biostratigraphy analysis which was focused on palynomorphs and foraminiferal.

1. BIOSTRATIGRAPHY AND PALEOENVIRONMENT OF STRATA FROM XY-WELL 1 AND XY-WELL2,
CENTRAL DEPOBELT NIGER DELTA BASIN, NIGERIA.
M.Sc. DISSERTATION
AKPATI, CHIDINMA CHUKS
PG/19/20/258925
B.Sc. Geology, (DELSU)
SUPERVISOR
DR A.A.I. ETOBRO.
BY

2. PRESENTATION OUTLINE
• INTRODUCTION
• STATEMENT OF PROBLEM
• OBJECTIVES
• GENERAL OBJECTIVE
• SPECIFIC OBJECTIVES
• LOCATION OF THE STUDY AREA
• REGIONAL GEOLOGY OF THE NIGER DELTA BASIN
• METHODOLOGY
• GRAIN-SIZE ANALYSIS
• PALYNOLOGICAL ANALYSIS
• FORAMINIFERA ANALYSIS
• PRESENTATION INTERPRETATION AND DISCUSSION
OF RESULTS
 SUMMARY CONCLUSION AND RECOMMENDATION
• CONTRIBUTIONS TO KNOWLEDGE

3. INTRODUCTION
• The Cenozoic Niger Delta overlies an area that is over 256,000 km2 (Kulke, 1995). It is
the youngest of the three large sediment bodies that filled the aulacogen formed
after the separation of the African and South American plates.
• Biostratigraphy is an essential tool for dating rocks and identifying the biotic record
through time.
• Biostratigraphy reduces risk of exploration and it is less expensive.
• Biostratigraphy also helps in reservoir characterization and Biosteering.
• Paleoenvironment of deposition is the study of the ancient environment of
deposition. It is also an environment that has been preserved in the rock record at
some time in the past, Kennedy (1998).
• The paleoenvironmental reconstruction can be done using textural analysis and the
analysis of the fossils contents in the rock units.

4. STATEMENT OF PROBLEM
• The Niger Delta Basin has been studied in recent times by both researchers and oil
companies because of its hydrocarbons potentials and economic importance.
• The Niger Delta Basin is heterogeneous and diachronous sedimentary basin having
diverse characteristics such as ages, and depositional environments from one location to
another.
• It is therefore important to establish the ages and paleoenvironment of the different oil
wells in the Niger Delta Basin.
• Both Foraminifera and Palynomorphs (Dinoflagellates, Spores and Pollen) have been
chosen to zone the strata penetrated by the studied wells (XY-well 1 and XY-well 2) since
not much work has been done on the biostratigraphy of this area; hence this forms the
basis of this present study.

5. General Objectives
The general objective of this study is to carry out a biostratigraphic study on the shale
sections, using both (Foraminifera and Palynomorphs) and Grain size analysis on the
sandstone sections within the studied intervals of XY-well 1 and XY-well 2 in the central
swamp Niger Delta Basin.
Specific Objectives
• To provide a lithostratigraphic framework for the strata penetrated by the two wells (XY-
wells).
• To determine the age of the formation(s) penetrated by the two XY-wells using index
microfossils (Foraminifera, Dinoflagellate, Spores and Pollen).
• To determine the paleoenvironment of deposition of XY-wells using index Foraminifera,
Dinoflagellate, Spores and Pollen and the textural characteristics of the sediments
penetrated by the two wells.
• To establish the Foraminifera and Palynological biozones associated with shale sections of
the two wells.
• To infer the petroleum systems of the studied sections of the two wells.

6. LOCATION OF THE STUDY AREA
Figure 1: map of the study area

7. REGIONAL GEOLOGY OF THE NIGER DELTA BASIN
Fig 2. Stratigraphy of the of the Niger Delta Basin (after Ige, 2010).

8. METHODOLOGY
Materials and methods
51 ditch cutting samples for XY-well 1
38 ditch cutting samples for XY-well 2
• Grain Size Analysis
Mechanical sieve techniques
• Palynological Analysis
Conventional acid maceration method:
Cleaning and Removal of Field Contaminants
Weighing and Crushing of Samples
Removal of Carbonates (HCl Digestion)
Removal of Silicates (HF Digestion)
HN03 digestion (Oxidation-1)
Schulze Solution (Oxidation – 2)
Gravity separation
Staining.
Dispersal of organic suspension and slide preparation
• Foraminifera Analysis
Kerosene method

9. PRESENTATION INTERPRETATION AND DISCUSSION OF RESULTS
Some of the Grain Size Results of Sandstone Samples from XY-well 1

10. PRESENTATION INTERPRETATION AND DISCUSSION OF RESULTS
XY-well 1
• This revealed three (3) lithofacies from bottom to top.
• Black shale: the black shale occurs between 2350 and 2470 m depth (120 m
thick). It is dark in colour, probably as a result of its organic matter contents. It is
fissile and moderately hard.
• Grey shale: it conformably overlies the black shale, and occurs at depth of 2070
to 2350 m (280 m thick).it’s colour ranges from light to grey to dark grey. It is
fissile and moderately hard.
• Sandstone: the sandstone is medium to coarsed grained, Smokey white to
orange colour. It is moderately to poorly sorted, containing some mica flakes. It is
about 110 m thick occurring between 1960 and 2070m.

11. Figure 3:Lithostratigraphy of XY-well 1

12. PRESENTATION INTERPRETATION AND DISCUSSION OF RESULTS
• XY-well 2
• This is characterized by two (2) lithofacies units from bottom to top.
• Sequence of shale, shaly-sand and sandy- shale.
• Sandstone.
• Shale, shaly-sand and sandy-shale: they occur between 2150 m and 2380 m
depth (230 m thick). The shaly-sand and sandy-shale are coated with some
mud which is black to grey in colour. The shale is grey in colour, fissile and
occasionally interbedded with the shaly sand and sandy shale.
• Sandstone: the sandstone is medium to coarse grained, Smokey white to grey
colour interbedded with thin shaly sand which is about 10 m thick. It is
moderately to poorly sorted and occurs between 2000 and 2150 m about 150
m thick.
• From lithostratigraphic point of view, the penetrated lithologies correspond to
those of the Agbada Formation.

13. Figure 4:lithostratigraphy of XY-well 2

14. Figure 6: Photomicrographs of some benthonic foraminifera recovered from the studied wells:
FORAMINIFERA RESULTS: Both benthonic and planktonic foraminifera species were
recovered from the studied wells. 40 benthonic Foraminifera species from XY Wells
(1)Vavulinera sp. (umbilical). (2) Quinqueloculina sp. (3) Eponides eshira (4) Uvigerina sp. (5) Eponides
africana. (6) Bolivina ihuoensis. (7) Bolivina sp. (8) Hopkinsina danvillensis. (9) Haplophragmoides
compressa. (10) Haplophragmoides sp. (11) Spiroculina sp (12) Nonion sp (13) Ammobaculites sp. (14)
Quinqueloculina microcostata (15) Saccammina complanata (16) Trochammina sp (17) Spirosigmoilina
oligocaenica (18) Arenaceous indeterminate (19) Altistoma tenuis (20) Nonion oyae.(x40)

15. PLANKTONIC FORAMINIFERA
13 planktonic foraminifera species were recovered from XY-wells.
Figure 7: Photomicrographs of some of the Planktonic Foraminifera recovered from XY-wells:
1)Chiloguembelina martini (2) chiloguembelina cubensis (3) Turborotalia cerrazuolensis (spiral) (4) Turborotalia
cerrazuolensis (umbilical) (5) Globigerina ampliapertura (spiral) (6) Globigerina ampliapertura (umbilical) (7)
Truncorotaloides rohri (spiral) (8) Truncorotaloides rohri (umbilical) (9) Morozovella wilcoxensis (umbilical) (10)
Morozovella wilcoxensis (spiral) (11) Cassigerinella chipolensis (12) Acarinina sp.(x40)

16. FORAMINIFERA DISTRIBUTION CHART FOR XY-WELL 1

17. FORAMINIFERA DISTRIBUTION CHART FOR XY-WELL 2

18. POPULATION DISTRIBUTION OF FORAMINIFERA IN XY-WELL 1 AND XY-WELL 2
Figure 8: Population distribution of Foraminifera

19. POPULATION DISTRIBUTION OF DINOFLAGELLATE CYSTS IN XY-WELL 1
2050
2100
2150
2200
2250
2300
2350
2400
2450
2500
0 20 40 60 80 100 120 140
DEPTH(M)
POPULATION

20. POPULATION DISTRIBUTION OF DINOFLAGELLATE CYSTS IN XY-WELL 2

21. 1
5
10
2 3 4 5
6
7
8 9 10
11 13 14 15
12
Figure 8: Photomicrographs of the recovered Spores and Pollen: 1). Verrucatosporites usmensis (Van der Hammen)
Gemeraad, Hopping and Muller, 1968 2. Retibrevitricolpites triangulatus3 & 10 Proxapertites cursus 4. Alnipollenites
verus 5):Peregrinipollis nigericus 6&7. Tricolpites hians Stanley, 1965 8, 13 &14. Psilatricolporites crassus 9.
Racemonocolpites hians 12. Retibrevitricolporites protrudens Legoux, 1971 10. Crassoretitriletes vanraadshooveni
Germeraad et al., 1968 15. Perretipollis spinosus 11. Verrutricolporites irregularis.(x40)
Palynomorphs results : 51 pollen and spores, 52 Dinoflagellates were recovered from XY-
well 1 and 37 pollen and spores , 43 dinoflagellates cysts from XY-well 2

22. 1
2 3 4
5
9
7 8
11
10
12
6
Figure 9: Photomicrographs of some Dinoflagellates cyst recovered from XY-well 1 and XY-well 2:
1. Cordosphaeridium funiculatum. 2. Polysphaeridium zoharyi. 3. Areoligera semicirculata. 4.Tuberculodinium vancampoae. 5.
Spiniferites ramosus. 6.Thalassiphora fenestrate. 7.Eocladopyxis peniculata. 8. Diphyes ficusoides. 9. Phthanoperidinium comatum.
10.Membranophoridium perforatum. 11&12. Cleistosphaeridium ancoriferum.(x40)
Dinoflagellate cysts

23. BIOZONATION
1). FORAMINIFERA BIOZONATION
According to Gradstein et al.(2012) and SPDC (2010) foraminiferal
zonation five zones were established on the basis of their population
and abundance of some associated index foraminifera in the studied
wells.
• Spirosigmoilina oligocaenica Zone (2260 -2180 m)
• Eponides africana Zone (2460-2260 m)
• Nonion oyae Zone (2440-2140 m)
• Chiloguembelina martini Zone (2420-2180 m)
• Chiloguembelina cubensis Zone (2200-2180 m)
DISCUSSION OF RESULTS

24. 2). PALYNOLOGICAL ZONATION
• According to Evamy et al. (1978), five (5) Palynological zones were
established for this study. This zones were established on the basis of
species abundance of the index palynomorphs recovered from the
studied sections:
• Magnastriatites howardi Zone (2280 -2090 m)
• Retibrevitricolporites obodoensis Zone (2460-2090 m)
• Crassoretitriletes vanraadshooveni Zone (2350-2090 m)
• Arecipites exilimuratus Zone (2410-2080 m)
• Racemonocolpites hians Zone (2290-2090 m)

25. Figure 12: Percentage frequency distribution chart for pollen and spores for XY-well 1
Zone I
Zone II
Zone III
Zone V
Biozonation for Pollen and Spores

26. AGE OF THE STRATA PENETRATED BY XY-WELLS
• The distribution of Stratigraphic important Palynomorphs such as
Retibrevitricolporites obodoensis, Racemonocolpites hians, Arecipites
exilimuratus, Praedapollisafricanus, and Crassoretitriletes vanraadshooveni,
etc dated the studied section as Late Oligocene to Early Miocene from
Palynological analysis.
• Also the age of the studied section XY-well 1 suggest Early Eocene to
Middle Eocene due to the high occurrence of Hopkinsina danvillensis and
Miocene to Early Pliocene due to the high occurrence of Haplophragmoides
sp. for XY-well 2 from Foraminifera analysis.
• The age of the strata penetrated by XY-wells ranges from Early Pliocene to
Early Miocene which suggest that the studied section falls within the
Agbada Formation.

27. Figure 13 Stratigraphic chart showing relative abundance (percentage frequency) of Palynomorphs with Lithostratigraphy
for XY-well 1 (after Haq et al. 1987).
SEQUENCE STRATIGRAPHY FOR XY- WELL 1

28. Figure 14 Stratigraphic chart showing relative abundance (percentage frequency) of Palynomorphs with
Lithostratigraphy for XY-well 2 (after Haq et al. 1987).
SEQUENCE STRATIGRAPHY FOR XY- WELL 2

29. PALEOENVIRONMENTAL RECONSTRUCTION
• The inner neritic zone is represented by Homotryblium plectilum and
Phthanoperidinium comatum. The middle to inner neritic components are
represented by Hystrichokopoma pusillum and Heterosphaeridium sp.
• From this study, Hopkinsina danvillensis and Haplophragmoides sp dominated the
Stratigraphy of XY-well 1 and XY-well 2 respectively. This H. danvillensis suggests
deposition in a middle neritic environment while Haplophragmoides sp suggests
deposition in an inner neritic environment.

30. SUMMARY AND CONCLUSION
• The sedimentary rock sequence penetrated by the studied well suggest that
lithostratigraphic unit is Agbada formation.
• Early Eocene to Middle Eocene age was inferred for XY-well 1 and Miocene to Early Pliocene
was inferred for XY-well 2 from the foraminifera analysis and Late Oligocene to Early
Miocene age was inferred for both well from the Palynological analysis.
• The occurrence of Verrucatosprites usmensis and Cyathidites minor suggests fresh water
swamps and marshes.
• Proxapertites operculatus, Longapertites marginatus and Proxapertites cursus suggests
mangrove swamp environment.
• Also the presence of Hopkinsina danvillensis and Haplophragmoides sp suggest middle
neritic environment and inner neritic environment respectively.

31. RECOMMENDATION
• The age inferred from this study can be used in correlation of Early
Eocene to Middle Eocene, Miocene to Early Pliocene and Late
Oligocene to Early Miocene Stratigraphic succession.
• The Paleobathymetry of the studied section ranges from middle to
inner neritic environment an indication of depth of burial of the micro
fauna and flora in the sediments which is significant in hydrocarbon
generation.
• Micropaleontological and sedimentological studies are recommended
for better understanding of paleodepth and paleoenvironment
penetrated by the well.

32. CONTRIBUTION TO KNOWLEDGE
• The study has established based on textural studies that the sediment
source ranges from unimodal to bimodal source.
• The study has also established based on Micropaleontological studies
that the age of the studied section (XY-well 1 and XY-well 2) penetrated
the Agbada Formation during Eocene to Middle Eocene, Miocene to
Early Pliocene and Late Oligocene to Early Miocene.
• The study has established that the paleoenvironment of the studied
section ranges from marine and middle neritic to inner neritic
environment.
• The study has also established four different stratigraphic systems tract,
TST, HST, LST and MFS from the studied sections.

33. THANKS