Y.WILEVEAU, J. DELAY Andra – National Radioactive Waste Management Agency , Bure, France

- D TR ADPE 06-0607/ A ©

FORCE shale seminar 18 &19 Sept. 2006 - Stavanger

Stress determination and pore pressure measurements performed

at the Meuse/Haute-Marne Underground Laboratory

Y.WILEVEAU, J. DELAYAndra – National Radioactive Waste Management Agency, Bure,

France

- D TR ADPE 06-0607/ A ©


Overview

Part 1• Methodology for regional stress determination• Hydrofrac, HTPF and Sleeve fracturing• Data examples • Stress profile

Part 2• Pore pressure measurement in clay formation• Pressure profile in the argillite

Comparison and open question

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Geological setting on Bure’s URL

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Methodology for stress determination at the Bure site

From shafts • Paleostress• Convergence measurements on several sections• Vertical Mine by Test experiment in the main Shaft of the URL

From boreholes• Deformations of vertical borehole walls• Breakouts and induced fractures in inclined boreholes (Etchecopar, 1997)• Classical hydro-fracturing (Haimson, 1993)• Hydraulic tests on Pre-existing Fractures (HTPF method, Cornet, 1986)• Sleeve fracturing and Sleeve reopening (Desroches, 1999)

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Convergence measurements in the Oxfordian limestonesH oriented at N155°E

• accuracy : 0,1 mm on a 6m diameter of the shaft

• maximum convergence measured : 2mm• horizontal stress anisotropy K=H/h: between 1.4 et 1.8

10 1112

12

3456

7

89

PP

A11

26P

PA

143

PP

A11

55P

PA

1100

PP

A11

62

10 1112

12

3456

7

89

223,6 m

10 1112

12

3456

7

89

289 m

L2a

10 1112

12

3456

7

89

338,6 m

375 m

10 1112

12

3456

7

89

PP

A11

68

10 1112

12

3456

7

89

L1a

396,3 m

415 m

L1a

C3b

C3b

C3a

Vol

ées

inde

nf.

And

ra

Uni

tés

N

91573

91574

91575

91576

91577

91578

91579

91580

91581

823068 823069 823070 823071 823072 823073 823074 823075 823076

X

Y

Convergences amplifiées 500 fois

H

Section at 223m

1091573

1091574

1091575

1091576

1091577

1091578

1091579

1091580

1091581

823068 823069 823070 823071 823072 823073 823074 823075 823076

X (m)

Y (m

)


H

Section at 375m

1091573

1091574

1091575

1091576

1091577

1091578

1091579

1091580

1091581

823068 823069 823070 823071 823072 823073 823074 823075 823076

X (m)

Y (m

)


H

Section at 415m

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UBI analysis and wall morphology (example for EST 204 borehole)

•Breakouts appears in the clay-rich area (less compressive strength)

•High dependence on the fluid for drilling (water based mud for EST204)

• oil based mud give us better well stability

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MDT tool (specific configuration for

inclined boreholes)

Hydraulic fracturing tests in Bure

Downhole pump

Straddle packer

Pressure record during a micro-hydraulic fracturing test

Fracture initiation

Closure pressure of the induced fracture (Detail of the first hydraulic fracturing cycle)

Closure pressure

Breakdown pressure

Closure pressure determined from the square root of the shut-in time

Closure pressure

Induced fractures detected and oriented on FMI image

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FORCE shale seminar 18 &19 Sept. 2006 - StavangerGeneral situation of hydraulic fracturing tests at Bure Site

29 successful testsin 5 boreholes :

- 6 in Oxfordian- 17 in C.Oxfordian- 6 in Dogger

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800

700

600

500

400

300

Dep

th (m

eter

s be

low

gro

und

leve

l)

7 8 9 10 11 12 13 14 15Stress magnitude (MPa)

Oxfordian

Callovo-Oxfordian

Dogger

In-situ stress in Oxfordian

H oriented in N155°E• Slight rotation at the

base of Oxfordian unit h 8 MPa (average

value)

Magnitude (MPa)

360

380

400

420

440

460

480

500

dept

h [m

]

90 120 150 180 210 240 270strike direction N over E [deg]

distinct

distinct

distinct

distinct faint

thick single trace

distinct

distinct

faint

distinct

distinct

distinct

faint

distinct

distinct

impression packer testspost-frac UBI-logs

H orientation (°/North)

Hh

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Induced fracture at 467m (horizontal)

Induced fracture at 471m (horizontal)

Hydraulic fractures mined back during the sinking of the shafts (in clay formation)

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Top view of EST205 borehole at 499m on the ground

……but vertical at 499m depth !!!

H

h

N E N S W

499.0 m

500.0 m

test

-sec

tion

UBI – acoustical logging after micro-hydraulic tests at depth

499m in EST205

Fractures initiated during Hydrofrac (H direction)

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Vertical stress measured in the Dogger (HTPF method)

Direct measurement : v = 14,7 MPa at 655 m depth

+ Others Pre-existing Fractures have been tested in the argillites (v 12,0 MPa)

Selection of a pre-existing lignite layer at 655m depth : possibility to measure v by HTPF method

FMI after test

Induced fracture by

packers

FMI before test

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Q=0

Stress regime: Extension

123

Q=0.5

Stress regime: Extension

Q=1

Stress regime: Strike-slip

Q=1.5


Q=2


Q=2.5

Stress regime: Compression

Q=3

Stress regime: Compression

Influence of the shape of the stress tensor on the breakout orientation(from Desroches and Etchecopar, 2005)

.. assuming constant orientation of the main stresses

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FORCE shale seminar 18 &19 Sept. 2006 - StavangerOrdering the stresses by breakout analysis in the argillites

(from Desroches and Etchecopar, 2005)

Q=0.5

Q=1

Q=2

Q=3

Q=2.5

Q=1.5

Q=0

2.3 >Q>1.8

H> V= h

h N 60-65

In agreement with hydrofrac results: h = V

Deviated borehole (60°/vert)

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Variation of h with lithology : Orientation

Orientations are roughly constant in the Callovio-Oxfordian and in the Dogger

Orientations in the Oxfordian turn 40 degrees when approaching the contact with the Callovio-Oxfordian

H N150°E : Major tectonic shortening during the last Alpine Orogeny

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σh and σv magnitudes : variation with lithology !• Huge difference between

limestone and shales

• σh magnitudes are very similar in the limestones surrounding the clays

• σh is 3 in the limestones and 2 in the middle of the clays formation

• And what’s about σH ?

h

V

Weight of sediments

Depth m.

Limestone

Limestone

Shale

?H

v

h

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Sleeve fracturing and sleeve reopening in the clay formation

Sleeve fracturingHydraulic testing

Sleeve reopening –H estimation

A special test has been performed at 504min a sub-horizontal well

In order to estimate H

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Sleeve reopening – Identification of packer pressure for opening of the fracture

UBI before test UBI after test

Estimation of σH

Max. value : Pr = 20,3 MPa

Min. value : Pr = 18,1 MPa

12.7 MPa ≤ H ≤ 14.8 MPaH – P0 = 3(v – P0) – (Pr – P0)

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Maximum horizontal stress H estimation

by• sleeve reopening• breakouts analysis• shaft convergence

H estimated : 14-15 MPa

Approximately constant with depth

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EPG – Long term monitoring at the laboratory location

28/10/01 26/04/02 23/10/02 21/04/03 18/10/03 15/04/04 12/10/04 10/04/05 07/10/05 05/04/06-100

0

100

200

300

400

500H

YD

RA

ULI

C H

EA

D (m

AS

L)

borehole EST212 (upper EPG )borehole EST212 (lower EPG )borehole EST211borehole EST103

M

D/e

pg p

rese

ntat

ion

E.gr

f

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EPG – pressure profile

270 290 310 330 350 370

Charges hydrauliques (mNGF)

800

700

600

500

400

300

Prof

onde

ur (m

/sol

)

charge théoriqueEST103 : W estbay e t EPGEST210 : su ivi de n iveauEST211 : EPGEST212 : EPGest207 : W estbay

s

ynth

èse

char

ges.

grf

Oxfordien

Callovo-Oxfordien

Dogger

Profil de charges apparentes(P rofondeurs ram enées à la co te

du rad ie r EST205 : 366,01 m N G F)

In situ stress profile

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Conclusions

• To determine the complete state of stress in a lithologic sequence a combination of methods is required

• Hydraulic fracturing and image analysis in deviated boreholes are perfectly complimentary

Such a combination allowed the determination of the complete state of stress

• In the studied sequence, there is a large difference in the state of stress in the limestones and that in the argillites

• The pore pressure profile looks like to stress profile but …..

• Is that a common behavior? How could one predict it?

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Thank you for your attention !

Y.WILEVEAU, J. DELAY Andra – National Radioactive Waste Management Agency , Bure, France

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