A borehole water storage plug device for use in wellbore geophysical prospecting

Abstract

The utility model belongs to geophysical exploration technical field especially, a kind of borehole water storage plug device for well geophysical prospecting, it is applicable to low water level well interseismic tomography disposable downhole water storage plug device.The device realizes temporary water storage by passive expansion structure, ensure the effective coupling of seismic source and detector, it is applicable to the operation scene of borehole aperture 89mm or more, downhole equipment diameter 63mm.It can also be used for single-hole method wave velocity test in water shortage area.The utility model provides a kind of disposable and portable downhole water storage plug, by CO2 driving air bag from expansion, realize temporary water storage without recovery.Single set cost is lower, complete deployment within 5 minutes, after expansion is completed, it can be filled with water and start operation, especially suitable for water shortage area, groundwater level deep well interseismic exploration.The utility model realizes the artificial well bottom rapid deployment and sealing of borehole local part by mechanical expansion structure, realizes the water storage of the part above expansion structure, provides reliable well fluid coupling condition for detection.

Description

Technical Field

[0001] This utility model relates to the field of geophysical exploration, and in particular to a borehole water storage plug device for well geophysical exploration. Background Technology

[0002] Inter-well seismic tomography originated in the field of geophysical exploration, initially primarily used for oil and gas resource exploration and crustal structure research. Traditional seismic exploration methods (such as surface seismic surveys) are limited by the influence of low-velocity zones near the surface, resulting in low resolution. Furthermore, they rely on artificial seismic sources (such as explosives or controlled seismic sources), leading to high costs and significant environmental impacts. With the increasing demand for engineering geology, this technology has gradually penetrated the engineering field, used to detect underground anomalies (such as karst, cavities, and fault zones), and its high precision has led to its widespread application in civil engineering, water conservancy, and hydropower.

[0003] In recent years, the technology has been further optimized. For example, natural background noise (such as electric sparks, ground vibrations, ocean waves, etc.) has been combined as a seismic source, which has reduced the dependence on artificial seismic sources and solved the problems of seismic source disturbance and environmental protection in urban environments.

[0004] However, since electric spark downhole seismic sources require water as the voltage breakdown medium, and hydrophones (downhole detectors) also require water as a coupling agent for vibration reception, the on-site data acquisition for inter-well seismic tomography is highly dependent on the natural water level within the borehole. However, in arid or low-water areas, these requirements are often difficult to meet, hindering effective data acquisition and becoming a significant factor limiting the application of electric spark downhole seismic source detection methods.

[0005] Therefore, existing electric spark downhole seismic source detection methods have the drawback of being unable to effectively collect data in arid or low-water-level areas. Utility Model Content

[0006] The purpose of this invention is to provide a borehole water storage plug device for well geophysical exploration, which can solve the technical problem that existing electric spark downhole seismic source detection methods cannot effectively collect data in arid or low-water areas.

[0007] To achieve the above objectives, this utility model provides the following technical solution: This utility model discloses a borehole water storage plug device for well geophysical exploration, comprising a hollow capillary tube, a piston, a membrane-breaking needle, a water storage plug, an air tank, and an air bladder. The end of the hollow capillary tube is threadedly connected to the water storage plug. The piston and the membrane-breaking needle are both arranged inside the hollow capillary tube, with one end of the membrane-breaking needle connected to the piston and the tip of the membrane-breaking needle pointing towards the water storage plug. The air tank is arranged below the water storage plug and is sealed by the water storage plug. The air bladder surrounds the air tank. (After the water-storage plug is delivered to the designated depth through a series of interconnected hollow tubes, high-pressure liquid is pumped into the hollow tubes. The piston pushes the rupture needle to puncture the water-storage plug and the gas tank in sequence, connecting the gas tank and the air bladder. The gas inside the gas tank expands and inflates the air bladder, which, along with the three-stage rubber claws, supports the well wall, thus fixing the device inside the well and completing the deployment of the water-storage plug device within the well. Then, the hollow tubes are rotated in the opposite direction to remove them, and water is pumped into the well until it reaches the surface. The electric spark source and hydrophone are then lowered into the well to begin the inter-well seismic tomography detection work.) As a preferred embodiment, a limiting shear pin is also included, which is arranged at the connection between the hollow capillary tube and the water storage plug. (By triggering the limiting shear pin, the hollow capillary tube is unlocked from the water storage plug, the piston pushes the membrane-breaking pin to puncture the water storage plug and the gas tank, and the gas inside the gas tank expands out, inflating the air bladder.) As a preferred embodiment, a locking pin is also included, which is located at the connection between the piston and the inner wall of the hollow capillary. (The locking pin is used to lock the piston. When high-pressure liquid is pumped into the hollow capillary, when the pressure reaches a threshold, the locking pin of the piston is sheared off, the piston pushes the rupture pin to puncture the gas tank, and the composite gasbag begins to inflate and anchor.) As a preferred embodiment, the system also includes stepped rubber claws, which are positioned outside the airbag and expand to form an annular sealing surface with the well wall as the airbag inflates. (The rubber claws deform under compression to fill microscopic gaps in the well wall, achieving a composite seal.) As a preferred embodiment, the hollow tube is formed by connecting multiple tube sections sequentially through threaded joints.

[0008] Furthermore, the connection joint between the end of the hollow capillary tube and the water storage plug adopts a left-hand thread, while the connection joints of each section of the hollow capillary tube in the middle adopt a right-hand thread. (This design ensures that when the operator rotates the hollow capillary tube clockwise on the ground to separate the downhole water storage plug, gas tank, and other devices, the applied torque will simultaneously tighten all intermediate connection joints, effectively preventing the intermediate tube from accidentally loosening due to torque transmission during the separation process, thus improving the reliability and safety of the operation.) As a preferred embodiment, the gas tank is filled with liquid CO2, and the gas tank opening is sealed with a thin metal membrane. After the membrane is punctured by a puncturing needle, the CO2 gas is released and drives the gas bag to expand.

[0009] As a preferred embodiment, the stepped rubber claw is made of butyl rubber and coated with a silicone-based adhesive layer on the outermost layer, which is used to fill the micro-gaps in the well wall after expansion to achieve a composite seal.

[0010] The beneficial effects of this utility model are: This invention provides a disposable downhole water plug device suitable for seismic tomography in low-water-level wells. The device achieves temporary water storage through a passive expansion structure, ensuring effective coupling between the seismic source and the geophone. It is suitable for operation scenarios with borehole diameters of 89mm and above and downhole equipment diameters of 63mm. It can also be used for single-hole wave velocity testing in water-scarce areas. This invention provides a low-cost, disposable, and portable downhole water plug that uses CO2 to drive an airbag to expand from a diameter of Φ63mm to a diameter of Φ89mm~130mm, achieving temporary water storage without the need for recovery. The cost per unit is low, deployment can be completed within 5 minutes, and water can be added immediately after expansion to begin operation. It is particularly suitable for seismic exploration in water-scarce areas and where the groundwater level is deep. This invention uses a mechanical expansion structure to achieve rapid deployment and sealing of a local artificial well bottom in the borehole, achieving water storage above the expansion structure and providing reliable well fluid coupling conditions for detection.

[0011] (1) Temporary water storage enables reliable coupling: After the airbag expands, it forms a sealing surface with the stepped rubber claws to prevent water leakage. The device forms a temporary water storage area above the expansion structure, providing a well fluid coupling medium for the electric spark source and hydrophone, ensuring the efficiency of seismic wave transmission. This effect is a direct result of the airbag expansion and sealing structure, and is suitable for scenarios with a borehole diameter of 89mm or more, improving coupling reliability (water level fluctuation is less than 8cm for 72 hours).

[0012] (2) Reliable trigger separation: The composite mechanical separation scheme of "left-hand thread + shear pin" is adopted, and the separation action is clear and reliable, ensuring 100% safe recovery of the thin tube. It avoids the uncertainty of mechanical impact or hydrostatic pressure triggering. This effect is an inevitable result of the pressure control mechanism and is applicable to various CO2 gas cylinder specifications.

[0013] (3) Simple operation: Ground personnel only need to follow three steps: "pressurize - confirm - rotate and lift". It is simple and intuitive, and does not require complicated judgment. The deployment time for a single deployment is ≤5 minutes. This effect is directly brought about by the triggering mechanism and the separation design, which reduces manual intervention and operation time and meets the efficiency requirements of field exploration.

[0014] (4) Low cost: Only the downhole equipment is a disposable item, while the core thin tube and pump system can be reused, resulting in extremely low cost per operation.

[0015] (5) High triggering force: The force provided by the hydraulic triggering method is much greater than that of mechanical impact or hydrostatic pressure, which can reliably puncture CO2 gas cylinders of various specifications. The device sealing pressure is ≥0.6MPa, which can withstand hydrostatic pressure and ensure stable operation in boreholes with a depth ≤50m.

[0016] This invention can solve the technical problem that existing electric spark downhole seismic source detection methods cannot effectively collect data in arid or low-water-level areas. Attached Figure Description

[0017] Figure 1 This is a schematic plan view of the entire utility model; Figure 2 This is a plan view of the hollow capillary tube after it has been removed. Figure 3 A schematic diagram showing the threaded connection between the end of the hollow capillary tube and the water storage plug; Figure 4 This is a schematic diagram of the threaded connection in the middle section of a hollow capillary tube. Figure 5 This is a schematic diagram showing the connection between the stepped rubber claw and the airbag. Explanation of reference numerals in the attached figures: Hollow capillary tube 1 (upper pipe section 11, lower pipe section 12), piston 2, film breaking pin 3, water storage plug 4, air tank 5, air bladder 6, stepped rubber claw 7, wellhead 8, well wall 9, well bottom 10, air bladder before expansion state A, air bladder after expansion state B. Detailed Implementation

[0018] To make the technical problem solved by this utility model, the technical solution adopted, and the technical effect achieved clearer, the technical solution of this utility model will be further described below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are only for explaining this utility model and not for limiting it. Furthermore, it should be noted that, for ease of description, only the parts related to this utility model are shown in the accompanying drawings, not all of them.

[0019] In the description of this utility model, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to fixed connections or detachable connections; mechanical connections or electrical connections; direct connections or indirect connections through an intermediate medium; and internal connections between two components. Those skilled in the art can understand the specific meaning of the above terms in this utility model based on the specific circumstances.

[0020] This invention belongs to the field of geophysical exploration technology, specifically a disposable downhole water plug device suitable for seismic tomography in low-water-level wells. This device achieves temporary water storage through a passive expansion structure, ensuring effective coupling between the seismic source and the geophone. It is suitable for operation scenarios with borehole diameters of 89mm and above and downhole equipment diameters of 63mm. It can also be used for single-hole wave velocity testing in water-scarce areas. This invention provides a low-cost, disposable downhole water plug that uses CO2 to drive an airbag to expand from Φ63mm to Φ89mm~130mm, achieving temporary water storage without the need for recovery. The cost per unit is low, deployment can be completed within 5 minutes, and water can be injected immediately after expansion to begin operation. It is particularly suitable for seismic exploration in water-scarce areas and where the groundwater level is deep. Addressing the problems of the prior art, this invention proposes a low-cost, disposable, and portable water plug that achieves rapid deployment and sealing of a localized artificial well bottom through a mechanical expansion structure, storing water above the expansion structure and providing reliable well fluid coupling conditions for detection.

[0021] This utility model provides a borehole water storage plug device for well geophysical exploration, including a hollow capillary tube 1, a piston 2, a membrane-breaking pin 3, a water storage plug 4, an air tank 5, an air bladder 6, a limiting shear pin, a locking pin, and a stepped rubber claw 7. The end of the hollow capillary tube 1 is connected to the water storage plug 4 by a thread. The piston 2 and the membrane-breaking pin 3 are both arranged inside the hollow capillary tube 1. One end of the membrane-breaking pin 3 is connected to the piston 2, and the tip of the membrane-breaking pin 3 points towards the water storage plug 4. The air tank 5 is arranged below the water storage plug 4 and is sealed by the water storage plug 4. The air bladder 6 is wrapped around the air tank 5. After the water-storage plug 4 is delivered to the designated depth through a series of interconnected hollow capillary tubes 1, high-pressure liquid is pumped into the hollow capillary tubes 1. The piston 2 pushes the membrane-breaking pin 3 to puncture the water-storage plug 4 and the gas tank 5 in sequence, connecting the gas tank 5 with the air bladder 6. The gas inside the gas tank 5 expands and inflates the air bladder 6, which, along with the three-stage rubber claws, supports the well wall, thus fixing the device inside the well and completing the deployment of the water-storage plug device within the well. Then, the hollow capillary tube 1 is rotated in the opposite direction to remove it, and water is pumped into the well until it reaches the surface. The electric spark source and hydrophone are then lowered into the well to begin the inter-well seismic tomography detection work.

[0022] The limiting shear pin is located at the connection between the hollow capillary tube 1 and the water storage plug 4. By triggering the limiting shear pin, the hollow capillary tube 1 is unlocked from the water storage plug 4, and the piston 2 pushes the membrane-breaking needle 3 to puncture the water storage plug 4 and the gas tank 5. After the gas in the gas tank 5 expands out, it inflates the air bag 6.

[0023] The locking pin is located at the connection between the piston 2 and the inner wall of the hollow capillary tube 1. The locking pin is used to lock the piston 2. When high-pressure liquid is pumped into the hollow capillary tube 1, when the pressure reaches the threshold, the locking pin of the piston 2 is sheared, the piston 2 pushes the rupture needle 3 to puncture the gas tank 5, and the composite airbag 6 begins to inflate and anchor.

[0024] The stepped rubber claws 7 are arranged on the outside of the airbag 6. As the airbag 6 expands, they expand to form an annular sealing surface with the well wall. Under compression, the rubber claws deform and fill the microscopic gaps in the well wall, achieving a composite seal.

[0025] The hollow capillary tube 1 is composed of multiple sections connected sequentially via threaded joints. The connection joint between the end of the hollow capillary tube 1 and the water storage plug 4 uses a left-hand thread, while the connection joints of each section of the hollow capillary tube 1 in the middle all use right-hand threads. This design ensures that when the operator rotates the hollow capillary tube 1 clockwise on the ground to separate the downhole water storage plug 4, gas tank 5, and other devices, the applied torque will simultaneously tighten all intermediate connection joints, effectively preventing accidental loosening of intermediate tubes due to torque transmission during the separation process, thus improving the reliability and safety of the operation.

[0026] The technical solution of this utility model will be further described below with reference to the accompanying drawings and specific embodiments.

[0027] like Figure 1 , 2 As shown, a disposable borehole water storage plug for well geophysical exploration includes a downhole expansion unit and a detachable connection mechanism. The downhole expansion unit is initially a cylinder with a diameter of 63 mm, and contains a hydraulic piston triggering mechanism, a CO2 gas tank, a polyurethane-PVA composite airbag, and a three-stage stepped rubber claw; the detachable connection mechanism is used to connect to an external hollow thin tube and achieves separation after triggering.

[0028] The hydraulic piston triggering mechanism includes a hydraulic cylinder, a piston, a membrane-breaking pin, and a locking pin with a predetermined shear strength. Its main function is to receive hydraulic pressure from the ground. The hydraulic cylinder, the piston that provides the driving action, the membrane-breaking pin, and the locking pin are located above the CO2 gas tank. The locking pin is used to lock the piston. The locking pin shear threshold of piston 2 is set to 0.6 MPa. When high-pressure liquid is pumped into the hollow capillary tube 1 and reaches this pressure, the locking pin is sheared, and piston 2 pushes the membrane-breaking pin 3 to actuate.

[0029] The CO2 gas cylinder's main function is to provide expansion power. It includes a small high-pressure liquid CO2 storage tank with its opening sealed with a thin metal membrane.

[0030] The polyurethane-PVA composite airbag primarily serves as the main sealing material, and further expands upon contact with water, enhancing the sealing effect. PVA refers to polyvinyl alcohol.

[0031] like Figure 5As shown, the three-stage stepped rubber claw is disposed on the outside of the polyurethane-PVA composite airbag, serving as the main mechanical seal structure in contact with the well wall, generating friction with the well wall to withstand most of the hydrostatic pressure. The outer surface of the three-stage stepped rubber claw is made of butyl rubber, forming multiple circumferential seals with the well wall. The three-stage stepped skeleton is covered with a butyl rubber layer on its outer surface and coated with a silicone-based adhesive layer on its outermost layer; the three-stage stepped skeleton is built into the outside of the water storage plug device, and its inner side is in direct contact with the polyurethane-PVA composite airbag. When the airbag inflates, it pushes the stepped skeleton outward, causing its three-stage structure to expand step by step and form multiple circumferential mechanical seal surfaces with the well wall. At the same time, the silicone-based adhesive layer deforms under compression to fill the microscopic gaps, achieving a composite seal inside the well. The airbag is shown in state A before inflation and state B after inflation. Figure 1 As shown.

[0032] The detachable connection mechanism is mainly used to realize the recovery of the thin tube. It adopts a composite design of "left-hand thread (reverse thread) + limit shear pin" to ensure reliable recovery of the thin tube.

[0033] The detachable connection mechanism is located at the top of the device and includes the following components: Left-hand reverse thread connector: The upper part of the device housing is machined with a left-hand (reverse) external thread. The bottom end of the matching hollow tube is connected to a left-hand internal thread connector.

[0034] Limiting shear pin: A brittle pin (such as a plastic or aluminum pin) inserted radially from the side, penetrating the connector and the device housing. This pin serves two purposes: Locking function: Used to lock the hollow tube and the water storage plug.

[0035] Limiting function: Ensures that the device will not come loose from the thin tube due to accidental rotation during the well lowering process.

[0036] like Figure 3 , 4 As shown, the hollow capillary tube 1 is composed of multiple tube sections connected sequentially by threaded joints, including an upper tube section 11 and a lower tube section 12. The joint at the bottom of the capillary tube, used to connect to the downhole water storage plug, uses a left-hand thread. Conversely, all intermediate connecting joints of the hollow capillary tube use right-hand threads. This design ensures that when the operator rotates the capillary tube clockwise on the surface to separate the downhole device, the applied torque will simultaneously tighten all intermediate connecting joints, effectively preventing accidental loosening of intermediate tube sections due to torque transmission during separation, thus improving the reliability and safety of the operation. The hollow capillary tube with threads at the bottom is used for inserting and unlocking the water storage plug.

[0037] The key parameters of this utility model are as follows: initial diameter of the airbag: 63mm; diameter of the airbag after expansion: 89~130mm; applicable well depth: ≤50m; sealing pressure: ≥0.6MPa; single deployment time: ≤5 minutes.

[0038] The working process of this water storage plug device is as follows: (1) Ground connection: Tighten the connector at the lower end of the hollow tube to the left-hand joint at the top of the water storage plug until the limit shear pin is inserted and locked.

[0039] (2) Lowering device: The water storage plug device is transported from the inlet 8 to the target depth by lowering the hollow thin tube, generally without touching the bottom of the well 10.

[0040] (3) Ground pressurization trigger: High pressure liquid is pumped into the hollow tube 1. When the pressure reaches the first threshold (e.g., 0.6MPa), the locking pin of piston 2 is sheared, piston 2 pushes the pin to puncture CO2 gas tank 5, composite gas bag 6 begins to expand and anchor, three-stage stepped rubber claw 7 expands step by step and forms multiple annular mechanical sealing surfaces with well wall 9.

[0041] (4) Confirming Trigger and Disconnection Preparation: A sudden drop in the ground pressure gauge indicates that the device has been successfully triggered. The operator stops pressurizing.

[0042] (5) Perform the separation operation: Ground personnel rotate the thin tube 1 clockwise several times (usually 1-3 times). Since the connection between the end of the hollow thin tube 1 and the water storage plug 4 is left-handed (reverse thread), clockwise rotation is the direction to loosen it. The torque generated by the rotation will immediately shear the low-strength limit shear pin. After the pin breaks, the hollow thin tube 1 and the water storage plug 4 are unlocked. At this time, the connection between the hollow thin tube 1 and the water storage plug 4 is maintained only by the loosened left-hand thread.

[0043] (6) Lift up the retraction tube: While maintaining a clockwise rotation trend, slowly lift the tube 1. The connector of the tube 1 will easily unscrew from the threaded joint of the water storage plug 4, achieving complete separation of the tube 1 from the water storage plug 4.

[0044] (7) Water injection operation: After the thin tube 1 is completely pulled out of the wellhead 8, water can be injected into the well from the wellhead 8 to carry out the operation. Figure 1 , 2 The direction indicated by the middle arrow is the direction of water flow, which continues until it reaches the surface.

[0045] (8) Conduct downhole exploration: lower the electric spark source, hydrophone (downhole detector), etc. into the well to conduct inter-well seismic tomography exploration.

[0046] Example: Tests were conducted in a granite borehole (Φ89mm, depth 30m): the inflated diameter of the airbag reached 88.7mm, with a contact pressure of 0.62MPa. Injecting 250L of water into the airbag took 2.5 minutes, and the water level remained stable with fluctuations of less than 8cm for 72 hours. Recovery tests showed that the PVA (polyvinyl alcohol) support mesh lost its pressure-bearing capacity after 28 days.

[0047] The advantages of this utility model are as follows: (1) Reliable separation: The composite mechanical separation scheme of "left-hand thread + shear pin" is adopted, the separation action is clear and reliable, and 100% of the thin tube can be safely recovered.

[0048] (2) Simple operation: Ground personnel only need to follow three steps: "pressurize - confirm - rotate and lift". It is simple and intuitive, and does not require complicated judgment.

[0049] (3) Low cost: Only the downhole equipment is a disposable item, while the core thin tube and pump system can be reused, resulting in extremely low cost per operation.

[0050] (4) Large triggering force: The force provided by the hydraulic triggering method is much greater than that of mechanical impact or hydrostatic pressure, and can reliably puncture CO2 gas cylinders of various specifications.

[0051] All other undescribed parts belong to the prior art. The above-described embodiments only illustrate several implementation methods of this utility model, and their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of this utility model patent. It should be noted that for those skilled in the art, several modifications and improvements can be made without departing from the concept of this utility model, and these all fall within the protection scope of this utility model. Therefore, the protection scope of this utility model patent should be determined by the appended claims.

Claims

1. A borehole water storage plug device for well geophysical exploration, characterized in that: The device includes a hollow capillary tube (1), a piston (2), a membrane-breaking needle (3), a water storage plug (4), an air tank (5), and an air bladder (6). The end of the hollow capillary tube (1) is connected to the water storage plug (4) by a thread. The piston (2) and the membrane-breaking needle (3) are both arranged inside the hollow capillary tube (1). One end of the membrane-breaking needle (3) is connected to the piston (2), and the needle tip of the membrane-breaking needle (3) points to the water storage plug (4). The air tank (5) is arranged below the water storage plug (4) and is sealed by the water storage plug (4). The air bladder (6) is wrapped around the air tank (5).

2. The borehole water storage plug device for well geophysical exploration according to claim 1, characterized in that: It also includes a limiting shear pin, which is arranged at the connection between the hollow tube (1) and the water storage plug (4).

3. A borehole water storage plug device for well geophysical exploration according to claim 2, characterized in that: It also includes a locking pin, which is arranged at the connection between the piston (2) and the inner wall of the hollow capillary (1).

4. A borehole water storage plug device for well geophysical exploration according to claim 3, characterized in that: It also includes a stepped rubber claw (7), which is arranged outside the airbag (6) and expands to form an annular sealing surface with the well wall after the airbag (6) expands.

5. A borehole water storage plug device for well geophysical exploration according to claim 1, characterized in that: The hollow tube (1) is composed of multiple tube sections connected sequentially by threaded joints.

6. A borehole water storage plug device for well geophysical exploration according to claim 5, characterized in that: The connection between the end of the hollow tube (1) and the water storage plug (4) adopts a left-hand thread, while the connection between each section of the hollow tube (1) adopts a right-hand thread.

7. A borehole water storage plug device for well geophysical exploration according to claim 1, characterized in that: The gas tank (5) is filled with liquid CO2. The opening of the gas tank (5) is sealed with a thin metal membrane. After the membrane-breaking needle (3) punctures the metal membrane, the CO2 gas is released and drives the air bag (6) to expand.

8. A borehole water storage plug device for well geophysical exploration according to claim 4, characterized in that: The stepped rubber claw (7) is made of butyl rubber and coated with a silicone-based adhesive layer on the outermost layer. It is used to fill the micro-gaps in the well wall after expansion to achieve a composite seal.

Images