Sand mixing and liquid supplying system, sand mixing and liquid supplying control method and sand mixing pry

Abstract

The invention relates to the technical field of fracturing construction, in particular to a sand mixing and liquid supplying system, a sand mixing and liquid supplying control method and a sand mixing pry. The sand mixing and liquid supplying system comprises a water tank, a suction pump, a suction valve, a sand mixing tank, a discharge pump and a discharge valve which are connected in sequence; the controller is electrically connected with the suction pump, the suction valve, the discharge pump, the discharge valve and the fracturing sand supply device. In the fracturing construction process, the controller adjusts the suction flow of the suction pump, the opening degree of the suction valve, the discharge flow of the discharge pump and the supply flow of the fracturing sand supply device according to the discharge flow of the discharge port of the discharge valve, and various water tanks and working conditions are automatically adapted through intelligent control of the controller; the opening degree of the suction valve is automatically adjusted according to different discharge flows of the discharge pump, the rotating speed of the suction pump is automatically adjusted through a control algorithm, the liquid level of the mixing tank is stably controlled, intelligent control over the liquid level and discharge pressure of the mixing tank is achieved, manual control is completely replaced, and equipment automation is achieved.

Description

Technical Field

[0001] The invention relates to the technical field of fracturing construction, and in particular to a sand mixing and liquid supply system, a sand mixing and liquid supply control method, and a sand mixing skid. Background Art

[0002] As the shale gas fracturing market continues to expand, the requirements for intelligent, digital, information-based equipment and less-manned well sites are constantly being put forward. The sand mixing skid (car) is the core equipment for fracturing construction. Its function is to suck the fracturing fluid provided by the outside into the mixing tank through the suction pump and suction valve, and mix it with fracturing sand and various types of additives in proportion according to the construction requirements, and then output it to the connected fracturing skid (car) at a certain pressure for fracturing construction.

[0003] The liquid level control and discharge pressure control of the mixing tank of the sand mixing skid (truck) are the most critical control steps in fracturing operation. The traditional liquid level and pressure control of the mixing tank is that the sand mixing operator observes the liquid level and discharge pressure of the mixing tank in real time through the host computer, and manually adjusts the potentiometer to control the opening of the suction valve and the speed of the discharge pump.

[0004] Since there are many types of water tanks supplying liquid to the sand mixing skids (trucks) on site, the liquid supply pressures of different water tanks vary greatly (0.01Mpa~0.07Mpa), and the liquid supply displacements of different construction stages and construction processes also vary greatly (0.3m³ / min-16m³ / min). These situations make the control operation of the mixing tanks of the sand mixing skids (trucks) complicated, increasing the difficulty of traditional manual control. It is difficult for novices to get started, and the control is unstable and the control accuracy is low, which cannot meet the requirements of intelligent and less-manned well sites. Summary of the invention

[0005] The present invention provides a sand mixing liquid supply system, a liquid supply control method and a sand mixing skid, which are used to solve the defects in the prior art that the control operation of a mixing tank of a sand mixing skid (car) is complicated and makes manual control difficult, and realize intelligent control of the liquid level and discharge pressure of the mixing tank of the sand mixing skid (car).

[0006] The present invention provides a sand mixing and liquid supply system, comprising a water tank, a suction pump, a suction valve, a sand mixing tank, a discharge pump and a discharge valve connected in sequence, and also comprising a controller. The sand mixing tank is connected to a fracturing sand supply device, and the controller is electrically connected to the suction pump, the suction valve, the discharge pump, the discharge valve and the fracturing sand supply device respectively.

[0007] According to a sand mixing and liquid supply system provided by the present invention, the controller is used to adjust the suction flow of the suction pump, the opening of the suction valve, the discharge flow of the discharge pump and the supply flow of the fracturing sand supply device according to the discharge flow of the discharge port of the discharge valve.

[0008] According to a sand mixing and liquid supply system provided by the present invention, the controller is respectively connected to the suction pump, the discharge pump, and the fracturing sand supply device through a frequency converter for frequency conversion control, and the sand mixing tank is provided with a liquid level meter, which is electrically connected to the controller.

[0009] According to a sand mixing and liquid supply system provided by the present invention, the suction valve is an electromagnetic regulating valve, which is suitable for adjusting the opening of the suction valve through the controller to match the discharge flow of the discharge port of the discharge valve; the discharge valve is an electromagnetic switch valve, which is suitable for controlling the opening and closing of the discharge valve through the controller.

[0010] The present invention further provides a sand mixing and liquid supply control method, which is applicable to any one of the sand mixing and liquid supply systems described above, and the sand mixing and liquid supply control method comprises: Based on the stage of the fracturing construction, the flow rate of the sand-mixing liquid required for the fracturing construction is obtained, and the actual discharge flow rate of the discharge pump is controlled by the controller to match the flow rate of the sand-mixing liquid required for the fracturing construction.

[0011] Based on the actual discharge flow rate of the discharge pump, the opening degree of the suction valve is determined, and the suction valve is controlled to be at the determined opening degree.

[0012] Based on the actual discharge flow rate of the discharge pump and the supply flow rate of the fracturing sand supply device, the suction flow rate of the suction pump is acquired, and the suction pump is controlled to perform the acquired suction flow rate.

[0013] Based on the comparison between the actual liquid level of the sand mixing tank and the set liquid level, the rotation speed of the suction pump is adjusted so that the actual liquid level of the sand mixing tank is equal to the set liquid level.

[0014] According to a sand mixing and liquid supply control method provided by the present invention, the determining the opening of the suction valve based on the actual discharge flow rate of the discharge pump comprises: testing the discharge pump at different calibrated discharge flow rates respectively, taking the unchanged liquid level in the sand mixing tank as a benchmark, testing the opening of the suction valve corresponding to the discharge pump at different calibrated discharge flow rates respectively, and statistically compiling a correspondence table between the calibrated discharge flow rate of the discharge pump and the opening of the suction valve; based on the correspondence table between the calibrated discharge flow rate of the discharge pump and the opening of the suction valve, obtaining the opening of the suction valve corresponding to the actual discharge flow rate of the discharge pump.

[0015] According to a sand mixing and liquid supply control method provided by the present invention, after the water tank is replaced during fracturing construction, the process of determining the opening of the suction valve includes: based on a correspondence table between the calibrated discharge flow of the discharge pump and the opening of the suction valve, obtaining the opening of the suction valve corresponding to the actual discharge flow of the discharge pump, and obtaining the actual required opening of the suction valve based on the product of the obtained opening of the suction valve and the valve coefficient.

[0016] The valve coefficient is determined by comparing the water level of the replaced water tank with the water level of the original water tank. When the water level of the replaced water tank is higher than that of the original water tank, the valve coefficient is in the range of 0.8~0.95. When the water level of the replaced water tank is lower than that of the original water tank, the valve coefficient is in the range of 1~1.1.

[0017] According to a sand mixing and liquid supply control method provided by the present invention, the sand mixing and liquid supply control method also includes sand mixing and liquid supply control of a small displacement sand mixing fluid fracturing operation condition, and the sand mixing and liquid supply control process of the small displacement sand mixing fluid fracturing operation condition includes: Based on the actual discharge flow of the discharge pump, when the actual discharge flow of the discharge pump is less than the minimum calibrated discharge flow of the discharge pump and fluctuates continuously, a small-displacement sand-mixing hydraulic fracturing operation condition is performed.

[0018] Under the fracturing operation condition of a small-displacement sand mixing fluid, the suction flow of the suction pump is obtained based on the actual discharge flow of the discharge pump and the supply flow of the fracturing sand supply device, and the suction pump is controlled to execute the obtained suction flow.

[0019] Based on the comparison between the actual liquid level of the sand mixing tank and the set liquid level, the opening of the suction valve is adjusted by the controller so that the actual liquid level of the sand mixing tank is equal to the set liquid level.

[0020] According to a sand mixing and liquid supply control method provided by the present invention, the sand mixing and liquid supply control method further includes sand mixing and liquid supply control in coordination with the oil mill bridge plug fracturing construction condition, and the sand mixing and liquid supply control process in coordination with the oil mill bridge plug fracturing construction condition includes: Based on the actual discharge flow of the discharge pump, when the actual discharge flow of the discharge pump is less than the minimum calibrated discharge flow of the discharge pump and the low flow operation is continuously maintained, the oil mill bridge plug fracturing construction condition is carried out.

[0021] In cooperation with the oil-mill bridge plug fracturing construction condition, the suction valve is controlled by the controller to open the minimum opening as the initial opening, the suction flow of the suction pump is obtained based on the actual discharge flow of the discharge pump and the supply flow of the fracturing sand supply device, and the suction pump is controlled to execute the obtained suction flow, which is recorded as the initial speed of the suction pump.

[0022] Based on the comparison between the actual liquid level and the set liquid level of the sand mixing tank, the rotation speed of the suction pump is adjusted: when the actual liquid level of the sand mixing tank is lower than the set liquid level, the rotation speed of the suction pump is increased until the rotation speed of the suction pump is greater than 30% of the initial rotation speed, and the controller is used to control the suction valve to increase the opening; when the actual liquid level of the sand mixing tank is higher than the set liquid level, the controller is used to control the suction valve to reduce the opening.

[0023] The comparison between the actual liquid level and the set liquid level of the sand mixing tank is repeated, and the rotation speed of the suction pump is adjusted until the opening of the suction valve satisfies that the actual liquid level of the sand mixing tank is equal to the set liquid level.

[0024] The present invention further provides a sand mixing skid, comprising any one of the sand mixing and liquid supply systems described above, or executing any one of the sand mixing and liquid supply control methods described above.

[0025] The sand mixing and liquid supply system, sand mixing and liquid supply control method, and sand mixing skid provided by the present invention can respectively control the suction pump, suction valve, discharge pump, discharge valve, and fracturing sand supply device through a controller during the fracturing construction process. The controller adjusts the suction flow of the suction pump, the opening of the suction valve, the discharge flow of the discharge pump, and the supply flow of the fracturing sand supply device according to the discharge flow of the discharge valve outlet. Through the intelligent control of the controller, it can automatically adapt to various water tanks and working conditions, automatically adjust the opening of the suction valve according to the different discharge flows of the discharge pump, automatically adjust the speed of the suction pump through the control algorithm, stably control the liquid level of the mixing tank, and realize intelligent control of the liquid level and discharge pressure of the mixing tank, completely replacing manual control and realizing equipment automation. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the technical solutions in the present invention or 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 some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0027] Figure 1 It is a structural schematic diagram of the sand mixing and liquid supply system provided by the present invention.

[0028] Figure 2 It is a schematic diagram of the working principle of the sand mixing and liquid supply system provided by the present invention.

[0029] Figure 3 It is a flow chart of the sand mixing and liquid supply control method provided by the present invention.

[0030] Figure 4 The present invention provides a flow chart of a sand mixing and fluid supply control process for a small displacement sand mixing fluid fracturing operation condition.

[0031] Figure 5 It is a schematic diagram of the flow of the sand mixing and fluid supply control process provided by the present invention in cooperation with the oil-connected mill bridge plug fracturing construction condition.

[0032] Figure numerals: 1. water tank; 2. suction pump; 3. suction valve; 4. sand mixing tank; 5. discharge pump; 6. discharge valve; 7. controller; 8. fracturing sand supply device; 9. frequency converter; 10. liquid level meter. DETAILED DESCRIPTION

[0033] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be clearly and completely described below in conjunction with the drawings of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0034] In the description of the embodiments of the present invention, it should be noted that the terms "center", "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the embodiments of the present invention and simplifying the description, and do not indicate or imply that the devices or elements referred to must have a specific orientation, be constructed and operate in a specific orientation, and therefore cannot be understood as limitations on the embodiments of the present invention. In addition, the terms "first", "second", and "third" are used for descriptive purposes only and cannot be understood as indicating or implying relative importance.

[0035] In the description of the embodiments of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "connected" and "connection" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium. For ordinary technicians in this field, the specific meanings of the above terms in the embodiments of the present invention can be understood according to specific circumstances.

[0036] In the embodiments of the present invention, unless otherwise clearly specified and limited, the first feature being "above" or "below" the second feature may mean that the first and second features are in direct contact, or the first and second features are in indirect contact through an intermediate medium. Moreover, the first feature being "above", "above" and "above" the second feature may mean that the first feature is directly above or obliquely above the second feature, or simply means that the first feature is higher in level than the second feature. The first feature being "below", "below" and "below" the second feature may mean that the first feature is directly below or obliquely below the second feature, or simply means that the first feature is lower in level than the second feature.

[0037] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the embodiment of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0038] Combine the following Figures 1 to 5 The invention describes a sand mixing and liquid supply system, a sand mixing and liquid supply control method, and a sand mixing skid.

[0039] One embodiment of the present invention provides a sand mixing and liquid supply system, combined with Figure 1 and Figure 2 As shown, the sand mixing and liquid supply system includes a water tank 1, a suction pump 2, a suction valve 3, a sand mixing tank 4, a discharge pump 5 and a discharge valve 6 which are connected in sequence, and also includes a controller 7. The sand mixing tank 4 is connected to a fracturing sand supply device 8, and the controller 7 is electrically connected to the suction pump 2, the suction valve 3, the discharge pump 5, the discharge valve 6 and the fracturing sand supply device 8 respectively.

[0040] It can be understood that the mixed sand and liquid supply system of this embodiment, during the fracturing construction process, controls the suction pump 2, the suction valve 3, the discharge pump 5, the discharge valve 6 and the fracturing sand supply device 8 respectively through the controller 7. In some specific examples, the controller 7 adjusts the suction flow of the suction pump 2, the opening of the suction valve 3, the discharge flow of the discharge pump 5 and the supply flow of the fracturing sand supply device 8 according to the discharge flow of the discharge outlet of the discharge valve 6. Through the intelligent control of the controller 7, it automatically adapts to various water tanks and working conditions, automatically adjusts the opening of the suction valve 3 according to the different discharge flows of the discharge pump 5, automatically adjusts the speed of the suction pump 2 through the control algorithm, stably controls the liquid level of the mixing tank 4, realizes the intelligent control of the liquid level and discharge pressure of the mixing tank 4, completely replaces manual control, and realizes equipment automation.

[0041] In some embodiments of the sand mixing and liquid supply system of the present invention, the controller 7 is connected to the suction pump 2, the discharge pump 5, and the fracturing sand supply device 8 through the frequency converter 9 for frequency conversion control, and the sand mixing tank 4 is provided with a liquid level meter 10, which is electrically connected to the controller 7. It can be understood that the controller 7 is the core control unit of the entire system. The controller 7 in this embodiment is connected and controlled by the frequency converter 9 to the suction pump 2, the discharge pump 5, and the fracturing sand supply device 8. The setting of the frequency converter 9 allows the controller 7 to accurately adjust the rotation speed of the suction pump 2 and the discharge pump 5 and the delivery flow of the fracturing sand supply device 8 according to the actual needs of the system. A liquid level meter 10 is installed in the sand mixing tank 4. The liquid level meter 10 is used to monitor the liquid level in the sand mixing tank 4 in real time and feed this information back to the controller 7. Based on the liquid data in the sand mixing tank 4, the controller 7 can perform more accurate control actions to ensure that the liquid level in the sand mixing tank 4 is maintained near the set value.

[0042] In some embodiments of the sand mixing and liquid supply system of the present invention, the suction valve 3 is an electromagnetic regulating valve, which is suitable for adjusting the opening of the suction valve 3 through the controller 7 to match the discharge flow of the discharge valve 6; the discharge valve 6 is an electromagnetic switch valve, which is suitable for controlling the opening and closing of the discharge valve 6 through the controller 7. The suction valve 3 is designed as an electromagnetic regulating valve, and the opening of the suction valve 3 can be continuously adjusted by an electronic signal. The controller 7 can dynamically adjust the opening of the suction valve 3 according to the discharge flow of the discharge valve 6 to ensure the stability and responsiveness of the system. The discharge valve 6 is an electromagnetic switch valve, which controls the opening or closing state of the valve through the controller 7 to manage the liquid flow path from the sand mixing tank 4 to the subsequent process.

[0043] When the system is running, the controller 7 receives data from different sensors (such as the liquid level meter 10) and calculates the optimal operating parameters in combination with the requirements of the current fracturing construction stage. For example, when it is necessary to increase the amount of liquid in the sand mixing tank 4, the controller 7 may increase the speed of the suction pump 2 through the frequency converter 9 and control the appropriate opening of the suction valve 3 through the controller 7; while in the case of reducing the liquid supply, the speed of the suction pump 2 is reduced or the opening of the suction valve 3 is reduced through the controller 7. In addition, for the discharge valve 6, the controller 7 is responsible for deciding when to open or close the valve to ensure that the discharge flow meets the construction requirements. At the same time, if it is detected that a different type of water tank 1 has been replaced or other factors that may cause changes in system characteristics, the controller 7 can also adjust the opening of the suction valve 3 accordingly to adapt to the new conditions.

[0044] Another aspect of the present invention further provides a sand mixing and liquid supply control method, which is applicable to the sand mixing and liquid supply system of any one of the above embodiments. In some embodiments of the sand mixing and liquid supply control method of the present invention, see Figure 3 As shown, the sand mixing and liquid supply control method includes the following steps S1-S4.

[0045] S1. Based on the stage of the fracturing construction, the flow rate of the sand mixing liquid required for the fracturing construction is obtained, and the actual discharge flow rate of the discharge pump 5 is controlled by the controller 7 to match the flow rate of the sand mixing liquid required for the fracturing construction.

[0046] The purpose of this step is to ensure that the actual discharge flow of the discharge pump 5 matches the sand-mixing liquid flow required for the fracturing operation. First, determine the specific requirements of the current fracturing operation stage, calculate or obtain the required sand-mixing liquid flow, and then use the controller 7 to adjust the working parameters of the discharge pump 5 so that its actual discharge flow meets the construction requirements, and start the fracturing operation. The sand-mixing liquid supply system sets different speed adjustment ranges for the discharge pump 5 according to the difference between the set pressure and the actual pressure. The larger the difference, the greater the speed increase or decrease, and vice versa. At the same time, the greater the sand concentration, the smaller the adjustment range, which can effectively reduce the pressure fluctuation at high sand concentration.

[0047] S2. Based on the actual discharge flow rate of the discharge pump 5, determine the opening degree of the suction valve 3, and control the suction valve 3 to be at the determined opening degree.

[0048] Specifically, this step determines the optimal opening of the suction valve 3 according to the real-time discharge flow data of the discharge pump 5 in combination with a pre-calibrated data table, controls the suction valve 3 to the determined opening position, and ensures that the liquid suction volume is adapted to the discharge volume.

[0049] S3. Based on the actual discharge flow rate of the discharge pump 5 and the supply flow rate of the fracturing sand supply device 8, the suction flow rate of the suction pump 2 is obtained, and the suction pump 2 is controlled to execute the obtained suction flow rate.

[0050] The discharge flow of the discharge pump 5, the sand adding speed of the fracturing sand supply device 8 and the suction flow of the suction valve 3 are the three most direct factors affecting the liquid level of the mixing tank 4. The most ideal state for controlling the liquid level to be stable is: the discharge flow of the discharge pump 5 = the suction flow of the suction valve 3 + the sand adding speed of the fracturing sand supply device 8 * the water-sand coefficient. The water-sand coefficient is the volume of sand dissolved in water per unit volume. The fracturing sand provided by the fracturing sand manufacturer can determine the true density and apparent density of the fracturing sand. The water-sand coefficient = apparent density / true density; the actual discharge flow of the current discharge pump 5 and the suction flow of the suction valve 3 required under the supply flow of the fracturing sand supply device 8 can be calculated by the above formula; the two factors that directly affect the suction displacement are the suction pressure and the opening of the suction valve 3, and the suction pressure is proportional to the rotation speed of the suction pump 2 and the liquid level height of the water tank 1. Under normal circumstances, the liquid level fluctuation of the same water tank 1 will not be too large. Step S2 has fixed the opening of the suction valve 3. Then, the suction pressure can be controlled by adjusting the rotation speed of the suction pump 2, thereby meeting the required suction displacement.

[0051] S4. Based on the comparison between the actual liquid level of the sand mixing tank 4 and the set liquid level, the rotation speed of the suction pump 2 is adjusted so that the actual liquid level of the sand mixing tank 4 is equal to the set liquid level.

[0052] The purpose of this step is to maintain the liquid level in the sand mixing tank 4 stable and avoid it being too high or too low. The actual liquid level in the sand mixing tank 4 is monitored in real time by the liquid level meter 10 and compared with the preset target liquid level. If a deviation is found, the frequency converter 9 changes the speed of the suction pump 2 to compensate until the actual liquid level in the sand mixing tank reaches the set value.

[0053] It is understandable that the requirements for the liquid level control and discharge pressure control of the mixing tank 4 are different. During the fracturing operation, the discharge displacement is different at different stages, and there are situations where the displacement is quickly increased and reduced. If the liquid level control is not timely, it is easy to cause the mixing tank 4 to overflow and suck empty. Therefore, the liquid level control of the mixing tank 4 requires a fast and stable response. The discharge pressure is basically proportional to the speed of the discharge pump 5. When adding sand, especially when the sand concentration is high, it is easy to cause discharge pressure fluctuations. At this time, the adjustment range of the discharge pump 5 should be reduced to achieve stable discharge pressure control. The sand mixing liquid supply control method of this embodiment can realize the intelligent management of the entire liquid supply process through the fine regulation of each key component (discharge pump 5, suction valve 3, suction pump 2) by the controller 7, thereby improving work efficiency, reducing operation difficulty, and enhancing the reliability and safety of the system.

[0054] In some embodiments of the sand mixing and liquid supply control method of the present invention, in the above step S2, determining the opening of the suction valve 3 based on the actual discharge flow rate of the discharge pump 5 includes: testing the discharge pump 5 at different calibrated discharge flow rates, taking the unchanged liquid level of the sand mixing tank 4 as a benchmark, testing the opening of the suction valve 3 corresponding to the discharge pump 5 at different calibrated discharge flow rates, and statistically compiling a correspondence table between the calibrated discharge flow rate of the discharge pump 5 and the opening of the suction valve 3; based on the correspondence table between the calibrated discharge flow rate of the discharge pump 5 and the opening of the suction valve 3, obtaining the opening of the suction valve 3 corresponding to the actual discharge flow rate of the discharge pump 5.

[0055] It can be understood that this embodiment achieves the determination of the opening of the suction valve 3 during fracturing construction by establishing a corresponding relationship between the calibrated discharge flow of the discharge pump 5 and the opening of the suction valve 3. Specifically, a series of different calibrated discharge flow values ​​are selected as test points. These calibration points should cover the possible range in practical applications and be dense enough to ensure data accuracy. For each selected calibrated discharge flow, the working parameters of the discharge pump 5 are adjusted to make it stably operate at this flow to conduct tests. During the test, the liquid level in the sand mixing tank 4 is maintained unchanged by adjusting the opening of the suction valve 3. This step is crucial because it ensures that the change in the discharge flow is completely compensated by the adjustment of the suction valve opening, so that the relationship between the two can be accurately mapped. For each calibrated discharge flow, the corresponding suction valve 3 opening value is recorded. After collecting all the calibration test data, statistical analysis is performed to construct a corresponding relationship table (or curve) between the calibrated discharge flow of the discharge pump 5 and the opening of the suction valve 3. This table / curve will serve as a basic reference for the subsequent control system.

[0056] When the system is in normal working condition, the controller 7 will monitor the actual discharge flow of the discharge pump 5 in real time, and consult the pre-established relationship table to find the calibration value closest to the current discharge flow and its corresponding opening of the suction valve 3. According to the corresponding relationship found, the controller 7 immediately adjusts the suction valve 3 to the required opening position to ensure the immediate responsiveness and stability of the system.

[0057] In some other embodiments of the sand mixing and liquid supply control method of the present invention, after the water tank 1 is replaced during fracturing construction, the process of determining the opening of the suction valve 3 includes: based on the correspondence table between the calibrated discharge flow of the discharge pump 5 and the opening of the suction valve 3, obtaining the opening of the suction valve 3 corresponding to the actual discharge flow of the discharge pump 5, and obtaining the actual required opening of the suction valve 3 based on the product of the obtained opening of the suction valve 3 and the valve coefficient.

[0058] It can be understood that the process of determining the opening of the suction valve 3 in the sand mixing and liquid supply control method of this embodiment is intended to provide a method for determining the opening of the suction valve 3 that can adapt to water tanks 1 of all sizes. Different water tanks 1 have different suction pressures. In order to make the method of this embodiment applicable to all water tanks 1, at a certain stage of fracturing construction, whether it is changing the site or directly replacing the water tank 1, the method for determining the opening of the suction valve 3 of this embodiment can be quickly adjusted, and the new suction valve opening can be quickly calculated and immediately applied to the system to ensure the continuity and stability of the system.

[0059] Specifically, the corresponding relationship table between the calibrated discharge flow of the discharge pump 5 and the opening of the suction valve 3 established in advance is first used to find the opening of the suction valve 3 corresponding to the actual discharge flow of the current discharge pump 5. Then, the water level of the newly replaced water tank 1 is compared with the water level of the original water tank 1 to determine the valve coefficient. The water level is higher than the original water tank: because a higher water level means a larger static pressure head, it may cause the speed of liquid flowing into the sand mixing tank to increase, so it is necessary to reduce the opening of the suction valve to compensate for this effect, so if the water level of the new water tank is higher than the original water tank, the valve coefficient range is 0.8~0.95. The water level is lower than the original water tank: because a lower water level will reduce the static pressure head and may reduce the liquid inflow speed, it is necessary to appropriately increase the opening of the suction valve to help maintain the required flow, so if the water level of the new water tank is lower than the original water tank, the valve coefficient range is 1~1.1. The opening of the suction valve 3 obtained from the calibration relationship table is multiplied by the valve coefficient determined according to the water level difference to obtain the actual required opening of the suction valve 3 after replacing the water tank.

[0060] During normal fracturing construction, there will be a few minutes to ten minutes of fluctuations in the flow range of small displacement (generally less than 0.8 m³ / min). The valve calibration of the suction valve 3 cannot accurately determine the specific opening of the suction valve 3. At this time, the opening of the suction valve 3 is controlled by the controller 7 according to the set liquid level and actual liquid level of the sand mixing tank 4, so that the liquid level can be stably controlled. In some specific embodiments of the sand mixing and liquid supply control method provided by the present invention, the sand mixing and liquid supply control method also includes the sand mixing and liquid supply control of the small displacement sand mixing fluid fracturing construction condition, see Figure 4 As shown, the sand mixing and fluid supply control process of the small displacement sand mixing fluid fracturing operation condition includes the following steps S10-S30.

[0061] S10. Based on the actual discharge flow of the discharge pump 5, when the actual discharge flow of the discharge pump 5 is less than the minimum calibrated discharge flow of the discharge pump 5 and fluctuates continuously, a small-displacement sand mixing hydraulic fracturing operation is performed.

[0062] This step is to determine through the controller 7 that the system needs to enter a small-displacement sand-mixing hydraulic fracturing operation condition based on the actual discharge flow of the discharge pump 5. Specifically, when the actual discharge flow of the discharge pump 5 is less than the minimum calibrated discharge flow of the discharge pump 5, and the flow fluctuates back and forth in a small-displacement (generally less than 0.8 m³ / min) flow range, the system needs to enter a small-displacement sand-mixing hydraulic fracturing operation condition. In this case, the sand-mixing fluid supply control method in the above embodiment may not be able to effectively maintain the stability of the system, so a special small-displacement control strategy needs to be adopted.

[0063] S20, under the fracturing operation condition of small-displacement sand mixing fluid, based on the actual discharge flow of the discharge pump 5 and the supply flow of the fracturing sand supply device 8, the suction flow of the suction pump 2 is obtained, and the suction pump 2 is controlled to execute the obtained suction flow.

[0064] Under low-displacement conditions, the suction flow that the suction pump 2 should perform is accurately calculated based on the actual discharge flow of the discharge pump 5 and the supply flow of the fracturing sand supply device 8. The suction pump 2 is controlled to provide the corresponding suction flow according to the calculation result to ensure that the construction requirements can be met even under low-flow conditions. Under such conditions, a small change in flow may lead to a large impact, so the control of the suction flow must be very precise and timely.

[0065] S30, based on the comparison between the actual liquid level of the sand mixing tank 4 and the set liquid level, the controller 7 adjusts the opening of the suction valve 3 so that the actual liquid level of the sand mixing tank 4 is equal to the set liquid level.

[0066] The actual liquid level in the mixing tank 4 is monitored in real time by the liquid level meter 10 and compared with the set target liquid level. If a deviation is found, the opening of the suction valve 3 is dynamically adjusted by the controller 7 to make the actual liquid level in the mixing tank 4 as close to the set value as possible. The controller 7 can provide a smoother and faster response control effect through PID control, which is particularly important for dealing with flow fluctuations under small displacement conditions. In this process, the controller 7 will continuously optimize the opening setting of the suction valve 3 to ensure that the liquid level in the mixing tank 4 can remain stable even in the face of continuously fluctuating discharge flow.

[0067] It can be understood that the sand mixing and fluid supply control method of this embodiment ensures the stability and accuracy of the sand mixing and fluid supply system under small-displacement sand mixing fluid fracturing construction conditions through a series of control measures. This method not only improves work efficiency, but also significantly enhances the reliability of the system and the safety of operation.

[0068] When the fracturing operation is in the stage of cooperating with the oil mill bridge plug, the displacement of the discharge pump 5 is generally 0.3 m 3 / min~0.8m 3 / min continuous operation for several days to dozens of days. Under this working condition, the valve calibration of the suction valve 3 is also unable to accurately determine the specific opening of the suction valve 3. In other embodiments of the sand mixing and liquid supply control method of the present invention, the sand mixing and liquid supply control method also includes the sand mixing and liquid supply control in conjunction with the oil mill bridge plug fracturing construction condition, see Figure 5 As shown, the mixed sand and fluid supply control process in cooperation with the oil mill bridge plug fracturing operation condition includes the following steps S100-S400.

[0069] S100, based on the actual discharge flow of the discharge pump 5, when the actual discharge flow of the discharge pump 5 is less than the minimum calibrated discharge flow of the discharge pump 5 and the low flow operation is continuously maintained, the oil mill bridge plug fracturing construction condition is carried out.

[0070] This step is to determine through the controller 7 that the system needs to enter the small-displacement sand mixing hydraulic fracturing operation condition based on the actual discharge flow of the discharge pump 5. Specifically, when the actual discharge flow of the discharge pump 5 is less than its minimum calibrated discharge flow (generally within 0.3 m 3 / min~0.8 m 3 / min), and when the system continues to work in this low flow state, the system needs to enter the oil mill bridge plug fracturing operation state. In this case, the sand mixing and liquid supply control method in the above embodiment may not be sufficient to meet the needs of long-term stable operation, so a special small flow control logic needs to be adopted.

[0071] S200, in cooperation with the oil mill bridge plug fracturing construction condition, the suction valve 3 is controlled by the controller 7 to open the minimum opening as the initial opening, based on the actual discharge flow of the discharge pump 5 and the supply flow of the fracturing sand supply device 8, the suction flow of the suction pump 2 is obtained, and the suction pump 2 is controlled to execute the obtained suction flow, which is recorded as the initial rotation speed of the suction pump 2.

[0072] In the case of oil mill bridge plug fracturing operation, the suction valve 3 is opened to the minimum opening as the initial opening by the controller 7 to ensure that a certain liquid flow can be maintained even under extremely low flow conditions, while avoiding unnecessary fluctuations caused by excessive opening of the suction valve. Based on the actual discharge flow of the discharge pump 5 and the supply flow of the fracturing sand supply device 8, the suction flow that the suction pump 2 should perform is accurately calculated, and the suction pump 2 is controlled to provide the corresponding suction flow according to the calculation result, and the speed at this time is recorded as the initial speed to ensure that the initial state of the system can meet the basic requirements under low flow conditions.

[0073] S300. Based on the comparison between the actual liquid level of the sand mixing tank 4 and the set liquid level, adjust the rotation speed of the suction pump 2: when the actual liquid level of the sand mixing tank 4 is lower than the set liquid level, increase the rotation speed of the suction pump 2 until the rotation speed of the suction pump 2 is greater than 30% of the initial rotation speed, and then control the suction valve 3 to increase the opening through the controller 7; when the actual liquid level of the sand mixing tank 4 is higher than the set liquid level, control the suction valve 3 to reduce the opening through the controller 7.

[0074] The actual liquid level in the sand mixing tank 4 is monitored in real time by the liquid level meter 10, and compared with the set target liquid level. If the actual liquid level in the sand mixing tank 4 is lower than the set liquid level, the speed of the suction pump 2 is gradually increased until the speed of the suction pump 2 exceeds 30% of the initial speed, and then the opening of the suction valve 3 is gradually increased by the controller 7. If the actual liquid level in the sand mixing tank 4 is higher than the set liquid level, the opening of the suction valve 3 is reduced by the controller 7 to reduce the amount of liquid inflow. This dynamic adjustment mechanism based on liquid level feedback can effectively cope with subtle changes under long-term low-flow conditions and maintain the stability of the system.

[0075] S400, repeatedly comparing the actual liquid level of the sand mixing tank 4 with the set liquid level, and adjusting the rotation speed of the suction pump 2 until the opening of the suction valve 3 satisfies that the actual liquid level of the sand mixing tank 4 is equal to the set liquid level.

[0076] The system continues to perform step S300 until the opening of the suction valve 3 finally makes the actual liquid level of the sand mixing tank 4 equal to the set liquid level. This process ensures that even in a long-term, low-flow working environment, the system can always maintain the optimal working state and meet the construction requirements.

[0077] It is understandable that long-term low-flow conditions place higher demands on the control system, especially how to achieve fine control while ensuring stability. The mixed sand supply control method of this embodiment effectively solves this problem by introducing a method of starting with a minimum opening and gradually adjusting the suction valve opening and the suction pump speed. It especially provides an optimization solution for cooperating with the oil-grinding bridge plug fracturing construction, enhancing the adaptability and reliability of the system. Through continuous monitoring and adjustment, the system can maintain stable performance for a long time to ensure the continuity and safety of construction. This method not only improves work efficiency, but also significantly enhances the reliability of the system and the safety of operation, especially under the condition of long-term continuous low-flow operation.

[0078] Another aspect of the present invention is to provide a sand mixing skid (sand mixing vehicle), see Figure 1 As shown, the sand mixing skid of the present invention includes the sand mixing liquid supply system of any one of the above embodiments, and can perform any one of the above sand mixing liquid supply control methods.

[0079] It can be understood that since the sand mixing skid provided by the present invention includes the sand mixing liquid supply system in any of the above embodiments, the sand mixing skid provided by the present invention has all the advantages of the above sand mixing liquid supply system. The sand mixing skid of the present invention can automatically control the opening degree of the suction valve 3 according to different displacement rates, completely replacing manual control and realizing equipment automation; according to different water tanks 1 on site, only need to set the valve coefficient once to meet the construction control of an entire platform, and can fully adapt to any water tank 1 currently in use. When in the small displacement working condition of fracturing construction, the construction working condition is automatically judged through the program, and different control methods are automatically selected to realize accurate and stable liquid level control, and the automatic switching between different control methods can be carried out without disturbance.

[0080] By integrating an advanced sand mixing liquid supply system and its control method, the operation efficiency, stability and reliability of the equipment are significantly improved. It not only solves the problems existing in the traditional control method, but also provides a more flexible and efficient solution, which is especially suitable for the requirements of modern shale gas fracturing projects. This system can cope with a variety of complex and changeable operating environments, ensuring the safety and continuity of construction, and is an ideal choice for improving the performance of fracturing operations.

[0081] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements on some of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A sand mixing and liquid supply system, characterized in that: The invention comprises a water tank (1), a suction pump (2), a suction valve (3), a sand mixing tank (4), a discharge pump (5) and a discharge valve (6) which are connected in sequence, and also comprises a controller (7), wherein the sand mixing tank (4) is connected to a fracturing sand supply device (8), and the controller (7) is electrically connected to the suction pump (2), the suction valve (3), the discharge pump (5), the discharge valve (6) and the fracturing sand supply device (8), respectively.

2. The sand mixing and liquid supply system according to claim 1, characterized in that: The controller (7) is used to adjust the suction flow of the suction pump (2), the opening of the suction valve (3), the discharge flow of the discharge pump (5) and the supply flow of the fracturing sand supply device (8) according to the discharge flow of the discharge port of the discharge valve (6).

3. The sand mixing and liquid supply system according to claim 1, characterized in that: The controller (7) is respectively connected to the suction pump (2), the discharge pump (5), and the fracturing sand supply device (8) via a frequency converter (9) for frequency conversion control. The sand mixing tank (4) is provided with a liquid level meter (10), and the liquid level meter (10) is electrically connected to the controller (7).

4. The sand mixing and liquid supply system according to claim 1, characterized in that: The suction valve (3) is an electromagnetic regulating valve, which is suitable for adjusting the opening of the suction valve (3) through the controller (7) to match the discharge flow rate of the discharge port of the discharge valve (6); the discharge valve (6) is an electromagnetic switch valve, which is suitable for controlling the opening and closing of the discharge valve (6) through the controller (7).

5. A sand mixing liquid supply control method, characterized in that: Applicable to the sand mixing and liquid supply system according to any one of claims 1 to 4, the sand mixing and liquid supply control method comprises: Based on the stage of the fracturing construction, the flow rate of the sand mixing liquid required for the fracturing construction is obtained, and the actual discharge flow rate of the discharge pump (5) is controlled by the controller (7) to match the flow rate of the sand mixing liquid required for the fracturing construction; Determining the opening of the suction valve (3) based on the actual discharge flow rate of the discharge pump (5), and controlling the suction valve (3) to be at the determined opening; Based on the actual discharge flow rate of the discharge pump (5) and the supply flow rate of the fracturing sand supply device (8), the suction flow rate of the suction pump (2) is obtained, and the suction pump (2) is controlled to execute the obtained suction flow rate; Based on a comparison between the actual liquid level of the sand mixing tank (4) and the set liquid level, the rotation speed of the suction pump (2) is adjusted so that the actual liquid level of the sand mixing tank (4) is equal to the set liquid level.

6. The sand mixing and liquid supply control method according to claim 5, characterized in that: Determining the opening degree of the suction valve (3) based on the actual discharge flow rate of the discharge pump (5) comprises: The discharge pump (5) is tested at different calibrated discharge flow rates, with the liquid level of the sand mixing tank (4) being constant as a benchmark, and the opening of the suction valve (3) corresponding to the discharge pump (5) at different calibrated discharge flow rates is tested respectively, and a corresponding relationship table between the calibrated discharge flow rate of the discharge pump (5) and the opening of the suction valve (3) is statistically obtained. Based on the corresponding relationship table between the calibrated discharge flow rate of the discharge pump (5) and the opening of the suction valve (3), the opening of the suction valve (3) corresponding to the actual discharge flow rate of the discharge pump (5) is obtained.

7. The sand mixing and liquid supply control method according to claim 6, characterized in that: After the water tank (1) is replaced during fracturing construction, the process of determining the opening of the suction valve (3) comprises: obtaining the opening of the suction valve (3) corresponding to the actual discharge flow of the discharge pump (5) based on a correspondence table between the calibrated discharge flow of the discharge pump (5) and the opening of the suction valve (3), and obtaining the actual required opening of the suction valve (3) based on the product of the obtained opening of the suction valve (3) and a valve coefficient; The valve coefficient is determined by comparing the water level of the replaced water tank (1) with the water level of the original water tank (1). When the water level of the replaced water tank (1) is higher than the water level of the original water tank (1), the valve coefficient is in the range of 0.8 to 0.

95. When the water level of the replaced water tank (1) is lower than the water level of the original water tank (1), the valve coefficient is in the range of 1 to 1.

1.

8. The sand mixing and liquid supply control method according to claim 6 or 7, characterized in that: The sand mixing and liquid supply control method also includes sand mixing and liquid supply control for a small-displacement sand mixing fluid fracturing operation condition. The sand mixing and liquid supply control process for a small-displacement sand mixing fluid fracturing operation condition includes: Based on the actual discharge flow rate of the discharge pump (5), when the actual discharge flow rate of the discharge pump (5) is less than the minimum calibrated discharge flow rate of the discharge pump (5) and is constantly fluctuating, a small-displacement sand-mixing hydraulic fracturing operation condition is performed; Under the condition of small-displacement sand mixing hydraulic fracturing, based on the actual discharge flow of the discharge pump (5) and the supply flow of the fracturing sand supply device (8), the suction flow of the suction pump (2) is obtained, and the suction pump (2) is controlled to execute the obtained suction flow; Based on a comparison between the actual liquid level of the sand mixing tank (4) and the set liquid level, the opening of the suction valve (3) is adjusted by a controller (7) so that the actual liquid level of the sand mixing tank (4) is equal to the set liquid level.

9. The sand mixing and liquid supply control method according to claim 6 or 7, characterized in that: The sand mixing and liquid supply control method further includes sand mixing and liquid supply control in coordination with the oil mill bridge plug fracturing construction condition. The sand mixing and liquid supply control process in coordination with the oil mill bridge plug fracturing construction condition includes: Based on the actual discharge flow rate of the discharge pump (5), when the actual discharge flow rate of the discharge pump (5) is less than the minimum calibrated discharge flow rate of the discharge pump (5) and the low flow rate operation is continuously maintained, a fracturing operation condition is performed in coordination with the oil mill bridge plug; In the case of oil-mill bridge plug fracturing operation, the controller (7) controls the suction valve (3) to open to a minimum opening as an initial opening, obtains the suction flow of the suction pump (2) based on the actual discharge flow of the discharge pump (5) and the supply flow of the fracturing sand supply device (8), and controls the suction pump (2) to execute the obtained suction flow, which is recorded as the initial rotation speed of the suction pump (2); Based on the comparison between the actual liquid level of the sand mixing tank (4) and the set liquid level, the rotation speed of the suction pump (2) is adjusted: when the actual liquid level of the sand mixing tank (4) is lower than the set liquid level, the rotation speed of the suction pump (2) is increased until the rotation speed of the suction pump (2) is greater than 30% of the initial rotation speed, and the controller (7) is used to control the suction valve (3) to increase the opening degree; when the actual liquid level of the sand mixing tank (4) is higher than the set liquid level, the controller (7) is used to control the suction valve (3) to decrease the opening degree; The comparison between the actual liquid level and the set liquid level of the sand mixing tank (4) is repeated, and the rotation speed of the suction pump (2) is adjusted until the opening of the suction valve (3) satisfies that the actual liquid level of the sand mixing tank (4) is equal to the set liquid level.

10. A sand mixing skid, characterized in that: The invention comprises the sand mixing and liquid supply system as described in any one of claims 1 to 4, or implements the sand mixing and liquid supply control method as described in any one of claims 5 to 9.

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