Because the Rock-Eval SI parameter measures the amount of oil...

Because the Rock-Eval SI parameter measures the amount of oil present in a source rock, the maturity at which a maximum in Sl/TOC is reached is likely to correspond to the onset of significant expulsion of oil from the coals, which is reached at c. 3300 m depth bsf in Tara-1 coals (Fig. 6A). The corresponding Rank(S) value is c. 13.5, somewhat higher than the value of c. 12 proposed for the onset of expulsion from Paleogene coals in the McKee and Kapuni fields of Taranaki Basin (Killops et al. 1994). The inferred required saturation threshold of coal before expulsion of oil occurs is c. 40 kg/t Corg (Fig. 6A). If
the true petroleum potential of the coals....

Rock-Eval data are available for a few coal samples from
onshore coalfields and outcrops, the lateral equivalents of
the Tara coals (e.g., Shag Point Group; Fry 1982; Rinaldi
1990). There is also a range of Late Cretaceous sediments
in exploration wells in which terrestrial contributions are
important and for which TOC and Rock-Eval data have been
obtained, including shales, mudstones, siltstones, and coals.

Occurrences of these sediments in exploration wells are
confined largely to Galleon-1, Toroa-1, Rakiura-1,
Endeavour-1, and Pukaki-1. Rock-Eval and TOC data are
available for the first three wells, Rock-Eval data only have been reported for a few coals in Endeavour-1 (Fry 1982),and no Rock-Eval data have been acquired for Pukaki-1. In order to assess the petroleum potential of these coaly sediments, it is again necessary to consider HI values in relation to maturity, as for Tara coals.