Method for calculating well kick allowance of directional well

Abstract

The invention belongs to the field of petroleum drilling, and provides a directional well kick margin calculation method, which considers the influence of a hole drift angle when establishing a kick margin calculation model, increases the factors for solving the kick margin, and can obtain a more accurate kick margin calculation result. Comprising the following steps: calculating the maximum allowable shut-in casing pressure; according to the maximum allowable shut-in casing pressure, the maximum allowable overflow invasion height is calculated; considering the influence of the hole drift angle, and calculating the actual section length of the maximum allowable overflow invasion height; according to the actual section length of the maximum allowable overflow invasion height, the overflow volume of fluid invading the shaft at the shaft bottom and the overflow volume of fluid invading the shaft at the casing shoe are calculated; a maximum allowable kick margin is determined based on the overflow volume at the bottom hole of the fluid invading the wellbore and the overflow volume at the casing shoe.

Description

Technical Field

[0001] This invention belongs to the field of oil drilling and relates to well control operation technology, specifically a method for calculating the well flow margin of directional wells. Background Technology

[0002] Well kick margin is an important factor affecting the design of casing running depth, which in turn is an important design parameter in well structure design, directly affecting the casing layer and operational safety of a well.

[0003] Specifically, kick margin is a crucial indicator for assessing whether a well can be safely shut in after a blowout during drilling, and whether circulating well control will prevent leakage into weak formations. It is one of the key parameters in deep drilling design and operations. Insufficient kick margin can lead to leakage into weak formations such as casing shoes, causing accidents like underground blowouts; while excessive kick margin requires more casing layers and a more complex wellbore structure, potentially preventing drilling to the target depth. Therefore, kick margin plays a vital role in well control operations. In the well design phase, kick margin determines the depth of each casing layer, thus affecting the wellbore structure. During drilling, kick margin determines whether drilling can continue safely and whether casing and cementing operations should be performed. During well control, kick margin is used to determine whether the volume of the blowout can be safely circulated out of the wellhead. The kick margin value affects the structure and risk level of a well; therefore, accurately determining the kick margin for each section of the well is crucial for drilling design and drilling operation safety.

[0004] Currently, the main methods for calculating shut-in kick margin are the continuous gas column model and the dynamic multiphase flow model. The continuous gas column model does not consider the actual solubility, compressibility, gas slippage, and temperature effects of the overflow gas, resulting in calculations that are biased towards theory. The dynamic multiphase flow model considers the dynamic effects after well penetration. Compared to the continuous gas column model, the distribution of dissolved / free gas in the annulus is more dispersed, and the maximum allowable shut-in casing pressure and kick margin obtained using the dynamic multiphase flow simulation are superior. However, these two calculation models are mainly applicable to vertical well kick margin calculations. Directional wells, on the other hand, are drilling methods that drill along a pre-designed inclination and azimuth to reach the target layer. Their characteristic is that the wellbore axis is not simply vertically downward, but rather drills along a specific trajectory in three-dimensional space according to geological conditions and production requirements. When applied to directional wells, the above two methods omit the most direct influence of the drilling wellbore trajectory, namely, the influence of the well inclination angle, a key controlling factor in directional wells. Therefore, the calculations are incomplete and inaccurate, and their accuracy will affect the wellbore structure and casing depth. In order to better assess the risk of safely circulating and discharging the kick during drilling operations, it is necessary to revise the value and calculation method of kick margin, so as to provide a theoretical reference for the reasonable design of casing running depth. Summary of the Invention

[0005] To address the problem that existing well kick margin calculation methods neglect the influence of the well inclination angle and the drilling trajectory of directional wells, this invention provides a method for calculating well kick margin in directional wells. This method considers the influence of the well inclination angle when establishing the well kick margin calculation model, increases the factors in obtaining the well kick margin, and can obtain more accurate well kick margin calculation results.

[0006] The technical solution adopted by this invention to solve its technical problem is as follows:

[0007] A method for calculating the wellbore inflow margin of a directional well includes the following steps:

[0008] Calculate the maximum allowable shut-in casing pressure;

[0009] Calculate the maximum permissible overflow intrusion height based on the maximum permissible shut-in casing pressure;

[0010] Considering the influence of well inclination angle, calculate the actual section length for the maximum allowable overflow intrusion height;

[0011] Calculate the overflow volume of fluid invading the wellbore at the bottom and the overflow volume at the casing shoe based on the actual length of the section with the maximum allowable overflow intrusion height;

[0012] The maximum permissible kick margin is determined based on the overflow volume of fluid entering the wellbore at the bottom of the well and the overflow volume at the casing shoe.

[0013] Furthermore, the formula for calculating the maximum permissible shut-in casing pressure is as follows:

[0014] P max =min{(ρ f -ρ m )×0.00981×H shoe ,P BOP / 1000,0.8P i / 1000-ρ m ×0.00981×H shoe}

[0015] Where: P max Indicates the maximum permissible shut-in casing pressure, in MPa; ρ f This represents the drilling fluid density equivalent to the leakage pressure at the casing shoe, expressed in g / cm³. 3 ;ρ m This indicates the current drilling fluid density, in g / cm³. 3 H shoe P indicates the vertical depth of the upper overshoes, in meters (m). BOP P indicates the maximum operating pressure of the blowout preventer, in MPa. iThis indicates the casing's resistance to internal pressure, expressed in MPa.

[0016] Furthermore, the formula for calculating the maximum permissible overflow intrusion height is as follows:

[0017]

[0018] Wherein: H max P represents the maximum permissible overflow intrusion height, in MPa. max P represents the maximum permissible shut-in casing pressure, in MPa. p ρ represents the formation pressure during a well kick, measured in MPa. m This indicates the current drilling fluid density, in g / cm³. 3 H TVD G represents the vertical depth of the well bottom at the time of a well kick, in meters (m). i This represents the pressure gradient of the intruding fluid, in MPa / m.

[0019] Furthermore, when calculating the actual length of the maximum allowable overflow intrusion height, the well inclination data is interpolated and divided into continuous micro-segments. The wellbore trajectory is divided into segments, and the wellbore trajectory is fitted and the well segment inclination data is obtained using the multiple spline interpolation method. The entire tubing string is divided into n units from the bottom of the well to the wellhead, with a total of n+1 nodes. Δh is the length of the unit segment, and finally, the inclination depth of the segment is calculated.

[0020] Furthermore, the formula for calculating the actual length of the maximum permissible overflow intrusion height is as follows:

[0021]

[0022] Where: h 斜 The actual segment length, in meters (m), represents the maximum permissible overflow intrusion height; H max The maximum permissible overflow intrusion height is indicated in MPa; α represents the well inclination angle in °.

[0023] Furthermore, the overflow volume of fluid invading the wellbore at the bottom of the well is determined based on the actual section length h of the maximum permissible overflow intrusion height. 斜 Length H of the assembly with the bottom hole drill string 钻铤 The calculations are performed by comparing the results:

[0024] When h 斜 ≦H 钻铤 When the fluid intrudes into the wellbore, the overflow volume V1 at the bottom of the well is calculated using the following formula:

[0025]

[0026] When h 斜 >H 钻铤When the fluid intrudes into the wellbore, the overflow volume V1 at the bottom of the well is calculated using the following formula:

[0027]

[0028] In the two formulas above: V1 represents the overflow volume of fluid entering the wellbore at the bottom of the well, in meters (m³). 3 V 钻铤环空 This represents the annulus volume between the drill collar and the wellbore, in meters (m). 3 V 钻杆环空 This represents the annulus volume between the drill pipe and the wellbore, in meters (m). 3 S 钻铤环空 This represents the annular area between the drill collar and the wellbore, in meters (m²). 2 S 钻杆环空 This represents the annular area between the drill pipe and the wellbore, in meters (m²). 2 ;D 钻铤 D indicates the outer diameter of the drill collar, in mm. 钻杆 D indicates the outer diameter of the drill pipe, in mm. 井径 Indicates wellbore size, unit: mm, D 井径 = (1+K)×D 钻头 D 钻头 The drill bit size is indicated in mm, and K represents the borehole enlargement ratio in %.

[0029] Furthermore, the overflow volume V2 of the fluid that invades the wellbore at the casing shoe is first calculated using the following formula:

[0030] V2 = h 斜 ×S 钻杆环空

[0031] Where: V2 represents the overflow volume of fluid entering the wellbore at the casing shoe, in meters. 3 h 斜 The actual segment length, in meters (m), represents the maximum permissible overflow intrusion height; S 钻杆环空 This represents the annular area between the drill pipe and the wellbore, in meters (m²). 2 ;

[0032] Then, according to Boyle's law, the overflow volume V2 of the fluid entering the wellbore at the casing shoe is converted into the bottom volume V3:

[0033]

[0034] Where: V3 represents the bottom hole volume converted from the overflow volume of fluid entering the wellbore at the casing shoe, in meters. 3 ;P f P represents the formation leakage pressure at the pipe shoe location, in MPa. p This indicates the formation pressure during a well kick, measured in MPa.

[0035] Furthermore, the method for determining the maximum allowable well kickback is as follows: compare the overflow volume V1 of the fluid that invades the wellbore at the bottom of the well with the bottom volume V3 converted from the overflow volume of the fluid that invades the wellbore at the casing shoe, and take the minimum value between V1 and V3 as the maximum allowable well kickback.

[0036] This application also provides a system for calculating the wellbore inflow margin of a directional well, for implementing the aforementioned calculation method, comprising at least:

[0037] The maximum permissible shut-in casing pressure calculation module is used to calculate the maximum permissible shut-in casing pressure.

[0038] The maximum permissible overflow intrusion height calculation module is used to calculate the maximum permissible overflow intrusion height;

[0039] The inclination depth calculation module is used to calculate the actual section length of the maximum allowable overflow intrusion height, and takes into account the influence of the well inclination angle during the calculation;

[0040] The overflow volume calculation module is used to calculate the overflow volume of fluid that has invaded the wellbore at the bottom of the well and at the casing shoe. The above calculations are based on the actual length of the section with the maximum allowable overflow intrusion height.

[0041] The maximum permissible well kick margin determination module is used to determine the size of the overflow volume of fluid invading the wellbore at the bottom of the well and the overflow volume at the casing shoe, and to determine the maximum permissible well kick margin.

[0042] This application also provides a terminal device, the terminal device including a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the computer program implements the aforementioned calculation method when executed by the processor.

[0043] This application also provides a computer-readable storage medium storing a computer program that, when executed by a processor, implements the aforementioned calculation method.

[0044] The beneficial effects of this invention include:

[0045] This method considers the wellbore inclination angle as a crucial factor when calculating the actual length of the maximum permissible kick height. It utilizes interpolation and fitting techniques to divide the wellbore trajectory into micro-segments, calculating the actual length of each segment. By incorporating the influence of the directional well inclination angle, it corrects the calculation method based on the continuous gas column model, making the results more consistent with actual field conditions. This method includes more factors affecting kick margin, such as wellbore inclination angle, drilling trajectory, formation pressure, and drilling fluid density, resulting in calculations that more closely approximate reality.

[0046] In summary, this invention, based on the continuous gas column theory and taking into account the influence of well inclination angle, modifies the calculation model for well kick margin, thereby obtaining a more accurate method for calculating well kick margin, providing a theoretical basis for well structure design, drilling design, and on-site safe well control operations. Attached Figure Description

[0047] Figure 1 This is a diagram of fluid distribution within the annulus;

[0048] Figure 2 This is a schematic diagram of the inclined section of the well. Detailed Implementation

[0049] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0050] Furthermore, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0051] Example 1

[0052] Kick margin is a crucial parameter for measuring blowout handling capacity in drilling well control operations, playing a vital role in wellbore structure design, safe drilling, and well control operations. This invention, based on continuous gas column theory and considering the influence of well inclination angle, modifies the calculation model for kick margin, resulting in a more accurate method for calculating kick margin. This provides a theoretical basis for drilling design and safe well control operations in the field.

[0053] This embodiment provides a method for calculating shut-in kick margin in directional wells. For ease of calculation, it is assumed that the kick fluid is a uniform and continuous gas column, and that the intruding fluid has just entered the bottom of the wellbore when the kick occurs. The casing shoe is considered a weak section within the wellbore. The solubility of the gas in the drilling fluid, as well as the effects of temperature, gas compressibility factor, and gas slippage, are ignored. During the upward movement of the gas column, it remains in the form of a gas column, and the fluid distribution within the annulus is as follows: Figure 1 As shown. When gas invasion occurs, the distribution of gas in the annulus has a significant impact on the calculation of well kick margin. In the calculation, it is assumed that the research object is a directional well and well control is performed using the driller's method. The calculation and analysis steps are as follows:

[0054] 1. Calculate the maximum allowable shut-in casing pressure:

[0055] The maximum permissible shut-in casing pressure refers to the maximum pressure that the wellhead can withstand without damaging the formation, casing, or wellhead sealing equipment. The maximum permissible shut-in casing pressure is determined by the minimum values ​​of the following three pressure limits: (1) the permissible rupture pressure of the weakest section in the wellbore (usually referring to the casing shoe location); (2) 80% of the minimum internal pressure resistance of the casing; and (3) the rated working pressure of the wellhead equipment. In well design, the strength of the wellhead sealing equipment and casing string is usually designed to be higher than the rupture strength of the weakest section in the wellbore. Therefore, the rupture pressure of the weakest section is used to determine the maximum permissible shut-in casing pressure. The formula for calculating the maximum permissible shut-in casing pressure is:

[0056] P max =min{(ρ f -ρ m )×0.00981×H shoe ,P BOP / 1000,0.8P i / 1000-ρ m ×0.00981×H shoe}

[0057] Where: P max Indicates the maximum permissible shut-in casing pressure, in MPa; ρ f This represents the drilling fluid density equivalent to the leakage pressure at the casing shoe, expressed in g / cm³. 3 ;ρ m This indicates the current drilling fluid density, in g / cm³. 3 H shoe P indicates the vertical depth of the upper overshoes, in meters (m). BOP P indicates the maximum operating pressure of the blowout preventer, in MPa. i This indicates the casing's resistance to internal pressure, expressed in MPa.

[0058] 2. Calculate the maximum permissible overflow intrusion height.

[0059] Based on the principle of atmospheric pressure at the bottom of the well, after a spill occurs and the well is shut in, a certain height of gas column will infiltrate the annular space between the wellbore and the drill string to achieve hydraulic equilibrium in the "U-shaped tube" system. The maximum permissible spill intrusion height H at this point can be derived from the pressure balance equation between the annulus and the waterhole. max for:

[0060]

[0061] Wherein: H max P represents the maximum permissible overflow intrusion height, in MPa. max P represents the maximum permissible shut-in casing pressure, in MPa. p ρ represents the formation pressure during a well kick, measured in MPa. m This indicates the current drilling fluid density, in g / cm³. 3 HTVD G represents the vertical depth of the well bottom at the time of a well kick, in meters (m). i This represents the pressure gradient of the intruding fluid, in MPa / m.

[0062] The kick margin is calculated based on the maximum permissible overflow intrusion height. The height of the overflow gas may be significant at two locations: the bottom of the well and the casing shoe. At the bottom of the well, due to the influence of the drill collar, the annular cross-sectional area is smaller, and the gas column height may be the greatest. At the casing shoe, due to the upward expansion of the gas, the height of the gas column reaching the casing shoe may be the greatest.

[0063] 3. Considering the influence of the well inclination angle, calculate the actual length of the section for the maximum allowable overflow intrusion height.

[0064] For directional wellbore trajectories, considering the influence of the inclination angle, the inclination data is interpolated and segmented into continuous micro-element segments during calculation. The wellbore trajectory is divided into segments, and cubic spline interpolation is used for wellbore trajectory fitting and segment inclination data acquisition. The entire tubing string, from the bottom to the wellhead, is divided into n elements, totaling n+1 nodes, with Δh representing the element segment length. Finally, the inclination depth of this segment is calculated. The formula for calculating the actual segment length of the maximum permissible overflow intrusion height is:

[0065]

[0066] Where: h 斜 The actual segment length, in meters (m), represents the maximum permissible overflow intrusion height; H max The maximum permissible overflow intrusion height is indicated in MPa; α represents the well inclination angle in °.

[0067] 4. Calculate the well kick margin under different conditions based on the actual section length of the maximum permissible overflow intrusion height.

[0068] 1) Calculate the overflow volume of fluid that invades the wellbore at the bottom of the well:

[0069] The overflow volume of fluid entering the wellbore at the bottom of the well is based on the actual section length h of the maximum permissible overflow intrusion height. 斜 Length H of the assembly with the bottom hole drill string 钻铤 The calculations are performed by comparing the results:

[0070] When h 斜 ≦H 钻铤 At this point, the height at which the gas that has invaded the wellbore reaches the top of the drill collar is the maximum, and the decrease in hydrostatic pressure is the greatest at this height. The overflow volume V1 of the fluid that has invaded the wellbore at the bottom of the well is calculated by the following formula:

[0071]

[0072] When h 斜 >H钻铤 When calculating the volume of the annulus between the drill string assembly and the wellbore, and the volume of the annulus between the drill pipe and the wellbore, it is necessary to consider them separately. When the gas column is at the bottom of the well, the height of the gas column is the greatest at the bottom of the well. The overflow volume V1 of the fluid invading the wellbore at the bottom of the well is calculated by the following formula:

[0073]

[0074] In the two formulas above: V1 represents the overflow volume of fluid entering the wellbore at the bottom of the well, in meters (m³). 3 V 钻铤环空 This represents the annulus volume between the drill collar and the wellbore, in meters (m). 3 V 钻杆环空 This represents the annulus volume between the drill pipe and the wellbore, in meters (m). 3 S 钻铤环空 This represents the annular area between the drill collar and the wellbore, in meters (m²). 2 S 钻杆环空 This represents the annular area between the drill pipe and the wellbore, in meters (m²). 2 ;D 钻铤 D indicates the outer diameter of the drill collar, in mm. 钻杆 D indicates the outer diameter of the drill pipe, in mm. 井径 Indicates wellbore size, unit: mm, D 井径 = (1+K)×D 钻头 D 钻头 The drill bit size is indicated in mm, and K represents the borehole enlargement ratio in %.

[0075] 2) Calculate the overflow volume of fluid entering the wellbore at the casing shoe:

[0076] The overflow volume V2 of the fluid entering the wellbore at the casing shoe is first calculated using the following formula:

[0077] V2 = h 斜 ×S 钻杆环空

[0078] Where: V2 represents the overflow volume of fluid entering the wellbore at the casing shoe, in meters. 3 h 斜 The actual segment length, in meters (m), represents the maximum permissible overflow intrusion height; S 钻杆环空 This represents the annular area between the drill pipe and the wellbore, in meters (m²). 2 ;

[0079] Then, according to Boyle's law, the overflow volume V2 of the fluid entering the wellbore at the casing shoe is converted into the bottom volume V3:

[0080]

[0081] Where: V3 represents the bottom hole volume converted from the overflow volume of fluid entering the wellbore at the casing shoe, in meters. 3 ;P f P represents the formation leakage pressure at the pipe shoe location, in MPa. p This indicates the formation pressure during a well kick, measured in MPa.

[0082] 5. Determination of well inflow margin

[0083] By comparing the overflow volume V1 of the fluid that invades the wellbore at the bottom of the well with the bottom volume V3 converted from the overflow volume of the fluid that invades the wellbore at the casing shoe, the maximum allowable well kick margin is taken as the minimum value between V1 and V3.

[0084] Example 2

[0085] This embodiment provides a computing system based on the method described in Embodiment 1, comprising:

[0086] The maximum permissible shut-in casing pressure calculation module is used to calculate the maximum permissible shut-in casing pressure.

[0087] The maximum permissible overflow intrusion height calculation module is used to calculate the maximum permissible overflow intrusion height;

[0088] The inclination depth calculation module is used to calculate the actual section length of the maximum allowable overflow intrusion height, and takes into account the influence of the well inclination angle during the calculation;

[0089] The overflow volume calculation module is used to calculate the overflow volume of fluid that has invaded the wellbore at the bottom of the well and at the casing shoe. The above calculations are based on the actual length of the section with the maximum allowable overflow intrusion height.

[0090] The maximum permissible well kick margin determination module is used to determine the size of the overflow volume of fluid invading the wellbore at the bottom of the well and the overflow volume at the casing shoe, and to determine the maximum permissible well kick margin.

[0091] Furthermore, this application also provides a terminal device, which includes a memory, a processor, and a computer program stored in the memory and executable on the processor. When the computer program is executed by the processor, it implements the calculation method described in Embodiment 1.

[0092] In addition, this application also provides a computer-readable storage medium storing a computer program that, when executed by a processor, implements the calculation method described in Embodiment 1.

[0093] Since the well kicking margin calculation program adopts all the technical solutions of all the aforementioned embodiments when it is executed by the processor, it has at least all the beneficial effects brought about by all the technical solutions of all the aforementioned embodiments, which will not be repeated here.

[0094] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A method for calculating the wellbore inflow margin of a directional well, characterized in that, Includes the following steps: Calculate the maximum allowable shut-in casing pressure; Calculate the maximum permissible overflow intrusion height based on the maximum permissible shut-in casing pressure; Considering the influence of well inclination angle, calculate the actual section length for the maximum allowable overflow intrusion height; Calculate the overflow volume of fluid invading the wellbore at the bottom and the overflow volume at the casing shoe based on the actual length of the section with the maximum allowable overflow intrusion height; The maximum permissible kick margin is determined based on the overflow volume of fluid entering the wellbore at the bottom of the well and the overflow volume at the casing shoe.

2. The method for calculating the wellbore inflow margin of a directional well according to claim 1, characterized in that, The formula for calculating the maximum permissible shut-in casing pressure is as follows: P max =min{(ρ f -r m )×0.00981×H shoe ,P BOP / 1000,0.8P i / 1000-r m ×0.00981×H shoe } Where: P max Indicates the maximum permissible shut-in casing pressure, in MPa; ρ f This represents the drilling fluid density equivalent to the leakage pressure at the casing shoe, expressed in g / cm³. 3 ;ρ m This indicates the current drilling fluid density, in g / cm³. 3 H shoe P indicates the vertical depth of the upper overshoes, in meters (m). BOP P indicates the maximum operating pressure of the blowout preventer, in MPa. i This indicates the casing's resistance to internal pressure, expressed in MPa.

3. The method for calculating the wellbore inflow margin of a directional well according to claim 2, characterized in that, The formula for calculating the maximum permissible overflow intrusion height is as follows: Wherein: H max P represents the maximum permissible overflow intrusion height, in MPa. max P represents the maximum permissible shut-in casing pressure, in MPa. p ρ represents the formation pressure during a well kick, measured in MPa. m This indicates the current drilling fluid density, in g / cm³. 3 H TVD G represents the vertical depth of the well bottom at the time of a well kick, in meters (m). i This represents the pressure gradient of the intruding fluid, in MPa / m.

4. The method for calculating the wellbore inflow margin of a directional well according to claim 3, characterized in that, When calculating the actual length of the maximum allowable overflow intrusion height, the well inclination data is interpolated and divided into continuous micro-segments. The wellbore trajectory is divided into segments, and the wellbore trajectory is fitted and the well segment inclination data is obtained using the multiple spline interpolation method. The entire tubing string is divided into n units from the bottom of the well to the wellhead, with a total of n+1 nodes. Δh is the length of the unit segment, and finally, the inclination depth of the segment is calculated.

5. The method for calculating the wellbore inflow margin of a directional well according to claim 4, characterized in that, The formula for calculating the actual length of the maximum permissible overflow intrusion height is as follows: Where: h 斜 The actual segment length, in meters (m), represents the maximum permissible overflow intrusion height; H max The maximum permissible overflow intrusion height is indicated in MPa; α represents the well inclination angle in °.

6. The method for calculating the wellbore inflow margin of a directional well according to claim 5, characterized in that, The overflow volume of fluid entering the wellbore at the bottom of the well is based on the actual section length h of the maximum permissible overflow intrusion height. 斜 Length H of the assembly with the bottom hole drill string 钻铤 The calculations are performed by comparing the results: When h 斜 ≦H 钻铤 When the fluid intrudes into the wellbore, the overflow volume V1 at the bottom of the well is calculated using the following formula: When h 斜 >H 钻铤 When the fluid intrudes into the wellbore, the overflow volume V1 at the bottom of the well is calculated using the following formula: In the two formulas above: V1 represents the overflow volume of fluid entering the wellbore at the bottom of the well, in meters (m³). 3 V 钻铤环空 This represents the annulus volume between the drill collar and the wellbore, in meters (m). 3 V 钻杆环空 This represents the annulus volume between the drill pipe and the wellbore, in meters (m). 3 ; S 钻铤环空 This represents the annular area between the drill collar and the wellbore, in meters (m²). 2 ; S 钻杆环空 This represents the annular area between the drill pipe and the wellbore, in meters (m²). 2 ;D 钻铤 D indicates the outer diameter of the drill collar, in mm. 钻杆 D indicates the outer diameter of the drill pipe, in mm. 井径 Indicates wellbore size, unit: mm, D 井径 = (1+K)×D 钻头 D 钻头 The drill bit size is indicated in mm, and K represents the borehole enlargement ratio in %.

7. The method for calculating the wellbore inflow margin of a directional well according to claim 6, characterized in that, The overflow volume V2 of the fluid entering the wellbore at the casing shoe is first calculated using the following formula: V2=h 斜 ×S 钻杆环空 Where: V2 represents the overflow volume of fluid entering the wellbore at the casing shoe, in meters. 3 h 斜 The actual segment length, in meters (m), represents the maximum permissible overflow intrusion height; S 钻杆环空 This represents the annular area between the drill pipe and the wellbore, in meters (m²). 2 ; Then, according to Boyle's law, the overflow volume V2 of the fluid entering the wellbore at the casing shoe is converted into the bottom volume V3: Where: V3 represents the bottom hole volume converted from the overflow volume of fluid entering the wellbore at the casing shoe, in meters. 3 ;P f P represents the formation leakage pressure at the pipe shoe location, in MPa. p This indicates the formation pressure during a well kick, measured in MPa.

8. The method for calculating the wellbore inflow margin of a directional well according to claim 7, characterized in that, The method for determining the maximum allowable well kick margin is as follows: compare the overflow volume V1 of the fluid that invades the wellbore at the bottom of the well with the bottom volume V3 converted from the overflow volume of the fluid that invades the wellbore at the casing shoe, and take the minimum value between V1 and V3 as the maximum allowable well kick margin.

9. A system for calculating the wellbore inflow margin of a directional well, used to implement the calculation method according to any one of claims 1-8, characterized in that, At least including: The maximum permissible shut-in casing pressure calculation module is used to calculate the maximum permissible shut-in casing pressure. The maximum permissible overflow intrusion height calculation module is used to calculate the maximum permissible overflow intrusion height; The inclination depth calculation module is used to calculate the actual section length of the maximum allowable overflow intrusion height, and takes into account the influence of the well inclination angle during the calculation; The overflow volume calculation module is used to calculate the overflow volume of fluid that has invaded the wellbore at the bottom of the well and at the casing shoe. The above calculations are based on the actual length of the section with the maximum allowable overflow intrusion height. The maximum permissible well kick margin determination module is used to determine the size of the overflow volume of fluid invading the wellbore at the bottom of the well and the overflow volume at the casing shoe, and to determine the maximum permissible well kick margin.

10. A terminal device, characterized in that, The terminal device includes a memory, a processor, and a computer program stored in the memory and executable on the processor. When the computer program is executed by the processor, it implements the calculation method as described in any one of claims 1-8.

11. A computer-readable storage medium, characterized in that, The computer-readable storage medium stores a computer program that, when executed by a processor, implements the calculation method as described in any one of claims 1-8.

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