Gunpowder pulse detonation modeling method based on coupling dynamics

Abstract

The invention relates to a gunpowder pulse detonation modeling method based on coupling dynamics. The method comprises the following steps: establishing a gunpowder detonation kinetic model; establishing a kinetic model of the motion law of the well killing fluid column; establishing a crack system dynamic model; three models of gunpowder deflagration, wellbore killing fluid column movement law, perforation gas leakage and crack expansion are combined with one another, the maximum explosive quantity required by construction is calculated, and deflagration pressure generated under the explosive quantity value does not cause safety influence on an underground pipe column and can expand stratum cracks to the maximum extent; according to the method, the model is established, so that the optimal design of the gunpowder amount of the pulse deflagration crack-making and blockage-removing construction before construction is realized, the damage of the overlarge gunpowder amount to the sleeve is prevented, and the construction safety is improved; meanwhile, the crack form formed by gunpowder on the stratum after construction can be accurately analyzed, and a powerful basis is provided for a subsequent construction scheme.

Description

Technical Field

[0001] The invention belongs to the technical field of gunpowder pulse deflagration engineering in oil and gas field development, and in particular relates to a gunpowder pulse deflagration modeling method based on coupled dynamics. Background Art

[0002] Various pollutions formed in the near-well area during the system measures such as drilling, cementing, oil testing, fracturing, acidizing, pump inspection, water injection, and oil production, as well as blockage by solid particles (wax, colloid, asphalt, rust, etc.), blockage by organic and inorganic scale, bacterial blockage, water lock, emulsification, clay expansion, etc., all of these factors will lead to "poor permeability" in the near-well area, reduced oil well production, increased water injection pressure in water wells, and reduced water injection volume, which will have a huge impact on the normal production of oil and water wells.

[0003] In order to effectively eliminate and break up perforation pollution, blockage and compaction zones, a pulse deflagration fracture creation and unblocking technology has been developed. The pulse deflagration fracture creation and unblocking technology uses a screen tube fracturing gun in series, which is equipped with a multi-stage solid gunpowder energy source. After ignition, the solid gunpowder burns to produce a large amount of high-energy gas, forming a multi-stage pressure pulse, and forming multiple cracks in the perforation phase direction (the direction of the cracks is not affected by formation stress). When necessary, it can carry proppants under the pulse loading and cavitation of high-temperature and high-pressure gas, thereby improving the seepage conditions near the wellbore, completing the unblocking and transformation of the reservoir, and improving the production increase effect.

[0004] At present, there are few and single simulation studies on gunpowder pulse deflagration at home and abroad. It is difficult to accurately control the influence of gunpowder quantity on wellbore before construction and evaluate the effect after construction. Therefore, how to establish a dynamic model for accurate simulation and evaluation of gunpowder pulse deflagration deserves in-depth study. Summary of the invention

[0005] The gunpowder pulse deflagration modeling method based on coupled dynamics of the present invention uses the wellbore gas pressure and temperature changes as the main line variables, and the limit peak pressure model as the connection condition, and couples the gunpowder deflagration model, the well killing fluid column movement model, and the rock fracture dynamic extension model to establish a combined model, which can perform dynamic simulation calculations on the entire process of gunpowder pulse deflagration.

[0006] The gunpowder deflagration kinetic model is based on the gunpowder burning rate model, and the physical model of gunpowder deflagration is established according to the wellbore conditions. Based on this, the gunpowder deflagration loading process kinetic model composed of the gunpowder burning rate equation, mass conservation equation, energy conservation equation and deflagration gas production state equation is established, and the quantitative solution technology is studied in combination with the boundary conditions of high-energy gas fracturing. The model can quantitatively describe the pressure and temperature changes in the gunpowder deflagration process, providing a dynamic basis for the later reasonable charge design and process coupling model research.

[0007] In the dynamic model of the movement law of the wellbore killing fluid column, the movement of the killing fluid is divided into two parts. On the one hand, it is dominated by the pressure of the construction section, and on the other hand, it also affects the explosive pulse deflagration process. The analysis provides theoretical support for the stress condition of the downhole pipe string.

[0008] The fracture system dynamics model and fracture extension analysis during pulse deflagration include three aspects of analysis: fluid flow and leakage analysis in fractures, fracture extension criteria, and fracture width analysis. Through analysis, the pressure distribution approximate model of high-pressure fluid in fractures, fluid leakage model, stress intensity factor calculation model of elastic-plastic rock fractures, fracture extension velocity model, and fracture width model are respectively given. The combination of these models can determine whether the fracture extends at any time, and quantitatively describe the underground fracture morphology at any time during the gunpowder pulse deflagration process.

[0009] The present invention solves the technical problem by adopting the following technical solutions:

[0010] The modeling method of gunpowder pulse deflagration based on coupled dynamics includes the following steps:

[0011] Establishing a gunpowder deflagration kinetic model, the gunpowder deflagration kinetic model includes a physical model and a mathematical model of gunpowder deflagration, the mathematical model includes a gunpowder burning rate equation, a mass conservation equation, an energy conservation equation, and a deflagration gas production state equation; solving the gunpowder deflagration kinetic model to obtain pressure and temperature changes during the gunpowder deflagration process;

[0012] A dynamic model of the movement law of the wellbore killing fluid column is established. The movement of the killing fluid is divided into two parts. On the one hand, it is dominated by the pressure of the construction section, and on the other hand, it also affects the explosive pulse deflagration process. The analysis provides theoretical support for the stress of the downhole pipe string.

[0013] Establish a fracture system dynamics model, a fracture fluid pressure distribution model, a fracture wall seepage model, a fracture initiation and arrest criterion model, a fracture extension velocity model, and a fracture width model. Use the mass conservation and energy conservation of high-pressure fluids to solve the model, thereby determining whether the fracture extends at any time, and quantitatively describing the downhole fracture morphology at any time during the explosive pulse deflagration process.

[0014] By combining the three models of gunpowder deflagration, wellbore pressure fluid column movement law, perforation gas leakage and crack expansion, the maximum amount of gunpowder required for construction is calculated. The deflagration pressure generated at this amount will not only have no safety impact on the downhole tubing, but also can expand the formation cracks to the maximum extent.

[0015] Furthermore, the physical model of gunpowder deflagration is the deflagration of a fixed amount of gunpowder in a confined space. The gunpowder bomb is cylindrical and the inner surface is ignited simultaneously. It is assumed that: the gunpowder deflagration space is closed and the volume does not change with time; the pressure and temperature of each point in the confined space remain consistent during the gunpowder deflagration; the gunpowder deflagration obeys the geometric deflagration law; the deflagration loading process is an adiabatic process, and it is a non-adiabatic process after loading; the fuel gas is a perfect gas with constant specific heat, which conforms to the perfect gas state equation; the propellant deflagrates completely and the composition of the deflagration products remains unchanged.

[0016] Furthermore, the mathematical model of gunpowder deflagration is established by combining comprehensive analysis of the gunpowder deflagration section in the enclosed area and the heat dissipation and pressure relief section after the completion of the gunpowder deflagration. The establishment method is as follows:

[0017] 1) The mathematical model includes the burning rate equation, mass conservation equation, energy conservation equation and deflagration gas production state equation of the gunpowder:

[0018]

[0019] Where V g is the deflagration volume of the charge, m 3 ; t is any time, s; p is the explosive pressure of gunpowder, MPa; w0 is the explosive burning rate coefficient (explosion rate when the pressure is 1MPa), m / s·(MPa); S0 is the explosive surface area of ​​gunpowder, m 2 ; n is the pressure index; R is the outer radius of the charge, m; T is the deflagration temperature, °C; M is the molecular weight of the gas; V r is the free volume occupied by the gas in the deflagration enclosed space (the center of the gunpowder has an initial volume. If the well-killing fluid method is used, the free volume should generally be larger than the volume reduced by the gunpowder deflagration due to the movement of the well-killing fluid column); ρ0 is the density of the gunpowder column, kg / m 3 ; ρ is the density of gunpowder gas, kg / m 3 ; F is the gunpowder force, J / kg; c g is the specific heat of propellant gas, J / kg·℃; m r is the mass of gunpowder burned, kg;

[0020] Combined with the model boundary conditions, quantitative solutions can be obtained to derive the pressure-time and temperature-time variation relationships in the deflagration confined space;

[0021] 2) Analysis of heat dissipation and pressure relief section after the explosion of gunpowder

[0022] According to the energy balance, the heat Q dissipated by the gas into the surrounding formation during the time dt c , the heat dissipation is calculated as:

[0023]

[0024] Where T0 is the formation temperature, °C; L is the wellbore length, m; D is the wellbore diameter, m; α is the convection heat transfer coefficient between gas and formation; λ f is the formation thermal conductivity; f(t) is the time function reflecting the non-steady-state properties, α is the thermal conductivity or thermal diffusivity of the formation;

[0025] Since it is an isochoric process, the relationship between temperature, pressure and time in the closed space of the aftereffect stage is:

[0026]

[0027]

[0028] Where, T m is the initial temperature in the wellbore of the descending section, °C;

[0029] Combined with the model boundary conditions, the relationship between the temperature and pressure of the system during the unloading stage and time can be quantitatively calculated.

[0030] Furthermore, the method for establishing the dynamic model of the movement law of the wellbore killing fluid column is:

[0031] (1) The liquid column above the fracturing bomb moves upward under the pressure of the construction section. The motion equation of the latter part of the well-killing liquid column is derived from its force condition. If the resistance is ignored, the differential equation of motion of the liquid column can be written as:

[0032]

[0033] Where: S L H is the distance the well-killing fluid moves upward, m; L is the height of the liquid on the fracturing bomb, m; g is the acceleration of gravity; p w is the wellbore pressure, MPa; ρ L is the density of the well-killing liquid, kg / m 3 ;

[0034] The volume of liquid displaced is:

[0035] V L =πD 2 S L

[0036] Where V L is the volume of well-killing fluid released upward, m 3 ;

[0037] Then, the volume occupied by gas in the wellbore at any time is:

[0038]

[0039] Where V0 is the initial free volume in the cartridge case, m 3 ; V e is the elastic increment of the wellbore volume (or this item is not considered); M0 is the initial main charge mass, kg; f is the shape function;

[0040] (2) The mass of gunpowder corresponding to the gas in the wellbore is:

[0041] M w =fM0-M d

[0042] Among them, M w is the mass of gunpowder corresponding to the gas in the wellbore, kg; M d is the mass of gunpowder corresponding to the gas leaking from the wellbore, kg;

[0043] At any time when the gunpowder has not been completely burned and part of the gas has leaked out, it can be considered that the wellbore pressure is generated by the combustion of the gunpowder corresponding to the gas remaining in the wellbore after deducting the part that has leaked out of the wellbore. At this time, the volume occupied by the gas corresponding to the volume of the closed container is composed of the original free volume, the original volume occupied by the burned gunpowder part, and the volume vacated by the liquid movement. The wellbore pressure is:

[0044]

[0045] In the formula, p y V is the well pressure at any time when the gunpowder has not yet been completely burned and some gas has leaked out, MPa; y is the volume occupied by gas in the wellbore, m 3 ; γ is the residual volume (volume occupied by solid matter after the gunpowder burns), m 3 / kg;

[0046] Furthermore, the fluid pressure distribution model in the slit is:

[0047] Considering the pressure attenuation characteristics at different positions in the fracture, the pressure distribution model formula in the fracture is:

[0048]

[0049] Where, p(x, t) is the pressure distribution in the crack, MPa; p1(t) is the pressure outside the casing (crack root) at time t, MPa; x is the crack coordinate from the crack root, m; L1(t) is the length of the liquid injected into the crack at time t, m;

[0050] Furthermore, the seepage model of the fracture wall includes the leakage of liquid on the fracture wall and the leakage of gas on the fracture wall, which are respectively:

[0051] ①Liquid leakage on the crack wall

[0052] If the liquid leakage in the high-energy gas fracturing process is still considered to be in accordance with Darcy's law, the fracture wall loss model in hydraulic fracturing can be used. Currently, the most widely used are the Carter model and the improved Carter model, whose basic equation is:

[0053]

[0054] Where u(x, t1) is the filtration rate at the fracture wall coordinate x at time t, m / s; C is the comprehensive fluid loss coefficient, m / s 1 / 2 ; t1 is the filtration time, s; τ(x) is the time when the cross section at point x starts to lose lateral filtration, s;

[0055] The comprehensive fluid loss coefficient C is:

[0056]

[0057] Where ΔP f is the pressure difference inside and outside the fracture, MPa; K0 is the permeability of the rock, μm 2 ; C f is the elastic compression coefficient, MPa -1 ; is the porosity, dimensionless; μ is the fluid viscosity, MPa·S;

[0058] It can be concluded that the filtration loss in the entire crack within time t is:

[0059]

[0060] Where q(t) is the filtration loss in the entire high-energy gas fracturing fracture system within time t, m 3 ; n is the number of cracks; L 1i (t) is the liquid injection length of the liquid in the i-th fracture at time t, m; h is the oil layer thickness, m;

[0061] ②Gas leakage on the crack wall

[0062] When the explosive gas migrates to the perforation position, the explosive gas begins to enter the fracture. At this time, the fluid lost on the fracture wall is gas. The loss and migration of high-pressure gas in porous media should be regarded as non-Darcy seepage. An item is added to Darcy's law to consider this difference, so Darcy's law becomes:

[0063]

[0064] Where u1(x, t) is the filtration rate of the explosive gas on the fracture wall, m / s; K is the permeability of the formation rock, μm 2 ; ρ1 is the fluid density, kg / m 3; β is the non-Darcy coefficient. The Geertsma method is generally used in the calculation, and its calculation formula is: μm -1 ;

[0065] Thus, the filtration rate at the fracture wall coordinate x at time t is obtained, u1(x, t). Substituting its value into the calculation formula of the filtration amount in the entire fracture, the gas filtration amount of all fracture systems within time t in the high-energy gas fracturing process is obtained.

[0066] Furthermore, the criterion model for crack initiation and crack arrest is:

[0067] The magnitude of the cohesion depends on the crack width. Fracture mechanics believes that there is a critical crack width w c , only when the crack width reaches this critical value, the crack tip will split. The calculation of the critical crack width is:

[0068]

[0069] In the formula, w c is the critical crack width, m; K 1C is the critical stress intensity factor at the crack tip, Nm -3 / 2 ; v is the rock fracture velocity, m / s; σ t is the tensile strength of rock, MPa;

[0070] Assuming that the cohesion at the crack tip is linearly distributed, and at the crack tip, where the crack width is zero, the cohesion is equal to the tensile strength of the rock, the relationship between the crack cohesion and the crack width is:

[0071]

[0072] In the formula, σ c (x) is the plastic cohesion at position x, MPa; c The crack width is equal to the critical width δ c The crack length coordinate at time; w(x) is the crack width at x;

[0073] Based on the stress analysis, the commonly used fracture mechanics theory is used to conduct mechanical analysis of crack initiation and extension. According to this theory, there is a length L in the infinite plate. f The general formula for the stress intensity factor of a crack is:

[0074]

[0075] The high-pressure fluid-driven fracture extension must not only overcome the closure strength factor caused by the ground stress on the fracture, but also overcome the strength factor caused by the cohesion of the rock tensile damage at the fracture tip. Therefore, the strength factor caused by the cohesion of a single fracture is:

[0076]

[0077] The tip stress intensity factor of the crack opening tendency caused by the high pressure fluid in the crack is:

[0078]

[0079] From the analysis of the elastoplastic crack morphology, it can be seen that the length of the high-pressure fluid injected into the crack should be equal to the crack width greater than the critical width δ c The stress intensity factor at the crack tip is:

[0080]

[0081] According to fracture mechanics theory, the crack initiation condition is: K ≥ K 1C , that is, when K ≥ K 1C When K<K 1C The cracks stopped when the cracks stopped.

[0082] Furthermore, the crack extension velocity model is:

[0083] Research shows that once a rock crack starts, it will extend forward at a constant speed. The speed value is:

[0084] v s =0.38C p

[0085]

[0086] In the formula, v s is the crack extension speed, m / s; C p is the propagation velocity of longitudinal waves in rocks, m / s; E is the energy of rock fractures, J; σ r is the rock density, kg / m 3 ;

[0087] Furthermore, the crack width model is:

[0088] The crack width calculation formula is:

[0089]

[0090] Where W(x, t) is the crack width at point x in the crack at time t, m; G is the rock shear modulus, MPa; ξ and ζ are the instantaneous length of the crack during expansion and the micro-segment length of the crack at that moment, respectively, m; p(ζ, t) and σ(ζ) are functions of the coordinates of the crack itself.

[0091] The advantages and positive effects of the present invention are:

[0092] The present invention achieves the optimal design of the amount of gunpowder for pulse deflagration cracking and unblocking construction before construction by establishing a model, thereby preventing damage to the casing by excessive gunpowder and improving construction safety. At the same time, the present invention can accurately analyze the crack morphology formed by the gunpowder on the stratum after construction, providing a strong basis for subsequent construction plans. BRIEF DESCRIPTION OF THE DRAWINGS

[0093] The technical solution of the present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments, but it should be understood that these drawings are designed only for explanation purposes and are not intended to limit the scope of the present invention. In addition, unless otherwise specified, these drawings are intended only to conceptually illustrate the structural configurations described herein and are not necessarily drawn to scale.

[0094] Figure 1 It is a flowchart of the maximum powder quantity confirmation process in an embodiment of the present invention;

[0095] Figure 2 Schematic diagram of an ideal model of gunpowder deflagration in an embodiment of the present invention;

[0096] Figure 3 A flowchart of a solution route for a gunpowder deflagration loading model in an embodiment of the present invention;

[0097] Figure 4 Schematic diagram of crack stress in an embodiment of the present invention. DETAILED DESCRIPTION

[0098] First of all, it should be noted that the specific structure, features and advantages of the present invention will be specifically described below by way of example, but all descriptions are only for illustration and should not be understood as limiting the present invention in any way. In addition, any single technical feature described or implied in the embodiments mentioned herein, or any single technical feature displayed or implied in the drawings, can still be combined or deleted between these technical features (or their equivalents) to obtain more other embodiments of the present invention that may not be directly mentioned in this document. In addition, in order to simplify the drawings, the same or similar technical features may be marked only in one place in the same drawing.

[0099] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application may be combined with each other.

[0100] Example 1

[0101] The method for modeling gunpowder pulse deflagration based on coupled dynamics provided in this embodiment includes the following steps:

[0102] Establishing a gunpowder deflagration kinetic model, the gunpowder deflagration kinetic model includes a physical model and a mathematical model of gunpowder deflagration, the mathematical model includes a gunpowder burning rate equation, a mass conservation equation, an energy conservation equation, and a deflagration gas production state equation; solving the gunpowder deflagration kinetic model to obtain pressure and temperature changes during the gunpowder deflagration process;

[0103] A dynamic model of the movement law of the wellbore killing fluid column is established. The movement of the killing fluid is divided into two parts. On the one hand, it is dominated by the pressure of the construction section, and on the other hand, it also affects the explosive pulse deflagration process. The analysis provides theoretical support for the stress of the downhole pipe string.

[0104] Establish a fracture system dynamics model, a fracture fluid pressure distribution model, a fracture wall seepage model, a fracture initiation and arrest criterion model, a fracture extension velocity model, and a fracture width model. Use the mass conservation and energy conservation of high-pressure fluids to solve the model, thereby determining whether the fracture extends at any time, and quantitatively describing the downhole fracture morphology at any time during the explosive pulse deflagration process.

[0105] The process of determining the maximum amount of gunpowder is as follows: Figure 1 As shown:

[0106] First, an initial charge value and a fixed charge increase amplitude value (smaller) are given; secondly, the change process of the deflagration pressure under this charge value is calculated according to the well-killing fluid column movement, perforation gas leakage and fracture extension model, and the maximum pressure value is obtained. Finally, the casing internal pressure resistance of the perforated part is calculated according to the perforation distribution, casing size, material properties, etc. Whether the maximum deflagration pressure value calculated in the previous step is greater than the casing internal pressure resistance, if not, a fixed charge amplitude value is added, and the calculation is jumped to the above maximum pressure value; if it is greater than the casing internal pressure resistance, then exit, and the previous charge value is the maximum allowable charge value required.

[0107] Specific:

[0108] (1) Establishing a physical model of the gunpowder deflagration process:

[0109] The gunpowder bomb of pulse deflagration is generally immersed in liquid and deflagrated. After the deflagration, it pushes the lower liquid or directly squeezes the gunpowder gas into the perforation hole to fractur e the oil layer, and on the other hand, it compresses and pushes the upper well-killing fluid column. Its quantitative calculation model is described in the following part. The research on the gunpowder deflagration model will be simplified as follows Figure 2The physical environment shown is: in a confined space, a fixed amount of gunpowder is deflagrated, the gunpowder bomb is cylindrical, and the inner surface is ignited at the same time. Under this condition, a quantitative relationship model of the pressure and temperature changes with time in the gunpowder deflagration process is established, which provides a basis for the establishment of the subsequent pulse deflagration process coupling model.

[0110] The entire process of gunpowder pulse deflagration is usually completed within a few milliseconds. The process is very complicated. In order to simplify the problem, the following assumptions are adopted:

[0111] The gunpowder deflagration space is closed and its volume does not change with time; the pressure and temperature of each point in the closed space remain consistent during the gunpowder deflagration process; the gunpowder deflagration obeys the geometric deflagration law; the deflagration loading process is an adiabatic process, and after loading it is a non-adiabatic process; the fuel gas is a perfect gas with constant specific heat and conforms to the perfect gas state equation; the propellant deflagrates completely and the composition of the deflagration products remains unchanged.

[0112] (2) Establish a mathematical model of the gunpowder deflagration process:

[0113] The mathematical model is established by combining comprehensive analysis of the gunpowder deflagration section in a closed area and the heat dissipation and pressure relief section after the completion of the gunpowder deflagration.

[0114] 1) The deflagration of gunpowder conforms to the geometric combustion law, that is, the deflagration of gunpowder gradually expands from the surface in a parallel layer to the inside perpendicular to the gunpowder surface; the combustion speed of gunpowder is affected by many factors. For gunpowder pulse deflagration, the environmental pressure has the most direct impact on the combustion speed;

[0115] The kinetic model of gunpowder deflagration process, which consists of the gunpowder burning rate equation, gas state equation, mass conservation equation and energy conservation equation, can be quantitatively solved in combination with the model boundary conditions to derive the pressure-time and temperature-time variation relationships in the deflagration confined space;

[0116]

[0117] Where V g is the deflagration volume of the charge, m 3 ; t is any time, s; p is the explosive pressure of gunpowder, MPa; w0 is the explosive burning rate coefficient (explosion rate when the pressure is 1MPa), m / s·(MPa); S0 is the explosive surface area of ​​gunpowder, m 2 ; n is the pressure index; R is the outer radius of the charge, m; T is the deflagration temperature, °C; M is the molecular weight of the gas; V r is the free volume occupied by the gas in the deflagration enclosed space (the center of the gunpowder has an initial volume. If the well-killing fluid method is used, the free volume should generally be larger than the volume reduced by the gunpowder deflagration due to the movement of the well-killing fluid column); ρ0 is the density of the gunpowder column, kg / m 3 ; ρ is the density of gunpowder gas, kg / m 3; F is the gunpowder force, J / kg; c g is the specific heat of propellant gas, J / kg·℃; m r is the mass of gunpowder burned, kg;

[0118] 2) Analysis of heat dissipation and pressure relief section after the explosion of gunpowder

[0119] After the explosion of gunpowder ends, no new gas is generated. If the gas volume remains unchanged, the system only loses heat, and the pressure and temperature gradually decrease. When the cracks in the late stage of stratum fracturing stop expanding, the heat dissipation and pressure relief process is similar to this process. According to the energy balance, the heat Q dissipated by the gas into the surrounding strata within dt time c , the heat dissipation is calculated as:

[0120]

[0121] Where T0 is the formation temperature, °C; L is the wellbore length, m; D is the wellbore diameter, m; α is the convection heat transfer coefficient between gas and formation; λ f is the formation thermal conductivity; f(t) is the time function reflecting the non-steady-state properties, a is the thermal conductivity or thermal diffusivity of the formation;

[0122] Since it is an isochoric process, the relationship between temperature, pressure and time in the closed space of the aftereffect stage is:

[0123]

[0124]

[0125] Where, T m is the initial temperature in the wellbore of the descending section, °C;

[0126] (3) Solution of the kinetic model of gunpowder deflagration process

[0127] 1) Solution of gunpowder deflagration loading model

[0128] When there is no explosion, that is, t = 0,

[0129] u(0)=0, p(0)=p0, T(0)=T0, δ=0, S0(0)=2πlr

[0130] The deflagration is complete, that is, t = t all hour,

[0131] δ=Rr,p(t)=p m ,T(t)=T m ,S0(t)=2πRl,

[0132] Where, u is the deflagration linear velocity of the gunpowder, m / s; δ is the deflagration thickness of the gunpowder column at any time t, m; r is the radius of the center hole in the gunpowder column, m; l is the length of the gunpowder column, m;

[0133] The experimental data of the segmented burning rate determination of the most commonly used RDT 11 high-temperature caseless projectile composite propellant are shown in Table 1.

[0134] Table 1 Burning rate test results of high temperature caseless ammunition

[0135]

[0136] From the above analysis, it can be concluded that Figure 2 Under given physical conditions, the calculation model of gunpowder deflagration is composed of four equations: gunpowder deflagration equation, gas state equation, mass conservation equation and energy conservation equation. The unknowns are gunpowder deflagration velocity, gas density, system pressure and system temperature. The four equations and four unknowns can be quantitatively solved in combination with the model boundary conditions. The specific solution route is as follows: Figure 3 As shown:

[0137] First, enter some basic data, such as solid thruster length, solid thruster outer radius, center hole radius, solid thruster burning rate coefficient, etc. After completing the basic parameter input, start calculating the pressure at the bottom of the well before ignition as the initial pressure. According to the parameters entered by the user, the iterative calculation step is divided (if it exceeds the range, there will be a prompt message).

[0138] Secondly, iterative calculations are started. Within a time step Δt, the burning rate, burning volume, and total burning thickness of the solid propellant at time t are calculated according to the mathematical model. Based on this, the mass conservation equation, energy conservation equation, gas state equation, and burning rate coefficient equation are used to calculate the volume, density, temperature, and pressure of the gas generated by the solid propellant within the same time step Δt.

[0139] Finally, after the iterative calculation is completed, it is determined whether the solid propellant is completely burned. If it is completely burned, the relationship diagram between pressure, temperature and time is output, and the calculation data can also be exported. If the combustion is not complete, the iteration is continued until the solid propellant is completely burned.

[0140] 2) Solution of the gunpowder deflagration unloading model

[0141] Assuming that the only energy loss in the system is the heat dissipation around the wellbore,

[0142] The deflagration is complete, that is, t = t all hour:

[0143] T=T m ,p=p m

[0144] Unloading is complete, that is, t = t m hour:

[0145] T=T0,p=p0

[0146] Then, based on the temperature and pressure analytical calculation formulas and combined with the model boundary conditions, the relationship between the temperature and pressure of the system during the unloading stage and time can be quantitatively calculated.

[0147] The method for establishing the dynamic model of the motion law of the wellbore killing fluid column is as follows:

[0148] (1) The liquid column above the fracturing bomb moves upward under the pressure of the construction section. The motion equation of the latter part of the well-killing liquid column is derived from its force condition. If the resistance is ignored, the differential equation of motion of the liquid column can be written as:

[0149]

[0150] Where: S L H is the distance the well-killing fluid moves upward, m; L is the height of the liquid on the fracturing bomb, m; g is the acceleration of gravity; p w is the wellbore pressure, MPa; ρ L is the density of the well-killing liquid, kg / m 3 ;

[0151] The volume of liquid displaced is:

[0152] V L =πD 2 S L

[0153] Where V L is the volume of well-killing fluid released upward, m 3 ;

[0154] Then, the volume occupied by gas in the wellbore at any time is:

[0155]

[0156] Where V0 is the initial free volume in the cartridge case, m 3 ; V e is the elastic increment of the wellbore volume (or this item is not considered); M0 is the initial main charge mass, kg; f is the shape function;

[0157] (2) The mass of gunpowder corresponding to the gas in the wellbore is:

[0158] M w =fM0-M d

[0159] Among them, M w is the mass of gunpowder corresponding to the gas in the wellbore, kg; M d is the mass of gunpowder corresponding to the gas leaking from the wellbore, kg;

[0160] At any time, the gas production pressure of gunpowder in the wellbore can be obtained by correcting the maximum internal pressure formula of the closed container; for a closed container that does not leak air, the pressure generated by the combustion of gunpowder is:

[0161]

[0162] Where p0 is the pressure generated by the combustion of gunpowder in a closed space, MPa; V is the volume of the closed container, m 3 ; γ is the residual volume (volume occupied by solid matter after the gunpowder burns), m 3 / kg;

[0163] At any time when the gunpowder has not been completely burned and part of the gas has leaked out, it can be considered that the wellbore pressure is generated by the combustion of the gunpowder corresponding to the gas remaining in the wellbore after deducting the part that has leaked out of the wellbore. At this time, the volume occupied by the gas corresponding to the volume of the closed container is composed of the original free volume, the original volume occupied by the burned gunpowder part, and the volume vacated by the liquid movement. The wellbore pressure is:

[0164]

[0165] In the formula, p y V is the well pressure at any time when the gunpowder has not yet been completely burned and some gas has leaked out, MPa; y is the volume occupied by gas in the wellbore, m 3 ;

[0166] The fluid pressure distribution model in the slit is:

[0167] After the explosive fracturing crack is initiated, the flow of high-pressure fluid in the crack can be regarded as a pressurized pipe flow in a narrow and long section. The continuity equation, momentum conservation equation and fluid state equation of the fluid can be established respectively, and the expansion flow velocity of the fluid in the crack can be obtained by numerical solution. However, the process of solving the equation group is complicated and the convergence is poor. Therefore, in most related studies, the fluid pressure in the crack is simplified to a uniform distribution or a trapezoidal, triangular and other distribution forms. Considering the pressure attenuation characteristics at different positions in the crack, the pressure distribution model formula in the crack is adopted as:

[0168]

[0169] Where, p(x, t) is the pressure distribution in the crack, MPa; p1(t) is the pressure outside the casing (crack root) at time t, MPa; x is the crack coordinate from the crack root, m; L1(t) is the length of the liquid injected into the crack at time t, m;

[0170] During the explosive pulse explosion, if the gas-liquid mixed flow stage in the crack is ignored, the fluid leakage on the crack wall is also divided into two stages, namely the early liquid leakage and the later gas leakage. This invention only considers the gas leakage. For the problem of fluid leakage under instantaneous high pressure, the linear Darcy seepage research method has certain limitations. Therefore, it is necessary to analyze the non-Darcy seepage model established in this environment, and establish the seepage model of the crack wall for liquid and gas respectively. Therefore, the seepage model of the crack wall includes the leakage of liquid on the crack wall and the leakage of gas on the crack wall, which are respectively:

[0171] ①Liquid leakage on the crack wall

[0172] If the liquid leakage in the high-energy gas fracturing process is still considered to be in accordance with Darcy's law, the fracture wall loss model in hydraulic fracturing can be used. Currently, the most widely used are the Carter model and the improved Carter model, whose basic equation is:

[0173]

[0174] Where u(x, t1) is the filtration rate at the fracture wall coordinate x at time t, m / s; C is the comprehensive fluid loss coefficient, m / s 1 / 2 ; t1 is the filtration time, s; τ(x) is the time when the cross section at point x starts to lose lateral filtration, s;

[0175] The comprehensive fluid loss coefficient C is:

[0176]

[0177] In the formula, ΔP f is the pressure difference inside and outside the fracture, MPa; K0 is the permeability of the rock, μm 2 ; C f is the elastic compression coefficient, MPa -1 ; is the porosity, dimensionless; μ is the fluid viscosity, MPa·S;

[0178] It can be concluded that the filtration loss in the entire crack within time t is:

[0179]

[0180] Where Q(t) is the filtration loss in the entire high-energy gas fracturing fracture system within time t, m 3 ; n is the number of cracks; L 1i (t) is the liquid injection length of the liquid in the i-th fracture at time t, m; h is the oil layer thickness, m;

[0181] ②Gas leakage on the crack wall

[0182] When the explosive gas migrates to the perforation position, the explosive gas begins to enter the fracture. At this time, the fluid lost on the fracture wall is gas. The loss and migration of high-pressure gas in porous media should be regarded as non-Darcy seepage. An item is added to Darcy's law to consider this difference, so Darcy's law becomes:

[0183]

[0184] Where u1(x, t) is the filtration rate of the propellant gas on the crack wall, m / s; ρ1 is the fluid density, kg / m 3 ; β is the non-Darcy coefficient. The Geertsma method is generally used in the calculation, and its calculation formula is: μm -1 ;

[0185] Thus, the filtration rate at the fracture wall coordinate x at time t is obtained, u1(x, t). Substituting its value into the calculation formula of the filtration amount in the entire fracture, the gas filtration amount of all fracture systems within time t in the high-energy gas fracturing process is obtained.

[0186] The criterion model for crack initiation and crack arrest is:

[0187] If the formation rock is regarded as an elastic-plastic body, the COD model in fracture mechanics can be used to analyze the fracture stress model, such as Figure 4 The force acting on the outside of the crack to cause the crack to close consists of two parts: one is the extrusion force caused by the ground stress on the crack, and the other is the cohesive force of the tensile damage of the rock at the crack tip.

[0188] Stress in the earth's crust refers to the force per unit area inside the medium caused by rock deformation. It generally consists of two parts: stress caused by the weight of the covering rock, which is caused by gravity and the centrifugal force of the earth's rotation inertia; and tectonic stress transmitted from adjacent blocks or the bottom. This stress refers to the part that is different from the standard state. In addition to the modern tectonic stress transmitted from the adjacent blocks or the bottom, it also includes the residual stress left over from past tectonic movements that have not yet been completely relaxed, as well as stress changes caused by nearby man-made projects (such as tunnels and mining surfaces). Tectonic stress directly reflects the power source of crustal movement, and it is an important factor in causing earthquakes.

[0189] The present invention simplifies the calculation and only considers the first part of the force. The magnitude of the cohesive force depends on the crack width. Fracture mechanics believes that there is a critical crack width w c , only when the crack width reaches this critical value, the crack tip will split. The calculation of the critical crack width is:

[0190]

[0191] In the formula, w c is the critical crack width, m; K 1C is the critical stress intensity factor at the crack tip, Nm -3 / 2 ; v is the rock fracture velocity, m / s; σ t is the tensile strength of rock, MPa;

[0192] Assuming that the cohesion at the crack tip is linearly distributed, and at the crack tip, where the crack width is zero, the cohesion is equal to the tensile strength of the rock, the relationship between the crack cohesion and the crack width is:

[0193]

[0194] In the formula, σ c (x) is the plastic cohesion at position x, MPa; c The crack width is equal to the critical width δ c The crack length coordinate at time; w(x) is the crack width at x;

[0195] Based on the stress analysis, the commonly used fracture mechanics theory is used to conduct mechanical analysis of crack initiation and extension. According to this theory, there is a length L in the infinite plate. f The general formula for the stress intensity factor of a crack is:

[0196]

[0197] The intensity factor of the crack tip controlled by the ground stress can also be calculated by the above formula. According to the analysis of the crack stress, the high-pressure fluid-driven crack extension must not only overcome the closure intensity factor caused by the ground stress on the crack, but also overcome the intensity factor caused by the cohesion of the rock tensile damage at the crack tip. Therefore, the intensity factor caused by the cohesion of a single crack is:

[0198]

[0199] The tip stress intensity factor of the crack opening tendency caused by the high pressure fluid in the crack is:

[0200]

[0201] From the analysis of the elastoplastic crack morphology, it can be seen that the length of the high-pressure fluid injected into the crack should be equal to the crack width greater than the critical width δ c The stress intensity factor at the crack tip is:

[0202]

[0203] According to fracture mechanics theory, the crack initiation condition is: K ≥ K 1C , that is, when K ≥ K1C When K<K 1C The cracks stopped when the cracks stopped.

[0204] The crack extension velocity model is:

[0205] Research shows that once a rock crack starts, it will extend forward at a constant speed. The speed value is:

[0206] v s =0.38C p

[0207]

[0208] In the formula, v s is the crack extension speed, m / s; C p is the propagation velocity of longitudinal waves in rocks, m / s; E is the energy of rock fractures, J; σ r is the rock density, kg / m 3 ;

[0209] The crack width calculation formula in the crack width model is:

[0210]

[0211] Where, W(x, t) is the crack width at point x in the crack at time t, m; G is the rock shear modulus, MPa; ξ and ζ are the instantaneous length of the crack during the expansion process and the micro-segment length of the crack at that moment, m; p(ζ, t) and σ(ζ) are functions of the coordinates of the crack itself;

[0212] Through the above analysis, the approximate model of pressure distribution of high-pressure fluid in the fracture, the fluid leakage model, the fracture start / stop criterion model, the fracture extension velocity model and the fracture width model are given respectively. The combination of these models can determine whether the fracture extends at any time and quantitatively describe the downhole fracture morphology at any time during the high-energy gas fracturing process.

[0213] In solving the coupled solution of fracture dynamic extension, the mass conservation and energy conservation of high-pressure fluid are mainly used. The specific solution method is as follows:

[0214] (1) Mass conservation equation

[0215] In a certain time unit, the amount of fluid flowing into the fracture through the perforation holes is equal to the sum of the fluid increment in the fracture and the fluid leaking into the formation from the fracture wall.

[0216] dQ1=dQ2+dQ3

[0217] Where, d Q1 is the mass of fluid flowing from the perforation hole into the fracture in a certain time unit, kg; d Q2is the fluid increment in the microelement at that time, kg; d Q3 is the fluid increment leaking into the formation from the fracture wall during this time unit, kg;

[0218] Assuming that the perforation flow velocity at a certain moment is q(t), the amount of fluid flowing into the fracture through the perforation in this time element is:

[0219] dQ1=q(t)dt

[0220] According to the above introduction, assuming that the explosion pressure of the wellbore gunpowder bomb is known at any time, the volume leakage in the time element is only related to the pressure at the hole outside the casing, so the total mass of the fluid in the fracture at time t is:

[0221]

[0222] In the formula, ρ f (x, t) represent the fluid density at point x in the fracture at time t;

[0223] Therefore, the change of fluid inside the fracture in any time element can be obtained as follows:

[0224]

[0225] Similarly, the leakage of fluid from the crack wall in the microelement at any time is:

[0226]

[0227] Substituting the total mass of the fluid in the crack at time t, the change of the fluid in the crack at any time unit, and the leakage of the fluid from the crack wall at any time unit into dQ1=dQ2+dQ3, the mass conservation equation in the dynamic extension process of the crack is obtained:

[0228]

[0229] Through the establishment and solution of the above model, the optimal design of the amount of gunpowder for pulse deflagration cracking and unblocking construction before construction is achieved, which prevents the casing from being damaged by excessive amount of gunpowder and improves the construction safety. At the same time, the present invention can accurately analyze the crack morphology formed by the gunpowder on the formation after construction, providing a strong basis for the subsequent construction plan.

[0230] The above embodiments describe the present invention in detail, but the contents are only preferred embodiments of the present invention and cannot be considered to limit the scope of the present invention. All equivalent changes and improvements made within the scope of the present invention should still fall within the scope of the present invention.

Claims

1. A method for modeling gunpowder pulse deflagration based on coupled dynamics, characterized in that: The steps include: Establishing a gunpowder deflagration kinetic model, the gunpowder deflagration kinetic model includes a physical model and a mathematical model of gunpowder deflagration, the mathematical model includes a gunpowder burning rate equation, a mass conservation equation, an energy conservation equation, and a deflagration gas production state equation; solving the gunpowder deflagration kinetic model to obtain pressure and temperature changes during the gunpowder deflagration process; A dynamic model of the movement law of the wellbore killing fluid column is established. The movement of the killing fluid is divided into two parts. On the one hand, it is dominated by the pressure of the construction section, and on the other hand, it also affects the explosive pulse deflagration process. The analysis provides theoretical support for the stress of the downhole pipe string. Establish a fracture system dynamics model, a fracture fluid pressure distribution model, a fracture wall seepage model, a fracture initiation and arrest criterion model, a fracture extension velocity model, and a fracture width model. Use the mass conservation and energy conservation of high-pressure fluids to solve the model, thereby determining whether the fracture extends at any time, and quantitatively describing the downhole fracture morphology at any time during the explosive pulse deflagration process. By combining the three models of gunpowder deflagration, wellbore pressure fluid column movement law, perforation gas leakage and crack expansion, the maximum amount of gunpowder required for construction is calculated. The deflagration pressure generated at this amount will not only have no safety impact on the downhole tubing, but also can expand the formation cracks to the maximum extent.

2. The method for modeling gunpowder pulse deflagration based on coupled dynamics according to claim 1, characterized in that: The physical model of gunpowder deflagration is the deflagration of a fixed amount of gunpowder in a confined space. The gunpowder bomb is cylindrical and the inner surface is ignited simultaneously. The following assumptions are made: the gunpowder deflagration space is confined and the volume does not change with time; the pressure and temperature of each point in the confined space remain consistent during the gunpowder deflagration process; the gunpowder deflagration obeys the geometric deflagration law; the deflagration loading process is an adiabatic process and a non-adiabatic process after loading; the fuel gas is a perfect gas with constant specific heat and conforms to the perfect gas state equation; the propellant deflagrates completely and the composition of the deflagration products remains unchanged.

3. The method for modeling gunpowder pulse deflagration based on coupled dynamics according to claim 2, characterized in that: The mathematical model of gunpowder deflagration is established by combining comprehensive analysis of the gunpowder deflagration section in the closed area and the heat dissipation and pressure relief section after the gunpowder deflagration is completed. The establishment method is as follows: 1) The mathematical model includes the burning rate equation, mass conservation equation, energy conservation equation and deflagration gas production state equation of the gunpowder: Where V g is the deflagration volume of the powder column; t is any time; p is the deflagration pressure of the powder; w0 is the burning rate coefficient of the powder; S0 is the deflagration surface area of ​​the powder; n is the pressure index; R is the outer radius of the powder column; T is the deflagration temperature; M is the molecular weight of the gas; V r is the free volume occupied by the gas in the deflagration enclosed space; ρ0 is the density of the powder column; ρ is the density of the gunpowder gas; F is the gunpowder force; c g is the specific heat of gunpowder gas; m r is the mass of gunpowder burned; Combined with the model boundary conditions, quantitative solutions can be obtained to derive the pressure-time and temperature-time variation relationships in the deflagration confined space; 2) Analysis of heat dissipation and pressure relief section after the explosion of gunpowder According to the energy balance, the heat Q dissipated by the gas into the surrounding formation during the time dt c , the heat dissipation is calculated as: Where T0 is the formation temperature; L is the wellbore length; D is the wellbore diameter; α is the convection heat transfer coefficient between gas and formation; λ f is the formation thermal conductivity; f(t) is the time function reflecting the non-steady-state properties, a is the thermal conductivity or thermal diffusivity of the formation; Since it is an isochoric process, the relationship between temperature, pressure and time in the closed space of the aftereffect stage is: Where, T m is the initial temperature in the wellbore of the descending section; Combined with the model boundary conditions, the relationship between the temperature and pressure of the system during the unloading stage and time can be quantitatively calculated.

4. The method for modeling gunpowder pulse deflagration based on coupled dynamics according to claim 1, characterized in that: The method for establishing the dynamic model of the motion law of the wellbore killing fluid column is as follows: (1) The liquid column above the fracturing bomb moves upward under the pressure of the construction section. The motion equation of the latter part of the well-killing liquid column is derived from its force condition. If the resistance is ignored, the differential equation of motion of the liquid column can be written as: Where: S L H is the distance the well-killing fluid moves upward; L is the height of the liquid on the fracturing bomb; g is the acceleration of gravity; p w is the wellbore pressure; ρ L is the density of the well-killing fluid; The volume of liquid displaced is: V L =πD 2 S L Where V L The volume of the well-killing fluid that is released upward; Then, the volume occupied by gas in the wellbore at any time is: Where V0 is the initial free volume in the cartridge case, m 3 ; V e is the elastic increment of the wellbore volume; M0 is the initial main charge mass; f is the shape function; (2) The mass of gunpowder corresponding to the gas in the wellbore is: M w =fM0-M d Among them, M w is the mass of gunpowder corresponding to the gas in the wellbore; M d is the mass of gunpowder corresponding to the gas leaking from the wellbore; At any time when the gunpowder has not been completely burned and part of the gas has leaked out, it can be considered that the wellbore pressure is generated by the combustion of the gunpowder corresponding to the gas remaining in the wellbore after deducting the part that has leaked out of the wellbore. At this time, the volume occupied by the gas corresponding to the volume of the closed container is composed of the original free volume, the original volume occupied by the burned gunpowder part, and the volume vacated by the liquid movement. The wellbore pressure is: In the formula, p y V is the pressure in the well at any time when the gunpowder has not yet been completely burned and some gas has leaked out; y is the volume occupied by gas in the wellbore; γ is the complementary capacity.

5. The method for modeling gunpowder pulse deflagration based on coupled dynamics according to claim 1, characterized in that: The fluid pressure distribution model in the slit is: Considering the pressure attenuation characteristics at different positions in the fracture, the pressure distribution model formula in the fracture is: Where p(x, t) is the pressure distribution in the crack; p1(t) is the pressure at the crack root outside the casing at time t; x is the crack coordinate from the crack root; L1(t) is the length of the liquid injected into the crack at time t.

6. The method for modeling gunpowder pulse deflagration based on coupled dynamics according to claim 1, characterized in that: The seepage model of the fracture wall includes the leakage of liquid and gas on the fracture wall, which are respectively: ①Liquid leakage on the crack wall If the liquid leakage in the high-energy gas fracturing process is still considered to be in accordance with Darcy's law, the fracture wall loss model in hydraulic fracturing can be used. Currently, the most widely used are the Carter model and the improved Carter model, whose basic equation is: Where, u(x, t1) is the filtration rate at the fracture wall coordinate x at time t; C is the comprehensive fluid loss coefficient; t1 is the filtration time; τ(x) is the time when the cross-section at point x begins to lateral filtration; The comprehensive fluid loss coefficient C is: In the formula, ΔP f is the pressure difference inside and outside the fracture; K0 is the permeability of the rock; C f is the elastic compression coefficient; is the porosity; μ is the fluid viscosity; It can be concluded that the filtration loss in the entire crack within time t is: Where q(t) is the filtration loss in the entire high-energy gas fracturing fracture system within time t; n is the number of fractures; L 1i (t) is the liquid injection length of the liquid in the i-th fracture at time t; h is the oil layer thickness; ②Gas leakage on the crack wall When the explosive gas migrates to the perforation position, the explosive gas begins to enter the fracture. At this time, the fluid lost on the fracture wall is gas. The loss and migration of high-pressure gas in porous media should be regarded as non-Darcy seepage. An item is added to Darcy's law to consider this difference, so Darcy's law becomes: Where, u1(x, t) is the filtration rate of the explosive gas on the fracture wall; K is the formation rock permeability; ρ1 is the fluid density; β is the non-Darcy coefficient; Thus, the filtration rate at the fracture wall coordinate x at time t is obtained. Substituting its value into the calculation formula of the filtration amount in the entire fracture, the gas filtration amount of all fracture systems within time t in the high-energy gas fracturing process is obtained.

7. The method for modeling gunpowder pulse deflagration based on coupled dynamics according to claim 1, characterized in that: The criterion model for crack initiation and crack arrest is: The magnitude of the cohesion depends on the crack width. Fracture mechanics believes that there is a critical crack width w c , only when the crack width reaches this critical value, the crack tip will split. The calculation of the critical crack width is: In the formula, w c is the critical crack width; K 1C is the critical stress intensity factor at the crack tip; v is the rock crack velocity; σ t is the tensile strength of rock; Assuming that the cohesion at the crack tip is linearly distributed, and at the crack tip, where the crack width is zero, the cohesion is equal to the tensile strength of the rock, the relationship between the crack cohesion and the crack width is: In the formula, σ c (x) is the plastic cohesion at x; c The crack width is equal to the critical width δ c The crack length coordinate at time; w(x) is the crack width at x; The infinite plate has a length L f The general formula for the stress intensity factor of a crack is: The high-pressure fluid-driven fracture extension must not only overcome the closure strength factor caused by the ground stress on the fracture, but also overcome the strength factor caused by the cohesion of the rock tensile damage at the fracture tip. Therefore, the strength factor caused by the cohesion of a single fracture is: The tip stress intensity factor of the crack opening tendency caused by the high pressure fluid in the crack is: From the analysis of the elastoplastic crack morphology, it can be seen that the length of the high-pressure fluid injected into the crack should be equal to the crack width greater than the critical width δ c The stress intensity factor at the crack tip is: According to fracture mechanics theory, the crack initiation condition is: K ≥ K 1C , that is, when K ≥ K 1C When K<K 1C The cracks stopped when they occurred.

8. The method for modeling gunpowder pulse deflagration based on coupled dynamics according to claim 1, characterized in that: The crack extension velocity model is: Research shows that once a rock crack starts, it will extend forward at a constant speed. The speed value is: V s =0.38C p In the formula, v s is the crack extension speed; C p is the propagation velocity of longitudinal waves in rocks; E is the energy of rock fractures; σ r is the rock density.

9. The method for modeling gunpowder pulse deflagration based on coupled dynamics according to claim 1, characterized in that: The crack width model is: The crack width calculation formula is: Where W(x, t) is the crack width at point x in the crack at time t; G is the rock shear modulus; ξ and ζ are the instantaneous length of the crack during expansion and the micro-segment length of the crack at that moment, respectively; p(ζ, t) and σ(ζ) are functions of the coordinates of the crack itself.

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