uncertainty analysis
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Volumetrics &
Uncertainty Management
EP00 - Introducing the E&P Businessp296
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EP00Terminology
STOIIP (GIIP) The volume of oil (gas) in an accumulation in a reservoir but corrected to the
volume it would occupy at surface temperature and pressure Ultimate Recovery (UR)
UR = STOIIP (GIIP) x Recovery Factor Reserves
Volume of oil or gas that remains at a specified date to be produced commercially from a field or area under prevailing economic conditions
Reserves = Ultimate Recovery - Cumulative Production
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EP00Why Volumetrics?
Knowing value of business Depreciation and Net Income calculation SEC reporting requirement Reserves Review (ARPR) Equity Determination Prospect Evaluation / Ranking Asset Management
Production Forecasting Field Development Planning
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EP00
Groups Resource Portfolio Build-up 1.1.2000
PRODUCEDEVELOPAPPRAISEEXPLORE
+/- 6 yrs to Prodn
ACQUISITIONS & DIVESTMENTS
UndiscoveredSFRc
*[bln boe]
DiscoveredSFRc
*Expectation
Undeveloped
*Proved
Undeveloped
*Proved
Developed* *bln boe
Externally Reported Figures
Yearly Production
UndiscoveredOutside Portfolio
Maturation Process needs to deliver ** bln boe/yr
+/- 10 yrs to Prodn
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EP00
Objectives
At the end of this session you should be able to: List sources of uncertainty and ways to
understand/manage them Use the STOIIP/GIIP expectation curves State the general justification of Appraisal
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EP00What do we need to know. ?
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EP00
STOIIP and GIIP Equation
( )o
ooo
B
SGNGRV
STOIIP o
=
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( )g
ggg
B
SGNGRV
GIIPg
=
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EP00Uncertainties in Volumetric Estimates
OWC?
Shale Out?
GOC?
Erosion?
DIP?
Seismic?
More Faults?
Fault Position?
STRUCTURALDip Error
Seismic ErrorFault Position
Additional Faulting
STRATIGRAPHICRock Development
Erosion
ACCUMULATIONPosition ContactsPossible Gas Cap
PROPERTIESPorosity
SaturationNet/Gross
Formation Volume Factors
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EP00
Dip Uncertainty
20Base Case
25Minimum
15Maximum
Seismic dip error 7 Dipmeter dip error 2
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EP00Top reservoir uncertaintyConger Garden Banks, GOM
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EP00
Fault Position Uncertainty
20Base Case
20
Minimum20
Maximum
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EP00North Cormorant Block IV : Development Strategies
0 1 2 km
Annex B - 1978(1974-75, 2D seismic)
1983-843D seismic
North CormorantPlatform
Oil producerWater injectorAbandoned with H/CSuspended with H/CPlanned producerPlanned injector
9 00 0
9000
WU
T10
000 7
1000
0
9500
ODT
9495
9500
6
2
5
6
5
2
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EP00
Sunrise-TroubadourWoodside
MOST LIKELY CASE - Fully Connected
INTERMEDIATE CASE - Large Compartments
WORST CASE - Small Compartments
Compartmentalisation Uncertainty
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EP00
Fault Dip Uncertainty
60
Base Case
70
Minimum
50
Maximum
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EP00
Fluid Contact Uncertainty
Base Case
Minimum Maximum
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EP00Uncertainty in top reservoir map3 development scenarios after appraisalDraugen Field, Norway
22 2
111
OWC
OWC
OWC
1600
1600
1620
1620
OWC
1620
1620
OWC
1620
1620
1600
1600 1620
1600
1600
1600
1620
OWC
10 PRODUCERS10 INJECTORS
8 PRODUCERS10 INJECTORS
15 PRODUCERS15 INJECTORS
OWC 1638MSS1600 CONTOUR VALUE, MSS
0 2 4
BASE CASE LOW CASE HIGH CASE
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Uncertainty with Fluid Contacts
SHELL OU P.E. DEPT THE HAGUEWOMBAT FIELD
CONTOUR MAPTOP X SAND
0 1 km
Date: June 1996
Report No: 31-422
Author: L.B. van Dijk
Draw No: 12
all depths in m below sea levelN
GDT 2040m
OUT 2060mODT 2085m
WUT 2115m
2000m2050m
2100m
well C2115m
well A2017m well B
2060m line of section
A
A
AA
2000m
2050m
2100m
2150m
WellC
WellA
WellB
WUT 2115m
ODT 2085m
OUT 2060m
GDT 2040m all depths in m below sea level
Cross-Section A-AWOMBAT FIELD
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Uncertainty with Fluid ContactsWell
CWell
AWell
BWell
CWell
AWell
B
WellC
WellA
WellB
WellC
WellA
WellB
CASE 1: GOC=2040m & OWC=2115m CASE 2: GOC=2040m & OWC=2085m
CASE 3: GOC=2060m & OWC=2115m CASE 4: GOC=2060m & OWC=2085m
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Uncertainty with Fluid Contacts
N
CASE 1: GOC=2040m & OWC=2115m
N
N
N
GIIP=1.3 million m3 : STOIIP=42 million bbl GIIP=1.3 million m3 : STOIIP=21 million bbl
GIIP=2.4 million m3 : STOIIP=14 million bblGIIP=2.4 million m3 : STOIIP=35 million bbl
CASE 2: GOC=2040m & OWC=2085m
CASE 3: GOC=2060m & OWC=2115m CASE 4: GOC=2060m & OWC=2085m
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EP00
Net/Gross Uncertainty
Measured
Maximum ?Minimum ?
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EP00
Combined Uncertainties
60
Base Case
70
Minimum
50
Maximum
20
2515
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EP00
Combining Uncertainties
p
STOIIPp>x
STOIIP
pp
pp
p
GRVN/G
So
1/Bo
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EP00
Expectation Curve
1.0
0.5
0
STOIIP (MMm3)0 50 100 150
Low STOIIP
High STOIIP
MediumSTOIIP
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Reporting VolumesShell
Low or Proved P85 not Minimum or WorstMedium P50 = most likely or base case High P15 not Maximum or BestExpectation = (Low + Medium + High)/3
Be careful: no consistent use in industrysome call High P85 & Low P15some take P10 & P90, or even P0 & P100some use min & max, or downside & upsideSome use proved, probable, possibleAlso no precise definition on what is taken as proven
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EP00Ultimate Recovery Estimates vs. Time
Time (not to scale)
ProspectEvaluation Explore Resource Management
Appraise Devel. Planning
Proj. Exec.
Devel. Drlg.
U
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R
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E
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1st hole dryDiscovery
A A A
D D D
CumulativeProduction
P85
P15Abandon
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a sample of fields, P10s & P90s vs P50
0
200
400
600
800
1000
1200
1400
0 200 400 600 800 1000 1200 1400P50, MMBOE
P
9
0
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P
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0
,
M
M
B
O
E
P10P90
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Soon dots will be shown in the oval; how many ???
What is your P50, P90 & P10 estimate ??
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EP00How many dots are there in total oval do you think ? You can only see through a small peephole
What is your P50, P90 & P10 estimate ??
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Actual ?? 160 dots
+/- 30% : 110 - 210
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What can we do about the uncertainties
Reduction of static uncertainty High quality seismic, PSDM Appraisal drilling (& logging, coring) Use of analogues
Reduction of dynamic uncertainty Core analysis, Production testing Extended production performance (pilot), 4D seismic Use of analogues
Managing uncertainty Quantifying possible ranges through modelling Identify possible up/downsides & fall-back options Phased development, keep options open
$$$
$$$
$$$
VOI ?
VOI ?
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Appraisal
The objective of Appraisal Activities is to:
Reduce Uncertainty
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Appraisal
Information obtained through appraisal is aimed at answering:
How much oil and gas is there? Where is it? At what rate and how much in total will it produce?
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Appraisal Activities
All forms of data gatheringExamples: Drilling wells Logging and testing Reprocessing seismic Obtaining additional seismic or 3D seismic surveys etc.
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EP00
No info
With info
Devmnt(mid case)
Hi Case
Mid Case
Low Case
50
80
-20
50%
25%
25%
EMV= 0.25 x 80 + 0.5 x 50 + 0.25 x -20= 40
Hi Case
Mid Case
Low Case
50
100
50%
25%
25% Hi Dev
Mid Dev
No Dev 0EMV= 0.25 x 100 + 0.5 x 50 + 0.25 x 0= 50
Info value= 50-40=10 , cost of info needs to be less !
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EP00
1.0
0.5
0
STOIIP (MMm3)0 50 100 150
Uncertainty Reduction with Appraisal
post appraisalnegative
post appraisalpositive
before appraisal
economic minimum
P90
P10
P50
Range before appraisal
Range after appraisal or
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Resource Characteristics Tree
StructuralExtent
Heterogeneity
Continuity
Aquifer
Probability
DevelopmentScenarios
Too small10%
Large enough90%
Unfavourable50%
Favourable50%
Good60%
Poor60%
Good40%
Poor40%
Weak100%
Strong0%
Weak50%
Strong50%
Weak30%
Strong70%
Weak100%
Strong0%
NPV 1 0 NPV 2 UR 3 NPV 5 NPV 6NPV 4 027% 0% 9% 9% 8% 19%18% 0%10%
Depl.10
wells
N/A WaterInj.
EOR? WaterInj.
Depl.20
wells
Depl.20
wells
N/AN/A
0
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EP00
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EP00
Schooner Field, Shell Expro UK SNSReservoir uncertainty scenarios
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Sub-Surface Uncertainty TreeUncertainty
Sand/Shale
PorosityPermeability
Compartments
Fault transmissibility
Shale Kv
Models
Low High
None
Yes
Low Geocap
ML
None
P50 Geocap
Dynamic Uncertainty
ML
Large
High Geocap
ML
NoneNone NoneMulti
No
ML
No
ML
No
ML
No
ML
No
ML
No
ML
No
ML
No
Low
No
High
TerminologyWhy Volumetrics?Groups Resource Portfolio Build-up 1.1.2000ObjectivesSTOIIP and GIIP EquationUncertainties in Volumetric EstimatesDip UncertaintyTop reservoir uncertaintyConger Garden Banks, GOMFault Position UncertaintyNorth Cormorant Block IV : Development StrategiesFault Dip UncertaintyFluid Contact UncertaintyUncertainty in top reservoir map3 development scenarios after appraisalDraugen Field, NorwayUncertainty with Fluid ContactsUncertainty with Fluid ContactsUncertainty with Fluid ContactsNet/Gross UncertaintyCombined UncertaintiesCombining UncertaintiesExpectation CurveReporting VolumesUltimate Recovery Estimates vs. TimeWhat can we do about the uncertaintiesAppraisalAppraisalAppraisal ActivitiesUncertainty Reduction with AppraisalResource Characteristics TreeSchooner Field, Shell Expro UK SNSReservoir uncertainty scenariosSub-Surface Uncertainty Tree
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