“Laboratory study of the shallow laterolog in high and low contrast zones,” The Log Analyst, Vol. 31, No.4, pp.189-197, 1990.
A laboratory study of the response of two types of shallow laterolog tools was performed. In the first type, the symmetrical electrodes were short-circuited so that only one focusing current was used. In the second type, the symmetrical electrodes were not shorted, and two focusing currents were used. The model tools were scaled down by approximately 20 : 1, and synthetic (digital) focusing, which is based on the principle of superposition, was used. Synthetic focusing requires the measurement of the potentials at the monitor electrodes for separately applied currents. The effects of the small but finite frequency used in the tool are discussed. Moreover, it is shown that the unshorted tool is more accurate than the shorted tool when the tool is near a high contrast zone. Furthermore, the logs obtained from scale modeling are shown to agree very well with logs computed using the finite-element method.