A deepwater drilling blowout emergency treatment device and method

Abstract

The present invention relates to a deepwater drilling blowout emergency treatment device and method, belonging to the field of marine oil and gas deepwater drilling well control. Downhole throttling nipple and wellhead data collection nipple collect temperature, pressure and flow data in real time, and the collected data is transmitted to the emergency treatment center in real time; the treatment center performs real-time analysis based on the collected data, and then controls the throttling valve opening to generate throttling pressure drop to block the annulus; by controlling the power of the well-killing fluid injection pump, the upper part of the downhole throttling nipple is filled with well-killing fluid, and well-killing fluid is injected into the bottom of the well while the throttle valve is opened to release gas, thereby realizing efficient treatment of deepwater drilling blowout. The present invention coordinately ensures safe and efficient treatment after deepwater drilling blowout through downhole throttling cooling and plugging and well-killing fluid wellbore pressure control, can quickly control the blowout problem in the deepwater drilling process, and avoid the problem of wellbore scrapping after a blowout in a deepwater drilling well, providing theoretical and technical support for safe deepwater oil and gas drilling.

Description

Technical Field

[0001] The invention relates to a deepwater drilling blowout emergency treatment device and method, belonging to the technical field of marine oil and gas deepwater drilling well control. Background Art

[0002] Drilling is a key link in the development of deepwater oil and gas resources. However, due to the complexity of the deepwater environment, deepwater oil and gas drilling is characterized by high technology, high cost and high risk. Among them, blowout is one of the most serious security threats faced by deepwater drilling activities. Once a blowout occurs during deepwater drilling, it will not only lead to the suspension of drilling operations, the scrapping of wells, damage to platforms and drilling equipment, and other related economic and property losses, but may even cause casualties and damage the fragile marine environment.

[0003] At present, the main methods for killing a well after a blowout include the driller method, engineer method, replacement method, pressure-back method, top well killing method, and rescue well killing method. For example, the Deepwater Horizon blowout accident in the Gulf of Mexico, USA, was achieved by using the top well killing method and the pressure-back method to permanently seal the well. However, the existing methods have disadvantages such as high cost or long cycle, and there is currently a lack of a safe and efficient deepwater drilling blowout treatment method, which is also a key difficulty restricting the safe and efficient drilling of deepwater oil and gas resources. For this reason, the present invention is proposed. Summary of the invention

[0004] In view of the shortcomings of the existing technology, especially the problems of low efficiency, long time and high cost of existing treatment methods after deepwater drilling blowout, the present invention proposes a deepwater drilling blowout emergency treatment device and method, which combines downhole throttling, cooling and plugging with well killing fluid wellbore pressure control to coordinately ensure safe and efficient treatment after deepwater drilling blowout, can quickly control the blowout problem in the deepwater drilling process, and avoid the problem of wellbore scrapping after a blowout in a deepwater drilling well, providing theoretical and technical support for safe deepwater oil and gas drilling.

[0005] The present invention adopts the following technical solutions:

[0006] On the one hand, the present invention provides a deepwater drilling blowout emergency treatment device, including a downhole throttling plugging device, a platform well-killing fluid injection device and a treatment control device;

[0007] The downhole throttling plugging device includes a casing, a downhole throttling nipple and a drill pipe; the drill pipe is located in the casing, a drill bit is provided at the bottom of the drill pipe, the drilling fluid / well-killing fluid in the drill pipe flows from the wellhead to the bottom of the well, the annulus is a channel for the fluid to flow from the bottom of the well to the wellhead, and the annulus includes the annulus between the drill pipe and the casing and the annulus between the drill pipe and the watertight pipe; the downhole throttling nipple is installed on the casing of the formation 100 meters below the mud line, and a throttling valve, a temperature sensor and a pressure monitoring sensor are installed on the downhole throttling nipple, the function of the throttling valve is to reduce the flow area of ​​the annular flow channel between the drill pipe and the casing, so as to generate a throttling temperature drop effect to generate hydrates or ice to plug the wellbore after the blowout, and the function of the temperature sensor and the pressure monitoring sensor is to monitor the temperature and pressure changes at the nipple;

[0008] The platform well-killing fluid injection device comprises a well-killing fluid injection pipeline A and a well-killing fluid injection pipeline B, a valve A, a valve B, a well-killing fluid injection pump A and a well-killing fluid injection pump B; the well-killing fluid injection pipeline A is connected to the drill pipe, the well-killing fluid injection pipeline A is connected with the valve A and the well-killing fluid injection pump A in sequence, so as to provide a flow channel for injecting well-killing fluid into the bottom of the well through the drill pipe; the well-killing fluid injection pipeline B is connected with the water-rising pipe, the water-rising pipe and the casing are in communication, the well-killing fluid injection pipeline B is connected with the valve B and the well-killing fluid injection pump B in sequence, so as to provide a flow channel for injecting well-killing fluid into the bottom of the well through the annulus;

[0009] The processing and control device comprises a wellhead data acquisition subsection, a signal actuator A, a signal actuator B, a signal actuator C and a computer processing center. The wellhead data acquisition subsection is equipped with a temperature sensor, a pressure monitoring sensor and a flow sensor. The signal actuator A and the signal actuator B are respectively connected to the well-killing fluid injection pump A and the well-killing fluid injection pump B to receive the well-killing fluid injection signal from the computer processing center to realize the dynamic injection and control of the well-killing fluid; the downhole throttling subsection is connected to the signal actuator C through a data transmission optical fiber; the wellhead data acquisition subsection, the signal actuator A, the signal actuator B, the signal actuator C and the downhole throttling subsection are all connected to the computer processing center signal;

[0010] The computer processing center receives data detected by the downhole throttling nipple and the wellhead data acquisition nipple, and transmits control signals to the signal actuator A, the signal actuator B and the signal actuator C in real time, which are used to control the well killing fluid injection pump A, the well killing fluid injection pump B and the throttle valve of the downhole throttling nipple respectively.

[0011] Preferably, the well-killing fluid injection pipeline B is provided with a wellhead vent valve.

[0012] On the other hand, the present invention provides a deepwater drilling blowout emergency treatment method, which is implemented by the above-mentioned deepwater drilling blowout emergency treatment device, wherein temperature, pressure sensors and flow meters installed at the downhole throttling short section and the wellhead collect temperature, pressure and flow data; different data collections are connected to the computer through transmission optical cables, and the collected data are transmitted to the emergency treatment center in real time; the processing center performs real-time automatic analysis and expert discussion based on the collected data, and then controls the reduction of the throttling valve opening on the downhole short section to generate a throttling pressure drop to block the annulus; then, the power of the well-killing fluid injection pump group on the platform is controlled to fill the upper part of the downhole short section with well-killing fluid, and while slowly opening the throttling valve on the downhole short section to release gas, well-killing fluid is injected into the bottom of the well, thereby realizing efficient treatment of deepwater drilling blowout.

[0013] The specific steps include:

[0014] (1) Post-blowout formation pressure assessment and kill fluid density design

[0015] According to the monitoring data (flow rate, pressure, etc.) of the short section of the wellhead data acquisition after the blowout, the actual formation pressure is inverted by combining the wellbore multiphase flow theory and model, and the density of the well killing fluid is designed, thereby laying a theoretical foundation for the subsequent well killing treatment;

[0016] (2) Throttling, cooling and plugging after blowout

[0017] After the blowout, the well-killing fluid is injected into the drill pipe and enters the annulus between the drill pipe and the casing through the drill bit. The throttling and cooling effect is generated by gradually reducing the opening of the throttle valve on the downhole throttling nipple, thereby generating hydrates or ice to plug the wellbore. At the same time, the temperature and pressure changes at the downhole throttling nipple are monitored in real time by installing a temperature and pressure monitoring sensor on the downhole throttling nipple, and then the plugging situation is analyzed. When the pressure increases to a stable value and remains unchanged, it means that the plugging is successful;

[0018] (3) Balance pressure of wellbore injection fluid

[0019] When the annulus is successfully plugged, high-density well-killing fluid is squeezed into the annulus at the wellhead, so that the gravity of the well-killing fluid in the annulus and the plugging effect of the throttle valve can coordinately stabilize the high-pressure fluid produced by the formation;

[0020] (4) Slowly open the valve to release the gas

[0021] The gas below the throttle valve is released by slowly opening the throttle valve on the downhole throttle nipple. At the same time, the wellbore fluid is synchronously injected into the annulus through the drill pipe through the drill bit to replenish the pressure lost by the released gas, until all the gas below the downhole throttle nipple is discharged, indicating that the blowout treatment is successful.

[0022] Preferably, in step (1), a wellhead data acquisition sub is installed on the casing of the wellhead to monitor wellhead temperature, pressure, flow rate and other data in real time, and the bottom hole pressure and formation pressure are calculated and inferred based on the monitored wellhead temperature, pressure and flow rate after the blowout;

[0023] During the blowout process, the wellbore flow is considered as a one-dimensional, stable problem, and the pressure gradient equation in the wellbore can be obtained:

[0024]

[0025] Where p is the fluid pressure in the wellbore, MPa; z is the well depth, MPa; ρ f is the fluid density, kg / m 3 ; g is the acceleration due to gravity, m·s -2 ; f is the friction coefficient of fluid flow in the wellbore, dimensionless; v is the fluid velocity, m·s -1 ; D is the inner diameter of the wellbore, m;

[0026] By dividing the entire wellbore into n parts, the bottom hole flow pressure is calculated by integrating each part in turn using formula (1); on this basis, the formation pressure can be obtained by substituting the relevant data obtained from field monitoring into the gas production binomial equation. The formation pressure after the blowout can be predicted by the gas production binomial equation of formula (2):

[0027]

[0028] Where P f is the formation pressure, MPa; P wf is the bottom hole flow pressure when blowout occurs, MPa; Q is the mass flow rate of blowout fluid, kg·s -1 ; A is the Darcy flow coefficient; B is the non-Darcy flow coefficient, where the calculation formulas for A and B are as follows:

[0029]

[0030]

[0031] Where T is the fluid temperature, °C; is the average gas viscosity of natural gas, mPa·s; is the average deviation coefficient of natural gas, dimensionless; r e is the formation boundary radius, m; r w is the wellbore radius, m, r w =D / 2; K is the effective permeability of the gas layer, μm 2 ; h is the effective thickness of the air layer, m; S is the skin coefficient, dimensionless, S = ln(r w / r c), where r c is the conversion radius, m; β is the coefficient describing the turbulence effect of porous media, called the velocity coefficient, m -1 , β=7.664×10 10 / K 1.5 ; γ g is the relative density of natural gas, generally between 0.5 and 0.7;

[0032] After predicting the formation pressure after the blowout, the density of the well killing fluid is designed according to the blowout well killing theory:

[0033]

[0034] In the formula, ρ k is the density of the well-killing fluid, kg / m 3 ; H is the vertical depth of the well, m;

[0035] After the density of the killing fluid is determined, the designed killing fluid is injected into the bottom of the well with the maximum displacement of the killing fluid injection pump A. The killing fluid enters the annulus through the drill pipe and the drill bit. The killing fluid flows toward the wellhead under the carrying effect of the high-pressure fluid produced by the formation. During the flow, the bottom hole pressure is increased by gravity and friction, thereby reducing the blowout volume of the formation fluid.

[0036] Preferably, in step (2), the deepwater drilling near the seabed has a low temperature and high pressure environment. In order to make the wellbore annulus throttling point more easily meet the temperature and pressure conditions for hydrate formation, a downhole throttling short section is installed on the casing 100 meters below the mud line, and a throttling valve, a temperature and pressure monitoring sensor are installed on the downhole throttling short section to monitor the temperature and pressure changes at the short section in real time;

[0037] After a blowout occurs, a large amount of gas produced by the formation flows at high speed in the annulus. Since the well-killing fluid that enters the annulus through the drill bit contains the water required for hydrate formation and freezing, it can provide a basis for throttling, cooling and plugging. Therefore, as long as the temperature and pressure conditions for hydrate formation are met, hydrate formation can occur, thereby achieving effective plugging of the blowout.

[0038] After a blowout occurs during deepwater drilling, the throttle valve control signal is transmitted to the downhole throttle nipple through the signal transmission optical fiber, and the throttle valve opening on the downhole throttle nipple is gradually reduced to produce a throttling cooling effect. According to the throttle valve opening, the throttling temperature drop △T can be calculated by the following formula:

[0039]

[0040] In the formula, μ J；T is the Joule-Thomson coefficient, K / Pa; △T is the throttling temperature drop, K; Δp is the throttling pressure drop, Pa; H is the enthalpy of the gas, J / Kmol;

[0041] Joule-Thomson coefficient μ J；T The calculation method is as follows:

[0042]

[0043] Where ρ is the molar density of the produced fluid, Kmol / m 3 ; C p is the specific heat capacity at constant pressure, J / (kg·K); R is the gas constant, 8.314 J / (mol.K); C1, C2, C3, C4, a, b, d, α are the intermediate parameters for calculation. For the specific calculation, please refer to the reference (Guo Tianmin. Multivariate Gas-Liquid Equilibrium and Distillation. Petroleum Industry Press, 2002);

[0044] When the fluid temperature T at the throttle valve drops to the hydrate phase equilibrium temperature T due to the throttling effect e When T <T e , hydrate formation will occur; when the fluid temperature T at the throttle valve drops below the freezing point due to the throttling effect, that is, T<0, freezing will occur; the temperature and pressure monitoring sensor installed on the downhole throttling nipple is used to monitor the temperature and pressure changes at the nipple in real time, and then analyze the plugging situation; when it is found that the fluid temperature at the downhole throttling nipple drops, the pressure increases, and the wellhead flow decreases, it means that hydrate formation or freezing has occurred. If it is found that the current throttle valve opening cannot further complete the blowout plugging, it means that the throttle valve opening needs to be further reduced until complete plugging is achieved, that is, the fluid flow monitored at the wellhead drops to zero and the pressure increases to a stable value and remains unchanged.

[0045] Preferably, in step (3), when the annulus is successfully plugged, the high-pressure gas above the plugging point will gradually be discharged from the wellhead due to the pressure difference; when the gas pressure in the annulus is exhausted, a well-killing fluid with a density of ρ is squeezed into the annulus at the wellhead through the well-killing fluid injection pump B. k The well-killing fluid is injected into the annulus until the annulus above the blockage is filled with the well-killing fluid. When the well-killing fluid is squeezed into the annulus, as the well-killing fluid in the annulus increases, the residual gas in the annulus will be compressed, which will cause the annulus casing pressure to increase. In this case, every time the annulus casing pressure increases to 1MPa, it is necessary to open the wellhead vent valve to release the high-pressure gas accumulated at the wellhead. When the annulus above the blockage is filled with well-killing fluid, the gravity of the well-killing fluid in the annulus and the plugging effect of the throttle valve will work together to stabilize the high-pressure fluid produced by the formation. The gravity pressure of the well-killing fluid in the annulus above the blockage can be calculated by the following formula:

[0046] P g ≥ρ k HkDJ d (8)

[0047] Where P g H is the gravity pressure of the well-killing fluid above the downhole throttling nipple, MPa;d is the vertical depth of the underground throttling short joint, m.

[0048] Preferably, in step (4), the throttle valve on the downhole throttle sub is slowly opened to release the gas in the lower part of the downhole throttle sub, and the temperature and pressure changes dP at the location are monitored in real time by the temperature sensor and pressure monitoring sensor on the downhole throttle sub; at the same time, a gas having a density of ρ is synchronously injected into the annulus through the drill pipe via the drill bit. k The killing fluid is then used to compensate for the pressure lost by the released gas. The amount of killing fluid that needs to be injected in the same time as the gas below the downhole throttling nipple is:

[0049]

[0050] Where V k is the amount of injection of well-killing fluid, m 2 ; dP is the pressure change of gas released from the lower part of the downhole throttling short joint, Pa; r w is the wellbore radius, m; r n is the outer diameter of the drill pipe, m;

[0051] At the same time, the sensor on the downhole throttling nipple transmits the monitored temperature and pressure changes to the data processing center in real time. During the release of the gas in the lower part of the downhole throttling nipple and the simultaneous injection of well-killing fluid into the annulus, the pressure fluctuation at the downhole throttling nipple should be kept within 0.3MPa, thereby preventing more formation fluid from entering the wellbore; in the process of releasing the gas in the lower part of the nipple, as the gas enters the upper annulus of the downhole throttling nipple, the wellhead annulus casing pressure will gradually increase. Whenever the annulus casing pressure increases to 1MPa, it is necessary to open the wellhead vent valve to release the high-pressure gas accumulated at the wellhead; in addition, if it is found that the well-killing fluid level in the annulus drops, the well-killing fluid should be squeezed into the annulus through the wellhead in time to maintain the liquid level in the annulus until all the gas in the lower part of the downhole throttling nipple is discharged, indicating that the blowout treatment is successful.

[0052] For any details not provided in the present invention, please refer to the prior art.

[0053] The beneficial effects of the present invention are:

[0054] The present invention aims at the characteristics of deepwater drilling blowouts and combines the low temperature and high pressure characteristics of deepwater. It proposes to quickly control blowout accidents through downhole throttling, cooling and plugging, and gradually restore the flow circulation condition of the wellbore by combining the well killing fluid circulation, and proposes a deepwater drilling blowout emergency treatment device and method. At the same time, by real-time monitoring of parameter changes during the blowout treatment process, safe and efficient treatment of deepwater drilling blowouts can be achieved. The present invention can quickly control blowout problems during deepwater drilling, and avoid the problem of wellbore scrapping after a blowout in a deepwater drilling well, providing theoretical and technical support for safe deepwater oil and gas drilling. BRIEF DESCRIPTION OF THE DRAWINGS

[0055] The drawings in the specification, which constitute a part of the present application, are used to provide further understanding of the present application. The illustrative embodiments of the present application and their descriptions are used to explain the present application and do not constitute improper limitations on the present application.

[0056] Figure 1 It is a structural schematic diagram of the deep-water drilling blowout emergency treatment device of the present invention;

[0057] In the figure, 1-formation, 2-seawater, 3-drill bit, 4-drill pipe, 5-cement ring, 6-casing, 7-downhole throttling short section, 8-data transmission optical fiber, 9-blowout preventer, 10-water-relief pipe, 11-wellhead data acquisition short section, 12-semi-submersible drilling platform, 13-well killing fluid injection pipeline A, 14-valve A, 15-well killing fluid injection pump A, 16-signal actuator A, 17-well killing fluid injection pipeline B, 18-valve B, 19-well killing fluid injection pump B, 20-signal actuator B, 21-signal actuator C, 22-computer processing center, 23-wellhead vent valve. DETAILED DESCRIPTION

[0058] In order to enable those skilled in the art to better understand the technical solutions in this specification, the technical solutions in the embodiments of the present invention are clearly and completely described below in conjunction with the drawings in the implementation of this specification, but are not limited to this. Anything not fully described in the present invention shall be based on the conventional technology in the art.

[0059] Example 1

[0060] A deepwater drilling blowout emergency treatment device, such as Figure 1 As shown, it includes a downhole throttling plugging device, a platform well-killing fluid injection device and a processing control device;

[0061] The downhole throttling plugging device includes a casing 6, a downhole throttling short section 7 and a drill pipe 4; a semi-submersible drilling platform 12 is arranged at the wellhead, the drill pipe 4 is located in the casing 6, a drill bit 3 is arranged at the bottom of the drill pipe 4, the drilling fluid / well-killing fluid in the drill pipe 4 flows from the wellhead to the bottom of the well, the annulus is a channel for the fluid to flow from the bottom of the well to the wellhead, and the annulus includes the annulus between the drill pipe and the casing and the annulus between the drill pipe and the water-tight pipe 10; the downhole throttling short section 7 is installed on the casing 100 meters below the mud line, a blowout preventer 9 is arranged at the contact point between the formation 1 and the seawater 2, a cement ring 5 is arranged at the bottom of the blowout preventer 9, a throttling valve, a temperature sensor and a pressure monitoring sensor are installed on the downhole throttling short section 7, the function of the throttling valve is to reduce the flow area of ​​the annular flow channel between the drill pipe and the casing, so as to produce a throttling temperature drop effect to generate hydrates or ice to plug the wellbore after the blowout, and the function of the temperature sensor and the pressure monitoring sensor is to monitor the temperature and pressure changes at the short section;

[0062] The platform well-killing fluid injection device includes a well-killing fluid injection pipeline A13 and a well-killing fluid injection pipeline B17, a valve A14, a valve B18, a well-killing fluid injection pump A15 and a well-killing fluid injection pump B19; the well-killing fluid injection pipeline A13 is connected to the drill pipe 4, and the valve A14 and the well-killing fluid injection pump A15 are connected to the well-killing fluid injection pipeline A13 in sequence, so as to provide a flow channel for injecting well-killing fluid into the bottom of the well through the drill pipe 4; the well-killing fluid injection pipeline B17 is connected to the water-proof pipe 10, and the water-proof pipe 10 is communicated with the casing 6, and the valve B18 and the well-killing fluid injection pump B19 are connected to the well-killing fluid injection pipeline B17 in sequence, so as to provide a flow channel for injecting well-killing fluid into the bottom of the well through the annulus;

[0063] The processing and control device comprises a wellhead data acquisition subsection 11, a signal actuator A 16, a signal actuator B 20, a signal actuator C 21 and a computer processing center 22. The wellhead data acquisition subsection 11 is equipped with a temperature sensor, a pressure monitoring sensor and a flow sensor. The signal actuator A 16 and the signal actuator B 20 are respectively connected to the well-killing fluid injection pump A 15 and the well-killing fluid injection pump B 19 to receive the well-killing fluid injection signal from the computer processing center to realize the dynamic injection and control of the well-killing fluid; the downhole throttling subsection 7 is connected to the signal actuator C 21 through the data transmission optical fiber 8; the wellhead data acquisition subsection 11, the signal actuator A 16, the signal actuator B 20, the signal actuator C 21 and the downhole throttling subsection 7 are all connected to the computer processing center 22 for signal connection;

[0064] The computer processing center 22 receives the data detected by the downhole throttling sub 7 and the wellhead data acquisition sub 11, and transmits the control signal to the signal actuator A 16, the signal actuator B 20 and the signal actuator C 21 in real time, which are used to control the well killing fluid injection pump A 15, the well killing fluid injection pump B19 and the throttle valve of the downhole throttling sub 7 respectively.

[0065] A wellhead vent valve 23 is provided on the well-killing fluid injection pipeline B17.

[0066] Example 2

[0067] A deepwater drilling blowout emergency treatment method is implemented by the deepwater drilling blowout emergency treatment device of embodiment 1, wherein temperature, pressure sensors and flow meters installed at the downhole throttling nipple and the wellhead collect temperature, pressure and flow data; different data collections are connected to a computer through a transmission optical cable, and the collected data are transmitted to an emergency treatment center in real time; the treatment center performs real-time automatic analysis and expert discussion based on the collected data, and then controls the reduction of the throttling valve opening on the downhole nipple to generate a throttling pressure drop to block the annulus; then, the power of the well-killing fluid injection pump group on the platform is controlled to fill the upper part of the downhole nipple with well-killing fluid, and while slowly opening the throttling valve on the downhole nipple to release gas, well-killing fluid is injected into the bottom of the well, thereby realizing efficient treatment of deepwater drilling blowout.

[0068] The specific steps include:

[0069] (1) Post-blowout formation pressure assessment and kill fluid density design

[0070] According to the monitoring data (flow rate, pressure, etc.) of the short section of the wellhead data acquisition after the blowout, the actual formation pressure is inverted by combining the wellbore multiphase flow theory and model, and the density of the well killing fluid is designed, thereby laying a theoretical foundation for the subsequent well killing treatment;

[0071] (2) Throttling, cooling and plugging after blowout

[0072] After the blowout, the well-killing fluid is injected into the drill pipe 4 and enters the annulus between the drill pipe and the casing through the drill bit. The throttling and cooling effect is generated by gradually reducing the opening of the throttle valve on the downhole throttling short sub 7, thereby generating hydrates or ice to block the wellbore. At the same time, the temperature and pressure changes at the downhole throttling short sub are monitored in real time by installing a temperature and pressure monitoring sensor on the downhole throttling short sub, and then the blocking situation is analyzed. When the pressure increases to a stable value and remains unchanged, it means that the blocking is successful;

[0073] (3) Balance pressure of wellbore injection fluid

[0074] When the annulus is successfully plugged, high-density well-killing fluid is squeezed into the annulus at the wellhead, so that the gravity of the well-killing fluid in the annulus and the plugging effect of the throttle valve can coordinately stabilize the high-pressure fluid produced by the formation;

[0075] (4) Slowly open the valve to release the gas

[0076] The gas below the throttle valve is released by slowly opening the throttle valve on the downhole throttle nipple 7, and the pressure loss of the released gas is supplemented by injecting well killing fluid into the annulus through the drill pipe 4 via the drill bit 3, until all the gas below the downhole throttle nipple is discharged, indicating that the blowout treatment is successful.

[0077] Example 3

[0078] A deepwater drilling blowout emergency treatment method, as described in Example 2, except that in step (1), a wellhead data acquisition sub 11 is installed on the casing 6 of the wellhead to monitor wellhead temperature, pressure, flow rate and other data in real time, and the bottom hole pressure and formation pressure are calculated and inferred based on the monitored wellhead temperature, pressure and flow rate after the blowout;

[0079] During the blowout process, the wellbore flow is considered as a one-dimensional, stable problem, and the pressure gradient equation in the wellbore can be obtained:

[0080]

[0081] Where p is the fluid pressure in the wellbore, MPa; z is the well depth, MPa; ρ f is the fluid density, kg / m 3 ; g is the acceleration due to gravity, m·s -2 ; f is the friction coefficient of fluid flow in the wellbore, dimensionless; v is the fluid velocity, m·s -1 ; D is the inner diameter of the wellbore, m;

[0082] By dividing the entire wellbore into n parts, the bottom hole flow pressure is calculated by integrating each part in turn using formula (1); on this basis, the formation pressure can be obtained by substituting the relevant data obtained from field monitoring into the gas production binomial equation. The formation pressure after the blowout can be predicted by the gas production binomial equation of formula (2):

[0083]

[0084] Where P f is the formation pressure, MPa; P wf is the bottom hole flow pressure when blowout occurs, MPa; Q is the mass flow rate of blowout fluid, kg·s -1 ; A is the Darcy flow coefficient; B is the non-Darcy flow coefficient, where the calculation formulas for A and B are as follows:

[0085]

[0086]

[0087] Where T is the fluid temperature, °C; is the average gas viscosity of natural gas, mPa·s; is the average deviation coefficient of natural gas, dimensionless; r e is the formation boundary radius, m; r w is the wellbore radius, m, r w =D / 2; K is the effective permeability of the gas layer, μm 2; h is the effective thickness of the air layer, m; S is the skin coefficient, dimensionless, S = ln(r w / r c ), where r c is the conversion radius, m; β is the coefficient describing the turbulence effect of porous media, called the velocity coefficient, m -1 , β=7.664×10 10 / K 1.5 ; γ g is the relative density of natural gas, generally between 0.5 and 0.7;

[0088] After predicting the formation pressure after the blowout, the density of the well killing fluid is designed according to the blowout well killing theory:

[0089]

[0090] In the formula, ρ k is the density of the well killing fluid, kg / m 3 ; H is the vertical depth of the well, m;

[0091] After the density of the killing fluid is determined, the designed killing fluid is injected into the bottom of the well with the maximum displacement of the killing fluid injection pump A. The killing fluid enters the annulus through the drill pipe and the drill bit. The killing fluid flows toward the wellhead under the carrying effect of the high-pressure fluid produced by the formation. During the flow, the bottom hole pressure is increased by gravity and friction, thereby reducing the blowout volume of the formation fluid.

[0092] Example 4

[0093] A deepwater drilling blowout emergency treatment method, as described in Example 3, except that, in step (2), the deepwater drilling area near the seabed has a low temperature and high pressure environment, and in order to make the wellbore annulus throttling point more easily meet the temperature and pressure conditions for hydrate formation, a downhole throttling nipple is installed on the casing 100 meters below the mud line, and a throttling valve, a temperature and pressure monitoring sensor are installed on the downhole throttling nipple to monitor the temperature and pressure changes at the nipple in real time;

[0094] After a blowout occurs, a large amount of gas produced by the formation flows at high speed in the annulus. Since the well-killing fluid that enters the annulus through the drill bit contains the water required for hydrate formation and freezing, it can provide a basis for throttling, cooling and plugging. Therefore, as long as the temperature and pressure conditions for hydrate formation are met, hydrate formation can occur, thereby achieving effective plugging of the blowout.

[0095] After a blowout occurs during deepwater drilling, the throttle valve control signal is transmitted to the downhole throttle nipple through the signal transmission optical fiber, and the throttle valve opening on the downhole throttle nipple is gradually reduced to produce a throttling cooling effect. According to the throttle valve opening, the throttling temperature drop △T can be calculated by the following formula:

[0096]

[0097] In the formula, μ J；T is the Joule-Thomson coefficient, K / Pa; △T is the throttling temperature drop, K; Δp is the throttling pressure drop, Pa; H is the enthalpy of the gas, J / Kmol;

[0098] Joule-Thomson coefficient μ J；T The calculation method is as follows:

[0099]

[0100] Where ρ is the molar density of the produced fluid, Kmol / m 3 ; C p is the specific heat capacity at constant pressure, J / (kg·K); R is the gas constant, 8.314 J / (mol.K); C1, C2, C3, C4, a, b, d, α are the intermediate parameters for calculation. For the specific calculation, please refer to the reference (Guo Tianmin. Multivariate Gas-Liquid Equilibrium and Distillation. Petroleum Industry Press, 2002);

[0101] When the fluid temperature T at the throttle valve drops to the hydrate phase equilibrium temperature T due to the throttling effect e When the following <T e , hydrate formation will occur; when the fluid temperature T at the throttle valve drops below the freezing point due to the throttling effect, that is, T<0, freezing will occur; the temperature and pressure monitoring sensor installed on the downhole throttling nipple is used to monitor the temperature and pressure changes at the nipple in real time, and then analyze the plugging situation; when it is found that the fluid temperature at the downhole throttling nipple drops, the pressure increases, and the wellhead flow decreases, it means that hydrate formation or freezing has occurred. If it is found that the current throttle valve opening cannot further complete the blowout plugging, it means that the throttle valve opening needs to be further reduced until complete plugging is achieved, that is, the fluid flow monitored at the wellhead drops to zero and the pressure increases to a stable value and remains unchanged.

[0102] Example 5

[0103] A deepwater drilling blowout emergency treatment method, as described in Example 4, except that in step (3), when the annulus is successfully blocked, the high-pressure gas above the blockage will gradually be discharged from the wellhead due to the pressure difference; when the gas pressure in the annulus is exhausted, a well-killing fluid with a density of ρ is squeezed into the annulus at the wellhead through a well-killing fluid injection pump B. kThe well-killing fluid is injected into the annulus until the annulus above the blockage is filled with the well-killing fluid. When the well-killing fluid is squeezed into the annulus, as the well-killing fluid in the annulus increases, the residual gas in the annulus will be compressed, which will cause the annulus casing pressure to increase. In this case, every time the annulus casing pressure increases to 1MPa, it is necessary to open the wellhead vent valve to release the high-pressure gas accumulated at the wellhead. When the annulus above the blockage is filled with well-killing fluid, the gravity of the well-killing fluid in the annulus and the plugging effect of the throttle valve will work together to stabilize the high-pressure fluid produced by the formation. The gravity pressure of the well-killing fluid in the annulus above the blockage can be calculated by the following formula:

[0104] P g ≥ρ k HkDJ d (8)

[0105] Where P g H is the gravity pressure of the well-killing fluid above the downhole throttling nipple, MPa; d is the vertical depth of the underground throttling short joint, m.

[0106] Example 6

[0107] A deepwater drilling blowout emergency treatment method, as described in Example 5, except that, in step (4), the throttle valve on the downhole throttle nipple is slowly opened to release the gas in the lower part of the downhole throttle nipple, and the temperature and pressure changes dP at the location are monitored in real time by the temperature sensor and pressure monitoring sensor on the downhole throttle nipple; at the same time, a fluid with a density of ρ is synchronously injected into the annulus through the drill pipe via the drill bit. k The killing fluid is then used to compensate for the pressure lost by the released gas. The amount of killing fluid that needs to be injected in the same time as the gas below the downhole throttling nipple is:

[0108]

[0109] Where V k is the amount of injection of well-killing fluid, m 2 ; dP is the pressure change of gas released from the lower part of the downhole throttling short joint, Pa; r w is the wellbore radius, m; r n is the outer diameter of the drill pipe, m.

[0110] At the same time, the sensor on the downhole throttling nipple transmits the monitored temperature and pressure changes to the data processing center in real time. During the release of the gas in the lower part of the downhole throttling nipple and the simultaneous injection of well-killing fluid into the annulus, the pressure fluctuation at the downhole throttling nipple should be kept within 0.3MPa, thereby preventing more formation fluid from entering the wellbore; in the process of releasing the gas in the lower part of the nipple, as the gas enters the upper annulus of the downhole throttling nipple, the wellhead annulus casing pressure will gradually increase. Whenever the annulus casing pressure increases to 1MPa, it is necessary to open the wellhead vent valve to release the high-pressure gas accumulated at the wellhead; in addition, if it is found that the well-killing fluid level in the annulus drops, the well-killing fluid should be squeezed into the annulus through the wellhead in time to maintain the liquid level in the annulus until all the gas in the lower part of the downhole throttling nipple is discharged, indicating that the blowout treatment is successful.

[0111] The above is a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A deepwater drilling blowout emergency treatment method, characterized in that: This is achieved through a deepwater drilling blowout emergency treatment device, which includes a downhole throttling plugging device, a platform well-killing fluid injection device, and a treatment control device; The downhole throttling plugging device includes a casing, a downhole throttling nipple and a drill pipe; the drill pipe is located in the casing, a drill bit is provided at the bottom of the drill pipe, the drilling fluid / well-killing fluid in the drill pipe flows from the wellhead to the bottom of the well, the annulus is a channel for the fluid to flow from the bottom of the well to the wellhead, and the annulus includes the annulus between the drill pipe and the casing and the annulus between the drill pipe and the water-tight pipe; the downhole throttling nipple is installed on the casing 100 meters below the mud line, and a throttling valve, a temperature sensor and a pressure monitoring sensor are installed on the downhole throttling nipple; The platform well-killing fluid injection device comprises a well-killing fluid injection pipeline A and a well-killing fluid injection pipeline B, a valve A, a valve B, a well-killing fluid injection pump A and a well-killing fluid injection pump B; the well-killing fluid injection pipeline A is connected to the drill pipe, the well-killing fluid injection pipeline A is connected with the valve A and the well-killing fluid injection pump A in sequence, so as to provide a flow channel for injecting well-killing fluid into the bottom of the well through the drill pipe; the well-killing fluid injection pipeline B is connected with the water-rising pipe, the water-rising pipe and the casing are in communication, the well-killing fluid injection pipeline B is connected with the valve B and the well-killing fluid injection pump B in sequence, so as to provide a flow channel for injecting well-killing fluid into the bottom of the well through the annulus; The processing and control device comprises a wellhead data acquisition subsection, a signal actuator A, a signal actuator B, a signal actuator C and a computer processing center. The wellhead data acquisition subsection is equipped with a temperature sensor, a pressure monitoring sensor and a flow sensor. The signal actuator A and the signal actuator B are respectively connected to the well-killing fluid injection pump A and the well-killing fluid injection pump B; the downhole throttling subsection is connected to the signal actuator C through a data transmission optical fiber; the wellhead data acquisition subsection, the signal actuator A, the signal actuator B, the signal actuator C and the downhole throttling subsection are all connected to the computer processing center by signal; The computer processing center receives data detected by the downhole throttling sub and the wellhead data acquisition sub, and transmits control signals to the signal actuator A, the signal actuator B and the signal actuator C in real time, which are used to control the well killing fluid injection pump A, the well killing fluid injection pump B and the throttle valve of the downhole throttling sub respectively; A deepwater drilling blowout emergency treatment method comprises the following steps: (1) Post-blowout formation pressure assessment and killing fluid density design Based on the monitoring data of the wellhead data acquisition sub after the blowout, the actual formation pressure is inverted in combination with the wellbore multiphase flow theory and model, and the killing fluid density is designed; (2) Throttling, cooling and plugging after blowout After the blowout, the well-killing fluid is injected into the drill pipe and enters the annulus between the drill pipe and the casing through the drill bit. The throttling and cooling effect is generated by reducing the opening of the throttling valve on the downhole throttling nipple, thereby generating hydrates or ice to plug the wellbore. At the same time, the temperature and pressure monitoring sensor installed on the downhole throttling nipple is used to monitor the temperature and pressure changes at the downhole throttling nipple in real time, and then the plugging situation is analyzed. When the pressure increases to a stable value and remains unchanged, it means that the plugging is successful; (3) Balance pressure of wellbore injection fluid When the annulus is successfully plugged, high-density well-killing fluid is squeezed into the annulus at the wellhead, so that the gravity of the well-killing fluid in the annulus and the plugging effect of the throttle valve can coordinately stabilize the high-pressure fluid produced by the formation; (4) Open the valve to release the gas The gas below the throttle valve is released by opening the throttle valve on the downhole throttle nipple. At the same time, the well killing fluid is injected into the annulus through the drill pipe through the drill bit to replenish the pressure lost by the released gas until all the gas below the downhole throttle nipple is discharged, indicating that the blowout treatment is successful. In step (2), after a blowout occurs, the gas produced by the formation flows in the annulus. Since the well-killing fluid that enters the annulus through the drill bit contains the water required for hydrate formation and freezing, it provides a basis for throttling, cooling and plugging. Therefore, as long as the temperature and pressure conditions for hydrate formation are met, hydrate formation can occur, thereby achieving effective plugging of the blowout. After a blowout occurs during deepwater drilling, the throttle valve control signal is transmitted to the downhole throttle nipple through the signal transmission optical fiber, and the throttle valve opening on the downhole throttle nipple is gradually reduced to produce a throttling cooling effect. According to the throttle valve opening, the throttling temperature drop △T is calculated by the following formula: In the formula, μ J；T is the Joule-Thomson coefficient, K / Pa; △T is the throttling temperature drop, K; Δp is the throttling pressure drop, Pa; H is the enthalpy of the gas, J / Kmol; Joule-Thomson coefficient μ J；T The calculation method is as follows: Where ρ is the molar density of the produced fluid, Kmol / m 3 ; C p is the specific heat capacity at constant pressure, J / (kg·K); R is the gas constant, 8.314J / (mol.K); C1, C2, C3, C4, a, b, d, α are the intermediate parameters of calculation; When the fluid temperature T at the throttle valve drops to the hydrate phase equilibrium temperature T due to the throttling effect e When the following <T e , hydrate formation will occur; when the fluid temperature T at the throttle valve drops below the freezing point due to the throttling effect, that is, T<0, freezing will occur; the temperature and pressure monitoring sensor installed on the downhole throttling nipple is used to monitor the temperature and pressure changes at the nipple in real time, and then analyze the plugging situation; when it is found that the fluid temperature at the downhole throttling nipple drops, the pressure increases, and the wellhead flow rate decreases, it means that hydrate formation or freezing has occurred; if it is found that the current throttle valve opening cannot further complete the blowout plugging, it means that the throttle valve opening needs to be further reduced until complete plugging is achieved, that is, the fluid flow monitored at the wellhead drops to zero and the pressure increases to a stable value and remains unchanged; In step (3), after the annulus is successfully plugged, the high-pressure gas above the plugging point will gradually be discharged from the wellhead due to the pressure difference; when the gas pressure in the annulus is exhausted, a well-killing fluid with a density of ρk is squeezed into the annulus at the wellhead through the well-killing fluid injection pump B until the annulus above the plugging point is filled with the well-killing fluid; when squeezing the well-killing fluid into the annulus, as the well-killing fluid in the annulus increases, the residual gas in the annulus will be compressed, which will cause the annulus casing pressure to increase; in this case, whenever the annulus casing pressure increases to 1MPa, it is necessary to open the wellhead vent valve to release the high-pressure gas accumulated at the wellhead; when the annulus above the plugging point is filled with the well-killing fluid, the gravity of the well-killing fluid in the annulus and the plugging effect of the throttle valve coordinately stabilize the high-pressure fluid produced by the formation; The gravity pressure of the wellbore pressure fluid in the upper annulus of the blockage is calculated by the following formula: P≥PkgHa(8) Where, Pg is the gravity pressure of the well-killing fluid above the downhole throttling nipple, MPa; Hd is the vertical depth of the downhole throttling nipple, m; In step (4), the throttle valve on the downhole throttle nipple is slowly opened to release the gas at the bottom of the downhole throttle nipple, and the temperature and pressure changes dP at the location are monitored in real time by the temperature sensor and pressure monitoring sensor on the downhole throttle nipple; at the same time, a well-killing fluid with a density of ρk is synchronously injected into the annulus through the drill pipe via the drill bit to supplement the pressure lost by the released gas; the amount of well-killing fluid that needs to be injected in the same time as the gas at the bottom of the downhole throttle nipple is released is: Where V k is the amount of injection of well-killing fluid, m 2 ; dP is the pressure change of gas released from the lower part of the downhole throttling short joint, Pa; r w is the wellbore radius, m; r n is the outer diameter of the drill pipe, m; At the same time, the sensor on the downhole throttling nipple transmits the monitored temperature and pressure changes to the data processing center in real time. During the release of the gas in the lower part of the downhole throttling nipple and the simultaneous injection of well-killing fluid into the annulus, the pressure fluctuation at the downhole throttling nipple should be kept within 0.3MPa, thereby preventing more formation fluid from entering the wellbore; in the process of releasing the gas in the lower part of the nipple, as the gas enters the upper annulus of the downhole throttling nipple, the wellhead annulus casing pressure will gradually increase. Whenever the annulus casing pressure increases to 1MPa, it is necessary to open the wellhead vent valve to release the high-pressure gas accumulated at the wellhead; in addition, if it is found that the well-killing fluid level in the annulus drops, well-killing fluid is squeezed into the annulus through the wellhead in time to maintain the liquid level in the annulus until all the gas in the lower part of the downhole throttling nipple is discharged, indicating that the blowout treatment is successful.

2. The deepwater drilling blowout emergency treatment method according to claim 1 is characterized in that: The well-killing fluid injection pipeline B is provided with a wellhead vent valve.

3. The deepwater drilling blowout emergency treatment method according to claim 2 is characterized in that: In step (1), a wellhead data acquisition sub is installed on the casing of the wellhead to monitor wellhead temperature, pressure, flow rate and other data in real time, and the bottom hole pressure and formation pressure are calculated and inferred based on the monitored wellhead temperature, pressure and flow rate after the blowout; During the blowout process, the wellbore flow is considered as a one-dimensional, stable problem, and the pressure gradient equation in the wellbore can be obtained: Where p is the fluid pressure in the wellbore, MPa; z is the well depth, MPa; ρ f is the fluid density, kg / m 3 ; g is the acceleration due to gravity, m·s -2 ; f is the friction coefficient of fluid flow in the wellbore, dimensionless; v is the fluid velocity, m·s -1 ; D is the inner diameter of the wellbore, m; The bottom hole flow pressure is obtained by dividing the entire wellbore into n parts and integrating each part in turn using formula (1). The formation pressure after the blowout is predicted by the gas production binomial equation of formula (2): Where P f is the formation pressure, MPa; P wf is the bottom hole flow pressure when blowout occurs, MPa; Q is the mass flow rate of blowout fluid, kg·s -1 ; A is the Darcy flow coefficient; B is the non-Darcy flow coefficient, where the calculation formulas for A and B are as follows: Where T is the fluid temperature, °C; is the average gas viscosity of natural gas, mPa·s; is the average deviation coefficient of natural gas, dimensionless; r e is the formation boundary radius, m; r w is the wellbore radius, m, r w =D / 2; K is the effective permeability of the gas layer, μm 2 ; h is the effective thickness of the air layer, m; S is the skin coefficient, dimensionless, S = ln(r w / r c ), where r c is the converted radius, m; β is the velocity coefficient, m -1 ; γ g is the relative density of natural gas; After predicting the formation pressure after the blowout, the density of the well killing fluid is designed according to the blowout well killing theory: In the formula, ρ k is the density of the well-killing fluid, kg / m 3 ; H is the vertical depth of the well, m; After the density of the killing fluid is determined, the designed killing fluid is injected into the bottom of the well with the maximum displacement of the killing fluid injection pump A. The killing fluid enters the annulus through the drill pipe and the drill bit. The killing fluid flows toward the wellhead under the carrying effect of the high-pressure fluid produced by the formation. During the flow, the bottom hole pressure is increased by gravity and friction, thereby reducing the blowout volume of the formation fluid.

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