Integrated petrographic – rock mechanic borecorestudy from the metamorphic basement of thePannonian Basin, Hungary

Abstract

Abstract The integrated evaluation of borecores from theMezősas-Furta fractured metamorphic hydrocarbon reservoirsuggests significantly distinct microstructural androck mechanical features within the analysed fault rocksamples. The statistical evaluation of the clast geometriesrevealed the dominantly cataclastic nature of the samples.Damage zone of the fault can be characterised byan extremely brittle nature and low uniaxial compressivestrength, coupled with a predominately coarse fault brecciacomposition. In contrast, the microstructural mannerof the increasing deformation coupled with higher uniaxialcompressive strength, strain-hardening nature andlow brittleness indicate a transitional interval betweenthe weakly fragmented damage zone and strongly grindedfault core. Moreover, these attributes suggest this unit ismechanically the strongest part of the fault zone. Gougerichcataclasites mark the core zone of the fault, with theirwidespread plastic nature and locally pseudo-ductile microstructure.Strain localization tends to be strongly linkedwith the existence of fault gouge ribbons. The fault zonewith ∼15 m total thickness can be defined as a significantmigration pathway inside the fractured crystalline reservoir.Moreover, as a consequence of the distributed natureof the fault core, it may possibly have a key role in compartmentalisationof the local hydraulic system.