Rock-Eval ratio

Figure 9. Relationship between the thiophene ratio, TR, and Rock-Eval Tmax f°r samples °f varying kerogen type. NB. All samples are immature with respect to oil generation (i.e. vitrinite reflectance, R0 < 0.5%).

Figure 10. FPD chromatograms from flash pyrolysis of Mahakam coals. Sample depth, vitrinite reflectance, Rock-Eval Tmax, hydrogen index (HI) and the thiophene ratio (TR) are shown. Peak identifications are given in Table V.

Initially kerogens were divided into four major types as illustrated on this diagram with well-defined boundaries, (b) With the development of the Rock Eval pyrolysis system it was found that the HI and 01 indicies were directly proportional to the H/C and O/C ratios and therefore a plot of HI to 01 could be used to replace the H/C and O/C values on the Tissot-Welte diagram (Hunt, 1996) (reproduced by permission of Freeman from Petroleum... 

Fig. 16. Rock-Eval 6 calibrations (a) calibration curve relating Rock-Eval 6 Y factor to oil API gravity and (b) predicted API for core samples from Rock-Eval 6 Y as a function of extract hydrocarbon/nonhydrocarbon ratio, (c) Plot of predicted API for core samples compared with API gravity measured from core extracts.

Increased tar or the incidence of viscous oil corresponds (a) to increased nonhydrocarbon content of petroleinn (lower hydrocarbon/nonhydrocarbon ratio), (b) increased high molecular weight organic matter observed in Rock-Eval 6 pyrograms and (c) an increased pore-filling petroleum density (as evidenced by lower predicted API gravity from Rock-Eval 6. 

Hydrogen index (HI) An expression of the relative abundance of hydrogen with respect to carbon derived from RockEval pyrolysis of sedimentary organic matter. The hydrogen index is derived from measurement of the amount of hydrocarbon-rich material released by Rock-Eval pyrolysis of organic matter, divided by the TOC concentration of the sediment sample. It is a proxy for the atomic H/C ratio of organic matter. 

Van Krevelen-type plot A cross-plot that employs Rock-Eval hydrogen index and oxygen index values instead of atomic H/C and 0/C ratios to identify the biotic origins and diagenetic alterations of sediment organic matter. 

Table 1. Monterey Miocene Formation samples, shown in Figs. 4 and 5 (a) sulfur percent, S/C ratio and Rock Eval for kerogens and oils, see also description in Figs. 4 and 5 (b) the same data on core samples at depth 1155-2490 m...

Turbidite samples from Sites 950, 951 and 952 (ODP Leg 157) on the MAP have between 0.75 and 1.68 wt% TOC and C/N ratios near 10. Rock Eval pyrolysis data indicate a fair source rock and immature sediments (Schmincke et al, 1995). The overall organic geochemical shipboard data indicate a predominantly marine origin of the OM (Schmincke et al, 1995), but including a terrigenous component. 

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