Publications

Growth of compaction bands: A new deformation mode for porous rock

Olsson, William A.; Holcomb, David J.

Compaction bands are thin, tabular zones of grain breakage and reduced porosity that are found in sandstones. These structures may form due to tectonic stresses or as a result of local stresses induced during production of fluids from wells, resulting in barriers to fluid (oil, gas, water) movement in sandstone reservoirs. To gain insight into the formation of compaction bands the authors have produced them in the laboratory. Acoustic emission locations were used to define and track the thickness of compaction bands throughout the stress history during axisymmetric compression experiments. Narrow zones of intense acoustic emission, demarcating the boundaries between the uncompacted and compacted regions were found to develop. Unexpectedly, these boundaries moved at velocities related to the fractional porosity reduction across the boundary and to the imposed specimen compression stress. This appears to be a previously unrecognized, fundamental mode of deformation of a porous, granular material subjected to compressive loading with significant implications for the production of hydrocarbons.