Minor non-carbonate authigenic components as indicators of late-stage diagenetic processes in the Smackover limestones

Thesis/Dissertation · Wed Jan 01 04:00:00 EST 1992

OSTI ID:6684123

Denham, Jr, M E

Variations in mineralogy and composition of late authigenic sulfur-bearing minerals in upper Smackover limestones recorded diagenetic events associated with hydrocarbon migration. This suite of minerals occurs in samples taken from 18 subsurface cores of the upper Smackover from northern Louisiana and southern Arkansas. Spatial variations in cadmium concentration of sphalerite, Ba concentration of celestite, and the [sigma][sup 34]S values of galena and sphalerite suggest that fluids associated with hydrocarbons in the lower Smackover migrated into the upper Smackover along faults at the Louisiana-Arkansas border. A second generation of sulfide mineralization and a [sigma][sup 34]S = +10.8[per thousand] CDT of a wurtzite-sphalerite mixture suggests that thermochemical sulfate reduction occurred after hydrocarbon migration resulting in the formation of the [open quotes]sour gas belt.[close quotes] Uranium concentration, as revealed by fission track imaging and instrumental neutron activation analyses, varies on a microscopic and regional scale in the upper Smackover limestones. Uranium is locally concentrated in stylolites and fine grained opaque material. Comparison of uranium and thorium concentrations in stylolites suggests these elements are insoluble residue of the pressure solution process. Regionally, uranium concentration varies with clay content of the host limestone indicating that sorption plays a major role in the geochemical behavior of uranium in the subsurface. Comparison of U/Th ratios of upper Smackover limestones to those of black shales from the Gray Sands tentatively suggests that uranium was redistributed from hydrocarbon source rocks to reservoir rocks. However, better understanding of the association of uranium with organic-rich rocks and the role of sorption are required before uranium can be used reliably as a pore fluid tracer.

• Research Organization: Texas A and M Univ., College Station, TX (United States)
• OSTI ID: 6684123
• Country of Publication: United States
• Language: English

Related Subjects

02 PETROLEUM
020200* -- Petroleum-- Reserves
Geology
& Exploration
03 NATURAL GAS
030200 -- Natural Gas-- Reserves
Geology
& Exploration
CALCITE
CARBONATE MINERALS
CARBONATE ROCKS
CHEMICAL COMPOSITION
DIAGENESIS
DOLOMITE
ENVIRONMENTAL TRANSPORT
HYDROCARBONS
LIMESTONE
MARCASITE
MASS TRANSFER
MINERALS
ORGANIC COMPOUNDS
ROCKS
SEDIMENTARY ROCKS
SULFIDE MINERALS
SULFUR COMPOUNDS