The experiments described in this paper were performed to illustrate certain changes which are believed to affect the oil-water and gas-oil contacts in actual oil fields under certain conditions of oil production. They demonstrate the fact that slow, uniformly distributed extraction yields more oil, and yields this oil more efficiently, than rapid and irregularly distributed extraction. They show that where fine and coarse layers of sand alternate, there is a tendency for more rapid water encroachment in the coarser layers, with resulting by-passing and loss of oil in the finer layers. And they show further that conservation of the gas, and therefore of the gas energy, in a reservoir effects a larger ultimate recovery of the oil than if the gas is produced contemporaneous y and without restriction. These experiments offer convincing proof of the advantages of proper utilization of the natural gas energy and the natural water drive within an oil reservoir.