Explore the unique geomechanical properties of Monterey Formation siliceous mudrocks

The Monterey Formation is a Miocene-age siliceous mudrock and one of the most prolific source and reservoir rock sequences in the western United States. Across three phases of silica diagenesis^{1Silica diagenesis is the stepwise transformation of biogenic opaline silica through burial: opal-A (amorphous) to opal-CT (cristobalite-tridymite) to quartz. Each step rearranges the silica fabric and fundamentally changes porosity, density, and hardness. Since Bramlette (1946): The Miocene Monterey Formation of California revisited, Behl, R. J. (1999).} rock strength, porosity, and reservoir quality dramatically shift.

With over 1,500 rebound hardness^{2Rebound (Leeb) hardness, HLD: a non-destructive surface-hardness measurement made by firing a small impact body at the rock and measuring the rebound velocity. Reported as a unit-less Leeb number (HLD); higher = harder. Quick, repeatable, and sensitive to composition and porosity in mudrocks.} measurements spanning five burial groups we quantify trends previously understood only qualitatively, revealing how these rocks are unlike most other shales. The implications apply to favorable production in transition zones, interpreting mechanical stratigraphy over time, and strategies to target the deep unconventional exploration in California. We want you to have your own ah-ha moment, so please explore, filter, and download the full dataset below.