East Africa Transform Margin The View from Tanzania and Madagascar - - PowerPoint PPT Presentation

East Africa Transform Margin – The View from Tanzania and Madagascar

Richard Higgins and Mark Sofield 10th PESGB/HGS Conference on African E & P, London, September 7-8, 2011

Legal Notice: No representation or warranty, express or implied, is or will be made in relation to the accuracy or completeness of the information in this presentation and no responsibility or liability is or will be accepted by Ophir Energy Plc, it’s joint venture partners or any of its respective subsidiaries, affiliates and associated companies (or by any of their respective officers, employees or agents) in relation to it.

Acknowledgements

1

Agenda

• Location & Recent Activity
• Regional Tectonic Elements
• Influence on Petroleum System Elements
• Summary

2

TANZANIA MOZAMBIQUE

Recent Activity – East Africa

Pweza Gas Discovery Chewa Gas Discovery Chaza Gas Discovery Windjammer Gas Discovery Barquentine Gas Discovery Ironclad Oil Shows Tubarão Gas Discovery Lagosta Gas Discovery

• Multiple 2D and 3D Seismic

surveys acquired since 2005

• Drilling campaigns conducted in

Tanzania (Ophir/BG) and Mozambique (Anadarko et al.) in 2010/2011

• Seven gas discoveries
• Various farmin/farm outs in

Tanzania and Kenya

• Licence signatures in Kenya

3

4

Recent Discoveries – Tanzania

• Strong relationship

between seismic amplitude anomalies and gas-bearing reservoirs.

• Nearby targets with

similar seismic characteristics now substantially de-risked.

• Further 3D seismic

surveys have been acquired and are currently being processed.

Regional Tectonics

• Karroo continental rifting
• Late Carboniferous to Early Jurassic
• Gondwanaland break-up
• Initial opening ~180Ma (NW-SE)
• N-S opening from 160Ma to 120 Ma
• Development of “passive margin” successor basins
• East African Tertiary Doming

5

Tanzania - Gravity

• Significant change in gravity signature

across the Davie Fracture Zone (DFZ), separating continental and oceanic crust.

• Continental crust dominated by N-S

trending anomalies that appear to step across NE-SW trending lineaments.

• NE-SW lineaments interpreted to

represent Early Jurassic rift faults

• N-S anomalies possibly represent

Cretaceous structures generated during Jurassic to Aptian, coincident with movement along the DFZ.

• N-S structures reactivated during

Oligocene to Recent.

Davie Fracture Zone

EP B1 B3 B4

Seagap Fault Zone

MASAI BASEMENT SPUR

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• Triassic/Jurassic Rift Faulting
• Generation of N-S Seagap Fault Zone during Jurassic to Aptian? Reactivation of rift faults?
• Oligocene onset of reactivation (transtensional in above example)
• Pliocene reactivation (generates transpressional anticline in above example)

Seagap Fault Zone

7

Seagap Fault Zone

Transpression Transtension

8

Seagap Fault Zone

SEMBLANCE A B C D A B C D Riedel?

9

Restraining Bend Releasing Bend

Modified from Mikenorton, Wikipedia, 2009

Tanzania - Onshore

From Nicholas et al., (2007) From Nicholas et al., (2007)

10

Structural Control on Reservoir Input

S N

East Pande

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Reservoir

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• Fault-controlled

sediment input

• Long-lived sediment

input from quartz-rich provenance

Quaternary Holocene Pleistocene Quaternary and Tertiary Tertiary Mesozoic Tertiary and Cretaceous Cretaceous Lower Cretaceous Cretaceous and Jurassic Jurassic Lower Jurassic Jurassic and Triassic Triassic Lower Triassic Mesozoic and Paleozoic Cretaceous through Carboniferous Jurassic through Carboniferous Paleozoic Permian Triassic and Permian Permian-Carboniferous Carboniferous Carboniferous and Devonian Devonian Upper and Middle Devonian Devonian and Silurian Silurian Silurian-Ordivician Ordivician Ordivician-Cambrian Cambrian Precambrian Paleozoic-Precambrian Proterozoic Quaternary extrusive and intrusive Tertiary extrusive and intrusivei Mesozoic extrusive and intrusive Mesozoic-Paleozoic extrusive and intrusive Paleozoic extrusive and intrusive Kimberlite Subsurface salt dome Open Water Bathymetry 0 to 200 200 to 1000 1000 to 2000 2000 to 3000 > 3000

Madagascar - Gravity

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• NE-SW rift faults
• NW-SE transfer

zones

• Deep structural control on

sediment input and fault linkage

• DSDP 330+511 – Barremian-Aptian organic rich shales up to 35m thick – TOCs 3 to 16%
• Aptian source rocks in Outeniqua Basin, South Africa.
• DSDP 249 – Thin Aptian shales with TOCs up to 9%
• DSDP 693 – Aptian organic rich sediments 68m thick – TOCs up to 4%

ANTARCTICA AFRICA

Early Aptian source rocks in Outenqua Basin 249 Thin Aptian Shales TOCs up to 9% 330+511 Barremian-Aptian organic rich shales up to 35m thick TOCs 3 to 16% 692 Valanginian organic rich sediments 45m thick. TOCs up to 18% 693 Aptian organic rich sediments 68m

• thick. TOCs up to 4%

MB NV APTIAN RECONSTRUCTION India Greater India Africa Antarctica APTIAN RECONSTRUCTION Duvalia Formation (Berriasian to Aptian shallow to deep marine facies) in Southern Morandava Basin – potential for an Excellent quality Lower Cret. source rock – TOCs average 3.74%, max 26.3%, HI Ave 167, Max 403. Alb-Cen-Tur in Northern Morandava Basin – potential for oil and gas source rock. TOC 0.8 to 3.4%, HI max 240. Serinam-1 North Morondava Basin– Light oil/wet gas source rock pot. in 15m Lwr Cret (Haut-Barrem). TOC 1.7 to 9.3%, HI max 248.

An East African Deepwater Cretaceous Source Rock?

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Open Circulation Semi-restricted circulation? Mid-Ocean Ridge Mocimboa-1 Apt-Alb Slope fan deposition “increasing TOC (>1%) with depth, with organic (type III) properties in Albian shales at the base of the well”

TANZANIA

Lower Cretaceous is considered to have gas-prone potential near-shore, but could the deepwater be oil-prone?

RTI

Songo Songo Lower Cretaceous (contamination?) SS 5 – TOCs up to 11% SS7 – TOC up to 5% SS8 – TOC up to 1.57% Winganyongo & Ruaruke Lower Cretaceous Samples measured TOCs of 18%

An East African Deepwater Cretaceous Source Rock?

Marginal ridges along the continental side of the (shear) margin perhaps provides local restricted circulation & anoxic conditions

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Recent discoveries to the west of the DFZ herald the start of an exciting period of hydrocarbon exploration offshore East Africa. Tanzanian acreage appears have been significantly influenced by strike slip tectonics associated with the DFZ and Tertiary reactivation. Deepwater Cretaceous source rock in East Africa? 2nd phase of 3D seismic acquired offshore Tanzania (Blocks 1, 3 and 4) in Q1 2011, with a further 3D survey planned for East Pande in Q4 2011. Drilling planned to recommence offshore Tanzania during late 2011 / early 2012.

Summary