Structural strain and structural heterogeneity of sandstone diagenesis: a case study for the Kuqa subbasin in the northern Tarim basin
构造应变与砂岩成岩的构造非均质性——以塔里木盆地库车坳陷研究为例

Structural strain of porous sandstones, evidently different from that of low porous limestones, will preferentially produce strain localization and form microscopic deformation bands. A case study shows that late structural deformation developed in the Kuqa subbasin in the northern Tarim basin, the southern foot of the Tianshan mountain and were characterized by north-southern zonation with east-western differentiation since Cretaceous. Based on structural deformation framework and sandstone physical features (porosity and permeability), six types of structural deformation patterns, controlling structural heterogeneity of sandstone reservoirs, are presented in this paper. The deep involved structural patterns (three types) and the shallow involved structural patterns principally occur in the western and eastern Kuqa subbasin respectively, which is controlled by basement blocks, salt-coal detachment beds, north-southern adjusting faults and basin-range boundary types as well as stress distribution. Except deformation bands of porous sandstones, the study also shows that structural strain properties of the Cretaceous tight sandstones buried bigger than 6500~7000m in depth are similar to that of limestones, which will easily produce more effective fractures accompanying late uplift and/or intense structural strain. This consideration is important for prediction of deep buried sandstone reservoirs in the study area.