Reasonably reliable resource estimation is basic to planning and investment decisions in petroleum exploration. The basic need is to improve this reliability, but it is doubtful that this can be accomplished in a constantly changing resource situation by introducing an extensive array of vaguely defined, questionably contributory, and time-consuming subcategory terminologies.
Similarly, the use of artificially chosen yardsticks has no assured value as the prime basis for estimating potential resources, although such yardsticks are useful for quantitatively representing or comparing the volumes or incidences of estimated occurrence. Geologic criteria, including geologic interpretation, are the only criteria having any measurement value in regard to the results of the worldwide exploration experience of the industry. Many factors determine or affect the incidence of petroleum occurrence.
Worldwide interest in world resources and their estimation, particularly that of energy, dates back to the founding of the United Nations. A conservative projection of the upward trend of overall world energy demand in the past 20 years indicates what the total demand might be during the next 100 years, if supplies of energy and all of the other required industrial raw materials are, or could continuously be made, readily and economically available. Projections extending so far into the future involve many elements of uncertainty other than those of availability; not the least of these are economic and political variables. Nevertheless, any reasonably possible projection of potential petroleum supply from conventional sources shows that they may reach their peak of production near or soon after the turn of the century; at that time petroleum will provide about 10–15 percent of the indicated potential world energy demand. It will supply a similar proportion of United States energy demand, and the greater part of it will be imported.
By the year 2020, the amount of energy supplied by petroleum will have decreased to about 6–8 percent of the larger world demand. Conventional petroleum supply will continue to decline for perhaps another 100 years, ending in a comparative trickle, although it still will be in demand. Its contribution to the indicated total energy demand over a period of 100 years from the present will be less than 4 percent.
Petroleum is unique as an energy and raw-material source by reason of its vast and unparalleled utility and convenience. For all forms of transportation, it is the only practicable energy source. It is unsurpassed not only as an energy source, but also as a raw material for a great host of industry uses because of its chemistry and end-product versatility. Above all, the cost of petroleum is still, and probably will continue to be, unmatched by any of the other presently known sources.