by U.S. Dept. of the Interior, U.S. Geological Survey in Denver, Colo .
Written in English
|Statement||by Robert A. Crovelli and James W. Schmoker|
|Series||Open-file report -- 99-419, U.S. Geological Survey open-file report -- 99-419|
|Contributions||Schmoker, J. W, Geological Survey (U.S.)|
|The Physical Object|
|Number of Pages||23|
U.S. Geological Survey Bulletin C: Probabilistic Method for Estimating Future Growth of Oil and Gas Reserves. EUR Estimate Ultimate Recovery, bbl Oil Content in produced liquid, % Water Content in produced liquid, % f (y|θ) Likelihood function GOR Gas Oil Ratio Oil relative permeability, d. imensionless Water relative permeability, dimensionless K. Potential EUR without imposing economic limits, Mcf. Oil and gas exploration is arguably the riskiest of all commercial activities. As a result, the utilization of probability and statistics in the oil and gas industry is becoming widely accepted as a method to estimate oil and gas exploration prospect size. Analysis typically utilizes the Monte Carlo simulation method and one of the commercial. ) Empirical methods of estimating reserves When performance trends have not been properly established with respect to oil and gas production, estimates of future production rate and proved reserves may be made by analogy to older reservoirs in the same geographic area that have similar characteristics and already established performance trends.
A probabilistic model for oil exploration can be developed by assessing the conditional relationship between perceived geologic variables and the subsequent discovery of petroleum. Such a model includes two probabilistic components, the first reflecting the association between a geologic condition (structural closure, for example) and the occurrence of oil, and the second reflecting the. The American Association of Petroleum Geologists president promotes wider reliance than exists now on probabilistic methods of estimating oil and gas reserves. Oil and gas reserves calculations. Oil and Gas Reserves Committee, and WPC with the assignment of drafting the joint definitions. is dependent on them being consistent with the purpose of the reserve estimate, appropriate contract obligations, corporate procedures, and government regulations involved in reporting the reserves. probabilistic methods. . ()=pdf.). Estimating volumes of reserves and resources to provide a “book value” (total assets of a company) is mandatory for any publicly listed oil and gas firm. The primary objective of this process is to arrive at a consistent volume and associated value assessment for companies, investors, lenders, and .
A hypothetical gas reservoir demonstrates some of the problems inherent in probabilistic methods. Table 1 lists the input parameters required to calculate reserves with a probabilistic method. Defining and modeling trends in these historical data and extrapolating these trends into the future to estimate some aspect of the remaining resources form the core in these methods. Simple decline rate models (e.g. exponential, hyperbolic) are sometimes used to describe exploration success and total resources (Dolton et al., ). of the volumetric contribution of reserve growth to the future supply of oil and natural gas. Understanding past methods of estimating future volumes based on the data assembly meth-ods that have been used can lead to a better understanding of their applicability. The statistical nature of past methods . Figure 1: Magnitude of uncertainty in reserves estimates The oil and gas reserves estimation methods can be grouped into the following categories: 1. Analogy, 2. Volumetric, 3. Decline analysis, 4. Material balance calculations for oil reservoirs, 5. Material balance calculations for gas reservoirs, 6. Reservoir simulation.