Cross-Axial Gyroscope Compensation for Dynamic Wellbore Surveys
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Solution Overview
Problem
Gyroscopic surveying tools in wellbores are affected by tool motion and magnetic interference, particularly in offshore operations, complicating accurate gyrocompass measurements, especially in low inclinations and near vertical wells.
Innovation Solution
Compensate cross-axial gyroscope measurements by combining them with cross-axial accelerometer measurements to remove tool motion-induced rotational components, using a method that includes making and evaluating these measurements to correct for tool motion, particularly in orthogonal axes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the gyroscopic surveying tool remains perfectly stationary with respect to the Earth, then the gyroscopic measurements are accurate and not affected by tool motion, but downhole tools are seldom perfectly stationary in the wellbore, particularly in offshore operations where sea motion moves the tool
Solution Approach 1:
The patent uses accelerometers to continuously monitor tool motion and feeds this information back to compute compensation values that are applied to the gyroscope measurements. This closed-loop feedback system dynamically corrects for tool motion effects, maintaining measurement accuracy despite the tool not being stationary.
Solution Approach 2:
The patent introduces accelerometers as an intermediary device that measures tool motion separately. These accelerometer measurements serve as a mediator that enables the computation of compensation values, which are then applied to the gyroscope data to eliminate the harmful effects of tool motion.
2Measurement precision
If magnetic surveying measurements are used in offshore operations, then they can be affected by magnetic interference, but gyroscopic measurements are generally not susceptible to magnetic interference
Solution Approach 1:
The patent replaces magnetic field-based surveying measurements with a mechanics-based gyroscopic system that uses inertial sensors (gyroscopes and accelerometers) to measure tool orientation and motion. This substitution eliminates susceptibility to magnetic interference while providing equivalent or superior measurement capabilities.
3Measurement precision
If the gyroscopic surveying tool is used at low depths where motion is greatest, then the tool is most affected by sea motion, but this is where gyroscopic measurements are most advantageous due to magnetic interference complications
Solution Approach 1:
The patent implements a feedback mechanism where accelerometers continuously monitor tool motion caused by sea motion, and this information is used to compute real-time compensation values that are applied to the gyroscope measurements, maintaining accuracy even in high-motion environments at low depths.
Solution Approach 2:
The patent converts the harmful effect of tool motion into a measurable quantity using accelerometers. By measuring the motion that would otherwise corrupt the data, the system can compute compensation values and transform the harmful motion effect into a correctable parameter, improving measurement reliability.
4Measurement precision
If cross-axial rotational components are not compensated, then gyroscopic measurements contain errors due to tool motion, but compensating requires additional accelerometer measurements and processing
Solution Approach 1:
The patent merges the functionality of gyroscope measurements with accelerometer measurements into a unified compensation system. By combining data from both sensor types and processing them together, the system achieves accurate cross-axial compensation without requiring separate independent systems, thereby limiting the increase in overall system complexity.
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
Enables accurate gyroscopic toolface and azimuth measurements under dynamic conditions, improving measurement accuracy in near vertical and horizontal wells by compensating for tool motion and magnetic interference.
Implementation Method 1
Gyroscopes are commonly utilized in wellbore surveying operations. Gyroscopic surveying measurements may be used to measure wellbore azimuth with respect to true north
Implementation Method 2
making accelerometer measurements including cross-axial accelerometer measurements in the subterranean wellbore
Data Source
Figure 1
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AI summary
A method for making downhole gyroscopic surveying measurements includes making at least one cross-axial gyroscope measurement in the subterranean wellbore; making accelerometer measurements including cross-axial accelerometer measurements in the subterranean wellbore; evaluating the cross-axial accelerometer measurements to determine at least one tool motion induced cross-axial rotational component; and removing the tool motion induced cross-axial rotational component from the at least one cross-axial gyroscope measurement to determine a compensated cross-axial gyroscope measurement.