Rotating Magnetometer Ranging for Earth Field Interference
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Solution Overview
Problem
Existing ranging techniques for determining distance and direction between wells in geological formations are limited by the accuracy of magnetic field measurements, particularly due to the interference from the Earth's magnetic field, which can overwhelm signals from target wells.
Innovation Solution
The use of a single rotating magnetometer with a frequency of excitation selected based on the rotation rate of the sensor and processing measurements in the rotational-phase-domain using Fourier transforms to reduce the effect of the Earth's magnetic field, allowing for more accurate ranging measurements by identifying null locations in the frequency spectrum for improved signal-to-noise ratios.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a rotating magnetometer is used to measure magnetic field signals from target wells, then ranging measurements can be obtained, but the Earth's magnetic field interferes with and overwhelms the target well signals, reducing measurement accuracy
Solution Approach 1:
The patent applies periodic action by rotating the magnetometer at a controlled frequency and using synchronous detection at the rotation frequency. The magnetometer rotates periodically to sample the magnetic field at different orientations, and the signal processing uses the known rotation frequency to extract the target well signal from the Earth's magnetic field interference through frequency-domain analysis.
Solution Approach 2:
The patent utilizes mechanical vibration by rotating the magnetometer assembly on the drill string. This rotation creates a time-varying signal pattern where the target well's magnetic field produces a specific frequency component related to the rotation rate, while the Earth's magnetic field produces different frequency characteristics that can be distinguished through spectral analysis.
2Measurement precision
If multiple sensors are deployed to improve measurement accuracy, then ranging precision can be enhanced, but the device complexity and cost increase
Solution Approach 1:
The patent applies segmentation by dividing the measurement process into distinct frequency components through Fourier transformation. Instead of using multiple physical sensors to capture different signal components simultaneously, the single sensor sequentially samples the magnetic field during rotation, and the signal processing segments the total signal into frequency components that correspond to different physical sources (target well vs. Earth's field).
Solution Approach 2:
The patent employs dynamics by using a rotating single sensor instead of multiple stationary sensors. The rotation transforms a spatial measurement problem into a temporal one, where the single sensor dynamically samples the magnetic field from different orientations over time. This dynamic approach allows one sensor to perform the equivalent measurement function of multiple stationary sensors.
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 enhances the accuracy of ranging measurements by minimizing the impact of the Earth's magnetic field, enabling more precise determination of distance and direction between wells, even during drill string rotation, and reduces the need for multiple sensors, thereby improving the precision and reliability of directional drilling.
Implementation Method 1
an electromagnetic source is located in the existing well and monitored via sensors on the drill string in the well under construction
Implementation Method 2
a rotating magnetometer... receiving an electromagnetic ranging signal
Implementation Method 3
processing measurements in the rotational-phase-domain using Fourier transforms to reduce the effect of the Earth's magnetic field
Data Source
AI summary
A well ranging apparatus, systems, and methods which operate to detect and determine a relative distance and/or azimuthal direction of nearby target well conductors such as pipes, well casing, etc., from within a borehole of a drilling well. An electromagnetic signal receiver is rotated in a first borehole. During the rotating, an electromagnetic ranging signal is received at the electromagnetic signal receiver. The electromagnetic ranging signal originates from an electromagnetic source in the first borehole or a second borehole. A null in an Earth electromagnetic signal spectrum associated with a signal induced by the rotating within a magnetic field of the Earth is determined. The electromagnetic source to is set to operate at an excitation frequency that is selected based, at least in part, on the determined null.