Magoon, Leslie B.¹, Kenneth E. Peters¹, Allegra Hosford Scheirer¹, Carolyn Lampe², Donald L. Gautier¹, Paul G. Lillis³
(1) U.S. Geological Survey, Menlo Park, CA
(2) Integrated Exploration Systems, Jülich, Germany 
(3) U.S. Geological Survey, Denver, CO

ABSTRACT: Modeling Petroleum Systems in the San Joaquin Basin, California

The north-trending Great Valley of California is an asymmetric forarc basin located between the Sierra Nevada and Coast Ranges. The east-trending (Stockton) arch separates the Great Valley into the Sacramento basin (north) and the San Joaquin basin (south). Stable carbon isotope and biomarker data identify three principal oil types that correlate to three different source rocks: the Eocene Kreyenhagen Formation, the Oligocene Tumey Formation, and the Miocene Antelope Shale within the Monterey Formation. Together, these three petroleum systems generated at least 15 billion barrels of recoverable oil and 19 trillion ft³ of recoverable gas. 
We generated 1D, 2D, and 3D models using PetroMod software to depict the evolution and geometry of the petroleum systems. The modeling and geochemical evidence indicate 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 that the different oil types seldom shared the same migration path and that most oil migration occurred in distinct stratigraphic intervals during the Late Cenozoic. Fully PVT-controlled n-component migration modeling allowed simulation of phase behavior for all components during each time step. Phases and compositions were predicted for each major accumulation for both in situ and surface conditions and compared to known accumulations.

AAPG Search and Discovery Article #90026©2004 AAPG Annual Meeting, Dallas, Texas, April 18-21, 2004.