Geology Reference
In-Depth Information
Table 18.1
Organic matter analytical data (Total Organic Carbon and Rock-Eval) for the JNOC samples (from JNOC 1988)
JNOC
Nr
Corg
(%)
S1
(mg/g)
S2
(mg/g)
S3
(mg/g)
HI (mg/g
Corg)
OI (mg/g
Corg)
Tmax
(
C)
Vr
(%)
Region
Group
Lithology
KS-26 Kisangani
Stanleyville Oil shales
10.1
0.54
108.1
2
1.067
20
435
KS-28 Kisangani
12
0.84
125.4
2.24
1.043
19
432
KS-32 Kisangani
5.55
0.1
58.4
1.77
1.052
32
433
KS-33 Kisangani
5.02
0.22
59.4
1.1
1.183
22
435
KS-34 Kisangani
6.21
0.21
72
1.24
1.159
20
437
KS-35 Kisangani
0.92
0.03
3.97
0.52
432
57
429
KS-36 Kisangani
1.24
0.06
6.43
0.71
519
57
430
KS-38 Kisangani
9.23
0.2
118.7
1.48
1.286
16
439
KS-45 Kisangani
15.5
2.58
172
3.16
1.112
20
422
KS-46 Kisangani
16.2
1
169
3.44
1.041
21
435
KS-47 Kisangani
17.6
0.94
169.3
2.18
960
12
437
KS-48 Kisangani
1.63
0.13
5.59
1.38
343
85
434
0.85
KS-52 Kisangani
9.61
0.22
108.4
2.66
1.128
28
438
KS-81 Kisangani
5.48
0.51
45.04
2.11
822
39
427
0.69
KS-82 Kisangani
2.8
0.21
25.06
0.98
895
35
429
KS-83 Kisangani
1.24
0.03
5.45
0.4
440
32
433
KS-84 Kisangani
8.23
1.82
98.24
1.51
1.194
18
432
KS-18 Kisangani
Stanleyville Limestones & calcareous
shales
0.38
0.03
0.65
0.21
171
55
423
KS-23 Kisangani
1.57
0.05
5.41
0.37
345
24
425
KS-24 Kisangani
2.05
0.07
12.65
0.49
617
24
427
KS-50 Kisangani
0.56
0.07
0.9
0.74
161
132
429
KS-53 Kisangani
6.74
0.16
62.68
1.94
930
29
427
KS-71 Kisangani
3.26
0.12
32.06
0.97
983
30
425
KS-21 Kisangani
Stanleyville Mudstones
0.71
0.11
2.45
0.44
345
62
426
KS-31 Kisangani
0.49
0.02
0.52
0.31
106
63
425
KS-41 Kisangani
0.44
0.01
0.65
0.34
148
77
432
KS-72 Kisangani
0.72
0.03
1.75
0.68
243
94
425
KS-77 Kisangani
Lukuga
Black varval shale
0.95
0.03
0.11
0.57
12
60
411
0.8
KS-78 Kisangani
1.02
0.03
0.14
0.43
14
42
453
0.5
KS-79 Kisangani
0.82
0.01
0.3
0.37
37
45
437
0.64
KS-87 Kisangani
1.42
0.01
0.16
1.18
11
83
434
0.48
KS-88 Kisangani
1.46
0.03
2.31
0.36
158
25
436
0.47
KS-104 Kindu
Lukuga Black shale
0.61 0.01 0.24 0.41 39 67 435
KS-105 Kindu 0.88 0.02 0.04 0.8 5 91 443 0.75
Corg: total organic carbon; CaCO3: Carbonates; Rock-Eval pyrolysis parameters; S1: free/absorbed hydrocarbons, S2: hydrocarbons released by
the pyrolysis of the kerogen, S3: oxygen-contained volatiles, hydrogen index (HI), oxygen index (OI), Tmax (temperature of the peak of S2
hydrocarbon generation during pyrolysis); vitrinite reflectance data (Vr)
Samples from the Mamungi shales, Lenda carbonates and
Bangu black limestones are all very poor in C
org.
,and
considered barren.
Permo-Carboniferous sediments from the Lukuga Group
(Dekese well and outcrop samples) contain moderate
contents of total organic carbon (
Loia Group contain type I/II kerogen of good to excellent
quality. They are derived from algae deposited in an
aquatic anoxic environment, likely lacustrine, and con-
tain small proportions of terrestrial
type III material
(Sachse et al.
2012
).
The Upper Cretaceous Kipala black shales are also excellent
source rock (C
org
.
2.4 %C
org
), with
hydrogen-poor type III/IV gas-prone kerogen and a low
hydrocarbon generation potential. They may have pro-
duced a limited amount of gas, but no oil.
The Jurassic (Stanleyville Group) and Middle Cretaceous
(Loia Group) samples from the Samba well, and outcrops
in the north eastern part of the CB, have up to 25 % C
org
.
Sediments from the Stanleyville Group contain type I
kerogen of excellent quality; and those of the overlying
<
¼
¼
8-9 %, with ca. 750 HI) but are
438-439
) and of limited lateral extent.
In summary, the new geochemical data confirm that the
Stanleyville Group is the most promising source rock unit in
the CB, although it is immature. Samples from this group
show a variety of organic matter content and composition,
reflecting different depositional environments. In the Samba
well, the Stanleyville Group comprises red siltstones and
immature (Tmax
¼
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