Observations in deep sedimentary basins around the world confirm the theory of gravity-induced cross-formational flow of groundwater. Thus, geologically mature basins are hydraulically continuous environments in which the relief of the water table, commonly a subdued replica of the land surface, generates interdependent systems of groundwater flow with patterns modified by permeability differences. In these systems, meteoric waters infiltrate and move downward in upland recharge areas, migrate laterally under regions of medium elevations, and are discharged in topographic depressions. Where flow systems meet or part, relatively stagnant zones develop and flow directions change abruptly.

The theory is advanced that in geologically mature basins, gravity-induced cross-formational flow is the principal agent in the transport and accumulation of hydrocarbons. The mechanism becomes operative after compaction of sediments and the concomitant primary migration cease, and subaerial topographic relief develops. Hydrocarbons from source or carrier beds are then moved along well-defined migration paths toward discharge foci of converging flow systems, and may accumulate en route in hydraulic or hydrodynamic traps. Accordingly, deposits are expected and observed to be associated preferentially with ascending limbs and stagnant zones of flow systems and hence to be characterized by relative potentiometric minima, downward increase in hydraulic heads possibly reaching artesian con itions, reduced or zero lateral hydraulic gradients, and relatively high groundwater salinity. Continuous flow of meteoric waters imports hydrocarbons into such traps until the trap capacity is reached. The excess becomes source material for new accumulations. A temporal change in surface topography causes a proportionate but delayed readjustment of the flow pattern and redistribution of petroleum. Nevertheless, some hydrocarbons may remain in place, constituting residual deposits in discharge and stagnant regions of relict flow systems.

This study reconfirms previous versions of the hydraulic theory of petroleum migration as valid representations of component parts of the migration-accumulation process. However, by introducing the geometry of migration paths in the form of quantitatively defined groundwater flow patterns it integrates existing concepts and observations into a generalized hydraulic theory of petroleum migration.