The objective of our work was to carry out a petroleum geological study regarding migration routes, hydraulic trapping, occurrence of potential reservoir rocks and spatial distribution of pressure and reservoir properties in a petroleum-bearing basin. Our work was based on an integrated geological and hydrogeological research on Late Miocene-Early Pannonian formations in the basin, particularly focusing on deep-water turbidites. We used the (hydro)geological model based on the results of this work as a key input for building a hydrodynamic model with which we could later assess the natural flow system and hydrodynamic conditions of the area studied.

Reconstructing the depositional environment types and the related lithological type units enabled us to estimate petrophysical and hydrogeological parameters in little-known areas of the basin. Based on these approximations a more reliable hydrodynamic model was built.

The model enabled us to determine the main directions of petroleum migration and to approximate the relative timeframe of hydrocarbon entrapment. We also identified possible areas for hydraulic trapping of HC's which were verified by exploration results. Using our model we are also able to predict the spatial distribution of pressure in the basin with special regards to the severity of overpressure.

The results of hydrodynamic modelling demonstrate several practical applications:

  • Predicting the spatial distribution of pressure and especially overpressure is of global importance from interrelated economic, technical and HSE aspects.

  • The determination of migration pathways is of crucial significance from the exploration point of view.

  • The presented method can be powerful in both well-explored mature areas and less-known territories and is independent of scale, there are numerous examples of successful application at both regional and local scale.

Geological setting

The focus of this study is a sub-basin of a larger neogene basin. When the basin was formed, the surroundings uplifted therefore intensive erosion was taking place and the erosional products (sediments) were transported by rivers towards the lowlands and started to fill-up the basin so a deltaic depositional system formed. Accordingly the succession above the pre-miocene basement starts with suspension-originated basal marls which are followed by distal and proximal turbidites that have a continuous transition to the deltaic sediments. Figure 1. shows a NE-SW seismic section from the area. Turbidites are indicated by a hummocky, clinoform internal reflection pattern and onlap reflection terminations on the basement highs. The deltaic sediments can also be seen clearly on the section.

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