Depositional environments and diagenesis of Oligocene Vicksburg Formation in Lyda and North Rincon fields, Starr County, Texas
Detailed examination of cores shows that Vicksburg sandstones in the lowermost intervals were deposited in the upper delta plain as lacustrine deltaic deposits. Although no core was available in the middle to upper sand intervals, the intervals appear to have been deposited in a shallow marine deltaic complex. The Vicksburg sandstones were studied in detail with the petrographic microscope, x-ray diffraction, and the scanning electron microscope to determine the paragenesis of the sands. The sandstones varied in lithology from feldspathic litharenites to lithic arkoses. An Eocene volcanic source in the Trans-Pecos region was responsible for the large amount of feldspars (mainly albite) and volcanic rock fragments found. The abundance of unstable mineral components resulted in a complex diagenetic sequence. Effective porosity in the Vicksburg sands is primarily secondary and was created by the dissolution of feldspars, volcanic rock fragments, and calcite cement. Permeability has been significantly reduced in some porous sands by the precipitation of calcite cement, iron chlorite (Chamosite), and to a lesser extent, kaolinite and illite/smectite mixed-layer clays. Chlorite was the most common authigenic clay and was found in significant amounts throughout the entire Vicksburg section. The best reservoirs in the Vicksburg sandstones were those with the largest average grain size and the greatest amount of feldspars and volcanic rock fragments prior to diagenesis.
- Research Organization:
- Sun Exploration and Production Co., Abilene, TX
- OSTI ID:
- 7152661
- Report Number(s):
- CONF-8610199-
- Journal Information:
- Am. Assoc. Pet. Geol., Bull.; (United States), Journal Name: Am. Assoc. Pet. Geol., Bull.; (United States) Vol. 70:9; ISSN AAPGB
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
020200* -- Petroleum-- Reserves
Geology
& Exploration
CENOZOIC ERA
DEPOSITION
DIAGENESIS
DRILL CORES
FEDERAL REGION VI
GEOLOGIC AGES
GEOLOGIC DEPOSITS
GEOLOGIC FORMATIONS
MINERAL RESOURCES
NORTH AMERICA
OIL FIELDS
PETROLEUM DEPOSITS
POROSITY
RESERVOIR ROCK
RESOURCES
ROCKS
SANDSTONES
SEDIMENTARY ROCKS
TERTIARY PERIOD
TEXAS
USA