Regional petroleum systems modelling in the Dutch offshore

Date

Venue/Event

A “hot” topic of conversation

Presentation courtesy of:

Regional petroleum systems modelling in the Dutch offshore

Wednesday 20th November2019 Dutch Exploration Day

David Gardiner1, Linda Janssen2,

Tiago Cunha1 & Kees van Ojik21IGI Ltd.

2EBN B.V.

OverviewWhat will we cover?

▪ Overview of petroleum

systems

▪ Source rock richness &

kerogen type

▪ Maturity calibration – getting

an eye into the past

▪ Integrated 3-D petroleum

systems model

▪ Summary

The 57,000 km2 AOI of

the entire Dutch

offshore. Note: the

distribution of gas fields

(source: EBN)N

Petroleum SystemSummary of existing knowledge

Kimmeridge/

Coervorden

shales

PosidoniaAalburg Fm.Sleen Fm.

ZechsteinBundandstein Sst.

Namurian

Visean coals

Shale

Pri

mar

y

Seco

ndar

y

Coal

Carbonate

Source Rocks Reservoir Rocks

Tubbergen Sst.

Zechstein (Z3)

Westphalian

Lwr. & Upr. Graben Fms.

Vlieland Sst.

Miocene-Pleistocene

unconsolidated sst.

Sandstone

CarbonateMain

Secondary

Charge

origin

Westphalian

Posidonia

Tectonic phase

Sudetian

Asturian

Saalian

Hardegsen

E.Cimmerian

M.Cimmerian

L.Cimmerian

Austrian

Subhercynian

Laramide

Pyrenean

Savian

Alp

ine

Var

isca

n

Major/Regional

Minor/Localised

Rotliegend

Source rocksJurassic: Kimmeridge Clay Fm., Posidonia, Aalburg Fm., Sleen Fm.

Carboniferous: Westphalian coal, Namurian shales, Visean coals

ReservoirsCretaceous: Chalk Gp., Lower Cretaceous turbidites, Vlieland sand

Jurassic: Upper & Lower Graben Fms., Kimmeridgian sands

Triassic: Bundandstein sandstone

Permian: Zechstein Gp. (e.g. Z3 carbonates), Upper Rotliegend Gp.

Carboniferous: Tubbergen Sandstone

Stratigraphic sealsCenozoic: Paleogene muds

Cretaceous: Chalk Gp., Lower Cretaceous shales

Jurassic: Kimmeridge Clay Fm.

Permian: Zechstein Gp. evaporites

Two main petroleum systems:

1) Paleozoic (Westphalian → Rotliegend)

2) Mesozoic (Posidonia → Lwr./Upr. Graben Fms.)

Major erosive unconformities Duin et al., 2006

Posidonia ShaleSource rock summary

25

25

25

25

25

25 25

2525

50

50

50

500 550 600 650 700

5700

5800

5900

6000

6100

6° 5° 4° 3°

55°

54°

53°

52°

A11-01

A16-01 B18-02

D12-03-S1

E12-02

E18-02

F04-03

F14-01

G17-01

K03-02

K04-03

K13-06

L02-02

L10-06 L11-12

L16-01

M03-01

M08-01

N04-01

P05-01

P10-01

P15-01

P16-01

Q08-01

S05-01

Gross Posidonia Isopach (m) (nlog)

0 20 40 60 80 100

80 km

Gross thickness

Posidonia

absent

Posidonia

absent

Posidonia

absent

0 20 40 60 80 100 120

Gross Posidonia Isopach (m) (nlog)

02

46

810

Fre

quency (

1000)

Mean=29.6339

N=79917

Std=10.933

1-D models

0 1 2 3 4 5 6 7 8 9 10 11 12

TOC (Wt%)

0

5

10

15

20

Fre

qu

en

cy

TOC (wt.%)

Fre

quency

Poor source

Fair source

Good source

Very good source

Location of Posidonia

samples with TOC &

Rock-Eval pyrolysis data

n 124

min 0.4

max 13.9

mean 5.6

TOC

(wt.%)

0 100 200 300 400 500 600 700 800 900 1000

HI (mg/gTOC)

400

410

420

430

440

450

460

470

480

490

500

510

520

T-m

ax (

°C)

Type I kerogen

Type II kerogen

Type III kerogen

Hydrogen Index (HI) (mg/gTOC)

Rock

Eva

l Tm

ax(°

C)

Bi-modal distribution,

relative homogeneity and

mean TOC of 5.6 wt.%

typical of world-class

source rock

Type I kerogen

Type II kerogen

Type III kerogen

TOC (wt.%)

0.0 - 1.0

1.0 - 2.0

2.0 - 4.0

4.0 - 6.0

6.0 - 10.0

10.0 - 15.0

15.0 - 20.0

20.0 - 40.0

40.0 - 100.0

The Posidonia shale

is thin and only

locally present, but

highly organic-rich

and oil-prone

Type II (marine) kerogen

componentType III/IV (terrestrial) kerogen

component

0 100 200 300 400 500 600 700 800 900 1000

HI (mg/gTOC)

400

410

420

430

440

450

460

470

480

490

500

510

520

T-m

ax (

°C)

Type I kerogen

Type II kerogen

Type III kerogen 500 550 600 650 700

5700

5800

5900

6000

6100

6° 5° 4° 3°

55°

54°

53°

52°

A11-01

A16-01 B18-02

D12-03-S1

E12-02

E18-02

F04-03

F14-01

G17-01

K03-02

K04-03

K13-06

L02-02

L10-06 L11-12

L16-01

M03-01

M08-01

N04-01

P05-01

P10-01

P15-01

P16-01

Q08-01

S05-01

Westphalian (10%) isopach (m)

0 50 100 150 200 250

80 km

0 10 20 30 40 50 60 70 80 90

TOC (Wt%)

0

25

50

75

100

125

150

175

200

Fre

qu

en

cy

Westphalian coals (Limburg Gp)Source rock summary

Net thickness

(10% N:G assumed)

1-D models

TOC (wt.%)

Fre

quency

Poor source

Rich shales

Oil shales

Coals

Location of Limburg Gp

samples with TOC &

Rock-Eval pyrolysis data

n 476

min 0.0

max 82.8

mean 8.2

TOC

(wt.%)

Hydrogen Index (HI) (mg/gTOC)

Rock

Eva

l Tm

ax(°

C)

Highly heterogeneous

clastic system with coals

(regionally) and organic-

rich shales (locally in ADB

& CBH)

Type I kerogen

Type II kerogen

Type III kerogen

TOC (wt.%)

0.0 - 1.0

1.0 - 2.0

2.0 - 4.0

4.0 - 6.0

6.0 - 10.0

10.0 - 15.0

15.0 - 20.0

20.0 - 40.0

40.0 - 100.0

The Westphalian is

thick and regionally

extensive, with

mainly gas-prone,

terrestrial kerogen

Some higher HI

samples in ADB & CBH(local oil-prone, marine

shales?)

Type III/IV (terrestrial) kerogen

component

Westphalian absent

0 100 200 300 400 500 600

Westphalian (20%) isopach (m)

040

80

120

160

200

240

Fre

quency (

1000)

Mean=208.724

N=901912

Std=150.34

Summary of source rocks offshoreTornado plot

0 2 4 6 8 10 12 14

U.North Sea Gp.

M.North Sea Gp.

L.North Sea Gp.

North Sea Gp. (all)

Chalk Gp.

Rijnland Gp.

Schieland Gp.

Scruff Gp.

Altena Gp.*

*not including Aalburg & Posidonia samples

Posidonia Fm.

Aalburg Fm.

U.Germanic Gp.

L.Germanic Gp.

Zechstein Gp.

U.Rotliegend Gp.

Limburg Gp.

Farne Gp.

Carb. Limestone Gp.

Banjaard Gp.

Hydrogen Index (HI) (mg/gTOC) Total Organic Carbon (TOC) (wt.%)

1.9 (σ = 3.0)

1.5 (σ = 0.5)

0.7 (σ = 0.1)

1.3 (σ = 2.1)

0.9 (σ = 1.8)

0.8 (σ = 1.2)

1.8 (σ = 3.2)

1.8 (σ = 0.9)

0.9 (σ = 0.7)

0.9 (σ = 2.1)

2.2 (σ = 5.6)

0.6 (σ = 1.0)

1.3 (σ = 1.1)

0.6 (σ = 0.4)

0.6 (σ = 0.3)

7.0 (σ = 12.1)

5.6 (σ = 3.4)

1.7 (σ = 0.9)

8.2 (σ = 13.4)

Poor source

Fair source

Good sourceVery good source

Oil shale

Inert

Gas-prone

Oil/Gas-proneOil-prone

0 4 8 12 16 20 22

Rock-Eval S2 (kg/t)(“Pyrolysate yield”)

0100200300400500600

121 (σ = 116)

124 (σ = 38)

100 (σ = 38)

118 (σ = 85)

284 (σ = 334)

173 (σ = 206)

129 (σ = 70)

167 (σ = 134)

113 (σ = 80)

376 (σ = 210)

164 (σ = 86)

127 (σ = 68)

206 (σ = 165)

268 (σ = 197)

312 (σ = 252)

130 (σ = 151)

60 (σ = 29)

63 (σ = 36)

22 (σ = 12)Values represent mean values,

ranges reflect the addition of 1SD

The Toarcian Posidonia shales and Pennsylvanian Limburg Gp. coals represent the best source rocks in the Dutch offshore,

although localized potential exists in other units (e.g. Zechstein, Kupferschiefer & Lwr. Cretaceous shales of the Schieland Gp.)

1.0

Vitrinite Reflectance (%Ro)

0

1000

2000

3000

4000

5000

Base-D

ep

th (

m)

Surface intercept at 0.18%Ro

MaturityVitrinite reflectance vs. depth trends

1.0


0

1000

2000

3000

4000

5000

Base-D

ep

th (

m)

Surface intercept at 0.18%RoK03-02

1.0


0

1000

2000

3000

4000

5000

Base-D

ep

th (

m)

Surface intercept at 0.18%RoA16-01 P16-01

500 550 600 650 700

5700

5800

5900

6000

6100

6° 5° 4° 3°

55°

54°

53°

52°

T.Westphalian (m)2000 4000 6000 8000 10000

P16-01

K03-02

A16-01Early oil

Mid oil

Mid gas

Late gas

Immature Late oil/Early gas

Maturity equivalences (background)

CGMW Chronostrat

Cenozoic

Pleistocene

Pliocene

Miocene

Oligocene

Eocene

Paleocene

Upper Cretaceous

Lower Cretaceous

Jurassic

Upper Jurassic

Middle Jurassic

Lower Jurassic

Upper Triassic

Middle Triassic

Lower Triassic

Lopingian

Cisuralian

Pennsylvanian

Mississippian

Devonian

<Un-named item>

CGMW Chronostrat

Cenozoic

Pleistocene

Pliocene

Miocene

Oligocene

Eocene

Paleocene

Upper Cretaceous

Lower Cretaceous

Jurassic

Upper Jurassic

Middle Jurassic

Lower Jurassic

Upper Triassic

Middle Triassic

Lower Triassic

Lopingian

Cisuralian

Pennsylvanian

Mississippian

Devonian

<Un-named item>

CGMW Chronostrat

Cenozoic

Pleistocene

Pliocene

Miocene

Oligocene

Eocene

Paleocene

Upper Cretaceous

Lower Cretaceous

Jurassic

Upper Jurassic

Middle Jurassic

Lower Jurassic

Upper Triassic

Middle Triassic

Lower Triassic

Lopingian

Cisuralian

Pennsylvanian

Mississippian

Devonian

<Un-named item>

Vitrinite reflectance (%Ro)

Depth

(T

VD

SS)


VR provenance

Indigenous

Non-indigenous

Saalian U/C (Variscan)

Cimmerian U/C


Cimmerian U/C

Laramide U/C

Pyrenean/Savian U/C Pyrenean/Savian U/C

Laramide U/C


Implied

Carboniferous

geothermal

gradient of 120

°C/km

Implied

Carboniferous

geothermal

gradient of 60

°C/km

Implied

Carboniferous

geothermal

gradient of 80

°C/km

Present day geothermal

gradients average 34.5 °C/km

in the Dutch offshore


Scenario 1: Constant Basal HF through time, no Saalian/Cimmerian erosion

Present geothermal gradient: 33.0 °C/km

Present day surface heat flow: 56.0 mW/m2

Peak palaeo basal heat flow: 56.0 mW/m2 (constant)

Good calibration to temperature, poor to vitrinite reflectance

Geologically unrealistic (no erosion at unconformities and constant HF)

Paleozoic maturity gradient not captured


Depth

(T

VD

SS)

Temperature (°C) Time (Ma)

Depth

(T

VD

SS)

Bas

al h

eat

flo

w (

mW

/m2)


Scenario 2: Constant Basal HF through time with 2,500 m Saalian erosion




Good calibration to temperature, mod. to vitrinite reflectance

Geologically unrealistic, Saalian U/C erosion too large



Depth

(T

VD

SS)


Depth

(T

VD

SS)

Bas

al h

eat

flo

w (

mW

/m2)


Scenario 3: Constant Basal HF through time with 3,100 m Cimmerian erosion




Good calibration to temperature, mod. to vitrinite reflectance

Geologically unrealistic, Cimmerian U/C erosion too large



Depth

(T

VD

SS)


Depth

(T

VD

SS)

Bas

al h

eat

flo

w (

mW

/m2)


Scenario 4: High Permo-Carboniferous heat flow and moderate erosion

Good calibration to temperature and vitrinite reflectance

Includes erosion at both Cimmerian (500 m) and Saalian (900 m) U/C

Only moderate erosion magnitudes required

High palaeo-heat flow required (mantle plume?)



Peak palaeo basal heat flow: 111 mW/m2 (295 Ma)


Depth

(T

VD

SS)


Depth

(T

VD

SS)

Bas

al h

eat

flo

w (

mW

/m2)

Palaeozoic Heat “Pulse”Mantle plume, adiabatic melting or rift development?

AOI

Although a mantle plume has been inferred in some

studies (e.g. Bonté et al., 2019), several aspects are not

fully consistent:

▪ The lack of a clear, age-progressive

volcanic track

▪ Pre-magmatic subsidence and not uplift

▪ The absence of a large igneous province

▪ Low to moderate values of 3He/4He

Overview of the distribution of late Carboniferous to early Permian

igneous material in the North Sea from Heeremans et al. (2004)

Between the uppermost Carboniferous and early

Permian, widespread igneous activity is observed

throughout the southern North Sea, including the

Dutch offshore and southern Norway. Calc-alkaline to

tholeiitic intrusions have been radiometrically dated to

ca.300 – 280 Ma (Wilson et al., 2004).

Melting was probably induced by local decompression

and thinning of lithosphere in response to regional

stretching north of the Variscan front, although the

PREMA affinity implies that involvement of a mantle

plume cannot be discarded (van Bergen & Sissingh,

2007).

Grid-based 3-D ModelStructural construction in Trinity T3

Distance along strike (km)

Depth

(km

)

0 50 100 150 200 250 300

Distance in meters (1000)

0

2

4

6

8

10

12

Depth

in m

ete

rs (

1000)

A11-01 A16-01 F04-03 F14-01 L02-02 N04-01

Bathymetry Offshore (m)

Base Upper North Sea

Base North Sea Super Gp

Base Chalk Gp

Base Rijnland Gp

Base Schieland Gp

Base Posidonia Fm/Top Aalburg

Base Altena Gp

Base Upper Germanic Trias Gp

Base Low er Germanic Trias Gp_2

Base Zechstein Gp

Saalian U/C (Top Westphalian)

T.Westphalian (m)

Base Westphalian (T.Namurian) (m)

Base Namurian

Base Elleboog Fm

Base Dinantian

B(North west)

B’(East)

Vertical exaggeration: 5 x

0 50 100 150 200 250 300 350 400


0

2

4

6

8

10

12

14

Depth

in m

ete

rs (

1000)

B18-02E12-02E18-02 F04-03K03-02L10-06L16-01P05-01P10-01P16-01S05-01




Base Chalk Gp

Base Rijnland Gp

Base Schieland Gp


Base Altena Gp


Base Low er Germanic Trias Gp_2

Base Zechstein Gp


T.Westphalian (m)


Base Namurian

Base Elleboog Fm

Base Dinantian

Depth

(km

)

A(South)

Colored by simplified chronostratigraphy Vertical exaggeration: 6.5 x

A’(North)

500 550 600 650 700

5700

5800

5900

6000

6100

6° 5° 4° 3°

55°

54°

53°

52°

A11-01

A16-01 B18-02

D12-03-S1

E12-02

E18-02

F04-03

F14-01

G17-01

K03-02

K04-03

K13-06

L02-02

L10-06 L11-12

L16-01

M03-01

M08-01

N04-01

P05-01

P10-01

P15-01

P16-01

Q08-01

S05-01

T.Westphalian (m)2000 4000 6000 8000 10000

80 km

A

A’

B

B’

0 50 100 150 200 250 300


0

2

4

6

8

10

12

Depth

in m

ete

rs (

1000)

A11-01 A16-01 F04-03 F14-01 L02-02 N04-01




Base Chalk Gp

Base Rijnland Gp

Base Schieland Gp


Base Altena Gp


Base Low er Germanic Trias Gp

Base Zechstein Gp


T.Westphalian (m)


Base Namurian

Base Elleboog Fm

Base Dinantian

0 50 100 150 200 250 300


0

2

4

6

8

10

12

Depth

in m

ete

rs (

1000)

A11-01 A16-01 F04-03 F14-01 L02-02 N04-01




Base Chalk Gp

Base Rijnland Gp

Base Schieland Gp


Base Altena Gp


Base Low er Germanic Trias Gp

Base Zechstein Gp


T.Westphalian (m)


Base Namurian

Base Elleboog Fm

Base Dinantian

3-D basin model constructed using 19 depth maps (mainly sourced from DGM-deep V3 Offshore, from nlog) across the AOI and

thermally-calibrated to 25 1-D models. No halokinesis has been included on this regional-scale but should be included on the local

1-D models

500 550 600 650 700

5700

5800

5900

6000

6100

6° 5° 4° 3°

55°

54°

53°

52°

A11-01

A16-01 B18-02

D12-03-S1

E12-02

E18-02

F04-03

F14-01

G17-01

K03-02

K04-03

K13-06

L02-02

L10-06 L11-12

L16-01

M03-01

M08-01

N04-01

P05-01

P10-01

P15-01

P16-01

Q08-01

S05-01

Present day Posidonia VR (LLNL) (%Ro)

0.1 0.2 0.5 1 2 4

80 km

Immature (<0.5 %Ro)Early-oil (0.5 – 0.7 %Ro)Mid-oil (0.7 – 1.0 %Ro)Late-oil/Early-gas (1.0 – 1.3 %Ro)Mid-gas (1.3 – 2.2 %Ro)Dry-gas (2.2 – 3.0 %Ro)Over-mature (>3.0 %Ro)

1-D models

500 550 600 650 700

5700

5800

5900

6000

6100

6° 5° 4° 3°

55°

54°

53°

52°

A11-01

A16-01 B18-02

D12-03-S1

E12-02

E18-02

F04-03

F14-01

G17-01

K03-02

K04-03

K13-06

L02-02

L10-06 L11-12

L16-01

M03-01

M08-01

N04-01

P05-01

P10-01

P15-01

P16-01

Q08-01

S05-01

Oil f ields/discoveries

Present day Posidonia TR (Type II kerogen) (%)

0 20 40 60 80 100

80 km

Immature (<5%)Oil generation begins (5 – 10%)Oil generation (10 – 25%)Main oil expulsion (25 – 70%)Oil cracking, gas generation (70 – 85%)Dry gas generation (85 – 95%)Over-mature (>95%)

F03-FB field(small gas kitchen

to the south)

Based on Type II kerogen

1-D models

Posidonia ShaleMaturity (VR & Transformation Ratio)

The Posidonia shale, where present/preserved,

is predicted to be mature for hydrocarbon

generation at present.

There is an excellent agreement between the

known oil fields/discoveries and the oil-mature

Posidonia, strongly suggesting a Lower Jurassic

marine shale is the predominant source of most

of these oil accumulations.

Exploration targeting oil should focus on charge

originating from the identified kitchen fairway,

unless an alternative oil-prone source rock is

present. This may be possible on a local scale,

e.g. Zechstein carbonates or Lower Cretaceous

shales (where mature).

500 550 600 650 700

5700

5800

5900

6000

6100

6° 5° 4° 3°

55°

54°

53°

52°

A11-01

A16-01 B18-02

D12-03-S1

E12-02

E18-02

F04-03

F14-01

G17-01

K03-02

K04-03

K13-06

L02-02

L10-06 L11-12

L16-01

M03-01

M08-01

N04-01

P05-01

P10-01

P15-01

P16-01

Q08-01

S05-01

Gas fields/discoveries

Present day Top Westphalian TR (%)

0 20 40 60 80 100

80 km

500 550 600 650 700

5700

5800

5900

6000

6100

6° 5° 4° 3°

55°

54°

53°

52°

Top Westphalian VR (LLNL) (%Ro)

0.1 0.2 0.5 1 2 4

80 km


1-D models


Based on Type III kerogen

1-D models

Top WestphalianMaturity (VR & Transformation Ratio)

The maturity of the upper Westphalian is not

consistent with the distribution of the known

gas fields in large areas of the Dutch offshore,,

namely the Anglo-Dutch Basin, Cleaver Bank

High and Central Offshore Platform, as well as

onshore.

The exceptions are the gas-mature kitchens

areas in the Dutch Central Graben, Broad

Fourteens Basin and West Netherlands Basin,

based on the Transformation Ratio.

However, the Westphalian is very thick in some

areas, notably in the east of the AOI (e.g.

Ameland Block & Terschilling Basin), and so it is

likely that a significantly higher maturity is found

near its base.

Alternatively, much higher amounts of Alpine

erosion could be envisaged, to explain the

widespread generation of dry-gas.

Westphalian absent

500 550 600 650 700

5700

5800

5900

6000

6100

6° 5° 4° 3°

55°

54°

53°

52°

A11-01

A16-01 B18-02

D12-03-S1

E12-02

E18-02

F04-03

F14-01

G17-01

K03-02

K04-03

K13-06

L02-02

L10-06 L11-12

L16-01

M03-01

M08-01

N04-01

P05-01

P10-01

P15-01

P16-01

Q08-01

S05-01


Present day Base Westphalian TR (%)

0 20 40 60 80 100

80 km

500 550 600 650 700

5700

5800

5900

6000

6100

6° 5° 4° 3°

55°

54°

53°

52°

Base Westphalian VR (LLNL) (%Ro)

0.1 0.2 0.5 1 2 4

80 km


1-D models



1-D models

Base WestphalianMaturity (VR & Transformation Ratio)

The Base Westphalian represents the highest

maturity while also providing a proxy for the

maturity of the underlying top Namurian source

rock section.

The maps show a good correlation between the

dry-gas generation window (and above) with

the distribution of gas fields/discoveries.

Westphalian absent

500 550 600 650 700

5700

5800

5900

6000

6100

6° 5° 4° 3°

55°

54°

53°

52°


Westphalian Gas Expelled (23-0 Ma) (bcf/km2)

0 100 200 300 400 500 600 700

80 km

1-D models

500 550 600 650 700

5700

5800

5900

6000

6100

6° 5° 4° 3°

55°

54°

53°

52°

Westphalian Gas Expelled (Total) (bcf/km2)

0 200 400 600

80 km

TOC: 35.0 wt.% (uniform)

HI: 150 mg/gTOC (uniform)

Kerogen type: P&C Type D/E (terrestrial wax/resin (coal))

Thickness: Variable, 10% net:gross (isopach, Slide 5)

DCG

BFB

WNB

1-D models1-D models


1-D models

Base WestphalianGas ExpulsionGas expulsion is a function of source quality(TOC & kerogen type), thickness (assumed 10%N:G) and maturity.

Here we demonstrate that most gas expulsionhas occurred in the BFB, DCG, COP & WNB,with a strong correlation to known gas fieldsand discoveries.

Geologically-recent gas expulsion, since theMiocene, also correlates to most fields andpredicts gas expulsion in the Ameland Block &Terschilling Basin areas.

Westphalian absent

Total expulsion

TOC: 35.0 wt.% (uniform)

HI: 150 mg/gTOC (uniform)

Kerogen type: P&C Type D/E (terrestrial wax/resin (coal))

Thickness: Variable, 10% net:gross (isopach, Slide 5)

Expulsion since 23 Ma

World-class source rock comparison

High-case

Low-case

Mill

ion b

arre

ls o

il equiv

alent

per

km

2

Eastern

Venezuela

0

50

100

150

200

Alberta Gulf of

Mexico

(Tithonian)

Maracaibo KCF NW

Australia

Westphalian

in AOI

High-case = maximum value predicted

Low-case = mean of predicted dataFrom Zhiyong He

TB

AP

DCG

COP

ConclusionsRegional petroleum systems modelling in the Dutch offshore

A geochemical database containing >10,000 samples has been constructed, containing high-level Rock-Eval and vitrinite

reflectance data. Our interpretation suggests the primary source rocks are the Toarcian Posidonia shales & Pennsylvanian

Westphalian coals.

Multiple erosion events across the Dutch offshore makes interpretation difficult, as VR (and AFTA) data are often

overprinted by subsequent burial. Our best-fit model is broadly consistent with previous authors which suggest Saalian

erosion was limited to 2,000 m (most likely ca. 500 – 1,000 m), while erosion at the Cimmerian unconformities is also

limited to < 1,000 m of erosion.

Mantle upwelling (plume emplacement), associated with magma underplating and/or igneous intrusions contemporaneous

of a transitional tectonic regime (compressive-to-wrenching) resulted in very high palaeo-heat flow (up to 140 mW/m2)

during the uppermost Carboniferous to lower Permian (300 – 280 Ma).

The predicted regions of Posidonia source rock maturity and oil expulsion correlate well with known oil fields/discoveries.

Westphalian source rock maturity, in particular in its lower section, also correlates well with the distribution of known gas

fields/discoveries, and abundant gas expulsion is predicted, continuing into the Miocene and possibly to the present day.

The model presented here also predicts significant gas expulsion in the Ameland Block & Terschilling Basin, where

relatively few discoveries have been made to date.This may be of consideration for future exploration.

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Regional petroleum systems modelling in the Dutch offshore

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Regional petroleum systems modelling in the Dutch offshore

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