- D TR ADPE / A © FORCE shale seminar 18 &19 Sept Stavanger Stress determination and pore pressure measurements performed at the Meuse/Haute-Marne Underground Laboratory Y.WILEVEAU, J. DELAY Andra – National Radioactive Waste Management Agency, Bure, France

- D TR ADPE / A © FORCE shale seminar 18 &19 Sept Stavanger 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

- D TR ADPE / A © FORCE shale seminar 18 &19 Sept Stavanger Geological setting on Bure’s URL

- D TR ADPE / A © FORCE shale seminar 18 &19 Sept Stavanger 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)

- D TR ADPE / A © FORCE shale seminar 18 &19 Sept Stavanger Convergence measurements in the Oxfordian limestones  H 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 HH Section at 223m HH Section at 375m HH Section at 415m

- D TR ADPE / A © FORCE shale seminar 18 &19 Sept Stavanger 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

- D TR ADPE / A © FORCE shale seminar 18 &19 Sept Stavanger 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

- D TR ADPE / A © FORCE shale seminar 18 &19 Sept Stavanger General situation of hydraulic fracturing tests at Bure Site 29 successful tests in 5 boreholes : - 6 in Oxfordian - 17 in C.Oxfordian - 6 in Dogger

- D TR ADPE / A © FORCE shale seminar 18 &19 Sept Stavanger 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)  H orientation (°/North) HH hh

- D TR ADPE / A © FORCE shale seminar 18 &19 Sept Stavanger Induced fracture at 467m (horizontal) Induced fracture at 471m (horizontal) Hydraulic fractures mined back during the sinking of the shafts (in clay formation)

- D TR ADPE / A © FORCE shale seminar 18 &19 Sept Stavanger Top view of EST205 borehole at 499m on the ground ……but vertical at 499m depth !!! HH hh UBI – acoustical logging after micro-hydraulic tests at depth 499m in EST205 Fractures initiated during Hydrofrac (  H direction)

- D TR ADPE / A © FORCE shale seminar 18 &19 Sept Stavanger 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

- D TR ADPE / A © FORCE shale seminar 18 &19 Sept Stavanger Q=0 Stress regime: Extension 123123 Q=0.5 Stress regime: Extension Q=1 Stress regime: Strike-slip Q=1.5 Stress regime: Strike-slip Q=2 Stress regime: Strike-slip 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

- D TR ADPE / A © FORCE shale seminar 18 &19 Sept Stavanger Ordering 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 In agreement with hydrofrac results:  h =  V Deviated borehole (60°/vert)

- D TR ADPE / A © FORCE shale seminar 18 &19 Sept Stavanger 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

- D TR ADPE / A © FORCE shale seminar 18 &19 Sept Stavanger σ h and σ v magnitudes : variation with lithology ! Huge difference between limestone and shales σ h magnitudes are very similar in the limestones surrounding the clays σ h is  3 in the limestones and  2 in the middle of the clays formation And what’s about σ H ? hh VV Weight of sediments Depth m. Limestone Shale ? HH vv hh

- D TR ADPE / A © FORCE shale seminar 18 &19 Sept Stavanger Sleeve fracturing and sleeve reopening in the clay formation A special test has been performed at 504m in a sub-horizontal well In order to estimate  H

- D TR ADPE / A © FORCE shale seminar 18 &19 Sept Stavanger Sleeve reopening – Identification of packer pressure for opening of the fracture UBI before test UBI after test Estimation of σ H 12.7 MPa ≤  H ≤ 14.8 MPa  H – P 0 = 3(  v – P 0 ) – (P r – P 0 )

- D TR ADPE / A © FORCE shale seminar 18 &19 Sept Stavanger Maximum horizontal stress  H estimation by sleeve reopening breakouts analysis shaft convergence  H estimated :  MPa Approximately constant with depth

- D TR ADPE / A © FORCE shale seminar 18 &19 Sept Stavanger EPG – Long term monitoring at the laboratory location

- D TR ADPE / A © FORCE shale seminar 18 &19 Sept Stavanger EPG – pressure profile In situ stress profile

- D TR ADPE / A © FORCE shale seminar 18 &19 Sept Stavanger 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?

- D TR ADPE / A © FORCE shale seminar 18 &19 Sept Stavanger Thank you for your attention !