focus on the thermal history of the East African Margin
providing new direct constraints for exploration
Quantitative thermal history analysis of selected areas of Kenya,
Tanzania, Madagascar & Mozambique will answer key questions
work program – expressions of interest sought
A focus on the thermal history
of the East African margin
EXPRESSIONS OF INTEREST SOUGHT
||Quantitative thermal history analysis
in a frontier margin – securing a basic understanding of the
real limits to source rock maturation and burial histories
Following discussions with prospective key players in petroleum exploration
on the east African margin (principally Kenya, Tanzania, also Mozambique
and Madagascar), Geotrack proposes the Thermal History Reconstruction
(THR) of selected wells and possible outcrop sections in this region.
THR is a method employing an appropriate suite of techniques designed
to define by direct measurement key thermal parameters for constraining
basin evolution – such parameters are:
- timing of maximum paleotemperature(s),
- magnitude of heating,
- amount of erosion,
- heatflow (or gradient) history, and
- reliability of conventional maturity data.
Although some models for petroleum systems for the
region have been in the public domain for many years, none has been
underpinned by firm constraints on the thermal history, using such
specialist techniques as AFTA (Apatite Fission Track Analysis), and
U-Th/He dating. Other important complementary techniques are VR (vitrinite
reflectance) and fluid inclusion data. Integration of these new constraints
with current basin models and local geological knowledge will be key
to refining petroleum systems for the prediction of commercial petroleum
of the problem – e.g. Kenya and Tanzania
Despite the uncertainties facing
frontier exploration around the world, strong enthusiasm for portions
of the east margin of Africa is driven by the presence of prolific
high-quality reservoirs and potential world-class source rocks.
Both structural and stratigraphic plays are believed to be present,
though greater confidence in various structural plays awaits acquisition
of additional seismic data to verify structural details. It is
speculated that portions of areas like the Simba-Pemba trend,
affecting both Tanzania and Kenya (figure to right, taken from
Antrim PESGB/HGS abstract publication) has acted in the past as
a paleo-high, with significant burial and heating on the flanks.
The presence of seeps on Pemba Island serves to reinforce a model
in which migrating hydrocarbons (during the Paleogene) were reservoired
in Cretaceous and/or Tertiary units at that time. Also central
to this model is denudation of the continental margin supplying
the overburden and heating mechanism to the offshore source rocks,
the timing, location and magnitude of which have not been quantified.
Other features along the margin, such as the Davie Inversion Ridge
off Kenya, are also speculated to represent important inversion
structures that may serve as either valuable foci for hydrocarbons,
or alternatively, offer additional risk to the play profile, by
having reduced the integrity of the trap at some time after entrapment.
In summary, petroleum system models in this area rely strongly
on assumed values for various key basin elements … such
as sediment supply, basin inversion (timing and magnitude), and
heatflow and maturity history. Great advances in constraining
these elements should be expected by using high-quality thermal
history analytical tools, based on AFTA, thus ultimately adding
far greater confidence to our understanding of the petroleum system(s).
Relevant government agencies from Kenya, Tanzania,
Mozambique and Madagascar have been contacted and all have offered their
support, and access to available well material and relevant outcrop
This study, undertaken in collaboration with Alconsult International
(Calgary), which has considerable exploration experience worldwide,
including E. Africa, will commence with subscriptions from at least
two companies. It is anticipated that the “study” will in
fact consist of a number of single well studies from various basins,
or a collection of outcrop samples, using initially both AFTA and VR.
Complementary techniques, U-Th/He, ZFTA and fluid inclusion data, will
complement the initial data set, as demanded. The sample material will
be collected in Kenya and Tanzania (Mozambique and/or Madagascar), and
expedited to Geotrack’s laboratory in Melbourne. Well information
and more regional background information have been promised from each
of the host countries.
We are presently refining the well selection list (and onshore localities)
based on advice from interested parties and invite your suggestions.