PETROLEUM PROSPECTS OF BOTSWANA

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PETROLEUM PROSPECTS OF BOTSWANA

• Presented By
• T. Hudson NgwisanyiDepartment of Geological
  SurveyBotswana

Botswana Resource Sector Conference, July 2007
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• prospect (pros'pekt') n.
• Something expected a possibility.
• prospects
• Chances.
• Financial expectations, especially of success.
• A potential customer, client, or purchaser.
• A candidate deemed likely to succeed.
• The direction in which an object, such as a
  building, faces an outlook.
• Something presented to the eye a scene a
  pleasant prospect.
• The act of surveying or examining.
• The location or probable location of a mineral
  deposit.
• An actual or probable mineral deposit.
• The mineral yield obtained by working an ore.

http//www.answers.com/topic/prospecting?catbiz-f
in
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Riding a Dead Horse

• Dakota tribal wisdom says that when you discover
  you are riding a dead horse, the best strategy is
  to dismount.
• However, in business we often try other
  strategies with dead horses, including

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• Buying a stronger whip.
• Changing riders.
• Appointing a committee to study the horse.
• Arranging to visit other countries to see how
  other culturesride dead horses.
• Lowering the standards so that the dead horse can
  be included.
• Reclassifying the dead horse as 'living
  impaired'.
• Hiring outside contractors to ride the dead
  horse.
• Harnessing several dead horses together to
  increase speed.
• Providing additional funding and / or training
  to increase dead    horse's performance.

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•     10. Doing a productivity study to see if
  lighter riders would improve the dead horse's
  performance.    11. Declaring that as the dead
  horse does not have to be fed, it is less costly,
  carries lower overheads and therefore contributes
  substantially more to the bottom line of the
  economy than do some other horses.    12.
  Rewriting the expected performance requirements
  for all horses.    And of course ..    13.
  Promoting the dead horse to a supervisory
  position!

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Legislation

• Petroleum (Exploration and Production) Act 1981
• Ownership and control of petroleum in Botswana
  are vested in the republic.
• PLs issued by the Minister
• Administration of exploration and development of
  petroleum deposits fully described in Act.

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Exploration History

• 1961 1963 Study by Standard Vacuum Oil
  Company to investigate availability and nature of
  source rocks.
• 1966 Philadelphia Oil Company granted an oil
  PL.
• Applications also filed from Kalahari Oil
  Exploration Company (1977) and Alpha Exploration
  (1967).
• No active exploration actually carried out by
  either of the companies.
• No oil PLs issued in Botswana since then

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• Shell Coal Botswana (Pty) Ltd 1977
• Indicated that there were good source rocks in
  the Karoo.
• Recognised potential reservoirs and cap rocks as
  well as structural traps.
• For maturity thickness gt 2,500m
• Such thickness possible in the Kalahari and
  Okavango.

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• Department of Geological Survey
• Mineral Resources Summary Report 1965
• Indicated that Dwyka contained probable marine
  formations, which could serve as suitable source
  rocks.
• Speculated that Karoo underlain by Nama in which
  oil seepages and asphalt veins reported from
  outcop in Namibia
• PCIAC 1989 (seismics drilling)
• STRAT-1 and STRAT-2 1998
• JOGMEC - 2007

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Encouraging Observations from elsewhereGas and
Oil Showing in Namibia

• Walter et al, 1996
• Seepages in fissures in the Fish River sandstones
• Oil in fault breccia in the Kuibis ss
• Oil in fluid inclusions
• Bitumen and coke-like material at Vreda-281

JOGMEC, Walter et al, 1996
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First Step

• Regional Gravity survey 1973
• 10 km stn interval
• Funded by UK

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Reconnaissance Aeromagnetic Survey of Botswana
Geological Interpretation
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• NOTABLE REFERENCES
• Clark-Lowes, D. D. and Yeats, A. K. (1977) The
  hydrocarbon prospects of Botswana, Shell Coal
  Botswana.
• ECL (1998a) Petroleum potential of the Karoo of
  Botswana, Exploration Consultant Ltd.
• ECL (1998b) Petroleum potential of the Nama
  Basin, western Botswana, Exploration Consultant
  Ltd.
• ECL (1998c) Oil and gas stratigraphic drilling
  project Botswana, Exploration Consultant Ltd.
• Hiller, K., Buttkus, B. and Bosum, W. (1990)
  Technical cooperation hydrocarbon exploration,
  investigation on selected samples of Masetlheng
  Pan-1/SW Kalahari, Ministry of Mineral Resources
  and Water Affairs, Geological Survey Department.
• Letullier, A. (1995) Southwest African offshore
  and Nama-Kalahari basins, Africa Exploration
  Opportunities, Petroconsultants S.A.
• Stoakes, F. A. and McMaster, D. W. (1990)
  Interpretation of the results of stratigraphic
  well Masetlheng Pan-1 in the Nosop/Ncojane basin
  of southwest Botswana, Boyd Exploration
  Consultants Ltd. and Stoakes Campbell
  Geoconsultting Ltd.
• Walter, M., Swart, R. and Summons, R. (1996) Oil
  and gas shows numerous in Nama Basin, southern
  Africa, Oil Gas Journal, Nov 25, 76-80
  Geological Interp

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Database

• PCIAC seismic data
• Masetlheng Pan 1, STRAT-1 and STRAT-2
• ECL reports
• VREDA 281
• ACP-20, ACP-21 (Anglo American Prospecting
  Services)
• Various reports

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Database

• Gravity map of southern Africa (modified after
  ULIS, 1990 by JOGMEC, 2007).

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Regional Karoo Basin Disposition
ECL, 1998
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SUMMARY LITHOSTRATIGRAPHY AND PALAEOENVIRONMENTS
Modie, 2007
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Petroleum Geology

• From ECL (1989, 1998) and JOGMEC (2007)
• Focus on Nama Basin situated in Botswana and
  Namibia

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• Masetlheng Pan-1 Drilled in 1989. TD 4016.3m.
  Located in an area where the youngest pre-Karoo
  sediments are present and preserved.
• About 2500m thick Nama Group penetrated.
• 143m thick diorite encountered (causing high
  maturity)
• Shales interpreted to be part of the basal Nama
  marine transgressive sequence TOC values of
  0.13 and 0.38 (At TSES-1 TOC is 0.12-0.34).
• Projection of around 1 TOC after correcting for
  present day maturity levels
• Algal/bacterial origin material, therefore oil
  prone
• STRAT-1 1996. TD2001m (Nama at 607m)
• STRAT-2 1997. TD2149m (Nama at 415m)
• Facies types encountered include red sandstones,
  siltstones and shales with occassional dark grey
  or black shale intervals towards the base
  (STRAT-1 only) fluvial sequence or marine
  influences

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Karoo Supergroup

• Source rock potential of Karoo Supergroup Ecca
  Group composed of black shales and coals. TOC
  values of 2.02-10.72 at W2 and W3 wells.
• Macerals in the coals composed of vitrinite and
  inertinite, indicating kerogen of type III (gas
  prone).
• Stokes and McMaster (1990) also documented the
  occurrence of type III-IV kerogen, although with
  minor generative potential for gas.

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• Liptinite, which may be able to generate and
  expel oil, has been reported in coal fields in
  the Mid-Zambezi Basin northeast of Botswana
  (Oesterlen and Lepper, 2005). If liptinite is
  abundant in the macerals of the Karoo Surpergroup
  in the Nama Basin, oil generation could be
  expected. Oesterlen and Lepper (2005) showed that
  coal from the Lubimbi coal mine in the Karoo
  Supergroup consists of 1033 liptinite.
• Hiller et al. (1990) reported vitrinite
  reflectances of 0.62 and 0.60 at depths of 925
  m and 934 m in the Dwyka Group at Masetlheng
  Pan-1.

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• Reservoir Properties
• The Karoo Supergroup has not undergone strong
  diagenesis and the reservoir quality of the rocks
  is good. Clark-Lowes and Yeats (1977) reported an
  average porosity of 8.6 for the Ecca Group, and
  a porosity of 15.3 and permeability of 414 md
  (millidarcies) for a Stormberg sandstone. The
  porosity values of rocks in this group range from
  23 to 31 (ECL, 1998a).
• The quality of reservoir rocks in the Nama Group
  is considered low due to diagenesis and
  overcooking of the source rock (ECL, 1998c). It
  is therefore unlikely that a petroleum system
  exists within the Nama Group.

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• ECL (1998) conducted 1D basin modeling for the
  geology at Masetlheng Pan-1 considering repeated
  uplift during the Jurassic and Cretaceous-Paleogen
  e periods.
• JOGMEC (2007) also carried out 1D basin modeling
  to evaluate the timing and volume of hydrocarbon
  generation and expulsion in the Karoo Supergroup.
  As Masetlheng Pan-1 is located at the center of
  the basin, and the Karoo Surpergroup is the
  deepest in the basin, the location of Masetlheng
  Pan-1 is regarded as a suitable site for 1D basin
  modeling.
• an optimistic scenario indicated the generation
  of hydrocarbons in the Ecca Group in the middle
  Jurassic. However, as the Nama Basin underwent
  significant uplift of more than 2000 m after this
  time, the seal would likely have been destroyed
  in the large-scale diastrophism, allowing any oil
  and/or gas accumulated before the uplift to
  escape. Furthermore, no trapping structures for
  the accumulation of hydrocarbons were found in
  the 2D seismic sections. Therefore, JOGMEC
  concluded that it is unlikely that oil and/or gas
  fields exist in the northern Nama Basin.

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Conclusions

• Hydrocarbons may have been generated and trapped
  in the Karoo sediments.
• Phases of uplift/cooling are recorded in Late
  Jurassic/ Early Cretatious and Mid Tertiary
• Petroleum source rocks are predicted in the Lower
  Nama on the basis of lithological and
  environmental considerations (transgressive
  marine shales)
• Thermal history reconstruction shows that lower
  Nama sediments probably attained tempretaures in
  excess of 200oC just prior to uplift and cooling
  at around 420Ma.
• STRAT-1 and STRAT-2 indicate the northern Nama
  basin is overcooked

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Recommendations

• The southern Nama basin has not been explored.
  Gravity shows that it is shallower than the
  north, therefore could have undergone lower
  temperatures than the north.
• Recommend seismics and exploratory holes in the
  south.
• There has been no follow-up of the seismics done
  in the Passarge Basin. No conclusions can
  therefore be made on its prospectivity.

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Fast forward to 2013

• Botswana discovers oil in the Passarge Basin!
• (after flogging the dead horse)