Porosity prediction in sandstones using erosional unconformities

Conference · Mon Feb 01 04:00:00 EST 1988 · AAPG Bull.; (United States)

OSTI ID:5793561

Shanmugam, G

Erosional unconformities of subaerial origin are created by tectonic uplifts and eustatic sea level fall. Most erosional unconformities developed on sandstones are planes of increased porosity because uplifted sandstones are exposed to undersaturated CO/sub 2/-charged meteoric waters that result in dissolution of unstable framework grains and cements. The chemical weathering of sandstones is intensified in humid regions by heavy rainfall, lush vegetation, soil zones, and the voluminous production of inorganic and organic acids. Erosional unconformities are considered hydrologically open systems because of abundant supply of fresh meteoric water and relatively unrestricted transport of dissolved constituents away from the site of dissolution. Thus, porosity in sandstones commonly increases toward overlying unconformities. Empirical models have been developed on the basis of the observed relationship between erosional unconformities and porosity in the underlying sandstones in the North Sea (Middle Jurassic Brent Group) and in the Alaskan North Slope (Triassic Ivishak Formation). An important practical attribute of these models is that they allow for the prediction of porosity in frontier areas by recognizing erosional unconformities in seismic reflection profiles and by constructing subcrop maps for underlying sandstones. Hydrocarbon-bearing sandstone reservoirs in Alaska, Algeria, Australia, China, Libya, Netherlands, North Sea, Norwegian Sea, and Texas occur immediately beneath major erosional unconformities.

• Research Organization: Mobil Research and Development Corp., Dallas, TX (USA)
• OSTI ID: 5793561
• Report Number(s): CONF-880301-
• Conference Information: Journal Name: AAPG Bull.; (United States) Journal Volume: 72:2
• Country of Publication: United States
• Language: English

Related Subjects

02 PETROLEUM
020200* -- Petroleum-- Reserves
Geology
& Exploration
ALASKA
ALASKAN NORTH SLOPE
ATLANTIC OCEAN
CARBON COMPOUNDS
CARBON DIOXIDE
CARBON OXIDES
CHALCOGENIDES
DISSOLUTION
FEDERAL REGION VI
FEDERAL REGION X
GEOLOGIC AGES
GEOLOGIC DEPOSITS
GEOLOGIC FORMATIONS
GROUND WATER
HYDROGEN COMPOUNDS
JURASSIC PERIOD
MESOZOIC ERA
MINERAL RESOURCES
NATURAL GAS DEPOSITS
NORTH AMERICA
NORTH SEA
OXIDES
OXYGEN COMPOUNDS
PETROLEUM DEPOSITS
POROSITY
RESERVOIR ROCK
RESOURCES
ROCKS
SANDSTONES
SEAS
SEDIMENTARY ROCKS
SURFACE WATERS
TECTONICS
TEXAS
TRIASSIC PERIOD
USA
WATER