Page 113 - The Petroleum System From Source to Trap

5. Applied Source Rock Geochemistry 107

II I
HYDROGEN , ORGANIC WELL HYDROCARBON
INDEX 11 CARBON 1 I DATA INDICATIONS
DErrH ..,. I
"" Iii . ... :: � � 1�1�11 HTDIOONS I
- � - MUD .....
I � II t; LOG IOCI-IVAL IOCIC-EVAL
FEET
15,/ TOC)lOO
TOC liWT j! <
S, .. W1 �
GAS I
IS 1.5
I I
• • • ,. 1 00 4 I J 2 I II D.S , : I 2 ·' .I J
I I � : ' I
i
I I
1000
'
'
'
' 500
'
'
' ' - , ---
- � ' ,- -T--
zooo - ,
1
1000
_ _ _ _ _ ' 1 _ ' l _ _ _ - - - - - -
4000
1500
5000
6000
2000
1000
8000
2500
9000
10000

]500
11000

llOOO
4000
14000
4500
15000

-� ' . - � ' - -
16000 ' I I
: : I I 5000
' ' I I I I
51 =HCS ALREADY IN ROCK �2 =HCS FRO� KEROGEN PYROLYSIS. S3 =C02 FROM KEROGEN PYROLYSIS.

Figure 5.8. Geochemical log for well V showing organic-lean, marginally mature Jurassic source rock. In situ bitumen from
this source rock has been geochemically correlated with oils in the area. An SPI of 2 t HC/m2 has been calculated from the
Jurassic source rock (see text� Sidewall cores indicated by dotted bars, drill cuttings by solid bars.

indicates a significant alginite component in the kerogen Well VII penetrates Mesozoic and Tertiary marine
from these rocks. Espitalie et at. (1985) and Huizinga et shales and sandstones, reaching Precambrian basement
al. (1988) have shown that T max is seldom useful as a at total depth (Figure 5.10). The geochemical log shows
maturation parameter for oil-prone algal kerogens the results for sidewall cores (dotted bars) and drill
because, unlike other kerogens, it shows little to no cuttings (solid bars). Thin shale beds sampled by
increase throughout the oil window. Facies effects on sidewall cores are more organic-rich than nearby
T ma x are discussed in Peters (1986). In this case, vitrinite samples, but are too thin to generate significant quanti­
reflectance represents a more useful thermal maturity ties of petroleum. When mixed with adjacent lithologies
in drill cuttings composited over 1(}-20 m intervals, these
parameter than T max·