What scientific ocean drilling has taught us about the permeability of marine sediments

Scientific ocean drilling has provided a significant amount of information about the marine subsurface over the last 57 years, including samples and data pertaining to physical properties, geochemistry, microbiology, lithology, stratigraphy, and structural geology. Our understanding of subsurface mass transport has benefited from many hundreds of permeability measurements performed on scientific ocean drilling samples. We assembled a database of 836 permeability measurements along with other physical properties measured shipboard, including determinations of porosity and grain density from moisture and density (MAD) measurements, natural gamma radiation and magnetic susceptibility from multisensory core logger (MSCL) measurements, total carbonate content, and lithological description, silt percentage, and clay percentage from smear slides. The goals of our study were assessing the state of our understanding of marine sediment permeability, assessing processes that control permeability, and the best ways to leverage legacy ocean drilling samples and datasets to improve our understanding of the subsurface. We found that the majority of permeability samples (71 %) come from the Pacific Ocean, particularly its active margins; that clays and silts are the most frequently tested lithologies; that the depth distribution of samples is similar to the overall depth distribution of drilled holes, indicating that the data are not biased towards particular depth ranges; and that the permeabilities obtained span nearly 11 orders of magnitude. We observed weak to no correlation between permeability and the physical properties we considered, but we were able to train a random forest regression model to predict permeability within about half an order of magnitude based on measurements that were performed previously or can be obtained from unpreserved, legacy cores. This presents an opportunity to be able to predict permeability in more locations globally and answer research questions about fluid flow and pore pressure.