Modeling the distribution of diagenetic elements within deltaic reservoirs of NE Brazil

Conference · Fri Mar 01 00:00:00 EST 1991 · AAPG Bulletin (American Association of Petroleum Geologists); (United States)

OSTI ID:7079027

Moraes, M A.S. ^[1]

---

1. 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-; CODEN: AABUD
• Journal Information: AAPG Bulletin (American Association of Petroleum Geologists); (United States), Vol. 75:3; Conference: Annual meeting of the American Association of Petroleum Geologists (AAPG), Dallas, TX (United States), 7-10 Apr 1991; ISSN 0149-1423
• Country of Publication: United States
• Language: English

Related Subjects

02 PETROLEUM
03 NATURAL GAS
58 GEOSCIENCES
BRAZIL
NATURAL GAS DEPOSITS
PETROLEUM DEPOSITS
RESERVOIR ROCK
DIAGENESIS
POROSITY
ALLUVIAL DEPOSITS
CALCITE
CHLORITE MINERALS
DOLOMITE
GEOLOGIC FAULTS
GEOLOGIC MODELS
MINERALOGY
RIVER DELTAS
SANDSTONES
SEDIMENTS
CARBONATE MINERALS
COASTAL REGIONS
DEVELOPING COUNTRIES
GEOLOGIC DEPOSITS
GEOLOGIC FRACTURES
GEOLOGIC STRUCTURES
LATIN AMERICA
MINERAL RESOURCES
MINERALS
RESOURCES
ROCKS
SEDIMENTARY ROCKS
SILICATE MINERALS
SOUTH AMERICA
020200* - Petroleum- Reserves
Geology
& Exploration
030200 - Natural Gas- Reserves
Geology
& Exploration
580000 - Geosciences