A proppant distribution optimization method based on pressure distribution control

Abstract

The present invention discloses a proppant distribution optimization method based on pressure distribution control, comprising: constructing a fracture pressure distribution model that considers the coupling of multiple physical fields; dividing the fracture into fracture regions based on the fracture pressure distribution model and combining geostatistical methods, and calculating the corresponding pressure gradient value for each fracture region using an optimization algorithm; controlling the proppant injection process based on the pressure gradient values ​​corresponding to each fracture region; and during the proppant injection process, monitoring the fracture pressure data in real time, and adjusting the proppant injection pressure in real time when the monitored fracture pressure data exceeds a preset pressure threshold. The present invention achieves uniform and efficient distribution of proppant in the fracture through precise fracture pressure distribution analysis, a scientific pressure gradient adjustment strategy, and real-time injection process adjustment.

Description

Technical Field

[0001] The present invention relates to the technical field of oil and gas field development, and in particular to a proppant distribution optimization method based on pressure distribution control. Background Art

[0002] In current oil and gas fracturing operations, the proper distribution of proppant plays a crucial role in determining fracturing effectiveness. However, traditional proppant injection methods have significant drawbacks. These methods often rely on historical experience or operate based on simple preset parameters. For example, they estimate the approximate width of the fracture before injection and determine the proppant injection pressure and flow rate, but they seriously ignore the complexity of pressure distribution within the fracture.

[0003] Underground fractures have diverse geometric forms, ranging from tens to hundreds of meters in length, with widths fluctuating on the millimeter or even micrometer scale, and significant height variations, often accompanied by irregular bends and branches. Taking a complex oil reservoir as an example, fractures can reach lengths of up to 300 meters, with widths fluctuating between 2 and 8 mm. Some fractures exhibit S-shaped bends, making the flow path of proppants within them highly variable. Furthermore, permeability varies significantly depending on reservoir characteristics, ranging from as little as 1 md in low-permeability reservoirs to over 100 md in high-permeability reservoirs. This directly impacts the proppant's propulsion speed and distribution uniformity within the fractures. Rock properties are equally complex: high-hardness rocks hinder proppant embedment, while brittle rocks are prone to generating numerous microcracks during fracturing. The presence of these microcracks alters the pressure transmission path and the space available for proppant filling.

[0004] Under such complex conditions, traditional injection methods can easily lead to uneven proppant distribution. In areas with narrow fractures and low permeability, improper injection pressure and flow rate settings make it difficult for proppant to enter smoothly, resulting in insufficient support. In areas with wider fractures and high permeability, proppant may over-aggregate due to excessive flow rates, which not only wastes resources but also reduces the conductivity of the fractures. This series of problems causes fractures to close prematurely, making it difficult to increase oil and gas well production and keeping extraction costs high, which seriously restricts the efficient development of the oil and gas extraction industry. In view of this, the present invention is proposed. Summary of the Invention

[0005] In order to solve the above problems, the present invention proposes a proppant distribution optimization method based on pressure distribution control. By precisely controlling the pressure distribution, the distribution of the proppant is optimized, which is of great significance for improving oil and gas production efficiency and economic benefits.

[0006] Specifically, the following technical solutions are adopted:

[0007] A proppant distribution optimization method based on pressure distribution control, comprising:

[0008] Construct a pressure distribution model within the fracture that considers the coupling of multiple physical fields;

[0009] Based on the fracture pressure distribution model and combined with geostatistical methods, the fractures are divided into fracture areas, and the corresponding pressure gradient value is calculated for each fracture area using an optimization algorithm;

[0010] Control the proppant injection process based on the pressure gradient values ​​corresponding to each area of ​​the fracture;

[0011] During the injection process of the proppant, the pressure data in the fracture is monitored in real time. When the pressure data in the fracture is monitored to exceed the preset pressure threshold, the injection pressure of the proppant is adjusted in real time.

[0012] As an optional embodiment of the present invention, in a proppant distribution optimization method based on pressure distribution control of the present invention, constructing a fracture pressure distribution model considering multi-physical field coupling includes:

[0013] Collect and organize fracture geometry parameters, fracture permeability and rock characteristic parameters;

[0014] Input the collected and sorted parameters into the finite element analysis software for meshing, discretize the crack area into multiple small units, and generate a discretized crack geometry model;

[0015] Combining fluid mechanics and rock mechanics equations, considering the flow of fluid in fractures and the mechanical properties of rocks, a mathematical model of multi-physical field coupling is established.

[0016] As an optional embodiment of the present invention, a proppant distribution optimization method based on pressure distribution control of the present invention includes:

[0017] The mathematical model of multi-physics field coupling is solved by numerical simulation method to obtain the pressure distribution in the crack;

[0018] The mathematical model of multi-physics field coupling is the coupling equation of fluid and rock, the fluid mechanics equation , rock deformation equation ,in, is the divergence operator, k is the permeability tensor, is the pressure gradient, is the porosity, t is the time is the rock stress tensor, is the fluid density.

[0019] As an optional embodiment of the present invention, in a proppant distribution optimization method based on pressure distribution control of the present invention, when using finite element analysis software to analyze the geometric parameters of the crack, the complex boundary conditions of the crack are accurately processed, and the influence of the roughness of the crack surface and the contact state factors on the pressure distribution are considered.

[0020] As an optional embodiment of the present invention, a proppant distribution optimization method based on pressure distribution control of the present invention includes:

[0021] The roughness coefficient is introduced to represent the effect of the roughness of the fracture surface on the flow resistance of the fluid in the fracture. The roughness coefficient is related to the roughness of the fracture surface. The effect of roughness on the flow resistance is quantified by the modified Forchheimer equation: , where μ is the fluid dynamic viscosity, k is the permeability, β is the roughness coefficient, which is calibrated by experiments, ρ is the fluid density, and q is the flow velocity. Indicates the absolute value of flow velocity, is the pressure gradient;

[0022] The influence of contact state factors on pressure distribution is calculated by establishing a contact mechanics model.

[0023] As an optional embodiment of the present invention, in a proppant distribution optimization method based on pressure distribution control of the present invention, the calculation of the corresponding pressure gradient value for each fracture region using an optimization algorithm includes:

[0024] Based on the geometric parameters of the fracture and the fracture permeability data, the gradient descent method is used to solve the optimal solution of the pressure gradient;

[0025] The gradient descent method solution process includes: defining an objective function ,in is the pressure gradient vector, which represents the degree of unevenness of proppant distribution. The gradient value of the objective function with respect to the pressure gradient is calculated;

[0026] The update formula of the gradient descent method is: ,in, is the pressure gradient vector of the nth iteration, is the learning rate, The objective function is The gradient value at ;

[0027] By continuously iterating the update formula of the gradient descent method until the objective function The optimal solution for the pressure gradient is obtained when the gradient value of the pressure gradient no longer changes significantly. As an optional embodiment of the present invention, in a proppant distribution optimization method based on pressure distribution control of the present invention, the corresponding pressure gradient value calculated using an optimization algorithm for each fracture region includes:

[0028] Based on the geometric parameters of the fracture and the fracture permeability data, the optimization algorithm of the genetic algorithm is used to solve the optimal solution of the pressure gradient;

[0029] The solution process of genetic algorithm includes: defining an objective function ,in is the pressure gradient vector, which represents the degree of heterogeneity of proppant distribution;

[0030] By calculating the fitness of each individual in the population, that is, the value of the objective function corresponding to the initial pressure gradient value, individuals with higher fitness are selected for crossover and mutation operations to generate new individuals;

[0031] Repeat the above process until the individuals in the population reach the convergence condition. The optimal individual at this time is the optimal solution of the pressure gradient.

[0032] As an optional embodiment of the present invention, a proppant distribution optimization method based on pressure distribution control of the present invention includes:

[0033] For areas in the fracture where the fracture width is greater than a first preset fracture width threshold and the fracture permeability is greater than a first preset fracture permeability threshold, variable frequency speed regulation technology is used to adjust the speed of the proppant injection pump to control the pressure gradient within the pressure gradient value range calculated by the optimization algorithm, so that the proppant injection rate is maintained within the set flow rate range;

[0034] For areas in the crack where the crack width is less than the second preset crack width threshold, or the crack permeability is less than the second preset crack permeability threshold, the pressure gradient value calculated by the optimization algorithm is increased by adjusting the throttle valve opening and changing the pipeline diameter.

[0035] As an optional embodiment of the present invention, in a proppant distribution optimization method based on pressure distribution control of the present invention, when using the optimization algorithm to calculate the corresponding pressure gradient value, the influence of the physical properties of the proppant's particle size distribution, density, and shape coefficient on the flow resistance of the proppant in the fracture is considered.

[0036] As an optional embodiment of the present invention, in a proppant distribution optimization method based on pressure distribution control of the present invention, during the proppant injection process, real-time monitoring of the pressure data within the fracture and adjusting the proppant injection pressure in real time when the monitored pressure data within the fracture exceeds a preset pressure threshold include:

[0037] Deploy downhole monitoring equipment to collect real-time fracture pressure data at a millisecond sampling frequency during proppant injection and transmit the data to the ground control center;

[0038] The ground control center filters and de-noises the collected data and compares it with the preset pressure distribution model.

[0039] When the pressure deviation in the fracture is detected to exceed the preset threshold, the automatic control program is immediately started to adjust the motor frequency of the injection pump, change the pressure setting value of the hydraulic control system, and adjust the injection pressure of the proppant in real time.

[0040] Compared with the prior art, the present invention has the following beneficial effects:

[0041] The present invention's proppant distribution optimization method based on pressure distribution control achieves uniform and efficient proppant distribution within fractures through precise fracture pressure distribution analysis, a scientific pressure gradient adjustment strategy, and real-time injection process regulation. This method effectively enhances fracture conductivity, significantly improves oil and gas well production and recovery efficiency, reduces production costs, and extends the production life of oil and gas wells. This method brings significant economic benefits and application prospects to the oil and gas production industry, promoting technological advancement and sustainable development in the industry. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 A process of a proppant distribution optimization method based on pressure distribution control in an embodiment of the present invention Figure 1 ;

[0043] Figure 2 A process of a proppant distribution optimization method based on pressure distribution control in an embodiment of the present invention Figure 2 ;

[0044] Figure 3 A process of a proppant distribution optimization method based on pressure distribution control in an embodiment of the present invention Figure 3 . DETAILED DESCRIPTION

[0045] To make the purpose, technical solutions and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them.

[0046] Therefore, the following detailed description of the embodiments of the present invention is not intended to limit the scope of the claimed invention, but merely represents some embodiments of the present invention. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention without creative effort shall fall within the scope of protection of the present invention.

[0047] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features and technical solutions therein may be combined with each other.

[0048] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, it does not need to be further defined or explained in subsequent drawings.

[0049] In the description of the present invention, it should be noted that the terms "upper" and "lower" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, or the orientations or positional relationships in which the inventive product is typically placed when in use, or the orientations or positional relationships commonly understood by those skilled in the art. Such terms are intended solely to facilitate the description of the present invention and simplify the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, be constructed, or operate in a specific orientation. Therefore, they should not be construed as limitations on the present invention. Furthermore, the terms "first" and "second" and the like are used solely for distinction and should not be construed as indicating or implying relative importance.

[0050] See also Figure 1 As shown, a proppant distribution optimization method based on pressure distribution control in this embodiment includes:

[0051] Construct a pressure distribution model within the fracture that considers the coupling of multiple physical fields;

[0052] Based on the fracture pressure distribution model and combined with geostatistical methods, the fractures are divided into fracture areas with a division accuracy of meter level. For each fracture area, the corresponding pressure gradient value is calculated using an optimization algorithm.

[0053] Control the proppant injection process based on the pressure gradient values ​​corresponding to each area of ​​the fracture;

[0054] During the injection process of the proppant, the pressure data in the fracture is monitored in real time. When the pressure data in the fracture is monitored to exceed the preset pressure threshold, the injection pressure of the proppant is adjusted in real time.

[0055] Therefore, the proppant distribution optimization method based on pressure distribution control in this embodiment achieves uniform and efficient distribution of proppant within the fracture through precise fracture pressure distribution analysis, a scientific pressure gradient adjustment strategy, and real-time injection process adjustment. This effectively enhances fracture conductivity, significantly improves oil and gas well production and recovery efficiency, reduces production costs, and extends the production life of oil and gas wells. This brings excellent economic benefits and application prospects to the oil and gas production industry, and promotes technological advancement and sustainable development in the industry.

[0056] As an optional embodiment of the present invention, see Figure 2 As shown, in a proppant distribution optimization method based on pressure distribution control of this embodiment, the construction of a fracture pressure distribution model considering the multi-physical field coupling effect includes:

[0057] Collect and organize fracture geometry parameters (such as length, width, height, etc.), fracture permeability, and rock characteristic parameters (such as hardness, brittleness, etc.);

[0058] Input the collected and organized parameters into finite element analysis software (such as COMSOL or ANSYS) for meshing, discretize the crack area into multiple small units, and generate a discretized crack geometry model;

[0059] Combining fluid mechanics and rock mechanics equations, considering the flow of fluid in fractures and the mechanical properties of rocks, a mathematical model of multi-physics field coupling is established. This embodiment uses nuclear magnetic resonance logging and core analysis experiments to obtain fracture permeability and rock characteristic parameters;

[0060] This embodiment constructs a pressure distribution model within a fracture that takes into account the coupling of multiple physical fields. The geometric parameters of the fracture, the fracture permeability, and the characteristic parameters of the rock are input into the pressure distribution model construction system to construct a pressure distribution model within the fracture that takes into account the coupling of multiple physical fields. The model must include key factors such as the conduction of pressure in different media and the interaction between fluid and rock to ensure that the model can accurately reflect the complex pressure distribution within the fracture.

[0061] As an optional embodiment of the present invention, in a proppant distribution optimization method based on pressure distribution control of the present invention, the intra-fracture pressure distribution model system discretizes the fracture area based on the finite element analysis method, combines fluid mechanics and rock mechanics equations, simulates the pressure conduction process in different media, and considers the interaction between fluid and rock to construct an intra-fracture pressure distribution model that considers the coupling of multiple physical fields, which can handle complex fracture pressure distribution problems.

[0062] In model construction, the system accurately simulates the pressure distribution within fractures. The implementation process is as follows: The finite element analysis method discretizes the continuous fracture region into a finite number of small elements, allowing complex fracture problems to be solved through numerical calculations. Fluid mechanics equations describe the flow of fluids within fractures, while rock mechanics equations consider the mechanical properties of rocks. By combining these two equations, the transmission of pressure through two different media, fluid and rock, can be simulated. At the same time, considering the interaction between fluid and rock, such as the pressure exerted by the fluid on the rock and the obstruction of the rock to the flow of fluid, further improves the accuracy of the model. The multi-physics coupling model constructed in this way can more realistically reflect the pressure distribution within the fracture.

[0063] Furthermore, in a proppant distribution optimization method based on pressure distribution control of this embodiment, constructing a fracture pressure distribution model considering the coupling of multiple physical fields includes:

[0064] Establishing a geometric model of the crack based on the geometric parameters of the crack;

[0065] The mathematical model of multi-physics field coupling is solved by numerical simulation method to obtain the pressure distribution in the crack;

[0066] The mathematical model of multi-physics field coupling is the coupling equation of fluid and rock, the fluid mechanics equation , rock deformation equation ,in, is the divergence operator, k is the permeability tensor, is the pressure gradient, is the porosity, t is the time is the rock stress tensor, is the fluid density.

[0067] In a proppant distribution optimization method based on pressure distribution control of this embodiment, solving a mathematical model of multi-physical field coupling by a numerical simulation method to obtain the pressure distribution within the fracture includes:

[0068] The flow of fluid in fractures follows the modified equation of Darcy's law, and the mechanical behavior of rock follows the linear elastic constitutive relation, resulting in the following equation:

[0069] Fluid flow uses Darcy's law to modify the equation: ;

[0070] The linear elastic constitutive relation is used for rock deformation: ;

[0071] Where: q-----flow rate;

[0072] μ-----fluid viscosity;

[0073] C-----elastic stiffness matrix;

[0074] -----Strain tensor.

[0075] The proppant distribution optimization method of this embodiment, when analyzing the geometric parameters of the fracture using finite element analysis software, accurately processes the complex boundary conditions of the fracture and considers the influence of the roughness of the fracture surface and the contact state factors on the pressure distribution.

[0076] Specifically, the roughness of the fracture surface increases the flow resistance of the fluid in the fracture. The effect of the roughness of the fracture surface on the flow resistance of the fluid in the fracture can be expressed by introducing a roughness coefficient. The roughness coefficient is related to the degree of roughness of the fracture surface. The effect of roughness on the flow resistance is quantified by the modified Forchheimer equation: , where μ is the fluid dynamic viscosity, k is the permeability, β is the roughness coefficient, which is calibrated by experiments, ρ is the fluid density, and q is the flow velocity. Indicates the absolute value of flow velocity, is the pressure gradient.

[0077] Contact state factors, such as the contact area and contact pressure on the fracture surface, affect the fluid flow path and pressure distribution within the fracture. The impact of these factors on pressure distribution can be calculated by establishing a contact mechanics model. For example, Hertzian contact theory can be used to calculate the contact pressure distribution on the fracture surface, thereby affecting pressure transmission within the fracture. The specific calculation formula can be selected and derived based on the actual situation.

[0078] As an optional implementation of this embodiment, see Figure 3 As shown, in a proppant distribution optimization method based on pressure distribution control of this embodiment, the corresponding pressure gradient value calculated by using an optimization algorithm for each fracture region includes:

[0079] Based on the geometric parameters of the fracture and the fracture permeability data, the optimization algorithm of gradient descent method or genetic algorithm is used to solve the optimal solution of pressure gradient to ensure that the proppant can be evenly distributed.

[0080] The gradient descent method solves the problem as follows: First, define an objective function that represents the degree of proppant distribution heterogeneity, such as the variance of proppant concentration across various regions within a fracture. Then, calculate the gradient of the objective function with respect to the pressure gradient. Based on the direction of the gradient, the pressure gradient is gradually adjusted to reduce the objective function until a local optimal solution is reached. The specific formula is as follows:

[0081] Define an objective function ,in is the pressure gradient vector, which represents the degree of unevenness of proppant distribution. The gradient value of the objective function with respect to the pressure gradient is calculated;

[0082] The update formula of the gradient descent method is: ,in, is the pressure gradient vector of the nth iteration, is the learning rate, The objective function is The gradient value at ;

[0083] By continuously iterating the update formula of the gradient descent method until the objective function When the gradient value of the pressure gradient no longer changes significantly, the optimal solution of the pressure gradient can be obtained.

[0084] The solution process of genetic algorithm includes: defining an objective function ,in is the pressure gradient vector, which represents the degree of heterogeneity of proppant distribution;

[0085] A set of initial pressure gradient values ​​is randomly generated as the population;

[0086] By calculating the fitness of each individual in the population, that is, the value of the objective function corresponding to the initial pressure gradient value, individuals with higher fitness are selected for crossover and mutation operations to generate new individuals;

[0087] Repeat the above process until the individuals in the population reach the convergence condition. The optimal individual at this time is the optimal solution of the pressure gradient.

[0088] The goal of the optimization algorithm of this embodiment is to minimize the unevenness of proppant distribution while satisfying the pressure constraints within the fracture.

[0089] Specifically, a proppant distribution optimization method based on pressure distribution control in this embodiment includes:

[0090] For areas in the fracture where the fracture width is greater than a first preset fracture width threshold and the fracture permeability is greater than a first preset fracture permeability threshold, variable frequency speed regulation technology is used to adjust the speed of the proppant injection pump to control the pressure gradient within the pressure gradient value range calculated by the optimization algorithm, so that the proppant injection rate is maintained within the set flow rate range;

[0091] For areas in the crack where the crack width is less than the second preset crack width threshold, or the crack permeability is less than the second preset crack permeability threshold, the pressure gradient value calculated by the optimization algorithm is increased by adjusting the throttle valve opening and changing the pipeline diameter.

[0092] Therefore, the pressure gradient adjustment strategy of this embodiment is as follows: in areas with wider fractures and higher permeability, variable frequency speed regulation technology is used to adjust the injection pump speed, so that the pressure gradient is controlled within a reasonable range obtained through calculation, so that the proppant injection rate is maintained within the set flow rate range, ensuring that the proppant enters slowly and evenly; in areas with narrower fractures and lower permeability, the pressure gradient is increased by adjusting the throttle valve opening, changing the pipe diameter, etc., to ensure that the proppant can overcome the flow resistance and be filled smoothly.

[0093] The proppant distribution optimization method based on pressure distribution control of this embodiment considers the influence of the physical properties of the proppant particle size distribution, density, and shape coefficient on the flow resistance of the proppant in the fracture when calculating the corresponding pressure gradient value using the optimization algorithm.

[0094] This affects the proppant's filling efficiency and flow resistance within the fracture. Smaller particle sizes can better fill fractures but may increase flow resistance, while larger particle sizes may result in uneven filling but relatively low flow resistance. A particle size distribution function can be introduced to describe the proppant's particle size distribution and used to calculate changes in flow resistance.

[0095] The density of a proppant affects its settling velocity and flow resistance in a fluid. Denser proppants settle faster in a fluid, potentially leading to uneven distribution within the fracture and increased flow resistance. Lower-density proppants settle more slowly, making them more evenly distributed within the fracture, but may require higher injection pressures to promote flow. The effect of density on flow resistance can be analyzed by calculating the forces acting on the proppant in the fluid.

[0096] The shape coefficient of a proppant affects its contact area and friction with the fracture wall, thereby affecting flow resistance. Irregularly shaped proppant may increase friction with the fracture wall, leading to increased flow resistance; more regularly shaped proppant may reduce friction and lower flow resistance. The effect of the shape coefficient on flow resistance can be analyzed by establishing a contact model between the proppant and the fracture wall. The specific calculation formula can be selected and derived based on actual conditions.

[0097] As an optional implementation of this embodiment, see Figure 3 As shown, in a proppant distribution optimization method based on pressure distribution control of this embodiment, during the proppant injection process, real-time monitoring of the pressure data within the fracture is performed, and when the monitored pressure data within the fracture exceeds a preset pressure threshold, real-time adjustment of the proppant injection pressure includes:

[0098] Deploy downhole monitoring equipment to collect real-time fracture pressure data at a millisecond sampling frequency during proppant injection and transmit the data to the ground control center;

[0099] The ground control center filters and de-noises the collected data and compares it with the preset pressure distribution model.

[0100] When the pressure deviation in the fracture is detected to exceed the preset threshold, the automatic control program is immediately started to adjust the motor frequency of the injection pump, change the pressure setting value of the hydraulic control system, and adjust the injection pressure of the proppant in real time.

[0101] The downhole monitoring equipment deployed in this embodiment includes distributed optical fiber sensors, high-precision pressure gauges, etc., which collect real-time pressure data in the fracture at a sampling frequency of milliseconds.

[0102] This embodiment provides a proppant distribution optimization method based on pressure distribution control. During the proppant injection process, the real-time monitoring pressure data within the fracture is filtered and denoised, and compared with a preset pressure distribution model. Once the pressure deviation exceeds the set threshold, the automatic control program is immediately activated to adjust the injection pressure in real time to ensure that the proppant is evenly distributed in the fracture, while maintaining the stress state of the fracture wall within a safe range to prevent the fracture from rupturing or closing.

[0103] The equipment for real-time monitoring of pressure changes in fractures described in this embodiment must be resistant to high temperature, high pressure, and corrosion, and meet the requirements for long-term stable operation in a complex underground environment.

[0104] This embodiment also provides a computer-readable recording medium storing a computer-executable program. When the computer-executable program is executed, the method for optimizing proppant distribution based on pressure distribution control is implemented.

[0105] The computer-readable recording medium described in this embodiment may include a data signal propagated in baseband or as part of a carrier wave, wherein readable program code is carried. Such propagated data signals may take various forms, including but not limited to electromagnetic signals, optical signals, or any suitable combination thereof. The readable recording medium may also be any readable medium other than a readable recording medium, which may send, propagate, or transmit a program for use by or in conjunction with an instruction execution system, device, or component. The program code contained on the readable recording medium may be transmitted using any suitable medium, including but not limited to wireless, wired, optical cable, RF, etc., or any suitable combination thereof.

[0106] Example 1

[0107] Basic information of the oil well: A certain oil well was subjected to fracturing operation. The fracture length was 180m, the average width was 4mm, the permeability was 10md, and the rock hardness was medium.

[0108] Pressure Analysis and Strategy Development: A pressure distribution model was developed based on analysis of fracture geometry, permeability, and rock properties. Based on the model results, the fractures were divided into three zones: the initial section (0-60 m), the middle section (60-120 m), and the terminal section (120-180 m). In the initial section, due to the relatively wide fracture and high pressure, a lower pressure gradient of 0.5 MPa / m was set. In the middle section, with moderate pressure and width, the pressure gradient was set to 1 MPa / m. In the terminal section, due to the narrower fracture and lower permeability, the pressure gradient was increased to 1.5 MPa / m.

[0109] Injection Process and Results: During the injection process, pressure changes within the fracture were monitored in real time. When pressure in a certain area of ​​the midsection was found to be slightly lower than expected, the injection pressure was promptly increased, adjusting the pressure gradient to 1.2 MPa / m. After the fracturing operation, the well's production increased by 35% compared to conventional methods, and subsequent production remained stable.

[0110] Example 2

[0111] Basic information of gas well: A gas well was fractured, with a crack length of 150 mm, an average width of 3 mm, a permeability of 5 md, and relatively brittle rock.

[0112] Pressure Analysis and Strategy Development: After analyzing the fracture parameters, a pressure distribution model was established. The fracture was divided into two sections: the front section (0-75m) with a pressure gradient of 1.2 MPa / m. In the back section (75-150m), due to the rock's brittleness, the pressure gradient was set to 0.8 MPa / m to prevent excessive fracture expansion.

[0113] Injection Process and Results: During the injection process, pressure was monitored in real time. When pressure in the later stages rose too rapidly, the injection pressure was reduced, adjusting the pressure gradient to 0.6 MPa / m. After fracturing, the well's gas production efficiency increased by 28%, and problems such as fracture rupture and proppant backflow caused by improper pressure were effectively avoided.

[0114] The above embodiments are only used to illustrate the present invention and are not intended to limit the technical solutions described in the present invention. Although this specification has described the present invention in detail with reference to the above embodiments, the present invention is not limited to the above specific implementation methods. Therefore, any modification or equivalent replacement of the present invention; and all technical solutions and improvements thereof that do not depart from the spirit and scope of the invention are included in the scope of the claims of the present invention.

Claims

1. A proppant distribution optimization method based on pressure distribution control, characterized in that: include: Construct a pressure distribution model within the fracture that considers the coupling of multiple physical fields; Based on the fracture pressure distribution model and combined with geostatistical methods, the fractures are divided into fracture areas, and the corresponding pressure gradient value is calculated for each fracture area using an optimization algorithm; Based on the geometric parameters of the fracture and the fracture permeability data, the optimal solution of the pressure gradient is solved; Control the proppant injection process based on the pressure gradient values ​​corresponding to each area of ​​the fracture; During the injection of proppant, the pressure data in the fracture is monitored in real time. When the pressure data in the fracture exceeds the preset pressure threshold, the injection pressure of the proppant is adjusted in real time. The construction of the pressure distribution model in the fracture considering the multi-physics field coupling effect includes: Collect and organize fracture geometry parameters, fracture permeability and rock characteristic parameters; Input the collected and sorted parameters into the finite element analysis software for meshing, discretize the crack area into multiple small units, and generate a discretized crack geometry model; Combining fluid mechanics and rock mechanics equations, considering the flow of fluid in fractures and the mechanical properties of rocks, a mathematical model of multi-physics field coupling is established; When using finite element analysis software to analyze the geometric parameters of the crack, the complex boundary conditions of the crack are accurately processed, and the influence of the roughness of the crack surface and the contact state factors on the pressure distribution are considered; The proppant distribution optimization method based on pressure distribution control comprises: The roughness coefficient is introduced to represent the effect of the roughness of the fracture surface on the flow resistance of the fluid in the fracture. The roughness coefficient is related to the roughness of the fracture surface. The effect of roughness on the flow resistance is quantified by the modified Forchheimer equation: , where μ is the fluid dynamic viscosity, k is the permeability, β is the roughness coefficient, which is calibrated by experiments, ρ is the fluid density, and q is the flow velocity. Indicates the absolute value of flow velocity, is the pressure gradient; The influence of contact state factors on pressure distribution is calculated by establishing a contact mechanics model; The proppant distribution optimization method based on pressure distribution control comprises: For areas in the fracture where the fracture width is greater than a first preset fracture width threshold and the fracture permeability is greater than a first preset fracture permeability threshold, variable frequency speed regulation technology is used to adjust the speed of the proppant injection pump to control the pressure gradient within the pressure gradient value range calculated by the optimization algorithm, so that the proppant injection rate is maintained within the set flow rate range; For areas in the crack where the crack width is less than a second preset crack width threshold, or where the crack permeability is less than a second preset crack permeability threshold, the pressure gradient value calculated by the optimization algorithm is increased by adjusting the throttle valve opening or changing the pipe diameter; During the injection of the proppant, real-time monitoring of the pressure data within the fracture and adjusting the injection pressure of the proppant in real time when the pressure data within the fracture exceeds a preset pressure threshold value include: Deploy downhole monitoring equipment to collect real-time fracture pressure data at a millisecond sampling frequency during proppant injection and transmit the data to the ground control center; The ground control center filters and de-noises the collected data and compares it with the preset pressure distribution model. When the pressure deviation in the fracture is detected to exceed the preset threshold, the automatic control program is immediately started to adjust the motor frequency of the injection pump, change the pressure setting value of the hydraulic control system, and adjust the injection pressure of the proppant in real time.

2. The method for optimizing proppant distribution based on pressure distribution control according to claim 1, characterized in that: include: The mathematical model of multi-physics field coupling is solved by numerical simulation method to obtain the pressure distribution in the crack; The mathematical model of multi-physics field coupling is the coupling equation of fluid and rock, the fluid mechanics equation , rock deformation equation , where ∇ is the divergence operator, k is the permeability tensor, is the pressure gradient, ϕ is the porosity, and t is the time is the rock stress tensor, is the fluid density.

3. The method for optimizing proppant distribution based on pressure distribution control according to claim 1, characterized in that: The method of calculating the corresponding pressure gradient value for each fracture region using an optimization algorithm includes: Based on the geometric parameters of the fracture and the fracture permeability data, the gradient descent method is used to solve the optimal solution of the pressure gradient; The gradient descent method solution process includes: defining an objective function ,in is the pressure gradient vector, which represents the degree of unevenness of proppant distribution. The gradient value of the objective function with respect to the pressure gradient is calculated; The update formula of the gradient descent method is: ,in, is the pressure gradient vector of the nth iteration, is the learning rate, The objective function is The gradient value at ; By continuously iterating the update formula of the gradient descent method until the objective function When the gradient value of the pressure gradient no longer changes significantly, the optimal solution of the pressure gradient can be obtained.

4. The method for optimizing proppant distribution based on pressure distribution control according to claim 1, characterized in that: The method of calculating the corresponding pressure gradient value for each fracture region using an optimization algorithm includes: Based on the geometric parameters of the fracture and the fracture permeability data, the optimization algorithm of the genetic algorithm is used to solve the optimal solution of the pressure gradient; The solution process of genetic algorithm includes: defining an objective function ,in is the pressure gradient vector, which represents the degree of heterogeneity of proppant distribution; A set of initial pressure gradient values ​​is randomly generated as the population; By calculating the fitness of each individual in the population, that is, the value of the objective function corresponding to the initial pressure gradient value, individuals with higher fitness are selected for crossover and mutation operations to generate new individuals; Repeat the above process until the individuals in the population reach the convergence condition. The optimal individual at this time is the optimal solution of the pressure gradient.

5. A proppant distribution optimization method based on pressure distribution control according to claim 3 or 4, characterized in that: When calculating the corresponding pressure gradient value using the optimization algorithm, the effects of the physical properties of the proppant, such as particle size distribution, density, and shape coefficient, on the flow resistance of the proppant in the fracture are considered.

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