--> ABSTRACT: Gas-Condensate Accumulations in the Badenian Reservoirs of the Moldavian Platform

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Gas-Condensate Accumulations in the Badenian Reservoirs of the Moldavian Platform

Tarigradschi, Victor 1; Visnevschi, Eugeniu 1; Slusari, Boris 1; Grigorescu, Stefan 1; Pene, Constantin 1
(1) Faculty of Geology & Geophysics, University of Bucharest, Bucharest, Romania.

The Moldavian Platform is a sub-unit of East European Platform. It is situated in the Moldavian Republic and in the north-eastern part of the Romania. In the western part, the Moldavian Platform sinks under Carpathians Orogene system at more than 5000 m.

This paper refers to only Badenian formations, because they contains the main reservoirs for the gas-condensate in the Moldavian Platform. The purpose of this paper is to describe the geological conditions of oil and gas accumulation in the Badenian formations and the identification of the Petroleum System.

The Badenian deposits cover the Eocene, Cretaceous and sometimes even Paleozoic formations. They outcrop in the slope of river Prut and cover all Moldavian Platform with maximum of 400 m in thickness. In the west of Moldavian Platform, the Badenian formations are represented in the lower part by sands and sandstones (the main oil and gas Badenian reservoirs) with 20-30 m in thickness. These reservoirs are interlayered with tuff and shales and is known as infraanhydritic complex. They are covered by the anhydrites with more than 50 m in thickness, which are the main seal for the hydrocarbons. The main gas-condensate fields in the Moldavian Platform have been discovered at: (1) the Frasin-Gura Humorului (the depth of hydrocarbon accumulation is more than 3700 m), (2) the Cuejdiu (the depth is more than 4500 m) and (3) Malini (the depth is more than 2200 m). The other fields are reservoired in Sarmatian deposits and contains only dry gas (more than 98% CH4). The main traps are anticlines and faulted monoclines.

The analysis of the thermal maturation shows that in the study area the main Petroleum System (PS) is of Paleozoic age. The source rocks of the thermogenic Paleozoic PS consist of Upper Vendian-Lower Cambrian and Middle-Upper Silurian bituminous shales. The burial of the Silurian shales diminishes eastwards and they outcrop to east of the Prut river, on the Moldavian Republic territory. Westwards, their burial increase to more than 3500 meters and their thickness also is greater than 1200 meters. The vitrinite reflectance map constructed for the Silurian shales shows that their thermal maturation level increases north-westwards of the study area. The vitrinite reflectance values suggest that the onset of the oil generation started in the Late Miocene.

 

AAPG Search and Discovery Article #90135©2011 AAPG International Conference and Exhibition, Milan, Italy, 23-26 October 2011.