Overview:
- Continuous gyro surveys run on wireline through casing with centroller centralization from surface to +/-60° inclination represent the best current means of surveying our wells to the depth of the 13-3/8” casing shoe.
- With enough good quality gyro and magnetic survey data, the uncertainty of the local magnetic field can be reduced.
- Independently check all reference data.
+/- 1,000 feet of comparison between magnetically clean MWD surveys
and subsequent continuous gyro survey using centroller centralisation
In 13-3/8” casing
MOQ Rules for the Application of an MSA Correction
- At the Planning Stage
• Never expect a successful MSA correction if the predominant direction of the planned horizontal hole is within +/- 30° of East/West
- Once the BHA-run is complete and the raw data have been inspected
• Survey management company uses rules based on SPE/IADC 125677 Nyrnes, Torkildsen & Wilson
Gyro-derived well inclination and azimuth
Input: final gyro-derived well paths
• Interpolated well path given at 25 ft intervals
• Cubic B-splines fit to well positions - continuous well path
• Take measured depth (MD) of MWD survey
• Compute inclination and azimuth by differencing the well path:
....
View the entire Presentation:
Combined Use of MWD and Gyro Surveying
Simon McCulloch, Maersk Oil Qatar and Stefan Maus - Magnetic Variation Services LLC