Fracture networks and mechanical stratigraphy in the Monterey-equivalent pismo formation and its relationship to primary sedimentology and stratigraphy at Montana de Oro State Park, California

The Monterey-equivalent Miguelito Member of the Pismo Formation at Montana de Oro State Park displays four orders of fracture length from several cm to tens of meters and three sets of fracture orientation in a ∼200-m-thick stratigraphic section north of Spooner's Cove. Characterization of fractures such as these is crucial to understanding reservoir behavior in low-permeability, fine-grained rocks that require natural or induced fractures for economic hydrocarbon production. Fracture spacing and fracture trace length are related to primary sedimentary lithologic cycles and vary with bed-thickness and lithologic composition. Three distinct fracture sets reflect the regional maximum horizontal stress direction and their frequency and length are affected by pre-existing fractures, tuffaceous horizons, and mudstone-dominated lithstratigraphic packages greater than 10 meters in thickness. The fracture networks differ from north to south and show significantly different manifestations of strain expressed in all orders of fractures.