Basin analysis and Prediction of the Basin analysis and Prediction of the development of anomalous fluiddevelopment of anomalous fluid

pressure at depths pressure at depths in the Western Foothills of Taiwanin the Western Foothills of Taiwan

Wataru Tanikawa, Toshihiko Shimamoto (Kyoto University in Japan)Wataru Tanikawa, Toshihiko Shimamoto (Kyoto University in Japan)WhengWheng--Kung Wey, WeiKung Wey, Wei--Yu Wu (Chinese Petroleum Corporation)Yu Wu (Chinese Petroleum Corporation)ChingChing--Weei Lin, WenWeei Lin, Wen--Chi Lai (ChengChi Lai (Cheng--Kong University in Taiwan)Kong University in Taiwan)

WeiWei--Min Donald Chen, JihMin Donald Chen, Jih--Hao Hung (National Central University in Taiwan)Hao Hung (National Central University in Taiwan)

Estimation to hydraulic properties Estimation to hydraulic properties →→permeability structure / porosity distribution / specific storagpermeability structure / porosity distribution / specific storage e

at the depth of the Western Foothills in Taiwanat the depth of the Western Foothills in Taiwan→→sedimentary basin / focal area / accretionary prism sedimentary basin / focal area / accretionary prism

by the way of surface samples and laboratory result!by the way of surface samples and laboratory result!

oil

INPORTANCEINPORTANCE①① Application forApplication for

⇒fluid / oil transport system of the basin / fault zone at depth⇒fault mechanism (ex. Thermal pressurization)

②② Help borehole test (inHelp borehole test (in--situ test)situ test)⇒In-situ test has a limit to cost and observation of internal structure⇒laboratory tests and surface samples are CHEAPER!!

PURPOSEPURPOSE

$10000

$10000

$10000

$10000

How to apply laboratory result to the real depth of natureHow to apply laboratory result to the real depth of nature？？(in the case of sedimentary rock)(in the case of sedimentary rock)

①Reproduce the depth condition ⇒ Generation of Temperature and Pressure ②Evaluate the overconsolidation affected by previous loading③Evaluate of time dependent – compaction ⇒ Comparison different ages of samples④Estimate the abnormal fluid pressure

⇒ analysis to the development of the sedimentary basins

1020(m)2342(m)

3847(m)

0

20

40

60

80

100

120

140

160

depth of sample

10-18 10-17 10-16 10-15

Effe

ctiv

e pr

essu

re (M

Pa)

Effe

ctiv

e pr

essu

re (M

Pa)

Permeability (㎡) Permeability (㎡)

burial

uplifting・erosion

over compaction

Cyclic testNon-Cyclic test(idealconsolidation curve)※using the similar sample

0

20

40

60

80

100

120

140

160

10-18 10-17 10-16 10-15 10-14

surface samples are over compacted and shows larger permeability than ideal consolidation curve.

older rocks showed lower permeability because of the time depending compaction effect

What's ABNORMAL FLUID PRESSURE?What's ABNORMAL FLUID PRESSURE?

0

1

2

3

5

4

Chinshui field

0 10 20 30 40 50 60 70 800

1

2

3

5

4

0 10 20 30 40 50 60 70 80

Chingtsaohu-ChitingPaoshanChunanPaishatun

fluid pressure(MPa)

abnormal fluid pressure= fluid pressure - hydrostatic pressure

Generated from the depth 3～4kmGetting larger at the deeper

fluid pressure(MPa)

lithostatics

hydrostatics

lithostatics

hydrostatics

abnormal fluid

×

○

geopressuregradient

hydrostatic

lager thanhydrostat

depth - Pe

proportional

×

Fluid pressure data from boreholes at the northwest of Taiwan（Suppe & Wittke1977)

abnorml fluid pressure

We Can Guess...

depth - permeability

？

Experimental dataPe - PermeabilityPe - Porosit

Why Why ABNORMALABNORMAL PRESSURE generated in the depth?PRESSURE generated in the depth?①Fluid in a basin undrained by increasing

loading pressure and decreasing permeabilitya. sedimentation b. tectonic loading

②Volume change in aquathermal expansiona. temperature gradientb. heat origin

③Fluid movement from subduction boundary (Rice 1992 )④Dehydration (diagenesis）effect

a. smectite → illite + waterb. gypsum → anhydrite + waterc. hydrocarbon generation

0

1

2

3

5

4

Chinshui field

0 10 20 30 40 50 60 70 80

abnormal fluid pressure

fluid pressure(MPa)

lithostatics

hydrostatics

It depend onthe sediment environmentand permeability structure

effective if SEALING LAYERdeveloped

we need to know PERMEABILITY STRUCTURE PERMEABILITY STRUCTURE at a depth of the Western Foothills

Study area and Sampling pointStudy area and Sampling pointThe Western Foothills

①sandstone rich sedimentary rock②Pleistocene to Miocene③take different ages of sample（tectonic collision）④1999 Chi-Chi earthquake⑤oilfield ･･･ a lot of drill data

Western Foothills Slate Terrain

3km

雙冬断層 水長流断層

OligocenePleistocenePliocene

UpperMiocene│

Pliocene

Holocene

PleistocenePliocene

Coastal Plain

B A車籠埔断層

10km

paleocene

miocene

pleistocene

pliocene

upper mioceneto pliocene

B A

Che

lung

puFa

ult

epicenter

台北

台南

高雄

0 20 40 60 km

台東

台中

Drilling site of ICDP

Philippine Sea Plate

EurasianPlate

8.2 cm/yr

Sun-and-Moon Lake

METHODSMETHODS

conditioncondition・temperature room temperature(≒20℃）・confining medium/pore fluid N2 gas・confining pressure 0～200MPa・sample size φ 20mm × L 10～50mm

permeabilitypermeability①steady flow method

Pp ＝ 0.2～2.0 MPa K ＝ 10-14～10-18 ㎡ (higher permeability）(1darcy = 10-12 ㎡ ≒10-3cm/sec)

②pore pressure oscillation method（Kranz1990) Pp ＝20 MPa (constant) K ＝10-15～10-21 ㎡ （lower permeability)

porosityporosity

error bar

10-18

10-17

10-16

10-15

10-14

0 50 100 150 200

GR431 sandstone

steady flowoscillation

effective pressure（MPa）

Spacemen assembly

Pressure vessel and Piston

Sample picture

Comparison of two methods

10-19

10-18

10-17

10-16

10-15

10-14

0 50 100 150 20010-18

10-17

10-16

10-15

10-14

10-13

0 50 100 150 200

GR435 12 conglomerateGR400 matrix in conglomerateGR392 sandy matrixGR535 12 conglomerate

RESULTS of PERMEABILITYRESULTS of PERMEABILITY①①sandstone (10-14～10-18㎡） conglomerate （10-13～10-17㎡）

Effective pressure (MPa)Effective pressure (MPa)

Per

mea

bilit

y (㎡

)

Per

mea

bilit

y (㎡

)

initialporosity (%)

sedimentaryage (Ma)

samplingpoint

441442449488501507516

430431432433434437438

46105172015726282528720

17.8 - 19.013.9 - 185.7 - 7.4

13.9 - 180 - 0.67

12.3 - 13.91.64 - 3.017.8 - 1920 - 23.317.8 - 1923.3 - 35.417.8 - 1917.8 - 1912.3 - 13.9

4.88.4

11.710.917.915.61210.28.4

13.114.413.49.17.3

Ⅰ

Ⅱ

RESULTS of PERMEABILITYRESULTS of PERMEABILITY②②

Effective pressure (MPa)Effective pressure (MPa)

Per

mea

bilit

y (㎡

)

Per

mea

bilit

y (㎡

)10-21

10-20

10-19

10-18

10-17

10-16

10-15

10-14

0 50 100 150 20010-20

10-19

10-18

10-17

10-16

10-15

10-14

0 50 100 150 200

gr393 clayey fine grained gougegr302 clayey fine grained gougegr352 foliated cataclasite

Initialporosity(%) age (Ma)

samplinglocation

gr489gr502gr503gr515gr518

gr346gr436gr439gr440gr451gr452

9162015253828273

20 - 23.30 - 0.67

12.3 - 13.91.64 - 3.023.3 - 35.423.3 - 35.417.8 - 1917.8 - 1918 - 2023.3 - 35.4

5.516.78.45.16.0fracture9.12.68.1

1．fault rock ≒ siltstone2．sandstone can be classified into 2 groups3．siltstone < sandstone < conglomerate → grain size

fault rock（Chelungpu Fault)(10-14～10-19㎡）siltstone・shale（10-14～10-21㎡）

TIMETIME--DEPENDENT COMPACTIONDEPENDENT COMPACTION

十四股段

卓蘭層

粗坑層

水長流層

Pliocene

福隆園層

猴洞坑層

炭寮地段

桂竹林層

沖積層

錦水頁岩Ple

isto

cene

Mio

cene

Olig

ocen

eHolocene

頭科山層

石門村層

time-dependent compaction（pressure solution/grain rearrangement/chemical cementation)

Permeability (㎡)

Age

of S

edim

enta

ry ro

ck (M

a)A

ge o

f Sed

imen

tary

rock

(Ma)

Ⅰ

※Pe = 80MPa

5

20

15

1

3.4

30

We can not identify impermeable layerclearly?

sandstonesiltstone・shaleconglomerate

POROSITY and SPECIFIC STORAGEPOROSITY and SPECIFIC STORAGE

0

5

10

15

20gr488 14.4 35.4-23.3gr501 13.4 19-17.8gr507 9.1 19-17.8gr516 7.3 13.9-12.3gr535gr536gr538

0 50 100 150 200

-2

0

2

4

6

8

10

12

0 50 100 150 200

gr502 9.1 19-17.8gr503 2.6 19-17.8gr515 8.1 20-18gr518 35.4-23.3

0 50 100 150 200

10-10

10-9

10-8

gr488 14.4 35.4-23.3gr501 13.4 19-17.8gr507 9.1 19-17.8gr516 7.3 13.9-12.3gr535gr536gr538

gr502 9.1 19-17.8gr503 2.6 19-17.8gr515 8.1 20-18gr518 35.4-23.3

10-10

10-9

0 50 100 150 200

5・10-9

Ss=1 ΔΦ

1-Φ ΔPe +Φ･βf

specific storage

Φ：porosityβf:compressibility of water

=4.4*10-10

①these parameters have pressure sensitivity

②sandstone and siltstone showed similar values

③specific storage shows smaller change to Pe(1 ～2 order)

compared to permeability

effective pressure (MPa)effective pressure (MPa)

effective pressure (MPa)effective pressure (MPa)

poro

sity

(%)

poro

sity

(%)

poro

sity

(%)

poro

sity

(%)

spec

ific

stor

age(

1/Pa

)sp

ecifi

c st

orag

e(1/

Pa)

spec

ific

stor

age(

1/Pa

)sp

ecifi

c st

orag

e(1/

Pa)

effective pressure (MPa)effective pressure (MPa)

effective pressure (MPa)effective pressure (MPa)siltstonesiltstone

sandstonesandstone

GENERATION MECHANISM of ABNORMAL FLUID PRESSUREGENERATION MECHANISM of ABNORMAL FLUID PRESSURE

① fluid undrained by decreasing permeability and increasing loading pressurea. sedimentation b. tectonic loading

② volume change in aquathermal expansiona. temperature gradientb. heat origin

③ fluid movement from subduction boundary (Rice 1992 )④ dehydration (diagenesis）effect

a. smectite → illite + waterb. gypsum → anhydrite + waterc. hydrocarbon generation

First of all we should evaluate Mechanism ① in the sedimentary basin

proceeding sedimentationpermeability - smaller in deeper horizonno drainfluid pressure - abnormal pressuredisturb sedimentation

beginning of sedimentationpermeability - largedrain rapidlyfluid pressure - hydrostaticsedimentation

hydrostatic

permeability

large

fluid pressure

hydrostatic

large

smallfluid pressure

IMAGE of MECHANISM ① - a

11--D NONLINEAR COMPACTION FLOW EQUATIOND NONLINEAR COMPACTION FLOW EQUATION

δuδt -

δlδt

g･ρe( )Ss･η = δuδz( K ) + γΦ

δ

δzδTδt

temperature effectdiffusion termcompaction term

continuingsedimentation

u(z,t)abnormal pressure

u:abnormal fluid pressure（Pa）K:permeability（㎡）η:fluid viscosity（Pa・s）Ss:specific storage（1/Pa)l:thickness of sediments（m) ρe:effective density

= ρ(saturated rock density)-ρf(fluid density)γ:coefficient of thermal expansibility of fluidΦ:porosityT:temperature（℃）

Assumption①permeability of base ＝ 0②fluid moves upward (1 dimension)③permeability does not show anisotropy④temperature gradient = constant⑤sedimentation rate = constant ⑥grain compressibility ≒ 0⑦water viscosity = constant

Gibson 1958/Bethke and Corbet 1988/Luo and Vasseur 1992

Darcy's law

effectivepressures law

conservation law

Vz = - Kη

δpδz +ρf・g)(

- δδz

(ρf･g･Vz)ΔxΔyΔz =δ

δt(ρf･Φ･ΔxΔyΔz)

Pe = Pc - p = g･(l-x)･ρe - u

impermeable base

water

sediments

sedimentation

z

model

l (t)

z = 0

HYDRAULIC PROPERTY for CALCULATIONHYDRAULIC PROPERTY for CALCULATION

sandstonesiltstoneconglomerate

0

20

40

60

80

100

12010-2110-2010-1910-1810-1710-1610-1510-14

A=20

0

20

40

60

80

100

12010 -10 10 -9 10 -8

α=0.0008

0.0004

0.0006

9

8

7

6

5

4

3

2

1

0 8　7　6　5　4　3　2　1　0

Pe=A・log( KK0) K0=10-13

12＜A＜20

log-linear approximation

Φ=Φ0･exp(-α･Pe

ρe･g)

g = 10(m/s

Φ0 = 50(%)ρe = 1500(kg/m

3)

2)

Ss =1 ΔΦ

1-Φ ΔPe+Φ･βf

-13βf(flud compressibility)

＝ 4.4･10

0.0004～α～0.0008

approximated from Athy's law burial rate＝thickness／age1000（m/Ma）

A = 20α = 0.0004

δuδt -

δlδt

g･ρe( )Ss･η =δuδz

( K )δδz

)+γΦ δTδt

30（℃/km）temperature gradient

effe

ctiv

e pr

essu

re (M

Pa)

effe

ctiv

e pr

essu

re (M

Pa)

permeability (㎡) specific storage (1/Pa)

accu

mul

atio

n th

ickn

ess

(km

)

age（Ma)

Teng (1990)

25～37 ℃/km (Suppe & Wittke 1977)

Permeability Specific storageSedimentation rate

Temperature gradient

FLUID PRESSURE DISTRIBUTIONFLUID PRESSURE DISTRIBUTION

lithostatics

hydrostatics

numerical result

borehole data

permeability specific storage

10

10-19

-18

-910-910

(㎡)

(㎡)

permeability・specific storage change with pressure (our study)

permeability / specific storage assumed to be constant (Gibson 1958)

dept

h(m

)

dept

h(m

)

fluid pressure (MPa)fluid pressure (MPa)

Pressure sensitivity for permeability is important !!Predicted fluid pressure distribution showed

similar result to the borehole data !!

α = 0.0004 A = 12 K0 = 10 -13

IN DETAILSIN DETAILS

α=0.00040.00060.00080.0004 (K0=10-14 )

10-20

10-19

10-18

10-17

10-16

10-15

0 10 20 40 5030

permeabilityvs

abnormal pressure

influence of fluid volume expansion

by temperature gradient

abnormal fluid pressure (MPa)abnormal fluid pressure (MPa)

perm

eabi

lity

(㎡)

dept

h (m

)

temperature=30℃/kmtemperature=constant

0 1 107 2 107 3 107

0

1000

2000

3000

4000

5000

6000

7000

8000

Temperature gradient has little influence to pressure generation（mostly by the effect of sedimentation）

Abnormal pressure generated from10-1810-17 ～ ㎡

hydrostaticsgeneration of abnormal pressure

permeability (㎡)

dept

h (m

)

dept

h (m

)

porosity (%)

effect of abnormal fluid pressure

PERMEABILITY STRUCTURE at The Western FoothillsPERMEABILITY STRUCTURE at The Western Foothills

depth vs permeability depth vs porosity

estimation ofabnormal pressure

depth vs

effective pressure

permeability ‐ depthporosity ‐ depth

CONCLUSIONCONCLUSION

◆We measured permeability and porosity of sedimentary rocks in the Western Foothills at high pressure condition and estimated the hydraulic properties - effective pressure relationship in this area.

◆We estimated the fluid pressure distribution from one-dimensional compressional flow model and the result agreed with real borehole data.

◆We estimated the hydraulic properties (permeability / specific storage / porosity) at a depth of the Western Foothills.