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Lecture 2
Courtesy of ExxonMobil
F W Schroeder ‘ 04
L 2 - Basics of Prospecting
The Basic Exploration Questions
Exploration’s Ultimate Goal is to Answer
Four Questions:
• Where to Drill?
Location & Depth
• What to Expect?
HC Volumes
• How Certain?
Chance of Success (Risk)
• How Profitable?
Economics
Courtesy of ExxonMobil
F W Schroeder ‘ 04
L 2 - Basics of Prospecting
What We Need for a Success
Correctly
Placed
Wells
A Rube Goldberg View
of a Hydrocarbon System
“Plumbing” To Connect
the Container to the Kitchen
A “Container”
From Which
Oil & Gas
Can Be
Produced
A “Kitchen”
Where Organic
Material Is
Cooked
Courtesy of ExxonMobil
F W Schroeder ‘ 04
L 2 - Basics of Prospecting
The Kitchen
A “Kitchen”
Where Organic
Material Is
Cooked
• Source
– Organic-Rich Rocks, usually shales
– Temperature & Pressure Conditions that Result
in Oil & Gas Generation
Courtesy of ExxonMobil
F W Schroeder ‘ 04
L 2 - Basics of Prospecting
The Container
• Reservoir
A “Container”
From Which
Oil & Gas
Can Be
Produced
– Porous & Permeable Rock Suitable for
Production
– Most Commonly Sandstones & Carbonates
• Trap
– 3-D Configuration that “Pools” the Oil & Gas
– Structural and/or Stratigraphic Traps
• Seal
– Rocks that Prevents Leakage from the Trap
– Most Commonly Shales and Evaporites
– Top Seals & Lateral Seals
Courtesy of ExxonMobil
F W Schroeder ‘ 04
L 2 - Basics of Prospecting
The Plumbing
“Plumbing” To Connect
the Container to the Kitchen
• Migration
– From source (shales) to porous reservoirs
– Strata-Parallel Component (sand & silt layers)
– Cross-Strata Component (faults, fractures)
Courtesy of ExxonMobil
F W Schroeder ‘ 04
L 2 - Basics of Prospecting
Petroleum System Elements
0
Depth (km)
2
4
6
Oil & Gas
Generation
Window
Gas
Generation
Window
Source
Reservoir
Trap & Seal
Migration
No More
HC Generation
Gas & Oil
8
Courtesy of ExxonMobil
F W Schroeder ‘ 04
L 2 - Basics of Prospecting
Other Important Components
• Timing
– Did the Trap form before HC Migration began?
• Fill & Spill
– Has HC Generation Exceeded Trap Volume?
– Has there been Spillage from Trap to Trap?
– Where is the Oil?
• Preservation
– Has Oil been degraded in the reservoir - thermal
cracking or biodegradation?
Courtesy of ExxonMobil
F W Schroeder ‘ 04
L 2 - Basics of Prospecting
HC Fill & Spill
1. Early Charge: Some Oil, Minor Gas
Trap B
Oil Spills
Up Fault
2. Peak Charge: Significant Oil, Some Gas
3. Late Charge: No Oil, Significant Gas
Trap A
Gas Cap
Displaces Oil
Fault Leak
Spill Point
Synclinal
Spill Point
Oil Spilled
from Trap A
to Trap B
Courtesy of ExxonMobil
F W Schroeder ‘ 04
L 2 - Basics of Prospecting