Main Areas of Geophysical Methods

Main areas of geophysical methods The geophysical methods can be used, for example, when one wants to characterize the properties of the shallow subsurface (ranging from a few meters to several hundred or thousand meters in depth), in situations such as: - groundwater search or in the investigation of its contamination; - provision of mechanical parameters for civil engineering works (bridges, roads, foundations, roads, dikes, etc.); - investigation of possible environmental contamination by landfills or cemeteries; - search for equipment and machinery in the event of a dam break or landslide; - characterization of mineral provinces of exploratory interest or investigation of the geometry of mineralized bodies; - monitoring of volcanic activity; - archaeological investigations; - forensic investigations. The most used techniques for the characterization of mineralizations involve direct methods of collection by rotary drilling, which is usually expensive and time-consuming. Geophysics reduces the need to use these drilling techniques, and it becomes particularly important in the case of small and medium-sized companies, since the rental value of machines of this type is beyond the capital normally provided by these companies. For comparison, using the geophysical electroresistance method as an example, only a battery or stable voltage source, low-cost cables and electrodes are required for data acquisition. In addition to the cost, the gain in execution time of a geophysical survey in comparison with traditional direct methods is usually significant. Even though geophysical techniques do not normally allow determining the purity levels of an ore, its use can provide very relevant information for further direct drilling, in addition to not interfering with the environment, because they do not require drilling. Studies show that the use of geophysical methods can reduce the amount of unsuccessful drilling by almost half for the assessment of mineral deposits of exploratory interest, depending on their characteristics. Geophysical methods can also be used to investigate structures and processes of deep origin, ranging from a few to several thousand kilometers deep, in situations such as: - mapping of structures that have potential to accumulate hydrocarbons; - studies on the generation and characteristics of the Earth's magnetic field, at present time and in the past; - analysis the distribution of earthquakes and use this information to characterize the global structure of the planet; - characterization of the seismic risk of a region and monitoring of tsunamis; - determination of the parameters of the gravity field and their use in the determination of the Earth's internal distribution of densities; - study and characterization of deep ocean areas The first stage of the search for hydrocarbons is done by looking for areas that, due to their geological characteristics, indicate a favorable history for the existence of rocks capable of being the generators and the reservoirs of the oil, normally conducted by geologists. From there, the recognition of layers and geological structures capable of accumulate oil usually has to be done using geophysical investigation methods, to validate or complement the geological information and indicate the possibility of the existence of such structures. Geological faults also need to be mapped, as they can cause large vertical displacements of the layers, and even cause loss of hydrocarbon or its displacement to areas at different depths. If exploration is carried out at the bottom of the ocean, which occurs very often, the search and drilling of a well oil is extremely expensive, and the use of geophysical methods is essential to minimize the costs and allow the best location of a well.