NIGER, WITH NEW OIL LEGISLATION, OFFERS LITTLE DRILLED ACREAGE FOR EXPLORATION
Alain Bruneton
Beicip
Rueil-Malmaison, France
The Ministry of Mines and Energy of Niger has released acreage in East Niger to the international oil industry.
Four blocks will be opened in a first step with no fixed time schedule for offers.
The blocks are largely underexplored and are near significant oil indications.
Niger, between Algeria and Nigeria, represents a transitional link between North Africa and Central Africa.
The Republic of Niger, with the exception of its capital Niamey, is sparsely populated with 7 million people on a 1.3 million sq mile territory (Fig. 1).
Easy communications exist with neighboring Nigeria, Mali, and Chad.
The arid climate allows for year round working conditions and easy access to opened areas.
COMPANIES INVITED
Niger's Ministry of Mines and Energy, in charge of the hydrocarbon sector, has called for foreign investments in oil exploration.
For this purpose, it has taken three main actions. They are:
- Working out new petroleum legislation. The new law provides better conditions for operators than the previous one (table).
- Elaboration of a petroleum evaluation report by the Ministry of Mines and Energy and Bureau d'Etudes Industrielles et de Cooperation de 'Institute Francais du Petrole Beicip).
- Opening of large acreage in East Niger to the international oil industry (Fig. 2).
EXPLORATION HISTORY
Societe de Participations Petrolieres (Petropar) of France pioneered exploration in 1960 for Paleozoic objectives in the Djado and Talak basins.
Global Energy was awarded a prospecting permit in 1970-79 for exploration of the northeastern areas, known as the Kafra-Seguedine grabens. Global and Sun Oil were granted exploration rights in the Dosso area during the same period.
Texaco and later Esso explored in 1970-80 in the Agadem basin, where they drilled seven wells. Some of the wells yielded good indications of oil.
Elf was granted exploration rights in 1978 in the Dosso, Manga, and Bilma areas. After relinquishing these blocks, Elf took participation on the Agadem permit in 1980.
The first modern extensive seismic was shot in Agadem and a few more wells were drilled. Two of the wells, drilled by Soekor in 1982 and Goumeri in 1990, yielded positive results.
Elf and Esso were awarded a new permit in the Agadem basin in 1985. The permit was renewed in 1990, and 50% of the acreage was released.
OPENED ACREAGE
Block delineation in the opened acreage has been supported by a two fold consideration.
- Propose to the investors large incentive areas.
- Give them the opportunity to choose among several exploration objectives, such as Paleozoic platform basins or rift basins from various ages and various structural styles.
Four blocks are proposed for licensing. The Djado block covers 142,000 sq km with Paleozoic objectives. The Kafra block covers 23,000 sq km with Tertiary, Cretaceous, and older rift sequences as objectives.
The Bilma block covers 60,800 sq km with early Cretaceous to older rift sequences as objectives. The Tenere block has 67,300 sq km as objectives with Tertiary, Cretaceous, or older objectives.
These four blocks do not encompass Niger's entire prospective domain.
Large areas in the lullemeden basin remain nearly unknown due to lack of data. Supplementary acreage in these areas could be granted to applicants.
GEOLOGY
Very briefly, the sedimentary basins of East Niger can be explained by the presence of two megastructures.
- An old Paleozoic platform basin. Due to subsequent tectonic and erosional phases this Paleozoic platform is presently limited to the relic Djado basin, the southern part of the Mourzouk basin of Libya.
- A younger rift basin system. The system is expressed by two sets of features.
One consists of elongated, north to northwest striking furrows interpreted as the result of successive rifts and sag phases, active since Permo-Triassic to as recent as Tertiary. These depressions are known as the Kafra, Bilma, Tenere, Grein, and Agadem grabens.
The other consists of large basement outcrops such as the Tenere, Air, and Zinder massifs, which correspond to the shoulders of the rifted zone.
STRATIGRAPHY, LITHOLOGY
Due to the scarcity of data in many places or to the important thickness of sediments in the grabens of more than 10,000 m, many stratigraphic intervals remain unknown or speculative.
A composite type section covering both the Paleozoic platform basins and rift basins is presented (Fig. 3).
RESERVOIRS, SEALS
Very good clastic reservoirs, mostly from fluviatile to lacustrine origin, are found in both types of basin.
Potential reservoirs are present in Eocene, Maastrichtian, Campanian, Albian, early Carboniferous, early Devonian, and Cambro-Ordovician.
Seals have been indicated at several stratigraphic levels such as Oligocene, Senonian, Carboniferous, and Silurian.
SOURCE ROCKS, MATURITY
Several source rocks are found in the drilled sections.
They are Eocene-Oligocene lacustrine shales, Senonian marine shales, and Silurian shales.
Because of various structural configuration in the sub-basins, each source rock may be found in a favorable situation regarding its maturation stage.
As they have never been drilled, some intervals such as early Cretaceous and older remain unknown as far as sourcing possibilities are concerned.
STRUCTURES, PLAYS
Several plays have been successfully tested, and others have been documented through the Beicip study (Fig. 4).
They include:
- Crests of tilted blocks in the various rift sequences.
- Composite structure (horstlike trends or flowers) in Cretaceous and Tertiary sequences.
- Large anticlines or the possibility of regional stratigraphic traps such as pinch out of early Devonian in the Djado basin.
HYDROCARBON POTENTIAL
Recent discoveries in South Agadem graben confirm the oil potential of this 1,000 km long rift system.
A major part of it remains underexplored.
On the other hand, the Paleozoic Djado basin should come in the limelight again, considering the oil reserves that have been reported from the Libyan Mourzouk basin further north.
Copyright 1991 Oil & Gas Journal. All Rights Reserved.