Low melting point metal plugging tool and method

Abstract

The present application relates to oil and gas field downhole plugging equipment technical field, specifically disclose a kind of low melting point metal plugging tool, including heater, cable, storage hopper, flexible receiving bag and flexible bag driving mechanism, storage hopper is used to store low melting point metal, and is connected on cable, heater is connected in the lower end of flexible bag driving mechanism, and with cable electric connection, flexible bag driving mechanism is connected in the lower end of storage hopper, flexible receiving bag is connected with the inner wall of storage hopper by flexible bag driving mechanism, flexible bag driving mechanism is used to drive flexible receiving bag from the inner wall of storage hopper and fall off, and flexible receiving bag one end is open and connected in the lower end of storage hopper, the other end is closed, the lower end of storage hopper is provided with for dumping low melting point metal to the automatic switch of flexible receiving bag.This tool has the characteristics of simple construction, lower operating cost, high plugging success rate.

Description

TECHNICAL FIELD

[0001] The application relates to a low-melting-point metal leak-stopping tool and method. BACKGROUND

[0002] Lost circulation is a common downhole complex accident in oil and gas well engineering. There are many methods for lost circulation classification, which can be classified according to the standards such as lost circulation speed, channel type, geological age, formation lithology and diagenetic type. Generally, it is considered according to the lost circulation channel, which can be divided into three types of porosity loss, fracture loss and dissolution loss. Lost circulation not only increases the exploration and development cost, causes serious reservoir damage, and leads to low oil and gas development efficiency, but also induces major accidents such as sticking, well collapse and blowout, causing loss of life and property and negative social impact. The problem of lost circulation is extremely serious, which seriously hinders the progress of oil and gas exploration and development.

[0003] Foreign countries have studied the lost circulation and leak-stopping mechanism in the drilling process early, and have developed and applied a large number of various types of conventional and new leak-stopping agents. The application of these leak-stopping materials effectively solves the problem of loss in permeable and microfractured formations. Domestic leak-stopping materials are based on bridging materials, and with the help of chemical reaction and composite methods, a variety of types of leak-stopping materials such as high-water-loss leak-stopping materials, soft and hard plug leak-stopping materials, inorganic gelation leak-stopping agents, temporary plugging materials, chemical leak-stopping materials, high-temperature leak-stopping materials and composite leak-stopping materials have been developed, which can basically meet the on-site leak-stopping demand for general loss.

[0004] Deep carbonate rocks are mainly fractured carbonate rocks, and fractures and caves are generally well developed. During drilling, drilling tools are often empty, accompanied by large loss of drilling fluid. Drilling into caves is accidental and sudden, with fast loss speed, large loss amount, and drilling fluid only entering but not exiting, which belongs to the most serious lost circulation. If it is not discovered in time or improper measures are taken, it will also cause wellbore collapse, sticking accidents, and even lead to wellbore abandonment. The caves formed by long-term corrosion of underground water have variable shapes, different sizes and irregular shapes of cave entrances, cave walls and cave roofs, and are often accompanied by underground water runoff, making it difficult to effectively plug the leakage.

[0005] The bridging-cement composite leak-stopping method can also be used for small and medium-sized cave loss, which first forms a skeleton bridge and then injects slurry to set. However, for large caves, conventional leak-stopping materials cannot effectively accumulate near the wellbore in the cave, and it is difficult to effectively bridge. Even after the injection of leak-stopping slurry, the leak-stopping layer formed by the bridging filling material has low strength due to the influence of underground water, and cannot effectively withstand pressure, which cannot meet the construction requirements.

[0006] The research and application of the lost circulation material and the lost circulation tool for large cave and large fracture are seldom in the world, and the lost circulation bellow is generally used as a temporary measure, the pipe is expanded by hydraulic or mechanical method, the cross section becomes a thin-walled pipe with a larger diameter closely adhering to the well wall, and then the purpose of plugging the lost circulation formation is achieved. However, the lost circulation bellow still has some problems in treating the large cave leakage. First, the lost circulation bellow may be blocked during the process of entering the well; second, for the leakage of the cave, the hollow, the underground river and other types, several processes such as drilling through the leakage layer, logging, reaming, lost circulation bellow running and expansion are needed, but the long construction time will cause a large amount of drilling fluid leakage; third, the hydraulic expansion is not complete, the leakage occurs at the welding position when the hydraulic expansion does not reach the design pressure, and the friction between the expanded bellow and the well wall is not enough, which will cause the expansion failure of the bellow; fourth, when the cave of the serious leakage formation is more, the technology is very complex to treat, and the cost is high. SUMMARY

[0007] In order to solve the above-mentioned large cave leakage treatment problem, the application provides a low melting point metal lost circulation tool, the low melting point metal in the tool is heated and melted, the liquid metal occupies the area to be plugged, and the metal plug is formed after cooling and solidification to plug the leakage layer. The tool has the characteristics of simple construction, low operation cost and high plugging success rate.

[0008] The purpose of the application can be achieved by the following technical solutions:

[0009] A low melting point metal lost circulation tool, comprising a heater, a cable, a storage hopper, a flexible receiving bag and a flexible bag driving mechanism, the storage hopper is used for storing the low melting point metal and is connected to the cable, the heater is connected to the lower end of the flexible bag driving mechanism and is electrically connected to the cable, the flexible bag driving mechanism is connected to the lower end of the storage hopper, the flexible receiving bag is connected to the inner wall of the storage hopper through the flexible bag driving mechanism, the flexible bag driving mechanism is used for driving the flexible receiving bag to fall off from the inner wall of the storage hopper, and one end of the flexible receiving bag is connected to the lower end of the storage hopper, and the other end is closed, an automatic switch for discharging the low melting point metal to the open end of the flexible receiving bag is arranged at the lower end of the storage hopper, and the low melting point metal can be in a solid state at the leakage layer position in the well, and in a liquid state after being heated.

[0010] Further, the flexible bag driving mechanism comprises a gravity block, a locking mechanism, L-shaped sliders and rolling seats, the locking mechanism is connected between the heater and the storage hopper, the gravity block is slidingly connected on the locking mechanism, the flexible receiving bag is annular and has double layers, the double-layer annular bottom is sealingly connected on the gravity block, an annular bagging opening is arranged between the double-layer annular top, the inner and outer rings of the annular bagging opening are connected on two groups of L-shaped sliders respectively, the two groups of L-shaped sliders are slidingly connected in two groups of rolling seats respectively, and the two groups of rolling seats are fixed on the inner wall of the storage hopper and the outer wall of the locking mechanism respectively, the locking mechanism is provided with a first lock rod at the upper portion for opening the automatic switch, a second lock rod at the middle portion for opening the sliding of the L-shaped sliders, and a third lock rod at the lower portion for opening the sliding of the gravity block.

[0011] Further, the locking mechanism comprises a hydraulic rod, and the first lock rod, the second lock rod and the third lock rod are all hydraulic control bolts, which are connected on the piston of the hydraulic rod.

[0012] Further, the second lock rod and the third lock rod are shear pins, the shearing force of the third lock rod is determined according to the weight of the low-melting-point metal, and the shearing force of the second lock rod is determined according to the pulling force when the storage hopper and the flexible bag driving mechanism are lifted.

[0013] Further, the automatic switch comprises a baffle, one end of the baffle is rotationally connected with the storage hopper, and the other end is connected with the first lock rod.

[0014] Further, the rolling seat comprises a spherical hinge, and the spherical hinge and the second lock rod connecting end are limited to rotate through the second lock rod.

[0015] Further, the spherical hinge and the second lock rod connecting end are limited by the mutual contact planes.

[0016] Further, the L-shaped slider away from the flexible receiving bag is slidingly inserted into the rotating end of the spherical hinge.

[0017] Further, the storage hopper is an annular cylindrical barrel, and a connecting seat for connecting with the flexible bag driving mechanism is arranged at the middle portion of the barrel.

[0018] Further, the low-melting-point metal is spherical.

[0019] The beneficial effects of the present application are as follows:

[0020] The present application can melt low-melting-point metal by using downhole plugging tool, and the low-melting-point metal is cooled and solidified from liquid state to form a metal plugging body in only a few minutes, and a metal plugging body with good sealing performance and high pressure-bearing capacity is established at a lost circulation location, the method does not need to use any large ground equipment, only a common cable car is used to realize the lifting and lowering of the plugging tool, and the whole plugging operation process is very simple and the operation cost is low.

[0021] The present application can realize complete storage of low-melting-point metal balls to a release point by designing a storage hopper, and prevent damage to a flexible receiving bag in the lowering process. The flexible receiving bag is separated from the storage hopper after plugging by a flexible bag driving mechanism, and the other parts of the tool are lifted.

[0022] The present application can realize automatic release of low-melting-point metal to fill a cave by designing a hydraulic control self-locking device, automatic shedding after filling, lifting of other parts of the tool, safety and reliability, and high efficiency. BRIEF DESCRIPTION OF DRAWINGS

[0023] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or prior art description. Obviously, the drawings in the following description are some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0024] Figure 1 Schematic diagram for downhole metal plugging tool plugging into a well;

[0025] Figure 2 Schematic diagram for stretching and unfolding of a flexible receiving bag;

[0026] Figure 3 Schematic diagram for pouring and filling of a flexible receiving bag with metal balls;

[0027] Figure 4 Schematic diagram for drilling out excess metal plugging body by downhole drill bit;

[0028] Figure 5 Principle diagram for shedding of a flexible receiving bag when the tool is recycled;

[0029] In the drawings: 1, heater; 2, cable; 3, storage hopper; 31, automatic switch; 311, baffle; 4, flexible receiving bag; 5, flexible bag driving mechanism; 51, gravity block; 52, locking mechanism; 521, first locking rod; 522, second locking rod; 523, third locking rod; 53, L-shaped sliding block; 54, rolling seat; 541, spherical hinge; 520, plane; 6, metal ball; 7, metal plugging body; 8, cable car; 9, formation; 10, lost circulation channel; 11, drill bit. DETAILED DESCRIPTION

[0030] 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.

[0031] like Figure 1 As shown, a low-melting-point metal plugging tool includes a heater 1, a cable 2, a storage hopper 3, a flexible receiving bag 4, and a flexible bag driving mechanism 5. The storage hopper 3 is used to store low-melting-point metal and is connected to the cable 2. The heater 1 is connected to the lower end of the flexible bag driving mechanism 5 and is electrically connected to the cable 2. The flexible bag driving mechanism 5 is connected to the lower end of the storage hopper 3. The flexible receiving bag 4 is connected to the inner wall of the storage hopper 3 through the flexible bag driving mechanism 5. The flexible bag driving mechanism 5 is used to drive the flexible receiving bag 4 to detach from the inner wall of the storage hopper. One end of the flexible receiving bag 4 is open and connected to the discharge end of the storage hopper 3, and the other end is closed. An automatic switch 31 for discharging material to the open end of the flexible receiving bag 4 is provided at the discharge end of the storage hopper 3.

[0032] Its working principle or implementation method is as follows: When a large amount of drilling fluid is detected to be lost on the ground, imaging logging technology is used to confirm whether a large karst cave has been encountered. Based on the measured data, such as the size of the leakage channel, the amount of metal balls 6 made of low-melting-point metals such as tin and lead in the low-melting-point metal plugging tool, the size of the flexible receiving bag 4, and the amount of thermite reaction material stored in the heater for heating the low-melting-point metal are adjusted.

[0033] The other parts of the downhole metal plugging tool connected to it can be lowered via ground cable car 8 and cable 2. The lowering depth is recorded and the lowering stops above the leakage layer. The flexible receiving bag 4 is set outside the heater 1 and arranged in a pleated compression manner in a certain order. Its material thickness is 0.5-2mm and has good extrusion deformation capacity, water permeability, tear resistance and flexibility.

[0034] The flexible receiving bag 4 has a double-layer structure. The upper ends of both the inner and outer bags are locked to the lower end of the storage hopper 3 and the flexible bag drive mechanism 5, and the lower ends of the inner and outer bags are closed. The multi-layer bag structure can also achieve the above-mentioned bagging operation of low melting point metal balls.

[0035] The upper and lower ends of the flexible receiving bag 4 are locked by the flexible bag driving mechanism 5 such as an electric rod or a hydraulic rod. Under the action of hydraulic or electric control, the automatic switch 31 is opened, the storage hopper 3 is opened, the metal balls 6 in the storage hopper 3 roll into the flexible receiving bag 4, the lower end of the flexible receiving bag 4 is unlocked, and the metal balls 6 fall along the axis under the action of gravity. Under the stretching action of the flexible receiving bag 4, the flexible receiving bag 4 is completely stretched, the flexible receiving bag 4 falls to the position of the solution cavity, and the flexible receiving bag 4 is filled into the solution cavity under the diffusion action of the metal balls 6, thereby preliminarily slowing down the leakage speed. The temperature of the heater 1 is controlled by an electric signal to reach the reaction temperature of the thermite, so as to melt the metal balls 6 around the heater 1. After a short time of heating, the metal balls 6 are completely melted into a liquid state, but most of the liquid metal is retained in the flexible receiving bag 4, and a metal plugging body 7 is formed after cooling and solidification.

[0036] The heater 1 can be an aluminum thermal reaction heater. The control terminal of the tool can be arranged above the flexible driving mechanism 5, so as to start the heater. The thermite is a high-energy exothermic material, which is stored in the heater as a reaction fuel. After starting the heater, the thermite reacts and releases heat, and the metal balls start to melt.

[0037] The amount of low-melting-point metal such as low-melting-point metal balls 6 in the low-melting-point metal plugging tool and the size of the flexible receiving bag 4 can be adjusted according to the measured data, which can refer to the existing method, such as:

[0038] Solution cavity size evaluation: first, the solution cavity size data obtained by imaging logging technology is the key to adjust the plugging tool. The diameter, depth and shape of the solution cavity will directly affect the amount of plugging material and the design of the plugging tool.

[0039] Amount of low-melting-point metal balls 6: the amount of low-melting-point metal balls needs to be calculated according to the volume of the solution cavity. Generally speaking, the larger the volume of the solution cavity, the more low-melting-point metal balls are needed to ensure that the solution cavity can be fully filled and an effective seal is formed.

[0040] Size of flexible receiving bag 4: the size of the flexible receiving bag 4 needs to be designed considering the diameter and depth of the solution cavity. The diameter of the flexible bag should be greater than the maximum diameter of the solution cavity to ensure that it can completely cover the solution cavity, and the length of the flexible bag should be determined according to the depth of the solution cavity to ensure that it can penetrate into the solution cavity and form an effective seal.

[0041] According to the working principle described above, some preferred embodiments or implementation modes are provided, the flexible bag driving mechanism 5 includes a gravity block 51, a locking mechanism 52, such asFigure 5 The L-shaped slider 53 and the rolling seat 54 are connected between the heater 1 and the storage hopper 3, the gravity block 51 is slidingly connected to the locking mechanism 52, the flexible receiving bag 4 is annular and has a double layer, the double layer annular bottom is sealingly connected to the gravity block 51, the annular bagging opening is arranged between the annular top double layer, the inner and outer rings of the annular bagging opening are connected to the two groups of L-shaped sliders 53 respectively, the two groups of L-shaped sliders 53 are slidingly connected in the two groups of rolling seats 54 respectively, and the two groups of rolling seats 54 are fixed to the inner wall of the storage hopper 3 and the outer wall of the locking mechanism 52 respectively. The first lock rod 521 is arranged at the upper portion of the locking mechanism 52 and is used for opening the automatic switch 31, the second lock rod 522 is arranged at the middle portion and is used for opening the sliding of the L-shaped slider 53, and the third lock rod 523 is arranged at the lower portion and is used for opening the sliding of the gravity block 51. The locking mechanism 52 locks the gravity block 51, the L-shaped slider 53 and the rolling seat 54, realizes the fixation of the upper and lower ends of the flexible receiving bag 4, and facilitates the stretching of the flexible receiving bag 4. The L-shaped slider 53 and the rolling seat 54 facilitate the locking of the two sides of the upper end of the flexible receiving bag 4. The first lock rod 521 can also be used to open the automatic switch 31 below the storage hopper 3. The whole structure is simple and can realize accurate control and unlocking of the positions such as the flexible receiving bag 4 and the automatic switch 31 that need to be unlocked.

[0042] The locking mechanism 52 includes a hydraulic rod, and the first lock rod 521, the second lock rod 522 and the third lock rod 523 are all hydraulic control piston rod type latches. The hydraulic control can realize the rapid retraction and extension of the piston, and facilitate the unlocking of the latch.

[0043] The automatic switch 31 includes a baffle 311, one end of the baffle 311 is rotationally connected to the storage hopper 3, so that it can rotate around the connection point. The other end of the baffle 311 is connected to the first lock rod 521. When the first lock rod 521 retracts, the baffle 311 is pushed to rotate, thereby unlocking the storage hopper 3. When the first lock rod 521 retracts, the baffle 311 is reset under the action of gravity or a spring, thereby achieving locking. This structure is simple and convenient to realize, and can effectively control the opening and closing of the storage hopper 3, and is suitable for various occasions that need to be automatically controlled.

[0044] As shown in Figure 5 The rolling seat 54 includes a spherical hinge 541, the spherical hinge 541 is rotationally connected to the second lock rod 522 through the second lock rod 522. The spherical hinge 541 is limited by the contact plane 520 through the second lock rod 522. The L-shaped slider 53 is slidingly inserted into the rotating end of the spherical hinge 541 away from the flexible receiving bag 4. As shown in Figure 5 a, it is a state diagram when the flexible receiving bag 4 is locked. The two groups of spherical hinges 541 are locked together by the extension of the second lock rod 522, and the L-shaped slider 53 is limited at the same time. Figure 5b, as a flexible receiving bag 4 unlocking state diagram, when the lock is released, it does not hinder the L-shaped slider 53 under the action of gravity to drive the flexible receiving bag 4 from the spherical hinge 541 to slide off.

[0045] The storage hopper 3 is an annular cylindrical barrel, and a connecting seat for connecting with the flexible bag driving mechanism 5 is arranged in the middle of the barrel. In this way, the installation of the flexible bag driving mechanism 5 and the cable 2 is facilitated.

[0046] The low-melting-point metal is spherical. In this way, it is convenient for it to roll into the flexible receiving bag 4. There are several reasons for making the low-melting-point metal into a spherical shape:

[0047] Energy minimization: the sphere is the shape with the smallest surface-to-volume ratio among all geometric shapes, which means that under the same volume, the surface energy of the spherical metal is the lowest and more stable. When the low-melting-point metal cools and solidifies, it will naturally form a spherical shape to achieve the lowest energy state.

[0048] Flowability: the sphere has good rolling properties, which makes the low-melting-point metal move and distribute more smoothly in specific applications, such as the flexible receiving bag, improving its efficiency in specific environments.

[0049] Uniform heat dissipation: the uniformity of the sphere allows the metal to dissipate heat more evenly during cooling, avoiding local overheating or uneven cooling caused by irregular shapes, thereby ensuring the performance and quality of the metal.

[0050] Stress concentration reduction: the spherical structure can uniformly disperse external forces, reducing stress concentration, which is particularly important for low-melting-point metals, as their strength and toughness may be lower and prone to breaking at stress concentration points.

[0051] Improved safety: when handling low-melting-point metals, the sphere can reduce the contact area between the metal and the container wall, reducing the risk of potential chemical reactions, and during transportation and storage, spherical metals are less likely to roll out of control, improving the safety of operations.

[0052] Convenient packaging and handling: spherical metals can be more easily automated during packaging and handling, such as automatic filling, automatic counting, etc., improving production efficiency.

[0053] Therefore, making low-melting-point metals into spheres not only improves their performance in specific applications, but also ensures their safety and efficiency during handling and use.

[0054] The low-melting-point metal can also be other shapes such as ellipsoidal.

[0055] The cable 2 provides power and control signals for the tool, enabling control of the downhole heating. The cable is connected with the downhole heater 1 and the storage hopper 3, and the plugging tool is lowered to the predetermined position by the lowering mechanism.

[0056] Cables are responsible for transmitting electrical energy from the ground to the equipment in the well, such as motors, hydraulic pumps, heaters, etc., to ensure the normal operation of these devices. Stable supply of electrical energy is the key to long-term reliable and stable operation of downhole operation equipment.

[0057] Control signal transmission: Cables not only transmit electrical energy, but also transmit control signals to achieve remote control of downhole equipment. For example, through the cable, the start and stop of the downhole heater can be controlled, the heating temperature can be adjusted, and the running status of the equipment can be monitored.

[0058] Data communication: Cables also undertake the task of data communication in downhole operations, transmitting real-time data collected by downhole equipment to the ground, such as downhole temperature, pressure, fluid flow, etc. Information provides the basis for ground monitoring and decision-making.

[0059] Cable winding and unwinding: In downhole operations, cable winding and unwinding is an important link. Cable winding and unwinding device can ensure the smooth movement of cable on and off the downhole equipment, avoid cable winding or damage, and provide necessary buoyancy to ensure the stability and safety of the cable.

[0060] Adapt to harsh environment: The downhole environment is usually characterized by high pressure and humidity, and the cable needs to have good pressure resistance, waterproofness and corrosion resistance to adapt to the special working conditions of downhole operations and ensure the normal operation of the equipment. Cable types: There are many types of cables used in downhole operations, including power cables, control cables, compensation cables, and shielded cables, each with its specific functions and application scenarios to meet the diverse needs of downhole operations.

[0061] The role of cables in downhole operations and the principle of control signal transmission are the key to ensuring the normal operation of downhole equipment, achieving remote control and data communication, and have important influence on the safety and efficiency of downhole operations.

[0062] The heater 1 is provided with a starter arranged on the upper end of the heater 1 and connected with the cable 2, and the cable 2 transmits an electric signal to control the starter to activate the fuel inside the heater 1.

[0063] The heater 1 has two working modes of aluminum thermal reaction heating and electric heating. If aluminum thermal agent is used as a heat source, the high temperature released by aluminum thermal reaction heating can quickly melt the small metal balls 6 around the heater 1. The first melted small metal balls 6 continue to melt the external metal by virtue of their high temperature, and after the reaction fuel is exhausted, the mode is changed to electric heating to continuously supplement the heat until all the small metal balls 6 are melted.

[0064] The flexible receiving bag 4 is arranged outside the heater 1 in a certain order of pleated compression, and has a thickness of 0.5-2 mm, and a length that can be adjusted according to the size of the cave. It has good extrusion deformation ability, water permeability, tear resistance, flexibility, and the outer bag can be fused after heating and has a certain viscosity to adhere to the well wall and the lost circulation channel 10 of the formation 9.

[0065] The flexible receiving bag 4 has a double-layer structure, and the upper ends of the inner bag and the outer bag are locked on the locking mechanism 52 through the L-shaped sliding block 53 and the rolling seat 54. The lower end of the inner bag is connected with the inner ring of the gravity block 51, and the lower end of the outer bag is connected with the outer ring of the gravity block 51. When the tool needs to be recovered, the hydraulic rod controls the piston to retract, and at the same time, the bolt on the piston is retracted. The spherical hinge 541 rotates under the condition of losing locking, so that the upper end of the flexible receiving bag 4 is unlocked with the bolt. At this time, the tool can be recovered by lifting the cable.

[0066] The annular gravity block 51 is sleeved on the outer wall of the flexible bag driving mechanism. The piston rod pushed by the hydraulic circuit or the bolt makes the gravity block 51 locked at the lower end of the hydraulic rod. The inner and outer rings of the gravity block 51 are connected with the inner and outer layers of the flexible receiving bag respectively. Under the control of the hydraulic system, after the locking of the gravity block 51 and the hydraulic rod is released, the gravity block 51 falls along the axial direction by relying on the gravity. The gravity block 51 is connected with the bottom of the flexible receiving bag 4. Under the stretching action of the gravity block 51 falling, the flexible receiving bag 4 is fully stretched.

[0067] The storage hopper 3 is annular funnel-shaped, and the annular space is used to store low-melting-point metal balls 6. The number of the stored metal balls 6 can be adjusted according to the size of the cave to meet the plugging requirements. The lower part of the storage hopper 3 is provided with circumferentially distributed baffles 311. The baffles 311 can be controlled to retract by the piston of the hydraulic compression circuit, so as to control the baffles 311 to open.

[0068] The low-melting-point metal balls 6 have excellent properties. The melting point can be adjusted by adjusting the alloy ratio to adapt to different downhole temperatures. In the liquid state, it has good fluidity. After cooling and solidification, it expands and can be anchored with the lost circulation channel 10, has good airtightness and pressure-bearing strength. By adjusting the alloy ratio, the melting point can be changed to adapt to different downhole temperature conditions. The following are several key characteristics of the low-melting-point metal balls 6:

[0069] Adjustable melting point: By adjusting the alloy composition, the melting point of the metal balls can be accurately controlled to melt at a specific temperature, suitable for different downhole temperature requirements.

[0070] Fluidity: In the liquid state, the low-melting-point metal balls have good fluidity, can smoothly flow into the downhole lost circulation channel 10, fill irregular gaps, and ensure that the material can be evenly distributed.

[0071] Expansion: After cooling and solidification, the metal pellets expand, which anchors them tightly to the lost circulation channel 10, creating a stable structure that prevents material from moving or falling out of the well.

[0072] Air tightness: The structure formed by the metal pellets after solidification has good air tightness, effectively preventing gas leakage through the lost circulation channel 10, improving the safety and efficiency of downhole operations.

[0073] Pressure resistance: The cooled metal pellets have high pressure resistance, capable of withstanding high pressure environments downhole, preventing structural damage due to excessive pressure, ensuring smooth downhole operations.

[0074] Adaptability: These characteristics of low-melting-point metal pellets make them highly adaptable in downhole operations, effectively dealing with high temperatures, high pressures, and complex geological conditions, improving operation success rates.

[0075] These characteristics of low-melting-point metal pellets 6 make them a very effective material in downhole operations, improving the safety and efficiency of operations, reducing the risk of lost circulation, and ensuring smooth downhole operations.

[0076] The general implementation of the low-melting-point metal plugging tool is as follows: after the entire tool is placed in position, the hydraulic or electric control system is controlled by an electric signal, such as Figure 2 , the third locking rod 523 with a piston rod is retracted to unlock the gravity block 51, which falls under gravity to a position below the lost circulation zone, while stretching the flexible receiving bag 4 to a certain extent. As shown in Figure 3 , the lower part of the storage hopper 3 is provided with a movable baffle 311, which is controlled by a hydraulic system to open and dump low-melting-point metal pellets 6. During the accumulation of metal pellets 6 into the flexible receiving bag 4, the flexible receiving bag 4 expands axially and radially, and under the extrusion of metal pellets 6, the flexible receiving bag 4 enters the lost circulation channel 10 without well wall constraints in the formation 9. Then start the heater 1 to melt the metal pellets 6 in the plugging bag, and the low-melting-point metal around the heater 1 melts into a liquid state as a heat transfer medium to continue melting the external metal. After the metal cools to form a plugging body, the upper end of the flexible receiving bag 4 is unlocked with the rolling seat, and the L-shaped sliding block 53 directly slides off, ensuring that the tool can be smoothly lifted to the ground. As shown in Figure 4 , after falling off, the excess metal plugging body 7 can be removed by the drill bit 11.

[0077] In some embodiments, the second locking rod 522 and the third locking rod 523 are shear pins, and the shear force of the third locking rod 523 is determined according to the weight of the low-melting-point metal, and the shear force of the second locking rod 522 is determined according to the pulling force when the storage hopper 3 and the flexible bag driving mechanism 5 are lifted. When the flexible receiving bag 4 carries a certain amount of small balls, the shear pins are broken under the action of gravity, and the upper part of the flexible receiving bag 4 is separated when the pulling force when the storage hopper 3 and the flexible bag driving mechanism 5 are lifted exceeds the shear force of the shear pin. Therefore, the shear pin structure has the characteristics of simple structure and convenient operation.

[0078] After the whole tool is placed in position, the piston rod or the electrically controlled lock clamp is controlled to open the automatic switch 31 by controlling the hydraulic or electric control system, and the low-melting-point metal balls 6 are poured. During the accumulation of the metal balls 6 into the flexible receiving bag 4, the weight block 51 falls into the position below the lost circulation layer under the action of gravity, and at the same time, the originally compressed and folded flexible receiving bag 4 is stretched to a certain extent. The flexible receiving bag 4 expands in the axial and radial directions, and under the extrusion of the metal balls 6, the flexible receiving bag 4 enters the lost circulation channel 10 in the formation 9 without the restriction of the well wall. Then, the heater 1 is started to melt the metal balls 6 in the plugging bag, and the low-melting-point metal around the heater 1 is first melted into a liquid state as a heat transfer medium to continue melting the metal outside. After the metal cools to form a plugging body, the storage hopper 3 is lifted, the shear pin at the second locking rod 522 at the upper end of the flexible receiving bag 4 is unlocked, and the rolling seat 54 ensures that the tool can be smoothly lifted to the ground.

[0079] When the second locking rod 522 and the third locking rod 523 are shear pins, the breaking shear force of the third locking rod 523 is related to the weight of the low-melting-point metal, which means that when the flexible receiving bag 4 carries a certain amount of small balls, the gravity will cause the third locking rod 523 to break. The breaking shear force of the second locking rod 522 is determined by the pulling force when the storage hopper 3 and the flexible bag driving mechanism 5 are lifted. When the pulling force exceeds the shear force of the shear pin, the upper part of the flexible receiving bag 4 will be separated. The automatic switch at the baffle 311 can also be a pulling shear pin, which is controlled to be stretched and broken by hydraulic control. This shear pin structure can realize automatic control without manual intervention, improving the efficiency and safety of the packaging process. The shear pin structure is simple in design, easy to implement and maintain, and reduces the complexity and cost of the equipment. The breaking condition of the shear pin is clear, and the operator can easily understand and control it, improving the convenience of operation and the user-friendliness of the equipment.

[0080] It should be noted that the terms "first", "second", etc. in the present application are used to distinguish similar objects, and do not necessarily describe a specific order or sequence. It should be understood that the data thus used can be interchanged under appropriate circumstances, so that the embodiments of the present application described herein can be implemented.

[0081] In the description of the specification, the description of the terms "one embodiment", "an example", "a specific example" and the like means that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present application. In the specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any appropriate way in one or more embodiments or examples.

[0082] The basic principles, main features and advantages of the present application are shown and described above. It should be understood by those skilled in the art that the present application is not limited by the above embodiments, and the above embodiments and descriptions in the specification are only to illustrate the principles of the present application. Without departing from the spirit and scope of the present application, various changes and improvements can be made to the present application, and these changes and improvements all fall within the scope of the claimed present application.

Claims

1. A low melting point metal patching tool characterized by, The application relates to a low-melting-point metal storage device which comprises a heater, a cable, a storage hopper, a flexible receiving bag and a flexible bag driving mechanism, the storage hopper is used for storing low-melting-point metal and is connected to the cable, the flexible bag driving mechanism is connected to the lower end of the storage hopper, the flexible receiving bag is connected to the inner wall of the storage hopper through the flexible bag driving mechanism, the flexible bag driving mechanism is used for driving the flexible receiving bag to fall off from the inner wall of the storage hopper, an automatic switch for discharging the low-melting-point metal to the open end of the flexible receiving bag is arranged at the discharging end of the storage hopper, the heater is connected to the lower end of the flexible bag driving mechanism and is electrically connected to the cable. The flexible bag driving mechanism comprises a gravity block, a locking mechanism, L-shaped sliding blocks and rolling seats, the locking mechanism is connected between the heater and the storage hopper, the gravity block is slidingly connected to the locking mechanism, the flexible receiving bag is annular and has double layers, the double-layer annular bottom is sealingly connected to the gravity block, an annular bagging opening is arranged between the double-layer annular top, the inner and outer rings of the annular bagging opening are connected to two groups of L-shaped sliding blocks respectively, the two groups of L-shaped sliding blocks are slidingly connected to two groups of rolling seats respectively, the two groups of rolling seats are fixed to the inner wall of the storage hopper and the outer wall of the locking mechanism respectively, the locking mechanism is provided with a first lock rod at the upper portion of the locking mechanism for opening the automatic switch, a second lock rod at the middle portion of the locking mechanism for opening the L-shaped sliding blocks to slide, and a third lock rod at the lower portion of the locking mechanism for opening the gravity block to slide; The locking mechanism comprises a hydraulic rod, the first lock rod, the second lock rod and the third lock rod are all hydraulic control bolts, and the bolts are connected to the piston of the hydraulic rod. The automatic switch comprises a baffle, one end of the baffle is rotationally connected to the storage hopper, and the other end of the baffle is connected to the first lock rod. The rolling seat comprises a spherical hinge, the spherical hinge is rotationally connected to the second lock rod through the second lock rod. The L-shaped sliding block is slidingly inserted into the rotating end of the spherical hinge.

2. A low melting point metal patch and repair kit as defined in claim 1, wherein, The spherical hinge is limited by the mutual contact planes.

3. A low melting point metal patch and repair kit as defined in claim 1, wherein, The storage hopper is an annular cylindrical barrel, and the barrel is provided with a connecting seat at the middle portion of the barrel for being connected to the flexible bag driving mechanism.

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