|
Parameter
|
Definition and comments
|
|---|---|
| F | Intensity of the local magnetic field |
| DEC | Tabulated declination at the site under study |
| Inc | Inclination of the local magnetic field |
| FNOR* | Filtered version of F using the Schlumberger algorithm |
| FINC* | Filtered version of Inc using the Schlumberger algorithm |
| P1AZ* | Tool orientation determined by the Schlumberger algorithm |
| Dec | Direct declination measured by the oriented GBM magnetometer |
| Rot | Direct GBM rotation measured by its gyroscopic system; optical-gyro-based tool orientation |
| Fx, Fy , Fz | Intensity of the local magnetic field measured by a three-axis magnetometer (GBM or GPI) |
| tdec | Declination computed from the raw magnetic measurements (Fx, Fy , and Fz). This measurement is made in the tool frame in respect to the x-axis. It integrates both the true local value of the declination and the rotation component of the tool. If the true local value (measurement) is different than that of the tabulated declination (DEC), the orientation of the tool is incorrect. For sub-vertical boreholes, tdec = arctan (Fy/Fx). |
| rot | Indirect tool rotation obtained by keeping the low-frequency component of tdec magnetometer-based orientation |
| dec | Local declination obtained by keeping the high-frequency component of tdec |
| Drot | Local difference between Rot and rot determined using the newly developed algorithm |
| drot | Local difference between rot determined using the developed algorithm and rot determined using the Schlumberger algorithm |
| Ddec | Local difference between Dec and dec |
Notes: * = Schlumberger acronym. GBM = Göttingen Borehole Magnetometer, GPI = general-purpose inclinometry module.