Development of an improved methodology to assess potential unconventional gas resources in North America

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Title: Development of an improved methodology to assess potential unconventional gas resources in North America
Author: Salazar Vanegas, Jesus
Abstract: Since the 1970s , various private and governmental agencies have conducted studies to assess potential unconventional gas resources , particularly those resources contained in tight sands , fractured shales , and coal beds . The US Geological Survey (USGS ) has assessed the amount of unconventional gas resources in North America , and its estimates are used by other government agencies as the basis for their resource estimates . While the USGS employs a probabilistic methodology , it is apparent from the resulting narrow ranges that the methodology underestimates the uncertainty of these undiscovered , untested , potential resources , which in turn limits the reliability and usefulness of the assessments . The objective of this research is to develop an improved methodology to assess potential unconventional gas resources that better accounts for the uncertainty in these resources . This study investigates the causes of the narrow ranges generated by the USGS analyticprobabilistic methodology used to prepare the 1995 national oil and gas assessment and the 2000 NOGA series , and presents an improved methodology to assess potential unconventional gas resources . The new model improves upon the USGS method by using a stochastic approach , which includes correlation between the input variables and Monte Carlo simulation , representing a more versatile and robust methodology than the USGS analytic -probabilistic methodology . The improved methodology is applied to the assessment of potential unconventional gas resources in the Uinta -Piceance province of Utah and Colorado , and compared to results of the evaluation performed by the USGS in 2002 . Comparison of the results validates the means and standard deviations produced by the USGS methodology , but shows that the probability distributions generated are rather different and , that the USGS distributions are not skewed to right , as expected for a natural resource . This study indicates that the unrealistic shape and width of the resulting USGS probability distributions are not caused by the analytic equations or lack of correlation between input parameters , but rather the use of narrow triangular probability distributions as input variables . Adoption of the improved methodology , along with a careful examination and revision of input probability distributions , will allow a more realistic assessment of the uncertainty surrounding potential unconventional gas resources .
URI: http : / /hdl .handle .net /1969 .1 /5894
Date: 2007-09-17

Citation

Development of an improved methodology to assess potential unconventional gas resources in North America. Available electronically from http : / /hdl .handle .net /1969 .1 /5894 .

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