Injection allocator anti-backflow valve for CO2 separate injection well

Abstract

The invention relates to the technical field of tertiary oil recovery, in particular to an injection allocator anti-backflow valve for a CO2 separate injection well. The anti-backflow valve comprises a valve body, the valve body is provided with an injection hole and a backflow hole, the valve body and an injection allocation device are arranged into a whole, the injection allocation device is arranged on the inner side of the valve body, a blanking plug is arranged on the other side of the injection allocation device, the top end of the valve body is connected with a centralizing body, the upper end of the outer side of the valve body is connected with an upper connector, the top end of the upper connector is connected with an oil pipe, and the oil pipe is connected with an oil pipe. The lower end of the outer side of the valve body is connected with a lower connector, a cavity is formed in the valve body, a valve head is installed at the top end of the cavity of the valve body, the lower end of the valve head is connected with a valve rod, the lower end of the valve rod is a limiting rod, the lower end of the limiting rod is a lower connector, and the lower end of the lower connector is connected with an oil pipe. The injection allocation device anti-backflow valve for the CO2 separate injection well is simple in overall structure and convenient to machine, and the service life of the anti-backflow valve is effectively prolonged.

Description

Technical Field

[0001] The invention relates to the technical field of tertiary oil recovery, and in particular to a backflow prevention valve for a dispenser used in a CO2 injection well. Background Art

[0002] Since long-term single CO2 injection underground is prone to cause gas channeling and reduce the swept volume of gas drive, water-gas alternating drive is generally used to improve the efficiency of gas drive development. After the water-gas alternating drive injection well is shut down, the fluid in the formation flows upward, which is easy to form a hydrate freezing section in the wellbore, so the injection device is required to have an anti-backflow function.

[0003] At present, there is no anti-backflow valve for CO2 injection wells in China. Water drive or chemical drive anti-backflow type injectors are generally used as substitutes. The anti-backflow valve of the water drive or chemical drive anti-backflow injector currently used is relatively complex in structure and has many sealing points. The anti-backflow valve is generally designed in the form of a built-in valve sleeve, and the sealing points generally exceed 8. The sealing surface of the valve head of the anti-backflow valve is generally made of nitrile rubber, and the limit device generally uses a compression spring. Due to the special physical properties of CO2, as the pressure and temperature increase during the downhole injection process, CO2 will be converted to a supercritical state. Supercritical CO2 will show strong corrosion to rubber and metal in a water-containing environment. If used in CO2 injection wells, the repeated erosion of CO2 in the supercritical state will accelerate the corrosion of the valve head sealing surface, and the excessive sealing points of the built-in valve sleeve will easily lead to the failure of the anti-backflow valve. At the same time, the corrosion of the spring by supercritical CO2 and the repeated pressure fluctuations also lead to a significant decrease in the service life of the spring, reducing the reliability of the tool. Therefore, in view of the above shortcomings, a backflow prevention valve for a dispenser of a CO2 injection well is proposed. Summary of the invention

[0004] 1. Technical issues to be resolved The present invention provides a backflow prevention valve for a CO2 injection well, so as to overcome the defects of the prior art that during the water-gas alternation process, the backflow prevention valve may be frozen due to the backflow of formation fluid, and the CO2 corrosion may easily lead to the failure of the backflow prevention valve and the reduction of tool reliability.

[0005] (II) Technical solution In order to solve the above problems, the present invention provides a backflow prevention valve for a CO2 injection well, comprising: A valve body, wherein the valve body is provided with an injection hole and a return hole, the valve body and the dispenser are integrated, the inner side of the valve body is the dispenser, and the other side of the dispenser is a plugger, the top end of the valve body is connected to a straightening body, the upper end of the outer side of the valve body is connected to an upper joint, the top end of the upper joint is connected to an oil pipe, the lower end of the outer side of the valve body is connected to a lower joint, the interior of the valve body is a cavity, a valve head is installed at the top end of the valve body cavity, the lower end of the valve head is connected to a valve stem, the lower end of the valve stem is a limiting rod, the lower end of the limiting rod is a lower joint, and the lower end of the lower joint is connected to an oil pipe.

[0006] Preferably, the dispenser is provided with a dispenser central channel inside, and the plug is provided with a plug throttling channel inside.

[0007] Preferably, the dispenser and the plug are connected via a bridge channel.

[0008] Preferably, the upper end of the outer side of the plug is connected to the upper joint, and the lower end of the outer side of the plug is connected to the lower joint.

[0009] Preferably, a sealing cavity is provided between the valve body and the valve stem.

[0010] Preferably, the valve stem comprises a piston rod and a piston, and the piston is connected to the piston rod.

[0011] Preferably, sealing rings are installed on the outer side of the piston and the outer side of the piston rod.

[0012] Preferably, one side of the piston rod is an injection hole, one side of the piston is a reflux hole, and the sealing ring of the piston faces the reflux hole.

[0013] Preferably, the valve body is provided with a shoulder, the limiting rod is positioned by the shoulder on the valve body, and a sealing ring is installed on the outer side of the limiting rod.

[0014] Preferably, the valve head is a cone, and the valve head forms a seal with the valve body.

[0015] (III) Beneficial effects The anti-backflow valve for the injector used in the CO2 injection well provided by the present invention integrates the valve body and the injector, and no spring is installed in the valve body. The overall structure is simple and the processing is convenient. It can not only effectively extend the service life of the anti-backflow valve, but also further improve the reliability of the anti-backflow valve. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 This is a schematic diagram of the installation of a backflow prevention valve of a dispenser for a CO2 injection well according to an embodiment of the present invention; Figure 2 This is a schematic diagram of the structure of a backflow prevention valve of a dispenser for a CO2 injection well according to an embodiment of the present invention; Figure 3 For the embodiment of the present invention Figure 2 The enlarged schematic diagram of point F in FIG.

[0017] Legend: 1-valve body; 2-valve head; 3-valve stem; 4-limit rod; 5-upper joint; 6-centering body; 7-lower joint; 8-dispenser center channel; 9-plug throttling channel; 10-injection hole; 11-reflux hole; 12-sealing chamber; 13-bridge channel. DETAILED DESCRIPTION

[0018] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0019] In the description of the present invention, it is necessary to understand that the orientations or positional relationships indicated by “upper”, “lower”, “inside”, “outside”, “top”, “bottom”, etc. are all based on the orientations or positional relationships shown in the accompanying drawings. The purpose is only to facilitate the description of the present invention and simplify the description. It does not indicate or imply that the referred parts must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention.

[0020] Figure 1 This is a schematic diagram of the installation of a backflow prevention valve of a dispenser for a CO2 injection well according to an embodiment of the present invention. Figure 2 This is a schematic diagram of the structure of the anti-backflow valve of the injection device used in the CO2 injection well according to an embodiment of the present invention. Figure 3 For the embodiment of the present invention Figure 2 The enlarged schematic diagram at F in FIG. Figures 1 to 3 As shown, the present invention provides a backflow prevention valve for a dispenser for a CO2 injection well, which specifically includes: a valve body 1, wherein the valve body 1 is provided with an injection hole 10 and a backflow hole 11, the valve body 1 and the dispenser are integrated, the inner side of the valve body 1 is the dispenser, and the other side of the dispenser is a plugger, the top end of the valve body 1 is connected to a straightening body 6, the upper end of the outer side of the valve body 1 is connected to an upper joint 5, the top end of the upper joint 5 is connected to an oil pipe, the lower end of the outer side of the valve body 1 is connected to a lower joint 7, the interior of the valve body 1 is a cavity, the top end of the cavity of the valve body 1 is installed with a valve head 2, the lower end of the valve head 2 is connected to a valve stem 3, the lower end of the valve stem 3 is a limiting rod 4, the lower end of the limiting rod 4 is a lower joint 7, and the lower end of the lower joint 7 is connected to an oil pipe.

[0021] In actual application, the valve body 1 and the dispenser are an integrated structure. The valve body 1 is not built into the dispenser. The inner side of the valve body 1 is the dispenser. The interior of the dispenser is provided with a dispenser center channel 8. The other side of the dispenser is a plug. The interior of the plug is provided with a plug throttling channel 9. The dispenser and the plug are connected by a bridge channel 13. In addition, the upper end of the outer side of the plug is connected to the upper joint 5, and the lower end of the outer side of the plug is connected to the lower joint 7.

[0022] In this anti-backflow valve, a sealing chamber 12 is provided between the valve body 1 and the valve stem 3. In actual application, the valve stem 3 includes a piston rod and a piston, the piston is connected to the piston rod, the outer side of the piston and the outer side of the piston rod are connected to the sealing ring, one side of the piston rod is an injection hole 10, and one side of the piston is a reflux hole 11, wherein the sealing ring of the piston faces the reflux hole.

[0023] It should be noted that the piston of the valve stem is installed with a one-way sealing ring, the lip of which faces the return hole 11, and the valve stem 3 and the valve body 1 form a sealing chamber 12 through the one-way sealing ring, which is a vacuum chamber.

[0024] In actual application, the piston and piston rod of the valve stem 3 are both set as cylinders, the piston is below the piston rod, a sealing ring is installed on the outer side of the upper end of the piston rod, the number of sealing rings of the piston rod is at least two, a sealing ring is installed on the outer side of the piston, the number of sealing rings of the piston is at least two, and the bottom diameter of the piston rod is smaller than the bottom diameter of the piston.

[0025] In this anti-backflow valve, the shape of the valve head 2 is set to be a cone, and the valve body 2 is mostly made of stainless steel. The surface of the cavity of the valve body 1 is a cone. The valve head 2 can directly form a metal seal with the conical surface on the valve body 1. At the same time, the straightening body 6 is connected to the valve body 1 through a pin. In addition, the limit rod 4 is directly inserted into the valve body 1, and the valve stem 3 is above the limit rod 4. The lower end of the limit rod 4 is the lower joint 7. A sealing ring is installed on the limit rod 4, and the valve body 1 is provided with a shoulder. The limit rod 4 can not only achieve positioning through the shoulder on the valve body 1, but also achieve sealing of the inner cavity of the valve body.

[0026] In actual application, the limit rod 4 is an integrated structure, and the limit rod 4 includes four components, namely a first cylinder, a second cylinder, a cone and a third cylinder. In the structure of this limit rod, the first cylinder is connected to the second cylinder, the second cylinder is connected to the cone, and the bottom end of the cone is connected to the third cylinder.

[0027] It should be noted that the cone is provided with two bottom circles, namely the first bottom circle and the second bottom circle, the diameter of the first bottom circle is larger than the diameter of the second bottom circle, the bottom diameter of the first cylinder is smaller than the bottom diameter of the second cylinder, the bottom diameter of the second cylinder is smaller than the bottom diameter of the first bottom circle, the bottom diameter of the first cylinder is larger than the bottom diameter of the third cylinder, the bottom diameter of the third cylinder is equal to the diameter of the second bottom circle, a sealing ring is installed on the outside of the second cylinder, and the number of sealing rings is at least two. In addition, the height of the first cylinder is smaller than the height of the second cylinder, and the height of the second cylinder is smaller than the height of the third cylinder.

[0028] In actual application, when the dispenser is injecting CO2, the CO2 fluid can flow through the central channel 8 of the dispenser and enter the throttling channel 9 of the plug; when the injection pressure is higher than the casing pressure, the CO2 fluid passes through the bridge channel 13, and the CO2 fluid pushes the valve head 2 and the valve stem 3 downward, so that the bridge channel 13 is connected with the injection hole 10, and the CO2 fluid is injected into the formation through the injection hole 10.

[0029] In the anti-reflux valve, the valve head 2 directly forms a metal seal with the conical surface on the valve body 1. The valve head 2 is also made of stainless steel that is not easily corroded by CO2, which can ensure long-term effective sealing during the CO2 injection process. The opening and closing of the valve head 2 is achieved through pressure difference. No spring is installed in the valve body 1, which can effectively extend the service life of the anti-reflux valve. In addition, since the valve body and the dispenser are integrated into one, the overall structure is simple and easy to process, which effectively reduces the sealing points and further improves the reliability of the anti-reflux valve.

[0030] In addition, in practical applications, the number of sealing points of the anti-backflow valve is reduced to 4, which effectively increases the success rate of the anti-backflow valve.

[0031] The following is a detailed description of the working principle of the anti-backflow valve of the dispenser for CO2 injection wells: In this embodiment, the valve body 1 is provided with an injection hole 10 and a return hole 11, and the valve body 1 and the injector are an integrated structure, wherein the inner side of the valve body 1 is the injector, and the interior of the injector is provided with a central channel 8 of the injector, and the other side of the injector is a plug, and the interior of the plug is provided with a throttling channel 9 of the plug, and the injector and the plug are connected by a bridge channel 13, the top end of the valve body 1 is connected to the straightening body 6, the upper end of the outer side of the valve body 1 is connected to the upper joint 5, the top end of the upper joint 5 is connected to the oil pipe, the lower end of the outer side of the valve body 1 is connected to the lower joint 7, the top end of the inner side of the valve body 1 is installed with a valve head 2, the lower end of the valve head 2 is connected to the valve stem 3, a sealing chamber 12 is provided between the valve body 1 and the valve stem 3, the lower end of the valve stem 3 is connected to the limiting rod 4, the lower end of the limiting rod 4 is the lower joint 7, and the lower end of the lower joint 7 is connected to the oil pipe.

[0032] In actual application, the valve stem 3 includes a piston and a piston rod, the piston is connected to the piston rod, and the piston is above the piston. An O-ring is installed on the piston rod of the valve stem 3, and the O-ring prevents CO2 fluid from penetrating. A Y-ring is installed on the piston of the valve stem 3, and the lip of the Y-ring is facing the reflux hole 11. An O-ring is installed on the limit rod 4, and the limit rod 4 is directly inserted into the valve body 1. The limit rod 4 limits the axial movement of the limit rod 4 through the shoulder of the valve stem 1.

[0033] In this embodiment, when the dispenser is injecting CO2, the CO2 fluid flows through the central channel 8 of the dispenser and enters the throttling channel 9 of the plug; when the injection pressure is higher than the casing pressure, the CO2 fluid passes through the bridge channel 13, and the CO2 fluid pushes the valve head 2 and the valve stem 3 downward, so that the bridge channel 13 is connected with the injection hole 10, and the CO2 fluid is injected into the formation through the injection hole 10.

[0034] In actual application, during the downward movement of the valve head 2 and the valve stem 3, the Y-shaped sealing ring on the valve stem 3 opens to prevent the fluid on one side of the reflux hole 11 from entering the sealing chamber 12. As the valve stem 3 continues to move downward, the valve stem 3 reaches the upper end of the limit rod 4, and the volume of the sealing chamber 12 continues to increase, forming an upward negative pressure suction force.

[0035] In this embodiment, when the injection device stops injecting, since the formation pressure is higher than the oil pipe pressure, the CO2 fluid in the formation begins to spit back. At this time, the anti-reflux valve is in an open state. Since the cross-sectional area of ​​the valve head 2 is smaller than the cross-sectional area of ​​the piston side in the valve stem 3, and the fluid pressures at the injection hole 10 and the reflux hole 11 are similar, the valve stem 3 continues to move upward under the combined action of the casing pressure and the negative pressure suction formed by the sealing chamber 12 until the valve head 2 fits the conical surface on the valve body 1 to form a metal seal, thereby closing the anti-reflux valve.

[0036] The anti-backflow valve for the injector used in the CO2 injection well provided by the present invention integrates the valve body and the injector, and the opening and closing of the valve head are realized by pressure difference. No spring is installed in the valve body. The overall structure is simple and the processing is convenient. It can not only effectively extend the service life of the anti-backflow valve, but also further improve the reliability of the anti-backflow valve.

[0037] The above implementation modes are only used to illustrate the present invention, but not to limit the present invention. Ordinary technicians in the relevant technical field can make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, all equivalent technical solutions also belong to the scope of the present invention. The patent protection scope of the present invention should be defined by the claims.

Claims

1. A backflow prevention valve for a CO2 injection well, characterized in that: include: A valve body (1), wherein the valve body (1) is provided with an injection hole (10) and a return hole (11), the valve body (1) and the dispenser are integrated, the inner side of the valve body (1) is the dispenser, and the other side of the dispenser is a plug, the top end of the valve body (1) is connected to a straightening body (6), the upper end of the outer side of the valve body (1) is connected to an upper joint (5), the top end of the upper joint (5) is connected to an oil pipe, the lower end of the outer side of the valve body (1) is connected to a lower joint (7), the interior of the valve body (1) is a cavity, the top end of the cavity of the valve body (1) is equipped with a valve head (2), the lower end of the valve head (2) is connected to a valve stem (3), the lower end of the valve stem (3) is a limit rod (4), the lower end of the limit rod (4) is a lower joint (7), and the lower end of the lower joint (7) is connected to the oil pipe.

2. The backflow prevention valve for a CO2 injection well according to claim 1, characterized in that: The dispenser is provided with an injector central channel (8) inside, and the plug is provided with a plug throttling channel (9) inside.

3. The backflow prevention valve for the CO2 injection well according to claim 2, characterized in that: The dispenser and the plug are connected via a bridge channel (13).

4. The backflow prevention valve for the CO2 injection well according to claim 3, characterized in that: The upper end of the outer side of the plug is connected to an upper joint (5), and the lower end of the outer side of the plug is connected to a lower joint (7).

5. The anti-backflow valve for the CO2 injection well according to claim 1, characterized in that: A sealing chamber (12) is provided between the valve body (1) and the valve stem (3).

6. The backflow prevention valve for the CO2 injection well according to claim 5, characterized in that: The valve stem (3) comprises a piston rod and a piston, and the piston is connected to the piston rod.

7. The backflow prevention valve for a CO2 injection well according to claim 6, characterized in that: Sealing rings are installed on the outer side of the piston and the outer side of the piston rod.

8. The backflow prevention valve for a CO2 injection well according to claim 7, characterized in that: One side of the piston rod is an injection hole (10), one side of the piston is a return hole (11), and the sealing ring of the piston faces the return hole (11).

9. The backflow prevention valve for a CO2 injection well according to claim 1, characterized in that: The valve body (1) is provided with a shoulder, the limiting rod (4) is positioned by the shoulder on the valve body (1), and a sealing ring is installed on the outer side of the limiting rod (4).

10. The backflow prevention valve for a CO2 injection well according to claim 1, characterized in that: The valve head (2) is a cone, and the valve head (2) forms a seal with the valve body (1).

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