Paleokarst reservoirs originate from dissolution (karstification) of soluble rocks and subsequent infill and collapse. Fluids percolating through fractures and faults as well and infiltrating porous beds can dissolve carbonate rocks and create connected systems cavities. This process can occur deep in the subsurface and be driven by hydrothermal fluids, but is best known as a near-surface process, involving surface water dissolving rock and forming caves and sinkholes.
The shape and geometry of these cave systems is linked to rock properties, the orientation and spatial distribution of fault and fracture networks, climatic conditions and sea level. During burial, cave systems may gradually be filled in by sediments from the outside or by rocks originating from collapse of the roof. This produces a highly heterogeneous subsurface reservoir with properties and production behaviour that are very difficult to forecast.
The FOPAK project aims to improve our fundamental understanding of paleokarst reservoirs by studying if and how their petrophysical properties, seismic characteristics and production behaviour can be linked back to the configuration of the initial cave system. The project is funded through a grant by the Norwegian Research council's Petromaks2 programme.
Uni Research CIPR (lead): Jan Tveranger, Øystein Pettersen, Bjarte Lønøy
Department of Earth Science, University of Bergen: Isabelle Lecomte,
Stein-Erik Lauritzen, Christos Pennos, Kristian Jensen
NORSAR: Tina Kaschwich