Page 111 - The Petroleum System From Source to Trap

5. Applied Source Rock Geochemistry 105

OXYGEN� HYDROGEN ORGANIC WELL 1 l HYDROCARBON SOURCE VITRINITE 1 HYDROCARBON
REFLECTANCE
INDEX l INDEX CARBON DATA POTENTIAL 1 AND TMAX ; INDICATIONS
DEPTH 1 I• ' ' '
I
'
!i'
II
I' 1: z, . """ '"' loooo "" I 3: iil : OIL ' 1 �" ' wo.r : II, UD
I
2
!!! g , I .... ' i ' ..... . � Ol I GAS !!' M
,
I ,
FEET J1 � j HYDIOCAIION , :irMAX • .. I LOG
i � ·· s ' ' YIELD ""' WT ', S, t S , ,;"', ' � ·�
!1.. •
u
""' : I z 3 4 s 10 JO I' •n u � . .. 1.15 u I GAS
1 ' 1 1 i , , '''ll"" ; 1,5 � u u u i
,

t
'
I ' ��:·D.·. ' II
·-·
(
2000
···
�;�·-
·s.
1000
1500
5000
6000
0
.
t--
2000
1
I
7000 I
i :
j,.
8000
9000
!
'i I I :
lOOO
10000
l I :
-� - - � - : - � - I
)� I
l� I
13000
4000
4!00
5000
16000
5000
i
S1 =HCS ALREADY IN ROCK S2 =HCS FROM KEROGEN PYROLYSIS. S3=CO, FROM KEROGEN PYROLYSIS.

Figure 5.6. Geochemical log for well Ill, located about 80 km northwest of well I (Figure 5.4). The Upper Cretaceous section In
well Ill is not as oil prone as in wells I or II and is more thermally mature, approaching the onset of oil generation. Geochem­
ical parameters on the logs in Figures 5.4 to 5.6 allow individual units to be correlated among the wells. Sidewall cores
indicated by dotted bars, drill cuttings by solid bars.

and underlying shales. Measured T max values are either yield reliable Tmax values. High molecular weight
anomalously high or low in the sandstone and siltstone components in oil commonly generate a spurious Sz
interval compared to the established trend based on Tmax peak with a corresponding low Tmax (e.g., Peters, 1986).
in the shales. The anomalously high T max values result Note the good correlation in the deeper shale between
from dominance of recycled organic matter in these free hydrocarbon indications (5-t) and the mud log gas.
coarse-grained, organic-poor rocks. The low T max values Well V penetrates Mesozoic marine shale and
correspond to zones impregnated by migrated oil or sandstone and Tertiary carbonate rocks (Figure 5.8).
where S2 peaks are too small (<0.2 mg HC/g rock) to Some fine-grained marine rocks are relatively lean in