Join AAPG Europe the Let's Connect Series, via Zoom Every Monday, Wednesday and Friday from 12-noon to 13:15pm BST. Today's session with Raffa di Cuia (Delteng) as moderator, and Gabor Tari (OMV) presenting "Inversion tectonics:a brief petroleum industry perspective". Grab a cup of coffee or your lunch and enjoy the discussion from where ever you are!
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Inversion tectonics: a brief petroleum industry perspective
Gábor Tari1, Didier Arbouille2, Zsolt Schléder1, Tamás Tóth3
1OMV Upstream, Exploration, 1020 Vienna, Austria
2IHS Markit, Geneva, Switzerland
3GeoMega Ltd, Budapest, Hungary
Correspondence to: Gabor Tari ()
Abstract
Whereas inversion tectonics could produce spectacular traps, inversion tectonics is a process which has profound implications on other elements of the petroleum systems and, therefore, the prospectivity, both in a positive and a negative sense. The most negative impact is attributed to the fact that during inversion source-rock sections are brought much closer to the paleo-surface and therefore previous mature source-rocks switch-off and become non-generative. Also, the main reservoir and source-rock sections may be brought to the surface and therefore breached. There are many other negative, but valid impacts listed by some giving the impression that inverted features may be more challenging for exploration than "regular" anticlines formed by simple contraction. Perhaps, this view is somewhat biased by considering examples from exhumed European Atlantic margins. In these regionally inverted rifts basins there are plenty of evidence for underfilled fields and former petroleum accumulations which were breached and leaked away due to inversion tectonics.
Yet, in many other basins of the world, inverted structures provided repeatable and highly successful plays. In particular, the examples we chose for this talk are located in the Sava Folds region of the western Pannonian Basin and the Syrian Arc anticlines in the deepwater Eastern Mediterranean basin turned out to be very successful, especially in the Levant.
We believe that the key for the success in these basins is that source rocks are not constrained to the extensional basin fill but rather occupy a higher, but pre-inversion stratigraphic position. These source rocks tend to be unconfined to the underlying extensional basins and more regional in character. This class of inverted structures can be therefore more successful at shallower reservoir levels. Given the position of the active source rock sequences in the post-rift basin fill in our examples, the hydrocarbon generation could be assumed regionally and the inverted anticlines becomes the focus of the ongoing charge, for example, in the giant Tamar gas field.
The other element in the sometimes negative perception of inversion is the fact that there are not that many successful examples described globally. Worldwide, with the exception of onshore US and Canada, only about 3% of the traps of hydrocarbon fields with reverse faulting or overthrusting are associated with inversion. We believe that this number should be significantly higher as many inverted structures may not be recognized as such.