A system and control method for automatic injection-production switching based on wellhead pressure

Abstract

The present application provides a system and control method for automatic injection-production switching based on wellhead pressure. The system includes: an injection-production switching switch and a ground controller. The injection-production switching switch is used to collect downhole data and send it to the ground controller, and is also used to switch between water injection and oil production. The downhole data includes the water content of the crude oil, the flow rate of the produced fluid, and the formation pressure. The ground controller determines a channel switching instruction based on the received downhole data and sends the channel switching instruction to the injection-production switching switch, so that the injection-production switching switch can switch between water injection and oil production according to the channel switching instruction. In this solution, the ground controller monitors the downhole data collected by the injection-production switching switch and automatically prompts the well to switch between water injection and oil production based on the well condition, thus achieving both oil production and water injection functions in a single well.

Description

Technical Field

[0001] The present invention belongs to the technical field of oil field production, and in particular relates to a system and a control method for automatic injection-production switching based on wellhead pressure. Background Art

[0002] Oilfield production methods refer to the method of pumping crude oil from the formation to the surface. Based on objective underground energy, they can be divided into two types: flow recovery and artificial lift. The choice of recovery method is determined by the reservoir energy level and reasonable economic benefits. Because flow recovery requires higher reservoir energy, artificial lift is currently the most widely used method. Artificial lift can be categorized by the lifting method as gas lift and deep-well pumping. Deep-well pumping is primarily divided into rod pumping and rodless pumping. Currently, rod pumping units are the primary production equipment in oilfields. Different recovery methods are used for different formation and reservoir conditions, such as viscosity, water content, and reservoir replenishment capacity.

[0003] In conventional oil production processes, layered oil production instruments are generally lowered into the well, and are independently equipped with surface or downhole oil production mechanisms. According to the well conditions at different times, the oil production speed and oil production method are manually adjusted, and even the pump and well may be stopped, which greatly reduces oil production efficiency and increases labor costs.

[0004] Furthermore, to maintain the energy of different layers of the oil well, after an oil field is put into development, as the production time increases, the energy of the oil layer itself will continue to be consumed, causing the oil layer pressure to continue to drop, a large amount of underground crude oil to be degassed, the viscosity to increase, and the oil well production to be greatly reduced, and even stop spraying and production, resulting in a large amount of dead oil remaining underground that cannot be extracted. In order to make up for the underground deficit caused by crude oil extraction, maintain or increase the oil layer pressure, achieve high and stable oil field production, and obtain a high recovery rate, the oil field must be water injected.

[0005] Currently, oilfield production generally uses a separate production and injection well network, meaning a single well is only responsible for either oil production or water injection. This approach is ideal for large, well-distributed reservoirs. However, some reservoirs are small and have scattered wells, making the construction of an injection-production network uneconomical. In addition, insufficient formation energy and low pressure levels make water injection uneconomical. At the same time, some strata have development potential, creating significant challenges for oilfield production. Summary of the Invention

[0006] The purpose of the embodiments of this specification is to provide a system and control method for automatic injection-production switching based on wellhead pressure.

[0007] To solve the above technical problems, the embodiments of the present application are implemented in the following ways:

[0008] In a first aspect, the present application provides a system for automatic injection-production switching based on wellhead pressure, the system comprising: an injection-production switching switch, a surface controller;

[0009] The injection-production switch is used to collect downhole data and send it to the surface controller. It is also used to switch between water injection and oil production. Downhole data includes the water content of crude oil, produced fluid flow rate, and formation pressure.

[0010] The ground controller determines a channel switching instruction based on the received downhole data and sends the channel switching instruction to the injection-production switch so that the injection-production switch can switch between water injection and oil production according to the channel switching instruction.

[0011] In one embodiment, the system further includes: a surface pressure device for collecting wellhead pressure data and sending it to a surface controller, so that in water injection mode, the surface controller controls the water injection pressure and flow according to the wellhead pressure data and the current pipeline pressure limit.

[0012] In one embodiment, the wellhead pressure data includes the wellhead tubing pressure and the wellhead casing pressure;

[0013] Surface pressure equipment includes tubing surface pressure gauges and casing surface pressure gauges; tubing surface pressure gauges are used to collect wellhead tubing pressure, and casing surface pressure gauges are used to collect wellhead casing pressure;

[0014] The surface pressure equipment also includes a water injection control valve, which is used to control the well water injection pressure and flow when the injection-production switch is switched to water injection mode.

[0015] In one embodiment, the surface controller is connected to the injection-production switch via a cable;

[0016] The injection-production switch includes a downhole acquisition device, which is used to collect downhole data;

[0017] The cable is used to power downhole acquisition equipment and transmit DC carrier signals between the surface controller and the injection-production switch;

[0018] When the ground controller sends a channel switching instruction to the injection-production switch, the DC carrier signal is the channel switching instruction;

[0019] When the injection-production switch sends downhole data to the ground controller, the DC carrier signal is the downhole data.

[0020] In one embodiment, the ground controller is connected to the ground pressure device via a communication module, which includes an RS485 communication module, a CAN bus, or an RS23 communication module.

[0021] In a second aspect, the present application provides a control method for the system for automatic injection-production switching based on wellhead pressure as in the first aspect, the control method comprising:

[0022] Obtain downhole data sent by the injection-production switch; downhole data includes formation pressure;

[0023] If the current formation pressure does not meet the production conditions, a channel switching instruction is sent to the injection-production switch to switch the injection-production switch to the water injection mode;

[0024] During water injection, if the difference between the current formation pressure and the initial formation pressure is detected to be within a preset range, water injection will be suspended; the initial formation pressure is the formation pressure before oil production;

[0025] During the first preset time period, the formation pressure is continuously obtained. If the formation pressure does not meet the preset condition, it is determined that the formation pressure has not recovered, and water is injected again until the formation pressure meets the preset condition.

[0026] In one embodiment, if the formation pressure meets a preset condition, a channel switching instruction is sent to the injection-production switching switch to switch the injection-production switching switch to the oil production mode.

[0027] In one embodiment, the downhole data further includes the water content of the crude oil;

[0028] After the injection-production switch is switched to the oil production mode, the method further includes:

[0029] Determine the current reservoir's crude oil production capacity based on the current formation pressure and crude oil water content;

[0030] When the crude oil production capacity is less than the expected production value, the method of switching to thermal drive or well suspension and waiting is adopted.

[0031] In one embodiment, the downhole data also includes produced fluid flow rate;

[0032] If the produced fluid flow rate does not change dramatically during the second preset time period and the change range of the crude oil water content is within the preset range, then the formation fluid supply capacity is significantly higher than the current oil production rate. The recovery rate is adjusted to increase the daily output; or if the target recovery rate is met, the current recovery rate is maintained to extend the single continuous production time.

[0033] It can be seen from the technical solutions provided in the above embodiments of this specification that:

[0034] The ground controller monitors the downhole data collected by the injection-production switch, and automatically prompts the well to switch between water injection and oil production according to the well conditions. A single well can achieve oil production and water injection functions, greatly reducing the cost of small oil reservoir extraction and improving the recovery efficiency of small-scale oil reservoirs on a large scale. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] In order to more clearly illustrate the embodiments of this specification or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments recorded in this specification. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative labor.

[0036] Figure 1 This is a schematic diagram of the structure of the system for automatic injection-production switching based on wellhead pressure provided in this application.

[0037] Reference numerals:

[0038] 1. Surface pressure equipment; 11. Oil pipe surface pressure gauge; 12. Casing surface pressure gauge; 13. Water injection control valve; 2. Injection-production switch; 3. Surface controller; 4. Cable; 5. Communication module; 6. Oil pipe; 7. Wire plug screen. DETAILED DESCRIPTION

[0039] To help those skilled in the art better understand the technical solutions in this specification, the following will provide a clear and complete description of the technical solutions in the embodiments of this specification, in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of this specification, not all of them. All other embodiments derived by those skilled in the art based on the embodiments in this specification without creative effort shall fall within the scope of protection of this specification.

[0040] In the following description, specific details such as specific system structures and techniques are provided for purposes of illustration rather than limitation to facilitate a thorough understanding of the embodiments of the present application. However, it will be apparent to those skilled in the art that the present application may be implemented in other embodiments without these specific details. In other cases, detailed descriptions of well-known systems, devices, circuits, and methods are omitted to avoid obscuring the description of the present application with unnecessary detail.

[0041] It will be apparent to those skilled in the art that various modifications and variations may be made to the specific embodiments described herein without departing from the scope or spirit of the present application. Other embodiments will be apparent to those skilled in the art from the present description. The present description and examples are intended to be illustrative only.

[0042] The words “include,” “including,” “have,” “contain,” etc. used in this document are open-ended terms, meaning including but not limited to.

[0043] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0044] Reference Figure 1 , which shows a structural schematic diagram of a system for automatic injection-production switching based on wellhead pressure provided in an embodiment of the present application.

[0045] like Figure 1 As shown, the system for automatic injection-production switching based on wellhead pressure includes: surface pressure equipment 1, injection-production switching switch 2, and surface controller 3.

[0046] The surface pressure device 1 is used to collect wellhead pressure data and send it to the surface controller 3. In the water injection mode, the surface controller 3 controls the water injection pressure and flow according to the wellhead pressure data and the current pipeline pressure limit.

[0047] The injection-production switch 2 is used to collect downhole data and send it to the surface controller 3. It is also used to switch between water injection and oil production. The downhole data includes the water content of crude oil, the flow rate of produced fluid, and the formation pressure.

[0048] The surface controller 3 determines a channel switching instruction based on the received downhole data, and sends the channel switching instruction to the injection-production switch 2, so that the injection-production switch can switch between water injection and oil production according to the channel switching instruction.

[0049] Among them, the wellhead pressure data includes the wellhead tubing pressure and the wellhead casing pressure;

[0050] The surface pressure device 1 includes an oil pipe surface pressure gauge 11 and a casing surface pressure gauge 12; the oil pipe surface pressure gauge 11 is used to collect the wellhead oil pipe pressure, and the casing surface pressure gauge 12 is used to collect the wellhead casing pressure;

[0051] The surface pressure equipment 1 further includes a water injection control valve 13, which is used to control the well water injection pressure and flow when the injection-production switching switch 2 is switched to the water injection mode.

[0052] The surface controller 3 is connected to the injection-production switch 2 via a cable 4. The cable 4 may be a single-core cable.

[0053] Specifically, in this embodiment, the system for automatic injection-production switching based on wellhead pressure (hereinafter referred to as the system) can be divided into four parts: a surface controller 3, a tubing section, a tool section, and surface pressure equipment 1. The tubing section includes the tubing 6 running from the injection-production switching tool to the wellhead Christmas tree, and the injection-production switching switch power cable 4 running outside the tubing 6. The tool section includes the injection-production switching switch 2. The surface pressure equipment 1 includes a tubing surface pressure gauge 11, a casing surface pressure gauge 12, and a water injection control valve 13.

[0054] The connection order of the system from top to bottom is ground controller 3, ground pressure equipment 1, cable 4 (single-core cable), and injection-production switch 2.

[0055] The ground controller 3 is mainly used to send downlink communication instructions to the injection-production switch 2, receive and process the uplink data signals returned by the downhole instrument (injection-production switch); and send ground pressure equipment control instructions to the ground pressure equipment 1, and receive and process the data signals returned by the ground pressure equipment 1.

[0056] The tubing surface pressure gauge 11 and casing surface pressure gauge 12 in the surface pressure equipment 1 collect data on the wellhead tubing pressure and casing pressure, respectively. When the injection-production switch 2 is switched to water injection mode, the water injection control valve 13 in the surface pressure equipment 1 automatically controls the water injection rate based on the water injection plan and the system-calculated water injection target. It also automatically controls the pressure based on the current pipeline pressure limit. The water injection plan is the injection rate for each well calculated by the oilfield company based on the production plan and the injection string conditions in different regions. This production plan may be adjusted in real time based on production conditions. This parameter requires user input. After obtaining the parameter, the system uses it as the target for parameter adjustment. The system then checks whether the well data model can achieve this target. If so, adjustments are made. If not, the user is prompted to make adjustments. The initial water injection target is determined based on the pre-production formation energy model (how this model is determined will be described later) and can be modified by the user at any time. Pipeline pressure limits refer to the inherent pressure limitations of the tubing used in oilfields in different regions. This limitation is due to the mechanical structure of the pipeline. Some surface and downhole pipelines have pressure limits. When the pressure exceeds a certain level, it can cause damage to the pipeline. Furthermore, when using special injection structures, such as pressurized injection methods, it is necessary to set a limit on the injection pressure. Sometimes, meeting the target injection volume will cause the injection pressure to exceed this limit. Therefore, when adjusting the injection volume, the injection pressure must be monitored in real time to prevent excessive pressure.

[0057] The ground controller 3 and the ground pressure device 1 may be connected via a communication module 5 , which includes an RS485 (Recommended Standard 485) communication module, a CAN (Controller Area Network) bus, or an RS232 (Recommended Standard 232) communication module.

[0058] The injection-production switch 2 includes downhole data acquisition equipment, which is used to collect downhole data, including the water content of the crude oil, the flow rate of the produced fluid, and the formation pressure. The downhole data acquisition equipment can also collect downhole data such as the pressure in the oil pipe and the wellbore temperature. Because the casing and the formation are connected, the formation pressure is equal to the pressure in the casing.

[0059] According to general physical laws, the corresponding pressure difference for every 100m of liquid surface in the tubing string is approximately 1MPa. Therefore, the corresponding change in liquid level can be calculated based on the pressure change. The change in liquid level within the casing directly reflects the relationship between the current oil production rate and the reservoir's fluid supply capacity. A significant decrease in the liquid level within the casing indicates that the oil production rate has significantly exceeded the reservoir's fluid supply capacity. A significant increase in the liquid level within the casing indicates that the oil production rate is lower than the reservoir's fluid supply capacity. This parameter clearly reflects the oil production stage and provides an important basis for the system to determine whether to switch modes. In water injection mode, formation pressure clearly reflects the formation's water absorption. When the formation is energy-deficient, when the water injection pressure increases from low to high, the formation pressure changes significantly more slowly, indicating a severe loss of formation pressure energy. After water injection stops, the change in formation pressure is a crucial parameter for determining whether the reservoir's formation capacity has been effectively restored.

[0060] The water content of crude oil can be used to infer the state of the oil layer. Due to the small scale of the oil reservoir itself, this parameter can indicate the current oil production situation at different stages. If the water content of crude oil drops significantly during a long period of production, it is recommended to shut down the well or perform thermal flooding treatment. In this case, water injection can no longer meet the conditions for the remaining oil reservoir to be produced. It may be due to geological or other reasons that the current oil reservoir cannot be effectively discharged with the produced fluid. In this case, the efficiency of continued production is low, which can effectively reduce costs.

[0061] Cable 4 is used to power downhole data acquisition equipment and transmit DC carrier signals between the surface controller 3 and the injection-production switch 2. When the surface controller 3 sends a channel switching instruction to the injection-production switch 2, the DC carrier signal represents the channel switching instruction; when the injection-production switch 2 sends downhole data to the surface controller 3, the DC carrier signal represents the downhole data.

[0062] After receiving power via cable 4, the injection-production switch 2 receives and executes commands sent by the surface controller 3, which may include channel switching commands. It also returns collected downhole data, allowing the system to summarize control parameters for the target recovery scenario based on the downhole data and production plan. Specifically, after switching between the water injection and oil production channels, the system records the amount of water injection required to restore the formation pressure of the current well, the number of water injections required, and the maximum formation pressure that can be restored. It also summarizes the formation pressure drop corresponding to the oil production rate. At this point, the user's production plan can be referenced to determine a recovery rate value. At this recovery rate, the user can determine how long water injection is required, the water injection pressure setting, and the number of times to reach the target formation pressure. If the user determines that restoring the formation pressure is taking too long, the target formation pressure can be lowered. Once the formation pressure is restored, oil production can resume. By controlling the oil production rate, target formation pressure, and water injection rate, production conditions such as well downtime and continuous production can be controlled.

[0063] During construction, the tool string is lowered from the top of the Christmas tree at the wellhead of the oil well according to the tool string structure. The connection sequence is the cable 4, oil pipe, injection-production switch 2, wire plug screen 7, and other structures. It is understandable that the decision to lower other instruments or structures can be made based on the string design. After the string construction is completed, wellhead construction and ground controller 3 installation are carried out, and the ground oil production pipeline and water injection pipeline are connected. The pipeline can be switched automatically or manually, and the switching operation can be completed by the ground controller 3 during automatic switching. The ground controller 3 is connected to the oil pipe surface pressure gauge 11 and casing surface pressure gauge 12, the water injection control valve 13, the injection-production switch 2, and connected to the corresponding communication interface according to their communication method.

[0064] The data communication process and path of the automatic injection-production switching system based on wellhead pressure are as follows:

[0065] The ground controller uses its internal coding circuitry to transmit commands to the injection-production switch via a cable carrier. The switch receives the data through a decoding circuit and executes the commands. When executing the acquisition function, the switch powers on the various acquisition devices and then performs the acquisition. After the acquisition is complete, the data is integrated and transmitted to the ground controller via the coding circuitry within the switch, also via a carrier wave. The ground controller uses a decoding circuitry to parse and store the data. Upon receiving the channel switching command, the switch automatically adjusts the channel accordingly, enabling downhole water injection and oil production channel switching.

[0066] The ground controller communicates with the tubing surface pressure gauge 11, the casing surface pressure gauge 12, and the water injection control valve 13 through the RS485 communication module 5 to collect surface pressure parameters (such as wellhead tubing pressure, wellhead casing pressure, etc.), control the opening of the water injection valve, and adjust parameters.

[0067] It is understandable that the ground controller can integrate all data and send it to the designated client through an external network or other communication modules, and the client can perform action control, parameter setting, etc.

[0068] The automatic injection-production switching system based on wellhead pressure provided in this embodiment utilizes conventional tubing technology in conventional oil production and water injection processes, replacing conventional instruments with an injection-production switch. A cable 4 is used to communicate data between the injection-production switch and the surface controller. The surface controller is also connected to surface pressure equipment to obtain real-time wellhead tubing and casing pressures. The surface controller monitors this data, including downhole data collected by the injection-production switch, and automatically prompts the well to switch between water injection and oil production based on well conditions.

[0069] After the well is installed, the surface controller of this automatic injection-production switching system based on wellhead pressure stores, analyzes, and integrates the collected data to control the switching between oil production and water injection. In water injection mode, the injection pressure and flow rate are adjusted based on the current downhole data and the string pressure limit. Specifically, before oil production, there is a pre-production data integration phase. This phase examines formation pressure and other data under a closed environment and, based on the collected data, creates a pre-production well model (also known as a pre-production formation energy model, which is used throughout the well production process). After the pre-production data integration phase is completed, the system enters the normal production phase, automatically collecting and summarizing formation pressure data at different production stages. Three phases are particularly important. The first is the reservoir opening phase, when the reservoir transitions from a closed phase to production. The second is the steady production phase, or production phase. During this phase, with a constant production rate, formation pressure does not fluctuate significantly, allowing for normal and stable production. The third stage is the stage where the reservoir formation energy is waiting to be replenished. This stage indicates that the formation pressure begins to drop significantly and the difficulty of reservoir recovery begins to increase significantly. At this time, continued oil production will require increased input but lower output. This indicates that the system needs to enter the stage of replenishing the reservoir formation energy.

[0070] The reservoir formation energy replenishment phase is divided into two steps. The first step is continuous water injection. When the system detects that the formation pressure is close to the initial formation pressure, the water injection will be suspended. Then the second step: formation pressure monitoring. This monitoring time is generally maintained for 24 hours. This stage is the formation pressure monitoring stage. This stage is to monitor whether the formation pressure can be maintained. If it is still in the water absorption stage, the formation pressure will drop rapidly and significantly. At this time, it can be judged that the formation pressure has not recovered. The above steps will be repeated until the formation pressure is significantly replenished and the formation pressure can be stabilized in the formation pressure range of the steady oil production stage for a longer period of time. Among them, the formation pressure close to the initial formation pressure means that the difference between the formation pressure and the initial formation pressure is within the preset range.

[0071] The present application also provides a control method for a system for automatic injection-production switching based on wellhead pressure, the control method comprising:

[0072] Obtain downhole data sent by the injection-production switch; downhole data includes formation pressure;

[0073] If the current formation pressure does not meet the production conditions, a channel switching instruction is sent to the injection-production switch to switch the injection-production switch to the water injection mode;

[0074] During water injection, if the difference between the current formation pressure and the initial formation pressure is detected to be within a preset range, water injection will be suspended; the initial formation pressure is the formation pressure before oil production;

[0075] During the first preset time period, the formation pressure is continuously obtained. If the rate of decrease of the formation pressure does not meet the preset condition, it is determined that the formation pressure has not recovered, and water is injected again until the formation pressure meets the preset condition.

[0076] If the formation pressure meets the preset conditions, a channel switching instruction is sent to the injection-production switching switch to switch the injection-production switching switch to the oil production mode.

[0077] Specifically, during the normal phase, the system will record and track the formation produced fluid flow rate, crude oil water content, formation pressure, current recovery rate, and target recovery rate. The following situations may occur: the produced fluid flow rate decreases significantly over time, and the rate of decrease is extremely rapid. This indicates that the original fluid supply capacity of the formation cannot meet the current recovery rate. At this time, if the target recovery rate is to be met, it is necessary to increase the formation pressure during the reservoir formation energy replenishment phase, or reduce the current recovery rate to match the formation produced fluid flow rate. If the produced fluid flow rate does not change drastically during the second preset time period, and the range of change in crude oil water content is within the preset range, then the formation fluid supply capacity is significantly higher than the current oil production rate. The recovery rate is adjusted to increase daily production; or, if the target recovery rate is met, the current recovery rate is maintained to extend the single continuous production time. The second preset time period, preset range, and preset range value can be set according to actual needs.

[0078] At the same time, the system will continue to monitor the formation pressure, produced fluid flow rate and crude oil water content. The system will judge the formation pressure based on this data. When the formation pressure no longer meets the production demand or the input-output ratio has dropped significantly, the system will automatically prompt and recommend entering the third stage, namely the reservoir formation energy replenishment stage.

[0079] Generally speaking, formation fluid production primarily involves two aspects: the flow rate of produced fluids and the proportion of crude oil in the produced fluids. During reservoir development, the oil content gradually decreases, and so does the flow rate of produced fluids. Therefore, it's necessary to inject gas or liquid into the formation to achieve oil recovery. Especially after formation pressure drops below a certain level, any recovery method will lead to a significant drop in the input-output ratio. Artificial lift recovery methods also increase costs. Therefore, the system needs to find a critical point, which is the equilibrium point for the input-output ratio. Below this critical point, excessive resource consumption occurs. Therefore, this system primarily relies on logical judgment based on formation pressure. When formation pressure is low, water injection is initiated to increase formation pressure, and then oil recovery can resume, repeating the process. Furthermore, when formation pressure is sufficient but the water content of the produced fluid is too high, this indicates poor oil recovery. At this point, it may be necessary to halt production and wait for the crude oil to be naturally released into the production fluid, or to employ other recovery methods.

[0080] As you can understand, during the second phase, the production phase, the system will monitor all production data over a long period of time, including wellhead tubing pressure, wellhead casing pressure, downhole produced fluid flow rate, crude oil water content, and other relevant parameters. The system will automatically integrate data based on the production phase, mapping downhole reservoir conditions at different production stages based on production time. This is to monitor whether the formation pressure can support the recovery rate after different periods of recovery. If the formation pressure drops rapidly during the initial recovery phase, it indicates that the recovery rate is significantly higher than the formation's fluid supply capacity, and the recovery rate should be minimized to extend the duration of continuous recovery. The system will record the formation's fluid supply capacity at each recovery stage, provide recovery rate recommendations based on the current stage, and promptly indicate when the recovery phase transitions to the waterflooding phase.

[0081] When formation pressure drops significantly and no longer meets production requirements, the system enters the third phase, the reservoir energy replenishment phase. This phase aims to replenish formation pressure, restore formation fluid production capacity, and maintain the input-output ratio for the production phase. This phase indicates that the input-output ratio for reservoir recovery has fallen below expectations, significantly reducing the economic benefits of continued production. To ensure sustained reservoir production, the system switches to the reservoir energy replenishment phase. During this phase, the downhole injection-production switch is controlled, switching from the recovery channel to the water injection channel. The injection flow and pressure are controlled based on formation pressure, pipeline pressure limits, and the target injection volume. Formation pressure recovery is monitored in real time. When pipeline pressure rises to the initial formation pressure, indicating that formation pressure has recovered to a certain extent, injection may need to be stopped due to formation water absorption or other structural issues. At this point, the system closes the injection valve and monitors the drop in formation pressure to determine the replenishment status. As can be understood, after closing the water injection valve, the formation pressure is monitored for a first preset period, which can be set based on actual conditions, typically 24 hours. The primary purpose is to monitor whether the formation pressure can be maintained. If the formation pressure is still in the water absorption phase, the formation pressure will drop rapidly and significantly (i.e., the rate of decrease meets the preset conditions), at which point it can be determined that the formation pressure has not recovered. It is also understood that during the initial few cycles of oil production and water injection, the oil water content is generally not the primary criterion for judgment. Starting in the middle and later stages, the oil water content will begin to decline, at which point a comprehensive assessment will be made. Initially, the primary factor affecting recovery is formation pressure. After water injection is completed, water injection is suspended, and oil production is not resumed. At this point, it is necessary to wait, for example, 24 hours to check whether the formation pressure has stabilized within a certain range. If the formation pressure drops significantly, for example, by more than 10% of the 24-hour pressure recovery value, it indicates that the formation pressure has not recovered effectively. The preset conditions can be empirical data provided by the system or user-defined, with the system prioritizing user-defined data. If the formation pressure has not recovered, water will be injected again until the formation pressure meets the preset conditions, that is, the formation pressure is greatly supplemented and the formation pressure can be stabilized in the formation pressure range of the stable production stage for a longer period of time.

[0082] During the reservoir energy replenishment phase, the system automatically plots a time-dependent pressure curve to indicate the formation pressure deficit at that time. The system then automatically generates the next water injection plan and adjusts the injection pressure and volume accordingly. The above test is repeated. After repeatedly entering the reservoir energy replenishment phase, the number of injection pauses is gradually reduced. The system gradually calculates the formation pressure replenishment time and plans the injection volume and time to ensure that formation pressure replenishment is completed within the shortest possible continuous time. Simultaneously, based on the data from the first and second phases, the target formation pressure is appropriately adjusted to minimize the duration of the reservoir energy replenishment phase without affecting the production plan. In other words, based on the formation pressure decline trend and the decrease in formation pressure per unit time, water injection parameters are adjusted again to ensure sufficient formation pressure replenishment. Once the system detects that the downhole formation pressure is sufficient for production again, it prompts a switch to the production phase and sends a channel switch command to the surface controller's injection-production switch, switching the downhole injection-production switch to the recovery channel, i.e., oil production mode.

[0083] After the system completes the formation pressure replenishment, it will prompt that the formation pressure replenishment is completed, and based on the most recent first and second stages before the cycle of the reservoir formation energy replenishment stage, it will infer the most ideal recovery situation that the formation pressure meets at this time. The user can redefine the recovery rate according to the system recommendation and production plan and enter a new round of system cycle.

[0084] In one embodiment, after the injection-production switch is switched to the oil production mode, the method further includes:

[0085] Determine the current reservoir's crude oil production capacity based on the current formation pressure and crude oil water content;

[0086] When the crude oil production capacity is less than the expected production value, the method of switching to thermal drive or well suspension and waiting is adopted.

[0087] Specifically, when repeatedly entering the production phase, the system will assess the formation pressure and the current water content of the produced oil to calculate the reservoir's current oil production capacity. Each well calculates this capacity differently, taking into account both the current formation pressure and the water content of the produced oil. Specifically, formation pressure affects the ease of recovering all the liquids, while the water content of the oil indicates the water content of these liquids. Therefore, both formation pressure and the water content of the produced oil are considered together to determine the reservoir's oil production capacity.

[0088] Production expectations can be configured individually for each well. Under normal circumstances, production expectations are based on initial production conditions. Normal oil wells initially produce high yields, but with continued production, both liquid and oil production decline. Oilfield departments will set production expectations for wells based on different regions and formation structures. When actual production significantly declines, the cost-effectiveness becomes very low, so monitoring this stage is essential. When this stage is detected, the system will automatically prompt a switch to other methods, including but not limited to thermal flooding or well shut-down, to ensure labor costs are met. For example, when formation pressure is sufficient but the crude oil water content is too high, continued production is no longer suitable. This means that formation pressure can be replenished, but the crude oil is locked in the geological structure and cannot be effectively produced. Therefore, it is necessary to shut down the well and wait for crude oil to precipitate, or to use thermal flooding to accelerate crude oil release.

[0089] In one embodiment, a pre-production formation energy model is determined in a pre-production data integration stage, where the pre-production data integration stage is the reservoir formation state before production, specifically:

[0090] Obtain the initial formation pressure, initial tubing pressure, initial wellbore temperature, and static water content before oil production;

[0091] The pre-mining formation energy model is drawn based on the initial formation pressure, initial tubing pressure, initial wellbore temperature, and static water content.

[0092] Specifically, before production begins, during the pre-production data integration phase, the surface controller collects downhole data for a long period of time to examine reservoir formation energy and pressure data in a closed environment. Based on this collected downhole data, a well model is constructed. This model integrates the current formation pressure, tubing pressure, crude oil water content, and wellbore temperature into a pre-production formation energy model.

[0093] Among them, the initial formation pressure is the formation pressure when the well is not in production, for example, the formation pressure when the well is just drilled or the formation pressure when no production is carried out after the tubing string is modified using the system of this application. The natural fluid production situation of the well can be analyzed based on the initial formation pressure.

[0094] The pre-production formation energy model serves as the target value for formation pressure recovery during water injection during the reservoir's energy replenishment phase. The fundamental reason for determining the pre-production formation energy model is that the state corresponding to this model most intuitively reflects the state of the reservoir. This state, combined with geological information, can be used to infer the actual conditions of the reservoir.

[0095] It should be noted that the terms "comprises," "includes," or any other variations thereof are intended to encompass non-exclusive inclusion, such that a process, method, commodity, or apparatus that includes a series of elements includes not only those elements but also other elements not explicitly listed, or includes elements inherent to such process, method, commodity, or apparatus. In the absence of further limitations, an element defined by the phrase "comprises a..." does not exclude the presence of other identical elements in the process, method, commodity, or apparatus that includes the element.

[0096] The various embodiments in this specification are described in a progressive manner. Similar parts between the various embodiments can be referred to in conjunction with each other. Each embodiment focuses on the differences between the other embodiments. In particular, the system embodiments are generally similar to the method embodiments, so the description is relatively simple. For relevant parts, refer to the description of the method embodiments.

Claims

1. A system for automatic injection-production switching based on wellhead pressure, characterized in that: The system includes: an injection-production switch and a ground controller; The injection-production switch is used to collect downhole data and send it to the surface controller, and is also used to realize the switching between water injection and oil production; the downhole data includes the water content of crude oil, the flow rate of produced fluid, and the formation pressure; The surface controller determines a channel switching instruction based on the received downhole data, and sends the channel switching instruction to the injection-production switch, so that the injection-production switch can switch between water injection and oil production according to the channel switching instruction; The system further comprises: a surface pressure device for collecting wellhead pressure data and sending the data to the surface controller, so that in the water injection mode, the surface controller controls the water injection pressure and flow rate according to the wellhead pressure data and the current pipeline pressure limit; Wherein, the wellhead pressure data includes wellhead tubing pressure and wellhead casing pressure; The surface pressure equipment includes an oil pipe surface pressure gauge and a casing surface pressure gauge; the oil pipe surface pressure gauge is used to collect the wellhead oil pipe pressure, and the casing surface pressure gauge is used to collect the wellhead casing pressure; The surface pressure equipment also includes a water injection control valve, which is used to control the well water injection pressure and flow when the injection-production switching switch is switched to the water injection mode.

2. The system for automatic injection-production switching based on wellhead pressure according to claim 1, characterized in that: The ground controller is connected to the injection-production switch via a cable; The injection-production switch includes a downhole acquisition device, and the downhole acquisition device is used to acquire the downhole data; The cable is used to power the downhole acquisition equipment and transmit the DC carrier signal between the surface controller and the injection-production switch; When the ground controller sends the channel switching instruction to the injection-production switch, the DC carrier signal is the channel switching instruction; When the injection-production switch sends the downhole data to the surface controller, the DC carrier signal is the downhole data.

3. The system for automatic injection-production switching based on wellhead pressure according to claim 1, characterized in that: The ground controller is connected to the ground pressure equipment via a communication module, and the communication module includes an RS485 communication module, a CAN bus, or an RS23 communication module.

4. A control method for a system for automatic injection-production switching based on wellhead pressure according to any one of claims 1 to 3, characterized in that: The control method includes: Acquiring downhole data sent by the injection-production switch; the downhole data includes formation pressure; If the current formation pressure does not meet the production conditions, a channel switching instruction is sent to the injection-production switching switch to switch the injection-production switching switch to the water injection mode; During water injection, if it is detected that the current formation pressure is close to the initial formation pressure, water injection is suspended; the initial formation pressure is the formation pressure before oil production; The formation pressure is continuously acquired within a first preset time period. If the formation pressure does not meet a preset condition, it is determined that the formation pressure has not recovered, and water is injected again until the formation pressure meets the preset condition.

5. The control method of the system for automatic injection-production switching based on wellhead pressure according to claim 4, characterized in that: If the formation pressure meets the preset condition, a channel switching instruction is sent to the injection-production switching switch to switch the injection-production switching switch to the oil production mode.

6. The control method of the system for automatic injection-production switching based on wellhead pressure according to claim 5, characterized in that: The downhole data also includes the water content of crude oil; After the injection-production switch is switched to the oil production mode, the method further includes: Determining the crude oil production capacity of the current oil reservoir by combining the current formation pressure and the water content of the crude oil; When the crude oil production capacity is less than the expected production value, the method of thermal drive or well suspension and waiting is adopted.

7. The control method of the system for automatic injection-production switching based on wellhead pressure according to claim 6, characterized in that: The downhole data also includes produced fluid flow rate; If the produced fluid flow rate does not change dramatically during the second preset time period and the change range of the crude oil water content is within the preset range, then the formation fluid supply capacity is significantly higher than the current oil production rate. The recovery rate is adjusted to increase the daily output; or, if the target recovery rate is met, the current recovery rate is maintained to extend the single continuous production time.

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