Stratigraphic controls on the source rock distribution, Llanos Orientales Basin, Colombia

Conference · Mon Jan 01 00:00:00 EST 1996 · AAPG Bulletin

OSTI ID:6586890

Ramon, J C; Fajardo, A; Rubiano, J; Reyes, A ^[1]

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1. ECOPETROL-Instituto Colombiano del Petroleo (Colombia)

All available rock and oil geochemistry analyses were tied to a high-resolution stratigraphic framework for more than 50 wells in the Central Llanos Orientates Basin. New Tertiary generation input is proposed. The best source rock intervals are at the base and top of the Gacheta Formation (Upper Cretaceous) and in the middle of the Barco-Cuervos (Paleocene) and Mirador (Eocene) formations. These organic-rich zones contain type II and III kerogen. TOC contents range from about 1% up to 15%. The four source rock intervals occur within marine shales near condensed sections, at the position maximum accommodation/sediment-supply (A/S) ratios. The development of conditions that allow accumulation and preservation of anomalously high fractions of organic matter might be explained by two mechanisms. Increased A/S ratio results in retention of more sediment in the coastal plain, thus reducing the tendency for siliciclastic sediment to dilute the organic matter accumulating on the shelf. Also, deeper water might restrict circulation, enhancing bottom anoxic conditions. In the more transitional and continental sequences, increased A/S ratio is associated with higher phreatic water level. A high ground water table enhances preservation of coaly intervals. The sea-level rise brings marine water into valleys and low-gradient coastal plains. The resulting embayments, marsh and swampy areas are organic-prone, contributing to the source rock potential of strata associated with high conditions and base-level rise-to-fall turnaround positions.

• OSTI ID: 6586890
• Report Number(s): CONF-960527-; CODEN: AABUD2
• Journal Information: AAPG Bulletin, Vol. 5; Conference: Annual convention of the American Association of Petroleum Geologists, Inc. and the Society for Sedimentary Geology: global exploration and geotechnology, San Diego, CA (United States), 19-22 May 1996; ISSN 0149-1423
• Country of Publication: United States
• Language: English

Related Subjects

02 PETROLEUM
COLOMBIA
OIL FIELDS
SEDIMENTARY BASINS
STRATIGRAPHY
PETROLEUM
EXPLORATION
GEOCHEMISTRY
VISCOSITY
CHEMISTRY
DEVELOPING COUNTRIES
ENERGY SOURCES
FOSSIL FUELS
FUELS
GEOLOGIC DEPOSITS
GEOLOGIC STRUCTURES
GEOLOGY
LATIN AMERICA
MINERAL RESOURCES
PETROLEUM DEPOSITS
RESOURCES
SOUTH AMERICA
020200* - Petroleum- Reserves
Geology
& Exploration
023000 - Petroleum- Properties & Composition