American Oil and Gas Reporter - June 2014 - 63

SpecialReport: Global Opportunities
the Falkland Plateau and Maurine Ewing
Bank rifted, moving southwest throughout
the Cretaceous and Tertiary.
An additional feature South Africa's
East Coast shares with the Transform
Margin is a narrow shelf break, moving
quickly into deeper waters. In the Transform Margin, this has enhanced the development of large channel fan systems,
which perform as excellent reservoirs, as
shown by discoveries such as Jubilee by
Tullow Oil in 2009, and the Saphir-1XB
well by Total S.A. earlier this year.
A number of crucial factors are required
for any working petroleum system, namely
the source rock, reservoir and seal. Source
rocks have been hypothesized in this area.
Strong seismic reflectors on vintage data
shot over the Transkei Basin indicate a
possible black shale, tentatively dated to
80 million-85 million years old. There is a
strong possibility this black shale is regional,
and where sufficiently buried, should be
mature enough to produce hydrocarbons.
Sedimentary input and its origin are
important to understanding how the reservoir system may have formed over the
past 150 million years. Although there are
river systems draining off the eastern South
African coastline, the major sedimentary
input is likely to have been from the Tugela
River farther northeast along the coast.
Little is known about the synrift development along this margin. However,
in the post-rift, there is a major fluvial,
deltaic, and deepwater sediment system
that has produced a thick sedimentary
section in the offshore. It is probable that
during periods of lower sea level, these
sediments also were deposited farther
south as large turbidite fan systems, thus
there may be a potential post-rift reservoir
in the area.
Sealing of any stratigraphic reservoirs
is likely to be from marine shales deposited
over the top of the fan systems during
periods of higher sea level.
Trapping mechanisms, hydrocarbon
migration, and maturity are still uncertain,
but with better imaging and the regional
nature of the broadband dataset, it will
not be long until these questions can be
answered, and we can begin to understand
fully the petroleum system along this
margin of South Africa.
Exploration And Prospectivity
Exploration to date has focused on
two main areas along the south to eastern
South African margin: the Outeniqua
Basin to the southwest and the Tugela

Cone to the northeast. The Outeniqua
Basin was licensed in the 1960s, with
exploration beginning in the same decade.
The first discovery was made in 1968
with the Ga-A No. 1 well, which was
drilled on a prominent synrift fault block
structure in the Pletmos sub-basin.
Completed in 1969, the well yielded
25 million cubic feet of gas a day and
100 barrels of condensate a day from
Cretaceous sandstones, and 10 MMcf/d
of gas from Devonian prerift basement
sandstones.
A series of important discoveries were
made in the 1980s, notably the E-M and
F-A fields (which led to the development
of a gas-to-liquids refinery) and Oryx,
the first oil producing field offshore South
Africa. In 1990, the Oribi Field was discovered, producing oil and gas from
Lower Albian Sandstone reservoirs-the
same as those found in the Oryx Field. A
further string of discoveries was made in
the 1990s, producing the Sable/ECE, FO, F-A and E-M fields.
Exploration remains immature in the
Tugela Cone. Only four offshore wells
have been drilled in the area with one
discovery. The JC-B1 well, drilled in
1983, found gas and oil shows in late
Cenomanian to Maastrichtian shaley sandstones.
Questions relating to the geological
structure and deepwater sedimentary system still remain for the East Coast South
African margin. However, even a brief
analysis of analogue petroleum systems
helps to derisk an area where there has
been limited geological and petroleum
systems knowledge.
Like da Gama finally reaching Calicut
(now Kozhikode, India) in May 1498,
the end of seismic acquisition is in sight
in one of the toughest areas in the world
to shoot seismic data. The broadband,
multiclient data acquired during the first
half of 2014 will provide the next big
step in understanding the petroleum system
in this frontier area. The data are providing
insights into the structure and possible
petroleum systems, and with processing
planned later this year, will give an even
clearer image of the offshore South African
subsurface.
Efforts by the survey operations and
acquisition teams to understand and predict
the Agulhas Current and how it would
impact the acquisition process significantly
reduced the subsequent impact, ensuring
that high-quality seismic data would result
from the survey program.
❒

PATRICK
COOLE

Patrick Coole is a reservoir geoscientist with Petroleum Geo-Services
with five years of experience in the
oil and gas industry. After graduating
from the University of Manchester
in geography and geology in 2008,
he went on to work for Neftex, a sequence stratigraphy-based consultancy where he work on Black Sea
and Greater Caspian, Indian Subcontinent, and Middle Eastern basins
and petroleum systems. Coole completed his master's in petroleum geoscience in 2012 at Imperial College
London, and Patrick joined PGS in
late 2013, specialising in West African
hydrocarbon exploration for the multiclient and reservoir teams in the
Weybridge, U.K., office.

JOHN
SHEEHAN

John Sheehan is project manager,
business development, for Petroleum
Geo-Services' African multiclient
team, with more than 30 years of oil
and gas industry experience with a
focus on exploration in frontier areas.
He holds a B.Sc. honours degree in
geology from Kings College London.
Sheehan has worked for SSL as a
seismologist and geophysicist, for
WesternGeco managing data processing centers, and in a business development role for Fugro-Robertson. He
joined PGS in late 2012, where he
has focused on frontier exploration
in Africa, with an emphasis on establishing seismic programs in southern Africa.
JUNE 2014 63

American Oil and Gas Reporter - June 2014

Table of Contents for the Digital Edition of American Oil and Gas Reporter - June 2014