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.