Petroleum Geology and Exploration Opportunities in Kenya 11th Africa Conference for Oil and Gas Kenyatta International Conference Centre, Nairobi, - Kenya, (23rd – 25th May, 2007) - PowerPoint PPT Presentation

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Petroleum Geology and Exploration Opportunities in Kenya 11th Africa Conference for Oil and Gas Kenyatta International Conference Centre, Nairobi, - Kenya, (23rd – 25th May, 2007)

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Title: Petroleum Geology and Exploration Opportunities in Kenya 11th Africa Conference for Oil and Gas Kenyatta International Conference Centre, Nairobi, - Kenya, (23rd – 25th May, 2007)


1
Petroleum Geology and Exploration Opportunities
in Kenya11th Africa Conference for Oil and Gas
Kenyatta International Conference Centre,
Nairobi, - Kenya, (23rd 25th May, 2007)
  • Mr. Don Riaroh
  • Director EP
  • Ministry of Energy
  • Kenya

NOT AN OFFICIAL UNCTAD RECORD
2
Contents
  • 1. Introduction
  • 2. Past Exploration Activity
  • 3. Why Past Petroleum Exploration Activity Failed
  • 4. Petroleum Geology Exploration Activity
  • 5. Conclusion

3
Introduction
  • The first Exploration Licence issued to dArcy
    in 1937 in Lamu Embayment near Mombasa in Kenya.
  • Active Oil exploration in Kenya commenced in 1954
    when Oil Exploration License (OEL1) was granted
    to B. P Shell Development Company to operate in
    Lamu Embayment.
  • Initial Exploration (1950s 1980s)
    concentrated in the Lamu Embayment. Interest
    later expressed in other areas, Anza 1975-1990,
    Tertiary Rift 1990, offshore (I) 1978-1985,
    offshore (II) 2003-present

4
Introduction
  • Sedimentary Basins of Kenya
  • Kenya has four major sedimentary Basins with
    approximate total area of 400,000 sq. km. These
    are
  • Anza Basin 82,000 sq km
  • Lamu Basin 170,000 sq. km
  • Mandera Basin 44,000 sq km
  • Tertiary Rift 105,000 sq km

5
Past Exploration Activity
6
Past Exploration Activity
No. of Wells 31
7
Past Exploration Activity
Seismic Coverage Map
8
Past Exploration Activity
Total Seismic Coverage 85,617 km
9
Past Exploration Activity
Past Air-Mag Surveys
10
Past Exploration Activity
Total Air-Mag Coverage 148,099 km
11
Why Past Exploration Efforts Failed
  • Many wells drilled were shallow stratigraphic
    tests, which did not fully evaluate the prospects
    /targets e.g (Walu-1, Pandangua-1 and Meri-1, in
    1959- 60, and Mararani-1 in 1961)
  • Many wells were drilled using poor quality
    seismic data eg Walu-2 (1963) and Wal Merer-1
    (1966)
  • Many wells were poorly sited and or drilled on
    poorly defined structures
  • Some wells were drilled without geological and
    geophysical justification e.g Ria Kalui Well
  • Premature abandonment eg Simba-1

12
Why Past Exploration Effort Failed
Many wells were drilled using poor quality
seismic data eg Walu-2 (1963) and Wal Merer-1
(1966)
Poor quality seismic data
13
Why Past Exploration Effort Failed
Many wells were drilled on poorly defined
structures
Most of the Anza Wells do not show full closure
Time Structure Map - Top Cretaceous
14
Why Past Exploration Effort Failed
Poorly sited well
Time Structure Map - Top Cretaceous
15
Why Past Exploration Effort Failed
  • Kaisut Well located off the Crest

16
Why Past Exploration Effort Failed
No defined Trap
17
CENTRAL AFRICAN RIFT SYSTEM
18
Petroleum Geology and Exploration Opportunities
  • Anza Graben
  • The Anza Graben is part of the Central Africa
    Fault system
  • trends northwest- southeast and extends across
    much of eastern and northern Kenya.
  • The Basin consists of three sub-basins the South
    Anza, North Anza, and North Anza Extension.
  • The total surface area of the entire Anza Basin
    is approximately 94,220 sq km.
  • Much of the South Anza Basin is separated from
    the Mandera Basin by the extensive Lagh Bogal
    fault and from the Lamu Embayment by the Muchesa
    Highborder fault.

19
Petroleum Geology and Exploration Opportunities
  • Anza Graben Contd..
  • Contains Late Jurassic to Mid-Cretaceous
    fluvial-Lacustrine sediments analogous to the
    Abu-Gabra Rift Basin where oil production has
    been established.
  • The Anza wells, however, may never have
    penetrated deeply enough to test the equivalent
    Neocomian to Lower Albian section which comprises
    the source and reservoir units of the Unity and
    Heglig fields of Sudan.

20
Petroleum Geology and Exploration Opportunities
  • Anza Graben Contd..
  • Reservoirs
  • Target reservoirs occur throughout the
    stratigraphic section. Reservoir objectives in
    the South Anza Basin include continental deposits
    of the Karroo Tertiary fluvial, deltaic, and
    occasional lacustrine sandstones and Lower
    Jurassic carbonates. Continental fluvial and
    lacustrine sandstones (Cretaceous through
    Tertiary) comprise the potential reservoir units
    of the North Anza Basin. In addition, Neocomian
    Nubian continental sandstones are postulated to
    occur in the North Anza Basin Extension.
  • Seals
  • Most reservoirs in the South Anza Basin are
    overlain by regional, transgressive marine
    shales. In the northern portions of the Anza
    Basin, evaporites (Jurassic), as well as
    interbedded shales and volcanics (Cretaceous
    through Tertiary), should provide very effective
    seals for the reservoirs in these areas.

21
Petroleum Geology and Exploration Opportunities
  • Anza Graben Contd..
  • Source Rocks
  • The most favorable source rocks throughout the
    entire Anza Basin are Neocomian through Lower
    Albian shales. Similar potential exists within
    the Lower Tertiary Paleogene.
  • Trapping Configurations
  • Structural traps have been observed in sections
    ranging from Karroo through Tertiary. Tilted
    fault blocks, horsts, and large rollover
    structures (related to listric faults) are
    common. There is also potential for untested,
    wrench-related structures in the South Anza
    Basin. In addition, stratigraphic traps may exist
    in the southern basinal areas where interbedded
    sequences of lacustrine sandstones and shales
    provide a very effective reservoir, source, and
    seal.

22
Petroleum Geology and Exploration Opportunities
Seismic Section Across Anza
23
Petroleum Geology and Exploration Opportunities
  • Lamu Embayment
  • This is Kenya's largest basin with an area of
    170,000 sq. km
  • encompasses depocenters located in both onshore
    and offshore southeast Kenya
  • Although the Lamu Embayment has a long history of
    onshore exploration, recent efforts have been
    limited. The last well drilled was the
    Petro-Canada KenCan Well (1986).
  • Although production has not been established in
    the Lamu Embayment, hydrocarbon potential has
    been indicated by cuttings, fluorescence and
    shows of gas in wells penetrating Cretaceous
    through Tertiary sections.

24
Petroleum Geology and Exploration Opportunities
Evolution of Lamu Embayment
  • Lamu Embayment
  • Continental sag, Karoo rifting 400km of
    continental deposits
  • Minor marine incursions
  • Break-up Gondwanaland drifting of Madagascar in
    upper Jurrassic giving rise to Major marine
    transgression and Deposition of deep/distal
    marine sediments
  • Drifting of Madagascar, India Antarctica
    continued until Aptian times creating the Davy
    Fracture Zone
  • Marine sedimentation continued along E. Africa
    Coast
  • Albian, Aptian limestones are observed in Hargaso
    1, Wal-Merer 1 wells.

25
Petroleum Geology and Exploration Opportunities
  • Lamu Embayment Evolution Contd..
  • Tertiary sedimentation controlled by the Davy
    Fracture Zone (DFZ)
  • The DFZ Divides offshore Lamu into two parts.
  • Northern section reduced sedimentation showing
    gravity sliding and mass movement structures
  • Southern section which show extensional basins
    which have undergone extension

26
Petroleum Geology and Exploration Opportunities
  • Off-Shore Lamu Embayment Contd..
  • Source
  • Hydrocarbon seeps in Pemba Island
  • Late Cretaceous black shales DSDP 241
  • Onshore evidence exists for the presence of
    potential source rocks in Lower Tertiary marine
    shales. Maturity of the known shale units may be
    suggested by oil and gas shows present in the
    Kipini and Dodori wells. In addition, significant
    quantities of gas were measured in the Pate Well
    while drilling through Lower Eocene sandstones.
  • Other possible source rocks include units within
    the rift sequence of the Early Jurassic and
    pre-rift sequences of the Karroo. Jurassic rift
    sediments, buried to depths of 6,OOOm before the
    Late Cretaceous uplift, may have generated
    hydrocarbons which then migrated into Neocomian
    sand- stones. The possibility of source rocks
    occurring in marine shales of the Karroo must
    also be considered.

27
Petroleum Geology and Exploration Opportunities
  • Off-Shore Lamu Embayment Contd..
  • Reservoirs
  • Drilling and outcrop studies have confirmed the
    presence of potential reservoirs which range in
    age from the Permian to the Neogene. Karroo
    continental sequences (as observed in outcrop)
    include Mazeras sandstones, Carbonates such as
    the Jurassic Kambe Limestone (oolitic),
    Cretaceous Freretown Limestone, and Tertiary
    carbonate build-ups. The best reservoir potential
    likely remains in Tertiary progradational
    sandstones.
  • Reservoir
  • Simba-1, Pomboo-1- encountered upper crateceous
    paleocene turbidite sands
  • Kofia -1, Kipini wells Eocene-Upper cretaceous
    Blockly argillaceous and calcareous sandstone (F
    15 to 25)
  • Seal Pomboo has encountered thick shale
    sequences
  • - Other seal facies could include evaporite
    sequences

28
Petroleum Geology and Exploration Opportunities
  • Off-Shore Lamu Embayment Contd..
  • Trapping Configurations
  • Four way structural traps
  • Simba, Pomboo,Tumbusi etc formed by sediment flow
    flow
  • Fault bounded structural closures along the
    Davy-Walu high
  • Prevalent trapping configurations include
    block-faulted anticlinal structures with
    associated antithetic faults. These structures
    are related to tension and compaction on the
    continental margin.
  • Seismic sections reveal that radially arranged
    fault traps over the crests of salt structures
    are common along the near-shore areas of the
    coast.
  • Potential leads for stratigraphic trapping have
    been observed where pinch-outs of the Tertiary
    sandstones onto the Cretaceous, or the Cretaceous
    onto the Jurassic, have occurred (on the flanks
    of the Garissa High, for example).

29
Petroleum Geology and Exploration Opportunities
Seismic Section Across Lamu
30
Petroleum Geology and Exploration Opportunities
Prospect in off-shore Lamu
31
Petroleum Geology Exploration Opportunities
Mandera Basin
  • The Mandera Basin is a broad basin which extends
    into Kenya, Ethiopia, and Somalia. The western
    flank of the Mandera Basin is located in
    northeast Kenya and covers approximately 51,920
    sq km

32
Petroleum Geology and Exploration Opportunities
  • Mandera Basin
  • The Basin is filled with up to 8,0OO -10,000m of
    Karroo post-Karroo fluvial-continental,
    lacustrine, and marine sediments.
  • Carboniferous rifting initiated the development
    of the Mandera Basin and the Lamu Embayment
  • From the Middle to Late Jurassic, the Mandera
    Basin developed as a slowly subsiding platform
    basin.
  • The Kenyan portion of the Mandera Basin is
    relatively unexplored. Only two stratigraphic
    wells Elgal I II have been drilled (1987) in
    the basin.

33
Petroleum Geology and Exploration Opportunities
Evolution of the Mandera Basin
34
Petroleum Geology and Exploration Opportunities
Geology of the Mandera Basin
35
Petroleum Geology and Exploration Opportunities
Stratigraphy of the Mandera-Ogaden Basin
36
Petroleum Geology and Exploration Opportunities
  • Mandera Basin Contd..
  • Source Rocks
  • The presence of the Tarbaj Hill oil seep
    (possibly charged from a mature Jurassic marine
    sequence within the basin), as well as oil shows
    in the Burmah Hol-1 Well of the Somali Mandera
    Basin, strongly suggest untapped hydrocarbon
    potential in this area.
  • Analysis of the Tarbaj Hill oil seep indicates
    the presence of mature marine source rock. The
    source for this oil is interpreted to be either
    the rift sequence of the Karroo (equivalent of
    the Maji-ya-Chumvi shales of the Mombasa area) or
    Lower Jurassic marine shales (located in the
    deeper, interior part of the basin)

37
Petroleum Geology and Exploration Opportunities
  • Mandera Basin contd..
  • Permo- Triassic
  • Elgal shales whose equivalent are Bokh Shale
    formation, that sourced Calub Reservoir in
    Ethiopia.
  • Triassic/Low Jurassic
  • Tarbaj Oil Seep, in Mansa Guda Triassic Formation
    points to marine source rocks. Related to
    transgressive Shales that were deposited just
    below the Didimku limestone interval.
  • In Ethiopia their equivalent are the Lower
    Hamanlei that sourced the Adigrat reservoir in
    Calub/Genale /Galadi wells where heavy to medium
    oil has been tested.
  • Jurassic
  • Deeper sediments could give encouraging results.
  • The Rhamu shales are equivalent to Uarandab
    shales in Ethiopia

38
Petroleum Geology and Exploration Opportunities
  • Mandera Basin Contd..
  • Reservoirs
  • Karoo clastic formations (grits, sandstones)
  • Triassic- Lower Jurassic
  • Coarse grained stream deposits of Mansa Guda
    sandstones, porosities ranging from 8 to 14.
  • Middle to Upper Jurassic
  • These are the Upper Murri and Rukesa grainstones
    with porosities between 10 to 20, their
    equivalent in Ethiopia are the Hamanlei with
    porosities ranging from 8 to 10
  • Seals
  • Seals are present at many levels
  • Elgal shales in Lower Karoo,
  • Base Liasic shales below Diidimtu limestones
  • Evaporites in Hamanlei.
  • Rukesa , Hereri and Rhamu shales Jurrassic

39
Petroleum Geology and Exploration Opportunities
  • Mandera Basin Contd..
  • Traps
  • Most play concepts are associated with structural
    leads e.g Sengif structure,
  • Golberole Hill fault zone
  • El-Wak structural lead
  • Structures related to tilted blocks.
  • Anticlinal features.

40
Petroleum Geology and Exploration Opportunities
  • Tertiary Rift Basins
  • Kenyan Rift is part of the East African system
  • The main basins of the Kenya Rift are the
    Turkana, Lokichar (Loperot), Suguta-Magadi, South
    Kerio, and Nyanza troughs, which cover a total
    surface area of approximately 105,000 sq km.
  • Kenya Rift contain sufficient sedimentary fill to
    form potential mature sources for hydrocarbons.
  • The northern part of the Kenya Rift, comprising
    the Suguta, Turkana, and South Kerio troughs, has
    had most petroleum exploration activity.
  • Two wells, Loperot-1, Eliye Springs were drilled
    in the Basin

41
Petroleum Geology and Exploration Opportunities
Eastern African Basins
42
Petroleum Geology and Exploration Opportunities
  • Tertiary Rift Contd..
  • Numerous productive analogs of the types of
    reservoirs expected in the Kenya Rift Basins
    include lacustrine sandstones such as those
    Albertine Graben in Uganda.
  • The oldest potential reservoirs are the probable
    Late Jurassic to Mid-Cretaceous
    fluvial-lacustrine sandstones occurring in the
    Turkana area. These sediments likely were
    deposited during the pre-rift to early rift
    development of the Cretaceous Anza-Abu Gabra
    rift-type graben, which was crossed by the
    younger (Late Cretaceous through Recent) north-
    south trending Turkana Trough. Elsewhere in the
    western Kenya Rift Basins, Neogene sequences were
    most likely deposited directly on metamorphic
    basement.Porous and permeable fluvial-lacustrine
    sandstones comprise the reservoirs in Neogene
    Rift Basins (such as the Nyanza and South Kerio
    troughs). These sandstone units are typically
    intercalated with siltstones and shales, which
    may act as both source rock and seal.

43
Petroleum Geology and Exploration Opportunities
  • Tertiary Rift Contd..
  • Seals
  • Potential seals exist in the fine- grained
    lacustrine sediments and compact volcanic
    sequences. These impermeable units provide
    intraformational cap rocks for lacustrine
    reservoirs.
  • Source Rocks
  • Miocene syn-rift sedimentary deposits,
    particularly the Ngorora Formation (Poi Shale
    Member), provide excellent lacustrine source
    rocks (ToC 14). Despite their young age, these
    organic-rich units could have undergone favorable
    maturation because of the high geothernlal
    gradients present in the Kenya Rift.
  • Trapping Configurations
  • The tectonic style of the Kenya Rift is
    characterized by block faulting in brittle
    material, rollover structures in more plastic
    deposits (Plio- Pleistocene of Turkana). These
    structures provide good potential for the
    entrapment of hydrocarbons.

44
Petroleum Geology and Exploration Opportunities
Seismic Section Lokichar-Kerio X-section
45
Petroleum Geology and Exploration Opportunities
Lobster Structural Leads
46
Conclusions
  • The failure to discover hydrocarbons may
    therefore be attributed to the selection of the
    well locations poor definition of the
    structures, little knowledge of local conditions,
    possible facies variations within the reservoirs,
    relative non mature source- rocks in the
    Tertiary.
  • Potential for hydrocarbon entrapment exists in
    Jurassic carbonate reservoirs charged by a
    mature, marine sequence in the Jurassic of the
    Mandera Basin.
  • Untested potential remains in the Anza through,
    to the Lotikipi Basins. Probable reservoirs
    include Lower Cretaceous (Neocomian through
    Albian) fluvial-lacustrine sediments with intra-
    formational source, reservoir, and seal
    potential. The analog for this potential is the
    productive Abu Gabra Rift Basin of Sudan.

47
Conclusions Contd..
  • There are many remaining opportunities for leads
    and prospects within the trend of near-shore
    structures of the Lamu Embayment where crestal,
    radially arranged fault blocks and favourable
    trapping configurations have been observed on
    seismic data. These structures are associated
    with good quality Tertiary reservoir sandstones.
    This play concept has never been tested in Kenya.
  • Stratigraphic trapping configurations also exist
    within the Lamu Embayment, where amplitude
    anomalies and pinchouts are commonly observed on
    seismic data.

48
Conclusions Contd..
  • Recent investigations have led to the up-grading
    of the South Kerio and Nyanza troughs of the
    western Kenya Rift Basin to prospective Neogene
    depocenters with favorable tectonic styles for
    hydrocarbon entrapment. Miocene, synrift
    sedimentary deposits, such as the Ngorora
    Formation, provide excellent lacustrine petroleum
    source rocks which are likely to be mature
    because of the high geothermal gradients present
    in the Kenya Rift.
  • Welcome to Kenya and we look forward to holding
    discussions with you on the acreages.

49
Thank you for your Attention !!!
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