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Deposition, diagenesis and reservoir potential of non-carbonate sedimentary rocks from the rift section of Campos Basin, Brazil

G. Armelenti, K. Goldberg, J. Kuchle and L. F. de Ros
Deposition, diagenesis and reservoir potential of non-carbonate sedimentary rocks from the rift section of Campos Basin, Brazil
Petroleum Geoscience (August 2016) 22 (3): 223-239

Abstract

A new petrographical study was performed on the rift section of the Lagoa Feia Group, Lower Cretaceous of the Campos Basin, eastern Brazilian margin. The primary constituents of the analysed rocks are siliciclastic and volcaniclastic grains, stevensite ooids and peloids, and bioclasts of bivalves and ostracods. This study focused on the clastic, stevensitic and hybrid rocks, as previous studies were limited to the bioclastic rudstones and grainstones that constitute the producing reservoirs. The rift sedimentation was mostly intrabasinal, with extrabasinal contribution concentrated close to half-graben border faults. The mixture of rounded volcanic fragments with angular quartz, feldspars and plutonic fragments in the sandstones and conglomerates indicates recycling of early rift epiclastic deposits, combined with first-cycle sediments eroded from uplifted plutonic basement blocks. Stevensitic ooids and peloids, formed in shallow, alkaline lacustrine environments, were mixed throughout the rift section with bivalve and ostracod bioclasts, and with the clastic sediments. Gravitational redeposition was promoted by intense and recurrent tectonism along the rift margins. The main diagenetic processes in clastic sandstones and conglomerates and hybrid arenites are cementation and grain replacement by smectite, zeolites, calcite and dolomite, mechanical compaction and dissolution of feldspars, volcanic fragments and bioclasts. Stevensitic arenites experienced early cementation and replacement of ooids and peloids by quartz, calcite and dolomite, or intense compaction of stevensitic grains in uncemented areas. Volcaniclastic sandstones and conglomerates with smectite rims, remnant intergranular porosity and grain dissolution may constitute fair hydrocarbon reservoirs. Stevensitic and hybrid arenites with dissolution of stevensite grains, bioclasts and calcite cement may also constitute reservoirs, although with potential quality limited by the poor connection of their pore systems. An understanding of the controls on the depositional and diagenetic evolution of the dominantly intrabasinal, gravitationally redeposited, rift succession will contribute to new exploration strategies for the Campos Basin.


ISSN: 1354-0793
EISSN: 2041-496X
Serial Title: Petroleum Geoscience
Serial Volume: 22
Serial Issue: 3
Title: Deposition, diagenesis and reservoir potential of non-carbonate sedimentary rocks from the rift section of Campos Basin, Brazil
Affiliation: Universidade Federal do Rio Grande do Sul, Instituto de Geociencias, Porto Alegre, Brazil
Pages: 223-239
Published: 201608
Text Language: English
Publisher: Geological Society Publishing House for EAGE (European Association of Geoscientists & Engineers), London, United Kingdom
References: 83
Accession Number: 2016-069369
Categories: Sedimentary petrologyEconomic geology, geology of energy sources
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 2 tables, geol. sketch map
S23°00'00" - S22°40'00", W42°30'00" - W42°00'00"
Country of Publication: United Kingdom
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Reference includes data from GeoScienceWorld, Alexandria, VA, United States. Reference includes data from The Geological Society, London, London, United Kingdom
Update Code: 201633
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