AN

ESSAY

WRITTEN BY

ALAO VICTOR OLUROTIMI

MST/11/4649

DEPARTMENT OF MARINE SCIENCE AND TECHNOLOGY

SCHOOL OF EARTH AND MINERAL SCIENCE

FEDERAL UNIVERSITY OF TECHNOLOGY AKURE

ON

NIGER DELTA REGIONAL STRATIGRPHY AND OIL AND GAS

PROSPECTING; BLESSING OR CURSE

JANUARY 2015

1.0 INTRODUCTION

Nigeria, once an agrarian society, has substantially

depended on oil and gas as the paramount natural resource

of the nation. Since Nigeria's first oil exploration at

Oloibiri as far back as 1908 and the first commercial oil

discovery at Oloibiri in the onshore Niger Delta in 1956,

oil and gas has played progressively indomitable role in

the nation's economy.

The Niger delta province, highlighted as one of the

distinguished sedimentary basins in Nigeria, is bordered

by Guinea and Cameroon at south-east and Benin at south

west with the onshore portion of the Niger Delta

delineated by the geology of these borders.

Globally and locally, in terms of reputation and

influential leadership role, the possession and

production of oil and gas has been of remarkable blessing

to the nation's economical progress.

2.0 NIGER DELTA STRATIGRAPHY

In Niger Delta, a petroleum system-the Tertiary Niger

delta petroleum system famously recognized as the Akata-

Agbada formation, has been discovered (Ekweozor et al,

this study 1995). The Delta, formed at a rift junction

that started developing in the late jurassic and ended in

late cretaceous, properly began developing in the Eocene

with sediments volume of 500,000km3 (Hospers, 1965) and

over 10km deep already accumulated sediments(fig 1)

(kaplan et al, 1964).

The tertiary Niger Delta section has been identified

with three formations that represent prograding

depositional facies mainly distinguished on the basis of

sand-shale ratios and they are the Akata, Agbada and

Benin formations. Akata formation situated at the base of

the delta is of marine origin and is composed of thick

shale sequences, turbidite sand and subtle amounts of

clay and silt(fig 2). Beginning in the Paleocene and

through the recent, Akata formation formed during

lowstands when terrestrial organic matter and clays were

transported to deep water areas characterized by low

energy conditions and oxygen deficiency(fig 2)

(Statcher,1995). The underlying overpressured Akata

formation has only been drilled little as it has an

estimated thickness of 7,000m.(Doust et al,1990).

Akata formation is overlain by the major petroleum-

unit bearing Agbada formation which was formed during

Eocene to recent age. Agbada formation has a thickness of

3,700m and the lower Agbada formation is composed of

equal deposition of shale and sand proportions while the

upper Agbada fomation is composed of mostly sand with

only minor shale interbeds.

Benin formation overlains Agbada formation being a

continental latest Eocene to recent ages deposits of up

to 2,000m thick deposits.

Marine shale facies of the upper Akata formation has

been arguably accepted to be the primary source rock of

the region with possible contribution from interbedded

marine shale of the Akata formation(fig 4). A faulting

system within Agbada formation provides pathways for oil

migration from the presumed Akata formation source rock

to Agbada formation where the dominant sands serve as the

reservoir rock while the shale act as seal above the

sand. The faulting in Agbada also serves as a structural

trap and jointly with stratigraphic traps play vital

roles in hydrocarbon entrapment.

Fig 2: Delta lithostratigraghic view

The extent of this petroleum system is defined by the

areal extents of the field containing approximately known

resources (cumulative production plus proved reserves) of

34.5 billion barrels of oil (BBO) and 93.8 trillion feet

of gas (TCFG) (14.9 billion barrels of oil equivalent,

BBOE) (Petrol consultants, 1996a).

Most of the oil fields are mainly based onshore or on

continental shelf in waters not less than 200 meters

deep(fig 1).

Fig 3: Stratigraphic framework

Fig 4: Sequence stratigraphic model of Niger Delta

3.0 NIGER DELTA OIL AND GAS

The physical and chemical properties of oil and gas in

the Niger Delta vary a lot as the causes are ascribed to

differences in the original organic material of the

source rock, differences in depositional environment,

initial processes in the transformation of the organic

matter, changes in physical and chemical conditions at

the time of oil generation e.t.c.

Based on API which is given as (141.5/specific

gravity)-131.5, the oil in Niger Delta has a gravity

range of 16-50 API with lighter oil having a greenish-

brown colour (whiteman 1982). 56% of the Niger Delta oils

have an API gravity between 30 and 40 (Thomas, 1995) and

for this reason, has been categorized as light crude oils

due to its high API. In addition, most oils in the delta

is classified as sweet crude oils because they contain

low sulphur content of 0.1-0.3% (mendi,1996) which makes

the crude oils to be highly marketable in the oil and gas

market.

The gas present in oil is only detectable with seismic

images usually viewed as bright spots. In the Delta, the

crude oils contain hydrocarbon gas in solution and is

said to be saturated, eventually, the hydrocarbon gas

caps the oil. Currently, only 15% of the gas produced is

marketed (Energy information, 1998b).

4.0 NIGER DELTA OIL AND GAS GRATIFICATION

As of today, in a technological global village and

with daily demanding activities of humanity, hardly will

a man not be involved in the consumption of oil and gas

be it directly or indirectly. To an attestable level, it

is obviously established that the possession of oil and

gas has grossly contributed to economy of Nigeria.

Among the provinces ranked in the U.S. Geological

Survey's World Energy Assessment (Klett and others,

1997), the Niger Delta province is the twelfth richest in

petroleum resources, with 2.2% of the world’s discovered

oil and 1.4% of the world’s discovered gas

(Petroconsultants, Inc. 1996a).

In terms of global recognition and reputation, Niger

Delta oil now boast a crude oil benchmark known as BONNY

LIGHT OIL as a reference oil price. Bonny light oil is

characterized by high API gravity and low sulphur

content. High API defines the oil to be less dense and

thus, much valuable in the oil and gas market and its low

sulphur content makes it a highly desired grade for its

low corrosiveness to refine metals and infrastructures

and for its lower environmental impact of its buy

products in refinery effluent. Bonny light is precisely

in high demand by American and European refineries. Even

though US have reduced their bonny light oil demand,

still, bonny light oil still pose a major source of

income for an oil rich Nigeria.

Based on recent assessment carried out on undiscovered

quantity of oil and gas in Niger Delta province, about

40.5 billion barrels of oil and 133 trillion cubic feet

of gas are yet to be discovered. Factually, there are

still enough oil and gas to be explored in order to cater

for the economic development of the nation.

5.0 CONCLUSION AND RECOMMENDATIONS

Today, petroleum resources account for about 99% of

the national economy. In the global scene, Nigeria is

ranked 6th in OPEC and 14th in the World in terms of oil

production. Currently, Nigeria has bountifully benefited

from the oil and gas resources of Niger Delta in order to

boost both economical and global reputation of the

country. However, in spite of the level of corruption,

over dependence on oil an gas and environmental effects

such as water pollution, oil spillage, global warming as

a result of gas flaring e.t.c caused through the

production of oil and gas, its rigidly established that

to the nearest future, the country can substantially glow

and productive provided adequate measure are taken.

In this report, I would recommend that the refineries

in Kaduna, Lagos and Delta are further equipped and

actively empowered to ease the need of refining oil in

oversea. Also, in addition to the refineries we have,

more refineries should be built in order to enhance oil

and gas production.

Currently, only 15% of the oil produced in Niger Delta

is marketed while 75% is flared and 10% is used for

reservoir maintenance. Alternatively, government can

invest in gas production which will be an addition to

production and also reduce flaring of gas which

contributes to global warming.

Despite inadequate documentations on the Cretaceous

rock underlying Akata formation, possibly, with the aid

of further research, there could be hydrocarbon formed

within the formation. To tackle environmental issues,

government should put down more measures to reduce the

effects and strictly monitor situations.

REFERENCES

USGS: The Niger Delta Petroleum System: Niger Delta

Province, Nigeria, Cameroon, and Equatorial Guinea,

Africa by Michele L. W. Tuttle,1 Ronald R. Charpentier, 1

and Michael E. Brownfield1 Open-File Report 99-50-H 1999

GEY 404: PETROLEUM GEOLOGY Bayonle A. Omoniyi ADEKUNLE

AJASIN UNIVERSITY, AKUNGBA, ONDO STATE, NIGERIA

DEPARTMENT OF GEOLOGY 6th September, 2012

Energy Information Administration, 1998b,

<http://www.eia.doe.gov/emeu/

world/country/cntry_NI.html>

Petroconsultants, 1996a, Petroleum exploration and

production database: Houston, Texas, Petroconsultants,

Inc., [database available from Petroconsultants, Inc.,

P.O. Box 740619, Houston, TX 77274-0619].