing chamber (10) in a vacuum state; A liquid injection mechanism (50), the liquid injection mechanism (50) being connected to an input end of the simulated wellbore (20) and being used for injecting drilling fluid and well-killing fluid into the simulated wellbore (20); The gas injection mechanism (31) is connected to the containing chamber (10) through a booster pump (30) and is used to inject pressurized gas into the gap (12) to simulate the mud blowout process in the well and the well shut-in state after the blowout.

2. The balance point method well killing simulation experimental device according to claim 1 is characterized in that: The simulated wellbore (20) comprises a vertical well section (21), a deflection section (22) and a horizontal section (23) which are connected in sequence; The horizontal section (23) is arranged horizontally, and one end of the horizontal section (23) away from the angle-making section (22) is in closed communication with the accommodation chamber (10); The vertical well section (21) is arranged vertically, and the vacuum pumping mechanism (40), the liquid injection mechanism (50) and the gas-liquid separation mechanism (60) are respectively connected to one end of the vertical well section (21) away from the deflection section (22).

3. The balance point method well killing simulation experimental device according to claim 2 is characterized in that: An injection pipe (24) is coaxially inserted into the simulated wellbore (20). The injection pipe (24) is used to guide well-killing fluid. One end of the injection pipe (24) is inserted into the rock sample (11).

4. The balance point method well killing simulation experimental device according to claim 3 is characterized in that: It also comprises a gas-liquid separation mechanism (60), which is connected to the input end of the simulated wellbore (20) and is used to separate the well-killing fluid and the pressurized gas.

5. The balance point method well killing simulation experimental device according to claim 4 is characterized in that: It also comprises a circulation mechanism (70), through which the gas-liquid separation mechanism (60) is connected to the liquid injection mechanism (50), so that the well-killing fluid separated by the gas-liquid separation mechanism (60) flows back to the liquid injection mechanism (50).

6. The balance point method well killing simulation experimental device according to claim 5 is characterized in that: It also includes an exhaust mechanism (80), which is in communication with the gas-liquid separation mechanism (60) so as to exhaust the gas separated by the gas-liquid separation mechanism (60).

7. The balance point method well killing simulation experimental device according to claim 6 is characterized in that: The top of the vertical well section (21) is connected to a multi-port (25), and the vacuum pumping mechanism (40), the liquid injection mechanism (50), the gas-liquid separation mechanism (60) and the emptying mechanism (80) are respectively connected to the multi-port (25).

8. The balance point method well killing simulation experimental device according to claim 7 is characterized in that: The vacuum extraction mechanism (40) and the liquid injection mechanism (50) are connected to the same side of the multi-port (25) through a blowout preventer (26).

9. A balanced point method for well killing simulation experiment, characterized in that: The method is carried out using the balance point method well killing simulation experimental device as described in any one of claims 1 to 8, comprising the following steps: The vacuuming mechanism (40) is used to vacuum the containing chamber (10) and the simulated wellbore (20); Using the injection mechanism (50) to inject a preset amount of drilling fluid into the simulated wellbore (20); The booster pump (30) is started to pressurize the gas source of the gas injection mechanism (31) to a preset pressure, and then the pressurized gas is continuously injected into the receiving chamber (10) at the preset pressure to simulate the mud blowout process in the well and the well shut-in state after the blowout; The liquid injection mechanism (50) is used to inject well-killing fluid into the simulated wellbore (20) until the well-killing fluid returns to the input end of the simulated wellbore (20); The balance point well depth and the density of the required well-killing fluid are calculated.

10. The equilibrium point method for well killing simulation experiment according to claim 9, characterized in that: The calculation to obtain the equilibrium point well depth and the required density of the well killing fluid comprises the following steps: Calculation formula for component formation pressure; Obtain the calculation formula for the gas density and gas velocity in the well; Substituting the calculation formula of the gas density and the gas flow velocity into the calculation formula of the formation pressure to obtain a conversion formula; The bottom hole pressure during the blowout process is calculated by the conversion formula using an iterative method; The calculation formula of the blowdown volume is obtained according to the first horizontal well productivity formula; Calculate the equilibrium formation pressure according to the bottom hole pressure, the calculation formula of the blowdown volume and the second horizontal well productivity formula; Calculating the required density of the well killing fluid according to the equilibrium formation pressure; The balance point well depth is calculated based on the required density of the well killing fluid.

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