Geological Condition and Characteristics for Formation of Deformation Bands - Example from Jizhong Depression, China

Deformation bands mainly developed in high porous rocks whose porosity more than 14.3%. Deformation bands and fissure simultaneously developed in rocks with porosity between 10.1% and 14.3%. In high porous rocks, fault zone has bipartite texture. The fault core has cataclasite features. Deformation bands developed in damage zone. This thesis describes geological condition and characteristics of deformation bands according to well Jin 93-41X which was drilled across fault zone in Shulu Sag. The main controlling factors of the types of deformation bands are clay content and diagenetic stage. In pure sandstones, the grain flow is the deformation mechanism during unconsolidated to semi-consolidated of diagenetic stage, which formed disaggregation bands. Cataclastic bands developed during consolidation of diagenetic stage. In impure sandstones，the phyllosilicate bands formed during unconsolidated to semi-consolidated of diagenetic stage. The features of deformation bands are that the thickness of single deformation bands is several millimeters, and displacement is a few centimeters. They change the physical characteristics of parent rock obviously, and lead to the changes of porosity, permeability and displacement pressure. Cataclastic bands and phyliosilicate bands have the largest reduction in permeability. The changes of physical property promote the heterogeneity of reservoir, which has significant influence on fluid flow.