A well washing method for geothermal exploration in karst areas

Abstract

The present application belongs to the technical field of well washing, and discloses a geothermal exploration well washing method in karst areas. Through the use of the plug injector in steps one to eleven, the jet well washing method can further improve the cleaning effect compared with the existing method, and the cleaning effect of the deep water-bearing section well wall is also better. Through the operation of the settling agent and the re-washing, the dirt after the previous cleaning is accelerated to settle, and the filter eye is cleaned to prevent the dirt from blocking the filter eye and to ensure the water passing rate of the filter eye, so that the water yield of the geothermal well is better.

Description

Technical Field

[0001] This invention belongs to the field of well washing technology, specifically relating to a well washing method for geothermal exploration. Background Technology

[0002] The geothermal well completion process includes drilling, mud replacement, well casing installation, gravel packing, sealing, well washing, pumping tests, and water sampling. Well washing, as a crucial step in the process, is indispensable. Geothermal wells extract geothermal resources through aquifers. Filter pipes are installed inside the aquifers. The geothermal medium enters the filter pipes through the filter openings, rises to the wellhead, and then sinks to the bottom through the annular space between the filter pipes and the well wall, thus achieving circulation.

[0003] Existing technologies generally use a combination of well cleaning methods, such as pump-driven jetting, polyphosphate cleaning, and compressed air cleaning. While this combination can clean the mud and some debris from the well wall to a certain extent, as the depth of the geothermal well increases, the radial pressure of the jetting water and compressed air decreases due to friction and other factors. This results in poor cleaning of the bottom of the aquifer section of the geothermal well. Furthermore, the mud and debris on the well wall are mainly concentrated below the aquifer section under the influence of gravity and water flow, and adhere to the outside of the filter pipe, clogging the filter holes. Therefore, existing well cleaning methods are ineffective for geothermal wells.

[0004] Invention Content

[0005] The present invention aims to provide a well-washing method for geothermal exploration in karst areas, in order to solve the problem that existing well-washing methods have poor well-washing effects on geothermal wells.

[0006] To achieve the above objectives, the present invention provides the following technical solution: a well-washing method for geothermal exploration in karst areas, characterized in that:

[0007] Step 1: Selection of the injection device. Select the injection device according to the inner diameter of the filter pipe in the current geothermal well.

[0008] Step 2: Assemble the well washing tools by assembling the injector, drill collar, plugger, and drill pipe from bottom to top.

[0009] Step 3: Lower the well cleaning tool into the well. Place the well cleaning tool into the filter pipe of the geothermal well and lower it at a constant speed until it reaches a distance of H1 from the top of the filter pipe.

[0010] Step 4: Cleaning the geothermal well. The well-cleaning medium is sprayed out through the ejector. After the ejector sinks to the bottom of the water-bearing section at a constant speed, the ejector is controlled to rise at a constant speed and the well-cleaning medium is sprayed until it reaches H1. Then the spraying of the well-cleaning medium is stopped.

[0011] Step 5: Remove the well-washing tool. After raising the well-washing tool to the geothermal wellhead, remove the well-washing tool.

[0012] Step 6: Settle the scale by injecting a settling agent into the geothermal well and soaking it for at least 24 hours;

[0013] Step 7: Replace the slurry with clean water. Replace the mixture in the geothermal well with clean water until clean water returns from the wellhead.

[0014] Step 8: Modification of well washing tools. Remove the plug and drill collar from the well washing tools to connect and fix the injector to the drill pipe.

[0015] Step 9: Re-wash, and repeat steps 3 and 4 in sequence;

[0016] Step 10: Replace the slurry again. After the well washing tool is raised to the geothermal wellhead, remove the well washing tool and repeat Step 7 to replace the slurry with clean water in the geothermal well.

[0017] Step 11: Finishing touches. Disassemble and store the well-washing tools in the designated location, and then proceed with the subsequent well-drilling process.

[0018] The principle and effects of this technical solution:

[0019] 1. Because the plugging device needs to be selected according to the internal diameter of the filter tube, when the gap between the plugging device and the filter tube wall is small enough, the well-washing medium sprayed from the well-washing tool is injected into a relatively confined and narrow space. Due to the reduced pressure leakage at the gap, the well-washing medium in the gap still has a large pressure. Therefore, when the well-washing medium in the gap enters the annular space through the filter hole of the filter tube, it still has a large scouring force, thereby scouring the collapsed material surrounding the filter tube. Furthermore, due to the influence of the collapsed material surrounding the filter tube, the well-washing medium circulates and scours between the geothermal well wall and the collapsed material, improving the scouring effect. The plugging device reduces the loss of the scouring velocity of the well-washing medium during jet well washing, improving the scouring effect. This allows the well-washing tool to still spray high-pressure well-washing medium at greater depths of the geothermal well, thus ensuring that the collapsed material at greater depths of the geothermal well can still be scourled away.

[0020] 2. After the well-washing tool is lowered into the well, the well-washing medium is sprayed in real time at various depths of the geothermal well's aquifer. The well-washing medium is clean water. The well-washing medium is sprayed when the well-washing tool sinks and rises, so that the ejector can more comprehensively sweep the filter pipe, and the well-washing medium can fully pass through the filter holes to flush away the dirt in the annular space.

[0021] 3. After flushing, a settling agent is used to settle the dirt in the geothermal medium suspended in the aquifer below the aquifer, thereby preventing the dirt from condensing again. Furthermore, the re-washing of the geothermal well by the ejector flushes the sediment in the filter tubes out of the filter tubes, preventing dirt deposits from clogging the filter tubes and increasing the water yield of the geothermal medium, thereby increasing the amount of geothermal resources.

[0022] 4. Through the two slurry replacements in steps seven and ten, the suspended matter in the geothermal medium is fully discharged, so that the suspended matter will not settle and clog the filter holes or adhere to the outside of the filter tube in the future, thus ensuring the exchange efficiency of the geothermal medium in the filter tube.

[0023] The invention is further configured such that: the plugging device has a plugging hole, and the plugging device also has a placement groove coaxially arranged with the plugging hole; a rotating cylinder is rotatably connected in the placement groove; and the bottom of the drill rod is threadedly connected to the rotating cylinder and communicates with the plugging hole.

[0024] The principle and effect of this technical solution: Because the plugging device is threadedly connected to the rotary drum, the drill pipe can be disassembled from the plugging device. Furthermore, the rotary drum is rotatably connected to the plugging device, so the plugging device can rotate relative to the drill pipe. When the ejector sprays the well-washing medium, due to the pressure difference between the upper and lower parts, it can irregularly drive the plugging device to rotate, thereby giving the well-washing medium sprayed by the ejector a higher shear force.

[0025] The present invention is further configured such that: a plurality of rotating devices are evenly distributed around the bottom of the injector, the rotating devices including a connecting rod and a rotating blade, the connecting rod being fixed to the bottom of the injector, and the rotating blade being fixed to the bottom of the connecting rod.

[0026] The principle and effect of this technical solution: Through the setting of the connecting rod and the rotating blade, when the injector sinks and rises at a constant speed along the filter tube, the well-washing medium sprayed by the ejector increases the water pressure below, so that the water flow has a tendency to float. Therefore, when the water flows through the bottom of the injector, it can compress the rotating blade like a windmill to drive the injector to rotate regularly, so that the injector drives the ejector to rotate. The well-washing medium sprayed by the rotating ejector has a higher scouring shear force, which can further improve the well-washing effect and make the geothermal well wash more thorough.

[0027] The present invention is further configured such that: there are 2-4 drill collars, and the drill collars are connected in series with each other; the top drill collar is fixed to the bottom of the plugging device and is connected to the plugging hole; and the bottom drill collar is fixed to and connected to the injector.

[0028] The principle and effect of this technical solution: The setting of 2-4 drill collars can increase the weight of the well washing tool, so that the well washing tool can still sink smoothly when it has a plugging device, without affecting the subsequent rise, and the plugging device and the ejector are connected through the drill collars.

[0029] The present invention is further configured such that, in step nine, step four is repeated at least three times.

[0030] The principle and effect of this technical solution: In step nine, by performing step four multiple times, the injector can fully flush the sediment in the filter tube, so that the sediment that was flushed by step three and four and settled in step six is ​​flushed out of the filter tube, preventing the filter tube from being blocked by sediment and ensuring the flow of geothermal medium into the filter tube.

[0031] The invention is further configured such that: the inner cross-sectional area of ​​the injector is less than or equal to the inner cross-sectional area of ​​the drill pipe, the diameter of the injection hole at the lower end of the injector is 5-7mm, and the sum of the areas of all injection holes is less than the inner cross-sectional area of ​​the injector.

[0032] The principle and effect of this technical solution: Since the inner cross-section of the ejector is less than or equal to the inner cross-sectional area of ​​the drill pipe, when the pressure applied by the working pump is constant, the well-washing medium flows from the drill pipe into the ejector under equal or increased pressure, thereby increasing the injection speed and injection pressure of the well-washing medium. In addition, the total area of ​​all injection holes is less than the inner cross-sectional area of ​​the drill pipe, thereby increasing the pressure again, increasing the speed of the well-washing medium ejected from the ejector, and improving the well-washing effect.

[0033] The present invention is further configured such that the number of injection holes is 90-110.

[0034] The principle and effect of this technical solution: Under the condition that the pressure applied by the working pump is constant, the number of injection holes determines the flushing speed of the well washing medium. And when the flushing effect of the well washing medium is not affected, the more injection holes there are, the more well washing medium is ejected at the same time, thereby improving the flushing rate and flushing effect. According to empirical methods, the effect is best when the number of injection holes is between 90 and 110.

[0035] The present invention is further configured such that: when step four is performed, step four is first repeated at least three times according to the rated cleaning pump pressure of the process parameters, and then the pump pressure of the working pump is increased and step four is repeated at least three more times.

[0036] The principle and effect of this technical solution: When step four is performed, it is repeated at least three times under the rated cleaning pump pressure. This allows the well-washing tool to gradually flush away the collapsed material surrounding the filter pipe and open up the annular space, thereby improving the well-washing effect, saving time and cost, and removing most of the mud and collapsed material. Furthermore, by increasing the working pump pressure to 110% of the rated cleaning pump pressure and repeating step four more times, even the stubborn deposits remaining in the geothermal well can be removed, further improving the cleaning effect and increasing the amount of geothermal resources. Attached Figure Description

[0037] Figure 1 This is a structural diagram of the geothermal well in this invention;

[0038] Figure 2 This is a structural diagram of the well-washing tool in the filter pipe according to the present invention;

[0039] Figure 3 for Figure 2 Enlarged view of a portion of the structure of the injection plug;

[0040] Figure 4 for Figure 3 The bottom view in the middle;

[0041] Figure 5 This is a partial structural diagram of the injector. Detailed Implementation

[0042] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments:

[0043] The reference numerals in the accompanying drawings include: 1, geothermal well; 201, filter pipe; 202, filter eye; 301, plugging device; 302, plugging hole; 303, placement groove; 304, rotating drum; 401, drill pipe; 402, drill collar; 501, connecting rod; 502, rotating blade; 601, ejector; 602, ejection hole.

[0044] Example:

[0045] As attached Figure 1-5 As shown, this invention discloses a well-washing method for geothermal exploration in karst areas.

[0046] Step 1: Selection of the plugging device 301. Select the plugging device 301 according to the inner diameter of the filter tube 201 in the current geothermal well 1, so that the side wall of the plugging device 301 can be close enough to the inner wall of the filter tube 201 without affecting its movement in the filter tube 201, so that the gap between the plugging device 301 and the inner diameter of the filter tube 201 is maintained between 5-10mm.

[0047] Step 2: Assemble the well cleaning tools by assembling the injector 601, drill collar 402, plugger 301, and drill pipe 401 from bottom to top.

[0048] Step 3: Lower the well cleaning tool into the well. Place the well cleaning tool into the filter pipe 201 of the geothermal well 1 and lower it at a constant speed until it reaches a distance of 0.8m-1.2m from the top of the filter pipe 201.

[0049] Step 4: Cleaning of Geothermal Well 1. The well-cleaning medium is sprayed out through the ejector 601, and the ejector 601 is made to sink to the bottom of the water-bearing section at a uniform speed, with the sinking speed controlled between 0.2-0.3 m / s. The ejector 601 is then controlled to rise at a uniform speed and the well-cleaning medium is sprayed until it reaches H1, and then the spraying of the well-cleaning medium is stopped. The well-cleaning medium can be clean water, and the rising speed is controlled between 0.2-0.3 m / s.

[0050] In step four, under the rated cleaning pump pressure, step four is repeated three times to allow the well-washing tool to gradually flush away the collapsed material surrounding the filter pipe, opening up the annular space and thus improving the well-washing effect. This saves time and cost, and removes most of the mud and collapsed material. Then, the pump pressure of the working pump is increased to 110% of the rated pump pressure, and step four is repeated three more times to remove the stubborn deposits remaining in geothermal well 1, thereby further improving the cleaning effect and increasing the amount of geothermal resources.

[0051] Because the plugging device 301 needs to be selected according to the internal diameter of the filter tube 201, when the gap between the plugging device 301 and the wall of the filter tube 201 is sufficiently small, the well-washing medium sprayed from the well-washing tool is injected into a relatively closed and narrow space. Due to the reduced pressure leakage at the gap, the well-washing medium in the gap still has a large pressure. Therefore, when the well-washing medium in the gap enters the annular space through the filter hole 202 of the filter tube 201, it still has a large scouring force, that is, the well-washing medium has a large pressure. When the well-washing medium is injected into the annular space through the filter hole 202, it forms a high-pressure scouring turbulence, thereby destroying the mud skin on the well wall outside the filter hole 202, and successively flushing away the collapsed material covering the filter tube 201, opening up the annular space, so that the well-washing fluid circulates and scours in the annular space, continuing to destroy the mud skin on the well wall, thereby achieving the purpose of improving the well-washing effect.

[0052] The setting of the injection plug 301 reduces the loss of the flushing speed of the flushing medium during jet flushing and improves the flushing effect, so that the flushing tool can still spray high-pressure flushing medium at a relatively deep depth of the geothermal well 1, so that the collapsed material at a relatively deep depth of the geothermal well 1 can still be flushed away.

[0053] Step 5: Remove the well-washing tool. After raising the well-washing tool to the wellhead of geothermal well 1, remove the well-washing tool.

[0054] Step 6: Settle the scale. Inject a settling agent into geothermal well 1. The settling agent is sodium hexametaphosphate solution (concentration 1.5%), and soak for at least 24 hours.

[0055] Step 7: Replace the slurry with clean water. Replace the mixture in the geothermal well 1 with clean water until clean water returns from the wellhead of the geothermal well 1. This step removes most of the suspended matter in the geothermal medium, thereby initially preventing the suspended matter from settling and clogging the filter 202.

[0056] Step 8: Modification of well washing tools. Remove the plug 301 and drill collar 402 from the well washing tools, and connect and fix the injector 601 to the drill pipe 401.

[0057] Step 9: Rewash, and repeat steps 3 and 4 in sequence, with step 4 repeated three times;

[0058] Step 10: Replace the slurry again. After the well washing tool is raised to the wellhead of geothermal well 1, remove the well washing tool and repeat step 7 to replace the slurry with clean water in the geothermal well. This will remove the suspended dirt caused by the re-washing in step 9 from the geothermal well, thereby completely preventing the suspended matter from settling in geothermal well 1 and ensuring the subsequent water output rate of geothermal well 1.

[0059] Step 11: Finishing. Take out the well-washing tools, disassemble and store them in the designated location, and then proceed with the subsequent well-drilling process.

[0060] The plugging device 301 is cylindrical in shape and has a plugging hole 302 inside. The inner diameter of the plugging hole 302 is the same as the inner diameter of the drill rod 401 and the drill collar 402. The plugging device 301 also has a placement groove 303 that is coaxially arranged with the plugging hole 302. A rotating cylinder 304 is rotatably connected in the placement groove 303. The bottom of the drill rod 401 is threadedly connected to the rotating cylinder 304 and communicates with the plugging hole 302. Several rotating devices are evenly distributed around the bottom of the plugging device 301. The rotating devices include a connecting rod 501 and a rotating blade 502. The connecting rod 501 is fixed to the bottom of the plugging device 301, and the rotating blade 502 is fixed to the bottom of the connecting rod 501. The longitudinal section of the rotating blade 502 near the connecting rod 501 is arc-shaped with an arc greater than 180°. Therefore, the working principle of the rotating blade 502 is the same as the rotation principle of a windmill.

[0061] In step two, the drill collar 402 has three roots, and the three drill collars 402 are connected in series from top to bottom. The top drill collar 402 is fixed to the bottom of the plugging device 301 and is connected to the plugging hole 302. The bottom drill collar 402 is fixed to and connected to the injector 601.

[0062] The rotating blade 502 drives the injection plug 301 to rotate as it rises and falls within the filter tube 201, so that the well-washing medium ejected by the ejector 601 not only has a high scouring intensity but also a tangential shearing force. This allows the well-washing medium entering the annular space to scour the well in the same direction and has a large tangential force, thus improving the well-washing effect.

[0063] In one embodiment, the filter tube 201 has an inner diameter of φ174mm, the plugger 301 has a height of 2800mm, the plugger 301 has an outer diameter of φ154mm, the drill rod 401, drill collar 402, and ejector 601 all have an inner diameter of φ89mm, the connecting rod 501 has a diameter of 5mm, the rotating blade 502 has a radial length of 15mm and a thickness of 3mm along the filter tube 201, the ejector 601 has a height of 2000mm, and the bottom of the ejector 601 is sealed by welding with a 12mm thick steel plate. The ejection hole 602 at the lower end of the ejector 601 has a diameter of 6mm, the number of ejection holes 602 is 100, and the sum of the areas of all ejection holes 602 is less than the inner cross-sectional area of ​​the ejector 601. The 100 ejection holes 602 are evenly arranged in the lower half of the ejector 601, and the overall distribution interval length does not exceed 1000mm in the ejector 601.

[0064] The above descriptions are merely embodiments of the present invention, and common knowledge regarding specific technical solutions or characteristics is not elaborated upon here. It should be noted that those skilled in the art can make various modifications and improvements without departing from the technical solutions of the present invention, and these should also be considered within the scope of protection of the present invention. These modifications and improvements will not affect the effectiveness of the implementation of the present invention or the practicality of the patent. The scope of protection claimed in this application should be determined by the content of its claims, and the specific embodiments described in the specification can be used to interpret the content of the claims.

Claims

1. A method for geothermal exploration well washing in karst areas, characterized in that: step one, selection of the injection plug, according to the inner diameter of the filter tube in the current geothermal well; step two, assembly of the well washing tool, the injector, drill collar, injection plug and drill pipe are sequentially spliced from bottom to top; step three, lowering the well washing tool into the filter tube of the geothermal well and sinking at a uniform speed, sinking to H1 from the top of the filter tube; step four, cleaning the geothermal well, spraying the well washing medium through the injector, and sinking the injector to the bottom of the water-bearing section at a uniform speed, then controlling the injector to rise at a uniform speed and continue to spray the well washing medium until reaching H1, then stopping spraying the well washing medium; step five, removing the well washing tool, controlling the well washing tool to rise to the wellhead of the geothermal well, and then removing the well washing tool; step six, settling the dirt, injecting a settling agent into the geothermal well and soaking for at least 24 hours; step seven, clean water replacement, replacing the mixture in the geothermal well with clean water until the clean water returns to the wellhead of the geothermal well; step eight, modification of the well washing tool, removing the injection plug and drill collar in the well washing tool, and fixing the injector in communication with the drill pipe; step nine, re-washing, sequentially performing steps three and four again; step ten, re-replacement, controlling the well washing tool to rise to the wellhead of the geothermal well, removing the well washing tool, and performing step seven again to replace the geothermal well with clean water; step eleven, finishing, disassembling and storing the well washing tool to the designated position, and then performing the subsequent well completion procedure; the injection plug is provided with an injection hole, and a placement groove coaxial with the injection hole is also provided on the injection plug, a rotating cylinder is rotatably connected in the placement groove, and the bottom of the drill pipe is threadedly connected in the rotating cylinder and in communication with the injection hole; a plurality of rotating devices are uniformly distributed around the bottom of the injection plug, the rotating device comprises a connecting rod and a rotating blade, the connecting rod is fixed to the bottom of the injection plug, and the rotating blade is fixed to the bottom of the connecting rod; the drill collar is 2-4, and the drill collars are connected in series and in communication with each other, the top drill collar is fixed to the bottom of the injection plug and in communication with the injection hole, and the bottom drill collar is fixed to the injector and in communication therewith; in step nine, step four is repeated at least three times; the inner cross-sectional area of the injector is less than or equal to the inner cross-sectional area of the drill pipe, the injection hole diameter of the lower end of the injector is 5-7 mm, and the sum of the areas of all the injection holes is less than the inner cross-sectional area of the injector. The number of injection holes is 90-110. In step four, first, according to the rated cleaning pump pressure of the process parameters, step four is repeated at least three times, and then the pump pressure is increased and step four is repeated at least three times again. ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ 2. The method for geothermal exploration and well washing in karst area according to claim 1, characterized in that: ​ 3. The method for geothermal exploration and well washing in karst area according to claim 1, characterized in that: ​

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