Austin Chalk (!) Petroleum System: Upper Cretaceous, Southeastern Texas
Journal Article
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· AAPG Bulletin
OSTI ID:150546
- Texaco EPTD, Houston, TX (United States)
- Texaco Central, Bellaire, TX (United States)
The Austin Group (Coniacian-Santonian) is a sequence of interstratified chalk and marl deposited during a sea-level highstand as a transgressive unit. Austin Chalk deposition occurred on a southeastward-dipping carbonate ramp that exhibits distinctive onshore and offshore chalk lithofacies. Discrete intervals within offshore Austin lithofacies display good to excellent source rock potential. Organic carbon content ranges upward to 20.0 wt. % with generation potentials exceeding 45 mg HC/g of rock measured. Source potential increases basinward where offshore chalk units exhibit increases in both organic richness and net thickness. These organically rich units display an affinity for the Type II reference curve. Hydrogen index values typically exceed 300 mg HC/g TOC. Several geochemical indices suggest that the oil-window is located at relatively shallow depths (6,700 ft). Offshore chalks sourced onshore Austin reservoirs through lateral migration (along fractures and stylolites) which occurred during the middle Tertiary. Hydrocarbons may also have been sourced from the underlying Eagle Ford Shale (Turonian). Austin Shale reservoirs are characterized by low porosity/low permeability dual pore systems consisting of microporous matrix and fractures. Diagenesis (mechanical compaction, styloitization, and calcite cementation) has strongly modified Austin Chalk pore systems. Matrix porosity generally decreases with increasing depth because of progressive burial diagenesis. Austin reservoirs typically have two major sets of fractures; reservoir performance is related to fracture connectivity. Austin Chalk reservoirs are sealed by the overlying Taylor Marl (Campanian).
- OSTI ID:
- 150546
- Report Number(s):
- CONF-9510222--
- Journal Information:
- AAPG Bulletin, Journal Name: AAPG Bulletin Journal Issue: 10 Vol. 79; ISSN 0149-1423; ISSN AABUD2
- Country of Publication:
- United States
- Language:
- English
Similar Records
Cyclic sedimentation, synsedimentary volcanism, microfabrics, and fracture intensity in the Austin Chalk, Texas
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Controls on fracture distribution in the Giddings Austin Chalk
Conference
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Tue Dec 31 23:00:00 EST 1991
· Geological Society of America, Abstracts with Programs; (United States)
·
OSTI ID:6136057
Trace fossils and paleoenvironments of lower and middle Austin Chalk (upper Cretaceous), north-central Texas
Conference
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Sat Sep 01 00:00:00 EDT 1990
· AAPG Bulletin (American Association of Petroleum Geologists); (USA)
·
OSTI ID:5922379
Controls on fracture distribution in the Giddings Austin Chalk
Conference
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Sat Sep 01 00:00:00 EDT 1990
· AAPG Bulletin (American Association of Petroleum Geologists); (USA)
·
OSTI ID:5968525