Cathodic protection apparatus and method for wellbore internal corrosion prevention using battery powered impressed current casing cathodes

Abstract

The application discloses an inner anticorrosion device and method of a casing cathode protection powered by a battery in a wellbore, and belongs to the technical field of oil exploitation. The inner anticorrosion device comprises a battery pack and an auxiliary anode. The battery pack is arranged on an oil pipe, 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. The inner wall of the casing is in contact with the oil pipe. The inner anticorrosion device is used in an oil-gas-water well with a produced liquid mineralization degree of 0.5-150 g / L and a bottom hole temperature of less than 60 DEG C.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of oil exploitation, and particularly relates to an inner anticorrosion device and method of casing cathodic protection by battery power supply in a wellbore. BACKGROUND

[0002] In the production process of oil fields, casing corrosion is a serious problem. The outer anticorrosion of casing uses technical means such as epoxy coating and cathodic protection to solve the problem of casing corrosion, but in the face of casing internal corrosion, the relatively mature method is to add corrosion inhibitor for corrosion protection, for example, a kind of oil casing inner anticorrosion coating process in Chinese patent, which separates metal from corrosive medium by coating inside the oil casing to achieve the effect of corrosion protection; a kind of oil production well casing inner anticorrosion method in Chinese patent, which changes the oil casing annulus oil-water separation protection casing by extending the pump hanging to the upper end of the perforation section, but its operation method is complex, which increases the complexity of the inner string of the wellbore; and the technology of using tubing to bring in anode, which is insulated from the tubing and contacts the inner wall of the casing through the metal touch wall, to protect the inner wall of the casing, but when the perforation section is deep, many tubing anodes are lowered and the lower position is deep, the disadvantage of sticking occurs. SUMMARY

[0003] In order to overcome the above-mentioned shortcomings of the prior art, the purpose of the present application is to provide an inner anticorrosion device and method of casing cathodic protection by battery power supply in a wellbore, which solves the problem of complex existing inner anticorrosion technology, reduces the complexity of the inner string of the wellbore and avoids the disadvantage of sticking when the perforation section is deep, many tubing anodes are lowered and the lower position is deep.

[0004] In order to achieve the above-mentioned purpose, the present application adopts the following technical scheme:

[0005] The present application provides an inner anticorrosion device of casing cathodic protection by battery power supply in a wellbore, which comprises a battery pack and an auxiliary anode.

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

[0007] The tubing contacts the inner wall of the casing, and the inner anticorrosion device is used in oil and gas water wells with produced liquid salinity of 0.5-150 g / L and bottom hole temperature <60℃.

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

[0009] In the specific implementation process, the battery pack is composed of several layers of batteries, and the battery comprises several series of lithium-hydrogen batteries.

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

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

[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, and the material consumption power of the auxiliary anode is 10 -6 kg / (A·a).

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

[0014] In the specific implementation process, the battery pack is threadedly connected with the oil pipe, and the auxiliary anode is threadedly connected with the oil pipe; the auxiliary anode is arranged at a position 50-100 m above the perforated section in the wellbore.

[0015] The application further provides an internal anticorrosion method of battery-powered impressed current casing cathodic protection in a wellbore, based on the internal anticorrosion device of battery-powered impressed current casing cathodic protection 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 oil pipe is lowered, the oil pipe is in contact with the inner wall of the casing, and the battery pack applies impressed current for cathodic protection.

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

[0019] The application provides an internal anticorrosion device of battery-powered impressed current casing cathodic protection in a wellbore, which reduces the corrosion problem in the casing by applying impressed current to the inner wall of the casing through a battery pack in the wellbore; the cylindrical battery pack is brought in through the oil pipe; the battery capacity of the battery pack is matched with the oil-water well pump inspection period; the battery pack can be replaced when the well pump is inspected; the device has long-term effectiveness and stability, continuously provides protection current to the inner wall of the key corrosion section of the oil-water well, greatly simplifies the impressed current cathodic protection process flow and equipment of cluster wells; the direct-current battery pack saves the electrical processes such as alternating current transformation, rectification and voltage stabilization, reduces the casing damage rate of the oil-water well, and achieves the purpose of improving quality and efficiency; the protection current is transmitted to the inner wall of the casing through the contact position of the oil pipe and the casing, and the protection current is provided from the inner wall of the casing, thereby improving the technical effect of internal anticorrosion; the auxiliary anode generates an electric field in the key corrosion section, thereby reducing the complexity of the pipe string in the wellbore; and the outer diameters of the battery pack and the auxiliary anode in the application are the same as those of the oil pipe, so that the risk of sticking the drill pipe is avoided, and the production of the oil-water well is not affected.

[0020] Further, the battery pack power supply effective period of the wellbore battery is more than 800 days, which is greater than the conventional oil and water well pump inspection period and can follow the pump inspection to replace the battery. BRIEF DESCRIPTION OF DRAWINGS

[0021] Figure 1 The figure is a schematic diagram of the wellbore battery power supply impressed current casing cathodic protection internal anticorrosion device of the present application.

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

[0023] In order to make the personnel in the technical field better understand the present application scheme, the technical scheme in the embodiment of the present application will be described clearly and completely in combination with the drawings in the embodiment of the present application. Obviously, the described embodiment is only a part of the embodiment of the present application, not all. Based on the embodiment in the present application, all other embodiments obtained by the person skilled in the art without creative labor should belong to the scope of protection of the present application.

[0024] It should be noted that the terms "first", "second" and the like in the specification and claims of the present application and the above-mentioned drawings are used to distinguish similar objects, and do not necessarily indicate a specific order or sequence. It should be understood that the data thus used can be interchanged under appropriate circumstances, so that the embodiments of the present application described herein can be implemented in an order other than that illustrated or described herein. In addition, the terms "include" and "have" and any variations thereof are intended to cover non-exclusive inclusion, for example, a process, method, system, product or device including a series of steps or units does not necessarily limit to those steps or units clearly listed, but can include other steps or units not clearly listed or inherent to these processes, methods, products or devices.

[0025] The present application will be described in further detail below in combination with the drawings:

[0026] As Figure 1 shown, the present application provides a wellbore battery power supply impressed current casing cathodic protection internal anticorrosion device, which comprises a battery pack 3 and an assistant anode 4; the internal anticorrosion 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 with the oil pipe 1, and the auxiliary anode 4 is threadedly connected with 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, the outer diameters of the battery pack 3 and the auxiliary anode 4 in the wellbore are the same as that of the oil pipe 1, no risk of sticking occurs, the production of the oil and water well is not affected, the inner wall of the casing 2 is in contact with the oil pipe 1, the current is protected from being transmitted to the inner wall of the casing through the contact position of the oil pipe 1 and the casing 2, and the auxiliary anode 4 produces an electric field effect in the key corrosion section without increasing the complexity of the string in the wellbore.

[0028] The internal corrosion prevention device is used in an oil and gas water well with a produced liquid salinity of 0.5-150 g / L and a bottom hole temperature of <60℃.

[0029] During pump inspection and well repair of the oil and water well, the battery pack 3 and the auxiliary anode 4 are brought into the wellbore with the oil pipe 1, and the connection with the oil pipe 1 through threads greatly simplifies the process flow and equipment of the external current cathodic protection technology of the cluster well, the direct-current battery pack saves the electrical processes such as AC voltage transformation, rectification and voltage stabilization, and the original production string, the battery pack 3 and the auxiliary anode 4 are sequentially arranged from the wellhead; the protection current is provided from the inner wall of the casing, and the effect of the internal corrosion prevention technology is greatly improved; the use of the battery pack 3 in the wellbore for power supply simplifies the process flow and equipment of the external current cathodic protection technology of the cluster well, and the direct-current battery pack saves the electrical processes such as AC voltage transformation, rectification and voltage stabilization.

[0030] The outer diameter of the battery pack 3 is 73 mm, the length distance of the battery pack 3 to the wellhead 7 is 5-25 m, the battery pack 3 is composed of a plurality of layers of batteries, and each battery comprises a plurality of series-connected lithium-hydrogen batteries; further, four lithium-hydrogen batteries in each layer are connected in series, and the battery capacity of each lithium-hydrogen battery is 40 A·h; the output current of the battery pack 3 is 0.3-0.5 A, the output voltage is 1-10 V, according to the wellhead protection potential of -0.85 V (relative to the copper sulfate reference electrode, referred to as CSE), the minimum effective period of the battery pack 3 is 800 days. The power supply effective period of the battery pack 3 in the wellbore is more than 800 days, which is greater than the conventional pump inspection period of the oil and water well, 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 arranged at a position 50-100 m away from the perforation section 5, the material is one of high-silicon cast iron, magnetic iron oxide and mixed metal oxide plating, and the working current density of the auxiliary anode 4 is 55-600 A / m 2 , the material consumption power (in the produced liquid with a salinity of 5-150 g / L) is 10 -6 kg / (A·a), the corrosion resistance is good, and the consumption rate is very low.

[0032] The application also provides an anticorrosion method of the battery-powered impressed current casing cathodic protection in a wellbore, which comprises the following steps based on the anticorrosion device of the battery-powered impressed current casing cathodic protection in a wellbore:

[0033] 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.

[0034] When the well is pumped, the oil pipe 1 is lowered and is in contact with the inner wall of the casing 2, and the battery pack 3 applies impressed current for cathodic protection.

[0035] The device is lowered to the bottom 8 of the well through the wellhead 7 along the oil pipe 1 and the casing 2, the battery pack 3 is arranged at a distance of 5-25 m from the wellhead 7, the auxiliary anode 4 is arranged above the perforation section 5 at a distance of 50-100 m, the outer diameter of the battery pack 3 and the auxiliary anode 4 is 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 anticorrosion device is used in an oil, gas and water well with a produced liquid salinity of 0.5-150 g / L and a bottom temperature of <60℃.

[0036] Example 1

[0037] The anticorrosion construction of the battery-powered impressed current casing cathodic protection in the wellbore of An A well is carried out, when the well is pumped, the battery pack 3 is lowered through the wellhead 7, the distance from the battery pack 3 to the wellhead 7 is 5 m, the oil pipe 1 is connected with the auxiliary anode 4 above the perforation section 5 at a distance of 50 m, and the auxiliary anode 4 is high-silicon cast iron with a weight of 15 kg.

[0038] The protection potential is measured as -0.95 V, and it is predicted that the casing will not be damaged for 5 years after the tool is lowered into the well, and whether the inner wall of the casing is intact is monitored by engineering logging.

[0039] Example 2

[0040] The anticorrosion construction of the battery-powered impressed current casing cathodic protection in the wellbore of Li A well is carried out, when the well is pumped, the battery pack 3 is lowered through the wellhead 7, the distance from the battery pack 3 to the wellhead 7 is 15 m, the oil pipe 1 is connected with the auxiliary anode 4 above the perforation section 5 at a distance of 50 m, and the auxiliary anode 4 is magnetic iron oxide with a weight of 20 kg.

[0041] The protection potential is measured as -1.35 V, and it is predicted that the casing will not be damaged for 6.5 years after the tool is lowered into the well, and whether the inner wall of the casing is intact is monitored by engineering logging.

[0042] Example 3

[0043] The well A is constructed by the battery-powered impressed current casing internal cathodic protection anticorrosion, when the pump is checked, the battery group 3 is lowered to the distance of 25 meters from the well head 7, the auxiliary anode 4 is connected above the perforated section 5 to the oil pipe 1 for 50 meters, the auxiliary anode 4 is mixed metal plated oxide, and the weight is 35 kg.

[0044] The measured protection potential is -1.44V. Since the tool is put into the well, it is predicted that the casing is not damaged for 4.5 years, and whether the inner wall of the casing is intact is monitored by engineering logging.

[0045] Example 4:

[0046] The well A is constructed by the battery-powered impressed current casing internal cathodic protection anticorrosion, when the pump is checked, the battery group 3 is lowered to the distance of 25 meters from the well head 7, the auxiliary anode 4 is connected above the perforated section 5 to the oil pipe 1 for 50 meters, the auxiliary anode 4 is mixed metal plated oxide, and the weight is 35 kg.

[0047] The measured protection potential is -1.44V. Since the tool is put into the well, it is predicted that the casing is not damaged for 4.5 years, and whether the inner wall of the casing is intact is monitored by engineering logging.

[0048] The present application provides a kind of wellbore battery-powered impressed current casing cathodic protection internal anticorrosion device and method, the inner wall of casing 2 is reduced by the battery group 3 in wellbore to the impressed current of casing 2, cylindrical battery group is brought in by oil pipe 2, the capacity of battery group 3 reaches 2-3 years and matches with oil-water well pump inspection period, and battery group is replaced while pump is checked, with long-acting, stability, it provides protection current to the inner wall of oil-water well key corrosion section continuously, simplify the impressed current cathodic protection process flow and equipment of cluster well, direct current battery group eliminates alternating current voltage, rectification, voltage stabilizing etc. Electrical process, reduce the casing damage rate of oil-water well, reach the purpose of quality and efficiency.

[0049] The above content is only for describing the technical idea of the present application, and cannot limit the protection scope of the present application, any modification made according to the technical idea of the present application on the basis of technical scheme falls within the protection scope of the claims of the present application.

Claims

1. A battery-powered, externally applied current bushing cathodic protection internal corrosion protection device for well casing, characterized in that, Includes battery pack (3) and auxiliary anode (4); The battery pack (3) is installed on the tubing (1) inside the wellbore, and the auxiliary anode (4) is installed at the lower end of the tubing (1); the outer diameter of the battery pack (3) and the auxiliary anode (4) is equal to the outer diameter of the tubing (1); the auxiliary anode (4) is installed above the perforation section (5) inside the wellbore. The tubing (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 salinity of the produced fluid is 0.5~150g / L and the temperature at the bottom of the well (8) is <60℃. The battery pack (3) is composed of several layers of batteries, including several lithium hydrogen batteries connected in series; 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).

2. The internal corrosion protection device for battery-powered impressed current bushing cathodic protection in wellbore as described in claim 1, characterized in that, The outer diameter of the battery pack (3) is 73 mm, and the distance from the battery pack (3) to the wellhead (7) is 5~25 m.

3. The internal corrosion protection device for battery-powered impressed current bushing cathodic protection in wellbore as described in claim 1, characterized in that, The capacity of the lithium hydrogen battery is 40A·h.

4. The internal corrosion protection device for battery-powered impressed current bushing cathodic protection in wellbore as described in claim 1, 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.

5. The internal corrosion protection device for battery-powered impressed current bushing cathodic protection in wellbore as described in claim 1, characterized in that, The auxiliary anode (4) has an outer diameter of 73 mm and an operating current density of 55~600 A / m; the material consumption power of the auxiliary anode (4) is 10. -6 kg / (A·a) 6. The internal corrosion protection device for battery-powered impressed current bushing cathodic protection in wellbore as described in claim 1 or 5, characterized in that, The auxiliary anode (4) is made of one of the following materials: high silicon cast iron, magnetic iron oxide, or mixed metal oxide.

7. The internal corrosion protection device for battery-powered impressed current bushing cathodic protection in wellbore as described in claim 1, characterized in that, The auxiliary anode (4) is located 50-100m above the perforation section (5) inside the wellbore.

8. A method for internal corrosion prevention of a battery-powered, externally current-driven bushing with cathodic protection in a wellbore, characterized in that... The wellbore battery-powered impressed current bushing cathodic protection internal corrosion protection device according to any one of claims 1 to 7 includes the following steps: The battery pack (3) is installed on the oil pipe (1) inside the wellbore, and the auxiliary anode (4) is installed at the lower end of the oil pipe (1); When the well is inspected, the tubing (1) is lowered and the tubing (1) comes into contact with the inner wall of the casing (2). The battery pack (3) applies an external current for cathodic protection.

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