ACTIVITY: Use the diagram below to answer these questions about source rocks .

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DISCUSSION: Recipe for Oil – Source , Reservoir, Seal, Trap. ACTIVITY: Use the diagram below to answer these questions about source rocks . 1. If the Earth gets hotter with depth at a rate of 10°C per 1 km, which layer(s) on the diagram is/are in the “oil window”?

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## ACTIVITY: Use the diagram below to answer these questions about source rocks .

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ACTIVITY: Use the diagram below to answer these questions about source rocks.

1. If the Earth gets hotter with depth at a rate of 10°C per 1 km, which layer(s) on

the diagram is/are in the “oil window”?

Oil Window = Temp of 50 – 180C = > so here, 5 km to 18 km

Answer: Bottom half of LAYER C and all of LAYER D

2. How long did it take LAYER C to be buried to 4km , if Layers A and B were

deposited at a rate of 0.1 mm/yr? (this includes the effects of burial compaction).

Conversion of “mm” to “km” => 0.1 mm x (1 cm / 10 mm) x (1 m / 100 cm) x (1 km / 1000m)

Rate = 0.0000001 km / year (Rate = Distance / Time)

(Time = Distance / Rate)

Time = 4 km / (0.0000001km / year) = 40,000,000 years

3. Which layer would be the best oil-prone source rock?

LAYER C: due to occurrence of marine organisms in the shale

(this doesn’t mean there will be no gas….just a tendency to form relatively more oil)

4. Which layer would be the best gas-prone source rock?

LAYER D: due to occurrence of lake organisms in the shale

(this doesn’t mean there will be no oil….just a tendency to form relatively more gas)

Earth’s surface = 10° C

0 km

LAYER A: deep marine shale

2 km

LAYER B: shallow marine limestone

4 km

LAYER C: organic-rich deep marine shale and sandstone

6 km

LAYER D: organic-rich lacustrine shale

8 km

BAESI Exploring for Oil and Gas

• ACTIVITY:
• Supplies = California Rocks kit; syringe; dixie cup of water
• Take the rock samples out of your “California Rocks” kit. Drop water on each sample and observe which samples absorb water fast and which ones do not. Divide the samples into two piles:
• In the diagram below, label which layer(s) would be better RESERVOIRS and
• which would be better SEALS.

Earth’s surface = 10° C

0 km

SEAL

LAYER A: deep marine shale

2 km

RESERVOIR, SEAL (if well cemented)

LAYER B: shallow marine limestone

4 km

LAYER C: organic-rich deep marine shale and sandstone

SEAL(shale) RESERVOIR (Sand)

6 km

LAYER D: organic-rich lacustrine shale

SEAL

8 km

BAESI Exploring for Oil and Gas

American Petroleum Institute, 1986

anticline

fault

anticline

pinchout

unconformity

DISCUSSION: Recipe for Oil – Source, Reservoir, Seal, Trap

ACTIVITY:

• Label each trap type below on the “fake” geologic cross section. Oil accumulations are shown in green. Gas accumulations are red, and reservoir water is blue.

2. Label each trap type below on the “real” geology cross section.

salt dome

salt

anticline

uncon-

formity

anti-

cline

fault

salt

dome

reef

BAESI Exploring for Oil and Gas

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Things you will need: Handouts (5: Introduction/images; question sheets; rock chart; cross section )

Rock samples (6: conglomerate/breccia. sandstone, greywacke, shale, chert, granite)

Colored pencils

• ROCK IDENTIFICATION: Common rocks of the Southern San Joaquin Valley

As a geologist, you have recently returned from a sampling and mapping trip from the southern San Joaquin Valley. In front of you on the table are 6 rock samples from your survey. Below, list each rock type you see. Also describe each sample as: reservoir, source,and/or seal.

1. ____conglomerate (reservoir)____ 4. __shale (source, seal)______

2. ____sandstone (reservoir)______ 5. __chert (source, seal)______

3. ____graywacke (OK reservoir)__ 6. ___granite (seal)___________

• GEOLOGIC MAPPING: Is there initial evidence for good petroleum traps?

On your survey trip, you noticed oil seeps in the San Joaquin Valley. You decide to look carefully at the geologic maps you made, to see if there is evidence for possible petroleum traps. On the west side of the San Joaquin Valley, you have mapped an interesting structure near Paso Robles (see map below). You draw a cross section to check for a trap.

1. Along the cross section line, place an angled tick mark below every rock contact.

Be sure the tick mark “dips” in the correct direction and at the correct angle.

2. Extend the tick marks below the surface line, so that matching rock types meet.

Do not cross lines.

3. Do you see a petroleum trap? If so, what kind is it? ______anticline_______

Geologic Map, Paso Robles area, Western San Joaquin Valley

N

W

E

S

Geologic Cross Section of the Paso Robles Area

W

E

anticline

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C. SEISMIC ANALYSIS: Common traps in the Southern San Joaquin Valley

Based on your initial observations from the rock sampling, geologic mapping, and oil seep survey, you feel fairly confident that a petroleum system exists beneath the valley floor. You have decided to invest \$10,000,000 for an initial low-resolution 3D seismic survey. This will allow you to get a view of the geology beneath the surface, to see if there are good “traps” for oil. Look at the seismic image called “3D Seismic Inline 743” below. What style of trap would be drilled at each hypothetical well (#1 – 6)? (hint: traps can be a combination of styles)

TRAPS:

1. _________________________

2. _________________________

3. _________________________ 4. _________________________

5. _________________________

6. _________________________

• DETAILED ANALYSIS: A working petroleum system?

The initial seismic survey was a success, and so you plan to invest \$120,000,000 for high-resolution 3D seismic surveys of several target areas (\$100,000,000), to hire geologists and geophysicists to interpret the data (\$5,000,000), and to drill an exploration well (\$15,000,000).

1. Complete the rock chart, indicating “source”, “reservoir”, and/or “seal” in the empty boxes.

2. Next to rocks labeled “source”, indicate if hydrocarbons would be “oil-prone” or “gas-prone.”

3. On the cross section, use color to highlight reservoirs,seals, and source.

4. Are the source rocks in the “oil window” (2 – 4 km deep)? ___yes_____________________

5. Make notes to indicate possible petroleum trap structures.

6. Check to see if there is good oil/gas migration path from the source rocks to the trap.

• EXPLORATION WELL SITES: Locate your top two choices on the cross section.

Look at the traps you noted in Part D. Decide which two traps can hold the most oil (i.e. the

reservoir beneath the trap is thick, and the trap structure is large). On the surface directly

above your two trap choices, draw an oil well to show your possible exploration well sites.

1

2

3

4

5

6

fault

pinchout

pinchout

anticline

faulted anticline

pinchout

BAESI Exploring for Oil and Gas

Rocks of the Southern San Joaquin Valley, CA

BAESI Exploring for Oil and Gas

anticlines

fault anticline

anticline

pinchout

WEST – EAST Cross Section Across the South San Joaquin Valley, CA (Mercer, 1996)

pinchouts

faults

BAESI Exploring for Oil and Gas