--> --> Abstract: Fracture Detection Using Multi-Azimuthal AVO At Y107, Jizhong Depression, Hebei Province, China; #90063 (2007)
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Fracture Detection Using Multi-Azimuthal AVO At Y107, Jizhong Depression, Hebei Province, China

 

Pan, Renfang1 (1) Yangtze University, Jingzhou, Hubei, China

 

Y107, located in Jizhong Depression, is a faulted block with conglomeratic reservoirs in Formation Shahejie IV. There are 22 wells drilled, 18 are producers and 4 are injectors. Current produced volume is about 5%. It's inferred that, by the fact that injected water break through the reservoir no late than injection, fractures occur in the production zone between faults. Therefore, 30 km2 of 3D seismic dataset was selected to be reprocessed involving pre-stack time migration. Then, two sets of CRP gathering were sorted by azimuth ranges that are fan shaped centrally both in inline and crossline directions. Azimuthally, two angle gathering sets were extracted after super gathering by rolling 3×3 inlines and crosslines, from which AVO anomalies were extracted, respectively. Comparatively, two sets of Previous HitvelocityNext Hit and amplitude coherence were derived from 3D volume stacked after migration. The study demonstrates that coherence is adequate to illustrate faults but fractures between them, and that the difference of shear Previous HitvelocityTop anomalies by AVO (Intercept minus Gradient) in two directions is consistent to the fracture zone revealed by drilling, and the fracture prediction from multi-azimuthal AVO is consistent to the data from 20 wells. Consequently, an animation made by step-slicing along with horizon interpretation clearly shows up fracture's orientation and vertical occurrence. It concludes that seismic coherence indicates only faults that are in large scale and visible changes in seismic wave traveling time, and the difference of azimuthal AVO's anomalies can indicate fractures that are in relatively small scale and affect seismic wave dynamically.

 

AAPG Search and Discover Article #90063©2007 AAPG Annual Convention, Long Beach, California