High-Precision Orientation of Three-Component Magnetic Downhole Logs

Common borehole methods provide data not allowing for an orientation with respect to a global reference, since this requires a highly accurate orienta tion system independent of the magnetic measurements. A first attempt to obtain the orientation of the sonde was made by Bosum et al. (1988) using a mechanical gyro and accelerometers. However, at that time the data quality of the gyro did not allow for a continuous 3-component measurement. Steveling et al. (2003) provide an example from the Hawaii Scientific Drilling Project (HSDP) drill hole, where directional information of magnetization was used to separate massive lavas from hyaloclastites. However, their directional analysis was limited to the inclination because information on the tool rotation around the vertical axis was not available.