Anode well structure, system and method for casing cathodic protection of a cluster well group

Abstract

The present invention belongs to the technical field of oilfield mining equipment, and specifically relates to an anode well structure, system and method for cathodic protection of cluster well casing. The anode well structure of the present invention includes an anode well shaft and at least two sets of anode body mechanisms; the two sets of anode body mechanisms are vertically placed in the anode well shaft and can operate independently. The anode well, cathode well, remote monitoring PC, digital cathodic protection monitoring cabinet and copper sulfate reference electrode constitute the cluster well casing cathodic protection system. The present invention adopts two anode body mechanisms, one main and one backup, which effectively extends the service life of the anode well. When the electron release capacity of the main and backup anode bodies cannot meet the system operation requirements when used simultaneously, the anode cores in the main and backup anode bodies can be extracted and replaced to enable the system to work normally, thereby achieving the purpose of reusing the anode bed, avoiding the work of repeated well drilling, and the replacement is simple and the construction period is short, which not only saves the cost of re-drilling the anode well, but also is beneficial to the environmental protection of the well site.

Description

Technical Field

[0001] The invention belongs to the technical field of oilfield mining equipment, and in particular relates to an anode well structure, system and method for cluster well group casing cathodic protection. Background Art

[0002] To adapt to the harsh external environment of oilfields, increase operational reliability, and reduce costs, the cathodic protection process for cluster wells utilizes a well group as a unit, with casing as the primary focus. Cluster well group cathodic protection implements this principle by connecting the negative terminal of a DC power supply to the casing of each individual well and the positive terminal of the DC power supply to the anode body of the anode well, thus forming a protection circuit.

[0003] As oilfield development progresses, corrosion of cluster well casing is becoming increasingly severe, with the rate accelerating in recent years. This directly impacts further oilfield production, poses a significant threat to stable production, and results in significant economic losses. The well sites are widely distributed and lack dedicated patrol and management personnel. Existing anode wells are open-hole completions, drilling through deep loess layers until the cliff rock layer reaches the water layer, typically to a depth of 200 to 300 meters. After a period of operation, the wellbore is prone to collapse, burying the anode body and pipelines. Anode well failures are difficult to repair and require reconstruction. Once the anode body is worn out, it cannot be directly replaced; reconstruction is required. Rebuilding a new anode well is costly, wasteful, and increases maintenance costs. Furthermore, maintenance personnel cannot be dispatched promptly after a failure, resulting in delays in management and maintenance, weakening the effectiveness of cathodic protection.

[0004] In summary, it is urgent to invent an anode well structure, system and method for cathodic protection of cluster well casing to meet the requirements of oil field development. Summary of the Invention

[0005] In order to improve the dust removal effect and enhance the performance of equipment, the present invention provides an anode well structure, system and method for cathodic protection of cluster well casing.

[0006] In order to achieve the above object, the technical solution adopted by the present invention is:

[0007] An anode well structure for cluster well casing cathodic protection comprises an anode well shaft and at least two sets of anode body mechanisms; the two sets of anode body mechanisms are both vertically placed in the anode well shaft and can operate independently.

[0008] The two sets of anode body mechanisms are a backup anode body mechanism and a main anode body mechanism, and both have the same structure.

[0009] The spare anode body mechanism comprises an anode well exhaust pipe and a spare anode body; the anode well exhaust pipe is connected to the upper end of the spare anode body and passes through the middle thereof.

[0010] The upper port of the spare anode body is provided with a steel sleeve flange for connecting to the exhaust pipe.

[0011] The spare anode body includes an anode body steel casing, a first cable, two anode cores connected in series up and down, and an anode string counterweight; the first cable, the two anode cores connected in series up and down, and the anode string counterweight are all placed in the anode body steel casing, and the two anode cores and the anode string counterweight are suspended in sequence from top to bottom at the lower end of the first cable; the mixed metal oxide titanium pole core leads of the two anode body anode cores are connected in parallel with the first cable; the upper end of the anode body steel casing is connected to the exhaust pipe, and a through hole is opened on its lower side wall.

[0012] The lower end of the anode steel sleeve is tapered.

[0013] The anode core is a metal oxide cylindrical titanium anode core.

[0014] The anode core adopts MMO / TI noble metal oxide anode, the outer surface is plated with platinum tantalum, the breakdown voltage is 160V, and the resistivity of the oxide coating is 10-7Ω.m.

[0015] A cluster well casing cathodic protection system includes at least one anode well structure for the cluster well casing cathodic protection, a cathode well, a remote monitoring PC, a digital cathodic protection monitoring cabinet, and a copper sulfate reference electrode; the cathode well is composed of oil and water well casing and an oil and water well shaft; the oil and water well casing is placed in the oil and water well shaft; the remote monitoring PC is electrically connected to the digital cathodic protection monitoring cabinet; the digital cathodic protection monitoring cabinet is electrically connected to the oil and water well casing in the cathode well and a first cable in the anode well; and the digital cathodic protection monitoring cabinet is grounded via the copper sulfate reference electrode.

[0016] A method for replacing cores in anode wells for cathodic protection of cluster well casings comprises the following steps:

[0017] Step 1: When the digital cathodic protection monitoring cabinet or the remote monitoring PC detects through the copper sulfate reference electrode that the protection potentials of the backup anode body mechanism and the main anode body mechanism do not meet the requirements or the detection potential value is zero, the power is cut off and the first cable connection between the digital cathodic protection monitoring cabinet and the backup anode body mechanism and the main anode body mechanism is disconnected;

[0018] Step 2: Pull out the old anode core from the exhaust pipe of the spare anode body mechanism and the main anode body mechanism through the first cable, replace it with a new anode core, and then lower it into the anode body steel casing through the exhaust pipe;

[0019] Step 3: Connect the first cable on the digital cathodic protection monitoring cabinet. After power is turned on, when the normal protection potential value can be detected on the digital cathodic protection monitoring cabinet or the remote monitoring PC, the replacement of the double anode core in the anode well is completed.

[0020] Beneficial effects:

[0021] (1) The present invention adopts a cluster well group casing cathodic protection double anode core extraction anode well, and adopts two anode bodies, one for main use and one for backup, which effectively prolongs the service life of the anode well.

[0022] (2) The wellbore of the present invention is cemented with steel casing throughout the entire section, down to the cliff rock layer at the bottom of the well. When the electron release capacity of both the main and backup anode bodies cannot meet the system operation requirements, the anode core in the main and backup anode bodies can be extracted and replaced through the first cable from the exhaust pipe, and then a new anode core can be lowered to enable the system to operate normally, thereby achieving the purpose of reusing the anode bed and avoiding the repeated drilling of wells. The replacement is simple and the construction period is short, thus filling the gap period of cathodic protection of cluster well groups, extending the service life of anode wells, and saving the cost of re-drilling anode wells. The economic benefits are obvious, and it is also beneficial to the well site environmental protection, achieving and meeting the needs of oil field development.

[0023] The above description is only an overview of the technical solution of the present invention. In order to more clearly understand the technical means of the present invention and implement it according to the contents of the specification, the preferred embodiments of the present invention are described in detail below. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0025] Figure 1 It is a structural schematic diagram of the present invention.

[0026] In the figure: 1-remote monitoring PC; 2-optical fiber; 3-digital cathodic protection monitoring cabinet; 4-second cable; 5-oil and water well casing; 6-oil and water well shaft; 7-copper sulfate reference electrode; 8-anode well exhaust pipe; 9-first cable; 10-anode well shaft; 11-anode well water level; 12-main anode body; 13-spare anode body; 14-anode core; 15-mixed metal oxide titanium electrode core lead; 16-through hole; 17-concrete weight; 18-cliff stone layer.

[0027] The above description is only an overview of the technical solution of the present invention. In order to more clearly understand the technical means of the present invention and implement it according to the contents of the specification, the following is a detailed description of the preferred embodiments of the present invention. DETAILED DESCRIPTION

[0028] The following will clearly and completely describe the technical solutions of the present invention in conjunction with the embodiments. Obviously, the embodiments described are only some of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0029] Example 1:

[0030] Reference Figure 1 The anode well structure for cluster well group casing cathodic protection shown includes an anode well shaft 10 and at least two sets of anode body mechanisms; the two sets of anode body mechanisms are both vertically placed in the anode well shaft 10 and can operate independently.

[0031] In practice, the entire anode wellbore 10 was cemented with steel casing, extending all the way to the rock formation at the bottom of the wellbore. Based on the casing protection potential requirements for cluster well groups, the anode body mechanism was configured with one primary and one backup. This effectively extended the anode well's service life and saved the cost of re-drilling the anode well.

[0032] Example 2:

[0033] Reference Figure 1 The anode well structure for cathodic protection of a cluster well group casing shown is based on the first embodiment, and the two sets of anode body mechanisms are a backup anode body mechanism and a main anode body mechanism, and the two have the same structure.

[0034] Furthermore, the backup anode body mechanism includes an anode well exhaust pipe 8 and a backup anode body 13; the anode well exhaust pipe 8 is connected to the upper end of the backup anode body 13 and penetrates the middle thereof.

[0035] In actual use, the two sets of anode body mechanisms are a backup anode body mechanism and a main anode body mechanism. The main anode body mechanism is used to work first. When the electron release ability of the main anode body mechanism decays to the point where it cannot meet the system operation requirements or the anode body fails, the backup anode body mechanism is used to work.

[0036] The technical solution of using the spare anode body mechanism and the main anode body mechanism with the same structure makes the anode body mechanism work stably and is easy to replace.

[0037] The anode well exhaust pipe 8 is connected to the upper end of the spare anode body 13 and the middle thereof is passed through, so as to facilitate the replacement of the pole core 14 .

[0038] Example 3:

[0039] Reference Figure 1 The anode well structure for the cathodic protection of a cluster well group casing shown is based on the second embodiment, and the upper port of the spare anode body 13 is provided with a steel casing flange for connecting to the exhaust pipe 8.

[0040] In actual use, the spare anode body 13 adopts this technical solution, which can conveniently connect the spare anode body 13 to the exhaust pipe 8.

[0041] Example 4:

[0042] Reference Figure 1 The anode well structure for cluster well group casing cathodic protection shown is based on the second embodiment, wherein the spare anode body 13 includes an anode body steel casing, a first cable 9, two anode cores 14 connected in series up and down, and an anode string counterweight 17; the first cable 9, the two anode cores 14 connected in series up and down, and the anode string counterweight 17 are all placed in the anode body steel casing, and the two anode cores 14 and the anode string counterweight 17 are suspended in sequence from top to bottom at the lower end of the first cable 9; the mixed metal oxide titanium core leads 15 of the two anode body anode cores 14 are connected in parallel with the first cable 9; the upper end of the anode body steel casing is connected to the exhaust pipe 8, and a through hole 16 is opened on its lower side wall.

[0043] Furthermore, the lower end of the anode steel casing is tapered.

[0044] Furthermore, the anode core 14 is a metal oxide cylindrical titanium anode core.

[0045] Furthermore, the anode core 14 is made of MMO / TI noble metal oxide anode, with platinum-plated tantalum on the outside, a breakdown voltage of 160V, and an oxide coating resistivity of 10-7Ω.m.

[0046] In actual use, a mixed metal oxide cylindrical titanium anode core 14 is suspended within the anode body steel casing via a first cable 9. The first cable 9 is a single-core cable, which ensures that the transmitted voltage and current signals have strong anti-interference performance and are not easily attenuated. Based on the protection potential requirements of the cluster well casing, two anode body systems are used, one primary and one backup. During initial operation, the primary anode body 12 operates. When the electron capacity released by the mixed metal oxide cylindrical titanium anode core 14 within the primary anode body 12 decays to a point where it cannot meet the system's operating requirements or a fault occurs, the backup anode body 13 is connected to operate. If the mixed metal oxide cylindrical titanium anode core 14 within the primary anode body 12 or the backup anode body 13 fails or the protection potential fails to meet the requirements, the old anode core 14 is removed from the anode well exhaust pipe 8 via the first cable 9. A new anode core 14 is then lowered through the anode well exhaust pipe 8 into the anode body steel casing, enabling the system to operate normally and achieving the goal of reusing the anode bed. The mixed metal oxide titanium core leads 15 of the two anode bodies in the main anode body 12 and the backup anode body 13 are connected in parallel to the first cable 9. The mixed metal oxide titanium core leads 15 are conventional. Each anode core 14 is connected by a separate first cable 9, so that if a problem with one cable does not affect the normal operation of other anodes.

[0047] The oilfield in this embodiment is located in deep loess, with thick, dry strata and low water content. The depth of the anode well directly affects the anode grounding resistance, which is generally less than 10Ω. The anode must be drilled through the loess layer until the cliff layer reaches the water layer, typically to a depth of 250-300 meters. Therefore, to prevent the well wall from collapsing after a period of operation, which could bury the anode body and pipelines, a plastic casing is installed after the anode well is drilled, typically 6-10 meters below the ground, depending on the anode well type and soil conditions. This limits the release of the cathodic protection current to near the surface, reducing corrosion interference with other metal structures.

[0048] The entire anode wellbore 10 is cemented with steel casing down to the lower cliff layer. 15 to 20 meters from the cliff layer, the anode body steel casing is uniformly provided with 10mm circular holes 16 around its perimeter to facilitate water inflow and enable the full operation of the metal oxide-containing cylindrical titanium anode core 14. When determining the anode well diameter, the space occupied by two 80mm diameter anode well exhaust pipes 8 should be fully considered. The anode well diameter is selected to be 300mm. Strict control should be exercised over the installation of the anode body, and the anode well diameter should be increased for higher output currents. Using steel casing cementing and maintaining the anode well water level 11 within the anode wellbore 10 prevents well wall collapse, avoids burying the anode body and exhaust pipe 8, and limits the release of cathodic protection current from near the surface.

[0049] The prefabricated anode steel casing has an outer diameter of 120 mm x 3000 mm and an inner diameter of 110 mm x 3000 mm. It connects to the 80 mm anode well exhaust pipe 8 via a steel casing flange at its upper end. The lower end of the anode steel casing is tapered, resting on a cliff rock layer 18. Through-holes 16 are located on both sides of the lower middle portion of the anode steel casing to facilitate water ingress into the anode cavity and reduce the grounding resistance of the mixed metal oxide cylindrical titanium anode core. Each anode cavity consists of two titanium anode cores. To ensure the smooth descent of the two series-connected anode cores 14 to the bottom of the anode string, an anode string counterweight 17 is attached to the bottom of the anode string. The counterweight 17 is typically a concrete block weighing between 2 and 3 kg and is connected to the bottom of the anode string with a plastic rope. The distance between the anode well and the oil and water well casing 5 of the cluster well group in the dual anode system is designed to be at least 200 meters, ensuring more uniform distribution of the protective current while minimizing corrosion interference with other buried metal structures.

[0050] In this embodiment, through holes 16 are provided in the lower and middle parts of both sides of the anode body steel casing in the main anode body 12 and the spare anode body 13. A soft cloth made of a water-absorbent material is wrapped around the walls of the anode body steel casing to cover the through holes 16, so as to facilitate long-term, sufficient and uniform water supply to the mixed metal oxide anode core.

[0051] Mixed metal oxide cylindrical anode core 14 adopts MMO / TI noble metal oxide anode, with platinum-plated tantalum on the outside, breakdown voltage is 160V, resistivity of oxide coating is 10-7Ω.m, the electrode is 100A / m 2 Operating at the operating current density, it has a service life of 20 years and a consumption rate of 2 mg / Aa. Its outer diameter is Φ25×1000. To facilitate installation and ensure quality, it is suspended inside the anode body cavity. The mixed metal oxide cylindrical anode core 14 can be evenly activated and dissolved in the aqueous medium, has excellent electrochemical properties, and has a strong self-regulating ability to emit current. The use of the mixed metal oxide cylindrical anode core 14 protects the oil and water well casing 5 of the cluster well group from corrosion in high-temperature environments, extending its service life and significantly reducing losses caused by corrosion and improving economic benefits.

[0052] The mixed metal oxide cylindrical anode core 14 has the advantages of no consumption, large current output, small size and light weight. Since the anode reaction will produce chlorine during operation, the first cable 9 is in an acidic medium. Therefore, the insulation layer of the first cable 9 must be able to resist the corrosion of chlorine. The insulation layer of the first cable 9 is PVDF / HMW-PE with a cross-sectional area of 16mm. 2 .

[0053] In addition to removing gas and reducing air resistance, the anode well exhaust pipe 8 can also be used to dissipate heat and re-inject water. In this embodiment, a PVC pipe is selected, and the outer diameter of the exhaust pipe is Φ80. When installing the anode body, the anode well exhaust pipe 8 can be used to assist in the installation of the anode body 12 and the spare anode body 13.

[0054] Embodiment 5:

[0055] Reference Figure 1 The cluster well group casing cathodic protection system shown includes at least an anode well structure for the cluster well group casing cathodic protection, and also includes a cathode well, a remote monitoring PC 1, a digital cathodic protection monitoring cabinet 3 and a copper sulfate reference electrode 7; the cathode well is composed of an oil and water well casing 5 and an oil and water well wellbore 6; the oil and water well casing 5 is placed in the oil and water well wellbore 6; the remote monitoring PC 1 is electrically connected to the digital cathodic protection monitoring cabinet 3; the digital cathodic protection monitoring cabinet 3 is electrically connected to the oil and water well casing 5 in the cathode well and the first cable 9 in the anode well respectively; the digital cathodic protection monitoring cabinet 3 is grounded through the copper sulfate reference electrode 7.

[0056] In actual use, the DC power supply in the digital cathodic protection monitoring cabinet 3 primarily consists of a power supply system consisting of a dual-circuit adjustable parallel switching power supply and a remote control terminal RTU module. It has an output voltage of 0-120V DC and a maximum current of 60A, capable of providing 4-5A of cathodic protection to each of nine oil and water well casings. The negative terminal of the DC power supply is connected to each oil and water well casing 5 via a second cable 4, and the positive terminal of the DC power supply is connected to a first cable 9 from the anode well. During operation of the cluster well casing cathodic protection system, the digital cathodic protection monitoring cabinet 3 operates based on the protection potential value provided by the copper sulfate reference electrode 7. The remote monitoring PC 1 enables remote monitoring of the cluster well casing cathodic protection via optical fiber 2, facilitating timely maintenance and comprehensive monitoring.

[0057] The copper sulfate reference electrode 7 in this embodiment has a specification of Φ95×200. The potential drift relative to the standard hydrogen electrode is +316mv, and the potential drift does not exceed ±10mv. When a current of 500μ passes through, the potential shift does not exceed ±5mv. The working density is ≦5μ / cm 2 A saturated copper sulfate solution containing chemically pure copper sulfate crystals has a service life of >10 years. A copper sulfate reference electrode 7 is buried 10 meters underground and 1.5 meters deep, 10 meters from the oil and water well casing. The copper sulfate reference electrode 7 measures the cathodic protection potential, displays it on a digital cathodic protection monitoring cabinet 3, and uploads it to a remote monitoring PC 1 via optical fiber 2 for remote monitoring.

[0058] The digital cathode protection monitoring cabinet 3 and the remote monitoring PC 1 both adopt existing technologies.

[0059] The main technical parameters of the digital cathodic protection monitoring cabinet 3 are as follows:

[0060] 1. Working environment: -20~+70℃, relative humidity ≤85%.

[0061] 2. Working power supply: AC220V±10%, 50Hz.

[0062] 3. Digital display: Four-digit 0.36-inch digital tube, maximum display 0 to 9999.

[0063] 4. Display accuracy: ±0.5%.

[0064] 5. Maximum output DC voltage: 0~120VDC.

[0065] 6. Output DC voltage accuracy: ±1%.

[0066] 7. Output rated current: 60A.

[0067] 8. Output over-power protection: 110%~130%.

[0068] In this embodiment, the second cable 4 is buried 1200 mm deep underground and then connected to the first cable 9 and the oil and water well casing 5. This can ensure that the cable is not easily broken by a vehicle on the one hand, and secondly, it effectively prevents external corrosion of the oil and water well casing.

[0069] Example 6:

[0070] A method for replacing cores in anode wells for cathodic protection of cluster well casings comprises the following steps:

[0071] Step 1: When the digital cathodic protection monitoring cabinet 3 or the remote monitoring PC 1 detects through the copper sulfate reference electrode 7 that the protection potentials of the backup anode body mechanism and the main anode body mechanism do not meet the requirements or the detection potential value is zero, the power is cut off and the first cable 9 connected to the digital cathodic protection monitoring cabinet 3 and the backup anode body mechanism and the main anode body mechanism is disconnected;

[0072] Step 2: Pull out the old anode core 14 from the exhaust pipe 8 of the spare anode body mechanism and the main anode body mechanism through the first cable 9, replace it with a new anode core 14, and lower it into the anode body steel casing through the exhaust pipe 8;

[0073] Step 3: Connect the first cable 9 on the digital cathodic protection monitoring cabinet 3, and after power is turned on, when the normal protection potential value can be detected on the digital cathodic protection monitoring cabinet 3 or the remote monitoring PC 1, the replacement of the double anode core in the anode well is completed.

[0074] In actual use, the entire section of the anode wellbore 10 is cemented with steel casing, extending all the way to the cliff rock layer below the well. The adoption of the technical solution of the present invention achieves the goal of reusing the anode bed, avoiding the need for repeated drilling work, and is simple to replace with a short construction period. This fills the gap in cathodic protection of the cluster well casing, extends the service life of the anode well, and saves the cost of re-drilling the anode well. This has significant economic benefits, is also beneficial to well site environmental protection, and meets the needs of oilfield development.

[0075] The cathodic protection of a cluster well casing is calculated by replacing the anode body once every five years on average, saving 90,000 yuan in new well drilling costs each time. Within the 25-year service life of the oil well, a single well group can save 450,000 yuan. This is the direction of development of forced current cathodic protection technology, effectively curbing the casing damage of cluster well groups in oil fields, and serving as a reference and demonstration for the corrosion protection of oil and water well casing in domestic and foreign oil fields.

[0076] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

[0077] In the absence of conflicts, those skilled in the art may combine the relevant technical features in the above examples according to actual circumstances to achieve corresponding technical effects. Specific descriptions of various combinations are omitted here.

[0078] It should be noted that all directional indications in the embodiments of the present invention (such as up, down, left, right, front, back, etc.) are only used to explain the relative position relationship, movement status, etc. between the various components under a certain specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indication will also change accordingly.

[0079] The above descriptions are merely preferred embodiments of the present invention. The present invention is not limited to these embodiments, but is intended to conform to the broadest scope consistent with the principles and novel features disclosed herein. Any simple modifications, equivalent variations, and modifications made to the above embodiments based on the technical essence of the present invention are still within the scope of the technical solution of the present invention.

Claims

1. An anode well structure for cathodic protection of cluster well casing, characterized by: It comprises an anode well shaft (10) and at least two sets of anode body mechanisms; the two sets of anode body mechanisms are both vertically placed in the anode well shaft (10) and can operate independently; The two sets of anode body mechanisms are a backup anode body mechanism and a main anode body mechanism, and the two have the same structure; The spare anode body mechanism comprises an anode well exhaust pipe (8) and a spare anode body (13); the anode well exhaust pipe (8) is connected to the upper end of the spare anode body (13) and penetrates the middle thereof; The spare anode body (13) comprises an anode body steel casing, a first cable (9), two anode cores (14) connected in series up and down, and an anode string counterweight (17); the first cable (9), the two anode cores (14) connected in series up and down, and the anode string counterweight (17) are all placed in the anode body steel casing, and the two anode cores (14) and the anode string counterweight (17) are suspended from the lower end of the first cable (9) in sequence from top to bottom; the mixed metal oxide titanium core leads (15) of the two anode body anode cores (14) are connected in parallel with the first cable (9); the upper end of the anode body steel casing is connected to the exhaust pipe (8), and a through hole (16) is opened on the lower side wall thereof; Each anode core (14) is connected with a separate first cable (9); The first cable (9) is a single-core cable; The outer surface of the anode core (14) is platinum-plated tantalum with a breakdown voltage of 160V and an oxide coating resistivity of 10-7Ω.m.

2. The anode well structure for cathodic protection of cluster well casing according to claim 1, characterized in that: The upper port of the spare anode body (13) is provided with a steel sleeve flange for connecting to the exhaust pipe (8).

3. The anode well structure for cathodic protection of cluster well casing according to claim 2, characterized in that: The lower end of the anode steel sleeve is tapered.

4. The anode well structure for cathodic protection of cluster well casing according to claim 1, characterized in that: The anode core (14) is a metal oxide cylindrical titanium anode core.

5. The anode well structure for cathodic protection of cluster well casing according to claim 4, characterized in that: The anode core (14) adopts MMO / TI noble metal oxide anode.

6. A cluster well casing cathodic protection system, characterized by: The invention discloses an anode well structure for cathodic protection of a cluster well casing according to any one of claims 1 to 5, and further comprising a cathode well, a remote monitoring PC (1), a digital cathodic protection monitoring cabinet (3) and a copper sulfate reference electrode (7); the cathode well comprises an oil-water well casing (5) and an oil-water well shaft (6); the oil-water well casing (5) is placed in the oil-water well shaft (6); the remote monitoring PC (1) is electrically connected to the digital cathodic protection monitoring cabinet (3); the digital cathodic protection monitoring cabinet (3) is electrically connected to the oil-water well casing (5) in the cathode well and the first cable (9) in the anode well; the digital cathodic protection monitoring cabinet (3) is grounded via the copper sulfate reference electrode (7).

7. A method for replacing anode well structures for cluster well casing cathodic protection according to any one of claims 1 to 5, characterized in that: The following steps are included: Step 1: When the digital cathodic protection monitoring cabinet (3) or the remote monitoring PC (1) detects through the copper sulfate reference electrode (7) that the protection potentials of the backup anode body mechanism and the main anode body mechanism do not meet the requirements or the detection potential value is zero, the power is cut off and the first cable (9) connected to the digital cathodic protection monitoring cabinet (3) and the backup anode body mechanism and the main anode body mechanism is disconnected; Step 2: Pull out the old anode core (14) from the exhaust pipe (8) of the spare anode body mechanism and the main anode body mechanism through the first cable (9), replace it with a new anode core (14), and then lower it into the anode body steel casing through the exhaust pipe (8); Step 3: Connect the first cable (9) on the digital cathodic protection monitoring cabinet (3), and after power is turned on, when the normal protection potential value can be detected on the digital cathodic protection monitoring cabinet (3) or the remote monitoring PC (1), the replacement of the double anode core of the anode well is completed.

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