Petroleum Geologyand the Permian Basin
Andrew McCarthyConcho Resources
Petroleum System
2
• Source: organic-rich mudrock• Heat (burial) and time• Reservoir: porous rock • Seal: low-permeability rock• Trap
Source
Sol (our sun)Fusion (of hydrogen
and helium)
Earth3,850,000 exajoules per year – Solar radiation3,000 exajoules per year – captured by plant life500 exajoules per year – total human use (fossil, nuclear, etc.)
3,850,000
EJ
3,000 EJ
burial
Source
Heat and pressure
Kerogen
Kerogen: geo-plastic or geo-chocolate.Lipids, proteins, carbohydrates
Gas (methane,ethane, propane)
Texas tea(light, sweet crude)
CO2N2
H2S
+
Shale:high organic material
How much heat?
• Low temps yield nothing: <60 C• High temps yield oil: 60C-120+C• Higher temps yield gas: 120+C
100% natural and organic
• Oil is 100% natural and organic• 95%++ of all oil ever generated has been
naturally leaked to the surface• Millions of natural oil seeps exist around the
planet, many under the oceans
Yummy!
NaturalOil seeps(BP not Involved)
NotIcedtea
An oil reservoir at the surface
Oil reservoirs are exposed and eroded away. The light oil is biodegraded, tar remains.
OK. So far we have:
• Source
• Heat and time
• Now we need a reservoir, a seal, and maybe a trap
ReservoirThe first key to a reservoir rock is porosity
intergranular fracture
Got porosity?
ReservoirThe second key to a reservoir rock is permeability
Seal
Imagine if this were clay…
We need something to slow the upward migration of oil and gas.A seal will do: it’s a layer of very low permeability.
Microscopic view of clay layers
TrapsRequired for conventional reservoirs…
A very conventional petroleum system:Concho
sandorganic shale
sealing shale oil
Organic mudstone, silty shale, with varying carbonate and silica content1 source
2 reservoir3 seal
Tight carbonate (seal/frac barrier)
Tight carbonate (seal/frac barrier)
Today: Unconventional plays
The Permian Basin
Geologic Time
Today
Active petroleum systems
Basins
basin
Low areas; tend to fill with sedimentTypically covered with water (ocean, sea or lake)Nature’s landfill
RiversCoral reefs
Wind blown
Pelagic rain
shelfslope
deep basin
Before the Permian Basin
• Shales: Devonian Mississippian Barnett
• Before 370 Ma (Devonian)
Ron Blakey, Colorado Plateau Geosystems, Inc.
Early Permian Basin
• 315 Ma• Late Miss/Early
Penn time• Shale
deposition
Ron Blakey, Colorado Plateau Geosystems, Inc.
Late Permian
• 255 Ma• Carbonates
(shallow marine carb factory)
• Later, evaporites
Ron Blakey, Colorado Plateau Geosystems, Inc.
Sources
Organic-rich shales
Reservoirs *Just about everything!
sands
Shale/silt
carbonates
What does a geologist do?
• Exploration very little data!
– Seismic, basin geochem, remote sensing– Everything changes with the first well
• Development increasing amounts of data!
– Well logs, core, production data• Operations– Day-to-day drilling
• When do we have “the answer”?
Thank you.