the gambia’s petroleum prospectivity the geological story · the gambia’s petroleum...
TRANSCRIPT
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The Gambia’s Petroleum ProspectivityThe Geological story
Jerreh Barrow
Commissioner for Petroleum
Ministry of Petroleum and Energy
10th November, 2017
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Presentation outline
• Introduction
• Location of The Gambia
• The MSGBC Basin
• Basin Evolution
• Regional Successful Plays
• The Gambia’s Prospectivity
• Blocks
• Seismic Database
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Introduction
• The Gambia’s geological story is very much part of the MSGBC Geological evolution
• We will look at the Evolution of the MSGBC and how this knowledge helps in reducing the ever high exploration risk,
• It is common knowledge that exploration is a risky business but Geological and geophysical knowledge can significantly reduce this risk and make a huge difference between success and failure in an exploration project,
• Intensification of exploration efforts over the past few years have boosted the understanding and knowledge of the subsurface of the MSGBC.
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Where is the Gambia?
• Location: North West Africa, bounded to N, S and East by Senegal and West by Atlantic
• Size: 11,300 km2
• Population: about 2 million
• Government: Democratic
• Official Language: English
• Geologically it is located in the MSGBC Basin
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What is the MSGBC Basin?
Mauritania, Senegal, Gambia, Bissau, Conakry
(MSGBC)Basin
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MSGBC Basin Extent
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Why: MSGBC
• Highly under explored, with under 300 exploration wells drilled it is truly a frontier for exploration
• Established working Petroleum System
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Basin Evolution
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Plate Reconstruction
The Basin has undergone a complex history that can be divided into 3 main stages of development:
• the pre-rift (Precambrian to Paleozoic)
• syn-rift (Permian to Early Jurassic)
• post-rift (Middle Jurassic onwards)
Adapted from outputs from Gplates - EarthByte Research Group, School of Geosciences, The University of Sydney, Australia
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Plate Reconstruction
Triassic ToarcianL Jurasic: Toarcian
Aptian Campanian
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Consequent: Extensively faulted Basin with grabens and normal faults forming sub basins
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Regional Success
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FAN-1(WD 1427 m)(TD 4927m)
W
E
SNE-1(WD 1100 m)(TD 3170 m)
24 km
Senegal
• FAN-1 set of stacked fans 100 km offshore• P50 reserves of 950 mmbbls with distinct oils ranging from 28° and 41°API• Aptian Source? Albian reservoir
BEL-1
(WD 1032 m)(TD 2742 m)
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Senegal
• Drilled (May 2016) north SNE
• NET 31m gas column in Lower Cenomanian good quality reservoir.
• Thick, stacked reservoir sands over a very large area with good porosity and permeability.
• Inboard play fairway estimates raised to 50 Tcf
Teranga-11800 m WD
4,485 TD
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Senegal
• Drilled (May 2017)
• Stacked Lower Cenomanian basin floor fairways fans.
• Thick, stacked reservoir sands over a very large area with good porosity and permeability.
• Gross gas column of 120 m. NET 45m
• Estimates of 15 Tcf.
Yakaar-12550 m WD
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Senegal - Mauritania
• Guembeul-1 found 101 m of net gas pay in same reservoirs as Tortue-1 - including 56 meters in the Lower Cenomanian and 45 meters in the underlying Albian
• Static pressure communication with Tortue-1 suggests single large accumulation
• Latest released figure ~25 TCF
W
E
Guembeul-1(WD 2700 m)(TD 5245 m)
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Mauritania
• Tortue-1 found 117 m of net gas pay in excellent poro-perm Cenomanian & Albian reservoirs
• Slope/channel reservoirs in structural /stratigraphic trap
• 5-8 TCF
W
E
Tortue-1(5100m)
Largest global thermogenic discovery of 2015
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Mauritania
• Marsouin-1 found 70 m of net gas pay in excellent poro-perm Upper and Lower Cenomanian reservoirs
• 60 km north of Tortue
• ~5 TCF gas
W
E
Marsouin-1(WD 2400m)
(TD ~ 5100m)
E
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Mauritania
• Ahmeyim-2 found thickening of gross reservoir sequences with excellent quality Cenomanian & Albian reservoirs.
• Defined the field limit and extended the productive field area from approximately 50 km2
90 km2
W E
Ahmeyim-2(5200m)
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Only production offshore in Mauritania
• Discovered by Woodside in 2001 ~ 34 MMBOE (2P reserves)• 80 km offshore Mauritania – 12km2 closure• Currently being produced by Petronas at about 6,000 bpd from Tertiary Sandstones• Production declining – decommissioning looming
Chinguetti Field
(WD 815 m)(TD 2654 m)
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Conjugate Success
Source: NASA Global Gravity Ocean Floor
ExxonMobil continues with its
successful exploration campaign
offshore Guyana with the discovery
of Turbot. This shows that
deepwater can still be attractive.
ExxonMobil's Liza and Payara
complex approach the 2 billion
barrel mark in commercial
reserves!!!
Expect around 350,000-400,000 b/d
of oil production by 2026
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MSGBC Basin Play Types
Play Concepts Stratigraphic Fans / Pinchouts Structural Closure Buried Hills Salt Related Reef Buildups
StratigraphyNeogene & QuaternaryPaleogeneCretaceousJurassicTriassicTop Syn-Rift (Paleozoic)
FeaturesReservoir SandsCretaceous Carbonate PlatformJurassic Carbonate Platform Salt
Source RocksCenomanian-Turonian Marine ShaleAptian Marine ShaleJurassic?Triassic Lacustrine?Silurian Marine Shale?
SR1
SR2
SR3
SR4
SR5
1
1
2
3
4
5
2
4SR1
SR2SR2
SR3
SR4
SR5
SR1
2
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Discovered MSGBC Volumes
• BP / Kosmos Group= Greater Tortue Complex is 25 TCF = 4.3 BBOE of C2 Reserves
• CAIRN Group= 0.6 ‐1.0 BBO of C2 Reserves
• Dome Flore= 1.3 BBO Heavy Oil in place, > 3.0 BBO generated
This means the MSGBC Basin is now a
Supergiant Petroleum System
with more than 5 BBO (or oil equivalent)
reserves already discovered.
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The Gambia’s Prospectivity
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Block Map
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Recent Seismic Data Coverage
Vintage Offshore
2D (km) 3D (km2)
1999 1096 Multi-Client
1999 102 Multi-Client
2001 720 Multi-Client
2003 500 Gov't
2011 612 Multi-Client : TGS
2011 2566 Multi-Client : TGS
2015 1504 Multi-Client : GeoPartners/Polarcus
2017 1513 Multi-Client : TGS/PGS
TOTAL 4043 km 4570 km2
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2D Seismic Example (2012)
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2D Seismic Example (2017 Fast Track)
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3D Seismic Example (A2/A5) thru Jammah-1
• The well targeted an Albian shelf-edge carbonate feature and encountered viable reservoir horizons but with only minor petroleum shows.
• The well was drilled on the basis of 2D seismic data and post well studies suggest the well was dry due to erosion of potential Turonian source rocks at the well location
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3D Seismic Example (A1/A4) Strike
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Conclusions
• Source Rocks:
• PRIMARY: Cenomanian-Turonian shales upto 150 meters thick • North: wells on shelf boundary with source rocks, up to 380 m thick,
• South: Turonian interval contains bituminous shales believed to be the richest source rocks thickness up to 150 m
• DSDP 367 and 368 identified potential Neocomian to Cenomanian source rocks
• Minor source rocks within Senonian and Maastrichtian
• SECONDARY: Graptolitic Silurian shale appx 400m thick in south Senegal, equivalent to oil-rich Silurian Tanezzuft Formation, in N Africa & M East
• TERTIARY: Syn-rift inferred Upper Permian-Lower Triassic lacustrine rocks. Analogies in Morocco, NW Africa, North America and West Central Africa which contain clastic, lacustrine, and evaporite rocks. The Newark Basin of North America is one of these rift basins that contain lacustrine source beds
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