Geoelectrical Measurements to Monitor a Hydrocarbon Leakage in the Aquifer: Simulation Experiment in the Lab

Abstract

Hydrocarbons represent one of the most dangerous sources of contamination for environmental resources. Petroleum contaminants released from leaking fuel storage tanks or accidental spillages represent serious worldwide problems. Knowledge of the contaminant distribution in the subsoil is very complex, and direct measurements, such as boreholes or drillings, are strongly required. Even if the direct measurements define accurate information, on the contrary, they have low spatial coverage. Geophysics can effectively support conventional methods of subsoil sampling by expanding the information obtainable, providing to analyze, with higher resolution, larger areas of investigation. Consequently, different geophysical techniques have been used to detect the presence and distribution of hydrocarbons in the subsurface. Electrical resistivity tomography is an efficient geophysical methodology for studying hydrocarbon contamination. Indeed, this methodology allows for the reduction of the number of drillings or soil samples, and several papers described its success. One of the advantages is the possibility to successfully perform analyses in time-lapse to identify the degradation of the contaminants. Indeed, natural attenuation of hydrocarbon contaminants is observed under aerobic conditions due to biodegradation, which should be the principal phenomenon of physical variations of the subsoil. Therefore, a laboratory experiment was conducted in a sandbox to simulate a spillage of common diesel occurring in the vadose zone. The sandbox was monitored for a long period (1 year, approximately) using time-lapse cross borehole electrical resistivity tomographies. Results highlight the usefulness of in-hole electrical tomography for characterizing underground hydrocarbon leakage and the variability of the subsurface physical behavior due to contaminant degradation. Therefore, the experiment demonstrates how the electrical method can monitor the biodegradation processes occurring in the subsoil, defining the possibility of using the methodology during remediation activities.

Estimation of the AC electrical properties of some clay ceramic samples under different compositions and firing temperatures

“…When a material is exposed to an alternating electric eld, charge carriers begin to travel across its conducting components; however, they come to a stop at the interfaces (Abd El Aziz and Gomaa, 2022a, b). As the electric eld's frequency and the distance between conducting grains get smaller, this process (polarization) becomes more intense (Capozzoli et al 2022; Gomaa 2022a, b, and c). The Maxwell-Wagner effect results from this dynamic nature of the interfacial charge accumulation as a function of frequency.…”

Estimation of the AC electrical properties of some clay ceramic samples under different compositions and firing temperatures

“…Figure (9) depicts the relationship between dielectric constant and frequency. All of the curves can be divided into two categories: low frequency (>1 kHz) and high frequency (<1 kHz).…”

“…Figures (9)(10)(11)(12)(13)(14) depict the variation of electrical properties versus frequency for clay ceramic samples red at various temperatures.…”

“…In contrast, Ba, Ni and Sc are low. The trace element concentrations of clay samples gathered from El-Sheikh Fadl are present at Table (1) and (3).The chemical composition of El-Minya clay samples, as determined by the XRF powder method, is summarized in Table4, Fig (9)…”