origin of overpressure and pore pressure - prediction
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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.
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
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
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
1979 Blowout, Offshore Brunei
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
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
Overpressure Origin and PPP in Brunei
INTRODUCTION DISTRIBUTION OF OVERPRESSURE OVERPRESSURE ORIGIN
PETROPHYSICAL RESPONSE TO OVERPRESSURE
IMPLICATIONS FOR PORE PRESSURE PREDICTION SUMMARY SUMMARY
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.
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.
(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
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
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
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).
Determining Overpressure Origin: Porosity-Effective Stress Plots
Modified after Bowers (1994)
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
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)
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)
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)
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
Overpressures on and off the loading curveOverpressures on and off the loading curve
(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)
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
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
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
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
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
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!
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
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
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
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
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)
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
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
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
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