System and method for monitoring annulus liquid level in drilling well leakage state

Abstract

The invention discloses a system and method for monitoring the annulus liquid level in the drilling well leakage state, and the system comprises a wellhead temporary plugging device which is used for achieving the temporary plugging of an upper port of a shaft during the drilling well leakage so as to block the upward propagation path of sound waves; the annulus liquid level monitoring device is arranged on the well killing manifold and is used for measuring a detection signal representing the dynamic change characteristics of the annulus liquid level by adopting a sound wave measurement technology; and the data processing device is used for obtaining a dynamic environmental control liquid level measurement value according to the detection signal. Under the leakage state, the blowout preventer can be not closed, the annular liquid level can be continuously monitored, and the injection amount of drilling fluid can be accurately controlled.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of annular space liquid level monitoring, in particular to a system and method for monitoring the annular space liquid level under the condition of drilling leakage. BACKGROUND

[0002] Drilling leakage is a frequent downhole accident in the drilling process, which has great loss and harm. Especially when drilling through ultra-low pressure formation or fractured formation, drilling fluid loss circulation often occurs. When drilling leakage occurs, the static liquid level cannot be directly observed at the wellhead, and the liquid column pressure in the well continues to decrease. During the treatment process, the leakage condition in the wellbore cannot be grasped in real time, and the position where the formation pressure and the drilling fluid column pressure reach equilibrium and the leakage rate cannot be predicted, which may result in excessive or insufficient drilling fluid injection, leading to drilling fluid waste and even well collapse and blowout accidents.

[0003] Currently, the annular space drilling fluid injection technology is generally used to treat drilling leakage, but has the following shortcomings: 1. The position of the annular space liquid level cannot be monitored in real time, and the leakage balance point position and the leakage rate cannot be grasped; 2. The real-time continuity of liquid level monitoring is poor, and the blowout preventer must be closed, which cannot meet the needs of field operations; 3. The timing and amount of drilling fluid injection are determined by experience, and the drilling fluid is basically injected in a "blind injection" state, and the drilling fluid is injected according to the displacement capacity of the drilling tool, resulting in waste of drilling fluid.

[0004] In addition, the traditional leakage grouting device generally calculates the total tank volume change of drilling fluid according to the liquid level height of the circulating tank, and calculates the required grouting amount, which has the following shortcomings: 1. The liquid level height change in the wellbore cannot be grasped in real time; 2. The amount of drilling fluid injection is generally calculated by experience, such as the volume of the drilling pipe raised in the wellbore, and the grouting amount is in a "blind injection" state.

[0005] Therefore, it is necessary to provide a scheme capable of continuously and accurately measuring the annular space liquid level when drilling leakage occurs, so as to solve one or more problems in the prior art, such as the need to close the blowout preventer (closing the blowout preventer wastes time), the inability to continuously monitor the annular space liquid level during tripping, the inability to adapt to complex production environments on the well, and the difficulty in accurately determining the timing and amount of drilling fluid injection, thereby easily causing waste of drilling fluid. SUMMARY

[0006] The purpose of the present application is to provide a scheme capable of continuously and accurately measuring the annular space liquid level when drilling leakage occurs, so as to solve one or more problems in the prior art, such as the need to close the blowout preventer (closing the blowout preventer wastes time), the inability to continuously monitor the annular space liquid level during tripping, the inability to adapt to complex production environments on the well, and the difficulty in accurately determining the timing and amount of drilling fluid injection, thereby easily causing waste of drilling fluid.

[0007] In order to solve the above technical problems, the embodiment of the present application provides a system for monitoring the annular fluid level in the state of drilling leakage, comprising: a wellhead temporary plugging device for achieving temporary plugging of the upper port of the wellbore when drilling leakage occurs to block the transmission path of the acoustic wave upward; an annular fluid level monitoring device arranged on the kill manifold for measuring a detection signal representing the dynamic change characteristics of the annular fluid level by using acoustic wave measurement technology; and a data processing device for obtaining a dynamic annular control fluid level measurement value according to the detection signal.

[0008] Preferably, the wellhead temporary plugging device comprises: a mounting bracket; and at least two rubber plugs arranged on the upper port of the wellbore by the mounting bracket to achieve temporary plugging of the upper port of the wellbore.

[0009] Preferably, the at least two rubber plugs are two rubber plugs, wherein the two rubber plugs are configured as a two-leaf clamping structure by a hinge, the hinge is connected with the mounting bracket, and the mounting bracket is fixed on the wellbore.

[0010] Preferably, the annular fluid level monitoring device comprises: infrasonic wave transmitting and receiving equipment for transmitting an infrasonic wave signal to the annular control fluid level and receiving an infrasonic wave reflection signal reflected by the infrasonic wave signal at the annular control fluid level; a filter for filtering the infrasonic wave reflection signal to obtain an infrasonic wave audio signal; and a communication device for transmitting the infrasonic wave audio signal to the data processing device.

[0011] Preferably, the annular fluid level monitoring device further comprises: a power lifting device arranged at the front end of the infrasonic wave transmitting and receiving equipment for power lifting of the required transmitted infrasonic wave signal by providing specified pressure energy, and the power lifting device adopts a nitrogen booster.

[0012] Preferably, the system further comprises: an inlet flow sensor arranged on the tank mud pipeline for real-time measurement of the grouting flow; and an automatic grouting device for controlling the internal grouting pump according to the real-time grouting amount to grout a specified amount of drilling fluid into the annulus, so as to ensure that the amount of grouted drilling fluid is the least under the condition that the formation pressure and the wellbore fluid column pressure are kept in balance, wherein the data processing device is further used for calculating an ideal grouting amount corresponding to the leakage balance position according to the dynamic annular control fluid level measurement value, and calculating the real-time grouting amount required for the annular fluid level to reach the vicinity above the leakage balance position according to the ideal grouting amount and the real-time grouting flow, so as to send the real-time grouting amount to the automatic grouting device.

[0013] Preferably, the data processing device comprises: a balanced position fitting unit configured to perform linear fitting on the annulus liquid level measurement values at different time instants to obtain a liquid level height-time curve, and identify a liquid level position at a loss balanced position based on the liquid level height-time curve; a loss rate function generating unit configured to calculate a loss rate at a corresponding time instant based on the annulus liquid level measurement values at different time instants according to an annulus cross-sectional area, and form a loss rate-liquid level height curve; and a drilling fluid volume calculating unit configured to obtain the ideal grouting volume by using the loss rate-liquid level height curve based on the liquid level position at the loss balanced position.

[0014] Preferably, the balanced position fitting unit is further configured to perform derivative calculation on an expression of the liquid level height-time curve, and determine a liquid level position at which a derivative value is zero as the liquid level position at the loss balanced position.

[0015] Preferably, the expression of the liquid level height-time curve is:

[0016] H(t)=a+b·e -t / c

[0017] wherein t represents a time instant, H(t) represents an annulus liquid level height at the time instant t, and a, b, and c respectively represent fitting coefficients of the liquid level height-time curve; and an expression of the loss rate-liquid level height curve is:

[0018] V=A+B·lnH

[0019] wherein V represents a loss rate, and A and B respectively represent fitting coefficients of the loss rate-liquid level height curve.

[0020] In another aspect, an embodiment of the present application provides a method for monitoring an annulus liquid level in a drilling loss state, which is implemented by the system as described above, and the method comprises: installing a wellhead temporary plugging device at a wellbore upper port to block a sound wave upward propagation path when drilling loss occurs; using a sound wave measurement technology, measuring a detection signal representing an annulus liquid level dynamic change feature by using an annulus liquid level monitoring device arranged on a blowout control manifold; and using a data processing device to obtain a dynamic annulus liquid level measurement value according to the detection signal.

[0021] Compared with the prior art, one or more embodiments in the above solution can have the following advantages or beneficial effects:

[0022] The application provides a system and method for monitoring the annular fluid level under the condition of drilling leakage.

[0023] Additional features and advantages of the application will be set forth in the description that follows, and in part will be apparent from the description, or can be learned by practice of the application. The objectives and other advantages of the application will be realized and attained by the structure particularly pointed out in the written description and claims thereof as well as the appended drawings. BRIEF DESCRIPTION OF DRAWINGS

[0024] The accompanying drawings are included to provide a further understanding of the application and are incorporated in and constitute a part of this specification, illustrate embodiments of the application and together with the description serve to explain the principles of the application. In the drawings:

[0025] Figure 1 It is a whole structure schematic diagram of the system for monitoring the annular fluid level under the condition of drilling leakage of the embodiment of the application.

[0026] Figure 2 It is a specific structure schematic diagram of the system for monitoring the annular fluid level under the condition of drilling leakage of the embodiment of the application.

[0027] Figure 3 It is an application scene schematic diagram of the wellhead temporary plugging device and the annular fluid level monitoring device in the system for monitoring the annular fluid level under the condition of drilling leakage of the embodiment of the application.

[0028] Figure 4 It is an installation scene schematic diagram of the wellhead temporary plugging device in the system for monitoring the annular fluid level under the condition of drilling leakage of the embodiment of the application.

[0029] Figure 5 It is a dynamic annular control fluid level measurement value generation process principle schematic diagram of the system for monitoring the annular fluid level under the condition of drilling leakage of the embodiment of the application.

[0030] Figure 6 It is a step schematic diagram of the method for monitoring the annular fluid level under the condition of drilling leakage of the embodiment of the application. DETAILED DESCRIPTION

[0031] The embodiments of the present application will be described in detail below with reference to the accompanying drawings and examples, so that the application can be understood as how to solve the technical problems and achieve the technical effects by using technical means. It should be noted that the various embodiments in the present application and the various features in each embodiment can be combined with each other, and the technical solutions formed thereby are all within the protection scope of the present application.

[0032] In addition, the steps shown in the flowchart of the accompanying drawings can be executed in a computer system such as a set of computer executable instructions. Moreover, although the logical order is shown in the flowchart, in some cases, the steps shown or described herein can be executed in an order different from that shown.

[0033] The terms used herein are merely used to describe specific embodiments and are not intended to limit exemplary embodiments. Unless the context clearly indicates otherwise, as used herein, the singular forms "a," "an," and "the" are intended to include the plural forms as well. It will be further understood that the terms "comprises" and / or "comprising," when used herein, specify the presence of stated features, integers, steps, operations, elements, and / or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof.

[0034] To solve one or several technical problems in the technical background, the present application provides a system and method for monitoring the annular fluid level under the condition of drilling leakage. The system and method can continuously monitor the actual position of the annular fluid level without closing the original well packer (38), and use the annular fluid level dynamic analysis method to fit and establish the mathematical model of the leakage balance point position and the leakage rate, analyze the change law of the annular drilling fluid leakage, calculate the grouting amount, and realize accurate grouting by monitoring the pump displacement. Figure 3

[0035] Figure 1 The present application provides a system for monitoring the annular fluid level under the condition of drilling leakage. As shown in FIG. 1, the system (hereinafter referred to as "the fluid level monitoring system") at least comprises an annular fluid level monitoring device 1, a wellhead temporary plugging device 9 and a data processing device 8. Figure 1

[0036] In the present application, the annulus in the monitored annular fluid level height refers to the annular space formed between the wellbore (anti-overflow pipe) 6 and the drill pipe 5.

[0037] The wellhead temporary plugging device 9 is arranged at the upper end face of the wellbore 6. The wellhead temporary plugging device 9 is used to temporarily plug the upper port of the wellbore when drilling leakage occurs, so as to block the upward propagation path of the sound wave (i.e. the infrasound wave reflection signal described below). ​​

[0038] The annular space fluid level monitoring device 1 is arranged on the surface blowout manifold. The annular space fluid level monitoring device 1 is used to measure the detection signal representing the dynamic change characteristics of the annular space fluid level 7 depth by using the acoustic wave measurement technology in the case of closing the acoustic wave upward propagation path.

[0039] The data processing device 8 is connected with the annular space fluid level monitoring device 1. The data processing device 8 is used to obtain the dynamic annular space fluid level measurement value according to the detection signal from the annular space fluid level monitoring device 1. In this way, after the well leakage occurs, the accurate and continuous measurement of the annular space fluid level can still be realized by the temporary plugging effect of the wellhead temporary plugging device 9 in the case of not closing the surface blowout preventer 38.

[0040] Figure 2 The specific structure diagram of the system for monitoring the annular space fluid level in the drilling leakage state according to the embodiment of the present application. Figure 3 The application scene diagram of the wellhead temporary plugging device and the annular space fluid level monitoring device in the system for monitoring the annular space fluid level in the drilling leakage state according to the embodiment of the present application. As shown in Figure 2 The wellhead temporary plugging device 9 includes at least two rubber plugs 33 and a mounting bracket 34.

[0041] As shown in Figure 3 The at least two rubber plugs 33 are arranged on the end face of the upper port of the wellbore to realize the temporary plugging of the upper port of the wellbore. In one embodiment, the at least two rubber plugs 33 are arranged on the end face of the upper port of the wellbore through the mounting bracket 34. Specifically, the at least two rubber plugs 33 are preferably two rubber plugs 33a, 33b, as shown in Figure 4 .

[0042] In a specific embodiment, the two rubber plugs 33a, 33b are constructed as left and right two-limb clamping structures through a hinge 20, the hinge 20 is connected with the bracket 34 arranged below the two-limb clamping structure, and the bracket 34 is fixed on the wellbore 36. In this way, after the two wellhead rubber plugs 33 are closed on the left and right limbs, the closed two-limb structure can be supported by the mounting bracket 34 arranged below the two-limb structure to realize the plugging of the end face of the upper port of the wellbore 36. Therefore, the opening and closing state of the two rubber plugs 33a, 33b is controlled to be fixed on the upper port of the wellbore through the mounting bracket 34 to realize the temporary plugging of the wellbore port.

[0043] As shown in Figure 2 The annular space fluid level monitoring device 1 includes at least a subsonic wave generating device 31.

[0044] In one embodiment, the subsonic wave generating device 31 has a subsonic wave transceiver, a filter and a communication device.

[0045] The infrasound wave transceiving device is used to emit an infrasound wave signal to the annulus liquid surface and receive an infrasound wave reflection signal reflected by the infrasound wave signal at the annulus liquid surface, so as to utilize the infrasound wave reflection signal to represent the dynamic change characteristics of the annulus liquid surface. A filter is arranged between the infrasound wave transceiving device and the communication device. The filter is used to filter the received infrasound wave reflection signal to obtain an infrasound wave audio signal. The communication device is used to transmit the current infrasound wave audio signal representing the detection signal to the above-mentioned data processing device 8.

[0046] In addition, as shown in Figure 2 The annulus liquid surface monitoring device 1 further comprises a power lifting device 32. As shown in Figure 3 The power lifting device 32 is arranged at the front end of the infrasound wave transceiving device in the infrasound wave generating device 31. The power lifting device 32 is used to power lift the required emitted infrasound wave signal by providing a specified pressure energy.

[0047] In one embodiment, the specified pressure energy is achieved by a gas pressurization method. Specifically, the power lifting device 32 adopts a nitrogen gas pressurizer.

[0048] For the annulus liquid surface monitoring device 1, in addition to being provided with an infrasound wave generating device, a nitrogen gas pressurizer is additionally installed, and a wellhead rubber plug is additionally installed at the wellhead. First, by installing a two-piece rubber plug at the upper end position of the wellbore, the loss of infrasound wave energy is reduced, the external environmental interference is reduced, and the downward propagation of the infrasound wave along the annulus is ensured, achieving the same effect as closing the well packer. Further, the liquid surface monitoring system described in the present application also amplifies the infrasound wave pulse wave signal generated by the infrasound wave generating device installed on the well killing manifold by pressurizing the nitrogen gas to a specified pressure (for example, 3 MPa), achieving the purpose of reducing external interference.

[0049] The two rubber plugs 33 are moved to above the wellbore 36 by the bracket 34 installed at the upper end position of the wellbore, the rubber plug 33 is set and lowered, the sound wave propagation path is closed, the nitrogen gas pressurizer 32 amplifies the pulse wave generated by the infrasound wave generating device 31 installed on the well killing manifold through nitrogen gas pressurization, and the received infrasound wave reflection signal is transmitted to the acquisition control processing center 8 after being processed by the filter to obtain the infrasound wave audio signal, as shown in Figure 3 .

[0050] In this way, by loading the wellhead temporary plugging device 1 or jointly loading the wellhead temporary plugging device 1 and the power lifting device 32, the accurate and continuous measurement of the annulus liquid surface can be achieved without closing the ground well packer 38 under the condition of drilling well leakage.

[0051] In addition, in order to ensure that the annulus liquid surface is kept above the loss balance position to achieve the purpose of precise grouting, as shown in Figure 1As shown, the liquid level detection system also includes an inlet flow sensor 3 and an automatic grouting device 4.

[0052] The inlet flow sensor 3 is arranged on the tank body mud pipeline. The inlet flow sensor 3 is used to measure the grouting flow (i.e. the grouting pump displacement) in real time. The inlet flow sensor 3 installed on the grouting mud pipeline collects grouting flow data in real time and transmits the real-time collected grouting flow data to the data processing device 8 by using wireless communication technology.

[0053] At this time, the data processing device 8 is also used to calculate the ideal grouting amount corresponding to the loss balance position according to the real-time monitored dynamic annulus control liquid level measurement value, and calculate the real-time grouting amount required for the annulus liquid level to reach the position above the loss balance position according to the ideal grouting amount and the real-time grouting flow from the inlet flow sensor 3, so as to send the real-time grouting amount to the automatic grouting device 4.

[0054] The automatic grouting device 4 is used to control the internal grouting pump 2 according to the real-time grouting amount calculated in real time, so as to grout a specified amount of drilling fluid into the annulus, thereby ensuring that the amount of grouted drilling fluid is the least under the condition that the formation pressure and the wellbore liquid column pressure are kept in balance. Specifically, the automatic grouting device 4 uses the internal control module to automatically adjust the on-off of the internal grouting pump 2 according to the monitored real-time grouting amount, so as to realize accurate control of the grouting amount and the annulus liquid level.

[0055] In one embodiment, as shown in Figure 2 The data processing device 8 includes a balance position fitting unit, a loss rate function generation unit and a drilling fluid amount calculation unit.

[0056] The balance position fitting unit is used to linearly fit the annulus control liquid level measurement values at different times according to the real-time monitored dynamic annulus control liquid level measurement values, to obtain a liquid level height-time curve, and to identify the liquid level height position at the loss balance position based on the liquid level height-time curve. The loss rate function generation unit is used to calculate the loss rate at the corresponding time according to the annulus control liquid level measurement values at different times based on the annulus control cross-sectional area, to form a loss rate-liquid level height curve. Finally, the drilling fluid amount calculation unit is used to obtain the ideal grouting amount based on the liquid level position at the loss balance position identified by the balance position fitting unit and the loss rate-liquid level height curve obtained by the loss rate function generation unit.

[0057] In the embodiment of the present application, the ideal grouting amount refers to the amount of drilling fluid that needs to be grouted exactly when the annulus liquid level is above the position adjacent to the loss balance position.

[0058] As the change in annular fluid level decreases, the pressure of the fluid column in the wellbore continuously decreases until the leakage rate drops to 0, at which point the fluid level no longer changes, and the leakage reaches equilibrium. Therefore, in this embodiment of the invention, the equilibrium position fitting unit in the data processing device 8 records the measured fluid level (height) value of each time based on the dynamic annular fluid level monitoring device 1 and plots a curve, then fits the leakage equilibrium position function using Python.

[0059] like Figure 5 As shown, the values ​​of the annular liquid level positions H1, H2, H3... are continuously measured over time. The equilibrium position fitting unit in the data processing device 8 is used to fit an exponential function to plot a curve, forming a curve of liquid level height changing with time, and the leakage equilibrium position H0 is calculated.

[0060] In one embodiment, the expression for the curve of liquid level change over time is:

[0061] H(t) = a + b·e -t / c

[0062] Where t represents time, H(t) represents the annular liquid level at time t, and a, b, and c represent the fitting coefficients of the liquid level change curve over time.

[0063] Furthermore, the equilibrium position fitting unit is also used to perform derivative calculations on the expression of the liquid level height change curve over time, and to determine the liquid level position H0 under the leakage equilibrium position when the derivative value is zero.

[0064] The function representing the change in the annular liquid level over time is H(t) = a + b·e. -t / c Differentiating, we get: When the derivative is 0, the location H0 of the leakage balance point is predicted, thus completing the identification of the liquid level height at the leakage balance point.

[0065] The leakage rate function generation unit in the data processing device 8 will also calculate the leakage rate at different times based on the measured values ​​of the controlled liquid level and the cross-sectional area of ​​the controlled liquid level at different times, and then form a curve of leakage rate changing with liquid level height by fitting a logarithmic function.

[0066] The drilling fluid loss rate is calculated by multiplying the change in fluid level per unit time by the cross-sectional area of ​​the annulus by dH during the time interval dt. Where D represents the wellbore diameter and d represents the drill pipe diameter.

[0067] In this embodiment of the invention, the expression for the leakage rate as a function of liquid level height is:

[0068] V = A + B·lnH

[0069] Where V represents the leakage rate, and A and B represent the fitting coefficients of the leakage rate versus liquid level curve.

[0070] Furthermore, the drilling fluid volume calculation unit in the data processing device 8 will substitute the fluid level height data at the leakage balance position into the expression of the leakage rate versus fluid level height curve to obtain the leakage rate at the leakage balance position, thereby obtaining the calculation result of the ideal grouting volume.

[0071] Then, the drilling fluid volume calculation unit will calculate the real-time grouting volume required when the annular fluid level reaches the position above the leakage balance position based on the ideal grouting volume and the grouting flow rate (i.e., pump discharge) measured in real time by the inlet flow sensor 3. The real-time grouting volume will then be sent to the automatic grouting device 4 to achieve automatic grouting control.

[0072] In other words, based on the model relating annular fluid level height to leakage time, the leakage rate at corresponding time points is calculated, and a curve showing the relationship between leakage rate and annular fluid level height is plotted. Based on this, a curve fitting method is used to establish a dynamic function of leakage velocity, predicting the leakage rate at different fluid level heights, and then calculating the grouting volume per unit time. Thus, based on the leakage rate at the leakage equilibrium position, the current grouting volume per unit time, i.e., the ideal grouting volume, can be obtained. Subsequently, the real-time grouting volume calculated by the data processing device 8 is used to control the grouting pump 2 to inject drilling fluid into the annulus, ensuring that the annular fluid level is always maintained at an ideal position above and near the leakage equilibrium position. This guarantees that the amount of drilling fluid injected is minimized while maintaining a balance between formation pressure and wellbore fluid column pressure.

[0073] On the other hand, based on the above-described fluid level monitoring system, this embodiment of the invention also provides a method for monitoring the annular fluid level under drilling leakage conditions (also referred to as a "fluid level monitoring method"). This fluid level monitoring method utilizes the fluid level monitoring system described above.

[0074] Figure 6 This is a schematic diagram illustrating the steps of a method for monitoring the annular fluid level under drilling leakage conditions, according to an embodiment of this application. Figure 6 As shown, the liquid level monitoring method described in this embodiment of the invention includes the following steps:

[0075] Step S601: When drilling leakage occurs, a temporary wellhead plugging device is installed at the upper end of the wellbore to block the upward propagation path of sound waves.

[0076] Step S602: Using acoustic measurement technology, the annular fluid level monitoring device installed on the kill manifold is used to measure the detection signal that characterizes the dynamic changes of the annular fluid level.

[0077] Step S603: Use a data processing device to obtain the dynamic environmental control liquid level measurement value based on the detection signal.

[0078] This invention discloses a system and method for monitoring the annular fluid level under drilling leakage conditions. Under leakage conditions, this system and method can continuously monitor the annular fluid level without shutting down the wellhead, and accurately predict the leakage equilibrium position and corresponding leakage rate through fitting and logical operations. This allows for the calculation of the real-time controlled injection volume of drilling fluid under the current equilibrium position and leakage rate conditions, achieving the goal of reducing drilling fluid loss and waste while ensuring well control safety.

[0079] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

[0080] In the description of this invention, unless otherwise stated, "a plurality of" means two or more; the terms "upper," "lower," "left," "right," "inner," "outer," "front end," "rear end," "head," "tail," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention. Furthermore, the terms "first," "second," "third," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0081] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "connected" and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0082] It should be understood that the embodiments disclosed herein are not limited to the specific structures, processing steps, or materials disclosed herein, but should be extended to equivalent substitutions of these features as understood by those skilled in the art. It should also be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting.

[0083] The phrase "an embodiment" or "an embodiment" used in this specification means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the invention. Therefore, the phrase "an embodiment" or "an embodiment" appearing in various places throughout the specification does not necessarily refer to the same embodiment.

[0084] While the embodiments disclosed in this invention are as described above, the content is merely for the purpose of facilitating understanding of the invention and is not intended to limit the invention. Any person skilled in the art to which this invention pertains may make any modifications and changes in form and detail of the implementation without departing from the spirit and scope disclosed herein; however, the scope of patent protection of this invention shall still be determined by the scope defined in the appended claims.

Claims

1. A system for monitoring an annulus fluid level in a lost circulation condition in a wellbore, comprising: The system comprises: a wellhead temporary plugging device for plugging the upper end of the wellbore to block the sound wave transmission path when the wellbore is leaking; an annulus liquid level monitoring device arranged on the blowout control manifold for measuring a detection signal representing the dynamic change of the annulus liquid level by using the sound wave measurement technology; a data processing device for obtaining a dynamic annulus control liquid level measurement value according to the detection signal.

2. The system of claim 1, wherein, The wellhead temporary plugging device comprises: a mounting bracket; at least two rubber plugs arranged on the upper end of the wellbore by the mounting bracket to achieve temporary plugging of the upper end of the wellbore.

3. The system of claim 2, wherein, The at least two rubber plugs are two rubber plugs, wherein the two rubber plugs are configured as a two-leaf clamping structure by a hinge connected with the mounting bracket, and the mounting bracket is fixed on the wellbore.

4. The system of claim 2 or 3, wherein, The annulus liquid level monitoring device comprises: a subsonic wave transceiver device for transmitting a subsonic wave signal to the annulus control liquid level and receiving a subsonic wave reflection signal reflected by the subsonic wave signal at the annulus control liquid level; a filter for filtering the subsonic wave reflection signal to obtain a subsonic wave audio signal; a communication device for transmitting the subsonic wave audio signal to the data processing device.

5. The system of claim 4, wherein, The annulus liquid level monitoring device further comprises: a power lifting device arranged at the front end of the subsonic wave transceiver device for power lifting the required transmitted subsonic wave signal by providing a specified pressure energy, and the power lifting device uses a nitrogen booster.

6. The system of any one of claims 1-5, wherein, The system further comprises: an inlet flow sensor arranged on the tank mud pipeline for real-time measurement of the grouting flow; an automatic grouting device for controlling the internal grouting pump according to the real-time grouting amount to inject a specified amount of drilling fluid into the annulus, so as to ensure that the amount of injected drilling fluid is the least under the condition that the formation pressure and the wellbore liquid column pressure are kept in balance, wherein the data processing device is further configured to calculate an ideal grouting amount corresponding to the loss balance position according to the dynamic annulus control liquid level measurement value, and calculate the real-time grouting amount required for the annulus liquid level to reach the vicinity above the loss balance position according to the ideal grouting amount and the real-time grouting flow, and send the real-time grouting amount to the automatic grouting device.

7. The system of claim 6, wherein, The data processing device comprises: a balance position fitting unit for linear fitting of the annulus control liquid level measurement values at different times to obtain a liquid level height-time curve, and identifying the liquid level position at the loss balance position based on the liquid level height-time curve; a loss rate function generation unit for calculating the loss rate at the corresponding time based on the annulus control liquid level measurement values at different times according to the annulus control cross-sectional area, and forming a loss rate-liquid level height curve; a drilling fluid amount calculation unit for obtaining the ideal grouting amount by using the loss rate-liquid level height curve based on the liquid level position at the loss balance position.

8. The system of claim 7, wherein the balance position fitting unit is further configured to calculate the derivative of the expression of the liquid level height-time curve, and determine the liquid level position with a derivative value of zero as the liquid level position at the loss balance position.

9. The system according to claim 7 or 8, characterized in that, an expression of the liquid level change over time curve is: H(t) = a + b - e -t / c wherein t represents time, H(t) represents the annular liquid level at time t, a, b, c respectively represent fitting coefficients of the liquid level change over time curve; an expression of the loss rate change over liquid level curve is: V = A + B - ln H wherein V represents the loss rate, A, B respectively represent fitting coefficients of the loss rate change over liquid level curve.

10. A method for monitoring the annulus fluid level in a lost circulation condition in a wellbore, the method comprising: The method is implemented by the system according to any one of claims 1 to 9, wherein the method comprises: when drilling loss occurs, installing a wellhead temporary plugging device at the wellbore upper port to block the sound wave upward propagation path; using a sound wave measurement technology, using an annular liquid level monitoring device arranged on the blowout manifold to measure a detection signal representing the annular liquid level dynamic change characteristics; using a data processing device to obtain a dynamic annular control liquid level measurement value according to the detection signal.

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