Freezing method of saturated brine stratum

Abstract

The invention relates to the technical field of stratum freezing, in particular to a freezing method of a saturated brine stratum. Comprising the following steps: 1) surveying the engineering geology and hydrogeology of the position of the mineral salt, and setting a mine for exploiting the mineral salt according to the surveying result; (2) forming double rows of freezing holes in the circumferential direction of the mine shaft; (3) sampling the stratum at the mine, performing an artificial frozen soil thermal physical mechanics test on the sample, and adjusting a freezing scheme of the double rows of freezing holes according to a test report; 4, freezing is started according to the freezing scheme until a frozen wall distributed in the circumferential direction of the mine shaft is formed in the saturated brine stratum.By means of the method, freezing can be rapidly conducted on the periphery of the mine shaft, the frozen wall is formed, the problems that fresh water leaks into the stratumand a medium salt layer is dissolved are solved, and the mining efficiency of the mine is improved.

Description

Technical Field

[0001] This invention relates to the field of formation freezing technology, and more particularly to a method for freezing saturated brine formations. Background Technology

[0002] Potash mines typically employ freezing methods during construction. However, geological exploration revealed that the intermediate-salt aquifer exhibits high salinity and typical characteristics of saturated brine. Research on the solid-state point-salinity relationship of NaCl-saturated brine indicates that the solid-state freezing point of saturated brine is as low as -21℃. A freezing temperature test report from the Underground Engineering Structure Research Institute of Anhui University of Science and Technology shows that the latent heat release point of saturated NaCl brine (which has properties similar to KCl brine in intermediate-salt layers), i.e., the brine freezing point, is -13.2℃.

[0003] In summary, freezing this type of stratum is quite difficult. The main challenges in freezing construction are as follows: (1) Freezing potash mines requires high water control standards to prevent fresh water from leaking into the strata and dissolving the intermediate salt layer. (2) Freezing saturated brine has a low freezing point and complex freezing design. (3) Potash mines lack well inspection data, and the specific geological conditions are uncertain. Therefore, these issues urgently need to be addressed. Summary of the Invention The present invention addresses the aforementioned technical problem by providing a method for freezing saturated brine formations. This method enables rapid freezing around the mine shaft to form a frozen wall, and solves the problems of freshwater leakage into the formation and dissolution of the intermediate salt layer, thereby improving the efficiency of mine operations.

[0004] A method for freezing saturated brine formations includes the following steps: 1) Conduct engineering geology and hydrogeology surveys of the location of the salt mine, and set up mines for mining the salt based on the survey results; 2) Double rows of freezing holes are installed along the circumference of the mine shaft; 3) Take samples of the strata at the mine and conduct thermophysical and mechanical tests on the samples to simulate frozen soil. Adjust the freezing scheme of the double-row freezing holes according to the test report. 4) Start freezing according to the freezing plan until a frozen wall is formed in the saturated brine strata, distributed along the circumference of the mine shaft; 5) After the frozen wall is formed, the mine shaft casing wall construction is carried out.

[0005] Preferably, after the well casing construction is completed, the freezing pipe and temperature measuring pipe are filled inside.

[0006] Preferably, the inner and outer rows of freezing holes in the double row are staggered to form a double row of small holes with a floral arrangement; the freezing depth of the double row of freezing holes penetrates the high-mineralization aquifer, and the minimum distance between the inner and outer rows of freezing holes is 670mm.

[0007] Preferably, the method further includes setting temperature measuring holes at the double-row freezing holes for observing the thickness of the circumferential frozen wall of the wellbore, and installing temperature monitoring equipment in the temperature measuring holes; before the freezing pipe in the freezing hole and the temperature measuring pipe in the temperature measuring hole are lowered, the mud in the annular space of the freezing pipe and the temperature measuring pipe in the rock stratum is replaced with slow-setting cement slurry.

[0008] Preferably, the system also includes two hydrological wells located in the mine, which are used to observe water level changes in the topsoil layer and the frozen wall of the brine rock layer, respectively.

[0009] Preferably, in step 3), there are at least three temperature measuring holes, with two temperature measuring holes arranged on the outer side of the frozen wall at the interface with the larger or maximum hole spacing, and the two temperature measuring holes are arranged symmetrically; and one temperature measuring hole is arranged on the inner side interface of the inner row of holes.

[0010] Preferably, it also includes setting up an emergency freezing plan to address the low efficiency of brine freezing; the process of the emergency freezing plan to address the low efficiency of brine freezing includes: using brine freezing for internal drainage holes and using liquid nitrogen freezing for external drainage holes.

[0011] Preferably, during the freezing process in step 4), the refrigerant is kept at a low temperature, and the temperature between the double rows of freezing holes is kept ≤-25℃, which is lower than the freezing point of the brine.

[0012] Preferably, the temperature measuring hole has measuring points arranged vertically, and the temperature measuring probes are arranged according to the stratum, with the spacing between the temperature measuring probes being less than 20m.

[0013] Preferably, the mine includes a main shaft and an auxiliary shaft.

[0014] The beneficial effects of this invention are reflected in: The method provided by this invention, through a double-row perforation system, ensures the formation of an effective water-proof curtain around the freezing pipe, thus rapidly forming a frozen wall around the mine shaft. This not only solves the existing problems of freshwater leakage into the formation and dissolution of the medium-salt layer, but also improves the safety of mine operations. Simultaneously, it allows for monitoring of the frozen wall formation and timely remedial measures, enhancing the safety and controllability of the freezing construction process. Attached Figure Description

[0015] Figure 1 This is a top view of the arrangement of the freezing tubes in this invention. Detailed Implementation

[0016] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Unless otherwise specified, the embodiments and features in the embodiments of this application can be combined with each other. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0017] Example like Figure 1 As shown, the present invention provides a method for freezing saturated brine formations, the method comprising the following steps: 1) Conduct engineering geology and hydrogeology surveys of the location of the salt mine, and set up mines for mining the salt based on the survey results; the mines include main shafts and auxiliary shafts.

[0018] 2) Double rows of freezing holes are set along the circumference of the mine shaft, that is, double rows of freezing holes are set in the circumference of both the main shaft and the auxiliary shaft.

[0019] In practice, the inner and outer rows of freezing holes in the double-row system are staggered, forming a double-row, interlaced arrangement of small holes. The freezing depth of the double-row freezing holes penetrates the high-mineralization aquifer, and the minimum distance between the inner and outer rows of freezing holes is 670 mm.

[0020] 3) Take samples of the strata at the mine and conduct thermophysical and mechanical tests on the samples to create artificial frozen soil. Adjust the freezing scheme of the double-row freezing holes according to the test report.

[0021] 4) Begin freezing according to the freezing plan until a frozen wall is formed along the circumference of the mine shaft in the saturated brine formation. During freezing, the refrigerant is kept at a low temperature, and the temperature between the double rows of freezing holes is kept ≤-25℃, below the freezing point of the brine.

[0022] This also includes installing temperature measuring holes at the double-row freezing holes to observe the thickness of the circumferential frozen wall of the wellbore, and installing temperature monitoring equipment in the measuring holes. There are at least three temperature measuring holes: two are arranged symmetrically on the outer side of the frozen wall at the interface with the largest or maximum hole spacing; one temperature measuring hole is arranged on the inner side interface of the inner row of holes. Measuring points are set along the vertical direction inside the temperature measuring holes, and temperature measuring probes are arranged according to the formation level, with a spacing of less than 20m between the temperature measuring probes.

[0023] It also includes two hydrological wells, which are located in the mine and are used to observe the water level changes in the topsoil layer and the frozen wall of the brine rock layer, respectively.

[0024] It also includes setting up an emergency freezing plan to address the low efficiency of brine freezing; the process of the emergency freezing plan to address the low efficiency of brine freezing includes: using brine freezing for internal drainage holes and using liquid nitrogen freezing for external drainage holes.

[0025] This application implements the APOT potash fertilizer project in Thailand using the methods described above. The APOT potash fertilizer project is located approximately 285 kilometers northeast of Bangkok. The mining area is demarcated by 14 turning points, covering an area of ​​approximately 15.5 km². 2 The ore body is large in scale. The ore body is located at a depth of 100–300 m, with an average depth of 150 m in the west and 200 m in the east. The resource quantity of carnallite (KCl·MgCl2·6H2O) in this deposit is 490.17 Mt, with a designed recoverable reserve of 156.90 Mt, and a comprehensive mining recovery rate of approximately 36%. The raw ore production scale is designed at 8.5 million t / a, with a KCl production capacity of 1.235 million t / a (average KCl grade approximately 16.25%), and a mine service life of approximately 16.6 years.

[0026] 1) Based on the on-site survey results, the mining area mainly consists of three aquifers: a topsoil aquifer, a medium-clastic rock aquifer, and a medium-salt aquifer. The mine is designed using a vertical shaft development method. Initially, two shafts will be arranged: a main shaft and an auxiliary shaft.

[0027] The well wall structure of both the main and auxiliary shafts in the frozen section adopts a double-layer reinforced concrete composite structure with an inner double-layer plastic panel. The lower bedrock section of the well wall adopts a reinforced concrete structure. It is initially planned that the frozen section of the main and auxiliary shaft walls will have a consistent vertical thickness. A wall base will be installed at the bottom of the frozen section. For the deep topsoil section, both the inner and outer well walls will be double-reinforced, with a concrete grade of C40.

[0028] According to on-site surveys, the ore-bearing strata are Cretaceous strata. The topsoil sediments from 16.45m to 33.85m above and the medium clastic rock layers from 33.85m to 54.53m above are relatively rich in water. The bottom plate of the medium clastic layer below can serve as a good aquitard. The freezing depth is considered to exceed the aquifer section and enter the medium salt layer stable strata.

[0029] In order to ensure that the water-bearing strata with extremely high mineralization in the lower part can be encircled and that the frozen section of the well can be safely excavated under the protection of the frozen wall, a freezing scheme of "double-row freezing holes with interlaced spacing" is adopted.

[0030] To prevent water leakage from freezing holes and temperature measuring holes, the bedrock strata were slurried with slow-setting cement slurry to replace the mud before the pipes were laid.

[0031] To prevent the freezing pipe from becoming a channel connecting various aquifers, the freezing pipe and temperature measuring pipe should be filled after the well casing is completed.

[0032] 2) Double rows of freezing holes are installed along the circumference of the mine shaft; 3) Take samples of the strata at the mine and conduct thermophysical and mechanical tests on the samples to create artificial frozen soil. Adjust the freezing scheme of the double-row freezing holes according to the test report.

[0033] The freezing plan includes: the freezing depth of the double-row freezing holes is planned to reach the medium-salt layer, tentatively set at 70m. The freezing depth will penetrate the high-mineralization aquifer, employing a "double-row freezing hole spacing interlaced arrangement" freezing scheme.

[0034] Freezing wall design principles: The freezing wall for the lower rock strata and saturated brine layer is designed for "water sealing," requiring a relatively low temperature to ensure the water sealing effect of the saturated brine layer; the upper surface soil strata are relatively shallow (≤38.5m), so the freezing wall thickness is not calculated. The drilling quality of the double-row freezing holes is controlled using the principle of target area control.

[0035] Frozen pipe structure design: The frozen pipe adopts GB8163-2018 low carbon seamless fluid steel pipe, model φ140×5mm seamless pipe, and is connected by φ127×5mm inner lining pipe.

[0036] Construction of double-row freezing holes: 1.1 Hole opening and normal drilling Before drilling, the drilling rig must be carefully aligned so that the center of the rotary table, the center of the borehole, and the center of the turret lifting are aligned. The gap between the drilling rig chassis and the foundation must be properly padded to ensure the verticality of the borehole. The allowable error for the spacing between the boreholes is ±20mm. During normal drilling, parameters such as drilling pressure, drilling speed, pump flow rate, and mud ratio should be adjusted in a timely manner according to the rock characteristics and specific conditions.

[0037] 1.2 Borehole Inclination The JDT-6A gyro-based inclination and directional logging instrument was used for drilling and borehole formation to guide the drilling process. Inclination measurements should be taken every 30 meters during drilling, with increased frequency in easily deviated formations. If the deviation exceeds the design specifications, it must be corrected promptly, and drilling can continue only after the deviation meets the requirements. After borehole formation, measurements must be repeated, and a borehole deviation plan view should be drawn every 30-50 meters. During borehole inclination measurement, the data should have good repeatability; that is, the same point must be measured both vertically and horizontally to maintain consistency. Any questionable points must be remeasured to ensure the reliability of the inclination data.

[0038] The drilling trajectory is strictly monitored, and measurements are taken according to regulations. Each inclination measurement result is repeatedly checked against the previous one. For boreholes with excessive deviation, additional measuring points are added during construction to correct the deviation in a timely manner, control the drill collar tip angle, and ensure the trajectory trend.

[0039] 1.3 Drilling deviation correction Drilling construction principle: prevention of deviation is the main focus, and correction of deviation is supplementary. The drilling shall start strictly according to the designed hole positions. When starting the drilling, it is necessary to ensure that the center of the crown block, the center of the rotary table, and the center of the hole position are on the same line. The chassis of the drilling rig shall be padded firmly to ensure the stability of the drilling rig and the quality of starting the drilling. During the construction, it shall be carefully operated according to the regulations, and the construction in the three stages of starting the drilling, normal construction, and ending the drilling shall be well controlled.

[0040] For deviation correction of the drilling, a downhole motor-driven positive displacement drill tool of 5LZ146 - 7.0 is adopted. This tool, in combination with a mud pump, long and short centralizers, and a gyroscopic orientation instrument, has the advantages of high efficiency and good accuracy in directional deviation correction, especially in controlling the internal deviation of the drilling.

[0041] 2. Installation of freezing pipes 2.1 Materials: The freezing pipes use low-carbon fluid seamless steel pipes of GB8163 - 2018 and welding electrodes of the same material.

[0042] 2.2 Pipe assembly: Pipe assembly shall be carried out according to the depth of each hole, and each pipe shall be accurately measured, numbered, grouped, and the original records shall be well made. When lowering the pipes, foreign matters inside the pipes shall be removed to keep them clean. The welder shall complete welding of one completed hole at one time without changing the welder halfway. After welding the pipes of one hole, the welder shall sign on the original record sheet in time. After pressure testing and sealing, the gaps around the freezing pipes shall be filled with soil in time to prevent mud cross-hole. The depth of the freezing pipes lowered shall be consistent with the hole depth and shall not be less than the designed freezing depth.

[0043] 2.3 Bottom cones: The freezing pipes, temperature measuring pipes, and hydrographic pipes are equipped with sealed bottom cones and strengthening partitions. The welding of the bottom cones of the freezing pipes must be double-layer. It is required that the thickness of the bottom cone steel plates and strengthening partitions is not less than the wall thickness of each type of pipe, and the material is the same as that of each type of pipe.

[0044] 2.4 Connection: The freezing pipes are connected by welding the inner lining pipes. The pipe ends are beveled and welded in layers. The distance between the upper and lower pipes shall be controlled between 4 - 7 mm. Before use, the quality of the freezing pipes shall be carefully inspected, and it is strictly prohibited to use freezing pipes that are bent, deformed, or have quality problems. During welding, it is required that the materials of the pipes, pipe collars, and welding electrodes must be the same. The welding electrode is E4303 low-carbon steel, and the welding thickness is not less than the wall thickness of each type of pipe. The seams shall be full without sand holes and cracks, and it is required that the pipe ends must be aligned to ensure concentricity. Welding shall be carried out strictly according to the welding process. After welding and cooling, the pipes can be lowered.

[0045] 2.5 Pressure test of freezing pipes: For the self-made low-carbon steel bottom cones, strengthening plates shall be added. After all the freezing pipes in each hole are lowered, the water pressure leak test shall be carried out in time. The test pressure shall be 2 times the sum of the pressure difference between the salt water column inside the whole freezing pipe and the clear water column outside the pipe and the working pressure of the salt water pump. After comprehensive calculation and consideration, the freezing holes are all tested under a pressure of​​2.6 After the pipe is finished and pressure tested and found to be qualified, the pipe opening should be capped and sealed firmly to prevent debris or mud from entering the pipe before proceeding to the next hole.

[0047] 2.7 Hole forming acceptance procedure, including pipe laying, pressure testing, and leak testing.

[0048] 4) Start freezing according to the freezing plan until a frozen wall is formed in the saturated brine strata, distributed along the circumference of the mine shaft.

[0049] Freezing and refrigeration construction plan: Freezing and refrigeration system design Calculation of cooling capacity required for wellbore freezing: Q T =πd t H0n t K t In the formula: Q T To account for the total heat dissipation capacity of the freezing tube, 10 4 kcal / h Q1 represents the freezing station's cooling capacity, 10 4 kcal / h, d t H0 is the outer diameter of the freezing pipe, m, and H0 is the freezing depth, m, n. t For the number of freeze holes, K t The heat dissipation coefficient of the freeze tube is taken as 270×10. 4 kcal / h, Calculation of cooling capacity required for the freezing station: Q1=m c Q T In the formula: m c The coefficient for cooling loss is 1.2.

[0050] brine system Brine preparation ratio: (1) Design temperature of brine: The brine is a CaCl2 aqueous solution. The brine outlet temperature during the active freezing period is below -30℃, and the maintenance freezing period is below -30℃. (2) Brine preparation ratio: The specific gravity of brine is 1260 kg / m³. 3 It has a salt content of 27.5% and a Baume degree of 29.9°Be.

[0051] saline circulation volume:

[0052] In the formula: - Cooling requirement for the wellbore, kcal / h; The density of the brine is kg / m³. 3 ; The specific heat of brine is 0.662 kcal / kg; To account for the temperature difference between the brine and the reflux, a temperature of 3℃ was selected based on experience in freezing engineering construction. Calculations show that Wbr_main = 318 m. 3 / h, Wbr_sub=359 m 3 / h.

[0053] The freezing wells use a series circulating brine system: 2 wells are connected in series in one group, for a total of 40 groups; 2 wells are connected in series in one group, for a total of 45 groups; the average total brine circulation volume per well during the active or enhanced freezing period is approximately 8 m³. 3 / h.

[0054] Liquid supply pipe selection:

[0055] In the formula: The inner diameter of the liquid supply pipe; The allowable flow velocity of brine in the supply pipe is taken as 1.3 m / s; n´ represents the number of supply pipes, with 80 pipes for the main well and 90 pipes for the auxiliary well. Calculations show that... Main = 0.0329m The auxiliary diameter is 0.0329m. All supply pipes are made of φ75×6mm polyethylene plastic flexible tubing with an inner diameter of 0.063m, meeting construction requirements.

[0056] Selection of saline trunk line and manifold:

[0057] In the formula: d m d is the diameter of the brine main pipe and the collection and distribution ring; ω" is the brine flow velocity within the collection and distribution ring of the main pipe, taken as 1.8 m / s. After calculation, d m Main = 0.250m, d m The auxiliary diameter is 0.265m. Both wells use φ273×7mm spiral welded pipes as brine trunk lines and distribution rings, employing a one-to-one distribution system for supply and return.

[0058] Calculation of calcium chloride dosage: G = 1.2gV / ρ In the formula: g represents the content of solid calcium chloride per unit volume of solution, taken as 346.5 kg / m³. 3 ρ represents the purity of solid calcium chloride, taken as 70%; V represents the total volume of calcium chloride brine, in m³. 3 Calculations show that Gmain = 66.1 t and Gsecondary = 72.5 t.

[0059] Choose a brine pump that meets the construction requirements.

[0060] Temperature measurement hole design: In order to accurately grasp the changes in the freezing temperature field, three temperature measurement holes are designed and arranged in each well to reflect the freezing temperature of different parts, especially the weak parts of the freezing wall.

[0061] Arrangement principle: Two holes should be placed symmetrically on the outer side of the frozen wall at the interface with the largest or maximum hole spacing; one hole should be placed on the inner side of the inner row of holes. The specific location depends on the drilling conditions.

[0062] Temperature measuring points are arranged vertically within each borehole according to the stratigraphic level, with a probe spacing of less than 20m. When the thickness of a single stratigraphic layer is greater than 20m, the number of probes is increased. Probes should preferably be placed in the middle of the stratigraphic layer to accurately monitor the thickness of the corresponding frozen wall. The specific location and depth will depend on the actual construction conditions and monitoring needs on site.

[0063] The temperature measuring tube is made of GB8163-2018 low carbon seamless steel (φ140×5mm), and is connected by welding with φ127×5mm inner pipe clamps. The welding quality is the same as that of the freezing hole. No water filling or pressure testing is required inside the tube, but water leakage is not allowed.

[0064] Arrangement and installation of temperature measuring holes To accurately monitor changes in the freezing temperature field, three temperature measurement wells are designed and installed in each well, such as... Figure 1 C1, C2, and C3 are shown in the figure to reflect the freezing temperature at different locations, depths, and weak points in the frozen wall.

[0065] Arrangement principles: One borehole should be placed on the outer side of the frozen wall at the interface with the largest or maximum borehole spacing; one borehole should be placed on the main face of the main drainage deep freezing borehole above the water flow; and one borehole should be placed on the inner interface of the anti-fracture borehole. The specific location depends on the drilling conditions.

[0066] Temperature measuring points are arranged vertically within each borehole according to the stratigraphic level, with a probe spacing of less than 20m. When the thickness of a single stratigraphic layer is greater than 20m, the number of probes is increased. Probes should preferably be placed in the middle of the stratigraphic layer to accurately monitor the thickness of the corresponding frozen wall. The specific location and depth will depend on the actual construction conditions and monitoring needs on site.

[0067] A φ140×5mm GB8163-2018 low-carbon seamless steel pipe is placed inside the temperature measuring hole and connected by a φ127×5mm inner pipe clamp. The welding quality is the same as that of the freezing hole. No water filling or pressure testing is required inside the pipe, but there must be no water leakage.

[0068] Monitoring Instruments and Their Accuracy: The freezing temperature is monitored using a domestically produced CW-500 multi-channel digital temperature acquisition instrument. Key performance characteristics of this instrument include: a maximum of 100 measurement points and a resolution of 0.1℃. The monitoring system is highly automated and exhibits stable performance.

[0069] Monitoring cycle: Temperature monitoring begins when the frozen soil begins to freeze and continues until the frozen section of the well is completed. During the active freezing process, monitoring is conducted once a day; during the maintenance freezing process, monitoring is conducted every 1-2 days.

[0070] Submitted deliverables: data record and analysis table; temperature distribution curves of the frozen wall along depth at different times; horizontal temperature distribution curves of the frozen wall at different layers at different times; curves showing the change of the measured thickness of the frozen wall over time.

[0071] Hydrological well design: Based on hydrogeological data, two hydrological wells are designed and arranged inside each well shaft, such as... Figure 1 As shown in S1 and S2, the intersection of the topsoil layer and the brine rock layer frozen walls are reported respectively. The hydrological pipe is made of GB8163-2018 low carbon seamless steel φ140×5mm, and is connected by welding with φ127×5mm inner pipe clamps. Single layer is reported.

[0072] Hydrological well water level: The changes in water level in the hydrological wells within the frozen wall can be used as one of the preliminary methods to determine whether the frozen wall has formed a normal ring.

[0073] Monitoring content: water level at the hydrological well and surrounding natural groundwater level.

[0074] Monitoring method: Based on existing hydrogeological data, two hydrological wells are designed and arranged in each well shaft to report the intersection of the frozen walls of the aquifer.

[0075] Monitoring instruments and their accuracy: The testing instrument used is an electrical water level gauge. The water level gauge reading accuracy is ±1mm, and the elevation of the pipe opening is periodically measured using a precision level connected to a benchmark.

[0076] Monitoring cycle: After the active freezing begins, observe once a day to check the water level changes inside the frozen wall in a timely manner.

[0077] Submitted results: a table showing the water level and cumulative change for each test; and a time-lapse graph showing the water level change.

[0078] Temperature field and thickness of frozen wall Monitoring objective: To comprehensively monitor the development of the entire frozen wall during the freezing process, understand the temperature distribution pattern during its construction, and accurately determine the freezing wall's transition time, thickness, and temperature in order to take appropriate measures in a timely manner.

[0079] Replacement of Annular Space with Slow-Setting Cement Slurry: In order to prevent groundwater from different layers from communicating through the annular space of the freezing hole after the freezing project is completed, thus affecting the next stage of construction, after the freezing borehole is completed, the slurry in the annular space of the freezing pipe and temperature measuring pipe in the rock stratum is replaced with slow-setting cement slurry.

[0080] System: Saturated brine or undersaturated brine cement slurry system.

[0081] Pulp preparation volume: 20m 3 .

[0082] Formula: Add 15m³ of [material] to the mud pit 3 Add 0.45 tons of national standard bentonite to clean water at 3% and stir for 30 minutes. Add 0.025 tons of caustic soda and 4.5 tons of sodium chloride until saturated, then add at 30%. Add 0.3 tons of anti-salt water loss reducing agent at 2% and 0.075 tons of low-viscosity polyanionic cellulose at 0.5%.

[0083] Marine cement replaces salt-containing mud to reduce freezing difficulty: In order to prevent water conduction hazards in freezing holes and temperature measuring holes, slow-setting cement slurry (marine cement) is used to replace salt-containing mud in the bedrock strata before pipe laying.

[0084] At the same time, the slow-setting cement slurry replaces the salt-containing mud, allowing the marine cement to displace the salt-containing mud between the salt layer and the freezing hole, thus reducing the difficulty of freezing around the freezing pipe.

[0085] Based on the above method, the APOT potash fertilizer project in Thailand of this application has achieved smooth mining, which not only ensures that the mining cycle is not affected, but also improves construction efficiency.

[0086] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method of freezing a saturated brine formation, characterized by, The method comprises the following steps: 1) surveying the engineering geology and hydrogeology of the location of the salt mine, and setting up a mine for mining the salt according to the survey results; 2) arranging double-row freezing holes along the circumference of the mine shaft; 3) sampling the strata at the mine and conducting artificial frozen soil thermophysical and mechanical tests on the samples, and adjusting the freezing scheme of the double-row freezing holes according to the test report; 4) starting freezing according to the freezing scheme until a freezing wall is formed along the circumference of the mine shaft in the saturated brine strata; 5) after the formation of the freezing wall, conducting mine shaft wall lining construction.

2. A method of freezing a saturated brine formation according to claim 1, characterized in that The inner row of freezing holes and the outer row of freezing holes of the double-row freezing holes are staggered to form a double-row small-hole spacing flower arrangement; the freezing depth of the double-row freezing holes penetrates the high salinity aquifer, and the minimum spacing between the inner row of freezing holes and the outer row of freezing holes of the double-row freezing holes is 670 mm.

3. A method of freezing a saturated brine formation according to claim 2, characterized in that It also includes arranging temperature measuring holes for observing the circumferential freezing wall thickness of the mine shaft at the double-row freezing holes, and arranging temperature measuring tubes in the temperature measuring holes, and the temperature measuring tubes are provided with temperature monitoring equipment; before the freezing pipes in the freezing holes and the temperature measuring tubes in the temperature measuring holes are lowered, the annular space of the freezing pipes and the temperature measuring tubes at the rock strata part is replaced with a slow-setting cement slurry.

4. The freezing method for saturated brine strata according to claim 3, characterized in that, After the end of the mine shaft wall lining construction, the freezing pipes and the temperature measuring tubes are filled in the pipes.

5. A method of freezing a saturated brine formation according to claim 1 or 4, characterized in that, It also includes two hydrological holes, and the two hydrological holes are located in the mine and are used to observe the water level changes in the surface soil layer and the brine rock strata freezing wall of the mine.

6. A method of freezing a saturated brine formation according to claim 4, wherein, In step 3), the temperature measuring holes are at least three, two temperature measuring holes are arranged at the interface of the larger or maximum hole spacing on the outside of the freezing wall, and the two temperature measuring holes are symmetrically arranged; one temperature measuring hole is arranged at the interface position on the inside of the inner row of holes.

7. A method of freezing a saturated brine formation according to claim 4 or 5, characterised in that, It also includes setting up a freezing emergency plan for solving the low freezing efficiency of brine; The process of the freezing emergency plan for solving the low freezing efficiency of brine includes that the inner row of freezing holes uses brine freezing, and the outer row of freezing holes uses liquid nitrogen freezing.

8. A method of freezing a saturated brine formation according to claim 7, characterized in that During freezing in step 4), the refrigerant remains in a low-temperature state, and the temperature between the double-row freezing holes remains ≤-25℃, which is lower than the freezing point of brine.

9. A method of freezing a saturated brine formation according to claim 8, wherein, The temperature measuring holes are provided with measuring points in the vertical direction, and the temperature measuring probes are arranged according to the strata positions, and the spacing between the temperature measuring probes is less than 20 m.

10. A method of freezing a saturated brine formation according to claim 1, wherein, The mine includes a main shaft and a subsidiary shaft.

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