Four-Arm Dipmeter Probe

The four-arm dipmeter measures microresistivity and tool orientation data. These can be processed to determine formation dips.

PRINCIPLE OF MEASUREMENT
The probe consists of a microresistivity section and a detachable verticality module that can also operate as a standalone logging tool. The microresistivity data is acquired by four high-resolution, button electrodes mounted on motorised caliper arms and maintained in contact with the borehole walls. Opposite caliper arms are mechanically linked and adjacent arms lie at 90ºC to each other. Any planar formation feature that does not lie perpendicular to the borehole axis is detected by each electrode at a different apparent depth. The four microresistivity measurements are correlated and combined with the verticality data using RG-DIP software to calculate the dip and dip direction relative to the probe axis. RG-DIP processing includes both interval-correlation and pattern-recognition options and stereoplots and histograms for advanced data analysis.