Samuel Oben Djan,Lead Geoscientist at GNPC spoke at the Oil & Gas Event June 2013

1. NEOPROTEROZOIC PLAYS AND
HYDROCARBON CONTROL
Samuel Obeng-Djan
Lead Geoscientist
THE EMERGING POTENTIAL OF THE
INLAND VOLTAIAN BASIN OF GHANA

2. OUTLINE
 Global Hydrocarbon Source Distribution
 The Global Neo-Proterozoic (Infra-Cambrian)
Hydrocarbon Prospectivity
 Implication to the Voltaian Basin
 Where next?
 History of Exploration in Voltaian Basin
 The Voltaian Basin: Emerging Potential in West Africa

3. THE GLOBAL NEO-PROTEROZOIC (INFRA-
CAMBRIAN) HYDROCARBON PROSPECTIVITY

4. WHAT DO WE KNOW ABOUT GLOBAL
HYDROCARBON OCCURRENCE?
Western Canada
& Onshore US
75,000 Reservoirs/Pools
Western Canada
& Onshore US
75,000 Reservoirs/Pools
Western Canada
& Onshore US
75,000 Reservoirs/Pools
GLOBAL DISTRIBUTION OF OIL & GAS POOLS – >120,000 fields Nadeau et al. (1995)

5. CIRCLE OF KNOWLEDGE
Fieldwork in North
Africa including the
Taoudenni Basin in
Mauritania, Algeria
and Mali; the Anti-
Atlas region of
Morocco and the
Cyrenaica, Kufra and
Murzuk basins in
Libya has added to the
understanding of
reservoir, source
and seal relationships
and confirmed the
widespread presence
of Precambrian
potential reservoir
facies.

6. WHAT DO WE KNOW ABOUT PRECAMBRIAN
PETROLEUM SYSTEMS OF AFRICA ?
1
EXPLORER’S QUESTIONS
1) ARE ALL THESE LOCATIONS THOROUGHLY EXPLORED
2) ARE SIMILAR GEOLOGICAL LOCATIONS UNEXPLORED/UNKNOWN
3) DO DIFFERENT GEOLOGICAL SCENARIOS EXIST THAT ARE UNTRIED
CRAIG et al, 2009

7. WHAT DO WE KNOW ABOUT PRECAMBRIAN
PETROLEUM SYSTEMS OF THE AFRICA ?
2
EXPLORER’S QUESTIONS
1) ARE ALL THESE LOCATIONS THOROUGHLY EXPLORED
2) ARE SIMILAR GEOLOGICAL LOCATIONS UNEXPLORED/UNKNOWN
3) DO DIFFERENT GEOLOGICAL SCENARIOS EXIST THAT ARE UNTRIED
CRAIG et al, 2009

8. WHAT DO WE KNOW ABOUT PRECAMBRIAN
PETROLEUM SYSTEMS OF THE AFRICA ?
3
EXPLORER’S QUESTIONS
1) ARE ALL THESE LOCATIONS THOROUGHLY EXPLORED
2) ARE SIMILAR GEOLOGICAL LOCATIONS UNEXPLORED/UNKNOWN
3) DO DIFFERENT GEOLOGICAL SCENARIOS EXIST THAT ARE UNTRIED
CRAIG et al, 2009

9. The Neoproterozoic–Early Cambrian period can
be broadly divided into three distinct phases
related to global tectonics and climate:
1. Tonian–Early Cryogenian: c.1000–750 Ma;
2. Mid-Cryogenian–Mid-Ediacaran: c. 750–
600 Ma;
3. Late Ediacaran–Early Cambrian: c. 600–500
Ma.
THE NEOPROTEROZOIC–EARLY CAMBRIAN
PERIOD

10. The Late Ordovician–Early Silurian petroleum system in North Africa – an analogue for
the Voltain Neoproterozoic reservoir–source rock relationships?

11. THE NEOPROTEROZOIC–EARLY CAMBRIAN PERIOD CON’T
• Recent fieldwork in the Taoudenni Basin in Mauritania
• The Anti-Atlas region of Morocco
• The Al Kufrah Basin in Libya,
• The Naguar–Ganganagar Basin of Rajasthan,
• The Son Valley of central India
• The Himalayan foothills of NW India by members of
the Maghreb Petroleum Research Group

12. Where next?
THE VOLTAIN BASIN
• One of the four (4) sedimentary
Basins of Ghana
• It is the largest sedimentary basin in
Ghana
• An Inland basin of size 103,600 sq
km (covers about 40% of Ghana’s
land mass)
• Basin extends into Togo and Benin
VOLTAIAN

13. ©GNPC 2013
Exploration History
• Romania Reconnaissance Geological Work
from 1925-1932
• P. Davis Gravity Survey from 1957-1958
• Ghana/USSR borehole drilling from 1962-
1965
• Shell/CGG Airborne Magnetic Survey from
1970-1971 (Premuase -1 Well)

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• EU/ GOG funded MSSP data
• Limited seismic data (208 km 2-D)
• Shallow Premuase-1 well (1167m) or 3830 feet
• Deep water borehole (700m)
• Various individual reports dealing with various
aspects of the basin’s geology and geophysics
DATA BASE

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Geology
• Thick Voltaian sediments, overlie non-conformably on
Precambrian to lower Paleozoic formations.
• The Voltaian is an asymmetrical depression filled with
sediments of Late Precambrian or Infra-Cambrian to
Lower Paleozoic age.
• Some areas are considered as young as Devonian
Carboniferous in age, with thickness of over 6,000m.
• The Lithology comprises of
sandstones, mudstone, shale and limestone. The
sandstones are massive and conglomeratic in places.

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GEOLOGICAL MAP

17. MSSP Data interpretation
• a major deep basin underlies
the centre of the survey
area, with a second shallower
sub-basin located to the
northeast
• Thickness of the various
sections of the basin ranges
from deepest (> 6000m); in the
northern & southern half of the
basin.
• Shallower zones of 500m
depth mapped in SW & fringes
basin.
• Averagely, the whole basin has
over 1000m sediment

18. ©GNPC 2013
• Gas shows were also reported from some
of the water bore-holes drilled.
• The basin deepened in the center and
stratigraphic traps were likely to occur.
• Some of the bore-holes showed traces of
heavy oil.
WHY SO MUCH INTEREST?

19. ©GNPC 2013
WHY SO MUCH INTEREST?
• Bitumen found impregnated in
limestone, shale and sandstone
sequence forming the middle Voltaian
• Saline waters that are associated with
hydrocarbons were found in these
bore- holes and were also found to be
of a chloro-calcic content

20. ©GNPC 2013
WHY SO MUCH INTEREST?
• > 6000m of sediment fill in the
basin.
• The lower members of the Voltaian
rocks are folded.
• It also revealed the occurrence of
limestone and other sandstones that
could serve as reservoir rocks.

21. ©GNPC 2013
WHAT’S NEXT?
• INITIAL PHASE
 General geological and geophysical (G&G) Studies, Review &
Interpretation of MSSP Data.
 Satellite Imagery and Aero-photo Acquisition and Interpretation
 Reconnaissance Geological Fieldwork
 Integration of all G&G information to form the basis of selection of
locations for slim hole drilling
 Actual Slim-hole Drilling Operations
 Laboratory Analyses & interpretation of field samples and conclusions

22. Voltaian Basin-Current Status
• Evaluation & Award of contract for the
drilling of slim holes is underway
• Analysis of the data will establish the
petroleum system and enhance the
knowledge base
• That will end Phase I ( expected to be
completed by the end of the year 2013)
• Phase II will begin with Investor
participation.

23. ©GNPC 2013
Join us in Phase II
Thank You
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