Modeling the distribution of diagenetic elements within deltaic reservoirs of NE Brazil
- Univ. of Wyoming, Laramie (United States)
Lacustrine deltaic sandstones are important reservoirs in Potiguar and Reconcavo rift basins of northeastern Brazil. They commonly occur as delta front deposits accumulated in lows associated with growth faults. Diagenetic elements, including calcite, secondary porosity, dolomite, and chlorite, present specific distribution patterns at different reservoir levels. Such distributions have been modeled based on thin section, core, and petrophysical data. At the microscopic level, the most significant heterogeneity is the association between reduced primary (RP) porosity and carbonate dissolution (CD) porosity. Reduced primary porosity commonly occurs as islands of small pores surrounded by zones presenting larger CD pores. This type of pore structure causes high irreducible water saturation to appear in many reservoirs. At a larger scale level, dolomite cement is observed associated with micas and mud clasts concentrated in discrete stratification planes, a feature that increases permeability anisotropy, lowering the effective permeability of cross-bedded zones. Chlorite rims cause permeability reduction in fine-grained sandstones but have little influence in coarser sandstones. This grain size dependent effect produces significant alterations in the permeability structure of the reservoirs. Relating the distribution of diagenetic elements to the facies architecture of deltaic sandstones permits generating reservoir models that integrate depositional and diagenetic heterogeneities at different levels, an approach that leads to more accurate determination of effective properties used for performance prediction and numerical simulation.
- OSTI ID:
- 7079027
- Report Number(s):
- CONF-910403--
- Journal Information:
- AAPG Bulletin (American Association of Petroleum Geologists); (United States), Journal Name: AAPG Bulletin (American Association of Petroleum Geologists); (United States) Vol. 75:3; ISSN AABUD; ISSN 0149-1423
- Country of Publication:
- United States
- Language:
- English
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580000 -- Geosciences
ALLUVIAL DEPOSITS
BRAZIL
CALCITE
CARBONATE MINERALS
CHLORITE MINERALS
COASTAL REGIONS
DEVELOPING COUNTRIES
DIAGENESIS
DOLOMITE
GEOLOGIC DEPOSITS
GEOLOGIC FAULTS
GEOLOGIC FRACTURES
GEOLOGIC MODELS
GEOLOGIC STRUCTURES
LATIN AMERICA
MINERAL RESOURCES
MINERALOGY
MINERALS
NATURAL GAS DEPOSITS
PETROLEUM DEPOSITS
POROSITY
RESERVOIR ROCK
RESOURCES
RIVER DELTAS
ROCKS
SANDSTONES
SEDIMENTARY ROCKS
SEDIMENTS
SILICATE MINERALS
SOUTH AMERICA