How could surface studies of salt tectonics help petroleum exploration: a collage of case studies from Madagascar, Yemen, Iran, Austria and Bulgaria
|Dates:||11 October 2018|
|Times:||10:00 - 11:00|
|What is it:||Seminar|
|Organiser:||Department of Earth and Environmental Sciences|
|Who is it for:||University staff, Current University students|
|Speaker:||Dr Garbor Tari|
This week's AAGP speaker is Dr Gabor Tari, Group Chief Scientist for Geology, OMV, Vienna.
In this talk a few case studies will be presented to highlight aspects of salt tectonics which are
not addressed by typical petroleum exploration workflows.Whereas in exploration we routinely rely
on subsurface data sets such as reflection seismic, potential field and well data, various surface
observations could also significantly contribute to the understanding of a salt basin.
In the Morondava Basin of Madagascar, edible salt (“siratany”) is being produced with very basic
methods from salt-rich soils. These very poorly documented surface salt occurrences may be a giveaway
for an underlying Jurassic salt basin. Using an analogue from the Illizi Basin of Algeria, deep salt brines
might have reached the uptilted basin margin during the exhumation of the basin causing the "siratany anomaly".
So far, Jurassic salt was only described from the offshore Majunga Basin in Madagascar and therefore a
confirmation of salt in the subsurface of the onshore Morondava Basin would have an impact on the perceived prospectivity.
In the Sab'atayn Basin of Yemen the internal lithologic complexity of the Tithonian evaporites was analysed by
analyzing a few outcropping salt diapirs. In particular, the Milh Kharwah diapir was studied by recently acquired
high-resolution satellite images integrated by outcrop sampling of the various lithologies of the diapir. Based on the
lithologic composition of 10 surface spot samples and their spectral signal in the infra-red satellite data sets, a detailed
geologic map of the diapir was compiled. The remote sensing evaluation was done in lieu of the time-consuming and
logistically challenging surface geologic mapping in this conflict-stricken region. In the South Fars segment of the Iranian
Zagros folded belt the Hormuz salt diapirs have typically very large (up to 2-3 km!) exotic megaclasts in them. The most
prominent lithology is a purple-red sandstone which is regarded as mid-Cambrian in age using analogues from northern Iran.
If correct, then there is an apparent contradiction as to this post-Hormuz lithologic unit being so preferentially
incorporated into the “dirty salt” observed on the surface.
The Iranian Zagros also offers a key natural laboratory to assess the influence of outcropping salt diapirs on
adjacent aquifers. Interestingly, about half of the diapirs have no significant impact on the quality of groundwater
around them. The hydrogeochemical signal found in groundwater and spring samples associated with the numerous
surface salt plugs in the same region points to three different types of interactions. We are in the process of trying to
extrapolate these findings to other folded belts influenced by salt tectonics at depth. In the Eastern Alps of Austria and
the Balkans of Bulgaria there are just a few outcrops of salt diapirs and many suspected salt structures stay completely
in the subsurface. As there are no seismic and well data in the more internal segments of these folded belts, the
map-view distribution of sulphury ("stinky") and salty springs could provide clues for the subsurface extent of the Permian
and Triassic evaporites.
All these examples highlight the potential benefits of using relatively "cheap" surface data in (sometimes only suspected)
salt basins other than just usual subsurface data sets the petroleum exploration industry typically tends to focus on.
Dr Garbor Tari
Role: Group Chief Scientist for Geology
Organisation: OMV, Vienna
Biography: Dr. Gabor C. Tari holds an MSc degree in Geophysics from Eötvös University of Budapest, Hungary, and a Ph.D. in Geology and Geophysics from Rice University, Houston, Texas. After starting with Amoco on various Romanian onshore exploration projects in 1994, he transferred to the Amoco Angola Team in 1996. After conducting regional basin studies for offshore bid-rounds, he joined the Block 18 project, where several major oil discoveries were made since then. Eventually joined Vanco Energy Company in 1999 as Chief Geophysicist, then as Vice President of Geosciences, he worked on a large number of projects around Africa. At Vanco, he also identified the Black Sea Basin as a promising and practically unexplored deep water basin in 2004. Since 2007, Gabor is with OMV in Vienna, Austria, working as the Group Chief Geologist on several projects including various European, Mediterranean, Middle Eastern and African basins.
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