Recharge anti-seepage system for controlling wellhead collapse of salt lake brine well and construction method thereof

Abstract

The application provides a backfill anti-seepage system for controlling wellhead collapse of a salt lake brine well and a construction method thereof. The backfill anti-seepage system for controlling wellhead collapse of a salt lake brine well comprises a water-stopping anti-seepage system, a saltwater backfill device, and the water-stopping anti-seepage system comprises a base artificial aquiclude located in a salt lake and a water-stopping anti-seepage wall arranged around the base artificial aquiclude in a circumferential direction, a bottom end of the water-stopping anti-seepage wall is embedded in the base artificial aquiclude, and a top end of the water-stopping anti-seepage wall can pass out of the salt lake; the saltwater backfill device comprises a backfill well, a pressurizing pump arranged on one side of the backfill well, and a saltwater preparation tank in communication with the pressurizing pump, wherein the backfill well is located in the water-stopping anti-seepage wall, the saltwater preparation tank is used for storing backfill saltwater liquid, and the pressurizing pump is used for pumping the backfill saltwater liquid into the backfill well. The technical scheme of the application can improve the bearing capacity of a salt layer skeleton at a wellhead, make the salt layer skeleton fully rebound, solve the problem of wellhead collapse of a brine well caused by continuous reduction of a groundwater level, and thus prolong the service life of the brine well.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of underground brine exploitation, in particular to a backfill anti-seepage system for controlling the wellhead collapse of a salt lake brine well and a construction method thereof. BACKGROUND

[0002] The underground water of a salt lake is generally divided into four aquifers, and the stratum of the aquifer is mainly composed of salt deposits, and the clastic sedimentary layers between the salt layers are separated as relative aquifuges. According to the hydrogeological conditions, the brine is divided into potential brine and confined brine, the potential brine is buried at a depth of 10 m or less, and the confined brine is buried at a relatively deep depth, and the brine below the first aquifuge is the confined brine. The brine exploitation methods mainly include channel mining and well mining. The channel mining is suitable for the surface potential brine of the salt lake, and this method is fast, simple, efficient, low in cost, small in difficulty and easy to construct, but the confined brine is buried at a great depth, and the brine channel is prone to collapse, resulting in insufficient channel depth and poor brine mining effect. At present, the well mining technology is mainly used for mining the S3 layer of the confined brine with a depth of 10 m to 30 m, but due to the influence of the stratum structure, brine mining activities, mining methods and atmospheric precipitation, etc., the salt field and brine well collapse accidents often occur in the salt lake mining, resulting in personnel death, loss of mineral brine and great loss.

[0003] At present, in the prior art, the brine well is directly installed in the salt lake to collect brine, and the long-term excessive brine pumping in the salt lake mining production process leads to the continuous reduction of the underground water level, the reduction of the brine level, the water release compression of the salt layer structure of the aquifer, the unsaturated brine filling support of the salt rock pore, the continuous backflow of the salt-containing fine sand layer and silt layer in the stratum to the well body, the reconstruction of the stratum rock-soil structure, the change of the structure from "rock salt layer + brine" to "rock salt layer + pore", the reduction of the stratum support capacity and the increase of the overall collapse risk. In addition, in the salt lake production, the discharge of low salinity brine, the increase of atmospheric precipitation in the process of warm and humid climate on the plateau, the leakage of the salt lake brine, the overflow of the confined brine due to the relatively low salinity, the dissolution of the easily soluble salt such as sodium salt and potassium salt and the cementing material between the silt and sand particles in the stratum, the generation of the cavity dissolution cavity and the large-scale collapse accidents of the salt field and the brine well. SUMMARY

[0004] The main purpose of the present application is to provide a backfill anti-seepage system for controlling the wellhead collapse of a salt lake brine well and a construction method thereof, so as to solve the problem of the overall collapse of the wellhead of the brine well caused by the continuous reduction of the underground water level in the prior art.

[0005] In order to achieve the above-mentioned purpose, according to one aspect of the present application, a kind of backfill anti-seepage system for controlling salt lake brine well wellhead collapse is provided, comprising: water-stop anti-seepage system, including the artificial aquiclude of base in salt lake and the circumferential water-stop anti-seepage wall of artificial aquiclude of base, the bottom end of water-stop anti-seepage wall is embedded in artificial aquiclude of base, and the top end of water-stop anti-seepage wall can pass out of salt lake;Salt water backfill device, including backfill well, pressurized pump being arranged in the side of backfill well and salt water configuration box being communicated with pressurized pump, wherein, backfill well is located in water-stop anti-seepage wall, and salt water configuration box is used to store backfill salt water liquid, and pressurized pump is used to pump backfill salt water liquid into backfill well.

[0006] Further, the longitudinal section of the water-stop anti-seepage wall is trapezoidal, and the thickness of the water-stop anti-seepage wall gradually increases from top to bottom.

[0007] Further, the depth of the water-stop anti-seepage wall embedded in the artificial aquiclude of base is 0.5m to 1m; and / or, the water-stop anti-seepage wall is located 2m inward from the outer edge of the artificial aquiclude of base.

[0008] Further, the backfill well comprises: a well body opened on the salt lake; a steel pipe set at the top end of the well body; a filter pipe located in the well body, with one end of the filter pipe extending into the bottom of the well body and the other end of the filter pipe extending out of the well body; a gravel layer located in the annular gap formed between the filter pipe and the inner wall of the well body; and a fresh water pipe set in the filter pipe.

[0009] Further, the backfill anti-seepage system further comprises a plurality of grouting pipes arranged in the water-stop anti-seepage system, with one end of each grouting pipe extending into the salt lake and the other end of each grouting pipe extending out of the salt lake; a plurality of clay balls are put into the salt lake through the grouting pipes to form the artificial aquiclude of base.

[0010] According to another aspect of the present application, a construction method of a backfill anti-seepage system is provided, which is used to construct the above-mentioned backfill anti-seepage system, and the construction method comprises: a first construction step of constructing the artificial aquiclude of base in the salt lake; a second construction step of constructing the water-stop anti-seepage wall in the salt lake; a third construction step of arranging the backfill well, the pressurized pump and the salt water configuration box in the water-stop anti-seepage system; and a backfill step of backfilling saturated salt water into the backfill well.

[0011] Further, in the first construction step, the artificial aquiclude of base is made of anti-seepage clay, the anti-seepage clay is made of clay, saturated brine, magnesium-based cementitious material and clay curing agent according to a first preset ratio, the compaction coefficient of the anti-seepage clay is greater than 92%, and the average dry bulk density of the anti-seepage clay after compaction is greater than 1.65g / cm 3 .

[0012] Further, the construction of the water-stopping cutoff wall comprises: digging a foundation trench on the first aquiclude of the salt lake; placing a wall support box in the foundation trench; and filling and compacting the cutoff clay on the wall support box.

[0013] Further, the speed of rolling the cutoff clay is less than or equal to 3 km / h; and / or, the dry bulk density of the compacted clay layer is greater than or equal to 1.65 g / cm 3 .

[0014] Further, the recharging step uses recharging brine liquid, and the recharging brine liquid is made of sodium chloride, sodium-based bentonite, salt-resistant copolymer tackifier, carboxymethyl starch gum protector and salt recrystallization inhibitor according to a second preset ratio.

[0015] Further, before the first construction step, the construction method further comprises: determining the permeability coefficient K of the first aquiclude of the salt lake, and determining whether the permeability coefficient K of the first aquiclude is greater than or equal to a preset permeability coefficient, if yes, the first construction step is performed, wherein the preset permeability coefficient is 10 -6 cm / s.

[0016] Further, the permeability coefficient K is determined by the following formula:

[0017]

[0018] wherein K is the permeability coefficient of the first aquiclude (cm / s); Q is the stable seepage water quantity (L / min); F is the seepage water area of the test pit (cm 2 ); Z is the water layer thickness in the test pit (cm); Hk is the capillary pressure water head (cm); and L is the seepage depth at the end of the test (cm).

[0019] The artificial water-resisting layer of the application can effectively prevent the erosion of the brine-bearing well pile and the salt layer skeleton stratum structure by the overflow of the brine under pressure, and can also prevent the leakage of the recharged brine. The brine recharging device is provided with a pressurizing pump, the pressurizing pump is connected with a brine (i.e. the recharged brine liquid) configuration tank, the flow rate of the recharged brine is increased by the pressurizing pump to fill the recharging well with the recharged brine liquid, and the salt layer pores are fully filled with the saturated brine to make the salt layer skeleton fully rebound. The pressurized recharging technology can increase the flow rate of the saturated brine with high density, high mineralization, relatively high viscosity and relatively slow flowability, and can ensure that the saturated brine fully fills the pores of the salt layer within the water-stopping and anti-seepage system around the wellhead, thereby increasing the recharging efficiency. On the one hand, the construction of the water-stopping and anti-seepage system can effectively prevent the erosion of the brine-bearing well pile and the salt layer skeleton stratum structure by the overflow of the brine under pressure, and can also prevent the leakage of the recharged brine. On the other hand, the saturated brine is recharged into the recharging well by the brine recharging device, the bearing capacity of the salt layer skeleton within the easy-caving range of the wellhead is improved in integrity, the salt layer skeleton fully rebounds, the problem of the wellhead collapse of the brine-bearing well is fundamentally solved, the service life of the brine-bearing well is continuously prolonged, and the mining efficiency and the brine production are improved. BRIEF DESCRIPTION OF DRAWINGS

[0020] The accompanying drawings, which form a part of this application, are included to provide a further understanding of the application and are incorporated in and constitute a part of this specification. The illustrations are shown to explain the present application and are not intended to limit the present application unduly.

[0021] Figure 1 A stratum structure diagram of a salt lake using the recharging and anti-seepage system of the application is shown;

[0022] Figure 2 A sectional view of an embodiment of the recharging and anti-seepage system according to the application is shown;

[0023] Figure 3 A top view of the recharging and anti-seepage system of the application is shown; Figure 2

[0024] A structure diagram of the recharging well of the recharging and anti-seepage system of the application is shown; Figure 4 Figure 2 A partial process flow diagram of the construction method of the recharging and anti-seepage system according to the application is shown; and

[0025] Figure 5 A process flow diagram of the construction method of the recharging and anti-seepage system according to the application is shown.

[0026] Figure 6 In the above drawings, the following reference signs are used:

[0027]

[0028] ​​1, artificial water barrier; 2, water-stopping and anti-seepage wall; 3, grouting pipe; 4, recharge well; 401, magnesium-based cementing layer; 402, steel pipe for wall protection; 403, water filter pipe; 404, gravel layer; 405, fresh water pipe; 406, well body. DETAILED DESCRIPTION

[0029] It should be noted that the embodiments in the present application and the features in the embodiments can be combined with each other without conflict. The present application will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0030] It should be noted that, as Figure 1 indicated, the modern salt lake (era Q3, Q4) stratum structure is divided into 8 layers from bottom to top, the salt layer codes are S1-S4, the detritus layer codes are L1-L4, the brine is stored in the intercrystalline pores of the salt layer, and the overall collapse of the stratum in the range of 5m to 8m from the wellhead of the recharge well 4 in the radial direction is caused by the continuous decrease of the underground water level, the water release compression of the salt layer skeleton, and the dissolution of the easily soluble salt of the stratum by the low salinity water.

[0031] It should be noted that the water release compression of the salt layer skeleton in the mined-out area and the dissolution of the easily soluble salt of the stratum by the low salinity water are the main causes of land subsidence, and to completely solve the overall collapse of the halite mining well, the mined-out area must be treated. At present, a large number of direct recharge methods (ground flooding infiltration method) or pipe well injection methods are used for underground fresh water mined-out area recharge at home and abroad, and the water head difference is used to make it naturally seep to supplement the mined-out area, but the solubility of each salt mineral in the salt lake determines that fresh water recharge is obviously not suitable for the salt lake area.

[0032] Among several prior arts known to the inventors: Patent with publication number CN103470304A discloses a method for backfilling mined-out area of soluble solid potash mine by underground burying of magnesium chloride mother liquor, which mixes the saturated mother liquor of by-product magnesium chloride from beneficiation of potassium chloride of underground mining of potash mine with coagulant to form slurry, and then backfills the slurry into the mined-out area through pipeline to solidify and form the backfilling strength of the mined-out area, thereby completing the backfilling of the mined-out area of the underground potash mine. The super-large mined-out area of solid potash mine is obviously different from the mined-out area of salt lake brine, which is the pore between the salt layer framework. Patent with publication number CN112647907A discloses that a drill bit is used to drill through the upper aquiclude, then a casing is lowered, and a magnesium-based cementing material is mixed with salt soil and then injected through the outer well wall to consolidate the casing, thereby forming a cementing layer around the casing to prevent the casing from sinking. Patents with publication numbers CN111287703A, CN112459752A and CN111287704A all disclose continuous drilling and grouting from the bottom to the top around the edge of the brine well mouth, each grouting drill hole group is composed of multiple grouting drill holes with a certain interval, and the grouting drill hole group extends to the first aquiclude. A grouting pump is used to inject different proportions of cementing materials composed of magnesium oxide, magnesium chloride, brine and salt soil into the stratum to form a partition wall, which includes multiple columnar bodies arranged in sequence and connected to each other to form a continuous and closed curtain wall.

[0033] In the above prior art, the anti-seepage curtain wall around the well mouth can cut off or reduce the seepage water flow around the well mouth, and can protect the well mouth to a certain extent, thereby preventing the stratum from subsiding. However, the above prior art still has the following technical problems: (1) The continuous grouting from the bottom to the top around the brine well mouth forms a closed curtain wall, the grouting amount is extremely large, and the price of magnesium-based cementing material is extremely high, so large-scale grouting significantly increases the mining cost; (2) The continuous curtain wall is formed by splicing single grouting bodies, and during the manual swinging grouting process, the slurry may not be sprayed uniformly, and the wall body may have void defects, especially in the joint of two grouting holes and the interface between the bedrock, which are high-defect areas, and there is a risk of seepage, and water seeps through these cracks and cavities, corrodes the wall structure, and damages the integrity of the anti-seepage wall; (3) The controlled range of the drilling and grouting is generally 0.5m to 1m at most, and the thickness of the anti-seepage wall formed is generally thin (50cm to 80cm), and the subsidence form of 168 brine wells in a certain mining area of the Qaidam Basin is generally the integrity subsidence of the stratum in the range of 5m to 8m around the well mouth, and obviously the drilling and grouting curtain technology is only suitable for a small range around the well wall, and cannot effectively prevent the integrity subsidence of the stratum around the well mouth.

[0034] Therefore, a method for controlling the subsidence of the well mouth of a salt lake brine well is needed to protect the salt layer framework and prevent the overall subsidence of the brine well, thereby ensuring the production of brine.

[0035] As Figures 2 to 4As shown, the embodiment of the present application provides a backfill anti-seepage system for controlling the wellhead collapse of a salt lake brine well. The backfill anti-seepage system for controlling the wellhead collapse of a salt lake brine well comprises: a water-stopping anti-seepage system, which comprises a base artificial aquiclude 1 located in a salt lake and a water-stopping anti-seepage wall 2 arranged in a circumferential direction around the base artificial aquiclude 1, the bottom end of the water-stopping anti-seepage wall 2 is embedded in the base artificial aquiclude 1, and the top end of the water-stopping anti-seepage wall 2 can pass out of the salt lake; and a salt water backfill device, which comprises a backfill well 4, a pressurizing pump arranged on one side of the backfill well 4, and a salt water preparation tank in communication with the pressurizing pump, wherein the backfill well 4 is located in the water-stopping anti-seepage wall 2, the salt water preparation tank is used to store backfill salt water liquid, and the pressurizing pump is used to pump the backfill salt water liquid into the backfill well 4.

[0036] In the above technical solution, the base artificial aquiclude 1 can effectively prevent the erosion of the brine well pile and the salt layer skeleton stratum structure caused by the overflow of the brine under pressure, and can also prevent the leakage of the backfill salt water. The salt water backfill device is provided with a pressurizing pump, the pressurizing pump is connected to the salt water (i.e. backfill salt water liquid) preparation tank, the flow rate of the backfill salt water is increased by pressurization, the backfill salt water liquid is filled into the backfill well, the salt layer pores are fully filled with saturated salt water, and the salt layer skeleton is fully rebounded. The pressurization backfill technology can increase the flow rate of the saturated salt water with high density, high mineralization, relatively high viscosity and relatively slow flowability, ensure that the saturated salt water fully fills the pores of the salt layer within the range of the water-stopping anti-seepage system around the wellhead, and thus increase the backfill efficiency.

[0037] Through the above arrangement, on the one hand, the construction of the water-stopping anti-seepage system can effectively prevent the erosion of the brine well pile and the salt layer skeleton stratum structure caused by the overflow of the brine under pressure, and can also prevent the leakage of the backfill salt water. On the other hand, the saturated salt water is backfilled into the backfill well 4 by the salt water backfill device, the salt layer skeleton bearing capacity within the wellhead collapse range is improved in integrity, the salt layer skeleton is fully rebounded, the problem of wellhead collapse of the brine well is fundamentally solved, the service life of the brine well is continuously prolonged, and the mining efficiency and the brine yield are improved.

[0038] Specifically, the pressurizing pump is a variable frequency constant pressure pump, and the salt water in the salt water preparation tank is high-density supersaturated salt water.

[0039] As shown in the drawings, Figure 2 In the embodiment of the present application, the longitudinal section of the water-stopping anti-seepage wall 2 is trapezoidal, and the thickness of the water-stopping anti-seepage wall 2 gradually increases from top to bottom.

[0040] In one embodiment of the present application, the depth at which the water-stopping anti-seepage wall 2 is embedded in the base artificial aquiclude 1 is 0.5m to 1m. The water-stopping anti-seepage wall 2 is located 2m inward from the outer edge of the base artificial aquiclude 1. The thickness of the water-stopping anti-seepage wall 2 ranges from 1m to 1.2m.

[0041] In one embodiment of the present invention, the distance between the outer circumferential wall of the base artificial water-proof layer 1 and the outer wall of the reinjection well 4 ranges from 10m to 11m, and the thickness of the base artificial water-proof layer 1 is greater than 2m.

[0042] like Figure 4 As shown, in an embodiment of the present invention, the reinjection well 4 includes: a well body 406, which is located on a salt lake; a protective steel pipe 402, which is disposed at the top of the well body 406; a filter pipe 403, which is located inside the well body 406, with one end of the filter pipe 403 extending into the bottom of the well body 406 and the other end of the filter pipe 403 extending out of the well body 406; a gravel layer 404, which is located in the annular gap formed by the filter pipe 403 and the inner wall of the well body 406; and a freshwater pipe 405, which is disposed inside the filter pipe 403.

[0043] In the above technical solution, a protective steel pipe 402 with a length ranging from 1.5m to 2.5m is installed at the wellhead of the well body 406. One end of the protective steel pipe 402 is embedded in the salt rock layer S4. A magnesium-based cementing layer 401 is installed between the protective steel pipe 402 and the well body 406, and the top of the magnesium-based cementing layer 401 extends out of the ground, which can reinforce the well wall of the well body 406 and prevent collapse. The entire section of the reinjection well 4 is equipped with a filter pipe 403, which can support the filter material and filter water and trap sand. To prevent deformation of the filter pipe and collapse of the well wall, the filter pipe 403 can be a round-hole filter pipe with high compressive strength and an opening rate of 7% to 10%. A freshwater pipe 405 is installed inside the filter pipe 403. After a period of saturated brine recharge, salt deposits may accumulate on the wall of the filter pipe 403 in the recharge well 4, clogging the pores. A pressure pump connected to the freshwater pipe 405 can flush away the salt deposits on the well wall, thus clearing the blockage. A gravel layer 404 is placed within the annular gap formed by the filter pipe 403 and the inner wall of the well body 406. This reinforces the well body and ensures stable recharge. The height of the gravel layer 404 is the same as the height of the filter pipe 403, and the particle size of the gravel layer 404 ranges from 20mm to 30mm.

[0044] Through the above-mentioned design, the reinjection well 4 can prevent collapse, sand control, and salt deposition, thus making it suitable for the geological conditions of salt lakes. On the one hand, the structure of the reinjection well 4 can reinforce the well wall, preventing the well body from collapsing due to the backflow of silt, and effectively preventing problems such as cavities, collapse, and well burial caused by the backflow of silt and mud from the fine debris interlayer. On the other hand, when one or more salts in the brine reach saturation, they rapidly crystallize and precipitate, and the crystals accumulate in the reinjection well 4, forming a thick layer of salt scale, which can block the formation pore channels. The freshwater pipe 405 can be used to clean the salt deposits on the well wall.

[0045] like Figure 2As shown, in an embodiment of the present invention, the reinjection seepage prevention system further includes multiple grouting pipes 3 disposed within the water-stopping seepage prevention system. One end of the grouting pipe 3 extends into the salt lake, and the other end of the grouting pipe 3 extends out of the salt lake. Multiple clay balls are injected into the salt lake through the grouting pipes 3 to form an artificial waterproof layer 1 at the base.

[0046] In the above technical solution, high-quality clay with high resistance to water dilution, rheology and water-blocking performance around the salt lake is mixed with saturated brine, magnesium-based cementitious material and special clay curing agent in a certain proportion to make clay balls. Multiple grouting pipes 3 are set within a radial distance of 10m to 11m from the wellhead of the reinjection well 4. Clay balls are put into the grouting pipes 3 and compacted to form the base artificial water-proof layer 1.

[0047] like Figure 5 As shown, an embodiment of the present invention also provides a construction method for a reinjection seepage prevention system. The construction method is used to construct the above-mentioned reinjection seepage prevention system. The construction method includes: a first construction step of constructing an artificial water-proof layer 1 in the salt lake; a second construction step of constructing a water-stop seepage prevention wall 2 in the salt lake; a third construction step of setting up a reinjection well 4, a booster pump and a brine preparation tank in the water-stop seepage prevention system; and a reinjection step of reinjecting saturated brine into the reinjection well 4.

[0048] In the above technical solution, in the first construction step, an artificial water-proof layer 1 is constructed within a radial distance of 8m to 9m from the wellhead of the reinjection well 4. In the second construction step, a water-stopping and seepage-proof wall 2 is constructed within a radial distance of 8m to 9m from the wellhead of the reinjection well 4. In the third construction step, the well body structure of the reinjection well 4 is set according to the specific geological conditions of the salt lake.

[0049] like Figure 6 As shown, in an embodiment of the present invention, before the first construction step, the construction method further includes: determining the permeability coefficient K of the first water-impermeable layer L4 of the salt lake, determining whether the permeability coefficient K of the first water-impermeable layer is greater than or equal to a preset permeability coefficient, and if so, proceeding to the first construction step, wherein the preset permeability coefficient is 10. -6 cm / s.

[0050] In the above technical solution, the permeability coefficient K is determined by the following formula: Where K is the permeability coefficient of the first impermeable layer (cm / s); Q is the stable infiltration rate (L / min); and F is the infiltration area of ​​the test pit (cm²). 2 Z is the water layer thickness in the test pit (cm); Hk is the capillary pressure (water head) (cm); L is the penetration depth at the end of the test (cm).

[0051] With the above setup, the permeability coefficient K of the waterproof layer can be determined through a permeation test, thereby evaluating the seepage prevention performance of the first waterproof layer L4 and determining whether seepage prevention reinforcement is needed.

[0052] In one embodiment of the present application, if the permeability coefficient K of the first water-resisting layer is less than the preset permeability coefficient, the first construction step is not needed and the second construction step is directly performed.

[0053] Generally, the standard for the anti-seepage performance is as follows: the thickness of the clay layer of the water-resisting layer is greater than 2 m, the permeability coefficient is less than 10 -6 cm / s, and the total salt content of the soil layer is less than 8%. When any index of the first water-resisting layer does not meet the above conditions, the first construction step is performed to reinforce the first water-resisting layer.

[0054] In one embodiment of the present application, in the first construction step, the base artificial water-resisting layer 1 is made of clay. In one embodiment of the present application, the compaction coefficient of the clay is greater than 92%, and the average dry bulk density of the compacted clay is greater than 1.65 g / cm 3 .

[0055] By setting the compaction coefficient of the clay to be greater than 92%, the water-resisting effect of the base artificial water-resisting layer 1 can be improved, and the base artificial water-resisting layer 1 can be prevented from being permeable. By setting the average dry bulk density of the compacted clay to be greater than 1.65 g / cm 3 , the problem that the base artificial water-resisting layer 1 is not formed due to too much water can be avoided, thereby ensuring the stability of the base artificial water-resisting layer 1.

[0056] In one embodiment of the present application, the base artificial water-resisting layer 1 further comprises saturated brine, magnesium-based cementitious material and clay stabilizer, wherein the first preset proportions are as follows: 70%-75% of clay, 2%-7% of saturated brine, 4%-10% of magnesium-based cementitious material, and 2%-9% of clay stabilizer, and the above first preset proportions are weight ratios.

[0057] In one embodiment of the present application, the weight proportions of the clay, the saturated brine, the magnesium-based cementitious material and the clay stabilizer are 70%:2%:4%:2%.

[0058] In another embodiment of the present application, the weight proportions of the clay, the saturated brine, the magnesium-based cementitious material and the clay stabilizer are 75%:7%:10%:9%.

[0059] The permeability coefficient of the base artificial water-resisting layer 1 made by using the above first preset proportions can be less than 10 -6 cm / s, thereby ensuring that the base artificial water-resisting layer 1 has a good anti-seepage effect.

[0060] In the above technical solution, the clay is selected from high-quality clay which is easily available around salt lakes, has low cost, high water dilution resistance, rheological property and water blocking performance. The selection criteria are as follows: in the compaction test, when the optimal content is reached, the horizontal permeation reduction of the soil layer is 3.5% to 16% lower than that before the compaction, the permeation coefficient reaches n x 10 -7 ~10 -6 cm / s, the vertical permeation reduction is about 30% of the natural state, the mechanical property strength of the soil layer is increased, the compression property is changed from medium compression to low compression, but the stability is reduced, and the wetting disintegration speed is accelerated by 5 times. The high-quality clay after optimization is mixed with saturated brine, magnesium-based cementing material and special clay curing agent in a certain proportion to form the anti-seepage clay. The compaction coefficient of the mixed anti-seepage clay is greater than 92%, and the average dry bulk density after compaction is greater than 1.65 g / cm 3 .

[0061] In the embodiment of the present application, the anti-seepage clay is twisted into clay balls with a diameter of 2 cm to 3 cm and is air-dried. The clay balls are put into the grouting pipe, and after reaching the predetermined thickness, the clay balls are extruded to the surrounding and compacted to form a columnar body by using a drill with a wooden plug. According to the size of the columnar body area, the distance of the next grouting hole is determined, and the process is repeated to form the artificial water-resisting layer 1 which is 10 m to 11 m away from the wellhead of the recharge well 4 in the radial direction.

[0062] In one embodiment of the present application, the water content of the anti-seepage clay is greater than or equal to 50% of the optimal water content in the compaction test and less than or equal to 120% of the optimal water content in the compaction test. That is, when the optimal water content is 10%, the water content of the anti-seepage clay ranges from 5% to 12%.

[0063] In the embodiment of the present application, the construction of the water-stopping and anti-seepage wall 2 includes: opening a foundation trench on the first water-resisting layer of the salt lake; placing a wall support box in the foundation trench; and filling and compacting the anti-seepage clay on the wall support box.

[0064] In the embodiment of the present application, the rolling speed of the clay is less than or equal to 3 km / h.

[0065] In the above technical solution, the waterproof cutoff wall 2 is arranged at the four peripheral edges of the base artificial water-resisting layer 1 inward by 2m, that is, the distance between the outer lateral surface of the waterproof cutoff wall 2 and the outer peripheral lateral surface of the base artificial water-resisting layer 1 is 2m; the thickness of the waterproof cutoff wall 2 ranges from 1m to 1.2m, and the waterproof cutoff wall 2 is embedded into the first water-resisting layer by 0.5-1m but cannot drill through the water-resisting layer. A trenching machine is used to excavate a base trench, and a wall body support box is placed in the base trench. The wall body support box comprises a plurality of side plates which are connected end to end to form a box with openings at both upper and lower ends. A triangular support frame is arranged between any two adjacent side plates, and a horizontal support frame is arranged between the two opposite side plates. After the wall body support box is built, the impermeable clay is filled and compacted layer by layer. The clay compaction ramming speed should be slow, preferably not more than 3km / h. The clay compaction ramming is performed from both sides to the middle and longitudinally in a reciprocating manner. The overlapping width of the transverse joint and the longitudinal joint should be 1 / 3-1 / 4 of the width, so as to ensure that there is no leakage, no dead angle and uniform compaction. After each layer is filled, the layer is filled again after hammering and compacting to meet the compaction degree inspection standard. The compaction degree inspection standard is that the average dry bulk density of the soil layer after compaction is measured by the ring knife method, and the dry bulk density of the soil layer after compaction in the salt lake area should not be less than 1.65g / cm 3 , and the detection points are at least 2 points.

[0066] In an embodiment of the present application, the dry bulk density of the compacted clay layer is greater than or equal to 1.65g / cm 3 .

[0067] In an embodiment of the present application, the third construction step comprises: arranging well positions according to design requirements, reverse circulation drilling, and the well hole should be round and vertical; the diameter of the well body 406 ranges from 500mm to 600mm, and the wall thickness of the wall protection steel pipe 402 and the water filter pipe 403 is greater than 8mm; the water filter pipe 403 is a circular hole water filter pipe with a porosity of 7%-10%, and a level instrument is used to find the straightness when the pipe is lowered to ensure that the water filter pipe 403 is vertical; hard round gravel with a diameter ranging from 20mm to 30mm is filled into the whole hole; after well completion, the piston is used to wash the well, and the porosity of the gravel layer 404 and the water filter pipe 403 is cleaned; the water is stopped after the sand is cleaned and the porosity is connected.

[0068] In an embodiment of the present application, the recharging step uses recharging brine liquid, and the recharging brine liquid is made of sodium chloride, sodium-based bentonite, salt-resistant copolymer tackifier, carboxymethyl starch gum protector and salt recrystallization inhibitor according to a second preset ratio.

[0069] It should be noted that the salt-dissolving formation is a lacustrine mechanical chemical deposition, the salt layer and the clastic layer frequently alternate interbed, after the incompatible fluid into the reservoir, the dissolution of the salt mineral in the reservoir, the hydration and dispersion migration of the clay mineral, and the collapse of the salt layer skeleton caused by the dissolution of the salt layer skeleton are caused. In order to effectively inhibit the salt dissolution of the salt mineral, the hydration and swelling of the clay mineral, the backfilling of the "water source" of the salt-dissolving formation must have the characteristics of high salinity, good fluidity, strong shear thinning effect, effective suspension weighting capacity and the like.

[0070] In an embodiment of the present application, the second preset proportion is: 30%-35% of sodium chloride, 4%-5% of sodium-based bentonite, 1%-2% of salt-resistant copolymer (GTQ) tackifier, 1%-1.5% of carboxymethyl starch (CMS) glue protector, and 0.2-0.4% of salt recrystallization inhibitor (NTA).

[0071] It should be noted that the proportions of the components in the above-mentioned second preset proportion are all volume percentages. Through the above-mentioned setting, the present application provides a high-density supersaturated salt water liquid suitable for backfilling of the salt lake potential water mining area, which can effectively inhibit the dissolution and mud making of the salt mineral and the clay mineral in the salt-dissolving formation. The backfilled salt water liquid can effectively inhibit the salt dissolution of the salt mineral, the hydration and swelling of the clay mineral and the like, and has the characteristics of high salinity, good fluidity, strong shear thinning effect and effective suspension weighting capacity.

[0072] In the embodiment of the present application, before the step of constructing the water-stopping and anti-seepage system, the construction method further comprises a geological exploration step of engineering geological exploration.

[0073] In the above technical solution, the core exploration hole constructed in the area to be built of the halogen extraction well is drilled to accurately measure the physical parameters such as the stratigraphic boundary, thickness, lithology, density, water content, porosity and salt content of the salt shell layer, salt rock layer, silty clay or silt clay layer (first water-resisting layer), investigate the development degree of the solution cavity and solution hole, and evaluate the stratum dissolution and the adverse effects on the stability of the halogen extraction project.

[0074] From the above description, it can be seen that the above-mentioned embodiments of the present application achieve the following technical effects: the artificial water-resisting layer of the base can effectively prevent the erosion of the brine-bearing brine overflow on the pile foundation of the brine extraction well and the structure of the salt layer skeleton, and can also prevent the leakage of the recharged brine. The brine recharging device is provided with a variable frequency constant pressure pump, the variable frequency constant pressure pump is connected to a high-density supersaturated brine (i.e. recharged brine liquid) configuration box, the flow rate of the recharged brine is increased by pressurization to fill the recharged brine liquid into the recharging well, and the saturated brine fully fills the pores of the salt layer, so that the salt layer skeleton fully rebounds. The pressurized recharging technology can increase the flow rate of the saturated brine with high density, high mineralization, relatively high viscosity and relatively slow flowability, and ensure that the saturated brine fully fills the pores of the salt layer within the range of the water-stopping and anti-seepage system around the wellhead, thereby increasing the recharging efficiency. On the one hand, the construction of the water-stopping and anti-seepage system can effectively prevent the erosion of the brine-bearing brine overflow on the pile foundation of the brine extraction well and the structure of the salt layer skeleton, and can also prevent the leakage of the recharged brine. On the other hand, the saturated brine is recharged into the recharging well by the brine recharging device, the bearing capacity of the salt layer skeleton within the easy collapse range of the wellhead is improved in integrity, the salt layer skeleton fully rebounds, the problem of collapse prevention of the wellhead of the brine extraction well is fundamentally solved, the service life of the brine extraction well is continuously prolonged, and the mining efficiency and the brine extraction amount are improved.

[0075] The above merely describes the preferred embodiments of the present application and is not intended to limit the present application. The present application can be variously changed and modified by those skilled in the art. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A backfill anti-seepage system for controlling the wellhead collapse of a salt lake brine well, characterized in that, The application relates to a water-stopping and seepage-preventing system, a brine recharging device and a construction method. The water-stopping and seepage-preventing system comprises a base artificial water-resisting layer (1) located in a salt lake and a water-stopping and seepage-preventing wall (2) arranged around the base artificial water-resisting layer (1), the bottom end of the water-stopping and seepage-preventing wall (2) is embedded in the base artificial water-resisting layer (1), and the top end of the water-stopping and seepage-preventing wall (2) can pass through the salt lake. The brine recharging device comprises a recharging well (4), a pressurizing pump arranged on one side of the recharging well (4) and a brine preparation tank in communication with the pressurizing pump, the recharging well (4) is located in the water-stopping and seepage-preventing wall (2), the brine preparation tank is used for storing recharging brine liquid, and the pressurizing pump is used for pumping the recharging brine liquid into the recharging well (4). The longitudinal section of the water-stopping and seepage-preventing wall (2) is trapezoidal, and the thickness of the water-stopping and seepage-preventing wall (2) gradually increases from top to bottom.

2. The recharge impervious system for controlling the collapse of the wellhead of a salt lake brine well according to claim 1, characterized in that, The depth of embedding the water-stopping and seepage-preventing wall (2) in the base artificial water-resisting layer (1) is 0.5-1 m; and / or the water-stopping and seepage-preventing wall (2) is located at the inner side of the outer edge of the base artificial water-resisting layer (1) by 2 m.

3. The backfill anti-seepage system for controlling the wellhead collapse of a salt lake brine well according to claim 1 or 2, characterized in that, The recharging well (4) comprises: a well body (406) arranged on the salt lake; a wall-protecting steel pipe (402) arranged at the top end of the well body (406); a water filter pipe (403) located in the well body (406), one end of the water filter pipe (403) extends into the bottom of the well body (406), and the other end of the water filter pipe (403) passes through the well body (406); a gravel layer (404) located in the annular gap formed by the water filter pipe (403) and the inner wall of the well body (406); and a fresh water pipe (405) arranged in the water filter pipe (403).

4. The control of the brine wellhead subsidence of the backfill anti-seepage system of the salt lake brine well according to claim 1 or 2, characterized in that, The recharging and seepage-preventing system further comprises a plurality of grouting pipes (3) arranged in the water-stopping and seepage-preventing system, one end of the grouting pipe (3) extends into the salt lake, and the other end of the grouting pipe (3) passes through the salt lake; a plurality of clay balls are put into the salt lake through the grouting pipe (3) to form the base artificial water-resisting layer (1).

5. A method of constructing a recharge impervious system, characterized in that, The construction method is used for constructing the recharging and seepage-preventing system for controlling the collapse of a salt lake brine well mouth, and comprises the following steps: a first construction step of constructing the base artificial water-resisting layer (1) in the salt lake; a second construction step of constructing the water-stopping and seepage-preventing wall (2) in the salt lake; a third construction step of arranging the recharging well (4), the pressurizing pump and the brine preparation tank in the water-stopping and seepage-preventing system; and a recharging step of recharging saturated brine into the recharging well (4).

6. The construction method of a recharge anti-seepage system according to claim 5, characterized in that, In the first construction step, the base artificial water-resisting layer (1) is made of anti-seepage clay, the anti-seepage clay is made of clay, saturated brine, magnesium-based cementitious material and clay curing agent according to a first preset ratio, the compaction coefficient of the anti-seepage clay is greater than 92%, and the average dry bulk density of the anti-seepage clay after compaction is greater than 1.65 g / cm 3 .

7. The construction method of a recharge anti-seepage system according to claim 5, characterized in that, The construction of the water-stopping and seepage-preventing wall (2) comprises the following steps: arranging a base groove on the first water-resisting layer of the salt lake; arranging a wall body supporting box in the base groove; and arranging seepage-preventing clay on the wall body supporting box and rolling and tamping the seepage-preventing clay.

8. The construction method of a recharge anti-seepage system according to claim 7, characterized in that, The speed of rolling the impermeable clay is less than or equal to 3 km / h; and / or, the dry bulk density of the compacted clay layer is greater than or equal to 1.65 g / cm 3 .

9. The construction method of a recharge anti-seepage system according to claim 5, characterized in that, The recharging step adopts recharging brine liquid, and the recharging brine liquid is prepared according to a second preset ratio by using sodium chloride, sodium-based bentonite, salt-resistant copolymer tackifier, carboxymethyl starch glue protector and salt recrystallization inhibitor.

10. The construction method of a recharge anti-seepage system according to claim 5, characterized in that, Before the first construction step, the construction method further comprises: determining a permeability coefficient K of a first aquifuge of the salt lake, judging whether the permeability coefficient K of the first aquifuge is greater than or equal to a preset permeability coefficient, and if yes, performing the first construction step, wherein the preset permeability coefficient is 10 -6 cm / s.

11. The construction method of a recharge anti-seepage system according to claim 10, characterized in that, The permeability coefficient K is determined by the following formula: ， wherein K is the permeability coefficient of the first aquiclude (cm / s); Q is the steady seepage water amount (L / min); F is the seepage water area of the test pit (cm 2 ); Z is the water layer thickness in the test pit (cm); H k is the capillary pressure water head (cm); and L is the seepage depth at the end of the test (cm).

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