North GOM Petroleum Systems: Modeling the Burial and Thermal History,

Organic Maturation, and Hydrocarbon Generation and Expulsion

Roger J. Barnaby2006 GCAGS MEETING

• Evaluate source rock hydrocarbon potential and maturity– Smackover geochemistry (TOC, kerogen)– Model burial history – Model thermal history

• Model hydrocarbon maturation, generation and expulsion – Key controls– Timing and burial depths– Volumes of oil and gas

• Assess secondary hydrocarbon migration

Previous studies of northern GOM crude oils: composition, 13C,document Type II algal kerogen in Smackover major source

Objectives

SA

BIN

E U

PLI

FT

N. LASALT BASIN

MONROEUPLIFT

Primary control for basin modeling 140 key wells (red) 44 sample wells (blue) 30 additional wells being analyzed

50 mi

CRETACEOUS SHELF MARGIN

Burial History: Depositional and Erosion Events

Geological time scale: Berggren et al. 1995Formation ages: Salvador 1991 Galloway et al. 2000 Mancini and Puckett 2002; 2003 Mancini et al 2004

Smackover

Cotton Valley

Hosston

Sligo

MooringsportGlen Rose

Paluxy

Austin

Wilcox

Miocene

Oligocene

TuscaloosaWash/Fred

Midway

Jackson

Burial History

• Reconstructed from present-day sediment thickness after correcting for compaction

• Compaction due to sediment loading• Maximum paleo water depths < few 100 meters,

no correction for water loading– Paleobathymetry– Sea level through time

Porosity-Depth Relationships

0

5000

10000

15000

20000

0.00 0.10 0.20 0.30 0.40 0.50 0.60

porosityd

epth

(ft

)

Limestone

Sandstone

Shale

= 0 exp (-Kz)

Where: = porosity0 = Initial porosityK = compaction factorz = depth

Exponential Compaction

0

5000

10000

15000

20000

0.00 0.10 0.20 0.30 0.40 0.50 0.60 0.70

porosity

dep

th (

ft)

Burial History: Decompaction

3

2

1

12

1

3

2

1y1

y2

y’1

y’2

t1Remove 2 & 3Decompact 1

t2 Add 2

Partially compact 1

t3Add 3

Compact 2 and 1

Present-daydepths

0

5000

10000

15000

20000

050100150200

Time (Ma)

Dep

th (

ft)

Compacted

Non-compacted

Burial History: Compacted vs Non-compacted

Lithology (Wilcox)

CALCULATE DECOMPACTION-lithology from digital logsEnd member lithologies-SS, SH, LS, ANHLog-derived lithology -mixture of end membersCompaction parameters formixed lithology – weighted arithmetic average

Lithology (Upper Glen Rose)

Smackover

Cotton Valley

Hosston

Sligo

MooringsportGlen Rose

Paluxy

Austin

Wilcox

Miocene

Oligocene

TuscaloosaWash/Fred

Midway

Jackson

Burial History

Smackover

Cotton Valley

Hosston

Sligo

Mooringsport Wash/FredGlen RoseTuscaloosa

Austin

Midway

Wilcox

Miocene

Oligocene

Jackson

2

Burial History

• Modeling formation temperature– Heat flow approach: temperature function of

basement heat flow, thermal conductivity overlying sediment

• Present-day heat flow– Well BHTs– Surface temp = 20oC– Thermal conductivity

• Porosity and lithology are major variables controlling thermal conductivity

• In-situ thermal conductivity computed by BasinMod

Thermal History

meter (103 . deg K)

T2, y2

T1, y1

= T2-T1 (103 . deg K)y2-y1 (meters)

W

meters2

Heat Flow

xW

TemperatureGradient

ThermalConductivity

Heat Flow Calculation

CalculatedHeat Flow = 50 mW/m2

BHTs

Calculated vs Measured BHTs

Thermal History: Paleoheat Flow• Constant vs. rift model

= 2.0

= 1.75

= 1.5

= 1.25

= 1.0

N. LA Beta1.25 ≤ ≤ 2.0

Nunn et al 1984 Dunbar & Sawyer 1987

170130026300

Moho Crust

Subcrustallithosphere

Aesthenosphere

= 230 km

120 km

= 1.25

= 1.5

= 1.75

= 2.0Dunbar and Sawyer 1987

Thermal History: Lithospheric Stretching

SA

BIN

E U

PLI

FT

MONROE UPLIFT

50 mi

17067006100

170612011700

170152087800

170152065500

170692007200

171190136200

170692023300

0

2000

4000

6000

8000

10000

12000

14000

0.10 1.00 10.00

%Ro (measured)

Dep

th (f

t)

Surface %Ro (expected)

17067006100

170612011700

Trend A

Trend B

Thermal HistoryLate K Igneous Event

Moody (1949)

Optimum match between BHTs and %Ro and modeled valuesusing rift model with Late Cretaceous thermal event

170670006100 (J-2)

Late K thermal event

Heat Flow History and Thermal Maturity, Monroe Uplift

6000 ft

Heat Flow: 170 Ma

Heat Flow: 119 Ma

Heat Flow: 95 Ma

Heat Flow: 17 Ma

• Thermal maturity (%Ro) calculated using kinetic model from LLNL• Standard type II kerogen • 1D steady-state heat flow at model base, heat transfer from conduction

Maturity Modeling

170692023300

Thermal History: Paleoheat Flow• Thermal maturity constrained by %Ro

170692023300

48 mW/m2, rift model, modeled maturity reasonably matches TAI and %Ro

171190164100

170152087800170812037000

170812042100

170692008800170692007200

Calculated %Ro vs. Measured

Present-day95 Ma

Smackover Maturity

Present-day

Hydrocarbon Generation & Expulsion

0

5

10

15

20

0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 2.0 3.0 4.0

TOC (%)

N

Smackover: oil-prone Type II kerogen

TOC data updip wells onlyExtrapolated downdip

Ran models with range TOC

Pepper (1991)

OIL-WATER SYSTEMWATER-WET LITHOLOGIES

TY

PIC

AL

RE

SE

RV

OIR

S

OIL SOURCEROCKS

PHASESEQUALLYMOBILE

OILINCREASINGLY

MOBILE

WATERINCREASINGLY

MOBILE

0.7 0.4 0.0

RE

LA

TIV

E P

ER

ME

AB

ILIT

Y:

OIL

/WA

TE

R

OIL SATURATION

0.01

0.1

1

10

100

KSwirr

Ex: saturation threshold = 0.20

Oil Expulsion Volumetrics

109 bbls oil

Expulsed Oil Volumetrics

peak expulsion (108 to 103 my)(late Early Cretaceous)

TOC = 2 x RKZSaturation Threshold = 0.15

Constant heat flow (present-day)

Rift heat flowmodel

Primary gas

Secondary gas

Average GOR, North Louisiana = 12,500, up to 500,000 or more

Gas Generation and Expulsion

TOC = 2%, saturation threshold = 0.2, rift heat flow w/ K event

Expelled Gas (Primary + Secondary)

Timing of gas expulsion

Saturation threshold = 0.2TOC = 1%Heat flow model with rifting and late K event

0.00

0.20

0.40

0.60

0.80

1.00

020406080100120140

M.a.

Cu

mu

lati

ve

Ex

pu

lse

d G

as

Fra

cti

on

N. LA Petroleum System

E M L E L

Source Rock

Reservoir Rocks

Overburden Rocks

Generation-Expulsion

Salt

Uplift

Jurassic Cretaceous Tertiary

200 150 100 50

TimeScale Petroleum

Systems Events

Critical Moments

Secondary Migration

Trap

oilgas

Conclusions

• Geochemical data and basin modeling indicate that Smackover mature for oil and gas

• Peak oil expulsion late Early Cretaceous, persisted into Late Cretaceous

• Most gas is secondary• Peak gas expulsion early to middle Tertiary• Cumulative production accounts for less than

1.0% of total expulsed volumes of oil and gas– Estimates in published literature 1-3%