Types, characteristics and genetic mechanism of deformation bands in high-porous sandstone

LIU Zhida; FU Xiaofei; MENG Lingdong; DU Qinglong; SUN Yonghe; WANG Sheng

Abstract：To explore the modification effect of fractures on high-porous reservoirs,we presented an analysis of deformation mechanism,types and characteristics of sub-seismic structures of high-porous sandstone on the basis of borehole core data and related research results in Bohai Bay Basin at home and abroad.It is indicated that the deformation of high-porous sandstone is different from that of the low/no-porous rock.For high-porous rock,the cataclasis cannot from fractures.The granular flow,cataclasis and cataclastic flow form another types of subseismic structures corresponding to fractures.The sub-seismic structures developed by rock deformation have reversal alteration effect on reservoirs.They are deformation bands with physical properties obviously lower than their host rocks.The results show that the porosity of deformation bands is 10％-25％ lower than that of the host rock.The permeability shows a reduction of one to seven orders of magnitudes with respect to the host rock.The types of deformation bands are disaggregation band,cataclastic band,solution and cementation band and phyllosilicate band.The permeability of the four types of deformation bands is in a decreasing manner.In conclusion,deformation bands developed in the deformed high-porous reservoir would reduce the petrophysical properties of the reservoir,while fractures occurred in the deformed low-porosity and non-porous reservoirs can improve petrophysical properties of the reservoir.