Wellbore Casing Short Circuit for Electromagnetic Heating
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Solution Overview
Problem
Coaxial transmission lines used for electromagnetic heating of underground hydrocarbon formations face risks of arcing due to high-energy density and electric fields, and the routing of these lines within wellbores can lead to additional arcing risks, while the return of current to the surface reduces efficiency and increases arcing hazards.
Innovation Solution
The implementation of a system with two wellbores and casings where the distal portions are electrically connected to form a short circuit, and the proximal portions are grounded, using electrically conductive cement and conductive fasteners to enhance conductivity and reduce current flow to the surface, thereby mitigating arcing risks and improving efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If coaxial transmission lines are used to transmit RF power to the load in the underground hydrocarbon formation, then electromagnetic heating can be achieved, but the high-energy density and electric fields present a risk of arcing
Solution Approach 1:
The invention extracts the harmful function of the wellbore casing (which was inadvertently acting as a return path for RF current) by removing its electrical continuity through intentional discontinuities. This eliminates the arcing risk while preserving the desired RF power transmission to the hydrocarbon formation through the coaxial transmission line.
Solution Approach 2:
The invention introduces an intermediary element (the discontinuity in the wellbore casing) that blocks the unwanted RF current return path while allowing the desired electromagnetic heating function to proceed. This intermediary effectively separates the harmful current flow from the useful heating operation.
2Reliability
If the wellbore casing provides a pathway for current to return to the surface, then current can complete its circuit, but the efficiency of the system is reduced and arcing risk increases
Solution Approach 1:
The invention removes the unwanted current return pathway by creating intentional discontinuities in the wellbore casing. This forces the RF current to complete its circuit through the intended load in the hydrocarbon formation, thereby eliminating the efficiency loss and arcing risk associated with the casing return path.
Solution Approach 2:
The invention converts the potentially harmful effect of the wellbore casing (acting as an unintended current return path) into a beneficial feature by using the discontinuity to guide current flow exclusively through the load. This ensures all RF energy is utilized for productive heating rather than being lost through the casing.
3Power
If coaxial transmission lines are routed within the wellbore, then RF power can be transmitted to the load, but additional arcing risk is introduced between the conductors and the inner surface of the wellbore
Solution Approach 1:
The invention extracts the source of the arcing problem by removing the continuous wellbore casing structure that was creating the harmful electric field configuration. The intentional discontinuities eliminate the capacitive coupling between the transmission line conductors and the wellbore inner surface, thereby preventing arcing while maintaining RF power transmission capability.
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
This configuration significantly reduces the risk of arcing and enhances the efficiency of electromagnetic heating by blocking current flow on the wellbore casings and surfaces, ensuring safer and more effective energy transmission to the hydrocarbon formations.
Implementation Method 1
a second electrical connection between the distal portions of the two or more wellbore casings to provide a short circuit that reduces current traveling on the two or more wellbore casings to the ground surface
Implementation Method 2
using electrically conductive cement and conductive fasteners to enhance conductivity and reduce current flow to the surface
Implementation Method 3
EM heating of hydrocarbon formations can be achieved by using a load, such as an EM radiator, antenna, applicator, or lossy transmission line, positioned inside an underground reservoir to radiate, or couple, EM energy to the hydrocarbon formation
Data Source
AI summary
Methods for providing wellbores for electromagnetic heating of a hydrocarbon formation positioned below a ground surface and apparatus thereof are provided. The apparatus includes two or more wellbore casings positioned within two or more wellbores. The two or more wellbores extend from a proximal end at the ground surface to a distal end at the underground hydrocarbon formation. Each of the two or more wellbore casings have a proximal portion and a distal portion. The two or more wellbores are in proximity to one another at a junction. The apparatus also includes a first electrical connection between the proximal portions of the two or more wellbore casings for grounding the two or more wellbore casings and a second electrical connection between the distal portions of the two or more wellbore casings. The second electrical connection is located at the junction and provides a short circuit that reduces current traveling on the two or more wellbore casings to the ground surface.