There has long been interest in the flow of fluids through permeable aqui- fers. Stratigraphic trapping of oil and gas by permeability changes in an aquifer and the amounts of hydrocarbons so trapped are major concerns to the oil industry. The variations of aquifer width and geometry and of the positions in an aquifer where hydrocarbons can be trapped by hydro- dynamic forces are intimately intertwined in determining the shape, and thus the volume, of hydrocarbons. Perhaps the seminal work in this area is reflected by King Hubbert's massive review paper "Entrapment of Petroleum under...