SIMULAÇÃO EM LABORATÓRIO DOS PRINCIPAIS POTENCIAIS ESPONTÂNEOS OBSERVADOS EM POÇOS DE PETRÓLEO PARA FINS DIDÁTICOS

Laboratory simulations of main spontaneous potentials observed in oil wells for educational purposes

Abstract

This work focuses on laboratory simulations of the main spontaneous potentials observed in oil wells. Liquid junction potential was simulated using a box filled with sand and divided by a porous membrane. On one side, brine was added (simulating the virgin zone in the reservoir rocks) and on the other side, drilling fluid was added (simulating the washed zone). In the first (second) situation, the measurements were carried out without (with) the addition of brine. In the first (second) situation, a potential of 0.40 ± 0.09 mV (-22.65 ± 0.31 mV) was measured and thus, the liquid junction potential was demonstrated. Membrane potential was simulated using a second box filled with sand and brine at the bottom (simulating the sandstone with the water formation) and clay at the top (simulating the shale). In the first (second) situation, the potentials were measured without (with) the addition of drilling fluid on the clay. The measured potential for the first (second) situation was -1.91 ± 0.10 mV (0.62 ± 0.12 mV). From the comparison between the measurements of the first and second situations, a positive potential difference was observed, that is, the membrane potential was simulated.

Keywords: Spontaneous potential. Liquid junction potential. Membrane potential. Oil wells.