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Hydrocarbon-Generating Potential of Eocene Source Rocks in the Abakaliki Fold Belt, Nigeria / Potencial za nastanek oglikovodikov v eocenskih izvornih kamninah nariva Abakaliki

O.A. Oluwajana
O.A. Oluwajana
, 
A.O. Opatola
A.O. Opatola
, 
O.B. Ogbe
O.B. Ogbe
 und 
T.D. Johnson
T.D. Johnson
   | 25. Juli 2020
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Article Category: Original scientific paper
Online veröffentlicht: 25. Juli 2020
Seitenbereich: 223 - 233
Eingereicht: 28. Sept. 2019
Akzeptiert: 22. Nov. 2019
DOI: https://doi.org/10.2478/rmzmag-2019-0014
Schlüsselwörter
© 2020 O.A. Oluwajana et al., published by Sciendo
This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 License.

Figure 1

Location of the study area showing the position of the Ihuo-1 well and other wells in the Abakaliki Fold Belt and the Calabar Flank. Insert: Map of Nigeria showing the location of the Abakaliki Fold Belt (marked by a red box), Southeastern Nigeria.
Location of the study area showing the position of the Ihuo-1 well and other wells in the Abakaliki Fold Belt and the Calabar Flank. Insert: Map of Nigeria showing the location of the Abakaliki Fold Belt (marked by a red box), Southeastern Nigeria.

Figure 2

A simplified regional section of the Cretaceous and Cenozoic stratigraphy of Anambra Basin, Abakaliki Fold Belt and Calabar Flank, with time stratigraphy and tectonic events [9–10].
A simplified regional section of the Cretaceous and Cenozoic stratigraphy of Anambra Basin, Abakaliki Fold Belt and Calabar Flank, with time stratigraphy and tectonic events [9–10].

Figure 3

Lithostratigraphy of Ihuo-1 well showing the different sedimentary intervals with relative ages. Note the gaps within the litholog, representing unconformity.
Lithostratigraphy of Ihuo-1 well showing the different sedimentary intervals with relative ages. Note the gaps within the litholog, representing unconformity.

Figure 4

Cross-plot of S1 against TOC for the Eocene source rocks in Ihuo-1 well [16], used in distinguishing the hydrocarbon (potential) types. The red dots indicate the analysed samples.
Cross-plot of S1 against TOC for the Eocene source rocks in Ihuo-1 well [16], used in distinguishing the hydrocarbon (potential) types. The red dots indicate the analysed samples.

Figure 5

Cross-plot of generation potential (GP) against total organic content (TOC) of Eocene source rocks in Ihuo-1 well [16], used to know the source potential of the sediment. The red dots represent the analysed samples.
Cross-plot of generation potential (GP) against total organic content (TOC) of Eocene source rocks in Ihuo-1 well [16], used to know the source potential of the sediment. The red dots represent the analysed samples.

Figure 6

Van Krevelen diagram for kerogen typing of Eocene shale samples in Ihuo-1 well [16], used to determine the kerogen types of the shale samples. The red dots represent the analysed samples.
Van Krevelen diagram for kerogen typing of Eocene shale samples in Ihuo-1 well [16], used to determine the kerogen types of the shale samples. The red dots represent the analysed samples.

Figure 7

Pseudo-Van Krevelen diagram of Eocene shale samples in Ihuo-1 well [20], used to determine the kerogen types of the shale samples. The red dots represent the analysed samples.
Pseudo-Van Krevelen diagram of Eocene shale samples in Ihuo-1 well [20], used to determine the kerogen types of the shale samples. The red dots represent the analysed samples.

Figure 8

Boundary condition used to model the most probable scenario for hydrocarbon generation in the Abakaliki Fold Belt. The figure indicates the heat flow trend for the Lower Eocene source rock.
Boundary condition used to model the most probable scenario for hydrocarbon generation in the Abakaliki Fold Belt. The figure indicates the heat flow trend for the Lower Eocene source rock.

Figure 9

Correlation of measured and modelled vitrinite reflectance data for Ihuo-1 well. The heat flow values were determined based on the tectonic history of the basins and were defined by streaming modelled and measured thermal data.
Correlation of measured and modelled vitrinite reflectance data for Ihuo-1 well. The heat flow values were determined based on the tectonic history of the basins and were defined by streaming modelled and measured thermal data.

Figure 10

One-dimensional history of the buried Eocene source unit in Ihuo-1 well extracted from the model. The coloured model indicates the modelled vitrinite reflectance maturity overlay.
One-dimensional history of the buried Eocene source unit in Ihuo-1 well extracted from the model. The coloured model indicates the modelled vitrinite reflectance maturity overlay.

Figure 11

Burial history of the Ihuo-1 well showing the transformation ratio overlay for the deeply buried Eocene source unit.
Burial history of the Ihuo-1 well showing the transformation ratio overlay for the deeply buried Eocene source unit.

Geochemical results of rock-eval/TOC analyses of Eocene samples in Ihuo-1 well

Depth (m)TOC (wt.%)Rock-eval pyrolysis
S1 (mgHC/gTOC)S2 (mgHC/gTOC)S1 + S2TmaxOI (mgHC/gTOC)HI (mgHC/gTOC)PI (mgHC/gTOC)
22040.82.72.585.284421713230.51
22651.83.912.886.794411581600.58
23201.53.702.406.104391561500.61
23550.82.561.454.014661291810.64
23750.76.523.289.804555574690.67
24151.14.142.036.174761771850.67
25100.91.600.832.4346917920.66
25201.05.032.187.214783532180.7
25570.82.531.213.744801161510.88

Input for 1D basin modelling of the Ihuo-1 well as used in the present study.

Layer nameDepth range (m)Thickness (m)Deposition period (Ma)Erosion period (Ma)Modelled TOC (wt.%)Modelled HI (gHC/gTOC)
Overburden0–28280.2–0
Mio-Oligocene (Coastal plain sands)28–58455627–0.2
Oligocene shaly sands584–132874428–27
Upper Eocene (Bende/Ameki Formation)1328–14269837.6–3434–28
Mid-Eocene (Bende/Ameki Formation)1426–186243641.2–3939–37.6
Lower Eocene (Bende/Ameki Formation)1862–265579349–41.21214
Lower Eocene (Bende/Ameki Formation)2655–27105554–49
Lower Eocene (Bende/Ameki Formation)2710–286315356–54
Palaeocene (Imo Shale)2863–322836566–56
Maastrichtian (Nkporo Shale)3228–345022271.2–66

Measured vitrinite reflectance values of Eocene stratigraphic levels in Ihuo-1 well.

WellDepth (m)Vitrinite reflectance values
Ihuo-122040.80
Ihuo-122650.78
Ihuo-123751.03
Ihuo-125571.48
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