Journal of Conference Abstracts

Dynamic Stratigraphy: Applications to Carbonate Reservoirs and Raw Materials

Thomas Aigner (t.aigner@uni-tuebingen.de)¹, Igor Borel¹, Sascha Braun¹, Thomas Pawellek¹ & Markus Schauer (schauer.markus@schwenk.de)²

¹ Dept. of Geology, Univ. of Tuebingen, 72076 Tuebingen, Germany

² E. Schwenk KG, Hindenburgring 15, 89077 Ulm, Germany

Knowledge of the subsurface stratigraphy is essential in reservoir, aquifer and in raw materials geology. A process understanding of the sedimentary architecture will help in subsurface characterisation and prediction. We propose a simple, process-based methodology to analyse carbonate stratigraphy in a rigorously hierarchical way, moving from the smallest to the largest sedimentary units (particles to basins). This approach of "dynamic stratigraphy" is illustrated by two case studies:

A. Reservoir outcrop analogs in Triassic ramp carbonates

Understanding the formative processes of each hierarchical scale allows to deduce "rules" and predictions on the distribution of reservoir heterogeneities:

1) Microscale heterogeneities: caused by particle and pore properties (size, composition, texture etc.), which are determined by depositional , biological and diagenetic fluid dynamics.

2) Mesoscale heterogeneities: caused by various stratification and biofabric styles, which are controlled by the major depositional/erosional and ecological processes.

3) Macroscale heterogeneities: caused by facies and architectural elements, which record the differing dynamics and preservation of facies tracts.

4) Megascale heterogeneities: caused by fundamental sedimentary cycles and sequences, which reflect the stratigraphic dynamics of small-scale baselevel fluctuations.

5) Gigascale heterogeneities: caused by the stacking of fundamental cycles within a cycle hierarchy, which is controlled by long-term baselevel dynamics. A combination with petrophysical and geophysical tools (porosity, permeability, gamma-ray logs) leads to an integrated data set for reservoir modelling from microscopic to seismic scale.

B. Ultra-pure limestone ressources in Jurassic carbonates

The exploration and exploitation of sedimentary raw materials again require predictions of the subsurface stratigraphy. Such predictions are most reliable, when the depositional processes creating these deposits are well understood. Again, we advocate a rigorously systematic breakdown of stratigraphic packages into a hierarchy of easily recognizable genetically defined units of various scales. Each scale of analysis at the same time provides critical data on the quality, volumes and preferred occurrence of economic minerals. This approach is illustrated for economic ultra-pure limestones from the Upper Jurassic of SW-Germany. The integration of this approach with petrophysical measurements (such as colourmetric data) and geophysical tools (such as georadar and well logs) will lead to an improved understanding and more cost-effective exploration and exploitation of carbonate mineral deposits.

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