The growth of world energy requirements over the last two decades has created an increasing demand for crude oil. Production has doubled in each of the decades to meet the demand and it is forecast that the demand for crude oil will continue to increase to 1985. The annual production rate has now reached the level of the average annual discoveries over the last 25 years, and the remaining proved recoverable reserves will probably decline continuously as production rates continue to grow. The declining reserves will be insufficient to support the forecast demand after about 1978 when the demand may be limited by the availability of crude oil. It is estimated that about half of the ultimate recoverable reserves have been found to date. The discovery of the remaining reserves will present difficult technical problems.