Radially Driven Grounded Casing for Deep EM Field Generation
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Solution Overview
Problem
Conventional borehole electromagnetic (EM) sounding methods face limitations in generating EM fields at substantial depths and lateral distances due to vertical current flow and the need for deep well access, which complicates subsurface resistivity measurements and resource detection.
Innovation Solution
The Radially Driven Grounded Casing (RDGC) system uses a conductive borehole casing as an electrode, with surface electrodes spaced laterally from the well to induce electrical currents deep within the earth, eliminating the need for a source electrode at depth and reducing voltage on the casing, thereby enhancing EM field generation and measurement capabilities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a source electrode is positioned at depth within a borehole to generate EM fields, then the EM field can be produced at desired depths, but the system requires deep well access which complicates the measurement process and increases device complexity
Solution Approach 1:
The invention extracts the source electrode from the deep borehole environment and relocates it to the ground surface. The borehole casing remains as a grounded conductor, eliminating the need to lower equipment deep into the well while still achieving deep EM field penetration through the radially oriented current paths between the surface electrode and the cased borehole.
Solution Approach 2:
The borehole casing serves as an intermediary element between the ground surface and deep subsurface targets. By using the casing as a grounded conductor and positioning the source electrode at the surface, the system uses the casing as a mediator to transfer electromagnetic energy to deep depths without requiring physical access to those depths.
2Device complexity
If conventional borehole EM sounding methods are used with vertical current flow, then the setup is simpler, but the EM field generation is limited at substantial lateral distances from the borehole
Solution Approach 1:
The invention changes the orientation of current flow from vertical (conventional borehole methods) to radial (outward from the borehole casing). By positioning the source electrode at the ground surface and using the cased borehole as a grounded conductor, current flows radially outward through the subsurface, significantly expanding the lateral coverage area while maintaining relative system simplicity.
3Ease of operation
If surface electrodes are used to induce currents in the earth, then the system is easier to operate, but the EM field attenuation limits the depth and lateral distance of effective measurement
Solution Approach 1:
The borehole casing serves multiple functions: it acts as a grounded conductor for the EM survey, provides structural support for the well, and serves as a return path for electrical current. This multi-functionality allows the system to achieve deep EM field penetration with surface-based electrodes, combining ease of operation with reduced energy attenuation by utilizing the existing casing infrastructure.
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 RDGC configuration allows for effective EM field generation and measurement at significant depths and lateral distances, improving subsurface resistivity determination and resource detection while avoiding the need for deep well access and reducing power consumption.
Implementation Method 1
The transmitter produces an oscillating voltage of the desired time-dependent waveform, which induces an electrical current to flow in the earth
Implementation Method 2
A current induced in the earth via a transmitter produces a primary magnetic field and also an electric field due to the electrical resistance of the ground
Implementation Method 3
an electric field due to the electrical resistance of the ground
Implementation Method 4
When oscillatory, these fields produce secondary EM fields. For example a time-varying magnetic field induces an electric field
Data Source
AI summary
A system enables a borehole casing to be used to connection with establishing electromagnetic fields within the earth at the depth of formations of interest over a significant surface area. A particular advantage is that a borehole casing can be used as an essential part of the system, without needing to open the borehole.