Reconcavo Basin Research Articles

Pearson Correlation Coefficient Applied to Petroleum System Characterization: The Case Study of Potiguar and Reconcavo Basins, Brazil

This study applied the Pearson correlation coefficient and principal component analysis as tools for unsupervised qualitative petroleum system evaluation techniques. A total of 252 oil samples (32 features per sample) representative of two Brazilian sedimentary basins (Recôncavo and Potiguar) were used to classify them according to their respective degrees of maturation and origin. The large initial set of variables comprises data on δ13C composition, saturate, aromatic, polar compound fractions, and the techniques reduced biomarkers to the most important variables, maintaining the global pattern of variance. The results were efficient in discriminating different petroleum systems from lacustrine, marine, and mixing sources, as observed in the studied accumulations from the Lower Cretaceous sediments of the Recôncavo and Potiguar basins. The methodology proved to be very useful to vene better characterize the petroleum systems. This methodology can be applied to analyze a large amount of oil samples, using simple software and spending relatively less time.

Agglutinated Foraminifera from the Barremian continental rift section of the Reconcavo Basin, Brazil: a microfossil enigma

Microfossils have been found in most of the Mesozoic basins of Brazil, allowing the establishment of important biozones. Despite being recognized for more than half century in the Barremian from the Reconcavo Basin, the taxonomy of the benthic foraminifera remained unsolved likewise its paleoenviromental implications. In this study, we have applied 2D and 3D imaging techniques to resolve this issue and have identified two agglutinated foraminiferal genera (Glomospirella and Paratrochamminoides) and a new species Paratrochamminoides kaminskii sp. nov. Moreover, based on the taxonomy, few paleoenvironmental insights on the foraminifera-bearing strata are discussed. The occurrence of the typically shallow marine species Glomospirella arctica in the studied section, does not allow the proposition of a marine ingression, since it is not supported by a marine/ transitional association of microfossils. On the other hand, the hypothesis of transport of foraminifera by birds (avian zoocoria) is plausible, although there are no further elements to corroborate it.

Stochastic modelling of gravity data for 2D basement reliefs, free of regularization coefficient

In this paper, a modified version of strength Pareto evolutionary algorithm SPEA (II) is used as a multi-objective optimization method in gravity data modelling. In this method, a two-dimensional gravity inversion problem is solved by iteratively random creation of forward models. It is shown that it can be used as a fast and effective inversion tool in the depth-modelling of two-dimensional layer problems with applications in depth-to-basements, Geometry of bedrocks and sedimentary basins modelling cases. As a result of direct use of the regularization term as a separate objective function, smooth models have a high chance of being selected as final solutions, which makes the results more acceptable and easier to interpret. The most important advantages of this method are that it works independently of the regularization coefficient; so there is no need to run the algorithm so many times to find a proper regularization parameter. Furthermore, there is no need to directly deal with inverse formulations. and the last but not the least, by using a multi-objective algorithm as a global optimization method, convergence to a stable solution does not depend on the initial model, the way classical inversion methods do. For testing the algorithm, a synthetic model is used for layer boundary modelling. To assess the stability of this algorithm, white Gaussian noise added to the synthetic model, Finally, to evaluate the validity of this method, real data from the Reconcavo basin in Brazil considered for processing and inversion, and the results are compared to the ones from previous studies. All computations have been done in the GNU Octave 5.1.0 environment.

CARACTERIZAÇÃO SEMIAUTOMÁTICA DE POROSIDADE UTILIZANDO A LINGUAGEM DE PROGRAMAÇÃO PYTHON: APLICAÇÃO NA BACIA DO RECÔNCAVO

A caracterização da porosidade de reservatórios de hidrocarbonetos é um grande desafio na indústria petrolífera, uma vez que o entendimento desta importante propriedade petrofísica irá exercer grande influência nos processos exploratórios e explotatórios. Ao se estudar diferentes tipos de reservatórios, o conhecimento dos variados tipos de porosidades é de extrema relevância, pois a permeabilidade, propriedade fundamental na produção e desenvolvimento de poços de hidrocarbonetos, irá ser afetada pela disposição dos poros. Sendo assim, este trabalho traz descrições petrográficas das lâminas dos principais reservatórios da Bacia do Recôncavo, tais como, Formação Água Grande, Formação Sergi e o Membro Gomo da Formação Candeias, com informações dos seus constituintes, arredondamento, esfericidade e tipo de porosidade. Além disso, o artigo aborda uma proposta de quantificar a porosidade de forma semiautomática, onde visa estimar porosidade por meio de imagens de lâminas delgadas através do método semiautomático desenvolvido que utiliza as informações do pixel, visto que, as lâminas usualmente são impregnadas com resina de cor azul, destacando a porosidade em um espectro de cor que a diferencia da matriz da rocha, possibilitando que um simples código de programação em python detecte, com o auxílio de um intérprete, a faixa de cor que representa os poros.
 Palavras-chave: petrografia, porosidade, pixel, python.

Lake level oscillations recorded in Buracica Stage (Barremian, Early Cretaceous) of Recôncavo Basin, Bahia State (N.E. Brazil)

This work studies the Buracica Stage (Barremian, Early Cretaceous) in the Reconcavo Basin, Bahia State (N.E. Brazil), comprising the Sao Sebastiao and Pojuca formations, from the analysis of 143 well logs and outcrop records. The Reconcavo Basin is a rift basin associated with the beginning of the South Atlantic Ocean. The basin started with very slow subsidence rates, leading to the formation of shallow lakes and the deposition of shales and sandstones, which compose the Brotas Group; later, subsidence accelerated and gave rise to the formation of a deep lake. Then the deep lake basin was filled throughout six depositional episodes making up the so-called Reconcavo tectonic sequence. Previous studies divided the last depositional event of Reconcavo Basin into seven fourth-order sequences concerning the Marker Bed “1” to the Marker Bed “F” stratigraphic interval. Sequence boundaries were marked by sharp flooding surfaces related to the transgression of lacustrine system due to rapid tectonic subsidence and generation of accommodation. In turn, the sequences are divided into three systems tracts: the lake lowstand systems tract, the transgressive systems tract and the lake highstand systems tract. The maximum flood surface of the sequences generally coincides with the stratigraphic marker “B” to “F”. Depositional systems like braided-fluvial plus eolian dunes, meandering-fluvial, deltaic, or moving-lake and near-shore deposits were identified in this work. Isopach, isolith and sand percentage maps indicate depocentre and source area distribution like the previous Aratu Stage. The primary sources of the sediments are located in the west and north areas; only from the third sequence, an eastern source could be described conspicuously. The fourth-order cyclicity is controlled by lake level changes, related to climatic factors (Milankovitch cycles). The results from the studies of cyclicity confirm the proposed stratigraphic model. They indicate 43,000 years for each fourth-order sequence and 150,000 years for the third-order sequences, which provide an accumulation rate of 1200 mm per 1000 years for the studied interval.

SISMOESTRATIGRAFIA CORRELATIVA ENTRE AS BACIAS DE TUCANO SUL E RECÔNCAVOo

A estratigrafia de sequências, aplicada a bacias do tipo rifte, consiste em uma adaptação do modelo clássico que se encontra em plena fase de consolidação. Os fundamentos norteadores da estratigrafia de sequências se aplicam em qualquer contexto de sedimentação e são fundamentais para entender a história deposicional de uma bacia. O presente trabalho teve como objetivo estudar o arcabouço sismoestratigráfico de Tucano Sul, sob o viés da estratigrafia de sequências aplicada a bacias rifte, a fim de correlacionar esse estudo com a bacia do Recôncavo. A partir da integração das seções sísmicas compostas associadas a dados de perfis geofísicos e litológicos de 15 poços, foi realizado o tratamento desses dados no software de interpretação sísmica IHS Kindle. A análise sismoestratigráfica de Tucano Sul aqui desenvolvida, envolveu a interpretação das terminações de refletores, definição das unidades sismoestratigráficas a partir do mapeamento de superfícies-chaves, além da caracterização das principais sismofácies. Como resultado, foram individualizadas cinco unidades sismoestratigráficas, segundo o modelo aqui adotado: unidade Pré-rifte, Rifte 1, Rifte 2, Rifte 3 e unidade Pós-rifte. Foram definidas cinco sismofácies, SF1 a SF5, cada qual com seus parâmetros característicos. Ao fim, propôs-se uma discussão acerca da correlação sismoestratigráfica com a bacia do Recôncavo. Para o intervalo rifte, Tucano Sul apresentou uma sequência sismoestratigráfica a menos comparada com a bacia do Recôncavo, indicando importante evento erosivo durante o seu desenvolvimento.
 Palavras-chave: Estratigrafia de sequências, sismoestratigrafia, rifte.

Rubiaceae na Flora Aquática e Palustre do Recôncavo da Bahia

Esse trabalho consiste no tratamento taxonômico dos representantes de Rubiaceae na flora aquática e palustre do Recôncavo da Bahia. Os materiais analisados foram coletados no período de outubro/2009 a abril/2019 totalizando ca. 30 expedições, cujas exsicatas foram depositadas no acervo do Herbário do Recôncavo da Bahia (HURB). Foram encontradas 12 espécies pertencentes a nove gêneros. Borreria, com três espécies (B. ocymifolia, B. scabiosoides e B. verticillata) e Spermacoce, com duas espécies (S. eryngioides e S. prostrata), são os gêneros mais representativos. Os demais gêneros apresentaram apenas uma espécie: Diodia saponariifolia, Gonzalagunia dicocca, Hexasepalum apiculatum, Mitracarpus baturitensis, Perama hirsuta, Richardia grandiflora e Sabicea grisea. Descrições, comentários, mapa de distribuição geográfica e chave para identificação das espécies são apresentados.

Study on the gravitational flow directions of the Maracangalha Formation (Early Cretaceous), Bom Despacho, NNE area of Itaparica Island, Bahia, Brazil

ABSTRACT: The objective of the present study was to interpret the direction of gravitational sedimentary flows in the turbidite deposits of the Maracangalha Formation (Reconcavo Basin), indicating their source areas. Thus, the indicative deformational structures existing in the formation were analyzed. The structures observed ranged from brittle to highly ductile and viscous states, with a diversity of deformational styles. A total of 284 planar and linear measurements was collected in three distinct subareas, separated according to their degree of deformation. The structures found were separated into four groups according to their formation process: (i) pre-deformation structures; (ii) plastic deformation structures; (iii) intrusion structures (fluidization), related to either early or syn-sedimentation events; and finally (iv) brittle deformation structures, with late sedimentation. Some structures were observed to be good indicators of apparent mass movement direction, which yielded predominantly SSW directions, suggesting a partially confined flow, parallel to the main axes of Reconcavo Basin, towards its depocenter.

Heteranthera longirachilla (Pontederiaceae), a Misinterpreted New Species of the H. reniformis Complex

Heteranthera longirachilla is a new species described from collections made since the 1960s that were mainly determined as H. reniformis. It is commonly found in streams and waterbodies in the Atlantic Forest and Reconcavo Basin of Bahia, Brazil, and can be distinguished by its long inflorescence rachis that surpasses the spathe apex, and glabrous (rarely with some sparse, short trichomes) filament of the longest stamen. The new species is described and illustrated. A distribution map of the Heteranthera reniformis complex in Brazil and an identification key to all Neotropical Heteranthera species are also provided.

Nuclear Magnetic Resonance and Pore Coupling in Clay-Coated Sandstones With Anomalous Porosity Preservation, Agua Grande Formation, Reconcavo Basin, Brazil

Nuclear Magnetic Resonance and Pore Coupling in Clay-Coated Sandstones With Anomalous Porosity Preservation, Agua Grande Formation, Reconcavo Basin, Brazil

O arcabouço estrutural da Bacia Sedimentar do Araripe, Província Borborema, baseado em dados aeromagnetométricos

Este trabalho apresenta uma interpretação atualizada da estruturação interna da Bacia Sedimentar do Araripe, localizada ao sul da porção setentrional da Província Borborema, por meio do processamento e da análise de dados aerogeofísicos de magnetometria pertencentes à Companhia de Pesquisa de Recursos Minerais – Serviço Geológico do Brasil. Essa bacia é reconhecida como um conjunto de meio-grábens assimétricos, fragmentados por altos de embasamento e complexos sistemas de falhas e lineamentos E-W a NE-SW, associados ao trend estrutural do Orógeno Borborema, e NW-SE, relacionados a processos extencionais cuja evolução poderia estar associada ao rift-valley na extremidade norte do rift abortado da Bacia do Recôncavo. A partir da imagem geofísica do campo magnético anômalo foram extraídas suas derivadas de primeira ordem nas direções x, y, z, seu gradiente horizontal total, sua amplitude do sinal analítico (ASA) e inclinação do sinal analítico. A deconvolução de Euler foi aplicada ao grid ASA, o que permitiu uma aproximação da posição horizontal e estimativa da profundidade do topo das principais fontes magnéticas. A análise conjunta dos diversos mapas gerados permitiu uma interpretação regional dos domínios e lineamentos magnéticos, os quais foram associados às principais estruturas em subsuperfície que compõem o arcabouço da bacia. Os resultados demonstram que a compartimentação estrutural da Bacia Sedimentar do Araripe é muito mais complexa do que a descrita anteriormente por outros autores. O padrão estrutural da bacia apresenta variação lateral, de W para E, conforme demonstrado pela divisão dos domínios magnéticos, indicando haver variações substanciais na espessura das rochas sedimentares, com áreas mais espessas a E e mais rasas a W.

Índice de qualidade de uso da água subterrânea (E-IQUAS): aplicação para comunicar o estado da água em dois estudos de caso - Camaçari (BA) e Verdelândia (MG)

O Índice de Qualidade de Uso da Água Subterrânea (e-IQUAS) tem as seguintes características: é flexível na seleção de parâmetros; pode ser aplicado para múltiplos usos da água; utiliza padrões de qualidade recomendados mundialmente; pode ser programado para cálculo em qualquer linguagem de programação e em qualquer plataforma computacional; sendo destinado para uso em portal de software público onde pode ser livremente utilizado pela comunidade. O e-IQUAS foi formulado agregando-se os parâmetros de qualidade das águas subterrâneas que produzem efeitos similares, por “Grupo de Alteração” (ou seja, por tipo de intemperismo associado à presença do parâmetro). O método de operador mínimo é usado para calcular a nota de cada grupo de alteração, gerando um subíndice; enquanto o índice final (e-IQUAS) é definido como a menor nota entre todos os subíndices. Os testes foram realizados em amostras de água de poços tubulares profundos perfurados no sistema aquífero São Sebastião, aquífero multicamadas, da Bacia Sedimentar do Recôncavo, utilizados para o abastecimento público da região metropolitana de Salvador (RMS), especificamente a área urbana do município de Camaçari, estado da Bahia, e poços de monitoramento de qualidade de água localizados no município de Verdelândia, ao norte do estado de Minas Gerais, na região da bacia do Médio São Francisco, pertencente ao contexto geológico do Grupo Bambuí. Os resultados obtidos para o índice, comparados com a qualidade da água, apontam para um método adequado para qualificação das águas subterrâneas, fácil de aplicar, isento de complexidade técnica e, totalmente flexível à inclusão de qualquer variável.

Análise de palinofácies na avaliação do potencial gerador da Formação Pojuca, Bacia do Recôncavo

This paper deals with the study of source rock potential and its depositional environment. These strata belong to Pojuca Formation and occur in syn-rift sequence of the Early Cretaceous age (Hauterivian-Barremian) in the region of Aramari, a little-explored area of the northwestern Reconcavo Basin. The potential generator of these sediments was evaluated based on studies of palynofacies, Total Organic Carbon (TOC) analysis and RockEval pyrolysis. For the evaluation of the maturation thermal of organic matter of the sediments was used the Spore Coloration Index (SCI); and the palynological study was used to identify the paleoenvironment of these strata. By integration of data from “Rock-Eval” pyrolysis and palynofacies it was possible to identify the prevalence of type II and III kerogen, with varying degrees of quality, allowing for individualization of three palynofacies. The material has predominance of amorphous organic matter of lacustrine origin, with TOC data ranging from 0.95% to 4.71%. The organic matter is a great potential hydrocarbon generator, indicated by S2 values that reach 26.33 mgHC/g rock. SCI values between 4.5-5.0 corresponding to 0.5 reflective of vitrinite (% Ro) demonstrated that the studied section is entering the maturation window. With the data acquired through palynofacies analysis and palynological associations, it can be inferred that a continental deposition environment (deltaiclake) characterizes the sedimentation of the Pojuca Formation with the presence of higrophytic and xerophytic elements, indicating that the vegetation developed in an arid and dry paleoclimate with wet niches locally and latitude next to the present. The data show that the studied area is placed in anoxic conditions containing good quality kerogen and suitable for the generation of hydrocarbons.

INHIBITION OF MICROBIAL SULFATE REDUCTION BY MOLYBDATE

Hydrogen sulfide generation in oil production is a constant cause of concern. In several cases this phenomenon occurs due to the action of sulfate-reducing bacteria. Various methods, including biocides and nitrate addition, have been used to control the activity of these microorganisms, but they are expensive and have side effects. Other inhibition methods, such as the use of molybdate, have received much less attention. This study performed a kinetic test for the inhibition of sulfate reduction, and short-term tests to determine the minimum inhibitory concentration of molybdate in liquid medium containing 10.4 and 20.8 mM of sulfate (1000 mg L-1 and 2000 mg L-1), respectively. An inoculum was prepared from a microbial consortium of sulfate-reducing bacteria dominated by Desulfovibrio vulgaris enriched from produced water from oil wells of the Reconcavo Basin, Brazil. The indicators of bacterial activity used were: sulfate reduction, sulfide production, culture medium color, pH, and redox potential. The tests show that, regardless of the concentration of molybdate, sulfate reduction is inhibited after the first hours of the start of the test. The conversion of sulfate in the kinetic experiment without molybdate is 78%, whereas the average conversion in the experiment with molybdate is approximately 30% in 216 h. The short-term test results show that 0.08 mM (12.8 mg L-1) molybdate, a molar ratio molybdate/sulfate of 0.004, is sufficient to inhibit the activity of sulfate-reducing bacteria for 168 h.

Whole-rock geochemistry and Sr–Nd isotopic composition of the pre-rift sequence of the Camamu Basin, northeastern Brazil

Abstract Whole-rock geochemistry, combined with Sr–Nd isotopic composition of pelitic sedimentary rocks, have been considered to be useful parameters to estimate not only their provenance but also to make inferences about their depositional environment as well as the weathering processes they have been through. The basal sedimentary units of the basins of the northeastern Brazilian continental margin, particularly those of the pre-rift sequence, have been subject of interest of studies based on chemical and isotopic data, since they lack fossil content to establish their age and, therefore, stratigraphic correlations are difficult. The major and trace element contents as well as Sr–Nd isotopic compositions of whole-rock shale samples from five outcrops attributed to the pre-rift supersequence of the Camamu Basin were analyzed with the purpose of characterizing and obtaining further information that would allow a better correlation between the sites studied. The geochemical data suggest that the rocks exposed in the studied outcrops are part of the same sedimentary unit and that they might be correlated to the Capianga Member of the Alianca Formation of the Reconcavo Basin, exposed to the north of the Camamu Basin. The chemical index of alteration (CIA) suggests conditions associated with a humid tropical/subtropical climate at the time of deposition. Nd isotopic compositions indicate provenance from the Paleoproterozoic rocks of the Sao Francisco craton. The results presented here, therefore, show that the combined use of chemical and isotopic analyses may be of great interest to characterize and correlate lithologically homogeneous clastic sedimentary sequences.

Depositional ages of Paleozoic and Mesozoic pre-rift supersequences of the Recôncavo Basin in northeastern Brazil: A Rb–Sr radiometric study of sedimentary rocks

Abstract The relative dating of sedimentary rocks can be carried out either from fossils or by stratigraphic correlation. In the absence of fossil content with unequivocal age significance, or in cases in which correlations are neither possible nor conclusive, the task of estimating the depositional age of a sedimentary rock is inviable. Rb–Sr whole-rock isochron method, combined with granulometric and X-ray diffraction studies, has been successfully used to date the deposition of fine-grained sedimentary rocks. In the present study, samples of argillites and siltstones of the Paleozoic and pre-rift sections of the Reconcavo Basin, in the northeastern coast of Brazil, have been investigated. Samples from the Afligidos (Cazumba Member), Alianca (Capianga Member) and Itaparica formations, yielded ages of 290 ± 21 Ma (Permian), 224 ± 32 Ma, and 226 ± 6 Ma (Neotriassic), respectively, which were interpreted as their original depositional ages. The age results for the units of the pre-rift section (Alianca and Itaparica formations) present significant implications to the paleogeographic model previously established for the Reconcavo Basin and other correlated basins, since these sedimentary units were traditionally considered to be Neojurassic.

Equivalent Source: A Natural Choice for Gridding Scatter Gravity Data

Measurements of the gravity field, specially those taken at ground level are acquired on a scatter distribution due to the difficulties imposed by terrain conditions. Most of the times, the irregular sampling interval leaves large empty areas that need to be interpolated during the gridding. For such situations, mathematical interpolation like minimum curvature technique, for instance, can lead to erroneous results. In this paper, I propose to address the gridding of scatter gravity data using the equivalent source technique and show that it has advantages over the minimum curvature. In addition, I also propose a simple method to efficiently estimate the true field. The method was successfully tested with a set of ground gravity data from Reconcavo Basin, Brazil.

A contribution to regional stratigraphic correlations of the Afro-Brazilian depression – The Dom João Stage (Brotas Group and equivalent units – Late Jurassic) in Northeastern Brazilian sedimentary basins

Abstract The Dom Joao Stage comprises an interval with variable thickness between 100 and 1200 m, composed of fluvial, eolian and lacustrine deposits of Late Jurassic age, based mainly on the lacustrine ostracod fauna (although the top deposits may extend into the Early Cretaceous). These deposits comprise the so-called Afro-Brazilian Depression, initially characterized as containing the Brotas Group of the Reconcavo Basin (which includes the Alianca and the Sergi Formations) and subsequently extended into the Tucano, Jatoba, Camamu, Almada, Sergipe, Alagoas and Araripe Basins in northeastern Brazil, encompassing the study area of this paper. The large occurrence area of the Dom Joao Stage gives rise to discussions about the depositional connectivity between the basins, and the real extension of sedimentation. In the first studies of this stratigraphic interval, the Dom Joao Stage was strictly associated with the rift phase, as an initial stage (decades of 1960–70), but subsequent analyses considered the Dom Joao as an intracratonic basin or pre-rift phase – without any relation to the active mechanics of a tectonic syn-rift phase (decades of 1980–2000). The present work developed an evolutionary stratigraphic and tectonic model, based on the characterization of depositional sequences, internal flooding surfaces, depositional systems arrangement and paleoflow directions. Several outcrops on the onshore basins were used to build composite sections of each basin, comprising facies, architectural elements, depositional systems, stratigraphic and lithostratigraphic frameworks, and paleocurrents. In addition to that, over a hundred onshore and offshore exploration wells were used (only 21 of which are showed) to map the depositional sequences and generate correlation sections. These show the characteristics and relations of the Dom Joao Stage in each studied basin, and they were also extended to the Gabon Basin. The results indicate that there were two main phases during the Dom Joao Stage, in which distinctive sedimentary environments were developed, reflecting depositional system arrangements, paleoflow directions were diverse, and continuous or compartmented basins were developed.

Carbon dioxide volume estimated from seismic data after six years of injection in the oil field of Buracica, Bahia

Abstract Carbon dioxide has been injected since 1991 in the oil field of Buracica in the Reconcavo Basin in Brazil for EOR purposes. The CO 2 gas is injected into the upper oil reservoirs, a 13 m-thick sandstone layer, at a depth of about 550 m. The reservoir is included in a tilted block dipping at an angle of 5 to 6° toward the south-east. A 3D seismic survey was carried out six years after the beginning of CO 2 injection. Sensitivity studies concluded that the gas-invaded and the oil-filled parts of the reservoir show only a weak contrast between their mechanical properties so that their interface might not appear in the seismic sections. Directional dip filtering of the seismic data underlines horizontal events crossing the dipping layer interfaces. Some of them can be interpreted as the gas/oil contact. A careful picking and mapping of these events reveal two accumulations of carbon dioxide on each side of a system of N-S faults, with slightly different gas/oil contact levels. Estimation of the gas volume and of the density leads to a rough estimate of the mass of CO 2 in place, indicating that about one third of the CO 2 injected was stored in the reservoir.

Solid state 13C NMR analysis of Brazilian cretaceous ambers

13C cross polarization with magic angle spinning nuclear magnetic resonance (13C CPMAS NMR) spectra have been obtained for the first time to three Cretaceous amber samples from South America. The samples were dated to Lower Cretaceous and collected in sediments from the Amazonas, Araripe and Reconcavo basins, Brazil. All samples have very similar spectra, consistent with a common palaeobotanical source. Some aspects of the spectra suggest a relationship between Brazilian ambers and Araucariaceae family, such as intense resonances at 38-39 ppm. All samples are constituted by polylabdane structure associated to Class Ib resins, constituted by polymers of labdanoid diterpenes. Finally, information concerning some structural changes during maturation, such as isomerization of Δ8(17) and Δ12(13) unsaturations, were obtained by 13C NMR analyses. The results concerning botanical affinities are in accordance with previous results obtained by gas chromatography-mass spectrometry (GC-MS).