QA/QC Instrument Tests to be performed for Gyro Surveys.
1. Inclination Values (In-run and Out-run)
The variance between the in-run and out-run inclination values for survey data from the same survey station shall not exceed 0.23 deg.
Note: A minimum of 10 survey stations shall be compared.
2. Azimuth Values (In-run and Out-run)
Stations with Inclination of 10 Degrees or Over
The variance between in-run and out-run azimuth values from the same survey station shall not exceed 1.0 deg for all stations having an inclination of 10 deg or over.
Note: A minimum of 10 survey stations shall be compared.
Stations with Inclination Below 10 Degrees
The variance between in-run and out-run azimuth values from the same survey station shall not exceed 5.0 deg for all stations having an inclination below 10 deg.
Note: A minimum of 10 survey stations shall be compared.
3. Gyro Temperature
Gyro temperature must continuously increase from start of the in-run to completion of the out run.
Gyro’s are accurately calibrated over a specific temperature range (typically 25ºC to 65ºC) and outwith this range, values are extrapolated.
Extrapolation details depend on the tool in use. Therefore, the temperature limitations should be identified prior to the job.
4. Slippage Gradient
The winch unit depth counter shall be zeroed at the start of the in-run and checked again at the end of the out-run.
The slippage gradient shall be less than 1 ft/1000 ft surveyed.
Slippage gradient is calculated as follows:
Slippage Gradient (ft/1000ft) = Total Slippage (ft) x 1000
2 x HUD (ft)
Where HUD = Hold Up Depth of survey run