Navegando por Assunto "Geophysics"

Agora exibindo 1 - 6 de 6

Acesso aberto (Open Access)
Exemplo de bom condicionamento inconveniente causado numericamente na inversão gravimétrica para a estimação das densidades de uma camada
(Universidade Federal do Pará, 2014) SOARES, William Pareschi; MARTINS, Cristiano Mendel; http://lattes.cnpq.br/8303640454649778
A well-conditioned sensitivity matrix can be inconvenient for estimating densities of a layer? We found an example of this inconvenience numerically caused in the gravimetric inversion when the horizontal dimensions of the elementary sources that make up the interpretive model are very small. Amazingly in this case a gravity inversion to obtain the equivalent layer is not effective and does not fit the data. We found that in this case the well-conditioning of the sensitivity matrix occurs simultaneously with low singular values. This feature of the sensitivity matrix leads to severe loss of resolution and leads to biased estimates and very smooth. It happens that part of the resolution would be mathematically possible to be obtained is lost due to this phenomenon numerical computational degradation of the sensitivity matrix . We present a procedure for repayment of the resolution for mapping the density distribution of a layer, which enables new perspectives on gravimetric applications, including environmental studies. We skirted the numerical problem with a semi-heuristic approach which extends the horizontal dimensions of the elementary sources and subsequently corrects the estimates. We obtained with this new procedure in synthetic tests the distribution of the density contrast outlining lateral contacts between regions of different density contrasts, which would only be possible to recover elemental sources larger. We apply this methodology to the dataset of the Thomas Farm landfill site landfill.
Acesso aberto (Open Access)
Identificação de fácies em perfis com algoritmo heurístico
(Universidade Federal do Pará, 2015-02-27) ALMEIDA, Thelson Luiz Pinheiro de; ANDRADE, André José Neves; http://lattes.cnpq.br/8388930487104926
The development of oil well drilling techniques and the optimization exploitation of various hydrocarbon reservoirs on the same time, an issue has drawn attention from researchers from the oil industry: identification of sedimentary facies in wells not core available. Therefore, this paper proposes the use of a heuristic algorithm based on the behavior of insects, which contributes to the interpretation of M-N Graphic on computational way. Using wells logs and plot your data in graphic M-N, we have aimed to sort of well log points in relation to fixed points, using the creation of groups (clusters) of data that have some similarity or symmetry, based on what we call attractiveness. Using the creation of these groups of points of the well log, in the neighborhood of fixed points through which suffered major attraction, we can do the identification of multiple data families which, in this work, will be taken as layers, depending on which mineral fixed point are closer, can have their main mineral composition identified without the help of the core and thus obtain the sedimentary facies knowledge overpassed by the well.
Acesso aberto (Open Access)
Investigação de pavimento asfáltico por meio do método geofísico radar de penetração do solo
(Universidade Federal do Pará, 2011) AMARAL, Carolina Narjara Mazzini; SILVA, Lúcia Maria da Costa e; http://lattes.cnpq.br/8612431024609774
Most public paved roads may have some sort of imperfection that leads to unsafe traffic, increased transport costs, and pollution. These problems could be avoided if the defects were identified on the floors before they show up at the surface because in general they begin in the underlying layers of the asphalt coverage. This paper proposes the use of GPR to identify problems in pavements based on numerical simulations of the GPR and on field surveys. Simulation of two physical models has been made: i) pavement in use, in which pipe and the most common defects (voids and infiltration) have been inserted, and ii) recent floors, both above a substrate. The interfaces of the pavement layers and the channeling were easily individualized whereas the imperfections show similar patterns of reflection, differing in the polarity of the signal amplitude and in its attenuation (smaller in the voids and higher in the infiltration). Differently from what occurs in other places, the layer interfaces in recent pavements were more easily identified with the frequency of 400 MHz than with a frequency of 900 MHz because of the conductivity of the products deriving from weathering, which occurs in the Amazon. These responses were used then to investigate two places in the city of Belém (PA): a sector of MauritiTv. which presents recurrent defects on pavement, and a newly paved stretch at Federal University of Pará (UFPA). The first survey identified and mapped defects and permitted to infer their possible causes (water loss from the drainage system) while the latter helped in delineating layers and the contact with the substrate (showing that the thickness of pavement layers differ from the projected ones). The results show how the GPR can be an important tool in maintaining and planning the recovery of paved roads by providing a diagnosis in a fast, safe, and low cost.
Acesso aberto (Open Access)
Investigação geofísica forense e antropológica com o método GPR no cemitério do Tapanã e no cemitério perdido de Mosqueiro (Belém, Pará)
(Universidade Federal do Pará, 2013-03-22) BRASIL, Diogenes Leão; SILVA, Lúcia Maria da Costa e; http://lattes.cnpq.br/8612431024609774
This work was accomplished with ground penetrating radar (GPR), a geophysical method used to investigate the shallow subsurface with high resolution in a non-destructive and noninvasive way. The survey was conducted in two locations in the metropolitan region of Belém, Pará State (Brazil), with 200 and 400 MHz antennas, both in the Tapanã cemetery: the first located in the test site for Controlled Testing of Forensic Geophysics, Environmental and Rescue (FORAMB) and the second one, in a burial zone with concrete cover. Surveys were also conducted in the northwest portion of Mosqueiro Island, across Marajó Bay, with a 400 MHz antenna, where reports of traces of a non-registered cemetery that would have been abandoned for about 80 years and could have been the final destination of cabanos, slaves and indians.These reports led researchers from the Federal University of Pará (UFPA) to visit the site in 1986 to test the veracity of the reports. At FORAMB the monitoring of the three targets that were buried there in 2007 was continued: a human body in a shallow grave 0.8 m deep, a tunnel simulated by a hollow wooden box placed 1 m deep and a box with metal, simulating weapons, deposited at 0.8 m depth. In the burial zone with concrete cover, the survey efforts focused on the effect of the concrete cover.The results obtained in the Tapanã cemetery show the usefulness of GPR in viewing targets under shallow soil cover and saturated clay, typical of the Amazon region, even when it is covered by a layer of concrete. These results reinforce the importance of pooling 2D and 3D data for interpretation of results; the GPR profiles over the concrete covering the bodies in various ages of burial, moreover, show significant variations of the responses, partly observed in other studies. The Mosqueiro results showed that ancient targets in climatic and geological conditions of the Amazon region, do not allow easy detection. It is possible that the remains of the decomposed bodies are not amenable to detection, but the discontinuity of the strata above the burial due to excavation, and the resulting concavity of the collapsed grave infill material may be diagnostic.
Acesso aberto (Open Access)
Prospecção de água subterrânea no município de Piçarra-PA usando VLF e resistividade
(Universidade Federal do Pará, 2011) SOUSA, Gilvana Bezerra de; LUIZ, José Gouvêa; http://lattes.cnpq.br/8676530374310847
This research was carried through in Piçarra city, located in the southeast of Pará state. The study had as main focus the mapping of lineaments associated with the basement fractures and the subsoil nature through geophysics, using the Very Low Frequency (VLF) electromagnetic and resistivity methods. The integrated analysis of geophysical data allowed the recognition of two hydrogeological domains in the area: Fractured zones and sediment thickness above the basement rocks, aiming to guide the location of groundwater captation wells. The study provided indications of the most promising locations for groundwater captation and the best sites to build water wells for the city supply.
Acesso aberto (Open Access)
Reconhecimento de fáceis em perfis geofísicos de poços com rede neural competitiva
(Universidade Federal do Pará, 2015-02-27) COSTA, Jéssica Lia Santos da; ANDRADE, André José Neves; http://lattes.cnpq.br/8388930487104926
The description of a depositional system based on the recognition of sedimentary facies is critical to the oil industry to characterize the petroleum system. In the absence of these facies description by cores or outcrop, we present a methodology based on intelligent algorithm able to identify facies of interest in wireline logs. This methodology uses a competitive neural network to extract geological information from the physical properties mapped in the M-N plot. The competition among neurons identifies the facies of interest, which have been previously identified in a cored borehole in other non-cored boreholes in the same oil field. The purpose of this methodology is to encode and transmit the geological information gained in cored boreholes to non-cored wells and thus achieve the geological interpretation of the facies of interest in an oil field. This methodology has been evaluated with synthetic data and actual wireline logs from two cored boreholes drilled in the Namorado oil field, Campos Basin, Brazil.