Definitions
Prospect Evaluation
Exploration Strategy
1. Global Basin Analysis
CRITICAL DECISIONS?
Complete Basin Studies
Acquire New Exploration Licenses
2. Develop Play Concepts
3. Define Exploration
Play Areas
Compile Full Lead &
Prospect Inventory
Which Play to Enter
Which Prospects to Drill
Play and Prospect Decisions Require
Disciplined Analysis
Technical Risk Evaluation
Economic Evaluation
4. Evaluate Prospects
5. Identify Drillable
Prospects
Drillable
Prospects/
Well proposals
6. Drill Exploration
Wells
A Play: An exploration concept that includes
a specific source, reservoir, and trap type
A Lead: An possible trap, data is not
sufficient to fully map it.
A Prospect: A specific trap that has been
identified and mapped but has not been
drilled yet.
Reserves: Oil and gas that have been drilled
and can be produced economically
Drill
Exploration
Wells
= New Reserves
7. Develop New Field
Basin/Play Evaluation
1.
2.
3.
4.
5.
Basin Scale Assessment
Estimation of undiscovered potential within each Play
Volumetric Calculations (Reserve estimates)
Assessment of Prospect-Specific Risk
Economic Analysis
Infrastructure
Market
Price
Taxes and royalties
Political Risks
To drill or not to drill?
Basin-scale Conventional Play Assessment:
1)
Identify areas of a basin where there are: source
rocks, reservoirs and traps
Identify prospects in those areas
Rank the prospects by risk
Drill the best one, then re-evaluate the others
2)
3)
4)
Drilling Success Rates
Example
Probability of Success
Risk Factor
Risk (0-1)
Probability hydrocarbon charge
0.80
Probability of good reservoir
0.80
Probability of a trap
0.70
(Multiply all the factors)
Chance of Success
0.44
Drilling of Exploration Wells in US
Drilling of Development Wells in US
EIA Data
More Detailed Risk Factors
Hydrocarbon charge
Source Rock Quality (TOC, Kerogen type)
Maturity of Source Rock
Migration Pathways
Reservoir
Porosity
Permeability
Trap
Closure (Trap volume)
Seal (Trapping efficiency)
Timing
Basin-wide Play Map
Prospects Evaluation, Barents Sea
Probability of Play Success
Claudius Lead
Jurassic
A. Everything is cool
(100%)
Gertrude Prospects
B. No structural traps
(20%)
C. Long migration
required (50%)
Polonius Prospect
D. Long migration
and bad reservoir
(30%)
CI = 300m
E. Poor source (50%)
HAMLET Prospect
Hamlet
GEOMETRY:
ESTIMATED RESERVES:
Risk Elements x Res. Potential
P50 = 138 billion scm (gas)
?
RISK ELEMENTS:
Source Presence =
Source Maturity =
Reservoir Quality* =
.34
1
1
RESERVOIR
POTENTIAL:
Pay Aerial Extent =
.6
Pay Thickness =
* (Multizone)
Porosity =
.8
Saturation =
Trap Quality =
Migration/Trap Timing =
CI = 500m
CI = 500m
50 m
Every risk element of a prospect is imperfectly
known before drilling.
750m
1050m
7%
15 %
40 %
60 %
Cumulative Probability
Min
P90 = I am 90% sure that it will be bigger than this
Most
Likely
P90
Min
P10
P10
340km2
411 Billion scm
.7
Probability Distribution
P90
200km2
Most
likely
Max
Max
Volumetric calculation
Volumetric Example
Reserves=
Area of trap x
Net reservoir thickness x
Porosity x
Hydrocarbon saturation x
Recovery factor x
Formation volume factor
Thickness: 48 ft
Net/Gross: 0.40
Net Thickness =
19 ft
Net Reservoir Set Porosity Cut off
Recovery Factor
Oil in place vs. Reserves
Most of the oil stays stuck in the reservoir
Reserves can be produced economically
Varies widely depending on permeability, oil
viscosity, reservoir pressure, etc.
30% average?
Only include the high porosity reservoir
Formation Volume Factor
Change in volume from reservoir to surface
conditions
Depends on Reservoir Temp, Pressure and gas-oil
ratio
1 to 3.0
High shrinkage oil Boi= 1.4
Low Shrinkage oil Boi = 1.2
Alaska North Slope Formation
Volume Factor (FVF)
GERTRUDE
Prospect
Gertrude
GEOMETRY:
ESTIMATED RESERVES:
Risk Elements x Res. Potential
?
P50 = 0.80 billion scm
RISK ELEMENTS:
Source Presence =
Source Maturity =
Reservoir Quality =
.12
.8
.6
RESERVOIR
POTENTIAL:
Pay Aerial Extent =
25km2
27km2
Pay Thickness =
140m
150m
9%
11 %
70 %
80 %
.7
Porosity =
.7
Saturationc =
Trap Quality =
CI = 50m
Migration/Trap Timing =
.5
How to compare two prospects?
Small size, Low Risk
Reserves= 6.8 billion
Chance of success=
30%
Big size, High Risk,
Reserves= 14 billion
Chance of success=
12%
Risked volume= 6.8
* 0.30= 2 billion scm
P90
P10
6.84 Billion scm
North Slope Basin Scale Assessment
Risked volume= 14*
0.12= 1.68 billion scm
Risked Reserves
NETL, 2009
