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Previous issue date: 2014-07-01 / A distribui??o das altera??es diagen?ticas em reservat?rio silicicl?stico do Cenomaniano
Superior da Bacia Potiguar sofreu influ?ncia do arcabou?o estratigr?fico e do sistema
deposicional. Se??es s?smicas e perfis geof?sicos de dois po?os perfurados na por??o SW da
citada bacia registram superf?cies estratigr?ficas regionais representativas de inunda??es
m?ximas relacionadas a evento transgressivo. Na an?lise sequencial de oitenta metros de
testemunhos (~450m de profundidade) foram reconhecidas nove f?cies deposicionais cujo
padr?o de empilhamento granodecrescente ascendente limita ciclos com base conglomer?tica
erosiva (lag) sobreposta por intercala??es de arenitos m?dios a muito finos com
estratifica??es cruzadas (acanalada, planar e de baixo ?ngulo) e horizontais (plano-paralela,
wave e flaser). O topo dos ciclos ? marcado pela deposi??o de pelitos e desenvolvimento de
paleossolos e laguna. A correla??o de f?cies geneticamente relacionadas revela associa??es de
preenchimento de canal, crevasse e plan?cie de inunda??o, depositadas em trato de sistema
transgressivo. Descri??es detalhadas de setenta e nove l?minas delgadas auxiliadas por
an?lises de MEV-EBSD/EDS, DRX e is?topos est?veis em arenitos revelaram composi??o
arcosiana e arranjos texturais complexos com abundantes franjas de esmectita cobrindo
continuamente constituintes prim?rios, cut?culas mecanicamente infiltradas e poros m?ldicos
e intragranulares. Crescimentos epitaxiais de K-feldspato cobrem continua ou
descontinuamente gr?os de microcl?nio e ortocl?sio antes de qualquer outra fase. Abundante
pseudomatriz da compacta??o de intraclastos lamosos, concentrados ao longo de planos de
estratifica??o, localmente substitu?da por calcita macrocristalina e pirita microcristalina e
framboidal. Caulinita (livrinhos e vermicular), esmectita microcristalina, minerais de tit?nio
microcristalinos e pirita substituem constituintes prim?rios. Porosidade intergranular
predomina sobre a m?ldica, intragranular e de contra??o. Os poros s?o mal conectados devido
? presen?a intergranular de esmectita, crescimentos de K-feldspato, argilas infiltradas e
pseudomatriz. Os arenitos foram sujeitos a condi??es eodiagen?ticas pr?ximas ? superf?cie e
mesodiagen?ticas de soterramento raso. As altera??es diagen?tica reduziram a porosidade e
permeabilidade deposicionais principalmente pela precipita??o de franjas de esmectita,
compacta??o de intraclastos lamosos ? pseudomatriz e cimenta??o por calcita poiquilot?pica,
caracterizando diferentes petrof?cies de reservat?rio. Esses produtos diagen?ticos atuaram
como barreiras e desvios ao fluxo de fluido reduzindo qualidade do reservat?rio. / The distribution of diagenetic alterations in Late Cenomanian siliciclastic reservoirs from
Potiguar Basin was influenced by the stratigraphic framework and the depositional system.
Seismic sections and geophysical logs of two wells drilled in the SW portion of the mentioned
basin above register regional stratigraphic surfaces representing maximum floods related to a
transgressive event. The sequential analysis of 80 m of drill core (~450 m deep) recognized
nine depositional facies with an upwards granodecrescent standard piling that limits cycles
with an erosional conglomeratic base (lag) overlain by intercalations of medium to very fine
sandstones showing cross bedding (channel, planar and low angled) and horizontal bedding
(plane-parallel , wave and flaser). The top of the cycles is marked by the deposition of pelites
and the development of paleosoils and lagoons. The correlation of genetically related facies
reveals associations of channel fillings, crevasse, and flood plains deposited in a transgressive
system. Detailed descriptions of seventy nine thin sections aided by MEV-EBSD/EDS, DRX
and stable isotope analyses in sandstones revealed an arcosian composition and complex
textural arrays with abundant smectite fringes continuously covering primary components,
mechanically infiltrated cuticles and moldic and intragrain pores. K-feldspar epitaxial
overgrowth covers microcline and orthoclase grains before any other phase. Abundant
pseudomatrix due to the compactation of mud intraclasts concentrate along the stratification
planes, locally replaced by macrocristalline calcite and microcrystalline and framboidal
pyrite. Kaolinite (booklets and vermicular), microcrystalline smectite, microcrystalline
titanium minerals and pyrite replace the primary components. The intergrain porosity prevails
over the moldic, intragrain and contraction porosities. The pores are poorly connected due to
the presence of intergranular smectite, k-feldspar overgrowth, infiltrated mud and
pseudomatrix. The sandstones were subjected to eodiagenetic conditions next to the surface
and shallow burial mesodiagenetic conditions. The diagenetic alterations reduced the porosity
and the permeability mainly due to the precipitation of smectite fringes, compactation of mud
intraclasts onto the pseudomatrix and cementing by poikilotopic calcite characterizing
different reservoir petrofacies. These diagenetic products acted as barriers and detours to the
flow of fluids thus reducing the quality of the reservoir.
| Identifer | oai:union.ndltd.org:IBICT/oai:repositorio.ufrn.br:123456789/20146 |
| Date | 01 July 2014 |
| Creators | Martins, Rosiney Ara?jo |
| Contributors | 83933212715, http://lattes.cnpq.br/0930845549110627, Coriolano, Ana Catarina Fernandes, 83744479404, http://lattes.cnpq.br/5552621403067808, Lima Filho, Francisco Pinheiro, 13893700382, http://lattes.cnpq.br/9888320802954176, Costa Neto, Le?o Xavier da, 24181790444, http://lattes.cnpq.br/1059276496317561, Srivastava, Narendra Kumar, 22232591468, http://lattes.cnpq.br/0257859086244893, Vieira, Marcela Marques |
| Publisher | Universidade Federal do Rio Grande do Norte, PROGRAMA DE P?S-GRADUA??O EM CI?NCIA E ENGENHARIA DE PETR?LEO, UFRN, Brasil |
| Source Sets | IBICT Brazilian ETDs |
| Language | Portuguese |
| Detected Language | English |
| Type | info:eu-repo/semantics/publishedVersion, info:eu-repo/semantics/doctoralThesis |
| Source | reponame:Repositório Institucional da UFRN, instname:Universidade Federal do Rio Grande do Norte, instacron:UFRN |
| Rights | info:eu-repo/semantics/embargoedAccess |
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