Construction method for sand blockage prevention of low-position brine discharging well of salt cavern storage cavern

Abstract

The invention relates to the technical field of salt cavern underground reservoir building, in particular to a construction method for sand blocking prevention of a salt cavern reservoir low-position brine discharging well. According to the method, drilling operation of a brine discharging well is conducted at a target position near a salt cavity of the salt cavern storage cavern, so that the bottom of the brine discharging well communicates with a bottom insoluble substance residue space of the salt cavity; a water injection pipe is put into the brine discharging well, water is injected into the bottom of the drilling well, and a dissolving cavity is formed between the bottom of the drilling well and the bottom insoluble substance residue space of the salt cavity; and the dissolving cavity is communicated with the brine discharging well to form a brine discharging channel, and construction is completed. According to the method, it can be effectively guaranteed that the sand blocking prevention function is achieved when the brine discharging well is used for discharging brine, the brine discharging efficiency of the brine discharging well is improved, and the sand blocking risk and the operation cost in the gas injection brine discharging process are reduced; the brine discharging efficiency and the utilization rate of the gas storage space are improved; cost is low, reliability is high, and the problem of sand blocking of the brine discharging well can be well solved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of salt cavern underground storage construction, in particular to a construction method for preventing sand plugging of a low-positioned halogen discharge well of a salt cavern storage. BACKGROUND

[0002] The geological conditions of salt cavern storage construction in China are complex, and most of the salt cavern underground gas storages are constructed in layered salt-containing strata composed of soluble salt layers and insoluble interlayers. The insoluble substances in such strata fall off, collapse and expand and accumulate at the bottom of the cavity during water-soluble cavity construction, forming residues that occupy part of the cavity space and reduce the gas storage volume. According to the residue conditions of the cavities designed in five salt mines in Jintan, Huai'an and Pingdingshan, etc. in China, the residue height ranges from 52.4 m to 120.7 m, with an average height of 74.2 m, and the average ratio of the residue height to the cavity construction height is 47.9%. Meanwhile, combined with the cavity construction experience of Jintan salt mine, the accumulation coefficient of the residues is about 1.6. If the expansion coefficient of the insoluble particles measured by salt enterprise component analysis is 1.2, 25% of the space in the residues is filled with pore water. If this part of pore water can be displaced and utilized, the gas storage space of the cavity will be expanded, the utilization efficiency of the salt cavity will be improved, and the construction investment will be reduced.

[0003] At present, the main method for discharging halogen from the residue space of the salt cavity is to enter the residue space through secondary halogen discharge tools or chemical separation, which is difficult to implement on site. Another technical idea is to connect the old cavity with the original old cavity through a newly drilled well or a dissolved cavity at the edge or bottom of the salt mine, to realize gas injection and halogen discharge in the upper cavity and the bottom residue space of the old cavity, and to maximize the utilization of the salt cavity space. This technical idea mainly uses a newly drilled halogen discharge well to discharge halogen. During actual halogen discharge, the sediment particles move along with the brine and are easily accumulated near the pipe shoe of the halogen discharge well, causing sand plugging and seriously affecting the halogen discharge effect. SUMMARY

[0004] The technical problem to be solved by the present application is to provide a construction method for preventing sand plugging of a low-positioned halogen discharge well of a salt cavern storage.

[0005] The technical solution for solving the above technical problem is as follows: The present application provides a construction method for preventing sand plugging of a low-positioned halogen discharge well of a salt cavern storage, comprising the following steps: S1. Drilling a halogen discharge well at a target position near a salt cavity of a salt cavern storage, and connecting the bottom of the halogen discharge well with the bottom insoluble residue space of the salt cavity; S2. Lowering a water injection pipe into the halogen discharge well and injecting water into the bottom of the drilling well, to form a dissolved cavity between the bottom of the drilling well and the bottom insoluble residue space of the salt cavity; S3, taking out the water injection pipe, communicating the solution cavity with the brine discharge well to form a brine discharge channel, and completing the construction.

[0006] Based on the technical scheme, the application further has the following improvements.

[0007] Further, in step S1, the well structure is a three-opening well structure.

[0008] Further, the drilling operation comprises the following steps: S1-1, performing a first-opening drilling operation, and lowering a brine discharge well surface casing into the first-opening well section for cementing; S1-2, performing a second-opening drilling operation, and stopping the drilling when the drilling tool reaches a target distance position from the boundary of the salt cavity, and lowering a brine discharge well production casing into the second-opening well section for cementing; S1-3, performing a third-opening drilling operation, and communicating the third-opening well section with the bottom insoluble residue space of the salt cavity.

[0009] Further, in step S1-2, the target distance is 25-35 meters.

[0010] Further, in step S2, the water injection is performed after the water outlet of the water injection pipe is located at the shoe position of the production casing, and the salt rock near the shoe position of the production casing is dissolved; after the water injection is completed, an empty pipe section is formed near the shoe position of the production casing, and the salt rock is dissolved to form the solution cavity.

[0011] Further, a bidirectional bridge plug is lowered into the empty pipe section, and a plurality of holes are obtained on the pipe wall of the empty pipe section through setting and perforation.

[0012] Further, the hole diameter of the holes is 8-12 mm.

[0013] Further, the hole density of the perforation is 150-200 holes / m.

[0014] Further, in step S1, the target position is a position 150-250 meters away from the well mouth of the salt cavern reservoir.

[0015] Further, the salt cavity is communicated with the salt cavern reservoir inlet through the injection-production well production casing and the injection-production well surface casing.

[0016] The application has the following beneficial effects: (1) The salt cavern reservoir low-position brine discharge well sand prevention and plugging construction method can use the bottom insoluble residue space of the salt cavity as a brine discharge starting point, form a stable fluid path through directional dissolution, effectively ensure the sand prevention and plugging function when the brine is discharged through the brine discharge well, improve the brine discharge efficiency of the brine discharge well, and reduce the sand plugging risk and operation cost in the gas injection and brine discharge process. (2) The construction method for preventing sand blockage in the low-level brine discharge well of the salt cavern storage of the present invention, by forming a cavitary cavity and a brine discharge channel, and by adopting a three-section well body structure and perforation technology, effectively prevents the occurrence of sand blockage during the brine discharge process, and has the advantages of improving brine discharge efficiency and gas storage space utilization. (3) The construction method for preventing sand blockage in the low-level brine discharge well of the salt cavern storage of the present invention has simple construction steps and equipment, low cost and high reliability, and can effectively solve the problem of sand blockage in the brine discharge well. It is highly advanced. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the construction structure for step S1 in an embodiment of the present invention; Figure 2 This is a schematic diagram of the construction structure for step S2 in an embodiment of the present invention; Figure 3 This is a schematic diagram of the construction structure for step S3 in an embodiment of the present invention; Figure 4 This is a schematic diagram of the construction method for preventing sand blockage in the low-level brine discharge well of the salt cavern storage according to the present invention. Figure 5 This is a schematic diagram of the construction process of the three-section wellbore structure in the construction method of the low-level brine discharge well for salt cavern storage of the present invention.

[0018] The attached diagram lists the components represented by each number as follows: 1. Surface casing of the brine discharge well; 2. Production casing of the brine discharge well; 21. Empty pipe section; 3. Three-section well section; 4. Surface casing of injection-production well; 5. Production casing of injection-production well; 6. Water injection pipe; 7. Solution cavity; 8. Two-way bridge plug; 81. Orifice. Detailed Implementation

[0019] The principles and features of the present invention are described below. The examples given are only for explaining the present invention and are not intended to limit the scope of the present invention.

[0020] like Figures 1-5 As shown, the construction method for sand plugging of low-level brine discharge wells in salt cavern storage according to the present invention includes the following steps: S1. Drill a brine discharge well at a target location near the salt cavity 100 of the salt cavern storage, and connect the bottom of the brine discharge well with the insoluble residue space at the bottom of the salt cavity 100. S2. Insert a water injection pipe 6 into the brine discharge well and inject water into the bottom of the well, so that a solution cavity 7 is formed between the bottom of the well and the bottom insoluble residue space of the salt cavity 100. S3. Remove the water injection pipe 6 and connect the melting chamber 7 to the brine discharge well to form a brine discharge channel, thus completing the construction.

[0021] The construction method of the present application can ensure the function of preventing sand blocking when using the brine drainage well to drain brine, and improve the brine drainage efficiency of the brine drainage well.

[0022] Specifically, in the traditional brine drainage operation of the salt cavern storage, the sediment particles easily gather near the pipe shoe of the brine drainage well due to the movement of the brine, which leads to sand blocking and seriously affects the brine drainage effect. The method of the present application uses the insoluble residue space at the bottom of the salt cavity as the starting point of brine drainage, forms a stable space of the solution cavity 7 through directional dissolution, prevents the sediment particles from gathering near the pipe shoe of the brine drainage well, and effectively maintains the brine drainage effect.

[0023] The drilling operation of the brine drainage well at the target position near the salt cavity 100 of the salt cavern storage refers to selecting a specific position of the brine drainage well that is in communication with the residue space at the bottom of the salt cavity 100. The drilling coordinates can be determined by using geological exploration and three-dimensional modeling technology to achieve this, and the position needs to avoid the top collapse area of the salt cavity to ensure that the bottom of the brine drainage well is directly connected with the residue space.

[0024] The communication between the bottom of the brine drainage well and the insoluble residue space at the bottom of the salt cavity 100 refers to forming a physical channel between the end of the wellbore and the sediment layer at the bottom of the salt cavity 100 through drilling technology. The channel can be achieved by using directional drilling or reaming technology, and the channel is used for the flow of brine and sediment particles during subsequent brine drainage.

[0025] The water injection pipe 6 is lowered to the bottom of the well to form a solution cavity 7 between the bottom and the salt cavity refers to expanding the original residue space by hydraulic dissolution of the salt rock layer. The solution cavity 7 can be formed by using a high-pressure water injection system to circulate and inject fresh water to dissolve the salt rock. The formation of the solution cavity 7 can increase the cross-sectional area of the brine drainage channel and reduce the accumulation of sand particles.

[0026] The water injection pipe 6 is removed and the solution cavity 7 is connected with the brine drainage well to form a brine drainage channel refers to removing the water injection pipe 6 and retaining the cavity formed by dissolution as a brine flow path. The channel can avoid the accumulation of sediment particles at the pipe shoe to cause blockage.

[0027] As a preferred embodiment, the scheme of the present application is implemented as follows: First, a suitable target position near the salt cavity 100 of the salt cavern storage is selected for the drilling operation of the brine drainage well. During the drilling process, the drilling depth and the formation are continuously monitored to ensure that the bottom of the brine drainage well is accurately connected with the insoluble residue space at the bottom of the salt cavity. After the connection, the wellbore is cleaned and detected as necessary to ensure the drilling quality.

[0028] Secondly, the water injection equipment and the water injection pipe 6 are prepared. The diameter of the water injection pipe 6 is appropriately smaller than the diameter of the wellbore of the brine discharge well, so as to be smoothly lowered and extracted. The water injection pipe is slowly lowered into the brine discharge well until it reaches the bottom of the well. The water injection equipment is started, and the injection rate and pressure are controlled to inject fresh water to the bottom of the well. During the water injection process, the injection amount and the backflow are monitored to determine the progress of the formation of the solution cavity 7.

[0029] The water injection is continuously performed until a solution cavity 7 of a sufficient size is formed between the bottom of the well and the insoluble residue space at the bottom of the salt cavity. The formation of the solution cavity 7 is determined by monitoring the injection amount of water, the backflow amount of water, and the change of the downhole pressure. When the solution cavity 7 reaches the predetermined size, the water injection is stopped.

[0030] Finally, the water injection pipe 6 is slowly extracted to avoid disturbing the newly formed solution cavity 7. After the extraction is completed, the wellbore is detected to confirm the connection condition between the solution cavity 7 and the brine discharge well. If necessary, a logging tool can be used to evaluate the shape and size of the solution cavity 7.

[0031] Preferably, in the method of the present application, the well structure is a three-opening well structure; the three-opening well structure can avoid the risk of sand plugging due to unstable well structure during the formation of the subsequent brine discharge channel, affecting the brine discharge efficiency.

[0032] Preferably, the three-opening well structure includes one-opening, two-opening and three-opening drilling operations performed in sequence, including the following steps: S1-1, performing one-opening drilling operation, and lowering the brine discharge well surface casing 1 into the one-opening well section for cementing to seal the shallow water layer and the easy leakage layer section.

[0033] S1-2, performing two-opening drilling operation, and stopping drilling when the drilling tool reaches the target distance position at the boundary of the salt cavity 100, and lowering the brine discharge well production casing 2 into the two-opening well section for cementing.

[0034] S1-3, performing three-opening drilling operation to obtain the three-opening well section 3, and connecting the three-opening well section 3 with the insoluble residue space at the bottom of the salt cavity 100. The three-opening drilling operation is completed by using a small-sized drill bit.

[0035] Specifically, after one-opening drilling, the surface casing 1 forms support to the shallow geological structure through cementing to prevent leakage of the shallow water layer and collapse of the stratum. After two-opening drilling to the predetermined distance, the brine discharge well production casing 2 is lowered and cemented to form rigid support of the intermediate layer section, avoiding deformation of the boundary of the salt cavity 100 due to subsequent operations. The three-opening drilling uses a small-sized drill bit to extend inside the cemented production casing to the residue space, ensuring the connectivity of the brine discharge channel.

[0036] Through layered cementing and size-reducing drilling, the overall stability of the wellbore structure is improved, and the well wall collapse or formation collapse during drilling can be effectively prevented, thereby improving the safety and stability of the drilling operation.

[0037] Preferably, the target distance is 25-35 meters, and the target distance is set by limiting the distance range between the drilling tool stop position and the boundary of the salt cavity 100, to ensure the stability of the cementing operation of the brine discharge well production casing 2. This range combines the mechanical properties of the salt rock formation and the process requirements of the dissolved cavity 7, which avoids excessive proximity of the drilling tool to the salt cavity boundary to cause formation disturbance, and reserves sufficient space for subsequent three-opening drilling.

[0038] In step S2 of the construction method of the present application, when the water outlet of the water injection pipe 6 is located in the three-opening well section 3 near the shoe position of the brine discharge well production casing 2, water injection is performed, and the shoe and the surrounding salt rock are dissolved; after the water injection is completed, the position of the brine discharge well production casing 2 near the shoe forms an empty pipe section 21, and the three-opening well section 3 forms a dissolved cavity 7 after being dissolved.

[0039] Preferably, the size of the water injection pipe 6 is one size smaller than that of the brine discharge well production casing 2, to ensure that the annular space between the pipe string and the wellbore is reasonable; the depth of the water injection pipe 6 is accurately controlled by the shoe position positioning system; the fresh water injection parameters are dynamically adjusted according to the salt rock dissolution rate, and the injection pressure is controlled within the compressive strength range of the brine discharge well production casing 2; the dissolution process can adopt an intermittent water injection mode, and the dissolution effect is monitored by the return brine turbidity; the length of the empty pipe section 21 is controlled by the dissolution time and the water injection flow rate, to form a length-controllable open hole section.

[0040] Preferably, the depth of the water injection pipe 6 can be controlled to be 1-2 meters away from the shoe 1 of the brine discharge well production casing 2. The water injection pressure is controlled to be 3-5 MPa, and the water injection flow rate is 30-50 m 3 / h. The duration of water injection is determined according to the actual situation, and is usually 24-48 hours. Thus, a diameter dissolved cavity 7 is formed at the position of the three-opening well section 3, and an empty pipe section 21 with a length of about 5-10 meters is formed in the brine discharge well production casing 2.

[0041] Preferably, a bidirectional bridge plug 8 is lowered into the empty pipe section 21, the end of the empty pipe section 21 is closed by setting the bridge plug, and a plurality of perforations 81 are obtained by perforating in the empty pipe section 21.

[0042] Preferably, the bidirectional bridge plug 8 is fixed at the end position of the empty pipe section 21 through a setting operation, and the setting operation is performed to physically isolate the empty pipe section 21 from the solution cavity 7; the perforation operation is performed at the empty pipe section 21 to form a plurality of perforation holes 81 on the pipe wall of the empty pipe section 21, so that the solution cavity 7 can communicate with the empty pipe section 21 through the perforation holes 81 to form a brine discharge channel. The number and distribution of these perforation holes 81 can be set according to actual needs.

[0043] Preferably, the hole diameter of the perforation hole 81 is designed according to the particle size distribution characteristics of the sediment particles, and the hole diameter needs to meet the brine passability requirement while limiting the entry of sediment particles into the channel.

[0044] Through the above technical solution, the present application forms a plurality of perforation holes 81 on the pipe wall of the brine discharge well, thereby increasing the number and area of the brine discharge channel. In this way, the brine can more fully enter the brine discharge well through these perforation holes 81, thereby improving the brine discharge efficiency. At the same time, the arrangement of the plurality of perforation holes 81 also reduces the risk of the single perforation hole 81 being blocked by the sediment, and even if some of the perforation holes 81 are blocked, the other perforation holes 81 can still work normally, thereby effectively preventing the occurrence of sand plugging and ensuring the long-term stable operation of the brine discharge well.

[0045] Preferably, the hole diameter of the perforation hole 81 is 8-12 mm; if the hole diameter of the perforation hole 81 is not reasonably controlled, the sediment particles may be accumulated at the perforation hole 81 or enter the brine discharge channel through the perforation hole 81 when flowing with the brine, thereby causing sand plugging or reducing the brine discharge efficiency.

[0046] Preferably, the hole density of the perforation needs to be comprehensively determined in combination with the length of the empty pipe section 21 and the setting position of the bidirectional bridge plug 8, so as to ensure that the perforation holes 81 are uniformly distributed in the empty pipe section.

[0047] Further preferably, the hole density is 150-200 holes / m. When the hole density is too small, the spacing between adjacent perforation holes 81 is too large, and the sediment particles are easy to accumulate at the gap between the perforation holes 81 during the brine discharge process; when the hole density is too large, the strength of the casing structure may be weakened. By setting the hole density to a value matched with the properties of the sediment particles, a dense and uniform brine discharge channel can be formed on the premise of ensuring the strength of the production casing 2 of the brine discharge well, so that the brine carrying the sediment particles is discharged through the plurality of perforation holes 81, thereby avoiding local high flow rate or particle accumulation.

[0048] In addition, the specific structure of the salt cavern storage is that the salt cavity 100 communicates with the salt cavern storage inlet through the injection-production well production casing 5 and the injection-production well surface casing 4; the injection-production well production casing 5 is used to establish a fluid transmission path between the inside of the salt cavity and the external injection-production system, and the injection-production well surface casing 4 is used to isolate the shallow formation and support the well wall structure. The combination of the two forms a complete injection-production well structure, thereby ensuring the connectivity between the salt cavity and the inlet.

[0049] Through the above technical solution, the present invention effectively establishes a directional brine discharge channel, realizes the directional flow of brine, avoids the disorderly accumulation of sediment in the brine discharge path, thereby preventing sand blockage caused by sediment accumulation at the pipe shoe position and ensuring the continuity of brine discharge operation.

[0050] The present invention will be illustrated by specific embodiments below.

[0051] Example This embodiment uses the construction method of the present invention to carry out sand-blocking operations on low-level brine discharge wells in salt cavern storage. The specific steps are as follows: S1, as attached Figure 1 As shown, the brine discharge well is undergoing normal drilling operations. Drilling for the brine discharge well is being carried out at a location 170m from the wellhead, 100 meters from the salt cavity.

[0052] This embodiment of drilling adopts a three-section wellbore structure, and the specific drilling operation includes the following steps: After drilling the first section of the brine discharge well, the surface casing 1 of the brine discharge well is installed and cemented to seal the upper shallow water layer and easily leaking sections. The drilling tool assembly is then installed for the second section of construction. Drilling is stopped 30 meters away from the boundary of the salt cavity. The production casing 2 of the brine discharge well is installed and cemented. The cementing cement returns to the surface. Then, a smaller drill bit is installed to complete the drilling of the third section of the well, connecting the insoluble residue space at the bottom of the salt cavity.

[0053] S2, as attached Figure 2 As shown, the water injection pipe 6 is lowered. A water injection pipe 6, which is one size smaller than the production casing 2 of the brine discharge well, is lowered into the production casing 2 of the brine discharge well. The water injection pipe 6 is lowered into the third section 3 of the well and close to the pipe shoe of the production casing 2 of the brine discharge well. Fresh water is injected to circulate and dissolve the salt rock near the third section 3, forming a solution cavity 7. At the same time, an empty casing 21 is formed in the production casing 2 of the brine discharge well.

[0054] S3, as attached Figure 3 As shown, the water injection pipe 6 is removed, and the bidirectional bridge plug 8 is inserted into the empty pipe section 21. Multiple holes 81 are obtained on the pipe wall of the empty pipe section 21 through setting and perforation, so that the melting cavity 7 is connected to the brine discharge well, forming a brine discharge channel and completing the construction.

[0055] In this embodiment, the aperture of the eyelet 81 is 10 mm, and the perforation density is 160 holes / m.

[0056] This embodiment establishes a low-level brine discharge well in a salt cavern storage facility using the construction method of the present invention. This well can prevent sand blockage during brine discharge, thereby improving the brine discharge efficiency. At the same time, the construction method and equipment are simple in structure, low in cost, and highly reliable. It can effectively solve the problem of sand blockage in brine discharge wells and is highly advanced.

[0057] In the description of the application, it should be understood that the orientation or positional relationship indicated by terms such as "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like is based on the orientation or positional relationship shown in the drawings, and is only for the purpose of facilitating the description of the application and simplifying the description, and does not indicate or imply that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation of the application.

[0058] In addition, the terms "first", "second" are only for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the technical features indicated. Therefore, the features defined with "first", "second" can explicitly or implicitly include at least one of the features. In the description of the application, the meaning of "a plurality of" is at least two, such as two, three, etc., unless otherwise explicitly specified and limited.

[0059] In the present application, unless otherwise explicitly specified and limited, the terms "mounting", "connecting", "connecting", "fixing" and the like should be understood broadly, for example, it can be fixedly connected, or it can be detachably connected, or it can be integrated; it can be mechanically connected, or it can be electrically connected; it can be directly connected, or it can be indirectly connected through an intermediate medium; it can be the internal communication of two elements or the interaction relationship between two elements, unless otherwise explicitly limited. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0060] In the present application, unless otherwise explicitly specified and limited, the first feature is "on" or "under" the second feature, which can be direct contact between the first and second features, or indirect contact between the first and second features through an intermediate medium. Moreover, the first feature "above", "above" and "above" the second feature can be directly above or obliquely above the first feature, or only indicate that the horizontal height of the first feature is higher than that of the second feature. The first feature "below", "below" and "below" the second feature can be directly below or obliquely below the first feature, or only indicate that the horizontal height of the first feature is less than that of the second feature.

[0061] In the description of the specification, the description using the terms "one embodiment", "some embodiments", "an example", "a specific example", or "some examples" etc. means that the particular feature, structure, material or characteristic being described is included in at least one embodiment or example of the present application. The illustrative appearances of the above-mentioned terms in various places in the specification are not necessarily referred to the same embodiment or example. Moreover, the particular features, structures, materials, or characteristics can be combined in any suitable manner in one or more embodiments or examples. Furthermore, the description herein of certain examples does not necessarily exclude these examples from the scope of the application, and these examples can be combined with each other for the purposes of one or more other examples.

[0062] Although the embodiments of the present application have been shown and described above, it is understood that the above-described embodiments are exemplary and are not to be interpreted as limiting the present application, and that variations, modifications, substitutions and changes can be made by those skilled in the art without departing from the scope of the present application.

Claims

1. A construction method for preventing sand blocking in a low-position brine discharge well of a salt cavern storage, characterized in that, The method comprises the following steps: S1, drilling a drainage well at a target position near a salt cavity (100) of a salt cavern storage, and making the bottom of the drainage well in space communication with the bottom of the salt cavity (100); S2, lowering a water injection pipe (6) into the drainage well and injecting water to the bottom of the well to form a solution cavity (7) between the bottom of the well and the bottom of the salt cavity (100); S3, removing the water injection pipe (6), connecting the solution cavity (7) with the drainage well to form a drainage channel, and completing the construction.

2. The construction method of the salt cavern storage low position brine discharge well sand control and plugging according to claim 1, characterized in that, In step S1, the well structure is a three-section well structure.

3. The construction method of the sand plug of the low position discharge well of the salt cavern storage according to claim 2, characterized in that, The drilling operation comprises the following steps: S1-1, performing a first drilling operation and lowering a drainage well surface casing (1) into the first well section to cement the well; S1-2, performing a second drilling operation, stopping the drilling when the drilling tool reaches a target distance position from the boundary of the salt cavity (100), and lowering a drainage well production casing (2) into the second well section to cement the well; S1-3, performing a third drilling operation to obtain a third well section (3) and connecting the third well section (3) with the bottom of the salt cavity (100).

4. The construction method of the sand plug of the low position discharge well of the salt cavern storage according to claim 3, characterized in that, In step S1-2, the target distance is 25-35 meters.

5. The construction method of the sand plug of the low position discharge well of the salt cavern storage according to claim 3, characterized in that, In step S2, the water injection is performed after the water outlet of the water injection pipe (6) is located at the shoe position of the production casing (2), and the salt rock near the shoe position of the production casing (2) is dissolved; after the water injection is completed, an empty pipe section (21) is formed near the shoe position of the production casing (2), and the salt rock is dissolved to form the solution cavity (7).

6. The construction method of the salt cavern storage low position discharge well sand control plug according to claim 5, characterized in that, A bidirectional bridge plug (8) is lowered into the empty pipe section (21), and a plurality of perforations (81) are obtained on the wall of the empty pipe section (21) by setting and perforating.

7. The construction method of the salt cavern storage low position discharge well sand control plug according to claim 6, characterized in that, The diameter of the perforations (81) is 8-12 mm.

8. The construction method of the sand plug of the low position discharge well of the salt cavern storage according to claim 6, characterized in that, The perforation density is 150-200 holes / m.

9. The construction method of the salt cavern storage low position discharge well sand control plug according to any one of claims 1-8, characterized in that, In step S1, the target position is 150-250 meters away from the wellhead of the salt cavern storage.

10. The construction method of a salt cavern storage low position brine discharge well sand control plug according to claim 9, characterized in that, The salt cavity (100) is in communication with the entrance of the salt cavern storage through an injection-production well production casing (5) and an injection-production well surface casing (4).

Images