TY - JOUR
T1 - Reflectance retardation (suppression) and source rock properties related to hydrogen-enriched vitrinite in Middle Jurassic coals, Danish North Sea
AU - Petersen, H.I.
AU - Rosenberg, P.
PY - 1998/7/1
Y1 - 1998/7/1
N2 - Middle Jurassic high volatile bituminous A coals from the Danish North Sea may yield vitrinite reflectance values retarded by 0.10-0.14%Rr. The coals are low in liptinite content, and the reflectance retardation is related to the vitrinite composition. Vitrain (assumed to be pure vitrinite) was hand-picked from eight samples and characterised by means of element analysis, Fourier Transform infrared spectroscopy and Rock-Eval pyrolysis. In contrast to the vitrinite from samples yielding 'true' reflectance values, the vitrinite from three of the samples yielding retarded reflectances is perhydrous in nature (5.57-5.79 wt-% (d.a.f.) H) and has H/C atomic ratios of 0.80-0.83. Vitrinite from another reflectance-retarded sample is enriched in sulphur. The hydrogen enrichment is inherited from oxygen-deficient, waterlogged and marine-influenced conditions in the precursor mires. FTIR spectra demonstrate that the perhydrous vitrinites have a lower aromaticity as measured by aromatic hydrogen vibrations in the region 900-700 cm-1 compared to the 'normal' vitrinites. This suggests a reduced maturation rate of the hydrogen-enriched vitrinite. S1(vitr), S2(vitr) and HIvitr values from the vitrinite concentrates indicate that the vitrinite is a significant contributor to the overall generative potential; this is particularly the case for the perhydrous vitrinite. Activation energies for the vitrinites are centred at 260 and 268 kJ/mole. It is not possible to detect a mwasurable difference in Ea between the perhydrous and 'normal' vitrinites. This may suggest more-or-less similar generation characteristics, or it may indicate that Rock-Eval kinetics do not replicate Nature in this regard.
AB - Middle Jurassic high volatile bituminous A coals from the Danish North Sea may yield vitrinite reflectance values retarded by 0.10-0.14%Rr. The coals are low in liptinite content, and the reflectance retardation is related to the vitrinite composition. Vitrain (assumed to be pure vitrinite) was hand-picked from eight samples and characterised by means of element analysis, Fourier Transform infrared spectroscopy and Rock-Eval pyrolysis. In contrast to the vitrinite from samples yielding 'true' reflectance values, the vitrinite from three of the samples yielding retarded reflectances is perhydrous in nature (5.57-5.79 wt-% (d.a.f.) H) and has H/C atomic ratios of 0.80-0.83. Vitrinite from another reflectance-retarded sample is enriched in sulphur. The hydrogen enrichment is inherited from oxygen-deficient, waterlogged and marine-influenced conditions in the precursor mires. FTIR spectra demonstrate that the perhydrous vitrinites have a lower aromaticity as measured by aromatic hydrogen vibrations in the region 900-700 cm-1 compared to the 'normal' vitrinites. This suggests a reduced maturation rate of the hydrogen-enriched vitrinite. S1(vitr), S2(vitr) and HIvitr values from the vitrinite concentrates indicate that the vitrinite is a significant contributor to the overall generative potential; this is particularly the case for the perhydrous vitrinite. Activation energies for the vitrinites are centred at 260 and 268 kJ/mole. It is not possible to detect a mwasurable difference in Ea between the perhydrous and 'normal' vitrinites. This may suggest more-or-less similar generation characteristics, or it may indicate that Rock-Eval kinetics do not replicate Nature in this regard.
UR - http://www.scopus.com/inward/record.url?scp=0032123329&partnerID=8YFLogxK
U2 - 10.1111/j.1747-5457.1998.tb00781.x
DO - 10.1111/j.1747-5457.1998.tb00781.x
M3 - Article
AN - SCOPUS:0032123329
VL - 21
SP - 247
EP - 263
JO - Journal of Petroleum Geology
JF - Journal of Petroleum Geology
SN - 0141-6421
IS - 3
ER -