Abstract

The latest estimates of the Nation’s conventional oil and natural gas resources have been published in a detailed report as Circular 725 by the U.S. Geological Survey, June 1975. This report was prepared at the request of the Federal Energy Administration by the Resource Appraisal Group in the Branch of Oil and Gas Resources, Denver, Colorado.

The report summarizes the estimates of undiscovered recoverable resources of oil, natural gas and natural gas liquids of the U.S. as assessed by the Resource Appraisal Group based upon a comprehensive evaluation by over 70 U.S. Geological Survey geologists on a large quantity of fundamental geological and geophysical data gathered on more than 100 potential petroleum provinces for onshore Alaska and the Lower 48 States, and all offshore U.S. Continental Shelves.

This paper describes briefly the evaluation methods, the data systems, and a series of mathematical and statistical procedures applied to the basic data. Probability distributions are discussed for each of the 15 regions, and various combinations of subtotals and totals.

The Resource Appraisal Group’s estimates (based upon a 95-5 percent probability range) for the Nation’s total undiscovered recoverable resources amount to 50–127 billion barrels of crude oil with a mean of 82 billion barrels (current national economic recovery factor of 32 percent); 322–655 trillion cubic feet of natural gas with a mean of 484 trillion cubic feet (current national economic recovery factor of 80 percent); and 11-22 billion barrels of natural gas liquids with a mean of 16 billion barrels.

The subeconomic portion of the remaining resources for oil is estimated to be an additional 28 percent recoverable, for a total of 60 percent recovery. This could amount to an additional 120–140 billion barrels presently identified but currently subeconomic and another 44–111 billion barrels currently undiscovered and subeconomic. The subeconomic portion of the natural gas resources is estimated to be an additional 10 percent recoverable, for a total of approximately 90 percent recovery. This could amount to an additional 90-115 trillion cubic feet presently identified but currently subeconomic and another 40-82 trillion cubic feet currently undiscovered and subeconomic. These relationships are discussed briefly in the paper.

A “best estimate” including both the total remaining identified reserves and the undiscovered recoverable resources reported from this study is: 144 billion barrels of oil, 923 trillion cubic feet of gas and 28 billion barrels of natural gas liquids. Total production through 1974 is 106 billion barrels of oil, 481 trillion cubic feet of gas and 16 billion barrels of NGL.

The Resource Appraisal Group is continuing the development of and improvement on a comprehensive resource appraisal system within the USGS. As new data, new interpretations and new procedures are incorporated into the system the current estimates will be subject to revision. However, on the basis of the estimating procedures used involving the concepts of total resource base these changes are not expected to be of any significant magnitude for the United States as a whole within the foreseeable future.