design and installation of gas borehole experiment: the

Design and installation of gas borehole experiment:

the PGZ2 experiment at Bure

FORGE Report D3.17 –VER.1

Name Organisation Signature Date

Compiled de La Vaissière Rémi ANDRA February 2010

Verified Talandier Jean ANDRA November 2013

Approved Shaw Richard BGS

29 November 2013

Keywords

PGZ, Test PGZ2, set-up, Bure URL.

Bibliographical reference

de La Vaissière, R. 2013. design and installation of the PGZ2 experiment at Bure. FORGE Report D3.17. 58pp.

Euratom 7th Framework Programme Project: FORGE

FORGE Report: D3.17– Ver.1

i

Fate of repository gases (FORGE)

The multiple barrier concept is the cornerstone of all proposed schemes for underground disposal of radioactive wastes. The concept invokes a series of barriers, both engineered and natural, between the waste and the surface. Achieving this concept is the primary objective of all disposal programmes, from site appraisal and characterisation to repository design and construction. However, the performance of the repository as a whole (waste, buffer, engineering disturbed zone, host rock), and in particular its gas transport properties, are still poorly understood. Issues still to be adequately examined that relate to understanding basic processes include: dilational versus visco-capillary flow mechanisms; long-term integrity of seals, in particular gas flow along contacts; role of the EDZ as a conduit for preferential flow; laboratory to field up-scaling. Understanding gas generation and migration is thus vital in the quantitative assessment of repositories and is the focus of the research in this integrated, multi-disciplinary project. The FORGE project is a pan-European project with links to international radioactive waste management organisations, regulators and academia, specifically designed to tackle the key research issues associated with the generation and movement of repository gasses. Of particular importance are the long-term performance of bentonite buffers, plastic clays, indurated mudrocks and crystalline formations. Further experimental data are required to reduce uncertainty relating to the quantitative treatment of gas in performance assessment. FORGE will address these issues through a series of laboratory and field-scale experiments, including the development of new methods for up-scaling allowing the optimisation of concepts through detailed scenario analysis. The FORGE partners are committed to training and CPD through a broad portfolio of training opportunities and initiatives which form a significant part of the project. Further details on the FORGE project and its outcomes can be accessed at www.FORGEproject.org.

Contact details: de La Vaissière, Rémi ANDRA Tel: 33 (0) 329 755 343 Fax 33 (0) 637 262 539 email: [email protected] web address: www.andra.fr Address Laboratoire de recherche souterrain de Meuse / Haute-Marne Route départementale 960 BP 9 55290 Bure FRANCE

http://www.forgeproject.org/�

FORGE Report: Dx.xx – Ver.1

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Foreword This report is the first ANDRA’s contribution to the Work Package 3 (deliverable 3.17: design and installation of the PGZ2 experiment at Bure).

Acknowledgements Claude Gatabin from CEA/LECBA and his team should be gratefully acknowledged for preparing the bentonite plug and the seats. He also helped me for the interpretation of total pressure sensors. The team of Solexperts provided the multi-packers systems, performed the installation. The teams of Colenco (JM. Lavanchy) and Intera (R. Senger) performed some calculation to evaluate the swelling of the plug. COFOR team had drilled the boreholes and Brisset-Veyrier make the topographic measurements. Egis team supervised the installation.

A large number of individuals have contributed to the project. In addition to the collection of data, many individuals have freely given their advice, and provided the local. Jean Talandier has helped to review draft chapters of this report. Of the many individuals who have contributed to the project we would particularly like to thank the following:

Philippe Tabani, Guillaume Hermand and Soldata for the data acquisition,

Laurent Lefebvre for the drawing,

The authors would like to thank J. Delay, H. Rebours, S. Dewonck, G. Armand and all the DS/MFS team.


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Contents Foreword ............................................................................................. ii

Acknowledgements ............................................................................. ii

Contents .............................................................................................. iii

Summary .............................................................................................. v

Introduction ......................................................................................... 1 1.1 Objectives PGZ2................................................................... 1 1.2 Progress of installation. ........................................................ 2 1.3 Configuration and geometry of the PGZ2 ............................ 4 1.4 Measurements ..................................................................... 20 1.5 Continuation of test PGZ2 .................................................. 32

Appendix 1 GED map ................................................................. 34

Appendix 2 Photographs ............................................................ 35

Appendix 3 Location of the temperature and relative-humidity sensors for the tests PGZ1 and PGZ2 ................................................................................ 41

Appendix 4 Layouts .................................................................... 42 PGZ1001 ...................................................................................... 42 PGZ1011 ...................................................................................... 43 Seat 1 for PGZ1011 ...................................................................... 44 Seat 2 for PGZ1012 ...................................................................... 45 PGZ1012 ...................................................................................... 46 Seat 3 for PGZ1012 ...................................................................... 47 Seat 4 for PGZ1012 ...................................................................... 48

Appendix 5 Water contents data................................................ 49 PGZ1001 ...................................................................................... 49 PGZ1011 ...................................................................................... 50 PGZ1012 ...................................................................................... 51

Glossary .............................................................................................. 52

FIGURES

Figure 1 Layout diagram for the equipment in Bore-holes PGZ1011 and PGZ1012 3

Figure 2 Photographs of breakouts in borehole PGZ1012 (at left, 8 m from the GMR wall, and at right about 10 m) ................................................................... 3

Figure 3 3-D view of the French URL ................................................. 4

Figure 4 3-D view of the boreholes for the PGZ tests ....................... 5


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Figure 5 Layout diagram for seats and bentonite core ..................... 8

Figure 6 Layout diagram for the bentonite core ............................... 8

Figure 7 Swelling pressure versus dry density of the bentonite (MX80 WH2) in the space (ESDRED project report) ................................................................... 9

Figure 8 View of internal face of rseat (frit and pressure sensors)... 10

Figure 9 Schematic representation of the theoretical volumes of the bentonite sections in boreholes PGZ1011 and PGZ1012 .................................................... 11

Figure 10 3-D view of the bentonite section in Bore-hole PGZ1011 (yellow: interstitial-pressure sensors, green: total-pressure sensor, blue: temperature sensor; black: hydraulic line to the crown, red: the two hydraulic lines to the frit ................ 14

Figure 11 3-D view of the bentonite section in Bore-hole PGZ1012 (colour legend same as for PGZ1011). Note: Seat 4 is offset by 45° (design error) ..................... 15

Figure 12 Photographs of climatic sensors (top: GMR/GED side with PGZ1081 at left and PGZ1082 at right; bottom: GEX side with PGZ1061 at left and PGZ1062 at right) 18

Figure 13 gas module system .............................................................. 19

Figure 14 Names of the measuring points in the gas modules ........... 20

Figure 19 Water-content profile in borehole PGZ1001 ...................... 21



Figure 18 Pressure monitoring in borehole PGZ1001 ......................... 23

Figure 19 Profile of pseudo-stabilised pressures between the GEX and GMR/GED drifts 24

Figure 20 Pressure monitoring in both measurement chambers of borehole PGZ1011 25

Figure 21 Pressure monitoring in both measurement chambers of borehole PGZ1012 25

Figure 22 Pressure monitoring in the bentonite section of borehole PGZ1011 26

Figure 23 Pressure monitoring in the bentonite section of borehole PGZ1012 26

Figure 24 CO2 pulse produced on 9/16/09 in PGZ1011 ...................... 27

Figure 25 CO2 pulse produced on 9/25/09 in PGZ1011 ...................... 28

Figure 26 CO2 pulse produced on 10/16/09 in PGZ1011 .................... 28

Figure 27 Total-pressure monitoring in Bore-hole PGZ1011 .............. 29

Figure 28 Total-pressure monitoring in Bore-hole PGZ1012 ............. 30

Figure 29 Typical variation of axial pressure during hydration of a clay core with a radial clearance. Top: low void fraction and high dry density; Bottom: high void fraction and low dry density ........................................................................................ 31

TABLES

Table 1 Chronology of the bore-hole drilling phase of Test PGZ2 ...... 2

Table 2 Geometry of boreholes in Test PGZ2 ..................................... 5

Table 3 Coordinates of measurement intervals in PGZ1201 .............. 6


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Table 9 Coordinates of measurement intervals in PGZ1011 and PGZ1012 7

Table 10 Characteristics of installed bentonite cores ........................ 9

Table 11 Calculation of the volumes of the hydraulic lines connected to the bentonite section in boreholes PGZ1011 and PGZ1012 ................................... 12

Table 12 Calculation of the volumes of the hydraulic lines connected to the bentonite section in drift 13 for boreholes PGZ1011 and PGZ1012 ......................

Table 13 Total volumes of hydraulic lines connected to the bentonite section 13

Table 14 Coordinates of measuring points in the bentonite sections of boreholes PGZ1011 and PGZ1012 ..................................................................................... 16

Table 9 List of cores (Cell T1 packaging) ............................................. 20

Summary This report describes the objectives, geometry and the first measurements of the in situ experiment PGZ2. PGZ2 is focus on the study of gas propagation in seals and interfaces.

This report is the first contribution to the Work Package 3 (deliverable 3.17: design and installation of the PGZ2 experiment at Bure).


1

Introduction The PGZ experiments are part of an experimental and demonstration test programme at the Meuse/Haute-Marne Underground Research Laboratory.

One of the objectives of this experimental and demonstration test programme is to study the response of argillites to disturbances caused by a repository. In the PGZ experiments, the subject is the disturbances caused by gases generated by the radiolysis or anoxic corrosion of some of the waste packages and, where applicable, by the corrosion of the repository's steel components, e.g. high-level waste cells. This will particularly include gas transfer in undisturbed and disturbed argillites, as well as transfer through the sealing plugs and at interfaces.

This report contributes to the WP3 (deliverable D3.17: Description of the in situ PGZ2 experiment at Bure). This report describes the PGZ2 experiment since the start of equipment installation in the GED programme unit.

It is intended to show the main dates for installing equipment, the exact geometry and positions of the measuring points, and measurements of the water contents of samples, as well as preliminary measurements and their implications for the rest of the testing programme, for each test.

We first present the objectives and the methods employed for these experiments.

1.1 OBJECTIVES PGZ2 The objectives of PGZ2 are to use gas-injection tests to characterise the gas-transfer properties of seals and interfaces:

• Study of the behaviour of the argillite/clay-based materials interface as regards gas transfer,

• Assessment of the resaturation and swelling behaviour of the plug, as a function of the gas pressure.

The primary objective of Test PGZ2 is to assess the impact of gas on the resaturation and swelling of a plug based on swelling clay. This sealing test in small-diameter boreholes is identified as “Test PGZ2”.

A plug will be inserted into a first borehole. The water resaturation will be done naturally.The objective is to quantify the dynamic of resaturation and the time it requires.

In a second borehole, a plug is inserted and gas is injected before reaching the full water saturation state full; the injection begins as soon as the clearances around the plug are closed up. The measurements of total pressure and interstitial pressure in the two boreholes will then be compared, to assess the effect of the gas on the plug.

The material selected for the plug is a mixture of MX80-type bentonite and sand, in the proportion of 70% to 30% by weight.

This test is divided into two operational phases. The first phase, described in this document, comprises three boreholes:

• A first bore-hole PGZ1001 enables measurement of the hydraulic head gradient between two drifts (GEX and GMR) by means of five measurement chambers,


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• Two others similarly equipped boreholes (PGZ1011 and PGZ1012). One will be used for the gas injection (PGZ1011), and the other will be devoted to monitoring the resaturation of the bentonite plug (PGZ1012).

The second operational phase will comprise three more boreholes. It is not described here.

1.2 PROGRESS OF INSTALLATION The following table shows the chronology of the drilling operations and the installation of equipment for Test PGZ2:

Table 1 Chronology of the bore-hole drilling phase of Test PGZ2

PGZ1001 PGZ1012 PGZ1011

Drilling April 21-22 2009 August 19 2009 August 24 2009

Installation of equipment April 22 2009 August 20-21 2009 August 25-27 2009

The boreholes were cored with air. The external diameter is 76 mm for PGZ1001 and 101.3 mm for PGZ1011 and PGZ1012.

Geologic logging of these boreholes was carried out by GEOTER. The water contents measured in samples from these three boreholes are presented in Paragraph 1.4.1.

• Layouts are given in Appendix 4

• For this test, four sensors to measure air temperature and humidity in the drift were installed on August 20, 2009.

• The gas modules were installed following the drilling of boreholes PGZ1011 and PGZ1012 in GEX and GMR drifts. Thermal-insulation cladding was placed around the hydraulic lines between the collars of the boreholes and the control panel, and between the control panel and the gas modules.

The drilling of a borehole from one drift to another was a tricky operation because the hole could not deviate by more than 50 cm in case it hit an arch support. Moreover, the positions of bolts in the drift walls were not known, and there was a danger of intersecting them. Depending on the angle of the coring bit with the bolt, the borehole could be deflected. Appendix 2 shows several photos taken during the drilling. For PGZ1012, no bolt was encountered and the borehole deviated 30 cm in the upward direction with respect to its intended exit point. On the other hand, two bolts were encountered while drilling borehole PGZ1011. The first was 1 m from the wall of the GMR/GED drift and the second 1 m from the wall of the GEX drift. Borehole PGZ1011 eventually deviated only 5 cm from its intended exit point.

The installation of a bentonite core inserted between two semi-completions in a borehole was a complex operation. In this case it was successful and in accordance with the projected programme.

However, after positioning borehole PGZ1012 at the level of the equipment and after inflating the packers with water, it was found that Packer No. 4 next to the bentonite core had leaked.

Figure 1 shows the layout diagram for the equipment installed in Bore-holes PGZ1011 and PGZ1012.


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Figure 1 Layout diagram for the equipment in Bore-holes PGZ1011 and PGZ1012

Following the incident in PGZ1012, all the packers in borehole PGZ1011 were inflated with CO2. After confirming that the packers were supporting the pressure, the packers were deflated and then re-inflated with water in two stages: first Packers 1, 2, 3, 6, 7, and 8, on August 26, 2009, and then Packers 4 and 5 on September 11, 2009.

It should be noted that the full installation of borehole PGZ1011 was completed once all the chambers that were to receive resin had received it. The application of resin to the areas between Packers 3-4 and 5-6 was carried out on October 22, 2009. The presence of breakouts1

Figure 2

along the borehole delayed the application of resin ( ). In a horizontal borehole, breakouts lead to bypassing along the hole and since the resin is very fluid, it could have run into the bentonite section.

Figure 2 Photographs of breakouts in borehole PGZ1012 (at left, 8 m from the GMR wall, and at right about 10 m)

1 Two camera logs (video D.RP.0GTR.09.0086 and D.RP.0GTR.09.0087 in Bore-holes PGZ1012 and PGZ1011

respectively) showed significant breakouts in the central portions of these holes.


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1.3 CONFIGURATION AND GEOMETRY OF THE PGZ2

1.3.1 Location of boreholes in drift PGZ1 is located in the new drift GED of the French URL (see Figure 3).

Figure 3 3-D view of the French URL

Borehole PGZ1001 was drilled in the GMR drift half way up the right wall, between Arch-supports 046GMR and 047GMR. This borehole is horizontal and is equipped with a multi-packer completion with five measurement chambers.

Boreholes PGZ1011 and PGZ1012 have the special feature of being piercing holes. They were drilled from the GMR/GED drift into the GEX drift:


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• The PGZ1011 borehole mouth is located half way up the right wall, between Arch-supports 004GED and 005GED,

• The PGZ1012 borehole mouth is located half way up the right wall, between Arch-supports 042GMR and 043GMR.

Appendix 2 presents photos of the boreholes at the conclusion of equipment installation.

1.3.2 Geometric configuration of the boreholes Figure 4 presents a 3-D view of all the PGZ boreholes, notably the holes for Test PGZ2.

Figure 4 3-D view of the boreholes for the PGZ tests

The table below gives details of the geometry of the boreholes drilled (coordinates of points given in the Lambert 1 coordinate system).

Table 2 Geometry of boreholes in Test PGZ2

PGZ1001 PGZ1011 PGZ1012

Coordinates of borehole

mouth

X (m) 823206.90 823210.574 823203.301

Y (m) 1091635.73 1091637.599 1091634.091

Z (m) -124.05 -124.604 -124.683

Diameter (mm) 76 101.3 101.3

3-D length

mouth - end (m) 15.12 19.864 19.565

Test PGZ2


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Azimuth (°) 154 155.54 155.09

Inclination (°) 0 + 0.89 + 1.37

Coordinates of end of hole

X (m) 823213.46 823218.798 823211.543

Y (m) 1091622.11 1091619.520 1091616.352

Z (m) -124.05 -124.294 -124.222

In Table 2, the 3-D length corresponds to the length drilled, because the mouth of the borehole represents the physical attack of the drill bit on the wall of the drift.

It should be noted that the coordinates of borehole PGZ1001 are not given with the same accuracy as those of the other holes. The operators and measurement techniques are not the same. The position of the end of borehole PGZ1001 falls within a radius of 5 cm, with a maximum error of 5 cm on its length.

There is no uncertainty about the positions of the ends of Boreholes PGZ1011 and PGZ1012 since these are piercing holes.

1.3.3 Location of measuring points

1.3.3.1 PGZ1001

Borehole PGZ1001 is equipped with a multi-packer, five-chamber completion. Appendix 4 shows the layout installed in situ. All the measurement intervals are 0.2 m long.

The positions of the intervals are shown in Table 3 below:

Table 3 Coordinates of measurement intervals in PGZ1201

X (m) Y (m) Z (m)

Chamber 5 PGZ1001_PRE_05

Head 823208.90 1091631.57 -124.05

Middle 823208.95 1091631.48 -124.05

Foot 823208.99 1091631.39 -124.05


Head 823209.99 1091629.32 -124.05

Middle 823210.03 1091629.23 -124.05

Foot 823210.08 1091629.14 -124.05


Head 823211.12 1091626.97 -124.05

Middle 823211.16 1091626.88 -124.05

Foot 823211.20 1091626.79 -124.05


Head 823212.25 1091624.63 -124.05

Middle 823212.29 1091624.54 -124.05

Foot 823212.33 1091624.45 -124.05


Head 823213.37 1091622.29 -124.05

Middle 823213.42 1091622.20 -124.05


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Foot 823213.46 1091622.11 -124.05

1.3.4 Details about the equipment in boreholes PGZ1011 and PGZ1012 Boreholes PGZ1011 and PGZ1012 are each equipped with two multi-packer, one-chamber semi-completions with a central bentonite section (see Figure 1). Appendix 4 shows the device installed in situ, for each borehole.

1.3.4.1 LOCATION OF INTERVALS

Both intervals have a length of 50 cm and the bentonite sections (distance from packer to packer) are 87.4 cm and 88.0 cm long for PGZ1011 and PGZ1012 respectively.

The positions of the intervals are shown in Table 4 below:

Table 4 Coordinates of measurement intervals in PGZ1011 and PGZ1012

X (m) Y (m) Z (m)

PGZ1

011


GED/GMR side

Head 823213.467 1091631.218 -124.515

Middle 823213.571 1091630.990 -124.512

Foot 823213.674 1091630.763 -124.508


GEX side

Head 823215.690 1091626.326 -124.433

Middle 823215.794 1091626.098 -124.429

Foot 823215.897 1091625.871 -124.424

PGZ1

012


GED/GMR side

Head 823206.169 1091627.895 -124.532

Middle 823206.274 1091627.669 -124.527

Foot 823206.379 1091627.442 -124.521


GEX side

Head 823208.433 1091623.017 -124.412

Middle 823208.539 1091622.790 -124.405

Foot 823208.644 1091622.563 -124.399

1.3.4.2 BENTONITE SECTION

The bentonite section is bounded by two packers (Packers 4 and 5 of Figure 1). In this section, it has three components (Figure 5) :

• A seat inserted into the semi-completion,

• A bentonite core inserted into the seats

• The other seat inserted into the other semi-completion.


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Figure 5 Layout diagram for seats and bentonite core

The seats and bentonite core are provided by CEA/LECBA. Figure 6 presents the layout diagram for the bentonite core:

Figure 6 Layout diagram for the bentonite core

The bentonite cores consist of a compacted mixture of 70% GELCLAY bentonite (MX80 WH2) and 30% TH1000 sand (dry weight). The characteristics of the cores installed are given in the table below, to obtain an inflated in situ pressure of 7 MPa:

2 hydraulic lines

i

1 hydraulic line running to the crown


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Table 5 Characteristics of installed bentonite cores

Borehole LECBA No. Water

content by weight

Total length

Nominal diameter Weight Bulk density Dry density Dry density of

pure bentonite

% mm mm g g/cm3 g/cm3 g/cm3

PGZ1011 2678i 8.84 400.1 93.9 6107 2.25 2.07 1.89

PGZ1012 2677i 8.80 400.4 94.1 6105 2.24 2.06 1.88

The dry density of bentonite in situ is 1.61 and 1.62 g/cm3 for the cores in boreholes PGZ1012 and PGZ1011 respectively. It was calculated after taking into account i) the available radial clearance (see §1.3.4.3) and ii) that 1 to 2% by weight of the bentonite may be extruded into the longitudinal clearances. Based on Figure 7, the swelling pressure in situ will be close to 7 MPa.

Figure 7 Swelling pressure versus dry density of the bentonite (MX80 WH2) in the space (ESDRED project report)

Each seat is fitted with:

• 2 total-pressure sensors,

• 2 interstitial-pressure sensors,

• 1 temperature sensor,

• 3 hydraulic lines:

2 lead to the top and bottom of the frit,


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1 leads to the outside part of the receptacle (on its crown) to enable the execution of a CO2 test, degassing, or injection/draining of water high up in the service space in the bentonite section.

The frit is made of stainless steel with a 20 µm porosity and is 3 mm thick. It is inserted between the receptacle and the bentonite core (Figure 8).

Figure 8 View of internal face of seat (frit and pressure sensors)

1.3.4.3 VOLUMES OF BENTONITE SECTIONS

The volume of the bentonite section is the volume of the initial void within a drilled diameter of 101.3 mm between Packers 4 and 5. It is theoretically equal to 1.22 L for both boreholes. For PGZ1012, the free volume is 4223 cm3 owing to the fact that Packer 4 could not be inflated and that the adjacent Resin Area 2 did not receive any resin (Figure 9).

The volume of bentonite able to swell radially corresponds to the volume of a cylinder 101.3 mm in diameter, minus the volume of the cylinder of bentonite included between the 340 mm-long sleeves of the two seats. For a core diameter of 94 mm, the radial clearance is 381 cm3; it is the same for both boreholes.

The volume of bentonite that can be extruded longitudinally on either side of the sleeves of the seats is:

• 419 cm3 for each seat in borehole PGZ1011,

• 419 cm3 for seat 4 and 3423 cm3 for seat 3 in borehole PGZ1012.

Interstitial-pressure sensors

Total-pressure sensors


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Figure 9 Schematic representation of the theoretical volumes of the bentonite sections in boreholes PGZ1011 and PGZ1012

None of these theoretical volumes take into account any breakouts (see Figure 2) or any closure by creep of argillite around the section.

1.3.4.4 INTERNAL VOLUMES

Volume of frit

• Thickness of the porous disks of fritted stainless: 3 +/-0.1mm

• Total porosity: 43%; the connected porosity is difficult to measure.

• Volume of a frit's porosity = Volume of total porosity - volume of sensor holes.

Frit volume = 15.843 cm3, Volume of PT sensor hole: 0.136 x 2 = 0.272 cm3, Volume of PI sensor hole: 0.151 x 2 = 0.302 cm3,

The porous volume to be used for a frit is 15.843 – (0.272+ 0.302) = 15.269 x 0.43 = 6.57 cm3.

Dead volumes of sensors

The volumes below are not available for gas:

• Long PI sensor: 0.348 cm3,

• Short PI sensor: 0.293 cm3,

• PT sensor: nil,

• Volume of 1/8" union tube receptacle connector: 0.073 cm3,

• Volume of seat's threaded hole-bottom union connector + frit connector hole: 0.785 cm3.

Volume of hydraulic lines

The internal cross-section of the hydraulic lines has an area of 0.02414 cm2. For 1 line meter (100 cm), this gives a volume available for gas of 2.414 cm3.


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These lines are connected to the seats via connectors, whose volumes are given below:

• Volume of seat’s 1/8" union tube connector: 0.073 cm3,

• Volume of seat's threaded hole-bottom union connector + frit connector hole: 0.785 cm3.

The table shows details of the calculation of the volumes of the hydraulic lines between the seats and the completion outlet (stick-up), for each side.

Table 6 Calculation of the volumes of the hydraulic lines connected to the bentonite section in

boreholes PGZ1011 and PGZ1012

PGZ1011 PGZ1012

GEX GMR GEX GMR

Length (cm)

I single hydraulic line running to the frit 998 991 985 981

2 hydraulic lines running to the frit 1.995 1.981 1.969 1.961

additional hydraulic line 995 988 982 978

Volume (cm3)

2 hydraulic lines running to the frit 48 48 48 47

I single hydraulic line running to the frit 24 24 24 24

Volume of connectors 3 3 3 3

Total 75 75 74 74

The hydraulic lines attached to the seats are connected to two control panels located in the GEX drift and the GMR drift. From each control panel, two hydraulic lines (one for PGZ1011 and one for PGZ1012) are connected to the gas module. The internal diameter of each hydraulic line is 4 mm, which gives a cross-section of 0.126 cm2, or a volume of 12.6 cm3 per line meter.

The lengths and volumes of the hydraulic lines from the stick-ups in the boreholes to the control panel to the gas module are shown in the table below:


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Table 7 Calculation of the volumes of the hydraulic lines connected to the bentonite section in drift

for boreholes PGZ1011 and PGZ1012

PGZ1011 PGZ1012

GEX GMR GEX GMR

Length (cm)

Stick-up – control panel 330 890 670 130

2 x Stick-up – control panel 660 1.780 1.340 260

Control panel – gas module 950 590 960 585

Volume (cm3)

2 x Stick-up – control panel 16 43 32 6

Control panel – gas module 119 74 121 74

TOTAL 135 117 153 80

Table 8 Total volumes of hydraulic lines connected to the bentonite section

GMR/GED GEX

PGZ1011 192 cm3 210 cm3

PGZ1012 154 cm3 227 cm3

The volumes shown in Table 8 are only indicative because they do not consider the volume in the gas module, or the uncertainties in the lengths of the lines. The uncertainty on the volume of each group of lines is about 10%.

1.3.4.5 LOCATION OF MEASURING POINTS IN THE BENTONITE SECTIONS

Figure 10 and Figure 11 present a 3-D view of the bentonite sections in boreholes PGZ1011 and PGZ1012 and the corresponding SAGD numbers. Appendix $ and $ present schematic views of the positions of the sensors in each frit. The hydraulic line connected to the external part of the seat is connected on surface to an interstitial-pressure sensor. On the GEX side, the SAGD number of this sensor is PGZ1011_PRE_07 / PGZ1012_PRE_07 and on the GMR/GED side, it is PGZ1011_PRE_08 / PGZ1012_PRE_08.


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Figure 10 3-D view of the bentonite section in Bore-hole PGZ1011 (yellow: interstitial-pressure sensors, green: total-pressure sensor, blue: temperature sensor; black: hydraulic line to the crown, red: the two hydraulic lines to the frit


15

Figure 11 3-D view of the bentonite section in Bore-hole PGZ1012 (colour legend same as for PGZ1011). Note: Seat 4 is offset by 45° (design error)

Table 9 shows the coordinates of the measuring points in the bentonite section. During the installation it was confirmed that the semi-completions had not rotated in the borehole. It is nevertheless possible that the receptacles rotated a few degrees. The uncertainty about the position of these sensors is a few centimetres and the table is therefore given for information only.


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Table 9 Coordinates of measuring points in the bentonite sections of boreholes PGZ1011 and PGZ1012

X (m) Y (m) Z (m)

PGZ1011 seat 1

GEX side

PGZ1011_PRE_02 823214.743 1091628.409 -124.470

PGZ1011_PRE_03 823214.780 1091628.369 -124.486

PGZ1011_PRT_01 823214.783 1091628.371 -124.447

PGZ1011_PRT_02 823214.745 1091628.353 -124.490

PGZ1011_TEM_02 823214.750 1091628.351 -124.452

PGZ1011_PRE_07 823214.793 1091628.297 -124.423

PGZ1011 seat 2

GMR side

PGZ1011_PRE_04 823214.620 1091628.679 -124.474

PGZ1011_PRE_05 823214.584 1091628.719 -124.492

PGZ1011_PRT_03 823214.579 1091628.717 -124.454

PGZ1011_PRT_04 823214.619 1091628.734 -124.496

PGZ1011_TEM_03 823214.612 1091628.737 -124.458

PGZ1011_PRE_08 823214.568 1091628.792 -124.432

PGZ1012 seat 3

GEX side

PGZ1012_PRE_02 823207.467 1091625.094 -124.465

PGZ1012_PRE_03 823207.505 1091625.054 -124.481

PGZ1012_PRT_01 823207.470 1091625.038 -124.485

PGZ1012_PRT_02 823207.508 1091625.057 -124.442

PGZ1012_TEM_02 823207.475 1091625.036 -124.447

PGZ1012_PRE_07 823207.518 1091624.983 -124.418

PGZ1012 seat 4

GMR side

PGZ1012_PRE_04 823207.342 1091625.363 -124.471

PGZ1012_PRE_05 823207.299 1091625.400 -124.473

PGZ1012_PRT_03 823207.320 1091625.410 -124.442

PGZ1012_PRT_04 823207.321 1091625.409 -124.502

PGZ1012_TEM_03 823207.340 1091625.424 -124.472

PGZ1012_PRE_08 823207.290 1091625.476 -124.429

1.3.5 Coordinates for modelling activities For PGZ1011, the point located at the middle of the bentonite section could be used as reference point. Its coordinates are: X = 823214.682 m; Y = 1091628.54 m; Z = -124.472 m. The new coordinates for PGZ1011 are calculated by subtraction of the coordinates indicated in tables 9 and 14 and the reference.


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For PGZ1012, the point located at the middle of the bentonite section could be used as reference point. Its coordinates are: X = 823207.405 m; Y = 1091625.23 m; Z = -124.468 m. The new coordinates for PGZ1011 are calculated by subtraction of the coordinates indicated in tables 9 and 14 and the reference.

1.3.6 Sensors in the drift

1.3.6.1 TEMPERATURE AND RELATIVE-HUMIDITY SENSORS IN DRIFT

It has been shown that in other boreholes the temperature fluctuations in the drift influenced the pressure measurements in the borehole because in some boreholes the hydraulic lines between the borehole collars and the control panel were several meters in length. For Test PGZ2, it is necessary to measure the temperature in the drift because during the gas-injection phase any variations in temperature are reflected in the gas pressure, even though thermal-insulation cladding has been installed

Four air temperature and relative-humidity sensors were positioned in the GEX drift and in the GMR/GED drift (Figure 12):

• Two sensors in GEX, one located in the left wall immediately to the right of Arch-support 046GEX (PGZ1061_TEM_01 and PGZ1061_HUM_01) and the other near the gas module (at the end of GEX) (PGZ1062_TEM_01 and PGZ1062_HUM_01),

• Two sensors in GED/GMR, one located in the right wall between Arch-supports 047GMR and 001GED (PGZ1081_TEM_01 and PGZ1081_HUM_01) and the other near the gas module at Arch-support 042GMR (PGZ1082_TEM_01 and PGZ1082_HUM_01).

The positions of these sensors are not given in the laboratory reference document. Appendix 3 shows the location of these sensors in the plane of the GED drift.


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Figure 12 Photographs of climatic sensors (top: GMR/GED side with PGZ1081 at left and PGZ1082 at right; bottom: GEX side with PGZ1061 at left and PGZ1062 at right)

1.3.6.2 GAS MODULES

Two gas modules are used for PGZ2. The two gas modules are identical. In one module, it is possible to inject gas in 5 boreholes simultaneously through 5 hydraulic lines (Figure 13).

For each hydraulic line:

• 1 reducing valve (200 bar),

• 1 gas pressure sensor (0 – 200 bar),

• 1 flowmeter (0.06 to 3 mLn/min) and 1 flow controller,

Jointly connected:

• 1 flowmeter (2 – 100 mLn/min) and 1 flow controller,

• 1 flowmeter (100 – 5000 mLn/min) and 1 flow controller,

• 1 flowmeter (0.06 to 3 mLn/min) and 1 flow controller for gas tracer injection.

Each flowmeter can be bypassed individually.

The gas used here is nitrogen and the flowrate are given in the standard reference conditions of temperature and pressure for expressing gas volumes, i.e. 0 °C (273.15 K) and 101.325 kPa (1 atm).

http://en.wikipedia.org/wiki/KPa�

http://en.wikipedia.org/wiki/Atmosphere_%28unit%29�


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Figure 13 gas module system

The names of the measuring points in the SAGD for the gas modules are presented in the Figure 14:


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Figure 14 Names of the measuring points in the gas modules

1.4 MEASUREMENTS

1.4.1 Samples GEOTER carried out the geologic logging of all the boreholes for the underground laboratory. They packaged the cores from the PGZ boreholes in Cell T1, for laboratories investigations. Table 10 presents details of the packaged cores.

Table 10 List of cores (Cell T1 packaging)

ANDRA Distance (m) from borehole mouth

Identifier Head Foot

PGZ1011

EST34006 6.33 6.63

EST34015 9.23 9.53

EST34018 9.83 10.13

EST34019 10.13 10.43

EST34024 12.48 12.78

PGZ1012

EST33940 7.04 7.34

EST33947 9.64 9.94

EST33949 10.14 10.46

EST33951 10.54 10.84

EST33957 12.64 12.94


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GEOTER also measured the water contents in samples from the PGZ2 boreholes.

A first measurement was performed at 105° C for geomechanical purposes, and a second measurement at 150° C for mineralogical and geochemical purposes. After drying in an oven for 24 hours the water content is obtained from the following equation:

All of the measurement tables are reported in Appendix 5.

Figures 7 to 9 present the water-content profiles (contents measured at 105 and 150° C) along the PGZ boreholes, against distance from the borehole mouth.

The water contents display a uniform profile for the (sub) horizontal boreholes, around 8%. We don’t observe a decrease in water contents in the last meter for boreholes PGZ1011 and PGZ1012 near the borehole wall in GEX side. Conversely, the high values in boreholes PGZ1011 and PGZ1012 at the ends of the boreholes (GEX side) are measured in concrete.

Figure 15 Water-content profile in borehole PGZ1001


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1.4.2 Measurement monitoring This section describes the variations observed in the measurements acquired, from the time the sensors were installed up to mid-November 2009. It does not provide a detailed analysis of the data but presents the significant facts and offers suggestions concerning the phenomena that may be involved in some of the observations.

The borehole temperature measurements, packer pressures, and climatic measurements are not included.

1.4.2.1 PORE PRESSURE MONITORING

PGZ1001

The rise in pressure in this borehole has been monitored for more than six months (Figure 18). The pressures are pseudo-stabilised for Chambers 1 and 5 at 20.3 and 25.7 bar respectively. In the other chambers the pressures are still rising. The pressure in Chamber 3 (the one located between the two drifts) reached 36.9 bar, and 33.4 bar in Chambers 2 and 4.

Figure 18 Pressure monitoring in borehole PGZ1001

The pseudo-stabilised pressure profile between the GEX and GMR drifts is shown in Figure 19. The pressure maximum is located half-way between the two drifts. However, this profile is asymmetric near the drift walls.


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Figure 19 Profile of pseudo-stabilised pressures between the GEX and GMR/GED drifts

PGZ1011 and PGZ1012

Figure 20 and Figure 21 show the pressure measurements in the measurement chambers in boreholes PGZ1011 and PGZ1012.

The pressure is rising in all the measurement chambers. The jump in pressure observed in borehole PGZ1011 corresponds to the rise in pressure in all the packers in the borehole. For PGZ1012, the sudden fall in pressure observed on October 11, 2009 is not connected to any action on the borehole. At present it is difficult to account for this drop. However, it is possible that the fall is related to the defective packer, because the measurement is located on the GEX side. A sudden rebalancing of the pressure in Packer 4 + Resin 2 is conceivable.


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Figure 20 Pressure monitoring in both measurement chambers of borehole PGZ1011

Figure 21 Pressure monitoring in both measurement chambers of borehole PGZ1012


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Figure 22 Pressure monitoring in the bentonite section of borehole PGZ1011

Figure 23 Pressure monitoring in the bentonite section of borehole PGZ1012


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Monitoring of the pressures of both boreholes in the bentonite section (Figure 22 and Figure 23) shows multiple jumps in pressure (positive and negative pressure). The positive-pressure jumps correspond to CO2 gas-injection tests in the bentonite section to determine the connectivity between two seats in the same borehole, and to assess the rigidity of the bentonite during hydration. These injection tests were performed by using the hydraulic line that runs to the crown of the seat (see Figure 10). The negative-pressure jumps were produced in the two resin zones located between Packers 3-4 and 5-6 of borehole PGZ1011, to assess the closing of the breakouts around Packers 4 and 5.

The next three figures illustrate the development of the response of the bentonite core, while it is being saturated, to a CO2 pulse in borehole PGZ1011. In qualitative terms:

• On Figure 24 the connectivity between the two seats is clear. The bentonite has not yet filled up the radial clearance

• On Figure 25, the bentonite has filled up the annulus in the bentonite section. However, the quick recovery of pressure shows a high permeability to gas. The gas passes through the bentonite in the radial clearance (density of bentonite in the radial clearance still low) and into the borehole's EDZ,

• On Figure 26, the bentonite section's permeability to gas has become much lower. These tests showed bypassing along the borehole until October 16, 2009. The zones requiring resin had by then received it.

Figure 24 CO2 pulse produced on 9/16/09 in PGZ1011


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1.4.2.2 TOTAL PRESSURE MONITORING

Figure 27 and Figure 28 show the monitoring of total pressures in boreholes PGZ1011 and PGZ1012.

Figure 27 Total-pressure monitoring in Bore-hole PGZ1011

For PGZ1012, an immediate response was observed from the sensors located on the GEX side following the leak from Packer No. 4 (GEX side). The pressures rise very quickly, reaching maxima of 76 and 85 bar after 17 days for the two sensors located on the GEX side. The maximum was reached eight days later for the sensors located on the GMR side.

For PGZ1011, the maximum was reached between 34 and 58 days after installation.

After this maximum-pressure phase, a more or less long and significant fall in total pressure is observed, ending in a plateau. Currently the pressures are rising sharply in PGZ1011 and less steeply in PGZ1012.


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Figure 28 Total-pressure monitoring in Bore-hole PGZ1012

The curves shown above are similar to the measurements obtained during model tests carried out by CEA/LECBA as part of the PGZ experiments. Moreover the Bentogaz test performed at CEA/LECBA for gas research program of Andra provides a qualitative interpretation of the observations. Bentogaz Test 1, currently in progress, examines the changes in the axial and radial pressures of a pellet/powder mixture.

Figure 29 presents the typical development of total (axial) pressures as seen in situ or in the laboratory, according to the bulk density of the core inside a free radial space available for swelling. The total-pressure measurements show two stages of bentonite resaturation: • A: increase in the axial pressure: The formation water hydrates the outer layers of the core,

which swell freely and take over the radial clearance in the form of a "gel" of low-density bentonite. There is an argillite/bentonite contact with little or no pressure and thus insufficient friction at the interface. Most of the force is transmitted longitudinally, owing to the rigidity of the as-yet unsaturated core. During this phase the core is not hydro-mechanically homogeneous (possibly fissured).

• B: partial collapse of the axial pressure: This phase is due to the rebalancing of the water in the material. As the saturation progresses, the drier internal portion of the core absorbs water from the outer layers, which become desaturated. As it becomes saturated the internal zone becomes more plastic and tends to compress the outer layers. The result is a rebalancing of the pressures in the core with a reduction in rigidity along the axis of the core (the axial pressure drops) but a compaction of the outer zones tangential to the axis of the core (the radial pressure increases). We then have close contact between the bentonite and argillite over the whole surface. if the bulk density of the material is low, the axial pressure tends to stabilise slowly

(Figure 29, Bottom). The quantity of swelling material is insufficient to enable an increase in the swelling pressure when the degree of saturation becomes uniform throughout the core. The swelling pressure becomes isotropic.

If the material's bulk density is high, a final phase of rising axial pressure is observed (Figure 29, Top)


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• C: rise in axial pressure: The degree of saturation becomes uniform throughout the core. The quantity of swelling material is such that this homogenisation of saturation causes an isotropic increase in the swelling pressure (axial and radial).

We see here a structural effect displayed in bentonite mixtures which have a dual porosity. This structural effect is related to the particular geometry of the system, with a radial space around the bentonite core.

Figure 29 Typical variation of axial pressure during hydration of a clay core with a radial clearance. Top: low void fraction and high dry density; Bottom: high void fraction and low dry density

A qualitative understanding of the stages of swelling of a bentonite core with a radial clearance, based on laboratory tests, is essential for defining the gas-injection programme in borehole PGZ1011 (see §1.5.2).

On Figure 28, after the beginning of October we see a different behaviour of the total pressure between the GEX side and the GMR/GED side of borehole PGZ1012. On the GMR side the free space into which the bentonite core can extrude from the seat is limited by Packer 5 (see Figure 9). In contrast, on the GEX side the space into which the bentonite can extrude is much greater, since Packer 4 could not be inflated. This behaviour therefore follows the typical development


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of axial pressure, depending on the local bulk density of the material. However, this anisotropic behaviour between the two sides of the core should become less marked with time.

1.5 CONTINUATION OF TEST PGZ2

1.5.1 PGZ1012 The interstitial and total pressures continue to be monitored in borehole PGZ1012. There are no current plans to carry out gas tests in this borehole.

Following the incident that occurred on one of the packers in borehole PGZ1012 a new borehole (PGZ1013) is planned, designed to monitor the natural resaturation of the bentonite core. This borehole should be drilled and equipped in February 2010. After full resaturation of the core, permeability tests for water and gas will be performed.

1.5.2 PGZ1011 In PGZ1011, the total-pressure measurements show a behaviour somewhat different from the figures obtained in the dimensioning calculations carried out. In particular, the total-pressure reduction phase in the plug is not represented in the models, which tend to give a constantly rising pressure as water is taken up.

Major uncertainties remain as regards the swelling of the bentonite core in the presence of a radial clearance. Based on the laboratory tests, the total-pressure measurements show a rise in the pressures (phase C in Figure 29), which indicate that the bentonite is homogenising and that the swelling pressure is tending to become isotropic.

On this basis, the start of gas injection was set for November 17, 2009 and the injection programme was modified with respect to the programme proposed in the preliminary report. The constant-pressure gas injection, in parallel on both faces of the core, is retained. However, the injection of gas will be carried out progressively, in stages, so as not to cause mechanical damage to the bentonite core.

The injection programme consists of raising the (nitrogen) gas pressure in successive stages; the injection gas flows are measured continuously. At two pressure stages, a pressure gradient is created, to measure the core's permeability to gas (interference test). The continuation of the gas injection will be adjusted according to the observed responses.

The injection of gas should last 30 to 40 days, after which the development of the system will be monitored.

After full resaturation of the core, its permeability to water and gas will be tested.


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Appendix 1 GED map


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Appendix 2 Photographs

Start of PGZ1011 in GMR/GED drift side

End of PGZ1011 borehole in GEX drift side


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Core-drilling : anchorage-bolt

Core-drilling : anchorage-bolt cut


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Anchorage-bolt cut-out near GMR drift in PGZ1011 View of seat 1 connected to packer n°4

View of interval for PGZ1011

View of PGZ1011 at the end installation in GMR/GED side

End of PGZ1012 borehole in GEX drift side. The cross is the theoretical end of the borehole

View of the seat 4 of PGZ1012 in GEX drift


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View of the bentonite buffer for PGZ1012

View of the bentonite buffer inserted into the seat 4 (PGZ1012)


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View of the gas module in GMR/GED drift

View of the gas module in GEX drift


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View of PGZ2 in GED/GMR drift

View of PGZ2 in GEX drift


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Appendix 3 Location of the temperature and relative-humidity sensors for the tests PGZ1 and PGZ2


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Appendix 4 Layouts

PGZ1001

Distances are given in reference to the borehole mouth.


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PGZ1011

Distances are given in reference to the borehole head. The borehole head is an imaginary point which represents the intersection between the borehole axis and the vertical plane from a geodesic target. This geodesic target is located near the borehole at wall.


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SEAT 1 FOR PGZ1011


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SEAT 2 FOR PGZ1012


46

PGZ1012

Distances are given in reference to the borehole mouth.


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SEAT 3 FOR PGZ1012


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SEAT 4 FOR PGZ1012

Warning : this plane is not conform to the in situ installation. Actually, there is a spin of 45° of sensors and hydraulic lines.

45°


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Appendix 5 Water contents data All distance are given in respect from borehole mouth

PGZ1001


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PGZ1011


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PGZ1012


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Glossary PGZ: experiment in the URL. French acronym for perturbation induced by gas experiment.

SAGD: french acronym for the data acquisition system in the URL.

Borehole head: the borehole head is an imaginary point which represents the intersection between the borehole axis and a vertical plan. This plane could be taken from a geodesic target at wall or between two inner sliding-ribs.

Borehole mouth: the borehole mouth represents the attack of the drilling machine in the wall.

design and installation of gas borehole experiment: the

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