CN102865062B - Physical analog device for electrical logging detector entity built by ultrafiltration - Google Patents

Abstract

The invention discloses an ultrafiltration method to construct an electrical logging detector entity physical simulation device, which includes a lower surrounding rock formation simulation layer connected from bottom to top, a target formation original formation simulation layer and an upper surrounding rock formation simulation layer. The inner side of the undisturbed formation simulation layer of the target layer is provided with the formation simulation layer of the target formation invasion zone, the central axis of the simulation device is provided with a wellbore, the detector is placed in the wellbore, and the periphery of the simulation device is provided with a wellbore. There is an outer ring zone, and the remote loop electrode of the detector is placed in the outer ring zone; the simulation layer of the lower surrounding rock formation, the original formation simulation layer of the target layer, the simulation layer of the upper surrounding rock formation and the invasion zone formation simulation layer of the target layer The simulated layers include container walls made of flat ultrafiltration membranes by hot melting or bonding. Each container wall is filled with insulating microbeads, and each simulated layer is injected with a corresponding concentration of inorganic salt ion solution to form a Each simulation layer is provided with a plurality of conductivity probes.

Description

Constructing physical simulation device of electrical logging detector by ultrafiltration method

technical field

The invention belongs to the research and development field of petroleum electrical logging equipment, and relates to a physical simulation device capable of performing complex formation logging response tests on full-scale electrical logging detectors, which is used to verify the theoretical derivation and performance of electrical logging detectors. Numerical simulation calculation results, in particular, relate to an ultrafiltration method to construct an electrical logging detector entity physical simulation device.

Background technique

As a special equipment, the detector physical simulation device is used for the physical simulation of the logging response characteristics (longitudinal and radial detection characteristics, measurement accuracy, longitudinal resolution, etc.) of the 1:1 full-scale detector. The numerical simulation algorithm and the key verification link of the detector manufacturing method and process, and provide a reliable basis for the optimal design of the detector. The physical simulation process (also known as logging method experiment) is an indispensable and important link in the development of electrical logging detectors, especially high-end imaging electrical logging detectors.

At present, the main methods of physical simulation and experiments in the research and production of electrical logging detectors are as follows.

1. Conductive rubber method

It is a traditional method to use conductive rubber to build physical simulation devices for electrical logging detectors. The disadvantage of this method is that the conductive medium often uses metal or non-metallic particles due to the non-hydrophilicity of rubber, which leads to a different electrical conductivity mechanism. The ionic conductivity of petroleum reservoirs is different, the coupling between different electrical modules is difficult, the large-volume vulcanization molding is very difficult, the uniformity is poor, the cost is high, and it is easy to age; therefore, it has not been widely used, especially in recent years. It is applied in the physical simulation of imaging electrical logging tools (such as array induction, three-component induction and array lateral, etc.).

2. Large volume pool method

A pool with a certain volume (beyond the effective detection range of the logging instrument, generally with a radius greater than 5 meters) contains water with a certain degree of salinity. Due to the ion conduction effect, it can simulate a certain conductivity environment in an infinite medium, which can be used to verify the instrument K value (instrument coefficient, used to complete the conversion between resistance and resistivity or conductance and conductivity); but this simple volume model device determines that it is completely impossible to examine the longitudinal and radial detection characteristics of the instrument, so for today's mainstream Detector characteristic verification and optimization in R&D of imaging electrical logging tools are invalid.

3. Conductive ring method

Using a metal conductive ring with impedance elements in series is a conventional method for inspection and calibration of traditional induction logging tools, which does not belong to physical simulation. Since the contribution of the actual formation distribution parameters to the receiving coil is simulated by using concentrated parameters, this method cannot be used to examine the longitudinal and radial detection characteristics of the tool. Ineffective, and this method is not suitable for electrode type electrical logging tools.

4. Experimental well method

Experimental wells generally refer to non-production wells that have a certain depth, can provide a certain pressure and temperature environment, and have typical lithology in the well (even part of the casing has been run), and can perform experimental detection of the work of the instrument; experimental wells It is effective for the comparison between instruments of different and the same manufacturer, type, and model and the investigation of instrument stability, so it is an important technical link in the later stage of detector development; Geometric model and electrical parameters) are actually unknown, so it is impossible to verify the geometric detection characteristics of electrical logging, especially electrical imaging logging detectors; another limitation in the application of experimental well method is that the detectors tested are actually It must be a complete instrument, and its detector subsystem (electrode system, coil system) and electronic control, signal amplification, data acquisition and transmission systems must all be formed in accordance with certain temperature and pressure resistance standards, which is essential for original innovation. In the early stage of research, it is actually unrealistic to compare and verify many different schemes.

In short, there is currently no method that can construct an applicable physical simulation device for electrical logging detectors, especially no method that can dynamically change and monitor the electrical parameters of the model in complex formation modes. As a result, for a long time, the electrical logging detectors designed using numerical simulation methods (many complex factors have been simplified and idealized in the research) cannot be effectively verified and optimized, which limits the improvement of the design level in research and development. The purpose of the invention is to solve the important technical bottleneck in the research and development of high-end electrical logging detectors.

Contents of the invention

The purpose of the present invention is to provide an ultrafiltration method to construct an electrical logging detector entity physical simulation device to solve the physical simulation problem of the electrical logging detector in a complex formation environment.

Above-mentioned purpose of the present invention can adopt following technical scheme to realize:

An ultrafiltration method constructs an electrical logging detector entity physical simulation device, the simulation device includes a lower surrounding rock formation simulation layer connected from bottom to top, a target layer original formation simulation layer and an upper surrounding rock formation simulation layer, the The inner side of the undisturbed formation simulation layer of the target layer is provided with the formation simulation layer of the target formation invasion zone, the central axis of the simulation device is provided with a wellbore, the detector is placed in the wellbore, and the periphery of the simulation device is provided with The outer ring zone, where the remote return electrode of the detector is placed; the simulation layer of the lower surrounding rock formation, the original formation simulation layer of the target layer, the upper surrounding rock formation simulation layer and the target layer intrusion zone formation simulation layer The layers include container walls made of flat ultrafiltration membranes by hot melting or bonding. Each container wall is filled with insulating microbeads, and each simulated layer is injected with a corresponding concentration of inorganic salt ion solution to form a specific resistivity. Each simulation layer is provided with a plurality of conductivity probes.

The above-mentioned ultrafiltration method is used to construct an electrical logging detector physical simulation device, and the surface of the container wall is provided with a non-metallic zipper.

The above-mentioned ultrafiltration method constructs the physical simulation device of the electrical logging detector, and each of the simulated layer of the lower surrounding rock formation, the undisturbed formation simulated layer of the target layer, the simulated layer of the invaded zone of the target layer and the simulated layer of the upper surrounding rock formation A liquid inlet pipe and a liquid outlet pipe are installed on the outer edge of the simulation layer, and the liquid inlet pipe and the liquid outlet pipe are respectively made of non-metallic materials.

The above-mentioned ultrafiltration method constructs the physical simulation device of the electrical logging detector, and the simulation device also includes four ionic liquid concentration adjustment systems, and each ionic liquid concentration adjustment system is connected to the liquid inlet pipe of each of the simulated layers. It is connected with the liquid outlet pipe and is used for adjusting the concentration of the inorganic salt ion solution entering each liquid inlet pipe.

The ultrafiltration method described above constructs the physical simulation device of the electrical logging detector, and each of the regulating systems includes a brine tank, a pure water tank, a regulating assembly and a circulation assembly; the regulating assembly includes a brine valve, a pure water valve and conductivity meter; the outlet of the pure water tank is connected to the pure water valve and the conductivity meter in turn, and the other end of the conductivity meter is connected to the liquid inlet pipe; the outlet of the brine tank is connected to the brine valve, and the other end of the brine valve is connected to the pure water valve Outlet; the circulation assembly includes a circulation valve, a circulation pump and a discharge valve connected in sequence, the other end of the circulation valve is connected to the outlet end of the pure water valve, and the connection ends of the circulation pump and the discharge valve are connected to the liquid outlet pipe at the same time.

Features and advantages of the embodiments of the present invention are:

1. It can be used for physical simulation of full-scale electrical logging detectors, and can be used to verify the logging response characteristics of detectors including longitudinal and radial detection characteristics, measurement accuracy, and longitudinal resolution.

2. Several conductivity probes are implanted in each simulated formation module, and the measurement performance of the detector can be accurately verified by monitoring the electrical properties of the simulated formation module in real time.

3. After each simulated formation is filled with insulating microbeads, the conductivity of the liquid in the pipeline is different from the actual conductivity of the model. The conductivity of the liquid in the pipeline is only used for monitoring. When the detector is physically simulated, it is buried in each module. Multiple resistivity probes for real-time measurements.

Description of drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings that need to be used in the description of the embodiments will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present invention. For those skilled in the art, other drawings can also be obtained based on these drawings without creative effort.

Fig. 1 is the schematic diagram that the ultrafiltration method of the embodiment of the present invention constructs the physical simulation device of electrical logging detector entity;

Fig. 2 is a schematic diagram of a resistivity adjustment system constructed by the ultrafiltration method of an embodiment of the present invention for an electrical logging detector entity physical simulation device.

Detailed ways

The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only some, not all, embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without making creative efforts belong to the protection scope of the present invention.

Embodiment 1

As shown in Figure 1, the ultrafiltration method proposed by the embodiment of the present invention constructs an electrical logging detector entity physical simulation device, which includes a lower surrounding rock formation simulation layer 1 connected from bottom to top, a target formation original formation simulation layer 2 and Surrounding rock stratum simulation layer 3, the inner side of the original formation simulation layer 2 of the target layer is provided with a target layer invasion zone stratum simulation layer 4, the central axis of the simulation device is provided with a wellbore 5, and the detector 6 Placed in the well hole 5, the periphery of the simulation device is provided with an outer ring 7, and the outer ring 7 is placed on the remote return electrode of the detector. Described lower surrounding rock stratum simulated layer 1, target stratum undisturbed stratum simulated layer 2, each simulated layer of upper surrounding rock stratum simulated layer 3 and target stratum intrusion zone stratum simulated layer 4 respectively comprise hot-melt or viscose Each container wall is filled with insulating microbeads, and each simulated layer is injected with a corresponding concentration of inorganic salt ion solution to form a simulated layer with a set resistivity. Each simulated layer is equipped with multiple conductance rate probe.

The simulation device is cylindrical here, but of course it is not limited thereto, and the simulation device may also be in other suitable shapes. The outer ring belt 7 can be floor tiles.

In this embodiment, the four simulated strata of the lower surrounding rock stratum simulation layer 1, the original stratum simulation layer 2 of the target layer, the upper surrounding rock stratum simulation layer 3 and the target stratum intrusion zone stratum simulation layer 4 are respectively passed through the respective simulated strata The insulating microbeads inside and the injected inorganic salt ion solution of the corresponding concentration are used to obtain the simulated formation with the required resistivity. For example, here, the spaces of these four simulated formations are filled with insulating microbeads respectively, and three kinds of inorganic salt ion solutions with different concentrations are respectively injected to obtain corresponding simulated formations with different resistivities. The types of insulating microbeads in the simulated layers 3 and 1 of surrounding rock formations are the same as the concentration of the injected inorganic salt ion solution. Of course, in other embodiments, the spaces of the four simulated formations can be filled with four different insulating microbeads respectively, and four kinds of inorganic salt ion solutions with different concentrations can be injected respectively.

A plurality of conductivity probes (also known as resistivity measurement probes) are respectively buried in each simulated stratum. In addition, no less than three conductivity probes are preset in each simulated stratum. The conductivity probes can be Bipolar four-wire mode, a pair of current loops and a pair of voltage loops, respectively connected to the shielded twisted pair and then wound as a whole and then drawn out; the conductivity probes in each simulated formation are divided equally along the circumference, as sensors for real-time measurement of module resistivity , these probes have negligible influence on the electrical properties of the simulated formation due to their small size.

Among them, the insulating microbeads filled in the ultrafiltration membrane are non-conductive microbeads with a specific gravity slightly heavier than water, such as plastics, porcelain, glass, resin, ceramics, hard rubber or mixed substances, and the specific gravity of microbeads is slightly heavier than water. In order to avoid the floating of microbeads, this can provide a more reasonable conductive channel for the model, especially beneficial to the simulation of higher resistivity, and avoid too strict requirements on the trace ion pollution of the solution and the circulation system. The diameter of the microbeads can be between 0.5-5mm. If the diameter of the microbeads is too large, the filling rate will be low and the effect will not be obvious. If the diameter of the microbeads is too small, the fluidity will be poor and the system equilibrium time will be prolonged. The diameters are mixed according to a certain ratio. Microbeads are effective at simulating high resistivity.

After filling with microbeads, the conductivity of the liquid in the pipeline is different from the actual conductivity of the model. The conductivity of the liquid in the pipeline is only used for monitoring. When the detector is physically simulated, multiple resistivity probes buried in each module are used. needle for real-time measurement.

In this example, in the manufacturing process of the model, the ultrafiltration membrane, as a special porous plastic, can be spliced and formed by hot melting or bonding. The local ultrafiltration function loss caused by the seam has an overall impact on the model. Small enough to be ignored. In other words, the flat ultrafiltration membrane is formed of ultrafiltration materials with filtration performance close to nanofiltration. The thickness of the membrane is sub-millimeter, and it is characterized by allowing water molecules to pass freely and restricting the passage of ions to a certain extent. Build a simulated formation module with different resistivities. Furthermore, it is permissible and necessary for a small amount of ions to pass through the ultrafiltration membrane. The reason why it can be allowed is due to the seepage between different modules. There are two specific points. One is that the resistivity of the stratum model simulated in this device can be dynamically adjusted and controlled (see Figure 2). The other is that the modules themselves have relatively large Ionic buffer capacity. In this way, the electric double layer created by the interface of different ion concentration acts on the electrical logging response mechanism that is actually closer to the permeable reservoir.

In this embodiment, the core function of using ultrafiltration membranes to separate formations with different conductivity is to make this complex formation physical model constructed by liquid ion conduction not only suitable for coil-type electrical logging detectors (induction logging based on the principle of electromagnetic induction) instrument, the induced current flows along the circumferential direction centered on the well axis), and is also suitable for electrode-type electrical logging detectors (current-focused laterologging instruments based on direct conduction, the conduction current flows along the radial direction, and after divergence flow along the layers).

According to one embodiment of the present invention, the surface of the container wall is provided with a non-metallic zipper 8 . The opening length of the zipper 8 on the container wall can be no less than 0.5m, which can be used to fill or replace insulating beads. Since the area of the zipper 8 is much smaller than the intersecting area between the model layers, the influence on the interlayer conduction can be ignored.

The lower surrounding rock stratum simulation layer 1, the original formation simulation layer 2 of the target layer, the target layer intrusion zone stratum simulation layer 4 and the upper surrounding rock formation simulation layer 3 are equipped with a liquid inlet pipe 9 and a liquid outlet on the outer edge of each simulation layer. The pipe 10, the liquid inlet pipe 9 and the liquid outlet pipe 10 are respectively made of non-metallic materials. Further, the outside of the four simulation layers of the lower surrounding rock formation simulation layer 1, the original formation simulation layer 2 of the target layer, the target layer invasion zone formation simulation layer 4 and the upper surrounding rock formation simulation layer 3 are respectively equipped with respective Inlet and outlet pipes 9, 10, that is, the whole device has four inlet pipes 9 and four outlet pipes 10. One of the more special structures is that the liquid inlet and outlet pipes of the formation simulation layer 4 in the invasion zone of the target layer must pass through the original formation simulation layer 2 of the target layer. In this embodiment, the liquid inlet pipe and the liquid outlet pipe of each simulated formation can be set at 180 degrees respectively, so that the inorganic salt ion solution with a corresponding concentration enters the corresponding simulated formation from the liquid inlet pipe, passes through the insulating microbeads, and flows from the The liquid outlet pipe at the other end flows out. Wherein, the pipe diameter of liquid inlet pipe 9 and liquid outlet pipe 10 can be no more than 2.5cm, and the end point of pipe is equipped with nonmetal filter screen, and the aperture of pipe is less than insulating microbead diameter, to prevent microbead from overflowing.

In order to prevent the inner and outer walls of each simulation layer in the device from deforming due to gravity, hard plastic clamp rings can be respectively placed on the inside of the simulation layer (i.e. the inner wall of the well hole 5) and the outside of the simulation layer (i.e. the inner side of the outer ring belt) . Among them, the height of the inner hoop ring should be less than 1cm, the thickness should be less than 0.5cm, and the distance between each hoop ring should not be less than 20cm, and the influence on the simulation results can be ignored; the placement of the outer hoop ring is much more free. Because the position of the outer clamp ring has exceeded the geometric detection range of the detector, it can be placed at a height of 5cm, placed continuously at a distance of 20cm, and pay attention to keep out of the liquid inlet and outlet pipes of the module.

The center of the device has a well hole 5, if the device is erected, the detector is conveniently arranged in the well hole 5; if the device is directly placed on the foundation (such as the ground), then the well hole needs to be set on the foundation The extension part 11, the wellbore extension part 11 extends downward from the wellbore 5, and the wellbore extension part is for the convenience of placing the detector.

A specific example of this device is given below, which simulates a typical high-resistivity surrounding rock, (drilling fluid) low immersion, and oil-water mixed sand-shale reservoir.

The diameter of the well hole 5 of the device may be 0.2m, and the typical resistivity of the well fluid is 2Ω·m. The thickness of the simulated layer 3 of the surrounding rock stratum may be greater than 1/2 the length of the detector, and the typical resistivity is 50Ω·m. The stratum simulation layer 4 in the invasion zone of the target layer can be 1m thick, and the typical resistivity of the invasion zone is 5Ω·m. The thickness of the undisturbed formation simulation layer 2 of the target layer can be 1m, and the typical resistivity is 10Ω·m. The thickness of the simulated layer 1 of the lower surrounding rock formation can be greater than 1/2 the length of the detector, and the typical resistivity is 50Ω·m. The depth of the extended part of the wellbore can be greater than 1/2 the length of the detector, the thickness of the outer ring 7 can be 0.5m, and the resistivity is less than 1Ω·m, and the remote return electrode of the detector is placed.

This embodiment can be used for physical simulation of a full-scale electrical logging detector, and can be used to verify the logging response characteristics of the detector including longitudinal and radial detection characteristics, measurement accuracy, and longitudinal resolution.

This embodiment is a solid physical simulation device that can perform complex formation logging response tests, and can be used to verify the theoretical and numerical simulation results of electrical logging detectors (including electrode type and coil type), and improve and optimize detector design parameters. The device has important practical value for the research and development of petroleum electrical logging equipment, especially high-end equipment. In addition, this embodiment uses ultrafiltration membranes to make the simulated formation framework (including upper and lower surrounding rocks, intrusion zones, undisturbed formations, wellbores, etc.), and each formation module is filled with a certain concentration of inorganic salt solution to simulate different resistivities. The electrical parameters in each module can be dynamically controlled and monitored by adjusting the system, so as to realize the solid physical model of the complex formation.

Embodiment 2

As shown in FIG. 2 , the physical simulation device A of the electrical logging detector constructed by the ultrafiltration method in this embodiment also includes an ionic liquid concentration adjustment system. The regulation system includes a brine tank 12, a pure water tank 13, a regulation component and a circulation component. The regulating assembly includes a brine valve 16 , a pure water valve 14 and a conductivity meter 15 . The outlet of the pure water tank 13 is sequentially connected to a pure water valve 14 and a conductivity meter 15 , and the other end of the conductivity meter 15 is connected to the liquid inlet pipe 9 . The outlet of the brine tank 13 is connected to a brine valve 16 , and the other end of the brine valve 16 is connected to the outlet of the pure water valve 14 . The circulation assembly includes a circulation valve 17 , a circulation pump 18 and a discharge valve 19 connected in sequence. The other end of the circulation valve 17 is connected to the outlet of the pure water valve 14 , and the other end of the discharge valve 19 is connected to the liquid outlet pipe 10 .

In this embodiment, by controlling the pure water valve 14 and the brine valve 16 , the concentration of the ionic liquid delivered to the liquid inlet pipe 9 can be adjusted. Furthermore, each simulated formation in the device is filled with conductive liquid, its pure water and saturated brine (an inorganic salt solution prepared according to needs, which can simulate different ion types, the most common ones in logging are sodium, calcium, magnesium, potassium The ratio of chloride) is mixed according to the designed resistivity simulation value, and can be dynamically adjusted at any time as needed. The self-circulation process achieved by the circulation component ensures the uniformity of resistivity within the module.

For the convenience of description, the description of the above-mentioned embodiment and shown in Figure 2 only show one of the set of liquid inlet pipe 9 and liquid outlet pipe 10, and an ionic liquid concentration is connected in this set of liquid inlet pipe 9 and liquid outlet pipe 10. Regulate the system. In this embodiment, there are four sets of liquid inlet pipes 9 and liquid outlet pipes 10, and each set of liquid inlet pipes 9 and liquid outlet pipes 10 is connected with an ionic liquid concentration adjustment system. Of course, during implementation, the pure water tank 12 and the brine tank 13 of each set of ionic liquid concentration adjustment systems can be shared, that is, four sets of ionic liquid concentration adjustment systems use one pure water tank 12 and brine tank 13 . According to the principles shown in the present invention, the valve group is replaced by electromagnetic valves, and data collection is performed on resistivity signals to form a modular electrical automatic control system.

If the model has a certain error in the manufacturing size and the unevenness after filling the microbeads is not greater than ± 3cm, the influence (on the radial and longitudinal response characteristics) caused by it can be ignored, because any electrical logging detector is affected by physical methods. The measurement accuracy and spatial resolution are not high due to the limitations of the response mechanism and the relative error is usually ±2% to ±10% (the error is even much larger at both ends of the measurement dynamic range).

Other structures, working principles, and beneficial effects of this embodiment are the same as those of Embodiment 1, and will not be repeated here.

The above descriptions are only a few embodiments of the present invention, and those skilled in the art can make various changes or modifications to the embodiments of the present invention according to the disclosed application documents without departing from the spirit and scope of the present invention.

Claims (5)

1. An ultrafiltration method builds an electric logging detector entity physical simulation device, it is characterized in that, the simulation device comprises a lower surrounding rock stratum simulation layer connected from bottom to top, an undisturbed formation simulation layer and an upper surrounding rock formation of the target layer Stratum simulation layer, the inner side of the original formation simulation layer of the target layer is provided with the target layer invasion zone formation simulation layer, the central axis of the simulation device is provided with a wellbore, the detector is placed in the wellbore, the The periphery of the simulation device is provided with an outer ring, and the outer ring is placed with the return electrode at the far end of the detector; Described lower surrounding rock stratum simulated layer, target stratum undisturbed stratum simulated layer, each simulated layer of upper surrounding rock stratum simulated layer and target stratum intrusion zone stratum simulated layer comprise respectively made by flat ultrafiltration membrane with hot-melt or bonding method Container walls, each container wall is filled with insulating microbeads, each simulation layer is injected with a corresponding concentration of inorganic salt ion solution to form a simulation layer with a set resistivity, and each simulation layer is equipped with multiple conductivity probes. 2. The ultrafiltration method according to claim 1 constructs an electrical logging detector physical simulation device, wherein the surface of the container wall is provided with a zipper made of non-metal. 3. the ultrafiltration method according to claim 1 builds the electrical logging detector entity physical simulation device, it is characterized in that, the surrounding rock stratum simulation layer, the original formation simulation layer of the target layer, and the target layer invasion zone formation simulation layer A liquid inlet pipe and a liquid outlet pipe are installed on the outer edge of each simulation layer of the upper surrounding rock formation simulation layer, and the liquid inlet pipe and the liquid outlet pipe are respectively made of non-metallic materials. 4. the ultrafiltration method according to claim 3 builds the electrical logging detector physical simulation device, it is characterized in that, the simulation device also includes four ionic liquid concentration adjustment systems, and each ionic liquid concentration adjustment system is respectively connected with The liquid inlet pipe and the liquid outlet pipe of each of the simulated layers are connected to adjust the concentration of the inorganic salt ion solution entering each liquid inlet pipe. 5. the ultrafiltration method according to claim 4 builds the electrical logging detector entity physical simulation device, is characterized in that, each described adjustment system comprises brine tank, pure water tank, adjustment assembly and circulation assembly; The assembly includes a brine valve, a pure water valve and a conductivity meter; the outlet of the pure water tank is connected to the pure water valve and the conductivity meter in turn, and the other end of the conductivity meter is connected to the liquid inlet pipe; the outlet of the brine tank is connected to the brine valve, the brine valve The other end of the circulation valve is connected to the outlet of the pure water valve; the circulation assembly includes a circulation valve, a circulation pump and a discharge valve connected in sequence, and the other end of the circulation valve is connected to the outlet of the pure water valve, the connection between the circulation pump and the discharge valve The end is connected with the outlet pipe at the same time.