A drilling fluid control system for fractured formations

Abstract

This invention relates to the technical field, specifically to a drilling fluid control system for fractured formations. The system includes a pressure difference extraction module, a flow velocity deviation extraction module, a fracture abrupt change identification module, a channel switching execution module, and a pump pressure adjustment execution module. In this invention, by analyzing the fluctuation amplitude of the pressure time series difference between different depths in the wellbore and comparing the flow velocity change trend, a joint identification mechanism for abnormal seepage path changes is established. This triggers control commands to drive adjustments to the delivery channel state, shortening the response cycle from identification to execution and improving the flexibility of path control. Furthermore, after the channel state switching is completed, pump pressure adjustment is performed based on the resistance characteristics of the current connection structure. By dynamically adapting the delivery frequency and pressure output, the matching and control of the fluid operating state are achieved, enhancing the drilling fluid's adaptability to fracture abrupt change environments, mitigating pressure disturbances caused by abnormal seepage, and maintaining a stable wellbore operating environment.

Description

Technical Field

[0001] This invention relates to the field of drilling fluid pressure and flow control technology, and in particular to a drilling fluid control system for fractured formations. Background Technology

[0002] The field of drilling fluid pressure and flow control technology involves the management and regulation of pressure and flow in the drilling fluid circulation system during the drilling process. Core aspects include monitoring downhole pressure changes, adjusting drilling fluid flow, maintaining wellbore stability, preventing well kicks and blowouts, and addressing fluid leakage and loss in complex formations. This overall technical field utilizes drilling fluid pumping control, pressure sensor deployment, automatic throttling devices, and wellhead pressure regulation structures to construct a system capable of responding to formation changes in real time and regulating drilling fluid performance to ensure the continuity and safety of the drilling process. Traditional fractured formation drilling fluid control systems refer to drilling fluid management devices used to address the problem of easy leakage or loss of drilling fluid in fractured formations. These systems typically limit the seepage of drilling fluid in fractures by adjusting drilling fluid density and viscosity, adding bridging particles or fiber materials to the drilling fluid, setting up segmented grouting structures, and using graded pressurized delivery, thereby controlling its flow path and residence time in the formation and achieving directional regulation of drilling fluid pressure and flow in fractured formations.

[0003] Traditional drilling fluid control systems for fractured formations often rely on parameter presets based on experience with fracture distribution. They lack dynamic analysis methods for the linkage between pressure and flow velocity during drilling. The monitoring mechanism is delayed in recognizing abrupt changes and cannot effectively judge sudden switching of the fracture seepage path, resulting in a lag in control response. Drilling fluid is prone to unexpected loss in abrupt fractures. The system relies on a single channel and fixed output strategy for path switching and pressure regulation, failing to achieve multi-channel coordination and adaptive pump pressure regulation based on differences in fluid state. This results in persistent leakage risk and aggravates fluid disturbance inside the wellbore, leading to wellbore instability and operation interruption. Summary of the Invention

[0004] To address the technical problems existing in the prior art, embodiments of the present invention provide a fractured formation drilling fluid control system. In one aspect, a fractured formation drilling fluid control system is provided, the system comprising:

[0005] The pressure difference extraction module collects the output values ​​of pressure sensors at different depths in the wellbore, arranges them according to a preset period to construct a pressure time series, calculates the pressure difference and time change amplitude between adjacent measuring points, and generates a pressure difference change command.

[0006] The flow velocity offset extraction module receives the pressure difference change instruction, obtains the return pipe section flow meter reading sequence, calculates the instantaneous flow velocity difference over a continuous period, and compares the current difference with the maximum difference in the previous period to generate a flow velocity offset instruction.

[0007] The crack abrupt change identification module synchronously compares the pressure difference change command with the flow velocity offset command to determine whether pressure fluctuation and flow velocity offset exist simultaneously, and generates a crack switching start command when the conditions are met.

[0008] The channel switching execution module receives the crack switching start command, controls the control valve assemblies of the main channel and the backup channel, executes the main channel closing and the backup channel opening, and outputs a channel switching completion command.

[0009] The pump pressure regulation execution module receives the channel switching completion command, adjusts the pumping frequency and outlet pressure to match the path resistance according to the borehole structure and connection characteristics of the backup channel, and outputs the drilling fluid control results for fractured formations.

[0010] As a further embodiment of the present invention, the pressure difference change command includes the pressure difference between adjacent measuring points, the time series change amplitude, and the pressure fluctuation characteristics; the flow velocity offset command includes the instantaneous flow velocity difference, the maximum difference in historical periods, and the difference change ratio; the fracture switching start command includes the pressure fluctuation judgment result, the flow velocity offset judgment result, and the synchronous change identification condition; the channel switching completion command includes the main channel closed state, the backup channel open state, and the channel switching confirmation signal; and the fractured formation drilling fluid control result includes the pumping frequency parameter, the outlet pressure setting, and the path resistance matching coefficient.

[0011] As a further aspect of the present invention, the pressure fluctuation and flow velocity deviation refer to the phenomenon that the pressure sensor and flow meter in the wellbore simultaneously detect the pressure difference change and the instantaneous flow velocity change within the same period.

[0012] The pipe diameter structural parameters include pipe diameter, length, number of elbows and their distribution locations.

[0013] As a further aspect of the present invention, the flow meter reading sequence in the return pipe section refers to the set of flow rate data recorded by the flow meter in the drilling fluid return channel in chronological order.

[0014] As a further aspect of the present invention, the pressure difference extraction module includes:

[0015] The pressure data receiving submodule acquires the output signals of pressure sensors deployed at different depths in the wellbore, arranges the pressure output values ​​of each measuring point in sequence according to a set time period, and classifies the arranged time series data into pressure data sequences of the corresponding depths to generate a layered pressure time series set.

[0016] The pressure difference calculation submodule extracts the time-synchronized pressure values ​​of adjacent measuring points based on the layered pressure time series set. By comparing the pressure value differences between two adjacent depths step by step, and converting them into difference curves with equal time resolution, the pressure difference sequence of adjacent measuring points is obtained.

[0017] The differential pressure change identification submodule calls the pressure difference sequence of the adjacent measuring points, calculates the numerical change range of each pressure difference value in a continuous time period, and performs interval calibration on the change range result of the preset sliding time window. It then identifies the change through a preset differential pressure amplitude threshold and obtains the pressure difference change instruction.

[0018] As a further aspect of the present invention, the flow velocity offset extraction module includes:

[0019] The flow velocity data acquisition submodule acquires continuous readings of the flow meters deployed in the return pipe section based on the pressure difference change command, arranges the flow velocity readings in sequence according to a uniform time step, and fills in the missing time points to generate a flow velocity time series of the return pipe section.

[0020] The instantaneous velocity difference calculation submodule extracts the velocity values ​​corresponding to adjacent time periods based on the velocity time series of the return pipe section, performs numerical subtraction on the velocity readings at consecutive time points, and arranges the difference results in chronological order to obtain a continuous time period velocity difference sequence.

[0021] The flow velocity offset discrimination submodule calls the continuous time period flow velocity difference sequence to obtain the flow velocity difference in the current period, compares it with the flow velocity difference obtained in the previous period, forms a status judgment mark based on the comparison result, and generates a flow velocity offset command.

[0022] As a further aspect of the present invention, the crack mutation identification module includes:

[0023] The instruction synchronization acquisition submodule acquires the pressure difference change instruction and the flow velocity offset instruction, aligns the two types of instructions according to a unified time base, aligns data points with timestamp offsets, and encodes and arranges the synchronized instruction sequence according to the time sequence structure to generate a synchronized instruction sequence set.

[0024] The mutation condition discrimination submodule calls the synchronization instruction sequence set to extract the joint state identifier of the corresponding pressure difference state and flow velocity state at each time point. It extracts the data points in the identifier that simultaneously contain pressure fluctuation markers and flow velocity offset markers, performs dual condition matching verification, and obtains the joint mutation identification result.

[0025] The crack switching generation submodule filters data segments that meet the dual-condition identifier within a continuous time period based on the joint mutation identification results, encodes the activation identifier for the intervals that meet the condition, converts the encoding structure into an identification format, and binds it to the current period execution state to generate a crack switching start command.

[0026] As a further aspect of the present invention, the channel switching execution module includes:

[0027] The switching command receiving submodule obtains the crack switching start command, parses the channel switching request information and execution priority identifier included in the command, reconstructs the parsed command structure according to the scheduling control format and associates it with the current cycle execution status to generate standardized switching control instructions.

[0028] According to the standardized switching control command, the control valve operation submodule sends a closing command to the main channel control valve assembly and an opening command to the backup channel control valve assembly. It monitors the response status signals of the two types of control valves and verifies whether the valve position feedback status conforms to the preset action logic, and obtains the control valve action status identifier.

[0029] The switching status verification submodule calls the control valve action status identifier, performs a logical joint judgment on the response identifiers of the main channel closed state and the backup channel open state, encodes the judgment result into a signal structure format, and synchronously writes it into the execution record queue to generate a channel switching completion command.

[0030] As a further aspect of the present invention, the pump pressure regulation execution module includes:

[0031] The path parameter extraction submodule obtains the channel switching completion command, extracts the current backup channel's diameter structure parameters and connecting component characteristic parameters, normalizes and encodes the structural dimension data and connecting component flow resistance coefficient, calculates the resistance constant corresponding to the path, and generates a backup channel resistance parameter set.

[0032] The pump pressure control adjustment submodule calls the backup channel resistance parameter set, calculates the adjustment function relationship between pumping frequency and outlet pressure under path conditions based on the pump head outlet design pressure and the current pumping frequency setting range, and adjusts the control signal frequency band to obtain the pump pressure control matching value.

[0033] The liquid delivery result generation submodule drives the pumping control unit to output corresponding frequency and pressure parameters according to the pump pressure control matching value, and monitors the flow rate response and pressure feedback of the drilling fluid in the backup channel in real time. It establishes a mapping relationship between the feedback data and the control parameters to generate drilling fluid control results for fractured formations.

[0034] As a further aspect of the present invention, the pressure difference amplitude threshold refers to a preset numerical limit used to determine the change in pressure difference between adjacent measuring points.

[0035] The beneficial effects of the technical solutions provided in the embodiments of the present invention include at least the following:

[0036] By analyzing the fluctuation amplitude of the pressure time series difference between different depths in the wellbore and comparing the flow velocity change trend, a joint identification mechanism for abnormal seepage path changes is established. This triggers control commands to drive the adjustment of the delivery channel status, shortens the response cycle from identification to execution, and improves the flexibility of path control. Furthermore, after the channel status switch is completed, pump pressure adjustment is performed based on the resistance characteristics of the current connection structure. By dynamically adapting the delivery frequency and pressure output, the matching and control of the fluid operation status is achieved, enhancing the drilling fluid's adaptability to the fracture sudden change environment, mitigating the pressure disturbance caused by abnormal seepage, and maintaining the stability of the wellbore operating environment. Attached Figure Description

[0037] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0038] Figure 1 This is a schematic diagram of the system of the present invention;

[0039] Figure 2 This is a schematic diagram of the system framework of the present invention;

[0040] Figure 3 This is a flowchart of the pressure difference extraction module in this invention;

[0041] Figure 4 This is a flowchart of the velocity offset extraction module in this invention;

[0042] Figure 5 This is a flowchart of the crack mutation identification module in this invention;

[0043] Figure 6 This is a flowchart of the channel switching execution module in this invention;

[0044] Figure 7 This is a flowchart of the pump pressure regulation execution module in this invention. Detailed Implementation

[0045] The technical solution of the present invention will now be described with reference to the accompanying drawings.

[0046] In embodiments of the present invention, words such as "exemplarily," "for example," etc., are used to indicate that something is an example, illustration, or description. Any embodiment or design described as "exemplary" in the present invention should not be construed as being more preferred or advantageous than other embodiments or designs. Specifically, the use of the word "exemplary" is intended to present the concept in a concrete manner. Furthermore, in embodiments of the present invention, the meaning expressed by "and / or" can be both, or either one.

[0047] In the embodiments of this invention, the terms "image" and "picture" may sometimes be used interchangeably. It should be noted that, without emphasizing the distinction between them, they convey the same meaning. Similarly, the terms "of," "corresponding (relevant)," and "corresponding" may sometimes be used interchangeably. It should be noted that, without emphasizing the distinction between them, they convey the same meaning.

[0048] In this embodiment of the invention, sometimes a subscript such as W1 may be written in a non-subscript form such as W1. When the difference is not emphasized, the meaning they express is the same.

[0049] To make the technical problems, technical solutions and advantages of the present invention clearer, a detailed description will be given below in conjunction with the accompanying drawings and specific embodiments.

[0050] This invention provides a drilling fluid control system for fractured formations, such as... Figure 1 , Figure 2 The diagram shown illustrates a drilling fluid control system for fractured formations. This system includes:

[0051] The pressure difference extraction module collects the output values ​​of pressure sensors set at different depths in the wellbore, arranges them according to a preset time period to form a pressure time series, calculates the pressure difference between adjacent measuring points in the series, performs time change amplitude calculation on the pressure difference value, and outputs pressure difference change command.

[0052] The flow velocity offset extraction module obtains the continuous reading sequence of the flow meter in the return pipe section based on the pressure difference change command, calculates the instantaneous flow velocity difference within the continuous time period, and then outputs the flow velocity offset command based on the numerical comparison between the current flow velocity difference and the maximum difference in the previous cycle.

[0053] The crack abrupt change identification module synchronously compares the pressure difference change command and the flow velocity deviation command to determine whether there are conditions for both drastic pressure fluctuation and drastic flow velocity deviation at the same time, and generates a crack switching start command when the conditions are met.

[0054] Based on the crack switching start command, the channel switching execution module operates the main channel control valve assembly and the backup channel control valve assembly, executes the control command response process of closing the main channel and opening the backup channel, and outputs a channel switching completion command.

[0055] The pump pressure regulation execution module executes the pump pressure adjustment process based on the channel switching completion command and the bore structure and connection characteristics of the backup channel. By controlling the pumping frequency and matching the pump head outlet pressure with the current path resistance conditions, it outputs the drilling fluid control results for fractured formations.

[0056] The pressure difference change command includes the pressure difference between adjacent measuring points, the time series change amplitude, and the pressure fluctuation characteristics. The flow velocity offset command includes the instantaneous flow velocity difference, the maximum difference in the historical period, and the difference change ratio. The fracture switching start command includes the pressure fluctuation judgment result, the flow velocity offset judgment result, and the synchronous change identification condition. The channel switching completion command includes the main channel closed status, the backup channel open status, and the channel switching confirmation signal. The fractured formation drilling fluid control results include the pumping frequency parameters, the outlet pressure setting, and the path resistance matching coefficient.

[0057] Specifically, such as Figure 2 , Figure 3 As shown, the pressure difference extraction module includes:

[0058] The pressure data receiving submodule acquires the output signals of pressure sensors deployed at different depths in the wellbore, arranges the pressure output values ​​of each measuring point in sequence according to a set time period, and classifies the arranged time series data into pressure data sequences of the corresponding depths to generate a layered pressure time series set.

[0059] First, a communication link was established with three pressure sensors deployed at different depths on the inner wall of the wellbore via the industrial Ethernet protocol. The measurement depths were calibrated as 1200 meters, 1205 meters, and 1210 meters, respectively. These sensors employ the high-precision single-crystal silicon resonant principle, enabling them to capture minute pulsations in formation fluid pressure in real time. The system was set to a sampling frequency of 2 Hz, meaning data was extracted every 500 milliseconds. Taking the 1200-meter measurement point as an example, within a continuous observation period, the raw voltage signal output by the sensor was converted from analog to digital to obtain a set of values: 42.31 MPa, 42.33 MPa, 42.32 MPa, and 42.35 MPa. The system retrieved its internal clock reference and strictly timestamped the readings at the three locations of 1200 meters, 1205 meters, and 1210 meters. For a depth of 1200 meters, the system arranges the first 120 data points collected in chronological order, removes outliers that are outside the normal logical range due to electromagnetic interference from the signal transmission line (such as values ​​that jump to zero or full scale instantaneously), and stores the processed data in the corresponding depth index address, ultimately forming a hierarchical pressure time series set covering three depth dimensions, providing a standardized data foundation for subsequent spatial pressure difference analysis.

[0060] The pressure difference calculation submodule is based on a layered pressure time series set. It extracts the time-synchronized pressure values ​​of adjacent measuring points, compares the pressure differences between two adjacent depths step by step, and converts them into difference curves with equal time resolution to obtain the pressure difference sequence of adjacent measuring points.

[0061] The system extracts synchronous pressure readings from two adjacent measuring points at the same second. Taking the adjacent depth pair of 1200 meters and 1205 meters as an example, the system extracts pressure values ​​of 42.31 MPa and 42.42 MPa at time point t1, respectively. A subtraction operation is performed, calculating the pressure difference at that moment as 0.11 MPa. The system performs the same subtraction operation on each set of synchronous data within the next 60 seconds, with a time step of 1 second. If a signal is lost at the 1205-meter measuring point within a certain second, the system automatically retrieves the pressure difference value of 0.11 MPa from the previous second and 0.13 MPa from the next second, calculates the arithmetic mean to obtain 0.12 MPa as the filler value, thus generating a difference curve reflecting the evolution of the pressure gradient between adjacent measuring points. This curve can accurately quantify the flow resistance loss generated by the formation fluid as it passes through these two depth intervals, obtaining a sequence of pressure differences between adjacent measuring points.

[0062] The differential pressure change identification submodule calls the pressure difference sequence of adjacent measuring points, calculates the numerical change range of each pressure difference value in a continuous time period, and performs interval calibration on the change range result of the preset sliding time window. It then identifies the change through the preset differential pressure amplitude threshold and obtains the pressure difference change instruction.

[0063] The system calculates the numerical fluctuation characteristics of the pressure difference within a 10-second sliding detection window. The system extracts the maximum pressure difference (0.25 MPa) and the minimum pressure difference (0.11 MPa) within the window, and performs a subtraction operation to obtain a change range of 0.14 MPa for this period. For the formation structure of this well section, the system presets a pressure difference threshold of 0.12 MPa. This threshold is determined with reference to the pressure benchmark of the formation under normal circulation conditions in this area. Statistical analysis of 5000 sets of stable operating condition data over the past 24 hours yielded a mean of 0.08 MPa for the normal fluctuation range. Combined with a safety check coefficient of 1.5, the threshold of 0.12 MPa is determined. The system logically compares the currently calculated 0.14 MPa with the threshold of 0.12 MPa, determining that it falls within the "significant fluctuation range." Since 0.14 MPa is greater than 0.12 MPa, the system immediately identifies a non-steady-state change in the bottom hole pressure environment and encapsulates this state as a binary trigger signal to obtain a pressure difference change command.

[0064] Specifically, such as Figure 2 , Figure 4 As shown, the flow velocity offset extraction module includes:

[0065] The flow velocity data acquisition submodule acquires continuous readings of the flow meters deployed in the return pipe section based on the pressure difference change command, arranges the flow velocity readings in sequence according to a uniform time step, and fills in the missing time points to generate a flow velocity time series of the return pipe section.

[0066] Immediately initiate high-frequency readings from the ultrasonic flowmeters deployed in the return pipe section. The flowmeters calculate flow velocity by measuring the time difference between the propagation of sound waves in the drilling fluid in the forward and reverse directions. The system sets a uniform time step of 1 second and retrieves flow velocity readings within the range of 10 seconds before and 20 seconds after the differential pressure command is triggered. Taking the real-time monitored data as an example, the reading sequence is 2.10 m / s, 2.12 m / s, and 2.11 m / s, respectively. If, during a certain acquisition cycle, readings are missing due to air bubble interference in the pipeline, the system will retrieve known values ​​before and after the current time point and, through linear interpolation logic, fill the missing points with the average of 2.13 m / s (2.12 m / s from the previous time and 2.14 m / s from the next time). Through this time-series reconstruction, the system ensures complete consistency between the flow velocity data and the pressure data on the time axis, generating a flow velocity time series for the return pipe section.

[0067] The instantaneous velocity difference calculation submodule extracts the velocity values ​​corresponding to adjacent time periods based on the velocity time series of the returned pipe section, performs numerical subtraction on the velocity readings at consecutive time points, and arranges the difference results in chronological order to obtain the velocity difference sequence for consecutive time periods.

[0068] Numerical evolution analysis is performed on readings at consecutive time points. The system extracts the flow velocity value of 2.12 m / s at second 11 and 2.25 m / s at second 12, and performs a subtraction operation to obtain an instantaneous flow velocity change of 0.13 m / s. The system performs this point-by-point subtraction operation on all adjacent time points throughout the entire monitoring period, and rearranges the resulting series of differences according to the acquisition order. These differences represent the acceleration characteristics of the outflow in a very short time; positive differences reflect an increase in displacement, while negative differences reflect a decrease in displacement. Through this process, the system transforms the original absolute flow velocity values ​​into dynamic fluctuation values, obtaining a sequence of flow velocity differences over continuous time periods.

[0069] The flow velocity offset discrimination submodule calls the continuous time period flow velocity difference sequence to obtain the flow velocity difference in the current period, and compares it with the flow velocity difference obtained in the previous period. Based on the comparison result, a status judgment mark is formed and a flow velocity offset instruction is generated.

[0070] The system executes cross-cycle comparison and judgment logic. It extracts the average flow velocity difference of the most recent 5 seconds within the current detection cycle (0.15 m / s) and retrieves the average flow velocity difference of the previous stable operating cycle (0.02 m / s). By performing numerical subtraction, the offset difference between the two is calculated to be 0.13 m / s. The system sets three judgment intervals: offset less than 0.05 m / s is judged as "stable"; 0.05 m / s to 0.10 m / s is judged as "normal offset"; and greater than 0.10 m / s is judged as "severe offset". In this example, since 0.13 m / s falls within the interval greater than 0.10 m / s, the system determines the current flow velocity state as a severe offset. Based on this logic result, the system status register is set to abnormal, and a flow velocity offset command is generated.

[0071] Specifically, such as Figure 2 , Figure 5 As shown, the crack mutation identification module includes:

[0072] The instruction synchronization acquisition submodule acquires pressure difference change instructions and flow velocity offset instructions, aligns the two types of instructions according to a unified time base, aligns data points with timestamp offsets, and encodes and arranges the synchronized instruction sequence according to the time series structure to generate a synchronized instruction sequence set.

[0073] The system receives pressure difference change commands from downhole and flow velocity offset commands from the surface. Due to the different physical lengths of the transmission paths of the two types of sensor signals, there is a communication delay of approximately 300 milliseconds. Using the system's master clock as a reference, the system performs a translational alignment process on the timestamps of the two types of commands, eliminating isolated command points that cannot find a matching pair on the same time scale. Subsequently, the system performs structured encoding on the synchronized data, encoding pressure difference changes as binary high-order "1"s and flow velocity offsets as binary low-order "1"s. This encoding method unifies two independent physical parameters into a single time series structure, generating a synchronized command sequence set.

[0074] The mutation condition discrimination submodule calls the synchronization instruction sequence set to extract the joint state identifier of the corresponding pressure difference state and flow velocity state at each time point. It extracts the data points in the identifier that simultaneously have pressure fluctuation markers and flow velocity offset markers, performs dual condition matching verification, and obtains the joint mutation identification result.

[0075] The generated sequence set is invoked, and a multi-criteria joint judgment is performed. The system extracts the status identifier at each synchronization time point one by one, checking whether the dual conditions of drastic pressure fluctuation (code 1) and drastic flow velocity shift (code 2) are simultaneously met. The system constructs a binary logic judgment matrix, and the corresponding position of the matrix outputs an activation signal if and only if both input items are 1. For example, at time T1, if the pressure difference identifier is 1 and the flow velocity identifier is 1, the matrix output is 1; if at time T2, only the pressure difference identifier is 1 and the flow velocity identifier is 0, the matrix output is 0. This logic filtering mechanism eliminates false alarms caused by interference from a single device (such as pump pressure regulation) and obtains the joint mutation identification result by extracting data points with double 1 identifiers.

[0076] The crack switching generation submodule filters data segments that meet the dual-condition identifier within a continuous time period based on the joint mutation identification results, encodes the activation identifier for the intervals that meet the condition, converts the encoding structure into an identification format, and binds it to the current period execution status to generate a crack switching start command.

[0077] The system filters continuous time periods that meet the combined dramatic change conditions. A stability check interval is set, requiring a logic result of 1 for two consecutive seconds (four sampling points) to be considered a valid fracture initiation signal. In this example, the system identifies a time period from 14.5 seconds to 16.5 seconds that meets both conditions and encodes this interval with an activation flag. The system further binds this encoding result to the current drilling system's "cycle state" to ensure the switching action is triggered while pumping is in operation. Through this complex nested condition, the system generates an instruction package containing information such as trigger time, formation depth, and switching target path, thus generating a fracture switching initiation command.

[0078] Specifically, such as Figure 2 , Figure 6 As shown, the channel switching execution module includes:

[0079] The switching command receiving submodule obtains the crack switching start command, parses the channel switching request information and execution priority identifier included in the command, reconstructs the parsed command structure according to the scheduling control format and associates it with the current cycle execution status to generate standardized switching control instructions.

[0080] The system immediately parses the control message it carries. It extracts the "channel switching request" field from the message, identifies the target path as a backup loop channel, and confirms its execution priority as "highest." Based on the communication protocol format of the field-programmable logic controller (PLC), the system reconstructs the parsed data into a hexadecimal control instruction stream and forcibly associates it with the current job cycle number. This reconstruction process ensures the uniqueness and traceability of the instructions at the execution level, and through verification of the scheduling format, generates standardized switching control instructions.

[0081] The control valve operation submodule sends a closing command to the main channel control valve assembly and an opening command to the backup channel control valve assembly according to the standardized switching control command. It monitors the response status signals of the two types of control valves and verifies whether the valve position feedback status conforms to the preset action logic, and obtains the control valve action status identifier.

[0082] A closing signal is sent to the electrically controlled valve group in the main circulation channel, driving the motor to rotate. Simultaneously, an opening signal is sent to the control valve group in the backup channel. During execution, the system monitors the feedback current of the valve position sensors in real time. The feedback current of the main channel valve gradually decreases from 20 mA (corresponding to fully open) to 4.2 mA (corresponding to fully closed), while the feedback current of the backup channel valve increases from 4.1 mA to 19.8 mA. The system verifies, through its built-in logic verification program, whether the main valve's closed state and the backup valve's open state simultaneously reach logical truth within a preset 5 seconds. If the valve position feedback fails to reach the desired state within the specified time, the system will automatically trigger secondary compensation control and obtain the control valve's action status indicator.

[0083] The switching status verification submodule calls the control valve action status flag, performs a logical joint judgment on the response flags of the main channel closed state and the standby channel open state, encodes the judgment result into a signal structure format, and writes it synchronously into the execution record queue to generate a channel switching completion command.

[0084] The system retrieves the action status flag and executes the final logical closed-loop judgment. It checks if the main channel closed flag is 1 and the backup channel open flag is 1. If both are true, the channel switching task is considered successfully completed. The system encodes this final judgment result, along with its corresponding timestamp and valve position accuracy (e.g., 99.5%), to form a status confirmation signal, which is then written to the system's execution history queue according to a first-in, first-out principle. This process not only provides real-time feedback on the operation but also provides detailed records for subsequent accident tracing, generating a channel switching completion command.

[0085] Specifically, such as Figure 2 , Figure 7 As shown, the pump pressure regulation execution module includes:

[0086] The path parameter extraction submodule obtains the channel switching completion command, extracts the current backup channel's diameter structure parameters and connecting component characteristic parameters, normalizes and encodes the structural dimension data and connecting component flow resistance coefficients, calculates the resistance constant corresponding to the path, and generates a backup channel resistance parameter set.

[0087] The system immediately retrieves the physical structure data of the backup passage from the equipment database. The system extracts the pipe diameter as 102 mm, the total straight pipe length as 45 meters, and the number of elbows at the connection points as 3. The system normalizes and encodes these non-standard parameters, performing a combined calculation on the local resistance coefficient of the elbows (0.75 for each) and the friction coefficient of the straight pipe (0.025). The calculated total local resistance is 2.25, and the friction coefficient, calculated based on the pipe diameter and length, is 11.03. The system adds these two values ​​together, determining the total flow resistance coefficient of the path to be 13.28. This parametric modeling generates the set of resistance parameters for the backup passage.

[0088] The pump pressure control adjustment submodule calls the backup channel resistance parameter set, calculates the adjustment function relationship between pumping frequency and outlet pressure under path conditions based on the pump head outlet design pressure and the current pumping frequency setting range, and adjusts the control signal frequency band to obtain the pump pressure control matching value.

[0089] The calculated resistance parameter of 13.28 is used. The system simultaneously acquires the current pump head's outlet design pressure of 20 MPa and the current pumping frequency of 30 Hz. Since the resistance constant of the backup channel (13.28) is higher than that of the original main channel (10.50), if the frequency remains unchanged, the outlet pressure will exceed the safety threshold due to increased resistance. The system establishes a regulation function relationship and calculates that, with a 26% increase in resistance, the pumping frequency needs to be appropriately adjusted to maintain stable system operation and match the pressure output characteristics. The calculated new frequency matching value is 32.8 Hz. The system adjusts the inverter's control signal frequency band, sends the target frequency command to the motor drive unit, and obtains the pump pressure control matching value.

[0090] The liquid delivery result generation submodule drives the pump control unit to output the corresponding frequency and pressure parameters based on the pump pressure control matching value, and monitors the flow rate response and pressure feedback of the drilling fluid in the backup channel in real time. It establishes a mapping relationship between the feedback data and the control parameters to generate drilling fluid control results for fractured formations.

[0091] Based on the calculated 32.8 Hz matching value, the mud pump is driven to output the corresponding pressure and flow rate. During execution, the system monitors the flow velocity response in the backup channel in real time via sensors. Feedback data shows that after frequency adjustment, the system pressure increases to approximately 25–26 MPa, while the flow velocity remains around 2.15 m / s, with the system completing regulation within the flow fluctuation range. The system establishes a one-to-one mapping relationship between these measured feedback data and the initial control parameters to evaluate the accuracy of the adjustment process. Through this closed-loop regulation, the stability of drilling fluid flow after switching to fractured formations is ensured, generating drilling fluid control results for fractured formations.

[0092] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A fractured formation drilling fluid control system, characterized by, include: The pressure difference extraction module collects the output values ​​of pressure sensors at different depths in the wellbore, arranges them according to a preset period to construct a pressure time series, calculates the pressure difference and time change amplitude between adjacent measuring points, and generates a pressure difference change command. The flow velocity offset extraction module receives the pressure difference change instruction, obtains the return pipe section flow meter reading sequence, calculates the instantaneous flow velocity difference over a continuous period, and compares the current difference with the maximum difference in the previous period to generate a flow velocity offset instruction. The crack abrupt change identification module synchronously compares the pressure difference change command and the flow velocity offset command to determine whether there are conditions of drastic pressure fluctuation and drastic flow velocity offset at the same time. If the conditions are met, a crack switching start command is generated. The channel switching execution module receives the crack switching start command, controls the control valve assemblies of the main channel and the backup channel, executes the main channel closing and the backup channel opening, and outputs a channel switching completion command. The pump pressure regulation execution module receives the channel switching completion command, adjusts the pumping frequency and outlet pressure to match the path resistance according to the borehole structure and connection characteristics of the backup channel, and outputs the drilling fluid control results for fractured formations. The crack mutation identification module includes: The instruction synchronization acquisition submodule acquires the pressure difference change instruction and the flow velocity offset instruction, aligns the two types of instructions according to a unified time base, aligns data points with timestamp offsets, and encodes and arranges the synchronized instruction sequence according to the time sequence structure to generate a synchronized instruction sequence set. The mutation condition discrimination submodule calls the synchronization instruction sequence set to extract the joint state identifier of the corresponding pressure difference state and flow velocity state at each time point. It extracts the data points in the identifier that simultaneously contain pressure fluctuation markers and flow velocity offset markers, performs dual condition matching verification, and obtains the joint mutation identification result. The crack switching generation submodule filters data segments that meet the dual-condition identifier within a continuous time period based on the joint mutation identification results, encodes the activation identifier for the intervals that meet the condition, converts the encoding structure into an identification format, and binds it to the current period execution state to generate a crack switching start command.

2. The fractured formation drilling fluid control system of claim 1, wherein: The pressure difference change command includes the pressure difference between adjacent measuring points, the time series change amplitude, and the pressure fluctuation characteristics. The flow velocity offset command includes the instantaneous flow velocity difference, the maximum difference in historical periods, and the difference change ratio. The fracture switching start command includes the pressure fluctuation judgment result, the flow velocity offset judgment result, and the synchronous change identification condition. The channel switching completion command includes the main channel closed status, the backup channel open status, and the channel switching confirmation signal. The fractured formation drilling fluid control results include the pumping frequency parameters, the outlet pressure setting, and the path resistance matching coefficient.

3. The fractured formation drilling fluid control system of claim 1, wherein: The pressure fluctuation and flow velocity deviation refer to the phenomenon that pressure sensors and flow meters in the wellbore simultaneously detect changes in differential pressure and instantaneous flow velocity within the same period. The structural parameters of the pipe include pipe diameter, length, number of elbows and their distribution.

4. The fractured formation drilling fluid control system of claim 1, wherein: The return pipe section flow meter reading sequence refers to the set of flow rate data recorded by the flow meter in the drilling fluid return channel in chronological order.

5. The drilling fluid control system for fractured formations according to claim 1, characterized in that, The pressure difference extraction module includes: The pressure data receiving submodule acquires the output signals of pressure sensors deployed at different depths in the wellbore, arranges the pressure output values ​​of each measuring point in sequence according to a set time period, and classifies the arranged time series data into pressure data sequences of the corresponding depths to generate a layered pressure time series set. The pressure difference calculation submodule extracts the time-synchronized pressure values ​​of adjacent measuring points based on the layered pressure time series set. By comparing the pressure value differences between two adjacent depths step by step, and converting them into difference curves with equal time resolution, the pressure difference sequence of adjacent measuring points is obtained. The differential pressure change identification submodule calls the pressure difference sequence of the adjacent measuring points, calculates the numerical change range of each pressure difference value in a continuous time period, and performs interval calibration on the change range result of the preset sliding time window. It then identifies the change through a preset differential pressure amplitude threshold and obtains the pressure difference change instruction.

6. The drilling fluid control system for fractured formations according to claim 1, characterized in that, The velocity offset extraction module includes: The flow velocity data acquisition submodule acquires continuous readings of the flow meters deployed in the return pipe section based on the pressure difference change command, arranges the flow velocity readings in sequence according to a uniform time step, and fills in the missing time points to generate a flow velocity time series of the return pipe section. The instantaneous velocity difference calculation submodule extracts the velocity values ​​corresponding to adjacent time periods based on the velocity time series of the return pipe section, performs numerical subtraction on the velocity readings at consecutive time points, and arranges the difference results in chronological order to obtain a continuous time period velocity difference sequence. The flow velocity offset discrimination submodule calls the continuous time period flow velocity difference sequence to obtain the flow velocity difference in the current period, compares it with the flow velocity difference obtained in the previous period, forms a status judgment mark based on the comparison result, and generates a flow velocity offset command.

7. The drilling fluid control system for fractured formations according to claim 1, characterized in that, The channel switching execution module includes: The switching command receiving submodule obtains the crack switching start command, parses the channel switching request information and execution priority identifier included in the command, reconstructs the parsed command structure according to the scheduling control format and associates it with the current cycle execution status to generate standardized switching control instructions. According to the standardized switching control command, the control valve operation submodule sends a closing command to the main channel control valve assembly and an opening command to the backup channel control valve assembly. It monitors the response status signals of the two types of control valves and verifies whether the valve position feedback status conforms to the preset action logic, and obtains the control valve action status identifier. The switching status verification submodule calls the control valve action status identifier, performs a logical joint judgment on the response identifiers of the main channel closed state and the backup channel open state, encodes the judgment result into a signal structure format, and synchronously writes it into the execution record queue to generate a channel switching completion command.

8. The drilling fluid control system for fractured formations according to claim 1, characterized in that, The pump pressure regulation execution module includes: The path parameter extraction submodule obtains the channel switching completion command, extracts the current backup channel's diameter structure parameters and connecting component characteristic parameters, normalizes and encodes the structural dimension data and connecting component flow resistance coefficient, calculates the resistance constant corresponding to the path, and generates a backup channel resistance parameter set. The pump pressure control adjustment submodule calls the backup channel resistance parameter set, calculates the adjustment function relationship between pumping frequency and outlet pressure under path conditions based on the pump head outlet design pressure and the current pumping frequency setting range, and adjusts the control signal frequency band to obtain the pump pressure control matching value. The liquid delivery result generation submodule drives the pumping control unit to output corresponding frequency and pressure parameters according to the pump pressure control matching value, and monitors the flow rate response and pressure feedback of the drilling fluid in the backup channel in real time. It establishes a mapping relationship between the feedback data and the control parameters to generate drilling fluid control results for fractured formations.

9. The drilling fluid control system for fractured formations according to claim 5, characterized in that: The pressure difference amplitude threshold refers to a preset numerical limit used to determine the change in pressure difference between adjacent measuring points.

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