Page 114 - The Petroleum System From Source to Trap

108 Peters and Cassa

OXYGEN WELL HYDROCARBON SOURCE HYDROCARBON
INDEX i DATA POTENTIAL INDICATIONS
DEPTH DEPTH
I ' I I 2 g dl,-1 FMI 1-1 WI!
:a:
1 .. '!. I , . :. :; ! I !!!1� F& PIIOIUYMn'
TOCI100 I IS. I TOC)� TOC %WT I ' i � � 81 YIELD ROCK-l:VAL
FEET I IIYDROCA:..
.-!h !
WT
%.
... m I ,.. .., .., ,.. m 4 3 2 ' I II � i � !I ., t 2 1 4 1 II 2G s1 •. wr .1 :z .3 .... 1
LL.
u u u
�
� I I I ! � I I I ! : � II I 1 1 1 1 1 1 1 1 .. , ,' I I : : I 1 1 1 1 1 , '1
,
I ��i==T � I! I
�, ::� I _ 500
1000 - i I
2000 - - - - -- --- , - - - --- - - - - -- :
I
lOOO
1000
5000 1500
'
- - - -
6000 - -- - _L _ _ _
�
-
2000
1000
8000
2500
9000

JOOO
10000
llOO
J500

0000
4000
14000
' '
' 4500
15000 '
'
' .
' '
' 5000
' '
S1 =HCS ALREADY IN ROCK S2 =HCS FRO� KEROGEN PYROLYSIS. SJ =C02 FROM KEROGEN PYROLYSIS.

Figure 5.9. Geochemical log for well VI showing a depressed T max trend compared to R0 in Lower Cretaceous lacustrine
rock. Type I kerogen, commonly associated with lacustrine source rock, shows little change in T max during maturation
throughout the oil window. For example, Espitalie et al. (1985) show that T max for type I kerogen does not exceed 440°-445°C
throughout the maturity range defined by R0 = 0.4-1.5%.

thin organic-rich shales are difficult to recognize. If the source rock does thicken and become more mature
drill cuttings samples had been used alone, these source where it is more deeply buried. If these thin shale beds
rocks would have been overlooked in the penetrated do not increase in thickness and maturity, there is little
section. These thin beds could represent the feather-edge chance they could charge nearby traps. In this case, other
of a source rock that thickens and is more deeply buried source rocks must be identified if this area is to remain
somewhere else in the basin fill. Based on the results in prospective for oil exploration.
this well, more of these types of geochemical analyses in Well VIII penetrates a thick Cretaceous marine
nearby wells could be obtained to determine if this sequence dominated by gas-prone organic matter