| Vertical seismic profiles obtained of Ardley coal zone strata near Red Deer, Alberta demonstrate the effectiveness of multicomponent seismic applications in coalbed methane development. Zero-offset surveys show that a broad-band mini-P vibratory source is ideal for imaging the coal zone, providing a measure of vertical continuity of the coal zone as well as delineating intra-coal events. The extraction of Vp/Vs from P-wave and S-wave seismic data yields a high Vp/Vs value in the near surface (∼5), decreasing to approximately 2.5 at 300 m depth. Reflectivity values extracted from walkaway surveys demonstrate that converted-wave data better resolve the upper coal contact than compressional-wave data, as they are less affected by tuning. Numerical modelling demonstrates "proof of concept" that time-lapse seismic imaging will be able to monitor changes in the reservoir resulting from dewatering, allowing producers to optimize enhanced coalbed methane production throughout reservoir life. |
