Global Deepwater Fold Blet Passive vs Active Shell

Global Overview of Tertiary Deepwater Foldbelts :Passive vs. Active Margin Systemsby Scott Sumner, Ciaran O’Byrne, Gary S. Steffens, Robin Hamilton, and Tim FarnhamShell International E&PMarch 8, 2006

Acknowledgements:

Dave Steele, Mike Bourque, Rod Nourse, John Karlo, Mark Rowan, Frank Peele, JohnStainforth, Mike Lentini, Scot Fraser, Larry Garmezy, Daniel Truempy, Dave Stewart, SveinAase, Guy Loftus, Allan Scardina,, Mark Depuck, Carlos Pirmez, Brad Prather, Mike Mahaffie, Peter Mullin, Aly Brandenburg, Eric Bartsch, Tim Chilsom, Gary Ingram, Jeff Lobao, Jim Booth,, Peter Tauvers, Fred Diegal, Brad Robison, Franz Kessler

Frogtech Consultants: Jon Teasdale, Peter Smith

New Zealand Petroleum Conference 2006: Putting energy into exploration

• Distribution, primary and secondary controls

• Examples:- Nigeria- Northwest Gulf of Mexico- Northwest Borneo

• Summary

OutlineOutline

Passive and Active Margin Deepwater FoldbeltsPassive and Active Margin Deepwater Foldbelts

Shelf Edge

Modified after Doust and Omstala (1989), Haan, (1994)

Continental CrustOceanic Crust

Nigeria

NW Borneo

Dangerous GroundsSouth China Seakm

0

4

8

? ? KU - Pg

NW SE

? 100 kmContinental

Crust

Mobilized Shale

Inversions/ FoldsFold/ thrust belt

Fold/ thrust belt

Rajang Basement

Growth Faulting

10 km

100 km

Mod. after Letouzey and Sage(1988)

Passive Margin

Active Margin

Updip extension and loading balanced by downdip contraction and emplacement of mobil substrate.

Unbalanced system with contraction throughout slope and shelf. May have “thin-skinned linked system” superimposed.

“Linked System”

Deepwater Tertiary Foldbelts

Passive Margin salt-based

? ?

Passive Margin shale-basedActive Margin shale-based

~6 BBOE Discovered in 4 basins ~170 MBOE mean field size (29 Discoveries)Data as of early 2004

Tectonic Settings of Deepwater FoldbeltsTectonic Settings of Deepwater Foldbelts

Foldbelt

km

5

0

Mod. after Bergman et al. (1996)

W km

5

0

10Offshore Nigeria

After Speed, 1990; Bouysee and Westercamp, 1988

Oceanic CrustMobilized Shale

Mod. after Doust and Omstala (1989)

Modified after Peel et al., (1995)

From Babonneau et al. (2002)

10 km

100 km

km

SaltPassive Margin


Active Margin

OceanicCrust

E

NESW

FoldbeltNigeria

West Sulawesi

BarbadosW

SENW

EWAngola

Uplift

Foldbelt

Foldbelt

~5.3 BBOE Discovered ~170 MBOE mean field size

Salt-Based

Shale-Based

CollisionalForeland

Subduction Prism

Salt-Based

CollisionalForelandNW Gulf of Mexico

? ? ?KU - Pg?

Shelf Edge

? ? ?KU - Pg?

Shelf EdgeNW Borneo SE

FoldbeltNW

Mobilized Salt

Mod. after Peel et al.(1990)

Foldbelt

ContinentalCrust

S N

Passive and Active Margin Deepwater Foldbelt Distribution

Salt Canopy

NW G.O.M.

Salt

Nigeria

ShaleNW

BorneoAngolaSalt

Fold, thrust, reverse fault

Shelf-edgeExtent of Linked system

100 Miles100 km

Passive Margin

Active Margin

Accretionary Prism

Barbados

West Sulawesi

CollisionalForeland

CollisionalForeland

NW Borneo

Secondary controls on structural styles of Deepwater Foldbelts

Mobile substrate thickness- thicker forms detachment “buckle” folds- thinner forms thrust faulted folds

From Stewart (1999)

thick substrate

thin substrate

Thick lower-strength substrate (salt)

Lower Congo Basin

Buckle folds

(from Rowan et al., 2004)

Mobile substrate/detachment strength- weaker forms detachment “buckle” folds- stronger forms thrust-faulted and duplexed folds

Thin higher-strength substrate (shale)

(from Costa and Vendeville, 2002)

Thick lower-strength substrate (salt)

Thin higher-strength substrate (shale)

Para-Maranhao Basin-

Imbricated thrusts

0 100Kilometers0 1000 100

Kilometers

Strike-length of fold axis

Deepwater Foldbelt Structural Metrics (n=25)average fold strike length of salt-based passive margin systems

is ~ half that of shale-based passive and active margin systems

Ave Fold Strike Length vs FB Type

0102030405060708090

100

Fold

Str

ike

Leng

th (k

m)

Passive / Salt

Passive / Shale

Active / Shale

17 km. ave.

37 km. ave.

49 km. ave.

Ave Fold Strike Length vs FB Type

0102030405060708090

100

Fold

Str

ike

Leng

th (k

m)

Passive / Salt

Passive / Shale

Active / Shale

17 km. ave.

37 km. ave.

49 km. ave.

Passive/ Salt Passive/ Shale Active/ Shale

883 msecs.twt ave. 755 msecs. twt ave.1000 msecs.twt ave.


10.3 km. ave 11.25 km. ave 11.7 km. ave


10.3 km. ave 11.25 km. ave 11.7 km. ave

Amplitude

wavelength

average fold amplitude and dip wavelengths are similar

NW Borneo seafloor

Illustrations of Structural Play Groups with Mobile Substratum (Salt or Clay)Regional Seismic Lines from 5 Deep Water Basins

P.R. Mullin/H.M. BürgisserDecember 2001

Relative Scales and Positions of Deepwater Foldbelts

NEFold/ Thrust belt

Shelf-edgeToe-of-slope

* Seismic courtesy of Mabon Ltd.

0

5

TWTSecs.

25 KM

Active Margin

Offshore NigeriaPassive Margin Shale-based

SW

SENW

Fold/ Thrust belt

* Mod. From Ingram et al. (2004)

NW BorneoNW SE

Duplex?

Duplexes?

Source rockbearing interval

Gas-prone(Type III)Oil-prone(Type I-II)

Deep marine clastic Deep marine shales / carbonatesShallow Marine carbonatesEvaporites

Synrift

Legend

Source rockbearing intervalSource rockbearing interval


Synrift

LegendDeep marine clastic Deep marine shales / carbonatesShallow Marine carbonatesEvaporites

Synrift

Legend0

50

100

150

200

Ma0

50

100

150

200

Ma NW G.O.M. Nigeria

PerdidoMiss. Fan

?

?

Salt-based Shale-basedAngolaSalt-based

Passive Margin Active MarginStratigraphic Megasequences in Deepwater Foldbelts

D

D

D

NW Borneo

Lower slope?

?

Foreland Shale-based

W. Sulawesi

?


DD

Foldbelt Deformation

Decollement

Subduction Prism Shale-basedBarbados

D

D

Reservoir Distribution in Deepwater FoldbeltsPassive Margin

Reservoirs are more predictable in passive margin settings than in active margin settings

Wide slopes with low gradients (1- 2o)

Folds are load-driven and occur at toe-of-slope

Pre-kinematic reservoirs are often toe-of slope unconfined fan systems

Active Margin

Narrow slopes with high gradients (2– 4o+)

Folds driven by extra-basinal forces occuring throughout slope and shelf

Pre-kinematic reservoirs depend on slope setting prior to deformation

Shortening

Toe of slope

Shelf edgePre-kinematic

(if present!)

Syn-kinematicFolding

TimeTime Toe of slope

Shelf edge

Progradation

Pre-kinematic

Syn-kinematic

Folding


Gas-prone(Type III)Oil-prone(Type I-II)


Synrift

Legend

Source rockbearing intervalSource rockbearing interval


Synrift

LegendDeep marine clastic Deep marine shales / carbonatesShallow Marine carbonatesEvaporites

Synrift

Legend0

50

100

150

200

Ma0

50

100

150

200

Ma NW G.O.M. Nigeria

PerdidoMiss. Fan

?

?

Salt-based Shale-basedAngolaSalt-based

Passive Margin Active Margin

Source Rocks and Hydrocarbons in Deepwater Foldbelts

D

D

D

NW Borneo

Lower slope?

?


W. Sulawesi

?


DD

Foldbelt Deformation

Decollement

Subduction Prism Shale-basedBarbados

D

D

Proven/Inferred HC Mix vs FB Type

0

1

2

3

4

5

6

7

8

Passive / Salt Passive / Shale Active / Shale

# of

FBs

Oil MixGas

HC Mix More GasMore Oil

? ? ?KU - Pg?

Shelf Edge

Thermal Maturity and Heat Flow in Deepwater FoldbeltsThermal Maturity and Heat Flow in Deepwater Foldbelts

NW Borneo

Foldbeltkm

5

0

Mod. after Bergman et al. (1996)

W km

5

0

10Offshore Nigeria

After Speed, 1990; Bouysee and Westercamp, 1988




From Babonneau et al. (2002)

10 km

100 km

SE

Passive Margin


Active Margin

OceanicCrust

E

FoldbeltNW

NESW Foldbelt NigeriaWest Sulawesi

BarbadosW

SENW

EW AngolaFoldbelt

km

Foldbelt

-

3540 25

35

Thermal maturity & Heat Flow (mw/m2)

40-60 40->60

50- 60

50

45

Modelled

NGDC

ModelledNGDC

Henry (2000)

40-60 3540->60 Analogy

5035

NW Gulf of Mexico

Mobilized Salt


Foldbelt

ContinentalCrust

S N

Hydrocarbon Migration and Entrapment in Deepwater Foldbelts

sea floor

Filled Traps

Wet Traps

maturitysource

rock

Complex, high relief structures inhibit long distance lateral HC migration within foldbelts

HC migration is generally short distance from nearby “kitchens”

Vertical HC migration pathways can be complicated by position of source rocks relative to detachments

Continental CrustContinental CrustContinental Crust

Oceanic CrustMobilized ShaleOceanic CrustMobilized Shale


Salt


FoldbeltNS

NESW

Passive Margin Salt-Based

Passive Margin Shale-BasedFoldbelt Nigeria

NW Gulf of Mexico


Shelf Edge

? ? ?KU - Pg?

NW Borneo SE


FoldbeltNWActive Margin Foreland

10 km

100 km

10 km

100 km

X-section scale

RajangBasement

Salt Canopy

NW G.O.M.

Nigeria

100 km


Shelf-edge

Linked system extent

Map LegendNW BorneoNW Borneo

Deepwater Foldbelts of NW Gulf of Mexico, Nigeria, and NW Borneo Deepwater Foldbelts of NW Gulf of Mexico, Nigeria, and NW Borneo

Mobilized Salt

Foldbelt

ContinentalCrust



• Summary

OutlineOutline

Continental CrustContinental CrustContinental Crust

Oceanic CrustMobilized ShaleOceanic CrustMobilized Shale


Salt


FoldbeltNS

NESW



NW Gulf of Mexico


Shelf Edge

? ? ?KU - Pg?

NW Borneo SE



10 km

100 km

10 km

100 km

X-section scale

RajangBasement

Salt Canopy

NW G.O.M.

Nigeria

100 km


Shelf-edge


Map LegendNW BorneoNW Borneo


Mobilized Salt

Foldbelt

ContinentalCrust

•Passive margin shale-based fold/ thrust belts

•Positioned on lower slope and toe-of-slope

•Miocene to Recent age

Nigeria Deepwater Fold/ Thrust Belts

Middle Miocene Depth Structure

Fold/ Thrust Belts

100 km

Offshore Nigeria Seafloor Structure

TWT(msec)

N

Fold/ Thrust belt

50 km

Seismic Data courtesy of Mabon Ltd.

AA’0

5

TWT(sec)

NE

A

A’

SW

Duplex?

3 secs. twt

5 km

AA’

Depth Structure Miocene

A

A’

5 km

Dominated by basinward-vergent thrusted folds…

Depth Structure Map

Nigeria Deepwater Fold/ Thrust Belts

B

B’ 5 km

5 km

BB’

… but complex back thrusts occur locally

Depth Structure Map

Back Thrusts

Seismic courtesy of Mabon Ltd.

Nigeria Deepwater Fold/ Thrust BeltsBasinward-vergent thrusted folds become younger and more imbricated downdip… caused by basinward increase in strength of decollement (decrease in fluid pressures)?

Mod. From Rowan et al. (2004)

Some updip folds may be underlain by duplex structures localized by decollement step-downs

Offshore Nigeria Drainage AnalysisOffshore Nigeria Drainage Analysis

From Steffens et al. (2003)

Long dip-oriented drainage paths bypass upper sloe, many making it to the toe-of-slope

Ponded Accommodation

Only small amounts of pondedaccommodation between actively growing folds

Nigeria Deepwater Foldbelt Petroleum Systems


Synrift


Legend


Synrift


Legend


Synrift


Legend

Tx

0

50

100

150

Ma Nigeria

??

Main source rocksPg –K marine clastics,oil and gas prone

Basinward decrease in heat flow and thermal maturity


Oceanic Crust

Mobilized Shale


10

100 km

NESWkm0

ContinentalCrust

Heat Flow and Thermal Maturity

Top Oil window

Ikija

Main reservoirs



• Summary

OutlineOutline



Salt


FoldbeltNS

NESW



NW Gulf of Mexico


Shelf Edge

? ? ?KU - Pg?

NW Borneo SE



10 km

100 km

Salt Canopy

NW G.O.M.

Nigeria

X-section scale

100 km


Shelf-edge


Map Legend

RajangBasement

NW Borneo


Mobilized Salt

Foldbelt

ContinentalCrust

NW Gulf of Mexico Deepwater Foldbelts

Passive margin salt-based foldbelts Positioned on lower slope/ toe-of-slopePg. to Late Miocene age

100 Miles

MSF Foldbelt

Perdido Foldbelt

Modified from Peel et al. (1995)

B B’A A’

B’A’

B

A

C

C’ C C’

Structural Styles in the G.O.M. Deepwater Foldbelts

10 k

m

50 km

Modified after Peel et al., 1995

Mississippi Fan Foldbelt

NW GOM Deepwater Foldbelts

100 Km

PerdidoFoldbelt

AB

C

D

SN K2 Mad Dog

Pleist.Pliocene

MiocenePg.

KJ

Line B N SLine A

W ETridentBaha

Eo.-Pc.

Line D N S

Eo.-Pc.

Line C

KJ

St MaloMiocene

Unconfined Fan Deposition, Toe of Slope, Atwater ValleyPre-Kinematic unconfined fan reservoir analogue for Mississippi Fan Foldbelt

Channelized debris lobe Ponded sheets Channel+margin Channelized sheetsA B

Overlapping and coalescing unconfined abyssal plain fans incorporated into prograding foldbelt

A

B

Mississippi Canyon & Atwater Valley, Upper Miocene (5.5 ma Messinian event)

Mississippi Canyon & Atwater ValleyUpper Miocene (5.5. ma Messinian event)

A

NW Gulf of Mexico Deepwater Foldbelt Petroleum Systems


Synrift


Legend


Synrift


Legend


Synrift


LegendNW G.O.M.

Tx. La.

0

50

100

150

200

Ma

?

Main source rocksUJ (Tith.) – UK (C-T)Type I/II Marine oil-prone

100 Miles100 Miles

MSF Foldbelt

NW G.O.M. Seafloor and Deepwater Source Type from Seepage and Oils

(modified from Cole et al, 1999)

Carbonate Province

Marl and Clastic Province

Clastic Province

Perdido Foldbelt

General basinward decay in heat flow and thermal maturity for source rocks

Salt locally modifies regional thermal maturityContinental

Crust

Mobilized Salt

Foldbelt

NS NW Gulf of Mexico


10

100 km

0


Top oil window

Multiple Source Rocks

Main reservoirs

Mod. From Cole et al. 1999)


100 Km

Mississippi FanFoldbelt

PerdidoFoldbelt


100 Km


100 Km100 Km

Mississippi FanFoldbelt

PerdidoFoldbelt

Perdido Foldbelt Oil Discoveries• large Oligocene-age detachment folds• Paleocene deepwater sand reservoirs

Mod. From Trudgill et al. (1999)

A

B

Oil discoveries on trend in buried “non-apex” anticlinal structures

Salt

A B

Miss. Fan Foldbelt Oil Discoveries• large Late Miocene subsalt detachment folds• Early Miocene deepwater sand reservoirs

K2 Mad Dog

Mod. From Grando and McClay (2004)



• Summary

OutlineOutline



Salt


FoldbeltNS

NESW



NW Gulf of Mexico


Shelf Edge

? ? ?KU - Pg?

NW Borneo SE



10 km

100 km

Salt Canopy

NW G.O.M.

Nigeria

X-section scale

100 km


Shelf-edge


Map Legend

RajangBasement

NW Borneo


Mobilized Salt

Foldbelt

ContinentalCrust

NW Borneo Active Margin Deepwater Foldbelt

0 100Kilometers

GPS measurements indicate that NW Borneo is a tectonically active setting with ~4 cm / yr NW-SE convergence (Rangin et al, 1999)

South China Sea

Sulu Sea

Celebes Sea

Borneo

400 km

Brunei

Bathymetry Map

South China Sea

Sulu Sea

Celebes Sea

Borneo

400 km

Brunei

Bathymetry Map

NW Borneo Seafloor~4 cm / yr convergence

NW Borneo Deepwater Foldbelt


0

4

8

? ? KU - Pg

NW SE

? 100 km100 kmContinental

Crust

Inversions/ FoldsFold/ thrust belt

Rajang Basement


Stepped Slope Profile

100 km

~4cm / yr of convergenceNW Borneo Seafloor

Active margin shale-based foldbelts Miocene – Recent age

Unbalanced structural system with coeval contractional features throughout basin

BB

BB’’

Borneo

NW Borneo Regional Crustal Framework

Dangerous Grounds - Reed Banks Terrane

Mantle (ρ=3.2g/cm3)

RajangTerrane Meratus Terrane

Rajang-CrockerFold-Thrust Belt

Lower Crust (ρ=2.9g/cm3)

Upper Crust (ρ=2.7g/cm3)

Rajang Group(ρ=2.5g/cm3)

Oceanic Crust (ρ=2.9g/cm3)

Sediment (ρ=2.3g/cm3)

Water (ρ=1.05g/cm3)

Counter-regionalnormal fault

MeratusTerrane

Measured Gravity

Modelled Gravity

No gravity data

200km

0

10

20

30

40

0

10

20

30

40

0

500

1000

-500

0

500

1000

-500

B B’NW SE

SubductedProto-South China Sea

B’B’ South China Sea

Modified from Frogtech (formerly SRK) Consultants

NW Borneo


0

4

8

? ? KU - Pg

NW SE

? 100 kmContinental

Crust

Inversions/ FoldsThrust-Foldbelt

Rajang Basement


Gravity interpretations suggest that parts of the NW Borneo slope are underpinned by high density outliers of Rajang Basement

NW Borneo Middle Miocene – Recent Kinematic Model

Modified from Ingram et al. (2004)

• NW moving basement allochthondriven by extra-basinal forces

• Allocthon bounded by major shears

• Folds are cored by allochthoninboard and detached outboard

0

8

sectwt

10 km

SENW

Rajang Rajang basementbasementD.GroundsD.Grounds--Reed Banks Reed Banks

TerraneTerrane BasementBasement

SABAH TROUGH

DETACHED FOLD & THRUST BELT

21.8 Ma21.8 Ma

OUTBOARD ALLOCHTHON

Complex trap history influenced by basement allochthon & shearing

Modified from Ingram et al. (2004)

Ridge

2.5 km

Brunei Slope Canyon

Effect of subtle topographic features on reservoir distribution

NW Borneo Deepwater Foldbelt ReservoirsHigh gradient (2 – 4 ) stepped profileHealed slope accommodation with significant bypassChannelized reservoirs common

NW Borneo

Lower slope?

?

Active Shale

Tx

0

50

100

Ma


Synrift


Legend

50 90

mW/m2

ModelledHeat Flow

*

Foldbelt

Main source rocks are Miocene Terrestrial gas and oil-prone

NW Borneo Deepwater Foldbelt Petroleum Systems

General basinward increase in heat flow and thermal maturity


NW Borneo

8100 km

? ? ?KU - Pg?

SE

FoldbeltNW

RajangBasement

kmo

Top oil window

Continental Crust

?

KikehGumusut



NW Borneo

8100 km

? ? ?KU - Pg?

SE

FoldbeltNW

RajangBasement

kmo

Top oil window

Continental Crust

?

KikehGumusut




• Summary

OutlineOutline

Global Overview of Tertiary Deepwater FoldbeltsSummary of Structure

• Passive margin DW foldbelts are driven by updip loading and extension (“linked system”)

• Active margin foldbelts are driven by extra-basinal plate-tectonic events often forming independent of loading in the basin

• Folding/ thrusting commonly occurs throughout basin on active margins and is confined to the lower slope/ toe-of slope on passive margins

• DW foldbelt structural styles are related to “secondary controls” such as presence / type of mobile substrate, rheology of overburden, and amount of shortening

Global Overview of Tertiary Deepwater FoldbeltsSummary of Reservoir

Passive margin reservoirs are usually closely associated with load-driven structural deformation (“linked systems”)

Active margins have higher slope gradients than passive margins resulting in increased bypass (“stepped profiles”)

Due to extra-basinal tectonism, active margin reservoir distribution can be independent of intra-basin structural history

Global Overview of Tertiary Deepwater FoldbeltsSummary of Petroleum Systems

Heat flow and thermal maturity generally decreases basinward on passive margins but can be highly variable on active margins

Active margins are more ephemeral systems with fewer potential source rocks than passive margins

Active margin source rocks are often more terrestrial and gas prone, while passive margin source rocks are often more marine and oil-prone

Passive margin DW foldbelts are generally more oil-prone than active margin foldbelts

Global Overview of Tertiary Deepwater Foldbelts

“Grand” Summary

• Differences in deepwater foldbelts may have huge implications for petroleum systems and prospectivity

• But differences may be systematic and predictable

Large untested scope still remains!

Thanks!

Documents

Global Deepwater Fold Blet Passive vs Active Shell