Petroleum Exploration Palynostratigraphy

Introduction

1.1. Introduction

Niger Delta is an important Basin because of its hydrocarbon resources. It is the largest basin in the West African Coast. Larger amount of data from the several thousands of drilled wells has led to a considerable understanding of the stratigraphy and regional geology of the delta. Over 90% of Nigerian foreign revenue is derived from the Niger Delta Basin/Region.

There has been a renewed call for a revisitation of the Niger Delta Basin vis-à-vis new technology for hydrocarbon exploration and exploitation as a result of increase demand for global energy, more so when the number of producing wells in a state, determines how much they get from the federal revenue allocation.

This has brought about increased interest and considerable research to the improvement of our understanding of the basin fill pattern. At various times, Geoscientist have continuously looked at the various aspects of the basin; the stratigraphy and sedimentation, the geohistory, the organic geochemistry, structures and paleontology; it is in the wake of these demand that this study is carried out to add to existing stratigraphic information for deep prospectivity of hydrocarbon .On this premise Palynological analysis was conducted on twenty samples obtained in the offshore, Niger Delta, Nigeria. This analysis was conducted to generate data which would support the age determination of the study area.

1.2 Statement of Research Problem

Increase in exploration and exploitation of hydrocarbons in the Niger Delta has made the search for oil and gas increasingly difficult. It has become important to acquire knowledge and expertise, in order to improve geological research and technology to field development and production of this vast hydrocarbon resource in the Niger Delta. This has necessitated the use of palynomorphs in the exploration and exploitation of hydrocarbons.

1.2.1 Justification

In recent times, the use of micro fossils have become popular in obtaining stratigraphic information on a wide variety of areas; age dating, paleoenvironmental studies, paleoclimatic studies and many more. Hence, this research is of great importance especially as these palynomorphs provide a better choronostratigraphic refinement for the purpose of age dating. Knowledge from the age dating of this well with the aid of these index forms will help to know if such area is within the age by which hydrocarbon can be generated. Since not all geological times are characterized by hydrocarbon presence.

1.2.2 Review of Previous Work.

Comprehensive biostratigraphic studies have been done in the recent times in the Niger Delta Basin by researchers (Reyment, 1965, Adegoke, 1978, Petters, 1982, Seglie, 1982, Ozumba, 1995, Adeniran, 1997). Biostratigraphic and foraminireral works have been done on some portions of the Niger Delta, (Bassey & Alalade 2005) studied the Tertiary planktonic foraminifera of the Paleogene and Neogene. The Paleogene was dominated with foraminifera species such as Globigerina, Globorotalia, Acaranina, Hantkenina etc. The Neogene showed dominance of foraminifera species such as Globorotalia and Globigernoides. (Ogbe, 1982) established the paleoecology phase based on micro fauna and flora in the Niger Delta. (Adeleye and Boboye, 2009) also worked on calcareous nannofossils biostratigraphy on deep offshore sequence of the Niger Delta.

Germeraad et al, (1968) carried out a twenty year study on the palynology of the Tertiary sediments from tropical areas (study area inclusive). He was able to erect zones based on palynological data.

Following an informal palynological zonation of the Tertiary Niger Delta by Evamy et al. (1978) in which he defined twenty-nine (29) palynological zones and subzones, other workers who have also presented results of their palynological investigations include, Oloto (1989, 1990, 1992, 1994), Umeji (2002, 2003, 2005).

Documentation of the upper Cretaceous and Tertiary Foraminiferal ages and paleoecological interpretations for the Nigerian basins have been presented by: Adegoke (1977); Adegokeet al, (1971, 1976, 1980); Akoet al; (1980), Dessauvagie (1972), Fayose and Asseez (1972), Fayose and De Klasz (1976) Kogbe et. al. (1976), and Ogbe (1972, 1974).

1.3 Aim and Objectives of this Research.

The aim of this research is to add to stratigraphic information of offshore Niger Delta Basin in the aspect of palynostratigraphy with special attention on the zonation, and relative age determination using palynomorphs.

Objectives

The objectives of the work include:

Lithologic description of collected samples

Preparation of palynological slides

Identification and analysis of the recorded palynomorphs

Identification of the marker species encountered at various depths.

Biotratigraphic zonation of the rock sequence and relative age determination.

1.4 Geology of the Studied Area

1.4.1 Geology of the Niger Delta

The Niger Delta is located between latitudes 4o00’N and 6o00’N and longitudes 3o00’E and 9o00’E. The Delta is bordered in the south by the Gulf of Guinea and in the North by older (cretaceous) sediments of the Anambra Basin, Abakiliki uplift and the Afikpo syncline. The Niger Delta is bounded in the East and West respectively by the Dahomey Basin and Cameroon volcanic line (Figure 1.1).