Extensional Faults in Sandstone – Analogue Input Data to Volumetric Fault Reservoir Grids
Alvar Braathen1, Jan Tveranger2, Haakon Fossen3, and Magne Espedal2
1University Centre in Svalbard, Longyearbyen, Norway
2Center for Integrated Petroleum Research (CIPR), University of Bergen, Bergen, Norway
3University of Bergen, Bergen, Norway
The concept of fault facies modelling address the fact that fault structures are generally modeled in production flow simulators using transmissibility multipliers. A more realistic representation of fault structures requires consideration of the full spatial distribution of fault rocks and the properties of faults as such. Volumetric fault evaluations necessitate reservoir grids of faults and conditioning of this grid. The conditioned grid has to be populated with distinct fault facies, which are based in analogue databases.
The concept of fault facies encompasses the deformational products of any host rock volume affected by a fault. The presented facies database describes extensional faults in sand-shale sequences, with datasets from Sinai, Utah, Corsica, and Norway. The analogue database is organized from the fault envelope downwards into core and surrounding damage zone, and further into Associations that consist of one or more Fault Facies. For example, the Core Architectural Element is commonly made up of various fault rock membranes, lenses, and fracture and deformation band sets. By considering for example lenses of host sandstone as one facies association, several facies can be identified, based in the occurrence of deformation band sets within the lenses. Statistical analysis of the fault facies database establishes dimensions, geometries and scales of various structural elements. Critical assessments of length and width relations of core and damage zone reveal complementary empirical trends.
In total, fault facies modelling represents a powerful reservoir assessment tool. It opens for evaluation of fault-parallel flow, capillarity effects and communication between non-juxtaposed cells.
AAPG Search and Discovery Article #90072 © 2007 AAPG and AAPG European Region Conference, Athens, Greece