STRUCTURAL CHARACTERISTICS AND FLUID EFFECTS OF NANBAIJIANTAN FAULT

Nanbaijiantan fault zone can be divided into slip damage zone and induced fracture zone. The slip damage zone within the fault core are characterized with strong consolidation and densification as well as low thickness, porosity and permeability; while the induced fracture zone is wide and with high fracture density as well as intense cementation and packing action. The fillings in the induced fracture zone are mainly calcites and analcites with minor silicates and asphalts. A great number of fluid inclusions, both saline water and organic, occur in the fillings and they are linear distribution along with cleavages and micro fractures of calcites. The analysis of saline water inclusions indicates that there are three confidence intervals of homogenization temperature data, which means that three episodes of great fluid activities have been present in the long geological history of Nanbaijiantan fault zone, and this is also supported by three different colors, brown, bright yellow and bluish green, of organic inclusions observed under the fluorescence microscope. Cementation has played an important role in trapping hydrocarbon around Nanbaijiantan fault zone. The initial sealed fault zone would reactivate triggered by later tectonic movements and more cement deposits for the new episode of fluid flow. Therefore, the sealing property of this fault zone has been strengthened by intense cementation resulting from multiple episodes of fluid activities.

Acknowledgements:This research was supported by the National Natural Science Foundation of China (Grant No. 41272142), the National Science-Technology Major Projects (No. 2011ZX05001) and Provincial Science Foundation of Shandong Province (No. ZR2012DM011). We specially thank Xinjiang Oil Field Company of PetroChina for the permission to use their geological and geophysical data.