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A Century of State Oil Production and a Quarter Century Seismic Acquisition Gap Are the Key to Future Exploration Success: A Case Study from The Pannonian Basin in Romania

Fink, Paul; Kovacs, Szilamer
ADX Energy, Vienna, Austria.

The consensus for the Neogene Pannonian Basin is that it is in a mature stage and most sizeable structures are drilled. Therefore it came as no surprise that after a century of state oil company activity in Romania, the National Champion Petrom decided that out of its vast exploration areas, it would relinquish the one (approx. 12,000 sqkm under EU rules) with the least favourable creaming curve. This presentation shows that conventional creaming curves are underestimating the remaining potential, especially in combination with not yet explored stratigraphic plays. Given that stratigraphic discoveries have however been drilled by chance and proven to work, there is a case to be made for remaining exploration potential in stratighraphic traps in an area which has seen little modern 2D seismic, and no 3D. THE CASE FOR STRAT- TRAPS: The area shown is the southeast continuation of the Mako trough. It contains up to 6 km of Neogene sediments and several source rock intervals. Two adjacent regional high trends contain a number of producing fields, including the Algyo field (217 mmbbls of oil, 2.5 tcf of gas). The field also contains a number of associated stratigraphic traps, especially in delta slopes on its flanks. The progradation of a number of Miocene sequences can be observed. These sequences tend to get younger and more distal from north to south. Third order sequences can be resolved on seismic and within these it is especially the (toe of) slope fans which are of interest. They are associated with two general exploration risks, i.e. updip leakage and reservoir quality. Due to the progradation and hence relatively higher shale content compared to the more proximal areas, toe of slope fans have a good chance for detachment from their respective delta systems. Indications of forced regressive wedges have also been observed. Due to tectonics, several areas have been identified where (toe of) slope fans sit in an updip position, a classic dip-reversal situation. Updip seal is provided by distal slope and basin floor shales. CONCLUSIONS: The Romanian part of the Pannonian basin has experienced no deliberate search for stratigraphic traps. Regional geology, creaming curve analysis and numerous proven stratigraphic traps which were found by coincidence, lead to the conclusion that a number of stratigraphically trapped oil and gas fields beyond the historic field size distribution can still be discovered in Western Romania.

 

AAPG Search and Discovery Article #90155©2012 AAPG International Conference & Exhibition, Singapore, 16-19 September 2012