Proppant distribution optimization method based on pressure distribution control

Abstract

The invention discloses a proppant distribution optimization method based on pressure distribution control. The method comprises the following steps: constructing an in-crack pressure distribution model considering a multi-physics field coupling effect; according to the fracture pressure distribution model, in combination with a geostatistics method, performing fracture region division on the fracture, and for each fracture region, calculating a corresponding pressure gradient value by using an optimization algorithm; based on the pressure gradient values corresponding to all the areas of the crack, the injection process of the proppant is controlled; in the injection process of the proppant, pressure data in the crack are monitored in real time, and when it is monitored that the pressure data in the crack exceed a preset pressure threshold value, the injection pressure of the proppant is adjusted in real time. According to the method, through accurate fracture pressure distribution analysis, a scientific pressure gradient adjustment strategy and real-time injection process adjustment, uniform and efficient distribution of the proppant in the fracture is achieved.

Description

Technical Field

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

[0002] In current oil and gas production fracturing operations, the rationality of proppant distribution plays a decisive role in the fracturing effect. However, traditional proppant injection methods have significant defects. Traditional methods mostly rely on past experience or only carry out operations based on simple preset parameters. For example, before injection, the approximate width of the fracture is roughly estimated, and then the proppant injection pressure and flow rate are determined, completely ignoring the complexity of the pressure distribution within the fracture.

[0003] The geometric shapes of underground fractures are diverse, with lengths ranging from dozens of meters to hundreds of meters, widths that may fluctuate at the millimeter or even micron level, large variations in height, and often accompanied by irregular bends and branches. Taking a certain complex oil reservoir as an example, its fracture length can reach 300m, the width fluctuates between 2 - 8mm, and some fractures are S-shaped bends, which makes the flow path of proppant within them full of variables. At the same time, the permeability varies greatly due to different reservoir characteristics. The low-permeability reservoir may only have 1md, while the high-permeability reservoir can reach more than 100md, which directly affects the advancing speed and distribution uniformity of proppant in the fracture. Rock properties are also complex. Hard rocks will hinder the embedding of proppant, and brittle rocks are prone to generating a large number of microfractures during fracturing. The existence of these microfractures changes the pressure conduction path and the filling space of proppant.

[0004] Under such complex conditions, traditional injection methods are extremely likely to cause uneven proppant distribution. In narrow and low-permeability areas of the fracture, due to unreasonable setting of injection pressure and flow rate, proppant is difficult to enter smoothly, resulting in insufficient support; while in wider and high-permeability areas of the fracture, proppant may over-accumulate due to too fast flow rate, not only wasting resources but also reducing the fracture conductivity. This series of problems causes the fracture to close prematurely, making it difficult to increase the production of oil and gas wells and keeping the production cost high, seriously restricting the efficient development of the oil and gas extraction industry. In view of this, the present invention is specifically proposed. Summary of the Invention

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

[0006] Specifically, the following technical solutions are adopted: An optimization method for proppant distribution based on pressure distribution control, comprising: Construct a pressure distribution model in the fracture considering the coupling effect of multiple physical fields; According to the fracture pressure distribution model, combined with the geostatistical method, divide the fracture into fracture regions. For each fracture region, use an optimization algorithm to calculate the corresponding pressure gradient value; Based on the pressure gradient values corresponding to each region of the fracture, control the injection process of the proppant; During the injection process of the proppant, monitor the pressure data in the fracture in real time. When the monitored pressure data in the fracture exceeds the preset pressure threshold, adjust the injection pressure of the proppant in real time.

[0007] As an alternative implementation mode of the present invention, in a method for optimizing proppant distribution based on pressure distribution control of the present invention, the construction of a pressure distribution model in the fracture considering the coupling effect of multiple physical fields includes: Collect and sort out the geometric shape parameters of the fracture, the fracture permeability, and the characteristic parameters of the rock; Input the collected and sorted parameters into the finite element analysis software for mesh generation, discretize the fracture region into multiple small elements, and generate a discretized fracture geometric model; Combined with the fluid mechanics and rock mechanics equations, considering the flow of fluid in the fracture and the mechanical properties of the rock, establish a mathematical model of multi-physical field coupling.

[0008] As an alternative implementation mode of the present invention, a method for optimizing proppant distribution based on pressure distribution control of the present invention includes: Solve the mathematical model of multi-physical field coupling by numerical simulation method to obtain the pressure distribution in the fracture; The mathematical model of multi-physical field coupling is the coupling equation of fluid and rock, the fluid mechanics equation , the rock deformation equation , where, 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.

[0009] As an alternative implementation mode of the present invention, in a method for optimizing proppant distribution based on pressure distribution control of the present invention, when analyzing the geometric shape parameters of the fracture by using the finite element analysis software, accurately process the complex boundary conditions of the fracture, and consider the influence of the roughness of the fracture surface and the contact state factors on the pressure distribution.

[0010] As an alternative implementation mode of the present invention, a method for optimizing proppant distribution based on pressure distribution control of the present invention includes: The influence of the roughness of the fracture surface on the flow resistance of fluid in the fracture is represented by introducing a roughness coefficient, which is related to the roughness degree of the fracture surface. The influence of roughness on the flow resistance is quantified by the modified Forchheimer equation: , where μ is the dynamic viscosity of the fluid, k is the permeability, β is the roughness coefficient calibrated through experiments, ρ is the fluid density, q is the flow velocity, represents the absolute value of the flow velocity, is the pressure gradient; The influence of the contact state factor on the pressure distribution is calculated by establishing a contact mechanics model.

[0011] As an alternative embodiment of the present invention, in a method for optimizing proppant distribution based on pressure distribution control of the present invention, for each fracture region, calculating the corresponding pressure gradient value by using an optimization algorithm includes: Based on the geometric shape 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 process of solving by the gradient descent method includes: defining an objective function , where is the pressure gradient vector, and this function represents the degree of non-uniformity of proppant distribution, and calculating the gradient value of the objective function with respect to the pressure gradient; The update formula of the gradient descent method is: , where, is the pressure gradient vector at the nth iteration, is the learning rate, is the gradient value of the objective function at ; By continuously iterating the update formula of the gradient descent method until the gradient value of the objective function with respect to the pressure gradient no longer changes significantly, the optimal solution of the pressure gradient can be obtained. As an alternative embodiment of the present invention, in a method for optimizing proppant distribution based on pressure distribution control of the present invention, for each fracture region, calculating the corresponding pressure gradient value by using an optimization algorithm includes: Based on the geometric shape parameters of the fracture and the fracture permeability data, the genetic algorithm is used as the optimization algorithm to solve the optimal solution of the pressure gradient; The solving process of the genetic algorithm includes: defining an objective function , where is the pressure gradient vector, and this function represents the degree of non-uniformity of proppant distribution; 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. At this time, the optimal individual is the optimal solution of the pressure gradient.

[0012] As an alternative embodiment of the present invention, an optimization method for proppant distribution based on pressure distribution control includes: For the area in the fracture where the fracture width is greater than the first preset fracture width threshold and the fracture permeability is greater than the first preset fracture permeability threshold, the variable frequency speed regulation technology is used to adjust the rotation speed of the proppant injection pump, and the pressure gradient is controlled within the range of the pressure gradient value calculated by the optimization algorithm, so that the proppant injection speed is maintained within the set flow rate range. For the area in the fracture where the fracture width is less than the second preset fracture width threshold or the fracture permeability is less than the second preset fracture permeability threshold, by adjusting the throttle valve opening and changing the pipe diameter, the pressure gradient value calculated by the optimization algorithm is increased.

[0013] As an alternative embodiment of the present invention, in an optimization method for proppant distribution based on pressure distribution control, when calculating the corresponding pressure gradient value using the optimization algorithm, the influence of the physical properties of the proppant particle size distribution, density, and shape factor on the flow resistance of the proppant in the fracture is considered.

[0014] As an alternative embodiment of the present invention, in an optimization method for proppant distribution based on pressure distribution control, during the injection process of the proppant, the pressure data in the fracture is monitored in real time. When the monitored pressure data in the fracture exceeds the preset pressure threshold, the real-time adjustment of the proppant injection pressure includes: Deploy downhole monitoring equipment. During the injection process of the proppant, the pressure data in the fracture is collected in real time at a sampling frequency of milliseconds and transmitted to the ground control center. The ground control center filters and denoises the collected data and compares it with the preset pressure distribution model. When it is monitored that the pressure deviation in the fracture exceeds the preset threshold, the automatic control program is immediately started to adjust the motor frequency of the injection pump and change the pressure setting value of the hydraulic control system to adjust the proppant injection pressure in real time.

[0015] Compared with the prior art, the beneficial effects of the present invention: An optimization method for proppant distribution based on pressure distribution control in the present invention realizes the uniform and efficient distribution of proppants in fractures through precise fracture pressure distribution analysis, scientific pressure gradient adjustment strategies, and real-time adjustment of the injection process. It effectively enhances the fracture conductivity, significantly improves the production and recovery efficiency of oil and gas wells, reduces the production cost, extends the production life of oil and gas wells, brings good economic benefits and application prospects to the oil and gas extraction industry, and promotes the technological progress and sustainable development of the industry. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 Flowchart of an optimization method for proppant distribution based on pressure distribution control in an embodiment of the present invention Figure 1 ; Figure 2 Flowchart of an optimization method for proppant distribution based on pressure distribution control in an embodiment of the present invention Figure 2 ; Figure 3 Flowchart of an optimization method for proppant distribution based on pressure distribution control in an embodiment of the present invention Figure 3 . DETAILED DESCRIPTION OF THE EMBODIMENTS

[0017] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, 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 some, but not all, of the embodiments of the present invention.

[0018] Therefore, the following detailed description of the embodiments of the present invention is not intended to limit the scope of the claimed present invention, but merely represents some embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts fall within the scope of protection of the present invention.

[0019] It should be noted that, without conflict, the embodiments in the present invention and the features and technical solutions in the embodiments may be combined with each other.

[0020] It should be noted that like reference numerals and letters denote like items in the following drawings. Therefore, once an item is defined in one drawing, it does not need to be further defined and explained in subsequent drawings.

[0021] In the description of the present invention, it should be noted that the orientation or positional relationship indicated by terms such as "upper" and "lower" is based on the orientation or positional relationship shown in the drawings, or the orientation or positional relationship in which the inventive product is customarily placed during use, or the orientation or positional relationship commonly understood by those skilled in the art. Such terms are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus should not be construed as a limitation to the present invention. In addition, terms such as "first" and "second" are only used for distinguishing descriptions and cannot be construed as indicating or implying relative importance.

[0022] As shown in Figure 1 a method for optimizing proppant distribution based on pressure distribution control in this embodiment includes: Constructing a pressure distribution model in the fracture considering the coupling effect of multiple physical fields; According to the fracture pressure distribution model, combining with the geostatistical method, dividing the fracture into fracture regions with a division accuracy reaching the meter level. For each fracture region, using an optimization algorithm to calculate the corresponding pressure gradient value; Based on the pressure gradient values corresponding to each region of the fracture, controlling the injection process of the proppant; During the injection process of the proppant, real-time monitoring of the pressure data in the fracture is carried out. When the monitored pressure data in the fracture exceeds the preset pressure threshold, the injection pressure of the proppant is adjusted in real time.

[0023] Therefore, a method for optimizing proppant distribution based on pressure distribution control in this embodiment realizes the uniform and efficient distribution of proppant in the fracture through accurate fracture pressure distribution analysis, scientific pressure gradient adjustment strategy, and real-time injection process adjustment. It effectively enhances the conductivity of the fracture, significantly improves the production and recovery efficiency of oil and gas wells, reduces the production cost, extends the production life of oil and gas wells, brings good economic benefits and application prospects to the oil and gas extraction industry, and promotes the progress and sustainable development of the industry technology.

[0024] As an alternative embodiment of the present invention, as shown in Figure 2 in a method for optimizing proppant distribution based on pressure distribution control in this embodiment, the construction of the pressure distribution model in the fracture considering the coupling effect of multiple physical fields includes: Collecting and sorting out the geometric shape parameters of the fracture (such as length, width, height, etc.), fracture permeability, and characteristic parameters of the rock (such as hardness, brittleness, etc.); Inputting the collected and sorted parameters into finite element analysis software (such as COMSOL or ANSYS, etc.) for mesh generation, discretizing the fracture region into multiple small units, and generating a discretized fracture geometric model; Combined with 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. In this embodiment, nuclear magnetic resonance logging and core analysis experimental means are used to obtain fracture permeability and rock characteristic parameters; The pressure distribution model in the fracture considering the coupling effect of multiple physical fields in this embodiment inputs the geometric shape parameters of the fracture, fracture permeability, and rock characteristic parameters into the pressure distribution construction model system to construct a pressure distribution model in the fracture considering the coupling effect of multiple physical fields. This model needs to cover 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 in the fracture.

[0025] As an alternative implementation of the present invention, in an optimized method for proppant distribution based on pressure distribution control of the present invention, the pressure distribution model system in the fracture discretizes the fracture area based on the finite element analysis method, combines fluid mechanics and rock mechanics equations, simulates the conduction process of pressure in different media, and considers the interaction between fluid and rock to construct a pressure distribution model in the fracture considering the coupling effect of multiple physical fields, which can handle complex fracture pressure distribution problems.

[0026] In the model construction, this system plays a role in accurately simulating the pressure distribution in the fracture. The implementation process is as follows: The finite element analysis method discretizes the continuous fracture area into a finite number of small elements, so that complex fracture problems can be solved by numerical calculation. The fluid mechanics equation describes the flow law of fluid in the fracture, and the rock mechanics equation considers the mechanical properties of the rock. By combining these two equations, the conduction process of pressure in the two different media of fluid and rock can be simulated. At the same time, considering the interaction between fluid and rock, such as the pressure effect of fluid on the rock and the hindrance effect of the rock on fluid flow, the accuracy of the model is further improved. The multi-physical field coupling model constructed in this way can more realistically reflect the pressure distribution in the fracture.

[0027] Furthermore, in an optimized method for proppant distribution based on pressure distribution control of this embodiment, the construction of a pressure distribution model in the fracture considering the coupling effect of multiple physical fields includes: Establish a geometric model of the fracture based on the geometric shape parameters of the fracture; Solve the mathematical model of multi-physical field coupling by numerical simulation method to obtain the pressure distribution in the fracture; The mathematical model of multi-physical field coupling is the coupling equation of fluid and rock, the fluid mechanics equation , the rock deformation equation , where, is the divergence operator, k is the permeability tensor, is the pressure gradient, is the porosity and t is the time is the rock stress tensor is the fluid density

[0028] In the method for optimizing proppant distribution based on pressure distribution control of this embodiment, the pressure distribution in the fracture obtained by solving the mathematical model of multi-physical field coupling through numerical simulation method includes: The flow of fluid in the fracture follows the modified Darcy's law, and the mechanical behavior of the rock follows the linear elastic constitutive relation, obtaining an equation in the following form: The modified Darcy's law is used for fluid flow: ; Linear elastic constitutive relation is used for rock deformation: ; Where: q-----flow velocity; μ-----fluid viscosity; C-----elastic stiffness matrix; -----strain tensor

[0029] In the proppant distribution optimization method of this embodiment, when analyzing the geometric shape parameters of the fracture by using finite element analysis software, the complex boundary conditions of the fracture are accurately processed, and the influence of the roughness and contact state factors of the fracture surface on the pressure distribution is considered

[0030] Specifically, the roughness of the fracture surface will increase the flow resistance of the fluid in the fracture. The influence of the roughness of the fracture surface on the flow resistance of the fluid in the fracture can be represented by introducing a roughness coefficient. The roughness coefficient is related to the roughness degree of the fracture surface, and the influence of roughness on the flow resistance is quantified through the modified Forchheimer equation: , where μ is the dynamic viscosity of the fluid, k is the permeability, β is the roughness coefficient calibrated through experiments, ρ is the fluid density, q is the flow velocity represents the absolute value of the flow velocity is the pressure gradient

[0031] Contact state factors, such as the contact area and contact pressure of the fracture surface, will affect the flow channel and pressure distribution of the fluid in the fracture. The influence of these factors on the pressure distribution can be calculated by establishing a contact mechanics model. For example, Hertz contact theory can be used to calculate the contact pressure distribution on the fracture surface, thereby affecting the transmission of pressure in the fracture. Specific calculation formulas can be selected and deduced according to the actual situation

[0032] As an alternative implementation of this embodiment, see Figure 3As shown in the figure, in an optimized method for proppant distribution based on pressure distribution control according to this embodiment, for each fracture region, calculating the corresponding pressure gradient value by using an optimization algorithm includes: Based on the geometric shape parameters of the fracture and the fracture permeability data, an optimization algorithm such as the gradient descent method or the genetic algorithm is used to solve the optimal solution of the pressure gradient to ensure uniform distribution of the proppant.

[0033] The solution process of the gradient descent method is as follows: First, define an objective function, which represents the degree of non-uniformity of proppant distribution. For example, it can be the variance of proppant concentration in each region within the fracture. Then, calculate the gradient of the objective function with respect to the pressure gradient. According to the direction of the gradient, gradually adjust the value of the pressure gradient so that the value of the objective function gradually decreases until a local optimal solution is reached. The specific formula is as follows: Define an objective function , where is the pressure gradient vector, and this function represents the degree of non-uniformity of proppant distribution, and calculate the gradient value of the objective function with respect to the pressure gradient; The update formula of the gradient descent method is: , where is the pressure gradient vector at the nth iteration, is the learning rate, is the gradient value of the objective function at ; By continuously iterating the update formula of the gradient descent method until the gradient value of the objective function with respect to the pressure gradient no longer changes significantly, the optimal solution of the pressure gradient can be obtained.

[0034] The solution process of the genetic algorithm includes: Define an objective function , where is the pressure gradient vector, and this function represents the degree of non-uniformity of proppant distribution; Randomly generate a set of initial pressure gradient values 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, select individuals with higher fitness for crossover and mutation operations to generate new individuals; Repeat the above process until the individuals in the population reach the convergence condition, and the optimal individual at this time is the optimal solution of the pressure gradient.

[0035] The goal of the optimization algorithm in this embodiment is to minimize the non-uniformity of proppant distribution while satisfying the pressure constraint conditions within the fracture.

[0036] Specifically, an optimized method for proppant distribution based on pressure distribution control according to this embodiment includes: For the area in the fracture where the fracture width is greater than the first preset fracture width threshold and the fracture permeability is greater than the first preset fracture permeability threshold, the variable frequency speed regulation technology is used to adjust the rotation speed of the proppant injection pump, and the pressure gradient is controlled within the range of the pressure gradient value calculated by the optimization algorithm, so that the proppant injection speed is maintained within the set flow rate range; For the area in the fracture where the fracture width is less than the second preset fracture width threshold or the fracture permeability is less than the second preset fracture permeability threshold, by adjusting the throttle valve opening and changing the pipe diameter, the pressure gradient value calculated by the optimization algorithm is increased.

[0037] Therefore, the pressure gradient adjustment strategy of this embodiment: in the area with a wider fracture and higher permeability, the variable frequency speed regulation technology is used to adjust the rotation speed of the injection pump, and the pressure gradient is controlled within the reasonable range calculated, so that the proppant injection speed is maintained within the set flow rate range, ensuring that the proppant enters slowly and evenly; in the area with a narrower fracture and lower permeability, by adjusting the throttle valve opening, changing the pipe diameter, etc., the pressure gradient is increased to ensure that the proppant can overcome the flow resistance and be filled smoothly.

[0038] A method for optimizing proppant distribution based on pressure distribution control in this embodiment, when calculating the corresponding pressure gradient value using the optimization algorithm, considers the influence of the physical properties of the proppant particle size distribution, density, and shape factor on the flow resistance of the proppant in the fracture.

[0039] It affects its filling effect and flow resistance in the fracture. Smaller particle sizes can better fill the fracture but may increase the flow resistance; larger particle sizes may result in uneven filling but relatively less flow resistance. A particle size distribution function can be introduced to describe the particle size distribution of the proppant, and the change in flow resistance can be calculated based on this function.

[0040] The density of the proppant affects its settling velocity and flow resistance in the fluid. Proppants with a larger density have a faster settling velocity in the fluid, which may lead to uneven distribution in the fracture and increase the flow resistance; proppants with a smaller density have a slower settling velocity and are more likely to be evenly distributed in the fracture, but may require a higher injection pressure to push their flow. The influence of density on flow resistance can be analyzed by calculating the force on the proppant in the fluid.

[0041] The shape factor of the proppant affects its contact area and friction with the fracture wall surface, thus affecting the flow resistance. Irregularly shaped proppants may increase the friction with the fracture wall surface, resulting in an increase in flow resistance; more regularly shaped proppants can reduce friction and lower the flow resistance. The influence of the shape factor on flow resistance can be analyzed by establishing a contact model between the proppant and the fracture wall surface. The specific calculation formula can be selected and derived according to the actual situation.

[0042] As an alternative implementation of this embodiment, refer to Figure 3 As shown, in an optimized proppant distribution method based on pressure distribution control in this embodiment, 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 real-time adjustment of the injection pressure of the proppant includes: Deploy downhole monitoring equipment. During the injection process of the proppant, the pressure data in the fracture is collected in real time at a sampling frequency of milliseconds and transmitted to the ground control center; The ground control center filters and denoises the collected data and compares it with the preset pressure distribution model. When the pressure deviation in the fracture is monitored to exceed the preset threshold, the automatic control program is immediately started to adjust the motor frequency of the injection pump and change the pressure setting value of the hydraulic control system to adjust the injection pressure of the proppant in real time.

[0043] The downhole monitoring equipment deployed in this embodiment includes a distributed optical fiber sensor, a high-precision pressure gauge, etc., and the pressure data in the fracture is collected in real time at a sampling frequency of milliseconds.

[0044] In an optimized proppant distribution method based on pressure distribution control in this embodiment, during the injection process of the proppant, the pressure data in the fracture is monitored in real time, filtered and denoised, and compared with the preset pressure distribution model. Once the pressure deviation is found to exceed the set threshold, the automatic control program is immediately started to adjust the injection pressure in real time to ensure that the proppant is evenly distributed in the fracture, and at the same time maintain the stress state of the fracture wall within a safe range to prevent the fracture from rupturing or closing.

[0045] The equipment for real-time monitoring of the pressure change in the fracture in this embodiment needs to have the performance of resisting high temperature, high pressure and corrosion, and meet the requirements of working stably for a long time in a complex downhole environment.

[0046] This embodiment also provides a computer-readable recording medium storing a computer-executable program. When the computer-executable program is executed, the optimized proppant distribution method based on pressure distribution control is implemented.

[0047] The computer-readable recording medium described in this embodiment may include a data signal propagated in a baseband or as part of a carrier wave, which carries readable program code. Such a propagated data signal may take various forms, including but not limited to electromagnetic signals, optical signals, or any suitable combination of the above. The readable recording medium may also be any readable medium other than the readable recording medium, which can send, propagate, or transmit a program for use by or in conjunction with an instruction execution system, apparatus, or device. The program code contained on the readable recording medium may be transmitted using any appropriate medium, including but not limited to wireless, wired, optical fiber, RF, etc., or any suitable combination of the above.

[0048] Example 1 Basic well conditions: A certain oil well is fractured. The fracture length is 180 m, the average width is 4 mm, the permeability is 10 md, and the rock hardness is medium.

[0049] Pressure analysis and strategy formulation: By analyzing the fracture geometry, permeability, and rock properties, a pressure distribution model is established. According to the model results, the fracture is divided into three regions: the starting section (0 - 60 m), the middle section (60 - 120 m), and the end section (120 - 180 m). In the starting section, due to the relatively wide fracture and high pressure, a lower pressure gradient of 0.5 MPa / m is set; in the middle section, the pressure and width are moderate, and the pressure gradient is set to 1 MPa / m; in the end section, the fracture is narrow and the permeability is low, so the pressure gradient is increased to 1.5 MPa / m.

[0050] Injection process and effect: During the injection process, the pressure change in the fracture is monitored in real time. When it is found that the pressure in a certain area of the middle section is slightly lower than expected, the injection pressure is increased in a timely manner, and the pressure gradient is adjusted to 1.2 MPa / m. After the fracturing operation, the production of this oil well has increased by 35% compared with the traditional method, and the production stability is good in the subsequent production process.

[0051] Example 2 Basic well conditions of a gas well: A certain gas well is fractured. The fracture length is 150 mm, the average width is 3 mm, the permeability is 5 md, and the rock brittleness is relatively large.

[0052] Pressure analysis and strategy formulation: After analyzing the fracture parameters, a pressure distribution model is established. The fracture is divided into two sections, the front section (0 - 75 m) with a pressure gradient set to 1.2 MPa / m, and the rear section (75 - 150 m). Due to the large rock brittleness, in order to prevent excessive fracture extension, the pressure gradient is set to 0.8 MPa / m.

[0053] Injection process and effects: During the injection process, the pressure is monitored in real time. When the pressure rises too rapidly in the latter stage, the injection pressure is reduced and the pressure gradient is adjusted to 0.6 MPa / m. After fracturing, the gas production efficiency of the gas well has increased by 28%, and the problems of fracture rupture and proppant backflow caused by improper pressure have been effectively avoided.

[0054] The above embodiments are only used to illustrate the present invention and do not limit the technical solutions described in the present invention. Although the present specification has described the present invention in detail with reference to the above embodiments, the present invention is not limited to the above specific embodiments. Therefore, any modification or equivalent replacement of the present invention; and all technical solutions and their improvements that do not depart from the spirit and scope of the invention are covered by the scope of the claims of the present invention.

Claims

1. An optimized proppant distribution method based on pressure distribution control, characterized in that Including: Construct a pressure distribution model in the fracture considering the coupling effect of multiple physical fields; According to the fracture pressure distribution model, combined with the geostatistical method, divide the fracture into fracture regions. For each fracture region, use an optimization algorithm to calculate the corresponding pressure gradient value; Based on the pressure gradient values corresponding to each region of the fracture, control the injection process of the proppant; During the injection process of the proppant, monitor the pressure data in the fracture in real time. When the monitored pressure data in the fracture exceeds the preset pressure threshold, adjust the injection pressure of the proppant in real time.

2. The optimized proppant distribution method based on pressure distribution control according to claim 1, wherein The construction of the pressure distribution model in the fracture considering the coupling effect of multiple physical fields includes: Collect and sort out the geometric shape parameters of the fracture, the fracture permeability, and the characteristic parameters of the rock; Input the collected and sorted parameters into the finite element analysis software for mesh generation, discretize the fracture region into multiple small elements, and generate a discretized fracture geometric model; Combined with the fluid mechanics and rock mechanics equations, considering the fluid flow in the fracture and the mechanical properties of the rock, establish a mathematical model of multi-physical field coupling.

3. The optimized proppant distribution method based on pressure distribution control according to claim 2, wherein, Including: Solve the mathematical model of multi-physical field coupling by numerical simulation method to obtain the pressure distribution in the fracture; The mathematical model of the multi-physical-field coupling is the coupling equation of fluid and rock, and the fluid mechanics equation , and the rock deformation equation , where 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.

4. The optimized proppant distribution method based on pressure distribution control according to claim 2, characterized in that When analyzing the geometric shape parameters of the fracture using the finite element analysis software, accurately process the complex boundary conditions of the fracture, and consider the influence of the roughness of the fracture surface and the contact state factors on the pressure distribution.

5. The optimized proppant distribution method based on pressure distribution control according to claim 4, wherein Including: The influence of the roughness of the fracture surface on the flow resistance of the fluid is represented by introducing a roughness coefficient, which is related to the roughness degree of the fracture surface. The influence of roughness on the flow resistance is quantified by the modified Forchheimer equation: , where μ is the dynamic viscosity of the fluid, k is the permeability, β is the roughness coefficient calibrated through experiments, ρ is the fluid density, q is the flow velocity, represents the absolute value of the flow velocity, is the pressure gradient; Calculate the influence of the contact state factors on the pressure distribution by establishing a contact mechanics model.

6. The optimized proppant distribution method based on pressure distribution control according to claim 1, characterized in that For each fracture region, using the optimization algorithm to calculate the corresponding pressure gradient value includes: Based on the geometric shape parameters of the fracture and the fracture permeability data, use the gradient descent method to solve the optimal solution of the pressure gradient; The solution process of the gradient descent method includes: defining an objective function , where is the pressure gradient vector, and this function represents the degree of non-uniformity of the proppant distribution, and calculating the gradient value of the objective function with respect to the pressure gradient; The update formula of the gradient descent method is as follows: , where is the pressure gradient vector at the n-th iteration, is the learning rate, is the gradient value of the objective function at ; By continuously iterating the update formula of the gradient descent method until the gradient value of the objective function with respect to the pressure gradient no longer changes significantly, the optimal solution of the pressure gradient can be obtained.

7. A method for optimizing the distribution of proppants based on pressure distribution control according to claim 1, wherein For each fracture region, using the optimization algorithm to calculate the corresponding pressure gradient value includes: Based on the geometric shape parameters of the fracture and the fracture permeability data, use the optimization algorithm of the genetic algorithm to solve the optimal solution of the pressure gradient; The solution process of the genetic algorithm includes: defining an objective function , where is the pressure gradient vector, and this function represents the degree of non-uniformity of proppant distribution; Randomly generate a set of initial pressure gradient values 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, select the individuals with higher fitness for crossover and mutation operations to generate new individuals; Repeat the above process until the individuals in the population reach the convergence condition. At this time, the optimal individual is the optimal solution of the pressure gradient.

8. A method for optimizing proppant distribution based on pressure distribution control according to claim 6 or 7, characterized in that Including: For the region in the fracture where the fracture width is greater than the first preset fracture width threshold and the fracture permeability is greater than the first preset fracture permeability threshold, use the variable frequency speed regulation technology to adjust the rotation speed of the proppant injection pump, control the pressure gradient within the range calculated by the optimization algorithm, and keep the proppant injection speed within the set flow rate range; For the region in the fracture where the fracture width is less than the second preset fracture width threshold or the fracture permeability is less than the second preset fracture permeability threshold, by adjusting the throttle valve opening and changing the pipe diameter, increase the pressure gradient value calculated by the optimization algorithm.

9. A method for optimizing proppant distribution based on pressure distribution control according to claim 6 or 7, characterized in that When calculating the corresponding pressure gradient value using the optimization algorithm, consider the influence of the physical properties of the proppant particle size distribution, density, and shape factor on the flow resistance of the proppant in the fracture.

10. A method for optimizing proppant distribution based on pressure distribution control according to claim 1, characterized in that, During the injection process of the proppant, the pressure data in the fracture is monitored in real time. When the monitored pressure data in the fracture exceeds the preset pressure threshold, the real-time adjustment of the injection pressure of the proppant includes: Deploy downhole monitoring equipment. During the injection process of the proppant, the pressure data in the fracture is collected in real time at a sampling frequency of milliseconds and transmitted to the ground control center; The ground control center filters and denoises the collected data and compares it with the preset pressure distribution model; When it is monitored that the pressure deviation in the fracture exceeds the preset threshold, the automatic control program is immediately started to adjust the motor frequency of the injection pump and change the pressure setting value of the hydraulic control system, and the injection pressure of the proppant is adjusted in real time.

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