Band-Stop Filter Mitigates Direct Coupling in Electromagnetic Well Ranging
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Solution Overview
Problem
Existing electromagnetic wellbore ranging systems face challenges in accurately determining the distance and direction of a first wellbore relative to a second wellbore due to direct coupling between transmitter and receiver coils, which interferes with signal processing and affects the reliability of gradient ranging formulas.
Innovation Solution
The implementation of a band-stop filter and a pre-processing scheme to mitigate direct coupling, allowing for the use of gradient ranging formulas and improving signal processing by rotating receiver coils to cancel out contributions from azimuthal and axial currents, thereby enhancing the accuracy of distance and direction measurements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If coil excitation is used to induce currents in the first wellbore, then electromagnetic ranging capability is achieved, but direct coupling between transmitter and receiver coils occurs causing non-target signals to be received
Solution Approach 1:
The patent extracts and removes the harmful direct coupling signal from the received electromagnetic signal using signal processing techniques, specifically gradient-based filtering that isolates and eliminates the direct coupling component while preserving the target wellbore signal
Solution Approach 2:
The patent introduces an intermediary signal processing step that processes the raw electromagnetic signal through gradient calculation and filtering operations, acting as a mediator between the raw signal and the final ranging measurement to eliminate direct coupling effects
2Productivity
If gradient ranging formulas are used to process signals, then ranging calculations can be performed, but the formulas assume only target wellbore signals are received which is violated by direct coupling
Solution Approach 1:
The patent applies preliminary signal processing actions before the ranging calculation to remove direct coupling signals, ensuring that when gradient ranging formulas are subsequently applied, their assumption of receiving only target wellbore signals is satisfied
Solution Approach 2:
The patent converts the harmful direct coupling signal into a removable artifact by exploiting its mathematical characteristics in gradient space, transforming the problem from an interference issue into a solvable signal processing task that actually improves measurement reliability
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 approach effectively reduces direct coupling, enabling more accurate determination of wellbore positions and allowing for precise drilling operations, such as intersecting or avoiding the first wellbore, even in close ranges and varying formation resistivities.
Implementation Method 1
an electromagnetic source may be used to induce currents in conductive tubulars disposed in the first wellbore wherein the induced currents may be received by receivers in the second wellbore
Implementation Method 2
applying a band-stop filter to the received signals to provide filtered signals
Data Source
AI summary
A method and system for electromagnetic well ranging. The method may comprise receiving signals from one or more receiver coils at different depths in a second wellbore, applying a band-stop filter to the received signals to provide filtered signals, and processing the filtered signals to determine a position of the first wellbore with respect to the second wellbore. An electromagnetic ranging system may comprise a transmitter coil disposed in a second wellbore, a receiver coil disposed in the second wellbore, an information handling system coupled to the transmitter coil and the receiver. The information handling system may be configured to receive signals from one or more receiver coils at different depths in the second wellbore, apply a band-stop filter in a frequency domain to provide filtered signals, and process the filtered signals to determine a position of the first wellbore with respect to the second wellbore.