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Open-File Report 2012–1146

Analytic Resource Assessment Method for Continuous (Unconventional) Oil and Gas Accumulations—The "ACCESS" Method

By Robert A. Crovelli, revised by Ronald R. Charpentier, 2012

Thumbnail of and link to report PDF (1.46 MB)Introduction

The U.S. Geological Survey (USGS) periodically assesses petroleum resources of areas within the United States and the world. The purpose of this report is to explain the development of an analytic probabilistic method and spreadsheet software system called Analytic Cell-Based Continuous Energy Spreadsheet System (ACCESS). The ACCESS method is based upon mathematical equations derived from probability theory. The ACCESS spreadsheet can be used to calculate estimates of the undeveloped oil, gas, and NGL (natural gas liquids) resources in a continuous-type assessment unit. An assessment unit is a mappable volume of rock in a total petroleum system. In this report, the geologic assessment model is defined first, the analytic probabilistic method is described second, and the spreadsheet ACCESS is described third. In this revised version of Open-File Report 00–044 , the text has been updated to reflect modifications that were made to the ACCESS program. Two versions of the program are added as appendixes.

First posted August 7, 2012

For additional information contact:
Director, Central Energy Resources Science Center
U.S. Geological Survey
Box 25046, MS-939
Denver Federal Center
Denver, CO 80225-0046

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Suggested citation:

Crovelli, R.A., 2012, Analytical resource assessment method for continuous (unconventional) oil and gas accumulations—The “ACCESS" Method: U.S. Geological Survey Open-File Report 2012–1146, 32 p. [Revised by Charpentier, R.R.]



Geologic Assessment Model

Analytic Probabilistic Method

Spreadsheet System


References Cited

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