A large channel anti-backflow steam injection string

Abstract

The present invention provides a large-channel anti-backflow steam injection string, comprising a telescopic tube, an insulated tube a, a piston-type steam injection valve A, an insulated tube b, a piston-type steam injection valve B, an insulated tube c, and a plug, connected in sequence from top to bottom. The outer walls of the insulated tubes a and b are each sleeved with a thermal packer. A steam injection port a is defined on the side wall of the valve body a of the piston-type steam injection valve A. A piston a is connected to the outer wall of the valve body a and engages with the steam injection port a. The piston a is defined by an axial through hole a and a plurality of radial through holes a, each communicating with the steam injection port a. A sliding sleeve is disposed within the valve body a and blocks the steam injection port a. A shear pin is provided between the side wall of the sliding sleeve and the side wall of the valve body a. A ball seat is fixedly connected to the inner wall of the bottom end of the sliding sleeve. When the valve ball is inserted into the sliding sleeve, it engages with the through hole of the ball seat. The present invention can prevent steam backflow after steam injection is completed, avoiding heat diffusion in non-producing strata and facilitating crude oil production.

Description

Technical Field

[0001] The invention belongs to the technical field of oil production engineering, and relates to a steam injection string for a steam-huffing oil well, and in particular to a large-channel backflow-proof steam injection string for steam-huffing. Background Art

[0002] Currently, Shuguang Oilfield primarily produces oil through steam stimulation, with staged steam injection as the primary method. However, during the soaking phase, the steam injection valves do not close properly, allowing steam to flow back into the tubing, dissipating heat to non-productive layers and resulting in significant energy loss. Although nitrogen injection insulation technology is employed, it is currently only used in the annulus of the casing, and the insulation effect is poor due to a loose seal. Insulation jackets are used on the surface, but due to frequent use and improper bundling, some energy is lost, hindering crude oil production. Summary of the Invention

[0003] In order to solve the problem of energy loss caused by backflow when steam is injected into the steam injection string during the well shut-in stage in the prior art, the present invention provides a large-channel anti-backflow steam injection string, which can prevent steam from being spit out after the steam injection is completed, avoiding heat diffusion in non-producing layers, and facilitating crude oil production.

[0004] The technical solution adopted by the present invention to solve the technical problem is: a large-channel anti-backflow steam injection string, comprising a telescopic pipe, an insulation pipe a, a piston steam injection valve A, an insulation pipe b, a piston steam injection valve B, an insulation pipe c, and a plug connected in sequence from top to bottom; the outer wall of the insulation pipe a is sleeved with a thermal packer a, and the outer wall of the insulation pipe b is sleeved with a thermal packer b;

[0005] The piston-type steam injection valve A includes a valve body a, a piston a, a shear pin, a sliding sleeve, a ball seat, a valve ball, and a steam injection port a; the valve body a is hollow inside, and a steam injection port a is provided on the side wall of the valve body a; the piston a is connected to the outer wall of the valve body a and is clamped at the steam injection port a; an axial through hole a and several radial through holes a are provided on the piston a, the axial through hole a is communicated with the several radial through holes a, and the several radial through holes a are communicated with the steam injection port a; the sliding sleeve is arranged inside the valve body a and sealed at the steam injection port a, a shear pin is provided between the side wall of the sliding sleeve and the side wall of the valve body a, a ball seat is fixedly connected to the inner wall of the bottom end of the sliding sleeve, a through hole is provided in the middle of the ball seat, the diameter of the through hole is smaller than the diameter of the valve ball, and when the valve ball is put into the sliding sleeve, it is clamped at the through hole.

[0006] As a further embodiment of the present invention, the piston a is bound to the valve body a via a hoop spring a.

[0007] As a further embodiment of the present invention, a sealing ring a is provided at the contact portion between the piston a and the outer wall of the valve body a.

[0008] As a further embodiment of the present invention, the outer wall of the valve body a is fixedly connected to a limit pin a extending outward to limit the moving direction and range of the piston a.

[0009] As a further embodiment of the present invention, the piston-type steam injection valve B5 includes a valve body b, a piston b, and a steam injection port b; the valve body b is hollow inside, and a steam injection port b is provided on the side wall of the valve body b; the piston b is connected to the outer wall of the valve body b and is clamped at the steam injection port b; an axial through hole b and several radial through holes b are provided on the piston b, the axial through hole b is connected to the several radial through holes b, and the several radial through holes b are connected to the steam injection port b.

[0010] As a further embodiment of the present invention, the piston b is bound to the valve body b via a hoop spring b.

[0011] As a further embodiment of the present invention, a sealing ring b is provided at the contact portion between the piston b and the outer wall of the valve body b.

[0012] As a further embodiment of the present invention, a limit pin b extending outward is fixedly connected to the outer wall of the valve body b to limit the moving direction and range of the piston b.

[0013] The present invention has the following beneficial effects: Currently, during crude oil steam huff and puff, when steam injection is stopped or injected into other oil layers, steam backflow occurs, causing heat to diffuse into non-productive layers, hindering normal production and increasing the insulation workload at the surface wellhead. The present invention provides a large-channel, backflow-proof steam huff and puff injection string that prevents steam backflow after steam injection, avoiding heat diffusion into non-productive layers, facilitating crude oil production, and improving heat utilization. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 It is a schematic diagram of the overall structure of the present invention;

[0015] Figure 2 This is a cross-sectional view of the structure of the piston-type steam injection valve B of the present invention;

[0016] Figure 3 It is a structural cross-sectional view of the piston type steam injection valve A of the present invention.

[0017] Explanation of reference numerals in the figures: 1, telescopic tube, 2, thermal packer a, 3, piston steam injection valve A, 4, thermal packer b, 5, piston steam injection valve B, 6, plug, 7, insulation tube a, 8, insulation tube b, 9, insulation tube c;

[0018] 3-1, valve body a, 3-2, piston a, 3-3, sealing ring a, 3-4, hoop spring a, 3-5, limit pin a, 3-6, shear pin, 3-7, sliding sleeve, 3-8, ball seat, 3-9, valve ball, 3-10, steam injection port a, 3-2-1, axial through hole a, 3-2-2, radial through hole a;

[0019] 5-1, valve body b, 5-2, piston b, 5-3, sealing ring b, 5-4, hoop spring b, 5-5, limit pin b, 5-6, steam injection port b5, 5-2-1, axial through hole b, 5-2-2, radial through hole b. DETAILED DESCRIPTION

[0020] The technical solution of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0021] In the description of the present invention, it should be noted that the terms "vertical," "horizontal," "inner," and "outer," etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings and are intended solely to facilitate and simplify the description of the present invention. They are not intended to indicate or imply that the devices or components referred to must have, be constructed, or operate in a specific orientation, and therefore should not be construed as limitations on the present invention. Furthermore, the terms "first," "second," and "third" are used solely to distinguish components and should not be construed as indicating or implying relative importance.

[0022] In addition, the technical features involved in different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0023] Example 1

[0024] A large-channel anti-backflow steam injection string prevents steam injected into the target layer from being spit back into the string, comprising a telescopic pipe 1, a thermal packer a2, a piston steam injection valve A3, a thermal packer b4, a piston steam injection valve B5, a plug 6, an insulation pipe a7, an insulation pipe b8, and an insulation pipe c9;

[0025] The telescopic tube 1 is connected to one end of the insulation tube a7 by a thread, the other end of the insulation tube a7 is connected to one end of the piston steam injection valve A3, the other end of the piston steam injection valve A3 is connected to one end of the insulation tube b8, the other end of the insulation tube b8 is connected to one end of the piston steam injection valve B5, the other end of the piston steam injection valve B5 is connected to one end of the insulation tube c9, and the end of the insulation tube c9 is provided with a screw plug 6;

[0026] In the above embodiment, the thermal packer a2 is sleeved on the middle portion of the outer wall of the thermal insulation tube a7, and the thermal packer b4 is sleeved on the middle portion of the outer wall of the thermal insulation tube b8.

[0027] like Figure 3 As shown, the piston steam injection valve A3 includes a valve body a3-1, a piston a3-2, a sealing ring a3-3, a hoop spring a3-4, a limit pin a3-5, a shear pin 3-6, a sliding sleeve 3-7, a ball seat 3-8, a valve ball 3-9, and a steam injection port a3-10;

[0028] The valve body a3-1 is hollow, with an internal thread at its upper end and an external thread at its lower end to facilitate connection with other components at both ends. A steam injection port a3-10 is provided on the side wall of the valve body a3-1. The piston a3-2 is connected to the outer wall of the valve body a3-1 and is clamped to the steam injection port a3-10. Preferably, the piston a3-2 is bound to the valve body a3-1 by a hoop spring a3-4. A sealing ring a3-3 is provided at the contact point between the piston a3-2 and the outer wall of the valve body a3-1.

[0029] The piston a3-2 is provided with an axial through hole a3-2-1 and several radial through holes a3-2-2. The axial through hole a3-2-1 is connected to the several radial through holes a3-2-2, and the several radial through holes a3-2-2 are connected to the steam injection port a3-10.

[0030] The sliding sleeve 3-7 is disposed inside the valve body a3-1 and is sealed at the steam injection port a3-10. A shear pin 3-6 is provided between the side wall of the sliding sleeve 3-7 and the side wall of the valve body a3-1 to fix the position of the sliding sleeve 3-7 inside the valve body a3-1.

[0031] A radially arranged ball seat 3-8 is provided inside the sliding sleeve 3-7, and the outer wall of the ball seat 3-8 is fixedly connected to the inner wall of the bottom end of the sliding sleeve 3-7; a through hole is opened in the middle of the ball seat 3-8, and the diameter of the through hole is smaller than the diameter of the valve ball 3-9. When needed, the valve ball 3-9 is dropped into the tubing string through the wellhead; when the valve ball 3-9 is dropped into the sliding sleeve 3-7, it is engaged at the through hole;

[0032] Preferably, the outer wall of the valve body a3-1 is fixedly connected to a limit pin a3-5 extending outward. There are two limit pins a3-5, one on each side of the steam injection port a3-10, to limit the movement direction and range of the piston a3-2.

[0033] like Figure 2 As shown, the piston-type steam injection valve B5 includes a valve body b5-1, a piston b5-2, a sealing ring b5-3, a hoop spring b5-4, a limit pin b5-5, and a steam injection port b5-6;

[0034] The valve body b5-1 is hollow inside, with an internal thread on the upper end and an external thread on the lower end to facilitate connection with other components at both ends;

[0035] A steam injection port b5-6 is provided on the side wall of the valve body b5-1. The piston b5-2 is connected to the outer wall of the valve body b5-1 and is engaged at the steam injection port b5-6. Preferably, the piston b5-2 is bound to the valve body b5-1 by a hoop spring b5-4. A sealing ring b5-3 is provided at the contact area between the piston b5-2 and the outer wall of the valve body b5-1.

[0036] The piston b5-2 is provided with an axial through hole b5-2-1 and a plurality of radial through holes b5-2-2. The axial through hole b5-2-1 is connected to the plurality of radial through holes b5-2-2, and the plurality of radial through holes b5-2-2 are connected to the steam injection port b5-6.

[0037] Preferably, the outer wall of the valve body b5-1 is fixedly connected with a limit pin b5-5 extending outward. There are two limit pins b5-5, which are located on both sides of the steam injection port b5-6 to limit the movement direction and range of the piston b5-2.

[0038] During operation, after the tubing string is lowered into the wellbore as designed, steam is injected from the surface to set thermal packers a2 and b4. The string is now divided into two injection units. Sleeve 3-7 seals steam injection port a3-10, allowing steam to be injected into the reservoir only through piston steam injection valve B5. When the initial pressure is low, the pressure differential between piston b5-2 and its interior causes it to move outward. Guided by stop pin b5-5, piston b5-2 can only move radially, opening a gap between piston b5-2 and valve body b5-1. Initially, steam enters the reservoir through radial throughhole b5-2-2 and axial throughhole b5-2-1, then flows through the gap between piston b5-2 and valve body b5-1 into the reservoir.

[0039] When the steam volume in the lower layer reaches the designed volume, the valve ball 3-9 is put into the wellhead. At this time, the interior of the pipe string is divided into two parts, the upper and lower parts. The pressure in the lower part of the valve ball 3-9 gradually decreases because there is no steam injected. The external pressure of the piston b5-2 of the piston steam injection valve B5 is greater than its internal pressure. Under the action of this pressure difference, the piston b5-2 and the valve body b5-1 are in close contact, preventing the steam in the oil layer from being swallowed back into the pipe string; the valve ball 3-9 is seated on the ball seat 3-8. Since the sliding sleeve 3-7 and the ball seat 3-8 are fixedly connected, when the injection pressure reaches the shear pressure of the shear pin 3-6, the shear pin is cut off. Pin 3-6 shears, sleeve 3-7 slides down, and steam injection port a3-10 is exposed, allowing steam to be injected into the reservoir only through piston steam injection valve A3. When the initial pressure is low, the pressure differential between the inside and outside of piston a3-2 causes piston a3-2 to move outward. Guided by limit pin a3-5, piston a3-2 can only move radially, creating a gap between piston a3-2 and valve body a3-1. Steam enters through radial throughhole a3-2-2 and axial throughhole a3-2-1, further along the gap between piston a3-2 and valve body a3-1 and into the reservoir. When the designed steam flow rate is reached, steam injection into the tubing string ceases. At this point, the formation pressure corresponding to piston steam injection valve A3 is greater than the internal pressure of piston steam injection valve A3. This pressure differential maintains close contact between piston a3-2 and valve body a3-1, preventing steam from the reservoir from flowing back into the steam injection string.

[0040] Since the amount of steam inside the string is much less than that inside a conventional steam injection string, steam waste is reduced, which is beneficial to crude oil production and reduces heat transfer to non-productive layers.

[0041] When the production layer is soaked for a certain period of time, as the temperature drops, the thermal packers a2 and b4 shrink, making the casing annular space connected from top to bottom. When the casing annular space is large enough to allow the tubing to be lifted, the steam injection string is pulled out and the production string is lowered, and the crude oil officially enters the production stage.

[0042] The large-channel anti-backflow steam injection string described in the above embodiment can prevent steam from being spit out after steam injection, avoids heat diffusion in non-producing layers, is beneficial to crude oil production, and improves heat utilization.

[0043] Obviously, the above embodiments are merely examples for clarity of explanation and are not intended to limit the implementation methods. Those skilled in the art will readily appreciate that other variations or modifications based on the above descriptions are possible. It is not necessary and impossible to enumerate all implementation methods here. Obvious variations or modifications arising therefrom remain within the scope of protection of the present invention.

Claims

1. A large channel anti-backflow steam injection string, characterized in that: The invention comprises a telescopic pipe (1), a heat-insulating pipe a (7), a piston-type steam injection valve A (3), a heat-insulating pipe b (8), a piston-type steam injection valve B (5), a heat-insulating pipe c (9), and a screw plug (6) connected in sequence from top to bottom; the outer wall of the heat-insulating pipe a (7) is sleeved with a heat-sensitive packer a (2), and the outer wall of the heat-insulating pipe b (8) is sleeved with a heat-sensitive packer b (4); The piston type steam injection valve A (3) comprises a valve body a (3-1), a piston a (3-2), a shear pin (3-6), a sleeve (3-7), a ball seat (3-8), a valve ball (3-9), and a steam injection port a (3-10); the valve body a (3-1) is hollow inside, the side wall of the valve body a (3-1) is provided with a steam injection port a (3-10), the piston a (3-2) is connected to the outer wall of the valve body a (3-1) and is clamped at the steam injection port a (3-10); the piston a (3-2) is provided with an axial through hole a (3-2-1) and a plurality of radial through holes a (3-2-2), the axial through hole a (3-2-1) and a plurality of radial through holes a (3-2-2) 2-1) is communicated with a plurality of radial through holes a (3-2-2), and a plurality of radial through holes a (3-2-2) are communicated with a steam injection port a (3-10); a sliding sleeve (3-7) is arranged inside the valve body a (3-1) and is sealed at the steam injection port a (3-10); a shear pin (3-6) is provided between the side wall of the sliding sleeve (3-7) and the side wall of the valve body a (3-1); a ball seat (3-8) is fixedly connected to the inner wall of the bottom end of the sliding sleeve (3-7); a through hole is opened in the middle of the ball seat (3-8); the diameter of the through hole is smaller than the diameter of the valve ball (3-9); when the valve ball (3-9) is put into the sliding sleeve (3-7), it is clamped at the through hole; The piston-type steam injection valve B (5) comprises a valve body b (5-1), a piston b (5-2), and a steam injection port b (5-6); the valve body b (5-1) is hollow inside, the steam injection port b (5-6) is provided on the side wall of the valve body b (5-1), the piston b (5-2) is connected to the outer wall of the valve body b (5-1) and is clamped at the steam injection port b (5-6); the piston b (5-2) is provided with an axial through hole b (5-2-1) and a plurality of radial through holes b (5-2-2), the axial through hole b (5-2-1) is communicated with the plurality of radial through holes b (5-2-2), and the plurality of radial through holes b (5-2-2) are communicated with the steam injection port b (5-6).

2. The large-channel anti-backflow steam injection string according to claim 1, characterized in that: The piston a (3-2) is bound to the valve body a (3-1) via a hoop spring a (3-4).

3. The large-channel anti-backflow steam injection string according to claim 2, characterized in that: A sealing ring a (3-3) is provided at the contact portion between the piston a (3-2) and the outer wall of the valve body a (3-1).

4. The large-channel anti-backflow steam injection string according to claim 1, characterized in that: The outer wall of the valve body a (3-1) is fixedly connected with a limiting pin a (3-5) extending outward, which is used to limit the moving direction and range of the piston a (3-2).

5. The large-channel anti-backflow steam injection string according to claim 1, characterized in that: The piston b (5-2) is bound to the valve body b (5-1) via a hoop spring b (5-4).

6. The large-channel anti-backflow steam injection string according to claim 5, characterized in that: A sealing ring b (5-3) is provided at the contact portion between the piston b (5-2) and the outer wall of the valve body b (5-1).

7. The large-channel anti-backflow steam injection string according to claim 1, characterized in that: The outer wall of the valve body b (5-1) is fixedly connected with a limit pin b (5-5) extending outward, which is used to limit the moving direction and range of the piston b (5-2).

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