The use of visible and near-infrared reflectance spectra for estimating organic matter thermal maturity

Journal Article · Sun Oct 01 04:00:00 EDT 1995 · AAPG Bulletin

OSTI ID:150530

Rowan, L C ^[1]; Poole, F G; Pawlewicz, M J ^[2]

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1. Geological Survey, Reston, VA (United States)
2. Geological Survey, Lakewood, CO (United States)

Measurements of visible and near-infrared spectral reflectance of 41 samples of mudstone, silt-stone, and carbonate rocks representing two major depositional settings in Nevada were compared to vitrinite reflectance (R{sub o}) and hydrogen index (HI) measurements to determine the relation between spectral reflectance and organic matter (OM) maturity. The samples range in age from Devonian to Paleogene and have highly variable total organic carbon (TOC) contents, recycled OM contents, and kerogen compositions. Visible and near-infrared spectral reflectance of the samples changes systematically as OM maturity increases from submature to supermature (R{sub o} range of 0.28 to 4.32); therefore, spectral reflectance generally can be used to estimate the thermal maturity of the contained OM. The sum of several ratios (compound ratio) used to express spectral changes in the visible and near-infrared wavelength region is high for most submature samples, decreases rapidly with increasing R{sub o} into the mature range, and then decreases less rapidly through the remaining mature range and the supermature range. A similar trend is displayed in the plot of HI vs. compound ratio. Some spectra are affected by iron absorption features and the presence of recycled OM. Iron absorption generally causes the compound ratio values to be anomalously high relative to the OM maturity, whereas recycled OM results in unusually low ratio values. Spectra affected by recycled OM were identified by using a pair of ratios that expresses the difference in spectral shape between these spectra and spectra of supermature samples, which they resemble. Samples containing recycled kerogen are much more numerous from the Mississippian prodelta basin of the Antler foreland basin than from the Antler orogene; this difference indicates derivation of much of the kerogen from the orogene.

• OSTI ID: 150530
• 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

Related Subjects

02 PETROLEUM
36 MATERIALS SCIENCE
MATURATION
NEVADA
OPTICAL PROPERTIES
ORGANIC MATTER
PETROLEUM DEPOSITS
RESERVOIR ROCK
THERMODYNAMIC PROPERTIES
VITRINITE