post-rift fault reactivation v3 - nlog

Rifting Systems and its significance for hydrocarbon exploration in the NetherlandsUtrecht, 5-6-2008

Post-rift fault reactivation in the Netherlandsimplications for exploration and production

Fred BeekmanJan-Diederik van WeesSierd Cloetingh

Post-rift fault reactivation in the Netherlandsimplications for exploration and production

Fred BeekmanJan-Diederik van WeesSierd Cloetingh

Post-rift fault reactivation in the Netherlands2

TOPO-EUROPE:geo-science of coupled surface and lithosphere & mantle processes of continental Europe and its margins

TOPO-EUROPE:geo-science of coupled surface and lithosphere & mantle processes of continental Europe and its margins

Neotectonic vertical motions and seismicity in Europe

Cloetingh et al., 2007 (GPC)

Earthquakes

Areas going down

Areas going up10W

0E 10E 20E30E

40E

40N

50N

60N

70N


Contents

reference

Strength evolution and seismicity of European rift systems

Fault reactivation in the NetherlandsRoer Valley Rift System: seismicity and reactivation potential

West Netherlands Basin inversion

Implications of fault reactivation for exploration

Production induced fault reactivation in the NE Netherlands

Strength evolution and seismicity of European rift systems

Fault reactivation in the NetherlandsRoer Valley Rift System: seismicity and reactivation potential

West Netherlands Basin inversion


Production induced fault reactivation in the NE Netherlands


European Cenozoic Rift System (ECRIS)


Lithosphere extension and rift basin formation

Lithosphere(Sub)basin

Reservoir

Coupled deformation at different spatial scalesCoupled deformation at different spatial scales


3-D rheological strength models

Cloetingh et al., 2005


Strength evolution of rift basins

In time the post-rift strength can even exceed the initial pre-rift strength of the lithosphere:

•Young (hot) rifts are weak

•Old (cold) rifts are strong

In time the post-rift strength can even exceed the initial pre-rift strength of the lithosphere:

•Young (hot) rifts are weak

•Old (cold) rifts are strong

syn-rift

post-rift

Ziegler et al., 1998

post-rift coolingpost-rift coolingsyn-rift

stretching & heating

syn-rift

stretching & heating


Present-day strength of the European lithosphere

Maps of integrated rheological strengthMaps of integrated rheological strength

Entire lithosphereEntire lithosphere Crust onlyCrust only



Present-day strength of ECRIS rift systems

2-D profiles extracted from the 3-D strength cubes2-D profiles extracted from the 3-D strength cubes



Correlation strong/weak zones with seismicity

Increased seismicity in ECRISIncreased seismicity in ECRIS

Cloetingh et al., 2006 World Stress Map project

Intraplate stress fieldIntraplate stress field


Seismicity in the Netherlands

Cloetingh et al. 2005

In the Netherlands also many earthquakes occur on pre-existing fault systems

In the Netherlands also many earthquakes occur on pre-existing fault systems

12

Seismicity and main structural elements

Worum et al. (2004)

Roer Valley Rift System (RVRS)


Paleo-seismicity studies in RVRS

Trenching across the Feldbiss fault zone, a border fault of the Roer Valley Graben(SE Netherlands):

250.000 yr old river deposits (left) have been displaced 5 m downwards along the fault

Trenching across the Feldbiss fault zone, a border fault of the Roer Valley Graben(SE Netherlands):

250.000 yr old river deposits (left) have been displaced 5 m downwards along the fault

Houtgast, 2002


0510

5

SW ROER VALLEY GRABEN NWSE-NETHERLANDS

0 20 40 60 80 100 200 600

Dirkzwager et al., 2001

Lithosphere memory of faults


Modelling of fault reactivation in RVRS

5

VERTICAL DISPLACEMENTS AT VARIOUS DEPTHS (x100)

0km

1km

2km

3km

4km

0km

1km

2km

3km

4km

5

DEFORMED MESH AFTER 200 M EXTENSION(x25)

-40010VERTICAL DISPLACEMENTS (M)

Dirkzwager et al., 2001

Finite element models assessing the role of fault friction are constrained by geometry of the graben systemFinite element models assessing the role of fault friction are constrained by geometry of the graben system


Likelihood of fault reactivation can be quantified by e.g. a slip tendency analysisLikelihood of fault reactivation can be quantified by e.g. a slip tendency analysis

Worum et al. (2004)

Potential for fault reactivation

Worum et al. (2004)

Post-rift fault reactivation in the Netherlands17 Worum et al. (2004)

Strike-slip faulting stress regimeNormal faulting stress regime

Worum et al. (2004)

Fault reactivation potential of the RVRS


erosionreactivated faults

West-Netherlands Basin

Basin inversion: reactivation of the pre-existing weak fault fabric and substantial regional uplift and erosionBasin inversion: reactivation of the pre-existing weak fault fabric and substantial regional uplift and erosion

Worum and Van Wees, submitted


After Ellis et al., 1999

Soultz


Migration pathwaysBarriersSeal capacity

Migration pathwaysBarriersSeal capacity

Change in fault permeability (along fault and across fault) Change in fault permeability (along fault and across fault)


Some faults show more fault slip than others

Reservoir

Seal

Overburden

Growthsequence

Implications for hydrocarbon exploration

Reactivated faults can disrupt reservoir seals -> (partial) loss of hydrocarbons Reactivated faults can disrupt reservoir seals -> (partial) loss of hydrocarbons


N S

2000m

BPLI

TM1

TM3

TE

KA

JO

KC

N S

BPLI

TM1

TM3

TE

KA

JO

KC

2000m

TWT

Juxtaposition SealSGR >60%

Both traps lost oil; both traps are bounded by reactivated “large strain” faults that were active at the seabedBoth traps lost oil; both traps are bounded by reactivated “large strain” faults that were active at the seabed

Juxtaposition SealSGR >60%

Example case

Implications for hydrocarbon exploration


Dynamic Fault Seal project

Integrated Field Studies

Numerical Modelling

Qf

Qm

Scaled Physical Modelling

σ3

σ1


Natural versus induced seismicity in the Netherlands

Cloetingh et al., 2006 Van Eck et al., 2006


Induced seismicity in the NE Netherlands

The induced seismicity also occurs predominantly on pre-existing faultsThe induced seismicity also occurs predominantly on pre-existing faults

Van Eck et al., 2006


Production induced seismicity

… which may induce fault reactivation.

Local effects:change in fault permeabilitychange in structural fabricstress reorganization

… which may induce fault reactivation.

Local effects:change in fault permeabilitychange in structural fabricstress reorganization

Relative shear displacements along Fault 1

050

100150200250300350400

0.00 0.10 0.20 0.30 0.40 0.50

Relative shear displacement [m]

Rela

tive

dist

ance

alo

ng

the

faul

t [m

]

3 years after the start of gas injection 4 yr 5yr 7 yr

Slip on the fault due to CO2 injection = induced micro-seismicity

Changes in pore pressure conditions during HC production (injection/depletion) or CO2 storage induce changes in effective stress, …

Changes in pore pressure conditions during HC production (injection/depletion) or CO2 storage induce changes in effective stress, …

Orlic (2008)

Orlic, 2008


Seismo-tectonic fault modelling of NE Netherlands

ISES – TNO project:

reproduce/predict the production induced seismicity in the NE Netherlands

ISES – TNO project:

reproduce/predict the production induced seismicity in the NE Netherlands

1. Build a 3D structural fault model

2. Compute 3D stress distribution

• loading by regional tectonic stress field

• incorporate effects of reservoir depletion

3. Perform slip tendency & fault reactivation analysis on fault planes

4. Verification/calibration with recorded and historical seismicity

• Seismological database KNMI

• LOFAR

1. Build a 3D structural fault model

2. Compute 3D stress distribution

• loading by regional tectonic stress field

• incorporate effects of reservoir depletion

3. Perform slip tendency & fault reactivation analysis on fault planes

4. Verification/calibration with recorded and historical seismicity

• Seismological database KNMI

• LOFAR


Construction of 3D structural fault model

From high resolution 3D seismic data …

Top of Upper Rotliegend Group (De Jager & Geluk, 2007)

… to 3D geometry …

…to a full 3D structural fault model.

Michon & Sokoutis, 2005

Buchmann, 2008


Quantification of fault reactivation potential

(Buchmann, 2008)

Dilation tendency Slip tendency


Prediction of surface uplift & subsidence

(Buchmann, 2008)

Surface displacements Vertical gradient of surface displacement


Verification and calibration

Van Eijs et al., 2006

Verification with independent seismic hazard studiesVerification with independent seismic hazard studies

Calibration with measured induced surface subsidenceCalibration with measured induced surface subsidence


High resolution 3D finite element modelling

Local scale modelling of reservoir depletion induced fault reactivation and subsidenceLocal scale modelling of reservoir depletion induced fault reactivation and subsidence

Calculated displacements due to gas extraction

Subsidence bowl

Induced seismicity hypocentres

Orlic, 2008


Conclusions

European ECRIS rift systems are still rheologically weak structures with increased seismicity

In the Netherlands, earthquakes tend to occur on pre-existing fault planes in the subsurface

Fault slip and dilation tendency analyses can quantify the faultreactivation potential of pre-existing faults, and thus seismic hazard

Fault reactivation may affect hydrocarbon recovery at exploration and production time scales

European ECRIS rift systems are still rheologically weak structures with increased seismicity

In the Netherlands, earthquakes tend to occur on pre-existing fault planes in the subsurface

Fault slip and dilation tendency analyses can quantify the faultreactivation potential of pre-existing faults, and thus seismic hazard

Fault reactivation may affect hydrocarbon recovery at exploration and production time scales

post-rift fault reactivation v3 - nlog

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