Papers by Luiz Fernando de Ros
Depositional and Diagenetic Conditions During Early South Atlantic Opening: Evidence from the Upper Aptian Oiteirinhos Member, Muribeca Formation, Sergipe-Alagoas Basin, Ne Brazil
Social Science Research Network, 2023
Residual oil saturation investigation in Barra Velha Formation reservoirs from the Santos Basin, Offshore Brazil: A sedimentological approach
Sedimentary Geology, Apr 1, 2023
Geochemistry and diagenesis of stratabound calcite cement layers within the Rannoch Formation of the Brent Group, Murchison Field, North Viking Graben (northern North Sea)—comment
Sedimentary Geology, Oct 1, 1994
New detrital petrographic and thermochronologic constraints on the Late Cretaceous–Neogene erosional history of the equatorial margin of Brazil: Implications for the surface evolution of a complex rift margin
Basin Research
The equatorial margin of Brazil is an example of a rift margin with a complex landscape, dominate... more The equatorial margin of Brazil is an example of a rift margin with a complex landscape, dominated by an escarpment perpendicular to the continental margin, which testifies to an equally complex rift and post‐rift surface and tectonic evolution. This has been the focus of a long debate on the driving mechanism for post‐rift tectonics and on the amount of exhumation. This study contributes to this debate with new petrographic and thermochronologic data on 152 samples from three basins, Pará‐Maranhão, Barreirinhas and Ceará, on the offshore continental platform. Our detrital record goes back to the rift time at ca. 100 Ma ago and outlines three major evolutionary phases of a changing landscape: a rift phase, with the erosion of a moderate rift escarpment, a Late Cretaceous‐Palaeogene post‐rift phase of major drainage reorganization and significant vertical erosion and a Late Oligocene‐to‐Recent post‐rift phase of moderate vertical erosion and river headwater migration. We estimate tha...
Depositional and diagenetic impacts on the porosity of post-salt carbonate reservoirs of southern Campos Basin, southeastern Brazilian margin
Journal of South American Earth Sciences, 2021
Wave-dominated lacustrine margin of Aptian pre-salt: Mucuri Member, Espírito Santo Basin
Journal of South American Earth Sciences, 2020
Abstract The Espirito Santo Basin, one of the Brazilian marginal basins formed during the Gondwan... more Abstract The Espirito Santo Basin, one of the Brazilian marginal basins formed during the Gondwana break-up, is composed by three main depositional units – rift, sag and drift phases. The Mucuri Member sandstones are the Aptian sag phase related, onshore reservoirs deposited at the margins of the lacustrine system were the pre-salt (pre-evaporitic succession) lacustrine carbonate reservoirs were generated. The main objective of this article focuses on the stratigraphic and sedimentological definition of depositional model from the top of the Mucuri Member, in the transition to Itaunas Member evaporites of Mariricu Formation, since the depositional conditions of this interval until date remain under discussions and can contribute to the understanding of the correlated pre-salt reservoirs. Core description in detailed scale (1:50) associated with gamma-ray logs allowed the identification of nineteen facies, grouped into five facies associations: gravelly fluvial channel, poorly confined fluvial channels, upper shoreface, lower shoreface and offshore. Stacking patterns of facies associations allowed the definition of four cycles: T, T-R, normal R and forced R cycles. Although these cycles are easily recognizable in the cores, their correlation between wells was not possible. Geochemical analyses of 87Sr/86Sr ratio from anhydrites layers interbedded with the Mucuri sandstones confirmed a non-marine composition for the precipitating fluids. The integrated evidence suggests a wave dominated lacustrine coastal environment for the subaqueous Mucuri Member deposits.
Pesquisas em Geociências, 2019
Os depósitos aluviais da Formação São Mateus (Albiano da Bacia do Espírito Santo, Brasil) consist... more Os depósitos aluviais da Formação São Mateus (Albiano da Bacia do Espírito Santo, Brasil) consistem em importantes reservatórios. Entretanto, existem poucos trabalhos detalhando a estratigrafia deste intervalo estratigráfico. Em decorrência disso, este trabalho teve por objetivo estabelecer um fatiamento estratigráfico de alta resolução da seção basal desta unidade, a qual é constituída por depósitos fluviais. Diante das dificuldades apresentadas para a correlação estratigráfica desses depósitos, a estratégia de correlação utilizada foi a subdivisão da sucessão aluvial em ciclos estratigráficos. Este método se baseia na variação na razão entre as taxas de criação de acomodação e suprimento sedimentar (A:S) que diretamente controla o grau de amalgamação dos corpos arenosos de canais fluviais. Com isso, foram definidos seis ciclos compostos internamente por tratos de sistemas de alta e baixa acomodação. Esses ciclos refletem a estruturação do arranjo da amalgamação dos canais fluviai...
Depositional and diagenetic processes in the pre-salt rift section of a Santos Basin area, SE Brazil
Journal of Sedimentary Research, Jun 5, 2020
ABSTRACT This study aims to provide a better understanding of the genesis and diagenetic evolutio... more ABSTRACT This study aims to provide a better understanding of the genesis and diagenetic evolution of the rift pre-salt deposits of the Santos Basin, in the context of evolution of the lake system in which the sediments were deposited. The study of the syngenetic and early diagenetic constituents and their paragenetic relations allowed reconstruction of the evolution of lacustrine environmental conditions during the rift stage in the central area of the basin. A petrological study was performed on cores and sidewall samples of a well drilled through the pre-salt rift section in the Lower Cretaceous of the central Santos Basin, eastern Brazilian coast. The studied rocks consist of carbonate and non-carbonate intrabasinal components, with extrabasinal non-carbonate contribution. During Barremian early rift sedimentation, intense syngenetic precipitation of magnesian clay minerals under highly alkaline conditions deposited arenites constituted by stevensite ooids and peloids, as well as hybrid, resedimented deposits of the Piçarras Formation. Freshening of the lacustrine environment provided the conditions required for the proliferation of bivalves and sedimentation of the coquinas of the Itapema Formation. The massive structure of the deposits, poor sorting, chaotic to concave-up orientation of the bioclasts, and mixing of bivalves with stevensite particles indicate redeposition by gravity flows. The main diagenetic processes in rift stevensite and hybrid rocks are the cementation and replacement of grains by calcite, dolomite, and subordinately, silica and smectite. Siliciclastic-volcaniclastic mudrocks present intense replacement by dolomite. In the bivalve rudstones, the main diagenetic processes were dissolution of the shells and cementation of the intraparticle and interparticle pores by calcite and, subordinately, dolomite and silica.
Sedimentary Geology, Apr 1, 2020
The forearc succession of Great Valley Group in Central California provides some of the best exam... more The forearc succession of Great Valley Group in Central California provides some of the best examples of giant sand injection complexes in the world and is therefore considered valuable analogues for injectite systems in subsurface. Several sand injection complexes are well described in the outcrop and subsurface, however the petrographic characteristics of injectites are still poorly documented. In this paper, we present the results of an integrated study of field observations, quantitative and qualitative sandstone petrography, provenance, and petrofacies analysis of the Tumey Giant Injection Complex (TGIC) in order to understand its lithostratigraphy and petrological evolution, and its impacts on reservoir petrofacies characteristics and fluid migration. The TGIC intrudes into a 450 m thick deep-water succession of slope mudrocks and sandy channel-fills of the Kreyenhagen Shale Eocene), forming an interconnected network of sandstone sills, dykes and injection breccias. The complex generated a horizontal and vertical plumbing system for fluid migration, connecting isolated sandy channel-fills 2 among low-permeability mudrocks. The primary detrital composition, diagenetic products, microtextures, and provenance signatures allowed for the definition and discrimination of depositional and intrusive petrofacies and their genetic relations. Petrofacies associations confirm that the gypsum-cemented feldspathic litharenites from the Kreyenhagen Shale channel-fills are the only source for the injection complex. Eodiagenetic compaction and extensive gypsum cementation reduced the primary porosity of the complex, while telodiagenetic dissolution of autigenic constituents formed pervasive secondary porosity. The underlying calcite-cemented arkosic sandstones of the Lodo and Domengine formations acted as barriers for fluid flow, aiding lateral fluid migration and overpressure buildup within the overlying Kreyenhagen channel-fills. Intense grain microfracturing occurred during sand remobilization and injection along with erosion of the host mudrocks. This study has significance for the generation of reliable stratigraphic and petrological models for sand injection complex genesis and evolution that consequently can help the understanding and exploration of injectite complexes elsewhere.
Kaolinitic meniscus bridges as an indicator of early diagenesis in Nubian sandstones, Sinai, Egypt - discussion
Sedimentology, Feb 3, 2005
The recently published paper by Du Bernard & Carrio-Schaffhauser (2003) described a v... more The recently published paper by Du Bernard & Carrio-Schaffhauser (2003) described a very interesting and peculiar case of mechanically infiltrated clays in the Nubian sandstones, Egypt. The interesting aspects of this occurrence are the vadose meniscus morphology, ...
Meteoric-water diagenesis in late Cretaceous canyon-fill turbidite reservoirs from the Espírito Santo Basin, eastern Brazil
Marine and Petroleum Geology, Nov 1, 2012
Parameters controlling the diagenetic evolution of passive margin, marine turbidites, which are i... more Parameters controlling the diagenetic evolution of passive margin, marine turbidites, which are important targets of hydrocarbon exploration, are poorly constrained in the literature. This study aims to unravel the conditions of diagenesis and its impact on the reservoir quality evolution from late Cretaceous canyon-filling turbiditic sandstones of the onshore portion of Espírito Santo Basin, eastern Brazil. Kaolinization (δ18O=+ 13.3‰ to+ 15.2‰; δ D=− 96.6‰ to− 79.6‰) and dissolution of framework silicate grains is attributed to ...
An operational classification system for the South Atlantic pre-salt rocks
Journal of Sedimentary Research, Jul 19, 2023
The giant Aptian reservoirs and associated lacustrine rocks of the South Atlantic Pre-Salt sectio... more The giant Aptian reservoirs and associated lacustrine rocks of the South Atlantic Pre-Salt section present a series of unique characteristics, which make the systems created for marine carbonate rocks quite inadequate for their classification. Based on our experience with the characterization of thousands of samples of the Pre-Salt reservoirs and associated deposits from the Brazilian basins, and on a wide literature evaluation, we propose an objective and operational system for the classification of the unusual, yet extremely important Pre-Salt lacustrine rocks. The system allows the coherent record of structure, fabric, primary texture and composition, and main diagenetic modifications of the in situ and resedimented rock types. The in situ rocks are directly classified according to the original proportion among calcite spherulites, fascicular shrubs and mud matrix. The resedimented rocks are classified according to the original volume of > 2mm particles and the proportion between sand and mud, using calcirudite, calcarenite and calcilutite as unbiased names. Such approach can also be applied for the classification of other particulate carbonate rocks, avoiding the conceptual problems and dubious interpretation of depositional environment and reservoir quality of currently used classification systems. The direct, objective and instinctive proposed classification system shall contribute to the understanding, exploration and production of the extraordinary South Atlantic Pre-Salt petroleum province.
Geochemical modeling of diagenetic reactions in Snorre Field reservoir sandstones: a comparative study of computer codes Modelagem geoquímica das reações diagenéticas nos arenitos-reservatório do Campo de Snorre: um estudo comparativo de códigos computacionais
Syngenetic, Diagenetic and Hydrothermal Processes in the Pre-Salt Sag Section of Santos and Campos Basins
Summary The Pre-salt reservoirs of the sag section from the Santos and Campos basins are the prod... more Summary The Pre-salt reservoirs of the sag section from the Santos and Campos basins are the product of a vast lacustrine system, formed during the early South Atlantic opening. The in situ deposits were formed by the syngenetic deposition of stevensite and similar magnesian phyllosilicates, which were replaced, displaced and covered by calcite spherulites and fascicular shrubs during early diagenesis. Frequent, high-frequency compositional changes, which may have been related to lake waters stratification, promoted the alternation of levels with predominance of calcite shrubs, spherulites, or of stevensite matrix, as well as its early diagenetic dissolution and replacement by silica, dolomite, magnesite or calcite. The flow of burial diagenetic and hydrothermal fluids through porous layers, faults and fracture zones caused the precipitation of quartz, chalcedony, dolomite, calcite, barite/celestite, pyrite and other sulphides in some areas, but also significant dissolution and porosity enhancement, responsible for the exceptional performance of some reservoirs. Although for the recent advances in the understanding of the origin and evolution of the South Atlantic Pre-salt reservoirs, the sources for the huge volume of Ca, Mg and Si precipitated in the Pre-salt sag succession, remain to the determined.
Sedimentary Geology, Feb 1, 1998
Silurian-Devonian sandstones of the Fumas Formation in the intracratonic Paran Basin, southern Br... more Silurian-Devonian sandstones of the Fumas Formation in the intracratonic Paran Basin, southern Brazil, display strongly heterogeneous distribution of quartz, kaolinite and illite authigenesis. The sandstones were affected by extensive dissolution/kaolinization of detrital feldspar, mica and clay under an eodiagenetic meteoric regime. Circulation of hot fluids through fractures related to the uplift and magmatism along the regional Ponta Grossa Arch promoted heterogeneous kaolinite and feldspar illitization and quartz cementation. This is supported by intense illitization of kaolinite at shallow depths, by WAr dating of the illite, whose age coincides with the magmatism, and by high fluid inclusion homogenization temperatures in quartz overgrowths from outcrop-samples. The progressive destruction of feldspar generated diagenetic quartzarenites with poorly connected pore systems and low reservoir potential. Evidence yielded by this study suggests that the application of simplified 'isochemical' models of diagenetic processes within the system Si02-A1203-K1O-Hz0 may have very limited validity, applying basically to the deep-burial mesodiagenesis of some sandstones in rapidly subsiding basins.
Deposition, diagenetic and hydrothermal processes in the Aptian Pre-Salt lacustrine carbonate reservoirs of the northern Campos Basin, offshore Brazil
Sedimentary Geology, Apr 1, 2019
Origin and impact of authigenic chlorite in the Upper Cretaceous sandstone reservoirs of the Santos Basin, eastern Brazil
Petroleum Geoscience, Apr 2, 2013
Depositional and diagenetic conditions during early South Atlantic opening: Evidence from the upper Aptian Oiteirinhos Member, Muribeca Formation, Sergipe-Alagoas Basin, NE Brazil
Journal of South American Earth Sciences, Jun 1, 2023
Pesquisas em geociências, Jun 30, 2000
Recebido em I !l99. Aceilo paTa publi ca~iio em 05/00) Abstncl _ Th e Taquarembo Plmeau. silualed... more Recebido em I !l99. Aceilo paTa publi ca~iio em 05/00) Abstncl _ Th e Taquarembo Plmeau. silualed in Ihe so ulhweslern pan of Sul-rio-grandcnse sh ield. is pan of Camaquil Basin, Ihat was formed at the end of the post-coll isional stage in Brasi lianolPan-African even!. Neo prOlero7.0ic in age. This plateau is composed of volcanic and shallo w in!rusions. Telmed 10 a silica-saturated alkaline series. ranging from alkaline mClaluminous basalt 10 comendiiti c flows, known as Taq uaTemho Volcano-Pluton ic ASSOCIation. The faeiologieal identification lead s to the reconstruclion of the volcanic pilc. fonncd from Ihe oose to thc top by: paniculatcd nows (ignimhrites and reo-ignimhrites); resscdimemed syneru ptivc deposits; surge and fall hori1.ons. c losely associated with alkaline metaluminou5 lava nows (basalts. mugeari tcs, rhyolites); and peralkaline lava nows (comcn!liites), and shallow intrus ions of quartz monzonite and syeni te that crosscut the volcanic pile. The facies identification suggests a highly explosivc volcanic regime, under sub-aerial condition. in a c lose association with the feeder necks. Keywords _ volcan ic sequences. Cambrian volcanism. volcan ic textures
Pesquisas em geociências, Dec 31, 1998
Sedimentary features in eolian sandstones with piane-panllcllarrunation of the Botucatu FQITI18ti... more Sedimentary features in eolian sandstones with piane-panllcllarrunation of the Botucatu FQITI18tion, situated in a quarry in Novo Hamburgo (RS), SOIIthcm BTlIZil, were previously interpreted as possible plant imprints, They show very variable shapes, comprising: a) !mall, isolated, lenticuhlT or lamellar molds with oblique borders; b) aggregated molds, comprising divergent or intercepting, flIJ'Cly rndiated geOlTlCtry; c) large, lenticular or lamellar molds with small molds transversally to their margins: d) rounded or oval-shaped molds, some with small molds along the ir margin s, The shapes and distribution of these imprints indicate their origin from the di$SOlution isolated and aggregated gypsum (CaSO.,2H,O) crystals, an evaporitic minernl common in descnic environments. The gypsum was precipitated as large crystals ("selenitic gypsum") within eolian sheet sand~ shonly aftcrthcir deposition. Gypsum di$SOlution was promoted by the laterptlColalion ofmctcoric groundwalers throughout the sandstones. leaving molds de lineated by iron and manganese oxides. Thercfore. the studied imprints represent pseudofossil s. without any relationship with plants.
Uploads
Papers by Luiz Fernando de Ros