Sealing element used in CO2 drive packer and CO2 drive packer

Abstract

The invention discloses a sealing element used in a CO2 drive packer and the CO2 drive packer, the sealing element is prepared by pouring TiNi shape memory alloy, and the TiNi shape memory alloy comprises the following components in percentage by mass: 45% of Ti, 54.5%-52.5% of Ni and 0.5%-2.5% of Ca. The Ti alloy has the characteristic of high corrosion resistance, so that the sealing performance can be maintained for a long time under the working conditions of high temperature and high CO2 partial pressure. The sealing element prepared by pouring the TiNi shape memory alloy can meet the operation working condition during underground CO2 flooding operation, and meanwhile, the shape memory alloy has the superelasticity and the shape memory effect, so that under the action of external force, the shape memory alloy has the deformation recovery capacity much larger than that of common metal, and the sealing element has the good sealing effect. In other words, large strain generated in the loading process can be recovered along with unloading, and the packer and the tubular column can be recovered successfully.

Description

Technical Field

[0001] The invention belongs to the technical field of CO2 drive packer seal manufacturing, and relates to a seal used in a CO2 drive packer and a CO2 drive packer. Background Art

[0002] CCUS technology is to utilize or inject CO2 emitted during industrial production into geological structures for storage and drive out crude oil. It is an important means for my country to reduce carbon emissions, ensure energy security and achieve sustainable development in the future. The injection conditions are generally in extreme environments of 80-120°C and CO2 partial pressure of 20-30MPa. Under this condition, traditional rubber seals are difficult to maintain their sealing performance for a long time. Therefore, it is necessary to develop new sealing materials to maintain their sealing performance for a long time under high temperature and high CO2 partial pressure conditions. Due to the need for unsealing, the seal needs to rebound after the steam injection so that the pipe column can be recovered. Therefore, traditional copper seals cannot be used because they cannot rebound. Shape memory alloy is a new functional material composed of two or more metal elements that can undergo phase change under temperature and stress. It has unique shape memory effect, phase change pseudo-elasticity and other characteristics through thermoelasticity and martensitic phase transformation and its inversion. However, the memory alloy in the prior art cannot be used to realize CO2 flooding operations underground due to its deformation temperature limitation. Summary of the invention

[0003] In view of the problems existing in the prior art, the present invention provides a seal for a CO2 drive packer and a CO2 drive packer, thereby solving the technical problem that the memory alloy in the prior art cannot be used to implement CO2 drive operations underground due to the limitation of its deformation temperature.

[0004] The present invention is achieved through the following technical solutions:

[0005] A seal for a CO2 drive packer is made by casting a TiNi shape memory alloy, wherein the TiNi shape memory alloy comprises, by mass percentage, 45% Ti, 54.5% to 52.5% Ni and 0.5% to 2.5% Ca.

[0006] Preferably, the sealing member is a hollow cylindrical structure.

[0007] Preferably, the outer diameter of the hollow cylindrical seal is 90 to 110 mm.

[0008] Preferably, the wall thickness of the hollow cylindrical seal is 6 to 10 mm.

[0009] A CO2 drive packer comprises the above-mentioned seal, wherein the seal is movably arranged inside the CO2 drive packer.

[0010] The method for using the CO2 flooding packer mentioned above comprises the following steps:

[0011] S1: placing the CO2 flooding packer at a location to be installed underground;

[0012] S2: applying stress to the sealing member to deform the sealing member and perform sealing;

[0013] S3: After setting, CO2 is injected. When the seal meets the sealing requirements, the applied stress is released and the CO2 flooding operation is carried out;

[0014] S4: When the CO2 flooding operation is completed, stop injecting CO2, and remove the packer after the seal returns to its original shape.

[0015] Preferably, in step S1, the temperature of the underground installation location is 80-150°C.

[0016] Preferably, in step S2, the deformation amount of the sealing component at the maximum deformation point during setting does not exceed 10%.

[0017] Preferably, in step S3, during the CO2 injection process, when the downhole temperature is lower than 50°C, the applied stress is released and the CO2 flooding operation is performed.

[0018] Preferably, in step S4, after the injection of CO2 is stopped, when the downhole temperature returns to 80-150°C, the seal returns to its original shape.

[0019] Compared with the prior art, the present invention has the following beneficial technical effects:

[0020] The present invention discloses a seal for a CO2 drive packer, wherein the seal is cast by a TiNi shape memory alloy, wherein the TiNi shape memory alloy comprises 45% Ti, 54.5% to 52.5% Ni and 0.5% to 2.5% Ca in terms of mass percentage. The Ti alloy has a high corrosion resistance, which enables it to maintain sealing performance for a long time under high temperature and high CO2 partial pressure conditions. The shape memory alloy has a shape memory effect under CO2 drive conditions, which is similar to an elastomer and has the ability to recover its shape, so it can meet the working conditions of downhole CO2 drive operations. At the same time, the shape memory alloy has a much greater deformation recovery ability than general metals under the action of external forces because it has superelasticity and shape memory effect, that is, the large strain generated during loading will recover with unloading, so that the packer and the pipe string can be successfully recovered. The TiNi shape memory alloy has a good shape memory effect and superelasticity at a nearly equiatomic ratio, and its phase transition temperature is closely related to the chemical composition. The present invention regulates the phase transition temperature of the TiNi shape memory alloy based on the characteristics of Ca in the TiNi alloy to adapt it to the working conditions stated in the present invention. Ca can regulate the phase transition temperature by occupying the position of solid solution atoms, so that the shape alloy can achieve the shape memory effect stated in the invention patent at the working temperature stated in the present invention.

[0021] Furthermore, the sealing member is in a hollow cylindrical shape, so that it can be compressed to deform and perform sealing.

[0022] Furthermore, the outer diameter of the hollow cylindrical seal is 90 to 110 mm, which can meet the function of the packer to separate the oil casing.

[0023] Furthermore, the wall thickness of the hollow cylindrical seal is 6 to 10 mm, which allows the memory alloy to achieve a sealing function within this size range while having a shape memory effect.

[0024] In addition, the present invention also discloses a CO2 drive packer, comprising the sealing member of the present invention, which is movably arranged inside the CO2 drive packer and can be effectively deformed to achieve a sealing effect.

[0025] At the same time, another inventive point of the present invention lies in the method of using the CO2 drive sealer, which utilizes stress to cause the seal to deform and form a sealing effect. When the CO2 drive operation is completed, the formation temperature automatically rises and the seal can return to its original shape for easy removal. The method of use is convenient and effectively improves the sealing effect.

[0026] Furthermore, during use of the CO2 drive packer of the present invention, the temperature of the downhole installation location is 80-150° C. At this temperature, the seal can undergo a good deformation process and achieve a good sealing effect.

[0027] Furthermore, during use of the CO2 flooding packer of the present invention, the deformation of the seal at the maximum deformation point during setting does not exceed 10%, otherwise it cannot completely restore its original size after heating, which may make the packer unable to be removed.

[0028] Furthermore, during the use of the CO2 flooding seal of the present invention, when the downhole temperature is lower than 50°C during CO2 injection, the applied stress is released and the CO2 flooding operation is carried out. When the downhole temperature is lower than 50°C, the deformed seal can effectively maintain its shape and maintain the sealing effect.

[0029] Furthermore, during use of the CO2 drive packer of the present invention, after the CO2 injection is stopped, when the downhole temperature returns to 80-150°C, the seal returns to its original shape. Within this temperature range, the shape of the seal can be effectively restored, and the seal can be effectively released. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments are briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without creative work.

[0031] Figure 1 It is a schematic diagram of the deformation process of the seal in the present invention during the CO2 flooding operation. DETAILED DESCRIPTION

[0032] In order to enable those skilled in the art to understand the characteristics and effects of the present invention, the following is a general description and definition of the terms and expressions mentioned in the specification and claims. Unless otherwise specified, all technical and scientific terms used in the text are the common meanings understood by those skilled in the art for the present invention. In the event of a conflict, the definition in this specification shall prevail.

[0033] The theories or mechanisms described and disclosed herein, whether correct or incorrect, should not limit the scope of the present invention in any way, that is, the present invention can be implemented without being limited by any specific theory or mechanism.

[0034] Herein, all features such as values, quantities, contents and concentrations defined in the form of numerical ranges or percentage ranges are for simplicity and convenience only. Accordingly, the description of numerical ranges or percentage ranges should be considered to have included and specifically disclosed all possible secondary ranges and individual values ​​within the range (including integers and fractions).

[0035] In this document, unless otherwise specified, “includes,” “including,” “contains,” “has,” or similar terms cover the meanings of “consisting of” and “mainly consisting of,” for example, “A includes a” covers the meanings of “A includes a and other” and “A only includes a.”

[0036] In this document, in order to make the description concise, not all possible combinations of various technical features in various embodiments or examples are described. Therefore, as long as there is no contradiction in the combination of these technical features, the various technical features in various embodiments or examples can be combined arbitrarily, and all possible combinations should be considered to be within the scope of this specification.

[0037] One of the inventive points of the present invention is to provide a TiNi shape memory alloy, which comprises 45% Ti, 54.5% to 52.5% Ni and 0.5% to 2.5% Ca by mass percentage. Further, Ni is most preferably 53% and Ca is most preferably 2%. Due to the control of chemical composition, the alloy has a shape memory effect suitable for CCUS working conditions.

[0038] TiNi shape memory alloy has good shape memory effect and superelasticity at a nearly equiatomic ratio, and its phase transition temperature is closely related to the chemical composition. The present invention regulates the phase transition temperature of TiNi shape memory alloy based on the characteristics of Ca in TiNi alloy to adapt it to the working conditions stated in the present invention. Ca can regulate the phase transition temperature by occupying the position of solid solution atoms. At the working temperature stated in the present invention, the shape alloy can achieve the shape memory effect stated in the invention patent. Ca must be less than 2.5%, the preferred content is less than 2%, and the optimal content is 1.2% to 1.7%.

[0039] Furthermore, another inventive point of the present invention is to obtain a seal for use in a CO2 drive packer by casting the TiNi shape memory alloy. During the casting process, the seal can be directly cast into a hollow cylindrical shape. Of course, the seal can also be directly melted into a cylinder by the TiNi shape memory alloy and then hollowed out to form a mesoporous cylindrical structure. The outer diameter of the hollow cylindrical seal is 90 to 110 mm, and the wall thickness is 6 to 10 mm. The seal deforms at high temperatures to play a sealing role, and then cools down, the seal maintains a sealing shape, and then the temperature is raised, and the original shape is restored after the load force is removed.

[0040] Furthermore, another inventive point of the present invention is to provide a CO2 drive packer, which includes a seal obtained by casting the TiNi shape memory alloy in the present invention, and the seal is movably arranged inside the CO2 drive packer.

[0041] At the same time, another inventive point of the present invention is to provide a method for using the CO2 drive packer in the present invention, and the implementation process is as follows: (1) going down the well, the packer with the seal installed is lowered into the well. Due to the high underground temperature, the seal is suitable for deformation, but the maximum temperature that the seal can withstand is 150°C. When the underground temperature is higher than 150°C, it is not suitable, that is, it does not have a shape memory effect; (2) setting the seal, setting the seal in a high temperature underground environment, that is, the seal is greatly deformed to expand, and the maximum deformation of the seal cannot exceed 10%, otherwise the shape memory requirement cannot be met; (3) cooling, the underground temperature is reduced after CO2 is injected, when the temperature drops below 50°C, the seal maintains its original shape due to the phase change effect, and can maintain the sealing function even without external force, as shown in the effect after setting; (4) unsealing, when it is necessary to remove the packer, stop injecting CO2 and unload, when the temperature is higher than 100°C, the seal returns to its original shape, and the packer can be withdrawn, as shown in the photo after unsealing.

[0042] The specific usage includes the following steps:

[0043] S1: placing the CO2 flooding packer at a location to be installed underground, where the temperature is 80-150° C.;

[0044] S2: Figure 1 As shown, the stress is applied to the seal to cause the seal to deform and then set. During setting, the deformation amount of the seal at the maximum deformation point does not exceed 10%;

[0045] S3: After setting, CO2 is injected. When the seal meets the sealing requirements, that is, when the downhole temperature is lower than 50°C, the applied stress is removed and the CO2 flooding operation is carried out;

[0046] S4: After the CO2 flooding operation is completed, stop injecting CO2. When the downhole temperature returns to 80-150°C and the seal returns to its original shape, remove the packer.

[0047] The key to making the seal return to its original shape after unsealing is that the shape memory compound has a shape memory effect. The shape memory effect originates from the reversibility of the thermoelastic martensitic phase transformation crystallography. There is a reversible relationship between the low-temperature martensitic phase and the high-temperature phase in crystallography at a coherent or semi-coherent interface. The shape memory effect can generally be described as: at a temperature below M fAt this temperature, the alloy sample is deformed to produce macroscopic residual strain. f In an environment above the temperature, its shape can return to its original state. f Indicates the temperature at which the matrix phase transforms into the martensite phase, A f The temperature at which the reverse phase transformation from martensite to parent phase is completed. The main mechanism of the shape memory effect is that temperature change triggers phase transformation, and the internal martensite structure is reoriented during the phase transformation process. f =150℃,A f =80℃.

[0048] The present invention will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and are not intended to limit the scope of the present invention. In addition, it should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms fall within the scope limited by the appended claims of the application equally.

[0049] The following examples use conventional instruments and equipment in the art. The experimental methods in the following examples where specific conditions are not specified are usually carried out under conventional conditions or under conditions recommended by the manufacturer. The various raw materials used in the following examples are conventional commercial products unless otherwise specified, and their specifications are conventional specifications in the art. In the specification of the present invention and the following examples, unless otherwise specified, "%" means weight percentage, "part" means weight part, and ratio means weight ratio.

[0050] Example 1

[0051] The chemical composition of the seal is Ti 45 Ni 54 Ca1, where the numbers are mass percentages. According to this composition, it is melted and then cast in a hollow mold with an outer diameter of 110 mm and an inner diameter of 105 mm. The cast seal is then installed on the packer.

[0052] After the packer is installed and lowered into the well, the packer is installed in the range of 4000-4500m underground. The temperature in this formation range is 100℃. At this time, the packer is tested for sealing and loaded with 14t stress. At this time, the maximum deformation of the seal is 10%, which fits the casing and plays a sealing role. Then CO2 is injected and the load is removed after the temperature drops to 20℃. Then the CO2 flooding operation is carried out. After the operation is completed, the injection of CO2 is stopped. At this time, due to the formation temperature, the temperature of the seal rises to 100℃. The pipe column is lifted, the seal returns to its original shape, and the packer can be taken out.

[0053] Example 2

[0054] The chemical composition of the seal is Ti 45 Ni 53 Ca2, where the numbers are mass percentages. The composition is melted and then cast in a hollow mold with an outer diameter of 90 mm and an inner diameter of 80 mm. The cast seal is then installed on the packer.

[0055] After the packer is installed and lowered into the well, the packer is installed in the range of 4200-4700m underground. The temperature in this formation range is 120℃. At this time, the packer is tested for sealing and loaded with 8t stress. At this time, the maximum deformation of the seal is 8%, which fits the casing and plays a sealing role. Then CO2 is injected and the load is removed after the temperature drops to 20℃. Then the CO2 flooding operation is carried out. After the operation is completed, the injection of CO2 is stopped. At this time, due to the formation temperature, the temperature of the seal rises to 120℃. The pipe column is lifted, the seal returns to its original shape, and the packer can be taken out.

[0056] Example 3

[0057] The chemical composition of the seal is Ti 45 Ni 54 Ca1, where the numbers are mass percentages, is melted according to this composition and then cast in a cylindrical mold. The seal with an outer diameter of 110 mm and an inner diameter of 104 mm is then installed on the packer.

[0058] After the packer is installed and lowered into the well, the packer is installed in the range of 5000-5200m underground. The temperature in this formation range is 140℃. At this time, the packer is tested for sealing and loaded with 12t stress. At this time, the maximum deformation of the seal is 9%, which fits the casing and plays a sealing role. Then CO2 is injected and the load is removed after the temperature drops to 20℃. Then the CO2 flooding operation is carried out. After the operation is completed, the injection of CO2 is stopped. At this time, due to the formation temperature, the temperature of the seal rises to 140℃. The pipe column is lifted, the seal returns to its original shape, and the packer can be taken out.

[0059] Example 4

[0060] This embodiment provides a seal for a CO2 drive packer, which is made by casting a TiNi shape memory alloy, wherein the TiNi shape memory alloy comprises, by mass percentage, 45% Ti, 53.5% Ni and 1.5% Ca. The seal is a hollow cylindrical structure with an outer diameter of 110 mm and a wall thickness of 10 mm.

[0061] Example 5

[0062] This embodiment provides a seal for a CO2 drive packer, which is made by casting a TiNi shape memory alloy, wherein the TiNi shape memory alloy comprises, by mass percentage, 45% Ti, 54.5% Ni and 0.5% Ca. The seal is a hollow cylindrical structure with an outer diameter of 90 mm and a wall thickness of 6 mm.

[0063] Example 6

[0064] This embodiment provides a seal for a CO2 drive packer, which is made by casting a TiNi shape memory alloy, wherein the TiNi shape memory alloy comprises, by mass percentage, 45% Ti, 53.5% Ni and 1.5% Ca. The seal is a hollow cylindrical structure with an outer diameter of 95 mm and a wall thickness of 8 mm.

[0065] Example 7

[0066] This embodiment provides a seal for a CO2 drive packer, which is made by casting a TiNi shape memory alloy, wherein the TiNi shape memory alloy comprises, by mass percentage, 45% Ti, 52.5% Ni and 2.5% Ca. The seal is a hollow cylindrical structure with an outer diameter of 95 mm and a wall thickness of 8 mm.

[0067] Example 8

[0068] This embodiment provides a seal for a CO2 drive packer, which is made by casting a TiNi shape memory alloy, wherein the TiNi shape memory alloy comprises, by mass percentage, 45% Ti, 53% Ni and 2% Ca. The seal is a hollow cylindrical structure with an outer diameter of 95 mm and a wall thickness of 9 mm.

[0069] Example 9

[0070] This embodiment provides a CO2 flooding packer, which includes the sealing member of the present invention, and the sealing member is movably disposed inside the CO2 flooding packer.

[0071] The CO2 flooding packer includes the following steps during use:

[0072] S1: placing the CO2 flooding packer at a location to be installed underground, where the temperature is 80°C;

[0073] S2: applying stress to the seal to deform the seal and setting the seal, wherein the deformation of the seal at the maximum deformation point during setting is 10%;

[0074] S3: After setting, CO2 is injected. When the downhole temperature reaches 20°C, the applied stress is released and CO2 flooding operation is carried out;

[0075] S4: After the CO2 flooding operation is completed, stop injecting CO2. When the downhole temperature returns to 150°C and the seal returns to its original shape, remove the packer.

[0076] Example 10

[0077] This embodiment provides a CO2 flooding packer, which includes the sealing member of the present invention, and the sealing member is movably disposed inside the CO2 flooding packer.

[0078] The CO2 flooding packer includes the following steps during use:

[0079] S1: placing the CO2 flooding packer at a location to be installed underground, where the temperature is 100°C;

[0080] S2: applying stress to the seal to deform the seal and setting the seal, wherein the deformation of the seal at the maximum deformation point during setting is 10%;

[0081] S3: After setting, CO2 is injected. When the downhole temperature reaches 40°C, the applied stress is released and CO2 flooding operation is carried out;

[0082] S4: After the CO2 flooding operation is completed, stop injecting CO2. When the downhole temperature returns to 80°C and the seal returns to its original shape, remove the packer.

[0083] Embodiment 11

[0084] This embodiment provides a CO2 flooding packer, which includes the sealing member of the present invention, and the sealing member is movably disposed inside the CO2 flooding packer.

[0085] The CO2 flooding packer includes the following steps during use:

[0086] S1: placing the CO2 flooding packer at a location to be installed underground, where the temperature is 130° C.;

[0087] S2: applying stress to the seal to deform the seal and setting the seal, wherein the deformation of the seal at the maximum deformation point during setting is 8%;

[0088] S3: After setting, CO2 is injected. When the downhole temperature reaches 30°C, the applied stress is removed and CO2 flooding operation is carried out;

[0089] S4: After the CO2 flooding operation is completed, stop injecting CO2. When the downhole temperature returns to 100°C and the seal returns to its original shape, remove the packer.

[0090] Example 12

[0091] This embodiment provides a CO2 flooding packer, which includes the sealing member of the present invention, and the sealing member is movably arranged inside the CO2 flooding packer. During use, the CO2 flooding packer includes the following steps:

[0092] S1: placing the CO2 flooding packer at a location to be installed underground, where the temperature is 150° C.;

[0093] S2: applying stress to the seal to deform the seal and setting the seal, wherein the deformation of the seal at the maximum deformation point during setting is 8%;

[0094] S3: After setting, CO2 is injected. When the downhole temperature reaches 30°C, the applied stress is removed and CO2 flooding operation is carried out;

[0095] S4: After the CO2 flooding operation is completed, stop injecting CO2. When the downhole temperature returns to 130°C and the seal returns to its original shape, remove the packer.

[0096] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

[0097] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the essence and scope of the technical solution of the present invention.

Claims

1. A seal for a CO2 flooding packer, characterized in that: The sealing member is made by casting a TiNi shape memory alloy, wherein the TiNi shape memory alloy comprises, by mass percentage, 45% Ti, 54.5% to 52.5% Ni and 0.5% to 2.5% Ca.

2. A seal for a CO2 flooding packer according to claim 1, characterized in that: The sealing element is a hollow cylindrical structure.

3. A seal for a CO2 flooding packer according to claim 2, characterized in that: The outer diameter of the hollow cylindrical sealing member is 90 to 110 mm.

4. A seal for a CO2 flooding packer according to claim 2, characterized in that: The wall thickness of the hollow cylindrical sealing member is 6 to 10 mm.

5. A CO2 flooding packer, characterized in that: The invention comprises a sealing member as claimed in any one of claims 1 to 4, wherein the sealing member is movably arranged inside the CO2 drive packer.

6. A method for using a CO2 flooding packer according to claim 5, characterized in that: The following steps are involved: S1: placing the CO2 flooding packer at a location to be installed underground; S2: applying stress to the sealing member to deform the sealing member and perform sealing; S3: After setting, CO2 is injected. When the seal meets the sealing requirements, the applied stress is released and the CO2 flooding operation is carried out; S4: When the CO2 flooding operation is completed, stop injecting CO2, and remove the packer after the seal returns to its original shape.

7. A method for using a CO2 flooding packer according to claim 6, characterized in that: In step S1, the temperature of the underground installation location is 80-150°C.

8. The method for using a CO2 flooding packer according to claim 6, characterized in that: In step S2, the deformation amount of the sealing component at the maximum deformation point during setting does not exceed 10%.

9. A method for using a CO2 flooding packer according to claim 6, characterized in that: In step S3, during the CO2 injection process, when the downhole temperature is lower than 50°C, the applied stress is released and the CO2 flooding operation is performed.

10. The method for using a CO2 flooding packer according to claim 6, characterized in that: In step S4, after the injection of CO2 is stopped, when the downhole temperature returns to 80-150°C, the seal returns to its original shape.

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