Bracelet Galvanic Anodes for Shielded Well Casing
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Solution Overview
Problem
Conventional cathodic protection systems, such as ICCP and GACP, fail to adequately protect subterranean well casing sections shielded by cement in the cellar area due to high resistance and non-homogeneous backfill, requiring frequent replacement of backfill to maintain effectiveness, which is costly and time-consuming.
Innovation Solution
An enhanced cathodic protection system using bracelet galvanic anodes with a unique shape and structure that decreases anode resistance and eliminates the need for backfill replacement, providing localized protection by minimizing the distance between the anode and cathode and increasing the anode's surface area, thus tolerating non-homogeneous backfill effectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional ICCP or GACP systems are used to protect well casing sections in the cellar area, then cathodic protection is provided, but the protection is inadequate due to high resistance and non-homogeneous backfill, requiring frequent backfill replacement
Solution Approach 1:
The patent applies local quality by positioning galvanic anodes in direct circumferential contact with the well casing surface at the cellar area, creating a localized protection zone where the anode-casing interface has optimal electrical contact. This localized approach ensures effective protection specifically where needed (cellar area) without requiring system-wide backfill replacement
Solution Approach 2:
The patent introduces an intermediary conductive medium (electrolyte solution or conductive paste) between the galvanic anode and the well casing surface. This intermediary ensures low-resistance electrical contact and facilitates ion transport, enabling effective cathodic protection even in non-homogeneous backfill conditions without requiring backfill replacement
2Reliability
If conventional GACP systems are used in the cellar area, then protection is provided, but anode resistance is high due to non-homogeneous backfill, reducing protection effectiveness
Solution Approach 1:
The patent extracts the anode from the traditional backfill-dependent configuration and positions it in direct contact with the well casing surface. By removing the anode from the non-homogeneous backfill environment and placing it where it can directly contact the casing, the system eliminates the harmful effect of high backfill resistance on anode performance
Solution Approach 2:
The patent introduces an intermediary conductive medium that facilitates low-resistance electrical contact between the anode and casing. This intermediary layer compensates for the non-homogeneous backfill conditions by providing a dedicated low-resistance path for current flow, thereby reducing the harmful effect of anode resistance
3Reliability
If conventional cylindrical anodes are used, then protection is provided, but the distance between anode and cathode is large, increasing resistance
Solution Approach 1:
The patent employs circumferential or ring-shaped galvanic anodes that conform to the cylindrical geometry of the well casing. This curved configuration minimizes the distance between the anode surface and the casing surface at all points, creating a uniform short gap that reduces resistance and enhances protection effectiveness
4Reliability
If conventional anode shapes are used, then protection is provided, but surface area is limited, requiring higher resistance tolerance
Solution Approach 1:
The patent transitions from using discrete cylindrical anodes to circumferential or ring-shaped anodes that extend around the well casing in the radial dimension. This dimensional expansion significantly increases the effective anode surface area in contact with or near the casing, thereby reducing resistance and improving protection effectiveness without requiring backfill replacement
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The enhanced system provides sustained and effective cathodic protection to well casing sections in the cellar area without the need for frequent backfill replacement, reducing costs and operational time, while ensuring better protection against corrosion.
Implementation Method 1
steel structures can be protected from corrosion ('a protected metal') by being positioned as a cathode in an electrochemical cell that includes an anode composed of a more highly reactive metal than the cathode
Implementation Method 2
the more reactive anode corrodes in preference to the protected metal structure, thereby preventing corrosion of the protected metal
Data Source
AI summary
A cathodic protection system is provided for a subterranean well casing having an enclosed upper section of the well casing being substantially shielded by a cellar from an impressed-current cathodic protection circuit passing through earth media. The impressed-current cathodic protection circuit is provided to protect an unenclosed lower section of the well casing. To protect the enclosed upper section of the well casing, a supplemental cathodic protection circuit is provided. The supplemental cathodic protection circuit is a galvanic anode cathodic protection circuit comprising the enclosed upper section of the well casing and one or more bracelet galvanic anodes being circumferentially mounted to the enclosed upper section. The enclosed upper section of the well casing and the one or more bracelet galvanic anodes are substantially surrounded by a cellar backfill, and the galvanic anode cathodic protection circuit is equally effective throughout a broad range of non-homogeneity within the cellar backfill.