Normal pressure wellhead drilling fluid annulus return flow monitoring device and method

Abstract

The invention discloses a normal-pressure wellhead drilling fluid annulus return flow monitoring device and method, and relates to the technical field of well drilling. An inlet of a bypass pipeline is connected with the side wall of a shaft, an inlet of a branch vertical pipe is connected with the bypass pipeline, an outlet of the branch vertical pipe is connected with an inlet of a downstream drain pipe, and the inlet of the branch vertical pipe is lower than the outlet of the branch vertical pipe; an outlet of the down drain pipe and an outlet of the bypass pipeline can be connected with an inlet of the riser manifold, an outlet of the riser manifold is communicated with a wellhead of a shaft, a main flow monitoring structure and a main valve are arranged on the branch riser, and a bypass flow monitoring structure and a bypass valve are arranged on the bypass pipeline. A return flow monitoring structure is arranged on the riser manifold, the liquid level monitoring structure is used for monitoring the liquid level in the shaft, and the main flow monitoring structure, the bypass flow monitoring structure, the return flow monitoring structure and the liquid level monitoring structure are all electrically connected with the data acquisition system. According to the invention, accurate flow measurement can be realized.

Description

Technical Field

[0001] This invention relates to the field of drilling technology, and in particular to a device and method for monitoring the return flow rate of drilling fluid annulus at atmospheric pressure wellheads. Background Technology

[0002] The frontiers of oil and gas resource exploration and development are expanding into complex formations characterized by high pressure and dense safety zones. These extreme operating conditions are highly susceptible to well leakage and overflow accidents. However, conventional monitoring methods suffer from drawbacks such as strong lag, weak anti-interference capabilities, and low detection sensitivity, failing to identify early-stage abnormal conditions at the wellhead and thus creating significant well control safety hazards. To obtain more real-time wellbore dynamic information and prevent delays, based on the drilling fluid inflow-outflow balance principle, monitoring points are moved to the return pipeline for flow detection, enabling timely feedback of dynamic changes within the wellbore.

[0003] Controlled pressure drilling achieves wellhead closure through a rotating blowout preventer and applies back pressure using a choke manifold, ensuring the return pipeline is pressurized and full, meeting the flow meter's requirement for a completely filled pipeline. However, in conventional drilling, the wellhead is open to the atmosphere, and the return pipeline becomes an "open channel" under atmospheric pressure, failing to meet flow meter measurement standards. Existing conventional drilling return pipeline flow measurement suffers from low accuracy and poor engineering adaptability, failing to meet the urgent need for early and accurate wellhead identification. Summary of the Invention

[0004] The purpose of this invention is to provide a device and method for monitoring the flow rate of drilling fluid annulus return at atmospheric pressure wellheads, so as to solve the problems existing in the prior art and achieve accurate flow rate measurement.

[0005] To achieve the above objectives, the present invention provides the following solution: This invention provides a device for monitoring the annular return flow of drilling fluid at atmospheric pressure wellheads, comprising: a main pipeline, a bypass pipeline, a riser manifold, a fluid level monitoring structure, and a data acquisition system. The main pipeline includes a branch riser and a downflow drain pipe. The inlet of the bypass pipeline is connected to the sidewall of the wellbore. The inlet of the branch riser is connected to the bypass pipeline, and the outlet of the branch riser is connected to the inlet of the downflow drain pipe. The inlet of the branch riser is lower than its outlet. The outlet of the downflow drain pipe and the outlet of the bypass pipeline are connected... All ports can be connected to the inlet of the riser manifold, the outlet of the riser manifold is connected to the wellhead of the wellbore, the branch riser is equipped with a main flow monitoring structure and a main valve, the bypass pipeline is equipped with a bypass flow monitoring structure and a bypass valve, the riser manifold is equipped with a return flow monitoring structure, the liquid level monitoring structure is used to monitor the liquid level in the wellbore, and the main flow monitoring structure, the bypass flow monitoring structure, the return flow monitoring structure and the liquid level monitoring structure are all electrically connected to the data acquisition system.

[0006] In some specific designs, the inlet of the downflow drain pipe is higher than the outlet of the downflow drain pipe.

[0007] In some specific implementations, the inlet of the bypass line is higher than the outlet of the bypass line.

[0008] In some specific designs, the highest point of the branch riser is not higher than the wellhead of the wellbore.

[0009] In some specific embodiments, the inner diameter of the branch riser is equal to the diameter of the bypass line; the inlet of the bypass line is lower than the outlet of the branch riser.

[0010] In some specific designs, a screening structure is also included, wherein the outlet of the downflow drain pipe and the outlet of the bypass pipe are both connected to the inlet of the screening structure, and the outlet of the screening structure is connected to the inlet of the riser manifold.

[0011] In some specific implementations, both the main valve and the bypass valve are electrically connected to the data acquisition system.

[0012] In some specific designs, a mud pump is also included, which is installed on the riser manifold.

[0013] In some specific designs, the diameter of the downflow drain pipe... d The value can be: ; In the formula, f Fanning friction factor; L This represents the length of the downflow drain pipe, in meters (m). Q The displacement of the mud pump is expressed in meters (m). 3 / min; g The acceleration due to gravity is m / s². 2 ; H Represents total head, in meters (m).

[0014] The present invention also provides a monitoring method using the aforementioned atmospheric pressure wellhead drilling fluid annulus return flow monitoring device, comprising: Step 1: Install downflow drain pipes of different diameters according to the flow rate of different openings; Step 2: Close the bypass valve, open the main valve, monitor the flow rate of the main pipeline and the riser manifold, and monitor the liquid level in the wellbore. When the flow rate of the riser manifold is less than the preset value, there are two possibilities: 1. If the fluid level in the wellbore continues to drop, it is determined that there is leakage in the wellbore. After dealing with the leakage, continue circulating drilling and return to step 2. 2. If the fluid level in the wellbore continues to rise, it is determined that the main pipeline is blocked. Close the main valve and open the bypass valve until the flow rate in the bypass pipeline is monitored to be stable. When the flow rate of the main pipeline continues to increase and the liquid level in the wellbore continues to rise, it is determined that the wellbore has overflowed. After shutting down the well and killing the well, drilling continues and the process returns to step two. Step 3: Determine if the opening needs to be changed: If you do not change the opening sequence, return to step two; If the opening sequence is changed, return to step one.

[0015] The present invention achieves the following technical effects compared to the prior art: This invention configures the main pipeline as branch risers and downflow drain pipes, with the inlet of the branch riser lower than its outlet. This allows the branch risers to achieve a better full-pipe state, ensuring the accuracy of the main flow monitoring structure. Furthermore, by installing a main valve on the branch riser and a bypass valve on the bypass pipeline, sand can be discharged when the branch riser is blocked by "closing the main valve and opening the bypass valve," fundamentally eliminating the hidden dangers of solid phase deposition and blockage in the pipeline. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1 This is a schematic diagram of a normal pressure wellhead drilling fluid annulus return flow monitoring device in some embodiments of the present invention; Figure 2 This is a schematic diagram of the main pipeline structure in some embodiments of the present invention; Figure 3 This is a schematic diagram of the liquid level monitoring structure in some embodiments of the present invention; Figure 4 This is a flowchart of the monitoring method in some embodiments of the present invention; In the diagram: 1-Main pipeline, 2-Bypass pipeline, 3-Main valve, 4-Bypass valve, 5-Return flow monitoring structure, 6-Main flow monitoring structure, 7-Bypass flow monitoring structure, 8-Liquid level monitoring structure, 9-Data transmission line, 10-Data acquisition and analysis terminal, 11-Alarm system, 12-Screwing structure, 13-Mud tank, 14-Mud pump, 15-Riser manifold, 16-Mud shield, 17-Overflow preventer, 18-Annular blowout preventer, 19-Gate blowout preventer, 20-Four-way valve, 21-Branch riser, 22-Downflow drain pipe. Detailed Implementation

[0018] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0019] The purpose of this invention is to provide a device and method for monitoring the flow rate of drilling fluid annulus return at atmospheric pressure wellheads, so as to solve the problems existing in the prior art and achieve accurate flow rate measurement.

[0020] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0021] like Figures 1 to 3 As shown, this embodiment provides a monitoring device for the return flow rate of drilling fluid annulus at atmospheric pressure wellheads, including: a main pipeline 1, a bypass pipeline 2, a riser manifold 15, a fluid level monitoring structure 8, and a data acquisition system. The main pipeline 1 includes a branch riser 21 and a downflow drain pipe 22. The inlet of the bypass pipeline 2 is connected to the sidewall of the wellbore. The inlet of the branch riser 21 is connected to the bypass pipeline 2, and the outlet of the branch riser 21 is connected to the inlet of the downflow drain pipe 22. The inlet of the branch riser 21 is lower than the outlet of the branch riser 21, and the outlet of the downflow drain pipe 22 is lower than the outlet of the branch riser 21. The outlets of bypass lines 2 can all be connected to the inlets of riser manifold 15. The outlets of riser manifold 15 are connected to the wellhead of the wellbore. A main flow monitoring structure 6 and a main valve 3 are installed on branch riser 21. A bypass flow monitoring structure 7 and a bypass valve 4 are installed on bypass lines 2. A return flow monitoring structure 5 is installed on riser manifold 15. A level monitoring structure 8 is used to monitor the level of the fluid in the wellbore. The main flow monitoring structure 6, bypass flow monitoring structure 7, return flow monitoring structure 5, and level monitoring structure 8 are all electrically connected to the data acquisition system. The branch riser 21 in this embodiment allows drilling fluid to fully fill the branch riser 21, eliminating air gaps within the branch riser 21 and improving flow measurement accuracy. In this embodiment, by setting the main pipeline 1 as a branch riser 21 and a downflow drain pipe 22, and setting the inlet of the branch riser 21 to be lower than the outlet, the branch riser 21 can achieve a better full pipe state, ensuring the accuracy of the main flow monitoring structure 6 measurement. Furthermore, a main valve 3 is set on the branch riser 21 and a bypass valve 4 is set on the bypass pipeline 2. By "closing the main valve 3 and opening the bypass valve 4", sand can be discharged when the branch riser 21 is blocked, fundamentally eliminating the hidden dangers of solid phase deposition and blockage in the pipeline.

[0022] In some specific embodiments, an overflow prevention pipe 17 is provided inside the wellbore, and a liquid level monitoring structure 8 is installed on the overflow prevention pipe 17. The liquid level monitoring structure 8 is located below the wellhead and is an ultrasonic liquid level sensor.

[0023] Existing conventional level gauges are typically connected to the four-way valve 20, which limits their ability to monitor only leakage conditions. When normal drilling or overflow causes the liquid level to rise above the four-way valve 20, the level gauge will fail. In contrast, this embodiment deploys the level monitoring structure 8 on the overflow prevention pipe 17. By optimizing the installation position, the ability to identify drilling conditions is significantly improved. During operation, the device emits ultrasonic waves downwards. These waves are reflected upon contact with the liquid surface. The system records the time difference between the emission and reception of the ultrasonic waves and calculates the distance between the device and the liquid surface by combining this with the ultrasonic velocity. This effectively overcomes the blind spots of traditional detection methods and achieves accurate measurement of the liquid level across the entire range.

[0024] In some specific embodiments, the branch riser 21 is preferably a riser pipe.

[0025] In some specific embodiments, the inlet of the downflow drain pipe 22 is higher than the outlet of the downflow drain pipe 22, and the downflow drain pipe 22 is a downflow pipeline.

[0026] In some specific embodiments, the bypass line 2 can be the original return line of drilling fluid, and the inlet of the bypass line 2 is higher than the outlet of the bypass line 2, usually consistent with the size of the technical casing.

[0027] In some specific embodiments, the highest position of the branch riser 21 is not higher than the wellhead of the wellbore.

[0028] In some specific embodiments, the inner diameter of the branch riser 21 is equal to the diameter of the bypass line 2, and the inlet of the bypass line 2 is lower than the outlet of the branch riser 21. The length of the branch riser 21 is ten times its diameter to meet the requirements of the flow meter.

[0029] In some specific embodiments, the main valve 3 is located near the inlet of the branch riser 21, the bypass valve 4 is located near the junction of the bypass line 2 and the branch riser 21, and is located downstream of the junction of the bypass line 2 and the branch riser 21, and the bypass flow monitoring structure 7 is located between the bypass valve 4 and the outlet of the bypass line 2.

[0030] In some specific embodiments, both the main valve 3 and the bypass valve 4 are electrically connected to the data acquisition system.

[0031] In some specific embodiments, a screening structure 12 is also included. The screening structure 12 is used to filter solid particles in the drilling fluid. The screening structure 12 is preferably a vibrating screen. The outlet of the downflow drain pipe 22 and the outlet of the bypass line 2 are both connected to the inlet of the screening structure 12. The outlet of the screening structure 12 is connected to the inlet of the riser manifold 15.

[0032] In some specific embodiments, a mud pump 14 is also included, which is installed on the riser manifold 15. The return flow monitoring structure 5 is installed on the riser manifold 15 between the mud pump 14 and the wellhead.

[0033] In some specific embodiments, a mud pit 13 is also included, located between the screening structure 12 and the mud pump 14. The fluid is filtered by the screening structure 12 to remove the solid phase, and the mud enters the mud pit 13. Under the action of the mud pump 14, it returns to the wellbore through the riser manifold 15 to continue the drilling cycle.

[0034] In some specific embodiments, a mud shield 16, an annular blowout preventer 18, a gate blowout preventer 19, and a four-way valve 20 are also provided. The mud shield 16 mainly prevents mud from falling onto the ground and polluting the site environment. The overflow pipe 17, the annular blowout preventer 18, the gate blowout preventer 19, and the four-way valve 20 are well control devices.

[0035] In some specific embodiments, the diameter of the downflow drain pipe 22 is adjusted according to the flow rate at different opening times to ensure back pressure formation, so that the branch riser 21 reaches a full pipe state and to prevent fluid from overflowing from the anti-overflow pipe 17. The diameter of the downflow drain pipe 22 d The value can be: ; In the formula, f Fanning friction factor; L This represents the length of the downflow drain pipe 22, in meters (m). Q The displacement of mud pump 14 is expressed in meters (m³). 3 / min; g The acceleration due to gravity is m / s². 2 ; H Represents total head, in meters (m).

[0036] The specific process for determining the diameter of the downflow drain pipe 22 is as follows: The diameter of the downflow drain pipe 22 needs to be changed according to the discharge volume of different openings. The purpose is to reduce the flow rate of drilling fluid return so that the branch riser 21 can reach a better full pipe state and prevent the wellbore fluid level from exceeding the fluid level monitoring structure 8 and flowing out of the wellhead.

[0037] When considering "preventing drilling fluid from overflowing the wellbore after the level exceeds the level monitoring structure 8": According to Bernoulli's equation, the total head equals the sum of the inlet velocity head of bypass line 2, local resistance, and friction loss along the route. H as follows: ; In the formula, H Total head, in meters (m); f Fanning friction factor; L This represents the length of the downflow drain pipe 22, in meters (m). v Drilling fluid flow rate, in m / s; d The diameter of the downflow drain pipe 22 is in meters (m). g Acceleration due to gravity, unit: m / s² 2 ; This represents the local resistance term.

[0038] Since drilling involves a constant flow rate, the flow rate and velocity are substituted into the formula, and the local pressure term is ignored. To prevent drilling fluid from overflowing from the wellhead, the following equation must be satisfied: ; In the formula, Q The displacement of mud pump 14 is expressed in meters (m³). 3 / min.

[0039] Therefore, to prevent drilling fluid from overflowing the wellbore after exceeding the level monitoring structure 8, the diameter of the downflow drain pipe 22 must meet the following formula: ; Among them, Fanning friction factor f Will be passed through Reynolds number Re Make a judgment: Reynolds number Re Satisfy the following formula: ; In the formula, Drilling fluid density, unit: kg / m³ 3 ; v Drilling fluid flow rate, in m / s; d The diameter of the downflow drain pipe 22 is in meters (m). The value represents the drilling fluid viscosity, expressed in mPa·s.

[0040] when Re When the coefficient is less than 2300, the flow is laminar, and the Fanning friction factor is... f The formula is as follows: ; when Re When the value is greater than 4000, the flow is turbulent, and the Fanning friction factor is... f The formula is as follows: ; In the formula, The absolute roughness of the wall of the downflow drain pipe 22 is expressed in meters (m). d The diameter of the downflow drain pipe 22 is in meters (m). When 2300≤ Re ≤4000, this is considered excessive flow, Fanning friction factor. f The formula is as follows: ; In the formula, f 1 Representing the Reynolds number Re The Vanninger coefficient at 2300; f 2 Representing the Reynolds number Re The Fanning friction coefficient at 4000; The absolute roughness of the wall of the downflow drain pipe 22 is expressed in meters (m).

[0041] When considering "to make branch riser 21 full and improve drilling fluid measurement accuracy, the downflow drain pipe 22 needs to be in a non-full state to avoid negative pressure caused by siphoning and to pump the liquid from branch riser 21": In order for the fluid flow in branch riser 21 to slow down and for the air bubbles to rise, the Froude number needs to be adjusted. Fr The value is less than the critical Froude number (0.35), which translates to a constraint on the diameter of the downflow drain pipe 22. (Froude number) Fr The formula is as follows: ; In the formula, v Drilling fluid flow rate, in m / s; d The diameter of the downflow drain pipe 22 is in meters (m). g Acceleration due to gravity, unit: m / s² 2 ; Converting the velocity in the formula to flow rate, we get: ; In the formula, Q The displacement of mud pump 14 is expressed in meters (m³). 3 / min; thus, we obtain: .

[0042] Therefore, the diameter of the downflow drain pipe 22 must meet the following requirements. Normally, when a and bWhen the dimensions are all smaller than the diameter of the outer sleeve, the outer sleeve is cut for installation to facilitate on-site installation; however, if max(a,b) is greater than the diameter of the outer sleeve, a pipeline with the same dimensions as max(a,b) is selected.

[0043] In some specific embodiments, the main flow monitoring structure 6, the bypass flow monitoring structure 7, and the return flow monitoring structure 5 are all electromagnetic flow meters.

[0044] In some specific embodiments, the data acquisition system includes a data transmission line 9, a data acquisition and analysis terminal 10, and an alarm system 11. The data transmission line 9 is used to interconnect the main flow monitoring structure 6, the bypass flow monitoring structure 7, the return flow monitoring structure 5, and the liquid level monitoring structure 8 with the data acquisition and analysis terminal 10. The data acquisition and analysis terminal 10 is responsible for receiving and processing flow and wellbore liquid level data, analyzing abnormal operating conditions based on real-time monitoring results, and then triggering the alarm system 11.

[0045] This embodiment includes a main pipeline 1 and a bypass pipeline 2, along with a main valve 3 and a bypass valve 4. When the main valve 3 is opened and the bypass valve 4 is closed, the branch riser 21 and the downflow drain pipe 22 prevent siphoning, ensuring the branch riser 21 is fully filled with drilling fluid. This eliminates the influence of air gaps or insufficient fluid saturation on the measurement, significantly improving the flow meter's accuracy.

[0046] Simultaneously, a fluid level monitoring structure 8 is installed at the wellhead. This structure, together with the main flow monitoring structure 6, forms a linked detection mechanism, enabling rapid and accurate assessment of critical drilling conditions (such as overflow, leakage, and sand blockage), providing a reliable basis for the validity screening of data records. Furthermore, if sand blockage is detected, the valve status can be switched immediately—closing the main valve 3 and opening the bypass valve 4—using the drilling fluid circulation power to discharge accumulated sand from the branch riser 21, quickly restoring normal drilling fluid circulation and ensuring operational continuity.

[0047] Example 2 like Figure 4 As shown, this embodiment provides a monitoring method using the atmospheric pressure wellhead drilling fluid annulus return flow monitoring device of Embodiment 1, including: Step 1: Start drilling. Based on the flow rate of different drilling sessions and the different strokes / displacements of the pump, install downflow drain pipes 22 with different diameters. Step 2: Close the bypass valve 4 and open the main valve 3. Monitor the flow rate of the main pipeline 1 (i.e., the overall outlet flow rate) through the main flow monitoring structure 6, and monitor the flow rate of the riser manifold 15 (i.e., the overall inlet flow rate) through the return flow monitoring structure 5. Also monitor the liquid level in the wellbore. After the on-site construction is determined, drilling is carried out at a fixed discharge rate, and the flow rate remains almost constant. If the flow rate changes, the following identification is required: When the return flow monitoring structure 5 detects that the flow rate of riser manifold 15 (i.e., the overall inlet flow rate) is less than the preset value, there are two possibilities: 1. If the fluid level in the wellbore continues to drop (even below the inlet of bypass line 2), it is determined that the wellbore is leaking and cannot flow back to the surface normally. Mud pump 14 stops working, and after the leak is repaired (repaired), the drilling continues and returns to step 2. 2. If the liquid level in the wellbore continues to rise (above the highest point of branch riser 21, or even close to the wellhead), it is determined that the main pipeline 1 is blocked. Close the main valve 3 and open the bypass valve 4 to perform sand removal. Observe the reading of the bypass flow monitoring structure 7 as it continuously increases until it remains unchanged, that is, the flow of bypass pipeline 2 is stable, and the main pipeline 1 has returned to normal. When the flow rate of the main pipeline 1 (i.e. the overall outlet flow rate) continues to increase and the liquid level in the wellbore continues to rise (even approaching the wellhead), it is determined that the wellbore has overflowed. Mud pump 14 stops working, and drilling continues after shutting in and killing the well, returning to step two. Step 3: Determine if the opening needs to be changed: If you do not change the opening sequence, return to step two; If the opening sequence is changed, return to step one.

[0048] In the description of this invention, it should be understood that the terms "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," 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 this invention, 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 this 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. Thus, a feature defined with "first," "second," etc., may explicitly or implicitly include one or more of that feature. In the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0049] In the description of this invention, unless otherwise expressly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to fixed connections, detachable connections, or integral connections; they can refer to mechanical connections or electrical connections; they can refer to direct connections or indirect connections through an intermediate medium; and they can refer to the internal communication between two components. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.

[0050] If this invention discloses or relates to components or structural parts that are fixedly connected to each other, then, unless otherwise stated, a fixed connection can be understood as: a detachable fixed connection (e.g., using bolts or screws) or a non-detachable fixed connection (e.g., riveting, welding). Of course, a fixed connection can also be replaced by an integral structure (e.g., manufactured in one piece using a casting process) (except where it is obviously impossible to use an integral molding process).

[0051] In addition, unless otherwise stated, the terms used in any of the technical solutions disclosed in this invention to indicate positional relationships or shapes include states or shapes that are similar to, close to, or approximate with those states or shapes.

[0052] Any component provided by this invention can be assembled from multiple individual components or can be a single component manufactured by a one-piece molding process.

[0053] It should be noted that the structures, proportions, sizes, etc., depicted in the accompanying drawings of this specification are only used to complement the content disclosed in the specification, so as to enable those skilled in the art to understand and read them, and are not intended to limit the conditions under which the present invention can be implemented. Therefore, they have no substantial technical significance. Any modifications to the structure, changes in the proportions, or adjustments to the size, without affecting the effects and objectives that the present invention can produce, should still fall within the scope of the technical content disclosed in the present invention.

[0054] It should also be noted that in the embodiments of this application, the same reference numerals are used to denote the same component or the same part.

[0055] Any adaptive changes made according to actual needs are within the scope of protection of this invention.

[0056] Specific examples have been used to illustrate the principles and implementation methods of this invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of this invention. Furthermore, those skilled in the art will recognize that, based on the ideas of this invention, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of this invention.

Claims

1. A monitoring device for the return flow rate of drilling fluid annulus at atmospheric pressure wellhead, characterized in that: include: The system includes a main pipeline, a bypass pipeline, a riser manifold, a liquid level monitoring structure, and a data acquisition system. The main pipeline includes a branch riser and a downflow drain pipe. The inlet of the bypass pipeline is connected to the side wall of the wellbore. The inlet of the branch riser is connected to the bypass pipeline, and the outlet of the branch riser is connected to the inlet of the downflow drain pipe. The inlet of the branch riser is lower than its outlet. The outlets of the downflow drain pipe and the bypass pipeline can both be connected to the inlet of the riser manifold. The outlet of the riser manifold is connected to the wellhead of the wellbore. The branch riser is equipped with a main flow monitoring structure and a main valve. The bypass pipeline is equipped with a bypass flow monitoring structure and a bypass valve. The riser manifold is equipped with a return flow monitoring structure. The liquid level monitoring structure is used to monitor the liquid level in the wellbore. The main flow monitoring structure, the bypass flow monitoring structure, the return flow monitoring structure, and the liquid level monitoring structure are all electrically connected to the data acquisition system.

2. The atmospheric pressure wellhead drilling fluid annulus return flow monitoring device according to claim 1, characterized in that: The inlet of the downflow drain pipe is higher than the outlet of the downflow drain pipe.

3. The atmospheric pressure wellhead drilling fluid annulus return flow monitoring device according to claim 1, characterized in that: The inlet of the bypass line is higher than the outlet of the bypass line.

4. The atmospheric pressure wellhead drilling fluid annulus return flow monitoring device according to claim 1, characterized in that: The highest point of the branch riser is not higher than the wellhead of the wellbore.

5. The atmospheric pressure wellhead drilling fluid annulus return flow monitoring device according to claim 1, characterized in that: The inner diameter of the branch riser is equal to the diameter of the bypass line; the inlet of the bypass line is lower than the outlet of the branch riser.

6. The atmospheric pressure wellhead drilling fluid annulus return flow monitoring device according to claim 1, characterized in that: It also includes a screening structure, wherein the outlet of the downflow drain pipe and the outlet of the bypass pipeline are both connected to the inlet of the screening structure, and the outlet of the screening structure is connected to the inlet of the riser manifold.

7. The atmospheric pressure wellhead drilling fluid annulus return flow monitoring device according to claim 1, characterized in that: Both the main valve and the bypass valve are electrically connected to the data acquisition system.

8. The atmospheric pressure wellhead drilling fluid annulus return flow monitoring device according to claim 1, characterized in that: It also includes mud pumps, all of which are installed on the riser manifold.

9. The atmospheric pressure wellhead drilling fluid annulus return flow monitoring device according to claim 8, characterized in that: The diameter of the downflow drain pipe d The value can be: ; In the formula, f Fanning friction factor; L This represents the length of the downflow drain pipe, in meters (m). Q The displacement of the mud pump is expressed in meters (m). 3 / min; g The acceleration due to gravity is m / s². 2 ; H Represents total head, in meters (m).

10. A monitoring method using the atmospheric pressure wellhead drilling fluid annulus return flow monitoring device as described in any one of claims 1-9, characterized in that: include: Step 1: Install downflow drain pipes of different diameters according to the flow rate of different openings; Step 2: Close the bypass valve, open the main valve, monitor the flow rate of the main pipeline and the riser manifold, and monitor the liquid level in the wellbore. When the flow rate of the riser manifold is less than the preset value, there are two possibilities:

1. If the fluid level in the wellbore continues to drop, it is determined that there is leakage in the wellbore. After dealing with the leakage, continue circulating drilling and return to step 2.

2. If the fluid level in the wellbore continues to rise, it is determined that the main pipeline is blocked. Close the main valve and open the bypass valve until the flow rate in the bypass pipeline is monitored to be stable. When the flow rate of the main pipeline continues to increase and the liquid level in the wellbore continues to rise, it is determined that the wellbore has overflowed. After shutting down the well and killing the well, drilling continues and the process returns to step two. Step 3: Determine if the opening needs to be changed: If you do not change the opening sequence, return to step two; If the opening sequence is changed, return to step one.

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