--> Ventura basin oil generation, timing, migration, and entrapment

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Ventura basin oil generation, timing, migration, and entrapment


Today in the Ventura basin large volumes of oil and gas are being generated in Miocene Monterey-Modelo source rocks and are actively migrating into high-relief late Quaternary structures. These structures contain much of the oil and gas found to date. The western Ventura basin kitchen is widespread and generation rates there are high. In contrast, the eastern kitchen is divided into generating synclines and presently growing anticlines whose uplift is shutting off previously generating source rock. During Pliocene and Miocene time significant hydrocarbon was generated, but because the basin was much wider and less structured, migration paths were different. In the east, numerous early-formed but low-relief anticlines were present to trap this early-generated oil. In the west, much oil was generated, but few anticlines were present, so mainly early-formed stratigraphic or fault-related pools were present. Migration pathways have strongly controlled oil field distribution as they varied over time. For example, today the fetch area for the Ventura-San Miguelito-Rincon anticlinorium is large, as are the oil pools. In contrast, the huge Pico anticline in the eastern Ventura basin is almost dry; it is mostly migration shadowed behind the Newhall-Potrero anticline. Much of the southern flank of the basin is now migration shadowed behind the Oak Ridge anticlinorium. The western basin contains the largest oil fields because Monterey-Modelo source rock facies are very rich there. Eastern source facies are much leaner in part because they were diluted by clastics shed from nearby San Gabriel basement complex highlands.