Self-sealing packer, use method thereof, and anti-corrosion pipe string for oil and water wells

Abstract

The present invention discloses a self-sealing packer and a method for using the same, as well as an anti-corrosion pipe string for oil and water wells, comprising: an expanded diameter screen pipe, comprising an expanded diameter section provided with a screen hole, the inner diameter of the expanded diameter section being larger than the inner diameter of the oil pipe and smaller than the inner diameter of the casing; a sealing structure, sleeved outside the expanded diameter section; and an expansion structure, arranged between the expanded diameter section and the sealing structure; wherein, after the oil and water in the oil pipe enter the expanded diameter section, the pressure increases and the expansion structure is squeezed outwardly, and the oil and water can flow from the screen hole into the expansion structure to expand the expansion structure, and the sealing structure can expand outwardly under the action of the expansion and squeezing of the expansion structure. The present invention has a larger deformation sealing space, implements a soft seal on the oil-casing annulus, can achieve the effect of sealing the annulus without being dead, can effectively seal the oil-casing annulus when the seal is set, the sealing effect is not affected by casing corrosion, deformation, and up and down creep of the pipe string, and will not be unable to be normally unsealed due to scaling, corrosion, etc., thereby avoiding the problem of well jamming and the need for overhaul.

Description

Technical Field

[0001] The present invention relates to the technical field of oilfield development, in particular to a self-sealing packer and a use method thereof, and an anti-corrosion pipe string for oil and water wells. Background Art

[0002] The corrosion protection process for oil and water well tubing strings involves two aspects: the use of packers and the application of corrosion inhibitor protective fluid to the annular space of the casing and tubing. Packers are generally either expandable or compression-type. Expandable and compression-type packers achieve a seal by compressing the packer element to push against the rubber seal. Consequently, they have a low expansion rate and a high packing pressure. The use of these two types of packers is often accompanied by wellbore scaling, corrosion, and deformation, which can prevent the packer from being properly released and removed, leading to tubing string sticking and the need for major repairs.

[0003] Based on how the packer achieves sealing, it can be divided into self-sealing, compression, expansion, and combination types. The self-sealing type achieves sealing by the interference fit between the packer and the inner diameter of the casing and the working pressure differential; the compression type achieves sealing by compressing the seal with axial force, causing the outer diameter of the seal to increase; the expansion type achieves sealing by increasing the outer diameter of the packer through radial force and the hydraulic pressure of the inner cavity of the seal; the combination type achieves sealing by combining any of the three types. Self-sealing packers are suitable for oil and water wells, but existing expansion-type self-sealing packers have a single sealing form and a relatively small expansion coefficient of the self-expanding rubber. In the case of scaling and corrosion in the oil and water well, there is still the problem of being unable to release the seal normally, causing the tubing to get stuck. Summary of the Invention

[0004] The purpose of the present invention is to provide a self-sealing packer, a method for using the same, and an anti-corrosion tubing string for oil and water wells, so as to solve the problem that the existing self-sealing packers cannot be properly unsealed and removed due to scaling, corrosion, deformation and other problems in the oil and water wells, thereby causing the tubing string to get stuck in the well and requiring major repairs.

[0005] The above-mentioned purpose of the present invention can be achieved by adopting the following technical solutions:

[0006] The present invention provides a self-sealing sealer, comprising: an expanded diameter screen pipe, comprising an expanded diameter section provided with screen holes, the inner diameter of the expanded diameter section being larger than the inner diameter of the oil pipe and smaller than the inner diameter of the casing; a sealing structure, which is sleeved outside the expanded diameter section; and an expansion structure, which is provided between the expanded diameter section and the sealing structure; wherein, after the oil and water in the oil pipe enter the expanded diameter section, the pressure increases and the expansion structure is squeezed to expand outward, and the oil and water can flow from the screen holes into the expansion structure and expand the expansion structure, and the sealing structure can expand outward under the action of the expansion and squeezing of the expansion structure.

[0007] In an embodiment of the present invention, the self-sealing packer further comprises a centralizing protection frame, which is sleeved outside the expanded diameter screen pipe, and the sealing structure and the expansion structure are located inside the centralizing protection frame. The centralizing protection frame can shrink inward and expand outward by utilizing its own elasticity.

[0008] In an embodiment of the present invention, the oil pipe includes a lower oil pipe and an upper oil pipe, the upper oil pipe is connected to the lower oil pipe through the expanded diameter screen pipe, and the two ends of the straightening protection frame clamp the two ends of the expansion structure to the lower oil pipe and the upper oil pipe.

[0009] In an embodiment of the present invention, the expanded diameter screen pipe further includes two reducing sections, the inner diameter of the reducing section gradually decreases in an arc shape from the inner diameter of the expanded diameter section to the inner diameter of the oil pipe, and the two ends of the expanded diameter section are connected to the lower oil pipe and the upper oil pipe through the two reducing sections.

[0010] In an embodiment of the present invention, a plug is provided at the sieve hole, and the plug can be dissolved by the oil and water.

[0011] In an embodiment of the present invention, the dissolution time of the plug is greater than the time required for the self-sealing packer to be lowered to a preset position.

[0012] In an embodiment of the present invention, the plug is made of a soluble metal.

[0013] In an embodiment of the present invention, the sealing structure includes a rubber water bag and an expansion rubber layer. The expansion rubber layer is located between the rubber water bag and the expansion structure. The expansion rubber layer can swell when exposed to water or oil.

[0014] In an embodiment of the present invention, the expansion structure is formed by an expansion material filled between the diameter-expanding section and the sealing structure, and the expansion material can swell when exposed to water or oil.

[0015] The present invention also provides a method for using a self-sealing packer, which is the above-mentioned self-sealing packer. The method for using the self-sealing packer comprises the following steps: sealing: oil and water enter the expanded diameter section of the expanded diameter screen tube from the oil pipe and flow out from the screen hole into the expansion structure, and the sealing structure expands outward under the pressure difference between the expanded diameter section and the oil casing annulus and the squeezing effect of the expansion structure after it expands with oil and water to achieve sealing; unsealing: lifting the oil pipe and increasing the axial pressure on the self-sealing packer to be greater than its axial sealing pressure, and the oil and water in the expansion structure flow back from the screen hole into the expanded diameter screen tube under the action of the axial pressure, causing the sealing structure to retract inward to achieve unsealing.

[0016] In an embodiment of the present invention, before the seating step, the method of use further includes the following steps: lowering: using a plug to block the sieve hole, and then lowering the self-sealing seal into the casing along with the oil pipe, and during the lowering process, the oil and water can enter the expanded diameter section from the oil pipe and dissolve the plug, until the self-sealing seal is lowered to a preset position and the plug is completely dissolved by the oil and water.

[0017] In an embodiment of the present invention, after the seating step, the oil casing annulus includes a lower oil casing annulus located below the self-sealing packer and an upper oil casing annulus located above the self-sealing packer, and the use method further includes the following steps: well washing: well washing fluid flows from the oil pipe to the bottom of the well and enters the lower oil casing annulus, so that the pressure of the lower oil casing annulus is greater than the pressure of the lower oil casing annulus, until the pressure difference between the lower oil casing annulus and the lower oil casing annulus is greater than the preset pressure difference, and the well washing fluid in the lower oil casing annulus enters the upper oil casing annulus from the gap between the self-sealing packer and the casing and is discharged.

[0018] The present invention also provides an anti-corrosion tubing string for oil and water wells, comprising: an oil pipe, including an upper oil pipe and a lower oil pipe; at least one of the above-mentioned self-sealing sealers, connecting the upper oil pipe and the lower oil pipe; an upper anti-corrosion device, arranged outside the upper oil pipe, and the upper anti-corrosion device can slowly release a fixed corrosion inhibitor into the annulus between the upper oil pipe and the casing.

[0019] In an embodiment of the present invention, there are multiple self-sealing packers, and the oil pipe also includes at least one middle oil pipe. The expanded diameter screen pipes of the multiple self-sealing packers are connected from top to bottom through at least one middle oil pipe. The oil and water well anti-corrosion pipe string also includes at least one lower anti-corrosion device, which is arranged outside the middle oil pipe. The lower anti-corrosion device can slowly release fixed corrosion inhibitor into the annulus between the middle oil pipe and the casing.

[0020] The characteristics and advantages of the present invention are:

[0021] The self-sealing packer, the method for using the same, and the anti-corrosion pipe string for oil and water wells of the present invention are connected to the oil pipe via an expanded diameter screen pipe. As oil and water flow into the oil pipe, the pressure in the oil pipe becomes greater than the pressure in the oil casing annulus. The present invention provides an expanded diameter section with a screen hole and an inner diameter greater than the oil pipe according to the Bernoulli equation, so that after oil and water flow from the oil pipe into the expanded diameter section, the flow rate decreases and the pressure increases, that is, the pressure difference between the expanded diameter section and the oil casing annulus is greater than the pressure difference between the oil pipe and the oil casing annulus, so that the expanded diameter section can squeeze the expansion structure to expand outward under the action of the internal and external pressure difference, and at the same time, oil and water can enter the expansion structure from the screen hole to expand the expansion structure, so that the sealing structure can be expanded and squeezed in the expansion and squeezing of the expansion structure. Under the dual action, it expands outward to achieve seating, thereby increasing the sealing pressure of the sealing structure and improving the seating effect. When the axial pressure is greater than the axial sealing pressure of the sealing structure, the water in the expansion structure can flow back from the sieve hole to the expanded diameter section to cause the sealing structure to retract. Therefore, the self-sealing packer of the present invention has a larger deformation sealing space, and implements soft sealing on the oil casing annulus, which can achieve the goal of sealing the oil casing annulus without dying. On the one hand, the oil casing annulus can be effectively sealed during seating, and the sealing effect is not affected by casing corrosion, deformation, and up and down creep of the casing and tubing. On the other hand, it will not be unable to be normally unsealed due to scaling, corrosion, etc., thereby avoiding the problem of well jamming and the need for overhaul. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0023] Figure 1 This is a diagram showing the self-sealing packer in the present invention in use.

[0024] Figure 2 This is a schematic diagram of oil and water flowing from the oil pipe into the expanded diameter section in the present invention.

[0025] Figure 3 This is a schematic structural diagram of the self-sealing packer of the present invention before use.

[0026] Figure 4 Schematic diagram of the structure of an anti-corrosion tubing string for oil and water wells in one embodiment of the present invention.

[0027] Figure 5 This is a schematic structural diagram of an anti-corrosion tubing string for oil and water wells in another embodiment of the present invention.

[0028] In the picture:

[0029] 1. Expanded diameter screen tube; 11. Expanded diameter section; 12. Reduced diameter section; 13. Sieve hole; 2. Expansion structure; 3. Sealing structure; 4. Centralizing protection frame; 5. Plug; 6. Oil pipe; 61. Upper oil pipe; 62. Lower oil pipe; 63. Middle oil pipe; 7. Upper anti-corrosion device; 8. Lower anti-corrosion device; 9. Casing; 91. Oil casing annulus; 92. Upper oil casing annulus; 93. Lower oil casing annulus; 10. Self-sealing packer; 10', self-sealing packer. DETAILED DESCRIPTION

[0030] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. 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 making creative efforts are within the scope of protection of the present invention.

[0031] Implementation Method 1

[0032] like Figure 1 As shown, the present invention provides a self-sealing packer 10, comprising: an expanded diameter screen 1, comprising an expanded diameter section 11 provided with a screen hole 13, the inner diameter D2 of the expanded diameter section 11 being larger than the inner diameter D1 of the oil pipe 6 and smaller than the inner diameter of the casing 9; a sealing structure 3, sleeved on the outside of the expanded diameter section 11; an expansion structure 2, provided between the expanded diameter section 11 and the sealing structure 3; wherein, after the oil and water in the oil pipe 6 enter the expanded diameter section 11, the pressure increases and the expansion structure 2 is squeezed to expand outward, and the oil and water can flow from the screen hole 13 into the expansion structure 2 and cause the expansion structure 2 to expand, and the sealing structure 3 can expand outward under the expansion and squeezing of the expansion structure 2.

[0033] Combine Figure 2 As shown, according to Bernoulli's equation, when oil and water flow from the oil pipe 6 with a smaller inner diameter into the expanded diameter section 11 with a larger inner diameter, Where p1 is the pressure of oil and water at section J1 of the oil pipe 6; p2 is the pressure of oil and water at section J2 of the expanded diameter section 11; ρ is the density of oil and water; v1 is the flow velocity of oil and water at section J1 of the oil pipe 6; v2 is the flow velocity of oil and water at section J2 of the expanded diameter section 11; g is the acceleration of gravity; H1 is the depth of section J1; H2 is the depth of section J2; since the flow rates are the same, v1*A1=v2*A2; where A1 is the area of ​​section 1; A2 is the area of ​​section J2. From this, it can be inferred that Where D1 is the inner diameter of the oil pipe 6; D2 is the inner diameter of the expanded diameter section 11. In addition, since H1 is the height difference between the sections J1 and J2, which can be ignored, it can be inferred that:

[0034]

[0035] It can be seen that after the oil and water enter the expanded diameter section 11 from the oil pipe 6, the flow rate decreases, but the pressure on the pipe wall of the expanded diameter section 11 is greater than the pressure on the pipe wall of the oil pipe 6, and the increased pressure is proportional to the square of the flow rate of the oil and water in the expanded diameter section 11; since the oil and water in the oil and water wells flow in the oil pipe 6, there will be a pressure head loss, so by increasing the internal and external pressure difference of the self-sealing seal 10, the sealing of the sealing structure 3 can be promoted.

[0036] The self-sealing packer 10 of the present invention is connected to the oil pipe 6 through the expanded diameter screen 1. As the oil and water flow into the oil pipe 6, the pressure in the oil pipe 6 is greater than the oil casing annulus 91 (i.e. Figure 4 The pressure in the annulus between the oil pipe 6 and the casing 9 shown in the figure is calculated. The present invention sets an expansion section 11 with a sieve hole 13 and an inner diameter larger than the oil pipe 6 according to the Bernoulli equation, so that after the oil and water flow from the oil pipe 6 into the expansion section 11, the flow rate decreases and the pressure increases, that is, the pressure difference between the expansion section 11 and the oil-casing annulus 91 is greater than the pressure difference between the oil pipe 6 and the oil-casing annulus 91, so that the expansion section 11 can squeeze the expansion structure 2 to expand outward under the action of the internal and external pressure difference, and at the same time, oil and water can enter the expansion structure 2 from the sieve hole 13 to expand the expansion structure 2. Therefore, the sealing structure 3 can expand outward under the dual action of expansion and extrusion of the expansion structure 2 to achieve sealing, thereby improving the sealing of the sealing structure 3. pressure, thereby improving the sealing effect, and when the oil pipe 6 is lifted so that the axial pressure on the self-sealing packer 10 is greater than its axial sealing pressure, the water in the expansion structure 2 can flow back from the sieve hole 13 to the expanded diameter section 11 to shrink the sealing structure 3. Therefore, the self-sealing packer 10 of the present invention has a larger deformation sealing space, and a soft seal is implemented on the oil casing annulus 91, which can achieve the effect of sealing the oil casing annulus 91 without being dead. On the one hand, the oil casing annulus 91 can be effectively sealed during seating, and the sealing effect is not affected by corrosion and deformation of the casing 9 and the up and down creep of the casing 9 and the oil pipe 6. On the other hand, it will not be unable to be unsealed normally due to scaling, corrosion, etc., thereby avoiding the problem of well stuck and the need for overhaul.

[0037] In addition, when washing an oil-water well, since formation water does not participate or rarely participates, positive washing is generally adopted (i.e., washing fluid flows from the wellhead oil pipe 6, passes through the oil casing annulus 91, and is discharged to the wellhead). After the self-sealing packer 10 is sealed, the oil casing annulus 91 includes the lower oil casing annulus 93 located below the self-sealing packer 10 and the upper oil casing annulus 92 located above the self-sealing packer 10. Therefore, when washing the well, the oil casing annulus 91 at the wellhead is opened, and the washing fluid flows from the oil pipe 6 at the wellhead to the wellhead. The fluid enters the well, passes through the oil pipe 6 and reaches the bottom of the well, and then enters the lower casing annulus 93, so that the pressure of the lower casing annulus 93 is greater than the pressure of the upper casing annulus 92. Therefore, when the pressure difference between the lower casing annulus 93 and the upper casing annulus 92 increases to a preset pressure difference, the self-sealing packer 10 contracts, and the flushing fluid can flow from the gap between the self-sealing packer 10 and the casing 9 into the upper casing annulus 92, and then reach the wellhead, and then be discharged from the wellhead. After the well washing is completed, the casing annulus 91 at the wellhead is closed.

[0038] Therefore, the present invention can not only meet the anti-corrosion needs of the tubing, but also solve the problem that the self-sealing packer 10 cannot be normally unsealed and removed due to scaling, corrosion, deformation, etc. of the casing 9 of the oil and water wells, which leads to tubing being stuck in the well and requiring major repairs, and at the same time can meet the well washing requirements; and it has a simple structure, low manufacturing cost, and is convenient to transport and store, and is suitable for soft isolation of the oil casing annulus 91 of oil and water wells. Combined with the protective liquid of the oil casing annulus 91, it not only meets the anti-corrosion needs of the pre-isolation casing 9 of the oil production well, but also meets the anti-corrosion needs of the isolation casing 9 of the water injection well.

[0039] Specifically, in its initial state, the expanded section 11 is generally a tubular structure extending axially along the casing 9 with equal diameter. The length of the sealing structure 3 is equal to or slightly less than the length of the expanded section 11, so that after expansion, it has a sufficiently large sealing contact area with the inner wall of the casing 9. The oil pipe 6 includes an upper oil pipe 61 and a lower oil pipe 62. The ends of the expanded section 11 are connected to the upper and lower oil pipes 61 and 62 via two reducing sections 12. The inner diameter of the reducing section 12 gradually decreases in an arc shape from the inner diameter of the expanded section 11 to the inner diameter of the oil pipe 6, providing a stronger pressure-bearing capacity and facilitating the outward expansion of the expanded section 11 under the influence of the internal and external pressure differential. The expanded screen 1 can be integrally formed with the upper and lower oil pipes 61 and 62, or the ends of the expanded screen 1 can be connected to the upper and lower oil pipes 61 and 62 by providing upper and lower joints.

[0040] Sealing structure 3 comprises a rubber bladder and an expandable rubber layer, located between the bladder and expansion structure 2, forming a double-safety seal. The expandable rubber layer swells in the presence of water or oil. When the self-sealing packer 10 is lowered into a preset position along with the oil pipe 6, oil and water flow from the oil pipe 6 into the expanded section 11 and, through the sieve holes 13, into the expansion structure 2 and the expandable rubber layer. The pressure differential between the inside and outside of the self-sealing packer 10 powers the rubber bladder's outward expansion and sealing. Simultaneously, the expansion structure 2 and the expandable rubber layer begin to absorb water and expand, squeezing the rubber bladder outward, thereby improving the bladder's sealing performance.

[0041] The expansion material filled between the expanded diameter section 11 and the sealing structure 3 forms the expansion structure 2. The expansion material can expand when it comes into contact with water or oil. Specifically, the expansion material includes but is not limited to water-absorbing and expanding fibers. The sealing structure 3 is embedded in the outer wall surface of the expansion structure 2. The amount of the expansion material is determined based on the axial sealing pressure requirement of the self-sealing packer 10 and the expansion coefficient of the expansion material. For example, in an embodiment of the present invention, the axial sealing pressure requirement of the self-sealing packer 10 is 10 MPa. When unsealing, the oil pipe 6 is lifted and the axial pressure on the self-sealing packer 10 exceeds 10 MPa. The water in the expansion structure 2 is squeezed back into the expanded diameter screen pipe 1, causing the sealing structure 3 to retract inward, thereby reducing the resistance when lifting the oil pipe 6 and effectively reducing the risk of well stuck.

[0042] like Figure 1 As shown, in an embodiment of the present invention, the self-sealing packer 10 further includes a centralizing protection frame 4, which is sleeved on the outside of the expanded diameter screen pipe 1, and the sealing structure 3 and the expansion structure 2 are located inside the centralizing protection frame 4. The centralizing protection frame 4 can shrink inward and expand outward by utilizing its own elasticity.

[0043] The present invention utilizes a centralizing frame 4 to ensure the centering of the tubing 6, ensuring uniform circumferential force between the sealing structure 3 and the casing 9 after seating, thereby improving the effectiveness and stability of the sealing structure 3 in isolating the casing annulus 91. Furthermore, the centralizing frame 4 effectively protects the sealing structure 3 during the lowering of the self-sealing packer 10 along with the tubing 6, preventing frictional damage and loss of sealing performance. Furthermore, after prolonged downhole operation of the self-sealing packer 10, if the casing 9 is subjected to scaling or shrinkage, the centralizing frame 4 can adaptively contract and compress the sealing structure 3 simultaneously, preventing wellbore sticking when the tubing 6 is lifted. Specifically, the centralizing frame 4 generally comprises a cage-like steel frame structure. Once lowered into the casing 9 along with the tubing 6, the centralizing frame 4 utilizes its inherent elasticity to adapt to the inner diameter of the casing 9, allowing the centralizing frame 4 to slide in contact with the casing 9, thereby centralizing the tubing 6 and positioning it precisely within the casing 9.

[0044] The ends of the centralizing protection frame 4 clamp and secure the ends of the expansion structure 2 to the lower oil pipe 62 and the upper oil pipe 61. By securing the ends of the expansion structure 2 with the centralizing protection frame 4, the expansion structure 2 is restricted to radial expansion and contraction, preventing oil and water from leaking into the casing annulus 91 through the gap between the expansion structure 2 and the expanded diameter screen 1. Specifically, the ends of the expansion structure 2 extend through the two reducing sections 12 to the lower oil pipe 62 and the upper oil pipe 61.

[0045] like Figure 3 As shown, in an embodiment of the present invention, a plug 5 is provided at the sieve hole 13, and the plug 5 can be dissolved by oil and water. The sieve hole 13 is sealed in advance by the plug 5, thereby preventing oil and water from flowing into the expansion structure 2 from the sieve hole 13 in advance and causing the expansion structure 2 to expand in advance, which is beneficial to reducing the resistance generated when the self-sealing packer 10 is lowered along the oil pipe 6. Specifically, the number of sieve holes 13 is preferably multiple, and the multiple sieve holes 13 are evenly distributed along the circumference and radial direction of the expanded diameter section 11. The material of the plug 5 can be a soluble metal, including a magnesium-aluminum alloy that can be dissolved by water. The material of the plug 5 can also include other soluble metals or other materials that can be dissolved by water and / or oil in the prior art.

[0046] To ensure that the expansion structure 2 does not expand before being lowered to the preset position, in an embodiment of the present invention, the dissolution time of the plug 5 is controlled to be greater than the time required to lower the self-sealing packer 10 to the preset position. Specifically, the dissolution time of the plug 5 is controlled by adjusting the material, size, shape, etc. For example, the larger the cross-sectional area of ​​the plug 5, the longer it takes to dissolve; and the longer the length of the plug 5 within the expanded diameter section 11, the longer it takes to dissolve.

[0047] Implementation Method 2

[0048] The present invention also provides a method for using the self-sealing packer 10. The self-sealing packer 10 in this embodiment is similar to the self-sealing packer 10 in the first embodiment. The method for using the self-sealing packer 10 includes the following steps:

[0049] Sealing: Oil and water flow from the oil pipe 6 into the expanded section 11 of the expanded screen 1 and out through the screen holes 13 into the expansion structure 2. The sealing structure 3 expands outward under the pressure differential between the expanded section 11 and the casing annulus 91, as well as under the squeeze of the expansion structure 2 after it swells in contact with oil and water, achieving sealing. Specifically, because the expansion structure 2 and the sealing structure 3 are located in the expanded section 11, in the initial state, the sealing structure 3 has a first expanded outer diameter that is larger than the outer diameter of the oil pipe 6 and smaller than the inner diameter of the casing 9. Furthermore, in the operating state, the sealing structure 3, under the dual effects of the internal and external pressure differential of the expanded section 11 and the expansion of the expansion structure 2 in contact with water, forms a second expanded outer diameter equal to the inner diameter of the casing 9, thereby achieving sealing. After sealing, the casing annulus 91 includes a lower casing annulus 93 located below the self-sealing packer 10 and an upper casing annulus 92 located above the self-sealing packer 10.

[0050] Unsealing: lift the oil pipe 6 and increase the axial pressure on the self-sealing packer 10 to a level greater than its axial sealing pressure, so that the oil and water in the expansion structure 2 flow back from the sieve holes 13 into the expanded diameter screen pipe 1 under the action of the axial pressure, causing the sealing structure 3 to retract inward to achieve unsealing.

[0051] In an embodiment of the present invention, before the seating step, the method of use further includes the following steps: lowering: using the plug 5 to block the sieve hole 13, and then lowering the self-sealing packer 10 into the casing 9 along with the oil pipe 6, and during the lowering process, oil and water can enter the expanded diameter section 11 from the oil pipe 6 and dissolve the plug 5, until the self-sealing packer 10 is lowered to the preset position and the plug 5 is completely dissolved by oil and water.

[0052] In an embodiment of the present invention, the method further comprises the following steps: Well washing: Well washing fluid flows from the oil pipe 6 to the bottom of the well and enters the lower casing annulus 93, causing the pressure in the lower casing annulus 93 to be greater than the pressure in the upper casing annulus 93, until the pressure difference between the lower casing annulus 93 and the lower casing annulus 93 is greater than a preset pressure difference. The well washing fluid in the lower casing annulus 93 enters the upper casing annulus 92 through the gap between the self-sealing packer 10 and the casing 9 and is discharged. Specifically, after the well washing is completed, the casing annulus 91 at the wellhead is closed.

[0053] Implementation Method 3

[0054] like Figure 4 As shown, the present invention also provides an anti-corrosion tubing string for oil and water wells, comprising: an oil pipe 6, including an upper oil pipe 61 and a lower oil pipe 62; at least one of the above-mentioned self-sealing packers 10, connecting the upper oil pipe 61 and the lower oil pipe 62; an upper anti-corrosion device 7, arranged outside the upper oil pipe 61, and the upper anti-corrosion device 7 can slowly release a fixed corrosion inhibitor into the annulus between the upper oil pipe 61 and the casing 9.

[0055] like Figure 5As shown, in an embodiment of the present invention, there are multiple self-sealing packers 10, the oil pipe 6 also includes at least one middle oil pipe 63, the expanded diameter screen pipes 1 of multiple self-sealing packers 10 are connected from top to bottom through at least one middle oil pipe 63, the oil and water well anti-corrosion pipe string also includes at least one lower anti-corrosion device 8, the lower anti-corrosion device 8 is arranged outside the middle oil pipe 63, and the lower upper anti-corrosion device 7 can slowly release the fixed corrosion inhibitor into the annulus between the middle oil pipe 63 and the casing 9.

[0056] like Figure 4 As shown, in one embodiment of the present invention, a produced water return oil well has a well depth of 1470m and a perforation section depth of 1440m-1450m. In the oil and water well anti-corrosion string, the upper anti-corrosion device 7 uses a solid corrosion inhibitor device, and the oil pipe 6 is N80 oil pipe 6. The oil and water well anti-corrosion string includes: an upper oil pipe 61 lowered from the wellhead into the casing 9; a solid corrosion inhibitor device installed on the upper oil pipe 61 and located at a depth of 650m; a self-sealing packer 10 connected at its upper end to the upper oil pipe 61 and seated at a depth of 1400m; and a lower oil pipe 62 connected to the lower end of the self-sealing packer 10 and lowered to a depth of 1420m.

[0057] like Figure 5 As shown in FIG. 1 , another embodiment of the present invention is a produced water recovery well with a well depth of 1470 m and a perforation section of 1440-1450 m. In the anti-corrosion tubing string, both the upper anti-corrosion device 7 and the lower anti-corrosion device 8 utilize solid corrosion inhibitors, and the oil pipe 6 is an N80 oil pipe 6. The anti-corrosion tubing string for the oil and water well includes: an upper oil pipe 61 lowered from the wellhead into the casing 9; a solid corrosion inhibitor installed on the upper oil pipe 61 and located at a depth of 650 m; a self-sealing packer 10 connected at its upper end to the upper oil pipe 61 and seated at a depth of 1350 m; a middle oil pipe 63 connected at its upper end to the lower end of the self-sealing packer 10; another self-sealing packer 10' connected at its upper end to the lower end of the middle oil pipe 63 and seated at a depth of 1400 m; and a lower oil pipe 62 connected to the self-sealing packer 10' and lowered to a depth of 1420 m.

[0058] The above descriptions are only several embodiments of the present invention. Those skilled in the art may make various changes or modifications to the embodiments of the present invention based on the contents disclosed in the application documents without departing from the spirit and scope of the present invention.

Claims

1. A self-sealing packer, characterized in that: include: An expanded diameter screen pipe, comprising an expanded diameter section provided with screen holes, wherein the inner diameter of the expanded diameter section is larger than the inner diameter of the oil pipe and smaller than the inner diameter of the casing; A sealing structure, sleeved outside the expanded diameter section; an expansion structure, disposed between the diameter-expanding section and the sealing structure; Among them, the pressure of the oil and water in the oil pipe increases after entering the expanded section, squeezing the expansion structure to expand outward, and the oil and water can flow into the expansion structure from the sieve hole and expand the expansion structure, and the sealing structure can expand outward under the action of the expansion and squeezing of the expansion structure.

2. The self-sealing packer according to claim 1, characterized in that The self-sealing packer further comprises a centralizing protection frame, which is sleeved outside the expanded diameter screen pipe. The sealing structure and the expansion structure are located inside the centralizing protection frame. The centralizing protection frame can shrink inwards and expand outwards by utilizing its own elasticity.

3. The self-sealing packer according to claim 2, characterized in that The oil pipe includes a lower oil pipe and an upper oil pipe. The upper oil pipe is connected to the lower oil pipe through the expanded diameter screen pipe. The two ends of the centralizing protection frame clamp and fix the two ends of the expansion structure to the lower oil pipe and the upper oil pipe.

4. The self-sealing packer according to claim 3, characterized in that The expanded diameter screen pipe also includes two reducing sections, the inner diameter of the reducing section gradually decreases from the inner diameter of the expanded diameter section to the inner diameter of the oil pipe in an arc shape, and the two ends of the expanded diameter section are connected to the lower oil pipe and the upper oil pipe through the two reducing sections.

5. The self-sealing packer according to claim 1, wherein: A plug is provided at the sieve hole, and the plug can be dissolved by the oil and water.

6. The self-sealing packer according to claim 5, characterized in that The dissolution time of the plug is greater than the time required for the self-sealing packer to be lowered to a preset position.

7. The self-sealing packer according to claim 5, characterized in that The material of the plug is soluble metal.

8. The self-sealing packer according to claim 1, wherein: The sealing structure includes a rubber water bag and an expansion rubber layer. The expansion rubber layer is located between the rubber water bag and the expansion structure. The expansion rubber layer can expand when exposed to water or oil.

9. The self-sealing packer according to claim 1, wherein: The expansion structure is formed by an expansion material filled between the diameter-expanding section and the sealing structure. The expansion material can expand when it comes into contact with water or oil.

10. A method for using a self-sealing packer, characterized in that: The self-sealing packer is the self-sealing packer according to any one of claims 1 to 9, and the method of using the self-sealing packer comprises the following steps: Sealing: Oil and water enter the expanded diameter section of the expanded diameter screen from the oil pipe and flow out from the screen holes into the expansion structure. The sealing structure expands outwards to achieve sealing under the pressure difference between the expanded diameter section and the casing annulus and the squeezing effect of the expansion structure after it expands with oil and water. Unsealing: The oil pipe is lifted and the axial pressure on the self-sealing packer is increased to be greater than its axial sealing pressure. Under the action of the axial pressure, the oil and water in the expansion structure flow back from the sieve hole into the expanded diameter screen pipe, causing the sealing structure to retract inward to achieve unsealing.

11. The method for using the self-sealing packer according to claim 10, characterized in that: Before the setting step, the method of use further includes the following steps: Lowering: Use a plug to block the sieve hole, and then lower the self-sealing packer into the casing along with the oil pipe. During the lowering process, the oil and water can enter the expanded diameter section from the oil pipe and dissolve the plug. After the self-sealing packer is lowered to a preset position, the plug is completely dissolved by the oil and water.

12. The method for using the self-sealing packer according to claim 10, wherein: After the setting step, the oil casing annulus includes a lower oil casing annulus located below the self-sealing packer and an upper oil casing annulus located above the self-sealing packer. The use method further includes the following steps: Well washing: the washing fluid flows from the oil pipe to the bottom of the well and enters the lower oil casing annulus, so that the pressure of the lower oil casing annulus is greater than the pressure of the upper oil casing annulus, until the pressure difference between the lower oil casing annulus and the upper oil casing annulus is greater than the preset pressure difference, and the washing fluid in the lower oil casing annulus enters the upper oil casing annulus from the gap between the self-sealing packer and the casing and is discharged.

13. An anti-corrosion pipe string for oil and water wells, characterized in that: include: Oil pipe, including upper oil pipe and lower oil pipe; At least one self-sealing packer according to any one of claims 1 to 9, connecting the upper oil pipe and the lower oil pipe; The upper anti-corrosion device is arranged outside the upper oil pipe and can slowly release the fixed corrosion inhibitor into the annulus between the upper oil pipe and the casing.

14. The anti-corrosion tubing string for oil and water wells according to claim 13, characterized in that: There are multiple self-sealing packers, and the oil pipe also includes at least one middle oil pipe. The expanded diameter screens of the multiple self-sealing packers are connected from top to bottom through at least one middle oil pipe. The oil and water well anti-corrosion pipe string also includes at least one lower anti-corrosion device, which is arranged outside the middle oil pipe. The lower anti-corrosion device can slowly release fixed corrosion inhibitor into the annulus between the middle oil pipe and the casing.

Images