A method for calculating perforating explosive pressure field considering charge structure of perforating charge

Abstract

The application discloses a method for calculating a perforating explosive pressure field by considering a charge structure of a perforating bullet, and relates to the technical field of perforating completion, which comprises the following steps: collecting parameters of the perforating bullet, parameters of a wellbore, parameters of a perforating pipe string and environmental parameters; dividing a wellbore annulus into a plurality of wellbore annulus nodes; dividing a charge area of the perforating bullet into a plurality of charge nodes; calculating an initial detonation pressure field of the perforating bullet charge explosion; and calculating the explosive pressure at each wellbore annulus node to obtain the perforating explosive pressure field. The application is used to solve the problem that there is no accurate quantitative relationship between the charge structure parameters and the distribution rule of the explosive pressure field in the prior art, the accuracy of the existing calculation method is insufficient, and the engineering applicability is poor, so that the perforating explosive pressure field distribution under different charge structure conditions can be accurately calculated, and the safety of the perforating completion operation and the predictability of the perforating effect are improved.

Description

Technical Field

[0001] This invention relates to the field of perforation completion technology, and more specifically to a method for calculating the perforation explosion pressure field considering the structure of the perforation projectile charge. Background Technology

[0002] Perforation completion technology is a key technology for achieving large-scale, efficient development of oil and gas resources by using a perforating charge to create a metal jet that forms a perforation channel between the wellbore and the reservoir. The perforation effect directly impacts the productivity and economic benefits of oil and gas wells, and the pressure field distribution generated by the perforating charge explosion is the core factor determining the perforation effect. Traditional perforation operation design often improves the perforation effect by changing the type, quantity, and geometry of the perforating charge. However, while these methods improve the perforation effect, they also affect the peak value and spatial distribution characteristics of the explosion pressure field within the wellbore, leading to accidents such as tubing buckling, screen breakage, and packer failure, posing a significant threat to the safety of the perforated tubing string and the integrity of the wellbore.

[0003] The structural parameters of a perforating projectile include key elements such as charge type, charge quantity, charge geometry, and detonation location. Different combinations of these parameters directly determine the peak intensity, spatial distribution characteristics, and attenuation law of the pressure field during the explosion. Traditional perforation designs are mostly based on empirical formulas and simplified assumptions, lacking in-depth analysis of the relationship between charge structural parameters and pressure field distribution, making it difficult to accurately predict the perforation effect and potential risks under complex well conditions.

[0004] In the existing technology, the following methods are mainly used to calculate the pressure field of perforation explosion: (1) Empirical formula method, which makes a rapid estimate through a simplified mathematical model. However, this method often simplifies the shape of the charge to a sphere or cylinder, ignoring the complex influence of the difference in charge structure on the pressure field. The calculation accuracy is limited and the scope of application is narrow. (2) Numerical simulation method, which uses finite element, finite difference or molecular dynamics methods to establish a refined model. Although the theoretical accuracy is high, the calculation cost is huge. Moreover, existing research focuses on the analysis of the influence of a single parameter and lacks a systematic consideration of the charge structure parameters. (3) Experimental testing method, which can obtain real pressure field data, but the experimental cycle is long, the cost is high, and it is difficult to cover the parameter space of all charge structure combinations.

[0005] Therefore, the main problems with the existing technology include: (1) insufficient matching with the perforation projectile charge structure; existing calculation methods are unable to fully reflect the influence of charge structure parameters such as charge type, charge quantity, and geometry on the explosion pressure field; (2) a contradiction between calculation accuracy and engineering practicality; high-precision methods have excessively high calculation complexity, while simplified methods cannot meet the accuracy requirements, making it difficult to balance calculation accuracy and efficiency; and (3) the applicability and universality of the calculation methods need to be improved, making it difficult to meet the engineering application needs of different types of perforation projectiles. These technical bottlenecks restrict the further development of perforation completion technology and affect the development efficiency and operational safety of oil and gas wells.

[0006] Therefore, there is an urgent need to develop a precise calculation method for the perforation explosion pressure field that can fully consider the structural characteristics of the perforation projectile charge, so as to provide a reliable theoretical basis and technical support for the optimization of perforation completion design and safety assurance. Summary of the Invention

[0007] This invention provides a method for calculating the perforation explosion pressure field considering the structure of the perforation projectile, in order to solve the problems of the lack of precise quantitative relationship between the parameters of the charge structure and the distribution law of the explosion pressure field in the prior art, the insufficient accuracy of the existing calculation methods and the poor engineering applicability. It aims to achieve the goal of accurately calculating the distribution of the perforation explosion pressure field under different charge structure conditions, improving the safety of perforation completion operations and the predictability of perforation effect.

[0008] This invention is achieved through the following technical solution:

[0009] A method for calculating the pressure field of a perforation explosion considering the structure of a perforation projectile charge includes the following steps:

[0010] S1. Based on the perforating projectile charge structure, collect perforating projectile parameters, including charge node density; and collect wellbore parameters, perforation string parameters, and environmental parameters.

[0011] S2. Set the annulus node density, divide the wellbore annulus into several nodes, and define them as wellbore annulus nodes;

[0012] S3. Based on the density of charging nodes, divide the charging area of ​​the perforated projectile into several nodes and define them as charging nodes, so that each charging node is evenly distributed in the charging area of ​​the perforated projectile.

[0013] S4. Based on the divided charge nodes, calculate the initial detonation pressure field of the perforated projectile charge explosion;

[0014] S5. Based on the divided wellbore annular nodes and the initial detonation pressure field, calculate the explosion pressure at each wellbore annular node to obtain the perforation explosion pressure field.

[0015] To address the lack of precise quantitative relationship between charge structure parameters and explosion pressure field distribution in existing technologies, as well as the insufficient accuracy and poor engineering applicability of existing calculation methods, this invention proposes a perforation explosion pressure field calculation method considering the perforation projectile charge structure. This method first collects perforation projectile parameters based on the perforation projectile charge structure, and also collects wellbore parameters, perforation string parameters, and environmental parameters to fully prepare for subsequent calculations. Then, based on the set annular node density, the wellbore annulus is divided into several wellbore annular nodes; and based on the charge node density, several charge nodes are divided within the charge region of each perforation projectile, ensuring that each charge node is evenly distributed within the perforation projectile charge region. Next, based on the divided wellbore annular nodes and charge nodes, the initial detonation field evolution under the perforation projectile charge characteristics is calculated to obtain the initial detonation pressure field of the perforation projectile charge explosion. Then, considering the subsequent pressure evolution process caused by the detonation products after the shaped charge jet penetrates the perforating gun, the explosion pressure at each wellbore annular node is calculated to obtain the perforation explosion pressure field.

[0016] In this application, the wellbore annulus node refers to the node in the wellbore annulus where explosion pressure evolution calculations are required. The purpose of this division is to calculate the pressure distribution and evolution within the wellbore annulus. The charge node in this application is a node uniformly divided within the perforated projectile charge area. The purpose of this division is to accurately calculate the detonation process of the perforated projectile charge and to provide corresponding data (explosion source pressure, propagation time, etc.) for subsequent pressure calculations at the wellbore annulus nodes.

[0017] In this application, the entire explosion process of the perforating projectile is divided into the detonation stage and the explosion shock wave propagation stage. The detonation stage refers to the process of the explosive products expanding when the perforating projectile is first detonated. At this time, the explosive is still undergoing a chemical reaction, which forms the initial detonation pressure field in this application. After the detonation stage ends, the explosion energy will propagate to the surrounding medium in the form of a shock wave, eventually forming the perforation explosion pressure field in this application.

[0018] Compared with existing technologies, this application fully considers the differentiated conditions of perforation projectile charge structures and can accurately calculate the distribution of perforation explosion pressure field under different charge structure conditions. It solves the technical problems that there are significant differences between traditional simplified models and the formation mechanism of actual explosion pressure field under differentiated perforation projectile charge structures, and that existing perforation parameter calculation models cannot correctly calculate the pressure field distribution in the perforation area under complex charge structures, making it difficult to meet the engineering application requirements of different types of perforation projectiles. It significantly improves the safety of perforation completion operations and the predictability of perforation effects, and is conducive to providing more scientific guidance for the design and optimization of perforation completion schemes.

[0019] Furthermore, in step S1:

[0020] The parameters of the perforating projectile also include any one or more of the following: TNT equivalent of explosive, initial specific volume of explosive, explosive detonation velocity, explosive density, charge node density, explosive mass per unit area, initial radius of explosive per unit area, perforating projectile charge geometry, perforating projectile charge size, perforating projectile charge area, explosive JWL constitutive model parameters, coordinates of the detonation point of each perforating projectile, and detonation time of each perforating projectile;

[0021] The wellbore parameters include any one or more of the following: wellbore radius, pocket length, casing inner radius, casing material density, and casing material sound velocity;

[0022] The parameters of the perforation string include any one or more of the following: outer radius of the perforation gun, inner radius of the perforation gun, density of the perforation gun material, sound velocity of the perforation gun material, and outer diameter of the string.

[0023] The environmental parameters include any one or more of the following: air medium density, air medium sound velocity, air medium pressure wave attenuation coefficient, perforating fluid medium density, perforating fluid medium sound velocity, perforating fluid medium pressure wave attenuation coefficient, and ambient pressure.

[0024] Furthermore, in step S2, when dividing the wellbore annulus into several nodes, the division is carried out with the wellhead as the starting point and the well section where the perforating gun is located as the center; in step S3, when dividing the perforating projectile charge area into several nodes, the detonation point of the perforating projectile charge is taken as the center and the charge area formed by the inner side of the perforating projectile casing and the outer side of the shaped charge liner is taken as the boundary.

[0025] In this application, the charging nodes are uniformly divided within the charging area of ​​the perforating projectile; however, the wellbore annulus nodes are not required to be uniformly divided. Depending on the specific working conditions, the wellbore annulus nodes can be divided into more densely in the key analysis section of the perforated pipe string, while the division density of the wellbore annulus nodes in the remaining parts can be appropriately reduced to reduce the amount of computation and improve computational efficiency.

[0026] Furthermore, the method for calculating the initial detonation pressure field of the perforated projectile charge includes:

[0027] S401. Determine the near-field boundary distance of the perforated projectile charge explosion to obtain the detonation area caused by the perforated projectile charge explosion.

[0028] S402. Calculate the initial impact pressure of each charge node on the wellbore annulus node within the detonation zone.

[0029] S403. Determine the impact time corresponding to each initial impact pressure.

[0030] S404. By combining each initial impact pressure with the corresponding impact time, the initial detonation pressure field of the perforated projectile charge explosion is obtained.

[0031] The core purpose of calculating the initial detonation pressure field in this application is to fully consider the influence of the perforated projectile's charge structure, which is significantly different from the prior art that simply simplifies the charge structure to a sphere.

[0032] This scheme first determines the near-field boundary distance of the perforating projectile's explosive charge detonation. The area within this near-field boundary distance is the region dominated by the explosive charge detonation, which is the detonation region defined in this application. The initial detonation pressure field is calculated only for the wellbore annulus nodes located within the detonation region. The initial detonation pressure field includes the initial impact pressure and the corresponding impact time. After calculating the initial impact pressure and corresponding impact time of each wellbore annulus node within the detonation region, the initial impacts caused by different explosive charge nodes can be superimposed along the time axis to obtain the initial detonation pressure field of the perforating projectile's explosive charge detonation.

[0033] This scheme considers the impact of the detonation process of each charge node on the annulus nodes of each wellbore within the detonation zone when calculating the initial impact pressure. Therefore, it fully matches the charging structure of the perforating projectile, significantly improving the calculation accuracy and engineering practicality.

[0034] Furthermore, the initial impact pressure is calculated using the following formula:

[0035] ;

[0036] In the formula: P nbji0 V represents the initial impact pressure exerted by the j-th charge node of the n-th perforation project on the annulus node i within the detonation zone; A, B, R1, R2, ω, and E0 are all parameters of the JWL constitutive model of the explosive; V nji R0 is the expansion volume of the explosive per unit area; R0 is the initial radius of the explosive per unit area; exp represents the natural exponential function.

[0037] Among them, the expansion volume of explosive per unit area V nji Calculated using the following formula:

[0038] ;

[0039] In the formula: L nji Let i be the distance from the annulus node in the wellbore to the j-th charge node of the n-th perforation projectile, satisfying the following formula:

[0040] ;

[0041] ; ;

[0042] In the formula: (x i ,y i (x) represents the coordinates of node i in the wellbore annulus;n ,y n (x) represents the coordinates of the detonation point of the nth perforation hole; j ,y j Let ) be the coordinates of the j-th loading node; x nj Let y be the distance along the X-axis between the j-th charge node and the detonation point of the n-th perforation hole; nj Let be the distance along the Y-axis between the j-th charge node and the n-th perforation point.

[0043] In this scheme, the JWL (Jones-Wilkins-Lee) constitutive model is existing technology, and its constitutive model parameters can be obtained based on existing technology. In addition, the X-axis extends radially along the wellbore and the Y-axis extends axially along the wellbore.

[0044] Furthermore, the impact time corresponding to the initial impact pressure is calculated using the following formula:

[0045] ;

[0046] In the formula: t nji0 P represents nbji0 The corresponding impact moment; D exp t represents the expansion velocity during the detonation phase of the explosive; j Let the delayed activation time of the explosive at the j-th charging node satisfy:

[0047] , ;

[0048] In the formula: L nj This represents the distance between the j-th charge node of the nth perforation project and the detonation point of the nth perforation project.

[0049] Furthermore, step S5 specifically includes:

[0050] S501. Calculate the evolution of the initial detonation pressure at each wellbore annulus node;

[0051] S502. Calculate the evolution of bubble pulsating pressure at each wellbore annulus node;

[0052] S503. Based on wellbore parameters and perforation string parameters, determine the pressure wave propagation path within the wellbore annulus node and calculate the evolution process of reflected pressure at each wellbore annulus node.

[0053] S504. By superimposing the evolution process of the initial detonation pressure at each wellbore annulus node, the evolution process of the bubble pulsation pressure at each wellbore annulus node, and the evolution process of the reflection pressure at each wellbore annulus node, the explosion pressure at each wellbore annulus node is calculated to obtain the perforation explosion pressure field.

[0054] Step S5 calculates the propagation and evolution of the explosion shock wave. This scheme uses the initial detonation pressure field calculated in the previous stage as the explosion source data for this propagation and evolution process. This scheme considers the initial detonation pressure, bubble pulsation pressure, and the propagation process of the pressure wave in the wellbore. The pressures of these three processes are calculated and superimposed to obtain the explosion pressure at each wellbore annulus node, thus obtaining the required perforation explosion pressure field.

[0055] Those skilled in the art should understand that the bubble pulsation pressure in this scheme refers to the pressure generated by the expansion and contraction of the bubble after the shaped charge of the perforating projectile forms a metal jet that penetrates the wall of the perforating gun under the action of detonation pressure during the perforation process.

[0056] Furthermore, the propagation path of the pressure wave within the annulus node of the wellbore needs to be determined according to specific operating conditions (such as wellbore parameters, perforation string parameters, etc.). For example, the reflection and / or transmission of the explosion pressure wave from the air medium to the perforation gun, the transmission of the explosion pressure wave from the perforation gun to the perforation fluid medium, and the reflection and / or transmission of the explosion pressure wave from the perforation fluid medium to the casing or perforation gun, etc.

[0057] Furthermore, the evolution of the initial detonation pressure at each wellbore annulus node is calculated using the following formula:

[0058] ;

[0059] In the formula: P nbji (t) represents the explosion pressure of the j-th charge node of the n-th perforation projectile and the impact pressure on the wellbore annulus node i at time t; P nbji t represents the initial impact pressure exerted by the j-th charge node of the n-th perforation projectile on the annulus node i in the wellbore; a b is the duration of positive pressure; a This is the attenuation coefficient.

[0060] For the wellbore annulus node within the detonation zone: ;

[0061] For wellbore annulus nodes outside the detonation zone:

[0062] ;

[0063] In the formula: L c L is the near-field boundary distance of the explosive charge of the perforation projectile. nji It is the distance from the wellbore annulus node i outside the detonation zone to the j-th charge node of the n-th perforation projectile.

[0064] It can be seen that for the wellbore annulus node within the detonation zone, the P calculated above can be directly used. nbji0 As P nbji That's sufficient; however, for the annular nodes outside the detonation zone, the corresponding P is calculated using the specific formula defined in this scheme. nbji0 Then, further evolutionary calculations will be performed.

[0065] Furthermore, the evolution of the bubble pulsating pressure in the wellbore annulus is calculated using the following formula:

[0066] ;

[0067] In the formula: P bni (t) represents the bubble pulsation pressure at the annulus node i of the wellbore at the axial position of the nth perforation projectile at time t; ρ q R is the density of the perforating fluid medium. b Where is the bubble radius; P0 is the velocity of the bubble wall; P0 is the ambient pressure; σ is the surface tension of the bubble; l ni P is the distance from the center of the bubble at the axial position of the nth perforation projectile to node i in the wellbore annulus; b The initial detonation pressure of the perforating projectile at the outer wall of the perforating gun in the perforation direction satisfies:

[0068] ;

[0069] ;

[0070] Where: m is the total number of charge nodes; A, B, R1, R2, ω, and E0 are all parameters of the JWL constitutive model of the explosive; exp represents the natural exponential function; R0 is the initial radius of the explosive per unit area; (x b ,y b (x) represents the coordinates of the perforating projectile on the outer wall of the perforating gun in the perforation direction; j ,y j () represents the coordinates of the j-th loading node; The outer radius of the perforating gun.

[0071] It can be seen that P b The calculation nodes are all located in the perforation direction of the perforating projectile and at the outer radius of the perforating gun, therefore, the P corresponding to each perforating projectile is... b The relative distance between the bubble pulsation and the shaped charge of the corresponding perforating projectile is the same, therefore the P corresponding to the bubble pulsation at the axial position of each perforating projectile is... b The values ​​are all the same.

[0072] Furthermore, the evolution of the reflected pressure at each wellbore annulus node is calculated using the following formula:

[0073] ;

[0074] In the formula: P nbjim (t) represents the explosion pressure of the j-th charge node of the n-th perforation projectile and the reflected pressure on the wellbore annulus node i at time t; The transmission coefficient of the pressure wave as it propagates from the air medium to the inner surface of the perforation gun; The transmission coefficient of the pressure wave as it propagates from the perforating gun to the perforating fluid medium; The reflection coefficient of the pressure wave as it propagates from the air medium to the inner surface of the perforation gun; The reflection coefficient of the pressure wave propagating from the perforating fluid medium to the inner surface of the casing; The number of internal reflections of the perforating gun; The number of reflections within the annular fluid; Let be the distance between the j-th charge node of the n-th perforation projectile and the annulus node i in the wellbore; The propagation paths of pressure waves represent different propagation stages, where s = 2, 3, ..., m g +m q +1; α is the peak pressure decay index.

[0075] In this scheme, the peak pressure decay exponent α and the positive pressure duration t a Attenuation coefficient b a The propagation path needs to be determined based on the wellbore structure and the characteristics of the propagation medium; the propagation path of the pressure wave needs to be determined based on the specific wellbore structure, wellbore parameters, perforation string parameters, etc. Therefore, in this scheme, the following is used: With several The sum is expressed as a whole. For example, when s=2, The distance of the second reflection / transmission path experienced by the j-th charge node of the perforating projectile n propagating to the annular node i.

[0076] Furthermore, the reflection coefficient of the pressure wave propagating from the air medium to the inner surface of the perforation gun is calculated using the following formula: ;

[0077] The reflection coefficient of the pressure wave propagating from the perforating fluid medium to the inner surface of the casing is calculated using the following formula: ;

[0078] The transmission coefficient of the pressure wave propagating from the air medium to the inner surface of the perforating gun is calculated by the following formula: ;

[0079] The transmission coefficient of the pressure wave propagating from the perforating gun to the perforating fluid medium is calculated by the following formula: ;

[0080] in:

[0081] The propagation impedance of explosion pressure in air medium. ;

[0082] The propagation impedance of explosion pressure in the perforation gun material: ;

[0083] The propagation impedance of explosion pressure in the perforating fluid medium: ;

[0084] The propagation impedance of explosion pressure in the casing material: ;

[0085] In the formula: The density of air. The speed of sound in air. Density of the perforating gun material; The velocity of sound for the perforating gun material; The density of the perforating fluid medium; The sound velocity of the perforating fluid medium; Density of the casing material; The velocity of sound is the velocity of the casing material.

[0086] Furthermore, in step S504, the method for calculating the explosion pressure at each wellbore annulus node includes:

[0087] Determine whether P is at the same time. nbji (t), P bni (t), P nbjim Is the value of (t) 0?

[0088] If two or more non-zero values ​​exist simultaneously, then Pi(t) = ;

[0089] If there exists only one non-zero value, then Pi(t) = ;

[0090] like If , then Pi(t) = 0;

[0091] In the formula, Pi(t) is the total pressure at wellbore annular node i at time t; k is the interference coefficient.

[0092] This scheme calculates the distribution and evolution of the pressure field during perforation explosions within the wellbore by superimposing the pressure fields at the same time points. Similarly, the interference coefficient k needs to be determined based on the specific wellbore structure, wellbore parameters, perforation string parameters, environmental parameters, etc., and is not specifically limited here. In practice, existing empirical values ​​can be used, or numerical simulation calculations can be performed using fluid dynamics software under special working conditions, or experimental testing can be used to obtain the values.

[0093] Compared with the prior art, the present invention has at least the following advantages and beneficial effects:

[0094] 1. This invention provides a method for calculating the perforation explosion pressure field considering the perforation projectile charge structure. It fully considers the differentiated conditions of the perforation projectile charge structure and can accurately calculate the distribution of the perforation explosion pressure field under different charge structure conditions. It solves the technical problems that there are significant differences between the traditional simplified model and the actual explosion pressure field formation mechanism under differentiated perforation projectile charge structure conditions, and that existing perforation parameter calculation models cannot correctly calculate the pressure field distribution in the perforation area under complex charge structures, making it difficult to meet the engineering application requirements of different types of perforation projectiles. It significantly improves the safety of perforation completion operations and the predictability of perforation effects, and is conducive to providing more scientific guidance for the design and optimization of perforation completion schemes.

[0095] 2. This invention provides a method for calculating the pressure field of a perforated explosion considering the structure of the perforated projectile charge. It establishes a method for calculating the pressure field of a perforated explosion based on the charge structure parameters, incorporating the characteristics of the shaped charge liner, the detonation parameters of the explosive, and the geometric configuration of the charge into the calculation model. This enables quantitative prediction of shock wave overpressure, pressure evolution, and bubble pulsation pressure. This method overcomes the limitations of traditional equivalent models for point sources or uniform spherical charges, and can accurately characterize the non-uniform distribution characteristics of the pressure field under complex charge structures. Attached Figure Description

[0096] The accompanying drawings, which are included to provide a further understanding of embodiments of the invention and form part of this application, do not constitute a limitation thereof. In the drawings:

[0097] Figure 1 This is a flowchart illustrating a specific embodiment of the present invention;

[0098] Figure 2 This is a schematic diagram of the wellbore structure in a specific embodiment of the present invention;

[0099] Figure 3 This is a partial schematic diagram of the perforation projectile loading structure in a specific embodiment of the present invention;

[0100] Figure 4 This is a schematic diagram of the propagation path of the explosion pressure wave in the wellbore in a specific embodiment of the present invention;

[0101] Figure 5 This is an overall comparison diagram of a specific embodiment of the present invention;

[0102] Figure 6 This is a partial comparison diagram of a specific embodiment of the present invention.

[0103] The attached diagram shows the markings and corresponding component names:

[0104] 1-Perforating string, 2-Wellbore annulus, 3-Casing, 4-Cement sheath, 5-Reservoir, 6-Perforating gun, 7-Perforating projectile, 8-Charged jet, 9-Perforating projectile casing, 10-Creature liner, 11-Detonation point. Detailed Implementation

[0105] To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the embodiments and accompanying drawings. The illustrative embodiments and descriptions of the present invention are only used to explain the present invention and are not intended to limit the present invention.

[0106] Example 1:

[0107] A method for calculating the pressure field of a perforation explosion considering the structure of a perforation projectile charge is proposed, based on the following assumptions: the casing and tubing are concentric; the perforation fluid medium is uniform and incompressible; the perforation projectile charge is a homogeneous explosive; and the wellbore environment temperature and pressure remain stable.

[0108] like Figure 1 As shown, the method for calculating the perforation explosion pressure field considering the structure of the perforation projectile includes the following steps:

[0109] Step S1: Based on the perforation projectile charge structure, collect the perforation projectile parameters, including the charge node density; and collect the wellbore parameters, perforation string parameters, and environmental parameters.

[0110] The wellbore structure in this embodiment is as follows: Figure 2 As shown, from the inside out, the structure consists of perforation string 1, wellbore annulus 2, casing 3, cement sheath 4, and reservoir 5; the wellbore annulus 2 contains perforating fluid; the perforating gun 6 is located on the perforation string 1, and the perforating gun 6 contains several perforating projectiles 7. The shaped jet 8 after the perforating projectiles 7 are detonated acts outward.

[0111] The parameters of the perforating projectile also include any one or more of the following: TNT equivalent of explosive, initial specific volume of explosive, explosive detonation velocity, explosive density, charge node density, explosive mass per unit area, initial radius of explosive per unit area, perforating projectile charge geometry, perforating projectile charge size, perforating projectile charge area, explosive JWL constitutive model parameters, coordinates of the detonation point of each perforating projectile, and detonation time of each perforating projectile.

[0112] The wellbore parameters include any one or more of the following: wellbore radius, pocket length, casing inner radius, casing material density, and casing material sound velocity.

[0113] The parameters of the perforation string include any one or more of the following: outer radius of the perforating gun, inner radius of the perforating gun, density of the perforating gun material, sound velocity of the perforating gun material, and outer diameter of the string.

[0114] The environmental parameters include any one or more of the following: air medium density, air medium sound velocity, air medium pressure wave attenuation coefficient, perforating fluid medium density, perforating fluid medium sound velocity, perforating fluid medium pressure wave attenuation coefficient, and ambient pressure.

[0115] Step S2: Set the annulus node density, divide the wellbore annulus into several nodes starting from the wellhead, and define them as wellbore annulus nodes.

[0116] In this embodiment, when dividing the wellbore annulus nodes, denser nodes are used in the key analysis section of the perforated pipe string, while the number of nodes is appropriately reduced in other sections to improve computational efficiency. The coordinates of wellbore annulus node i are denoted as (x... i ,y i ).

[0117] Step S3: Based on the charge node density, divide the perforated projectile charge area into several nodes and define them as charge nodes, so that each charge node is evenly distributed in the perforated projectile charge area.

[0118] In this embodiment, as Figure 3 As shown, with the detonation point 11 as the center, the shape of the explosive charge formed by the inner side of the perforated projectile casing 9 and the outer side of the shaped charge liner 10 serves as the boundary, and the explosive charge node density is set accordingly. The distribution of the charge nodes is calculated to ensure that the charge nodes uniformly fill the shape of the perforated projectile charge. The coordinates of the j-th charge node are denoted as (x... j ,y j ).

[0119] Step S4: Based on the divided charge nodes, calculate the initial detonation pressure field of the perforated projectile charge explosion.

[0120] The specific calculation steps for the initial detonation pressure field include:

[0121] Step S401: Determine the near-field boundary distance L of the perforation projectile charge explosion. c ,by The range is defined as the detonation zone caused by the explosion of the perforating projectile's explosive charge. Among them, L... ni Let be the distance from the detonation point of the nth perforation projectile to node i in the wellbore annulus.

[0122] Preferably, the near-field boundary distance of the perforated projectile charge explosion is calculated using the following formula:

[0123] ;

[0124] In the formula: W is the TNT equivalent of the explosive; m is the explosive mass per unit area; S is the explosive loading area of ​​the perforation projectile.

[0125] Step S402: Calculate the initial impact pressure at each charge node on the wellbore annulus node within the detonation zone:

[0126] ;

[0127] In the formula: P nbji0 V represents the initial impact pressure exerted by the j-th charge node of the n-th perforation project on the annulus node i within the detonation zone; A, B, R1, R2, ω, and E0 are all parameters of the JWL constitutive model of the explosive; V nji R0 is the volume of explosive expansion per unit area; R0 is the initial radius of explosive per unit area; exp represents the natural exponential function.

[0128] Among them, the expansion volume of explosive per unit area V nji Calculated using the following formula:

[0129] ;

[0130] In the formula: L nji Let i be the distance from the annulus node in the wellbore to the j-th charge node of the n-th perforation projectile, satisfying the following formula:

[0131] ;

[0132] ; ;

[0133] In the formula: (x i ,y i (x) represents the coordinates of node i in the wellbore annulus; n ,y n (x) represents the coordinates of the detonation point of the nth perforation hole; j ,y j Let ) be the coordinates of the j-th loading node; x nj Let y be the distance along the X-axis between the j-th charge node and the detonation point of the n-th perforation hole; nj Let be the distance along the Y-axis between the j-th charge node and the n-th perforation point.

[0134] In this embodiment, the explosive in the unit area is Figure 3 Within the firing range of the projectile, centered on each detonation point... RDX explosive is uniformly distributed per unit area; in Figure 3 In the text, the × symbol represents a trigger point.

[0135] S403. Determine the impact time corresponding to each initial impact pressure:

[0136] ;

[0137] In the formula: t nji0 P represents the initial impact pressure nbji0 The corresponding impact moment; D exp t represents the expansion velocity during the detonation phase of the explosive; j Let the delayed activation time of the explosive at the j-th charging node satisfy:

[0138] , ;

[0139] In the formula: L nj This represents the distance between the j-th charge node of the nth perforation project and the detonation point of the nth perforation project.

[0140] Preferred, D represents the detonation velocity of the explosive.

[0141] Step S404: Combine each initial impact pressure with the corresponding impact time to obtain the initial detonation pressure field of the perforated projectile charge explosion.

[0142] Step S5: Based on the divided wellbore annulus nodes and the initial detonation pressure field, calculate the explosion pressure at each wellbore annulus node to obtain the perforation explosion pressure field.

[0143] Specifically, it includes:

[0144] Step S501: Calculate the evolution of the initial detonation pressure at each wellbore annulus node using the following formula;

[0145] ;

[0146] In the formula: P nbji (t) represents the explosion pressure of the j-th charge node of the n-th perforation projectile and the impact pressure on the wellbore annulus node i at time t; t a b is the duration of positive pressure; a P is the attenuation coefficient; nbji The initial impact pressure exerted by the j-th charge node of the n-th perforation projectile on the annulus node i of the wellbore is represented by this pressure.

[0147] P nbji Determined using the following method:

[0148] For the wellbore annulus node within the detonation zone: ;

[0149] For wellbore annulus nodes outside the detonation zone:

[0150] ;

[0151] In the formula: L c L represents the distance from the boundary of the detonation zone.nji It is the distance from the wellbore annulus node i outside the detonation zone to the j-th charge node of the n-th perforation projectile.

[0152] Step S502: Calculate the evolution of bubble pulsating pressure at each wellbore annulus node using the following formula:

[0153] ;

[0154] In the formula: P bni (t) represents the bubble pulsation pressure at the annulus node i of the wellbore at the axial position of the nth perforation projectile at time t; ρ q R is the density of the perforating fluid medium. b Where is the bubble radius; P0 is the velocity of the bubble wall; P0 is the ambient pressure; σ is the surface tension of the bubble; l ni P is the distance from the center of the bubble at the axial position of the nth perforation projectile to node i in the wellbore annulus; b The initial detonation pressure of the perforating projectile at the outer wall of the perforating gun in the perforation direction.

[0155] In this embodiment, P b Calculated using the following formula:

[0156] ;

[0157] Where: m is the total number of charge nodes; A, B, R1, R2, ω, and E0 are all parameters of the JWL constitutive model of the explosive; exp represents the natural exponential function; R0 is the initial radius of the explosive per unit area; (x j ,y j ) represents the coordinates of the j-th loading node.

[0158] In addition, (x b ,y b ( ) represents the coordinates of the perforating projectile on the outer wall of the perforating gun in the perforation direction. Let be the outer radius of the perforating gun. It satisfies: .

[0159] Step S503: Based on the wellbore parameters and perforation string parameters, determine the pressure wave propagation path within the wellbore annulus node. In this embodiment, the propagation path of the pressure wave within the wellbore annulus node after m reflections is as follows: Figure 4 As shown, Figure 4 The solid arrows represent the partial propagation path of the pressure wave inside the perforating gun, and the dashed arrows represent the partial propagation path of the pressure wave outside the perforating gun.

[0160] This embodiment calculates the evolution of reflected pressure at each wellbore annulus node using the following formula:

[0161] ;

[0162] In the formula: P nbjim (t) represents the explosion pressure of the j-th charge node of the n-th perforation projectile and the reflected pressure on the wellbore annulus node i at time t; The transmission coefficient of the pressure wave as it propagates from the air medium to the inner surface of the perforation gun; The transmission coefficient of the pressure wave as it propagates from the perforating gun to the perforating fluid medium; The reflection coefficient of the pressure wave as it propagates from the air medium to the inner surface of the perforation gun; The reflection coefficient of the pressure wave propagating from the perforating fluid medium to the inner surface of the casing; The number of internal reflections of the perforating gun; The number of reflections within the annular fluid; Let be the distance between the j-th charge node of the n-th perforation projectile and the annulus node i in the wellbore; The propagation paths of pressure waves represent different propagation stages, where s = 2, 3, ..., m g +m q +1; α is the peak pressure decay index.

[0163] in:

[0164] The reflection coefficient of the pressure wave propagating from the air medium to the inner surface of the perforation gun is calculated by the following formula: ;

[0165] The reflection coefficient of the pressure wave propagating from the perforating fluid medium to the inner surface of the casing is calculated using the following formula: ;

[0166] The transmission coefficient of the pressure wave propagating from the air medium to the inner surface of the perforating gun is calculated by the following formula: ;

[0167] The transmission coefficient of the pressure wave propagating from the perforating gun to the perforating fluid medium is calculated by the following formula: .

[0168] in:

[0169] The propagation impedance of explosion pressure in air medium. ;

[0170] The propagation impedance of explosion pressure in the perforation gun material: ;

[0171] The propagation impedance of explosion pressure in the perforating fluid medium: ;

[0172] The propagation impedance of explosion pressure in the casing material: ;

[0173] In the formula: The density of air. The speed of sound in air. Density of the perforating gun material; The velocity of sound for the perforating gun material; The density of the perforating fluid medium; The sound velocity of the perforating fluid medium; Density of the casing material; The velocity of sound is the velocity of the casing material.

[0174] Step S504: By superimposing the evolution process of the initial detonation pressure at each wellbore annulus node, the evolution process of the bubble pulsation pressure at each wellbore annulus node, and the evolution process of the reflection pressure at each wellbore annulus node, the explosion pressure at each wellbore annulus node can be calculated, and thus the perforation explosion pressure field can be obtained.

[0175] Specifically, this embodiment calculates the explosion pressure at each wellbore annulus node using the following method:

[0176] Determine whether P is at the same time. nbji (t), P bni (t), P nbjim Is the value of (t) 0?

[0177] If two or more non-zero values ​​exist simultaneously, then Pi(t) = ;

[0178] If there exists only one non-zero value, then Pi(t) = ;

[0179] like If , then Pi(t) = 0;

[0180] In the formula, Pi(t) is the total pressure at wellbore annular node i at time t; k is the interference coefficient.

[0181] Example 2:

[0182] A method for calculating the pressure field of a perforation explosion considering the structure of the perforation projectile is presented in this embodiment, which is verified using an oil well in an oil field, based on Example 1.

[0183] The well has a depth of 1360m, a pocket length of 61.9m, and a hydrostatic pressure of 12.43MPa in the perforated section. A 5-1 / 2'' casing is used in the reservoir. The perforation string used consists of: tubing + mechanical ignition head + safety gun + perforation gun + PT instrument holder + gun tail.

[0184] The perforating gun uses DPxxRDX25 perforating ammunition with a phase angle of 60° and a perforation density of 16 per meter. The perforation intervals and the number of perforating ammunition are as follows:

[0185] Perforation section 1: 1268.7m-1272.0m, 53 perforating shells;

[0186] Perforation section 2: 1292.2m-1294.2m, 32 perforating shells;

[0187] Perforation section 3: 1295.2m-1298.1m, 46 perforation shells.

[0188] Using the perforation explosion pressure field calculation method described in this application, the perforation explosion pressure at a point 0.99 meters below the last perforation projectile in the third perforated section was calculated and compared with the field measurement results. The overall comparison within 800 ms after the perforation explosion is also presented. Figure 5 As shown, local comparisons within 70ms are as follows: Figure 6 As shown.

[0189] from Figure 5 and Figure 6 As can be seen from this, the calculation method of the perforation explosion pressure field in this application is basically consistent with the field measurement results.

[0190] Furthermore, the peak positive pressure, secondary peak positive pressure, and peak negative pressure of the perforation explosion pressure field were extracted and compared precisely. The results are shown in Table 1.

[0191] Table 1. Precise Comparison Results

[0192] On-site measured values The calculation value of this application method error(%) Peak positive pressure (MPa) 48.20 48.14 0.12 Second peak value (MPa) 17.90 18.23 1.84 Peak negative pressure (MPa) 6.60 6.63 0.46

[0193] As can be seen from Table 1, the errors of the positive pressure peak, secondary peak, and negative pressure peak are all small and within the acceptable range, which further verifies the accuracy and engineering applicability of the method in this application.

[0194] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

[0195] It should be noted that, in this document, terms such as “comprising,” “including,” or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

Claims

1. A method for calculating the pressure field of a perforation explosion considering the structure of a perforation projectile charge, characterized in that, Includes the following steps: S1. Based on the perforating projectile charge structure, collect perforating projectile parameters, including charge node density; and collect wellbore parameters, perforation string parameters, and environmental parameters. S2. Set the annulus node density, divide the wellbore annulus into several nodes, and define them as wellbore annulus nodes; S3. Based on the density of charging nodes, divide the charging area of ​​the perforated projectile into several nodes and define them as charging nodes, so that each charging node is evenly distributed in the charging area of ​​the perforated projectile. S4. Based on the divided charge nodes, calculate the initial detonation pressure field of the perforated projectile charge explosion; The calculation method for the initial detonation pressure field of the perforated projectile charge explosion includes: S401. Determine the near-field boundary distance of the perforated projectile charge explosion to obtain the detonation area caused by the perforated projectile charge explosion. S402. Calculate the initial impact pressure of each charge node on the wellbore annulus node within the detonation zone. S403. Determine the impact time corresponding to each initial impact pressure. S404. By combining each initial impact pressure with the corresponding impact time, the initial detonation pressure field of the perforated projectile charge explosion is obtained. The initial impact pressure is calculated using the following formula: ； In the formula: P nbji0 V represents the initial impact pressure exerted by the j-th charge node of the n-th perforation project on the annulus node i within the detonation zone; A, B, R1, R2, ω, and E0 are all parameters of the JWL constitutive model of the explosive; V nji R0 is the expansion volume of the explosive per unit area; R0 is the initial radius of the explosive per unit area; exp represents the natural exponential function. Among them, the expansion volume of explosive per unit area V nji Calculated using the following formula: ； In the formula: L nji Let i be the distance from the annulus node in the wellbore to the j-th charge node of the n-th perforation projectile, satisfying the following formula: ； ； ； In the formula: (x i ,y i (x) represents the coordinates of node i in the wellbore annulus; n ,y n (x) represents the coordinates of the detonation point of the nth perforation hole; j ,y j Let ) be the coordinates of the j-th loading node; x nj Let y be the distance along the X-axis between the j-th charge node and the detonation point of the n-th perforation hole; nj The distance along the Y-axis between the j-th charge node and the initiation point of the n-th perforation projectile; S5. Based on the divided wellbore annulus nodes and the initial detonation pressure field, calculate the explosion pressure at each wellbore annulus node to obtain the perforation explosion pressure field; Step S5 specifically includes: S501. Calculate the evolution of the initial detonation pressure at each wellbore annulus node; S502. Calculate the evolution of bubble pulsating pressure at each wellbore annulus node; S503. Based on wellbore parameters and perforation string parameters, determine the pressure wave propagation path within the wellbore annulus node and calculate the evolution process of reflected pressure at each wellbore annulus node. S504. By superimposing the evolution process of the initial detonation pressure at each wellbore annulus node, the evolution process of the bubble pulsation pressure at each wellbore annulus node, and the evolution process of the reflection pressure at each wellbore annulus node, the explosion pressure at each wellbore annulus node is calculated to obtain the perforation explosion pressure field.

2. The method for calculating the pressure field of a perforation explosion considering the structure of a perforation projectile charge, as described in claim 1, is characterized in that... In step S1: The parameters of the perforating projectile also include any one or more of the following: TNT equivalent of explosive, initial specific volume of explosive, explosive detonation velocity, explosive density, charge node density, explosive mass per unit area, initial radius of explosive per unit area, perforating projectile charge geometry, perforating projectile charge size, perforating projectile charge area, explosive JWL constitutive model parameters, coordinates of the detonation point of each perforating projectile, and detonation time of each perforating projectile; The wellbore parameters include any one or more of the following: wellbore radius, pocket length, casing inner radius, casing material density, and casing material sound velocity; The parameters of the perforation string include any one or more of the following: outer radius of the perforation gun, inner radius of the perforation gun, density of the perforation gun material, sound velocity of the perforation gun material, and outer diameter of the string. The environmental parameters include any one or more of the following: air medium density, air medium sound velocity, air medium pressure wave attenuation coefficient, perforating fluid medium density, perforating fluid medium sound velocity, perforating fluid medium pressure wave attenuation coefficient, and ambient pressure.

3. The method for calculating the pressure field of a perforation explosion considering the structure of a perforation projectile charge, as described in claim 1, is characterized in that... In step S2, when dividing the wellbore annulus into several nodes, the wellhead is taken as the starting point and the section of the well where the perforating gun is located is taken as the center. In step S3, when dividing the perforating projectile charge area into several nodes, the detonation point of the perforating projectile charge is taken as the center and the charge area formed by the inner side of the perforating projectile casing and the outer side of the shaped charge liner is taken as the boundary.

4. The method for calculating the pressure field of a perforation explosion considering the structure of a perforation projectile charge, as described in claim 1, is characterized in that... The impact time corresponding to the initial impact pressure is calculated using the following formula: ； In the formula: t nji0 P represents nbji0 The corresponding impact moment; D exp t represents the expansion velocity during the detonation phase of the explosive; j Let the delayed activation time of the explosive at the j-th charging node satisfy: ， ； In the formula: L nj This represents the distance between the j-th charge node of the nth perforation project and the detonation point of the nth perforation project.

5. The method for calculating the pressure field of a perforation explosion considering the structure of a perforation projectile charge, as described in claim 1, is characterized in that... The evolution of the initial detonation pressure at each wellbore annulus node is calculated using the following formula: ； In the formula: P nbji (t) represents the explosion pressure of the j-th charge node of the n-th perforation projectile and the impact pressure on the wellbore annulus node i at time t; P nbji t represents the initial impact pressure exerted by the j-th charge node of the n-th perforation projectile on the annulus node i in the wellbore; a b is the duration of positive pressure; a The attenuation coefficient; For the wellbore annulus node within the detonation zone: ; For wellbore annulus nodes outside the detonation zone: ； In the formula: L c L is the near-field boundary distance of the explosive charge of the perforation projectile. nji The distance from wellbore annulus node i outside the detonation zone to the j-th charge node of the n-th perforation projectile; The evolution of the bubble pulsating pressure in the wellbore annulus is calculated using the following formula: ； In the formula: P bni (t) represents the bubble pulsation pressure at the annulus node i of the wellbore at the axial position of the nth perforation projectile at time t; ρ q R is the density of the perforating fluid medium. b Where is the bubble radius; P0 is the velocity of the bubble wall; P0 is the ambient pressure; σ is the surface tension of the bubble; l ni P is the distance from the center of the bubble at the axial position of the nth perforation projectile to node i in the wellbore annulus; b The initial detonation pressure of the perforating projectile at the outer wall of the perforating gun in the perforation direction satisfies: ； ； Where: m is the total number of charge nodes; A, B, R1, R2, ω, and E0 are all parameters of the JWL constitutive model of the explosive; exp represents the natural exponential function; R0 is the initial radius of the explosive per unit area; (x b ,y b (x) represents the coordinates of the perforating projectile on the outer wall of the perforating gun in the perforation direction; j ,y j () represents the coordinates of the j-th loading node; The outer radius of the perforating gun; The evolution of the reflected pressure at each wellbore annulus node is calculated using the following formula: ； In the formula: P nbjim (t) represents the explosion pressure of the j-th charge node of the n-th perforation projectile and the reflected pressure on the wellbore annulus node i at time t; The transmission coefficient of the pressure wave as it propagates from the air medium to the inner surface of the perforation gun; The transmission coefficient of the pressure wave as it propagates from the perforating gun to the perforating fluid medium; The reflection coefficient of the pressure wave as it propagates from the air medium to the inner surface of the perforation gun; The reflection coefficient of the pressure wave propagating from the perforating fluid medium to the inner surface of the casing; The number of internal reflections of the perforating gun; The number of reflections within the annular fluid; Let be the distance between the j-th charge node of the n-th perforation projectile and the annulus node i in the wellbore; The propagation paths of pressure waves represent different propagation stages, where s = 2, 3, ..., m g +m q +1; α is the peak pressure decay index.

6. The method for calculating the pressure field of a perforation explosion considering the structure of a perforation projectile charge, as described in claim 5, is characterized in that... The reflection coefficient of the pressure wave propagating from the air medium to the inner surface of the perforation gun is calculated by the following formula: ; The reflection coefficient of the pressure wave propagating from the perforating fluid medium to the inner surface of the casing is calculated using the following formula: ; The transmission coefficient of the pressure wave propagating from the air medium to the inner surface of the perforating gun is calculated by the following formula: ; The transmission coefficient of the pressure wave propagating from the perforating gun to the perforating fluid medium is calculated by the following formula: ; in: The propagation impedance of explosion pressure in air medium. ; The propagation impedance of explosion pressure in the perforation gun material: ; The propagation impedance of explosion pressure in the perforating fluid medium: ; The propagation impedance of explosion pressure in the casing material: ; In the formula: The density of air. The speed of sound in air. Density of the perforating gun material; The velocity of sound for the perforating gun material; The density of the perforating fluid medium; The sound velocity of the perforating fluid medium; Density of the casing material; The velocity of sound is the velocity of the casing material.

7. The method for calculating the pressure field of a perforation explosion considering the structure of a perforation projectile charge, as described in claim 5, is characterized in that... In step S504, the method for calculating the explosion pressure at each wellbore annulus node includes: Determine whether P is at the same time. nbji (t), P bni (t), P nbjim Is the value of (t) 0? If two or more non-zero values ​​exist simultaneously, then Pi(t) = ; If there exists only one non-zero value, then Pi(t) = ; like If , then Pi(t) = 0; In the formula, Pi(t) is the total pressure at wellbore annular node i at time t; k is the interference coefficient.

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