Comparison of Mesozoic and Cenozoic

Source Rock Characteristics

Puale Bay Outcrops and NAS COST 1 Well

Alaska Peninsula – North Aleutian Basin

Author(s) and affiliations:

Paul L. Decker

Alaska Division of Oil & Gas

Date presented:

March 27, 2008

Presentation Forum:

DNR Spring Technical Review Meeting, BP Energy Center

Acknowledgments of any external funding sources and in-kind contributors:

Field work and analyses for this study were conducted during 2004, 2005, and 2007 with funding

from multiple sources, including a U.S. Department of Energy grant from the Arctic Energy

Technology Development Laboratory at the University of Alaska Fairbanks to Rocky Reifenstuhl

(program head) and Paul McCarthy (principal investigator, UAF); Bristol Bay Native Corporation;

and Division of Geological & Geophysical Surveys and Division of Oil and Gas operating and

capital improvement project budgets. Field samples were collected by Rocky Reifenstuhl, Robert

Gillis, Emily Finzel, and Karen Clautice (DGGS); the author, David Shafer, and Timothy Ryherd,

(DOG); Michael Whalen (UAF); and Robert Blodgett (consulting geologist).

Cs

Cs

CsCs

CsIs

Puale

BayN o r t h A l e u t i a n /

NAS

COST 1

Alaska Peninsula

Stratigraphic Column

• Upper Triassic Kamishak Fm- Shallow Marine carbonate

• Middle Jurassic Kialagvik Fm

(Tuxedni Gp equivalent)

- Marine-nonmarine? sh-slts-ss

• Miocene Bear Lake Fm

• Eocene-Oligocene Stepovak Fm

• Paleocene-Eocene Tolstoi Fm

- Nonmarine (coaly) to shallow marine

Puale Bay outcrops

NAS COST 1 well

07RR027-038

07BG225-233(SE-NW)

07PD183-188 (SE-NW)

05EF100-103 (NW-SE)

05RR208-210 (SE-NW)

07PD191-194 (W-E)

07RR041-042 (W-E)

07BG237,07MW005

07RB11

07PD181-182

07MW003-004

07RB04-08 05RR211-213 (S-N)

05EF105

07PD195-199 (E-W)

07RR043-047 (E-W)

Puale Bay Sample Locations

Kamishak Fm (n=38)

Kialagvik Fm (n = 39)

lower Kamishak Fm biostromal facies

micritic-fossiliferous faciesbasal unconformity

Pv?

Trk

angular

unconformity

minor

fault (?)

U D

Upper Triassic Kamishak Fm Outcrops Puale Bay

upper contact, rusty ss-siltstone

carbonaceous

ss, thin coals

upward coarsening slts-ss

middle Kialagvik Fm

Js

Jk

Q

Jk

Middle Jurassic Kialagvik Fm Outcrops Puale Bay

dark gray fissile slts

lower Kialagvik Fm

Modified Van

Krevelen Diagram

Mesozoic

Units

Puale Bay

outcrops

Oil-prone Type I-II

kerogens

A A’Quaternary

Bear Lake Fm

Unga equivStepovak Fm

Tolstoi

Fm

Mz?

Mz?Mz?

Tolstoi

Fm?

MMS-75-17-36

(~52 mi long)

Milky River Fm A

A’

B

B’

50 mi

N Aleutian

COST #1

B’BQuaternary

Milky River Fm

Bear Lake Fm

Unga equiv

Stepovak FmMz?

Mz?

Mz?

Tolstoi

Fm?

Mz?

Mz?

Mz?

Tolstoi

Fm?

Bear Lake Fm

Black Hills Uplift

(transpressional margin)

N Aleutian/

Bristol Bay

Basin

MMS-75-17-09

(~155 mi shown)A TA T

A T?

A T

North Aleutian Basin

Modified Van

Krevelen Diagram

Cenozoic

Units

NAS COST 1 well

• 420 Rock-Eval/TOC

analyses

anomalous coaly kerogens

highly anomalous

coaly kerogens

Oil-Prone Coals??

• Pyrolysis can overestimate

HC liquid-generation potential

of coaly source rocks

• Kerogen microscopy and

H/C, O/C atomic ratios data

Modified Van

Krevelen Diagram

Mesozoic

and Cenozoic

Units

Puale Bay and

NAS COST 1

Hydrogen Index, mg

0

100

200

300

400

500

600

700

800

900

0.10 1.00 10.00 100.00

Hyd

roge

n In

de

x, m

g/g

TOC, %

Milky River-COST 1

Bear Lake-outcrop

Bear Lake-COST 1

Stepovak-COST 1

Tolstoi-COST 1

Kialagvik coal

Kialagvik silty mudst

Kamishak-outcrop

lean gas-prone

good-excellent gas-prone shales, carbonates

good-excellent mixed oil- & gas-prone

shales, carbonates

Type II oil-prone shales, carbonates

“oil shales”, oil-prone cannel & boghead

coals, tasmanites, etc..

dry gas-prone

potentially mixed oil- & gas-or condensate-prone (?)

non-source or

overmature

carbonaceous shales

carbonaceous shales

coals

lean oil-prone

Type I oil-prone shales, carbonates

coals

non-source or overmature

Hydrogen Index vs TOCH

ydro

gen

Ind

ex, m

g/g

TOC, %

Type and Quantity

of Organic Matter

0.00

50.00

100.00

150.00

200.00

250.00

300.00

0.00 20.00 40.00 60.00 80.00 100.00

S2, m

g/g

TOC, %

Kamishak

Kialagvik silty mudst

Kialagvik coal

Tolstoi-COST 1

Stepovak-COST 1

Bear Lake-COST 1

Bear Lake-outcrop

Milky River-COST 1

Bear Lake outcrop -- coals only y = 5.942x - 221.9

Pyrolyzed HC (S2) vs TOCTrue Average

Hydrogen Index

Full Data

Range

(coals)

y = 7.4478x - 2.663

y = 6.5359x - 3.1453

y = 3.1936x - 3.6462

y = 1.6664x - 1.0885

y = 1.2263x - 0.7252

0.00

5.00

10.00

15.00

20.00

25.00

30.00

35.00

40.00

45.00

50.00

0.00 5.00 10.00 15.00 20.00

S2, m

g/g

TOC, %

Kamishak

Kialagvik silty mudst

Tolstoi-COST 1

Stepovak-COST 1

Bear Lake-COST 1

Bear Lake-outcrop

Milky River-COST 1

Pyrolyzed HC (S2) vs TOCTrue Average

Hydrogen Index

Restricted

Data Range

(no coals)

-155.44

-155.43

-155.42

-155.41

-155.40

-155.39

-155.38

-155.37

-155.36

-155.35

-155.34

0.01 0.10 1.00 10.00

Total Organic Carbon

0 500 1000

Hydrogen Index

Kialagvik

Kamishak

Longitude

(u

p-s

ecti

on

)

Typ

e I

Typ

e II

Typ

e II-

III

Typ

e III

co

als

so

urc

e

no

n-s

ourc

e

biostromal facies

Variation by Stratigraphic PositionKamishak and Kialagvik Fms, Puale Bay

Milky

River

Bear

Lake

Unga eq

Quat

Ste

po

va

kTo

lsto

i

Lean Elev Coal Gas-Prone Oil-ProneGas-

Cond Imm

Oil &

Assoc

Gas

Gas

North Aleutian Shelf COST #1

Geochemical Profile

TOC HI Ro

Sherwood and others, 2006 (MMS)

NAS COST 1 Vitrinite Reflectance

Conclusions

Puale Bay Mesozoic units include highly oil-

prone source rocks • Upper Triassic Kamishak Fm: especially brown-gray

micritic limestone facies (avg HI = 745 mg/g)

• Middle Jurassic Kialagvik Fm: lower part, fissile dark

gray siltstone facies (avg HI = 654 mg/g)

NAS COST 1 well Cenozoic units are coaly &

dominantly gas-prone, minor liquid-prone

coals?• Eocene Tolstoi Fm: (avg HI = 319 mg/g)

• Eo-Oligocene Stepovak Fm: (avg HI = 167 mg/g)

• Miocene Bear Lake (avg HI = 123 mg/g)