Impact of Laboratory-Induced Deformation and Naturally-Occurring Faults on Fluid Flow in Carbonates
I. Kaminskaite, Q.J. Fisher and E.H. Michie
Event name: Fifth International Conference on Fault and Top Seals
Session: Laboratory Investigations II
Publication date: 08 September 2019
Info: Extended abstract, PDF ( 2.36Mb )
Price: € 20
Faults were studied in a broad range of carbonates and cover all carbonate rock types from Dunham classification: from mudstones to crystalline, with porosities ranging from <1 to 52%. Protolith samples were used for the triaxial testing. Laboratory-deformed and naturally-faulted samples were compared with the host rocks in a petrophysical, macrostructural and microstructural sense. The results show that transition from dilatant to compactive cataclastic flow in carbonates occurs at the porosity of c.10%. Samples with porosity <10% typically dilate during failure and show an increase in permeability after the deformation, whereas samples with porosity >10% compact and show reduced permeability. Deformation bands formed in outcrops with carbonates with a porosity >50% may form significant barriers to fluid flow because cataclasis is often accompanied by recrystallization and cementation which could not be produced in the laboratory. Fault cores in low-porosity outcrops (<1%) consisting of cataclasites and cemented chaotic breccias may form seals to fluid flow because they reduce the permeability by up to a magnitude of 6 and are not cross-cut by fractures. Transitional shear planes or breccias formed both in the laboratory and in damage zones of naturally-formed fault zones show enhanced fracture connectivity, which creates conduits to flow.