Hydrocarbon generation and brine migration in the central Appalachian basin
- Georgia Southern Univ., Statesboro (United States)
Fluid inclusions in mineralized natural fractures from six Devonian shale cores were used to document hydrocarbon generation and brine migration in the central Appalachian basin. The sequence of formation of four regional fracture sets containing the inclusions was used to constrain the relative timing of fluid evolution. The earliest formed fluid inclusions are single-phase liquid inclusions containing a complex mixture of methane, ethane, higher hydrocarbons, and nitrogen. These inclusions formed during burial of the Devonian shales and early hydrocarbon generation in the oil window. As burial proceeded to a maximum and hydrocarbon generation entered the gas phase, later formed fluid inclusions record the presence of a more methane-rich fluid with minor ethane and nitrogen. Either during maximum burial or early uplift of the Devonian shale section, regional stress relaxation was accompanied by regional brine migration. Fluid inclusions record the influx of a methane-saturated, sodium chloride-rich brine and subsequent mixing with a presumably in situ-calcium-rich brine and subsequent mixing with a presumably in-situ calcium-rich brine. The migration pathway is presumed to be the Devonian shale detachment zone and underlying Devonian Oriskany Sandstone. This migration may be related to the fluids forming Mississippi Valley-type ore deposits. Present-day brine compositions reflect this ancient mixing. Brines from deep Cambrian through Silurian rocks are more calcium-chloride rich than brines from shallower Devonian and younger rocks. The sodium chloride-rich brines from Upper Devonian through Pennsylvanian rocks become more dilute as a result of mixing with meteoric water.
- OSTI ID:
- 5893580
- Report Number(s):
- CONF-9109238-; CODEN: AABUD
- Journal Information:
- AAPG Bulletin (American Association of Petroleum Geologists); (United States), Vol. 75:8; Conference: American Association of Petroleum Geologists (AAPG) eastern section meeting, Pittsburgh, PA (United States), 8-10 Sep 1991; ISSN 0149-1423
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
58 GEOSCIENCES
APPALACHIAN BASIN
PETROLEUM DEPOSITS
BRINES
ENVIRONMENTAL TRANSPORT
GEOCHEMISTRY
PETROLEUM
MATURATION
DEVONIAN PERIOD
ETHANE
GEOLOGIC FRACTURES
GEOLOGIC HISTORY
HYDROCARBONS
INCLUSIONS
METHANE
PETROLEUM GEOLOGY
SHALES
SOURCE ROCKS
ALKANES
CHEMISTRY
ENERGY SOURCES
FOSSIL FUELS
FUELS
GEOLOGIC AGES
GEOLOGIC DEPOSITS
GEOLOGIC STRUCTURES
GEOLOGY
MASS TRANSFER
MINERAL RESOURCES
ORGANIC COMPOUNDS
PALEOZOIC ERA
RESOURCES
ROCKS
SEDIMENTARY BASINS
SEDIMENTARY ROCKS
020200* - Petroleum- Reserves
Geology
& Exploration
580000 - Geosciences