Unbalanced Magnetic Field Ranging System
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Solution Overview
Problem
The existing magnetic ranging methods face challenges in accurately measuring the magnetic fields due to the opposing direction of current flow, which results in a reduced total magnetic field received at the sensors, making it difficult to determine the distance and direction between wells.
Innovation Solution
The generation of unbalanced magnetic fields by using different orientations of cable windings and magnetic shielding, such as high permeability mu-metal, to enhance the measurable magnetic fields, allowing for more accurate distance and direction determination between wells.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If current is launched down the casing to generate magnetic fields, then magnetic fields can be generated surrounding the target well, but the current flowing uphole through the casing reduces the total magnetic field received at the sensors
Solution Approach 1:
The patent segments the current path into two separate paths: a current injection path (cable) and a current return path (casing). By separating these paths, the magnetic fields generated by each path do not cancel each other out, as they are spatially separated. The injection path carries current downhole while the return path carries current uphole, but through different physical conduits, preventing magnetic field cancellation and enabling measurable unbalanced magnetic fields at the sensors.
2Ease of operation
If current flows through the casing for downhole contact, then power can be delivered downhole, but the opposing current direction reduces the measurable magnetic field
Solution Approach 1:
The patent introduces a cable as an intermediary current injection path that terminates at a downhole termination device. This cable acts as a mediator between the surface power supply and the casing, allowing current to be injected into the casing at a specific downhole location without requiring continuous contact along the entire casing length. The cable provides the necessary downhole contact while separating the injection function from the return path, enabling both ease of operation and accurate magnetic field measurement.
3Ease of manufacture
If standard cable configuration is used, then simple installation is achieved, but magnetic fields are balanced and difficult to measure for ranging
Solution Approach 1:
The patent creates an asymmetric current path configuration where the current injection path (cable) and return path (casing) are deliberately made different and spatially separated. This asymmetry ensures that the magnetic fields generated by the two paths are unbalanced and do not cancel each other. The asymmetric configuration maintains relative simplicity in installation while enabling measurable magnetic field differences that are essential for accurate ranging operations.
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 use of unbalanced magnetic fields generated by varied cable configurations and shielding materials significantly increases the measurable magnetic fields, enabling precise determination of the relative distance and direction between wells, even in scenarios with lossy pipe properties and geological formations.
Implementation Method 1
The power supply at the surface typically employs a cable coupled to a weight bar (to provide downhole contact to the well casing) to deliver the current downhole so that magnetic fields can be generated surrounding the target well
Implementation Method 2
The generation of unbalanced magnetic fields by using different orientations of cable windings and magnetic shielding, such as high permeability mu-metal, to enhance the measurable magnetic fields
Data Source
AI summary
A system for ranging between a target well and a ranging well using unbalanced magnetic fields. The system comprises a current injection path associated with a target well casing. The current injection path is configured to generate a first magnetic field. A return path is coupled to the current injection path. The return path is configured to generate a second magnetic field such that the first and second magnetic fields are unbalanced with respect to each other. The unbalanced magnetic fields can be measured and used to range with the target well.