origin of overpressure and pore pressure - prediction

38
Origin of Overpressure and Pore Pressure Prediction in the Baram Delta Province, Brunei* Mark Tingay 1 , Richard Hillis 1,2 , Richard Swarbrick 3 , Chris Morley 4 , and Razak Damit 5 Search and Discovery Article #40709 (2011) Posted March 11, 2011 *Adapted from oral presentation at AAPG Geoscience Technology Workshop, Singapore, October 28-29, 2010 1 Australian School of Petroleum, Adelaide, Australia ([email protected] ) 2 Deep Exploration Technologies CRC, Adelaide, Australia 3 GeoPressure Technology, Durham, England 4 PTT Exploration and Production, Bangkok, Thailand 5 Brunei Shell Petroleum, Seria, Brunei Conclusions Distinguish between disequilibrium compaction and fluid expansion overpressures. Disequilibrium compaction and fluid expansion overpressures occur in geographically and geologically distinct areas. Sonic log data successfully predicts pore pressure in disequilibrium overpressures using an Eaton exponent of 3.0. Sonic log data responds to inflationary overpressures, and we can reasonably predict pore pressure using an Eaton exponent of 6.5. Foundations for PPP from seismic velocities and LWD. References Bowers, G.L., 1994, Pore pressure estimation from velocity data: accounting for overpressure mechanisms besides undercompaction: International Association of Drilling Contractors/SPE Drilling Conferences, SPE Paper 27488, p. 515-530, Web accessed 4 March 2011, http://www.onepetro.org/mslib/servlet/onepetropreview?id=00027488&soc=SPE Eaton, B.A., 1972, The effect of overburden stress on geopressure prediction from well logs: JPT, v. 24/8, p. 929-934. Hermanrud, C., L. Wensaas, G.M.G. Teige, H.M. Nordgard Bolas, S. Hansen, and E. Vik, 1998, Shale porosities from well logs on Haltenbanken (Offshore Mid-Norway) show no influence of overpressuring, in B.E. Law, G.F. Ulmishek, and V.I. Slavin (eds.) Abnormal Pressures in Hydrocarbon environments: AAPG Memoir 70, p. 65-85. Copyright © AAPG. Serial rights given by author. For all other rights contact author directly.

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Page 1: Origin of Overpressure and Pore Pressure - Prediction

Origin of Overpressure and Pore Pressure Prediction in the Baram Delta Province, Brunei*

Mark Tingay1, Richard Hillis1,2, Richard Swarbrick3, Chris Morley4, and Razak Damit5

Search and Discovery Article #40709 (2011) Posted March 11, 2011

*Adapted from oral presentation at AAPG Geoscience Technology Workshop, Singapore, October 28-29, 2010 1Australian School of Petroleum, Adelaide, Australia ([email protected]) 2Deep Exploration Technologies CRC, Adelaide, Australia 3GeoPressure Technology, Durham, England 4PTT Exploration and Production, Bangkok, Thailand 5Brunei Shell Petroleum, Seria, Brunei

Conclusions

• Distinguish between disequilibrium compaction and fluid expansion overpressures. • Disequilibrium compaction and fluid expansion overpressures occur in geographically and geologically distinct areas. • Sonic log data successfully predicts pore pressure in disequilibrium overpressures using an Eaton exponent of 3.0. • Sonic log data responds to inflationary overpressures, and we can reasonably predict pore pressure using an Eaton exponent of 6.5. • Foundations for PPP from seismic velocities and LWD.

References

Bowers, G.L., 1994, Pore pressure estimation from velocity data: accounting for overpressure mechanisms besides undercompaction: International Association of Drilling Contractors/SPE Drilling Conferences, SPE Paper 27488, p. 515-530, Web accessed 4 March 2011, http://www.onepetro.org/mslib/servlet/onepetropreview?id=00027488&soc=SPE Eaton, B.A., 1972, The effect of overburden stress on geopressure prediction from well logs: JPT, v. 24/8, p. 929-934. Hermanrud, C., L. Wensaas, G.M.G. Teige, H.M. Nordgard Bolas, S. Hansen, and E. Vik, 1998, Shale porosities from well logs on Haltenbanken (Offshore Mid-Norway) show no influence of overpressuring, in B.E. Law, G.F. Ulmishek, and V.I. Slavin (eds.) Abnormal Pressures in Hydrocarbon environments: AAPG Memoir 70, p. 65-85.

Copyright © AAPG. Serial rights given by author. For all other rights contact author directly.

Page 2: Origin of Overpressure and Pore Pressure - Prediction

Origin of Overpressure and PoreOrigin of Overpressure and Pore Pressure Prediction in the Baram Delta

Province BruneiProvince, Brunei

Mark Tingay1 Richard Hillis1,2Mark Tingay1, Richard Hillis1,2,Richard Swarbrick3, Chris Morley4 & A. Razak Damit5

1 Australian School of Petroleum, Adelaide, Australia 2 Deep Exploration Technologies CRC, Adelaide, Australiap p g , ,3 GeoPressure Technology, Durham, England 4 PTT Exploration and Production, Bangkok, Thailand 5 Brunei Shell Petroleum, Seria, Brunei

Page 3: Origin of Overpressure and Pore Pressure - Prediction

Geological Features associated with Overpressure in Brunei

Interpreted shale diapirs, BruneiMud Volcano,

near Miri Sarawaknear Miri, Sarawak

Seismic image adapted from PGS Bru

Jerudong nticline

Page 4: Origin of Overpressure and Pore Pressure - Prediction

00 10 20 30 40 50 60 70

Pressure (MPa)

Well X

500

Pore pressure rises over 20 MPa in 100 m (from 12.5 to 21 5 MPa/km)500

Well XRFT

21.5 MPa/km)

Pore pressures are at approximately lithostatic

1000

m) Well X

RFTs approximately lithostatic gradients at 2000 m depth

W ll Y1500

Dep

th (m Mud Weight

Well Y

Well Y Located 800m from Well X and

separated by single resolvable2000

Well YRFTs

LOPsseparated by single resolvable fault of 60m throw.

2500 LithostatHydrostat

RFTsHighly compartmentalized pore pressures and horizontal stresses

3000Hydrostat 22 MPa/km1412 16 18 20

Hydrostat

Page 5: Origin of Overpressure and Pore Pressure - Prediction

1979 Blowout, Offshore Brunei

Page 6: Origin of Overpressure and Pore Pressure - Prediction

Goal: accurate PPP from seismic & LWD data.

But what do we need to know first?

What are the overpressure generation mechanisms?

Wh d diff t t f ? Where do different types of overpressure occur?

How do different types of overpressure affect rock properties – How do different types of overpressure affect rock properties

can we detect overpressure from log data?

Can we predict pore pressure from log data?

Can we detect overpressure and predict pore pressure from

seismic velocities and ‘Logging While Drilling’ data?gg g g

Page 7: Origin of Overpressure and Pore Pressure - Prediction

Overpressure Origin and PPP in Brunei

INTRODUCTION INTRODUCTION DISTRIBUTION OF OVERPRESSURE OVERPRESSURE ORIGIN

PETROPHYSICAL RESPONSE TO OVERPRESSURE

IMPLICATIONS FOR PORE PRESSURE PREDICTION IMPLICATIONS FOR PORE PRESSURE PREDICTION SUMMARY

Page 8: Origin of Overpressure and Pore Pressure - Prediction

Overpressure Origin and PPP in Brunei

INTRODUCTION DISTRIBUTION OF OVERPRESSURE OVERPRESSURE ORIGIN

PETROPHYSICAL RESPONSE TO OVERPRESSURE

IMPLICATIONS FOR PORE PRESSURE PREDICTION SUMMARY SUMMARY

Page 9: Origin of Overpressure and Pore Pressure - Prediction
Page 10: Origin of Overpressure and Pore Pressure - Prediction

Distribution of Overpressure in Brunei RFTs, mud weights,

LOTs, DSTs, kicks and losses collected forlosses collected for 157 wells in 61 fields.

Overpressures

observed in 101 wells in 54 fields (P >11 5in 54 fields (Pp >11.5 MPa/km).

Sub-lithostatic pore

pressure magnitudes observed in 42 fieldsobserved in 42 fields.

Page 11: Origin of Overpressure and Pore Pressure - Prediction

Depth to Top of Overpressure in Brunei Overpressures can be

split into Outer and Inner Shelf DomainsInner Shelf Domains

Inner shelf overpressures haveoverpressures have sharply varying depth to onset and are highly compartmentalized.

Outer shelf Outer shelf

overpressures gradually shallow

d NWtowards NW, onset at top of pro-delta shales.

Page 12: Origin of Overpressure and Pore Pressure - Prediction

(a) (b)Depth to Top of Overpressure in Brunei

Inner and o terInner and outer shelf have different

petroleum play types and sampletypes and sample

different stratigraphic units:

Inner: Deltaics

O t P d ltOuter: Pro-delta shales

Page 13: Origin of Overpressure and Pore Pressure - Prediction

Overpressure Origin and PPP in Brunei

INTRODUCTION INTRODUCTION DISTRIBUTION OF OVERPRESSURE OVERPRESSURE ORIGIN

PETROPHYSICAL RESPONSE TO OVERPRESSURE

IMPLICATIONS FOR PORE PRESSURE PREDICTION IMPLICATIONS FOR PORE PRESSURE PREDICTION SUMMARY

Page 14: Origin of Overpressure and Pore Pressure - Prediction

Disequilibrium Compaction Overpressure Occurs when fluid expulsion is impeded during compaction Occurs when fluid expulsion is impeded during compaction Pore fluids support some of the overburden and become OP’d

Page 15: Origin of Overpressure and Pore Pressure - Prediction

Fluid Expansion/Inflation Overpressure

Increase in fluid volume within a confined pore space.p p Kerogen-to-gas maturation, clay diagenesis, aquathermal

expansion, vertical transfer along faults and fractures into shallower i (i fl ti )reservoirs (inflation).

Page 16: Origin of Overpressure and Pore Pressure - Prediction

Determining Overpressure Origin: Porosity-Effective Stress Plots

Modified after Bowers (1994)

Page 17: Origin of Overpressure and Pore Pressure - Prediction

Brunei Bowers Type Plot

4 5Overpressured RFTs

UnloadingVelocity at city

4

4.5 Unloading Curve

yMaximum Burial

Depth

Son

ic V

eloc

4

Fluid Expansion Overpressure

3.5

city

(km

/s)

Disequilibrium Compaction

Overpressure

Fl id3

Soni

c Ve

loc Normally

Pressured RFTs

pOverpressure Fluid

Retention Point

2.5

2

Loading Curve

1.50 10 20 30 40 50 60

Effective Vertical Stress (MPa)Vertical Effective Stress

Page 18: Origin of Overpressure and Pore Pressure - Prediction

Laksamana-1 & Perdana-1 Bowers PlotWell A Sonic Velocity-Effective Stress Plot4.5

Well A Sonic Velocity-Effective Stress PlotOuter shelf well – Disequilibrium Compaction

4

m/s

)

L di

3

3.5

ocity

(km

Well A Overpressured

LoadingCurve

2.5

3

Soni

c Ve

l

Loading CurveWell A

2

S Lak-1 & Per-1 HydrostaticLak-1 & Per-1 Overpressured

Well ANormally Pressured

1.50 10 20 30 40 50 600 10 20 30 40 50 60

Effective Vertical Stress (MPa)

Page 19: Origin of Overpressure and Pore Pressure - Prediction

PGM-1 Bowers PlotWell B Sonic Velocity-Effective Stress Plot4.5

Well B Sonic Velocity-Effective Stress PlotInner shelf well - Fluid Expansion / Inflation

4

m/s

) Well B OverpressuredL di

3.5

ocity

(km Loading

Curve

2 5

3

onic

Vel

o

Loading Curve

PGM 1 H d t ti & d l t d

2

2.5S PGM-1 Hydrostatic & depleted

PGM-1 OverpressuredWell BNormally Pressured

1.50 10 20 30 40 50 60

y

0 10 20 30 40 50 60Effective Vertical Stress (MPa)

Page 20: Origin of Overpressure and Pore Pressure - Prediction

Bugan-1 Bowers Plot Well C Sonic Velocity-Effective Stress Plotg

4.5

Well C Sonic Velocity-Effective Stress PlotInner shelf well that penetrates pro-delta shales,

Fluid expansion overlying disequilibrium compaction4

/s)

L di

Well C Overpressured

3.5

ocity

(km Loading

Curve

Overpressured

2 5

3

onic

vel

o

Loading Curve

Normally PressuredWell C

2

2.5S

y

Overpressured

Very High Magnitude OverpressuresW ll C V Hi h

Well CNormally Pressured

1.50 10 20 30 40 50 60

Very High Magnitude OverpressuresWell C Very High Magnitude Overpressured

0 10 20 30 40 50 60Vertical effective stress (MPa)

Page 21: Origin of Overpressure and Pore Pressure - Prediction

Brunei Bowers Type Plot

4 5

Brunei Bowers Plot

UnloadingVelocity at city

4

4.5 Unloading Curve

yMaximum Burial

Depth

Son

ic V

eloc

4

Fl id E i

Fluid Expansion Overpressure

3.5

city

(km

/s) Fluid Expansion

(Inner Shelf)Disequilibrium

Compaction

Overpressure

Fl id3

Soni

c Ve

loc

Loading Curve

pOverpressure Fluid

Retention Point

2.5

S

2Disequilibrium Compaction

(Outer Shelf) Loading Curve

1.50 10 20 30 40 50 60

Effective Vertical Stress (MPa)Vertical Effective Stress

Page 22: Origin of Overpressure and Pore Pressure - Prediction

Overpressures on and off the loading curveOverpressures on and off the loading curve

Page 23: Origin of Overpressure and Pore Pressure - Prediction

(a) (b)Which Fluid Expansion Mechanism?

No conventionalNo conventional fluid expansion

mechanism exists for overpressures in p

the inner shelf deltaics.

Inner shelf region has undergone

extensive inversionextensive inversion resulting in

migration of huge volumes of fluid outvolumes of fluid out of pro-delta shales (including oil & gas)

Page 24: Origin of Overpressure and Pore Pressure - Prediction

Overpressure Origin and PPP in Brunei

INTRODUCTION INTRODUCTION DISTRIBUTION OF OVERPRESSURE OVERPRESSURE ORIGIN

PETROPHYSICAL RESPONSE TO OVERPRESSURE

IMPLICATIONS FOR PORE PRESSURE PREDICTION IMPLICATIONS FOR PORE PRESSURE PREDICTION SUMMARY

Page 25: Origin of Overpressure and Pore Pressure - Prediction

Petrophysical Response of Overpressure

C d t t ti ll t f d ?

Petrophysical Response of Overpressure

Can we detect vertically transferred overpressures? Calibrate sonic and density derived porosities in normally Calibrate sonic and density derived porosities in normally

compacted, normally pressured shales

Compare porosity estimated from density and sonic logs in p p y y g

different overpressure mechanisms

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Page 26: Origin of Overpressure and Pore Pressure - Prediction

Well A: Disequilibrium CompactionBowers Plot

0 0 1 0 2 0 3 0 4 0 5Porosity

4.50

0 0.1 0.2 0.3 0.4 0.5

Normally pressured follows normal compaction curve

DisequilibriumCompaction

4500

1000Density P it

3.5

(km

/s)

1000

1500eabe

d)

Top ofOverpressure

PorosityLoadingCurve

3

nic

Velo

city

1500

2000th (m

Sub

se

Sonic W ll A

2.5Son

2500D

ept

PorosityWell ANormally Pressured

2 Loading Curve

Laksmana-1 Hydrostatic

Laksamana-1 Overpressured3000

Sonic and density both

Well A Overpressured

1.50 10 20 30 40 50 60

Effective Vertical Stress (MPa)

Laksamana 1 Overpressured

3500

yexhibit undercompaction.

Sonic shows greater response

Page 27: Origin of Overpressure and Pore Pressure - Prediction

Well B: Fluid Expansion

0 0 1 0 2 0 3 0 4 0 5PorosityBowers Plot

00 0.1 0.2 0.3 0.4 0.5

4.5 FluidExpansion Uplifted

5004

Well B Overpressured 1000

1500eabe

d)

3.5

m/s

)

Top ofOverpressure

Density PorosityLoading

Curve

Overpressured

1500

2000h (m

sub

se

3

Soni

c Ve

loci

ty (k

m

Sonic Porosity

2500D

epth

2.5

S

Loading Curve

PGM-1 Hydrostatic & depleted

PGM-1 Overpressured

y

No porosity anomaly

Well BNormally Pressured

3000

2

No porosity anomaly detected by density log

35001.5

0 10 20 30 40 50 60Effective Vertical Stress (MPa)

Sonic log is responding directly to overpressure

Page 28: Origin of Overpressure and Pore Pressure - Prediction

Well C: Fluid Expansion & Disequilibrium CompactionBowers Plot

0 0 1 0 2 0 3 0 4 0 5Porosity

4.5

00 0.1 0.2 0.3 0.4 0.5

Only the sonic log responds to fluid expansion.

B th d it d i d4

500

FluidExpansion Sonic

Both density and sonic respond to disequilibrium compaction

3.5

km/s

)

1000

1500eabe

d)

p

Top ofOverpressure

Porosity

Density Porosity

LoadingCurve

3

ic v

eloc

ity ( 1500

2000h (m

sub

se pPorosity

Top of Very High2.5So

ni

Loading Curve

Normally Pressured2500

Dep

t Top of Very HighMagnitude

Overpressure

2

Normally Pressured

Overpressured

Very High MagnitudeOverpressures

3000

DisequilibriumCompaction

Top ofLithostatic

1.50 10 20 30 40 50 60

Vertical effective stress (MPa) 3500

LithostaticOverpressure

Page 29: Origin of Overpressure and Pore Pressure - Prediction

Petrophysical Response of OverpressurePetrophysical Response of Overpressure

Sonic log shows response in vertically transferred

overpressures – even though there is no porosity change.p g p y g

H d t l (1998) t th i l i l i fl id Hermanrud et al. (1998) suggest the sonic log is slower in fluid

expansion overpressures due textural changes in the rock.

There is hope for reliable pore pressure prediction in fluid

expansion overpressures!

Page 30: Origin of Overpressure and Pore Pressure - Prediction

Overpressure Origin and PPP in Brunei

INTRODUCTION INTRODUCTION DISTRIBUTION OF OVERPRESSURE OVERPRESSURE ORIGIN

PETROPHYSICAL RESPONSE TO OVERPRESSURE

IMPLICATIONS FOR PORE PRESSURE PREDICTION IMPLICATIONS FOR PORE PRESSURE PREDICTION SUMMARY

Page 31: Origin of Overpressure and Pore Pressure - Prediction

Pore Pressure Prediction

E t th d (1972)

Pore Pressure Prediction

Eaton method (1972):

Pp = v - (v-Pnorm)(tnorm/tobs)X p

Di ilib i ti ( t h lf) 3 0 Disequilibrium compaction (outer shelf): x=3.0

Fluid expansion (inner shelf): x=6.5

Page 32: Origin of Overpressure and Pore Pressure - Prediction

Bowers Plot0 20 40 60 80

Pressure (MPa)

Well A: Disequilibrium Compaction

4.50

0 20 40 60 80

DisequilibriumCompaction

4500

RFTMud Weight

3.5

(km

/s)

1000

1500)

Mud WeightPredicted PpHydrostatVertical Stress

LoadingCurve

3

nic

Velo

city

1500

2000

Dep

th (m

ss)

Predicted Ppx=3 0W ll A

2.5Son

2500D x=3.0Well ANormally Pressured

2 Loading Curve

Laksmana-1 Hydrostatic

Laksamana-1 Overpressured3000

Well A Overpressured

1.50 10 20 30 40 50 60

Effective Vertical Stress (MPa)

Laksamana 1 Overpressured

3500 12 20 MPa/km181614

Page 33: Origin of Overpressure and Pore Pressure - Prediction

Bowers Plot0 20 40 60 80

Pressure (MPa)

Well B: Vertical Transfer

4.50

0 20 40 60 80

FluidExpansion

4

500

1000

Well B Overpressured

3.5

m/s

)

1000

1500s)

RFTPredicted Pp

LoadingCurve

Overpressured

3

Soni

c Ve

loci

ty (k

m 1500

2000Dep

th (m

ss Hydrostat

Vertical Stress

Predicted Pp

2.5

S

Loading Curve

PGM-1 Hydrostatic & depleted

PGM-1 Overpressured 2500D p

x=6.5Well BNormally Pressured

2

3000

Pp Predictionusing x=3.0

1.50 10 20 30 40 50 60

Effective Vertical Stress (MPa)3500 12 20 MPa/km181614

Page 34: Origin of Overpressure and Pore Pressure - Prediction

0 20 40 60 80Pressure (MPa)Bowers Plot

Well C: Vertical Transfer & Disequilibrium Compaction

00 20 40 60 80

4.5

500 RFT

Mud Weight

Predicted Pp

4 FluidExpansion

1000

1500s)

X=3.0

Hydrostat

Vertical Stress

3.5

km/s

)

p

1500

2000Dep

th (m

ss

3

ic v

eloc

ity (

2500

2.5Soni

Loading Curve

Normally Pressured

Predicted Ppx=6.5

3000

2

Normally Pressured

Overpressured

Very High MagnitudeOverpressures

DisequilibriumCompaction

Predicted Ppx=3.0

3500 12 20 MPa/km181614

1.50 10 20 30 40 50 60

Vertical effective stress (MPa)

Page 35: Origin of Overpressure and Pore Pressure - Prediction

Pore Pressure PredictionPore Pressure Prediction

Issues with pore pressure prediction:

effect of uplifte ect o up t

x=6.5 results in ‘noisy’ prediction in normal pressures

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sharp Pp increases are underestimated
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Page 36: Origin of Overpressure and Pore Pressure - Prediction

Overpressure Origin and PPP in Brunei

INTRODUCTION INTRODUCTION DISTRIBUTION OF OVERPRESSURE OVERPRESSURE ORIGIN

PETROPHYSICAL RESPONSE TO OVERPRESSURE

IMPLICATIONS FOR PORE PRESSURE PREDICTION IMPLICATIONS FOR PORE PRESSURE PREDICTION SUMMARY

Page 37: Origin of Overpressure and Pore Pressure - Prediction

Summary of Conclusions

Distinguish between disequilibrium compaction and fluid

expansion overpressuresp p

Disequilibrium compaction and fluid expansion overpressures

occur in geographically and geologically distinct areas

S i l d t f ll di t i Sonic log data successfully predicts pore pressure in

disequilibrium overpressures using an Eaton exponent of 3.0

Sonic log data responds to inflationary overpressures and we can

reasonably predict pore pressure using an Eaton exponent of 6.5

Foundations for PPP from seismic velocities and LWD Foundations for PPP from seismic velocities and LWD

Page 38: Origin of Overpressure and Pore Pressure - Prediction

Acknowledgements Brunei Shell Petroleum and Total Fina Elf for providing data for this research and for permission to publish the results Australian Research Council for providing research fundingAustralian Research Council for providing research funding.

TOTAL FINA ELFTOTAL FINA ELF