While-drilling pressure monitoring and regulating device for complex fractured reservoir

Abstract

The invention discloses a while-drilling pressure monitoring and regulating device for a complex fractured reservoir, and relates to the technical field of well drilling automatic control, and the while-drilling pressure monitoring and regulating device comprises a data acquisition module which comprises a micro-resistivity imaging logging device and a well drilling data acquisition device; the micro-resistivity imaging logging device is used for acquiring well wall imaging data to obtain crack characteristic parameters; the drilling data acquisition device is used for acquiring operation parameters in the drilling process; the data analysis module is used for evaluating the total fracture pressure, calculating the pressure gradient while drilling and constructing a seepage model to obtain the fracture flow according to the fracture characteristic parameters and the operation parameters; and the self-adaptive control module is used for calculating the optimal bottom hole pressure according to the fracture flow in combination with the operation parameters, and controlling the pressure while drilling based on the optimal bottom hole pressure. Real-time evaluation of the fracture pressure state and self-adaptive regulation and control of the bottom hole pressure can be achieved, and the safety of the drilling process is effectively improved.

Description

Technical Field

[0001] The invention relates to the technical field of automatic drilling control, and in particular to a device for monitoring and regulating pressure while drilling in a complex fractured reservoir. Background Art

[0002] Under the background of the continuous advancement of deep energy development and unconventional reservoir development, fractured reservoirs, especially complex fractured reservoirs, have become important targets in exploration and development due to their strong conductivity and great transformation potential. However, compared with conventional reservoirs, complex fractured reservoirs have high heterogeneity, multi-scale spatial distribution characteristics, and significant nonlinear seepage characteristics. These characteristics make it difficult for traditional drilling and pressure control technologies to achieve safe, stable, and efficient penetration and control operations in such geological bodies. Therefore, real-time monitoring and intelligent regulation of the pressure state of complex fractured reservoirs while drilling has become one of the technical bottlenecks in current oil and gas drilling projects.

[0003] In existing studies, the identification and modeling of fractured reservoirs mainly rely on geophysical techniques such as microresistivity imaging, acoustic logging, and seismic data inversion, supplemented by core observation and experimental testing. Although such technologies can reveal the existence and distribution of fractures to a certain extent, they still have great limitations in terms of real-time, continuity, and quantitative modeling capabilities. For example, microresistivity imaging technology is usually carried out after well completion, and its data cannot be used for real-time regulation while drilling; acoustic or microseismic technology is greatly affected by noise interference and has insufficient resolution, making it difficult to accurately capture the spatiotemporal evolution of microscale fractures; and traditional pressure prediction models based on static logging parameters usually use simplified fracture equivalent models, ignoring the complex coupling relationship between the nonlinear opening and closing behavior of fractures and the dynamic interference of the wellbore, resulting in large prediction errors.

[0004] In the study of fracture seepage behavior, most classical models are based on Darcy's law, and are extended into dual medium models, triple medium models or nested mesh seepage models, attempting to describe the impact of fracture systems on pressure and flow through the average of physical properties on a macro scale. However, most of these models are based on static assumptions and fail to accurately reflect the nonlinear evolution of fractures under drilling disturbances, such as dynamic deformation, periodic conduction and closure. Especially under extreme conditions such as high pressure difference, high well deviation, and rapid drilling, these models often have deviations in the estimation of fracture flow and cannot provide an accurate basis for real-time bottom hole pressure control. In addition, there is spatial correlation and coupling between fractures in the fracture system, and fracture conductivity is jointly affected by multiple parameters such as angle, length, and distribution density. Existing models often oversimplify or only make empirical corrections to these geometric structural factors, and lack system modeling capabilities. Summary of the invention

[0005] In order to solve the above technical problems, a pressure monitoring and control device for complex fractured reservoirs while drilling is provided. The present invention can realize real-time evaluation of fracture pressure state and adaptive control of bottom hole pressure, effectively improving the safety of the drilling process.

[0006] In order to achieve the above purpose, the technical solution adopted by the present invention is: The pressure monitoring and control device for complex fractured reservoirs while drilling includes: The data acquisition module includes: a microresistivity imaging logging device and a drilling data acquisition device; the microresistivity imaging logging device is used to acquire well wall imaging data to obtain fracture characteristic parameters; the drilling data acquisition device is used to acquire operating parameters during the drilling process; Data analysis module: used to evaluate the total fracture pressure, calculate the pressure gradient while drilling, build the seepage model, and obtain the fracture flow rate based on the fracture characteristic parameters and operating parameters; The adaptive control module is used to calculate the optimal bottom hole pressure according to the fracture flow rate and the operating parameters, and control the drilling pressure based on the optimal bottom hole pressure.

[0007] Furthermore, the fracture characteristic parameters include: original formation pressure , unit is MPa; fracture pressure conductivity ; Fracture connectivity index ; Fracture fractal dimension ; Matrix permeability , unit is mD; fracture porosity ; Fluid viscosity , unit is mPa·s; The weight coefficient of each crack ;No. The angle between the fracture and the wellbore , unit is rad; monitoring time , unit is s; fracture equivalent permeability , unit is mD; effective reservoir thickness , unit is m; average crack curvature ; Average crack surface roughness , in μm; crack permeability ; Equivalent connected length of crack , in m; the length of the matrix middle path , unit is m; The length of the crack , unit is m; The area of ​​the crack , the unit is ; Total number of cracks ; Matrix pressure , unit is MPa; the current well depth is The relative depth of the cracks , unit is m.

[0008] Furthermore, the fracture pressure conductivity for: ; No. The weight coefficient of each crack for: .

[0009] Furthermore, the operating parameters include: wellbore radius , in m; wellbore advancement distance , unit is m; critical shear stress , unit is MPa; pressure fluctuation tolerance , unit is MPa; effective thickness of reservoir , unit is m; bottom hole pressure , in MPa; drilling fluid density, in kg / m³; vertical depth , unit is m; well inclination , unit is rad; drilling fluid flow rate , unit is m / s; equivalent viscosity , unit is mPa·s; effective annular area , in m²; equivalent circulation density , unit is kg / m³; Equivalent circulation density tolerance , unit is kg / m³; outer boundary radius , unit is m.

[0010] Furthermore, the data analysis module evaluates the total fracture pressure based on the fracture characteristic parameters as follows: ; in, is the total crack pressure.

[0011] Furthermore, the pressure gradient while drilling is calculated as: ; in, is the pressure gradient while drilling, in MPa / m; is the critical pressure threshold.

[0012] Furthermore, when the formation is a tight sandstone reservoir, The value range is 20MPa to 35MPa; when the formation is a fractured shale reservoir, The value range is 20MPa to 45MPa; when the formation is high-pressure deep carbonate rock, The value range is 30MPa to 60MPa. When the formation is medium-shallow mudstone or low-pressure reservoir, The value range is 10MPa to 25MPa.

[0013] Furthermore, the seepage model is: ; in, is the fracture flow rate; is the minimum support pressure, indicating that when the formation pressure or fracture pressure drops below this value, the fracture will begin to close irreversibly and the permeability will decrease, as determined by experiments; is the reference porosity.

[0014] Furthermore, the adaptive control module calculates the optimal bottom hole pressure according to the fracture flow rate and the operating parameters: ; in, is the friction coefficient; is the optimal bottom hole pressure; is the critical equivalent circulating density, in kg / m³.

[0015] Compared with the prior art, the beneficial effects of the present invention are: it can realize real-time evaluation and dynamic regulation of the pressure state of the fracture system during the drilling process, and has significant engineering application value and safety guarantee effect. Through the joint acquisition of microresistivity imaging and drilling parameters, the device can obtain the geometric morphology and operating status of the fracture, and establish a multi-parameter fracture characterization model; with the help of the data analysis module, a pressure evolution model integrating fracture conductivity, connectivity, fractal characteristics and spatial orientation is constructed to achieve high-precision prediction of the total pressure and pressure gradient of the fracture; further combined with real-time seepage calculation and control feedback mechanism, the control module can dynamically output the optimal bottom hole pressure according to the fracture flow and drilling parameters, actively adjust the circulation system, and effectively prevent complex geological risks such as fracture closure, well leakage or well wall collapse. Compared with the prior art that relies on empirical methods or only performs passive measurements downhole, the present invention realizes a closed-loop automation system from data perception, model analysis to control and regulation, which has obvious advantages in improving the safety of drilling operations, the recoverability of fracture reservoirs and the adaptability to complex formations. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 This is a schematic diagram of the structure of the device for pressure monitoring and regulation while drilling for complex fractured reservoirs proposed by the present invention. DETAILED DESCRIPTION

[0017] The following description is used to disclose the present invention so that those skilled in the art can implement the present invention. The preferred embodiments described below are only examples, and those skilled in the art may think of other obvious variations.

[0018] Reference Figure 1 As shown, the device for monitoring and controlling pressure while drilling in a complex fractured reservoir in an embodiment of the present invention comprises: The data acquisition module includes: a microresistivity imaging logging device and a drilling data acquisition device; the microresistivity imaging logging device is used to acquire well wall imaging data to obtain fracture characteristic parameters; the drilling data acquisition device is used to acquire operating parameters during the drilling process; In the traditional drilling process, due to the natural spatial heterogeneity, non-uniformity and multi-scale connectivity of fractured reservoirs, wellbore stability, bottomhole pressure control and fracture conductivity prediction become particularly difficult. Based on this core problem, the present invention starts with real-time data perception and proposes a dual-modal data acquisition framework with a microresistivity imaging logging device and a drilling data acquisition device as a combined structure, ensuring that static fracture geometry characteristics and dynamic drilling parameter changes can be captured simultaneously, providing complete initial boundary conditions and real-time evolution information for subsequent fracture state modeling and pressure regulation.

[0019] The core function of the micro-resistivity imaging logging device is to carry out close scanning of the well wall with high-resolution imaging means to form a two-dimensional or three-dimensional resistivity image. These images can reveal the key geometric information such as the distribution state, direction, inclination, length, density and opening of the cracks around the well wall. Compared with traditional acoustic imaging or density logging technology, resistivity imaging can more accurately identify micro-cracks, especially under the influence of cement sheath discontinuity, wellbore expansion or casing. It still maintains a high recognition accuracy. In addition, the conductive environment characteristics of the cracks can also be inverted by the device, providing an important basis for the subsequent estimation of the fracture seepage capacity. Since the complex fracture network has significant fractal characteristics in space, and the connectivity and dominant flow path between fractures are not always obvious, it is often impossible to form an effective understanding of the overall fracture system by analyzing discrete measurement points alone. This device uses continuous image reconstruction and data extraction algorithms to convert the microscopic characteristic parameters of the fractures into standardized physical quantities that can be used for modeling, thereby significantly improving the accuracy and practicality of modeling.

[0020] In coordination with it is the drilling data acquisition device, whose main responsibility is to collect various operating parameters during the drilling process, including drilling fluid density, well inclination, drilling rate, bottom hole pressure, circulating pump speed, annular pressure, drilling pressure, rotation speed, etc. These parameters reflect the response behavior of the formation to the drilling process on the one hand, and on the other hand, they are also the input variables that must be referred to for pressure control while drilling. During the drilling process, the fluctuation of bottom hole pressure depends not only on the formation pore pressure and fracture structure characteristics, but also on the drilling fluid system, annular return efficiency and wellbore structure. If these parameters cannot be obtained and corrected in real time, it will lead to deviations in the prediction of pressure while drilling, and then cause safety problems such as well leakage, blowout or fracture closure. Therefore, the present invention ensures the continuity and real-time nature of the data by installing high-frequency sensors on the drill string, combining measurement while drilling (MWD) and logging while drilling (LWD) technology. At the same time, all the acquired parameters are initially filtered and time-series integrated in the local or edge computing node to eliminate the fluctuations caused by signal noise and human intervention, and provide high-quality input data for subsequent high-precision analysis algorithms.

[0021] Data analysis module: used to evaluate the total fracture pressure, calculate the pressure gradient while drilling, build the seepage model, and obtain the fracture flow rate based on the fracture characteristic parameters and operating parameters; The data analysis module assumes the core responsibility of connecting perception and control, and its principle construction is based on the deep fusion modeling of the spatial structure of fractures, formation response characteristics and nonlinear behavior of the drilling process. Since there are usually multi-scale, heterogeneous, and multi-directionally connected natural fracture systems inside complex fractured reservoirs, these fractures are not only the main fluid channels, but also have a key influence on the evolution of the bottom hole pressure field. Therefore, it is difficult to accurately predict the actual pressure change trend downhole based on the traditional seepage model based on simplified assumptions. The present invention constructs a multivariable-driven dynamic pressure analysis framework by integrating fracture characteristic parameters and drilling operation parameters, which can evaluate the total fracture pressure in real time, calculate the pressure gradient while drilling, and construct a seepage model, thereby accurately reflecting the fluid response mechanism of the well wall fractures under drilling disturbance.

[0022] The data analysis module first quantifies the conductivity, connectivity and spatial influence weight of each fracture based on the fracture parameters extracted by microresistivity imaging. The morphology, direction, length and area of ​​the fracture constitute an important basis for its influence on the wellbore. At the same time, its position in the reservoir, the angle with the wellbore, porosity and surface roughness and other factors jointly determine the conduction efficiency and pressure response capacity of the fracture pressure. By introducing the weight function and the conduction coefficient, the system can perform a weighted average of the influence of the fracture at different spatial positions, establish an evolutionary expression of the total fracture pressure, and reflect the combined force of multiple fracture clusters under formation disturbance conditions. At the same time, the dynamic parameters such as bottom hole pressure, propulsion speed, and drilling fluid characteristics provided by the drilling data acquisition module are synchronously input into the analysis module as driving variables to participate in the calculation of the pressure gradient while drilling. This calculation process is not a simple linear difference, but a nonlinear function that integrates the pressure difference, critical shear response, pressure fluctuation tolerance and fracture space periodic characteristics, so that the evolution of the pressure gradient can not only reflect the instantaneous state, but also has a certain trend prediction ability.

[0023] It is particularly worth emphasizing that the seepage model constructed in this module breaks through the traditional Darcy linear flow assumption. By considering multiple factors such as fracture effective permeability, reservoir effective thickness, fracture nonlinear opening behavior, reference porosity deviation and fracture closure risk, a nonlinear seepage expression with dynamic response and sensitivity adjustment capabilities is established. This model can reflect the nonlinear mutation behavior of fracture conductivity under critical conditions such as large changes in bottom hole pressure and fractures tending to close or expand, and realize feedforward capture of flow fluctuations. In addition, a time evolution control term is embedded in the analysis module to correct the hysteresis of fracture response in the early drilling stage and fit the non-stationary characteristics of pressure conduction to improve the stability and robustness of the model under dynamic drilling conditions.

[0024] In the actual operation of the entire system, the data analysis module plays the role of a "real-time digital twin". It constructs an underground pressure response model that is continuously iterated and updated through fracture geometry parameters and real-time drilling status, so that the complex fracture structure of the formation can be virtually reproduced in the upper system and guide the formulation of subsequent control decisions. Furthermore, the module also embeds a set of parameter boundary recognition mechanisms for different reservoir types. When the formation is identified as a typical reservoir type such as tight sandstone, shale or carbonate rock, the system will automatically call the corresponding critical pressure threshold and response function to adapt to the differences in fracture behavior under different geological conditions. This multi-dimensional mapping mechanism between formation-fracture-pressure is the prerequisite for realizing intelligent and adaptive pressure regulation, and it also significantly improves the versatility of the device in multi-condition and multi-region adaptation.

[0025] The adaptive control module is used to calculate the optimal bottom hole pressure according to the fracture flow rate and the operating parameters, and control the drilling pressure based on the optimal bottom hole pressure.

[0026] The adaptive control module is the core execution system for active intervention and closed-loop regulation. Its principle is not only to adjust the pressure statically, but also to dynamically perceive the coupling changes of fracture flow and drilling parameters, calculate and update the optimal bottom hole pressure control strategy in real time, so as to ensure that the drilling process is carried out under the multi-objective conditions of safety, efficiency and low loss. The design concept of this module is based on the nonlinear seepage characteristics of complex fractured reservoirs and the uncertainty of formation response, and fully considers the evolution of fracture conductivity, the propagation path of bottom hole disturbance pressure and the circulation behavior of drilling fluid in the wellbore annulus, so as to construct a control feedback mechanism that can automatically adjust with formation changes.

[0027] The operation of the control module begins with the real-time call of the fracture flow and pressure gradient output by the data analysis module. Fracture flow is a direct indicator of reservoir conductivity efficiency. Its numerical fluctuation usually corresponds to changes in fracture opening, pore pressure or critical support pressure. If the bottom hole pressure is not adjusted in time for response matching, it is very easy to cause unexpected fracture closure, rupture or leakage. Therefore, this module does not simply provide feedback based on the pressure difference, but introduces a nonlinear model of the dynamic evolution of fractures, with fracture flow as the main driving variable, combined with multiple operating parameters such as drilling fluid density, drilling fluid flow rate, well depth, well inclination, friction coefficient, annular space area and circulation density, and forms a dynamic optimal bottom hole pressure expression through coupling calculation. This pressure value not only has an immediate adjustment function, but also can predict the pressure trend of fracture response in the future, realizing the extension from response control to predictive control.

[0028] What is particularly critical is that the module's built-in adaptive regulation mechanism can automatically adjust the regulation sensitivity according to time evolution, fracture conductivity decline, or permeability mutation. When the system recognizes that the current fracture is in a highly connected state and has good conductivity, it will reduce the regulation amplitude to avoid system oscillation caused by over-regulation; and when it detects that the fracture flow rate drops rapidly or the pressure gradient fluctuates abnormally, it will automatically increase the feedback gain to quickly restore the bottom hole pressure to the fracture stability range to ensure reservoir integrity. In addition, the module also introduces a hyperbolic tangent function to compress the bottom hole pressure regulation factor during the calculation process, aiming to make nonlinear corrections when the equivalent circulating density approaches the limit state to avoid "overshoot" behavior in the control system. This design makes the control output more flexible and robust, and can maintain the stability and reliability of the control in actual working conditions with high noise and high uncertainty.

[0029] It is worth noting that the adaptive control module also has multi-layer protection logic. When the system recognizes that the current equivalent circulating density is close to the set critical density threshold and the fracture conductivity is significantly reduced, indicating that there is a risk of fracture closure or inelastic deformation, the module will automatically increase the bottom hole pressure to increase the degree of fracture opening, while reducing the drilling fluid density or reducing the drilling speed to reduce formation disturbance. In addition, the control law parameters in this module can be automatically switched according to different types of reservoirs to ensure that the control strategy can be adapted in the best form under different geological conditions such as dense sandstone, fractured shale or high-pressure carbonate rock, reflecting the powerful working condition adaptive ability of the device.

[0030] Furthermore, the fracture characteristic parameters include: original formation pressure , unit is MPa; fracture pressure conductivity ; Fracture connectivity index ; Fracture fractal dimension ; Matrix permeability , unit is mD; fracture porosity ; Fluid viscosity , unit is mPa·s; The weight coefficient of each crack ;No. The angle between the fracture and the wellbore , unit is rad; monitoring time , unit is s; fracture equivalent permeability , unit is mD; effective reservoir thickness , unit is m; average crack curvature ; Average crack surface roughness , in μm; crack permeability ; Equivalent connected length of crack , in m; the length of the matrix middle path , unit is m; The length of the crack , unit is m; The area of ​​the crack , the unit is ; Total number of cracks ; Matrix pressure , unit is MPa; the current well depth is The relative depth of the cracks , unit is m.

[0031] The original formation pressure, as the initial pressure benchmark of the formation in the undisturbed state, determines the starting boundary of the opening or closing of the fracture during the drilling process; the fracture pressure conductivity coefficient characterizes the response speed and amplitude of the fracture to the pressure disturbance. Its calculation process takes into account the ratio of the permeability and the connection path between the fracture and the matrix, reflecting the non-uniform transmission characteristics of pressure in the multi-media system; the fracture connectivity index and fractal dimension reveal the distribution complexity of the fracture in space and the formation probability of the dominant flow channel from the perspective of topological structure. The combination of the two provides a structural basis for the modeling of nonlinear seepage channels.

[0032] The settings of matrix permeability and fracture porosity correspond to the storage capacity of non-fracture media and fracture zones in the reservoir, respectively. They are used in the joint model to determine the overall conductivity and pressure drop capacity of the reservoir. The introduction of fluid viscosity is a physical description of the actual formation fluid characteristics such as crude oil, natural gas or water-containing systems. It plays a core role in regulating viscous resistance in the construction relationship between flow and pressure difference. The two parameters of the weight coefficient of the i-th fracture and the angle with the wellbore reflect the spatial influence of the fracture on the wellbore pressure response. The weight coefficient is determined by the proportional function of the fracture length and area, reflecting the contribution of the fracture to the total conductivity in the fracture cluster, while the angle directly affects the distribution of the pressure gradient along the fracture direction, which is a directional factor that cannot be ignored in modeling.

[0033] The introduction of monitoring time parameters provides the system with a time scale for pressure evolution, so that the fracture pressure response under drilling conditions has a physical basis for dynamic changes. The distinction between fracture equivalent permeability and fracture permeability is to represent the overall conductivity and local seepage capacity of fractures in actual calculations. The former is often used for overall flow estimation, while the latter is more accurate in fracture detail modeling. At the same time, the effective thickness of the reservoir, as a key dimension affecting the fluid storage space, determines the upper limit of the vertical conductivity. The two parameters of average fracture curvature and surface roughness belong to the microstructural characteristics of the fracture. The former reflects the tortuosity of the fracture channel, thereby affecting the effective flow path length, and the latter affects the friction between the fluid and the fracture wall, which is an important factor in the calculation of pressure loss.

[0034] The fracture equivalent connection length and the matrix intermediate path length together constitute the dominant flow path network in the fracture-matrix system. The former reflects the lateral connectivity of the fracture, and the latter describes the seepage return path in the non-fracture zone. They play a weight adjustment role in the estimation of fracture pressure conduction efficiency. The length and area of ​​the i-th fracture are the geometric parameters of the specific fracture, which are the basic inputs for constructing weight coefficients, flow terms and spatial response functions. The total number of fractures defines the scale of the fracture system and is an indispensable dimensional indicator in statistical analysis. In the modeling of the evolution of the formation pressure field, the matrix pressure is the basic variable for differential comparison with the fracture pressure, and its dynamic changes determine the fracture closure risk and the pressure driving direction. The relative depth of the current well depth at the i-th fracture is used to construct the relative displacement relationship between the wellbore and the fracture. Especially in the drilling state, this parameter is crucial for the calculation of the pressure propagation direction, the intensity of periodic disturbances and the formation feedback behavior.

[0035] Furthermore, the fracture pressure conductivity for: ; No. The weight coefficient of each crack for: .

[0036] Furthermore, the operating parameters include: wellbore radius , in m; wellbore advancement distance , unit is m; critical shear stress , unit is MPa; pressure fluctuation tolerance , unit is MPa; effective thickness of reservoir , unit is m; bottom hole pressure , in MPa; drilling fluid density, in kg / m³; vertical depth , unit is m; well inclination , unit is rad; drilling fluid flow rate , unit is m / s; equivalent viscosity , unit is mPa·s; effective annular area , in m²; equivalent circulation density , unit is kg / m³; Equivalent circulation density tolerance , unit is kg / m³; outer boundary radius , unit is m.

[0037] In the pressure monitoring and control device for complex fractured reservoirs, in order to accurately evaluate the response behavior of the fracture system to pressure disturbance, a series of parameters and function forms with physical meaning and quantifiable characteristics must be introduced to construct a fracture-matrix coupling model with high-precision fitting ability. It is an important quantitative indicator to measure the response rate and transmission capacity of the fracture system in the formation to pressure disturbance. Its definition takes into account two core factors: one is the fracture permeability Matrix permeability The second is the length of the fracture connection path. Path length between substrate and The former characterizes the permeability comparison at the microscopic scale, while the latter reveals the degree of dominance of fractures over fluid transmission paths from the perspective of geometric structure. The product of the two is The expression of reflects that this device comprehensively considers the physical property differences and spatial structural relationships between reservoir media when evaluating formation pressure response, avoiding the error accumulation problem of traditional models that only rely on fracture permeability and ignore spatial heterogeneity. and This indicates that cracks are extremely dominant in the seepage process. When it approaches 1, the system shows the characteristics of high voltage conduction and high response rate; on the contrary, when the crack is only a part of the flow auxiliary structure, As it approaches 0, the system's response to pressure changes tends to be lagging.

[0038] Introduced the Weight coefficient of cracks This factor is based on the length of the crack and area The weighted ratio is constructed and normalized by the sum of the geometric indicators of all cracks to form a dimensionless indicator that reflects the relative contribution of each crack. When the number of fractures is large, the model will not show abnormal phenomenon of excessive concentration on a single fracture, and can also maintain the system's sensitivity to the difference in fracture scale, so it is suitable for pressure estimation in the environment of heterogeneous fracture development. Especially during the drilling process, the interaction between the drill bit and the wellbore wall leads to frequent local opening or closing of fractures near the wellbore.

[0039] In order to more comprehensively describe the dynamic mechanics and fluid disturbance behavior during drilling, the present invention also defines multiple operating parameters, which, on the one hand, participate in the calculation of the optimal bottom hole pressure in the control module, and on the other hand, are also an important basis for modeling the real-time pressure change trend. and advancement distance Together they define the spatial scale of drill bit movement and are the spatial boundaries for constructing pressure gradient and fluid transport models; critical shear stress and pressure fluctuation tolerance It is used to evaluate the response threshold of the fracture under critical state. When the bottom hole disturbance approaches or exceeds this range, the fracture may be irreversibly closed or expanded, thus triggering automatic adjustment of the control system. It is an important target variable output by the control system, and its change directly affects the fracture conductivity and formation stability; drilling fluid density , drilling fluid flow rate and equivalent viscosity are the basic parameters describing the physical state of the fluid in the wellbore. and vertical depth Together they form the basis for calculating the flow pressure field in the wellbore. The term reflects the influence of the gravity term, while The term reflects the effect of viscous resistance.

[0040] In addition, the direct annular area Equivalent circulation density Together they define the spatial scale and density disturbance capability of fluid circulation and flowback efficiency in the wellbore. With its tolerance The ratio of is used to establish a nonlinear control function such as Or the correction term of the exponential function to express the flexible compression of the pressure control output when approaching the limit state, to prevent the system from "overshooting" or control oscillation. Outer boundary radius It is a key physical quantity for establishing seepage boundary conditions, and its setting directly affects the pressure difference driving mechanism between fractures and wellbore. Through the systematic introduction of the above physical parameters, the present invention can dynamically sense the changes in the fracture state during drilling, and implement accurate model-driven control strategies based on structural geometry, fluid state and pressure response characteristics, effectively improving the stability and safety of drilling operations in complex fractured reservoirs.

[0041] Furthermore, the data analysis module evaluates the total fracture pressure based on the fracture characteristic parameters as follows: ; in, is the total crack pressure.

[0042] Total fracture pressure Original formation pressure As the initial reference state, it shows that the computational model is based on an initial pressure field under static geological conditions, and then the benchmark is dynamically modulated by a series of multiplicative terms. The most critical modulation factor is the exponential function structure, which reflects the nonlinear amplification or attenuation mechanism of the fracture system pressure response. The numerator of the exponential term contains the fracture pressure transmission coefficient , fracture connectivity index and crack fractal dimension The square of , this combination directly reflects the strengthening effect of crack conductivity on pressure response. In physical terms, Describes the pressure propagation capability of the fracture relative to the matrix during seepage, describes the degree of interconnection between fractures, and As a geometric measurement item of fractal structure, it reflects the influence of the spatial complexity of fractures on the propagation path of fluid disturbance. The three are multiplied together to form a weighted correction term for the original pressure disturbance. The larger the value, the denser the fracture network and the easier it is to form the main path of pressure conduction, thereby amplifying the ability of bottom hole disturbance to propagate to the far-field fracture system.

[0043] The denominator introduces the matrix permeability , fracture porosity and fluid viscosity , which is used to comprehensively describe the inhibitory effect of non-fracture media on pressure conduction. Lower permeability or porosity means that the matrix is ​​not easy to conduct fluid, thereby increasing the pressure response lag; while high viscosity means that the fluid itself has a large flow resistance, which will also slow down the propagation speed of pressure disturbances. Overall, this exponential precondition, as an "acceleration factor" of the pressure conduction response, takes into account both the enhancement effect dominated by fractures and the blocking effect brought about by the physical properties of the matrix and fluid, thereby achieving a nonlinear and accurate expression of the overall pressure drop structure of the reservoir.

[0044] Another key structure within the exponential function is the crack weight coefficient With spatial functions and This part reflects the weighted effect of multiple cracks at different geometric positions and angles on the total pressure response. Specifically, By The length of the crack and area The coefficient with unified dimension obtained by weighted normalization is used to express the relative contribution of the fracture to flow conductivity and pressure transmission among all fractures. The term introduces the wellbore radius The logarithmic ratio of the pressure disturbance to the fracture length reflects the spatial attenuation effect of the pressure disturbance during the propagation from the wellbore to the far end of the fracture. The larger the value, the negative value indicates that the pressure response is attenuated, and vice versa. It is used to describe the effect of the angle between the fracture and the wellbore on the direction of pressure. When the fracture and the wellbore are in the same direction, this term approaches 1, indicating that the pressure can be transmitted to the fracture to the greatest extent; if the angle tends to be vertical, this term approaches 0, and the pressure response can hardly be effectively projected to the fracture direction. The spatial responses of all fractures are integrated together by summing to form a pressure response mapping of the entire fracture system under the current drilling disturbance.

[0045] In addition, to reflect the temporal dynamics of the fracture pressure response, the formula is multiplied by a time evolution factor , its physical meaning is to simulate the process of gradual establishment of fracture pressure during drilling. When the drill bit just approaches the target reservoir or new fracture area, the pressure has not been fully transmitted to the entire fracture system, and the system is still in a low response state; as time goes on, the fracture system gradually establishes a stable coupling with the wellbore, the pressure transmission effect is enhanced, and finally tends to be stable. The form of this exponential decay function ensures the physical consistency of the slow growth of the initial response and the saturation in the later stage, which better reflects the non-stationary response characteristics of the fracture system during dynamic drilling.

[0046] Furthermore, the pressure gradient while drilling is calculated as: ; in, is the pressure gradient while drilling, in MPa / m; is the critical pressure threshold.

[0047] Furthermore, when the formation is a tight sandstone reservoir, The value range is 20MPa to 35MPa; when the formation is a fractured shale reservoir, The value range is 20MPa to 45MPa; when the formation is high-pressure deep carbonate rock, The value range is 30MPa to 60MPa. When the formation is medium-shallow mudstone or low-pressure reservoir, The value range is 10MPa to 25MPa.

[0048] From the overall structure, the pressure gradient while drilling The first term is the total fracture pressure and matrix pressure The difference divided by the wellbore advancement distance , which is a classical pressure gradient calculation framework, describing the pressure change caused by unit drilling length. However, in the application environment of the present invention, the fracture system is not a uniform and continuous seepage channel, but presents a multi-scale non-uniform connected structure. Therefore, a simple pressure difference ratio cannot fully reflect the dynamic process of actual pressure evolution. In order to introduce the adjustment and constraint mechanism, an exponential nonlinear adjustment factor is added to the second term, and its exponential term is is the main variable, and the denominator is the pressure fluctuation tolerance , which mathematically forms a The physical meaning of the adjustment function is to express the sensitivity and self-adjustment characteristics of the fracture system to the critical pressure area during drilling.

[0049] when near When , that is, the current fracture pressure reaches a critical state, whether it breaks upward to cause the fracture to expand, or breaks downward to cause closure, the system enters a highly sensitive area. At this time, the exponential function approaches 1, indicating that the pressure gradient should be completely released according to the real pressure difference; and when and When the difference is large, the exponential term approaches 0, which means that the current pressure state has not yet approached the critical point. The system automatically suppresses the pressure gradient exponentially to avoid unnecessary drastic regulation. This design achieves an early buffer for the risk of sudden pressure changes. While ensuring smooth fracture drainage, it effectively prevents well wall instability such as leakage or fracturing penetration caused by excessive regulation. This regulation function reflects the present invention's deep understanding of the dynamic response mechanism of the critical pressure state, and is also one of the core reasons why the pressure regulation system while drilling can achieve stable operation in complex reservoirs.

[0050] In order to further consider the local amplification effect of periodic disturbance of formation structure and spatial fluctuation of fracture on pressure gradient, a product term modulated by sine function is introduced into the formula, which is: The structure is for the well depth Equivalent period to crack The geometric relationship between them is periodically mapped, and its essence is to express the periodic enhancement effect of the local pressure disturbance caused by the distribution of fractures along the wellbore. Since the fractures in the actual reservoir are often distributed in joints, strips or nets, and have a certain spatial periodicity, the drill bit will periodically encounter fracture development zones and sparse fracture areas during the advancement process. If the spatial adjustment term is not introduced, it is easy to ignore the interference of these structures on the pressure field in the short scale. Therefore, the sine function product term can periodically amplify or weaken the fracture structure disturbance caused by the advancement of the wellbore during the drilling process, so that the pressure gradient not only has global response capabilities, but also can respond quickly to local structural changes.

[0051] It is worth noting that the multiple The values ​​correspond to multiple fracture periodic structures, each term represents the geometric influence of a specific fracture family, and the overall product constructs a multi-scale periodic enhancement effect superposition model, which makes the pressure gradient calculation not only affected by the main fracture, but also by the joint influence of secondary fractures or hidden fracture networks, thereby enhancing the adaptability of the system to work in heterogeneous structures. In addition, this periodic modulation model also helps to explain the cause of periodic bottom hole pressure fluctuations during drilling, providing theoretical support for fracture identification and structural inversion.

[0052] At the critical pressure threshold In the setting, the present invention fully considers the geomechanical background of different types of reservoirs and the actual critical state of fracture closure / expansion behavior. For tight sandstone, due to its low porosity and permeability, fractures are often the main diversion channels, so its critical fracture pressure threshold is relatively concentrated and is set between 20 and 35 MPa; fractured shale has natural fractures and micro-nano pore networks, and the fracture behavior is more complex, so the threshold is set to 20~45 MPa to adapt to its wider pressure response range; and for deep high-pressure carbonate rocks, due to the strong reservoir stress field and the easy shear expansion of fractures, the upper limit of the critical pressure is relatively high and needs to be set at 30~60 MPa to avoid misjudgment; on the contrary, for medium and shallow mudstone or low-pressure reservoirs, most of their fractures are in an open state and do not have effective closure stress, so the critical pressure range is relatively low, only 10~25 MPa. Dynamic setting through formation classification The present invention realizes the intelligent matching of parameters and the differentiated design of control strategies, and improves the application versatility and control accuracy in multiple geological environments.

[0053] Furthermore, the seepage model is: ; in, is the fracture flow rate; is the minimum support pressure, indicating that when the formation pressure or fracture pressure drops below this value, the fracture will begin to close irreversibly and the permeability will decrease, as determined by experiments; is the reference porosity.

[0054] In the pressure monitoring and control device for complex fractured reservoirs, the establishment of the fracture flow model is crucial. It is not only the core calculation basis for the output of the pressure control algorithm, but also deeply reflects the dynamic seepage behavior and nonlinear response characteristics of the fracture system under the action of the formation stress field. The fracture flow expression adopted in the present invention combines the basic framework of Darcy's law, the quantitative adjustment terms of fracture physical parameters, and the dynamic evolution factors of fracture deformation-closure behavior, forming a model that has both physical basis and A high-order seepage prediction model based on geological adaptability and response sensitivity. It represents the fracture flow rate. It constructs the main driving structure based on the fracture equivalent permeability, effective reservoir thickness, pressure difference, fluid viscosity and wellbore-external boundary space characteristics, and simultaneously superimposes the porosity ratio and exponential response term to realize nonlinear adjustment, thereby accurately expressing the real-time changes of fracture conductivity during drilling.

[0055] The first part of the model is the classical radial Darcy flow expression, which is Fracture equivalent permeability and effective thickness represented by Multiply by the pressure difference , the denominator is the fracture fluid viscosity Wellbore radius and outer border radius This structure constitutes a linear driving framework for flow, in which the equivalent permeability represents the overall conductivity of the fracture. Its value integrates multiple microscopic factors such as fracture width, density and connectivity, and can reflect the clustering effect of fractures under the intersection or interference of different fracture families; and the logarithmic ratio between the wellbore and the boundary expresses the spatial attenuation path experienced by the wellbore pressure disturbance propagating to the far field of the formation, which is the core spatial scale parameter for measuring flow resistance. This part of the structure directly establishes the dominant relationship between differential pressure drive and spatial resistance, which is the basis of all fracture seepage models and the core condition for ensuring the engineering applicability of the model.

[0056] On this basis, the model further introduces the porosity ratio adjustment term , which is used to express the correction of the conductivity of the actual reservoir porosity compared to the reference state. This term reflects the sensitivity of the present invention to the impact of pore structure changes on flow, especially during drilling, because the dynamic changes in fracture opening will significantly change its porosity, and the square root form of this term makes the model moderately sensitive to porosity changes but not drastically amplified, thereby maintaining the stability of the model while taking into account the local dynamic adjustment ability. Through this construction, the model can not only adapt to the porosity differences between different reservoirs, but also dynamically track the porosity changes caused by fracture compression or expansion in the same reservoir, providing structural support for the dynamic determination of fracture conductivity.

[0057] The most innovative and intelligent part is the pressure-structure response function constructed in an exponential form. This part directly expresses the nonlinear enhancement effect of whether the fracture is in a stable opening state on the flow rate. represents the current fracture pressure, and is the minimum support pressure, which represents the threshold value below which the fracture will enter an irreversible closure state, and is usually determined through rock mechanics experiments. , the exponential function is positive, and the flow rate shows an exponential upward trend, indicating that the crack is in a good conductive state; if Close to or below , the exponential function approaches zero or is negative, and the flow rate decays rapidly, indicating that the fracture conductivity is limited or almost lost. This design reflects the in-depth understanding of the coupling relationship between fracture mechanical behavior and fluid seepage behavior in the present invention.

[0058] In addition, the denominator of the exponential term middle, represents the average crack curvature, and Represents the surface roughness of the crack, and its product adjusts the amplification degree of the crack opening pressure. The more curved and rough the crack is, the greater the path return and wall friction the fluid encounters when passing through it. Even at a higher pressure state, the crack flow may still be limited, which is reflected in the exponential term as a "slowdown" in the overall growth rate. This structure that adjusts the exponential response sensitivity with geometric-physical joint characteristics is an important innovation of the present invention at the model construction level, so that the fracture conductivity assessment no longer relies solely on the pressure difference itself, but is linked to the fracture microstructure, thereby constructing a more realistic and controllable flow mechanism.

[0059] Furthermore, the adaptive control module calculates the optimal bottom hole pressure according to the fracture flow rate and the operating parameters: ; in, is the friction coefficient; is the optimal bottom hole pressure; is the critical equivalent circulating density, in kg / m³.

[0060] From the formula structure, the optimal bottom hole pressure is the current bottom hole pressure The result of dynamic incremental adjustment based on the pressure gradient while drilling. To drive the core, through the time evolution factor Multiplying together, it reflects the gradualness and feedforward prediction ability of pressure regulation behavior. The initial stage is slow to adjust slowly to avoid excessive disturbances that lead to violent reactions of the fracture structure; as drilling progresses, the adjustment force increases to achieve continuous optimization control of the fracture flow pattern and conductivity. This time factor is crucial in dynamic systems. It gives the system good response lag compensation and trend prediction capabilities, and is an important guarantee for achieving highly robust control.

[0061] After the adjustment factor, the control model introduces a key composite fraction structure, the molecular part of which integrates two core mechanical factors: one is the projection of the gravity of the drilling fluid itself in the well inclination direction. , which reflects the contribution of wellbore depth and well inclination to the static pressure of the liquid column and is the main source of bottom hole static pressure; the second is the friction term , reflects the shear resistance generated when the drilling fluid flows in the wellbore annulus, which is affected by the viscosity of the drilling fluid, the flow rate and the roughness of the wellbore wall. The superposition of the two represents the total pressure resistance that the system needs to overcome under the current drilling conditions, which is the basis for the pressure regulation system to balance energy and compensate for power.

[0062] The denominator couples the control behavior with the fracture conductivity, Construct the effective flow conversion scale that can be generated by unit pressure difference. The fracture flow rate calculated in the previous article is a direct reflection of the fracture conductivity. The effective cross-sectional area of ​​the annulus determines the drilling fluid return capacity and the bottom hole pressure conduction efficiency. The product of the two constitutes a flow capacity reference value, which converts the mechanical load term in the numerator into the adjustment amplitude of the fracture system, so that the pressure control has feedback limitation and physical boundary constraint.

[0063] More importantly, the fraction structure also introduces a hyperbolic tangent function The density response factor expressed as the equivalent cyclic density Its critical value The deviation is used as input to correct the adjustment range of the system when it is close to the limiting circulation density state. During the drilling process, when the drilling fluid density gradually approaches the critical value, the system becomes extremely sensitive. A slight overshoot may trigger crack rupture or strong wellbore disturbance. Traditional linear control is very easy to lose control in this area. The function has a natural saturation characteristic when approaching the boundary, which can compress the adjustment term to a limited range, thereby suppressing overshoot behavior and improving the stability and response flexibility of the control system under extreme conditions. This design is a key link in the adaptive control mechanism of the present invention, and also reflects the active prevention thinking of high-risk nodes in the drilling process.

[0064] At the same time, the friction coefficient The introduction of reflects the device's parametric expression of the wellbore surface structural characteristics and fluid shear response. Through the dynamic adjustment of this parameter, the system can adapt to changes in flow resistance caused by different well diameters, tubing structures or lithology changes. This parameter can be dynamically estimated through on-site calibration or historical experience curves to ensure the on-site feasibility and adjustability of the control model. In addition, the entire formula structure supports edge computing and real-time iteration in implementation, and can be combined with on-site real-time data streams for second-level refresh, thereby achieving continuous tracking and instant adjustment of bottom hole pressure.

[0065] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The above embodiments and descriptions only describe the principles of the present invention. The present invention may be subject to various changes and improvements without departing from the spirit and scope of the present invention. These changes and improvements fall within the scope of the present invention. The scope of protection claimed by the present invention is defined by the attached claims and their equivalents.

Claims

1. A pressure monitoring and control device for complex fractured reservoirs while drilling, characterized in that: include: The data acquisition module includes: a microresistivity imaging logging device and a drilling data acquisition device; the microresistivity imaging logging device is used to acquire well wall imaging data to obtain fracture characteristic parameters; the drilling data acquisition device is used to acquire operating parameters during the drilling process; Data analysis module: used to evaluate the total fracture pressure, calculate the pressure gradient while drilling, build the seepage model, and obtain the fracture flow rate based on the fracture characteristic parameters and operating parameters; The adaptive control module is used to calculate the optimal bottom hole pressure according to the fracture flow rate and the operating parameters, and control the drilling pressure based on the optimal bottom hole pressure.

2. The device for monitoring and controlling pressure while drilling in a complex fractured reservoir according to claim 1, characterized in that: The fracture characteristic parameters include: original formation pressure , unit is MPa; fracture pressure conductivity ; Fracture connectivity index ; Fracture fractal dimension ; Matrix permeability , unit is mD; fracture porosity ; Fluid viscosity , unit is mPa·s; The weight coefficient of each crack ;No. The angle between the fracture and the wellbore , unit is rad; monitoring time , unit is s; fracture equivalent permeability , unit is mD; effective reservoir thickness , unit is m; average crack curvature ; Average crack surface roughness , in μm; crack permeability ; Equivalent connected length of crack , in m; the length of the matrix middle path , unit is m; The length of the crack , unit is m; The area of ​​the crack , the unit is ; Total number of cracks ; Matrix pressure , in MPa; the current well depth is The relative depth of the cracks , unit is m.

3. The device for monitoring and controlling pressure while drilling for a complex fractured reservoir according to claim 2, characterized in that: Fracture pressure conductivity for: ； No. The weight coefficient of each crack for: 。 4. The device for monitoring and controlling pressure while drilling in a complex fractured reservoir according to claim 3, characterized in that: The operating parameters include: wellbore radius , in m; wellbore advancement distance , unit is m; critical shear stress , unit is MPa; pressure fluctuation tolerance , unit is MPa; effective thickness of reservoir , unit is m; bottom hole pressure , in MPa; drilling fluid density, in kg / m³; vertical depth , unit is m; well inclination , unit is rad; drilling fluid flow rate , unit is m / s; equivalent viscosity , unit is mPa·s; effective annular area , in m²; equivalent circulation density , unit is kg / m³; Equivalent circulation density tolerance , unit is kg / m³; outer boundary radius , unit is m.

5. The device for monitoring and controlling pressure while drilling in a complex fractured reservoir according to claim 4, characterized in that: The data analysis module evaluates the total fracture pressure based on the fracture characteristic parameters as follows: ； in, is the total crack pressure.

6. The device for monitoring and controlling pressure while drilling for a complex fractured reservoir according to claim 5, characterized in that: The pressure gradient while drilling is calculated as: ； in, is the pressure gradient while drilling, in MPa / m; is the critical pressure threshold.

7. The device for monitoring and controlling pressure while drilling in a complex fractured reservoir according to claim 6, characterized in that: When the formation is a tight sandstone reservoir, The value range is 20MPa to 35MPa; when the formation is a fractured shale reservoir, The value range is 20MPa to 45MPa; when the formation is high-pressure deep carbonate rock, The value range is 30MPa to 60MPa. When the formation is medium-shallow mudstone or low-pressure reservoir, The value range is 10MPa to 25MPa.

8. The device for monitoring and controlling pressure while drilling in a complex fractured reservoir according to claim 7, characterized in that: The seepage model is: ； in, is the fracture flow rate; is the minimum support pressure, indicating that when the formation pressure or fracture pressure drops below this value, the fracture will begin to close irreversibly and the permeability will decrease, as determined by experiments; is the reference porosity.

9. The device for monitoring and controlling pressure while drilling in a complex fractured reservoir according to claim 8, characterized in that: The adaptive control module calculates the optimal bottom hole pressure based on the fracture flow rate and operating parameters: ； in, is the friction coefficient; is the optimal bottom hole pressure; is the critical equivalent circulating density, in kg / m³.

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