Downhole Energy Harvesting From Cathodic Protection Currents
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Solution Overview
Problem
Providing power to downhole devices in oil and gas wells without relying on surface-cabled or hydraulic power delivery, which is challenging due to high temperatures shortening battery life and the complexity of cable penetration, especially in subsea environments.
Innovation Solution
A downhole electrical energy harvesting system that utilizes the potential difference in cathodic protection currents flowing through metallic structures to generate power, eliminating the need for separate power sources and reducing system complexity by integrating energy harvesting modules with existing cathodic protection systems.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If batteries are used to power downhole devices, then power can be provided without surface cables, but battery life is shortened due to high temperatures
Solution Approach 1:
The patent combines the cathodic protection system (which provides corrosion protection current) with the power supply system for downhole devices. The harvesting module extracts electrical energy from the cathodic protection current flowing through the metallic well structure, merging two existing systems to simultaneously provide both corrosion protection and device power without adding separate power sources or sacrificing battery life.
Solution Approach 2:
The system uses the cathodic protection current that is already flowing through the well structure for dual purposes: maintaining corrosion protection and powering downhole devices. The metallic structure serves as both the protected object and the power transmission medium, eliminating the need for separate power delivery infrastructure.
2Reliability
If surface-cabled power delivery is used, then reliable power can be provided to downhole devices, but system complexity increases due to cable penetration requirements
Solution Approach 1:
The patent extracts the power delivery function from the traditional surface-cabled system and relocates it to the downhole environment by utilizing the existing cathodic protection current. This eliminates the need for complex surface cable penetration systems while maintaining reliable power supply to downhole devices.
Solution Approach 2:
The metallic well structure serves multiple functions: it provides structural support, enables cathodic protection, and acts as the power transmission conductor. This multi-functionality eliminates the need for dedicated power cables and their associated penetration complexity.
3Ease of operation
If hydraulic power delivery is used, then power can be provided without electrical cables, but the system becomes complex and limited in application
Solution Approach 1:
The patent replaces the hydraulic power transmission system with an electrical energy harvesting system that utilizes the existing cathodic protection current. This substitution eliminates the complexity of hydraulic pumps, fluid management, and mechanical power conversion while providing reliable electrical power to downhole devices.
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
Enables reliable and long-term power supply to downhole devices without batteries or surface cables, optimizing energy harvesting through variable impedance control and efficient communication using existing cathodic protection currents, suitable for both land and subsea wells.
Implementation Method 1
a harvesting module electrically connected to the metallic structure at a first location and to a second location spaced from the first location, the first and second locations being chosen such that, in use, there is a potential difference therebetween due to the electric current flowing in the structure; and the harvesting module being arranged to harvest electrical energy from the electric current
Data Source
AI summary
Downhole electrical energy harvesting and communication in systems for well installations having metallic structure carrying electric current, for example CP current. In some instances there is a harvesting module (4) electrically connected to the metallic structure (2) at a first location and to a second location spaced from the first location, the first and second locations being chosen such that, in use, there is a potential difference therebetween due to the electric current flowing in the structure (2); and the harvesting module (4) being arranged to harvest electrical energy from the electric current. In addition or alternatively, there may be communication apparatus (4, 5, 6) for communication by modulation of the current, for example CP current, in the metallic structure (2).