A água subterrânea abastece grande parte da população e sua contaminação é assunto de interesse público. Os postos de combustíveis são fontes potenciais de contaminação, devido à sua extensa malha de distribuição e pelo armazenamento de produto ser predominantemente subterrâneo. Dentre os métodos para detecção de hidrocarbonetos, os geofísicos proporcionam investigação em maiores extensões, com mais rapidez e menor custo. Este estudo apresenta os resultados de quatro métodos geofísicos (eletrorresistividade, polarização induzida, georradar e eletromagnético EM-34) na investigação de dois perfis a jusante de um posto de combustível com histórico de vazamento. Os objetivos foram de detectar a pluma de contaminação e identificar qual dos métodos apresenta os melhores resultados nesta situação. A eletrorresistividade apresentou a melhor correlação com a zona contaminada e com as análises químicas. Os dados da polarização induzida também se relacionaram com a pluma. Os valores do sistema EM-34 ficaram aquém das expectativas. Os do georradar não possibilitaram nenhuma correlação com o substrato contaminado, certamente devido a pouca profundidade de penetração. Foi constatado que a contaminação por hidrocarbonetos não oferece assinatura geoelétrica previsível, devido às condições dinâmicas do campo e suas inter-relações. Enquanto muitos trabalhos associam baixas resistividades aos vazamentos antigos, outros trabalhos mostram o inverso. Neste estudo, a anomalia encontrada apresentou alta resistividade associada às cargabilidades mais altas. / A large portion of the population is supplied with groundwater, and this is a matter of public interest. Gas stations are potential sources of contamination for its extensive distribution network and for the underground storage. Among the existing methods for hydrocarbon detection, the geophysical ones provide a larger range, faster results at smaller costs. This work presents the results of four geophysical methods (electrical resistivity, induced polarization, ground penetrating radar and electromagnetic EM-34) applied to the study of two profiles downwards of a leaking gas station. The objectives were detecting the contamination plume and identify which of the methods employed presents the best results on this site. The electrical resistivity method presented the best correlation with the contaminated zone and chemical analysis. The results of the induced polarization were also associated with the contamination plume. Values obtained with the EM-34 didn?t fulfill the expectations. GPR data didn?t correlate with the contaminated substrate, certainly due to the shallow penetration depth. It was observed that the hydrocarbon contamination does not offer a predictable geoelectrical signature, due to the dynamic conditions of the field and its inter relations. Whilst several paper associate low resistivities to older leakages, in other papers it was found the opposite. In this case study, the anomaly has shown characteristics of high resistivity associated to higher chargeabilities.

The integrated use of Electromagnetic Ground Conductivity, Ground Electrical Resistivity and Seismic Refraction geophysics methods was made in Alia valley, Eritrea for the aim of developing a methodology best suited for ground water exploration in hard rock areas with limited professional and financial resources. A total area of 25 square kilometer was covered with the geophysical surveys. The effective use of information from wells and geological information from outcrops and existing literature helped to create a preliminary conceptual hydrogeologic model that in turn provided a general picture of the research site in terms of its groundwater potential and related factors. The optimum configuration of the geophysical methods and their interpretation was researched by the use of synthetic mathematical models and experimental surveys in areas of known hydrogeological characteristics like lithology and depth of water table. Two approximately parallel electromagnetic ground conductivity profile lines crossed the survey area in approximately north-south direction to assess the variation in the electrical conductivity of the major geological structures. Vertical electrical sounding (VES) surveys were conducted close to existing wells with lithological information and at some selected sites. Survey sites for the two dimensional electrical resistivity imaging and the seismic refraction surveys were selected based on the results from the electromagnetic ground conductivity surveys. The formal geophysical surveys results were correlated with nearby boreholes and with each other. The responses of the different geophysical methods for each lithological layer were recognized. In addition, the location and characteristics of the major geological structures of the area were studies based on the information from the geophysical surveys and other available information. At the end of the research, parts of the research area with better groundwater potential were identified. As a result of the research, an efficient and cost effective geophysical approach was developed for groundwater exploration in hard rock areas of Eritrea and similar places of the world. Recommendations were made on the wider and effective use of the approach with due consideration for the limited financial, human resource and material capacities available for ground water exploration in most countries of Africa and other countries of the world.

No description available.

No description available.

No description available.

The need for accurate reference bases for any gravimetric work can hardly be overemphasized. During the months of March, April, and May, 1964, about 130 gravity observations were made in Arizona, with LaCoste Romberg Gravity Meter DL-1 and Worden Gravity Meter (Educator) No. 461. The purpose of this program was to establish 1) a 1st order control airport gravity base network, 2) a standard calibration range for the State of Arizona, and 3) to gain a structural interpretation of the Tucson Basin. Gravity data were analyzed as to their accuracies and reliabilities, taking into consideration errors involved in tidal corrections, drift corrections, reference datum, and nonlinearity of scale factor of the meters. It is concluded that the reliability of these data is .1 milligal or better. While correcting for the tidal variation of gravity, it was noticed that there was a discrepancy between the theoretical and observed tidal correction values. For any additional precise work, it is desirable to correct for tidal variations from actual records, if available, in conjunction with the theoretical tables. Causes for this discrepancy in tidal gravity variation need further study. Programs were written for a digital computer to calculate 1) the theoretical gravity values from the International Gravity Formula, and 2) Free-Air Anomalies, Bouguer Anomalies and Special Bouguer Anomalies from field data for various stations. Free-Air and Bouguer Anomaly values for different stations were analyzed as to their implications in terms of isostasy, crustal structures and local geological structures. Results from Simple Bouguer Anomaly values indicate a crustal thickness of 49 km to 33 km for Arizona with broad isostatic compensation for regional surface irregularities. An analysis of residual Bouguer gravity anomalies of the Tucson Basin in terms of local geological structures, indicates a basin and range structure for this region. The thickness of sediments ranges from more than 700 feet on the north to more than 8000 feet towards the south of the basin with faults indicated in it. Application of a limiting -depth interpretation method implies that the tops of the disturbing bodies can be no deeper than 2 miles below sea level. A total mass deficiency corresponding to the residual gravity low in this basin comes out to be 1.8 x 10¹⁷ grams according to two – dimensional form of Gauss' Theorem. This corresponds to a 135 cubic mile volume of material with a density .3 grams per cubic centimeter less than the enclosing rocks. From porosity and volume considerations of the sediments in the Tucson Basin, it is estimated that the total water holding capacity may be of the order of 4.6 x 10⁷ acre feet.

Οι θαλάσσιες γεωφυσικές μέθοδοι αποτελούν ένα πολύ χρήσιμο μέσο για τη μελέτη της ενάλιας αρχαιολογίας γιατί βοηθούν στη γρήγορη επισκόπηση μεγάλων εκτάσεων του πυθμένα και στον εντοπισμό αρχαιολογικών στόχων που μπορεί να βρίσκονται θαμμένοι κάτω από πετρώματα του πυθμένα. Επίσης οι θαλάσσιες γεωφυσικές μεθόδοι χρησιμοποιούνται για για τον προσδιορισμό των παλαιοακτών. Με αυτό τον τρόπο μπορει να γίνει ανάπλαση του παλαιόπεριβάλλοντος και της μορφολογίας μιας περιοχής και να συγκεντρωθούν πολύ σημαντικα στοιχεία για τη γεωλογία της περιοχής έρευνας και τον τρόπο με τον οποίο εξελίχθηκε με το πέρασμα των χρόνων. Η διπλωματική αυτή πραγματεύεται τον τρόπο έρευνας και τις γεωφυσικές μεθόδους που χρησιμοποιήθηκαν για την ανάπλαση των παλαιοακτών στην περιοχή Πόρου- Μοδίου, τα συμπεράσματα που προέκυψαν και οι`αρχαιολογικοί στοχοι οι οποιοι βρέθηκαν. Κατασκευάστηκε ο βυθομετρικός χάρτης της περιοχής, και έγινε η ανάπλαση των εντοπισμένων παλαιοακτών. Τέλος καταγράφηκε ο εντοπισμός ενός μυκηναικου ναυαγίου στο ένα άκρο της νήσου Μόδι. / Marine geophysical methods are a very useful tool for the study of underwater archeology, because they help in quick overview of large areas of the seafloor and identify archaeological objectives which can be found buried under the rock bottom. Also marine geophysical methods used to determine palaeoshorelines. In this way can be palaeoenvironmental reconstruction and morphology of an area and gather crucial information on the geology of the study area and how they evolved over the years. This dissertation discusses the research and the geophysical methods which were used for regeneration palaeoshorelines in Poros-Modi and the conclusions and the 'archaeological objectives which were found. Build a bathymetric map of the area, and became the regeneration of localized palaeoshorelines. Finally recorded the location of a Mycenaean wreck at one end of the island of Modi.

A água subterrânea abastece grande parte da população e sua contaminação é assunto de interesse público. Os postos de combustíveis são fontes potenciais de contaminação, devido à sua extensa malha de distribuição e pelo armazenamento de produto ser predominantemente subterrâneo. Dentre os métodos para detecção de hidrocarbonetos, os geofísicos proporcionam investigação em maiores extensões, com mais rapidez e menor custo. Este estudo apresenta os resultados de quatro métodos geofísicos (eletrorresistividade, polarização induzida, georradar e eletromagnético EM-34) na investigação de dois perfis a jusante de um posto de combustível com histórico de vazamento. Os objetivos foram de detectar a pluma de contaminação e identificar qual dos métodos apresenta os melhores resultados nesta situação. A eletrorresistividade apresentou a melhor correlação com a zona contaminada e com as análises químicas. Os dados da polarização induzida também se relacionaram com a pluma. Os valores do sistema EM-34 ficaram aquém das expectativas. Os do georradar não possibilitaram nenhuma correlação com o substrato contaminado, certamente devido a pouca profundidade de penetração. Foi constatado que a contaminação por hidrocarbonetos não oferece assinatura geoelétrica previsível, devido às condições dinâmicas do campo e suas inter-relações. Enquanto muitos trabalhos associam baixas resistividades aos vazamentos antigos, outros trabalhos mostram o inverso. Neste estudo, a anomalia encontrada apresentou alta resistividade associada às cargabilidades mais altas. / A large portion of the population is supplied with groundwater, and this is a matter of public interest. Gas stations are potential sources of contamination for its extensive distribution network and for the underground storage. Among the existing methods for hydrocarbon detection, the geophysical ones provide a larger range, faster results at smaller costs. This work presents the results of four geophysical methods (electrical resistivity, induced polarization, ground penetrating radar and electromagnetic EM-34) applied to the study of two profiles downwards of a leaking gas station. The objectives were detecting the contamination plume and identify which of the methods employed presents the best results on this site. The electrical resistivity method presented the best correlation with the contaminated zone and chemical analysis. The results of the induced polarization were also associated with the contamination plume. Values obtained with the EM-34 didn?t fulfill the expectations. GPR data didn?t correlate with the contaminated substrate, certainly due to the shallow penetration depth. It was observed that the hydrocarbon contamination does not offer a predictable geoelectrical signature, due to the dynamic conditions of the field and its inter relations. Whilst several paper associate low resistivities to older leakages, in other papers it was found the opposite. In this case study, the anomaly has shown characteristics of high resistivity associated to higher chargeabilities.

Orientadores: Saul Barisnik Suslick, Alexandre Campane Vidal / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecanica e Instituto de Geociencias / Made available in DSpace on 2018-08-12T08:19:21Z (GMT). No. of bitstreams: 1 Rosa_Henrique_D.pdf: 5323611 bytes, checksum: 9779cc866a624b65a3932fa6ade79e78 (MD5) Previous issue date: 2006 / Resumo: Este estudo se foca na elaboração de um método de caracterização de eletrofácies, o qual utiliza dados de perfis geofísicos de poços referentes às classes litológicas identificadas nos testemunhos desses poços, por meio do emprego de análises qualitativas associadas a tratamentos estatísticos multivariados. A princípio, o estudo visa estabelecer uma rotina de análises qualitativas para os dados litológicos extraídos dos testemunhos e associados aos perfis, por meio de ferramentas estatísticas básicas, com o objetivo de identificar agrupamentos de classes litológicas e caracterizar as eletrofácies presentes no intervalo testemunhado. Numa segunda etapa, aplica-se a técnica estatística multivariada da Análise de Agrupamentos em dois passos, a qual gera agrupamentos (eletrofácies) por meio da associação dos dados dos perfis com as classes litológicas descritas nos testemunhos. Numa terceira etapa, esses agrupamentos são avaliados quantitativamente por intermédio de ferramentas estatísticas, as quais incluem a Análise de Variância Simples (one way Anova), o Teste de Médias e a Análise Discriminante. Como exemplo de aplicação, utiliza-se um conjunto de dados que inclui perfis e descrições de testemunhos de três poços verticais do Campo Escola de Namorado, localizado na Bacia de Campos, no Estado do Rio de Janeiro. Os resultados obtidos mostram um bom desempenho da Análise de Agrupamentos em dois passos para a caracterização de eletrofácies, e permitem que se obtenham informações acerca da qualidade da amostragem, no que se refere aos ajustes das mesmas com as profundidades de perfis, além de proporcionar agilidade ao processo de investigação exploratória de dados de perfis em relação às classes litológicas a estes associadas. / Abstract: This study is focused on the elaboration of a method for electrofacies characterization which uses well log data related to the lithological classes identified in the core samples of the wells, based upon qualitative approach and multivariate statistics analysis. The first step of this method involves the establishment of a qualitative approach routine which includes the analysis of a package of well log data, which are extracted from the cored intervals, using basic statistics tools (histograms and cross plots) and aiming to delineate and characterize electrofacies. The second step involves the utilization of a classical multivariate technique called Two Steps Cluster Analysis, which generates clusters (electrofacies) based upon the association between well log data and the lithological classes identified from the core samples. The details of the Cluster Analysis technique are showed during the development of this study. During the third step of proposed method, all the clusters generated in the previous steps are quantitatively evaluated by ordinary statistical tools, which include one-way Anova, Test of Means and Discriminant Analysis. As an example of application of this method it is used a complete package of data which includes well logs and macroscope reports of three sets of core samples, extracted from three vertical wells, located in the producing Oil Field of Namorado, in the Campos Basin, Rio de Janeiro State, Brazil. The results of the statistical tests show a good performance for the Two Steps Cluster Analysis tool in characterizing electrofacies. Furthermore, all the statistical tests applied in this study allow the researcher to obtain information about the quality of the sampling process and the accuracy related to the correlation between the sampling and the logging depth, speeding-up the process of the exploratory investigation by using well log data and associated to the lithological classes present in the cored intervals of the oil wells. / Doutorado / Reservatórios e Gestão / Doutor em Ciências e Engenharia de Petróleo

Inversion and Depth Range of Dipole Electromagnetic Induction Measurements in Geophysics Fernando César Moura de Andrade Institute of Hydrogeology, Engineering Geology and Applied Geophysics Faculty of Science, Charles University Electromagnetic induction geophysical methods are, basically, composed by a transmitter which produces a magnetic field and a set of receivers which measure the primary magnetic field, from the transmitter, superimposed by secondary magnetic fields inducted in the subsurface. Equipment operating at, relatively, low frequencies and with short distances between the transmitter and the receivers are usually called conductivity meters and operate at low inductions numbers. The depth of investigation, in such kind of equipment, depends mainly on the transmitter-receiver distance, on the orientations of the magnetic dipoles and the height of the instrument from the ground, in order that a depth sounding can be done changing these parameters in a single measurement location. Making a series of these multi-configuration measurements, two-dimensional, or even three-dimensional surveys, can be performed and, subsequently, inverted in order to produce an image of the subsurface of the earth. Forward modelling and inversion of multi-configuration electromagnetic induction data can be made...