MWD Heading Transfer via Surface Master North Finder
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Solution Overview
Problem
Current measurement while drilling (MWD) and gyroMWD techniques face challenges in accurately determining instrument heading due to movement and magnetic interference, requiring the instrument to be kept still and isolated from external magnetic sources.
Innovation Solution
A method and system that utilize a master north finder positioned at the surface to determine true north and gravity, which is then transferred to a MWD tool via a heading transfer unit, allowing for alignment and communication of the heading through a base alignment feature, enabling accurate heading determination even in moving conditions and reducing interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the instrument is kept still during sampling to eliminate movement effects, then measurement precision is improved, but productivity deteriorates due to loss of drilling time
Solution Approach 1:
The system performs preliminary calibration by establishing a reference heading at the surface before drilling begins. This pre-established reference allows continuous heading determination during drilling without requiring the instrument to be kept still, thus maintaining both measurement precision and drilling productivity
Solution Approach 2:
The patent introduces an intermediary reference frame established at the surface that mediates between the moving downhole instrument and the fixed Earth reference. By transferring the reference heading to the downhole tool through this intermediary, the system enables continuous measurement without requiring the instrument to be stationary
2Measurement precision
If the instrument is spaced sufficiently from external magnetic sources, then measurement precision is improved, but adaptability deteriorates due to restricted drilling locations
Solution Approach 1:
The system uses an intermediary reference heading established at the surface as a mediator that allows accurate heading determination even in the presence of external magnetic sources. By referencing against this pre-established surface baseline rather than relying solely on local magnetic field measurements, the tool can operate adaptably in various locations including areas with magnetic interference
Solution Approach 2:
The patent replaces reliance on magnetic field sensing with an inertial reference system that uses acceleration sensors and a pre-established reference heading. This substitution eliminates the need to be spaced from magnetic sources, thereby improving adaptability while maintaining measurement precision through inertial navigation principles
3Reliability
If magnetometers are replaced with gyrocompass assembly, then reliability is improved in magnetic interference, but device complexity increases
Solution Approach 1:
The system extracts and removes the magnetometer component from the sensor assembly, replacing it with a gyrocompass assembly that uses rate gyroscopes and acceleration sensors. This extraction eliminates sensitivity to external magnetic sources while maintaining heading measurement capability through inertial reference
Solution Approach 2:
The patent changes the fundamental measurement parameter from magnetic field orientation to inertial orientation relative to the Earth's rotation vector. By measuring the direction of the Earth's rotation vector using rate gyroscopes rather than magnetic field direction, the system achieves improved reliability in magnetic interference environments
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 solution allows for precise and continuous heading determination in MWD tools, improving measurement accuracy and reducing the need for isolation from external magnetic sources, enhancing the reliability of MWD operations.
Implementation Method 1
determining a heading with respect to true north and gravity with the master north finder
Implementation Method 2
uses a rate gyroscope to measure the direction of the Earth's rotation vector relative to the tool
Data Source
AI summary
A heading transfer unit may be used to transfer a heading from a surface base to a MWD tool. The surface base may have a master north finder to determine a heading. The heading may be transferred to the heading transfer unit, which is in turn transferred to the MWD unit. The heading on the heading transfer unit is transferred to the MWD tool.