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R. A. Crovelli

Publications and source records attributed to R. A. Crovelli.

50 records · Page 3Linked to original sources
USGS1989

Estimates of undiscovered conventional oil and gas resources in the United States: A part of the Nation's energy endowment

In 1987, the U.S. Geological Survey and the Minerals Management Service completed a new assessment of the undiscovered conventional resources of crude oil and natural gas in the United States. This assessment responded to a national need for such estimates, considered new geological, technologic, and economic information, and used more definitive methods of resource appraisal than previous assessments. The conventional resources assessed were (1) those considered recoverable under current technology and (2) those that could be developed and produced economically under specified price and cost relationships, excluding exploration costs. This study did not include resources from tar deposits, intractable heavy oil deposits, oil shales, gas in low-permeability (less than 0.1 millidarcy in situ) "tight" reservoirs, coal bed methane, gas in geopressured shales and brines, and natural gas hydrates (clathrates). For this study, the United States was divided into 13 regions (9 onshore and 4 offshore), including the Exclusive Economic Zone (EEZ). The 13 regions were further divided into 115 provinces (appendix A, figs. Al and A2). The resource estimates were based fundamentally upon review and analysis of petroleum geology and the exploration history of oil and gas plays in these provinces. Probability procedures were used in their derivation. Because of the uncertainty in estimating undiscovered resources, the estimated quantities are reported as a range of values that correspond to different probability levels. The undiscovered recoverable conventional resources of oil for the United States, as of January, 1, 1987, are estimated to range from 33 to 70 billion barrels, with a mean estimate of 49 billion barrels: the estimates of gas range from 307 to 507 trillion cubic feet, with a mean estimate of 399 trillion cubic feet (table 1). Range estimates correspond to 95-percent probability (19 in 20 chance) and 5-percent probability (1 in 20 chance) of there being more than those amounts, respectively. Corresponding estimates for natural gas liquids (NGL) range from 6 to 12 billion barrels, with a mean estimate of 9 billion barrels. Further, the assessed undiscovered economically recoverable oil and gas resources for the United States, as of January 1, 1987, are estimated to range from 21 to 54 billion barrels of oil and 208 to 326 trillion cubic feet of gas, corresponding to the 95-percent and 5-percent probabilities of there being more than these amounts, respectively (table 1). The mean value for oil is 35 billion barrels and for gas is 263 trillion cubic feet. Corresponding estimates for NGL range from 5 to 8 billion barrels, with a mean of 6 billion barrels. Distribution of these resources by region is shown in figure 1.

Report↗
USGS1988

Multi-model approach to petroleum resource appraisal using analytic methodologies for probabilistic systems

The geologic appraisal model that is selected for a petroleum resource assessment depends upon purpose of the assessment, basic geologic assumptions of the area, type of available data, time available before deadlines, available human and financial resources, available computer facilities, and, most importantly, the available quantitative methodology with corresponding computer software and any new quantitative methodology that would have to be developed. Therefore, different resource assessment projects usually require different geologic models. Also, more than one geologic model might be needed in a single project for assessing different regions of the study or for cross-checking resource estimates of the area. Some geologic analyses used in the past for petroleum resource appraisal involved play analysis. The corresponding quantitative methodologies of these analyses usually consisted of Monte Carlo simulation techniques. A probabilistic system of petroleum resource appraisal for play analysis has been designed to meet the following requirements: (1) includes a variety of geologic models, (2) uses an analytic methodology instead of Monte Carlo simulation, (3) possesses the capacity to aggregate estimates from many areas that have been assessed by different geologic models, and (4) runs quickly on a microcomputer. Geologic models consist of four basic types: reservoir engineering, volumetric yield, field size, and direct assessment. Several case histories and present studies by the U.S. Geological Survey are discussed. ?? 1988 International Association for Mathematical Geology.

Mathematical Geology↗
USGS1987

Probability theory versus simulation of petroleum potential in play analysis

An analytic probabilistic methodology for resource appraisal of undiscovered oil and gas resources in play analysis is presented. This play-analysis methodology is a geostochastic system for petroleum resource appraisal in explored as well as frontier areas. An objective was to replace an existing Monte Carlo simulation method in order to increase the efficiency of the appraisal process. Underlying the two methods is a single geologic model which considers both the uncertainty of the presence of the assessed hydrocarbon and its amount if present. The results of the model are resource estimates of crude oil, nonassociated gas, dissolved gas, and gas for a geologic play in terms of probability distributions. The analytic method is based upon conditional probability theory and a closed form solution of all means and standard deviations, along with the probabilities of occurrence. ?? 1987 J.C. Baltzer A.G., Scientific Publishing Company.

Annals of Operations Research↗
USGS1986

FASP, an analytic resource appraisal program for petroleum play analysis

An analytic probabilistic methodology for resource appraisal of undiscovered oil and gas resources in play analysis is presented in a FORTRAN program termed FASP. This play-analysis methodology is a geostochastic system for petroleum resource appraisal in explored as well as frontier areas. An established geologic model considers both the uncertainty of the presence of the assessed hydrocarbon and its amount if present. The program FASP produces resource estimates of crude oil, nonassociated gas, dissolved gas, and gas for a geologic play in terms of probability distributions. The analytic method is based upon conditional probability theory and many laws of expectation and variance. ?? 1986.

Computers & Geosciences↗
USGS1985

Comparative study of aggregations under different dependency assumptions for assessment of undiscovered recoverable oil resources in the world

The U.S. Geological Survey assessed all significant sedimentary basins in the world for undiscovered conventionally recoverable crude-oil resources. Probabilistic methodology was applied to each basin assessment to produce estimates in the form of probability distributions. Basin probability distributions were computer aggregated to produce resource estimates for the entire world. Aggregation was approximated by a three-parameter lognormal distribution by combining the first three central moments of basin distributions. For purposes of experiment and study, world aggregation was conducted under four different sets of assumptions. The four cases are (1) dependent assessments of all basins, (2) dependent assessments within continental areas, but independent assessments among continental areas, (3) dependent assessments within countries, but independent assessments among countries, and (4) independent assessments of all basins. Mean estimate remained the same in all four cases, but the width of interval estimate formed using the 95th and 5th fractiles decreased with reduced dependency in going from first to fourth case. ?? 1985 Plenum Publishing Corporation.

Journal of the International Association for Mathe↗
USGS1984

U.S. Geological Survey probabilistic methodology for oil and gas resource appraisal of the United States

Probabilistic methodology used by the U.S. Geological Survey is described for estimating the quantity of undiscovered recoverable conventional resources of oil and gas in the United States. A judgmental probability distribution of the "quantity of resource" and its properties is determined for a geologic province or basin. From this distribution, point and interval estimates of the quantity of undiscovered resource are obtained. Distributions and their properties are established for each of the following resources: (1) oil and nonassociated gas from estimates of the probability of the resource being present and the conditional probability distribution of the quantity of resource given that the resource is present, (2) associated-dissolved gas from its corresponding oil distribution, (3) total gas, (4) oil and total gas in two or more provinces. Computer graphics routines are illustrated with examples from the U.S. Geological Survey Circular 860. ?? 1984 Plenum Publishing Corporation.

Journal of the International Association for Mathe↗