Method for calculating the volume of the drilling fluid invasion based on the control of the oil and gas upward migration speed being zero

Abstract

The present application relates to oil and gas development well control technical field, especially relates to a kind of based on the drilling fluid hoisting irrigation volume calculation method for controlling oil and gas upflow speed zero.It includes the following steps: after finding well leakage loss returns, fully circulating drilling fluid, master oil and gas upflow speed;Calculate the density distribution of oil and gas, drilling fluid in wellbore;Calculate the critical leakage speed that oil and gas no longer upflow in the process of stopping drilling static;Determine the hoisting irrigation volume of drilling fluid during static, obtain the drilling fluid speed during tripping and the change of drilling fluid viscosity during tripping;Calculate the migration speed of bubble after being disturbed during tripping;Get critical leakage speed and drilling fluid hoisting irrigation volume.The beneficial effects of the present application are: the oil and gas upflow speed obtained by field measurement, the oil and gas upflow speed calculation model in the process of tripping is established, the critical leakage speed that controls oil and gas upflow speed not more than zero is determined, the hoisting irrigation volume of drilling fluid in the process of drilling string tripping is accurately calculated, so as to ensure operation safety.

Description

Technical Field

[0001] This invention relates to the field of well control technology for oil and gas development, and in particular to a method for calculating the volume of drilling fluid used for well filling based on controlling the upward flow rate of oil and gas to zero. Background Technology

[0002] As oil and gas development expands into deeper areas and the deep sea, the geological conditions encountered during drilling and completion are becoming increasingly complex. Drilling fluid injection is a crucial method for achieving pressure balance between the wellbore and formation by intermittently and continuously injecting drilling fluid into the wellbore, thereby slowing down oil and gas upwelling and reducing risks such as blowouts and spills. Drilling fluid injection technology has demonstrated significant application value in tripping, completion, and plugging operations. However, the implementation of drilling fluid injection often relies on the experience of field engineers, leading to insufficient or excessive injection. Existing technicians have established a functional relationship between annular fluid level height and leakage rate using fluid level monitoring and proposed a safe time calculation model for drilling fluid injection. However, this method does not consider the impact of oil and gas upwelling rate, which can easily cause oil and gas to migrate to the wellhead, thus increasing well control risks.

[0003] In addition, Chinese patent application number CN202311496107.5, entitled "Calculation Method of Mud Supplementation Volume Based on Annular Fluid Level Monitoring," includes the following steps: establishing a model of the relationship between the leakage rate and fluid level during drilling fluid loss, predicting the location of the leakage equilibrium point, and calculating the leakage pressure difference at each measuring point; establishing a model of the relationship between the leakage pressure difference and the leakage rate, and establishing a leakage dynamic function; calculating the fluid level height required to compensate for the drill string shortage; calculating the fluid level height required to balance the formation high pressure and determining the safe fluid level height; and calculating the time from the current fluid level to the safe fluid level to obtain the mud suspension volume. This invention also utilizes fluid level monitoring technology, observing the fluid level drop rate to fit a model of the relationship between the leakage rate and fluid level during drilling fluid loss, determining whether drilling fluid suspension is needed and the suspension volume. However, it still has the following shortcomings: the aforementioned invention application does not consider the oil and gas surge rate during the suspension and tripping process. If this factor is not considered during tripping, it can easily lead to oil and gas surging to the wellhead, causing risks such as blowouts. Summary of the Invention

[0004] The purpose of this invention is to address the aforementioned deficiencies in existing technologies by providing a method for calculating drilling fluid loading volume based on controlling the oil and gas upward velocity to zero. This method utilizes field measurements of the oil and gas upward velocity, combined with wellbore structure and drill string assembly, to calculate the influence of tripping speed on the oil and gas upward velocity. A calculation model for the oil and gas upward velocity during tripping is established, determining the critical leakage rate to ensure the oil and gas upward velocity is not greater than zero. This allows for precise calculation of the drilling fluid loading volume during drill string tripping, thereby ensuring operational safety.

[0005] The present invention discloses a method for calculating drilling fluid injection volume based on controlling the upward velocity of oil and gas to zero. The technical solution includes the following steps:

[0006] 1. After discovering well leakage and return, fully circulate the drilling fluid and monitor the rate of oil and gas surge.

[0007] II. Calculate the density distribution of oil, gas, and drilling fluid in the wellbore based on the temperature and pressure distribution in the wellbore;

[0008] (1) The distribution of wellbore temperature after drilling stops is equivalent to the formation temperature. By selecting a point every 100 meters, the distribution of wellbore pressure and drilling fluid density is calculated using the superposition method.

[0009] (2) Calculate the density of natural gas downhole based on the temperature and pressure field;

[0010] III. Calculate the critical leakage rate at which oil and gas no longer rise during the shutdown and stagnant process, taking into account the wellbore size and drill string assembly;

[0011] IV. Determining the drilling fluid loading volume during the static period based on the critical leakage rate:

[0012] ,

[0013] in: V The volume of drilling fluid being poured in is in meters. 3 ; t For time, s;

[0014] 5. After a period of time, monitor the liquid level and determine whether the irrigation volume is reasonable based on the changes in the liquid level.

[0015] (1) When the liquid level is equal to the previous liquid level, it means that the drilling fluid filling volume meets the filling requirements during the static period;

[0016] (2) When the fluid level is higher than the previous fluid level, reduce the amount of drilling fluid poured in; when the fluid level is lower than the previous fluid level, increase the amount of drilling fluid poured in.

[0017] (3) Once the liquid level has stabilized, prepare to pull up the drill string;

[0018] VI. Determine the size of the air bubbles in the wellbore based on the upward velocity of oil and gas;

[0019] 7. Based on the wellbore size and drill string assembly, the drilling fluid velocity and viscosity changes during the tripping process are obtained;

[0020] 8. Calculate the migration speed of the air bubble after it is disturbed during the drilling process;

[0021] The rising velocity of bubbles during tripping in drilling fluid is obtained based on the calculation method for bubble migration velocity in drilling fluid. The actual migration velocity of bubbles during tripping can be calculated using the following formula:

[0022] ,

[0023] in: The actual upward velocity of the bubble is expressed in m / s; v g The upward velocity of the bubble under the influence of drilling fluctuations, in m / s; C 0 is the distribution coefficient;

[0024] 9. Based on the fundamental principle that the drilling fluid descent rate is greater than the oil and gas upflow rate, the critical leakage rate and drilling fluid loading volume are obtained.

[0025] 10. Calculate the required leakage pressure differential based on the functional relationship between leakage pressure differential and leakage velocity:

[0026] ,

[0027] Where: Δ p Leakage pressure differential, MPa; a , b The coefficient for calculating leakage pressure difference;

[0028] 11. For every three drill strings or one drill collar drilled, liquid level monitoring technology should be used to monitor the liquid level height at this time and compare it with the liquid level. The subsequent operation procedure should be determined based on the change in liquid level height.

[0029] (1) When the fluid level is equal to the previous fluid level, it means that the drilling fluid grouting volume meets the grouting requirements during the tripping period. At this time, continue grouting according to this volume.

[0030] (2) When the liquid level is higher than the previous liquid level, it is necessary to determine whether the higher liquid level is caused by excessive drilling fluid injection or by insufficient grouting volume leading to increased overflow. The judgment method is to observe statically. If the liquid level drops, it indicates that the drilling fluid injection volume is excessive.

[0031] (3) When the fluid level is lower than the previous fluid level, it indicates that the drilling fluid injection volume is insufficient and it is necessary to increase the drilling fluid injection volume.

[0032] 12. After reaching the target well section, proceed with other operations.

[0033] Preferably, the specific method in step three above includes the following:

[0034] (1) The relationship between the drilling fluid descent rate and the leakage rate during the static period is shown in the following formula:

[0035] ,

[0036] in: v msThe drilling fluid descent velocity during the stationary period, in m / s; v loss Let m be the leakage rate. 3 / h; D w The diameter of the wellbore is in meters (m). D d Drill pipe diameter, in meters (m);

[0037] (2) The critical leakage rate was calculated based on the principle of balancing the drilling fluid descent rate and the oil and gas upflow rate;

[0038] ,

[0039] in: v gm The velocity of the oil and gas rises is expressed in m / s.

[0040] Preferably, the specific steps in step six above include the following:

[0041] (1) The calculation method for the transport velocity of a single bubble in a static fluid is as follows:

[0042] ,

[0043] in: d The diameter of the oil droplet / bubble is in meters (m). v is the upward velocity of a single bubble in a static liquid column, in m / s; ρ g The density of the gas is in g / cm³. 3 ; ρ m Density of drilling fluid at the bottom of the well, in g / cm³ 3 ; C d The drag coefficient is dimensionless.

[0044] (2) Due to the mutual influence between bubbles, the corrected bubble migration velocity in the drilling fluid is shown in the following formula:

[0045] ,

[0046] Where: α is the gas content; This is a correction factor;

[0047] (3) Where C d The drag coefficient can be calculated using the following formula:

[0048] ,

[0049] Where: Re is the Reynolds number;

[0050] (4) The Reynolds number for the transport of bubbles in a static liquid column is calculated using the following formula:

[0051] ,

[0052] in: K The viscosity coefficient is Pa·s^n;

[0053] (5) The bubble size is calculated by combining the oil and gas upwelling velocity measured on site with the above formula.

[0054] Preferably, the specific steps in step seven above include the following:

[0055] (1) During the tripping process, drilling fluid will replenish the original drill string position, and the faster the tripping speed, the faster the drilling fluid replenishment speed; the relationship between the drilling fluid annular velocity and the tripping speed is shown in the following formula:

[0056] ,

[0057] in: v m The annular velocity is m / s; v q The drilling speed is measured in m / s.

[0058] (2) Due to the shear dilution effect of drilling fluid, the viscosity of drilling fluid is calculated using the following formula as it flows:

[0059] ,

[0060] ,

[0061] Where: γ is the shear rate, s -1 ; μ p ρ represents the drilling fluid viscosity, Pa·s.

[0062] Preferably, the specific steps in step nine above include the following:

[0063] (1) The calculation method for the drilling fluid descent rate during tripping is as follows:

[0064] ,

[0065] in: v mu The drilling fluid descent rate during tripping out of the well is expressed in m / s.

[0066] (2) Based on the fundamental principle that the drilling fluid descent rate is greater than the oil and gas upflow rate, a method for calculating the critical leakage rate required for the drilling fluid is derived. When the leakage rate is greater than 10m... 3When the drilling speed is reduced to 0.1 m / s, the leakage rate is recalculated. Even when the speed is reduced to 0.1 m / s, the leakage rate is still greater than 10 m / s. 3 / h, start drilling at a speed of 0.1m / s:

[0067] ;

[0068] (3) The ratio K between the volume of drilling fluid injected and the volume of drill string pulled out B The calculation method is as follows:

[0069] ,

[0070] in: L The height of the drill string to be pulled out is in meters (m). V 钻柱 This represents the drill string volume; K B This represents the ratio between the volume of drilling fluid injected and the volume of the drill string pulled out.

[0071] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0072] This invention addresses the well control risks caused by excessive or insufficient drilling fluid volume during tripping after well loss of circulation. By measuring the oil and gas upwelling velocity before tripping and combining it with parameters such as well structure, drill string assembly, and drilling fluid properties, the invention calculates the variation law of oil and gas upwelling velocity during tripping. By controlling the loss of circulation velocity, the invention enables the suspension or reversal of air bubbles downhole, achieving accurate calculation of drilling fluid volume and thus ensuring operational safety.

[0073] In addition, the critical leakage rate proposed in this invention is calculated for controllable downhole micro-leakage. The safe leakage rate of drilling fluid under different tripping speed conditions is calculated. Under this leakage rate condition, the air bubbles are suspended or turned in the wellbore, thereby calculating the volume of drilling fluid poured during tripping. The downhole is kept in a micro-leakage state during the tripping operation, and the drilling is safely and quickly tripped to the target area. Attached Figure Description

[0074] Figure 1 This is a layout diagram of the hoisting and drilling system of the present invention;

[0075] Figure 2 The required drilling fluid volume and corresponding leakage rate under different tripping speeds for a certain well;

[0076] Figure 3 The required drilling fluid injection volume and corresponding leakage rate are given for a certain well under different oil and gas upwelling rates.

[0077] In the diagram: 1. Drilling fluid tank; 2. Drilling pump; 3. Wellhead blowout preventer; 4. Fluid level monitoring system. Detailed Implementation

[0078] The preferred embodiments of the present invention will be described below with reference to the accompanying drawings. It should be understood that the preferred embodiments described herein are for illustration and explanation only and are not intended to limit the present invention.

[0079] Example 1, referring to Figure 1 The present invention mentions a drilling fluid tank 1, a drilling pump 2, a wellhead blowout preventer 3, and a fluid level monitoring system 4. The wellhead blowout preventer 3 is installed at the top of the wellbore. The drilling pump 2 and the drilling fluid tank 1 are connected to the wellhead blowout preventer 3 by pipelines. One side of the wellhead blowout preventer 3 is connected to the fluid level monitoring system 4 by a data cable.

[0080] The present invention provides a method for calculating the volume of drilling fluid injection based on controlling the upward velocity of oil and gas to zero, comprising the following steps:

[0081] 1. After discovering well leakage and return, fully circulate the drilling fluid and monitor the rate of oil and gas surge.

[0082] II. Calculate the density distribution of oil, gas, and drilling fluid in the wellbore based on the temperature and pressure distribution in the wellbore;

[0083] (1) The wellbore temperature distribution after drilling is stopped can be equivalent to the formation temperature. The wellbore pressure can be calculated by selecting a point every 100 meters and using the superposition method to obtain the wellbore pressure and drilling fluid density distribution:

[0084] ,

[0085] ,

[0086] in: ρ 0 Density of drilling fluid at the surface, in g / cm³ 3 ; ρ mi The drilling fluid density at a well depth of 100 m is given in g / cm³. 3 ; g The acceleration due to gravity is m / s². 2 ; a 1. a 2 represents the temperature coefficient; a 3 represents the pressure coefficient; a 4 represents the temperature-pressure interaction coefficient; P i The wellbore pressure at a depth of 100i meters, in MPa; T i The wellbore temperature at a depth of 100 m, in K; h n Let the depth be m;

[0087] (2) Calculate the density of natural gas downhole based on the temperature and pressure field;

[0088] ,

[0089] in: ρ g The density of the gas is in g / cm³. 3 ; The specific gravity of natural gas; Z It is the compression factor; T Temperature, K; P Pressure, MPa;

[0090] III. Calculate the critical leakage rate at which oil and gas no longer rise during the shutdown and quiescent process by combining wellbore size, drill string assembly and other relevant parameters;

[0091] (1) The relationship between the drilling fluid descent rate and the leakage rate during the static period is shown below;

[0092] ,

[0093] in: v ms The drilling fluid descent velocity during the stationary period, in m / s; v loss Let m be the leakage rate. 3 / h; D w The diameter of the wellbore is in meters (m). D d Drill pipe diameter, in meters (m);

[0094] (2) The critical leakage rate can be calculated based on the principle of balancing the drilling fluid descent rate and the oil and gas upflow rate;

[0095] ,

[0096] in: v gm The velocity of oil and gas rising upwards is expressed in m / s.

[0097] IV. Determining the drilling fluid loading volume during the static period based on the critical leakage rate:

[0098] ,

[0099] in: V The volume of drilling fluid being poured in is in meters. 3 ; t For time, s;

[0100] 5. After a period of time, monitor the liquid level and determine whether the irrigation volume is reasonable based on the changes in the liquid level.

[0101] (1) When the liquid level is equal to the previous liquid level, it means that the drilling fluid grouting volume meets the grouting requirements during the static period;

[0102] (2) When the fluid level is higher than the previous fluid level, reduce the amount of drilling fluid poured in; when the fluid level is lower than the previous fluid level, increase the amount of drilling fluid poured in.

[0103] (3) Once the liquid level has stabilized, prepare to pull up the drill string;

[0104] VI. Determine the size of the air bubbles in the wellbore based on the upward velocity of oil and gas;

[0105] (1) The calculation method for the transport velocity of a single bubble in a static fluid is as follows:

[0106] ,

[0107] in: d The diameter of the oil droplet / bubble is in meters (m). v is the upward velocity of a single bubble in a static liquid column, in m / s; ρ g The density of the gas is in g / cm³. 3 ; ρ m Density of drilling fluid at the bottom of the well, in g / cm³ 3 ; C d The drag coefficient is dimensionless.

[0108] (2) Due to the mutual influence between bubbles, the corrected bubble migration velocity in the drilling fluid is shown in the following formula:

[0109] ,

[0110] Where: α is the gas content; This is a correction factor, typically taken as 1.5-2;

[0111] (3) Where C d The drag coefficient can be calculated using the following formula:

[0112] ,

[0113] Where: Re is the Reynolds number;

[0114] (4) The Reynolds number for the transport of bubbles in a static liquid column is calculated using the following formula:

[0115] ,

[0116] in: K The viscosity coefficient is Pa·s^n;

[0117] (5) The bubble size can be calculated by combining the oil and gas upwelling velocity measured on site with the above formula;

[0118] 7. Based on the wellbore size and drill string assembly, calculate the drilling fluid velocity and the change in drilling fluid viscosity during the tripping process;

[0119] (1) During the tripping process, the drilling fluid will be rapidly replenished to the original position of the drill string, and the faster the tripping speed, the faster the drilling fluid replenishment speed; the relationship between the annular velocity of the drilling fluid and the tripping speed is shown in the following formula:

[0120] ,

[0121] in: v m The annular velocity is m / s; v q The drilling speed is measured in m / s.

[0122] (2) Due to the shear dilution effect of drilling fluid, the viscosity of drilling fluid is calculated using the following formula as it flows:

[0123] ,

[0124] ,

[0125] Where: γ is the shear rate, s -1 ; μ p The value is the drilling fluid viscosity, Pa·s;

[0126] 8. Calculate the migration speed of the air bubble after it is disturbed during the drilling process;

[0127] (1) The rising velocity of the bubbles during the tripping disturbance process is obtained according to the calculation method of the bubble migration velocity in the drilling fluid. The actual migration velocity of the bubbles during tripping can be calculated according to the following formula:

[0128] ,

[0129] in: The actual upward velocity of the bubble is expressed in m / s; v g The upward velocity of the bubble under the influence of drilling fluctuations, in m / s; C 0 is the distribution coefficient;

[0130] 9. Based on the fundamental principle that the drilling fluid descent rate is greater than the oil and gas upflow rate, the critical leakage rate and drilling fluid loading volume are calculated.

[0131] (1) The calculation method for the drilling fluid descent rate during tripping is as follows:

[0132] ,

[0133] in: v mu The drilling fluid descent rate during tripping out of the well is expressed in m / s.

[0134] (2) Based on the fundamental principle that the drilling fluid descent rate is greater than the oil and gas upflow rate, a method for calculating the critical leakage rate required for the drilling fluid is derived. When the leakage rate is greater than 10m... 3 When the drilling speed is reduced to 0.1 m / s, the leakage rate is recalculated. Even when the speed is reduced to 0.1 m / s, the leakage rate is still greater than 10 m / s. 3 / h, start drilling at a speed of 0.1m / s:

[0135] ;

[0136] (3) The ratio K between the volume of drilling fluid injected and the volume of drill string pulled out B The calculation method is as follows:

[0137] ,

[0138] in: L The height of the drill string to be pulled out is in meters (m). V 钻柱 This represents the drill string volume; K B This represents the ratio between the volume of drilling fluid injected and the volume of drill string pulled out.

[0139] 10. Calculate the required leakage pressure differential based on the functional relationship between leakage pressure differential and leakage velocity:

[0140] ,

[0141] Where: Δ p Leakage pressure differential, MPa; a , b The coefficient for calculating leakage pressure difference;

[0142] 11. For every three drill strings or one drill collar drilled, liquid level monitoring technology should be used to monitor the liquid level height and compare it with the liquid level. The subsequent operation procedure should be determined based on the change in liquid level height.

[0143] (1) When the fluid level is equal to the previous fluid level, it means that the drilling fluid grouting volume meets the grouting requirements during the tripping period. At this time, continue grouting according to this volume.

[0144] (2) When the liquid level is higher than the previous liquid level, it is necessary to determine whether the higher liquid level is caused by excessive drilling fluid injection or by insufficient grouting volume leading to increased overflow. The judgment method is to observe statically. If the liquid level drops, it indicates that the drilling fluid injection volume is excessive.

[0145] (3) When the fluid level is lower than the previous fluid level, it indicates that the drilling fluid injection volume is insufficient and it is necessary to increase the drilling fluid injection volume.

[0146] 12. After reaching the target well section, proceed with other operations.

[0147] Example 2, refer to Figure 2 and Figure 3 A well was selected with an open hole diameter of 215 mm, a casing diameter of 244.5 mm, and a drill string diameter of 127 mm. The measured oil and gas upwelling velocity was 30 m / h. Based on these simulation conditions, the variation of drilling fluid injection volume and critical leakage velocity under different tripping speeds was established, as shown in the figure. When the tripping speed is 0.1 m / s, three times the volume of drilling fluid needs to be injected into the wellbore for each drill string pulled out, while the critical leakage velocity needs to be controlled at 9.13 m / s. 3 At a certain speed ( / h), it can be ensured that oil and gas will not migrate upwards during the tripping process. Furthermore, the higher the tripping speed, the smaller the volume of drilling fluid required for injection, but the corresponding critical leakage rate must be higher. In addition, as the upward velocity of oil and gas increases, the required volume of drilling fluid increases, and the critical leakage rate also increases accordingly.

[0148] The above description is merely a partial preferred embodiment of the present invention. Any person skilled in the art can modify the above-described technical solutions or modify them into equivalent technical solutions. Therefore, any simple modifications or equivalent transformations made based on the technical solutions of the present invention fall within the scope of protection claimed by the present invention.

Claims

1. A method for calculating drilling fluid injection volume based on controlling the upward velocity of oil and gas to zero, characterized in that: Includes the following steps:

1. After discovering well leakage and return, fully circulate the drilling fluid and monitor the rate of oil and gas surge. II. Calculate the density distribution of oil, gas, and drilling fluid in the wellbore based on the temperature and pressure distribution in the wellbore; (1) The distribution of wellbore temperature after drilling stops is equivalent to the formation temperature. By selecting a point every 100 meters, the distribution of wellbore pressure and drilling fluid density is calculated using the superposition method. (2) Calculate the density of natural gas downhole based on the temperature and pressure field; III. Calculate the critical leakage rate at which oil and gas no longer rise during the shutdown and stagnant process, taking into account the wellbore size and drill string assembly; IV. Determining the drilling fluid loading volume during the static period based on the critical leakage rate: ， in: V The volume of drilling fluid being poured in is in meters. 3 ; t For time, s; 5. After a period of time, monitor the liquid level and determine whether the irrigation volume is reasonable based on the changes in the liquid level. (1) When the liquid level is equal to the previous liquid level, it means that the drilling fluid filling volume meets the filling requirements during the static period; (2) When the fluid level is higher than the previous fluid level, reduce the amount of drilling fluid poured in; when the fluid level is lower than the previous fluid level, increase the amount of drilling fluid poured in. (3) Once the liquid level has stabilized, prepare to pull up the drill string; VI. Determine the size of the air bubbles in the wellbore based on the upward velocity of oil and gas; 7. Based on the wellbore size and drill string assembly, the drilling fluid velocity and viscosity changes during the tripping process are obtained; 8. Calculate the migration speed of the air bubble after it is disturbed during the drilling process; The rising velocity of bubbles during tripping in drilling fluid is obtained based on the calculation method for bubble migration velocity in drilling fluid. The actual migration velocity of bubbles during tripping can be calculated using the following formula: ， in: The actual upward velocity of the bubble is expressed in m / s; v g The upward velocity of the bubble under the influence of drilling fluctuations, in m / s; C 0 is the distribution coefficient; 9. Based on the fundamental principle that the drilling fluid descent rate is greater than the oil and gas upflow rate, the critical leakage rate and drilling fluid loading volume are obtained.

10. Calculate the required leakage pressure differential based on the functional relationship between leakage pressure differential and leakage velocity: ， Where: Δ p Leakage pressure differential, MPa; a , b The coefficient for calculating leakage pressure difference; 11. For every three drill strings or one drill collar drilled, liquid level monitoring technology should be used to monitor the liquid level height at this time and compare it with the liquid level. The subsequent operation procedure should be determined based on the change in liquid level height. (1) When the fluid level is equal to the previous fluid level, it means that the drilling fluid grouting volume meets the grouting requirements during the tripping period. At this time, continue grouting according to this volume. (2) When the liquid level is higher than the previous liquid level, it is necessary to determine whether the higher liquid level is caused by excessive drilling fluid injection or by insufficient grouting volume leading to increased overflow. The judgment method is to observe statically. If the liquid level drops, it indicates that the drilling fluid injection volume is excessive. (3) When the fluid level is lower than the previous fluid level, it indicates that the drilling fluid injection volume is insufficient and it is necessary to increase the drilling fluid injection volume.

12. After reaching the target well section, proceed with other operations.

2. The drilling fluid injection volume calculation method based on controlling the oil and gas upward velocity to zero, as described in claim 1, is characterized in that: The specific methods in step three include the following: (1) The relationship between the drilling fluid descent rate and the leakage rate during the static period is shown in the following formula: ， in: v ms The drilling fluid descent velocity during the stationary period, in m / s; v loss Let m be the leakage rate. 3 / h; D w The diameter of the wellbore is in meters (m). D d Drill pipe diameter, in meters (m); (2) The critical leakage rate was calculated based on the principle of balancing the drilling fluid descent rate and the oil and gas upflow rate; ， in: v gm The velocity of the oil and gas rises is expressed in m / s.

3. The drilling fluid injection volume calculation method based on controlling the oil and gas upward velocity to zero, as described in claim 2, is characterized in that: The specific steps in step six include the following: (1) The calculation method for the transport velocity of a single bubble in a static fluid is as follows: ， in: d The diameter of the oil droplet / bubble is in meters (m). v is the upward velocity of a single bubble in a static liquid column, in m / s; ρ g The density of the gas is in g / cm³. 3 ; ρ m Density of drilling fluid at the bottom of the well, in g / cm³ 3 ; C d The drag coefficient is dimensionless. (2) Due to the mutual influence between bubbles, the corrected bubble migration velocity in the drilling fluid is shown in the following formula: ， Where: α is the gas content; This is a correction factor; (3) Where C d The drag coefficient can be calculated using the following formula: ， Where: Re is the Reynolds number; (4) The Reynolds number for the transport of bubbles in a static liquid column is calculated using the following formula: ， in: K The viscosity coefficient is Pa·s^n; The bubble size is calculated by combining the oil and gas rise velocity measured on-site with the above formula.

4. The drilling fluid injection volume calculation method based on controlling the oil and gas upward velocity to zero, as described in claim 3, is characterized in that: The specific steps in step seven include the following: (1) During the tripping process, drilling fluid will replenish the original drill string position, and the faster the tripping speed, the faster the drilling fluid replenishment speed; the relationship between the drilling fluid annular velocity and the tripping speed is shown in the following formula: ， in: v m The annular velocity is m / s; v q The drilling speed is expressed in m / s. (2) Due to the shear dilution effect of drilling fluid, the viscosity of drilling fluid is calculated using the following formula as it flows: ， ， Where: γ is the shear rate, s -1 ; μ p ρ represents the drilling fluid viscosity, Pa·s.

5. The drilling fluid injection volume calculation method based on controlling the oil and gas upward velocity to zero, as described in claim 4, is characterized in that: The specific steps in step nine include the following: (1) The calculation method for the drilling fluid descent rate during tripping is as follows: ， in: v mu The drilling fluid descent rate during tripping out of the well is expressed in m / s. (2) Based on the fundamental principle that the drilling fluid descent rate is greater than the oil and gas upflow rate, a method for calculating the critical leakage rate required for the drilling fluid is derived. When the leakage rate is greater than 10m... 3 When the drilling speed is reduced to 0.1 m / s, the leakage rate is recalculated. Even when the speed is reduced to 0.1 m / s, the leakage rate is still greater than 10 m / s. 3 / h, start drilling at a speed of 0.1m / s: ； (3) The ratio K between the drilling fluid injection volume and the drill string tripping volume B The calculation method is as follows: ， in: L The height of the drill string to be pulled out is in meters (m). V 钻柱 This represents the drill string volume; K B This represents the ratio between the volume of drilling fluid injected and the volume of the drill string pulled out.

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