Experimental apparatus for non-contact resistivity measurements of the rock core plug based on magnetic induction

A new apparatus has been developed to measure the conductivity of rock samples. The probe, which consists of multi-coil transmitters and receivers doesn't require physical contact with the samples. The measurement is based on the induction principle. The measurement system is validated by using saline solutions and water-saturated sands of known conductivity. This work presents details of the development of a system of magnetic resistivity measurements by magnetic induction for petrophysical applications. The first application consists of measuring the resistivity of the core plug which is 0.038 m in diameter. Currently the system is operating properly at a frequency of 50 kHz with a current of up to 500 mA at 20 {\deg}C. During the study two types of samples were investigated: aqueous solutions with conductivities between 1 to 100 mS/cm and rocks. Several tests were carried out with the objective of investigating the performance of the instrument, such as the experiment to obtain sensitivity for the measurement system as a function of the current applied to the transmitter coil.