Casing shoe

Abstract

The utility model relates to the technical field of casing running in well drilling, in particular to a casing shoe which comprises a pipe body, the upper end of the pipe body is a female buckle end, the lower end of the pipe body is a milling shoe end, milling teeth are arranged at the lower end of the milling shoe end, and a plurality of alloy teeth are welded on the outer surfaces of the milling shoe end and the milling teeth. The device is extremely simple in structure, safe, reliable, not prone to damage and capable of punching, scratching and damaging settled sand or steps, so that a casing pipe can be smoothly put into the device.

Description

Technical Field

[0001] The utility model relates to the technical field of downhole casing running, in particular to a casing shoe for running conductor pipes and shallow surface casings. Background Art

[0002] During the operation of running casing in oil drilling, due to geological reasons such as loose bonding of shallow surface geology, developed faults and karst caves, well leakage and well collapse are extremely likely to occur, resulting in wellbore instability, collapse or cave-in, causing resistance when running the casing. Conventional casing shoes are installed at the bottom of the casing, with a round and smooth bottom and small holes opened at the bottom. During the process of pumping and scouring, the accumulated sediment or steps cannot be effectively scoured and repaired, resulting in difficulties in lowering the casing, and even casing sticking faults may occur, requiring pulling out the drill string to ream the well, which greatly affects the drilling construction progress and increases the drilling construction cost.

[0003] In the prior art, when the casing encounters resistance and cannot pass through even after pumping and scouring, Method 1 is to pull out the casing in the wellbore and run a drill string with a bit for reaming operation. This method involves casing pulling operation and has a high risk of personal injury. Method 2 is to run a small-sized drill string combination in the casing and lower the casing while scouring. This method operates inside the casing and has a risk of damaging the casing, and both methods greatly delay the construction progress.

[0004] CN 201120558020 discloses a rotatable casing shoe. Through the ratchet between the inner and outer cylinders, the outer cylinder can rotate to break the downhole steps and improve the passing rate of the casing when encountering resistance. This rotating structure is relatively complex, and impurities are likely to enter the components during the downward process, resulting in the failure of the rotating structure. Summary of the Invention

[0005] The purpose of the utility model is to solve the above technical problems, and provide a casing shoe with an extremely simple structure, safe and reliable, not easily damaged, capable of scouring and breaking sediment or steps, and enabling the casing to be smoothly run in.

[0006] The casing shoe of the utility model includes a pipe body. The upper end of the pipe body is a female thread end, and the lower end is a milling shoe end. The lower end of the milling shoe end has milling teeth, and a plurality of alloy teeth are inlaid and welded on the outer surfaces of the milling shoe end and the milling teeth.

[0007] The milling teeth are rectangular milling teeth; the alloy teeth are at least one of trapezoidal teeth or conical teeth.

[0008] The width of the rectangular milling teeth is 8 cm and the height is 5 cm; the height of the alloy teeth is 15 mm.

[0009] The distribution height of the plurality of alloy teeth on the pipe body of the milling shoe end 3 accounts for 20 - 25% of the total length of the pipe body.

[0010] The alloy tooth is composed of a cylindrical section at the lower part and a trapezoidal section or a conical section at the upper part.

[0011] The outer wall and the bottom end of the milled tooth are both provided with a hard alloy powder layer.

[0012] The thickness of the hard alloy powder layer on the outer wall is 3 - 6 mm.

[0013] The thickness of the hard alloy powder layer at the bottom end is 5 - 8 mm.

[0014] The length of the pipe body is 150 - 200 cm.

[0015] The female thread end is a female thread coupling provided with an internal thread.

[0016] The bottom end of the milled tooth has a 45° chamfer inward.

[0017] Beneficial effects:

[0018] In the present utility model, the mill shoe end of the pipe body is divided into rectangular milled teeth, which is beneficial to starting the pump after encountering resistance and reducing the circulating pump pressure; multiple alloy teeth are inlaid and welded on the rectangular teeth and the pipe body of the mill shoe end, which has an excellent destructive effect on the fallen blocks in the well and the wellbore steps, and the fallen blocks are also easy to be carried out of the wellbore after being broken; the outer wall and the bottom end of the milled teeth are both welded with hard alloy powder, which increases the anti-abrasion property of the mill shoe, has a scraping effect on the deposited sand, and is also convenient for stirring and carrying the deposited sand; the bottom end of the milled tooth has a 45° chamfer inward to prevent scratching the drill bit and the protruding parts of the drill string during the process of pulling out the drill in the next step of construction. The structure of the present utility model is extremely simple, safe and reliable, not easy to be damaged, can scour and destroy the deposited sand or steps, and enables the casing to be smoothly lowered. Description of the drawings

[0019] Figure 1 It is a schematic structural diagram of the present utility model.

[0020] Figure 2 Partial enlarged view of the milled tooth.

[0021] Figure 3 It is a schematic diagram of the alloy tooth of the trapezoidal tooth.

[0022] Figure 4 It is a schematic diagram of the alloy tooth of the conical tooth.

[0023] Among them, 1 - pipe body, 2 - female thread end, 3 - mill shoe end, 4 - alloy tooth, 4.1 - cylindrical section, 4.2 - trapezoidal section, 4.3 - conical section, 5 - hard alloy powder layer, 6 - milled tooth. Specific embodiments

[0024] The present utility model will be further explained below in conjunction with the drawings:

[0025] See Figure 1, the casing shoe of the present utility model includes a pipe body 1. The upper end of the pipe body 1 is a female thread end 2, and the female thread end is a female thread coupling with internal threads. The lower end is a mill shoe end 3. The lower end of the mill shoe end 3 has evenly arranged milling teeth 6, which is beneficial to starting the pump after encountering resistance and reducing the circulating pump pressure. The milling teeth 6 are preferably rectangular milling teeth with a width of 8 cm and a height of 5 cm. The bottom end of the milling teeth 6 has an inward 45° chamfer to prevent scraping the drill bit and the protruding parts of the drill string during the drilling process of the next step.

[0026] See Figure 2 , multiple alloy teeth 4 are inlaid and welded on the outer surface of the mill shoe end 3 and the milling teeth 4 of the pipe body 1, which has an excellent destructive effect on the fallen blocks in the well and the wellbore steps. After the fallen blocks are broken, they are also easy to be carried out of the wellbore. The alloy teeth 4 are at least one of trapezoidal teeth or conical teeth. See Figure 3 and Figure 4 , the alloy teeth 4 are composed of a cylindrical section 4.1 at the lower section and a trapezoidal section 4.2 or a conical section 4.3 at the upper section, which can effectively break while ensuring a reliable connection with the pipe body and avoid the shedding of the alloy teeth. The alloy teeth 4 can be polycrystalline diamond compact, with an overall height of 15 mm.

[0027] The total length L1 of the pipe body 1 is 150 - 200 cm. Preferably, the distribution height L2 of the multiple alloy teeth 4 on the pipe body of the mill shoe end 3 accounts for 20 - 25% of the total length L1 of the pipe body 1.

[0028] See Figure 2 , a hard alloy powder layer is provided on both the outer wall and the bottom end of the milling teeth 6. The thickness of the hard alloy powder layer on the outer wall is 3 - 6 mm; the thickness of the hard alloy powder layer at the bottom end is 5 - 8 mm. The hard alloy powder layer can adopt YT535 hard alloy material, and the hardness can reach above HRC67, which can increase the anti-abrasion property of the mill shoe, has a scraping effect on the settled sand, and is also convenient for stirring and carrying the settled sand.

[0029] Comparative experiment:

[0030] In Well Jiaoye ## - 2 in Fuling shale gas, a Φ609.6 mm bit was used to drill to 390 m in the first section, and a Φ473.1 mm conductor was run in. During the drilling process, well collapse occurred. When casing was run for the first time, a casing shoe was added at the bottom. The length of the pipe body was 180 cm. The bottom end of the casing shoe was evenly provided with rectangular teeth 6 (without alloy teeth), with a width of 8 cm and a height of 5 cm. A hard alloy powder layer 5 was welded on both the outer wall and the bottom end of the casing shoe. The thickness of the hard alloy powder layer on the outer wall was 5 mm, and the thickness of the hard alloy powder layer at the bottom end was 6 mm. When casing was run to 256 m, resistance was encountered. The top drive was connected and the pump was started to wash and cut. The pump started smoothly, but the progress of washing down was slow. It took 11 hours to ream 0.5 m, and no settled sand was returned.

[0031] After pulling out the drill pipe, 15-mm alloy teeth 4 were welded within a range of 40 cm above the bottom of the casing shoe. Then, the casing was run again and encountered resistance at 253 m. The pump was started to ream the hole. With pressure applied, it passed through. Reaming continued until 285 m, and 1.2 cubic meters of cuttings were returned. Subsequently, the remaining casing was run to the bottom of the well normally.

Claims

1. A casing shoe, comprising a pipe body, characterized in that: The upper end of the tube body is a female buckle end, and the lower end is a milling shoe end. The lower end of the milling shoe end has milling teeth, and the milling teeth are rectangular milling teeth. The milling shoe end and the outer surface of the milling teeth are welded with a plurality of alloy teeth, and the alloy teeth are at least one of trapezoidal teeth or conical teeth, and are composed of a cylindrical section in the lower section and a trapezoidal section or a conical section in the upper section.

2. The casing shoe according to claim 1, characterized in that: The rectangular milling teeth are 8 cm wide and 5 cm high; the overall height of the alloy teeth is 15 mm.

3. The casing shoe according to claim 1, characterized in that: The alloy teeth are distributed on the tube body at the milling shoe end at a height that accounts for 20-25% of the total length of the tube body.

4. The casing shoe according to any one of claims 1 to 3, characterized in that: The outer wall and the bottom of the milling tooth are both provided with a hard alloy powder layer.

5. The casing shoe according to claim 4, characterized in that: The thickness of the cemented carbide powder layer on the outer wall is 3-6 mm; the thickness of the cemented carbide powder layer on the bottom is 5-8 mm.

6. The casing shoe according to any one of claims 1 to 3, characterized in that: The length of the tube is 150-200 cm.

7. The casing shoe according to any one of claims 1 to 3, characterized in that: The box buckle end is a box buckle coupling provided with internal threads.

8. The casing shoe according to any one of claims 1 to 3, characterized in that: The bottom surface of the milling tooth has an inward chamfer of 45°.

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