Page 112 - The Petroleum System From Source to Trap

106 Peters and Cassa

OXYGEN I HYDROGEN ORGANIC WELL HYDROCARBON SOURCE I VITRINITE 1, HYDROCARBON
INDEX INDEX CARBON DATA POTENTIAL 'I REFLECTANCE ; INDICATIONS
AND TMAX i
. , I W! l DEPTH
DEPI'H 1 I .
=.
l

OIL � GM 8 �-1 .... l.o.; ' I ll i .:;�, !1 i
: , I Oll GAS I ' """
Nat* ' � f f Iii§,; M UD
g
!10 � 'I HYDRO�RBON 1[ ¥ ' ! ROCK--EVAL
FEET , TMAX • LOG IOCit-fiAL
(S,i TOqlOO , (S,/ TOC)IOO 0 : s I YIELD ... WT I S, I S, ' .. , ' '!' �0 ,"" '[
�
I : tiG 1: - � - : � l 2 1 . 5 J � II , 1 3 ! , . 5 , , 1 , "· I, .. , I 2j 5 • , , 0.2 .40 lO us U 4.0 GAS S, " "' 2 ·' . . .
20 �
1 1
u
1 1 .. • u
1.5 2.5
0.5
.
I I I I
'I , � � I i I I
I I I! r
i i
I
1000 '
I , ! ill I : I '
i ! ! • ' I I ' ' ! 500
-
2000 - I · + - - - 1 ,-,- - �- -- t - , - �-
I
� I ' • i I I
:
! I . ,
JOOO !
II 1000
I '
!
mo - - - - - _._ __
. .
•
5000
6000
2000
1000
8000
2500
9000
]000
10000
1000
]500
12000
IlOilO
4000
1�000
15000
16000
5000
51 =HCS ALREADY IN ROCK S2=HCS FRO� KEROGEN PYROLYSIS. Sl =C02 FROM KEROGEN PYROLYSIS.
Figure 5.7. Geochemical log for well IV shows a clear thermal maturity trend established by T max for shales above 2400 m
(poor source) and below 3500 m (presently active source rock). The intermediate zone consists of sandstones and siltstones
where T max values are either anomalously high or low compared to the above trend. The high T max values result from a
dominance of recycled kerogen in coarse-grained, organic-poor rocks. The low T max values correspond to zones impreg­
nated by migrated oil. Heavy ends in the oil generate a spurious S:z peak with an anomalously low T max (Peters, 1986).
Sidewall cores indicated by dotted bars, drill cuttings by solid bars.

organic matter, but still may be source rocks for An SPI of 2 t HC/m 2 has been calculated for this Jurassic
petroleum accumulations because they are thick and/ or source rock using samples that have a genetic potential
widespread. The geochemical log for well V shows (S1 + S 2 ) � 1 mg HC/g rock.
organic-lean Jurassic source rock from 2880 m to total The geochemical log for well VI shows a depressed
depth. In situ bitumen in this presently active source rock trend in T m a x in the Lower Cretaceous lacustrine rocks
has been geochemically correlated with oils in the area. below 2500 m (Figure 5.9). Organic petrography data