Underground working fluid level identification and automatic liquid filling control method and device

Abstract

The invention provides an underground working fluid level identification and automatic liquid filling control method and device, and the method comprises the steps: collecting an echo pulse signal through a working fluid level measuring instrument, obtaining an echo sampling signal, and calculating the underground average sound velocity of the echo sampling signal; performing data analysis on the echo sampling signal, performing filtering processing on the echo sampling signal to obtain a wavelet decomposition coefficient and an estimated wavelet decomposition coefficient, performing wavelet de-noising processing on the echo sampling signal, and reconstructing the echo sampling signal to obtain a de-noised echo sampling signal; searching a sudden change peak value of a working fluid level position and a sampling point of the working fluid level by utilizing a wavelet singular value detection method, and calculating round-trip time of an echo sampling signal; calculating the actual working fluid level height; and whether the obtained actual working fluid level height reaches the minimum threshold value of the preset working fluid level height or not is judged, and if yes, the PLC triggers a liquid filling system to conduct automatic liquid filling. The problem that working fluid level signals are submerged by noise and are difficult to directly recognize is solved.

Description

Technical Field

[0001] The invention belongs to the technical field of oil and gas field development, and in particular relates to a method and a device for identifying a downhole dynamic liquid level and automatically controlling liquid filling. Background Art

[0002] As the oil field enters the middle and late stages of development, the formation energy deficit is becoming increasingly serious, resulting in the pressure coefficient of some old wells and gas storage injection and production wells being far below 1. In order to protect the formation, the construction party tends to inject less or no fluid, which puts higher requirements on the dynamic liquid level monitoring and precise fluid injection technology of the wellbore. The existing technology has the following shortcomings:

[0003] (1) Existing liquid level monitoring devices cannot accurately identify and automatically correct liquid level information under the interference of multiple factors. Subsequent manual processing and calibration are required, which can easily cause a lag in the acquisition of dynamic liquid level information and affect real-time decision-making on site;

[0004] (2) When using the acoustic wave method to measure the dynamic liquid depth of an oil well, due to the complex structure of the casing, the collar wave and liquid surface echo of the acoustic wave signal received at the wellhead are easily interfered by noise, making it difficult for traditional signal processing methods to calculate the speed and travel time of the acoustic wave, and thus unable to obtain the dynamic liquid depth of the oil well;

[0005] (3) Existing wellbore hydraulic wells mainly rely on relatively conventional electric pump technology, and lack leakage evaluation and precise liquid filling pressure control technology linked to the liquid level monitoring device. During construction, there is a high risk of wellhead overpressure, overflow and other well control hazards due to inadequate liquid filling.

[0006] With the increasing requirements for well control quality in the field of oil and gas field development, it is urgently necessary to tackle the above shortcomings in the existing liquid level monitoring and hydraulic well filling technologies, develop an intelligent identification method for downhole dynamic liquid level and automatic filling control method, and form a precise monitoring of wellbore liquid level and automatic filling linkage pressure control technology. Summary of the invention

[0007] The purpose of the present invention is to make up for the shortcomings of the prior art and provide a method for identifying the dynamic liquid level in a well and automatically filling the well. By collecting echo signals, solving the average sound velocity in the well, using wavelet denoising and singular value decomposition methods, the sudden change peak value of the dynamic liquid level position and the sampling point of the dynamic liquid level position are found to solve the problem that the dynamic liquid level signal is submerged by noise and difficult to directly identify. Combined with the real-time control function of the PLC controller, high-precision automatic filling is achieved to improve the efficiency of well killing construction.

[0008] In a first aspect, a method for downhole dynamic liquid level recognition and automatic liquid filling control includes the following contents:

[0009] S1. Collect echo pulse signals using a dynamic liquid level measuring instrument to obtain echo sampling signals and calculate their average sound velocity in the well;

[0010] S2. Based on the acquired echo sampling signal, data analysis is performed on it, specifically including:

[0011] S201, filtering the echo sampling signal to obtain wavelet decomposition coefficients and estimated wavelet decomposition coefficients;

[0012] S202, performing wavelet denoising processing on the echo sampling signal, reconstructing the echo sampling signal using estimated wavelet decomposition coefficients, and obtaining a denoised echo sampling signal;

[0013] S3, based on the reconstructed echo sampling signal, using the wavelet singular value decomposition method to find the sudden change peak value of the dynamic liquid surface position and the sampling point of the dynamic liquid surface, and calculate the round-trip time of the echo sampling signal;

[0014] S4. Calculate the actual dynamic liquid level based on the average sound velocity and round-trip time of the acquired echo sampling signal;

[0015] S5. Determine whether the actual dynamic liquid level obtained reaches the preset minimum threshold of the dynamic liquid level. If so, the PLC control system triggers the automatic filling system to automatically fill the liquid.

[0016] Furthermore, the average sound velocity V in S1 w Calculated by the following formula:

[0017]

[0018] Among them, H c is the length of the oil pipe, T c It is the time for the echo signal to pass through the oil pipe.

[0019] Furthermore, the S201 further comprises: performing wavelet transform on the echo sampling signal, wherein the amplitude of the wavelet coefficient of the useful signal is larger and the amplitude of the wavelet coefficient of the noisy signal is smaller, thereby obtaining the wavelet decomposition coefficient;

[0020] Selecting thresholds at different scales of the wavelet decomposition coefficients, setting the wavelet coefficients below the threshold to 0, and obtaining estimated wavelet decomposition coefficients;

[0021] Specifically: including soft threshold function and hard threshold function,

[0022] Soft threshold function: The absolute value of the wavelet coefficient is set to zero if it is lower than the threshold, and the coefficient above the threshold is shrunk. The formula is as follows:

[0023]

[0024] Hard threshold function: The absolute value of the wavelet coefficient is set to zero if it is lower than the threshold, and remains unchanged if it is higher than the threshold. The formula is as follows:

[0025]

[0026] Where: w represents the wavelet coefficient, T represents the given threshold, and sgn(*) is the sign function.

[0027] Furthermore, in S3, the number of collected data points m is calculated:

[0028] Where, L is the distance between the installation location of the dynamic liquid level measuring instrument and the wellhead, f s is the sampling frequency of the dynamic liquid level measuring instrument, V w is the average sound velocity of the echo sampling signal in the well;

[0029] Calculate the round trip time T of the echo sampling signal:

[0030] Where n is the number of peak or trough positions in the echo wave data array, and m is the number of data points collected by calculation.

[0031] Furthermore, in S4, the actual depth of the dynamic liquid surface is:

[0032] Among them, V w is the average sound velocity of the echo sampling signal in the well, and T is the round-trip time of the echo sampling signal.

[0033] Furthermore, the S5 also includes: when the actual dynamic liquid level reaches the lowest threshold of the preset dynamic liquid level, the PLC control system receives a control signal and controls the automatic filling system to perform a filling well operation;

[0034] During the filling process, the filling status is monitored and the real-time status data is fed back to the Raspberry Pi system and PLC control system for adjustment and optimization.

[0035] In a second aspect, a downhole dynamic liquid level recognition and automatic liquid filling control device comprises:

[0036] Signal acquisition module: Use the dynamic liquid level measuring instrument to collect echo pulse signals, obtain echo sampling signals and calculate their average sound velocity in the well;

[0037] Signal analysis module: based on the acquired echo sampling signal, data analysis is performed on it, specifically including filtering the echo sampling signal to obtain wavelet decomposition coefficients and estimated wavelet decomposition coefficients; performing wavelet denoising on the echo sampling signal, reconstructing the echo sampling signal using the estimated wavelet decomposition coefficients, and obtaining a denoised echo sampling signal;

[0038] Determination module: Based on the reconstructed echo sampling signal, the wavelet singular value decomposition method is used to find the sudden change peak of the dynamic liquid surface position and the sampling point of the dynamic liquid surface, and the round-trip time of the echo sampling signal is calculated; based on the average sound velocity and round-trip time of the acquired echo sampling signal, the actual dynamic liquid surface height is calculated;

[0039] Judgment execution module: judge whether the actual dynamic liquid level obtained reaches the preset minimum threshold of the dynamic liquid level. If so, the PLC control system triggers the automatic filling system to automatically fill the liquid.

[0040] The embodiments of the present invention bring the following beneficial effects:

[0041] 1. The present invention uses wavelet denoising and wavelet singular value decomposition methods to process the echo signal, solving the problem that the dynamic liquid surface signal is submerged by noise and cannot be directly identified. It can quickly and accurately identify the liquid level height and take corresponding measures in time.

[0042] 2. Combined with the real-time control function of the PLC control system, the present invention can realize fully automatic filling control without manual intervention, greatly reducing labor costs and the risk of human error, and achieving high efficiency and high precision of automatic filling.

[0043] 3. The present invention can intelligently adjust the filling time and the water volume of the filling well operation to adapt to changes in different environmental factors, reduce waste, and improve water resource utilization efficiency.

[0044] 4. The present invention adopts advanced technologies such as Raspberry Pi single-board computer and PLC, has the characteristics of high efficiency and stability, and can operate normally in various complex environments.

[0045] Other features and advantages of the present invention will be described in the following description, and partly become apparent from the description, or understood by practicing the present invention. The purpose and other advantages of the present invention are realized and obtained by the structures particularly pointed out in the description, claims and drawings.

[0046] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, preferred embodiments are given below and described in detail with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] Figure 1 The present invention provides a flowchart of a method for downhole dynamic liquid level recognition and automatic liquid filling control.

[0048] Figure 2 A flow chart of wavelet denoising of echo signals provided by an embodiment of the present invention;

[0049] Figure 3A schematic diagram of raw echo data provided by an embodiment of the present invention;

[0050] Figure 4 A schematic diagram of wavelet denoising of echo data provided by an embodiment of the present invention;

[0051] Figure 5 A singular value decomposition flow chart provided by an embodiment of the present invention;

[0052] Figure 6 A schematic diagram of detecting liquid surface reflection points by wavelet singular values ​​provided in an embodiment of the present invention;

[0053] Figure 7 A circuit principle block diagram of the sound wave generator, echo receiver, dynamic liquid level detector, and automatic liquid filling system provided in an embodiment of the present invention;

[0054] Figure 8 This is a schematic diagram of the oil well structure provided by an embodiment of the present invention.

[0055] Among them, 1-sound wave generator; 2-echo receiver; 3-dynamic liquid level measuring instrument; 4-liquid filling system; 5-oil pipe coupling; 6-oil pipe; 7-annular space; 8-casing; 9-liquid level. DETAILED DESCRIPTION

[0056] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only 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.

[0057] First, as Figure 1 As shown, a method for identifying a downhole dynamic liquid level and automatically controlling liquid filling includes the following contents:

[0058] S1. Collect echo pulse signals using a dynamic liquid level measuring instrument to obtain echo sampling signals and calculate their average sound velocity in the well;

[0059] Taking 10 sections of oil pipe as an example, the average sound velocity V w Calculated by the following formula:

[0060]

[0061] Among them, H c is the length of 10 sections of oil pipe, T c It is the time for the echo signal to pass through 10 sections of the oil pipe.

[0062] S2. Based on the acquired echo sampling signal, data analysis is performed on it, including:

[0063] S201, filtering the echo sampling signal to obtain wavelet decomposition coefficients and estimated wavelet decomposition coefficients;

[0064] Specifically, the echo sampling signal is subjected to wavelet transform, the amplitude of the wavelet coefficient of the useful signal is larger, and the amplitude of the wavelet coefficient of the noisy signal is smaller, thereby obtaining the wavelet decomposition coefficient;

[0065] Select thresholds at different scales of the wavelet decomposition coefficients, set the wavelet coefficients below the threshold to 0, and obtain estimated wavelet decomposition coefficients.

[0066] Furthermore, the soft threshold function is used: the absolute value of the wavelet coefficient is set to zero if it is lower than the threshold, and the coefficient is shrunk if it is higher than the threshold. The formula is as follows:

[0067] Hard threshold function: The absolute value of the wavelet coefficient is set to zero if it is lower than the threshold, and remains unchanged if it is higher than the threshold. The formula is as follows:

[0068]

[0069] Where: w represents the wavelet coefficient, T represents the given threshold, and sgn(*) is the sign function.

[0070] S202, such as Figure 2 As shown, the echo sampling signal is subjected to wavelet denoising, and the echo sampling signal is reconstructed using the estimated wavelet decomposition coefficients to obtain a denoised echo sampling signal;

[0071] Specifically, the wavelet function and decomposition layer number of the noisy echo sampling signal are determined, wavelet decomposition is performed on it, the corresponding high-frequency coefficients are set to 0 according to the threshold, the echo sampling signal is reconstructed using the estimated wavelet decomposition coefficients, and the denoised echo sampling signal is output.

[0072] like Figure 3-Figure 4 As shown, wavelet denoising removes noise and redundant information while retaining important signal features. In this embodiment, the wavelet type is db6, and the number of decomposition layers is 3.

[0073] S3, based on the reconstructed echo sampling signal, using the wavelet singular value decomposition method to find the sudden change peak value of the dynamic liquid surface position and the sampling point of the dynamic liquid surface, and calculate the round-trip time of the echo sampling signal;

[0074] Specifically: Figure 5 As shown in the figure, using wavelet singular value detection, due to the sudden appearance of the liquid surface reflection wave, the received reflection wave signal will mutate within this period of time. The reconstructed wavelet coefficient vector is used to form a feature matrix. Assume that the denoised echo signal sequence is {x1,x2,x3,L x n}, the reconstructed attractor matrix is:

[0075]

[0076] Assume that the matrix X∈R m×n According to the formula: there exist orthogonal matrices U and V:

[0077] U=[u1,u2,L,u m ]∈R m×n ,V=[v1,v2,L,v m ]∈R m×n

[0078] Make U T AV=diag[σ1,σ2,L,σ p ]=∑p=min(m,n), then it is called the singular value decomposition of A. i and v i are the i-th column vectors of matrix U and matrix V respectively, σ1≥σ2≥σ3≥σ p ≥0,σ i (i=1,2,Lp) is the singular value of A.

[0079] By solving AA * ,A * A eigenvector gets U, V matrix, calculates AA * ,A * The eigenvalues ​​of A are taken, and then the square root is taken to obtain the singular values, forming a diagonal matrix D.

[0080] Among them A * Denotes the adjoint matrix of matrix A.

[0081] Furthermore, the number of collected data points m is calculated:

[0082] Where, L is the distance between the installation location of the dynamic liquid level measuring instrument and the wellhead, f s is the sampling frequency of the dynamic liquid level measuring instrument, V w is the average sound velocity of the echo sampling signal in the well;

[0083] Calculate the round trip time T of the echo sampling signal:

[0084] Where n is the number of peak or trough positions in the echo wave data array.

[0085] In this embodiment, if Figure 6 As shown in the schematic diagram of the continuous wavelet transform coefficients of the echo sampling signal after wavelet denoising, it can be clearly seen that around n=850, an inverted cone-shaped area appears in the wavelet coefficients, from which it can be inferred that there is a mutation point in this area.

[0086] Depending on the type of device, low-voltage devices look for the minimum value in the data measured by the low-pass filter, and high-voltage devices look for the maximum value in the data measured by the low-pass filter.

[0087] S4. Calculate the actual dynamic liquid level based on the average sound velocity and round-trip time of the acquired echo sampling signal. The formula is:

[0088] Among them, V w is the average sound velocity of the echo sampling signal in the well, and T is the round-trip time of the echo sampling signal.

[0089] S5. Determine whether the actual dynamic liquid level obtained reaches the preset minimum threshold of the dynamic liquid level. If so, the PLC control system triggers the automatic filling system to automatically fill the liquid.

[0090] Specifically: when the actual dynamic liquid level reaches the preset minimum threshold of the dynamic liquid level, the PLC control system receives the control signal of the GPIO interface and controls the automatic filling system to perform the operation of filling the hydraulic well. The electromagnetic valve can be used to control the flow of water, and the motor can be used to control the rotation of the sprinkler head.

[0091] Equipment such as ultrasonic sensors can be used to monitor the filling status and feed the real-time status data back to the Raspberry Pi system and PLC control system for adjustment and optimization.

[0092] Furthermore, control signals can be transmitted to the PLC system using communication protocols such as Modbus, Ethernet / IP, and PROFINET. The specific protocol to be selected needs to be determined based on actual conditions, such as device type, distance, speed, etc.

[0093] Second, as Figure 7-Figure 8 As shown, a downhole dynamic liquid level identification and automatic liquid filling control device comprises:

[0094] Signal acquisition module: Use the dynamic liquid level measuring instrument to collect echo pulse signals, obtain echo sampling signals and calculate their average sound velocity in the well;

[0095] Signal analysis module: based on the acquired echo sampling signal, data analysis is performed on it, specifically including filtering the echo sampling signal to obtain wavelet decomposition coefficients and estimated wavelet decomposition coefficients; performing wavelet denoising on the echo sampling signal, reconstructing the echo sampling signal using the estimated wavelet decomposition coefficients, and obtaining a denoised echo sampling signal;

[0096] Determination module: Based on the reconstructed echo sampling signal, the wavelet singular value decomposition method is used to find the sudden change peak of the dynamic liquid surface position and the sampling point of the dynamic liquid surface, and the round-trip time of the echo sampling signal is calculated; based on the average sound velocity and round-trip time of the acquired echo sampling signal, the actual dynamic liquid surface height is calculated;

[0097] Judgment execution module: judge whether the actual dynamic liquid level obtained reaches the preset minimum threshold of the dynamic liquid level. If so, the PLC control system triggers the automatic filling system to automatically fill the liquid.

[0098] In the embodiment of the present invention, the nitrogen in the nitrogen bottle is used as power to manually control the sound wave generator 1 to emit a sonar pulse wave. The pulse wave is reflected by the oil pipe coupling 5, the oil pipe 6 and the liquid surface 9 in the annular space 7 formed between the oil pipe 6 and the casing 8 to form an echo signal. The echo receiver 2 receives the echo pulse signal, and the dynamic liquid level measuring instrument 3 uses the sampling frequency f s The echo pulse signal is collected to obtain the echo sampling signal s(i), which is transmitted to the Raspberry Pi system qt data analysis software. The height of the liquid level at this time is calculated by analysis and compared with the pre-set threshold to determine whether to control the filling system to fill the liquid.

[0099] In the embodiment of the present invention, the acoustic wave transmitter 1 and the echo receiver 2 are both required to be installed at the wellhead of the oil well, the output section of the acoustic wave generator 1 is connected to the oil pipe 5, the output end of the echo receiver 2 is connected to the input of the dynamic liquid level measuring instrument 3, and the dynamic liquid level measuring instrument 3 is connected to the input end of the downhole filling system 4 by wire; the oil pipe 5 is arranged in the casing 7, the oil pipe 5 is composed of multiple sections of pipes, and two adjacent oil pipes 5 are connected by an oil pipe coupling 6.

[0100] It should be noted that, in this article, the terms "comprises", "includes" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, article or apparatus that includes a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or apparatus.

[0101] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for identifying a downhole dynamic liquid level and automatically controlling liquid filling, characterized in that: The following steps are included: S1. Collect echo pulse signals using a dynamic liquid level measuring instrument to obtain echo sampling signals and calculate their average sound velocity in the well; S2. Based on the acquired echo sampling signal, data analysis is performed on it, specifically including: S201, filtering the echo sampling signal to obtain wavelet decomposition coefficients and estimated wavelet decomposition coefficients; S202, performing wavelet denoising processing on the echo sampling signal, reconstructing the echo sampling signal using estimated wavelet decomposition coefficients, and obtaining a denoised echo sampling signal; S3, based on the reconstructed echo sampling signal, using the wavelet singular value decomposition method to find the sudden change peak value of the dynamic liquid surface position and the sampling point of the dynamic liquid surface, and calculate the round-trip time of the echo sampling signal; S4. Calculate the actual dynamic liquid level based on the average sound velocity and round-trip time of the acquired echo sampling signal; S5. Determine whether the actual dynamic liquid level obtained reaches the preset minimum threshold of the dynamic liquid level. If so, the PLC control system triggers the automatic filling system to automatically fill the liquid.

2. The method for identifying the dynamic liquid level and automatically controlling the downhole filling according to claim 1, wherein the average sound velocity of the echo sampling signal in the downhole is calculated in S1, characterized in that: Average sound speed V w Calculated by the following formula: Among them, H c is the length of the oil pipe, T c It is the time for the echo signal to pass through the oil pipe.

3. The method for identifying the downhole dynamic liquid level and automatically filling the liquid according to claim 1, characterized in that: The step S201 performs filtering processing on the echo sampling signal to obtain wavelet decomposition coefficients and estimated wavelet decomposition coefficients, including: Perform wavelet transform on the echo sampling signal. The amplitude of the wavelet coefficient of the useful signal is larger, while the amplitude of the wavelet coefficient of the noisy signal is smaller, thus obtaining the wavelet decomposition coefficient; Thresholds are selected at different scales of the wavelet decomposition coefficients, and wavelet coefficients below the threshold are set to 0 to obtain estimated wavelet decomposition coefficients.

4. The method for downhole dynamic liquid level recognition and automatic filling control according to claim 3, wherein thresholds are selected at different scales of the wavelet decomposition coefficients, characterized in that: Including soft threshold function and hard threshold function, specifically: Soft threshold function: The absolute value of the wavelet coefficient is set to zero if it is lower than the threshold, and the coefficient above the threshold is shrunk. The formula is as follows: Hard threshold function: The absolute value of the wavelet coefficient is set to zero if it is lower than the threshold, and remains unchanged if it is higher than the threshold. The formula is as follows: Where: w represents the wavelet coefficient, T represents the given threshold, and sgn(*) is the sign function.

5. The method for downhole dynamic liquid level recognition and automatic filling control according to claim 1, wherein the round trip time of the echo sampling signal is calculated in S3, characterized in that: Calculate the number of collected data points m: Where, L is the distance between the installation location of the dynamic liquid level measuring instrument and the wellhead, f s is the sampling frequency of the dynamic liquid level measuring instrument, V w is the average sound velocity of the echo sampling signal in the well; Calculate the round trip time T of the echo sampling signal: Where n is the number of peak or trough positions in the echo wave data array, and m is the number of data points collected by calculation.

6. The method for downhole dynamic liquid level identification and automatic filling control according to claim 1, wherein the actual dynamic liquid level height is calculated in S4, characterized in that: Actual depth of dynamic liquid surface: Among them, V w is the average sound velocity of the echo sampling signal in the well, and T is the round-trip time of the echo sampling signal.

7. The method for downhole dynamic liquid level recognition and automatic liquid filling control according to claim 1, characterized in that: The S5 includes: When the actual dynamic liquid level reaches the minimum threshold of the preset dynamic liquid level, the PLC control system receives a control signal and controls the automatic filling system to perform the filling well operation; During the filling process, the filling status is monitored and the real-time status data is fed back to the Raspberry Pi system and PLC control system for adjustment and optimization.

8. A device using the method for downhole dynamic liquid level recognition and automatic liquid filling control according to claim 1, characterized in that: Signal acquisition module: Use the dynamic liquid level measuring instrument to collect echo pulse signals, obtain echo sampling signals and calculate their average sound velocity in the well; Signal analysis module: based on the acquired echo sampling signal, data analysis is performed on it, specifically including filtering the echo sampling signal to obtain wavelet decomposition coefficients and estimated wavelet decomposition coefficients; performing wavelet denoising on the echo sampling signal, reconstructing the echo sampling signal using the estimated wavelet decomposition coefficients, and obtaining a denoised echo sampling signal; Determination module: Based on the reconstructed echo sampling signal, the wavelet singular value decomposition method is used to find the sudden change peak of the dynamic liquid surface position and the sampling point of the dynamic liquid surface, and the round-trip time of the echo sampling signal is calculated; based on the average sound velocity and round-trip time of the acquired echo sampling signal, the actual dynamic liquid surface height is calculated; Judgment execution module: judge whether the actual dynamic liquid level obtained reaches the preset minimum threshold of the dynamic liquid level. If so, the PLC control system triggers the automatic filling system to automatically fill the liquid.

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