Agenda
- gyroMWD and GyroCompassing Overview
- gyroMWD Gross Error Definitions
- Typical gyroMWD Deployment
- Current Published QC Techniques
- Recommended Additional QC Actions
gyroMWD and Gyrocompassing: Overview
- gyroMWD Summary
- At each survey station, the tool is held very still.
- A multiposition gyrocompass survey (independent north finding) is performed
- Gyrocompassing
- Gyro sensors measure horizontal direction of earth’s rotation.
- The horizontal direction is used to compute azimuth and gyro toolface
Properties of Spinning Mass Gyros: Overview
- Spinning Mass Gyros
- Floated Rate Integrating SDFG
- Dry Tuned Gyro
- Why Spinning Mass?
- Short Acquisition Time, Small Bias, Small Size
- Key Error Sources
- Bias(es) (Minimized due to carousel/indexing)
- Noise (Minimized by system design)
- Gravity-Dependent Errors (Mass Unbalance
Typical gyroMWD Deployment
- Top Hole – Under the Platform
- Other wells are very close, right from the start
- Greatest collision risk may occur right away
- Well plans are low angle, and often have minimal azimuthal variatio
- Start by Drilling Cement
- Drilling cement is rough
- If drilling out of a batch-set conductor, it can be even harder.
- Gyro tools are sensitive to shocks and vibrations.
- Floating and Riserless
- Surface movement can cause significant noise on the downhole gyro, which adds to other challenges
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Gross Error Detection for Typical gyro-MWD Operations
Ben Hawkinson