geographic extent of petroleum - west virginia …pages.geo.wvu.edu/~tcarr/petroleum/lecture...

Tim Carr - West Virginia University

GEOGRAPHIC EXTENT OF PETROLEUM

SYSTEM

STRATIGRAPHIC

EXTENT OF

PETROLEUM SYSTEM

Petroleum accumulation Top of oil window

Bottom of oil window

Trap Trap Trap

Seal

Reservoir

Source Underburden

Overburden

A A’

Source Rock

Migration Route

Reservoir Rock

Seal Rock

Trap

Elements

Generation

Migration

Accumulation

Preservation

Processes

4

Modified from ExxonMobil

1. Define prospect elements

2. Estimating trap volume

3. HC Presence & Type

4. Assessment

5. Risk

5

Courtesy of ExxonMobil




4. Assessment

5. Risk

A “Kitchen” Where Organic

Material Is Cooked

A “Container” From Which Oil & Gas Can Be

Produced

“Plumbing” To Connect the Container to the Kitchen

Correctly Placed Wells

6

Accumulation

PetroleumMigration

Seal

Reservoir

Leakage

PetroleumCharge

Source Rock

Migration Pathways

Determine Age of Oils

CoalySource Model

..............................................................................

..........................

....

..................................

....

........

........... ....................

....................

................

........ ........

........

GammaDensityResistivity

HeavyOil

LiteOil

Gas

0 my

Generation Rate

Predict Oil Quality

100 my

Source Rock Prediction

Sequence Stratigraphy

Characterizing the type, history and origin of petroleum

7

Does the rock have sufficient organic matter? Is the organic matter capable of generating? Has this organic matter generated

petroleum? Has the generated petroleum migrated out? Is the organic material oil-prone or gas-

prone? Are there sufficient trap volumes

Questions for Exploration Geologist

8

Kerogen Types Type 1 Type 2 Type 3

9

Tissot & Welte, 1984 10

11 After Tissot & Welte, 1984

Expulsion of oil and gas from low-permeability source rocks (shale-coal).

Most major accumulations originated in source rocks with total organic carbon (TOC) >2.5 weight percent

During generation (katagenesis) and primary migration, bitumen resides in pore space including fractures of the matrix.

Primary migration accompanies peak generation

12

Magoon and Dow, 1994

Petroleum System – Hydrocarbon Generation

GEOGRAPHIC EXTENT OF PETROLEUM SYSTEM

Present-Day

STRATIGRAPHIC

EXTENT OF

PETROLEUM SYSTEM

Petroleum accumulation

Top of oil window

Bottom of oil window

Trap Trap Trap

Seal

Reservoir

Source

Underburden

Overburden

A A’

14


Brent Sandstone acts as a reservoir

Heather Shale Sognefjord Shale

both organic poor

Facies Change

Draupne Shale organic rich

serves as a source rock

HC Generation & Expulsion oil & gas from the Draupne, gas from coals in the Brent

HC Migration into Brent carrier beds and up faults

HC Fill & Spill

Fault

Leak

Point

Oil

Spill

Point

late gas displaces early oil 15

Driving Force

Resisting Forces

Phase Behavior

Rates of migration

Efficiency

Long distance migration

16

Movement from source to trap

Along carrier bed

As separate hydrocarbon phase (mostly)

19

Wetting q <90o Nonwetting q >90o

20

Pw-Pnw = (rw-rnw) h g

Pw

Pw

Pw

Pw* Pw* Pw*

h

h

h

Pnw

Pnw

Water

r

Free Water Level Pnw=Pw

Pnw

21

(after Berg, 1975) 22

(after Berg, 1975) 23

(Modified from Schowalter, 1979) 24

29 England, Mann & Mann, 1991

5 Km 32

Modified from ExxonMobil




4. Assessment

5. Risk

34


Exploration’s Ultimate Goal is to Answer

Four Questions:

Where to Drill? Location & Depth

What to Expect? HC Volumes & Type

How Certain? Chance of Success (Risk)

How Profitable? Economics

35


Source Organic-Rich Rocks, usually shale - coal

Temperature & Pressure Conditions that Result in Oil & Gas Generation

A “Kitchen” Where Organic

Material Is

Cooked

36


Migration From source (shale) to porous reservoirs

Strata-Parallel Component (sand & silt layers)

Cross-Strata Component (faults, fractures)

“Plumbing” To Connect

the Container to the Kitchen

37


Reservoir Porous & Permeable Rock Suitable for

Production Most Commonly Sandstone & Carbonate

Trap 3-D Configuration that “Pools” the Oil &

Gas Structural and/or Stratigraphic Traps

Seal Rocks that Prevents Leakage from the Trap Most Commonly Shale and Evaporite Top Seals & Lateral Seals

A “Container” From Which

Oil & Gas

Can Be

Produced

38

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?

39


Trap A

Trap B

Synclinal

Spill Point

Fault Leak

Spill Point

1. Early Charge: Some Oil, Minor Gas

2. Peak Charge: Significant Oil, Some Gas

Gas Cap

Displaces Oil

Oil Spilled

from Trap A

to Trap B

Oil Spills

Up Fault

3. Late Charge: No Oil, Significant Gas

40

Given the geologic framework and the results of our data analysis, our next task is to analyze and assess viable prospects:

Analyze prospect elements

Source, Migration, Reservoir, Trap, Seal

Consider the most-likely scenario

Consider other cases - the range of possibilities

Assess the prospect

What volumes of HCs can we expect?

Will it be oil or gas?

Risk the Prospect

What is our level of confidence that all the prospect elements work?

41


Brent Sandstone acts as a reservoir

Heather Shale Sognefjord Shale

both organic poor

Facies Change

Draupne Shale organic rich

serves as a source rock

HC Generation & Expulsion oil & gas from the Draupne, gas from coals in the Brent

HC Migration into Brent carrier beds and up faults

HC Fill & Spill

Fault

Leak

Point

Oil

Spill

Point

late gas displaces early oil 42


Alpha Beta

Reservoir

Seal

Source

Basement

Overburden

18 Ma Oil

Generation

Oil Migration

Oil Fill & Spill

Sea Water

43


Alpha Beta

Reservoir

Seal

Source

Basement

Overburden

10 Ma Oil

Generation

Oil Migration

Oil Migration

Sea Water

44


Reservoir

Seal

Source

Basement

Overburden

Present

Alpha Beta

Oil Generation

Gas Generation

Oil & Gas Migration

Oil Migration

Sea Water

45


Map of the Reservoir Unit

Alpha Beta

Oil

Oil

18 Ma

46



Beta Alpha

Oil

Oil

10 Ma

47


Alpha Beta

Oil Oil

Gas


Present

48


Development Drop Area

Drill

Wildcats

Confirmation

Well

Identify

Opportunities

Process

Seismic Data

Capture

Prime Areas

Interpret

Seismic Data

Acquire

Seismic Data

Assess

Prospects

Success

Success

Failure

Uneconomic 1. Volume 2. HC Type 3. Assessment 4. Risk

49

50

Take Home Ideas

Primary Migration

Secondary Migration – Direction & Magnitude Hydrocarbon Buoyancy – Hydrostatic

Fluid Flow & Buoyancy - Hydrodynamic

Migration Paths and Timing Critical

Capillary Pressure Pore Size Dependent

Seal Competency

Trap Size and Fill Amount

Filling Fluid (Oil, Gas or Water)

Fill and Spill

Seal Failure

51

Assignments Reading for this week

Jacobson, Petroleum Source Rocks p. 3-11

England et al. Migration Source to Trap, p.23-46

Read Today in Energy for Thursday (2/19) at http://www.eia.gov/

Be Prepared to Discuss in Class - Wednesday

Discussion Leader – Sean Kotter

Quiz on Friday 2/20 Open at 1:00pm – Closes on 2/23 at 11:00am

Test on Friday 2/27

http://www.eia.gov/

geographic extent of petroleum - west virginia …pages.geo.wvu.edu/~tcarr/petroleum/lecture...

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