A multi-stage sealing structure of an oil and gas well casing head

Abstract

The utility model discloses a kind of multistage sealing structures of oil and gas well casing head, including casing head sealing seat, for circumferential closed inflation cavity, coaxially sleeved and locked at casing head outer thread coupling, its top wall is inwardly opened one annular recess;Expansion packer air bag, is embedded in the recess;Flow guide micropore, through the bottom wall of the recess, make casing head sealing seat and the inner capsule cavity of expansion packer air bag communicate;Wherein, when injecting pressure gas to casing head sealing seat, gas enters expansion packer air bag through flow guide micropore, drives expansion packer air bag radial inflation and tightly holds oil layer casing passing through casing head, realize the sealing of casing head annulus. Drive expansion packer air bag radial inflation, and form first elastomer seal between oil layer casing. Casing head sealing seat itself is circumferential closed inflation cavity, constitute second pressure self-tightening seal, two seals are in series, effectively improve sealing performance.

Description

Technical Field

[0001] This utility model specifically relates to a multi-stage sealing structure for oil and gas well casing heads. Background Technology

[0002] In oil and gas drilling and completion engineering, the casing head is not only the core component for suspending the casing string and establishing the wellhead pressure control system, but also a key barrier to prevent high-pressure oil and gas from leaking out of the annulus. With the increasing proportion of deep wells, ultra-deep wells, and high-pressure, high-production gas wells, the grease injection channels of the casing head annulus seal are blocked by solidified grease, making secondary pressure replenishment impossible. When temperature fluctuations or casing creep cause a decrease in the sealing specific pressure, micro-leakage can only be allowed to expand until the well is forced to be killed and the sealing ring replaced. Utility Model Content

[0003] The purpose of this invention is to provide a multi-stage sealing structure for oil and gas well casing heads to solve the problems mentioned in the background art.

[0004] To achieve the above objectives, this utility model provides the following technical solution: a multi-stage sealing structure for oil and gas well casing heads, comprising: The casing head sealing seat is a circumferentially closed air-filled cavity, coaxially sleeved and locked at the external thread coupling of the casing head, with an annular groove opened inward on its top wall. An inflatable sealing airbag is fitted into the groove. The flow-guiding micropores are opened through the bottom wall of the groove, so that the sleeve head sealing seat is connected to the inner cavity of the expansion sealing airbag; When pressurized gas is injected into the casing head sealing seat, the gas enters the expansion sealing airbag through the guide microhole, driving the expansion sealing airbag to expand radially and tightly hold the oil layer casing that passes through the casing head, thereby achieving a seal on the casing head annulus.

[0005] Preferably, the bottom surface of the groove gradually slopes downward from the outer periphery of the sleeve head sealing seat towards the center, forming a conical support surface.

[0006] Preferably, the lower surface of the inflatable sealing airbag is fitted with the conical support surface, so that the wall thickness of the inflatable sealing airbag gradually decreases radially from the outside to the inside.

[0007] Preferably, the flow-guiding micropores are formed through the conical support surface and the expansion sealing airbag.

[0008] Preferably, a one-way inflation valve is provided on the outside of the sleeve head sealing seat, and the one-way inflation valve is connected to the inflation cavity of the sleeve head sealing seat.

[0009] Preferably, the one-way inflation valve has a removable dustproof plug.

[0010] Preferably, the one-way inflation valve has an internally threaded valve seat, and the dustproof plug is a rubber plug with external threads, and the end of the rubber plug is provided with a turning groove.

[0011] The technical effects and advantages of this utility model are as follows: This multi-stage sealing structure for oil and gas well casing heads injects pressurized gas into the casing head sealing seat through a one-way inflation valve. The gas enters the expansion packer through the guide micro-holes, driving the expansion packer to expand radially, forming the first elastic seal between the expansion packer and the oil layer casing. The casing head sealing seat itself is a circumferentially closed inflation cavity, forming a second pressure self-tightening seal. The two seals are connected in series, effectively improving the sealing performance. Furthermore, pressurized gas can be injected into the casing head sealing seat again at any time through the one-way inflation valve, ensuring continuous sealing of the expansion packer and extending the seal life. Attached Figure Description

[0012] Figure 1 This is a first-view structural diagram of the entire present invention; Figure 2 This is a schematic diagram of the overall second-view structure of this utility model; Figure 3 This is a schematic diagram of the twisting groove of this utility model; Figure 4 This is a schematic diagram of the conical support surface of this utility model; Figure 5 This is a schematic diagram of the flow-guiding micropore structure of this utility model.

[0013] In the figure: 1. Sleeve head sealing seat; 2. Groove; 3. Expansion sealing airbag; 4. Guide micropore; 5. Conical support surface; 6. One-way inflation valve; 7. Dustproof plug; 8. Twisting groove. Detailed Implementation

[0014] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention.

[0015] refer to Figure 1 , Figure 2 and Figure 3As shown, the casing includes a casing head sealing seat 1, which is a circumferentially closed inflatable cavity, coaxially fitted and locked at the external threaded coupling of the casing head, with an annular groove 2 formed inward on its top wall; an expansion sealing airbag 3, which is embedded in the groove 2, and a guide microhole 4, which is formed through the bottom wall of the groove 2, so that the casing head sealing seat 1 and the inner cavity of the expansion sealing airbag 3 are connected; wherein, when pressurized gas is injected into the casing head sealing seat 1, the gas enters the expansion sealing airbag 3 through the guide microhole 4, driving the expansion sealing airbag 3 to expand radially and tightly hold the oil layer casing passing through the casing head, thereby achieving a seal on the annulus of the casing head; pressurized gas is injected into the casing head sealing seat 1 through a one-way inflation valve 6, and the gas enters the expansion sealing airbag 3 through the guide microhole 4, driving the expansion sealing airbag 3 to expand radially, forming a first elastic seal between the expansion sealing airbag 3 and the oil layer casing. The casing head sealing seat 1 itself is a circumferentially closed inflatable cavity, forming a second pressure self-tightening seal. The two seals are connected in series, which effectively improves the sealing performance. Furthermore, pressurized gas can be injected into the casing head sealing seat 1 again at any time through the one-way inflation valve 6, so that the expansion sealing airbag 3 can continue to seal.

[0016] refer to Figure 1 , Figure 2 , Figure 3 , Figure 4 and Figure 5 As shown, the bottom surface of the groove 2 gradually slopes downwards from the outer periphery of the sleeve head sealing seat 1 towards the center, forming a conical support surface 5. After inflation, the expansion sealing airbag 3 generates a positive pressure perpendicular to the conical support surface. Its axial component can press the expansion sealing airbag 3 downwards, forming a self-locking mechanism to prevent the expansion sealing airbag 3 from being squeezed upwards out of the groove under high pressure. The lower surface of the expansion sealing airbag 3 fits against the conical support surface 5, causing the wall thickness of the expansion sealing airbag 3 to gradually decrease radially from the outside to the inside. The thin-walled area first adheres tightly to the sleeve, quickly establishing an initial seal, while the thick-walled area deforms later to provide high specific pressure, achieving a two-stage effect of low-pressure fast sealing and high-pressure strong sealing. The guide microholes 4 are opened through the conical support surface 5 and the expansion sealing airbag 3, with multiple guide microholes 4 evenly distributed circumferentially to ensure 360-degree synchronous air intake. A one-way inflation valve 6 is provided on the outside of the casing head sealing seat 1. The one-way inflation valve 6 is connected to the inflation chamber of the casing head sealing seat 1. When annular pressure occurs at the wellhead, a portable air supply cylinder can be directly connected to complete secondary pressurization without stopping production. A dustproof plug 7 is removable inside the one-way inflation valve 6. The dustproof plug 7 can be manually disassembled and reassembled multiple times. It can be replaced individually after the rubber sealing surface is worn. The one-way inflation valve 6 has an internal threaded valve seat. The dustproof plug 7 is a rubber plug with external threads. The end of the rubber plug is provided with a turning groove 8. The turning groove 8 is a composite groove of slotted or Phillips head, compatible with general hex wrenches and screwdrivers.

[0017] In use, first push the lower surface of the expansion sealing airbag 3 into the conical support surface 5 to ensure that the wall thickness is correct (thicker on the outside and thinner on the inside). Use a special jig to press it in, so that the guide micro-holes 4 are aligned with the horn holes of the expansion sealing airbag 3. Screw in the rubber dust plug 7 with external threads until the end face is in close contact with the metal surface of the one-way inflation valve 6. Coaxially fit the pre-assembled casing head sealing seat 1 onto the external thread coupling of the casing head, and lock it axially with the matching clips or locking ring. Remove the dust plug 7 and connect the gas hose to the one-way inflation valve 6. The gas enters the inflation chamber of the casing head sealing seat 1 and then enters the inner cavity of the expansion sealing airbag 3 through the guide micro-holes 4. The thin-walled area expands first, gripping the oil layer casing and forming an elastic seal.

[0018] Finally, it should be noted that the above description is only a preferred embodiment of the present utility model and is not intended to limit the present utility model.

Claims

1. A multi-stage sealing structure for oil and gas well casing heads, characterized in that, include: The casing head sealing seat (1) is a circumferentially closed air-filled cavity, which is coaxially sleeved and locked at the external thread coupling of the casing head, and an annular groove (2) is opened inward on its top wall. An inflatable sealing airbag (3) is fitted into the groove (2); The flow guide microhole (4) is opened through the bottom wall of the groove (2) so that the sleeve head sealing seat (1) is connected to the inner cavity of the expansion sealing airbag (3); When pressurized gas is injected into the casing head sealing seat (1), the gas enters the expansion sealing airbag (3) through the guide microhole (4), driving the expansion sealing airbag (3) to expand radially and tightly hold the oil layer casing that passes through the casing head, thereby achieving a seal on the casing head annulus.

2. The multi-stage sealing structure for oil and gas well casing heads according to claim 1, characterized in that: The bottom surface of the groove (2) gradually slopes downward from the outer periphery of the sleeve head sealing seat (1) towards the center, forming a conical support surface (5).

3. The multi-stage sealing structure for oil and gas well casing heads according to claim 2, characterized in that: The lower surface of the inflatable sealing airbag (3) is in contact with the conical support surface (5), so that the wall thickness of the inflatable sealing airbag (3) gradually decreases radially from the outside to the inside.

4. The multi-stage sealing structure for oil and gas well casing heads according to claim 3, characterized in that: The flow-guiding micropores (4) are opened through the conical support surface (5) and the expansion sealing airbag (3).

5. The multi-stage sealing structure for oil and gas well casing heads according to claim 1, characterized in that: A one-way inflation valve (6) is provided on the outside of the sleeve head sealing seat (1), and the one-way inflation valve (6) is connected to the inflation cavity of the sleeve head sealing seat (1).

6. The multi-stage sealing structure for oil and gas well casing heads according to claim 5, characterized in that: The one-way inflation valve (6) has a removable dustproof plug (7).

7. The multi-stage sealing structure for oil and gas well casing heads according to claim 6, characterized in that: The one-way inflation valve (6) has an internal threaded valve seat, and the dustproof plug (7) is a rubber plug with external threads, and the end of the rubber plug is provided with a turning groove (8).

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