Petrobras (Brazil)

The Amazonian rainforest is arguably the most species-rich terrestrial ecosystem in the world, yet the timing of the origin and evolutionary causes of this diversity are a matter of debate. We review the geologic and phylogenetic evidence from Amazonia and compare it with uplift records from the Andes. This uplift and its effect on regional climate fundamentally changed the Amazonian landscape by reconfiguring drainage patterns and creating a vast influx of sediments into the basin. On this "Andean" substrate, a region-wide edaphic mosaic developed that became extremely rich in species, particularly in Western Amazonia. We show that Andean uplift was crucial for the evolution of Amazonian landscapes and ecosystems, and that current biodiversity patterns are rooted deep in the pre-Quaternary.

Abstract A unified scale is recommended for reporting the NMR chemical shifts of all nuclei relative to the 1 H resonance of tetramethylsilane (TMS). The unified scale is designed to provide a precise ratio, Ξ , of the resonance frequency of a given nuclide to that of the primary reference, the 1H resonance of TMS in dilute solution (volume fraction, φ < 1%) in chloroform. Referencing procedures are discussed, including matters of practical application of the unified scale. Special attention is paid to recommended reference samples, and values of Ξ for secondary references on the unified scale are listed, many of which are the results of new measurements. Some earlier recommendations relating to the reporting of chemical shifts are endorsed. The chemical shift, δ , is redefined to avoid previous ambiguities but to leave practical usage unchanged. Relations between the unified scale and recently published recommendations for referencing in aqueous solutions (for specific use in biochemical work) are discussed, as well as the special effects of working in the solid state with magic-angle spinning. In all, nine new recommendations relating to chemical shifts are made. Standardized nuclear spin data are also presented in tabular form for the stable (and some unstable) isotopes of all elements with nonzero quantum numbers. The information given includes quantum numbers, isotopic abundances, magnetic moments, magnetogyric ratios and receptivities, together with quadrupole moments and line-width factors where appropriate.

Abstract IUPAC has published a number of recommendations regarding the reporting of nuclear magnetic resonance (NMR) data, especially chemical shifts. The most recent publication [ Pure Appl. Chem. 73 , 1795 (2001)] recommended that tetramethylsilane (TMS) serve as a universal reference for reporting the shifts of all nuclides, but it deferred recommendations for several aspects of this subject. This document first examines the extent to which the 1 H shielding in TMS itself is subject to change by variation in temperature, concentration, and solvent. On the basis of recently published results, it has been established that the shielding of TMS in solution [along with that of sodium-3-(trimethylsilyl)propanesulfonate, DSS, often used as a reference for aqueous solutions] varies only slightly with temperature but is subject to solvent perturbations of a few tenths of a parts per million (ppm). Recommendations are given for reporting chemical shifts under most routine experimental conditions and for quantifying effects of temperature and solvent variation, including the use of magnetic susceptibility corrections and of magic-angle spinning (MAS). This document provides the first IUPAC recommendations for referencing and reporting chemical shifts in solids, based on high-resolution MAS studies. Procedures are given for relating 13 C NMR chemical shifts in solids to the scales used for high-resolution studies in the liquid phase. The notation and terminology used for describing chemical shift and shielding tensors in solids is reviewed in some detail, and recommendations are given for best practice.

Abstract We present a multidimensional multiple-attenuation method that does not require any subsurface information for either surface or internal multiples. To derive these algorithms, we start with a scattering theory description of seismic data. We then introduce and develop several new theoretical concepts concerning the fundamental nature of and the relationship between forward and inverse scattering. These include (1) the idea that the inversion process can be viewed as a series of steps, each with a specific task; (2) the realization that the inverse-scattering series provides an opportunity for separating out subseries with specific and useful tasks; (3) the recognition that these task-specific subseries can have different (and more favorable) data requirements, convergence, and stability conditions than does the original complete inverse series; and, most importantly, (4) the development of the first method for physically interpreting the contribution that individual terms (and pieces of terms) in the inverse series make toward these tasks in the inversion process, which realizes the selection of task-specific subseries. To date, two task-specific subseries have been identified: a series for eliminating free-surface multiples and a series for attenuating internal multiples. These series result in distinct algorithms for free-surface and internal multiples, and neither requires a model of the subsurface reflectors that generate the multiples. The method attenuates multiples while preserving primaries at all offsets; hence, these methods are equally well suited for subsequent poststack structural mapping or prestack amplitude analysis. The method has demonstrated its usefulness and added value for free-surface multiples when (1) the overburden has significant lateral variation, (2) reflectors are curved or dipping, (3) events are interfering, (4) multiples are difficult to identify, and (5) the geology is complex. The internal-multiple algorithm has been tested with good results on band-limited synthetic data; field data tests are planned. This procedure provides an approach for attenuating a significant class of heretofore inaccessible and troublesome multiples. There has been a recent rejuvenation of interest in multiple attenuation technology resulting from current exploration challenges, e.g., in deep water with a variable water bottom or in subsalt plays. These cases are representative of circumstances where 1-D assumptions are often violated and reliable detailed subsurface information is not available typically. The inverse scattering multiple attenuation methods are specifically designed to address these challenging problems. To date it is the only multidimensional multiple attenuation method that does not require 1-D assumptions, moveout differences, or ocean-bottom or other subsurface velocity or structural information for either free-surface or internal multiples. These algorithms require knowledge of the source signature and near-source traces. We describe several current approaches, e.g., energy minimization and trace extrapolation, for satisfying these prerequisites in a stable and reliable manner.

New biostratigraphic, isotopic, and well log data from exploration wells on the outer continental shelf and uppermost Amazon deep-sea fan, Brazil, reveal that the Amazon River was initiated as a transcontinental river between 11.8 and 11.3 Ma ago (middle to late Miocene), and reached its present shape and size during the late Pliocene. Prior to the late Miocene the continental shelf was a carbonate platform that received moderate siliciclastic sediment supply from the Proterozoic basement in eastern Amazonia. Average sedimentation rates on the Amazon Fan show three stages of development: (1) 11.8-6.8 Ma ago, low sedimentation rates (0.05 m/ka) prevailed on the fan, because the Amazon River was not yet entrenched and some sediments were partially trapped in continental basins; (2) 6.8-2.4 Ma ago, sedimentation rates (0.3 m/ka) increased, the river entrenched, and deposition fully migrated onto the Amazon Fan; (3) 2.4 Ma ago to the present, very high sedimentation rates (1.22 m/ka, with peaks of 11 m/ka) prevailed on the fan and the modern Amazon River developed. All these paleogeographic and depositional events are closely related to Andean tectonism (late Miocene-Pliocene) and were exacerbated by global cooling and sea-level fall during the late Miocene.

This paper presents an overview and a detailed description of the key logic steps and mathematical-physics framework behind the development of practical algorithms for seismic exploration derived from the inverse scattering series.

Many years have passed since the first genetically modified Saccharomyces cerevisiae strains capable of fermenting xylose were obtained with the promise of an environmentally sustainable solution for the conversion of the abundant lignocellulosic biomass to ethanol. Several challenges emerged from these first experiences, most of them related to solving redox imbalances, discovering new pathways for xylose utilization, modulation of the expression of genes of the non-oxidative pentose phosphate pathway, and reduction of xylitol formation. Strategies on evolutionary engineering were used to improve fermentation kinetics, but the resulting strains were still far from industrial application. Lignocellulosic hydrolysates proved to have different inhibitors derived from lignin and sugar degradation, along with significant amounts of acetic acid, intrinsically related with biomass deconstruction. This, associated with pH, temperature, high ethanol, and other stress fluctuations presented on large scale fermentations led the search for yeasts with more robust backgrounds, like industrial strains, as engineering targets. Some promising yeasts were obtained both from studies of stress tolerance genes and adaptation on hydrolysates. Since fermentation times on mixed-substrate hydrolysates were still not cost-effective, the more selective search for new or engineered sugar transporters for xylose are still the focus of many recent studies. These challenges, as well as under-appreciated process strategies, will be discussed in this review.

Abstract This paper provides both an introduction to and summary for the Atlas of Contourite Systems that has been compiled as part of the International Geological Correlation Project - IGCP 432. Following the seminal works of George Wust on the physical oceanography of bottom currents, and Charley Hollister on contourite sediments, a series of significant advances have been made over the past few decades. While accepting that ideas and terms must remain flexible as our knowledge base continues to increase, we present a consensus view on terminology and definitions of bottom currents, contourites and drifts. Both thermohaline and wind-driven circulation, influenced by Coriolis Force and molded by topography, contribute to the oceanic system of bottom currents. These semi-permanent currents show significant variability in time and space, marked by periodic benthic storm events in areas of high surface kinetic energy. Six different drift types are recognized in the ocean basins and margins at depths greater than about 300 m: (i) contourite sheet drifts; (ii) elongate mounded drifts; (iii) channel related drifts; (iv) confined drifts; (v) infill drifts; and (vi) modified drift-turbidite systems. In addition to this overall geometry, their chief seismic characteristics include: a uniform reflector pattern that reflects long-term stability, drift-wide erosional discontinuities caused by periodic changes in bottom current regime, and stacked broadly lenticular seismic depositional units showing oblique to downcurrent migration. At a smaller scale, a variety of seismic facies can be recognized that are here related to bottom current intensity. A model for seismic facies cyclicity (alternating transparent/reflector zones) is further elaborated, and linked to bottom current/climate change. Both erosional features and depositional bedforms are diagnostic of bottom current systems and velocities. Many different contourite facies are now known to exist, encompassing all compositional types. We propose here a Cl-5 notation for the standard contourite facies sequence, which can be interpreted in terms of fluctuation in bottom current velocity and/or sediment supply. Several proxies can be utilized to decode contourite successions in terms of current fluctuation. Gravel lag and shale chip contourites, as well as erosional discontinuities are indicative of still greater velocities. There are a small but growing number of land-based examples of fossil contourites, based on careful analysis using the recommended three-stage approach to interpretation. Debate still surrounds the recognition and interpretation of bottom current reworked turbidites.

Abstract A major cause of seismic attenuation in fluid-saturated rocks is the flow of the pore fluid induced by the passing wave. At sonic and ultrasonic frequencies, attenuation appears to be dominated by the local (pore-scale) flow between pores of different shapes and orientations. A simple squirt flow model is developed in which all of the parameters can be independently measured or estimated from measurements. The pore space of the rock is assumed to consist of stiff porosity and compliant (or soft) pores present at grain contacts. The effect of isotropically distributed compliant pores is modeled by considering pressure relaxation in a disk-shaped gap between adjacent grains. This derivation gives the complex and frequency-dependent effective bulk and shear moduli of a rock, in which the compliant pores are liquid saturated and stiff pores are dry. The resulting squirt model is consistent with Gassmann's and Mavko–Jizba equations at low and high frequencies, respectively. The magnitude of attenuation and dispersion given by the model is directly related to the variation of dry bulk modulus with pressure and is relatively independent of fluid properties.

ABSTRACT Pressure transient response in stress-sensitive formations is obtained by solving analytically the radial flow equation with pressure-dependent rock properties. In cracked rock systems and tight formations, hydraulic permeability is very sensitive to pore pressure change. The mathematical model presented in this paper takes into account the reduction in permeability caused by an increase in effective stress. The dependence of permeability on pore pressure makes the flow equation strongly nonlinear. A perturbation technique is applied to determine approximate analytical solutions for transient flow in an infinite radial system with constant rate inner boundary. The model includes a new parameter, the permeability modulus, which measures the permeability dependency on pressure. The solution of the model leads to the construction of type curves that can be applied to drawdown and buildup analysis of well test data from stress-sensitive reservoirs. Type curve matching provides a way to estimate initial permeability and permeability modulus. From buildup data, initial permeability may be obtained from the slope of the semi-log straight line on Horner plot, as shown in an example using field data from a low permeability gas reservoir.

Methane is an important greenhouse gas and energy resource generated dominantly by methanogens at low temperatures and through the breakdown of organic molecules at high temperatures. However, methane-formation temperatures in nature are often poorly constrained. We measured formation temperatures of thermogenic and biogenic methane using a "clumped isotope" technique. Thermogenic gases yield formation temperatures between 157° and 221°C, within the nominal gas window, and biogenic gases yield formation temperatures consistent with their comparatively lower-temperature formational environments (<50°C). In systems where gases have migrated and other proxies for gas-generation temperature yield ambiguous results, methane clumped-isotope temperatures distinguish among and allow for independent tests of possible gas-formation models.

The main objective of this work is to investigate the effect of a set of crude oil emulsion variables, including pH and salt and water contents, upon the microwave demulsification process. A series of batch demulsification runs were carried out to evaluate the final emulsified water content of emulsion samples after the exposure to microwaves. Tests were performed at distinct heating temperatures, using water-in-heavy crude oil emulsion samples containing different salt and water contents and pH. Well-defined temperature programs were established to control the amount of energy applied to the emulsion and, ultimately, the viscosity. Higher microwave demulsification efficiencies were achieved for emulsions containing high water contents, except when high pH and salt contents were simultaneously involved.

Summary Hydraulic fracturing is a dominant technology in unconventional resources development. Recent advances in fracture-diagnostic tools and fracture-propagation models make it necessary to model fractures with complex geometries in reservoir-simulation studies. In this paper, we present an efficient method to model fractures with complex geometries with reservoir simulators. Through nonneighboring connections (NNCs), an embedded discrete-fracture modeling (EDFM) formulation is applied to reservoir simulators to properly model fractures with complex geometries such as fracture networks and nonplanar hydraulic fractures. We demonstrate the accuracy of the approach by performing a series of case studies with two commercial reservoir simulators and comparing the results with local-grid-refinement (LGR) models and a semianalytical solution. The limitations of the model are also discussed. In addition, the results show its computational efficiency as the complexity of fractures increases. We also present two numerical case studies to demonstrate the applicability of our method in naturally fractured reservoirs. The nonintrusive application of the EDFM allows insertion of the discrete fractures into the computational domain and the use of original functionalities of the simulators without having access to the source code of the simulators. It may be easily integrated into existing frameworks for unconventional reservoirs to perform sensitivity analysis, history matching, and production forecasting.

Abstract The reaction of N ‐alkylimidazole with alkyl sulfonates at room temperature affords 1,3‐dialkylimidazolium alkanesulfonates as crystalline solids in high yields. The alkanesulfonate anions can be easily substituted by a series of other anions [BF 4 , PF 6 , PF 3 (CF 2 CF 3 ) 3 , CF 3 SO 3 and N(CF 3 SO 2 ) 2 ] by simple reaction of anions, salts, or acids in water at room temperature. Extraction with dichloromethane, filtration through a short basic alumina column and solvent evaporation affords the desired ionic liquids in 80–95% yield. The purity (&gt;99.4%) of these ionic liquids can be determined by 1 H NMR spectra using the intensity of the 13 C satellites of the imidazolium N ‐methyl group as internal standard.

Abstract The South Atlantic Ocean evolved after rupture of the São Francisco–Congo–Rio de la Plata–Kalahari cratonic landmass and the Late Proterozoic fold belts. Break-up in the South Atlantic realm developed diachronously: rifting started in the south (Argentina) during the Jurassic and progressed towards the equatorial segment. The central portion was controlled by a rift-resistant cratonic nucleus (the São Francisco–Congo craton) and as a result underwent development of narrow basins; parts controlled by Neoproterozoic fold belts developed wide basins. The final break-up of western Gondwana and the onset of plate divergence were marked by thick wedges of seaward-dipping reflectors, located near the incipient ocean-ridge spreading centre that had already been formed by the time Aptian evaporites were deposited. Subsequently, a few episodes of intraplate tectonic and magmatic activity affected the Santos, Campos and Espírito Santo basins. Post-break up development of the offshore basins was affected by gravity gliding over the Aptian evaporites. Continental uplift may be invoked as the main cause of salt mobilization, generating prograding clastic wedges that thickened basin-wards and produced a loading effect on the salt basin. Coupled with onshore erosional unloading and the effects of the gravity gliding, this probably resulted in further flexural uplift of the continental margin.

Research Article| April 01, 1986 The deltaic nature of Amazon shelf sedimentation C. A. NITTROUER; C. A. NITTROUER 1Department of Marine, Earth and Atmospheric Sciences, North Carolina State University, Raleigh, North Carolina 27695 Search for other works by this author on: GSW Google Scholar S. A. KUEHL; S. A. KUEHL 1Department of Marine, Earth and Atmospheric Sciences, North Carolina State University, Raleigh, North Carolina 27695 Search for other works by this author on: GSW Google Scholar D. J. DEMASTER; D. J. DEMASTER 1Department of Marine, Earth and Atmospheric Sciences, North Carolina State University, Raleigh, North Carolina 27695 Search for other works by this author on: GSW Google Scholar R. O. KOWSMANN R. O. KOWSMANN 2CENPES/PETROBRAS, Rio de Janeiro, Cep. 21910, Brazil Search for other works by this author on: GSW Google Scholar Author and Article Information C. A. NITTROUER 1Department of Marine, Earth and Atmospheric Sciences, North Carolina State University, Raleigh, North Carolina 27695 S. A. KUEHL 1Department of Marine, Earth and Atmospheric Sciences, North Carolina State University, Raleigh, North Carolina 27695 D. J. DEMASTER 1Department of Marine, Earth and Atmospheric Sciences, North Carolina State University, Raleigh, North Carolina 27695 R. O. KOWSMANN 2CENPES/PETROBRAS, Rio de Janeiro, Cep. 21910, Brazil Publisher: Geological Society of America First Online: 01 Jun 2017 Online ISSN: 1943-2674 Print ISSN: 0016-7606 Geological Society of America GSA Bulletin (1986) 97 (4): 444–458. https://doi.org/10.1130/0016-7606(1986)97<444:TDNOAS>2.0.CO;2 Article history First Online: 01 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn Email Tools Icon Tools Get Permissions Search Site Citation C. A. NITTROUER, S. A. KUEHL, D. J. DEMASTER, R. O. KOWSMANN; The deltaic nature of Amazon shelf sedimentation. GSA Bulletin 1986;; 97 (4): 444–458. doi: https://doi.org/10.1130/0016-7606(1986)97<444:TDNOAS>2.0.CO;2 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGSA Bulletin Search Advanced Search Abstract Despite the annual discharge of more than a billion tons of sediment by the Amazon River, the sedimentary environment near the river mouth has little subaerial expression and thus does not meet the classic definition of a delta. The river mouth, however, is not an estuary, either. These observations raise a major question as to what type of sedimentary environment the Amazon river mouth represents.Seismic stratigraphy has been examined on the continental shelf at the mouth of the Amazon River using high-frequency (3.5-kHz) seismic records from about 6,000 km of ship track. These records demonstrate three regions. (1) <40-m water depth—topset strata composed primarily of muddy sediment with sandy interbeds that dip gently and diverge seaward; stratification (sandy interbeds) that becomes less predominant northwestward along the dispersal system. (2) ∼40- to ∼60-m water depth—foreset strata that dip relatively steeply (but <1°) and converge seaward. (3) ∼60- to ∼100-m water depth—bottomset strata that form a thin, acoustically transparent layer of mud, which is burying sandy bedforms on the surface of a basal (transgressive) sand layer. The large-scale structure which the deposits of these regions create is a sigmoidal clinoform. Fine-scale sedimentary structures have been examined from the inner continental shelf using X-radiographs of about 140 cores (box cores and large gravity cores). These X-radiographs reveal: (1) physically stratified sand near the river-mouth bar, (2) interbedded mud and sand (in the shelf adjacent to the river mouth, and (3) faintly laminated and mottled mud surrounding the interbedded deposits. This fine-scale stratification resembles deposits of (respectively) the distributary-mouth bar, distal bar, and prodelta observed for the Mississippi and other deltas.The Amazon River has built a subaqueous feature which stretches for hundreds of kilometres offshore and alongshore from its mouth. The feature is prograding seaward and accreting upward, and it contains fine-scale stratification typical of classic deltas. The feature forming at the mouth of the Amazon is a subaqueous delta; it differs from classic deltas primarily in its lack of subaerial expression. Subaqueous deltas, such as the Amazon, represent the general case of a major river entering an energetic oceanic regime. First Page Preview Close Modal You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

Abstract Unsupervised seismic facies analysis provides an effective way to estimate reservoir properties by combining different seismic attributes through pattern recognition algorithms. However, without consistent geological information, parameters such as the number of facies and even the input seismic attributes are usually chosen in an empirical way. In this context, we propose two new semiautomatic alternative methods. In the first one, we use the clustering of the Kohonen self-organizing maps (SOMs) as a new way to build seismic facies maps and to estimate the number of seismic facies. In the second method, we use wavelet transforms to identify seismic trace singularities in each geologically oriented segment, and then we build the seismic facies map using the clustering of the SOM. We tested both methods using synthetic and real seismic data from the Namorado deepwater giant oilfield in Campos Basin, offshore Brazil. The results confirm that we can estimate the appropriate number of seismic facies through the clustering of the SOM. We also showed that we can improve the seismic facies analysis by using trace singularities detected by the wavelet transform technique. This workflow presents the advantage of being less sensitive to horizon interpretation errors, thus resulting in an improved seismic facies analysis.

River water is a small percentage of the total freshwater on Earth but represents an essential resource for mankind. Microbes in rivers perform essential ecosystem roles including the mineralization of significant quantities of organic matter originating from terrestrial habitats. The Amazon river in particular is famous for its size and importance in the mobilization of both water and carbon out of its enormous basin. Here we present the first metagenomic study on the microbiota of this river. It presents many features in common with the other freshwater metagenome available (Lake Gatun in Panama) and much less similarity with marine samples. Among the microbial taxa found, the cosmopolitan freshwater acI lineage of the actinobacteria was clearly dominant. Group I Crenarchaea and the freshwater sister group of the marine SAR11 clade, LD12, were found alongside more exclusive and well known freshwater taxa such as Polynucleobacter. A metabolism-centric analysis revealed a disproportionate representation of pathways involved in heterotrophic carbon processing, as compared to those found in marine samples. In particular, these river microbes appear to be specialized in taking up and mineralizing allochthonous carbon derived from plant material.

The Brazilian and West African Equatorial margins comprise an unique example of a transform margin, characterized by a series of on- and offshore Mesozoic-Cenozoic basins, distributed over 2,200 km along the South Atlantic. Although a multi-stage stretching process evolved throughout the Aptian-Cenomanian, an almost instantaneous Aptian stage was responsible for a widespread fracturing of the Equatorial Atlantic. Conventional extensional processes can not explain the kinematics and rift geometry of the Equatorial SouthAtlantic basins. Accepted pure-shear or simple-shear rift mechanisms, typical of divergent margins, cannot be promptly used in basins generated as a response to major transform motions along a continental-scale plate boundary. The commonly accepted causal processes for rifting, such as passive/active or diffuse/discrete rifting, can not accommodate the South Atlantic Equatorial data set. Even though shearing signatures and pull-apart features are easily recognized throughout the margin, their magnitude and basin architecture varies significantly as a function of the distance from the main transform faults. These factors resulted in significant differences in thermal evolution, tectonic subsidence, facies distribution and uplift history. The tectonic evolution of the sedimentary basins along the Equatorial Atlantic is better understood by considering three stages: pre, syn and post-transform movements. These are related to kinematic and dynamic controls provided by the emplacement of fractured swells as proto mid ocean ridges, followed by the creation of oceanic crust and the onset of transform shearing between Africa and Brazil.

Abstract The genesis and evolution of lacustrine pre-salt carbonate reservoirs, which contain giant hydrocarbon accumulations along the South Atlantic margins, has attracted major research interest. The huge extension and volume, and unusual textural and compositional features, are key elements for understanding the tectonic, structural, stratigraphic, and sedimentological generation and early evolution of the region, as well as potentially of other lacustrine carbonate systems. A systematic petrographic and petrophysical study has been performed on the Lower Cretaceous lacustrine carbonate reservoirs from northern Campos Basin, Offshore Brazil, in order to unravel the main controls on the origin and evolution of pore systems. The main lithologic types recognized in the rift section are bivalve–gastropod grainstones and rudstones, arenites constituted by ooids of syngenetic magnesian clay minerals (mostly stevensite), and dolostones, while stevensitic claystones with calcite spherulites, fascicular calcite crusts, intraclastic rudstones and grainstones, and dolostones are the main lithologic types in the sag section. The eogenetic evolution of bioclastic reservoirs was controlled by the balance between dissolution and neomorphism of the aragonitic bivalve and gastropod bioclasts, favoring either the generation of poorly connected moldic porosity or the preservation of well-connected interparticle porosity. The stevensitic arenites were strongly affected by meteoric dissolution and replacement by dolomite and silica, related to regional uplift and erosion after the rift phase, which generated highly heterogeneous pore systems with moldic, intercrystalline, vugular, and microcrystalline pores. Stevensitic claystones that are replaced by calcite spherulites and dolomite normally show low porosity, but locally constitute reservoirs, where secondary porosity was generated by stevensite dissolution. The precipitation of crystal shrubs of fascicular-optic calcite in coalescent crusts generated growth-framework primary porosity, which was reduced mostly by dolomite cementation, or enlarged by dissolution, enhancing their permeability. Non-coalescent calcite crusts contain abundant syngenetic magnesian clay minerals. Their porosity is related to dissolution of these clays, which generated poor permeability. Intraclastic grainstones and rudstones are compacted and cemented, or rich in clay matrix (“hybrid packstones”). Where they display preserved interparticle primary porosity or matrix dissolution, they may have good porosity and permeability. The heterogeneous dolomitization of both the rift and the sag deposits either destroyed their primary or early diagenetic porosity, or generated high porosity and permeability values in the dolostones. Relationships between replacement and compaction indicate that most of the diagenetic processes occurred during eodiagenesis, controlled mostly by the instability of the aragonite in the bioclastic reservoirs and of the stevensite in the claystones, ooidal arenites, and fascicular calcite crusts. This study characterizes the major primary and diagenetic aspects of the pre-salt reservoirs, providing insights on the evolution of their porosity and permeability. This is expected to contribute to the prediction of quality during exploration and to enhance hydrocarbon recovery from producing oilfields, as well as to increase the understanding of the origin, evolution, and quality distribution in analogous lacustrine reservoirs.