Automatic injection-production switching system based on wellhead pressure and control method

Abstract

The invention provides an automatic injection and production switching system based on wellhead pressure and a control method. The system comprises an injection and production switching switch and a ground controller. The injection-production change-over switch is used for collecting underground data, sending the underground data to the ground controller and switching water injection and oil production; the underground data comprises crude oil water content, output liquid flow and formation pressure; and the ground controller determines a channel switching instruction according to the received underground data and sends the channel switching instruction to the injection-production switching switch, so that the injection-production switching switch realizes switching between water injection and oil production according to the channel switching instruction. According to the scheme, the ground controller automatically prompts a well to switch water injection or oil extraction according to well conditions by monitoring underground data collected by the injection-production change-over switch, and the oil extraction and water injection functions of a single well are achieved.

Description

Technical Field

[0001] The 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 ground. From the perspective of objective underground energy, it can be divided into two types: self-flowing production and artificial lifting. The oil production method to be adopted is determined by the energy size of the oil layer and the reasonable economic effect. Since self-flowing production has high requirements for oil layer energy, artificial lifting is currently widely used. Among them, artificial lifting can be divided into gas lift production and deep well pump production according to the lifting method. Deep well pump production is mainly divided into rod pump production and rodless pump production. At present, rod pumping units are the main oil production equipment in oil fields, and different oil production methods will be used for different formation conditions and oil layer conditions, such as viscosity, water content, oil layer replenishment capacity, etc.

[0003] In conventional oil production processes, stratified oil production instruments are generally lowered into the well, and independently equipped with ground or underground 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 are stopped, which greatly reduces the oil production efficiency and increases labor costs.

[0004] In order to maintain the formation energy of different layers of the oil well, after the oil field is put into development, as the mining time increases, the energy of the oil layer itself will be continuously consumed, causing the oil layer pressure to continue to drop, underground crude oil to degas in large quantities, viscosity to increase, 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 the extraction of crude oil, maintain or increase the oil layer pressure, achieve high and stable production of the oil field, and obtain a higher recovery rate, the oil field must be water injected.

[0005] At present, in the process of oilfield production, the separation of oil production wells and water injection wells is generally adopted, that is, a single well is only responsible for oil production or water injection. This method is very suitable when the oil reservoir reserves are large and the distribution is regular. However, in the process of oilfield production, some oil reservoirs have small reserves and scattered wells, and it is not cost-effective to build an injection and production well network. Due to insufficient formation energy and low pressure level, it is not economical to build a water injection station. At the same time, some individual strata have development potential, which makes oilfield production more difficult. 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: 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; The injection-production switch is used to collect downhole data and send it to the ground controller. It is also used to switch between water injection and oil production. Downhole data includes water content of crude oil, output fluid flow rate, and formation pressure. The ground controller determines the channel switching instruction according to the received downhole data, and sends the channel switching instruction to the injection-production switching switch, so that the injection-production switching switch can realize the switching between water injection and oil production according to the channel switching instruction.

[0008] 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 rate according to the wellhead pressure data and the current pipeline pressure limit.

[0009] In one embodiment, the wellhead pressure data includes the wellhead tubing pressure and the wellhead casing pressure; The surface pressure equipment includes the tubing surface pressure gauge and the casing surface pressure gauge; the tubing surface pressure gauge is used to collect the wellhead tubing 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.

[0010] In one of the embodiments, the surface controller is connected to the injection-production switch via a cable; The injection-production switching switch includes a downhole acquisition device, and the downhole acquisition device is used to collect downhole data; The cable is used to power downhole acquisition equipment and transmit DC carrier signals between the surface controller and the injection-production switch; When the ground controller sends a channel switching command to the injection-production switch, the DC carrier signal is the channel switching command; When the injection-production switch sends downhole data to the ground controller, the DC carrier signal is the downhole data.

[0011] In one embodiment, the ground controller is connected to the ground pressure device via a communication module, and the communication module includes an RS485 communication module or a CAN bus or an RS23 communication module.

[0012] In a second aspect, the present application provides a control method for a system for automatic injection-production switching based on wellhead pressure as in the first aspect, the control method comprising: Obtain downhole data sent by the injection-production switch; 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 the difference between the current formation pressure and the initial formation pressure is detected to be within a preset range, water injection is suspended; the initial formation pressure is the formation pressure before oil production; 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 been restored, and water is injected again until the formation pressure meets the preset condition.

[0013] In one of the embodiments, 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.

[0014] In one embodiment, the downhole data further includes water content of crude oil; After the injection-production switch is switched to the oil production mode, the method further includes: Determine the crude oil production capacity of the current 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.

[0015] In one embodiment, the downhole data also includes produced fluid flow rate; If the output 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 at this time, and 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.

[0016] It can be seen from the technical solution provided in the above embodiments of this specification that: 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 exploitation and providing large-scale recovery efficiency for small-scale oil reservoirs. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the embodiments of this specification or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. 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 creative labor.

[0018] Figure 1A schematic diagram of the structure of the system for automatic injection-production switching based on wellhead pressure provided in this application.

[0019] Reference numerals: 1. Ground pressure equipment; 11. Oil pipe ground pressure gauge; 12. Casing ground pressure gauge; 13. Water injection control valve; 2. Injection-production switching switch; 3. Ground controller; 4. Cable; 5. Communication module; 6. Oil pipe; 7. Wire plug screen. DETAILED DESCRIPTION

[0020] In order to enable those skilled in the art to better understand the technical solutions in this specification, the technical solutions in the embodiments of this specification will be clearly and completely described below in conjunction with the drawings in the embodiments of this specification. Obviously, the described embodiments are only part of the embodiments of this specification, not all of the embodiments. Based on the embodiments in this specification, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of this specification.

[0021] In the following description, specific details such as specific system structures, technologies, etc. are provided for the purpose of illustration rather than limitation, so as to provide a thorough understanding of the embodiments of the present application. However, it should be clear to those skilled in the art that the present application may also 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 prevent unnecessary details from obstructing the description of the present application.

[0022] It will be apparent to those skilled in the art that various modifications and variations may be made to the specific embodiments of the present application description without departing from the scope or spirit of the present application. Other embodiments derived from the present application description will be apparent to those skilled in the art. The present application description and examples are exemplary only.

[0023] The words “include,” “including,” “have,” “contain,” etc. used in this document are open-ended terms, meaning including but not limited to.

[0024] The present invention is further described in detail below with reference to the accompanying drawings and embodiments.

[0025] 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.

[0026] like Figure 1 As shown, the system for automatic injection-production switching based on wellhead pressure includes: ground pressure equipment 1, injection-production switching switch 2, and ground controller 3.

[0027] The surface pressure device 1 is used to collect wellhead pressure data and send it to the surface controller 3, so that 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.

[0028] The injection-production switch 2 is used to collect downhole data and send it to the ground controller 3, 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 ground controller 3 determines a channel switching instruction according to the received downhole data, and sends the channel switching instruction to the injection-production switching switch 2, so that the injection-production switching switch can switch between water injection and oil production according to the channel switching instruction.

[0029] Among them, the wellhead pressure data includes the wellhead tubing pressure and the wellhead casing pressure; The surface pressure device 1 includes a tubing surface pressure gauge 11 and a casing surface pressure gauge 12; the tubing surface pressure gauge 11 is used to collect the wellhead tubing pressure, and the casing surface pressure gauge 12 is used to collect the wellhead casing pressure; The surface pressure equipment 1 further comprises a water injection control valve 13, which is used to control the water injection pressure and flow rate of the well when the injection-production switching switch 2 is switched to the water injection mode.

[0030] The ground controller 3 is connected to the injection-production switch 2 via a cable 4. The cable 4 may be a single-core cable.

[0031] 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 a surface pressure device 1. The tubing section includes a tubing 6 from the injection-production switching switch tool to the wellhead Christmas tree and a power supply cable 4 of the injection-production switching switch passing through the outside of the tubing 6. The tool section includes an injection-production switching switch 2. The surface pressure device 1 includes a tubing surface pressure gauge 11, a casing surface pressure gauge 12, and a water injection control valve 13.

[0032] The connection sequence of the system from top to bottom is ground controller 3, ground pressure equipment 1, cable 4 (single-core cable), and injection-production switching switch 2.

[0033] The ground controller 3 is mainly used to send downlink communication instructions to the injection-production switching switch 2, receive and process the uplink data signal returned by the downhole instrument (injection-production switching switch); and send ground pressure equipment control instructions to the ground pressure equipment 1, receive and process the data signal returned by the ground pressure equipment 1.

[0034] The surface pressure gauge 11 of the oil pipe and the surface pressure gauge 12 of the casing in the surface pressure equipment 1 respectively collect data of the wellhead oil pipe pressure and the wellhead casing pressure. The water injection control valve 13 in the surface pressure equipment 1 automatically controls the water injection amount according to the water injection plan and the water injection target calculated by the system when the injection-production switching switch 2 is switched to the water injection mode, and automatically controls the pressure according to the current pipeline pressure limit. Among them, the water injection plan is the water injection amount of each well calculated by the oilfield company according to the production plan and the water injection pipe column conditions in different regions, and the production plan may be adjusted in real time according to the production situation. This parameter needs to be input by the user. After obtaining the parameter, the system will use this parameter as the target of parameter adjustment, and then check whether the data model of the well can achieve this target. If it can be achieved, it will be adjusted. If it cannot be achieved, the user will be reminded whether to adjust. The initial water injection target is formulated according to the pre-exploitation formation energy model (how to determine this model will be described in the subsequent section), and the user can modify it at any time. Pipeline pressure limit refers to the pressure limit of the pipe string used in oil fields in different regions. This limit is limited by the mechanical structure of the pipeline. Some ground pipelines and downhole oil pipes have pressure limits. When the pressure exceeds a certain level, it will cause pipeline damage. In addition, when using special water injection structures, such as pressurized water injection methods, it is necessary to limit the water injection pressure. Sometimes, when the target water injection volume is met, the water injection pressure will be higher than this limit. Therefore, when adjusting the water injection volume, the water injection pressure needs to be monitored in real time to prevent excessive pressure.

[0035] The ground controller 3 and the ground pressure device 1 may be connected via a communication module 5 , and the communication module 5 includes an RS485 (Recommended Standard 485) communication module or a CAN (Controller Area Network) bus or an RS232 (Recommended Standard 232) communication module.

[0036] The injection-production switch 2 includes a downhole acquisition device, which is used to collect downhole data, including the water content of crude oil, the flow rate of produced fluid, and the formation pressure. The downhole acquisition device can also collect downhole data such as the pressure in the oil pipe and the wellbore temperature. Since the casing and the formation are connected, the formation pressure is the pressure in the casing.

[0037] According to general physical laws, the pressure difference corresponding to each 100m of the liquid surface in the tubing is about 1MPa, so the corresponding change in liquid level can be calculated based on the pressure change. Among them, the change in the liquid level in the casing can directly reflect the relationship between the oil production rate and the oil layer's liquid supply capacity at this time. When the liquid level in the casing drops significantly, it means that the oil production rate is significantly higher than the oil layer's liquid supply capacity. When the liquid level in the casing rises significantly, it means that the oil production rate is lower than the oil layer's liquid supply capacity. This parameter can clearly reflect the oil production stage and provide an important basis for the system to judge whether to switch modes. In the water injection mode, the formation pressure can clearly reflect the water absorption of the formation. When the formation is in a state of energy deficiency, when the water injection pressure changes from small to large, the formation pressure changes significantly slowly, indicating that the formation pressure energy is seriously lacking, and after the water injection is stopped, the change in formation pressure is an important parameter for judging whether the reservoir formation capacity has been effectively restored.

[0038] The water content of crude oil can be used to infer the state of the oil layer. Since the oil reservoir itself is small in scale, 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 drive treatment. In this case, water injection can no longer meet the production conditions of the remaining oil reservoir. 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.

[0039] The cable 4 is used to power the downhole acquisition equipment and transmit the DC carrier signal between the surface controller 3 and the injection-production switching switch 2. When the surface controller 3 sends a channel switching instruction to the injection-production switching switch 2, the DC carrier signal is the channel switching instruction; when the injection-production switching switch 2 sends downhole data to the surface controller 3, the DC carrier signal is the downhole data.

[0040] After the injection and production switch 2 is powered by the cable 4, it receives and executes the instructions sent by the ground controller 3, wherein the instructions may include channel switching instructions; and returns the collected downhole data, so that the system can summarize the control parameters under the recovery target according to the downhole data and the production plan. Specifically: after the switching cycle of the water injection and oil production channel, the system records how much water injection is needed to restore the formation pressure of the current well, how many times water injection is needed, and the highest formation pressure that can be restored, and can summarize the formation pressure drop corresponding to the oil production rate. At this time, you can refer to the production plan formulated by the user, and then get a recovery rate value. At this recovery rate, how long it takes to inject water, how much water injection pressure is set, and how many times to reach the target formation pressure. If the user feels that it takes too long to restore this formation pressure, the target formation pressure can be reduced. After the formation pressure is restored, the oil production work begins. By controlling the oil production rate, the target formation pressure, and the rate of water injection, the well stop time, continuous production time and other related production conditions can be controlled.

[0041] During construction, the tool section string is lowered from the upper end of the Christmas tree at the wellhead of the oil well according to the tool section string structure. The connection sequence is the cable 4, oil pipe, injection and production switching switch 2, wire plug screen 7 and other structures. It can be understood that whether to lower other instruments or structures can be decided according to the string design. After the string construction is completed, the wellhead construction and the ground controller 3 installation construction are carried out, and the ground oil production pipeline and the water injection pipeline are connected. The pipeline can be switched automatically or manually. When it is switched automatically, the switching operation can be completed by the ground controller 3. The ground controller 3 is connected to the oil pipe ground pressure gauge 11 and the casing ground pressure gauge 12, the water injection control valve 13, and the injection and production switching switch 2, and connected to the corresponding communication interface according to its communication method.

[0042] The data communication process and path of the automatic injection-production switching system based on wellhead pressure are as follows: The ground controller sends the command to the injection and production switch through the cable carrier through the internal coding circuit. The injection and production switch receives data through the decoding circuit and executes different commands. When executing the acquisition function, the injection and production switch will turn on the power supply of different acquisition devices, and then execute the acquisition action. After the acquisition is completed, the data will be integrated and sent to the ground controller through the coding circuit inside the injection and production switch, also through the carrier. The ground controller parses and stores the data through the decoding circuit. When the injection and production switch receives the channel switching command, it will automatically adjust the channel according to the command situation to realize the function of switching the downhole water injection and oil production channels.

[0043] 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 the surface pressure parameters (such as wellhead tubing pressure, wellhead casing pressure, etc.), control the opening of the water injection valve, and adjust the parameters.

[0044] It can be understood 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.

[0045] The automatic injection-production switching system based on wellhead pressure provided in this embodiment replaces conventional instruments with injection-production switching switches based on the pipe string technology in conventional oil production and water injection processes, and the injection-production switching switch and the ground controller can use a cable 4 for data communication. At the same time, the ground controller will be connected to the ground pressure equipment to obtain the wellhead tubing pressure and the wellhead casing pressure in real time. The ground controller automatically prompts the well to switch between water injection or oil production according to the well conditions by monitoring data, including downhole data collected by the injection-production switching switch.

[0046] After the oil well is installed, the ground controller of the automatic injection-production switching system based on wellhead pressure will store the collected data, analyze and integrate the data, realize the switching control of oil production and water injection, and adjust the water injection pressure and flow rate according to the current downhole data and the string pressure limit in the water injection mode. Specifically, there will be a pre-production data integration stage before oil production, which aims to check the formation pressure and other data in a closed environment, and draw the pre-production well condition model of the reservoir (or the pre-production formation energy model, which is used in the production of the entire well) according to the collected data. After the pre-production data integration stage is completed, the normal production stage is entered, and the system will automatically collect and summarize the formation pressure conditions under different oil production stages. Among them, three stages are the most important. The first stage is the reservoir opening stage, that is, when the reservoir enters the production stage from the closed stage. The second stage is the stable oil production stage, that is, the production stage. In this stage, when the oil production rate is constant, the formation pressure will not change significantly. In this stage, normal and stable production can be achieved. The third stage is the stage where 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. Continuing oil production at this time will require increased input but less output. This indicates that the system needs to enter the stage of replenishing reservoir formation energy.

[0047] The energy replenishment stage of the reservoir formation 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, and 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 aims 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 been restored. The above steps will be repeated until the formation pressure is greatly replenished and the formation pressure can be stabilized in the formation pressure range of the stable oil production stage for a long 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.

[0048] The present application also provides a control method for a system for automatic injection-production switching based on wellhead pressure, the control method comprising: Obtain downhole data sent by the injection-production switch; 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 the difference between the current formation pressure and the initial formation pressure is detected to be within a preset range, water injection is suspended; the initial formation pressure is the formation pressure before oil production; 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.

[0049] 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.

[0050] Specifically, in the normal stage, the system will record and track the formation output fluid flow rate, crude oil water content, formation pressure, current recovery rate and target recovery rate. The following situations may occur: the output fluid flow rate decreases significantly over time, and the rate of decrease is extremely fast. At this time, it means that the original fluid supply capacity of the formation cannot meet the current recovery rate. If the target recovery rate is to be met at this time, it is necessary to increase the formation pressure during the reservoir formation energy replenishment stage, or reduce the current recovery rate to match the formation output fluid flow rate. If the output fluid flow rate does not change dramatically during the second preset time, and the range of change 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 at this time, and the recovery rate is adjusted to increase the daily output; or when the target recovery rate is met, the current recovery rate is maintained to extend the single continuous production time. Among them, the second preset time, preset range, and preset range value can be set according to actual needs.

[0051] At the same time, the system will continue to monitor the formation pressure, output 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.

[0052] Generally speaking, the formation fluid production mainly includes two aspects, the output fluid flow rate and the proportion of crude oil in the output fluid. During the development of the reservoir, the oil content will slowly decrease, and the output fluid flow rate will also decrease. Therefore, it is necessary to inject gas or liquid into the formation to achieve the purpose of oil recovery. Especially when the formation pressure drops to a certain level, no matter what oil recovery method is used, the input-output ratio will be seriously reduced. The artificial lift oil recovery method will increase the cost. Therefore, the system needs to find the critical point, which is the equilibrium point of the input-output ratio. When it is lower than this critical point, it consumes too many resources. Therefore, this system mainly makes logical judgments on the formation pressure. When the formation pressure is low, the water injection mode is turned on to inject water to increase the formation pressure, and then continue to recover oil and repeat this process. Moreover, when the formation pressure is sufficient, but the water content in the produced liquid is too high, it means that the oil recovery effect is not good. At this time, it may be necessary to stop oil recovery and wait for the crude oil to be produced into the production liquid, or use other methods to recover oil.

[0053] It is understandable that in the second stage, the production stage, the system will monitor all data during the production period for a long time, including the pressure in the wellhead tubing, the casing pressure at the wellhead, the downhole production fluid flow rate, the water content of crude oil and other related parameters. The system will automatically integrate the data according to the situation of the production stage, and correspond the downhole reservoir conditions at different production stages according to the production time. The purpose is to monitor whether the formation pressure of the reservoir can support the recovery rate at this time after different recovery times. If the formation pressure drops rapidly at the beginning of recovery, it means that the recovery rate at this time is significantly higher than the formation fluid supply capacity, and the recovery rate should be reduced as much as possible to extend the continuous recovery time. The system will record the formation fluid supply capacity corresponding to different recovery stages, and provide recovery rate recommendations based on the current stage, and provide timely signs for the recovery to enter the water injection stage.

[0054] When the formation pressure drops significantly and does not meet the production conditions, the system enters the third stage, the reservoir formation energy replenishment stage, which is to replenish the formation pressure, restore the formation fluid production capacity, and ensure the input-output ratio of the production stage. This stage indicates that the input-output ratio of reservoir recovery has been lower than expected. At this time, the economic benefits of continued exploitation are greatly reduced. In order to ensure the continuous output of the reservoir, the system will switch to the reservoir formation energy replenishment stage. At this time, the downhole injection and production switch will be controlled, and the recovery channel will be switched to the water injection channel. The water injection flow and pressure will be controlled according to the formation pressure, pipeline pressure limit and target water injection volume, and the formation pressure recovery will be monitored in real time. When the pipeline pressure rises to the initial formation pressure, it means that the formation pressure has been restored to a certain extent. According to the water absorption of the formation or other structural problems, it is necessary to stop the injection first. At this time, the system will close the water injection valve and monitor the formation pressure drop to determine the formation pressure replenishment at this time. It is understandable that after closing the water injection valve, the formation pressure is monitored, and the monitoring time is the first preset time, which can be set according to the actual situation, generally maintained at 24 hours, mainly monitoring whether the formation pressure can be maintained. If it is still in the water absorption stage, the formation pressure will drop rapidly and significantly (that is, the reduction rate meets the preset conditions), and it can be judged that the formation pressure has not been restored. It is also understandable that in the first few cycles of oil production and water injection, the water content of crude oil is generally not used as the main basis for judgment. From the middle and late stages, the water content of crude oil will decrease. At this time, a comprehensive judgment will be made. The main factor affecting the recovery in the early stage is the formation pressure. When the water injection is completed, the water injection is suspended first, and oil production is not started at the same time. At this time, it is necessary to wait for 24 hours to check whether the formation pressure can be stabilized within a certain range. If the formation pressure drops significantly, for example, more than 10% of the 24-hour drop in pressure recovery value, it means that the formation pressure has not been effectively restored at this time. The preset conditions can be the empirical data given by the system, and the user can also define them by himself. The system will use the user-defined data as the priority parameter. If the formation pressure has not recovered, water is 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.

[0055] During the reservoir formation energy replenishment stage, the system automatically draws a curve of time and pressure changes to mark the lack of formation pressure at this time. After that, the system will automatically generate the next water injection plan and adjust the water injection pressure and volume according to this plan. Repeat the above test. After entering the reservoir formation energy replenishment stage for many times, the above test gradually reduces the number of stop injections. The system will gradually calculate the formation pressure replenishment time, plan the water injection volume and injection time, and ensure that the formation pressure is replenished in the shortest possible continuous time. At the same time, according to the data of the first and second stages, the target formation pressure will be appropriately adjusted to ensure that the reservoir formation energy replenishment stage time is the shortest and does not affect the production plan. That is, according to the formation pressure decline trend and the formation pressure decline value per unit time, the water injection parameters are adjusted again to ensure that the formation pressure is fully replenished. When the system detects that the downhole formation pressure has met the situation of production again, the system will prompt the production stage to switch, and the ground controller injection and production switch will send a channel switching instruction to switch the downhole injection and production switch to the recovery channel, that is, the oil production mode.

[0056] 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.

[0057] In one embodiment, after the injection-production switch is switched to the oil production mode, the method further includes: Determine the crude oil production capacity of the current 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.

[0058] Specifically, when repeatedly entering the production stage, the system will comprehensively judge the formation pressure and the current crude oil water content of the produced liquid to calculate the crude oil production capacity of the current reservoir. The way to calculate the crude oil production capacity of the current reservoir is different for each well, and it is necessary to comprehensively consider the current formation pressure and the crude oil water content of the produced liquid. Specifically: the formation pressure will affect the difficulty of recovering all the liquids, but the crude oil water content represents the water content in these liquids. Therefore, it is necessary to comprehensively consider the formation pressure and the current crude oil water content of the produced liquid to determine the crude oil production capacity of the current reservoir.

[0059] The expected production value can be configured separately for each well condition. Under normal circumstances, the expected production value is determined based on the initial production conditions. Normal oil wells have a high production rate in the initial state. With continued production, the liquid production and oil production will decrease. According to different regions and formation structures, the oil field department will make production expectations for the wells. When the actual situation drops significantly, the cost performance will become very low, so it is necessary to monitor the arrival of this stage. When this stage is detected, in order to ensure labor costs, the system will automatically remind you to switch to other methods, including but not limited to thermal drive or well stop waiting. For example, when the formation pressure is sufficient and the water content of crude oil is too high, it is no longer suitable to continue oil production. This means that the formation pressure can be well supplemented, but the crude oil is locked in the geological structure and cannot be effectively produced. Therefore, it is necessary to stop the well and wait for the crude oil to precipitate or use thermal drive to accelerate the precipitation of crude oil.

[0060] In one embodiment, the pre-production formation energy model is determined in the pre-production data integration stage, where the pre-production data integration stage is the reservoir formation state before oil production, specifically: Obtain the initial formation pressure, initial tubing pressure, initial wellbore temperature, and static water content before oil production; The pre-mining formation energy model is drawn based on the initial formation pressure, initial tubing pressure, initial wellbore temperature, and static water content.

[0061] Specifically, before oil production, i.e., during the pre-production data integration stage, the ground controller will collect downhole data for a long time in order to check the reservoir formation energy, formation pressure and other data in a closed environment. A well condition model is drawn based on the collected downhole data. The current formation pressure, pressure in the oil pipe, water content of crude oil and wellbore temperature are integrated into a pre-production formation energy model.

[0062] 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 performed after the tubing is transformed using the system of the present application. The natural fluid production of the well can be analyzed based on the initial formation pressure.

[0063] The pre-exploitation formation energy model can be used as the target value for the formation pressure to be restored during water injection in the reservoir formation energy replenishment stage. The fundamental reason for determining the pre-exploitation formation energy model is that the state corresponding to this model can most intuitively reflect the state of the oil layer, and this state combined with geological information can infer the actual situation of the oil layer.

[0064] It should be noted that the terms "include", "comprises" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, commodity or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, commodity or device. In the absence of further restrictions, the elements defined by the sentence "comprises a ..." do not exclude the existence of other identical elements in the process, method, commodity or device including the elements.

[0065] Each embodiment in this specification is described in a progressive manner, and the same or similar parts between the embodiments can be referred to each other, and each embodiment focuses on the differences from other embodiments. In particular, for the system embodiment, since it is basically similar to the method embodiment, the description is relatively simple, and the relevant parts can be referred to the partial description of the method embodiment.

Claims

1. A system for automatic injection-production switching based on wellhead pressure, characterized in that: The system comprises: an injection-production switching 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 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; The ground controller determines a channel switching instruction according to 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.

2. The system according to claim 1, characterized in that The system further comprises: a surface pressure device for collecting wellhead pressure data and sending the data to the surface controller, so that in 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.

3. The system according to claim 2, characterized in that The wellhead pressure data includes wellhead tubing pressure and wellhead casing pressure; The surface pressure equipment includes a tubing surface pressure gauge and a casing surface pressure gauge; the tubing surface pressure gauge is used to collect the wellhead tubing 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.

4. The system according to claim 1, characterized in that The ground controller is connected to the injection-production switch via a cable; The injection-production switching switch includes a downhole acquisition device, and the downhole acquisition device is used to collect the downhole data; The cable is used to supply power to the downhole acquisition equipment and transmit a DC carrier signal between the surface controller and the injection-production switching switch; When the ground controller sends the channel switching instruction to the injection-production switching switch, the DC carrier signal is the channel switching instruction; When the injection-production switching switch sends the downhole data to the ground controller, the DC carrier signal is the downhole data.

5. The system according to claim 2, 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.

6. A control method for a system for automatic injection-production switching based on wellhead pressure as claimed in any one of claims 1 to 5, characterized in that: The control method comprises: Acquire downhole data sent by the injection-production switching 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 difference between the current formation pressure and the initial formation pressure is within a preset range, water injection is suspended; the initial formation pressure is the formation pressure before oil production; The formation pressure is continuously obtained within a first preset time period. If the formation pressure does not meet the preset condition, it is determined that the formation pressure has not been restored, and water is injected again until the formation pressure meets the preset condition.

7. The control method according to claim 6, 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.

8. The control method according to claim 7, 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: Determine 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 stoppage and waiting is adopted.

9. The control method according to claim 8, 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 at this time, and 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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