Compensation packer in the same well production and irrigation pipe

Abstract

The present invention belongs to the technical field of geothermal well production and irrigation in the same well, and specifically discloses a compensating packer in the same well production and irrigation pipe, the packer is arranged inside the cylinder, and is characterized in that it includes an upper compensation area, a sealing area, a lower compensation area and an anti-scratch area connected in sequence, the upper compensation area is used to compensate for the upward movement of the plunger position caused by the positive measurement error, the sealing area is used to achieve the sealing and isolation of geothermal water and reinjection water, the lower compensation area is used to compensate for the downward movement of the plunger position caused by the elongation of the heating line and the negative measurement error, and the anti-scratch area is used to prevent the oil pipe from scratching the inner hole during the well washing operation; the top end of the upper compensation area and the bottom end of the lower compensation area are both coaxially connected to the casing. The present invention arranges a packer in the inner pipe, so that the reinjection water and the produced water are safely and reliably sealed in the annulus formed by the inner and outer pipes.

Description

Technical Field

[0001] The invention belongs to the technical field of geothermal well production and irrigation, and in particular relates to a compensating packer in a geothermal well production and irrigation pipe. Background Art

[0002] In the application of the same-hole production and top filling technology for medium-deep geothermal wells, when the pipe string (hereinafter referred to as the inner pipe) composed of Φ244.5 pump chamber pipe and Φ139.7 production casing connected by a reducer is lowered, on the one hand, it is necessary to carry out a seat seal suspension at the upper end, and on the other hand, the annulus formed by the inner hole of the Φ219.08 technical casing and the outer diameter of the Φ139.7 casing should be subjected to stratum isolation in the production and filling boundary section. On the surface, stratum isolation can be completed by cementing or using an in-pipe packer. Because the upper end of the inner pipe needs to be fixed by the seat seal suspension, if the above scheme is still used in the production and filling boundary section, the two ends of the inner pipe string will form a fixed connection at both ends in the diameter of the Φ339.7 surface casing and the Φ219.08 technical casing (hereinafter referred to as the outer pipe) that have been combined with the formation.

[0003] The existing problems of hanging on the same pipe:

[0004] Generally, when the casing is lowered into the wellbore, due to the weight of the casing itself, the force on the pipe string is axial tension. Even if the well is cemented, the cement solidification process makes the casing and the formation temperature balanced. However, in the same well production and injection, if the upper end is fixed by the seat seal suspension, the production and injection boundary section is sealed by cementing and in-pipe packers. This method of fixing the two ends is completed before water production and reinjection. In this process, it can be considered that the temperature of the inner pipe and the outer pipe is the same, the linear elongation of the inner and outer pipes due to thermal expansion is the same, and the internal stress generated by thermal expansion in the system composed of the inner and outer pipes is zero.

[0005] However, when the geothermal well is put into use and begins production and reinjection, if the reinjection temperature is t1 and the water production temperature is t2, a temperature difference Δt=t2-t1 will be generated inside and outside the inner tube. This temperature difference will cause the inner tube to expand linearly relative to the outer tube, and its linear elongation is ΔL. Assume that the linear expansion coefficient is α and the fixed end distance is L,

[0006] Then ΔL=αLΔt=αL(t2-t1)

[0007] At 20℃~100℃, the linear expansion coefficient of alloy steel oil casing is α=11.2×10 -6 / ℃;

[0008] If the water temperature is 100℃ and the recharging temperature is 35℃,

[0009] Then ΔL = 11.2 × 2500 (100-35) = 1.82m

[0010] This elongation ΔL will be released in the following three ways:

[0011] like Figure 1 If the two fixed ends are strong enough, the weak part of the inner tube string, Φ139.7 casing, will bend and deform in the inner hole of Φ219.08 technical casing with the slender pressure rod, and bend and become unstable in the inner hole of Φ219.08 technical casing. If the length of this unstable deflection is not enough to offset ΔL, the only way to release its internal stress is to compress and destroy the Φ139.7 casing.

[0012] Assuming that the cementing or in-pipe packer at the production-injection boundary point is firm and the inner pipe string is strong enough, when the increase in the flexural instability length is not enough to offset the thermal expansion elongation ΔL, the upper Φ244.5 casing suspension part will be lifted up, causing the seat seal suspension to fail.

[0013] If the Φ244.5 hanging seat seal at the upper end is firm, the cementing cement or the packer in the pipe at the boundary between production and injection will be damaged, making the seal between the production and injection layers ineffective.

[0014] According to the above analysis, when there is a temperature difference between the inside and outside of the inner pipe string, it is not appropriate to use a two-section fixed form for suspension and isolation.

[0015] The measurement error of the inner tube string length is ΔL`.

[0016] The aforementioned inner tube string should not be fixed in two sections, and it is also not advisable to use upper and lower suspension.

[0017] First, the thermal expansion length can only be calculated theoretically based on the theoretically given filling temperature, but it is impossible to correctly determine the temperature difference that changes at any time during the production process. Therefore, the ΔL value is only a range quantity, not a definite and error-free value.

[0018] Secondly, since only a single casing can be measured manually when the inner pipe string is lowered, the length error cannot be determined. In addition, the screwing of the male and female buckles during the buckling will also cause length errors. The superposition of these two errors will form a cumulative error in the total length of the string. According to conventional experience, within the range of 2500 meters of pipe string length, the cumulative error allowable is ±2.5 meters.

[0019] To achieve accurate suspension and sealing when the upper and lower ends are suspended at the same time, both in theory and in practice, the actual length error of both ends must be guaranteed to be 0. Due to the above two reasons, this is impossible to achieve in actual operation.

[0020] Therefore, providing a new compensating packer in the same well production and irrigation pipe is a technical problem that technical personnel in this field urgently need to solve. Summary of the invention

[0021] The purpose of the present invention is to overcome the defects existing in the prior art, the only method is to use a fixed connection of the upper end seal suspension, and a movable hinge connection is used in the extraction and injection decomposition area. That is, only the vertical movement of the inner tube string axis and the rotation of the string are restricted, but the expansion and contraction along the axis within the set stroke range are not restricted, and the sealing is achieved within the set expansion and contraction range to cut off the channel between the geothermal water and the recharging water.

[0022] The present invention provides a compensating packer in a well production and injection pipe. The packer is arranged inside a cylinder 2, and comprises an upper compensation area, a sealing area, a lower compensation area and an anti-scratch area connected in sequence. The upper compensation area is used to compensate for the upward movement of the plunger position caused by a positive measurement error, the sealing area is used to achieve sealing and isolation between geothermal water and reinjection water, the lower compensation area is used to compensate for the downward movement of the plunger position caused by elongation of the heated line and a negative measurement error, and the anti-scratch area is used to prevent the oil pipe from scratching the inner hole during well washing operations; the top end of the upper compensation area and the bottom end of the lower compensation area are both coaxially connected to the casing 1.

[0023] A further solution is that both the upper compensation area and the lower compensation area are high-strength silicone tubes, and the high-strength silicone is heat-resistant at 200°C.

[0024] A further solution is that the stroke dimension of the upper compensation zone is 2.5 meters, and the stroke dimension of the lower compensation zone is 3.07 meters.

[0025] A further solution is that the sealing area includes a plunger body 3, on which a sealing assembly 4 and a flexible straightening member 5 are sleeved, and the plunger body 3 is precisely matched with the inner hole of the cylinder 2 and can move freely in the axial direction of the cylinder according to a set stroke.

[0026] A further solution is that conical guide cones are provided at both upper and lower ends of the plunger body 3 .

[0027] A further solution is that the sealing component 4 is made of high-strength silicone and the flexible straightening member 5 is made of EPDM rubber.

[0028] A further solution is that the sealing assembly 4 and the flexible straightening member 5 are interference connected with the plunger body 3 .

[0029] A further solution is that the anti-scratch area is a scratch protector 6 arranged inside the cylinder 2, and the scratch protector 6 is fixed inside the cylinder 2 through a tapered hole guide.

[0030] A further solution is that the casing 1 is a Φ139.7 production casing.

[0031] Compared with the prior art, the present invention has the following beneficial effects:

[0032] (1) The present invention provides a packer in the inner tube, so that the annulus formed between the inner and outer tubes can safely and reliably isolate the reinjection water and the produced water.

[0033] (2) Under the premise that the upper end of the pump chamber pipe Φ244.5 is suspended, the packer can freely expand and contract along the axis of the inner pipe string within a certain range as the temperature difference between the geothermal water and the reinjection water changes, so as to compensate for the cumulative length error caused by the superposition of the linear increase and decrease ΔL caused by thermal expansion and the measurement error ΔL`.

[0034] (3) The interior of the anti-scraper of the present invention is guided by a tapered hole so that the well-washing oil pipe is confined in the reduced diameter hole, and a contact-free annular gap is formed between the well-washing oil pipe body and the outer diameter of the coupling and the inner hole of the cylinder barrel, so that the inner hole of the cylinder barrel is not scratched or damaged, thereby ensuring that the sealing of the production and injection isolation is not affected. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] The following drawings are only used to illustrate and explain the present invention, and are not used to limit the scope of the present invention, wherein:

[0036] Figure 1 : Schematic diagram of the inner tube bending deformation;

[0037] Figure 2 : Schematic diagram of the structure of the compensation isolation area in the pipe;

[0038] In the figure: 1 sleeve, 2 cylinder barrel, 3 plunger body, 4 sealing assembly, 5 flexible straightening member, 6 anti-scraper. DETAILED DESCRIPTION

[0039] In order to make the purpose, technical solution, design method and advantages of the present invention clearer, the present invention is further described in detail by specific embodiments in conjunction with the accompanying drawings. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0040] like Figure 2 As shown, the present invention provides a compensating packer in a same-well production and injection pipe, the packer is arranged inside a cylinder 2, and comprises an upper compensation zone, a sealing zone, a lower compensation zone and an anti-scratch zone connected in sequence, the upper compensation zone is used to compensate for the upward movement of the plunger position caused by a positive measurement error, the sealing zone is used to achieve sealing and isolation between geothermal water and reinjection water, the lower compensation zone is used to compensate for the downward movement of the plunger position caused by elongation of the heated line and a negative measurement error, and the anti-scratch zone is used to prevent the oil pipe from scratching the inner hole during well washing operations; the top end of the upper compensation zone and the bottom end of the lower compensation zone are both coaxially connected to the casing 1.

[0041] Wherein, the upper compensation area and the lower compensation area are both high-strength silicone tubes, and the high-strength silicone tubes are heat-resistant at 200°C.

[0042] In this embodiment, the stroke dimension of the upper compensation zone is 2.5 meters, and the stroke dimension of the lower compensation zone is 3.07 meters.

[0043] Continue to see Figure 2 The sealing area includes a plunger body 3, on which a sealing assembly 4 and a flexible straightening member 5 are sleeved. The plunger body 3 is precisely matched with the inner hole of the cylinder 2 and can move freely in the axial direction according to a set stroke in the cylinder.

[0044] Optionally, the plunger body 3 is provided with conical guide cones at both upper and lower ends.

[0045] Optionally, the sealing component 4 is made of high-strength silicone and the flexible straightening member 5 is made of EPDM rubber.

[0046] Optionally, the sealing assembly 4 and the flexible straightening member 5 are interference connected with the plunger body 3 .

[0047] Optionally, the anti-scratch area is an anti-scratch device 6 disposed inside the cylinder 2, and the anti-scratch device 6 is fixed inside the cylinder 2 by means of a tapered hole guide.

[0048] In this embodiment, the casing 1 is a Φ139.7 production casing.

[0049] During the specific use of the present invention, the upper part of the Φ139.7 production casing is connected to the Φ244.5 pump chamber pipe through a diameter change, and is suspended and fixed at the upper end of the pump chamber pipe using a suspended reinjection composite wellhead. When the cylinder is lowered into the Φ219.08 technical casing at the second opening, it is lowered according to the set production and injection boundary position. Inside the cylinder, there is a plunger body that is precisely matched with the inner hole of the cylinder and can move freely in the axial direction according to the set stroke in the cylinder. The conical surface part at the front end of the plunger body serves as a guide cone to ensure that the isolation area safely enters the cylinder. When the guide cone enters the cylinder, it guides the flexible straightening member on the plunger body to smoothly enter the cylinder. The flexible straightening member is composed of high-strength rubber, and its fit with the inner hole of the cylinder has a certain interference. Under the action of its elastic force, the concentricity of the inner hole of the cylinder and the plunger body is corrected again to ensure that the micro annulus formed between the inner hole of the cylinder and the outer circle of the plunger is uniform and consistent, and the sealing component is guided to smoothly enter the inner hole of the cylinder to achieve the sealing and isolation of geothermal water and reinjection water. In the inner hole of the cylinder, in addition to the isolation zone, an upper compensation zone is reserved in the upper part to compensate for the upward movement of the plunger position caused by the positive measurement error. And a lower compensation zone is reserved in the lower part to compensate for the downward movement of the plunger position caused by the elongation of the heating line and the negative measurement error. The stroke size of the upper compensation zone is M = ΔL` = 2.5 meters, and the stroke size of the lower compensation zone is N = ΔL` + ΔL = 2.5 + 1.82 = 3.07 meters. The total stroke of the compensation packer is L = M + N = 2.5 + 3.07 = 5.57 meters.

[0050] To ensure the sealing performance of the compensating packer, its inner hole is finely processed by grinding, with high dimensional accuracy and surface roughness. To prevent the oil pipe from scratching the inner hole during well washing operation, a scratch preventer is configured at the head of the cylinder. The inside of the scratch preventer is guided by a tapered hole to circle the well washing oil pipe in the reduced diameter hole, and to ensure that a contact-free annular gap is formed between the well washing oil pipe body and the outer diameter of the coupling and the inner hole of the cylinder, so that the inner hole of the cylinder is not scratched and damaged, so as to ensure that the sealing of the production and injection packer is not affected.

[0051] The cylinder and plunger of the compensating packer should be made of corrosion-resistant materials to prevent leakage due to surface oxidation. The sealing component should be made of high-strength silicone material with a heat resistance of 200°C, and the flexible straightening part should be made of heat-resistant and high-strength EPDM rubber. The present invention is subjected to a pressure test, and the compensating packer sample should be subjected to a pressure test with a test pressure of 2Mpa and a pressure maintenance of 5 minutes.

[0052] The embodiments of the present invention have been described above, and the above description is exemplary, not exhaustive, and is not limited to the disclosed embodiments. Many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the described embodiments. The selection of terms used herein is intended to best explain the principles of the embodiments, practical applications, or technical improvements in the market, or to enable other persons of ordinary skill in the art to understand the embodiments disclosed herein.

Claims

1. A compensating packer in a well production and irrigation pipe, the packer being arranged inside a cylinder (2), characterized in that: It comprises an upper compensation area, an isolation area, a lower compensation area and an anti-scratch area which are connected in sequence, wherein the upper compensation area is used to compensate for the upward movement of the plunger position caused by the positive measurement error, the isolation area is used to achieve the sealing and isolation of the geothermal water and the reinjection water, the lower compensation area is used to compensate for the downward movement of the plunger position caused by the elongation of the heating line and the negative measurement error, and the anti-scratch area is used to prevent the oil pipe from scratching the inner hole during the well washing operation; the top end of the upper compensation area and the bottom end of the lower compensation area are both coaxially connected to the casing (1); The sealing area comprises a plunger body (3), a sealing assembly (4) and a flexible straightening member (5) are sleeved on the plunger body (3), and the plunger body (3) is precisely matched with the inner hole of the cylinder barrel (2) and can freely move axially in the cylinder barrel according to a set stroke; The sealing assembly (4) and the flexible straightening member (5) are interference-connected with the plunger body (3); The anti-scratch area is an anti-scratch device (6) arranged inside the cylinder barrel (2), and the interior of the anti-scratch device (6) is fixed inside the cylinder barrel (2) through a tapered hole guide; The upper compensation area and the lower compensation area are both high-strength silicone tubes, and the high-strength silicone is heat-resistant at 200°C.

2. The compensating packer in the same well production and irrigation pipe according to claim 1 is characterized in that: The stroke dimension of the upper compensation zone is 2.5 meters, and the stroke dimension of the lower compensation zone is 3.07 meters.

3. The compensating packer in the same well production and irrigation pipe according to claim 1 is characterized in that: Conical guide cones are provided at both the upper and lower ends of the plunger body (3).

4. The compensating packer in the same well production and irrigation pipe according to claim 3 is characterized in that: The sealing component (4) is made of high-strength silicone rubber, and the flexible centralizing member (5) is made of EPDM rubber.

5. The compensating packer in the same well production and irrigation pipe according to any one of claims 1 to 4, characterized in that: The casing (1) is a Φ139.7 production casing.

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