Seismic Methodologies Adapted for Use in Acoustic Logging

Abstract

As our industry transitions to a dependence on the more costly unconventional reservoirs, we strive to find new and more efficient ways to produce from those reservoirs. There has been much focus on drilling and hydraulic fracturing technologies, but what about identifying natural fractures? It is well known that natural fractures exist in the producing zones. It is also well known that only about twenty percent of the fraced area actually produces. If we, as an industry, were better able to identify the naturally fractured zones – we would be able to focus on that twenty percent of producing zones. Currently, the industry uses acoustic logging or imaging to infer or find fractured zones. Unfortunately, however, the move to unconventional reservoirs has brought shortcomings in those techniques to the forefront. For images, widespread use of oil-based mud and the common practice of drilling high angle wells render image data mostly unusable. For shear wave anisotropy, fractures are simply inferred and, for many reasons, that inference cannot be relied on, particularly in unconventional reservoirs. Perhaps imaging and shear wave anisotropy need to make way for different processing techniques. Furthermore, present day tools are only able to detect anisotropy when logged sections are more than five percent anisotropic, leaving the subtle fracture systems undetected. For this last issue, we need look no further than seismic and microseismic techniques for guidance. Due to issues with signal attenuation and a high signal-to-noise ratio, seismic has long used several techniques, such as stacking, to improve results and amplify anomalies. In this discussion, we explore how we have adopted techniques from seismic and microseismic to provide useful and informative results on fractures creating a new processing technique for acoustic logging.

AAPG Datapages/Search and Discovery Article #90216 ©2015 AAPG Annual Convention and Exhibition, Denver, CO., May 31 - June 3, 2015