Chapters authored
Estimation of Hydrological Parameters from Geoelectrical Measurements
In the coastal aquifer of the lowlands on the right side of the river Sinaloa there is need for fresh water for agricultural development since, around 15% of the water used in agricultural irrigation, is from underground sources. This situation is exacerbated in periods of drought, which promotes drilling with the risk of finding brackish water in them; besides, there is the risk of not meeting water demand due to low hydraulic transmissivity (T) of the aquifer, putting at risk the drilling costs that this implies. In this sense, the determination of T and K (hydraulic conductivity) is important for the development and management of groundwater exploitation of the study area. Generally by means of pumping tests in wells, T is obtained, with high costs, so there are few values of T. K is generally obtained by wells and laboratory test. The aim of this chapter is to establish an empirical relationship between T and K with Dar-Zarrouk parameter in porous media, transverse resistance (T R ), in addition to a characterization of the water quality through the electrical resistivity. This parameter is estimated from surface resistivity measurements, which are more economical in relation to the pumping tests; thus, T was characterized in the study area. The coefficient of correlation of the exponential adjustment is 0.79 and the relation is T=137185.7 TR0.020758−156691 and K=367.210.0548−518.813 with coefficient of correlation of 0.678.
Part of the book: Electrical Resistivity and Conductivity
Characterization of Hydrocarbon-Contaminated Sites Based on Geoelectrical Methods of Geophysical Exploration
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.
Part of the book: Geophysics