Integrated application of geophysical loggings and fracture survey on rock exposures for identifying transmissive fractures in crystalline aquifer: case study in the city of São Paulo

Abstract

The integrated analysis of geophysical loggings for identifying transmissive fractures has had a limited use in Brazil, although a large number of studies have been conducted so far throughout the world. The application of those tools has gained a crescent importance as they are needed for characterizing groundwater contamination in fractured rock aquifers at a great number of industrial sites worldwide and in Brazil. This paper presents the analysis of data collected by caliper, optical televiewer (OPTV), acoustic televiewer (ATV) and flowmeter loggings in four deep supply wells located in the industrial area of Jurubatuba, city of São Paulo. Five fracture sets (G1 through G5) were identified based on OPTV and ATV borehole loggings. The main fracture set (G1), NE-striking with low to intermediate dip, is subparallel to the foliation, being at great extent the result of the reactivation of this previous discontinuity. Fractures on ATV and OPTV images were visually classified with regard to flow evidence, and a positive correlation between high flow evidence and significant flow rate, measured by a flowmeter, was identified. On the other hand, the majority of fractures with insignificant, low or intermediate flow evidence are located in depth intervals with no significant flow rate. Fractures that belong to G1 are of major importance for flow, as in 9 of the 16 intervals with significant flow, they are the only fractures present. Data were inconclusive regarding transmissivity of high dip fractures, because few of them were intercepted by the well boreholes. However, there is evidence that subvertical fractures of sets G3 and G5, NE and NW striking, respectively, are also transmissive, which corroborates outcrop observations. Although geophysical loggings are essential to identify the most important segments of boreholes for water input and output, and to collect detailed data of low dip fracture sets at greater depths, the structural geology characterization of fractured aquifers cannot rely on borehole geophysical loggings alone. For proposing realistic conceptual models of the fracture network, data from boreholes should be complemented with data from large rock exposures (quarries), in order to describe geometrical parameters, such as spacing, length, and physical connectivity of low, intermediate and high dip fractures, as well as evidence of flow along individual fractures.

Semantic Terrain Segmentation in the Navigation Vision of Planetary Rovers—A Systematic Literature Review

“…[ 101 , 102 , 103 ]) found by combining (ii-a), (iii-a), (iii-b), and the new search command, two surveys (refs. [ 104 , 105 ]) found by combining (ii-a), (ii-b), (iii-b), and the new search command, and no surveys found by combining (ii-a), (ii-b), (iii-a), and the new search command.…”

“… This survey studied the autonomous spacecraft relative navigation technology instead of the terrain for planetary rover navigation. [ 104 ] This survey is not an SLR. This survey did not concentrate on the impact of computer vision and artificial intelligence.…”

Potential and prospects for hydrogeological exploration according to lithostructural criteria in Antioquia department, Colombia

“…Studies on aquifers in fractured environments have increased given the extent of hard rocks in the global geological context and the growing dependence on the water that circulates through them (Fiume et al, 2020). Hard rocks constitute the basement of all continents (Lachassange et al, 2021) and are particularly exposed on the surface of the great shields of Africa, India, North America, South America, Australia, and Europe.…”

Litho-structural conditioning in the exploration of fractured aquifers: a case study in the Crystalline Basement Aquifer System of Brazil

“…More robust techniques, such as geophysical profiling, for example, thermal, sonic, optical profiling, etc. (Danielsen et al 2007;Fiume et al 2020), as well as more traditional techniques, such as field mapping (Gleeson and Novakowski 2009;Fernandes et al 2016) and well monitoring (Comte et al 2012;Hammond 2018) are important to improve the conceptual model of the aquifer, however this study aims to make an initial contribution to the region's crystalline aquifer, in a regional and remote way, using, therefore, investigative techniques that will serve as a basis in the future for further studies in greater detail such as outcrop analysis, geophysical profiling and hydraulic well monitoring. In this sense, we address in this study the location of the wells and their production values, and the remote sensing mapping of outcropping structures in the relief and magnetized structures, associating these mapped structures and the wells with the spatial distribution of the lithologies and the tectonic context past and current of Paraná's crystalline basement.…”