Deformation Bands in Chalk and Their Impact on Fluid Flow - An Example from Pegwell Bay, Kent
I. Kaminskaite, Q.J. Fisher and C.A. Grattoni
Event name: Fourth International Conference on Fault and Top Seals
Session: Poster Session
Publication date: 20 September 2015
Info: Extended abstract, PDF ( 1.73Mb )
Price: € 20
Compactive faulting was systematically investigated on highly porous chalk containing deformation bands from Pegwell Bay. The pore grain radius, porosity, and Klinkenberg-corrected gas permeability were determined for both deformed and undeformed rock. CT-scans show a decrease in porosity by more than 10% in deformation bands compared to the associated undeformed chalk. Microstructural analysis suggests that the porosity reduction occurred due to the collapse of fossils that contained macroporosity. The gas permeabilities range from 0.9 mD to 3.1 mD for the core plugs containing deformation bands and from 1.8 mD to 2.8 mD for the core plugs of the host rock. Mercury injection analysis show that there is considerable overlap between the pore size distribution and threshold pressures of the undeformed chalk and the samples containing the deformation bands. Permeability and threshold pressures are not significantly affected by the presence of the deformation bands because the destroyed macroporosity did not form a connected network.