Abstract
Deformation bands are common subseismic structures in porous sandstones that varywith respect to deformation mechanisms, geometries and distribution. The amount of cataclasisinvolved largely determines how they impact fluid flow, and cataclasis is generally promoted bycoarse grain size, good sorting, high porosity and overburden (usually.500–1000 m). Mostbands involve a combination of shear and compaction, and a distinction can be made betweenthose where shear displacement greatly exceeds compaction (compactional shear bands orCSB), where the two are of similar magnitude (shear-enhanced compaction bands or SECB),and pure compaction bands (PCB). The latter two only occur in the contractional regime, are char-acterized by high (70–1008) dihedral angles (SECB) or perpendicularity (PCB) tos1(the maxi-mum principal stress) and are restricted to layers with very high porosity. Contraction generallytends to produce populations of well-distributed deformation bands, whereas in the extensionalregime the majority of bands are clustered around faults. Deformation bands also favour highlyporous parts of a reservoir, which may result in a homogenization of the overall reservoir perme-ability and enhance sweep during hydrocarbon production. A number of intrinsic and external var-iables must therefore be considered when assessing the influence of deformation bands on reservoirperformance.