A method for cleaning a two-open-structure horizontal wellbore

Abstract

The present application belongs to the technical field of drilling process, and particularly relates to a method for cleaning a wellbore of a two-opening structure horizontal well. The present application effectively solves the problem of wellbore cleaning difficulty in the construction process of the two-opening structure horizontal well by using different wellbore cleaning methods in the drilling or well passing process, effectively reduces the friction and torque in the drilling and well completion operation process, reduces the rock debris volume fraction in the annulus by 25%-30%, reduces the construction difficulty and the risk of sticking and leakage, and realizes safe and efficient drilling. The wellbore cleaning method is used in 12 two-opening structure horizontal wells in a gas field for field test, and the wellbore cleaning effect is good. After using the method, the tripping friction is reduced from 40-50 tons to 15-25 tons, the maximum drilling torque is reduced from 35000 N.m to 28000 N.m, and no resistance or other downhole complications occur in the tripping and well completion casing operation.

Description

Technical Field

[0001] This invention belongs to the field of drilling technology, specifically relating to a method for cleaning the wellbore of a two-section horizontal well. Background Technology

[0002] The presence of cuttings beds and suspended cuttings affects the cleanliness of the wellbore. Actual drilling data shows that when a large number of cuttings beds form on the wellbore, the concentration of suspended cuttings in the drilling fluid increases significantly, causing abnormal changes in torque during drilling and hook load during tripping. This can even lead to the rotary table or top drive stalling or stuck pipe. In particular, for horizontal well drilling, when the well inclination angle exceeds a certain value, there is a common technical challenge of difficult wellbore cleaning, resulting in abnormally high friction and equivalent circulating density (ECD). This increases the difficulty of construction and the risk of stuck pipe and leakage, seriously restricting safe and efficient drilling. This is especially true for horizontal wells with a two-stage structure, where the open hole section is long, and the impact on wellbore cleaning is even more severe.

[0003] A search revealed that application number CN202211679638.3, entitled "A Novel Integrated Wellbore Cleaning Tool," integrates multiple functions including well cleaning, tubing scraping, well washing, retrieval, and drilling / milling. Multiple wellbore cleaning targets can be achieved in a single drilling run. The design features a modular combination: firstly, the magnetic retrieval and well cleaning tools are integrated, optimizing and shortening the tool length; secondly, a non-rigid hydraulic centering and scraping unit structure improves passability, reduces friction, and enhances cleaning effectiveness for deviated and horizontal well operations; and thirdly, a hydraulic screw drilling and milling power unit design allows for the rotation of the lower drill bit and milling tool without rotating the tubing string in high-friction scenarios, broadening its application scenarios. However, it also presents the technical challenge of difficult wellbore cleaning during horizontal well drilling when the well inclination angle exceeds a certain value. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention provides a method for cleaning the wellbore of a two-section horizontal well.

[0005] The technical solution adopted in this invention is: A method for cleaning the wellbore of a two-section horizontal well includes the following steps: Step 1: Determine whether it is cleaning the wellbore during horizontal drilling or cleaning the wellbore during a traverse; if it is cleaning the wellbore during horizontal drilling, proceed to Step 2; if it is cleaning the wellbore during a traverse, proceed to Step 3. Step 2: For each preset drilling depth in the horizontal section, perform a short trip down drill bit and continuously optimize the wellbore cleaning plan until cleaning is completed; Step 3: After cleaning the sand in the horizontal section, proceed to Step 4; for the inclined section, proceed to Step 5. Step 4: Using the single-handle drill string assembly, after drilling to the bottom of the well and circulating once, start reverse reaming and sand removal using the preset displacement, top drive speed, maximum torque and drill string lifting speed; after reverse reaming and sand removal, circulate once after pulling out the preset drill string, and then pull out the preset drill string normally after circulation; then start the second and third reverse reaming and sand removal until the single-handle drill string assembly has cleaned the cuttings bed in the horizontal section and then circulate and pull out the drill string. Step 5: Using the dual-steering drill string combination, drill down to the preset position in the horizontal section. After one cycle, start reverse reaming and sand removal using the preset displacement, top drive speed, maximum torque, and drill string lifting speed. After reverse reaming and sand removal, drill string is pulled out 5 times and circulated. After sand removal and circulation are complete, drill down to the bottom of the well. After circulating and injecting lubricant, drill string is pulled out to perform casing installation.

[0006] The preset drilling depth in step two is 300-500m.

[0007] The specific method for optimizing the wellbore cleaning scheme in step two is as follows: When the deviation between the actual drilling friction torque and the simulated data exceeds the preset value and the relative thickness of the cuttings bed H > 10%, increase the drilling fluid displacement Q and the rotary table speed N; if the drilling fluid displacement Q and the rotary table speed N reach the maximum allowable conditions of the pump and machinery, but H is still > 10%, adjust the drilling fluid properties, that is, increase the drilling fluid flowability index n, the drilling fluid consistency coefficient K, and the drilling fluid density ρ; if increasing the drilling fluid flowability index n, the drilling fluid consistency coefficient K, and the drilling fluid density ρ has reached the maximum allowable conditions, but H is still > 10%, reduce the mechanical speed v, briefly start to destroy the cuttings bed, and use wellbore cleaning tools until the actual drilling friction torque returns to normal and the relative thickness of the cuttings bed H ≤ 10%.

[0008] In step four, the preset displacement is 28-32 L / s; the preset top drive speed is 80-90 r / min; the maximum torque is limited to idling torque + 5000 N·m; and the drill string lifting speed is less than 0.25 m / s.

[0009] The single-handle drill assembly used in step four includes a drill bit, a double female connector, a reaming stabilizer, a weighted drill rod, three sand-cleaning drill rods, and four ordinary drill rods; connected in the order from bottom to top are the drill bit, double female connector, first inverted reaming stabilizer, weighted drill rod, sand-cleaning drill rod, ordinary drill rod, sand-cleaning drill rod, ordinary drill rod, sand-cleaning drill rod, and ordinary drill rod.

[0010] The drill bit is Ø215.9mm; the reaming stabilizer is Ø210mm; the weighted drill rod is Ø127mm HWDp Dp drill rod 150m; the ordinary drill rod is 150m Ø127mm drill rod.

[0011] The preset displacement in step five is 30-33 L / s, the top drive speed is above 100 r / min, the maximum torque is limited to idling torque + 5000 N·m, and the drill string lifting speed is less than 0.25 m / s.

[0012] The dual-steering drill assembly used in step five includes a drill bit, a double female connector, a first reaming stabilizer, a second reaming stabilizer, a first heavy drill rod, a second heavy drill rod, three sand-cleaning drill rods, and three ordinary drill rods; connected in the following order from bottom to top are the drill bit, double female connector, first reaming stabilizer, first heavy drill rod, second reaming stabilizer, second heavy drill rod, sand-cleaning drill rod, ordinary drill rod, sand-cleaning drill rod, ordinary drill rod, sand-cleaning drill rod, and ordinary drill rod.

[0013] The drill bit is Ø215.9mm; the first reaming stabilizer is Ø210mm; the second reaming stabilizer is Ø208mm; the first weighted drill is 19m Ø127mm; the second weighted drill is 150m HWDp Dp Ø127mm drill rod; and the ordinary drill rod is 150m Ø127mm drill rod.

[0014] In step five, the preset position for the horizontal segment is 95-105m from the beginning of the horizontal segment.

[0015] In step four, the preset number of drilling columns for back-scraping and sand-clearing is 5-10, and the preset number of columns for normal drilling after the cycle is 3 times that of the preset number of drilling columns for back-scraping and sand-clearing.

[0016] The beneficial effects of this invention are: This invention effectively solves the problem of difficult wellbore cleaning during the construction of two-stage horizontal wells by adopting different wellbore cleaning methods during drilling or well completion. It effectively reduces friction and torque during drilling and well completion operations, reduces the volume fraction of cuttings in the annulus by 25%–30%, reduces construction difficulty and the risk of stuck drill and leakage, and enables safe and efficient drilling.

[0017] Using this invention, 12 horizontal wells in a gas field with a second-stage structure were tested in the field. The wellbore cleaning effect was good. After using this method, the friction of tripping in and out of the well was reduced from 40-50 tons to 15-25 tons, and the maximum drilling torque was reduced from 35000 N·m to 28000 N·m. No obstruction or other downhole complications occurred during tripping in, out of the well, and casing completion operations.

[0018] The above description is merely an overview of the technical solution of the present invention. In order to better understand the technical means of the present invention and to implement it in accordance with the contents of the specification, the preferred embodiments of the present invention are described in detail below with reference to the accompanying drawings. Attached Figure Description

[0019] 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.

[0020] Figure 1 This is a schematic diagram illustrating the optimization of the wellbore cleaning scheme during horizontal drilling in this invention. Detailed Implementation

[0021] 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 the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0022] Example 1: During horizontal well construction, the cuttings removal rate is slow in steeply angled and horizontal sections, leading to the formation of static cuttings beds. These cuttings beds need to be cleaned up promptly during drilling.

[0023] A method for cleaning the wellbore of a two-section horizontal well includes the following steps: Step 1: Determine whether it is cleaning the wellbore during horizontal drilling or cleaning the wellbore during a traverse; if it is cleaning the wellbore during horizontal drilling, proceed to Step 2; if it is cleaning the wellbore during a traverse, proceed to Step 3. Step 2: For each preset drilling depth in the horizontal section, perform a short trip down drill bit and continuously optimize the wellbore cleaning plan until cleaning is completed; Step 3: After cleaning the sand in the horizontal section, proceed to Step 4; for the inclined section, proceed to Step 5. Step 4: Using the single-handle drill string assembly, after drilling to the bottom of the well and circulating once, start reverse reaming and sand removal using the preset displacement, top drive speed, maximum torque and drill string lifting speed; after reverse reaming and sand removal, circulate once after pulling out the preset drill string, and then pull out the preset drill string normally after circulation; then start the second and third reverse reaming and sand removal until the single-handle drill string assembly has cleaned the cuttings bed in the horizontal section and then circulate and pull out the drill string. Step 5: Using the dual-steering drill string combination, drill down to the preset position in the horizontal section. After one cycle, start reverse reaming and sand removal using the preset displacement, top drive speed, maximum torque, and drill string lifting speed. After reverse reaming and sand removal, drill string is pulled out 5 times and circulated. After sand removal and circulation are complete, drill down to the bottom of the well. After circulating and injecting lubricant, drill string is pulled out to perform casing installation.

[0024] In the horizontal section, perform a short trip every 300-500m, using the top drive to retrace the borehole and start the pump before tripping. Maximize the flow rate. With sufficient flow rate, the high-speed flow area at the higher edge of the horizontal wellbore is larger, making it easier for cuttings to enter the conveyor belt during drill string rotation. With insufficient flow rate, the high-speed flow area is smaller, resulting in lower cuttings transport efficiency. Use the highest possible rotation speed during short trips, retrace, and sand removal. At high rotation speeds, the drill string's revolution within the wellbore increases, the surrounding drilling fluid viscosity coupling thickness is greater, and the bottom edge of the wellbore reaches a turbulent state, better agitating the cuttings at the bottom edge and carrying them forward into the upper conveyor zone.

[0025] In practical use, a short trip is performed every 300-500 meters of drilling. If the short trip is less than 300 meters, the frequency of short trips is too high, affecting the construction cycle; if the short trip is greater than 500 meters, the drilled section is longer, resulting in a thicker cuttings bed, which is more difficult to clean. It is preferable to drill within the 300-500 meter section. If the friction and torque are normal during drilling, the wellbore is considered to be in good condition, and drilling can continue. If the friction and torque increase significantly during drilling, the wellbore is considered to be in poor condition, and a cuttings bed may have formed, requiring a short trip to break up the cuttings bed.

[0026] Specifically, when the deviation between the actual drilling friction torque and the simulated data exceeds the preset value, and the relative thickness of the cuttings bed H > 10%, the drilling fluid displacement Q and rotary table speed N are increased. If the drilling fluid displacement Q and rotary table speed N reach the maximum allowable conditions of the pump and machinery, but H still > 10%, the drilling fluid properties are adjusted, i.e., the drilling fluid flowability index n, drilling fluid consistency coefficient K, and drilling fluid density ρ are increased. If increasing the drilling fluid flowability index n, drilling fluid consistency coefficient K, and drilling fluid density ρ has reached the maximum allowable conditions, but H still > 10%, the mechanical speed v is reduced, the cuttings bed is briefly disturbed, and wellbore cleaning tools are used until the actual drilling friction torque returns to normal and the relative thickness of the cuttings bed H ≤ 10%. Figure 1 As shown.

[0027] This invention effectively solves the problem of difficult wellbore cleaning during the construction of two-stage horizontal wells by adopting different wellbore cleaning methods during drilling or well completion. It effectively reduces friction and torque during drilling and well completion operations, reduces the volume fraction of cuttings in the annulus by 25%-30%, reduces construction difficulty and the risk of stuck drill and leakage, and enables safe and efficient drilling.

[0028] Before running casing in horizontal wells, a drilling and wellbore cleaning process must be performed to verify the dogleg alignment of the wellbore trajectory and the accessibility of the wellbore. For ordinary wells, a standard drilling and wellbore cleaning assembly can be used for rapid tripping and verification. For wells with high friction, the drilling assembly should include a cuttings bed breaker and a reamer to effectively clear the cuttings bed.

[0029] Specifically, the first wellbore run used a single-steering drill string assembly for sand removal in the horizontal section, carrying three sand removal drill pipes. The drill string assembly consisted of: a Ø215.9mm drill bit, a double female connector, a Ø210mm reamer stabilizer, Ø127mm drill pipe (HWDp+Dp) × 150m, sand removal drill pipe, Ø127mm drill pipe × 150m, sand removal drill pipe, Ø127mm drill pipe × 150m, sand removal drill pipe, and Ø127mm drill pipe. The single-steering assembly has relatively low rotational torque and weak drill string rigidity, making it suitable for cleaning cuttings beds in horizontal sections. The horizontal section has a higher torque and lower dogleg.

[0030] The specific method for sand removal in the horizontal section is as follows: After drilling to the bottom of the well and circulating once, begin reverse reaming for sand removal. The displacement is 28-32 L / s, the top drive speed is 80-90 r / min, the maximum torque is limited to idle torque + 5000 N·m, and the drill string lifting speed is less than 0.25 m / s. After reverse reaming and sand removal, pull back 5 drill strings (approximately 150 m), then circulate once more. The total sand-removed section is 450 m long. After circulation, pull back 15 drill strings (approximately 450 m) normally. Then begin the second and third reverse reaming sand removal operations. After the single-support assembly has cleaned the cuttings bed in the horizontal section, circulate and pull back the drill string.

[0031] The second wellbore run used a dual-steering drill string assembly for sand removal in the deviated section. The assembly, carrying three sand-removing drill pipes, consisted of: a Ø215.9mm drill bit, a double female connector, a Ø210mm first reaming stabilizer, a Ø127mm first heavy-duty drill pipe (19m), a Ø208mm second reaming stabilizer, a Ø127mm second drill pipe (HWDp Dp) (150m), sand-removing drill pipe, a Ø127mm drill pipe (150m), sand-removing drill pipe, and a Ø127mm drill pipe. The dual-steering assembly has relatively high rotational torque and strong drill string rigidity, making it suitable for cleaning cuttings beds in the deviated section. However, the torque is relatively low in the deviated section, resulting in a large dogleg.

[0032] The specific method for sand removal in the deviated well section is as follows: Drill down to approximately 100m into the horizontal section, circulate once, and then begin reverse reaming for sand removal. Use a displacement of 30-33L / s, a top drive speed of over 100r / min, and limit the maximum torque to idle torque + 5000N·m. The drill string lifting speed should be less than 0.25m / s. After reverse reaming and sand removal, circulate again after pulling back 5 drill strings. The total sand-removed section is 450m long. After sand removal and complete circulation, continue drilling to the bottom of the well, circulate lubricant, and then pull back to begin casing installation.

[0033] In this invention, the preset position of the horizontal section in step five is any position that can be reached from 95 to 105 meters into the horizontal section, depending on the actual situation. Since the single-support combination in step four mainly cleans the horizontal section, and the double-support combination in step five mainly cleans the inclined shaft section, and the preset position of the horizontal section in step five is 95-105 meters into the horizontal section, there is a 100-meter overlap between the two combinations. This can improve the cleaning effect and avoid the existence of cleaning blind spots.

[0034] The sand-cleaning drill pipe used in this invention, also known as a cuttings bed disruptor, is existing technology. The sand-cleaning drill pipe consists of two adjacent 500mm long joints with swirling breaking grooves in the middle of the drill pipe, with an outer diameter larger than that of the drill pipe coupling. The swirling groove design creates turbulent flow of the drilling fluid at the bottom as the drill string rotates. Combined with the faster flow velocity of the drilling fluid at the sand-cleaning drill pipe, the combined hydraulic and mechanical effects effectively agitate and disrupt the cuttings bed. The sand-cleaning drill pipe can reduce the volume fraction of annular cuttings by 25%-30%.

[0035] This invention utilizes existing technology. The wellbore reaming stabilizer features several specially designed cutting teeth at both the upper and lower ends of the stabilizer's working zone. This allows the stabilizer to perform bidirectional cutting during drilling and tripping. During drilling, it helps to smooth the wellbore, ensuring the wellbore trajectory reaches an ideal state and preventing doglegs. During tripping, the reverse reaming teeth perform cutting to eliminate sand bridges and necking, improving wellbore reaming efficiency and reducing friction by an average of 40%.

[0036] In some embodiments, the preset number of drilling columns for reverse shaving and sand cleaning in step four is 5-10 columns, and the preset number of drilling columns for normal tripping after circulation is 3 times that of the preset number of drilling columns for reverse shaving and sand cleaning. This ensures that the entire wellbore is cleaned once, which is efficient and has a good cleaning effect.

[0037] Example 2: Practical applications of the present invention.

[0038] The wellbore cleaning method of this invention was successfully tested in 12 horizontal wells in a gas field, demonstrating good wellbore cleaning results. After using this method, the tripping friction decreased from 40-50 tons to 15-25 tons, and the maximum drilling torque decreased from 35,000 N·m to 28,000 N·m. No obstructions or other downhole complications occurred during tripping, tripping, and casing completion operations.

[0039] Where there is no conflict, those skilled in the art can combine the relevant technical features in the above examples according to the actual situation to achieve the corresponding technical effects. Specific details of the various combinations will not be elaborated here.

[0040] It should be noted that all directional indications (such as up, down, left, right, front, back, etc.) in the embodiments of the present invention are only used to explain the relative positional relationship and movement of each component in a certain specific posture (as shown in the figure). If the specific posture changes, the directional indication will also change accordingly.

[0041] Furthermore, the use of terms such as "first" and "second" in this invention is for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined with "first" or "second" may explicitly or implicitly include at least one of those features.

[0042] The above description is merely a preferred embodiment of the present invention. The present invention is not limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein. Any simple modifications, equivalent variations, and alterations made to the above embodiments based on the technical essence of the present invention shall still fall within the scope of the present invention.

Claims

1. A method for cleaning the shaft of a two-section horizontal well, characterized in that: Including steps, Step 1: Determine whether it is cleaning the wellbore during horizontal drilling or cleaning the wellbore during a traverse; if it is cleaning the wellbore during horizontal drilling, proceed to Step 2; if it is cleaning the wellbore during a traverse, proceed to Step 3. Step 2: For each preset drilling depth in the horizontal section, perform a short trip down drill bit and continuously optimize the wellbore cleaning plan until cleaning is completed; Step 3: After cleaning the sand in the horizontal section, proceed to Step 4; for the inclined section, proceed to Step 5. Step 4: Using a single-drive drill string assembly, after drilling to the bottom of the well and circulating once, start reaming and sand removal using the preset displacement, top drive speed, maximum torque and drill string lifting speed; After the reverse reaming and sand removal process is completed and the drill string is pulled out to the preset column, the process is repeated once. After the cycle is completed, the drill string is pulled out normally. Then, the second and third reverse reaming and sand removal processes are started until the cuttings bed in the horizontal section is cleared by the single-support combination and the drill string is pulled out. Step 5: Using the dual-drive drill bit assembly, drill down to the preset position in the horizontal section. After one cycle, start back-reaming and sand removal using the preset displacement, top drive speed, maximum torque, and drill bit lifting speed. After clearing sand and pulling out 5 drill strings, the drill string is circulated. After clearing sand and circulating cleanly, the drill string continues to the bottom of the well. Lubricant is then injected and the drill string is pulled out to run casing.

2. The method for cleaning a two-section horizontal wellbore as described in claim 1, characterized in that: The preset drilling depth in step two is 300-500m.

3. A method for cleaning the shaft of a two-section horizontal well as described in claim 1 or 2, characterized in that: The specific method for optimizing the wellbore cleaning scheme in step two is as follows: When the deviation between the actual drilling friction torque and the simulated data exceeds the preset value and the relative thickness of the cuttings bed H > 10%, increase the drilling fluid displacement Q and the rotary table speed N; if the drilling fluid displacement Q and the rotary table speed N reach the maximum allowable conditions of the pump and machinery, but H is still > 10%, adjust the drilling fluid properties, that is, increase the drilling fluid flowability index n, the drilling fluid consistency coefficient K, and the drilling fluid density ρ; if increasing the drilling fluid flowability index n, the drilling fluid consistency coefficient K, and the drilling fluid density ρ has reached the maximum allowable conditions, but H is still > 10%, reduce the mechanical speed v, briefly start to destroy the cuttings bed, and use wellbore cleaning tools until the actual drilling friction torque returns to normal and the relative thickness of the cuttings bed H ≤ 10%.

4. The method for cleaning a two-section horizontal wellbore as described in claim 1, characterized in that: In step four, the preset displacement is 28-32 L / s; the preset top drive speed is 80-90 r / min; the maximum torque is limited to idling torque + 5000 N·m; and the drill string lifting speed is less than 0.25 m / s.

5. The method for cleaning a two-section horizontal wellbore as described in claim 1, characterized in that: The single-handle drill assembly used in step four includes a drill bit, a double female connector, a reaming stabilizer, a weighted drill rod, three sand-cleaning drill rods, and four ordinary drill rods; connected in the order from bottom to top are the drill bit, double female connector, first inverted reaming stabilizer, weighted drill rod, sand-cleaning drill rod, ordinary drill rod, sand-cleaning drill rod, ordinary drill rod, sand-cleaning drill rod, and ordinary drill rod.

6. The method for cleaning a two-section horizontal wellbore as described in claim 5, characterized in that: The drill bit is Ø215.9mm; the reaming stabilizer is Ø210mm; the weighted drill rod is Ø127mm HWDp Dp drill rod 150m; the ordinary drill rod is 150m Ø127mm drill rod.

7. The method for cleaning a two-section horizontal wellbore as described in claim 1, characterized in that: The preset displacement in step five is 30-33 L / s, the top drive speed is above 100 r / min, the maximum torque is limited to idling torque + 5000 N·m, and the drill string lifting speed is less than 0.25 m / s.

8. The method for cleaning a two-section horizontal wellbore as described in claim 1, characterized in that: The dual-steering drill assembly used in step five includes a drill bit, a double female connector, a first reaming stabilizer, a second reaming stabilizer, a first heavy drill rod, a second heavy drill rod, three sand-cleaning drill rods, and three ordinary drill rods; connected in the following order from bottom to top are the drill bit, double female connector, first reaming stabilizer, first heavy drill rod, second reaming stabilizer, second heavy drill rod, sand-cleaning drill rod, ordinary drill rod, sand-cleaning drill rod, ordinary drill rod, sand-cleaning drill rod, and ordinary drill rod.

9. The method for cleaning a two-section horizontal wellbore as described in claim 8, characterized in that: The drill bit is Ø215.9mm; the first reaming stabilizer is Ø210mm; the second reaming stabilizer is Ø208mm; the first weighted drill is 19m Ø127mm; the second weighted drill is 150m HWDp Dp Ø127mm drill rod; and the ordinary drill rod is 150m Ø127mm drill rod.

10. The method for cleaning a two-section horizontal wellbore as described in claim 1, characterized in that: In step five, the preset position for the horizontal segment is 95-105m from the beginning of the horizontal segment.

11. The method for cleaning a two-section horizontal wellbore as described in claim 1, characterized in that: In step four, the preset number of drilling columns for back-scraping and sand-clearing is 5-10, and the preset number of columns for normal drilling after the cycle is 3 times that of the preset number of drilling columns for back-scraping and sand-clearing.

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