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Natural Resources Research

, Volume 19, Issue 4, pp 253–268 | Cite as

Development of an Improved Methodology to Assess Potential Unconventional Gas Resources

  • Jesus Salazar
  • Duane A. McVay
  • W. John Lee
Article

Abstract

Considering the important role played today by unconventional gas resources in North America and their enormous potential for the future around the world, it is vital to both policy makers and industry that the volumes of these resources and the impact of technology on these resources be assessed. To provide for optimal decision making regarding energy policy, research funding, and resource development, it is necessary to reliably quantify the uncertainty in these resource assessments. Since the 1970s, studies to assess potential unconventional gas resources have been conducted by various private and governmental agencies, the most rigorous of which was by the United States Geological Survey (USGS). The USGS employed a cell-based, probabilistic methodology which used analytical equations to calculate distributions of the resources assessed. USGS assessments have generally produced distributions for potential unconventional gas resources that, in our judgment, are unrealistically narrow for what are essentially undiscovered, untested resources. In this article, we present an improved methodology to assess potential unconventional gas resources. Our methodology is a stochastic approach that includes Monte Carlo simulation and correlation between input variables. Application of the improved methodology to the Uinta–Piceance province of Utah and Colorado with USGS data validates the means and standard deviations of resource distributions produced by the USGS methodology, but reveals that these distributions are not right skewed, as expected for a natural resource. Our investigation indicates that the unrealistic shape and width of the gas resource distributions are caused by the use of narrow triangular input parameter distributions. The stochastic methodology proposed here is more versatile and robust than the USGS analytic methodology. Adoption of the methodology, along with a careful examination and revision of input distributions, should allow a more realistic assessment of the uncertainty surrounding potential unconventional gas resources.

Keywords

Resource assessment unconventional resources natural gas uncertainty quantification 

Nomenclature

Bcf

billion cubic feet

CBM

coalbed methane

EIA

Energy Information Administration

N

number of potential untested cells

NPC

National Petroleum Council

P0

minimum value for triangular distribution

P5

percentile representing a 5% probability that at least the value exists

P50

percentile representing a 50% probability that at least the value exists

P95

percentile representing a 95% probability that at least the value exists

P100

maximum value for triangular distribution

PGC

Potential Gas Committee

R

untested percentage of assessment-unit area

S

potential percentage of untested AU area

T

potential untested percentage of AU area

Tcf

trillion cubic feet

TPS

total petroleum system

U

assessment-unit area

USGS

United States Geological Survey

V

area per cell of untested cells

W

potential untested area of assessment unit (AU)

X

total recovery per cell

Y

total gas resources in the assessment unit

σ

standard deviation

μ

mean value

Notes

Acknowledgments

This research project was funded by the ConocoPhillips and the Crisman Institute for Petroleum Research at the Harold Vance Department of Petroleum Engineering at Texas A&M University. We acknowledge the important contributions of Loring P. White, a USGS consultant. This paper was originally presented as SPE 107974 at the 2007 Rocky Mountain Oil & Gas Technology Symposium, held April 16–18 in Denver, Colorado.

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Copyright information

© International Association for Mathematical Geology 2010

Authors and Affiliations

  1. 1.Department of Petroleum Engineering, 3116 TAMUTexas A&M UniversityCollege StationUSA

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