RESUMO - As ocorrências de hidrogênio natural (Nat H2) são relativamente comuns na superfície da Terra. A maioria dos primeiros estudos sobre o tema mostraram que rochas pré-cambrianas, especialmente aquelas do Proterozóico, apresentam as ocorrências mais significativas Nat H2. O Nat H2 pode ter origens diferentes como, por exemplo, radiólise, redução da água, serpentinização, exsudação do manto em associação com movimentos de grandes falhas, decomposição de H2S, intemperização de formações ferríferas bandadas e a partir de querogênios senis. Nesta investigação é proposta a hipótese de trapas potenciais para Nat H2 estarem associadas aos mounds no pré-sal da Bacia de Santos. Estes mounds cresceram em resposta a migração de fluidos profundos, concomitantes a deposição de evaporitos logo após a deposição dos calcários que formaram os reservatórios de idade Aptiana no Atlantico Sul, exatamente na ruptura final formação da crosta oceânica que separou de vez os continentes Africano e Sul Americano, em uma época de tectonismo extenso. Estão relacionados a vents hidrotermais acima dos quais os mounds se evidenciam. Tais condições são favoráveis a formação de Nat H2 através da redução da água sob altas temperaturas e em presença de minerais com ferro, ou outro metal, além de exsudação de fluidos aquecidos do manto através de falhas. Desta forma, os sistemas hidrogeníferos se completam com o estabelecimento de vias de migração (falhas profundas), e deposição em rochas reservatórios capeados por evaporitos (selos eficientes). Esses sistemas foram controlados pela evolução tectônica ocorrida no sudeste do Brasil, principalmente da direção NW-SE, e.g., zona de deformação Cruzeiro do Sul. Na exploração petrolífera atual, a atenção na presença de anomalias de hidrogênio tem sido pouco perceptiva e maior detalhamento pode servir como possibilidade de ter um novo alvo secundário dos prospectos petrolíferos que poderia reduzir os custos e trazer recompensa extra as atividades exploratórias. Palavras-chave: Hidrogênio. Bacia de Santos. Sísmica. ABSTRACT - Occurrences of natural hydrogen (Nat H2) are relatively common in surface and in other different geologic environments. Pionner studies have shown that Precambrian rocks, especially those Proterozoic, hold the most significant occurrences of Nat H2. Nat H2 can have different origins, e.g., radiolysis, reduction of the water, serpentinization, leaking from the mantle, associated with movements of large faults, decomposition of H2S, and from overmature kerogen. In this investigation is discussed the hypothesis of potential traps for Nat H2 are associated by mounds in the pre-salt of the Santos Basin. These mounds grown in response to the upward migration of deep fluids, concomitant with the deposition of evaporites right after the deposition of the limestones. Such conditions favored the formation of Nat H2 through water reduction under high temperature and in presence of minerals with iron, or other metal, leaking from the mantle, through the deep-seated faults, or even derived from the overmature petroleum kitchens. Hydrogen systems are complete with the network for fluid migration (deep-seated faults), and deposition of reservoir rocks covered by efficient seal (evaporites). Hydrogen systems were controlled by the tectonic evolution of the Southeastern Brazil, principally the direction NW-SE, e.g., Cruzeiro do Sul tectonic belt. In the ongoing petroleum exploration, the attention to the presence of anomalies of hydrogen, as a secondary target in petroleum prospect, will reduce costs, and could bring extra reward to the exploration. Keywords: Hydrogen. Santos Basin. Seismic.

The application of SAR satellite oil slick identification, using artificial intelligence and machine learning technologies, together with a novelty 4D inverse modeling advanced technology allowed, for the first time, to identify and document the presence of a super-giant “Seepage Slick/seep Cluster” (SSC) in the ultra-deepwater realm of the Brazilian offshore basins. This typical “Seepage Slick Cluster” was interpreted in the Outer High of the Tupinambá exploration sharing Block, Santos Basin, in a water depth of around 2,389 meters. It presentsa temporal persistence of 43 oil slicks, spreading over almost 40 km, clustering in a centroid on the sea surface, where 31 of those oil slicks, were documented by satellite images obtained in different acquisition dates. Although the supercluster oil slick has been documented, it does not mean it originated in that area. Most offshore regions of Southern Santos are influenced by an intense hydrodynamic process of ocean currents that could move the oil slicks far away from their origin. To circumvent and definitively locate the origin of the supercluster, a novelty 4D inverse modeling advanced technology was applied. The model successfully backtracked the oil slick and positioned it in a seafloor area where the sediment thickness decreases considerably above the Aptian Salt sequence. In such geological scenery, the salt seal integrity component in the area must have failed in a way that a migration pathway was established, allowing the pre-salt trapped oil to escape and leak towards the seafloor and, from there, to the sea surface. Aiming to confirm such an assumption, shallow 2D seismic interpretation over the area shows attributes presenting typical features of fluid leakages close to the seafloor (e.g., gas/oil chimneys, pockmarks, and mounds). In conclusion, the existence of an overcharged active pre-salt oil generation system in the subsurface of the Tupinamba Outer High, mitigate exploration risk and costs, for petroleum exploration in the area, to a never before level of confidence.

We present a multi-scale conceptual model based on structural controls of the migration of mantle-derived CO2 offshore in the Santos Basin (Southeastern Brazil). We assembled the model from a regional 2D seismic reflection line integrated with potential gravimetric field data and a local 3D seismic reflection volume integrated with well data (lithologies and in situ stress). (i) The geochemical isotope range of δ13CCO2 falls mostly within −7‰ and −5‰ and shows relatively high values for 3He/4He represented by an R/Ra rate of up to 5.60, indicating CO2 mantle generation and degassing. (ii) Seismic interpretation feasibly validated by potential gravimetric responses of the crustal structure (Moho discontinuity) show CO2 migration through deep-seated faults in a region of highly stretched continental crust with oceanward mantle uprising. (iii) Early Cretaceous basement highs generated in an obliquely syn-rift faulting system control CO2 accumulation in thermogenic travertines (hydrothermal carbonate reservoirs of continental lakes), and Aptian evaporites subsequently trap it.

The Santos Basin, offshore Brazil, is approximately 700 km in width and is probably the largest in area of the basins created by the breakup of the Gondwana supercontinent and creation of the South Atlantic Ocean. The crust underlying the basin was intensively stretched north of a major transform fault that affected both continents. Complex rifting within this highly stretched area created a broad marginal basin in the Santos sector of Brazil not replicated on the African side. During the opening in the Early Cretaceous, volcanic features bounded to the south of the Santos Basin: Walvis Ridge, Rio Grande Rise, and the S (a) over tildeo Paulo Ridge. The segmented mid-ocean rift valleys developed as far north as the equatorial Atlantic. Organic-rich shales were deposited in lacustrine environments in the early rift valleys. These synrift shales became the primary source rock for the main hydrocarbon systems present in all the South Atlantic basins. As the separation between South America and Africa continued, shallow-water carbonates were deposited that were later covered by a thick layer of evaporites, creating excellent reservoirs and seals resulting in a prolific petroleum system revealed in 2006 by the supergiant Tupi field discovery. In the relatively shallower waters of the Santos Basin, other gas and light oil accumulations exist in Albian oolitic limestones and Upper Cretaceous turbidites. In addition to the synrift-sourced hydrocarbons, these younger accumulations also received significant contributions from the Cenomanian-Turonian marine shales.

This work aims to improve the understanding of how fracture zones affect carbonate reservoir properties based on observations of a pre-salt well located in the Santos Basin, Brazil. The identification of fracture zones allowed for the observation of a relationship between the occurrence of rock fractures and the silicification, as the latter plays an important role in determining porosity (higher silica content may increase brittleness of the rocks therefore increasing the likelihood of creating fractures zones and fractures may be filled up reducing the total porosity). To support the proposed observation, an integrated study was conducted using borehole imaging, spectroscopy logs, and sidewall core samples. The porosities were defined using nuclear magnetic resonance log analysis, alongside sidewall core samples, and thin sections. The integration of rock samples and well data with seismic analysis was performed to analyze the presence of a regional fault system that could explain high fracture densities as well as observed silica content characteristics. The results show how different types of cement filling up the formation pores affect fracture densities and total porosity. Furthermore, it was possible to infer that the amount of silica content observed in well logs and thin sections relates to hydrothermal fluids reaching out the reservoir through regional fault systems detected in the seismic section. Therefore, this paper supports the comprehension of how diagenetic processes can significantly affect the properties of pre-salt reservoirs.

The Florianopolis Fracture Zone (FFZ), Brazil, delimits the Pelotas and Santos basins and marks a major change in the geology of the continental margins from south to north, along both sides of the South Atlantic Ocean. The continental prolongation of it is represented by Lower and Upper Cretaceous alkaline rocks, Paleocene hydrothermal manifestations and river catchments. Geological review along with total magnetic field reduced to the pole map (EMAG 2) were used to investigate and analyze the Florianopolis Fracture Zone. Our results indicate that the intra-continental NW-SE transfer zones control Upper Cretaceous sedimentation and Lower Cretaceous carbonatitic intrusions. The transition from continental crust to oceanic crust is achieved by the formation of normal faults and horse tail structures near the coastline verging to the FFZ at the already attenuated crust. Alkaline rocks, including carbonatitic ones, arose in the continental crust at the southwest projection of Luis Alves Craton and at the intersection between the transfer zones and the Brusque Metamorphic Complex. The integrated analyses indicated that the location of the FFZ was governed by the geological events in the continental crust. This oceanic/continental trend was later reactivated well past the South Atlantic opening.

Our second and third authors recognized in the late 1990s odd signatures in the oil geochemistry from wells southeast of the Merluza Graben (MG) trend in Brazil’s Santos Basin. We consider oil samples from seven wells which present a lesser question and a greater mystery. Our explanation first involves the lesser question of separating two structural influences in the early opening of the Austral South Atlantic and its penetration into the Santos Basin. We then address the genesis of oil samples that because of distinct geochemical markers avoid grouping into the dominant marine and sag families. Structural trends understood from answering the initial, ‘lesser question’ provide the means to explain the ‘oddball’ geochemistry. Mystery solved while opening a path for ongoing research into mixed-signature oils.

Topographic, gravimetric and magnetic data has been employed to map regional tectonic elements in the South Atlantic presenting major oceanic tectonic structures which had previously lacked continuity when approaching the continental margin. The creation of such contoured maps has proven that numerical transform methods involving regional/residual separation and derivatives of gravity and magnetics can enhance geophysical signatures and unveil hidden structures, especially in the transition from the continental margins to the oceanic basin. In assessing the tectonic trend of the Florianopolis and Rio de Janeiro fracture zones close to the Brazilian continental margin, the fracture zones change direction from E-W in the oceanic region to NE-SW in the continental margin, probably displaced by the cretaceous hinge line in the northern portion of the Santos Basin. The continental structures associated with possible transcurrent and transfer zones that gave rise to the fracture zones of Rio de Janeiro and Florianopolis, probably played an essential role in the evolution of both the SE margin of the Santos Basin and the African conjugated margin. Analysis demonstrates the magnetic and gravimetric signatures of fracture zones can serve as important constraints for reconstructing continental margins in the rift and post-rift.

在新西兰,东海岸盆地是主要页岩油气区,广泛分布着Whangai组储层.该地层易生油气,在东海岸盆地的大部分地区普遍存在,通常由上Calcareous、Porangahau和Rakauroa段组成.这项研究的主要目的 是开发一种综合方法,以确定页岩储层最佳增产改造层段.作者评估了Rakauroa段脆性指标的四种不同定义,在3口研究井中只钻了Rakauroa段.为此专门开发了一个基于Python的自动化处理方法,该方法使用四个指标:弹性参数、内部摩擦系数、矿物学参数和总有机碳含量.通过这一过程,将这四个指标进行了分析组合,以选择脆性值最高的层段,并确定了产层中的最佳增产层段和最理想的射孔层段.作者的研究结果表明,Whangai组的粘土含量为25％(在某些层段内粘土含量达到70％),最大有机物含量为2.54％.地质力学模型表明高孔隙压力在整个储层段内分布均匀.位于沿海区块的Opoutama-1井在1497-1750 m之间的层段表现出较高的综合脆性指数,从增产角度看,表明具有出色的特性.

Within New Zealand, the East Coast Basin represents the primary shale oil and gas play in which the Whangai Formation is widespread. This formation is oil and gas prone and prevalent throughout a large area of the East Coast Basin and is typically composed of the Upper Calcareous, Porangahau, and Rakauroa Members. The primary goal of this study was to develop an integrated methodology to define the best stimulation intervals in the formation. To do this, we evaluated four different definitions of the brittleness index for the Rakauroa Member, the only member drilled in the three study wells. A Python-based automated process was specifically developed for this purpose and uses four indexes: elastic parameters, internal friction coefficient, mineralogy, and total organic carbon content. Through this process, these four indexes were analytically combined to select intervals with the highest brittleness values and identify the optimum stimulation interval and most desirable perforation intervals in the pay zone. Our results show that the Whangai Formation contains 25% clay (and reaching up to 70% clay content in some intervals) and a maximum organic matter content of 2.54%. The geomechanical model indicates a uniform distribution of high pore pressure across the entire reservoir section. The interval between 1497 and 1750 m in the Opoutama-1 well located in the Coastal block presents high combined brittleness indexes, indicating excellent characteristics from a stimulation standpoint.

The oil industry utilizes seismic techniques to image the Earth's subsurface. The number of reflected rays generated at a single point that return to the receivers impacts directly the quality of seismic data and, in turn, seismic interpretation. Seismic illumination is used as a quality control measure to find poor coverage zones, which are commonly found in pre-salt reservoirs of eastern Brazilian marginal basins. The Santos Basin has a wide evaporite section featuring some complex structures such as overhangs, mini-basins, salt domes, salt tongues and walls more than 3 km thick. Those structures change the paths of the seismic rays and reduce the coverage of seismic imaging below the evaporite layer in some regions. In this study, a quantitative and qualitative illumination analysis of a pre-salt horizon was performed comparing four different velocity model scenarios and the behavior of the seismic ray path was analyzed. The results show that both stratification and the geometric structures existing in the salt layer have a direct impact on the imaging of the pre-salt reservoirs. Each factor influences imaging in a different way and, when associated, can generate regions of low illumination quality. Consequently, it is of extreme importance to obtain a suitable understanding of the upper salt layer as it will govern the ray paths towards the layers below the evaporites. Furthermore, the mapping of the anomalies generated by the stratification should also be considered in the creation of the velocity model.

Venezuela’s largest heavy-oil deposits are found primarily in the Faja del Orinoco Belt. These deposits exhibit a low production rate under the cold flow method. The objective of this study is to model the impact of steam injection on the fluid dynamics, geomechanics, and seismic attributes for the Faja del Orinoco steam-assisted gravity drainage pilot project. In order to make core testing more representative under this operation conditions, a new heating system was developed to execute triaxial tests with heavy oil samples under elevated temperature and the results were used as input in a new thermo-poro-elastic–plastic coupled fluid flow and geomechanics simulator. Our simulation show that, after 8 years of steam injection, the temperature increased, reaching 280 °C around the injection well. In addition, oil saturation decreased from 0.803 to 0.13, pore pressures dropped to approximately 8.68 MPa, and the volumetric strain changes reached 0.00078 close to injector well. The results also indicated that the effects of compressibility on cumulate oil production with thermo-hydro-mechanical coupling reached 35% more than without coupling in 8 years of steam stimulation. The cumulative steam-oil rate was approximately 2.70 for 100 tons of steam per day, with 0.203 × 106 m3 (1.28 mmstb) cumulative oil volume and 0.548 × 106 m3.

Mapping of seismic and lithological facies is a very complex process, especially in regions with low seismic resolution caused by extensive salt layers, even when only an exploratory view of the distribution of the reservoir facies is required. The aim of this study was to apply multi-attribute analysis using an unsupervised classification algorithm to map the carbonate facies of an exploratory presalt area located in the Outer high region of the Santos Basin. The interval of interest is the Barra Velha Formation, deposited during the Aptian, which represents an intercalation of travertines, stromatolites, grainstones and spherulitic packstones, mudstones, and authigenic shales, which were deposited under hypersaline lacustrine conditions during the sag phase. A set of seismic attributes, calculated from a poststack seismic amplitude volume, was used to characterize geological and structural features of the study area. We applied k-means clustering in an approach for unsupervised seismic facies classification. Our results show that at least three seismic facies can be differentiated, representing associations of buildup lithologies, aggradational or progradational carbonate platforms, and debris facies. We quantitatively evaluated the seismic facies against petrophysical properties (porosity and permeability) from available well logs. Seismic patterns associated with the lithologies helped identify new exploration targets.

The Mero Field was discovery in October 2010 and is currently an oil producer, having an area of 316 km².The high quality and high productivity carbonate reservoirs in this field are characterized by microbial carbonates of the Barra Velha Formation (Aptian) and coquinas of the Itapema Formation (Barremian).The focus of this study is the facies evaluation and classification of the carbonates of the Barra Velha Formation using borehole images.Those images were integrated with the sidewall core information and helped in the understanding of four different facies (stromatolites, spherulites, grainstones and laminates), based on their textures, structures and how they interact with each other.The integration between borehole images, conventional logs, lithogeochemical logs and magnetic resonance log contributed for a better understanding and classification of facies.

Oceanic plateaus, such as the Rio Grande Rise (RGR), comprise crucial pieces of information about the opening of the South Atlantic Ocean and the evolution of associated lithospheric plate margins. A detailed seismostratigraphic assessment of the volcano-sedimentary package of the RGR was conducted in its western portion based on correlations between seismic data and DSDP Site 516F. The approximately 330-km long seismic transect is characterized by a complex array of normal faults related to extensional tectonics from Late Cretaceous to the Miocene, and probably into the present-day, along the Cruzeiro do Sul Rift. The bathymetric and seismic data reveal: a) the presence of deep faults that rise from the basement to the sea floor; b) the occurrence of several seamounts with tops at a water depth below 1000 m; and c) prominent graben structures that represent unidentified volcanic intrusions, indicative of the reactivation of Lower Miocene faults by younger extensional events. Based on integration of older data with the results presented here, we propose a five-stage tectono-sedimentary model for the western portion of the RGR: 1) the first basaltic flow began to form the Rio Grande Rise in the Coniacian/Santonian; 2) extensional movements caused lifting during the uplift of the large volcanic structures; 3) volcanic islands emerged above sea level increasing the deposition of volcanic breccia and ash layers; 4) after the volcanism ceased, thermal subsidence took place over the entire rise with intense erosion and sedimentation; and 5) the uppermost sedimentary layers were deposited in pelagic conditions and offset by sub-vertical normal faults.

[Formula: see text] occurrences are common in hydrocarbon reservoirs in different geologic and geotectonic environments. In most of the Brazilian sedimentary basins, carbon dioxide occurs in minimal amounts. However, more recent deepwater exploration in the Santos Basin discovered significant concentrations of [Formula: see text] in some petroleum fields geographically dispersed. Adjacent fields within a very similar geologic context can hold a few percent to 80% of [Formula: see text] creating great scientific challenges for understanding the origin of [Formula: see text] and the identification of the main controls that govern its erratic distribution. That is the case of the Tupi (Lula) field, which has low [Formula: see text] content, and the neighbor Jupiter field, with an abnormal 80% of [Formula: see text] in the gas cap. The origin of this [Formula: see text] from earth’s mantle was already proved by isotopic analyses of noble gases. We have developed some hypotheses to explain this mantle sourced carbon dioxide in hydrocarbon reservoirs of the Santos Basin, namely, regional crustal thinning, deep-seated faults, high fault density, igneous intrusions, among others. The [Formula: see text] is abundant in the mantle, and the continental crust can act as a seal that inhibits these fluids from flowing toward the earth’s surface. The highly stretched continental crust in the Santos Basin allows [Formula: see text]-rich mantle material to intrude the upper levels of the continental crust in some locations. Fault systems associated with these magmatic intrusions can direct the carbon dioxide into the upper sedimentary section in a trajectory toward the surface. Understanding the crustal structure of a sedimentary basin is an important step in the exploratory process for the assessment of [Formula: see text] risk. The integration of geophysical (grav-mag) and geochemical data prove great efficacy in identifying the origin of [Formula: see text] and the most important controls on its distribution in the Santos Basin. Such results strongly suggest this approach as a valuable tool for derisking new exploration projects.

ABSTRACT. Studies on evaporitic rocks are of great importance for the oil and gas industry as they can create traps and seals for the hydrocarbon accumulations. Also, salt high ductility allows the formation of complex structures associated with halokinesis posing thus major challenges for imaging the rocks at their flanks and below the structures. This paper discusses the effects of salt tectonics on post-salt layers and the difficulties in interpreting the top salt surface in a particularly complex area of the Santos Basin. The available seismic and migration velocity model data are from an area located in the distal portion of the Santos Basin where the existing salt structures had a profound effect on the post-salt layers. Complex salt structures were formed in this area due to the intrinsic characteristics of salt rocks as it flew away from the terrigenous depocenters, pushed in the Atlantic Ocean realms. Structures such as overhangs are common and sometimes difficult to be mapped. Their geometry generates multiple points with the same latitude and longitude, but at different depths as they are interpreted and thus represent a challenge for current surface interpolation algorithms. A workflow is proposed to optimize multi-z surfaces generation from the top of the salt layer from the interpretation this surface in conjunction with the analysis of the migration velocity model. Finally, a zonation map of the salt walls, mini-basins, salt domes, overhang and salt window in the region is presented.Keywords: halocynesis, seismic interpretation, salt structures zonation, top of the salt layer.RESUMO. Estudos sobre rochas evaporíticas são de grande importância para a indústria de petróleo e gás, pois podem criar armadilhas e selos para o acúmulo de hidrocarbonetos. Além disso, a alta ductilidade do sal permite a formação de estruturas complexas associadas à halocinese, representando assim grandes desafios para a visualização das rochas em seus flancos e abaixo das estruturas salinas. Este artigo discute os efeitos da tectônica de sal nas camadas do pós-sal e as dificuldades em interpretar a superfície do topo do sal em uma área particularmente complexa da Bacia de Santos. Os dados sísmicos e de poços utilizados são de uma área localizada na porção distal da Bacia de Santos, onde as estruturas de sal existentes tiveram um grande efeito nas camadas do pós-sal. Estruturas complexas de sal foram formadas nesta área devido às características intrínsecas das rochas salinas à medida que se distanciaram dos depocentros terrígenas, empurradas para o domínio do Oceano Atlântico. Estruturas como overhangs são comuns e às vezes difíceis de serem mapeadas. Sua geometria gera múltiplos pontos com a mesma latitude e longitude, mas em profundidades diferentes conforme são interpretadas e, portanto, representam um desafio para os algoritmos existentes de interpolação de superfície. Um fluxo de trabalho é proposto para otimizar a geração de superfícies multi-z do topo da camada de sal a partir da interpretação sísmica desta superfície em conjunto com a análise do modelo de velocidade de migração. Por fim, é apresentada um zoneamento das muralhas de sal, mini-bacias, domos de sal e janela de sal na área de estudo.Palavras-chave: halocinese, interpretação sísmica, zoneamento das estruturas do sal, topo da camada do sal.

Presalt reservoirs of the Santos Basin accounted for more than 50% of Brazilian hydrocarbon production in the first two months of 2019. Its most important reservoirs are found in the Barra Velha Formation; thus understanding its genesis and geologic history is essential. This formation is composed of carbonates deposited in an alkaline lacustrine environment with a multiplicity of facies from boundstones and grainstones to mudstones. We have performed a sedimentary analysis based on the integration of sidewall core (SWC) samples and well logs from two wells coupled with seismic patterns discrimination to characterize the tectonic and depositional evolution of the Barra Velha Formation in a sector of the Outer High of the Santos Basin in this study. Our method initially consisted of the evaluation of well logs, aiming to identify shallowing and flooding upward cycles of the second and third orders for the paleoenvironmental conceptualization upper rift and sag phases. Then, we defined electrofacies through the integration of SWCs, gamma ray, and acoustic impedance logs using the crossplot approach. Finally, we described seismic patterns throughout the study area and correlated with results from well data analysis. Therefore, the Barra Velha Formation was subdivided into three zones: the lower, intermediate, and upper zones. Well 1 has a facies association characteristic of a proximal and stable environment during deposition, whereas well 2 initially presents in a distal environment sedimentation that evolves to a more proximal setting. This fact evidenced differences with respect to base-level variations indicating compartmentalization within the lacustrine environment of the upper rift and sag phase that corroborated with the detailed seismic pattern interpretation of the study area.

Exploratory work for hydrocarbons along the southeastern Brazilian Margin discovered high concentrations of CO2 in several fields, setting scientific challenges to understand these accumulations. Despite significant progress in understanding the consequences of high CO2 in these reservoirs, the role of several variables that may control such accumulations of CO2 is still unclear. For example, significant differences in the percentages of CO2 have been found in reservoirs of otherwise similar prospects lying close to each other. In this paper, we present a hypothesis on how the rifting geodynamics are related to these CO2-rich accumulations. CO2-rich mantle material may be intruded into the upper crustal levels through hyper-stretched continental crust during rifting. Gravimetric and magnetic potential methods were used to identify major intrusive bodies, crustal thinning and other geotectonic elements of the southeastern Brazilian Margin. Modeling based on magnetic, gravity, and seismic data suggests a major intrusive magmatic body just below the reservoir where a high CO2 accumulation was found. Small faults connecting this magmatic body with the sedimentary section could be the fairway for the magmatic sourced gas rise to reservoirs. Mapping and understanding the crustal structure of sedimentary basins are shown to be important steps for “de-risking” the exploration process.