constraining the thermal history of carbonate reservoirs kristin... · 2017. 6. 5. · nafun abu...

Constraining the thermal history of carbonate reservoirsKristin BergmannVictor P. Starr Assistant Professor Department of Earth, Atmospheric and Planetary Sciences

MIT Earth Resources Laboratory 2017 Annual Founding Members Meeting May 31, 2017

Carbonate reservoirs reflect shallow crustal processes that occlude or enhance porosity

METAMORPHICREALM

METEORIC REALM

SUBSURFACE REALM

DOLOMITIZATION

DOLOMITIZATION

DISSOLUTION

DISSOLUTION

DISSOLUTION

CEMENTATION

CEMENTATION

CEMENTATION

DISSOLUTIO

N

DOLOMITIZATIO

N MARINE REALM

CCD

ACD

BRINE

SEAWATER

RAINW

ATER

(Modified from Moore, 1989)DOLOMITIZATION

Modified from Moore, 1989

Fe

250 μm 250 μm

250 μm 60 μm

Plane Polarized Light

SEM Backscatter Image




Electron Microprobe Elemental Map

110

25

{001}

50 μm

Tracking when and where key events occur is a function of T and W

METAMORPHICREALM

METEORIC REALM

SUBSURFACE REALM

DOLOMITIZATION

DOLOMITIZATION

DISSOLUTION

DISSOLUTION

DISSOLUTION

CEMENTATION

CEMENTATION

CEMENTATION

DISSOLUTIO

N

DOLOMITIZATIO

N MARINE REALM

CCD

ACD

BRINE

SEAWATER

RAINW

ATER

(Modified from Moore, 1989)DOLOMITIZATION

Modified from Moore, 1989

Traditional δ18O measurements depend on both T and W

Tem

pera

ture

(˚C)

100

200

0

0 +10 -10

δ18Ocalcite(VSMOW) = 30 ‰

δ18Owater (‰; VSMOW)

CaC16O3 + H218O CaC18O16O2 + H216O<-----> Keq

Clumped isotope thermometry primer

Ca13C16O3 + Ca12C18O16O Ca13C18O16O2 + Ca12C16O3<-----> Keq

1.0005

1.0004

1.0003

1.0002

1.0001

0 2 4 6 8 10 12 14

300 100 25 0

Keq

106/T2 (K)

Calcite

More Clumped Bonds

Random Bonds

T (°C)

DFT Model of clumping in calcite from Schauble et al., 2006

Tem

pera

ture

(˚C)

water Lakes and Evaporating

marine

Late diagenesis

Early diagenesis

Meteoric hydrothermal

Metamorphic

100

200

0

0 +10 -10

Sea soils

δ18Ocalcite (VSMOW) = 30 ‰

δ18Owater (‰; VSMOW)

CaC16O3 + H218O CaC18O16O2 + H216O<-----> Keq

Solid state reordering

• Apatite and aragonite will begin to reorder >100°C over 106 years (Stolper and Eiler, 2015 and Piasecki et al., 2015)

• Calcite will begin to reorder at >150°C over 106 - 108 years and fully-equilibrates above 200°C (Henkes et al., 2014; Stolper and Eiler, 2015)

• Dolomite does not reorder over ~ 250°C over 108 years (Lloyd and Eiler, 2014)

Stolper and Eiler, 2015

The Bergmann Lab approach

Mn

100 200 300 400

100

200

300

400 0

20

40

60

80

100

Precipitating temperature and fluid compositions

Trace metal and isotopic heterogenetity

Sedimentological context andpetrographic preservation

SIMS, Electron Microprobe, XRD, XANES, ICP-AES

Clumped Isotope Thermometry

Field observations and EBSD mapping

Jurassic

Silurian

Ordovician

Cambrian

Period

Triassic

Carbonif.

Permian

Ediacaran

Cryogenian

Quaternary–

Palaeogene

Cretaceous

Devonian EDIA

CARA

NCA

MBR

IAN

ARA541 Ma

Perio

dG

roup

NAF

UN

ABU

MAH

ARA~635 Ma

CRYO

GEN

IAN

I II

III

66 Ma

252 Ma

541 Ma

Diagenetic trends in marine carbonatesSultanate of Oman

Modified from Forbes et al., 2010

Group 1: Eocene to Permian■ Thick limestones to mixed limestones and siliclastics

■ Minor dolomite in the Permian■ Range of petrographic fabrics from micrite to grainstone

with varying degrees of fossil preservation and cementation

Group II: PC-C Ara Group■ Carbonate ‘stringers’ floating in evaporites■ Dominantly dolomite although some calcite

■ Range of petrographic fabrics with fine to coarse grained interlocking recrystallized fabrics

Group III: Ediacaran Nafun Group

■ Thick dolomites to mixed limestones and siliclastics■ Range of petrographic fabrics from micrite to

grainstone to boundstone with similar preservationcharacter to Group I

Diagenetic trends in marine carbonates:Cross section of central Oman

0 100 kmN

Arabian Sea

500 km

SAUDIARABIA

IRAN

A

A’

CentralOman High

0

3

6

9

12Ghaba SaltBasin

CentralOman High

South OmanSalt Basin

Depth (km

)

Paleozoic siliciclasticsAra SaltAra Carbonate StringersNafun GroupAbu Mahara

Basement

Map Legend

Precambrian OutcropSalt Basin

Well locationsSalt Dome locationOutcrop locations


Ghaba SaltBasin

Al Huqf

A A’

Permian - present carbonates

Modified from Al Siyabi, 2005

20 μm500 μm

Eocene [357m, BT = 43°C]: T = 30 ± 2°C δ18Owater = 0.2 ± 0.5‰ (n=3)

Plane Polarized Light SEM Backscatter Image

Jurassic [1038 m, BT = 54°C]: T = 34 ± 2°C δ18Owater = 0.3 ± 0.3‰ (n=2)

40 μm500 μm


Cretaceous [500.8 m, BT = 49°C]: T = 32 ± 4°C δ18Owater = 0.2 ± 0.8‰ (n=2)

2 cm

spar T = 48 ± 4°C; δ18Owater = 2.3 ± 0.7‰ (n=2)

1.4

1.2

1.0

0.8

0.6

0.4

0.2

0.0

●

●

●

●

●

●

●

●●●

●●

●

●●

●

●

25 50

Perm

ian

Jur.

Cret

aceo

usTe

rtia

ry

Dep

th (k

m)

Temperature (ºC)

Group I: Eocene to Permian carbonatesA subsurface well

Eocene-Permian calcite

Permian dolomite

●Void and fracture calcite

limestone

dolomite

evaporitesandstone

siltstone geothermal gradient

Bulk carbonatesshow ‘stabilization’ at low temperatures and very shallow depths(30-35°C)

0

5

●

●

●●

●●● ●●

●●

●●●●

●● ●

●

●●

●●●●●●●

●●●●●●

-5 0

-5

0

●

●

●●●

●●●● ●●●●

●●●●

25 50Temperature (°C)

δ18O

min

eral (‰

; PD

B)δ18

Ow

ater

(‰; V

SMO

W)

δ18Omineral (‰; PDB)


Permian dolomite

●Void and fracture calcite

Group I: Eocene to Permian carbonates v. shallow stabilization - mod. W/R

Low W

/R

High W/R

100 μm500 μm

PC-C (Ara Group) [3148 m, BT = 77°C] T = 75 ± 5°C δ18Owater = 7 ± 1‰ (n=2)


Group II: Precambrian-Cambrian Ara GroupA subsurface well

3.0

2.5

2.0

1.5

1.0

0.5

0.0

●

●

●

●●

●

●●●

●

●●

●●●●●

●●●

●●

● ●●

25 50 753.5

Cam

bria

nO

rdov

icia

nPe

rmia

nJu

r.Cr

etac

eous

Tert

iary

Carb

.

Dep

th (k

m)

Temperature (ºC)

Non-SOSB Birba dolomite


Permian dolomite

●Void and fracture calcite●

Nafun Group calcite

Nafun Group dolomite

●● SOSB calcitelimestone

dolomite

evaporitesandstone


●

●●●● ●●●●●●

●●●●●● ●●●●● ●●●

25 50 75 100 125Temperature (°C)

5

4

3

2

1

0D

epth

(km

)

Eocene - PermianPrecambrian-Cambrain Ara GroupPrecambrian Birba carbonates

Group II: Precambrian-Cambrian Ara Groupsample Ts approach the current geotherm

0 100 kmN

Arabian Sea

500 km

SAUDIARABIA

IRAN

A

A’

CentralOman High

0

3

6

9

12Ghaba SaltBasin

CentralOman High


Depth (km

)


Basement

Map Legend




Ghaba SaltBasin

Al Huqf

A A’


0 100 kmN

Arabian Sea

500 km

SAUDIARABIA

IRAN

A

A’

CentralOman High

0

3

6

9

12Ghaba SaltBasin

CentralOman High


Depth (km

)


Basement

Map Legend




Ghaba SaltBasin

Al Huqf

A A’


0 100 kmN

Arabian Sea

500 km

SAUDIARABIA

IRAN

A

A’

CentralOman High

0

3

6

9

12Ghaba SaltBasin

CentralOman High


Depth (km

)


Basement

Map Legend




Ghaba SaltBasin

Al Huqf

A A’


Group II: Precambrian-Cambrian Ara Groupδ18Owater compositions are enriched

●

● ●●●●● ●●●●

●●●●●● ●●●●●●● ●

−5 0 5 10 15δ18Owater (VSMOW, ‰)

5

4

3

2

1

0D

epth

(km

)

Eocene - PermianPrecambrian-Cambrain Ara GroupPrecambrian Birba carbonates

0 100 kmN

Arabian Sea

500 km

SAUDIARABIA

IRAN

A

A’

CentralOman High

0

3

6

9

12Ghaba SaltBasin

CentralOman High


Depth (km

)


Basement

Map Legend




Ghaba SaltBasin

Al Huqf

A A’


0 100 kmN

Arabian Sea

500 km

SAUDIARABIA

IRAN

A

A’

CentralOman High

0

3

6

9

12Ghaba SaltBasin

CentralOman High


Depth (km

)


Basement

Map Legend




Ghaba SaltBasin

Al Huqf

A A’


0 100 kmN

Arabian Sea

500 km

SAUDIARABIA

IRAN

A

A’

CentralOman High

0

3

6

9

12Ghaba SaltBasin

CentralOman High


Depth (km

)


Basement

Map Legend




Ghaba SaltBasin

Al Huqf

A A’


●

●

●

●

●

●

●

●

●

●

●

●

●

●

0

●●

●

●

●●

●

25 75 125Temperature (°C)

-5

δ18O

min

eral (‰

; PD

B)

0

5

10

15

δ18O

wat

er (‰

; VSM

OW

)

-5δ18Omineral (‰; PDB)

Burial Fluids Burial Fluids

0

5

10 ●●●

●

●

●

●●● ●●●

●

●

●

●●●

-10 -5 0

-10

-5

0●●●●

●

●

●●

●

25 50 75 100Temperature (°C)

δ18O

min

eral (‰

; PD

B)δ18

Ow

ater

(‰; V

SMO

W)


● Qarn Alam Salt Dome

● SOSB calcite

non-SOSB Birba dolomite

SOSB dolomite

Group II: Precambrian-Cambrian Ara Group low W/R ratio Lo

w W/R

High W/R

Ediacaran (Nafun Group) [surface, est. 1-2km max] T = 55 ± 1°C, δ18Owater = -1.6 ± 0.4‰ (n=3)

80 μm500 μm


4.0

3.8

3.6

3.4

3.2

3.0

● ●

●

50 75 1004.5

Naf

unAr

a

Edia

cara

n

Dep

th (k

m)

Temperature (ºC)

Group III: Ediacaran Nafun Group A subsurface well


Nafun Group calcite


●limestone

dolomite

evaporitesandstone


limestone

dolomite

boundstone including stromatolites and laminites

grainstone including oolitic

mudstone

wackestone and packstone

teepees sandstone

siltstone


Nafun Group calcite


●

2800

2600

2400

2200

2000

200

400

600

800

1000

4200

4000

3800

3600

3400

3200

3000

200

400

600

800

1000

1200

Well “T”

25 50 7525 50 75 25 50 75

25 50 75

Temperature (˚C)

Khufai Dome Well “MQ”Mukhaibah Dome

T range is spatially and stratigraphically consistentfor both dolomite and calcite in Nafun Group

(sedimentology from Bergmann, 2013 and Osburn, 2013)

0 100 kmN

Arabian Sea

500 km

SAUDIARABIA

IRAN

A

A’

CentralOman High

0

3

6

9

12Ghaba SaltBasin

CentralOman High


Depth (km

)


Basement

Map Legend




Ghaba SaltBasin

Al Huqf

A A’

Permian - present carbonatesAl Huqf Outcrop

Well A

Well B

-5

0

5

-10 -5 0

-10

-5

0

25 50 75

0

5

●●

●●

●

●

●●●●

●

●

●

●

●●

●●●

●

●●

● ●●●

●●

●

●

●

●

●●

●● ●●

●●

●

●

●●●●

●

●

●

●

●●

●●●

●

●●

●●● ●

●●

●

●

●

●

●●

●●

-10 -5

-10

-5

●● ●

●●●

●●●●

● ●●

●

●●

●

●●● ●●

●

●

●

●●

●

●

● ●

●

● ●●●

25 50 75Temperature (°C)

δ18O

min

eral (‰

; PD

B)δ18

Ow

ater

(‰; V

SMO

W)


Temperature (°C)δ18

Om

iner

al (‰

; PD

B)δ18

Ow

ater

(‰; V

SMO

W)


Nafun Group calciteNafun Group dolomite

●

Low W

/R

High W/R

Group III: Ediacaran Nafun Group change in fluid comp., low W/R in calcite

●

●●●● ●●●●●●

●●●●●● ●●●●● ●●●

25 50 75 100 125Temperature (°C)

5

4

3

2

1

0

Dep

th (k

m)

Eocene - PermianPrecambrian-Cambrain Ara Group

Precambrian Nafun GroupPrecambrian Birba carbonates

Group III: Ediacaran Nafun Group Ts in between Groups I & II

0

3

6

9

12D

epth

(km

)Ghaba Salt

BasinCentral

Oman HighSouth Oman

Salt Basin

A A’

●

● ●●●●● ●●●●

●●●●●● ●●●●●●●●

−5 0 5 10 15δ18Owater (VSMOW, ‰)

5

4

3

2

1

0

Dep

th (k

m)

Eocene - PermianPrecambrian-Cambrain Ara Group

Precambrian Nafun GroupPrecambrian Birba carbonates

Group III: Ediacaran Nafun Group δ18Owater marine-like

Observations:■ Nafun Group carbonates are petrographically well-preserved

■ Co-occuring calcite and dolomite indicate similar T

■ δ18Owater compositions areseawater like for both calcite and dolomite

Options: ■ partial solid state diffusion and long term change in δ18Owater

■ change in temperature of shallowburial ‘stabilization’ or initial temperature

Summary

■ Using a combination of petrographic, microanalytical and clumped isotope analyses of specific textures we can reconstruct the timing of events critical to the evolution of carbonate reservoirs and the thermal history of basins

■ Results from Oman indicate dolomites and limestones are more susceptible to burial diagenetic processes than solid state diffusion between 0-6 km over geologic timescales.

■ Group I of Eocene-Permian limestones and dolomites suggest very early ‘stabilization’. Group II Ara Group limestones and dolomites show variable closed system behavior. Group III Nafun Group data are consistent with a higher temperature of ‘stabilization’ at very shallow depths which could indicate the Ediacaran was 5-20°C warmer than the recent Phanerozoic.

constraining the thermal history of carbonate reservoirs kristin... · 2017. 6. 5. · nafun abu...

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