Cathode protection internal corrosion prevention device and method for battery-powered impressed current casing in shaft

Abstract

The invention discloses a battery power supply impressed current casing cathode protection internal corrosion prevention device and method in a shaft, and belongs to the technical field of oil exploitation. The inner anti-corrosion device comprises a battery pack and an auxiliary anode; the battery pack is arranged on the oil pipe, and the auxiliary anode is arranged at the lower end part of the oil pipe; the outer diameters of the battery pack and the auxiliary anode are equal to the outer diameter of the oil pipe; the inner wall of the casing pipe makes contact with an oil pipe, and the inner corrosion prevention device is used in an oil gas well with the produced liquid mineralization degree being 0.5-150 g / L and the bottom hole temperature being lower than 60 DEG C.

Description

Technical Field

[0001] The invention belongs to the technical field of oil extraction, and in particular relates to a battery-powered impressed current casing cathode protection internal anti-corrosion device and method in a wellbore. Background Art

[0002] During the production process of oil fields, there are serious casing corrosion problems. Epoxy coating, cathodic protection and other technical means are used to solve the problem of external casing corrosion. However, in the face of internal casing corrosion, the more mature ones are to add corrosion inhibitors for corrosion prevention. For example, China patents a process for internal anti-corrosion coating of oil casing, which isolates metal from corrosive media by coating the inside of the oil casing to achieve the effect of corrosion prevention; China patents a method for internal anti-corrosion of oil well casing, which protects the casing by extending the pump hanger to the upper end of the perforation section to change the oil-water separation in the casing annulus, but its operation is complicated and increases the complexity of the pipe string in the wellbore; and the technology of bringing anodes into the tubing is adopted, in which the sacrificial anode is insulated from the tubing and contacts the inner wall of the casing through the metal contact wall to transmit current to protect the inner wall of the casing, but it will cause the unfavorable situation of drill stuck when the perforation section is deep, many tubings are brought in and the anodes are brought in and the position is deep. Summary of the invention

[0003] In order to overcome the shortcomings of the above-mentioned prior art, the purpose of the present invention is to provide a battery-powered external current casing cathodic protection internal anti-corrosion device and method in the wellbore, which solves the problem of complex internal anti-corrosion technology in the existing wellbore, reduces the complexity of the tubing in the wellbore and avoids the unfavorable situation of drill sticking when the perforation section is deep, many oil pipes are lowered into the anode and the lowering position is deep.

[0004] In order to achieve the above object, the present invention adopts the following technical solutions:

[0005] The present invention provides a battery-powered impressed current casing cathodic protection internal anti-corrosion device in a wellbore, comprising a battery pack and an auxiliary anode;

[0006] The battery pack is arranged on the oil pipe in the wellbore, and the auxiliary anode is arranged at the lower end of the oil pipe; the outer diameter of the battery pack and the auxiliary anode is equal to the outer diameter of the oil pipe;

[0007] The oil pipe is in contact with the inner wall of the casing, and the internal anti-corrosion device is used in oil, gas and water wells with a produced fluid salinity of 0.5-150 g / L and a bottom hole temperature of <60°C.

[0008] In a specific implementation process, the outer diameter of the battery pack is 73 mm, and the distance from the battery pack to the wellhead is 5 to 25 m.

[0009] In a specific implementation process, the battery pack is composed of several layers of batteries, and the batteries include several lithium hydrogen batteries connected in series.

[0010] In a specific implementation process, the battery capacity of the hydrogen lithium battery is 40A·h.

[0011] In a specific implementation process, the output current of the battery pack is 0.3-0.5A; the output voltage of the battery pack is 1-10V.

[0012] In the specific implementation process, the outer diameter of the auxiliary anode is 73 mm, the working current density of the auxiliary anode is 55-600 A / m; the material power consumption of the auxiliary anode is 10 -6 kg / (A·a).

[0013] In a specific implementation process, the material of the auxiliary anode is one of high silicon cast iron, magnetic iron oxide, and mixed metal plated oxide.

[0014] In the specific implementation process, the battery pack is threadedly connected to the oil pipe, and the auxiliary anode is threadedly connected to the oil pipe; the auxiliary anode is arranged 50 to 100 meters above the perforation section in the wellbore.

[0015] The present invention also provides a method for internal corrosion protection of battery-powered impressed current casing cathodic protection in a wellbore, based on the battery-powered impressed current casing cathodic protection internal corrosion protection device in a wellbore, comprising the following steps:

[0016] The battery pack is arranged on the oil pipe in the wellbore, and the auxiliary anode is arranged at the lower end of the oil pipe;

[0017] When the well pump is inspected, the tubing is lowered so that the tubing contacts the inner wall of the casing and the battery pack applies an impressed current for cathodic protection.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] The present invention provides a battery-powered impressed current casing cathodic protection internal anti-corrosion device in a wellbore. The battery group in the wellbore impressed current on the inner wall of the casing reduces the problem of corrosion in the casing. The cylindrical battery group is brought in through the oil pipe. The capacity of the battery group matches the pump inspection cycle of the oil and water wells. The battery group can be replaced during the pump inspection. The device has long-term effectiveness and stability, and continuously provides protective current to the inner wall of the key corrosion section of the oil and water wells, greatly simplifying the impressed current cathodic protection process and equipment of cluster wells. The DC battery group eliminates electrical processes such as AC transformation, rectification, and voltage stabilization, reduces the casing loss rate of the oil and water wells, and achieves the purpose of improving quality and efficiency. The protective current is transmitted to the inner wall of the casing through the contact point between the oil pipe and the casing, and the protective current is provided from the inner wall of the casing, thereby improving the effect of the internal anti-corrosion technology. The auxiliary anode generates an electric field effect in the key corrosion section, thereby reducing the complexity of the pipe string in the wellbore. In addition, the outer diameter of the battery group and the auxiliary anode in the wellbore of the present invention is the same as that of the oil pipe, so there will be no risk of drill sticking and no impact on the production of the oil and water wells.

[0020] Furthermore, the effective period of power supply of the battery pack in the wellbore of the present invention exceeds 800 days, which is longer than the conventional oil and water well pump inspection cycle and the battery can be replaced following the pump inspection. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 A schematic diagram of the battery-powered impressed current casing cathodic protection internal anti-corrosion device in the wellbore of the present invention;

[0022] Among them: 1- tubing; 2- casing; 3- battery pack; 4- auxiliary anode; 5- perforation section; 6- surface casing; 7- wellhead; 8- bottom of well. DETAILED DESCRIPTION

[0023] In order to enable those skilled in the art to better understand the scheme of the present invention, the technical scheme in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0024] It should be noted that the terms "first", "second", etc. in the specification and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the data used in this way can be interchanged where appropriate, so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units that are clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0025] The present invention is further described in detail below in conjunction with the accompanying drawings:

[0026] like Figure 1 As shown, the present invention provides a battery-powered impressed current casing cathodic protection internal anti-corrosion device in a wellbore, comprising a battery pack 3 and an auxiliary anode 4; the internal anti-corrosion device is arranged in the wellbore.

[0027] The battery pack 3 is arranged on the oil pipe 1 in the wellbore, and the auxiliary anode 4 is arranged at the lower end of the oil pipe 1; the battery pack 3 is threadedly connected to the oil pipe 1, and the auxiliary anode 4 is threadedly connected to the oil pipe 1; the outer diameters of the battery pack 3 and the auxiliary anode 4 are equal to the outer diameter of the oil pipe 1, and the outer diameters of the battery pack 3 and the auxiliary anode 4 in the wellbore are the same as the oil pipe 1, so there is no risk of drill sticking, and the production of oil and water wells is not affected. The inner wall of the casing 2 is in contact with the oil pipe 1, and the protective current is transmitted to the inner wall of the casing through the contact point between the oil pipe 1 and the casing 2. The auxiliary anode 4 generates an electric field effect in the key corrosion section without increasing the complexity of the pipe string in the wellbore.

[0028] The internal anti-corrosion device is used in oil, gas and water wells with produced fluid salinity of 0.5-150g / L and bottom hole temperature of <60℃.

[0029] When inspecting and repairing the oil and water wells, the battery pack 3 and the auxiliary anode 4 are brought into the wellbore along with the oil pipe 1 and connected to the oil pipe 1 through threads, which greatly simplifies the process flow and equipment of the cathodic protection of the cluster wells. The DC battery pack 3 eliminates the electrical processes such as AC transformation, rectification, and voltage stabilization. From the wellhead downward, they are the original production tubing, the battery pack 3, and the auxiliary anode 4; the protection current is provided from the inner wall of the casing, which greatly improves the effect of the internal anti-corrosion technology; the battery pack 3 in the wellbore is used to supply power, which simplifies the process flow and equipment of the cathodic protection of the cluster wells. The DC battery pack eliminates the electrical processes such as AC transformation, rectification, and voltage stabilization.

[0030] The outer diameter of the battery pack 3 is 73 mm, and the distance from the battery pack 3 to the wellhead 7 is 5 to 25 m. The battery pack 3 is composed of several layers of batteries, and the batteries include several hydrogen-lithium batteries connected in series; further, each layer has 4 hydrogen-lithium batteries connected in series, and the battery capacity of each hydrogen-lithium battery is 40A·h; the output current of the battery pack 3 is 0.3 to 0.5A, and the output voltage is 1 to 10V. According to the wellhead protection potential of -0.85V (relative to the copper sulfate reference electrode, referred to as CSE), the minimum validity period of the battery pack 3 is 800 days. The power supply validity period of the battery pack 3 in the wellbore exceeds 800 days, which is longer than the conventional oil and water well pump inspection cycle, and the battery can be replaced following the pump inspection.

[0031] The outer diameter of the auxiliary anode 4 is 73 mm. The auxiliary anode 4 is set 50 to 100 m above the perforation section 5. The material is high silicon cast iron, magnetic iron oxide, mixed metal plated oxide, etc. The working current density of the auxiliary anode 4 is 55 to 600 A / m 2 , material consumption power (mineralization degree in produced fluid 5-150g / L) is 10 -6 kg / (A·a), it has good corrosion resistance and very low consumption rate.

[0032] The present invention also provides a method for internal corrosion protection of battery-powered impressed current casing cathodic protection in a wellbore, comprising the following steps, based on the above-mentioned battery-powered impressed current casing cathodic protection internal corrosion protection device in a wellbore:

[0033] The battery group 3 is arranged on the oil pipe 1 in the wellbore, and the auxiliary anode 4 is arranged at the lower end of the oil pipe 1;

[0034] When the well pump is inspected, the oil pipe 1 is lowered, the oil pipe 1 contacts the inner wall of the casing 2, and the battery group 3 applies an impressed current for cathodic protection.

[0035] The above-mentioned device is placed along the oil pipe 1 and the casing 2 through the wellhead 7 to the bottom of the well 8. The battery group 3 is arranged at a set distance of 5 to 25m from the oil pipe 1 to the wellhead 7, and the auxiliary anode 4 is arranged 50 to 100m above the perforation section 5. The outer diameters of the battery group 3 and the auxiliary anode 4 are equal to the outer diameter of the oil pipe 1. The inner wall of the casing 2 is in contact with the oil pipe 1, and the surface casing 6 is flush with the wellhead 7. The internal anti-corrosion device is used in oil, gas and water wells with a produced fluid salinity of 0.5 to 150g / L and a bottom hole temperature of <60°C.

[0036] Embodiment 1:

[0037] An A well is equipped with a battery-powered impressed current casing cathodic protection and anti-corrosion construction. When the pump is inspected, it is lowered through the wellhead 7. The distance from the pump to the battery pack 3 and the wellhead 7 is 5 meters. The oil pipe 1 is connected to the auxiliary anode 4 for 50 meters above the perforation section 5. The auxiliary anode 4 is high-silicon cast iron and weighs 15 kg.

[0038] The measured protection potential is -0.95V. It is predicted that there will be no casing damage in the five years since the tool was put into the well. The integrity of the inner wall of the casing is monitored through engineering logging.

[0039] Embodiment 2:

[0040] In the well A, a battery-powered impressed current cathodic protection anti-corrosion construction is carried out in the casing. When the pump is inspected, it is lowered through the wellhead 7. The distance from the pump to the battery pack 3 and the wellhead 7 is 15 meters. The auxiliary anode 4 is connected to the oil pipe 1 for 50 meters above the perforation section 5. The auxiliary anode 4 is magnetic iron oxide and weighs 20 kg.

[0041] The measured protection potential is -1.35 V. Since the tool was put into the well, it is predicted that there will be no casing damage in 6.5 years. The integrity of the inner wall of the casing is monitored through engineering logging.

[0042] Embodiment 3:

[0043] In the wellbore of Yuan A Well, a battery-powered impressed current cathodic protection anti-corrosion construction was carried out in the casing. When the pump was inspected, it was lowered through the wellhead 7. The distance from the pump to the battery pack 3 and the wellhead 7 was 25 meters. The oil pipe 1 was connected to the auxiliary anode 4 for 50 meters above the perforation section 5. The auxiliary anode 4 was a mixed metal oxide-plated anode weighing 35 kg.

[0044] The measured protection potential is -1.44 V. Since the tool was put into the well, it is predicted that there will be no casing damage in 4.5 years. The integrity of the inner wall of the casing is monitored through engineering logging.

[0045] Embodiment 4:

[0046] In the wellbore of Yuan A Well, a battery-powered impressed current cathodic protection anti-corrosion construction was carried out in the casing. When the pump was inspected, it was lowered through the wellhead 7. The distance from the pump to the battery pack 3 and the wellhead 7 was 25 meters. The oil pipe 1 was connected to the auxiliary anode 4 for more than 100 meters from the perforation section 5. The auxiliary anode 4 was a mixed metal oxide-plated anode weighing 35 kg.

[0047] The measured protection potential is -1.44 V. Since the tool was put into the well, it is predicted that there will be no casing damage in 4.5 years. The integrity of the inner wall of the casing is monitored through engineering logging.

[0048] The present invention provides a battery-powered impressed current casing cathodic protection internal anti-corrosion device and method in a wellbore. The battery group 3 in the wellbore is used to impressed current on the inner wall of the casing 2 to reduce the corrosion inside the casing 2. The cylindrical battery group is brought in through the oil pipe 2. The capacity of the battery group 3 reaches 2 to 3 years to match the pump inspection cycle of the oil and water wells. The battery group is replaced while the pump is inspected, which has long-term effectiveness and stability, and continuously provides protective current to the inner wall of the key corrosion section of the oil and water wells, simplifies the impressed current cathodic protection process and equipment of cluster wells, and the DC battery group omits the electrical processes such as AC transformation, rectification, and voltage stabilization, thereby reducing the casing loss rate of the oil and water wells and achieving the purpose of improving quality and efficiency.

[0049] The above contents are only for explaining the technical idea of ​​the present invention and cannot be used to limit the protection scope of the present invention. Any changes made on the basis of the technical solution in accordance with the technical idea proposed by the present invention shall fall within the protection scope of the claims of the present invention.

Claims

1. A battery-powered impressed current casing cathodic protection internal anti-corrosion device in a wellbore, characterized in that: It comprises a battery pack (3) and an auxiliary anode (4); The battery group (3) is arranged on the oil pipe (1) in the wellbore, and the auxiliary anode (4) is arranged at the lower end of the oil pipe (1); the outer diameters of the battery group (3) and the auxiliary anode (4) are equal to the outer diameter of the oil pipe (1); the auxiliary anode (4) is arranged above the perforation section (5) in the wellbore; The oil pipe (1) is in contact with the inner wall of the casing (2), and the internal anti-corrosion device is used in oil, gas and water wells where the mineralization of the produced fluid is 0.5-150 g / L and the temperature of the bottom of the well (8) is less than 60°C.

2. The battery-powered impressed current casing cathodic protection internal anti-corrosion device in the wellbore according to claim 1, characterized in that: The outer diameter of the battery pack (3) is 73 mm, and the distance between the battery pack (3) and the wellhead (7) is 5 to 25 m.

3. The battery-powered impressed current casing cathodic protection internal anti-corrosion device in the wellbore according to claim 1, characterized in that: The battery pack (3) is composed of several layers of batteries, and the batteries include several lithium hydrogen batteries connected in series.

4. The battery-powered impressed current casing cathodic protection internal anti-corrosion device in the wellbore according to claim 3, characterized in that: The battery capacity of the lithium hydrogen battery is 40A·h.

5. The battery-powered impressed current casing cathodic protection internal anti-corrosion device in the wellbore according to claim 3, characterized in that: The output current of the battery pack (3) is 0.3-0.5A; the output voltage of the battery pack (3) is 1-10V.

6. The battery-powered impressed current casing cathodic protection internal anti-corrosion device in the wellbore according to claim 1, characterized in that: The outer diameter of the auxiliary anode (4) is 73 mm, the working current density of the auxiliary anode (4) is 55-600 A / m; the material power consumption of the auxiliary anode (4) is 10 -6 kg / (A·a).

7. The battery-powered impressed current casing cathodic protection internal anti-corrosion device in the wellbore according to claim 1 or 6, characterized in that: The material of the auxiliary anode (4) is one of high silicon cast iron, magnetic iron oxide, and mixed metal plated oxide.

8. The battery-powered impressed current casing cathodic protection internal anti-corrosion device in the wellbore according to claim 1, characterized in that: The battery pack (3) is threadedly connected to the oil pipe (1), and the auxiliary anode (4) is threadedly connected to the oil pipe (1).

9. The battery-powered impressed current casing cathodic protection internal anti-corrosion device in the wellbore according to claim 1, characterized in that: The auxiliary anode (4) is arranged 50 to 100 m above the perforation section (5) in the wellbore.

10. A method for internal corrosion protection of battery-powered impressed current casing cathodic protection in a wellbore, characterized in that: The battery-powered impressed current casing cathodic protection internal anti-corrosion device in a wellbore according to any one of claims 1 to 9 comprises the following steps: The battery group (3) is arranged on the oil pipe (1) in the wellbore, and the auxiliary anode (4) is arranged at the lower end of the oil pipe (1); When the well pump is inspected, the oil pipe (1) is lowered, the oil pipe (1) contacts the inner wall of the casing (2), and the battery group (3) applies an impressed current for cathodic protection.

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