MODELING THE PETROLEUM SYSTEMS IN THE SAN JOAQUIN BASIN, CALIFORNIA

The Great Valley of California is a petroleum-productive forarc basin located between the Sierra Nevada and Coast Ranges. The north-trending basin is asymmetric with its structural axis shifted to the west. An east-trending (Stockton) arch separates the Great Valley into the Sacramento basin (north) and the San Joaquin basin (south).

Based on carbon isotopic and biomarker data, three oil types each representing a discrete petroleum system are identified in the San Joaquin basin that compare favorably to three different source rocks: the Eocene Kreyenhagen Formation, an unnamed Oligocene source rock, and the Miocene Antelope Shale within the Monterey Formation. Together, these three petroleum systems are known to have generated at least 15 billion barrels of recoverable oil and 19 trillion ft³ of recoverable gas.

Petroleum system modeling history and geochemical evidence indicates that maximum burial occurred in latest Pliocene to Pleistocene time. Except on the west flank of the basin, where steep dips in outrcop and seismic data indicate substantial uplift and erosion, only a minor amount of section has been eroded. Geochemical evidence indicates the different oil types seldom shared the same migration path and that most oil migration occurred in distinct stratigraphic intervals during the Late Cenozoic. Using PetroMod software, 1D, 2D, and 3D models depict the evolution and geometry of the petroleum systems.