TRACProject Asoftwaretointerprettracertests inporousmedium - - PDF document

Asoftwaretointerprettracertests inporousmedium

TRACProject

07/09/2016 1

GUTIERREZAlexis1,KLINKAThomas1, THIERYDominique1

Water Division

Tracer6Conference Oslo68June 2011 InternationalConferenceonTracersandTracingMethods

1BRGM - Water Division

3 avenue C. Guillemin BP 36009 45060 Orléans Cedex 2 France

Planofthepresentation

> Usesoftracertestsinhydrogeology

• Applications
• Tracers

> Motivationstodevelop TRAC > Example ofapplication

• Interpretation

> TRACfeatures > Conclusion

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Usesoftracertestsinhydrogeology

> Qualitative:existenceofhydraulic connection between two

points?

> Firstknown scientific tracertestinhydrogeology in1887

(Immendingen,Danube<>Ach spring)

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Injectionoffluorescenttracers inskinholes

Usesoftracertestsinhydrogeology

> Quantitative:characterize thetransportproperties oftheaquifer,

i.e.:kinematic porosity (c),dispersivity (),filtrationvelocity (u)

> Possibility totake into account ofothers process :

• Adsorption:(linear equilibrium adsorption)
• Degradation :

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L T V

C C C C C u D D D t x x x y y z z

• L

L

D u

• T

T

D u

• V

V

D u

• D

c c

V Ki u

• 0 exp

M t M t

• ; 1 2

ln 2 t

• 1

d

K R

Applications

> Theinterpretationoftherestitutioncurveisveryinstructiveonthepotential

transferofcontaminantsandinthedescriptionofhydrodispersiveparameters

> Toimprovemanagementandprotectionofgroundwaterresources

> Groundwater :

• Delineation ofthecatchment;
• Studyoftherespectivecontributionsofdifferentwaters

> Areasofgroundwater protection:

• Studyoftransittime/protectionzone
• 50daystransittime

> Determine thetransportparameters of

theaquiferfordiscretizedmodeling

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Tracers

> Totrackthemovementofwatermolecules,onemustchoosea

tracerthatis(ideally):

• chemicallystableandinerttomineralconstituentrocksoftheaquifer,sothat

thetracerisnotdisturbedsorptionreactions;

• stilldetectableinveryhighdilution,itsmovementcanbetrackedoverlong

distances;

• nontoxictohumansandtheenvironment;

> Thetypeoftraceruseddependson:

• objectivestracing
• constraintsofthetracing(waterchemistry,etc.).
• means(technicalandfinancial)available(sampling,analysis,...)

> Theartificialtracerscommonlyusedarewatersolubletracers

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Tracercomparison

>

Source:Utilisationdestraceursartificielsenhydrogéologie– SSH,2002

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Motivationstodevelop atool

> Lack ofsimpletool > CATTIsoftware(Sauty,Kinzelbach,1991) > Atool that helps theinterpretation anddesignoftracertests > Basedontheuseofanalyticalsolutions(nospatialdiscretization):

• Homogeneousaquifer;
• Infiniteintermsofextension;
• Dimensionsofflow(1D,2D,3D,radial);
• Monolayer;
• Uniformflow(notforradial).

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Analytical solutions

> TRACoffersapanelof12analyticalsolutions

• Compared with numericalmodels, analyticalmodels are generally

useful atafirststage of a projectwheninformation regarding the complexity oftheenvironment isnotknown

• Advantage of numericalmodels istheirability to take into account this

complexity, including heterogeneity ofthe geology or theboundary conditions

• Analyticalsolutionsassume that the geometryofsimulated

domain is relatively simple. Despite theirlimitations,analyticalmodels can be very useful for simplified analysis and are therefore widelyused inpractice.

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Asetofanalytical solutions

> Analyticalsolutionsofadvectivedispersivesolutetransport

equation(ADE)areusefulinpredictingthefateofsolutesin groundwater

> Actual available methods :

• 1D,2D,radialconverging/diverging flow;
• Instantaneous (Dirac),continuous,stepinjection;
• Delayfactor(indevelopment);
• Degradation constant(exponential form);
• Variabledirectionofthegroundwater flow.

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Applications

> Hypothesis ofuniform flowis valid :

• Inlaboratory,forsoilcolumn experiments (Qconstant,uconstant)
• Onthefield,fortracertestsunder natural conditionsinanhomogenous and

isotropeaquifer

> Forced flow:radialconvergent

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Observation point Injection point Observation point Injection point

TRAC– Sessionsample

> Two modes:« simulate anddesign »/« interpret tracertest »

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Tracertestconfiguration

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Parameterization

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International System of Units are used in TRAC, you can still add units from other systems : feet, inch, gallon …

Theorical breakthrough

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Optimalmasstoinject

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Sampling frequency

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Interpretation mode

> Fill thedescriptionoftracertestandthetechnical informations > Importyour field/lab data:concentration,time,flow > Selectanadequate solution > Adjust theparameters bytrialanderrors

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Soil column tracertest

> Filled with differents materials (glassball,small gravel) > Fixed flow > Injectionoffluoresceine inthemiddlewith aneedle > Measure ofconcentrationwith fluorimeter > Tracertestswith :

• Variableheight ofcolumn
• Variablediameter ofcolumn
• Differents flows
• Differents concentrationsoftracer

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Q

Injection (M0) sampling & analyse

x d

Context informations

> Descriptionofthetracertest > Technical informations > Opening anexisting project

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Importdata

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Selection ofanadequate solution

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Parameterization

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Optimization process

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Estimationoftransportparameters

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Estimationoftransportparameters

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small gravel medium gravel

0.00 0.20 0.40 0.60 0.80 1.00 0.00 0.50 1.00 1.50 2.00 2.50 Diamètre moyen du matériau (cm) Dispersivité (cm)

Relation dispersivité/diamètre moyen

Ø=f() Linéaire (Ø=f())

mix of small and medium gravel glass ball

Fieldscale

> Pollutionofdrinkable watersupply

bytwo industrials sites (chloronitobenzen)

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Features – Radialconverging/diverging flow

> Tracerexperimentsongroundwaterradialflowprovidean

economicalmethodofdeterminingtransportparameters

> Theinterpretationofthebreakthroughcurvesgivesrisetosome

difficultiessincethereisnoexactanalyticalsolutionthatcaneasily beusedfortransportinradialflow

> Developmentofanaccuratesemianalyticalsolution(D.Thiéry,to

bepublished)

• Maximizetherecoveryoftracer;
• Acceleratetheexperimentalprocedure(highervelocity);

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Features – Stepinjection

> Thehypothesisof an instantaneousinjection is valid whenthe

injectionperiod is negligiblecomparedwiththat ofthe average transittime.

> Useofsuperpositionprincipleforcontinuousinjection

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For t < Ti :

t C t C

c

• For t Ti :
• c

c i

C t C t C t T

• time

Cin

j

C0 Ti

• C0

Features – Stepinjection

> Example totake into account ofinjectionlength

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time Cinj C1 C2 C3 C4 t1 t2 t3 t4 For t < t1 : C(t) = Cc(C1,t) For t1 t < t2 : C(t) = Cc(C1,t) Cc(C1,t-t1) + Cc(C2,t-t1) For t2 t < t3 : C(t) = Cc(C1,t) Cc(C1,t-t1) + Cc(C2,t-t1) Cc(C2,t-t2) + Cc(C3,t-t2) And so on …

Features – Add your own analytical solution

> Tracertesting methods continuetoevolve > Newinterpretation methods arebeing developped

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2

( ) ( , ) exp exp( ) 4 4

L L

M x ut C x t t D t A D t

• Crank, 1956 – Bear 1972, modified

Injection of mass in an infinite medium Translation of formula in TRAC : M_0/(A*omega*2*sqrt(Pi*D_L*t))*exp(-pow(x-u*t,2)/(4*D_L*t))*exp(-lambda*t)

Features – Basiccalculations

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t c t dt t c t t T c t t c t dt

• Mass recovered (at constant rate) :

R n échantillons

m Q c t dt c t t

• For an ideal tracer : Vmoy = u

Conclusion

> Now :

• Simpletool
• Versatile
• Free(firstbetaversionreleased inJanuary 2011)
• Available infrench,spanish andenglish

> Future:

• Expecting thecommunity ofusers tosuggest analytical solutions/needs

– Pushpullsolution – Dualporosity solution – Firstorder chemical reactions

> Tobe published :

• Validationreport
• Usermanual /tutorial
• Semianalytical solutionradialconverging flow

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Acknowledgements

> Ourpartners : > J.Bodin(HydrASA,university ofPoitiers)forillustrations

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Thank you

QualitativetracertestinLaTouvre,France,30092008

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