Campos Basin Research Articles

Caracterização petrográfica da Formação Emborêcom base em dados dos poços 2-CST-1-RJ e 9-BRF-1D-RJ(região emersa da Bacia de Campos)

O presente estudo teve como objetivo a caracterização sedimentológica e petrográfica da Formação Emborê, com base na descrição de amostras de arenitos de dois poços profundos localizados na área emersa da Bacia de Campos (2-CST-1-RJ e 9-BRF-1D-RJ). Buscou-se ampliar o conhecimento sobre os aspectos texturais e composicionais dessa unidade litoestratigráfica, ainda muito pouco estudada e que apresenta um grande potencial hídrico, contendo o mais importante aquífero do estado do Rio de Janeiro, foco da pesquisa que ensejou este artigo. No poço 2-CST-1-RJ foram descritas amostras de testemunhos e no poço 9-BRF-1D-RJ foram analisadas amostras de calha e plugs laterais. Os intervalos sedimentares analisados nos dois poços são semelhantes quanto aos aspectos sedimentológicos, sendo predominantemente areníticos, com intercalações de lamitos. Após a caracterização sedimentológica dos testemunhos e amostras de calha, foram selecionadas amostras de arenitos dos testemunhos do poço 2-CST-1-RJ e os plugs laterais do poço 9-BRF-1D-RJ para a descrição microscópica em lâminas petrográficas. Os arenitos são, em geral, finos a grossos, moderadamente a mal selecionados, de coloração acinzentada a esverdeada, com grãos angulosos a subangulosos, quartzosos e feldspáticos, com presença significativa de litoclastos graníticos nas amostras do poço 9-BRF-1D-RJ. Correspondem principalmente a arcósios, subarcósios e arcósios líticos, sendo atribuídos ao Membro São Tomé da Formação Emborê. Os aspectos texturais e mineralógicos evidenciam uma baixa maturidade. Na maior parte das amostras, verificou-se a presença de matriz argilosa do tipo epimatriz, proveniente da dissolução de grãos de feldspatos e a sua posterior infiltração nos poros. A porosidade atinge até cerca de 20%, sendo essencialmente de origem secundária, gerada pelo encolhimento da matriz, dissolução ou fraturamento dos grãos, com baixa conectividade entre os

English

Strains previously isolated from offshore oil reservoirs in Campos Basin (RJ, Brazil) and Potiguar Basin (RN, Brazil) were tested for production of antimicrobial compounds. Sixteen bacteria produced compounds with antimicrobial activity. The strain chosen for further study was Bacillus safensis SG-32 based on its ability to inhibit 76% of the strains tested. The bacterium was grown in Marine Broth (MB) and the hexane extract was investigated for minimal inhibitory concentration (MIC) (highest activity 0.4 mg/mL against Staphylococcus aureus), antiproliferative activity against human cancer cell lines (highest activity TGI = 69.83 µg/mL against melanoma cell lines), and antiparasitic tests (maximum activity 22.49% against Trypanosoma cruzi). Bioactive extract from B. safensis SG-32 was purified using silica column chromatography. Fractions collected were tested by bioautography in order to select the fraction with antimicrobial activity. The active molecule was identified by Nuclear Magnetic Resonance (NMR) as a diterpene of the Cyathin family. In addition to the antimicrobial and antitumor activity, Cyathin type compounds are known to stimulate the synthesis of Nerve Growth Factor (NGF), a capacity that implicates their potential as therapeutic agents to treat neurodegenerative ailments such as Alzheimer’s or Parkinson’s disease. In conclusion, this study showed that B. safensis SG-32 produces metabolites with antibacterial, antiproliferative and antiparasitic activities, and opens perspectives for further study of its potential also for nerve protection. Key words: Antimicrobial, antiproliferative, Bacillus safensis, Cyathin, nerve grow factor, drug discovery.

Petrophysical Characteristics of Arenito Namorado - Campos Basin: The Use of Laboratory Data

1. Abstract In reservoir characterization, due to information-acquisition’s high costs, frequently only indirect measurements of the subsurface properties such as seismic reflection data is available. In this work it is showed how data acquisition from practical analyses can help to understand the reservoir behavior. We used data disposed online by Petrobras S.A., from 3-NA-01-RJS, 3-NA-02-RJS and 3-NA-04-RJS wells, sampled in 1982. Therefore, it was showed that the compressibility is the most unpredictable of the Petrophysical properties, and must be taken serious when understanding uncertainties involved in reservoir modeling, which is an essential tool to support decisions in the petroleum industry. Porosity and permeability can be positive related, and they have not shown good correlations to compressibility or deep. 2. Keywords : Campos Basin (Brazil); Namorado Field; Petrophysical Properties

THREE‐DIMENSIONAL SEISMIC GEOMORPHOLOGY OF PALEOKARST IN THE CRETACEOUS MACAÉ GROUP CARBONATES, CAMPOS BASIN, BRAZIL

Three‐dimensional seismic data from an oilfield in the Campos Basin, SE Brazil, was used to characterize a karstified unconformity surface at the top of the Albian – Cenomanian Macaé Group. Macaé Group carbonates underwent intense karstification associated with subaerial exposure during a period of some 10 to 15 Ma resulting in the development of canyons, valleys, sinkholes and cave systems. The carbonates host commercial oil accumulations at a number of important oil fields. Understanding how the karstification process has affected the carbonates' reservoir properties is essential for future exploration, not only to improve recovery rates but also to avoid drilling‐related issues such as thief zones. In this context, this study aims to characterize the top‐Macaé Group paleokarst system by investigating the morphology of the associated reflectors recorded on seismic data, together with endokarst features in the underlying carbonate succession such as cave systems and collapse structures. The top‐Macaé Group seismic horizon can be divided into two principal geomorphological domains: highlands, characterized by abrupt relief with well‐developed erosional features; and lowlands, marked by a smoother topography. Collapse sinkholes occur in both domains and take the form of closed circular depressions. The study of endokarst features from an analysis of amplitude anomalies (bright spots) indicates the presence of heterogeneous cave systems. The interpreted data contributes to a better understanding of the spatial distribution of the paleokarst system in the Macaé Group carbonates and may assist with future hydrocarbon exploration in the Campos Basin.

Exploratory Analysis of Campos Basin Crude Oils via Geochemical Parameters by Comprehensive Two-Dimensional Gas Chromatography/Time-of-Flight Mass Spectrometry

Comprehensive two-dimensional gas chromatography coupled to time-of-flight mass spectrometry (GC×GC–TOFMS) was used for geochemical characterization of 18 oil samples from Campos Basin, Brazil. Con...

The family Phoxocephalopsidae (Crustacea: Amphipoda) from Brazilian coastal waters with description of four new species.

Phoxocephalopsids are fossorial amphipods endemic to the Southern Hemisphere and currently encompass five genera and 15 species, including the four new species herein described. Previous records of the family along the Brazilian coast are limited to Phoxocephalopsis zimmeri Schellenberg, 1931. Based on material from the Crustacean Collection of Museu Nacional/UFRJ four new species of Phoxocephalopsidae areherein described: Phoxocephalopsis ruffoi sp. nov. from Rio de Janeiro, São Paulo, Paraná and Rio Grande do Sul (23o-30oS); Puelche irenae sp. nov. from Espírito Santo and Rio de Janeiro (19o-23oS); Puelche longidactylus sp. nov. from Bahia, Espírito Santo and Rio de Janeiro (12o-23oS) and Puelche mourae sp. nov. found only at Rio de Janeiro. High diversity was recorded from the Campos Basin region, which extends from the north of Rio de Janeiro to south of Espírito Santo (21o-23oS), with the presence of all four phoxocephalid species. A key to Phoxocephalopsidae species from Brazil, including P. orensanzi Barnard and Clark, 1982 is provided.

Palinologia do Cretáceo Superior do Poço Campos-01, Norte da Bacia de Campos: Inferências Paleoambientais

A detailed palynological analysis was conducted on 29 samples obtained from the Cretaceous interval of the well Campos- 01, drilled in the Northern portion of the offshore Campos Basin. The main objectives of this study were to precise the age the rocks and to perform an analysis and interpretation of the depositional environment of the interval. The material consists of mainly shales, marls, calcareous mudstones and sandstones deposited in a deep marine environment. The palynological analysis consisted on identification and counting of all palynomorphs. The paleoenvironmental and paleoecological investigations were supported by cluster analysis, ecological indices (e.g. diversity, dominance) and ratios (e.g. continental:marine) were used. A total of 97 taxa was identified, which included 46 genera of dinoflagellates cysts, 25 genera of spores, 21 genera of pollen grains, 2 genera of freshwater algae and microforaminiferal linings. The recorded assemblage (e.g. Trichodinium castanea, Dinogymnium acuminatum, Zlivisporis blanensis) was assigned to a late Campanian—late Maastrichtian age for the studied section. The interval is clearly dominated by the dinoflagellate cysts that reach 90.7% of total of palynomorphs. On the basis of cluster analysis (r-mode) three dinoflagellate associations were recognized: Systematophora, Areoligera and Spiniferites. The stratigraphic distribution of dinoflagellates associations indicates three intervals (I1-I3). The intervals I1 and I2, dominated by Systematophora and Spiniferites respectively, are interpreted as open marine environment. In the interval I3, the dominance of Areoligera Association indicates a nearshore environment, also supported by the large amount of continental elements, including the genus Callialasporites, which is attributed to high altitude flora, suggesting the presence of highland feeding areas.

Shell concentration dynamics driven by wave motion in flume experiments: Insights for coquina facies from lake-margin settings

Coquinas are important carbonate oil reservoirs in the sin-rift sequence of the Brazilian marginal basins, mainly in Campos and Santos basins. They are generated from shell accumulations in lake-margin environments in which waves and bottom currents, at storm conditions, were the main hydrodynamic agents of transport and reworking. In order to investigate the role of wave transformation processes in shallow waters – swash, breaking and wave shoaling – in shell concentrations, a physical modelling of the coastal environment was performed in laboratory. The experimental setup consisted of a 2D flume, a wave generator, and a sedimentary bottom composed by quartz sand and shells (bivalves, gastropods, and fragments). An underwater camera, wave gauges and an ADV were used to record the sedimentary processes and to perform a quantitative analysis of the hydrodynamics. The experimental scenario reproduced a rift-lake margin. A coastal sector of Lake Tanganyika, Tanzania, Africa, was used to set the model boundary conditions (in a 1/20 scale) as well as the coastal gradient and wave conditions. From 54 h of wave experiments which alternated from fair-weather to storm wave conditions, three shell concentration dynamics were observed: reworking, winnowing, and dynamic bypassing. The reworking (erosion) was characterized by traction, rolling, and saltation of bioclasts, together with the traction and suspension of sand. The occurrence of the latter was restricted to the breaking and swash zone in both fair-weather and storm conditions. The winnowing (erosion) was featured by sand suspension and the gentle traction and rotation of the bioclasts on the bottom. The winnowing occurred at the proximal area of the shoaling zone, just behind the first wave-breaking point in storm wave conditions. The dynamic bypassing (omission) was identified by the ripples migration over static shells on the bottom of the distal shoaling zone, which produced alternated burial and exhumation of bioclasts. The quantitative analysis of the oscillatory flow indicated higher velocities at the breaking zone (reworking domain) than at the shoaling zone (winnowing domain) mainly during storm conditions. This study provided new and more accurate insights to depositional models of lake-margin coquinas, suggesting that each wave transformation process control a specific dynamic of shell concentration. Also, the limit between the breaking zone and the shoaling zone in storm conditions (1st wave-breaking point), was identified as a better criterion to bound the reworking domain, where fragmented coquinas are produced, from the winnowing and dynamic bypassing domains, where non-fragmented coquinas occur, in contrast to the fair-weather wave base criterion.

Evaluation of Barium Sulfate Scale Inhibition Using Relative Permeability Modifier Polymers as Adsorption Enhancer for Mature Offshore Well Treatments in Campos Basin, Brazil

In many mature offshore fields, high water cuts and potential scale deposition are some of the toughest challenges operators need to face. Two common practices used to deal with these challenges are relative permeability modifiers (RPM) polymer injection and scale inhibitor squeeze treatments. Even though many fields face these two challenges simultaneously, little is known about concomitant application of these treatments. In this paper, the effect of applying RPM polymers prior to inhibitor squeeze in the effectiveness of the last treatment is evaluated for sandstone rocks of Campos Basin, Brazil. Sequential laboratory injections in Campos Basin rocks of commercial cationic and anionic polyacrylamide and polyaluminum chloride (PAC) as cross-linking agent were employed prior to the injection of a commercial organophosphonic acid type inhibitor for barium sulfate scale. It was found that the polymers employed are capable of reducing the permeability of porous media to water and increasing the retention time of the scale inhibitor simultaneously. The tests also indicated that the inhibitor’s longer retention time is associated with the interaction with an outer cationic layer of the cross-linking agent. The adsorption isotherms were calculated and compared with Langmuir, Freundlich, Sips, and Toth models, the last two being the most accurate in representing the adsorption system for these tests.

Technology Focus: Subsea Hardware and Technology (August 2018)

Technology Focus A long-standing truism is that ideas that change one industry dramatically often are the result of innovations from a different industry altogether. In the realm of subsea exploration and production, with its high levels of risk and expense, concepts pioneered or used elsewhere are positioned to initiate important advances, a fact reflected in the three papers chosen for this year’s feature on Subsea Hardware and Technology. Paper OTC 28051 uses the strength, weakness, opportunity, and threat (SWOT) analysis technique often used in organizational and personal strategy-building to compare four different development concepts that hold promise for meeting the environmental and economic challenges posed by presalt fields in the Santos and Campos basins. In its discussion of fiber-communications technology that has been widely used in other industries, paper OTC 27987 describes the search for optimal use of wet-mate connectors in subsea applications, stressing that the significant opportunities in data collection offered by this hardware are of limited value without rigorous quality control. Finally, paper OTC 29069 delves into the world of marine mining, where developments in artificial intelligence and robotics are redefining the roles of autonomous underwater vehicles (AUVs). These innovations, including diverse aspects such as increased mobility and manipulation abilities and enhanced inspection capabilities for extended AUV missions, may increase cost-effectiveness while creating minimal disruption to the seafloor—innovations that will likely have a powerful echo in the oil and gas industry. With hard work, the progress outlined in these three papers may help create a better balance between cost, production, and ecological stability in offshore operations. The papers illustrate the inter-dependence of both technological and environmental systems, a truth of which operators in all realms of the industry must remain perpetually aware. Recommended additional reading at OnePetro: www.onepetro.org. OTC 28992 Horizontal Well Placement in a Thin Heterogeneous Carbonate Reservoir Using Azimuthal Sonic and Resistivity Measurements: A Case Study From Offshore Abu Dhabi by Amr M. Serry, ADMA-OPCO, et al. OTC 28562 Electric-Controls Technology: The Role in Future Subsea Systems by Sigurd Moe, TechnipFMC, et al.

Facies and paleoenvironments of the Coqueiros Formation (Lower Cretaceous, Campos Basin): A high frequency stratigraphic model to support pre-salt "coquinas" reservoir development in the Brazilian continental margin

Lacustrine carbonatic deposits are generally little studied, partly because of their lesser representativity in the global geological record, as well as the smaller amount of oil reservoirs associated with these types of rock. But the Cretaceous (Aptian \\ Barremian) lacustrine carbonates recorded on the eastern Brazilian coast from Santos to Sergipe-Alagoas basins, attributed to the rift and post-rift phases that preceded the opening of the Atlantic Ocean, has been registering important hydrocarbon discoveries since the 1970s to the present day. This study aimed to expand the knowledge of these deposits by analysing the facies and associations, defining sequences according to the current understanding of the sequence stratigraphy concepts. Rock samples were described associated with core and seismic profile data from the Badejo, Linguado, Pampo and Trilha fields in the Campos Basin. As the main lithology sampled was bioclastic (bivalves) carbonates. Were defined fifteen facies according to sedimentological criteria associated to taphonomy concepts and also grouped in four associations interpreted according to the hydrodynamic gradient of a wave-dominated shelf. This enabled the definition of high and medium frequency sequences, which aided the description of three internal sequences in the interval known as Lower Coquina. This methodology can be used to interpret facies spatial distribution and serves as an analogue for cycles definition in similar depositional systems.

Facies and paleoenvironments in Paraíba do Sul Deltaic Complex area, North of Rio de Janeiro state, Brazil

The Paraíba do Sul Deltaic Complex (PSDC) is a large Quaternary coastal plain located along Rio de Janeiro's northern coast and forms part of the onshore portion of Campos Basin. The main studies of the PSDC focused on modeling the paleoenvironmental evolution and were based on paleogeographic reconstructions, surface sampling, radiocarbon datings (14C), drillcores from shallow wells (<40 m depth) and results of ground penetrating radar (GPR) surveys. The paucity of deep subsurface data, in particular continuous drillcores, has led to divergent interpretations of not only the age, paleoenvironmental conditions and stratigraphic position of the PSDC deposits, but also of the underlying sedimentary units. In order to improve the knowledge about the evolution of PSDC, this study aims the stratigraphic characterization and paleoenvironmental interpretation by facies analyzes of a deep drillcore (410 m) recovered at the central area of PSDC. Fourteen sedimentary facies, grouped in six facies associations related to a wide variety of depositional paleoenvironments have been identified. The depositional history of the PSDC began with a transgressive event that led to the drowning of an incised valley cutting the continental deposits of the São Tomé Member, which is represented by the distal alluvial fan (DAF) and fluvial (F-I) facies associations in the analyzed drillcore. The valley infill is marked by two Pleistocene depositional sequences representing estuarine (FE-I facies association) and estuarine to open marine (FE-II facies association) paleoenvironments deposited in response to high-frequency base-level oscillations within a major transgressive sequence after the Marine Isotope Stage 6 (Penultimate Marine Transgression - 123.000 years B.P.). This transgression was followed by a regressive phase (normal to forced) that promoted the development of extensive Pleistocene beach-ridge terraces (BR facies association), which are still partially preserved at the surface of the study area. Marine and lagoonal deposits associated with the transgressive period occurred after the Marine Isotope Stage 2 (Last Marine Transgression - 5.100 years B.P.) documented in the previous studies, were not found in the analyzed drillcore, suggesting that these deposits may have discontinuously preserved within the study area or that they were eroded by Holocene fluvial systems represented by F-II facies association.

Catalogue of the Order Amphipoda from Brazil (Crustacea, Peracarida):Suborders Amphilochidea, Senticaudata and Order Ingolfiellida.

This catalog documents 303 species within 142 genera and 56 families distributed in the suborders Amphilochidea, Senticaudata and order Ingolfiellida that have been described or reported for the Brazilian coast and continent. Data for these species such as type material, type locality, geographic and bathymetric distribution, ecological notes and remarks, when pertinent, was given. From these, 268 species (~ 90%) are benthonic, marine and/or estuarine occurring from a diverse type of substrates as sediment, algae, sponges, cnidarians, ascideans, mangrove roots, fouling habitats, coral rubble, rodolith banks, etc. In terms of bathymetry, there are 214 species (~ 80%) reported for the Brazilian continental shelf (0-200 m) and 60 (~20%) for the deep sea zone (&gt; 200 m, 50% from the Campos Basin area). There are 35 non-marine amphipods reported from Brazil. Hyalella is the restricted and dominant epigean group and is represented by 22 species, including some hypogean and cave species. Cave dwellers includes 15 species within 6 genera as: Hyalella (5); Megagidiella (1); Potiberaba (1); Spelaeogammarus (7), and Seborgia (1). Among the Bogidiellidae, Bogidiella neotropica Ruffo, 1952 and Marigidiella brasiliensis (Siewing, 1953) are hypogean, but not from caves. The former is the only amphipod species recorded from the Brazilian Amazon Biome, within the Tapajós River, Pará and the latter are found in marine coastal groundwater of Bahia and São Paulo. Considering the landhoppers (truly terrestrial), only two introduced species, Talitroides alluaudi (Chevreux, 1896) and Talitroides topitotum (Burt, 1934) have been found in the Atlantic forest biome, urban parks and sylviculture plantations from the southeast and south of Brazil. Moreover, several amphipod records for Brazil were noticed to be dubious or misidentifications and are listed in a table with pertinent literature.

A new methodology for history matching combining iterative discrete Latin Hypercube with multi-start simulated annealing

This paper introduces a new method for history matching, combining the Iterative Discrete Latin Hypercube (IDLHC) with multi-start Simulated Annealing methods. The proposed method, named IDLHCSA, combines the potential of the IDLHC in finding good matched models while preserving the diversity of solutions and the potential of the SA with local control in finding local (refined) solutions. The IDLHCSA was applied in two cases. The first is a simple reservoir model used as proof of concept. The second is a complex benchmark case (UNISIM-I-H) based on the Namorado field, located at the Campos Basin, Brazil. The robustness and effectiveness of the proposed method are demonstrated by comparison with other consolidated methods. It is demonstrated here that, when compared to other methodologies, the proposed method is more effective in finding multiple solutions for the history matching problem while maintaining solution diversity. The production forecast is analyzed and the predictive capacity of the matched models is assessed. The paper reveals that obtaining good matched models does not ensure reliable forecasts. The proposed method was able to find matched models which provided more reliable forecasts when compared to other methods.

Improved epicentral relocation in the offshore Campos basin, SE Brazil, with the RSTT 3D model

Earthquake location on the continental shelf is often poor because: a) the seismic stations are mainly located on the continent, to one side of the epicenter (which means that any error in the velocity model causes a large epicentral error), and b) 1D models are commonly used in a region with strong lateral variations in the crustal structure. We tested the use of the 3D regional seismic travel time (RSTT) model to relocate an event of magnitude 3.8 mb that occurred on July the 1 st, 2010, in the Campos basin, southeast (SE) Brazil. This event was also recorded by a seismic vessel, which allowed an estimate of the azimuth of the incoming P-waves. The new location based on the 3D model is more consistent with the data recorded by the streamers, which shows that the use of 3D RSTT models can improve earthquake locations offshore. Several other events in the SE offshore basins were relocated with the 3D RSTT model, which confirmed the trend of epicenters lying beneath the continental slope where sediment thickness tends to be highest.

Hole Cleaning, Torque Management Lead to Longest Extended-Reach Well in Brazil

This article, written by Special Publications Editor Adam Wilson, contains highlights of paper OTC 28091, “The Longest Horizontal Section Ever Drilled in an Extended-Reach Well in Brazil,” by Rafael Kenupp, Affonso Lourenço, Stian Soltvedt, and Ian Thomson, Baker Hughes, a GE company, and Grazielli Simoes, Daniela L. Morosov, and Raquel Andrade, Statoil, prepared for the 2017 Offshore Technology Conference Brasil, Rio de Janeiro, 24–26 October. The paper has not been peer reviewed. Copyright 2017 Offshore Technology Conference. Reproduced by permission. The Peregrino project, located in the post-salt zone of the Campos Basin, presents immense challenges for drilling extended-reach wells. This paper shares challenges imposed by the well profile and downhole environment on the design and execution phases. Information is included about the solutions used that led to reaching the target depth as planned, including the well-planning methodology, bottomhole-assembly (BHA) design, drill-bit selection, data monitoring, and procedures for maximizing the transfer of power downhole and minimizing rock-cutting energy. Introduction The Peregrino oil field is in the BM-C-7 area of the Campos Basin. Of 47 wells drilled from two fixed platforms in the field (Peregrino A and B), 20 were from Peregrino A, where the longest horizontal sections have been drilled. The average horizontal length was 1419 m, and the operator is pushing the technical limits to extend the overall lateral stepout, increase reservoir lengths, and maximize hydrocarbon exposure. Drilling horizontal sections beyond the field average length has several additional challenges including mud quality along the sections, high friction factors, and surface-equipment operational limits. For extended-reach wells, hole-cleaning efficiency and proper torque management have been shown to be key factors for flawless execution. Proposed Approach Considering the typical well setup in off-shore Brazil, Well A-27 had a considerable total length. The planned length of the well was 8400-m measured depth (MD), with a possible extension to 8740-m MD. The landing of a 9⅝-in.-casing shoe was planned to be at 6520-m MD with approximately 82° of inclination, and the 8½-in.-section lateral displacement was to start at 5673 m from the wellhead (Fig. 1). With a possible horizontal section of 2220 m, a rotary-steerable system was to be used, with the addition of a drilling dynamics sub and a modular motor, to reduce the demanded weight on bit (WOB) and surface rate of revolution while maintaining sufficient energy at the bit. Management of torque and equivalent circulating density (ECD) would be helped by the use of 4-in. drill-pipe, which would also provide lower torque values with less cross-sectional area. The final measure required to reduce overall friction along the horizontal well path was to add lubricant to the drilling fluid to reduce metal-to-metal friction at the drillpipe/casing interaction. Lubricant was also to be added while drilling, with the idea that drops of lubricant deposited into the mudcake would help reduce friction when drill-pipe tool joints pass through.

Reinterpreting the South Atlantic Pre-Salt ‘Microbialite’ reservoirs: petrographic, isotopic and seismic evidence for a shallow evaporitic lake depositional model

The first encounter of the Pre-Salt Aptian ‘Microbialite’ carbonate reservoirs (the Barra Velha Fm) in 2005, in the Parati field, Santos Basin, was followed by additional discoveries such as the multi-billion barrel Lula (Tupi) field. Now, nearly 30 more discoveries have been made in the basin such as Libra and Sapinhoa, with recoverable reserves estimated as >30 BBOE, according to ANP. In addition, discoveries have been made in the adjacent Campos Basin, including the Pao de Acucar field (Viera de Luca et al., 2017), where the same unit is known as the Macabu Fm., and also in the Kwanza Basin, West Africa (Saller et al., 2016). After deposition in a late rift setting, the Barra Velha Fm and its equivalents were buried by more than 1 km of marine origin evaporites of the Ariri Fm and its equivalents, as the Albian Ocean seeped and poured into the basin.

Estimation of clay minerals from an empirical model for Cation Exchange Capacity: An example in Namorado oilfield, Campos Basin, Brazil

Abstract Clay minerals are important components of shales and occur predominantly in clastic sedimentary basins. Although the classification of such minerals arouses the interest of oil exploration practitioners, this is a hard task to accomplish. In order to typify the main clay minerals of turbidite sandstones in Campos Basin, this study comprises an empirical model to estimate Cation Exchange Capacity. The basic parameter for applying the empirical model is shale volume, whose values are calculated from natural gamma ray, neutron and bulk density measurements. Two-dimensional maps of Cation Exchange Capacity in specific depths are also provided in order to extend the analysis to the whole Namorado oilfield, Campos Basin, in southeast Brazil. The application of this methodology in two wells drilled in Namorado oilfield reveals, despite significant differences in shale content estimation, the predominance of kaolinite in the selected sedimentary interval, while layers of illite and chlorite are noticed at the top of the sediments. There is a total absence of smectite in all studied area. Two-dimensional maps for specific depths of Namorado reservoir enhance discrepancies associated with limitations of both methods to obtain shale content.

Palynology of the Morro do Chaves Formation (Lower Cretaceous), Sergipe Alagoas Basin, NE Brazil: Paleoenvironmental implications for the early history of the South Atlantic

The break-up of Gondwana and the origin of related source rocks and reservoir intervals of the Brazilian coastal basins are being increasingly studied in the last decades. In this context the Sergipe-Alagoas Basin, which lies to the north of the Campos Basin hydrocarbon province, becomes relevant for the completeness of its depositional sequences. This paper presents, for the first time, the detailed palynological record from the Morro do Chaves Formation, located at the InterCement Quarry, near São Miguel dos Campos, Alagoas. The analysis of samples from the mudstone intervals of the unit mainly composed by coquinas has enabled new biostratigraphic, paleoenvironmental and paleogeographic interpretations of the evolution of the South Atlantic. The occurrence of the species Dicheiropollis etruscus, with a vertical distribution ranging from the Berriasian to the Barremian, supports the late Barremian age for the lowermost part of the Morro do Chaves Formation, traditionally interpreted as having been deposited in a lacustrine environment, close to herbaceous plants, surrounded by remote mountainous areas with arboreal vegetation. The occurrence of algae phycomata of the Class Prasinophyceae, associated with Scenedesmus and Botryoccocus, organisms that tolerate some salinity in its uppermost part, together with other biotic and abiotic data, corroborate the possibility of relating the Morro do Chaves Formation to a marine and/or brackish depositional environment, which may have resulted from a marine flooding in the northern sector of the Sergipe-Alagoas Basin during Early Cretaceous times. The results of this work support a paleogeographic model characterized by an episodic input of Tethyan waters towards the north of the South American continent.

Deepwater slope valley reservoir architecture and connectivity, Brazil

A detailed interpretation was undertaken to improve the description of connectivity and reservoir distribution for a field in the Campos Basin, Brazil. The Miocene reservoir was deposited in a deepwater, channelized turbidite fairway in a slope valley setting. Static pressure data acquired after production start-up indicated communication across the reservoir, but the values varied significantly, implying that the efficiency of communication varies. High-quality 3D seismic in combination with production and well data led to a hierarchical interpretation, from channel element to complex-set scale, which defined key stratigraphic and pressure surfaces. Integration of a high-repeatability 4D monitor survey showed that the 4D response changed at stratigraphic boundaries. The 4D data tied to production indicate that an aquifer is traveling along the base of the reservoir in discrete channels. The use of 4D depth shift data increased confidence in the waterfront interpretation in areas without production data. Aggradational channel complexes in the upper part of the reservoir show baffling at the margins of channel complexes down to the channel element scale. The channel elements are also likely baffled on the margins with greater connectivity downward into the lower, amalgamated unit. The lower unit shows greater lateral continuity in 4D signal, consistent with pressure data that indicate larger depletion over greater distances than the overlying aggradational complexes where producer wells are located. In summary, mapping of reservoir architecture and identification of key stratigraphic surfaces from 3D have reduced uncertainty in reservoir distribution and connectivity. Integration of 4D seismic and production data has provided confirmation of connectivity through the identification of waterfronts and unswept areas of the reservoir.