Geoelectrical characterization of an oil-contaminated site in Tabasco, Mexico (original) (raw)
Related papers
InTech eBooks, 2018
Electrical methods are effective tools for the characterization of oil-contaminated sites and are applied in defining the geometry of the contaminated plume and in designing the remedial process. The optimal methodology integrates geoelectric methods, data processing, and interpretation techniques. Electromagnetic profiling is a reliable and fast method used to provide the configuration of oil-contaminated plume from apparent resistivity map and used to guide the subsequent electrical resistivity tomography survey. From advanced field work methods, data processing, and interpretation procedures, electrical resistivity tomography survey provides the three-dimensional (3D) configuration of the contaminated plume, migration pathways, location of active contaminated sources, and information about lithology. For separate contaminated and clean zones, a petrophysical modeling is used for the calculation of soil resistivity based on groundwater salinity. Taking the pore-water salinity value into account, an inversion algorithm recalculates resistivity maps into maps of clay content, porosity, and cation exchange capacity, allowing a more accurate determination of the volume of contaminated soil. From clay content data, hydraulic conductivity values are calculated for determining the groundwater vulnerability due to vertical migration of contaminants from upper layers. The optimal geoelectric methodology is an efficient procedure to assess hydrocarbon-contaminated sites, with emphasis on large sites with deeper groundwater table.
Study of Petroleum Contaminated Sites in Mexico with Resistivity and EM Methods
Symposium on the Application of Geophysics to Engineering and Environmental Problems 2005, 2005
Hydrocarbons are among the main factors of geological medium contamination. We differentiate long-term contaminations lasting years or decades of years and short-term contaminations or single accidents. The first produces give more evident geophysical anomalies, whereas anomaly strength of the second depends on the time since the accident occurred. After 6-12 months following the accident this type of contamination gives measurably low resistivity anomalies.
Geoelectrical characterization of a site with hydrocarbon contamination caused by pipeline leakage
Geofísica …, 2006
El método Sondeo Eléctrico Vertical (SEV) es ampliamente utilizado en estudios de impacto ambiental incluyendo el caso de contaminación por hidrocarburos. En este trabajo se presentan los resultados de la caracterización geoeléctrica de un sitio contaminado por hidrocarburos relacionado con una fuga en línea de ducto. El estudio geoeléctrico fue realizado utilizando el método SEV en la variante de tomografía, realizándose una interpretación 2D de los datos observados. Seis perfiles paralelos de SEV fueron medidos y presentados sus resultados en secciones y mapas. Se determinó un modelo estratificado que incluye acuitardo y acuífero. Aunque el grado de contaminación en este sitio es bajo fue posible localizar dos zonas contaminadas dentro del acuífero. El acuífero y el acuitardo fueron caracterizados con base en su resistividad, contenido de arcilla, porosidad y capacidad de intercambio catiónico. Los valores de resistividad fueron recalculados a valores de parámetros petrofísicos utilizando un algoritmo de inversión que toma en cuenta la salinidad del agua de poro. En zonas no contaminadas los parámetros petrofísicos estimados a partir de datos de resistividad presentan valores cercanos a los reales, mientras que en zonas contaminadas se obtienen valores anómalos. Efectos similares de la influencia contaminación sobre los parámetros petrofísicos fueron encontrados en laboratorio realizando mediciones de resistividad en muestras de arena limpia y contaminada.
Investigations of geoelectrical signatures at a hydrocarbon contaminated site
Journal of Applied Geophysics, 2000
This study provides an evaluation of the utility and resolution of different geoelectrical methods in mapping contaminant distribution in the subsurface, and provides a window into the processes that may control their response at a site in Central Ž. Ž. Michigan. In situ and 2D surface resistivity, ground penetrating radar GPR , and electromagnetic methods EM constrained Ž. by soil boring data were used to investigate the electrical properties of a light nonaqueous phase liquid LNAPL contaminant plume that resulted from 50 years of leakage into a glacio-fluvial geologic setting. Overall, the electrical signature from the in situ resistivity measurements were best able to image the subsurface stratigraphy and the associated contamination zone. GPR also mapped the subsurface stratigraphy. In particular, the GPR recorded a reflector that is subparallel to the water table, and occurs a few meters above the current free product level, which is coincident with the top Ž. of an oil-stained, light-gray sand layer. Further, regions of attenuated GPR reflections shadow zones due to enhanced conductivities were found to be coincident with low apparent resistivities. 2D geoelectrical measurements successfully imaged the top of the saturated zone and the underlying clay layer, but was unable to resolve any anomalous region that could be attributed to the hydrocarbon contamination. Likewise, the EM results provided no evidence of the presence of the free product plume at depth. Throughout this investigation, geoelectric measurements consistently recorded low resistivities Ž. high apparent conductivities associated with zones containing the freerresidual product plume instead of high resistivities as has been suggested by the simple intuitive model. From this, it is inferred that substantial modification of the geochemical characteristics of the plume, surrounding media, and associated groundwater has occurred as a result of biogeochemical reactions. It is evident from this study that in situ resistivity measurements combined with surface geoelectrical measurements can characterize the distribution of conductive zones that may be associated with the biodegradation of LNAPL in the subsurface. Thus, the application of these techniques to hydrogeologic, contaminant monitoring, and remediation studies are far reaching.
SEG Technical Program Expanded Abstracts 2004, 2004
Resistivity method is used extensively in environmental impact studies. In this work, the results of the geoelectrical characterization of a hydrocarbons contaminated site are presented. Although the contamination grade of the study area is low, were mapped two contaminated zones into sandy aquifer. In addition, petrophysical parameters were estimated by recalculate of ground and water resistivity values in clay content, porosity and CEC values. Anomalous values of clay content, porosity and CEC indicate the presence of hydrocarbon contaminants. The correlation between geoelectrical results, petrophysical parameters and hydrocarbons contamination was verified in laboratory by electrical measurements made in pure and contaminated sand samples.
Application of Electrical Resistivity Tomography in Mapping Subsurface Hydrocarbon Contamination
Earth Science Research, 2012
The subsurface soil around Baruwa community was reportedly contaminated by hydrocarbon not because the area falls within oil-producing community but it suffers from inceasant leakage from petroleum pipeline that supply petroleum products to hydrocarbon terminar located within the area. Thus, to ascretain the extent of contamination of the subsurface soil around the area, an integrated geophysical methods involving vertical electrical sounding (VES) and electrical resistivity tomography (ERT) supported with induced polarization (IP) and spontaneous potential (SP) methods were carried out. The hydrocarbon contaminated layers were marked out beneath each VES point by high resistivity ranging between 943Ωm and 4749Ωm at a depth of 1 to 35.44m below the surface. Similarly, ERT result shows that the subsurface soil around the investigated area has been contaminated at a shallow depth of about 2m downward with resistivity value above 1000Ωm. IP and SP data were Integrated to identify the sandy contaminated layers from clayey layer. IP value of 0 to 10mV/V and SP values of <+10mV were obtained over the sandy formation. The work shows that hydrocarbon leaking from the pipeline laid a few meters beneath the earth surface actually flow both upwardly (possibly due to seasonal variation in the water table which is usually close to the surface during rainy season) to the surface and downwardly at greater depth into the subsurface, through a porous medium-sandy layer. This may probably accounts for the reason while most of the handdug wells in the area are reportedly contaminated with hydrocarbon products.
The effect of crude oil and gas on soil resistivity was evaluated in order to characterize and determine the level of hydrocarbon contamination in the soil and the depth of groundwater contamination. Twelve vertical electrical soundings (VES) was carried out in the area using ABEM SAS 1000 TERRAMETER with electrode spacing (AB/2) ratio of 60m at intervals thus probing to a depth of about 20m. The data was interpreted with WINGLINK computer software. The result showed that there are four layers in the area with thickness varying between 0.11m and 5.12m. The apparent resistivity values of the contaminated soil at Alesa ranged from 93.37Ωm to 5336.63Ωm while that of the uncontaminated soil at Okirika ranged from 0.57Ωm to 113.60Ωm. The soil at Alesa thus depicts a random distribution of contaminant at the subsurface ranging from low impact zone to a very high impact zone to a depth of about 20m. It is therefore recommended that a deep and well grouted borehole be sunk to a depth beyond 35m to abstract clean, portable and uncontaminated water from the aquifer in the Alesa area.
Geoelectrical investigation for the assessment of groundwater conditions: a case study
Annals of Geophysics, 2005
An electrical resistivity survey involving Vertical Electrical Soundings (VES) was carried out in the Shooro Basin in Southeast Iran in order to study groundwater conditions such as depth, thickness and aquifer boundaries. Vertical electrical soundings by Schlumberger array were conducted in this area. The resistivity Schlumberger soundings which have a maximum current electrode spacing (AB) ranging from 200 m to 600 m were carried out at 207 positions in 19 profiles. Interpretation of these soundings indicates the presence of an alluvial aquifer. This aquifer is divided into eastern and western parts by the Shooro River, which comprises a variable thickness and resistivity of deposits. The average permeability coefficient and resistivity in the western part, especially southwest is higher than the eastern part of the aquifer. Therefore, it seems that Shooro River follows a fault zone in the region. The high resistivity of west part is due to the water quality and the existence of alluvial fan with coarse grain materials. Low aquifer resistivities in the east are associated with finer materials and also brackish water infiltration from the adjacent basin mainly in the central part of the aquifer. Furthermore, zones with high yield potential have been determined in this research based on the resistivity data.
Mapping of Aquifer Contamination Using Geoelectric Resistivity: Case Studies
Direct Current (DC) resistivity techniques of geophysical exploration are popular and proved to be successful and have many implications in the fields of engineering, geoenvironment and hydrogeology. In this paper, the electric resistivity technique proved to be successful method for mapping of Quaternary aquifer conditions in the East Nile Delta, Egypt and in Wadi Ham, United Arab Emirates (UAE). The application of this technique gave excellent information, about the aquifers lithology, their thicknesses, salinity, contamination and other valuable information. In the Eastern Nile Delta area, a detailed Vertical Electrical Soundings (VES) were implemented to explore the Quaternary aquifer subsurface conditions at this area. While at Wadi Ham, UAE, Two Dimensional (2-D) earth resistivity imaging survey was conducted to delineate the seawater intrusion for this coastal aquifer. The interpretation of the acquired resistivity data with aid of the available borehole information at both a...
Journal of Physics: Conference Series, 2019
Geoelectrical resistivity survey has been conducted within the Kurata dump site in Ota, southwestern Nigeria. This present study focuses on the use of 2D resistivity imaging and Vertical Electrical Sounding to delineate conductive leachate point and degree of movement within the subsurface for conceivable groundwater pollution. The 2D resistivity survey was carried out using the ABEM Terrameter (SAS 1000/4000) System with multiple-gradient array electrode configuration. The Vertical Electrical Sounding was conducted using the schlumberger electrode configuration. One 2-D imaging profile of length 100m and one Vertical Electrical Sounding of length 200m were acquired on the established traverse. The resistivity data was inverted utilizing RES2DINV and WinResist to obtain the inverse model resistivity distribution. The 2D inverse resistivity models of the subsurface showed that the study site has a multi-layered aquifer system, four geoelectrical layers were inferred from the resistivity imaging and they are lateritic clay, clayey sand, sandy clay and coarse sand units. There is one aquifer system about 13 m which is highly polluted. The unpolluted aquifer system is localized around 19 m with inverted resistivity range 498Ωm-685Ωm in the traverse. Also there might be conceivable sullying of deep groundwater system in the long term if appropriate moderation procedures are not thought about at the area.