The Evolution In The Development Of The Petroleum Resource Appraisal Procedures In The U.S. Geological Survey And A Summary Of Current Assessments For The United States
Authors: Miller Betty M. 
Published: December 2007

Abstract
Since the organization within the U.S. Geological Survey of the Oil and Gas Resource Appraisal Group in 1974, development of petroleum-resource-appraisal procedures has been significant. Newly evolved and developed resource-appraisal methods have been applied successfully to comprehensive investigations made for the Permian Basin and the Gulf of Mexico. Specific examples are reported for resource appraisals by age and depth increments in the Permian Basin and for discovery rate studies in the Gulf of Mexico. Estimates of the petroleum resources of the United States are summarized and current activities in resource appraisal work within the U.S. Geological Survey are reviewed.

Introduction
An understanding of the availability and distribution of our petroleum resources is a fundamental requirement for the formulation of a national energy policy. Predicting undiscovered petroleum resources is particularly risky, because in addition to the geologic uncertainty, economic and political uncertainties exist which may also determine whether a resource is available for development and is recoverable. We must be willing, however, to address the need for estimating the physical amounts of petroleum resources that remain available for use in order to plan for the rational exploration and development of these resources in the future.
In 1973, the political developments in the Middle East and the action of OPEC brought about critical oil shortages and a sharp increase in prices throughout most of the world. This situation highly dramatized for the public, as well as many government agencies, the critical importance of the availability of conventional oil and as resources from outside the United States. The crisis has served to focus attention on the need for domestic and foreign petroleum-resource assessments and the significance of the resource estimates in appraising the world's energy supply. The implications of energy shortages on the economic, social and strategic policies of our Nation has brought the subject of 'resource estimates' to the attention of the media, the public, congressmen and many government agencies.
The following discussion on the evolution in the development of resource-appraisal methods in the U.S. Geological Survey and the various problems related to resource appraisal is intended to provide a background such that the significance of estimating our petroleum resources can be better understood by the media and the public, and by those who formulate our national energy policy, both in and outside government.

Problems

Terminology
One of the major problems association with the application of conventional petroleum-resource estimates has arisen primarily from a confusion in defining the terms reserves and resources. Nearly every expert or group of experts has a different classification scheme which they use to define reserves and resources. Many of the terms in one classification are basically noncomparable to similar terms in another classification.

Terminology
One of the major problems association with the application of conventional petroleum-resource estimates has arisen primarily from a confusion in defining the terms reserves and resources. Nearly every expert or group of experts has a different classification scheme which they use to define reserves and resources. Many of the terms in one classification are basically noncomparable to similar terms in another classification.