10/10/2011
Production Forecasting for
Unconventional Resources
Lecture 1
Overview
Why Do We Need to Forecast Production?
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Provide estimate of reserves for internal or external
reporting purposes
Provide basis for economic analysis of future
production
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10/10/2011
What Forecasting Techniques Are Used?
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Extrapolation of decline curves
 Basic – e.g., Arps model
 Advanced – e.g., Fetkovich, Blasingame
models
Analytical well or reservoir simulators
Numerical well or reservoir simulators
Analogy with similar wells or reservoirs
 Type curves with distinguishing parameters
Standard solutions to flow equations
describing transient or stabilized flow
Forecasting Methods of Special Interest in
Unconventional Reservoirs
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Production decline curves – rate-time and
rate-cumulative
Type curves based on analogy and models
Production data analysis software
 Advanced decline curve analysis
 Empirical and theoretical models
Analytical and numerical models
 History match for model calibration
 Forecasting using calibrated model
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10/10/2011
Topics Featured in This Course – 1
Basic fluid flow theory
 Transient flow
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Radial flow
Linear flow
Constant rate and constant BHP
production
Radius of investigation
Boundary-dominated flow
Topics Featured in This Course – 2
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Fundamentals of type curve analysis
Arps’ decline model and modifications
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Original Arps model and limitations
Minimum terminal decline methodology
A priori determination of Arps decline
constant
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Topics Featured in This Course – 3
Alternative decline models
 Advanced decline curve analysis
 Stretched exponential decline model
(SEDM)
 Power-law and modified power-law
model
 Long-duration linear flow model
 Duong model
What’s Required of a Method to Estimate
Reserves Under the U.S. SEC Regulations?
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Regulations now ‘principles based,’ no
longer ‘rules based’
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Implication: More focus on outcomes
(results), less on inputs (how results were
obtained)
Any method that meets criteria (and
demonstrated to be ‘reliable technology’)
should be acceptable – from basic Arps
decline model to sophisticated numerical
reservoir simulator
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Criteria for SEC Reserves Categories
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1P (proved)
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2P (proved plus probable)
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‘Reasonably certain’
Much more likely than not (e.g., 90+% probability)
Given more data with time, EUR should increase or
remain constant most of the time
As likely as not (50% probability)
Business-decision case
3P (proved plus probable plus possible)
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Possible, but not likely (10% probability)
What Does PRMS Require?
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Basically, same as SEC
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PRMS also principles-based system
PRMS even more flexible than SEC
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10/10/2011
How Can We Demonstrate That We’ve Met
Regulators’ Criteria?
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Select method to estimate reserves
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Choice is ours
For unchanging group of wells, compare
EUR estimates using preferred method
as reserves estimates are updated
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If EUR consistently constant or increasing, 1P criterion met;
method should be acceptable
If EUR increasing or constant as often as not, 2P criterion
met
If EUR, although generally decreasing, appears reasonable
using other checks (e.g., volumetrics and recovery
efficiencies), 3P criterion met
Plan for Course
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Critique methods that have the potential
to satisfy SEC (and PRMS) criteria for 1P
and 2P reserves – the most important
categories
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10/10/2011
Production Forecasting for
Unconventional Resources
Lecture 1
Overview
7