A formation pressure inversion system and inversion method under the condition of gas well blowout and fire

Abstract

The present invention relates to a formation pressure inversion system and method under the condition of gas well blowout and fire, belonging to the field of petroleum and natural gas engineering technology. A wellhead parameter calculation model is established based on the calculated flame length, and the gas flow rate at the wellhead under the blowout and fire condition is obtained by solving the calculation model, and finally the formation pressure is inverted according to the calculated wellhead parameters. With the help of the formation pressure inversion system under the condition of gas well blowout and fire of the present invention, the flame height under the blowout and fire condition is accurately measured. The formation pressure inversion system and method under the condition of gas well blowout and fire of the present invention can accurately determine the gas flow rate and flow rate at the blowout and fire wellhead, and provide guidance for formation pressure inversion and emergency rescue operations under the condition of blowout and fire.

Description

Technical Field

[0001] The invention relates to a formation pressure inversion system and an inversion method under the condition of gas well blowout and fire, belonging to the technical field of petroleum and natural gas engineering. Background Art

[0002] The ejected materials of a blowout are mainly crude oil, natural gas, drilling fluid and groundwater, among which the most harmful is the blowout of a gas well. A blowout of a gas well or even an uncontrolled blowout will cause great harm. Because most of the natural gas is hydrocarbon gas such as methane and ethane, these flammable and explosive substances are easily combusted and exploded when mixed with air and exposed to open flames and high temperatures. The main characteristics and hazards of gas well blowout fire are: uncontrolled gas well blowout fire is generally sudden and violent, which can easily cause casualties; the flame column is high, generally 50 to 100 meters; the flame temperature is high and the thermal radiation is strong. The surface temperature of the fire column is generally around 1500℃. In the absence of water or shelter, it is difficult for people to stay about 100 meters away from the wellhead; the oil and gas are sprayed with high pressure and high output, and carry a large amount of rock cuttings to rush to the casing and wellhead, which is extremely destructive; due to the high pressure and high output of the sprayed oil and gas, coupled with the high frequency of combustion and explosion, the sound is high, the noise is loud, and deafening, causing great damage to the environment, posing a great threat to rescue personnel, and causing great difficulties to the rescue command system; the rescue time is long, the water consumption is large, the manpower and material resources are greatly consumed, and the rescue environment and conditions are poor, which brings difficulties to the rescue operation. In the case of a gas well blowout and fire, it is impossible to access the drilling platform, and the shut-in standpipe pressure and shut-in casing pressure cannot be obtained by traditional methods. Therefore, the conventional method of determining the formation pressure by reading the casing pressure and standpipe pressure after shutting in the well cannot be used in the case of a blowout and fire. In addition, conducting a study on gas well blowout and fire can help formulate accident handling plans and carry out emergency rescue operations. Summary of the invention

[0003] In view of the shortcomings of the prior art and to overcome the defects of the prior art, the present invention provides a method for determining the formation pressure in the case of a gas well blowout and fire; this method solves the problems that the prior methods cannot solve and can provide a basis for subsequent well killing design and well killing construction.

[0004] The technical solution of the present invention is as follows:

[0005] A formation pressure inversion system in the case of a gas well blowout and fire, comprising a surface blowout flame height measurement system and a data information inversion system;

[0006] The ground blowout flame height measurement system includes: infrared thermal imaging camera, visible light camera, small weather station, and distance sensor; infrared thermal imaging camera and visible light camera are used to take on-site images of gas well blowout flames to study, analyze and determine the height of the flames; the small weather station is used to continuously record the following meteorological conditions: wind direction, wind speed and ambient temperature, which are important variables because they may directly or indirectly affect the jet flame; the distance sensor is used to reasonably calculate the distance between the infrared thermal imaging camera and the visible light camera and the blowout flame;

[0007] The data information inversion system includes: data acquisition pipeline, computer, display;

[0008] The data acquisition pipeline connects the computer and the ground blowout flame height measurement system to transmit the measurement data to the computer; the computer inverts the formation information based on the obtained measurement data to obtain the formation pressure; the display is connected to the computer to output the formation pressure inversion results intuitively.

[0009] Preferably, the flame height is determined by images captured by an infrared thermal imaging camera and a visible light camera, which are processed and identified by a computer, with a temperature of 800K being used as the blowout flame boundary.

[0010] Preferably according to the present invention, the distance measuring sensor is an explosion-proof laser distance measuring sensor, which is suitable for on-site operations of blowout fires.

[0011] The connection between the data acquisition pipeline and the measuring equipment can be based on the existing technology. The computer is used to analyze the formation pressure using the invented formation pressure inversion method; the display is connected to the computer and is mainly used to intuitively output the formation pressure inversion results in the process of continuously enriching the measurement data.

[0012] The inversion method of the formation pressure inversion system in the case of a gas well blowout and fire mentioned above comprises the following steps:

[0013] Under the premise of ensuring the safety of personnel and the normal operation of equipment, an explosion-proof laser ranging sensor is used to determine the safe distance; the infrared thermal imaging camera and visible light camera on site are set to recording mode, and the measured flame image and the distance measured by the explosion-proof laser ranging sensor are imported into the computer through the data acquisition pipeline, and processed and analyzed through formation pressure inversion to obtain the formation pressure.

[0014] A formation information inversion method in the case of a gas well blowout and fire, the specific steps include the following:

[0015] (1) Determine the engineering parameters required for formation pressure inversion based on on-site drilling construction data;

[0016] (2) The flame height is calculated based on the flame images measured by the infrared thermal imaging camera and the visible light camera. Due to the presence of ambient wind, the flame height calculation formula is:

[0017]

[0018] In formula (1), L0 is the length of the blowout flame, m; H is the measured flame height, m; θ is the angle between the blowout flame and the horizontal line (0°~90°); uW is the local wind speed, m / s;

[0019] (3) Since the jet velocity of the uncontrolled well blowout is usually in the supersonic region and belongs to the gas jet, the Spalart-Allmaras model is used to describe the uncontrolled well blowout:

[0020]

[0021] Where t represents time, s; ρ represents the density of the mixed gas, kg / m 3 ;x i , x j Represent tensor symbols at different positions respectively; represents the turbulent viscosity coefficient; u i G represents the uniform velocity component; v represents the term of turbulent viscosity generation; Y v represents the turbulent viscosity reduction term caused by wall obstruction and viscous damping; and C b2 is a constant; μ represents molecular viscosity, Pa·s;

[0022] (4) In the supersonic jet process, since the real gas is compressible, the Poisson equation and pV = ZnRT are used to obtain:

[0023] p -γ =C (3)

[0024] Combined with the Euler equation, the real gas Bernoulli equation is derived:

[0025]

[0026] Where p is the pressure at the blowout outlet, Pa; V is the gas volume, m 3 ; Z is the natural gas compressibility coefficient; n is the amount of gas in mol; R is the molar gas constant; J / (mol·k); T is the absolute temperature, k; γ is the specific heat ratio; v is the blowout gas velocity, m / s; g is the gravitational acceleration, m / s 2 ; H is the flame height, m; C is a constant;

[0027] (5) The flame height and flow rate expression formula is established based on the real gas Bernoulli equation:

[0028]

[0029] Where p0 is the bottom hole pressure, Pa; ρ0 is the bottom hole gas density; p is the pressure at the blowout outlet, Pa; f is the resistance coefficient, m / s; l is the casing length, m; r is the casing radius, m; represents the average speed after Reynolds averaging, m / s;

[0030] (6) The gas composition is determined based on the on-site construction data, and the relative molecular mass of the blowout gas can be calculated using formula (6):

[0031]

[0032] Where M g Indicates the relative molecular mass of natural gas; x i represents the number of moles of natural gas component i; n represents the number of components; M i is the relative molecular mass of component i;

[0033] (7) Combining the gas ideal state equation (7) with formula (5) can obtain the gas flow rate expression at the wellhead of gas blowout ignition (8):

[0034]

[0035]

[0036] Where ρ g Indicates gas density kg / m 3 ; T0 represents relative temperature, k; R is the molar gas constant; J / (mol·k);

[0037] (8) Based on the wellhead flow rate, the blowout gas production Q is calculated using formula (9):

[0038]

[0039] Where K represents the conversion coefficient of blowout gas production and flow, which can be found in the gas mass flow conversion coefficient table;

[0040] (9) In the process of solving the formation pressure, it is necessary to first calculate the bottom hole flow pressure P s After solving the bottom hole flow pressure, the formation pressure can be obtained. s The solution is as follows:

[0041] 9-1. Basic equations

[0042] In the process of gas flowing from the bottom of the well along the wellbore to the wellhead, assuming that the fluid is a steady flow, the pipe section of length dl is taken as the control body for study, and then it can be written as equation (10) based on the energy equation:

[0043] d p +ρvgdv+dW+dL w =0 (10)

[0044] Where d p is the total pressure drop corresponding to the pipe length dl; ρ is the gas density under flow state, kg / m 3 ; g is the acceleration due to gravity m / s 2 ; v is the gas velocity, m / s; dv is the corresponding velocity change within the tube length dl; dW is the work done by the outside world on the gas; dL w Pressure loss due to friction;

[0045] For vertical pipe gas flow: (1) there is no change in work from the bottom of the well to the wellhead, that is, dW = 0; (2) the kinetic energy loss is negligible, that is, vdv = 0; then formula (10) can be written as:

[0046]

[0047] Where d is the pipe diameter, m, and f is the resistance coefficient, which can be expressed using the Colebrook formula:

[0048]

[0049] Where e is the absolute roughness of the inner wall of the casing, m;

[0050] Under standard conditions, take the atmospheric pressure p under standard conditions sc =0.01325MPa, standard temperature T sc =293k,q sc is the gas flow rate under standard conditions, m 3 / d, then at any point (p, T) in the tube:

[0051]

[0052]

[0053] In the formula, B g is the non-Darcy flow coefficient of gas; A is the Darcy flow coefficient; γ g is the mole fraction of blowout gas; Substitute formula (13) and (14) into formula (12) and divide by the gravitational acceleration to obtain formula (15):

[0054]

[0055] Considering that when the gas in the well flows upward, the pressure of the gas gradually decreases due to the pressure difference, the above formula can be transformed and written in integral form:

[0056]

[0057] Where p2 is the flow pressure at the end of the calculation segment, MPa; p1 is the flow pressure at the beginning of the calculation segment, MPa; H2 is the height at the end of the calculation segment, m; H1 is the height at the beginning of the calculation segment, m;

[0058] 9-2. Solution method

[0059] In formula (16), p and T are functions of l, and Z is a function of T and p. Therefore, the solution of formula (16) can be calculated by iteration. The length H of the entire wellbore is divided into n sections, each with a length of ΔH. In each section, Z and T are the average values ​​of the corresponding section, that is, Formula (16) can be written as follows:

[0060]

[0061] Simplifying formula (17) yields formula (18):

[0062]

[0063] Where, p2 is the flow pressure at the end of the calculation section, MPa; p1 is the flow pressure at the beginning of the calculation section, MPa; exist The compression coefficient is obtained under the following conditions; is the average temperature of the gas in the flow column ΔH section, k;

[0064] Starting from the known wellhead pressure, calculate downward step by step until the bottom of the well to find the bottomhole flowing pressure p s ;

[0065] (10) After solving the bottom hole flow pressure, the gas production of the blowout is substituted into the gas production binomial equation to obtain the formation pressure; the formation pressure after the blowout can be obtained by applying the gas production binomial equation (19) based on the predicted natural gas blowout volume and the bottom hole flow pressure during the blowout;

[0066] P f =(P s 2 +AQ+BQ 2 ) 0.5 (19)

[0067] Where P f is the formation pressure, Pa; P sis the bottom hole flow pressure when blowout occurs, Pa; A is the Darcy flow coefficient; B is the non-Darcy flow coefficient.

[0068] Preferably, according to the present invention, the engineering parameters in step (1) refer to the required calculation parameters determined according to the on-site construction data, including: wellbore size, casing pressure, ground temperature, resistance coefficient, gas viscosity, gas specific heat ratio, number of moles of produced gas, relative density of produced gas, relative molecular mass of produced gas, absolute roughness of the inner wall of the blowout pipeline, blowout gas compressibility coefficient, Darcy flow coefficient, and non-Darcy flow coefficient.

[0069] According to the present invention, preferably, in step (2), the flame height is determined by using an infrared thermal imaging camera image 800k as the flame boundary and a visible light camera to determine the flame height.

[0070] The beneficial effects of the present invention are:

[0071] The system and method of the present invention can timely and accurately obtain formation information under gas well blowout and fire conditions, and can provide a theoretical basis for the determination of natural gas production in uncontrolled wells and the subsequent development of uncontrolled wells. At the same time, it has practical guiding significance for the emergency rescue work of uncontrolled natural gas wells, and can help to formulate reasonable emergency rescue plans, reduce personal injuries and economic losses, and reduce environmental pollution. BRIEF DESCRIPTION OF THE DRAWINGS

[0072] Figure 1 This is the flow chart of formation pressure inversion in the case of gas well blowout and fire;

[0073] Figure 2 This is a schematic diagram of flame height measurement;

[0074] Among them, 1: infrared thermal imaging camera; 2: visible light camera; 3: small weather station; 4: ranging sensor; 5: data acquisition pipeline; 6: computer; 7: display. DETAILED DESCRIPTION

[0075] The present invention is further described below by way of examples and in conjunction with the accompanying drawings, but is not limited thereto. The experimental methods used in the examples are conventional methods unless otherwise specified. The equipment used in the examples, etc., can be obtained from commercial sources unless otherwise specified.

[0076] Embodiment 1:

[0077] like Figure 1 As shown, a formation pressure inversion system in the case of gas well blowout and fire includes a surface blowout flame height measurement system and a data information inversion system.

[0078] The ground blowout flame height measurement system includes: an infrared thermal imaging camera 1, a visible light camera 2, a small meteorological station 3, and a distance measuring sensor 4.

[0079] The infrared thermal imaging camera 1 and the visible light camera 2 take on-site images of the gas well blowout flame to study, analyze and determine the height of the flame; the small meteorological station 3 is used to continuously record the following meteorological conditions: wind direction, wind speed and ambient temperature. These variables are important because they may directly or indirectly affect the jet flame; the ranging sensor 4 is used to reasonably arrange the distance between the infrared thermal imaging camera 1 and the visible light camera 2 and the blowout flame.

[0080] The data information inversion system includes: a data acquisition pipeline 5, a computer 6, and a display 7;

[0081] The data acquisition pipeline 5 connects the computer and the surface blowout flame height measurement system to transmit the measurement data to the computer; the computer inverts the formation information based on the obtained measurement data to obtain the formation pressure; the display 7 is connected to the computer 6 for intuitively outputting the formation pressure inversion result.

[0082] The infrared thermal imaging camera 1 and the visible light camera 2 adopt the existing technology to capture the fire scene image and determine the flame height of the gas well jet flow.

[0083] The distance measuring sensor 3 is an explosion-proof laser distance measuring sensor, which is suitable for on-site operations of blowout fires.

[0084] The connection between the data acquisition pipeline 5 and the measuring device can be based on the existing technology. The computer 6 is used to analyze the formation pressure using the inventive formation pressure inversion method; the display 7 is connected to the computer 6 and is mainly used to intuitively output the formation pressure inversion results in the process of continuously enriching the measurement data.

[0085] Example 2

[0086] An inversion method using the formation pressure inversion system in the case of a gas well blowout and fire described in Example 1, the specific steps include:

[0087] (1) Determine the engineering parameters required for formation pressure inversion based on the on-site drilling construction data; the engineering parameters refer to the required calculation parameters determined based on the on-site construction data, including: wellbore size, casing pressure, ground temperature, resistance coefficient, gas viscosity, gas specific heat ratio, number of moles of produced gas, relative density of produced gas, relative molecular mass of produced gas, absolute roughness of the inner wall of the blowout pipe line, blowout gas compressibility coefficient, Darcy flow coefficient, non-Darcy flow coefficient

[0088] (2) The flame height is calculated based on the flame images measured by the infrared thermal imaging camera and the visible light camera. Due to the presence of ambient wind, the flame height calculation formula is:

[0089]

[0090] In formula (1), L0 is the length of the blowout flame, m; H is the measured flame height, m; θ is the angle between the blowout flame and the horizontal line (0°~90°); u W is the local wind speed, m / s; the flame height is determined by the infrared thermal imaging camera image 800k as the flame boundary and the visible light camera to determine the flame height.

[0091] (3) Since the jet velocity of the uncontrolled well blowout is usually in the supersonic region and belongs to the gas jet, the Spalart-Allmaras model is used to describe the uncontrolled well blowout:

[0092]

[0093] Where t represents time, s; ρ represents the density of the mixed gas, kg / m 3 ;x i , x j Represent tensor symbols at different positions respectively; represents the turbulent viscosity coefficient; u i G represents the uniform velocity component; v represents the term of turbulent viscosity generation; Y v represents the turbulent viscosity reduction term caused by wall obstruction and viscous damping; and C b2 is a constant; μ represents molecular viscosity, Pa·s;

[0094] (4) In the supersonic jet process, since the real gas is compressible, the Poisson equation and pV = ZnRT are used to obtain:

[0095] p -γ =C (3)

[0096] Combined with the Euler equation, the real gas Bernoulli equation is derived:

[0097]

[0098] Where p is the pressure at the blowout outlet, Pa; V is the gas volume, m 3 ; Z is the natural gas compressibility coefficient; n is the amount of gas in mol; R is the molar gas constant; J / (mol·k); T is the absolute temperature, k; γ is the specific heat ratio; v is the blowout gas velocity, m / s; g is the gravitational acceleration, m / s 2 ; H is the flame height, m; C is a constant;

[0099] (5) The flame height and flow rate expression formula is established based on the real gas Bernoulli equation:

[0100]

[0101] Where p0 is the bottom hole pressure, Pa; ρ0 is the bottom hole gas density; p is the pressure at the blowout outlet, Pa; f is the resistance coefficient, m / s; l is the casing length, m; r is the casing radius, m; represents the average speed after Reynolds averaging, m / s;

[0102] (6) The gas composition is determined based on the on-site construction data, and the relative molecular mass of the blowout gas can be calculated using formula (6):

[0103]

[0104] Where M g Indicates the relative molecular mass of natural gas; x i represents the number of moles of natural gas component i; n represents the number of components; M i is the relative molecular mass of component i;

[0105] (7) Combining the gas ideal state equation (7) with formula (5) can obtain the gas flow rate expression at the wellhead of gas blowout ignition (8):

[0106]

[0107]

[0108] Where ρ g Indicates gas density kg / m 3 ; T0 represents relative temperature, k; R is the molar gas constant; J / (mol·k);

[0109] (8) Based on the wellhead flow rate, the blowout gas production Q is calculated using formula (9):

[0110]

[0111] Where K represents the conversion coefficient of blowout gas production and flow, which can be found in the gas mass flow conversion coefficient table;

[0112] (9) In the process of solving the formation pressure, it is necessary to first calculate the bottom hole flow pressure P s After solving the bottom hole flow pressure, the formation pressure can be obtained. s The solution is as follows:

[0113] 9-1. Basic equations

[0114] In the process of gas flowing from the bottom of the well along the wellbore to the wellhead, assuming that the fluid is a steady flow, the pipe section of length dl is taken as the control body for study, and then it can be written as equation (10) based on the energy equation:

[0115] d p +ρvgdv+dW+dL w =0 (10)

[0116] Where d p is the total pressure drop corresponding to the pipe length dl; ρ is the gas density under flow state, kg / m 3 ; g is the acceleration due to gravity m / s 2 ; v is the gas velocity, m / s; dv is the corresponding velocity change within the tube length dl; dW is the work done by the outside world on the gas; dL w Pressure loss due to friction;

[0117] For vertical pipe gas flow: (1) there is no change in work from the bottom of the well to the wellhead, that is, dW = 0; (2) the kinetic energy loss is negligible, that is, vdv = 0; then formula (10) can be written as:

[0118]

[0119] Where d is the pipe diameter, m, and f is the resistance coefficient, which can be expressed using the Colebrook formula:

[0120]

[0121] Where e is the absolute roughness of the inner wall of the casing, m;

[0122] Under standard conditions, take the atmospheric pressure p under standard conditions sc =0.01325MPa, standard temperature T sc =293k,q sc is the gas flow rate under standard conditions, m 3 / d, then at any point (p, T) in the tube:

[0123]

[0124]

[0125] In the formula, B g is the non-Darcy flow coefficient of gas; A is the Darcy flow coefficient; γ g is the mole fraction of blowout gas; Substitute formula (13) and (14) into formula (12) and divide by the gravitational acceleration to obtain formula (15):

[0126]

[0127] Considering that when the gas in the well flows upward, the pressure of the gas gradually decreases due to the pressure difference, the above formula can be transformed and written in integral form:

[0128]

[0129] Where p2 is the flow pressure at the end of the calculation segment, MPa; p1 is the flow pressure at the beginning of the calculation segment, MPa; H2 is the height at the end of the calculation segment, m; H1 is the height at the beginning of the calculation segment, m;

[0130] 9-2. Solution method

[0131] In formula (16), p and T are functions of l, and Z is a function of T and p. Therefore, the solution of formula (16) can be calculated by iteration. The length H of the entire wellbore is divided into n sections, each with a length of ΔH. In each section, Z and T are the average values ​​of the corresponding section, that is, Formula (16) can be written as follows:

[0132]

[0133] Simplifying formula (17) yields formula (18):

[0134]

[0135] Where, p2 is the flow pressure at the end of the calculation section, MPa; p1 is the flow pressure at the beginning of the calculation section, MPa; exist The compression coefficient is obtained under the following conditions; is the average temperature of the gas in the flow column ΔH section, k;

[0136] Starting from the known wellhead pressure, calculate downward step by step until the bottom of the well to find the bottomhole flowing pressure p s ;

[0137] (10) After solving the bottom hole flow pressure, the gas production of the blowout is substituted into the gas production binomial equation to obtain the formation pressure; the formation pressure after the blowout can be obtained by applying the gas production binomial equation (19) based on the predicted natural gas blowout volume and the bottom hole flow pressure during the blowout;

[0138] P f =(P s 2 +AQ+BQ 2 ) 0.5 (19)

[0139] Where P f is the formation pressure, Pa; P sis the bottom hole flow pressure when blowout occurs, Pa; A is the Darcy flow coefficient; B is the non-Darcy flow coefficient.

Claims

1. An inversion method for a formation pressure inversion system in the case of a gas well blowout and fire, characterized in that: The formation pressure inversion system under the condition of gas well blowout and fire includes a surface blowout flame height measurement system and a data information inversion system; The ground blowout flame height measurement system includes: infrared thermal imaging camera, visible light camera, small weather station, and distance sensor; the infrared thermal imaging camera and visible light camera are used to take on-site images of gas well blowout flames to study, analyze and determine the flame height; the small weather station is used to continuously record the following meteorological conditions: wind direction, wind speed and ambient temperature; the distance sensor is used to calculate the distance between the infrared thermal imaging camera and the visible light camera and the blowout flame; The data information inversion system includes: data acquisition pipeline, computer, display; The data acquisition pipeline connects the computer and the surface blowout flame height measurement system to transmit the measurement data to the computer; the computer inverts the formation information based on the obtained measurement data to obtain the formation pressure; the display is connected to the computer to output the formation pressure inversion result intuitively; The specific steps include the following: (1) Determine the engineering parameters required for formation pressure inversion based on on-site drilling construction data; (2) The flame height is calculated based on the flame images measured by the infrared thermal imaging camera and the visible light camera. Due to the presence of ambient wind, the flame height calculation formula is: In formula (1), L0 is the length of the blowout flame, m; H is the measured flame height, m; θ is the angle between the blowout flame and the horizontal line, 0° to 90°; u W is the local wind speed, m / s; (3) Since the jet velocity of the uncontrolled well blowout is usually in the supersonic region and belongs to the gas jet, the Spalart-Allmaras model is used to describe the uncontrolled well blowout: Where t represents time, s; ρ represents the density of the mixed gas, kg / m 3 ;x i , x j Represent tensor symbols at different positions respectively; represents the turbulent viscosity coefficient; u i G represents the uniform velocity component; v represents the term of turbulent viscosity generation; Y v represents the turbulent viscosity reduction term caused by wall obstruction and viscous damping; and C b2 is a constant; μ represents molecular viscosity, Pa·s; (4) In the supersonic jet process, since the real gas is compressible, the Poisson equation and pV = ZnRT are used to obtain: pρ -γ =C(3) Combined with the Euler equation, the real gas Bernoulli equation is derived: Where p is the pressure at the blowout outlet, Pa; V is the gas volume, m 3 ; Z is the natural gas compressibility coefficient; n is the amount of gas in mol; R is the molar gas constant; J / (mol·k); T is the absolute temperature, k; γ is the specific heat ratio; v is the blowout gas velocity, m / s; g is the gravitational acceleration, m / s 2 ; H is the flame height, m; C is a constant; (5) The flame height and flow rate expression formula is established based on the real gas Bernoulli equation: Where p0 is the bottom hole pressure, Pa; ρ0 is the bottom hole gas density; p is the pressure at the blowout outlet, Pa; f is the resistance coefficient, m / s; l is the casing length, m; r is the casing radius, m; represents the average speed after Reynolds averaging, m / s; (6) Determine the gas composition based on the on-site construction data and calculate the relative molecular mass of the blowout gas using formula (6): Where M g Indicates the relative molecular mass of natural gas; x i represents the number of moles of natural gas component i; n represents the number of components; M i is the relative molecular mass of component i; (7) The ideal state equation of gas (7) and formula (5) are combined to obtain the gas velocity expression at the wellhead of gas blowout (8): Where ρ g Indicates gas density kg / m 3 ; T0 represents relative temperature, k; R is the molar gas constant; J / (mol·k); (8) Based on the wellhead flow rate, the blowout gas production Q is calculated using formula (9): Where K represents the conversion coefficient of blowout gas production and flow, which can be found in the gas mass flow conversion coefficient table; (9) In the process of solving the formation pressure, it is necessary to first calculate the bottom hole flow pressure P s After solving the bottom hole flow pressure, the formation pressure is calculated. s The solution is as follows: 9-1. Basic equations In the process of gas flowing from the bottom of the well along the wellbore to the wellhead, assuming that the fluid is a steady flow, the pipe section of length dl is taken as the control body for study, and then it is written as equation (10) according to the energy equation: d p +ρvgdv+dW+dL w =0(10) Where d p is the total pressure drop corresponding to the pipe length dl; ρ is the gas density under flow state, kg / m 3 ; g is the acceleration due to gravity m / s 2 ; v is the gas velocity, m / s; dv is the corresponding velocity change within the tube length dl; dW is the work done by the outside world on the gas; dL w Pressure loss due to friction; For vertical pipe gas flow: (1) there is no change in work from the bottom of the well to the wellhead, that is, dW = 0; (2) the kinetic energy loss is negligible, that is, vdv = 0; then formula (10) is written as: Where d is the pipe diameter, m, and the resistance coefficient f is calculated using the Colebrook formula: Where e is the absolute roughness of the inner wall of the casing, m; Under standard conditions, take the atmospheric pressure p under standard conditions sc =0.01325MPa, standard temperature T sc =293k,q sc is the gas flow rate under standard conditions, m 3 / d, then at any point (p, T) in the tube: In the formula, B g is the non-Darcy flow coefficient of gas; A is the Darcy flow coefficient; γ g is the mole fraction of blowout gas; Substitute formula (13) and (14) into formula (12) and divide by the gravitational acceleration to obtain formula (15): Considering that when the gas in the well flows upward, the pressure of the gas gradually decreases due to the pressure difference, the above formula is transformed and written in integral form: Where p2 is the flow pressure at the end of the calculation segment, MPa; p1 is the flow pressure at the beginning of the calculation segment, MPa; H2 is the height at the end of the calculation segment, m; H1 is the height at the beginning of the calculation segment, m; 9-2. Solution method In formula (16), p and T are functions of l, and Z is a function of T and p. Therefore, the solution of formula (16) is calculated by iteration. The length H of the entire wellbore is divided into n sections, each with a length of ΔH. In each section, Z and T are the average values ​​of the corresponding section, that is, Formula (16) can be written as follows: Simplifying formula (17) yields formula (18): Where, p2 is the flow pressure at the end of the calculation section, MPa; p1 is the flow pressure at the beginning of the calculation section, MPa; exist The compression coefficient is obtained under the following conditions; is the average temperature of the gas in the flow column ΔH section, k; Starting from the known wellhead pressure, calculate downward step by step until the bottom of the well to find the bottom hole flowing pressure p s ; (10) After solving for the bottom hole flow pressure, the blowout gas production is substituted into the gas production binomial equation to obtain the formation pressure; the formation pressure after the blowout is obtained by applying the gas production binomial equation (19) based on the predicted natural gas blowout volume and the bottom hole flow pressure during the blowout; Where P f is the formation pressure, Pa; P s is the bottom hole flow pressure when blowout occurs, Pa; A is the Darcy flow coefficient; B is the non-Darcy flow coefficient.

2. The inversion method of the formation pressure inversion system in the case of gas well blowout and fire according to claim 1, characterized in that: The engineering parameters in step (1) refer to the required calculation parameters determined according to the on-site construction data, including: wellbore size, casing pressure, ground temperature, resistance coefficient, gas viscosity, gas specific heat ratio, number of moles of produced gas, relative density of produced gas, relative molecular mass of produced gas, absolute roughness of the inner wall of the blowout pipe line, blowout gas compressibility coefficient, Darcy flow coefficient, and non-Darcy flow coefficient.

3. The inversion method of the formation pressure inversion system in the case of gas well blowout and fire according to claim 1, characterized in that: In step (2), the flame height is determined by the infrared thermal imaging camera image 800k as the flame boundary and the visible light camera to determine the flame height.

4. The inversion method of the formation pressure inversion system in the case of gas well blowout and fire according to claim 1, characterized in that: The flame height is determined by the images captured by infrared thermal imaging cameras and visible light cameras, which are processed and identified by computers, with a temperature of 800K as the blowout flame boundary.

5. The inversion method of the formation pressure inversion system in the case of gas well blowout and fire according to claim 1, characterized in that: The distance measuring sensor is an explosion-proof laser distance measuring sensor.

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