Permeability distribution and scaling in multi-stages carbonate damage zones: Insight from strike-slip fault zones in the Tarim Basin, NW China

• Published in: Marine and petroleum geology Vol. 114; p. 104208
• Main Authors: Wu, Guanghui, Zhao, Kuanzhi, Qu, Haizhou, Scarselli, Nicola, Zhang, Yintao, Han, Jianfa, Xu, Yifeng
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.04.2020
• Subjects: Carbonate damage zone; Diagenesis; Fracture; Permeability; Scaling; Scaling; Diagenesis; Fracture; Permeability; Carbonate damage zone
• ISSN: 0264-8172; 1873-4073
• DOI: 10.1016/j.marpetgeo.2019.104208

Architecture and permeability of fault damage zones are important for understanding faulting mechanisms and fluid flow in fractured rocks. Nevertheless, this understanding is often hindered by limited availability of data, especially in the subsurface. A comprehensive suite of cores, logs and production data is here presented to unravel petrophysical properties and fracture characteristics of deep (>6000 m) Ordovician limestones within strike-slip fault zones of the Tarim intracratonic basin (NW China). The results show that (1) the carbonate porosity is mainly secondary dissolution porosity and comprises low porosity (<5%) and low permeability (<0.5 mD) of carbonate matrix reservoirs, and “sweet spots” of fractured reservoirs with high permeability (>5 mD) and high porosity (>8%); (2) fault damage zones are generally tight with fracture aperture < 0.05 mm that formed during multiple genetic events and were successively affected by marked diagenesis; (3) fracture porosity is negligible, but fracture related dissolution is of critical significance and enhance permeability by more than two orders of magnitude higher than the tight matrix reservoirs in fault damage zones; (4) fracture attributes (frequency and aperture), permeability and production across fault zones displayed a distinct dichotomy between an inner and outer damage zones, with high permeability and production mainly within 500 m of the inner damage zone; (5) the permeability had no distinct logarithmic or power-law scale to distance to fault, but a large scatter and slow decrease in inner damage zones was observed. The results indicate that the deeply buried carbonate reservoirs along fault zones in the Tarim basin: (1) permeability can be characterized by integrating cores, log and production data at different scales; (2) multi-stages fracture diagenesis, particularly of the late stage fracturing and fracture related dissolution, dominated the permeability in the carbonate damage zones; (3) an increased cementation and fracture diagenesis of fault cores led to a scattered permeability distribution in the inner damage zones. •Permeability across fault zones in tight carbonate rocks.•A distinct dichotomy between the inner and outer damage zones with fracture attributes and permeability and production.•Large scattered permeability in inner damage zones.•Diagenesis dominated the permeability in the carbonate damage zones.