Well cementation method for in-situ leaching uranium mining drilling

Abstract

According to the well cementation method for in-situ leaching uranium mining drilling, liquid pumping and drilling are carried out at a designated position, after drilling construction is completed, the consistency of slurry in a drilled hole is adjusted, a needed in-well casing pipe is selected, the in-well casing pipe extends into the drilled hole and moves downwards to the designated position, and then the drilling hole is drilled. The method comprises the steps that an underground casing pipe is arranged in a well, a grouting opening is formed in the bottom of the in-well casing pipe, then a needed first grouting pipe is selected, the first grouting pipe is lowered to a designated position in the in-well casing pipe, the first grouting pipe is plugged between the top end of the underground casing pipe and the first grouting pipe through a needed sealing mechanism, then well cementation liquid preparation is completed, and then reverse grouting is conducted. And the first grouting pipe is cleaned, forward grouting is conducted after the first time of cement waiting is completed, the second time of cement waiting is conducted till the needed time, the bridging phenomenon in well cementation is prevented, and the well cementation quality is guaranteed.

Description

Technical Field

[0001] This invention relates to the field of in-situ leaching uranium mining technology, and in particular to a cementing method for boreholes used in in-situ leaching uranium mining. Background Technology

[0002] Cementing is a crucial step in the drilling and well completion process for uranium leaching. The purpose of cementing is to protect the casing from groundwater corrosion, maintaining its stability and strength; and to ensure complete isolation of the target formation from other aquifers after drilling, thus protecting them from contamination. Therefore, employing appropriate cementing fluids and methods is paramount. Currently, common cementing methods include forward grouting and reverse grouting. Forward grouting involves injecting cementing fluid through the wellhead between the casing and the borehole, but it suffers from the drawback of incomplete compaction during the cementing process. Reverse grouting, on the other hand, involves forcing cementing fluid into the casing through a grouting port at the bottom of the casing, sealing the annular space between the casing and the borehole wall. However, reverse grouting suffers from the drawback of cementing fluid settling, resulting in poor cementing quality in the upper part of the borehole. Summary of the Invention

[0003] The purpose of this invention is to provide a cementing method for boreholes in in-situ leaching uranium mining, so as to solve the problems existing in the prior art, prevent bridging in cementing, and ensure cementing quality.

[0004] To achieve the above objectives, the present invention provides the following solution: The present invention provides a cementing method for boreholes used in in-situ leaching uranium mining, comprising the following steps:

[0005] S1. Drill a slurry-drilling hole at a designated location, and after the drilling is completed, adjust the consistency of the mud in the hole.

[0006] S2. Select the required well casing and insert the well casing into the borehole, lowering it to the designated position, with a grouting port at the bottom of the well casing;

[0007] S3. Select the required first grouting pipe and lower the first grouting pipe into the well casing to the designated position;

[0008] S4. Select the required sealing mechanism and seal it between the top of the downhole casing and the first grouting pipe;

[0009] S5. Prepare cementing fluid;

[0010] S6. Reverse grouting: The cementing fluid is injected into the first grouting pipe through the grouting equipment. The cementing fluid enters the annular space between the downhole casing and the borehole wall through the grouting port at the bottom of the downhole casing. Under pressure, the cementing fluid replaces the slurry in the borehole.

[0011] S7. After the cementing fluid returns from the borehole opening, add the required volume of clean water into the first grouting pipe to wash out the cementing fluid in the first grouting pipe.

[0012] S8. The required settling time, and after the pressure inside the downhole casing reaches the required level, the first settling is completed;

[0013] S9. Forward grouting: After the cementing fluid between the borehole wall and the downhole casing has settled for the first time, the required second grouting pipe is selected and lowered to the exposed annular space between the borehole wall and the downhole casing. The cementing fluid is injected into the second grouting pipe through the grouting equipment. The second grouting pipe is simultaneously lifted until it is completely pulled out, and forward grouting is completed.

[0014] S10. After the second grouting process has been completed to the required time, the grouting equipment and the sealing mechanism are removed.

[0015] Preferably, in step S5, the cementing fluid is prepared in the following proportions: 1000-1500 parts water, 1000-1500 parts silicate cement, 100-200 parts fly ash, 50-100 parts polycarboxylate superplasticizer, 50-100 parts thickener polyacrylamide, and 50-100 parts reinforcing agent.

[0016] Preferably, in step S5, the formula for calculating the required amount of cementing fluid is:

[0017] T=π{D×k)2-d 2} / 4×h×ρ

[0018] Where T is the required amount of cementing fluid in tons; D is the borehole diameter in meters; d is the outer diameter of the downhole casing in meters; h is the borehole depth in meters; ρ is the weight density required to add 1 cubic meter of cementing fluid, 0.75 t / m3; and k is the borehole diameter enlargement factor.

[0019] Preferably, in step S7, the volume of clean water added into the first grouting pipe is the same as the internal volume of the first grouting pipe.

[0020] Preferably, in step S7, the formula for calculating the volume of clean water to be injected is:

[0021]

[0022] Where V is the volume of clean water to be injected, in cubic meters; d is the inner diameter of the first grouting pipe, in meters; and h is the length of the first grouting pipe, in meters.

[0023] Preferably, in step S4, the middle part of the sealing mechanism has a through hole for the first grouting pipe to pass through, and the side of the sealing mechanism near the downhole casing has a thread that is threaded to the downhole casing, and the thread surrounds the outer periphery of the through hole.

[0024] Preferably, in step S6, the grouting equipment includes a grouting pump connected to the inlet of the first grouting pipe, and the grouting pressure of the grouting pump is less than the burst pressure of the casing inside the well.

[0025] Preferably, an on / off valve is provided at the inlet of the first grouting pipe, and a pressure gauge connected to the first grouting pipe is provided between the on / off valve and the sealing device.

[0026] Preferably, in step S2, the well casing includes multiple casing segments that are detachably connected in sequence along the grouting direction, and each casing segment is sealed to the other.

[0027] Preferably, in step S3, the first grouting pipe includes a plurality of grouting segments that are detachably connected in sequence along the grouting direction, and adjacent grouting segments are sealed together.

[0028] The present invention achieves the following technical effects compared to the prior art:

[0029] By combining forward and reverse grouting, the "bridging" phenomenon in cementing is prevented, thus ensuring the quality of cementing. Attached Figure Description

[0030] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0031] Figure 1 This is a schematic diagram of reverse grouting in one embodiment of the present invention;

[0032] Figure 2 This is a schematic diagram of forward grouting in one embodiment of the present invention;

[0033] Among them, 1-drill hole, 2-cementing fluid, 3-on / off valve, 4-first grouting pipe, 5-sealing mechanism, 6-pressure gauge, 7-downhole casing, and 8-second grouting pipe. Detailed Implementation

[0034] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0035] The purpose of this invention is to provide a cementing method for boreholes in in-situ leaching uranium mining, so as to solve the problems existing in the prior art, prevent bridging in cementing, and ensure cementing quality.

[0036] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0037] like Figures 1 to 2 As shown, this embodiment provides a cementing method for uranium mining boreholes through in-situ leaching, comprising the following steps:

[0038] S1. Drill a pumping borehole at the designated location. After borehole 1 is completed, adjust the mud consistency within borehole 1 to facilitate subsequent casing installation. After the bare borehole for in-situ leaching uranium mining is completed, adjust the mud consistency again. During mud consistency adjustment, the mud density changes from its original 1.2 g / cm³. 3 ~1.3g / cm 3 Viscosity: 30 Pa·s to 40 Pa·s, adjusted to a density of 0.9 g / cm³ 3 ~1.0g / cm 3 Viscosity: 20 Pa·s to 25 Pa·s.

[0039] S2. Select the required well casing and insert it into borehole 1, lowering it to the designated position. The bottom of the well casing has a grouting port. Preferably, the well casing includes multiple casing segments that are detachable and interconnected along the grouting direction. That is, each casing segment is lowered to the design position in a "1+N" manner. Adjacent casing segments are connected by threaded holes, and each casing segment is sealed. Specifically, 3 to 5 layers of PTFE tape are wrapped around the connection between adjacent casing segments, and 704 sealant is applied.

[0040] The casing sections are made of UPVC (rigid PVC) material, with an outer diameter of 148-166mm, a wall thickness of 10-12mm, a length of 8m, and a pressure bearing capacity of 8-12MPa. The bottommost casing section is 0.8-1m long and has multiple triangular or round slurry outlets at its bottom. When using triangular slurry outlets, the outlets are distributed at 180° or 120°, with an oblique length of 10-12cm. When using round slurry outlets, the outlets are also distributed at 180° or 120°. There are 3-4 outlets on the same side of the casing section, evenly spaced along the vertical direction. The interval between two adjacent outlets on the same side is 5cm, and the diameter of the outlet is 8-12cm.

[0041] S3. Select the required first grouting pipe 4 and lower it into the well casing to the designated position. Preferably, the first grouting pipe 4 comprises multiple grouting segments that are detachably connected sequentially along the grouting direction. That is, each grouting segment is lowered in a "1+N" manner to a position 1 meter from the bottom of the well casing. The outer diameter of each grouting segment is 40-59 mm, and the wall thickness is 3-8 mm. Adjacent grouting segments are sealed together. Adjacent grouting segments are connected by threaded holes. Specifically, 3-5 layers of PTFE tape are wrapped around the connection between adjacent grouting segments, and 704 sealant is applied.

[0042] S4. Select the required sealing mechanism 5 and seal it between the top of the downhole casing 7 and the first grouting pipe 4. Preferably, the middle part of the sealing mechanism 5 has a through hole for the first grouting pipe 4 to pass through for sealing, and the side of the sealing mechanism 5 near the downhole casing 7 has a thread that is threaded to the downhole casing 7. The thread is wrapped around the outer periphery of the through hole. The sealing mechanism 5 is connected to the downhole casing 7 through the thread to seal the top of the downhole casing 7.

[0043] S5. Prepare cementing fluid 2; preferably, the proportions of cementing fluid 2 are 1000-1500 parts water, 1000-1500 parts silicate cement, 100-200 parts fly ash, 50-100 parts polycarboxylate high-performance water-reducing agent, 50-100 parts thickener polyacrylamide, and 50-100 parts reinforcing agent, to achieve faster cementing, reduce cementing settling time, and improve cementing quality and construction efficiency. Preferably, the silicate cement used is grade 42.5 silicate cement, and the reinforcing agent is composed of triethanolamine, glycerol, and anhydrous sodium sulfite. In a specific embodiment, the proportions of cementing fluid 2 are 1200 parts water, 1200 parts silicate cement, 150 parts fly ash, 60 parts polycarboxylate high-performance water-reducing agent, 60 parts thickener polyacrylamide, and 60 parts reinforcing agent.

[0044] The formula for calculating the required amount of cementing fluid 2 is as follows:

[0045] T=π{D×k)2-d 2} / 4×h×ρ

[0046] Where T is the required amount of cementing fluid 2 in tons; D is the diameter of borehole 1 in meters; d is the outer diameter of the downhole casing 7 in meters; h is the depth of borehole 1 in meters; ρ is the weight density required to add 1 cubic meter of cementing fluid 2, 0.75 t / m³; and k is the borehole diameter enlargement factor of borehole 1. The corresponding amount of cementing fluid 2 is calculated using the formula to ensure that cementing fluid 2 is neither wasted nor insufficient, and to prevent "bridging" phenomenon in cementing.

[0047] S6. Reverse grouting: Cementing fluid 2 is injected into the first grouting pipe 4 through grouting equipment. The cementing fluid 2 enters the annular space between the downhole casing 7 and the borehole wall 1 through the grouting port at the bottom of the downhole casing 7. Under pressure, the cementing fluid 2 replaces the slurry in the borehole 1. Specifically, a high-pressure flexible hose connects the inlet of the first grouting pipe 4 to the grouting pump. The high-pressure pump injects the prepared cementing fluid 2 into the bottom of the borehole 1 along the first grouting pipe 4. Since the top of the downhole casing 7 is sealed by the sealing mechanism 5, the cementing fluid 2 can easily enter the annular space between the downhole casing 7 and the borehole wall 1 through the grouting port at the bottom of the downhole casing 7. Preferably, the grouting equipment includes a grouting pump connected to the inlet of the first grouting pipe 4, and the grouting pressure of the grouting pump is less than the burst pressure of the downhole casing. Specifically, the pressure when injecting the cementing fluid 2 should be controlled below 1.5 MPa to prevent excessive pressure from causing the downhole casing to burst.

[0048] A shut-off valve 3 is provided at the inlet of the first grouting pipe 4 to complete the grouting or shut-off work in the first grouting pipe 4. A pressure gauge 6 connected to the first grouting pipe 4 is provided between the shut-off valve 3 and the sealing device. Preferably, the range of the pressure gauge 6 is 0 to 3 MPa, which is used to monitor the pressure of the casing in the well during grouting.

[0049] S7. After the cementing fluid 2 returns from the borehole opening of borehole 1, the required volume of clean water is injected into the first grouting pipe 4 to flush out the cementing fluid 2 inside the first grouting pipe 4. Preferably, the volume of clean water injected into the first grouting pipe 4 is the same as the internal volume of the first grouting pipe 4. The volume of clean water injected must be counted with a stopwatch, strictly calculated and controlled, and over-injection or under-injection of clean water is strictly prohibited. It should also be noted that after the injected clean water has completed the cleaning of the first grouting pipe 4, the clean water will settle at the bottom of the downhole casing 7 and gradually seep into the ground.

[0050] The formula for calculating the volume of clean water that needs to be injected is:

[0051]

[0052] Where V is the volume of clean water to be injected, in cubic meters; d is the inner diameter of the first grouting pipe 4, in meters; and h is the length of the first grouting pipe 4, in meters.

[0053] S8. The preferred setting time is 6-8 hours after the grouting pump is turned off, and the first settling is completed after the pressure inside the downhole casing 7 reaches the required level.

[0054] S9. Forward grouting: After the cementing fluid 2 between the borehole wall of borehole 1 and the downhole casing 7 has settled after the first settling, the required second grouting pipe 8 is selected and lowered to the exposed annular space between the borehole wall of borehole 1 and the downhole casing 7. Cementing fluid 2 is injected into the second grouting pipe 8 through the grouting equipment. The second grouting pipe 8 is simultaneously lifted, preferably at a lifting speed of 2-3 m / min, until the second grouting pipe 8 is completely pulled out, and forward grouting is completed. Since the cementing fluid 2 between the borehole wall of borehole 1 and the downhole casing 7 will settle after the first settling, forward grouting is used to solve the problem of poor cementing quality in the upper part of borehole 1. The preferred second grouting pipe 8 is provided in two parts, and is lowered from the top of the borehole 1 to the target position in the annular space between the borehole wall of the borehole 1 and the downhole casing 7. Then, the grouting pump and the second grouting pipe 8 are connected by a high-pressure soft rubber hose to start forward grouting. The outer diameter of the two second grouting pipes 8 is 32mm and they are distributed at 180° to ensure the uniformity of forward grouting.

[0055] S10. The second curing time is preferably 4-6 hours. The grouting equipment and sealing mechanism 5 are then removed.

[0056] Any adaptive changes made according to actual needs are within the scope of protection of this invention.

[0057] It should be noted that, for those skilled in the art, it is obvious that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered illustrative and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention. No reference numerals in the claims should be construed as limiting the scope of the claims.

[0058] Specific examples have been used to illustrate the principles and implementation methods of this invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of this invention. Furthermore, those skilled in the art will recognize that, based on the ideas of this invention, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of this invention.

Claims

1. A cementing method for boreholes used in in-situ leaching uranium mining, characterized in that, Includes the following steps: S1. Drill a hole at a designated location to extract the fluid, and after the drilling is completed, adjust the consistency of the mud in the hole. S2. Select the required well casing and insert the well casing into the borehole, lowering it to the designated position, with a grouting port at the bottom of the well casing; S3. Select the required first grouting pipe and lower the first grouting pipe into the well casing to the designated position; S4. Select the required sealing mechanism and seal it between the top of the downhole casing and the first grouting pipe; S5. Prepare cementing fluid; S6. Reverse grouting: The cementing fluid is injected into the first grouting pipe through the grouting equipment. The cementing fluid enters the annular space between the downhole casing and the borehole wall through the grouting port at the bottom of the downhole casing. Under pressure, the cementing fluid replaces the slurry in the borehole. S7. After the cementing fluid returns from the borehole opening, add the required volume of clean water into the first grouting pipe to wash out the cementing fluid in the first grouting pipe. S8. The required settling time, and after the pressure inside the downhole casing reaches the required level, the first settling is completed; S9. Forward grouting: After the cementing fluid between the borehole wall and the downhole casing has settled for the first time, the required second grouting pipe is selected and lowered to the exposed annular space between the borehole wall and the downhole casing. The cementing fluid is injected into the second grouting pipe through the grouting equipment. The second grouting pipe is simultaneously lifted until it is completely pulled out, and forward grouting is completed. S10. After the second grouting process has been completed to the required time, the grouting equipment and the sealing mechanism are removed.

2. The cementing method for uranium mining boreholes according to claim 1, characterized in that, In step S5, the cementing fluid is prepared in the following proportions: 1000-1500 parts water, 1000-1500 parts silicate cement, 100-200 parts fly ash, 50-100 parts polycarboxylate high-performance water-reducing agent, 50-100 parts thickener polyacrylamide, and 50-100 parts reinforcing agent.

3. The cementing method for uranium mining boreholes according to claim 2, characterized in that, In step S5, the formula for calculating the required amount of cementing fluid is as follows: T=π{D×k)2-d 2} / 4×h×ρ Where T is the required amount of cementing fluid in tons; D is the borehole diameter in meters; d is the outer diameter of the downhole casing in meters; h is the borehole depth in meters; ρ is the weight density required to add 1 cubic meter of cementing fluid, 0.75 t / m3; and k is the borehole diameter enlargement factor.

4. The cementing method for uranium mining boreholes according to claim 2 or 3, characterized in that, In step S7, the volume of clean water added into the first grouting pipe is the same as the internal volume of the first grouting pipe.

5. The cementing method for uranium mining boreholes according to claim 4, characterized in that, In step S7, the formula for calculating the volume of clean water to be injected is as follows: Where V is the volume of clean water to be injected, in cubic meters; d is the inner diameter of the first grouting pipe, in meters; and h is the length of the first grouting pipe, in meters.

6. The cementing method for uranium mining boreholes according to claim 5, characterized in that, In step S4, the middle part of the sealing mechanism has a through hole for the first grouting pipe to pass through, and the side of the sealing mechanism near the downhole casing has a thread that is threaded to the downhole casing, and the thread surrounds the outer periphery of the through hole.

7. The cementing method for uranium mining boreholes according to claim 6, characterized in that, In step S6, the grouting equipment includes a grouting pump connected to the inlet of the first grouting pipe, and the grouting pressure of the grouting pump is less than the burst pressure of the casing inside the well.

8. The cementing method for uranium mining boreholes according to claim 7, characterized in that, An on / off valve is provided at the inlet of the first grouting pipe, and a pressure gauge connected to the first grouting pipe is provided between the on / off valve and the sealing device.

9. The cementing method for uranium mining boreholes according to claim 8, characterized in that, In step S2, the well casing includes multiple casing segments that are detachably connected in sequence along the grouting direction, and each casing segment is sealed to the other.

10. The cementing method for uranium mining boreholes according to claim 9, characterized in that, In step S3, the first grouting pipe includes multiple grouting segments that are detachably connected in sequence along the grouting direction, and adjacent grouting segments are sealed together.

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