Dissertações em Geofísica (Mestrado) - CPGF/IG

URI Permanente para esta coleçãohttps://repositorio.ufpa.br/handle/2011/4993

O Mestrado Acadêmico pertente a o Programa de Pós-Graduação em Geofísica (CPGF) do Instituto de Geociências (IG) da Universidade Federal do Pará (UFPA).

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Acesso aberto (Open Access)
Análise das aproximações RPP e RSP para meios isotrópicos
(Universidade Federal do Pará, 2002-08-16) SANTOS, Darcicléa Ferreira; PROTÁZIO, João dos Santos; http://lattes.cnpq.br/4210442535067685
This work presents linear and quadratic approximations of the Zoeppritz equations for the derivation of reflection and transmission coefficients from P-P and P-S events as a function of incidence angles and angular average, as well as the linear inversion analysis, AVO, in respect to the disassociated and combined P-P and P-S reflection events. The use of the so-called pseudoquadratic approximations was applied for the derivation of quadratic approximations only for PPevents, around the average contrasts of compressional and shear waves velocities and Vs/Vp ratio. The results of approximations derived in this work show that quadratic approximations were more precise than the linear ones in the two angular versions. The comparisons between these approximations in terms incidence angle and angular average show that the quadratic approximations are equivalent within the angular limit of [0º to 30º]. In the other hand, the linear approximations as a function of incidence angle are more precise than the linear approximations as a function of the angular average. In the linear inversion, sensitivity and ambiguity analyses were carried out and one could see that in the case of disassociated reflection P-P and P-S events, just a parameter can be estimated and the combination of these events can stabilize the inversion permitting the estimation of two physical parameters for the media (impedance, P-wave velocity and shear bulk module contrasts).
Acesso aberto (Open Access)
Uma análise de métodos de supressão de múltiplas de superfície livre aplicados a um dado real
(Universidade Federal do Pará, 2011-10-14) OLIVEIRA, Andrei Gomes de; GOMES, Ellen de Nazaré Souza; http://lattes.cnpq.br/1134403454849660
The seismic record in 2D linear events are common features in the seismograms. These events are overlap with interesting reflections (early reflections) complicating the stages of seismic processing and identification of possible subsurface geological horizons. It possible highlight multiple surface that distinguished from others by a low frequency, high amplitude and low velocity of propagation. The identification and removal of multiple reflflections in seismic data is a real step of great importance in seismic processing, because the attenuation can prevent many of these errors in the interpretation of geological images seismic. This study is the determination of a processing flow for multiple attenuation free surface. Methods of elimination of multiple surface (SRME, Radon filtering, predictive deconvolution domain τ - p and fk filltering) applied to a real data 2D were used in different combinations. These are analyzed and presented the results are the best combinations.
Acesso aberto (Open Access)
Análise de velocidade por otimização do semblance na reflexão sísmica
(Universidade Federal do Pará, 2010) VIEIRA, Wildney Wallacy da Silva; LEITE, Lourenildo Williame Barbosa; http://lattes.cnpq.br/8588738536047617
This work had as a general aim to develop a systematic methodology for the inversion of seismic reflection data organized in common-midpoint gathers (CMP), starting from 1D vertical variation of velocity and thickness that allows to obtain interval velocity, vint,n, in time, the correspondent interval thickness, zn, and the correspondent mean-square velocity, vRMS,n in individualized CMP gathers. A direct consequence of this work the transformation of these values from time to depth. Two methods were developed to attack the problem defined as velocity analysis based on the estimation of interval velocity. The first method was based on manual picking of reflection events on CMP gathers, and inversion by curve fitting in the least-square sense. The second method was based on the otimization of the semblance function to obtain an automatic picking. The methodology combined two types of optimization: a Global Method (Price or Simplex), and Local Method (second order gradient or cojugate), subject to a priori information and constraints. The picking of events in time-distance section is of fundamental importance in the process of inversion, and the picked points are the input data along with a priori information of the model to be adjusted. The picking must, in principle, avoid events that represent multiples, diffractions and intersections, and in a section over 50 pickings can be made, while in a semblance map not more than 10 events could usually be picked by eye. The application of this work is focused on seismic data of marine sedimentary basins to obtain a distribution of velocities for the subsurface, where a plane-horizontal model is applied for individual CMP sections, and that the solution can be used as an initial model in subsequent processes. The real data used in this study were collected by Petrobras in 1985, and the selected seismic line was of number L5519 of the Camamu Basin, and the CMP presented is of number 237. The line consists of 1098 shot points with right-lateral arrangement. The sampling interval is 4 ms. The spacing between the geophones is 13.34 m with the first geophone located at 300 m from the source. The spacing between the sources is 26.68 m. As a general conclusion, the method for estimating interval velocity in this work stands as an alternative support to velocity analysis, where it is necessary a control over the sequential inversion of CMP gathers along the seismic line such that the solution can be used as an initial model for imaging, and further tomographic inversion. As future work, we can be propose studies directely and specifically related to seismic velocity analysis by extending the 2D semblance optimization method to 3D, and extending the present studies to the method based on the image ray, aiming at producing a continuous velocity map for the entire section in an automatic way.
Acesso aberto (Open Access)
Aplicação de métodos hidroacústicos para estudo e dragagem na região portuária de Cabedelo - PB, Brasil
(Universidade Federal do Pará, 2014-11-17) LOPES, Victor Hugo Rocha; GOMES, Ellen de Nazaré Souza; http://lattes.cnpq.br/1134403454849660
This paper presents the use of hydroacoustic methods used for mapping and detection of subsurface stratigraphic features to support a project of dredging and demolishing of the left edge of the navigation channel of the Paraíba do Norte's River to expand the port zone of Cabedelo/PB. High-resolution seismic data and bathymetric data are used to map two main objectives: top of the Acoustic Rocky Basement (TARB) and the superimposed sedimentary package. This information is important to support the volume calculation of the material to be dredged and/or demolished along the navigation channel. The data analysis indicates that the expansion of the Cabedelo's Port firstly suggested by the Docas do Paraíba Company to be in the Forte Velho's locality becomes expensive due to the large volume of sedimentary and rocky material to be dredged. Thus, the Lucena region is presented as an alternative to the port expansion since presents lower volume of material to be dredged that reduces substantially the costs and time of execution of the work.
Acesso aberto (Open Access)
Aplicação dos métodos elétrico e eletricomagnético para o estudo hidrogeológico no município de Altamira-Pará
(Universidade Federal do Pará, 1998-11-20) BAPTISTA, João Júnior; RIJO, Luiz; http://lattes.cnpq.br/3148365912720676
This work due application of the electroresistivity and electromagnetic geophysical methods in the municipal district of Altamira, in the central area of the State of Pará, with the purpose of mapping the thickness of the aquifer layers and occurrence of diabase intrusions for finding a groundwater wells. In this area are many outcrops of basement crystalline rocks covered with sediments of ages from the Paleozioc to Quaternary. The objective is to obtain water from the sediments of Inferior Devonian, more exactly in the Maecuru Formation. There were made thirty four vertical electric soundings using the Shlumberger arrangement, the AB/2 distance varying from 100 to 500 meters. Also there were made 108 transient electromagnetic soundings with "coincident loop" arrangement, using an square loop of 50 meters. Due to electronic problems and supraparamagnetic noises, the results of this electromagnetic soundings became very distorted, impossible to get from them important geologic information. Then, electromagnetic synthetic models were created to represent the geology of the area. The data were obtained from the field were presented as apparent resistivity curves. They were plotted using a log-log scale and interpreted using the EGSLIB/SEV1D first and then with the EGSLIB/SEV1DIN program. The models used were horizontal, isotropic and homogeneous layers. The interpretation results allowed to determine approximate geoelectrical models which reflects the underground geological situation. The interpretation results from the electric surveys were confronted with the results of the qualitative interpretation from the isogams map of the total magnetic field, allowing to delimit with more precision the zone of incidence of diabase sills, located at the north of the area. From the four distinguished geoeletric horizons, the third is essentially constituted by sands, therefore it is best for groundwater storage.
Acesso aberto (Open Access)
Aplicação dos métodos gravimétrico e magnetométrico para a definição do comportamento estrutural da faixa de dobramentos Araguaia
(Universidade Federal do Pará, 1988-04-25) CARVALHO, João da Silva; SAUCK, William August; http://lattes.cnpq.br/6655455534234531
Interpretation of gravimetric and aeromagnetometric informations of the northern region on the Araguaia Orogenic Belt covering an area of aproximately 129.000km2 is presented in this thesis. The area lies between is 47º50’W and 50º30’W longitudes and between 4º50’S and 9º00’S latitudes, over southeast Pará State, north-northwest of Goiás State and west of Maranhão State. The gravimetric and altimetric measurements were carried out along highways and roads in the region. The gravity data, after corrections and reductions are presented in the form of Bouguer anomalies map on scale 1:500.000. The gravimetric pattern of Araguaia Orogenic Belt shows features principally of longitudinal extension, with approximately meridional direction. These features are correlated with the known lithological and structural units in the area. In the central-meridional portion of the map, appears an extended zone of intensive negative anomaly (less than -100mgal). This zone suffers two inflexios, one in the northwest (NW) which correlates to Carajás Lineament, and the other along latitude 5°30’S. The higher gravimetric values, notably in the northwest portion (cratonic domain), are related to the influence of the metavulcanics Grão Pará Group, and those in the northeast portion are attribuited to the denser mass intruded in the crust. Notable, also a gravimetric peak on the eastern flank of the brachyanticlines. This peak could be linked to a denser mass placed under this region tectonially, creating elevations in crust base-level and consequently of the basement. Generally, the eastern flank of orogenic belt show a gradient more intensive than the western, due to principally the geometric configuration of structures. In the similar way there is a notable ascendent regional gradient from south to north. Through the analysis of magnetic intensity maps, of the Projeto Geofísico Brasil-Canadá (PGBC), diferent individual domains were identified. These domains correlate lithologically and structuraly with the geotectonics units that constitute the regional framework and their subunits. Analytical gravity and magnetic modelling were carried out for semi-quantitative interpretation with the objective to establish the basement geometric pattern of the Araguaia Orogenic Belt, and the vinculated structures. On the basis of gravimetric informations, we could verify a geometric higher pattern in the form of imbricated slices over the substratum. The higher negative anomaly in the center-meridional portion of the orogenic belt could be related with the deficiency of deeper mass (a depression in the crust bottom), or due to the presence of a low density mass in the supercrustal layers, in that zone. The gravity depression in the southwest of the area, between Guarai and Tupirama, could be attribuited to a depression in the basement, and in the similar way the negative anomaly associated with Carajás Lineament is related to a sinformal structure.
Acesso aberto (Open Access)
Arranjos coplanar e coaxial nas sondas de perfilagem de poço: ferramentas triaxiais em reservatórios laminados
(Universidade Federal do Pará, 2007) SANTOS, Walleson Gomes dos; RÉGIS, Cícero Roberto Teixeira; http://lattes.cnpq.br/7340569532034401; CARVALHO, Paulo Roberto de; http://lattes.cnpq.br/6761774273543163
The triaxial or multicomponent induction tool was recently developed to solve the problems of conventional induction logging measurements in anisotropic formations. In this work are presented the triaxial induction sonde answers in reservoirs with thinly laminated sand-shale sequences. Reservoirs as these present the known macrocospic anisotropy, therefore, the results will demonstrate to the existence of both horizontal and vertical resistivity. Due the triaxial induction sonde to present two pairs of coplanar coils, which in general provide the values of vertical resistivity, this work presents initially an analytical and qualitative study of the answers obtained for coplanar array where the transmitter is considered a dipole. Also will be presented the analytical solution where the transmitter coil is evaluated as a loop of finite dimension.
Acesso aberto (Open Access)
Avaliação do modelo hidrodinâmico SMC: uma aplicação na Costa Norte Brasileira
(Universidade Federal do Pará, 2016-05-24) MOTA, Fabíola Cardoso da; ROLLNIC, Marcelo; http://lattes.cnpq.br/6585442266149471
Coastal environments are highly dynamic because of complex processes that occur in the transition between the ocean and the continent. Climate changes induce changes in the coastal zone that cause decline in economic, environmental and subsistence values. The integrated coastal zone management is a continuous and dynamic process, in which decisions should be taken in order to sustainable development and protection of resources of coastal and marine areas. The main goal of integrated coastal zone management is to improve the life quality of human communities that are dependent of coastal resources, taking into account the maintenance of biological diversity and ecosystems productivity. The coastal modelling system called SMC Brazil was introduced in Brazil by the Ministry of Environment in order to standardize the modeling throughout the coastal zone of the country. This study aims to implement the model SMCBrasil in North Coast of Brazil (Princesa beach- Algodoal Island), evaluate it and analyze the hydrodynamic answers, in order to know more about coastal processes that govern this region. In order to understand the processes in the study area, the methodology consisted in collect in situ data to know about the intensity of coastal parameters. 6 cases were created in the model to represent the wave theories (Linear, Stokes and Composite) and sediment transport (Bailard and Soulsby) for two moments of tide: low tide and high tide. Two mesh grids were created in the study area, and one entry point that would fit better to it and the conditions limits of the model was chosen. The propagated waves by the composed theory represented the study area in question more than the others, and the simulated sediment transport simulated by Soulsby theory suffered less interference of interpolation than the Bailard, since it considers the bed transport and suspension. The simulated cases in this study were based on boundary conditions that more often occur on the study area, so the results can be used as a basin to understanding how the coastal processes occur in it in general way.
Acesso aberto (Open Access)
Avaliação geofísica e geológica de um porção de quebra de talude da Bacia do Jequitinhonha
(Universidade Federal do Pará, 2013) SANTOS, Renata Vieira dos; SARGES, Roseane Ribeiro; http://lattes.cnpq.br/9737447758598999; GOMES, Ellen de Nazaré Souza; http://lattes.cnpq.br/1134403454849660
The seismic reflection methods use at the exploration and development hydrocarbon reservoirs is due to its vast and dense sampling in both area and depth, combined with techniques refinement to processing seismic reflection data, from these data, are generated seismic sections, which after applying appropriate treatment, are used in the interpretation of the strata and/or the subsurface geologic structures. At this paper have made one Geophysics Geological analysis at two real marine seismic lines 2D of break portion embankment Jequitinhonha Basin. Therefore, we performed a set of seismic processing in order to mitigate the multiple reflections common marine data, moreover, were estimated velocity models in depth, used to determine the depth migrated seismic sections. At these were identified reflective surfaces. Through analysis at these surfaces markings of sismofacies. have made based on the initial concepts seismic stratigraphy in order to evaluate the product quality derived from the seismic processing used at this study for seismic stratigraphic interpretation, which is based on the analysis termination patterns of reflectors and internal standard of sismofacies.
Acesso aberto (Open Access)
Características hidrodinâmicas da plataforma interna do nordeste paraense
(Universidade Federal do Pará, 2014-08-28) ALVES, Alex Costa; BÉRGAMO, Alessandro Luvizon; http://lattes.cnpq.br/9711842025835463
This study aims to characterize the hydrodynamics of the continental shelf near the northeast coast of Pará state of in adjacent points to the municipalities of Salinópolis and Marapanim. The choice of the period of data acquisition took into account the contribution of the Tocantins River, which has a higher discharge during the month of April and lower discharge during September. Data were collected at two anchored stations on September 11, 2013 and April 25, 2014, both of 25 hours duration. Each as obtained data were not only hydrodynamic (longitudinal component of current) and hydrographic data (temperature, salinity and density), it was possible to calculate the transport of mass and volume. The observations were performed using a couple of acoustic Doppler current profilers and salinity, temperature and pressure data recorders. The data processing included filtering by moving averages and interpolation to analyze the results in dimensionless depth. The hydrographic results revealed a possible influence of continental drainage during the acquisition period. The comparison between water currents and wind during the experiments showed that the influence of the wind was not relevant in the circulation. The transport calculations indicate a circulation predominantly influenced by tide and freshwater contributions.
Acesso aberto (Open Access)
Caracterização física do estuário do rio Mojuim em São Caetano de Odivelas - PA
(Universidade Federal do Pará, 2015-02-25) ROCHA, Adriano Santos da; ROLLNIC, Marcelo; http://lattes.cnpq.br/6585442266149471
The present study has as objective describe the hydrodynamics, hydrologic and morphological aspects, of estuary of Mojuim River, it is localized in São Caetano de Odivelas city –PA (Salgado Paraense),it is analyzing the variations that happen according sea cycle seasonality (rain regime).The hydrologic and hydrodynamics data was collected in two seasonal period in 2014:March,it corresponds to rainy period (~500 mm)and September, it corresponds to dry period (~100 mm),both during tide of syzygy. The bathymetric survey happened only in the rainy period and it was realized with an echo sounder in a sampling grid with 116 spaced cross profile of 200m.In the estuarine channel,it was defined a section where it was realized profiles of strength measurement and current intensity and output, with ADCP, and in three fixed stations,right bank (RB), center(C),and left bank (LB)it was realized collections of conductivity and turbidity with a CDT and an OBS, in the water column. The pattern of tidal and the salinity they were also obtained with a pressure sensor and conductivity fixed in the LB during 56 days in the rainy period and 57 days in dry ones. The estuarine is shallow (4,5 m of average depth) and it is restrained by a regime of semidiurnal macrotidals. During a tidal cycle the salinity increases in the floods and decreases in the ebb tide in both seasonal periods. Turbidity increases in the floods and it decreases in the ebb tide of the rain period and the value measured in the center (C) is double found in the banks. In the dry period, the salinity was higher to rainy period (average 20 and 8, respectively) .This estuarine presents well mixed; it is vertically homogeneous in the rainy period and highly stratified in the dry. The flood flows occur predominantly at the center section, while the ebb flows predominate in the RB, in the two situations the highest intensity of the current occurs in the rainy season. The estuary is an importer in the two periods, however, more entering in the rainy period (resulting transport of 95,87 m³/s) .These data correspond to the first information on the hydrological and hydrodynamics characteristics of the estuary and they can support further studies in the region.
Acesso aberto (Open Access)
Caracterização geoelétrica da área de curtume localizado no Distrito Industrial de Icoaraci, Belém-Pará
(Universidade Federal do Pará, 2005-11-28) NUNES, Lana Patrícia Martins; LUIZ, José Gouvêa; http://lattes.cnpq.br/8676530374310847
A study covering the shallow subsurface was developed in order to investigate the possibility of underground contamination by liquids used in the treatment of animal skin. The study was carried out inside the area of the Couro do Norte industry, located in the Icoaraci Industrial District (Belém – Pará). During the study they were made measures for the determination of the flow of water of the first aquifer and applied geophysical methodology with the purpose of detecting the possible contamination of the underground for pollutant liberated by the tanning. The geophysical methodology applied was: resistivity (imaging and vertical electric soundings), spontaneous potential, electromagnetic (Slingram) and ground penetrating radar (GPR). Analyses of electromagnetic data lead to the identification of conductive zones (Contamination) and resistive zones (sandy material). Spontaneous potential gave information on the direction of local underground flow of water. Vertical electric soundings allowed to know the resistivity distribution in subsurface. The resistivity sounding models could be correlated to the electrical images obtained in electrical profiling. Through the GPR data was possible to identify the presence of lateritic blocks, metal piping and zones with high attenuation (shadow zones) that indicate the presence of contamination.
Acesso aberto (Open Access)
Condutividade elétrica complexa de rochas
(Universidade Federal do Pará, 1979-08-14) ROCHA, Brígida Ramati Pereira da; SAUCK, William August; http://lattes.cnpq.br/6655455534234531
Laboratory measurements of complex conductivity were made on 28 drill-core samples from area MM1-Prospect 1 of the Carajás Mining District. The objective of this research was to help interpret field geophysical survey of the area using Induced Polarization and AFMAG methods. The laboratory measurements of amplitude and phase of conductance were taken in the frequency interval of 10-3Hz to 104Hz. The method used was the direct measurement of impedance using a memory osciloscope, a signal generator, and two high input impedance differential preamplifiers. The electrode system chosen for the measurements was the 2 electrode platinized-platinum because its frequency response is flat in the frequency range used. AlI the measurements were made at a constant temperature of 24°C±1°C. A petrographic study of the samples was done, using thin sections, polished sections and X-ray diffraction. Copper content, in the form of sulfides, was determined using atomic absorption. As a result of the petrographic study, the samples were classified in five distinct groups: granite, biotite schist, amphibolite and magnetite quartzite-iron formation. The grade of Cu was variable in the five groups, ranging from 50 ppm to 6000 ppm. In the conductivity measurements it was observed that, among the five groups, the samples of iron formation gave the largest variations with frequency. The granite samples had spectra flatter than those of schist or amphibole. In conclusion, these measurements show that the field Induced Polarization and AFMAG anomalies near these three drill holes (F1, F2 and F3) are due primarily to the magnetic iron formation, and secondarily due to associated low-grade chalcopyrite mineralization.
Acesso aberto (Open Access)
Determinação de modelo de velocidades para a migração em profundidade de dados sísmicos 2-D da Bacia do Jequitinhonha
(Universidade Federal do Pará, 2013-12-13) OLIVEIRA, Lelis Araújo de; GOMES, Ellen de Nazaré Souza; http://lattes.cnpq.br/1134403454849660
The migration time domain is quite employed by the oil industry for its low computational requirements, however in areas where the velocity field has great lateral variation as result of the environment is complex subsurface structures, such as faults, salt domes, etc.., this technique becomes inefficient in the characterization of geological features. Although the computational cost is high, migration in the field of depth, proves more effective than time migration to deal with these structures. However for a section in depth there is a need for a velocity model in depth with some degree of precision. In this paper, two methodologies for time to depth conversion for obtaining the velocity model in depth to two real 2-D marine lines Jequitinhonha Basin are applied. The accuracy of the models generated were analyzed from migrated seismic sections obtained by means of these velocityes.
Acesso aberto (Open Access)
Determinação estatística dos contatos fluidos em perfis de poço
(Universidade Federal do Pará, 2001-11-23) FLEXA, Roosevelt Tavares; ANDRADE, André José Neves; http://lattes.cnpq.br/8388930487104926
In oil reservoirs, the effect of gravity naturally produces the fluid segregation. Due to capillary forces, there is no defined surface of separation between two differents fluids. However, it is common in petroleum engineering to admit a conventional fluid separation surface, called fluid interface or fluid contact. The depth location of the fluid contacts (oil-water, gas-water and gas-oil) inside the reservoir rocks, without the complete well log interpretation or the accomplishment of the direct procedures involved in formation tests, is a petroleum industry problem. The knowledge of this parameter can be used for well completation procedures and for positioning perforating services in vertical wells. Another application of fluid contact mapping can be to control the drilling bit in directional and horizontal wells, where such information is used to maintain the well axis inside the hydrocarbon zone in order to avoid water production. We present a methodology which can identify and locate fluid contacts, through an application of the multivariate statistical technique called discriminant analysis. For clastics deposits, with sand-shale sequences, discriminant analysis may provide the indication of lithology and the apparent thicknesses of the reservoirs. The well logs applied for the evaluation of this methodology (resistivity (RT), gamma ray (RG), density (ρb), neutronic porosity (ΦN), caliper (Cal) and shaleness (Vcla) are from wells in Lake Maracaibo, Venezuela.
Acesso aberto (Open Access)
Estimativa de porosidade em lâminas petrográficas através da morfologia matemática binária
(Universidade Federal do Pará, 2013-08-02) CASTELO, Fernando Walleson Louzada; ANDRADE, André José Neves; http://lattes.cnpq.br/8388930487104926
Oil exploration in offshore basins needs for drilling boreholes with high angle and horizontal wells, aimed at optimizing the number of exploration targets hit by a single platform. In these cases, it is technically impossible to carry out the coring operations, which prevents core analysis for direct measurement of porosity. In some situations in formation evaluation the geological knowledge of the area may help when there is low confidence in the porosity values. For the semi-submerged basins, the lateral continuity of geologic layers may allow sampling of outcrops in the immersed part of the basin. In the case of offshore basins, may be collected hand samples in outcrops of analogous formations. A relatively common problem in a petrophysical laboratory is the extraction of plugs adapted to the measuring equipment, directly from rock samples collected from outcrops. On the other hand, for this type of rock sample is trivial to obtain thin sections. The objective of this work is to estimate porosity directly on the petrographic images using the image processing method, known as mathematical morphology, which aims to describe quantitatively the geometric structures (forms) in this image.
Acesso aberto (Open Access)
Estimativas da condutividade térmica dos minerais e rochas e influência de parâmetros térmicos e petrofísicos na resistividade aparente da formação
(Universidade Federal do Pará, 1995-08-09) COZZOLINO, Klaus; HOWARD JUNIOR, Allen Quentin; http://lattes.cnpq.br/6447166738854045
The present study carries out estimates of thermal conductivity in the principal rock-forming minerals, as well as estimates of the average conductivity of the solid phase of five common lithologies (sandstones, dolomites, limestones, anhydrites, clay lithologies). Several thermal models were compared, permitting the verification of one as the most appropriate to represent the aggregate of minerals and fluids of which rocks are composed. The results of this study can be applied to a wide variety of thermal models. The chosen methodology is based on a non-linear regression algorithm denominated Random Search. The algorithm's behaviour is evaluated with sinthetic data before being applied to real data. The geometric mean model is used in the regression to obtain the values of thermal conductivity in these rock-forming minerals. The regression method used in each lithological sub-group gave the following values for average thermal conductivity in the solid phase: sandstones 5.9 ± 1.33 W/mK, limestones 3.1 ± 0.12 W/mK, dolomites 4.7 ± 0.56 W/mK anhydrites 6.3 ± 0.27 W/mK and for argillceous lithologies 3.4 ± 0.48 W/mK. In the sequence the fundaments for the study of heat diffusion are presented in cylindrical coordinates. The effects of invasion of mud filtrate into the formation are considered using an adaption of simulation of well injection techniques originating in theories developed in reservoir engineering. Assuming the original temperature of the formation as a reference, the relative errors in apparent resistivity can be estimated. In this phase of the work the finite differences method is used to measure distribution of the well-formation temperature. Simulation of the invasion is carried out in cylindrical coordenates via an adaptation of the Buckley-Leverett equation into carthesian coordenates. Effects such as the appearance of mudcakes in the borehole, gravity and capilliary pressure are not taken into consideration. The radial distribution of resistivity is obtained via the distribution of saturation and temperature, and is convolved with the radial geometrical factor of the induction tool (transmissor-receiver), resulting in the apparent resistivity of the formation. Admitting as reference the original temperature of the formation, the relative errors in apparent resistivity are obtained at each time. Through variation of certain parameters, it becomes clear that the porosity and original saturation of the formation can be responsible for serious errors in the measurement of resistivity, especially if such readings are taken immediately after drilling (MWD). The difference in temperature between well and formation is the principal cause of such errors. In situations where this difference is large, therefore, profiles with- induction tools should only be carried out between 24 and 48 hours after the well has been drilled.
Acesso aberto (Open Access)
Estudo comparativo entre estereotomografia e da tomografia da onda NIP: aplicação em dados sintéticos e reais
(Universidade Federal do Pará, 2010) PRAXEDES FILHO, José Ribamar; CALLAPINO, German Garabito; http://lattes.cnpq.br/6064981270181319
The determination of an accurate velocity model is a fundamental requirement for the seismic imaging. New methods, such as prestack stereotomography and poststack NIP wave tomography, are powerful and very suggestive tools for this task. The prestack stereotomography is basically based on the concept of locally coherent events interpreted as primary reflections and that are associated to ray segments that are linked through the same reflection point in depth. In NIP wave tomography a seismic event is represented by a hypothetic NIP wave that is associated to a reflection point in depth. The NIP wave attributes are determined during Common Reflection Surface (CRS) procedure. The objective of this work is to compare both methods of velocity model determination in depth. Then a review of the theoretical foundations of both tomographic methods are made, considering its main differences, and then applied to a synthetic data and a real marine dataset (seismic line 214-2660 of the Jequitinhonha Basin, Brazil). In order to evaluate the velocity models determined by these two approximations, the data were prestack depth migrated using the Kirchhoff algorithm and also generated Common Image Gathers (CIG). The results have shown that both tomographic methods yield representative velocity models. However, it was noticed that the velocity model estimated by stereotomography behaved better in laterally varying media, but only applied in prestack data with a high signal-to-noise ratio.
Acesso aberto (Open Access)
Estudo da hidrogeologia no município de Palestina do Pará usando o método de eletroresistividade
(Universidade Federal do Pará, 1998) MONTEIRO, Edson Cardoso; RIJO, Luiz; http://lattes.cnpq.br/3148365912720676
This work of geophysics applied to hydrogeology was carried out in the southeast of Pará in the Palestina district at the margin of Araguaia river. Ironically there exists problems of water supply for the city population. This is due to the fact that it is not economical to mantein a treatment station and to transport the water from the river to the city. Since is this case pumping groundwater wells are more economical than take water from the river, the Geophysics Department (UFPa) was asked to cooperate with the Health National Fundation (NSF) to carry out a electroresistivity survey to help the groundwater investigation of the area. There were made 21 vertical electrical soundings (SEV) with the Schlumberger array with 500 m and 50 m maximum AB and MN respectively. For the interpretation it was used the programs EGSLIB/SEV1D for forward modeling and EGSLIB/SEV1D1N for the inversion of homogeneous isotropic layered models. Based on the results of the interpretation of the 21 electrical soundings and the local geology, three contour maps and six geoelectrical sections were made. From the six horizons that are shown in these sections, the fourth one with thickness of 10 to 79 m at the depth of 50 m and resistivity of 150 — 850 ohm-m is the most suitable for groundwater exploration. The final analysis of the maps and geoelectrical sections show that the best place to locate the wells is near the area used today for capturing water.
Acesso aberto (Open Access)
Estudo da resposta de perfilagem de indução de camadas finas com diferentes arranjos de bobinas: modelamento analógico
(Universidade Federal do Pará, 1993-12-16) CARVALHO, Paulo Roberto de; VERMA, Om Prakash; http://lattes.cnpq.br/2723609019309173
Analog model studies were carried out comparing the eletromagnetic responses of various two-coil systems in a borehole, in order to improve the vertical resolution of the indution tools. For this purpose geoeletric models, simulating well-logging situations in the stratified beds of varying thicknesses, with or without fluid invasion, were constructed at a reduced scale of 20. The sensitivity of the system to measure relative fields (secondary/primary) is of the order of 0.01 %. Following conclusions were drawn after analysing the response profiles obtained for a coaxial and a coplanar coil systems: • In case of thin conducting beds placed in relatively resistive beds, such as shale beds in sandstones containing hydrocarbons, the coaxial system shows a better resolution than coplanar system both in determination and estimating the thickness of thin beds; • On the other hand, in the presence of thin resistive beds placed in relatively conductive zone, such as sandstone containing hydrocarbons lying in a shale, the coplanar coil system gives a better vertical resolution than the coaxial system; • "Shoulder effect" is much more pronounced in the coaxial system than the coplanar coils; • In case of thick beds, bed-boundaries are well defined in the coplanar coil system response. However, when the thickness is reduced the small oscillating signal indicating the interfaces disappears.