Focused fluid-flow structures potentially caused by solitary porosity waves

Gas chimneys, fluid-escape pipes, and diffused gas clouds are common geohazards above or below most petroleum reservoirs and in some CO2 storage sites. However, the processes driving the formation of such structures are poorly understood, as are the time scales associated with their growth or their role as long-term preferential fluid-migration pathways in sedimentary basins. We present results from a multidisciplinary study integrating advanced seismic processing techniques with high-resolution simulations of geological processes. Our analyses indicate that time-dependent rock (de)compaction yields ascending solitary porosity waves forming high-porosity and high-permeability vertical chimneys that will reach the surface. The size and location of chimneys depend on the reservoir topology and compaction length. Our simulation results suggest that chimneys in the studied area could have been formed and then lost their connection to the reservoir on a time scale of a few months.

Automated summary

Gas chimneys, fluid-escape pipes, and diffused gas clouds are common geohazards in petroleum reservoirs and CO2 storage sites. The processes behind the formation of these structures and their role as long-term fluid-migration pathways are poorly understood. Through a multidisciplinary study, including advanced seismic processing techniques and high-resolution simulations, we found that time-dependent rock (de)compaction leads to the formation of high-porosity and high-permeability vertical chimneys that reach the surface. Our simulation results suggest that chimneys in the studied area could have formed and lost their connection to the reservoir within a few months.