Fracture responses of conventional logs in tight-oil sandstones: A case study of the Upper Triassic Yanchang Formation in southwest Ordos Basin, China

AAPG Bulletin ◽  
2016 ◽  
Vol 100 (09) ◽  
pp. 1399-1417 ◽  
Author(s):  
Wenya Lyu ◽  
Lianbo Zeng ◽  
Zhongqun Liu ◽  
Guoping Liu ◽  
Kewei Zu
Keyword(s):  
Ordos Basin ◽  
Upper Triassic ◽  
Tight Oil ◽  
Yanchang Formation ◽  
Conventional Logs

Fault damage zone characterization in tight-oil sandstones of the Upper Triassic Yanchang Formation in the southwest Ordos Basin, China: Integrating cores, image logs, and conventional logs

2017 ◽  
Vol 5 (4) ◽  
pp. SP27-SP39 ◽  
Author(s):  
Wenya Lyu ◽  
Lianbo Zeng ◽  
Zonghu Liao ◽  
Yuanyuan Ji ◽  
Peng Lyu ◽  
...  
Keyword(s):  
Ordos Basin ◽  
Damage Zone ◽  
Upper Triassic ◽  
Tight Oil ◽  
Vertical Wells ◽  
Yanchang Formation ◽  
Fractured Zones ◽  
Fracture Intensity ◽  
Fault Damage Zone ◽  
Conventional Logs

Fault damage zones around faults have a significant influence on fluid flow in tight-oil sandstones because they commonly act as localized conduits. Faults are developed in the tight-oil sandstones of the Upper Triassic Yanchang Formation in the southwest Ordos Basin, China. We integrate cores, image logs, and conventional logs from vertical wells to characterize subsurface fault damage zones in the tight-oil sandstones of the Upper Triassic Yanchang Formation in the southwest Ordos Basin, China. The results indicate that fault damage zones are intensively fractured or intensely broken in the cores. These fault damage zones present borehole collapse and widen sinusoidal curves in the image logs. The fractures in fault damage zones are predominant high dip angles. The fracture intensity decays with the increasing orthogonal distance from the faults within a fault damage zone. In fault damage zones, acoustic log (AC) values and compensated neutron log (CNL) values increase; density log (DEN) values decrease, dual induction log (ILD and ILM) and laterolog 8 (LL8) values decrease, the caliper log (CAL) presents borehole enlargement, and comprehensive fracture index log (CFI) values are greater than 0.43 and average 0.78. To identify fault damage zones by conventional logs in vertical wells, it is critical to distinguish fault damage zones from the background fractured zones. The ILM, CNL, ILD, LL8, and AC logs would be more useful than DEN logs for the distinction between background fractured zones and fault damage zones. The responses of fault damage zones in conventional logs are more intensive than those of background fractured zones, and the heights of fault damage zones are much greater than those of background fractured zones, which can be used for the distinction between fault damage zones and background fractured zones.

Natural fractures in tight-oil sandstones: A case study of the Upper Triassic Yanchang Formation in the southwestern Ordos Basin, China

AAPG Bulletin ◽  
2019 ◽  
Vol 103 (10) ◽  
pp. 2343-2367 ◽  
Author(s):  
Wenya Lyu ◽  
Lianbo Zeng ◽  
Sibin Zhou ◽  
Xiaosheng Du ◽  
Dongling Xia ◽  
...  
Keyword(s):  
Ordos Basin ◽  
Upper Triassic ◽  
Tight Oil ◽  
Natural Fractures ◽  
Yanchang Formation
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