Micrologging

a method of studying boreholes by measuring the electrical resistivity of rocks near their walls. In micrologging, electrodes are mounted on a pad made of insulating material that is pressed against the wall of the borehole by means of springs. This decreases the distorting effect of the drilling fluid and makes possible measurement of the electrical resistivity of rocks even in small intercalated beds. The distance between the electrodes is approximately 2.5 cm.

Micrologging makes possible the detailed study of geological sections composed of thick and thin beds, the detection of permeable beds, and the determination of their porosity. There are two types of micrologging: normal and lateral. In the first instance, the electrical resistivity is measured according to a circuit of conventional three-electrode probes; in the second it is measured by the shielded electrical ground method.