System, apparatus, and method for utilization of bracelet galvanic anodes to protect subterranean well casing sections shielded by cement at a cellar area

Patent metadata

Field	Value
Publication number	US-9809888-B2
Application number	US-201514807255-A
Country	US
Kind code	B2
Filing date	Jul 23, 2015
Priority date	Sep 29, 2011
Publication date	Nov 7, 2017
Grant date	Nov 7, 2017

Abstract

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.

First claim

That claimed is:

1. An enhanced cathodic protection system for a subterranean well casing having an upper vertical well casing section thereof in a cellar area and one or more lower well casing sections below the cellar area, the cellar area being bounded by a cellar ring, the vertical well casing section in the cellar area defining a cellar-area well casing, the enhanced cathodic protection system comprising:
an impressed current cathodic protection system comprising a subterranean anode bed surrounded by a ground electrolyte in communication with the one or more of the lower well casing sections, the subterranean anode bed adapted to provide a first ion pathway through the ground electrolyte to the one or more of the lower well casing sections, the subterranean anode bed further being electrically connected to the subterranean well casing through one or more cables and one or more cathodic protection rectifiers to provide a first electron pathway to the subterranean well casing, the impressed current cathodic protection system providing primary cathodic protection to the subterranean well casing; and
an enhanced galvanic anode cathodic protection system comprising one or more bracelet anodes being circumferentially mounted to the cellar-area well casing and being surrounded by a cellar electrolyte, the cellar electrolyte being bounded by the cellar ring and also surrounding an outer surface of the cellar-area well casing, the one or more bracelet anodes circumferentially surrounding the cellar-area well casing and providing a second ion pathway through the cellar electrolyte to the cellar-area well casing, the one or more bracelet anodes further being electrically connected to the cellar-area well casing through one or more shorting screws to provide a second electron pathway to the subterranean well casing, the enhanced galvanic anode cathodic protection system providing secondary cathodic protection to the subterranean well casing;
wherein the impressed current cathodic protection system and the enhanced galvanic anode cathodic protection system operate simultaneously.

2. A cathodic protection system as defined in claim 1 , wherein the cellar ring substantially shields the first ion pathway from the subterranean anode bed to the cellar-area well casing.

3. A cathodic protection system as defined in claim 1 , wherein one or more of the lower well casing sections are surface-coated and one or more deeper sections of the lower well casing sections are uncoated bare metal operable to route the first electron pathway to the deeper sections of the lower well casing sections.

4. A cathodic protection system as defined in claim 1 , wherein the cellar-area well casing has an outer surface that is uncoated bare metal.

5. A cathodic protection system as defined in claim 1 , wherein:
the cellar electrolyte is a non-homogenous electrolytic composition having a resistivity greater than sea water.

6. A cathodic protection system as defined in claim 1 , wherein a tip of the shorting screw is pointed to operably enhance the effectiveness of the second electron pathway.

7. A cathodic protection system as defined in claim 1 , the enhanced galvanic anode cathodic protection system further comprising a cable electrically connected to one or more bracelet anodes and electrically connected to the cellar-area well casing to provide a third electron pathway that is redundant with the second electrical pathway in completing an enhanced galvanic anode cathodic protection circuit to protect the cellar-area well casing from corrosion in the cellar electrolyte.

8. A method for providing enhanced cathodic protection to a subterranean well casing having an upper vertical well casing section thereof in a cellar area and one or more lower well casing sections below the cellar area, the cellar area being bounded by a cellar ring, the vertical well casing section in the cellar area defining a cellar-area well casing, the method comprising steps of:
completing an impressed current cathodic protection system circuit comprising a subterranean anode bed surrounded by a ground electrolyte in communication with the one or more of the lower well casing sections, the subterranean anode bed adapted to provide a first ion pathway through the ground electrolyte to the one or more of the lower well casing sections, the subterranean anode bed further being electrically connected to the subterranean well casing through one or more cables and one or more cathodic protection rectifiers to provide a first electron pathway to the subterranean well casing, the impressed current cathodic protection system providing primary cathodic protection to the subterranean well casing; and
completing an enhanced galvanic anode cathodic protection system circuit comprising one or more bracelet anodes being circumferentially mounted to the cellar-area well casing and being surrounded by a cellar electrolyte, the cellar electrolyte being bounded by the cellar ring and also surrounding an outer surface of the cellar-area well casing, the one or more bracelet anodes circumferentially surrounding the cellar-area well casing and providing a second ion pathway through the cellar electrolyte to the cellar-area well casing, the one or more bracelet anodes further being electrically connected to the cellar-area well casing through one or more shorting screws to provide a second electron pathway to the subterranean well casing, the enhanced galvanic anode cathodic protection system providing secondary cathodic protection to the subterranean well casing;
wherein the impressed current cathodic protection system and the enhanced galvanic anode cathodic protection system operate simultaneously.

9. A method for providing enhanced cathodic protection as defined in claim 8 , wherein the cellar ring substantially shields the first ion pathway from the subterranean anode bed to the cellar-area well casing.

10. A method for providing enhanced cathodic protection as defined in claim 8 , wherein one or more of the lower well casing sections are surface-coated and one or more deeper sections of the lower well casing sections are uncoated bare metal operable to route the first electron pathway to the deeper sections of the lower well casing sections.

11. A method for providing enhanced cathodic protection as defined in claim 8 , wherein:
the cellar electrolyte is a non-homogenous electrolytic composition having a resistivity greater than sea water.

12. A method for providing enhanced cathodic protection as defined in claim 8 , wherein a tip of the metallic shorting screw is pointed to operably enhance the effectiveness of the second electron pathway.

13. A method for providing enhanced cathodic protection as defined in claim 8 , the enhanced galvanic anode cathodic protection system further comprising a cable electrically connected to one or more bracelet anodes and adapted to be operably electrically connected to the cellar-area well casing to provide a third electron pathway that is redundant with the second electrical pathway in completing an enhanced galvanic anode cathodic protection circuit to protect the cellar-area well casing from corrosion in the cellar electrolyte.

Assignees

• Saudi Arabian Oil Co

Inventors

• Al-Mubasher Mohammed H

Classifications

• E21B33/0375

  Corrosion protection means · CPC title

• C23F2213/32

  Pipes · CPC title

• C23F13/18

  Means for supporting electrodes · CPC title

• C23F13/06 Primary

  Constructional parts, or assemblies of cathodic-protection apparatus · CPC title

• C23F13/16 Primary

  Electrodes characterised by the combination of the structure and the material · CPC title