Timing and velocity of petroleum migration in the Los Angeles Basin

Petroleum in the Los Angeles Basin took a relatively short time to migrate through carrier beds from the deep basin to present-day reservoirs. A numerical model is used to reconstruct, beginning in Miocene time, subsidence, sedimentation, compaction, thermal evolution, and fluid migration in the basin's central block. The modeling indicates that the heat flow is currently near the continental average but was higher during the early evolution of the basin. The thermal history predicted by the model suggests deeply subsided source rocks of late Miocene age began to generate oil about 2.2 Ma. The buoyant force acting on the oil phase along the steeply dipping carrier beds was as much as an order of magnitude greater than the hydrodynamic force acting on both oil and water. This difference, along with the assumption that capillary forces segregated oil into the most porous and permeable laminae of the carrier beds, leads us to estimate conservatively that the oil migrated through the carrier beds at velocities 6 to >100 times faster than water. -from Authors