Resistivity monitoring of oil migration in heterogeneous water-bearing soil

The heterogeneous soil layer was established by self-made three-dimensional plexiglass tank, and two leakage points in shallow and interior soil layer were set up to simulate the mobile phase crude oil migration and redistribution process under the condition of water level fluctuation in water-bearing soil layer. The corresponding resistivity response characteristics were revealed using self-made high density electrode arrays and electrometer. The results showed that the migration of crude oil in soil was affected by the leakage source location, the leakage volume and the soil layer structure. The transverse diffusion of the leakage point in the same soil layer was more obvious in the vertical direction, and oil around the shallow leakage point diffused around. The larger the leakage volume, the wider the pollution range. The higher the permeability of the soil layer, the deeper the pollution depth. There were two kinds of anomalies in high resistance and low resistance after crude oil leakage. When the soil layer structure was simple and the oil content was high, the high resistance anomaly was obvious. When the composition of soil layer was complex, especially the salt and clay mineral contents were high, or the water and oil contents were low, the low resistance anomaly was easy to occur. After the water level rose, the overall soil resistivity decreased and the crude oil was concentrated to the center of the polluted area. After the water level dropped, the resistivity increased, the crude oil dispersed around. From the above, the water level fluctuation caused the oil to diffuse further. Affected by the internal leakage point, the closer near the leakage point (0.08m), the more serious the pollution at the depth. In addition, the oil content in the lower part of the leakage point(0. 15m) was higher than that in the upper part (0.04m), indicating that the downward migration of oil was more obvious than the upper one around the internal leakage point. © 2020, Editorial Board of China Environmental Science. All right reserved.