Near-bit Azimuth Estimation Using Uncalibrated Magnetometers
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Solution Overview
Problem
Current drilling technologies face challenges in precisely determining the direction of highly deviated and horizontal wellbores during hydrocarbon extraction, leading to inefficiencies and increased costs due to the lack of accurate near-bit azimuth measurements, which can result in azimuthal walk and doglegs in the borehole path.
Innovation Solution
The method involves using uncalibrated near-bit magnetometers to estimate the axial component of the magnetic field, combining it with remote measurements to calculate the near-bit azimuth, and correcting for scale and orientation errors, allowing for early detection of azimuthal walk and precise control of drilling direction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of information
If uncalibrated near-bit magnetometers are used to measure magnetic field components, then measurement coverage is improved, but measurement precision deteriorates due to scale and orientation errors
Solution Approach 1:
The system uses remote magnetometer measurements as feedback to continuously correct the scale and orientation errors of near-bit magnetometers. The correction factors are calculated from the ratio of remote to near-bit measurements and applied in real-time to maintain measurement precision despite using uncalibrated sensors near the bit.
Solution Approach 2:
Remote magnetometers serve as intermediary reference sensors that provide accurate baseline measurements. These measurements mediate the correction process by establishing a reference frame that compensates for the errors in near-bit magnetometer readings, enabling precise azimuth determination.
2Ease of operation
If near-bit magnetometers are used for azimuth measurement, then drilling direction control is improved, but device complexity increases due to additional sensors and correction algorithms
Solution Approach 1:
Both near-bit and remote magnetometers perform multiple functions: near-bit sensors provide real-time azimuth data for steering control, while remote sensors provide reference measurements for error correction. The same sensor system serves both measurement and calibration purposes, reducing the need for separate correction devices.
Solution Approach 2:
The magnetometer system performs self-calibration using the ratio of remote to near-bit measurements. The system automatically calculates and applies correction factors without external intervention, enabling the sensors to self-correct their scale and orientation errors through the correction algorithm.
3Measurement precision
If remote magnetometer measurements are used for correction, then measurement precision is improved, but loss of time occurs due to additional correction processing
Solution Approach 1:
The system pre-calculates correction factors by establishing the relationship between remote and near-bit magnetometer readings during normal operation. These correction factors are prepared in advance and applied continuously, rather than performing full correction calculations for each measurement, reducing processing time while maintaining precision.
Solution Approach 2:
The correction process transforms the problem from correcting individual azimuth measurements to correcting fundamental sensor parameters (scale factors and orientation angles). By changing the correction parameters from per-measurement to per-sensor Basis, the system reduces processing complexity and time for continuous azimuth monitoring.
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 enables real-time estimation and correction of drilling direction, reducing the occurrence of azimuthal walk and doglegs, thereby improving the accuracy and efficiency of wellbore placement and hydrocarbon extraction.
Implementation Method 1
obtaining the non-axial component using a measurement from an uncalibrated magnetic sensor on the BHA. The uncalibrated magnetic sensor may be a near-bit magnetometer. The measurement may comprise a cross-axial component of the magnetic field.
Data Source
AI summary
Apparatus and methods for estimating an azimuth of at least part of a bottomhole assembly (BHA) in a borehole intersecting an earth formation, the BHA comprising magnetic material. Methods include conveying the BHA into the borehole; using a first sensor disposed on the BHA to produce a first measurement of a component of a magnetic field at a first borehole depth; estimating the axial component at the first borehole depth in dependence upon the first measurement; estimating an azimuth of at least a part of the BHA at the first borehole depth using the axial component; and controlling drilling operations with the BHA in dependence upon the azimuth. The magnetic field includes an axial component and a plurality of non-axial components unaligned with the axial component. The magnetic field is affected by the magnetic material and the first measurement is representative of at least one non-axial component of the plurality.