Fracture Network Modelling of the Latemar Platform: Alternative Workflow for Effective Property Calculation and Analysis

Boro, Herman ¹; Rosero, Enrique ²; Bertotti, Giovanni ³
(1)VU University Amsterdam, Amsterdam, Netherlands. (2) Exxonmobil Upstream Research Company, Houston, TX. (3) Delft University of Technology, Delft, Netherlands.

In carbonate reservoirs, fluid flow is largely influenced by fractures. However, obtaining fracture characteristics in sub-surface reservoirs is often difficult. On the other hand, outcrops provide information on fracture distributions, geometry and their controlling factors.

In this study we use fracture network data obtained at the Latemar platform to test a workflow for calculation of effective hydraulic properties and investigation of fluid-flow behavior at the platform scale. The Latemar platform is located in the Dolomites region in northern Italy. Its facies is characterized by widespread platform interior and steeply dipping slope. The fracture data were obtained throughout different environments of deposition.

In characterizing fracture properties, discrete fracture network (DFN) modeling has been used to upscale hydraulic parameters. However, implementing DFN at full-field geologic model often overlooks the inherent uncertainty about complex network geometries and their controlling factors. Differently in this study, sector-based DFN modeling has been implemented. The workflow starts with digital acquisition of fracture geometries and statistical analysis is used to investigate potential controlling factors. Several templates are then constructed to represent combinations of distinctive fracture patterns and geologic features. Effective hydraulic properties of each template are calculated and then used to populate the full-field geologic model.

In Latemar, fractures in slope are typically tall with low intensity. In the platform interior, fractures are shorter with wide range of fracture intensity. Further analyses emphasize the importance of facies and mechanical units in constraining fracture intensities and lengths in the platform interior. Observed fracture corridors typically have tall fractures with high intensity. Based on these settings, nine template DFN models are constructed.

The up-scaling results clearly indicate differences in flow behavior. Permeabilities in the platform interior and margin are significantly higher than in the slope. Differences in preferential flow paths are also observed: in the platform interior the horizontal displacement is nearly isotropic but not for margin and slope. In general, sector-based DFN is clearly able to capture and preserve the heterogeneity in fracture patterns, and constitutes a way to realistically populate the full-field geologic model while accounting for inherent sources of uncertainty.

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