160
Statistical Methods for Estimating Petroleum Resources
years ago and the gas window 2 million years ago. The plot was based
on the principle adopted by the DIAGEN program (du Rouchet, 1980;
Lepoutré, 1986).
The advantage of this approach is that the method requires very little information yet can provide vital information about the maturity of
PREDICTED GEOTHERMAL
GRADIENT
OIL WINDOW
18.5 Ma
GAS WINDOW
2 Ma
26 Ma
DEPTH - meters
TIME - Ma
10
4561.4
0
6
12
18
24
30
33.5
4000
3500
3000
2500
2000
1500
1000
500
0
0
1
2
3
4
5
6
7
8
9
1 0
40
70
TEMPERATURE - ЊC
THERMAL INDEX
100
130
160
Figure 7.3. Burial history study for source bed ES2 from the Huang-Hua Basin
of eastern China. The diagram indicates that the source bed started to generate
oil 26 million years ago and entered into the oil and gas windows 18.5 million and
2 million years ago respectively.