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The largest carbonate condensate field in China has been found in the central Tarim Basin. Ordovician carbonate reservoirs are generally attributed to reef-shoal microfacies along a platform margin. However, recent production success has been achieved along the NE-trending strike-slip fault zones that intersect at the platform margin. For this contribution, we analyzed the strike-slip fault effects on the reef-shoal reservoirs by using new geological, geophysical, and production data. Seismic data shows that some NE-trending strike-slip faults intersected the NW-trending platform margin in multiple segments. The research indicated that the development of strike-slip faults has affected prepositional landforms and the subsequent segmentation of varied microfacies along the platform margin. In addition, the strike-slip fault compartmentalized the reef-shoal reservoirs into multiple segments along the extent of the platform margin. We show that fractured reef-shoal complexes are favorable for the development of dissolution porosity along strike-slip fault damage zones. In the tight matrix reservoirs (porosity < 6%, permeability < 0.5 mD), the porosity and permeability could be increased by more than 2–5 times and to 1–2 orders of magnitude in the fault damage zone, respectively. This suggests that high production wells are correlated with "sweet spots" of fractured reservoirs along the strike-slip fault damage zones, and that the fractured reservoirs in the proximity of strike-slip fault activity might be a major target for commercial exploitation of the deep Ordovician tight carbonates. [ABSTRACT FROM AUTHOR]

Understanding the scaling relation of damage zone width with displacement of faults is important for predicting subsurface faulting mechanisms and fluid flow processes. The understanding of this scaling relationship is influenced by the accuracy of the methods and types of data utilized to investigate faults. In this study, seismic reflection data are used to investigate the throw and damage zone width of five strike-slip faults affecting Ordovician carbonates of the Tarim intracraton basin, NW China. The results indicate that fault slips with a throw less than 200 m had formed wide damage zones up to 3000 m in width. Also, damage zone width is found to have both a positive correlation and a power-law relation with throw of two orders of magnitude, with a ratio of these values varying in a range of 2–15. The relationship between throw and damage zone width is not a simple power-law and changes its slope from small to larger size faults. The results indicate that throw scales well with damage zone width for the studied faults, and hence these can be used to predict fault geometries in the Tarim Basin. The study of the wide carbonate damage zones presented here provides new insights into scaling of large-size faults, which involve multiple faulting stages. [ABSTRACT FROM AUTHOR]

[Display omitted] • A Tensor Thickness seismic method has been successfully applied for imaging of fault damage zone. • Abnormally wide fault damage zones form as a result of fault interaction and overlapping. • Performance of fractured reservoirs is intimately linked to architecture of fault damage zone. Understanding fault damage zone is of significant importance for the characterization and modeling of ultra-deep (greater than 6000 m) fractured reservoirs. However, seismic detection of fracture networks in deep fault zone it is still challenging. For this contribution, we propose a seismic Tensor Thickness Method for optimal imaging of the ultra- strike-slip fault damage zones in the Tarim Basin. The results show reasonable distinction through seismic methods of boundary of fault damage zones in carbonate host rock that is consistent with the fractured reservoirs constrained from borehole data. In addition, this study suggests that fault damage zones in ultra deep settings exhibit width ranging 100–800 m, with a linear correlation between fault damage zone width and throw. Isolated fault zones are characterized with linear relationship between the width and displacement of the strike-slip fault zones, but the abnormally wide fault damage zone is likely attributed to fault interaction and overlapping. The results of this work are applicable for fractured reservoir characterization in deep and tight carbonate rocks elsewhere. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]