Milagrosa Aldana

Milagrosa Aldana
Simon Bolívar University · Departamento de Ciencias de la Tierra

Dr.

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98
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January 1989 - present
Simon Bolívar University
Position
  • Full Professor (Titular)

Publications

Publications (98)
Article
Satellite images have been widely used to characterize mineral alteration zones in surface rocks affected by hydrocarbons' upward seepage. Likewise, magnetic surveys over oil fields have been employed for similar purposes. This work integrates satellite image spectral analyses with rock magnetic and geochemical data (i.e., mass-specific magnetic su...
Article
Among the different natural sources of drinking water, aquifers are the most exposed to the environmental pressures posed by old landfills. Conventional monitoring methods to follow up the migration of leachate into groundwater and the generation of biogases in landfills are costly, time-consuming, and only provide a partial picture of these comple...
Article
This study was carried out on sediment cores collected with a gravity corer from Laguna Cháltel, an almost circular crater lake located in Patagonia, Argentina (49.9°S, 71°W). The main magnetic carrier was Ti-magnetite in the pseudo–single domain range. A model using magnetic grain size and concentration, previously applied to Laguna Potrok Aike to...
Conference Paper
The objective of this research was to estimate the best gridding interval that avoids aliasing in maps of ground gravity measurements in the northwestern region of Venezuela, before using any interpretive method. To achieve this goal, the self-similarity of the network was studied, since significant improvements in the characterization and design o...
Article
A combined study of rock-magnetism and electronic-paramagnetic resonance (EPR) was performed in core samples from an oil well in the Vaca Muerta Formation (SW Argentina). The aim of this work was to characterize the effects of hydrocarbon-related diagenesis on the magnetic signature of oil shales. Similar research has been previously conducted in n...
Conference Paper
A rock magnetism and electronic paramagnetic resonance (EPR) combined study was performed in samples from an oil well drilled in the Vaca Muerta Formation (northern Neuquén Basin, SW Argentina). The aim of this work was to characterize the diagenetic processes involved in the origin of the magnetic mineralogy present in hydrocarbon-impregnated rock...
Article
Full-text available
This work presents a preliminary rock magnetic characterization of four Fe-oxides samples (MDaloe, MDpectin, P1 and P2 samples). The study was performed in order to know the nature, oxidation state, particle sizes and approximate shapes of these oxides, synthesized at room temperature via co-precipitation of Fe salts in pectin from Aloe vera. All t...
Conference Paper
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The objective of this research, done in the scope of the GIAME (Integrated Geosciences of the Merida Andes) project, wasto contribute to the determination of the crustal structure of the mountain chain, and its relation to the development of the adjacent sedimentary basins by means of fractal analysis of gravity data. In order to determine theBougu...
Article
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A study of surface sediments from the Anllóns riverbed (northwestern Spain) was conducted to assess the use of their magnetic properties as proxies of recent trace element contamination (i.e., As, Zn, Pb, Cr, Ni and Cu). Thermomagnetic curves, hysteresis parameters, specific magnetic susceptibility χ, frequency-dependent magnetic susceptibility κFD...
Article
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El Niño Southern Oscillation (ENSO) is an internal forcing of the climate system. This event has an actual frequency of 2 to 8 years. Evidence from a paleoclimate proxy database of gray scale (GS), in samples from Pallcacocha lake in Ecuador, indicates that the ENSO had a frequency of 35 to 75 years during the Late Pleistocene. In this work we expl...
Conference Paper
Full-text available
A spectral analysis of an ASTER image was performed in an oil prospective area of The Cerro Pelado Anticlinal (CPA) in the Western Falcón Basin, Venezuela, to determine the existence of mineral alteration zones, related to the presence of hydrocarbon seepages, in order to guide the oil exploration to better defined areas, integrating a fieldwork, M...
Article
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In this work we use neuro fuzzy system (NFS) in order to obtain inference equations of shear velocity (Vs) of a well in terms of the logarithmic of its porosity (ϕ), its water saturation (Sw) and its clay volume (Vsh) data. The data belong to a well of the Guafita Field located in the Sub-basin of Apure, Venezuela. For training of NFS were used as...
Chapter
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In this work, some strategies and methods, based on finite-difference schemes, are introduced to model the propagation of acoustic waves in a three-dimensional fluid-solid configuration. Specifically, we have considered a heterogeneous propagation medium placed inside a 3D rectangular volume. A plane interface separates the volume into two regions:...
Conference Paper
The aim of this study is to compute, compare, analyze and integrate different seismic attribute techniques with geological and petrophysical information in order to characterize a gas reservoir and identify new exploratory prospects in a proven gas field, Lower Magdalena Valley basin, Colombia. Attribute and rock physics analysis, fluid substitutio...
Article
Full-text available
A stochastic characterization of a hydrocarbon reservoir, constituted by a sedimentary sequence of sandstones interbbeded with siltstones and shales, has been performed. The stratigraphic unit studied here mainly comprises the C4 sands of the Misoa Formation, located in the Lama Field, Maracaibo Lake (Venezuela). A Markov Chain algorithm, based on...
Article
The in situ stresses constraint is one of the most difficult parameter in a geomechanics model. Most of them are simple models in which is not involved the influence of geological discontinuities such as complex fault system, bedding plane, folds and joints. Recent studies have pointed out that these can significantly impact on the in situ stress s...
Article
In this article we stochastically characterize a reservoir through the modeling of stratigraphic columns using two algorithms: Metropolis-Hasting and Gibbs sampling by blocks; both constitute Markov chain Monte Carlo (MCMC) methods. The stratigraphic unit considered corresponds to the C4 sands of the Misoa Formation, on Lama Field, at the Maracaibo...
Article
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The Neuro Fuzzy System (NFS) is a hybrid algorithm that combines fuzzy logic with neural networks. Since it can be used as a pattern recognition technique, we explore its potential to characterize the major lithological units encompassed by the first 512 m of the Colombian stratigraphic well Saltarin 1A (Guayabo and León Formations). Thus, we emplo...
Article
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The complexity of most geological and geophysical problems prompts sometimes the use of non linear mathematical methods to handle them. An adaptive neuro fuzzy inference system (ANFIS) that combines fuzzy logic with neural networks, is applied here to study a paleoclimate section from the Quaternary sedimentary fill of the Lake Mucubají (western Ve...
Article
A relationship between hydrocarbons and their magnetic signatures has previously been alluded to but this is the first study to combine extensive geochemical and magnetic data of hydrocarbon-associated samples. We report a detailed study that identifies a connection between magnetic mineralogy and oil biodegradation within oil-bearing sedimentary u...
Article
Well tying to a seismic volume has been historically based on the correlation of post-stack seismic amplitudes to impedance contrasts filtered by a wavelet (the convolutional model of the seismic trace). Pre-stack data contains a more pristine representation of the geology and also more phase information because it is not affected by the stacking...
Article
In this work, we have applied a Wavelet Based Fractal Analysis (WBFA) to well logs and seismic data at the Teapot Dome Field, Natrona Country, Wyoming-USA, trying to characterize a reservoir using fractal parameters, as intercept (b), slope (m) and fractal dimension (D), and to correlate them with the sedimentation processes and/or the lithological...
Conference Paper
Full-text available
In this work we employ the Neuro Fuzzy System hybrid algorithm to infer S - ratio through the experimental magnetic susceptibility (Χ) data measured in 90 samples, from a 670 meters - thick sedimentary sequence, at the stratigraphic well Saltarin 1A (Colombia). The method is applied here as a means for pattern recognition of the major lithostratigr...
Article
A well to well correlation has been performed at the Guafita Oil filed, Western Venezuela, based solely on the decomposition of the Isothermal Remagnetization (IRM) curves of the studied samples. We have determined and quantified the main magnetic phases present in samples, taken at shallow depth levels (upper 1200 m) of the studied wells, applying...
Article
Chemical remagnetization is a very common phenomenon in sedimentary rocks and developing a greater understanding of the mechanisms has several benefits. Acquisition of a secondary magnetization is usually tangible evidence of a diagenetic event that can be dated by isolation of the chemical remanent magnetization and comparison of the pole position...
Article
Full-text available
We have carried out rock magnetic characterizations of different lithofacies along the stratigraphic well Saltarín 1A, in order to learn about the various diagenetic events that could have affected the Miocene sequence of the Llanos foreland basin (Colombia). Thermomagnetic and low-temperature susceptibility measurements performed on some selected...
Conference Paper
Full-text available
RESUMEN En este trabajo utilizamos el sistema neuro difuso (SND) con la finalidad de obtener ecuaciones que permitan predecir Velocidad de Cizalla (Vs) a partir de datos registro de porosidad (φ), saturación de agua (S w) y volumen de arcilla (Vsh), pertenecientes a un pozo perteneciente del Campo Guafita, ubicado en la subcuenca de Apure, Venezuel...
Conference Paper
En este trabajo, se muestra la interacción en 3D entre un campo de ondas y una interfase plana (horizontal e inclinada, respectivamente). Particularmente se considera una interfase del tipo fluido-sólido (f-s). El comportamiento del campo de ondas se describe mediante las ecuaciones elastodinámicas formuladas en desplazamiento-esfuerzo (EDE). Se r...
Conference Paper
A multiattribute analysis, combined with a spectral decomposition study, was used here to characterize heavy oil reservoirs, located at the south flank of the Maturín Sub-Basin. The main goal was to obtain volumes of pseudo-properties that allow identifying lithologies in the study area. Crossplots of petrophysical properties and GR log data showed...
Article
Full-text available
In this work, the behavior of a wave field in a 3D solid-fluid configuration has been modeled. The elastodynamic equations that describe the problem were expressed, independently, in terms of both displacement- stress (EDE) and velocity-stress (EVE). Both systems were solved using a staggered-grid Finite Difference approach (SFD). A horizontal and...
Article
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In this work we try to discriminate near surface magnetic anomalies related to hydrocarbon microseepage using just magnetic parameters. We present preliminary results for two oil fields located at Eastern Venezuela and characterized by different geochemical conditions. Cross-plots that combine hysteresis data (Mrs/Ms and Hcr/Hc), Magnetic Susceptib...
Article
Full-text available
En el presente trabajo se modela el comportamiento de un campo de ondas en una configuración tridimensional fluido-sólido mediante las ecuaciones Elastodinámicas expresadas en desplazamiento-esfuerzo (EDE) y en velocidad-esfuerzo (EVE), respectivamente. Ambos, EVE y EDE, se resuelven en forma aproximada por diferencias finitas sobre una staggered-g...
Article
Full-text available
Rock magnetic, petrographic and dielectric analyses were carried out, in a number of archeological ceramic potsherds, in order to characterize the different manufacturing techniques used by Prehistoric Venezuelan Amerindian potters. Samples were excavated in 7 Venezuelan islands and ascribed to distinct cultural groups on purely stylistic grounds (...
Article
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We have studied near-surface magnetic contrasts in nine oil wells from an oil prospective area in eastern Venezuela (compressive deformation front of the northeastern Maturín Sub-Basin). Samples are drill cuttings taken at intervals of about 15 m within approximately the first 1200 m of most of these wells. Rock magnetic experiments, electron param...
Article
Full-text available
In this work we try to better characterise the shallow magnetic signature of hydrocarbon microseepage in oil fields from eastern and western Venezuela. To get a better insight of the processes involved, we attempt to find out the main magnetic phases responsible for the observed oil-related shallow magnetic anomalies. In this way, a new and alterna...
Conference Paper
The wave propagation problem across a 3D fluid-solid interface was solved using a Finite Difference Staggered-Grid method. The elastodynamic equations were treated in the velocity-stress domain. The interface was modeled using an implicit strategy that assumed a linear variation of the medium parameters between the fluid and the solid. Coarse and f...
Article
Full-text available
In this work we have assessed the hybrid algorithm of NeuroFuzzy logic (NFL), to establish a correlation between global climatic changes (benthic foraminiferal δ18O data), experimental S-ratio (factor characterizing stability of remanent magnetization) and magnetic susceptibility (κ). Magnetic proxies have been measured in 44 samples of the Colombi...
Conference Paper
Full-text available
We have used the hybrid algorithm of neuro fuzzy logic (NFL), to establish a correlation between global climatic changes (benthic foraminiferal δ18O data), experimental S-ratios and magnetic susceptibility (χ), in 44 samples of the Colombian stratigraphic well Saltarín 1A (Llanos foreland basin). χ and S-ratios were linked to global δ18O data based...
Conference Paper
In the present study we have applied a Truncated Gaussian Simulation (TGS) analysis to a reservoir at the Oritupano-Leona field, Venezuela. This analysis was intended to obtain a facies model that could help in the reduction of the uncertainties on the reservoir characterization and a better definition of the prospective areas. Previous studies per...
Article
The knowledge of S-wave velocity values is important for a complete characterization and understanding of reservoir rock properties. It could help in determining fracture propagation and also to improve porosity prediction (Cuddy and Glover, 2002). Nevertheless the acquisition of S-wave velocity data is rather expensive; hence, for most reservoirs...
Article
Two implicit strategies and an explicit approach have been used to solve the problem of a fluid-solid interface in a 3D medium. One of the implicit strategies considers a transitional zone and the other is the traditional one. To solve the boundary conditions at the interface using the explicit strategy, two planes of “fictitious points” were added...
Article
Two implicit strategies and an explicit approach have been used to solve the problem of a fluid-solid interface in a 3D medium. One of the implicit strategies considers a transitional zone and the other is the traditional one. To solve the boundary conditions at the interface using the explicit strategy, two planes of "fictitious points" were added...
Conference Paper
Full-text available
Preliminary rock magnetic, petrographic and dielectric analyses were performed in Prehistoric Venezuelan Amerindian potsherds in order to characterize different clay provenances and pottery manufacturing techniques. The studied samples were excavated in seven Venezuelan islands, but belong to three different mainland cultures: Valencioide, Ocumaroi...
Article
During the last few years we have performed surface reservoir characterization at some Venezuelan oil fields using rock magnetic properties. We have tried to identify, at shallow levels, the "oil magnetic signature" of subjacent reservoirs. Recent data obtained from eastern Venezuela (San Juan field) emphasizes the differences between rock magnetic...
Article
Full-text available
We have used different techniques for permeability prediction using porosity core data from one well at the Maracaibo Lake, Venezuela. One of these techniques is statistical and uses neuro-fuzzy concepts. Another has been developed by Pape etal. (Geophysics 64(5):1447–1460, 1999), based on fractal theory and the Kozeny–Carman equations. We have als...
Article
Full-text available
Hydrocarbon reservoirs are characterized by seismic, well-log, and petrophysical information, which is dissimilar in spatial distribution, scale, and relationship to reservoir properties. We combine this diverse information in a unified inverse-problem formulation using a multiproperty, multiscale model, linking properties statistically by petrophy...
Article
Full-text available
We have measured NRM, room temperature magnetic susceptibility, S ratios and Königsberger ratios in 134 samples that encompass aproximately 670 meters of depth in an oil well drilled in eastern Colombia. These samples are sandstones and siltstones from the Guayabo, León and Carbonera Formations (Oligocene/Miocene/Pliocene). Our main goal is to asse...
Article
First break picking is a pattern recognition problem in the area of seismic signal processing, a problem difficult to automate and that requires a lot of human effort to be solved. The objective of this project was to develop an algorithm, based on Fuzzy Inference Systems, using fuzzy rules of the form If - Then to perform automatically first break...
Conference Paper
Full-text available
Análisis magnéticos, petrográficos y dieléctricos en Cerámicas Prehispánicas Venezolanas para determinar su origen y los procesos de manufactura empleados en su elaboración
Conference Paper
Attenuation is an important measurement for our understanding of rock properties. The extraction of accurate values of attenuation could be useful for enhancing the interpretation of seismic data for reservoir definition. We present here a study using attenuation, velocity and reflectivity from crosswell seismic to optimize imaging of a carbonate r...
Article
Full-text available
SUMMARY Preliminary rock magnetic studies of 12 prehistoric Amerin- dian pottery shards (Dos Mosquises Island, Los Roques, Venezu- ela) have been carried out in order to characterize different clay sourcings and pottery manufaacturing techniques. Although these ceramics have been excavated in a single archeological site, sty- listic features sort t...
Article
Full-text available
Con el fin de caracterizar diferentes fuentes de arcilla y técnicas alfareras, se hizo un estudio magnético preliminar de 12 muestras de cerámicas prehistóricas Amerindias (Isla de Dos Mosquises, Los Roques, Venezuela). Aunque estas cerámicas se encontraron en un único sitio arqueológico, pueden ser clasificadas, de acuerdo a características estilí...
Article
Full-text available
We invert short offset stacked seismic data to jointly estimate reservoir and elastic parameters following a statistical model that relates medium properties with well-logs and petrophysical relations in a gas reservoir area. Our petrophysical model combines the Wyllie equation tointegrate matrix and fluid properties, the Wood equation to account f...
Article
Full-text available
We have used three different techniques for permeability prediction from porosity data in well PX12 at El Lago de Maracaibo. One of these techniques is statistical and is based in Fuzzy Logic. Another has been developed by H. Pape et al, based in Fractal Theory and the Kozeny-Carman equations, and the other one is an empirical model obtained in 194...
Article
Full-text available
We have used a Wavelet Based Fractal Analysis (WBFA) and a Waveform Classifier (WC) to recognize lithofacies at the Oritupano A field (Oritupano-Leona Block, Venezuela). The WBFA was applied first to Sonic, Density, Gamma Ray and Porosity well logs in the area. The logs that give the best response to the WBFA are the Gamma Ray and NPHI (porosity) l...
Article
During the last years, the Paleomagnetic and Rock Magnetic Laboratory at the Simon Bolivar University has incorporated studies of rock magnetism and non conventional techniques in geophysics (as Electronic Paramagnetic Resonance or EPR) to solve diverse problems at the Venezuelan oil industry. Particularly, surface reservoir characterization and EP...
Article
In the last few years the paleomagnetism research group, at the Universidad Simon Bolivar in Caracas (Venezuela), has undertaken combined studies of rock magnetism (e.g. natural magnetic remanence, magnetic susceptibility, hysteresis parameters etc.) and dielectric properties (maximum current depolarization temperatures and average activation energ...
Article
Many studies concerning seismic attenuation and the resultant Quality Factor (Q), which may be calculated from it, reveal its value in reservoir descriptions. Attenuation is an important measurement for our understanding of rock properties and has been used to quantify such characteristics as: Porosity, permeability, viscosity, saturation and rock...
Article
Full-text available
In this work we present a review of our current research on the subject of near-surface hydrocarbon-induced magnetic contrasts. Samples are drill cuttings from number of Venezuelan and Colombian oil fields, and some soils from an oil prospective area. Results from rock magnetic, electronic paramagnetic resonance (EPR), extractable organic matter (E...
Article
Full-text available
Potsherds from 7 Venezuelan islands have been studied using a two-fold magneto/dielectric technique in order to identify clay sources and characterize different stages of pottery craftsmanship. This is the first study of archeological material using this technique. Petrographic analyses appear to agree with the clusters of data identified in scatte...
Article
Electron paramagnetic resonance (EPR), magnetic susceptibility (SM) and extractable organic matter (EOM) measurement were carried out in drilling fines, from near-surface levels, from producer and non-producer wells, with the purpose of examining a possible causal relationship between magnetic contrasts and underlying hydrocarbon.
Article
Full-text available
Electron paramagnetic resonance (EPR), magnetic susceptibility (MS) and extractable organic matter (EOM) measurements were carried out in drilling fines, from near-surface levels, from producer and non-producer wells, with the purpose of examining a possible causal relationship between magnetic contrasts and underlying hydrocarbons. Organic matter...
Article
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In this work we have studied plasticization and antiplasticization effects using the thermal stimulated depolarization current (TSDC) technique in rocks samples from Cretaceous strata located in North–Eastern (group A) and South–Western (group B) Venezuela . Drying and rehydration treatments show that the dielectric relaxation peaks of both groups...
Article
This work explores the application of the electron paramagnetic resonance (EPR) technique, a high sensitivity spectral method, as a means of characterizing stratigraphic facies and identifying depositional environments. We have studied two marine sedimentary sections, of mid-Cretaceous and mid-Eocene ages, that are located in southwestern Venezuela...
Conference Paper
We show the most recent advances and features incorporated to the acoustic code installed on the Centro de Cómputo de Alto Rendimiento (CAR) at Universidad Simón Bolívar(USB). the code is suitable for solving the acosutic wave equation for heterogeneous media suppressing boundary effects. The algorithm consists of an explicit finite difference sche...
Article
Full-text available
Analyses of electron paramagnetic resonance (EPR), in order to determine the organic matter free radical concentration (OMFRC), and magnetic susceptibility (MS) measurements were carried out in soil (surface and depth (≈ 1-2 meters)) samples from a prospective area located at the southern flank of the Andean Range in Venezuela. The results indicate...