A buoyancy plug for ultra-heavy and extra-large casing lower pipe

Abstract

The present invention discloses a buoyancy plug for an ultra-heavy and extra-large casing, and relates to the technical field of pipeline construction. It comprises a working casing, in which a cement buoyancy plug body is fixedly arranged; a first retaining ring is arranged above the cement buoyancy plug body, the first retaining ring is welded on the inner wall of the working casing, and a sealing ring is plugged between the first retaining ring and the working casing; a serpentine gas pipeline is arranged in the cement buoyancy plug body, and an enlarged cavity with an air inlet facing downward is arranged in the middle of the gas pipeline, and a sealing steel ball is slidably arranged in the enlarged cavity; spiral ribs and a plurality of hook ribs are also welded on the inner wall of the working casing. The present invention improves the overall air tightness by arranging a sealing ring, an enlarged cavity and a sealing steel ball; the gas pipeline adopts a serpentine arrangement to enhance the structural strength and prevent the gas pipeline from slipping; spiral ribs and a plurality of hook ribs are used to fix the cement buoyancy plug body to reduce the probability of slipping of the cement buoyancy plug body.

Description

Technical Field

[0001] The invention relates to the technical field of pipeline construction, in particular to a buoyancy plug for an ultra-heavy and extra-large casing lower pipe. Background Art

[0002] The floating method is usually used in the construction of coal mine gas extraction holes. The buoyancy of the mud in the hole on the well pipe column is increased by the buoyancy plug, thereby greatly reducing the hanging weight when the well pipe is lowered into the hole to adapt to the load capacity of the drilling tower and the drilling rig winch, and reduce the tensile stress caused by the deadweight of the well pipe itself. Commonly used buoyancy plugs include steel buoyancy plugs, cement buoyancy plugs, wood buoyancy plugs, etc.

[0003] Special, large, deep and precision drilling holes are widely used in deep rock underground engineering, especially for ground gas extraction, nitrogen injection, feeding, cable, underground risk avoidance and deep geothermal wells to ensure safe production in mines. All types of drilling holes above require the use of super-heavy and super-large casings. For example, the ground gas extraction well of the "Huai-Zhe Coal and Electricity Gubei Coal Mine Gas Extraction System Expansion (Drilling) Project" has a designed drilling volume of 675m, a well depth of 495m, a hole diameter of Φ1400mm, and a Φ1140mm spiral welded pipe with a pipe weight of 295 tons; the second well depth is 675m, the hole diameter is Φ1050mm, and a seamless steel pipe with an inner diameter of D800 mm is placed in the whole hole, with a pipe weight of 362 tons. The pulling force of the construction drilling rig can generally only reach about 150 tons, so a special pipe lowering method is required. For the construction of extra-large, deep and precision drilling holes, a complete, scientific and efficient system has not yet been formed. At the same time, there are problems such as the low safety of the large-diameter, extra-heavy and extra-large casing lowering and lifting system.

[0004] With the development of the industry, the mining depth is getting deeper and deeper, the diameter of the pipeline is also increasing, and the total weight of the working casing is also increasing, which increases the volume demand of the empty pipe section above the cement buoyancy plug, and also increases the length and weight of the empty pipe section above the cement buoyancy plug, which requires greater buoyancy support. A Chinese patent with publication number CN102650203B discloses a self-balancing pipe lowering method for a buoyancy valve and a gas extraction hole working casing containing the valve. By providing a gas pipeline in the buoyancy valve, high-pressure air is filled into the working casing on the lower side of the buoyancy valve. The high-pressure gas displaces the mud and forms a closed high-pressure gas pipe section in the working casing on the lower side of the buoyancy valve to increase buoyancy. Although this inflation method can increase buoyancy, gas is more likely to leak than liquid, which increases the risk of slippage of the buoyancy plug, and the gas pipeline also has the risk of slippage. Summary of the invention

[0005] The main purpose of the present invention is to provide a buoyancy plug for an ultra-heavy and extra-large casing lower pipe to solve the above-mentioned problem.

[0006] To achieve the above-mentioned purpose, the present invention provides a buoyancy plug for an ultra-heavy and extra-large casing downpipe, comprising a working casing, in which a cement buoyancy plug body is fixedly arranged; a first retaining ring is arranged above the cement buoyancy plug body, the first retaining ring is welded to the inner wall of the working casing, and a sealing ring is plugged between the first retaining ring and the working casing; a serpentine gas pipeline is arranged in the cement buoyancy plug body, the air inlet of the gas pipeline is located at the top of the cement buoyancy plug body, the air outlet of the gas pipeline is located at the bottom of the cement buoyancy plug body, an expansion cavity with an air inlet facing downward is arranged in the middle of the gas pipeline, and a sealing steel ball is slidably arranged in the expansion cavity; spiral ribs and a plurality of hook ribs are also welded to the inner wall of the working casing.

[0007] Furthermore, the rotation direction of the spiral rib is the same as that of the drill bit of the drilling rig, and the hook rib is arranged in a spiral shape, and the rotation direction is opposite to that of the spiral rib.

[0008] Furthermore, the bottom of the cement buoyancy plug body is conical.

[0009] Furthermore, a second retaining ring is arranged below the cement buoyancy plug body, and a cement sliding plug is slidably arranged between the second retaining ring and the cement buoyancy plug body, and the diameter of the cement sliding plug is smaller than the inner diameter of the working casing and larger than the inner diameter of the second retaining ring; the top of the cement sliding plug is conical and matched with the bottom of the cement buoyancy plug body, and the gas outlet of the gas pipeline is projected within the top range of the cement sliding plug.

[0010] Furthermore, a sealing gasket is pasted on the bottom of the cement buoyancy plug body.

[0011] Furthermore, a first through hole is transversely arranged on the cement sliding plug, and a second through hole communicating with the first through hole is arranged at the bottom of the cement sliding plug.

[0012] The present invention has the following beneficial effects:

[0013] 1. The present invention improves the overall air tightness by providing a sealing ring, expanding the cavity and blocking the steel ball;

[0014] 2. The gas pipeline of the present invention adopts a serpentine arrangement to enhance the structural strength and prevent the gas pipeline from slipping;

[0015] 3. The present invention uses spiral ribs and multiple hook ribs to fix the cement buoyancy plug body, thereby reducing the probability of slippage of the cement buoyancy plug body. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 The present invention is a cross-sectional view of a buoyancy plug for an ultra-heavy and extra-large casing lower pipe.

[0017] Figure 2The present invention is an overall schematic diagram of a gas pipeline with a buoyancy plug for an ultra-heavy and extra-large casing lower pipe.

[0018] Among them, 1-working casing; 2-gas transmission pipeline; 3-first retaining ring; 4-sealing ring; 5-cement buoyancy plug body; 6-spiral ribs; 7-hook ribs; 8-sealing pad; 9-cement sliding plug; 10-second retaining ring; 21-expanding cavity; 22-sealing steel ball; 91-first through hole; 92-second through hole. DETAILED DESCRIPTION

[0019] In order to achieve the above-mentioned purpose and effect, the technical means and structures adopted by the present invention are described in detail with reference to the accompanying drawings for the features and functions of the preferred embodiments of the present invention.

[0020] like Figure 1-2 As shown, the present invention provides a buoyancy plug for an ultra-heavy and extra-large casing lower pipe, comprising a working casing 1, in which a cement buoyancy plug body 5 is fixedly arranged; a first retaining ring 3 is arranged above the cement buoyancy plug body 5, the first retaining ring 3 is welded to the inner wall of the working casing 1, and a sealing ring 4 is plugged between the first retaining ring 3 and the working casing 1; the gap between the cement buoyancy plug body 5 and the working casing 1 is blocked by the sealing ring 4 to prevent air leakage; a serpentine gas pipeline 2 is arranged in the cement buoyancy plug body 5, the air inlet of the gas pipeline 2 is located at the top of the cement buoyancy plug body 5, and the air outlet of the gas pipeline 2 is located at the bottom of the cement buoyancy plug body 5, and the serpentine arrangement is used to enhance the fixing strength of the gas pipeline 2 in the cement buoyancy plug body 5 to prevent the gas pipeline 2 from slipping; an enlarged cavity 21 with an air inlet facing downward is arranged in the middle of the gas pipeline 2, and a sealing steel ball 2 is slidably arranged in the enlarged cavity 21 2; When inflating, slow pressurized inflation is adopted. Under the action of airflow, the plugging steel ball 22 is suspended, and the air path is opened to inflate the underground. After stopping pressurized inflation, the pressure on the upper and lower sides of the plugging steel ball 22 is the same, and it automatically falls back under the action of its own gravity to achieve plugging and avoid air leakage. Spiral ribs 6 and multiple hook ribs 7 are also welded on the inner wall of the working casing 1. The rotation direction of the spiral ribs 6 is the same as that of the drill bit of the drilling rig. The hook ribs 7 are arranged in a spiral shape, and the rotation direction is opposite to that of the spiral ribs 6. The fixing strength of the cement buoyancy plug body 5 is improved by the spiral ribs 6 and the multiple hook ribs 7, and the probability of slippage of the cement buoyancy plug body 5 is reduced. Before the cement buoyancy plug body 5 has a tendency to slip, it must first overcome the spiral resistance brought by the spiral ribs 6, and change from linear slippage to spiral slippage, thereby reducing the difficulty of slippage. In addition, the upward sliding of the cement buoyancy plug body 5 will squeeze the sealing ring 4, making the seal tighter; the reverse spiral arrangement of multiple hook ribs 7 will also prevent the tendency of slippage.

[0021] In another embodiment, the bottom of the cement buoyancy plug body 5 is conical, a sealing gasket 8 is pasted to the bottom of the cement buoyancy plug body 5, a second retaining ring 10 is arranged below the cement buoyancy plug body 5, a cement sliding plug 9 is slidably arranged between the second retaining ring 10 and the cement buoyancy plug body 5, the diameter of the cement sliding plug 9 is smaller than the inner diameter of the working casing 1 and larger than the inner diameter of the second retaining ring 10; the top of the cement sliding plug 9 is conical to match the bottom of the cement buoyancy plug body 5, the gas outlet of the gas pipeline 2 is projected within the top range of the cement sliding plug 9, a first through hole 91 is transversely arranged on the cement sliding plug 9, and a second through hole 92 connected to the first through hole 91 is arranged at the bottom of the cement sliding plug 9. When inflating, the high-pressure gas enters the well through the gas pipeline 2, the first through hole 91 and the second through hole 92 in sequence. After the pipe is lowered, the buoyancy plug needs to be drilled open. When the gas pipeline 2 is drilled through, the high-pressure gas downhole will lift the cement sliding plug 9 to block the gas pipeline 2 to prevent blowout. When the cement buoyancy plug body 5 is drilled through, the drill bit will press against the cement sliding plug 9, and the high-pressure gas downhole will be discharged from the second through hole 92 to the first through hole 91, that is, discharged to both sides, thereby reducing the discharge pressure and preventing blowout.

[0022] The above descriptions are only preferred embodiments of the present invention, not all embodiments. Anyone should be aware that any structural changes made under the inspiration of the present invention, and any technical solutions that are the same or similar to the present invention, belong to the protection scope of the present invention.

Claims

1. A buoyancy plug for an extra-heavy and extra-large casing lower pipe, characterized in that: It comprises a working sleeve, in which a cement buoyancy plug body is fixedly arranged; a first retaining ring is arranged above the cement buoyancy plug body, the first retaining ring is welded to the inner wall of the working sleeve, and a sealing ring is plugged between the first retaining ring and the working sleeve; a serpentine gas pipeline is arranged in the cement buoyancy plug body, the gas inlet of the gas pipeline is located at the top of the cement buoyancy plug body, the gas outlet of the gas pipeline is located at the bottom of the cement buoyancy plug body, an expansion cavity with a downward gas inlet is arranged in the middle of the gas pipeline, and a sealing steel ball is slidably arranged in the expansion cavity; spiral ribs and a plurality of hook ribs are also welded on the inner wall of the working sleeve; The bottom of the cement buoyancy plug body is conical; A second retaining ring is arranged below the cement buoyancy plug body, and a cement sliding plug is slidably arranged between the second retaining ring and the cement buoyancy plug body. The diameter of the cement sliding plug is smaller than the inner diameter of the working casing and larger than the inner diameter of the second retaining ring; the top of the cement sliding plug is conical and matched with the bottom of the cement buoyancy plug body, and the gas outlet of the gas pipeline is projected within the top range of the cement sliding plug.

2. The buoyancy plug for an extra-heavy and extra-large casing lower pipe according to claim 1, characterized in that: The rotation direction of the spiral reinforcement is the same as that of the drill bit of the drilling rig, and the hook reinforcement is arranged in a spiral shape, and the rotation direction is opposite to that of the spiral reinforcement.

3. The buoyancy plug for an extra-heavy and extra-large casing lower pipe according to claim 1, characterized in that: A sealing pad is pasted on the bottom of the cement buoyancy plug body.

4. A buoyancy plug for an extra-heavy and extra-large casing lower pipe as claimed in claim 3, characterized in that: A first through hole is transversely arranged on the cement sliding plug, and a second through hole communicating with the first through hole is arranged at the bottom of the cement sliding plug.

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