Large-diameter halogen extraction well shaft structure suitable for salt lake mines

Abstract

A kind of large-diameter brine well well structure suitable for salt lake mine, including brine well, the outside of the well mouth of brine well is equipped with well platform, the center of brine well is placed well pipe, the hole depth of brine well is greater than well pipe installation depth, forms well bottom buffer adjustment section at bottom, well pipe includes upper well mouth section solid pipe, middle gushing section screen pipe and solid pipe in vertical direction, bottom sand setting section solid pipe, gravel is filled between the well wall of brine well and well pipe and well bottom buffer adjustment section, the well platform includes well pipe frame and well platform outer frame, the well mouth of brine well is also equipped with water injection pipe, the nozzle of water injection pipe is fixed on well pipe frame, water injection hole is equipped on the panel of well platform outer frame.The present application can guarantee the sustained stable and safe operation of brine well.

Description

Technical Field

[0001] This invention relates to a brine well shaft structure, specifically a large-diameter brine well shaft structure suitable for salt lake mines. Background Technology

[0002] Currently, as underground brine levels have gradually declined due to years of mining, most salt lake mines under development in China have shifted from the early single-channel mining method to a mining method that primarily uses brine wells and supplements channel mining, or a single brine well mining method. Brine wells mostly use large-diameter wells with diameters of 600–1200 mm. Common well structures include bare well structure, wellhead casing + bare well structure, well casing structure, and well casing + gravel-filled structure (as shown in the attached diagram). Figure 5-8 (As shown). The first two types of brine well platforms are mostly constructed with a steel wellbore approximately 0.5–1m high. Support rods or pipes can be welded to the bottom of the wellbore as needed, and a steel plate with a central borehole can be welded to the top of the wellbore for coverage. The latter two types of brine well platforms are generally constructed with a steel plate with a central borehole or a ring-shaped concrete platform approximately 0.25–0.35m high and 0.25–0.35m wide, cast around the well circumference (see attached). Figure 5 ).

[0003] Based on a comprehensive analysis of the actual operation of brine wells in various salt lake mines in China over many years, the above four well structures are generally only suitable for formations with relatively good self-stability or water stability, such as those with thick and continuous salt layers, few mud and sand interlayers between salt layers, and small single-layer thickness.

[0004] When the formation around the well has relatively poor self-stability or water stability, the above-mentioned well structure is prone to excessively rapid and thick sedimentation at the bottom of the well, or even well collapse or wellhead collapse. This increases the production and maintenance costs of brine wells, reduces production stability, and increases production safety risks. In severe cases, it may even be unable to meet normal production needs. Among them, the well casing + gravel filling structure is also prone to damage to the seepage channels constructed by "gravel + screen pipe". On the one hand, the instability of the formation around the well causes a significant drop in gravel, eventually leading to misalignment between the gravel and the screen pipe in the well casing. On the other hand, during operation, the gravel is affected by brine salt formation, which easily causes salt to accumulate on the surface, reducing pore connectivity. In addition, the instability of the formation causes a large amount of fine debris to enter the gravel pores, forming blockages.

[0005] In the northwestern part of the Biele Beach mining area of ​​the Qarhan Salt Lake, the underground brine is mainly located between the salt crystals and is pressurized. Above the salt layer to the surface, there are generally silty clay or silt layers with obvious dissolution characteristics and easy collapse of water bubbles. The clastic interlayers between the salt layers are relatively well-developed and are mainly composed of mud or silt with poor self-stability, with a local thickness of more than 3 meters. The depth of the brine wells in this area is generally 25-35 meters. The well structure has successively adopted the bare well structure, wellhead casing + bare well structure, well casing, and well casing + gravel filling structure, but all of them could not meet the normal production needs due to wellhead collapse.

[0006] For example, in the Xingyuan mining area of ​​Dalangtan Salt Lake, underground brine is mainly found between salt crystals and is primarily pressurized brine. Salt and mud layers in this mining area are often interbedded, with the mud layer being soft and lacking self-stability; the thickness of a single mud layer can reach over 10 meters. Existing brine wells in this area are generally 150-260 meters deep, with most being bare wells and a few having tubular structures. Due to slag shedding or local collapses of the well walls, sediment buildup is severe. In relatively better areas, well cleaning is required approximately every 5-6 months, while in poorer areas it is required every 3-4 months. During this period, sediment thickness varies from 50-100 meters. Furthermore, to avoid burying or burning out pumps, multiple pumping operations are necessary, and some wells produce turbid brine. This not only significantly increases brine extraction costs but also limits the extraction capacity and stable operating time of individual wells, thus hindering the effective expansion of brine extraction scale to some extent. According to feedback from technicians at Xingyuan Mining Area, several test wells with a well casing and gravel filling structure were constructed, but they all failed to be successful due to problems such as reduced water output or salt accumulation.

[0007] Furthermore, when salt lake mines need to carry out large-scale solid-liquid conversion and dissolution mining of their solid salt ore, or when the brine is severely salt-contaminated and requires the addition of appropriate amounts of anti-salt-contaminated fresh water to the brine well pumps, the safety risks of the currently commonly used large-diameter brine well structure will increase, and in severe cases, well collapse may occur. For example, in the CITIC Guoan Xitai Jinaier Lake mining area, the brine wells originally adopted a wellhead casing + bare well structure. Before the implementation of large-scale solid-liquid conversion and dissolution mining of solid potassium ore in the mining area, the brine wells operated relatively safely and stably. However, before and after the implementation of large-scale solid-liquid conversion and dissolution mining of solid potassium ore, the solid salt layer around the brine wells was subjected to a certain degree of erosion and damage due to long-term solvent injection and contact under the solid-liquid conversion production mode, and the brine wells began to collapse one after another. Summary of the Invention

[0008] The technical problem to be solved by this invention is to provide a safe and reliable wellbore structure for large-diameter brine extraction wells suitable for salt lake mines.

[0009] The technical solution adopted by this invention to solve its technical problem is: a well body structure suitable for large-diameter brine mining wells in salt lake mines, including a brine mining well, characterized in that: a well platform is provided on the outside of the wellhead of the brine mining well, a well pipe is placed in the center of the brine mining well, the drilling depth of the brine mining well is greater than the installation depth of the well pipe, and a bottom buffer adjustment section is formed at the bottom, the well pipe includes an upper wellhead section solid pipe, a middle water inflow section screen pipe and solid pipe, and a bottom sand settling section solid pipe in the vertical direction, gravel is filled between the well wall and the well pipe and the bottom buffer adjustment section of the brine mining well, the well platform includes a well pipe frame and a well platform outer frame, the wellhead of the brine mining well is also provided with a water injection pipe, the pipe opening of the water injection pipe is fixed on the well pipe frame, and the well platform outer frame panel is provided with a water injection hole, the water injection hole is correspondingly connected to the water injection pipe, and is used to inject fresh water.

[0010] Furthermore, the intermediate water-flow section screen pipe and solid pipe include screen pipes set in the salt layer section and solid pipes in the remaining sections. The screen pipes have screen holes evenly arranged, with a porosity of 15% to 30%. The screen hole shape is preferably strip-shaped, with a width of 5 to 8 mm.

[0011] Furthermore, the length of the well pipe frame is 2 to 2.5 times the diameter of the brine well. The well pipe frame and the well pipe are fixed in a "well" shape. The outer frame of the well platform consists of side plates and a panel. The panel is square or nearly square, with a side length of 2 to 2.5 times the diameter of the well. The panel has a hole in the center with a diameter matching the outer diameter of the well pipe. The height of the side plates matches the height of the well pipe frame. The top of the well pipe is 0.6 to 0.8 meters higher than the well platform panel.

[0012] Furthermore, the brine extraction well is provided with a wellhead protective pipe at the shallow part of the wellhead. The wellhead protective pipe penetrates the shallow strata with relatively poor self-stability or water stability and enters the strata with relatively good stability below. The diameter of the wellhead protective pipe is 200-400 mm larger than the diameter of the brine extraction well below it.

[0013] Furthermore, the wellhead casing is provided with multiple grouting pipes on the outer side of the casing wall. After the wellhead casing is installed, grouting is performed through the grouting pipes to ensure a tight fit between the casing wall and the surrounding strata.

[0014] Furthermore, the drilling depth of the brine extraction well exceeds the well casing installation depth by 0.5% to 2%.

[0015] Furthermore, the diameter of the brine extraction well is 600-1200 mm, and the outer diameter of the well pipe is 200-400 mm smaller than the diameter of the brine extraction well.

[0016] Furthermore, the well platform panel is provided with several gravel inlets for observing the descent of gravel on the outside of the well casing or for replenishing gravel.

[0017] Furthermore, the particle size of the gravel is matched with the sieve aperture size, which is 1.5 to 3 times the slit width.

[0018] Furthermore, the well casing is a steel pipe, fiberglass pipe, or PE pipe with a wall thickness of 6-10mm.

[0019] The beneficial effects of this invention are as follows: Under formation conditions with relatively poor formation self-stability or water stability, compared with the currently commonly used wellbore structures, it enables brine wells to achieve safe and stable operation and produce clear brine, effectively reducing the production and maintenance costs and production safety risks of brine wells, which is conducive to reducing the brine extraction costs of enterprises and improving brine extraction efficiency; in addition, when the solid salt layer around the brine well is subjected to long-term solid-liquid conversion solvents or anti-salt-forming freshwater erosion and damage, compared with the currently commonly used wellbore structures, it can promptly fill and repair the erosion cavities, eliminate safety hazards in a timely manner, and avoid continuous deterioration. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the structure of Embodiment 1 of the present invention; Figure 2 This is a schematic diagram of the structure of Embodiment 2 of the present invention; Figure 3 This is a schematic diagram of the outer frame elevation structure of the well platform in Example 1 / 2; Figure 4 This is a schematic diagram of the planar structure of the well platform in Example 1 / 2; Figure 5 This is a schematic diagram of the structure of a bare well in the existing technology; Figure 6 This is a schematic diagram of the structure of wellhead casing and bare well in the existing technology; Figure 7 This is a schematic diagram of the structure of a well casing in the existing technology; Figure 8 This is a schematic diagram of the well casing and gravel packing structure in the existing technology.

[0021] In the diagram: 1. Brine well, 2. Well platform, 2-1. Well pipe frame, 2-2. Well platform outer frame, 2-21. Side plate, 2-22. Panel, 2-3. Water injection hole, 3. Well pipe, 3-1. Upper wellhead section solid pipe, 3-2. Middle water inflow section screen pipe and solid pipe, 3-21. Screen pipe, 3-22. Solid pipe, 3-3. Bottom sand settling section solid pipe, 4. Buffer and regulating section, 5. Gravel, 6. Water injection pipe, 7. Wellhead protective pipe, 7-1. Grouting guide pipe, 8. Well wall. Detailed Implementation

[0022] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments.

[0023] Example 1 See attached document Figure 1 , 34. The large-diameter brine well structure of this embodiment is suitable for use in shallow strata with relatively good self-stability or water stability. The well diameter is 1000mm. A well platform 2 is provided on the outside of the wellhead of the brine well 1. The dimensions (length × width × height) of the well platform 2 are 2m × 2m × 0.3m. The well pipe 3 is installed in the center of the brine well 1. The outer diameter of the well pipe 3 is 660mm. Based on factors such as the underground brine water level, the vertical distribution of the brine strata, and the function of the well pipe, the well pipe 3 can be roughly divided into three parts in the vertical direction: the upper wellhead section solid pipe 3-1, the middle water-flow section screen pipe and solid pipe 3-2, and the bottom sand-falling section solid pipe 3-3. To ensure that the well pipe 3 is installed in place, the drilling depth of the brine well 3 exceeds the installation depth of the well pipe 3 by about 1 meter. 0.5%, forming a buffer adjustment section 4 at the bottom of brine well 3; after the well pipe 3 is installed in place, gravel 5 is filled between the well wall of brine well 1 and the well pipe 3 and the buffer adjustment section 4 at the bottom of the well. After the gravel filling is completed, the well platform 2 is installed. The well platform 2 includes a well pipe frame 2-1 and a well platform outer frame 2-2. During the operation of the brine well, gravel 5 can be replenished in time according to the sinking of gravel 5 to maintain the integrity and stability of the well body structure. In order to prevent salt accumulation or blockage of the well pipe 3 and its surroundings during the operation of brine well 1, a water injection pipe 6 of appropriate length is left at the wellhead of brine well 1 when filling gravel 5. The pipe opening of the water injection pipe 6 is fixed on the well pipe frame 2-1, and a water injection hole 2-3 is opened on the panel of the well platform outer frame 2-2. The water injection hole 2-3 is connected to the water injection pipe 6 to facilitate the subsequent injection of fresh water.

[0024] Well casing 3 is made of 8mm thick steel pipe according to strength requirements. The length of the bottom sand-laden section 3-3 is 5m.

[0025] The intermediate water-flow section screen pipe and solid pipe 3-2 includes screen pipe 3-21 installed in the salt layer section where the underground brine to be extracted is mainly located, and solid pipe 3-22 installed in the remaining sections. Screen pipe 3-21 has screen holes evenly arranged, with a porosity of 15% to 30%. The shape of the screen holes is a strip slit with a slit width of 5 to 8 mm, which needs to be reasonably determined based on the composition of salt layer particles.

[0026] The bottom buffer adjustment section 4 serves two purposes. First, it prevents excessive slag buildup at the bottom of the well due to well wall collapse or partial collapse during well construction. This would prevent the screen pipe 3-21 from being accurately installed in the designed position during the pre-processed well pipe 3 installation, which would be detrimental to the later operation of the brine well 1. Second, by filling the bottom buffer adjustment section 4 with gravel 5 to form a gravel layer of a certain thickness, it can prevent slag, salt, or soil from being squeezed into the well pipe due to negative pressure. It can also form a gravel layer foundation of a certain thickness at the bottom of the well pipe 3, which is beneficial to avoid or reduce the settlement of the well pipe 3.

[0027] The well frame 2-1 can be made of 28# channel steel according to strength requirements. The length of the well frame 2-1 is twice the diameter of the brine well 1. The well frame 2-1 and the well pipe 3 are welded and fixed in a "well" shape. If the well pipe 3 is long and heavy, appropriate reinforcing ribs can be added between the well frame 2-1 and the well pipe 3 for welding connection. The well platform outer frame 2-2 can be made of 12mm thick steel plate according to strength requirements. It consists of side plates 2-21 and front panel 2-22. The front panel is square, with a side length twice the diameter of the brine well 1. The plate has a central hole with a diameter matching the outer diameter of the well pipe 3. The side plate 2-21 is 0.3m high and needs to match the height of the well pipe frame 2-1. To facilitate installation, the well platform outer frame 2-2 is made into two symmetrical parts, and bolt holes are welded at the interface of the side plate 2-22. After installation, it is fixed with bolts. The top of the well pipe 3 needs to be 0.6m higher than the well platform panel. On the one hand, this is beneficial for safety protection and reduces safety hazards. On the other hand, this height facilitates the disassembly of flange bolts when installing the brine well 1 pump pipe.

[0028] Gravel 5 is made of hard, rounded sand and pebbles that are not easily corroded. The particle size matches the sieve aperture size, which is generally 1.5 to 3 times the sieve width.

[0029] This embodiment requires backfilling the entire well section with gravel 5. The gravel 5 is backfilled section by section from the bottom of the borehole to the wellhead of the brine well 1 along the outer perimeter of the well casing 3. Unlike the commonly used well casing + gravel backfilling structure, gravel is only backfilled in the section of screen pipe 3-21, and the backfilling height is only appropriately extended beyond the upper limit of the screen pipe to account for the possibility of gravel 5 settling during actual construction. Backfilling with gravel 5 can fill, repair, and support the deformed area of ​​the well wall during the well completion process of the brine well 1. It can also form a composite filter layer with the screen pipe 3-21 to reduce the mud and sand content in the brine, effectively mitigating sedimentation in the well. During the operation of the brine well 1, the gravel 5 can also be used to adjust the backfilling height according to the specific conditions. In case of sinking, gravel should be added in a timely manner. The sinking of gravel 5 will fill and repair the deformation cavities caused by the falling of blocks or molten salt in the well wall of brine well 1 during operation. On the one hand, it can effectively maintain the integrity and stability of the well structure. On the other hand, the filling and replacement of the surrounding strata by gravel 5 will also expand the effective radius of brine well 1 to a certain extent, which is conducive to improving the brine extraction capacity of brine well 1. In order to facilitate the observation of gravel 5 and the replenishment of gravel, 2 to 4 gravel inlets can be opened on the panel of the outer frame 2-2 of the well platform. When the amount is small, gravel can be filled through the gravel inlets. When the amount is large, the outer frame 2-2 of the well platform can be disassembled and gravel can be filled.

[0030] The main purpose of the water injection pipe 6 is to ensure the safety and stability of the brine wellhead 1 and to prevent direct contact between fresh water and the shallow formation at the wellhead of brine well 1 during the fresh water injection process, which could cause dissolution and damage. The water injection pipe 6 can effectively solve the problem of salt accumulation or blockage of the well pipe 3 and gravel 5 during the operation of brine well 1. In the early stage of well completion, the water injection pipe 6 can also be used to inject an appropriate amount of fresh water to accelerate the flushing and pumping of brine well 1.

[0031] In this embodiment, a test well was constructed in September 2021 in the Liangdong brine mining area of ​​the Xingyuan mining area in Dalangtan Salt Lake, with a depth of 164m. The underground brine in this area is mainly located between salt crystals and is predominantly pressurized brine. Salt and mud layers often occur in alternating layers; the mud layers are soft, have poor self-stability, and the maximum thickness of a single mud layer can reach over 10m. For a long time, existing brine wells in this area have suffered from poor surrounding strata stability, resulting in severe wellbore collapse, frequent pumping and cleaning, short effective operating time, shallow effective brine extraction depth, and significant production safety hazards.

[0032] To date, the test well has been in trial operation for nearly four months, with overall continuous and stable operation, water volume meeting standards, water quality being clear, wellhead being stable, gravel channels being unobstructed, and sediment thickness at the bottom of the well being only tens of centimeters. This has basically verified the rationality, applicability, and reliability of the well structure in this embodiment.

[0033] Example 2 See attached document Figure 2 , 3 4. The wellbore structure of the large-diameter brine extraction well in this embodiment is suitable for use in surface conditions where the self-stability or water stability of the shallow strata at the wellhead is relatively poor. The difference between this embodiment and embodiment 1 is that a wellhead protective pipe 7 is added to the shallow part of the wellhead of the brine extraction well 1. The wellhead protective pipe 7 needs to penetrate the shallow strata with relatively poor self-stability or water stability and enter the strata with relatively good stability below by about 0.5m. The diameter of the wellhead protective pipe 7 is 220mm larger than the diameter of the brine extraction well 1 below it, and the outer diameter of the well pipe 3 is 720mm.

[0034] Well casing 3 is made of steel pipe with a wall thickness of 8mm, based on strength requirements.

[0035] According to strength requirements, the wellhead casing 7 is made of 10mm thick steel pipe. If the water stability of the shallow formation at the wellhead is poor and the water bubble is prone to collapse, and the underground pressurized brine level in the brine well 1 can reach the section of the wellhead casing 7, 2 to 4 grouting pipes 7-1 can be installed on the outside of the pipe wall during the processing of the wellhead casing 7. After the wellhead casing 7 is installed, appropriate post-grouting is carried out to ensure that the pipe wall is tightly bonded to the surrounding formation. The presence of the wellhead casing 7 can provide good support and protection for the shallow formation at the wellhead where the water stability is poor, and can also ensure the smooth and stable passage of the gravel material 5 at the wellhead, which is convenient for subsequent gravel replenishment.

[0036] In this embodiment, five test wells were drilled in the northwestern part of the Biele Beach mining area of ​​the Qarhan Salt Lake in June and July 2021, with a depth of 23-25m. The underground brine in this area is mainly located between salt crystals and is pressurized. Above the salt layers and down to the surface, there are generally silty clay or silt layers with obvious dissolution characteristics and prone to collapse, with a total thickness of 5-8m. Clastic interlayers between the salt layers are relatively well-developed, mainly composed of mud or sand with poor self-stability, and locally reaching a thickness of over 3m. Previously drilled brine wells in this area generally suffered from large-scale wellhead collapse, and some wells also experienced well casing subsidence.

[0037] To date, the test well has been in trial operation for nearly 7 months. Overall, the operation has been continuous and stable, with water volume meeting standards, water quality being clear, wellhead being stable, gravel channels being unobstructed, and the thickness of sediment at the bottom of the well mostly not exceeding 1 meter. This has effectively verified the rationality, applicability, and reliability of the well structure in this embodiment.

[0038] Those skilled in the art can make various modifications and variations to this invention. If such modifications and variations are within the scope of the claims of this invention and their equivalents, then such modifications and variations are still within the protection scope of this patent.

[0039] The contents not described in detail in the specification are prior art known to those skilled in the art.

Claims

1. A shaft structure for a large-diameter brine extraction well suitable for salt lake mines, comprising a brine extraction well, characterized in that: A well platform is provided on the outer side of the brine extraction well. A well casing is installed at the center of the brine extraction well. The drilling depth of the brine extraction well is greater than the installation depth of the well casing, forming a bottom buffer adjustment section. The well casing vertically includes an upper wellhead section (solid pipe), a middle water-flow section (screen pipe and solid pipe), and a bottom sand-sinking section (solid pipe). Gravel is filled between the well wall and the well casing, as well as in the bottom buffer adjustment section. The well platform includes a casing frame and an outer frame. A water injection pipe is also provided at the wellhead of the brine extraction well, with its inlet fixed to the casing frame. The outer frame of the well platform... The panel is equipped with water injection holes, which are connected to corresponding water injection pipes for injecting fresh water. The intermediate water-flow section screen pipe and solid pipe include screen pipes installed in the salt layer section and solid pipes in the remaining sections. The screen pipes are evenly arranged, with a porosity of 15% to 30% and a strip-shaped slit shape, with a slit width of generally 5 to 8 mm. The length of the well pipe frame is 2 to 2.5 times the diameter of the brine well. The well pipe frame and well pipe are fixed in a "well" shape. The outer frame of the well platform consists of side plates and a panel, with the panel being square or nearly square. The wellhead has a side length of 2 to 2.5 times the well diameter, a central opening in the panel with a diameter matching the outer diameter of the well casing, and a side plate height matching the height of the well casing support. The top of the well casing is 0.6 to 0.8 meters higher than the well platform panel. A wellhead casing is installed at the shallow part of the brine wellhead. This casing penetrates the shallow strata with relatively poor self-stability or water stability and enters the lower, more stable strata. The diameter of the wellhead casing is 200 to 400 mm larger than the diameter of the brine well below it. Multiple grouting guides are installed on the outer side of the wellhead casing. After the wellhead casing is installed, post-grouting is carried out through the grouting pipe to ensure a tight fit between the casing wall and the surrounding formation. Gravel is then filled throughout the well section, and the gravel is backfilled from the bottom of the well to the brine wellhead section by section along the outer perimeter of the casing. The gravel filling is used to fill, repair, and support the deformed areas of the well wall during the brine well formation process, forming a composite filter layer with the screen pipe. During the operation of the brine well, gravel is replenished in a timely manner according to the gravel sinking situation. The gravel sinking is used to promptly fill and repair the deformation cavities caused by the falling of blocks or dissolved salt in the brine well wall during operation.

2. The shaft structure for large-diameter brine wells suitable for salt lake mines according to claim 1, characterized in that: The drilling depth of the brine extraction well exceeds the well casing installation depth by 0.5% to 2%.

3. The shaft structure for large-diameter brine wells suitable for salt lake mines according to claim 1, characterized in that: The diameter of the brine extraction well is 600-1200 mm, and the outer diameter of the well pipe is 200-400 mm smaller than the diameter of the brine extraction well.

4. The shaft structure for large-diameter brine wells suitable for salt lake mines according to claim 1, characterized in that: The well platform panel has several gravel inlets for observing the descent of gravel on the outside of the well casing or for replenishing gravel.

5. The shaft structure for large-diameter brine wells suitable for salt lake mines according to claim 1, characterized in that: The particle size of the gravel is matched with the sieve aperture size, which is 1.5 to 3 times the slit width.

6. The shaft structure for large-diameter brine wells suitable for salt lake mines according to claim 1, characterized in that: The well casing is made of steel, fiberglass, or PE pipe with a wall thickness of 6-10mm.

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